ORCID Profile
0000-0002-4934-0458
Current Organisations
Imperial College London
,
Max Planck Institute für Eisenforschung
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Publisher: Wiley
Date: 22-08-2023
Abstract: MXenes are a family of 2D transition metal carbides and nitrides with remarkable properties and great potential for energy storage and catalysis applications. However, their oxidation behavior is not yet fully understood, and there are still open questions regarding the spatial distribution and precise quantification of surface terminations, intercalated ions, and possible uncontrolled impurities incorporated during synthesis and processing. Here, atom probe tomography analysis of as‐synthesized Ti 3 C 2 T x MXenes reveals the presence of alkali (Li, Na) and halogen (Cl, F) elements as well as unetched Al. Following oxidation of the colloidal solution of MXenes, it is observed that the alkalies enriched in TiO 2 nanowires. Although these elements are tolerated through the incorporation by wet chemical synthesis, they are often overlooked when the activity of these materials is considered, particularly during catalytic testing. This work demonstrates how the capability of atom probe tomography to image these elements in 3D at the near‐atomic scale can help to better understand the activity and degradation of MXenes, in order to guide their synthesis for superior functional properties. This article is protected by copyright. All rights reserved
Publisher: Elsevier BV
Date: 09-2017
Publisher: Public Library of Science (PLoS)
Date: 21-12-2018
Publisher: Wiley
Date: 03-06-2022
Abstract: Fuel cells recombine water from H 2 and O 2 thereby can power, for ex le, cars or houses with no direct carbon emission. In anion‐exchange membrane fuel cells (AEMFCs), to reach high power densities, operating at high pH is an alternative to using large volumes of noble metals catalysts at the cathode, where the oxygen‐reduction reaction occurs. However, the sluggish kinetics of the hydrogen‐oxidation reaction (HOR) hinders upscaling despite promising catalysts. Here, the authors observe an unexpected ingress of B into Pd nanocatalysts synthesized by wet‐chemistry, gaining control over this B‐doping, and report on its influence on the HOR activity in alkaline conditions. They rationalize their findings using ab initio calculations of both H‐ and OH‐adsorption on B‐doped Pd. Using this “impurity engineering” approach, they thus design Pt‐free catalysts as required in electrochemical energy conversion devices, for ex le, next generations of AEMFCs, that satisfy the economic and environmental constraints, that is, reasonable operating costs and long‐term stability, to enable the “hydrogen economy.”
Publisher: Springer Science and Business Media LLC
Date: 02-2021
Publisher: Elsevier BV
Date: 2019
Publisher: Oxford University Press (OUP)
Date: 07-2009
DOI: 10.1017/S1431927609093003
Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009
Publisher: Elsevier BV
Date: 09-2018
Publisher: Elsevier BV
Date: 11-2022
DOI: 10.1016/J.PTSP.2022.10.013
Abstract: The aims of this study were to determine the prevalence of sport specialisation in youth football, and to investigate the associations of sport specialisation and volume of sport participation with injury history. Cross-sectional questionnaire. New Zealand youth football teams. 414 youth football players aged 10-15 years. The level of specialisation, average weekly sport participation and free-play volume were recorded. 12-month injury history was captured and grouped by injury type. Associations between level of specialisation and demographic variables were analysed using chi square tests. Logistic regression was used to investigate associations between injury history, level of specialisation, and volume of participation. Participants were classified as high (43%), moderate (38%), or low (19%) specialised (n = 399 complete). High specialisation was more likely in boys, older participants, and those from large schools. Highly specialised participants were more likely to report a history of gradual onset injury than those who were low specialised (n = 340 with complete injury data). Odds of reporting a gradual onset injury also increased with greater weekly and annual sport participation volume. There is a high prevalence of sport specialisation in youth football, and it is associated with increased incidence of gradual onset injury.
Publisher: Oxford University Press (OUP)
Date: 29-07-2014
DOI: 10.1017/S1431927614012872
Abstract: Atom probe is a powerful technique for studying the composition of nano-precipitates, but their morphology within the reconstructed data is distorted due to the so-called local magnification effect. A new technique has been developed to mitigate this limitation by characterizing the distribution of the surrounding matrix atoms, rather than those contained within the nano-precipitates themselves. A comprehensive chemical analysis enables further information on size and chemistry to be obtained. The method enables new insight into the morphology and chemistry of niobium carbonitride nano-precipitates within ferrite for a series of Nb-microalloyed ultra-thin cast strip steels. The results are supported by complementary high-resolution transmission electron microscopy.
Publisher: IEEE
Date: 07-2006
Publisher: Elsevier BV
Date: 12-2021
Publisher: Elsevier BV
Date: 09-2019
Publisher: American Physical Society (APS)
Date: 24-04-2006
Publisher: AIP Publishing
Date: 04-2006
DOI: 10.1063/1.2194089
Abstract: A tomographic atom probe (TAP) in which the atoms are field evaporated by means of femtosecond laser pulses has been designed. It is shown that the field evaporation is assisted by the laser field enhanced by the subwavelength dimensions of the specimen without any significant heating of the specimen. In addition, as compared with the conventional TAP, due to the very short duration of laser pulses, no spread in the energy of emitted ions is observed, leading to a very high mass resolution in a straight TAP in a wide angle configuration. At last, laser pulses can be used to bring the intense electric field required for the field evaporation on poor conductive materials such as intrinsic Si at low temperature. In this article, the performance of the laser TAP is described and illustrated through the investigation of metals, oxides, and silicon materials.
Publisher: American Chemical Society (ACS)
Date: 05-09-2017
DOI: 10.1021/ACS.LANGMUIR.7B01820
Abstract: Atom probe tomography was used to analyze self-assembled monolayers of thiophene on different surfaces, including tungsten, platinum, and aluminum, where the tungsten was examined in both pristine and oxidized forms. A glovebag with controlled atmospheres was used to alter the level of oxidation for tungsten. It was shown that different substrates lead to substantial changes in the way thiophene adsorbs on the surface. Furthermore, the oxidation of the surface strongly influenced the adsorption behavior of the thiophene molecules, leading to clear differences in the amounts and compositions of field evaporated ions and molecular ions.
Publisher: Elsevier BV
Date: 03-2011
Publisher: Elsevier BV
Date: 09-2020
Publisher: Springer Science and Business Media LLC
Date: 16-02-2022
DOI: 10.1038/S41586-021-04343-Z
Abstract: Ever more stringent regulations on greenhouse gas emissions from transportation motivate efforts to revisit materials used for vehicles 1 . High-strength aluminium alloys often used in aircrafts could help reduce the weight of automobiles, but are susceptible to environmental degradation 2,3 . Hydrogen ‘embrittlement’ is often indicated as the main culprit 4 however, the exact mechanisms underpinning failure are not precisely known: atomic-scale analysis of H inside an alloy remains a challenge, and this prevents deploying alloy design strategies to enhance the durability of the materials. Here we performed near-atomic-scale analysis of H trapped in second-phase particles and at grain boundaries in a high-strength 7xxx Al alloy. We used these observations to guide atomistic ab initio calculations, which show that the co-segregation of alloying elements and H favours grain boundary decohesion, and the strong partitioning of H into the second-phase particles removes solute H from the matrix, hence preventing H embrittlement. Our insights further advance the mechanistic understanding of H-assisted embrittlement in Al alloys, emphasizing the role of H traps in minimizing cracking and guiding new alloy design.
Publisher: Elsevier BV
Date: 05-2019
Publisher: Springer Science and Business Media LLC
Date: 24-06-2020
Publisher: AIP Publishing
Date: 15-03-2012
DOI: 10.1063/1.3695461
Abstract: The unidirectional laser illumination of atom probe tomography specimens can result in changes of the apex morphology from nearly hemispherical to asymmetrical with different local radii of curvature, implying an anisotropic field distribution across the s le surface. In the analysis of III-V semiconductors, this affects the process of field dissociation of group-V cluster ions and introduces variations in the apparent composition across the field of view. We have studied this phenomenon in GaSb and propose an explanation for these compositional variations in terms of the locally varying extent of field dissociation of group-V cluster ions and ion pile-up effects on the detector. The optimization of experimental conditions and possible modifications to the instrument design are discussed to mitigate the compositional variations.
Publisher: Trans Tech Publications, Ltd.
Date: 06-2014
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.794-796.926
Abstract: Two ex les of precipitation studies (in Al-Li-Cu and Al-Li-Mg alloys) are shown to demonstrate the complementarity of atom probe tomography, small-angle-scattering and differential scanning calorimetry for precipitation studies. It will be used to unravel an unexpected two-step precipitation behavior of T 1 in Al-Li-Cu and to ascertain precipitates size in Al-Li-Mg. through a model free comparison between atom probe and SAXS.
Publisher: American Physical Society (APS)
Date: 17-10-2023
Publisher: Springer Science and Business Media LLC
Date: 11-12-2020
DOI: 10.1038/S41524-020-00456-7
Abstract: Segregation to grain boundaries affects their cohesion, corrosion, and embrittlement and plays a critical role in heterogeneous nucleation. In order to quantitatively study segregation and low-dimensional phase separation at grain boundaries, here, we apply a density-based phase-field model. The current model describes the grain-boundary thermodynamic properties based on available bulk thermodynamic data, while the grain-boundary-density profile is obtained using atomistic simulations. To benchmark the performance of the model, Mn grain-boundary segregation in the Fe–Mn system is studied. 3D simulation results are compared against atom probe tomography measurements conducted for three alloy compositions. We show that a continuous increase in the alloy composition results in a discontinuous jump in the segregation isotherm. The jump corresponds to a spinodal phase separation at grain boundary. For alloy compositions above the jump, we reveal an interfacial transient spinodal phase separation. The transient spinodal phenomenon opens opportunities for knowledge-based microstructure design through the chemical manipulation of grain boundaries. The proposed density-based model provides a powerful tool to study thermodynamics and kinetics of segregation and phase changes at grain boundaries.
Publisher: Elsevier BV
Date: 11-2020
Publisher: Oxford University Press (OUP)
Date: 18-02-2019
DOI: 10.1017/S1431927618016252
Abstract: The process of building an open source library of simulated field desorption maps for differently oriented synthetic tips of the face-centered cubic, body-centered cubic, and hexagonal-close-packed crystal structures using the open source software TAPSim is reported. Specifically, the field evaporation of a total set of 4 × 101 single-crystalline tips was simulated. Their lattices were oriented randomly to s le economically the fundamental zone of crystal orientations. Such data are intended to facilitate the interpretation of low-density zone lines and poles that are observed on detector hit maps during Atom Probe Tomography (APT) experiments. The datasets and corresponding tools have been made publicly available to the APT community in an effort to provide better access to simulated atom probe datasets. In addition, a computational performance analysis was conducted, from which recommendations are made as to which key tasks should be optimized in the future to improve the parallel efficiency of TAPSim.
Publisher: Elsevier BV
Date: 08-2019
Publisher: Elsevier BV
Date: 05-2021
Publisher: Elsevier BV
Date: 03-2021
Publisher: Springer Science and Business Media LLC
Date: 20-01-2020
DOI: 10.1038/S41467-019-14062-9
Abstract: Single crystal Ni-based superalloys have long been an essential material for gas turbines in aero engines and power plants due to their outstanding high temperature creep, fatigue and oxidation resistance. A turning point was the addition of only 3 wt.% Re in the second generation of single crystal Ni-based superalloys which almost doubled the creep lifetime. Despite the significance of this improvement, the mechanisms underlying the so-called “Re effect” have remained controversial. Here, we provide direct evidence of Re enrichment to crystalline defects formed during creep deformation, using combined transmission electron microscopy, atom probe tomography and phase field modelling. We reveal that Re enriches to partial dislocations and imposes a drag effect on dislocation movement, thus reducing the creep strain rate and thereby improving creep properties. These insights can guide design of better superalloys, a quest which is key to reducing CO 2 emissions in air-traffic.
Publisher: Elsevier BV
Date: 04-2018
Publisher: Elsevier BV
Date: 07-2015
DOI: 10.1016/J.ULTRAMIC.2015.02.009
Abstract: In this article, after a brief introduction to the principles behind atom probe crystallography, we introduce methods for unambiguously determining the presence of crystal planes within atom probe datasets, as well as their characteristics: location orientation and interplanar spacing. These methods, which we refer to as plane orientation extraction (POE) and local crystallography mapping (LCM) make use of real-space data and allow for systematic analyses. We present here application of POE and LCM to datasets of pure Al, industrial aluminium alloys and doped-silicon. Data was collected both in DC voltage mode and laser-assisted mode (in the latter of which extracting crystallographic information is known to be more difficult due to distortions). The nature of the atomic planes in both datasets was extracted and analysed.
Publisher: Elsevier BV
Date: 12-2015
Publisher: Elsevier BV
Date: 07-2010
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.ULTRAMIC.2015.02.005
Abstract: Picosecond-pulsed ultraviolet-laser (UV-355 nm) assisted atom probe tomography (APT) was used to analyze protective, thermally grown chromium oxides formed on stainless steel. The influence of analysis parameters on the thermal tail observed in the mass spectra and the chemical composition is investigated. A new parameter termed "laser sensitivity factor" is introduced in order to quantify the effect of laser energy on the extent of the thermal tail. This parameter is used to compare the effect of increasing laser energy on thermal tails in chromia and chromite s les. Also explored is the effect of increasing laser energy on the measured oxygen content and the effect of specimen base temperature and laser pulse frequency on the mass spectrum. Finally, we report a preliminary analysis of molecular ion dissociations in chromia.
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.ULTRAMIC.2013.03.010
Abstract: Atom probe tomography stands out from other materials characterisation techniques mostly due to its capacity to map in idual atoms in three-dimensions with high spatial resolution. The methods used to transform raw detector data into a three-dimensional reconstruction have, comparatively to other aspects of the technique, evolved relatively little since their inception more than 15 years ago. However, due to the importance of the fidelity of the data, this topic is currently attracting a lot of interest within the atom probe community. In this review we cover: (1) the main aspects of the image projection, (2) the methods used to build tomographic reconstructions, (3) the intrinsic limitations of these methods, and (4) future potential directions to improve the integrity of atom probe tomograms.
Publisher: Elsevier BV
Date: 04-2018
Publisher: Wiley
Date: 06-05-2021
Abstract: The poor carrier mobility of polycrystalline Mg 3 Sb 2 at low temperatures strongly degrades the thermoelectric performance. Ionized impurities are initially thought to dominate charge carrier scattering at low temperatures. Accordingly, the increased electrical conductivity by replacing Mg with metals such as Nb is also attributed to reduced ionized impurity scattering. Recent experimental and theoretical studies challenge this view and favor the grain boundary (GB) scattering mechanism. A reduction of GB scattering improves the low‐temperature performance of Mg 3 (Sb, Bi) 2 alloys. However, it is still elusive how these metal additions reduce the GB resistivity. In this study, Nb‐free and Nb‐added Mg 3 Sb 2 are studied through diffraction, X‐ray absorption spectroscopy, solid‐state nuclear magnetic resonance spectroscopy, and atom probe tomography. It is shown that Nb does not enter the Mg 3 Sb 2 matrix and remains in the metallic state. Besides, Nb diffuses along the GB forming a wetting layer, which modifies the interfacial energy and accelerates grain growth. The GB resistivity appears to be reduced by Nb‐enrichment, as evidenced by modeling the electrical transport properties. This study not only confirms the GB scattering in Mg 3 Sb 2 but also reveals the hitherto hidden role of metallic additives on enhancing grain growth and reducing the GB resistivity.
Publisher: Springer Science and Business Media LLC
Date: 22-02-2017
DOI: 10.1038/SREP42547
Abstract: Manipulating structure, defects and composition of a material at the atomic scale for enhancing its physical or mechanical properties is referred to as nanostructuring. Here, by combining advanced microscopy techniques, we unveil how formation of highly regular nano-arrays of nanoparticles doubles the strength of an Fe-based alloy, doped with Ti, Mo, and V, from 500 MPa to 1 GPa, upon prolonged heat treatment. The nanoparticles form at moving heterophase interfaces during cooling from the high-temperature face-centered cubic austenite to the body-centered cubic ferrite phase. We observe MoC and TiC nanoparticles at early precipitation stages as well as core-shell nanoparticles with a Ti-C rich core and a Mo-V rich shell at later precipitation stages. The core-shell structure h ers particle coarsening, enhancing the material’s strength. Designing such highly organized metallic core-shell nanoparticle arrays provides a new pathway for developing a wide range of stable nano-architectured engineering metallic alloys with drastically enhanced properties.
Publisher: The Electrochemical Society
Date: 05-2020
DOI: 10.1149/MA2020-01371557MTGABS
Abstract: The oxygen evolution reaction (OER) underpins electrochemical technologies for hydrogen generation [1]. The sluggish kinetics of the OER and the instability of most of the anode materials hinder widespread application of proton exchange membrane water electrolyzers (PEMWE). Up to now, only iridium-based catalysts meet the necessary requirements and are currently employed in PEMWE [2]. Despite the scarcity and high cost of iridium, its relatively high reactivity and superior stability make it irreplaceable to optimize the durability of the electrolyzer. Understanding what governs the electrocatalytic activity as well as the long-term stability of iridium is crucial for the development of novel catalysts that will enable efficient energy conversion and storage technologies. Gaining this knowledge requires establishing the correlation between the atomic-scale structure of the catalysts, their electronic properties and the mechanisms of the OER and other side reactions that lead to the material’s degradation. In this presentation, I give an overview of our recent results, with a special focus on the mechanisms of the reactions ongoing at the surface of an array of iridium-based anodes during the OER [2-4]. The mechanistic insights are obtained from combination of X-ray photoelectron spectroscopy, online electrochemical mass spectrometry, electron microscopy and atom probe tomography. During the presentation, specific structural and compositional features that we recently revealed are responsible for high reactivity and/or instability of catalytic systems will be discussed in detail [4]. In addition several approaches to improve both the reactivity and the stability will be proposed, and can serve as guiding principles for the development of materials with superior electrocatalytic performance towards the OER. [1] V. R. Stamenkovic, D. Strmcnik, P. P. Lopes and N. M. Markovic, Nat. Mater., 16 (2017) 57. [2] T. Li, O. Kasian, S. Cherevko, et al., Nat. Catalysis 1 (2018) 300. [3] O. Kasian, J.-P. Grote, S. Geiger, S. Cherevko, K. J. J. Mayrhofer, Angew. Chem., Int. Ed., 57 (2018) 2488. [4] O. Kasian, S. Geiger, T. Li, J-P. Grote, K. Schweinar, S. Zhang, C. Scheu, D. Raabe, S. Cherevko, B. Gault, K. Mayrhofer, Energy & Environmental Science (2019), DOI: 10.1039/C9EE01872G.
Publisher: Elsevier BV
Date: 06-2021
Publisher: Elsevier BV
Date: 12-2018
Publisher: Springer London
Date: 26-11-2013
Publisher: IEEE
Date: 07-2006
Publisher: Elsevier BV
Date: 02-2020
Publisher: Wiley
Date: 27-11-2022
Abstract: Layered LiMO 2 (M = Ni, Co, Mn, and Al mixture) cathode materials used for Li‐ion batteries are reputed to be highly reactive through their surface, where the chemistry changes rapidly when exposed to ambient air. However, conventional electron/spectroscopy‐based techniques or thermogravimetric analysis fails to capture the underlying atom‐scale chemistry of vulnerable Li species. To study the evolution of the surface composition at the atomic scale, cryogenic atom probe tomography is used herein and the surface species formed during exposure of a LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathode material to air are probed. The compositional analysis evidences the formation of Li 2 CO 3 . Site‐specific examination from a cracked region of an NMC811 particle also reveals the predominant presence of Li 2 CO 3 . These insights will help to design improved protocols for cathode synthesis and cell assembly, as well as critical knowledge for cathode degradation.
Publisher: Elsevier BV
Date: 10-2010
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 05-2018
Publisher: Wiley
Date: 2011
DOI: 10.1002/JEMT.20958
Abstract: A limiting characteristic of the atom-probe technique is the nondetection of ions and this embodies a significant "missing information" problem in investigations of atomic clustering phenomena causing difficulty in the interpretation of any atom-probe experiment. It is shown that the measurable cluster-size distribution can be modeled by a mixed binomial distribution. A deconvolution method based upon expectation-maximization (EM) algorithm is presented to obtain the original physical distribution from an efficiency-degraded distribution, thereby providing means to calculate accurate cluster number densities from atom probe results. The accuracy of this restoration was predominantly dependent upon the detector efficiency and was proved to be highly accurate in the case of conventional atom-probe detector efficiencies (ε = 57%). Such considerations and measures are absolutely necessary when the number density of clusters and small precipitates is in any way regarded as important. We conclude that limitations in detector efficiency are more limiting for cluster-finding analyses via atom-probe techniques than spatial resolution issues, and therefore the current endeavors for improving detector technologies are well found.
Publisher: Oxford University Press (OUP)
Date: 08-2022
DOI: 10.1017/S1431927621013994
Abstract: Imaging of liquids and cryogenic biological materials by electron microscopy has been recently enabled by innovative approaches for specimen preparation and the fast development of optimized instruments for cryo-enabled electron microscopy (cryo-EM). Yet, cryo-EM typically lacks advanced analytical capabilities, in particular for light elements. With the development of protocols for frozen wet specimen preparation, atom probe tomography (APT) could advantageously complement insights gained by cryo-EM. Here, we report on different approaches that have been recently proposed to enable the analysis of relatively large volumes of frozen liquids from either a flat substrate or the fractured surface of a wire. Both allowed for analyzing water ice layers which are several micrometers thick consisting of pure water, pure heavy water, and aqueous solutions. We discuss the merits of both approaches and prospects for further developments in this area. Preliminary results raise numerous questions, in part concerning the physics underpinning field evaporation. We discuss these aspects and lay out some of the challenges regarding the APT analysis of frozen liquids.
Publisher: Elsevier BV
Date: 07-2018
Publisher: Elsevier BV
Date: 2013
DOI: 10.1016/J.ULTRAMIC.2012.08.014
Abstract: Atom probe tomography (APT) is capable of simultaneously revealing the chemical identities and three dimensional positions of in idual atoms within a needle-shaped specimen, but suffers from a limited field-of-view (FOV), i.e., only the core of the specimen is effectively detected. Therefore, the capacity to analyze the full tip is crucial and much desired in cases that the shell of the specimen is also the region of interest. In this paper, we demonstrate that, in the analysis of III-V nanowires epitaxially grown from a substrate, the presence of the flat substrate positioned only micrometers away from the analyzed tip apex alters the field distribution and ion trajectories, which provides extra image compression that allows for the analysis of the entire specimen. An array of experimental results, including field desorption maps, elemental distributions, and crystallographic features clearly demonstrate the fact that the whole tip has been imaged, which is confirmed by electrostatic simulations.
Publisher: The Electrochemical Society
Date: 05-2020
DOI: 10.1149/MA2020-01482713MTGABS
Abstract: Dealloying of Ag-Au alloys is known to produce Au-rich, bicontinous, nanoporous layers [1-2]. The high functionality of nanoporous gold, demonstrated in a variety of applications [3-4], invites us to study the fabrication of other nanoporous metals of interest by exploiting corrosion processes. Recent studies have shown how the use of ruthenium, which is the cheapest Pt-group metal, for catalysis could be expanded from the classical ex le of CO oxidation [5], to other important reactions such as hydrogen evolution [6]. Although several porous/non-porous Ru-containing systems have been studied before [7-8], there remains a knowledge-gap with regards to the design and optimization of Ru-based catalysts. As a first step towards the development of nanoporous ruthenium by metal corrosion, this work shall focus on the design of binary transition metal-Ru systems. High resolution APT (atom probe tomography) studies of Ru-lean alloys (Fe-Ru and Ni-Ru) will assess the bulk microstructure of as-cast alloys and how it is affected by processing conditions [9]. Furthermore, pathways to inducing Ru-surface enrichment in different thermochemical environments (oxidative/inert/reductive) will be investigated by combined APT and XPS (X-ray photoelectron spectroscopy) [10]. The results of this study will provide guidance to making low-cost, high surface area nanoporous ruthenium catalysts by dealloying in acidic media. References [1] H. W. Pickering and P. R. Swann. Electron metallography of chemical attack upon some alloys susceptible to stress corrosion cracking, Corrosion, 1963, 19, 373t. [2] R.C. Newman. Dealloying, Shreir's Corrosion (fourth ed.), 2, Elsevier (2010), 801-809. [3] A.A. Vega, R.C. Newman. Methanol electro-oxidation on nanoporous metals formed by dealloying of Ag–Au–Pt alloys, Journal of Applied Electrochemistry, 2016, 46, 995-1010. [4] Y. Xue, J. Markmann, H. Duan, J. Weissmüller and Patrick Huber. Switchable imbibition in nanoporous gold, Nature Communications, 2014, 5, 4237. [5] N.W. Cant, P.C. Hicks and B.S. Lennon. Steady-state oxidation of carbon monoxide over supported noble metals with particular reference to platinum, Journal of Catalysis, 1978, 54, 372-383. [6] B. Lu, L. Guo, F. Wu, Y. Peng, J.E. Lu, T.J. Smart, N. Wang, Y.Z. Finfrock, D. Morris, P. Zhang, N. Li, P. Gao, Y. Ping and S. Chen. Ruthenium atomically dispersed in carbon outperforms platinum toward hydrogen evolution in alkaline media, Nature Communications, 2019, 10, 631. [7] T. Li, P.A.J. Bagot, E.A. Marquis, S.C.E. Tsang and G.D.W. Smith. Characterization of oxidation and reduction of Pt-Ru and Pt-Rh-Ru alloys by atom probe tomography and comparison with Pt-Rh, Journal of Physical Chemistry C, 2012, 116, 17633–17640. [8] M. Hakamada, J. Motomura, F. Hirashima and M. Mabuchi. Preparation of nanoporous ruthenium catalyst and Its CO oxidation characteristics, Materials Transactions, 53, 2012, 524-530. [9] L. Li, Z. Li, A.K. da Silva, Z. Peng, H. Zhao, B. Gault, D. Raabe. Segregation-driven grain boundary spinodal decomposition as a pathway for phase nucleation in a high-entropy alloy, Acta Materialia, 2019, 178, 1-9. [10] K. Schweinar, O. Kasian, R.L. Nicholls, C.R. Rajamathi, P. Zeller, M. Amati, L. Gregoratti, D. Raabe, M. Greiner, and B. Gault. An integrated workflow to investigate electrocatalytic surfaces by correlative X-ray Photoemission Spectroscopy, Scanning Photoemission Electron Microscopy and Atom Probe Tomography, Microscopy and Microanalysis, 2019, 25, 306–307.
Publisher: Elsevier BV
Date: 06-2023
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 02-2018
Publisher: IOP Publishing
Date: 29-09-2020
Publisher: Oxford University Press (OUP)
Date: 20-02-2017
DOI: 10.1017/S1431927617000034
Abstract: In the course of a thorough investigation of the performance-structure-chemistry interdependency at silicon grain boundaries, we successfully developed a method to systematically correlate aberration-corrected scanning transmission electron microscopy and atom probe tomography. The correlative approach is conducted on in idual APT and TEM specimens, with the option to perform both investigations on the same specimen in the future. In the present case of a Σ9 grain boundary, joint mapping of the atomistic details of the grain boundary topology, in conjunction with chemical decoration, enables a deeper understanding of the segregation of impurities observed at such grain boundaries.
Publisher: Oxford University Press (OUP)
Date: 20-03-2017
DOI: 10.1017/S1431927617000277
Abstract: An automated procedure has been developed for the reconstruction of field ion microscopy (FIM) data that maintains its atomistic nature. FIM characterizes in idual atoms on the specimen’s surface, evolving subject to field evaporation, in a series of two-dimensional (2D) images. Its unique spatial resolution enables direct imaging of crystal defects as small as single vacancies. To fully exploit FIM’s potential, automated analysis tools are required. The reconstruction algorithm developed here relies on minimal assumptions and is sensitive to atomic coordinates of all imaged atoms. It tracks the atoms across a sequence of images, allocating each to its respective crystallographic plane. The result is a highly accurate 3D lattice-resolved reconstruction. The procedure is applied to over 2000 tungsten atoms, including ion-implanted planes. The approach is further adapted to analyze carbides in a steel matrix, demonstrating its applicability to a range of materials. A vast amount of information is collected during the experiment that can underpin advanced analyses such as automated detection of “out of sequence” events, subangstrom surface displacements and defects effects on neighboring atoms. These analyses have the potential to reveal new insights into the field evaporation process and contribute to improving accuracy and scope of 3D FIM and atom probe characterization.
Publisher: AIP Publishing
Date: 20-02-2012
DOI: 10.1063/1.3688045
Abstract: Pulsed laser atom probe tomography was employed to study the interfacial chemistry in an InAs/GaSb superlattice nanostructure. The InAs-on-GaSb anion sublattice interface was found to be wider than the GaSb-on-InAs interface, in good agreement with previous electron microscopy studies. Hetero-nuclear group-V cluster ions at the InAs-on-GaSb interface as detected by atom probe are indicative of a strong As for Sb exchange reaction when InAs is grown onto GaSb.
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.ULTRAMIC.2012.12.012
Abstract: We electrostatically model a local electrode atom probe microscope using the commercial software IES LORENTZ 2D v9.0 to investigate factors affecting the reconstruction parameters. We find strong dependences on the specimen geometry and voltage, and moderate dependences on the tip-aperture separation, which confirm that the current approach to atom probe reconstruction overlooks too many factors. Based on our data, which are in excellent agreement with known trends and experimental results, we derive a set of empirical relations which predict the values of the reconstruction parameters. These may be used to advance current reconstruction protocols by enabling the parameters to be adjusted as the specimen geometry changes.
Publisher: Elsevier BV
Date: 2012
DOI: 10.1016/J.ULTRAMIC.2011.10.003
Abstract: Nitrided steels are widely used in the engineering field due to their superior hardness and other attractive properties. Atom probe tomography (APT) was employed to study two Nb-microalloyed CASTRIP steels with different N contents. A major challenge of using APT to study this group of materials is the presence of tails after Fe peaks in the mass spectra, which overestimates the composition for alloying elements such as Nb and Cu in the steels. One important factor that contributes to the tails is believed to be delayed field evaporation from Fe²⁺. This artefact of the mass spectrum was observed to be the most severe when voltage pulsing was used. The application of laser pulses with energy ranging from 0.2 to 1.2 nJ successfully reduced the tails and lead to better compositional measurement accuracy. Spatial resolution in the z-direction (along the tip direction) was observed to be less affected by changing laser energy but deteriorates in x-y direction with increasing laser energy. This investigation suggests that pulsed-laser atom probe with ∼0.4 nJ laser energy can be used to study this group of materials with improved mass resolution while still maintaining high spatial resolution.
Publisher: Elsevier BV
Date: 04-2019
Publisher: AIP Publishing
Date: 11-2011
DOI: 10.1063/1.3657846
Abstract: Modern atom probes typically incorporate an ultrafast pulsed-laser source with wavelength ranging from infrared (IR) to ultraviolet (UV) depending on the specific instrument. In order to estimate the influence of the wavelength on the accuracy of the technique, the achievable in-depth spatial resolution has been measured for atom probe analyses of the same pure W specimen using three different wavelengths and across a range of laser pulse energies. UV illumination is shown to yield superior spatial resolution to both IR and visible (green) wavelengths. We propose that this improvement relates to a faster decay of temperature enabled by light absorption confined to the near apex region.
Publisher: Research Square Platform LLC
Date: 19-07-2023
DOI: 10.21203/RS.3.RS-3181035/V1
Abstract: Local chemical order (LCO) can exert pronounced effects on both structural and functional properties, tailoring LCO domains at (sub-)nanoscale could offer an alternative material-design concept for yet unexplored performance. However, the origin of LCO remains an open question, making accurate manipulation of LCO extremely challenging. Here we selected the Fe-Ga magnetostrictive materials and demonstrated that LCO tetragonal structures play a significant role in optimizing the magnetostrictive properties. The “full-lifecycle”, including formation, evolution and dissolution of LCO, is concretely studied from the atomic-scale up by combined experimental and theoretical studies. The dynamic precipitation and dissolution processes of LCO L6 0 domains during isothermal aging are directly observed based on in-situ high-resolution transmission electron microscopy images, and the corresponding mechanisms are revealed by first-principles calculation. Based on the results, we evidence that LCO domain is a frozen-intermediate-states of a kinetically-slow solid-state phase transformation leading to the formation of the long-range-ordered equilibrium phase with a face-center-cubic structure. We confirm the reversibility of LCO during cycling treatments. Our findings shed light on the origin of LCO in a range of material systems, and we discuss directions for developing materials with superior performance by manipulating LCO domains.
Publisher: The Electrochemical Society
Date: 05-2020
DOI: 10.1149/MA2020-01452561MTGABS
Abstract: Developing electrocatalysts with enhanced properties requires a fundamental understanding of the processes that occur during operation as well as side reactions during the synthesis. Many of those processes, e.g. solute segregation to defects [1], the hydroxylation of near-surface regions [2], or the preferential oxidation/reduction of certain regions, are often governed by the local microstructure. Such phenomena commonly result in significant chemical heterogeneities within the material at the nanoscale, affecting the potential distribution across the surface during operation. This way, localized heterogeneities can control the local binding energetics for reactants, intermediates and products, and determine the overall reactivity and stability of the material. Atom probe tomography (APT) offers the opportunity to measure the composition of localized chemical fluctuations at the near-atomic scale and in three dimensions. Targeted APT specimen preparation of regions-of-interest, e.g. at specific grains or grain boundaries, enables the correlation of local structure and local composition. Recent method developments have enabled the measurement of free surfaces with APT [2,3], offering a new perspective into the first few atomic layers of electrocatalytic materials. APT thereby provides the chance to elucidate chemical processes within the near-surface region which underpin the electrochemical performance of the material. In this contribution, we showcase how APT can be instrumental to the precise characterization of various electrocatalytic materials. In a first ex le, we demonstrate how APT revealed the structural features in hydrous Ir oxides that are responsible for an accelerated degradation of the catalyst during the oxygen evolution reaction, due to release of molecular oxygen from the lattice [4]. Secondly, we present how APT can be combined with scanning photoemission electron microscopy to obtain spatially correlated chemical state information of the surface investigated with APT [1,3]. And finally, we show how APT enables the investigation of trace-element distribution in nanostructured materials, such as nanoparticles [5] or nanorods [6]. For ex le, APT can shed light on the incorporation of B, Na and N during the hydrothermal synthesis and partial reduction of hollow TiO 2 nanorods, that are commonly used as a photocatalyst or catalyst support. Trace amounts of such light elements often remain undetected with other methods but may have a dramatic effect on the functionality of the material. References [1] K. Schweinar, R.L. Nicholls, C.R. Rajamathi, et al. , submitted. [2] T. Li, O. Kasian, S. Cherevko, et al. , Nat. Cat. 1 (2018), pp. 300-305. [3] K. Schweinar, O. Kasian, R.L. Nicholls, et al. , Microscopy and Microanalysis 25 (S2) (2019), pp. 306-307 [4] Kasian, S. Geiger, T. Li, et al. , Energy & Environ. Sci (2019). [5] S. Kim, P.W. Kang, O.O. Park, et al. , Ultramicroscopy 190 (2018), pp. 30-38. [6] J. Lim, S. Kim, R.A. Armengol, et al. , submitted.
Publisher: Wiley
Date: 06-12-2017
DOI: 10.1002/PIP.2966
Publisher: Elsevier BV
Date: 05-2023
Publisher: Elsevier BV
Date: 12-2018
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 05-2016
Publisher: Springer Science and Business Media LLC
Date: 08-07-2021
DOI: 10.1038/S41563-021-01050-Y
Abstract: The antagonism between strength and resistance to hydrogen embrittlement in metallic materials is an intrinsic obstacle to the design of lightweight yet reliable structural components operated in hydrogen-containing environments. Economical and scalable microstructural solutions to this challenge must be found. Here, we introduce a counterintuitive strategy to exploit the typically undesired chemical heterogeneity within the material’s microstructure that enables local enhancement of crack resistance and local hydrogen trapping. We use this approach in a manganese-containing high-strength steel and produce a high dispersion of manganese-rich zones within the microstructure. These solute-rich buffer regions allow for local micro-tuning of the phase stability, arresting hydrogen-induced microcracks and thus interrupting the percolation of hydrogen-assisted damage. This results in a superior hydrogen embrittlement resistance (better by a factor of two) without sacrificing the material’s strength and ductility. The strategy of exploiting chemical heterogeneities, rather than avoiding them, broadens the horizon for microstructure engineering via advanced thermomechanical processing.
Publisher: Springer Science and Business Media LLC
Date: 12-01-2017
DOI: 10.1038/SREP40704
Abstract: High-entropy alloys (HEAs) consisting of multiple principle elements provide an avenue for realizing exceptional mechanical, physical and chemical properties. We report a novel strategy for designing a new class of HEAs incorporating the additional interstitial element carbon. This results in joint activation of twinning- and transformation-induced plasticity (TWIP and TRIP) by tuning the matrix phase’s instability in a metastable TRIP-assisted dual-phase HEA. Besides TWIP and TRIP, such alloys benefit from massive substitutional and interstitial solid solution strengthening as well as from the composite effect associated with its dual-phase structure. Nanosize particle formation and grain size reduction are also utilized. The new interstitial TWIP-TRIP-HEA thus unifies all metallic strengthening mechanisms in one material, leading to twice the tensile strength compared to a single-phase HEA with similar composition, yet, at identical ductility.
Publisher: Springer Science and Business Media LLC
Date: 05-07-2018
Publisher: Elsevier BV
Date: 10-2018
Publisher: Elsevier BV
Date: 02-2023
Publisher: Research Square Platform LLC
Date: 31-05-2023
DOI: 10.21203/RS.3.RS-2873882/V1
Abstract: Permanent magnets draw their properties from a complex interplay, across multiple length scales, of the composition and distribution of their constituting phases, that act as building blocks, each with their associated intrinsic properties 1 . Gaining a fundamental understanding of these interactions is hence key to decipher the origins of their magnetic performance 2 and facilitate the engineering of better-performing magnets, through unlocking the design of the “perfect defects” for ultimate pinning of magnetic domains 3 . Here, we deployed advanced multiscale microscopy and microanalysis on a bulk Sm 2 (CoFeCuZr) 17 pinning-type high-performance magnet with outstanding thermal and chemical stability 4 . Making use of regions with different chemical compositions, we showcase how both a change in the composition and distribution of copper, along with the atomic arrangements enforce the pinning of magnetic domains, as imaged by nanoscale magnetic induction mapping. Micromagnetic simulations bridge the scales to provide an understanding of how these peculiarities of micro- and nanostructure change the hard magnetic behaviour of Sm 2 (CoFeCuZr) 17 magnets. Unveiling the origins of the reduced coercivity allows us to propose an atomic-scale defect and chemistry manipulation strategy to define ways toward future hard magnets.
Publisher: AIP Publishing
Date: 13-03-2006
DOI: 10.1063/1.2186394
Abstract: In this letter, we report results obtained from the atom-probe tomography (APT) analysis of an oxide layer developed on a pure iron specimen under low pressure of oxygen. These specimens are generally fragile, and hard to analyze in APT. Here we show that by the use of femtosecond laser pulses, the oxide layer could be field evaporated atom by atom allowing its chemical identification at the atomic scale. The evidence of iron atomic planes through the whole oxide layer suggests that oxygen atoms diffuse though the oxide layer during the first stages of the oxidation process.
Publisher: IOP Publishing
Date: 09-11-2011
Publisher: Elsevier BV
Date: 11-2020
Publisher: Oxford University Press (OUP)
Date: 04-07-2008
DOI: 10.1017/S1431927608080690
Abstract: The application of wide field-of-view detection systems to atom probe experiments emphasizes the importance of careful parameter selection in the tomographic reconstruction of the analyzed volume, as the sensitivity to errors rises steeply with increases in analysis dimensions. In this article, a self-consistent method is presented for the systematic determination of the main reconstruction parameters. In the proposed approach, the compression factor and the field factor are determined using geometrical projections from the desorption images. A three-dimensional Fourier transform is then applied to a series of reconstructions, and after comparing to the known material crystallography, the efficiency of the detector is estimated. The final results demonstrate a significant improvement in the accuracy of the reconstructed volumes.
Publisher: Elsevier BV
Date: 04-2016
Publisher: Elsevier BV
Date: 09-2018
Publisher: Oxford University Press (OUP)
Date: 07-2009
DOI: 10.1017/S1431927609092599
Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009
Publisher: American Physical Society (APS)
Date: 06-07-2018
Publisher: Elsevier BV
Date: 03-2014
Publisher: Oxford University Press (OUP)
Date: 04-04-2023
Abstract: Workflows have been developed in the past decade to enable atom probe tomography analysis at cryogenic temperatures. The inability to control the local deposition of the metallic precursor from the gas-injection system (GIS) at cryogenic temperatures makes the preparation of site-specific specimens by using lift-out extremely challenging in the focused-ion beam. Schreiber et al. exploited redeposition to weld the lifted-out s le to a support. Here, we build on their approach to attach the region-of-interest and additionally strengthen the interface with locally sputtered metal from the micromanipulator. Following standard focused-ion beam annular milling, we demonstrate atom probe analysis of Si in both laser pulsing and voltage mode, with comparable analytical performance as a presharpened microtip coupon. Our welding approach is versatile, as various metals could be used for sputtering, and allows similar flexibility as the GIS in principle.
Publisher: IEEE
Date: 2005
Publisher: Elsevier BV
Date: 09-2023
Publisher: Springer Berlin Heidelberg
Date: 2008
Publisher: Springer Science and Business Media LLC
Date: 10-08-2022
DOI: 10.1038/S41586-022-04935-3
Abstract: Soft magnetic materials (SMMs) serve in electrical applications and sustainable energy supply, allowing magnetic flux variation in response to changes in applied magnetic field, at low energy loss 1 . The electrification of transport, households and manufacturing leads to an increase in energy consumption owing to hysteresis losses 2 . Therefore, minimizing coercivity, which scales these losses, is crucial 3 . Yet meeting this target alone is not enough: SMMs in electrical engines must withstand severe mechanical loads that is, the alloys need high strength and ductility 4 . This is a fundamental design challenge, as most methods that enhance strength introduce stress fields that can pin magnetic domains, thus increasing coercivity and hysteresis losses 5 . Here we introduce an approach to overcome this dilemma. We have designed a Fe–Co–Ni–Ta–Al multicomponent alloy (MCA) with ferromagnetic matrix and paramagnetic coherent nanoparticles (about 91 nm in size and around 55% volume fraction). They impede dislocation motion, enhancing strength and ductility. Their small size, low coherency stress and small magnetostatic energy create an interaction volume below the magnetic domain wall width, leading to minimal domain wall pinning, thus maintaining the soft magnetic properties. The alloy has a tensile strength of 1,336 MPa at 54% tensile elongation, extremely low coercivity of 78 A m −1 (less than 1 Oe), moderate saturation magnetization of 100 A m 2 kg −1 and high electrical resistivity of 103 μΩ cm.
Publisher: Elsevier BV
Date: 09-2012
Publisher: Elsevier BV
Date: 03-2018
Publisher: Oxford University Press (OUP)
Date: 12-11-2020
Publisher: Elsevier BV
Date: 05-2023
Publisher: AIP Publishing
Date: 02-2009
DOI: 10.1063/1.3068197
Abstract: Modern wide field-of-view atom probes permit observation of a wide range of crystallographic features that can be used to calibrate the tomographic reconstruction of the analyzed volume. In this study, methodologies to determine values of the geometric parameters involved in the tomographic reconstruction of atom probe data sets are presented and discussed. The influence of the tip to electrode distance and specimen temperature on these parameters is explored. Significantly, their influence is demonstrated to be very limited, indicating a relatively wide regime of experimental parameters space for sound atom probe tomography (APT) experiments. These methods have been used on several specimens and material types, and the results indicate that the reconstruction parameters are specific to each specimen. Finally, it is shown how an accurate calibration of the reconstruction enables improvements to the quality and reliability of the microscopy and microanalysis capabilities of the atom probe.
Publisher: Wiley
Date: 19-09-2018
Publisher: Elsevier BV
Date: 05-2011
DOI: 10.1016/J.ULTRAMIC.2010.12.033
Abstract: In this work, the importance of optimising experimental conditions for the analysis of reactor pressure vessel (RPV) steels using atom probe tomography is explored. The quality of the resultant atom probe data is assessed in terms of detection efficiency, noise levels and mass resolution. It is demonstrated that artefacts can exist even when experimental conditions have been optimised. In particular, it is shown that surface diffusion of some minority species, including P and Si, to major poles prior to field evaporation can be an issue. The effects were most noticeable during laser pulsing. The impact of surface migration on the characterisation of dislocations and grain boundaries is assessed. The importance of selecting appropriate regions of the reconstructed data for subsequent re-analysis is emphasised.
Publisher: Elsevier BV
Date: 2020
Publisher: American Chemical Society (ACS)
Date: 18-03-2010
DOI: 10.1021/LA904459K
Abstract: We have achieved three-dimensional imaging of decanethiol self-assembled monolayers (SAMs) on metal surfaces by atom probe tomography (APT). The present Letter provides preliminary results on Ni [001] and Au [111], shows the analytical potential of APT analysis of SAMs, and details developments in specimen preparation and in data-treatment methodologies. Importantly, the investigation of the mass spectra from analysis of the SAMs revealed no combination of sulfur and hydrogen at the interface between the metal substrates and the organic materials, potentially providing insight about the bonding of the thiols on the substrate.
Publisher: Elsevier BV
Date: 07-2023
Publisher: Elsevier BV
Date: 02-2021
Publisher: Springer New York
Date: 2012
Publisher: Elsevier BV
Date: 05-2022
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.ULTRAMIC.2013.02.005
Abstract: We report on the change in the shape, size and composition of spherical precipitates, found in an Fe-Cu and an Al-Ag alloy, as the base temperature, pulsing mode and parameters are adjusted. In the case of the Al-Ag alloy, the difference in the evaporation field between precipitates and matrix can be minimised at low temperature, while in the Fe-Cu alloy minimal changes are observed within the range of experimental conditions investigated. Comparison with transmission electron microscopy shows that some experimental conditions yield accurate precipitates size, while others enable reaching accurate composition measurements.
Publisher: Springer New York
Date: 2012
Publisher: Springer New York
Date: 2012
Publisher: Springer New York
Date: 2012
Publisher: Springer New York
Date: 2012
Publisher: Springer New York
Date: 2012
Publisher: Springer Science and Business Media LLC
Date: 04-2017
DOI: 10.1038/NATURE22032
Abstract: Next-generation high-performance structural materials are required for lightweight design strategies and advanced energy applications. Maraging steels, combining a martensite matrix with nanoprecipitates, are a class of high-strength materials with the potential for matching these demands. Their outstanding strength originates from semi-coherent precipitates, which unavoidably exhibit a heterogeneous distribution that creates large coherency strains, which in turn may promote crack initiation under load. Here we report a counterintuitive strategy for the design of ultrastrong steel alloys by high-density nanoprecipitation with minimal lattice misfit. We found that these highly dispersed, fully coherent precipitates (that is, the crystal lattice of the precipitates is almost the same as that of the surrounding matrix), showing very low lattice misfit with the matrix and high anti-phase boundary energy, strengthen alloys without sacrificing ductility. Such low lattice misfit (0.03 ± 0.04 per cent) decreases the nucleation barrier for precipitation, thus enabling and stabilizing nanoprecipitates with an extremely high number density (more than 10
Publisher: Springer New York
Date: 2012
Publisher: Informa UK Limited
Date: 02-2010
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.ULTRAMIC.2015.05.011
Abstract: The following manuscript presents a novel approach for creating lattice based models of Sb-doped Si directly from atom probe reconstructions for the purposes of improving information on dopant positioning and directly informing quantum mechanics based materials modeling approaches. Sophisticated crystallographic analysis techniques are used to detect latent crystal structure within the atom probe reconstructions with unprecedented accuracy. A distortion correction algorithm is then developed to precisely calibrate the detected crystal structure to the theoretically known diamond cubic lattice. The reconstructed atoms are then positioned on their most likely lattice positions. Simulations are then used to determine the accuracy of such an approach and show that improvements to short-range order measurements are possible for noise levels and detector efficiencies comparable with experimentally collected atom probe data.
Publisher: Elsevier BV
Date: 05-2011
DOI: 10.1016/J.ULTRAMIC.2010.12.004
Abstract: State-of-the art atom probe tomography (APT) combined with transmission electron microscopy (TEM) were used to investigate the microstructure at different stages of the ageing process of an alloy of composition (at%) Al-1.68%Cu-4.62%Li-0.33%Mg-0.1%Ag. These alloys were shown to exhibit a complex microstructure of T(1) plates and several metastable phases, including θ' and S. We will highlight the early stages of clustering, precipitate interactions and possible solute segregation at the matrix recipitate interfaces and detail the chemical composition of the different phases.
Publisher: Elsevier BV
Date: 10-2018
Publisher: Elsevier BV
Date: 2007
Publisher: Elsevier BV
Date: 03-2023
Publisher: Elsevier BV
Date: 09-2018
Publisher: Elsevier BV
Date: 2013
Publisher: Elsevier BV
Date: 04-2021
Publisher: Elsevier BV
Date: 09-2018
Publisher: Elsevier BV
Date: 07-2021
Publisher: Elsevier BV
Date: 09-2021
Publisher: Springer Science and Business Media LLC
Date: 07-2022
DOI: 10.1557/S43577-022-00373-8
Abstract: The search for a new energy paradigm with net-zero carbon emissions requires new technologies for energy generation and storage that are at the crossroad between engineering, chemistry, physics, surface, and materials sciences. To keep pushing the inherent boundaries of device performance and lifetime, we need to step away from a cook-and-look approach and aim to establish the scientific ground to guide the design of new materials. This requires strong efforts in establishing bridges between microscopy and spectroscopy techniques, across multiple scales. Here, we discuss how the complementarities of x-ray- and electron-based spectroscopies and atom probe tomography can be exploited in the study of surfaces and subsurfaces to understand structure–property relationships in electrocatalysts. Graphical abstract
Publisher: Springer Science and Business Media LLC
Date: 15-06-2023
DOI: 10.1038/S41467-023-39302-X
Abstract: Grain boundaries, the two-dimensional defects between differently oriented crystals, tend to preferentially attract solutes for segregation. Solute segregation has a significant effect on the mechanical and transport properties of materials. At the atomic level, however, the interplay of structure and composition of grain boundaries remains elusive, especially with respect to light interstitial solutes like B and C. Here, we use Fe alloyed with B and C to exploit the strong interdependence of interface structure and chemistry via charge-density imaging and atom probe tomography methods. Direct imaging and quantifying of light interstitial solutes at grain boundaries provide insight into decoration tendencies governed by atomic motifs. We find that even a change in the inclination of the grain boundary plane with identical misorientation impacts grain boundary composition and atomic arrangement. Thus, it is the smallest structural hierarchical level, the atomic motifs, that controls the most important chemical properties of the grain boundaries. This insight not only closes a missing link between the structure and chemical composition of such defects but also enables the targeted design and passivation of the chemical state of grain boundaries to free them from their role as entry gates for corrosion, hydrogen embrittlement, or mechanical failure.
Publisher: Elsevier BV
Date: 06-2023
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.ULTRAMIC.2013.02.012
Abstract: Controllable doping of semiconductor nanowires is critical to realize their proposed applications, however precise and reliable characterization of dopant distributions remains challenging. In this article, we demonstrate an atomic-resolution three-dimensional elemental mapping of pristine semiconductor nanowires on growth substrates by using atom probe tomography to tackle this major challenge. This highly transferrable method is able to analyze the full diameter of a nanowire, with a depth resolution better than 0.17 nm thanks to an advanced reconstruction method exploiting the specimen's crystallography, and an enhanced chemical sensitivity of better than 8-fold increase in the signal-to-noise ratio.
Publisher: Oxford University Press (OUP)
Date: 19-10-2023
Publisher: Oxford University Press (OUP)
Date: 08-2022
DOI: 10.1017/S1431927621000362
Abstract: We report on comparative atom probe tomography investigations of γ/γ′-forming Co–12Ti–4Mo–Cr alloys. Moderate additions of Cr (2 and 4 at%) reduced the γ/γ′ lattice misfit and increased the γ′ volume fraction of a Co–12Ti–4Mo alloy significantly. These microstructural changes were accompanied by changes in the elemental partitioning between γ and γ′ and site-occupancy in γ′. Spatial distribution maps revealed that Mo occupied both Co and Ti sub-lattice sites in γ′. In agreement with the experimental data, thermodynamic calculations predicted a stronger tendency for Mo to occupy the Co-sites than for Cr and an increase in Cr fraction on the Ti-sites with increasing Cr content.
Publisher: Elsevier BV
Date: 09-2013
DOI: 10.1016/J.ULTRAMIC.2013.02.014
Abstract: Two methods for separating the constituent atoms of molecular ions within atom probe tomography reconstructions are presented. The Gaussian Separation Method efficiently deconvolutes molecular ions containing two constituent atoms and is tested on simulated data before being applied to an experimental HSLA steel dataset containing NbN. The Delaunay Separation Method extends separation to larger complex ions and is also tested on simulated data before being applied to an experimental GaAs dataset containing many large (>3 atoms) complex ions. First nearest neighbour (1NN) distributions and images of the reconstruction before and after the separations are used to show the effect of the algorithms and their validity and practicality are also discussed.
Publisher: Elsevier BV
Date: 11-2018
DOI: 10.1016/J.ULTRAMIC.2018.06.017
Abstract: Atom probe tomography is known for its accurate compositional analysis at the nanoscale. However, the patterns created by successive hits on the single particle detector during experiments often contain complementary information about the specimen's crystallography, including structure and orientation. This information remains in most cases unexploited because it is, up to now, retrieved predominantly manually. Here, we propose an approach combining image analysis techniques for feature selection and deep-learning to automatically interpret the patterns. Application of unsupervised machine learning techniques allows to build and train a deep neural network, based on a library generated from theoretically known crystallographic angular relationships. This approach enables direct interpretation of the detector hit maps, as shown here on the ex le of numerous pure-Al, and is robust enough to function under various conditions of base temperature, pulsing mode and pulse fraction. We benchmark our approach against recent attempts to automate the pattern identification via Hough-transform and discuss the current limitations of our approach. This new automated approach renders crystallographic atom probe tomography analysis more efficient, feature-sensitive, robust, user-independent and reliable. With that, deep-learning algorithms show a great potential to give access to combined atom probe crystallographic and compositional analysis to a large community of users.
Publisher: Springer Science and Business Media LLC
Date: 31-05-2018
DOI: 10.1007/S11661-018-4709-X
Abstract: Oxidized MC carbides which act as main crack initiation sites in a polycrystalline superalloy under thermal-mechanical fatigue (TMF) conditions at 850 °C were studied. Microstructural observations in the TMF tested specimens were compared to findings from bulk s les exposed isothermally in air at 850 °C for 30 hours in the absence of any external applied load. Carbides were found to oxidize rapidly after exposure at 850 °C for 30 hours resulting in surface eruptions corresponding to oxidation products, from where micro-cracks initiated. Plastic deformation due to volume expansion of the often porous oxidized carbides led to high dislocation densities in the adjacent matrix as revealed by controlled electron channeling contrast imaging. The high dislocation density facilitated the dissolution kinetics of γ ′ precipitates by segregation and diffusion of chromium and cobalt along the dislocations via pipe diffusion, resulting in the formation of soft recrystallized grains. Atom probe tomography revealed substantial compositional differences between the recrystallized grains and the adjacent undeformed γ matrix. Similar observations were made for the TMF tested alloy. Our observations provide new insights into the true detrimental role of oxidized MC carbides on the crack initiation performance of polycrystalline superalloys under TMF.
Publisher: Elsevier BV
Date: 12-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2014
DOI: 10.1039/C4NR00415A
Abstract: Advanced microscopy techniques and computational simulation to reveal the atomic-scale mechanisms for the highest ever recorded enhancement of supercurrent in MgB 2 -based superconductors.
Publisher: The Electrochemical Society
Date: 05-2020
DOI: 10.1149/MA2020-01371520MTGABS
Abstract: Hydrogen is likely to play a key role as central energy carrier in the world’s transition towards a more sustainable future. Electricity from renewable sources can be used to power water electrolyzers to generate carbon-neutral hydrogen [1]. ‘Green’ hydrogen can then, for ex le, be used for the synthesis of carbon-neutral fuels, in the transportation sector to power H 2 fuel-cell fitted vehicles, as a carbon-neutral agent for the direct reduction of metals from ores, or to re-generate electricity in time of high demand. However, the technological upscaling of proton exchange membrane water electrolysis (PEM) devices is currently hindered by the low reactivity and instability of most catalyzing materials for the anodic oxygen evolution reaction (OER). The development of electrocatalysts with superior performance requires a detailed understanding of how their surfaces evolve during OER, ideally at the atomic scale [2,3]. The identification of the role of in idual atoms in different chemical and structural environments in the near-surface region of the catalyst is crucial to understand the electrochemical performance and degradation processes. Here, we provide atomic scale insights into the degradation mechanism of an Ir-Ru model alloy during electrochemical oxygen evolution. Ir-Ru alloys are promising candidates for PEM electrolysis combining the stability of Ir and high activity of Ru towards OER. The changes in electronic state of the catalysts induced by OER are studied by X-ray photoelectron spectroscopy (XPS), while an in-situ activity-stability analysis was performed online using an inductively coupled plasma mass spectrometer. Atom probe tomography (APT) was used to reveal the structure and composition of the first few atomic layers of the catalyst in three dimensions. APT reveals strong compositional differences between intragranular and grain boundary regions in the pristine alloy, resulting from significant Ru segregation to crystalline defects during the deposition process [4,5]. Significant Ru dissolution occurs during the OER, as revealed by online dissolution measurements, resulting in a few surface layers enriched in Ir, consistent with XPS results. APT further shows that the entire near-surface region affected by the oxidation exhibits signs of Ru dissolution. In addition, oxides formed in Ru-rich regions across the catalyst´s surface, i.e. in the proximity of grain boundaries, generally exhibit a higher oxygen content, compared to oxides on top of intergranular regions. Our data suggests that the defect structure of the material governs the enrichment of Ru in grain boundaries with consecutive preferential oxidation of these regions. This preferential oxidation potentially contributes to an accelerated, localized formation of volatile RuO 4 species during the OER, leading to an enhanced Ru leaching along defect regions, eventually resulting in the deterioration of the overall reactivity of the material. Finally, using the new insights gained by this study, we discuss potential design strategy improvements of Ir-Ru alloys, to engineers an OER catalyst with a higher performance and longer durability. With this work we stress the need to investigate processes in catalytic materials with a combination of independent methods and at the near-atomic scale. Only the combination of insights enables the establishing of reliable structure-function relationships of electrocatalytic materials. References [1] M. Carmo, D.L. Fritz, J. Mergel, et al. , Int. J. of Hydrogen Energy 37 (12) (2013), pp. 4901 - 4934 [2] T. Li, O. Kasian, S. Cherevko, et al. , Nat. Cat. 1 (2018), pp. 300-305. [3] O. Kasian, S. Geiger, T. Li, et al. , Energy & Environ. Sci. (2019). [4] K. Schweinar, O. Kasian, R.L. Nicholls, et al. , Microscopy and Microanalysis 25 (S2) (2019), pp. 306-307 [5] K. Schweinar, R.L. Nicholls, C.R. Rajamathi, et al. , submitted.
Publisher: Elsevier BV
Date: 02-2021
Publisher: AIP Publishing
Date: 23-02-2005
DOI: 10.1063/1.1871342
Abstract: We report the experimental evidence of controlled field evaporation of atoms from the surface of a tip-like-shape specimen with subwavelength dimensions by means of subpicosecond laser pulses. It is shown that the evaporation is assisted by the intrinsic laser electric field without any significant thermal activation. The single-atom detection sensitivity of the field ion microscope is used to get an accurate measurement of the electric field enhancement factor at the tip apex as a function of the wave polarization. The absence of thermal diffusion of atoms at the tip surface prior to field evaporation, demonstrates the feasibility of a laser assisted three-dimensional atom probe.
Publisher: Elsevier BV
Date: 11-2018
Publisher: Research Square Platform LLC
Date: 10-12-2021
DOI: 10.21203/RS.3.RS-1145535/V1
Abstract: Soft magnetic materials (SMMs) are indispensable components in electrified applications and sustainable energy supply, allowing permanent magnetic flux variations in response to high frequency changes of the applied magnetic field, at lowest possible energy loss1. The global trend towards electrification of transport, households and manufacturing leads to a massive increase in energy consumption due to hysteresis losses2. Therefore, minimizing coercivity, which scales the losses in SMMs, is crucial3. Yet, meeting this target alone is not enough: SMMs used for instance in vehicles and planes must withstand severe mechanical loads, i.e., the alloys need high strength and ductility4. This is a fundamental design challenge, as most methods that enhance strength introduce stress fields that can pin magnetic domains, thus increasing coercivity and hysteretic losses5. Here, we introduce a new approach to overcome this dilemma. We have designed a Fe-Co-Ni-Ta-Al multicomponent alloy with ferromagnetic matrix and paramagnetic coherent nanoparticles of well-controlled size (~91 nm) and high volume fraction (55%). They impede dislocation motion, enhancing strength and ductility. Yet, their small size, low coherency stress and small magnetostatic energy create an interaction volume below the magnetic domain wall width, leading to minimal domain wall pinning, thus maintaining the material’s soft magnetic properties. The new material exhibits an excellent combination of mechanical and magnetic properties outperforming other multicomponent alloys and conventional SMMs. It has a tensile strength of ~1336 MPa at 54% tensile elongation, an extremely low coercivity of ~78 A/m ( Oe) and a saturation magnetization of ~100 Am2/kg. The work opens new perspectives on developing magnetically soft and mechanically strong and ductile materials for the sustainable electrification of industry and society.
Publisher: Oxford University Press (OUP)
Date: 06-02-2019
DOI: 10.1017/S1431927618016112
Abstract: We introduce an efficient, automated computational approach for analyzing interfaces within atom probe tomography datasets, enabling quantitative mapping of their thickness, composition, as well as the Gibbsian interfacial excess of each solute. Detailed evaluation of an experimental dataset indicates that compared with the composition map, the interfacial excess map is more robust and exhibits a relatively higher resolution to reveal compositional variations. By field evaporation simulations with a predefined emitter mimicking the experimental dataset, the impact of trajectory aberrations on the measurement of the thickness, composition, and interfacial excess of the decorated interface are systematically analyzed and discussed.
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.ULTRAMIC.2015.05.006
Abstract: Whilst atom probe tomography (APT) is a powerful technique with the capacity to gather information containing hundreds of millions of atoms from a single specimen, the ability to effectively use this information creates significant challenges. The main technological bottleneck lies in handling the extremely large amounts of data on spatial-chemical correlations, as well as developing new quantitative computational foundations for image reconstruction that target critical and transformative problems in materials science. The power to explore materials at the atomic scale with the extraordinary level of sensitivity of detection offered by atom probe tomography has not been not fully harnessed due to the challenges of dealing with missing, sparse and often noisy data. Hence there is a profound need to couple the analytical tools to deal with the data challenges with the experimental issues associated with this instrument. In this paper we provide a summary of some key issues associated with the challenges, and solutions to extract or "mine" fundamental materials science information from that data.
Publisher: Springer Science and Business Media LLC
Date: 02-03-2017
Publisher: IOP Publishing
Date: 19-02-2018
Publisher: Elsevier BV
Date: 08-2021
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 08-2021
Publisher: Elsevier BV
Date: 09-2020
Publisher: American Chemical Society (ACS)
Date: 23-10-2018
Abstract: Capturing and converting waste heat into electrical power through thermoelectric generators based on the Seebeck effect is a promising alternative energy source. Among thermoelectric compounds, PbTe can be alloyed and form precipitates by aging at elevated temperatures, thus reducing thermal conductivity by phonon scattering. Here, PbTe is alloyed with Ag to form Ag-rich precipitates having a number density controlled by heat treatments. We employ complementary scanning transmission electron microscopy and atom probe tomography to analyze the precipitate number density and the PbTe-matrix composition. We measure the temperature-dependent transport coefficients and correlate them with the microstructure. The thermal and electrical conductivities, as well as the Seebeck coefficients, are found to be highly sensitive to the microstructure and its temporal evolution, e.g., the number density of Ag-rich precipitates increases by ca. 3 orders of magnitude and reaches (1.68 ± 0.92) × 10
Publisher: Elsevier BV
Date: 08-2021
Publisher: American Physical Society (APS)
Date: 20-01-2023
Publisher: Elsevier BV
Date: 05-2022
Publisher: AIP Publishing
Date: 20-07-2009
DOI: 10.1063/1.3182351
Publisher: Springer Science and Business Media LLC
Date: 27-07-2022
DOI: 10.1038/S41467-022-31969-Y
Abstract: In conventional processing, metals go through multiple manufacturing steps including casting, plastic deformation, and heat treatment to achieve the desired property. In additive manufacturing (AM) the same target must be reached in one fabrication process, involving solidification and cyclic remelting. The thermodynamic and kinetic differences between the solid and liquid phases lead to constitutional undercooling, local variations in the solidification interval, and unexpected precipitation of secondary phases. These features may cause many undesired defects, one of which is the so-called hot cracking. The response of the thermodynamic and kinetic nature of these phenomena to high cooling rates provides access to the knowledge-based and tailored design of alloys for AM. Here, we illustrate such an approach by solving the hot cracking problem, using the commercially important IN738LC superalloy as a model material. The same approach could also be applied to adapt other hot-cracking susceptible alloy systems for AM.
Publisher: Elsevier BV
Date: 2022
Publisher: Springer Science and Business Media LLC
Date: 26-02-2019
DOI: 10.1038/S41467-019-08752-7
Abstract: Hydrogen pick-up leading to hydride formation is often observed in commercially pure Ti (CP-Ti) and Ti-based alloys prepared for microscopic observation by conventional methods, such as electro-polishing and room temperature focused ion beam (FIB) milling. Here, we demonstrate that cryogenic FIB milling can effectively prevent undesired hydrogen pick-up. Specimens of CP-Ti and a Ti dual-phase alloy (Ti-6Al-2Sn-4Zr-6Mo, Ti6246, in wt.%) were prepared using a xenon-plasma FIB microscope equipped with a cryogenic stage reaching −135 °C. Transmission electron microscopy (TEM), selected area electron diffraction, and scanning TEM indicated no hydride formation in cryo-milled CP-Ti lamellae. Atom probe tomography further demonstrated that cryo-FIB significantly reduces hydrogen levels within the Ti6246 matrix compared with conventional methods. Supported by molecular dynamics simulations, we show that significantly lowering the thermal activation for H diffusion inhibits undesired environmental hydrogen pick-up during preparation and prevents pre-charged hydrogen from diffusing out of the s le, allowing for hydrogen embrittlement mechanisms of Ti-based alloys to be investigated at the nanoscale.
Publisher: Wiley
Date: 13-01-2020
Abstract: Molybdenum disulfide (MoS
Publisher: Elsevier BV
Date: 03-2020
Publisher: Springer Science and Business Media LLC
Date: 23-08-2019
Publisher: Elsevier BV
Date: 06-2009
DOI: 10.1016/J.ULTRAMIC.2009.03.016
Abstract: New and improved spatial distribution map (SDM) methods are developed to identify and extract crystallographic information within atom probe tomography three-dimensional (3D) reconstructions. Detailed structural information is retrieved by combining z-SDM offset distribution analyses computed in multiple crystallographic directions, accurately determining inter-planar spacings and crystallographic angles. The advantages of this technique in comparison to applying the complete z-SDM and complementary xy-SDM analysis to a single crystallographic direction are investigated. Further, in determining these multidirectional z-SDM and xy-SDM profiles, background noise reduction and automatic peak identification algorithms are adapted to attain increased accuracy and is shown to be particularly effective in cases where crystal structure is present but poorly resolved. These techniques may be used to calibrate the reconstruction parameters and investigate their dependence on the design of in idual atom probe experiments.
Publisher: Springer Science and Business Media LLC
Date: 29-01-2021
DOI: 10.1038/S41524-020-00486-1
Abstract: The development of strong-scaling computational tools for high-throughput methods with an open-source code and transparent metadata standards has successfully transformed many computational materials science communities. While such tools are mature already in the condensed-matter physics community, the situation is still very different for many experimentalists. Atom probe tomography (APT) is one ex le. This microscopy and microanalysis technique has matured into a versatile nano-analytical characterization tool with applications that range from materials science to geology and possibly beyond. Here, data science tools are required for extracting chemo-structural spatial correlations from the reconstructed point cloud. For APT and other high-end analysis techniques, post-processing is mostly executed with proprietary software tools, which are opaque in their execution and have often limited performance. Software development by members of the scientific community has improved the situation but compared to the sophistication in the field of computational materials science several gaps remain. This is particularly the case for open-source tools that support scientific computing hardware, tools which enable high-throughput workflows, and open well-documented metadata standards to align experimental research better with the fair data stewardship principles. To this end, we introduce paraprobe, an open-source tool for scientific computing and high-throughput studying of point cloud data, here exemplified with APT. We show how to quantify uncertainties while applying several computational geometry, spatial statistics, and clustering tasks for post-processing APT datasets as large as two billion ions. These tools work well in concert with Python and HDF5 to enable several orders of magnitude performance gain, automation, and reproducibility.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 16-04-2021
Abstract: Combined atomic-scale characterization and simulation reveal the complexity and ersity of the chemical nature of dislocations.
Publisher: Elsevier BV
Date: 03-2019
Publisher: Oxford University Press (OUP)
Date: 17-01-2017
DOI: 10.1017/S1431927616012654
Abstract: Cemented tungsten carbide has been analyzed using laser-pulsed atom probe tomography (APT). The influence of experimental parameters, including laser pulse energy, pulse repetition rate, and specimen base temperature, on the acquired data were evaluated from different aspects, such as mass spectrum, chemical composition, noise-to-signal ratio, and multiple events. Within all the applied analysis conditions, only 1 MHz pulse repetition rate led to a strong detector saturation effect, resulting in a largely biased chemical composition. A comparative study of the laser energy settings showed that an ~12 times higher energy was required for the less focused green laser of the LEAP TM 3000X HR system to achieve a similar evaporation field as the finer spot ultraviolet laser of the LEAP TM 5000 XS system.
Publisher: Elsevier BV
Date: 2021
Publisher: Research Square Platform LLC
Date: 16-06-2022
DOI: 10.21203/RS.3.RS-1652464/V1
Abstract: Identifying the chemical and bonding state of all atoms in a material in three-dimensions remains an unresolved issue. Here, we demonstrate that this information was always intrinsically present within atom probe tomography experimental data, but until now it was overlooked or consciously suppressed. Using an analytical model and robust simulations, we show that the mass peak shape contains information on the ion’s energy loss related to how the atom was bound to the surface, and its neighbourhood. We introduce a complete data processing approach, termed field evaporation energy loss spectroscopy (FEELS), that retrieves and maps variations of the chemical state in 3D with nanometric resolution. We showcase the application of FEELS by analyzing microstructural features and defects in an array of metallic materials. FEELS can be applied on any atom probe data set to more profoundly analyse a material’s characteristics.
Publisher: Elsevier BV
Date: 2018
Publisher: American Physical Society (APS)
Date: 08-05-2020
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.ULTRAMIC.2011.08.005
Abstract: Progress in the reconstruction for atom probe tomography has been limited since the first implementation of the protocol proposed by Bas et al. in 1995. This approach and those subsequently developed assume that the geometric parameters used to build the three-dimensional atom map are constant over the course of an analysis. Here, we test this assumption within the analyses of low-alloyed materials. By building upon methods recently proposed to measure the tomographic reconstruction parameters, we demonstrate that this assumption can introduce significant limitations in the accuracy of the analysis. Moreover, we propose a strategy to alleviate this problem through the implementation of a new reconstruction algorithm that dynamically accommodates variations in the tomographic reconstruction parameters.
Publisher: Elsevier BV
Date: 02-2017
Publisher: IEEE
Date: 07-2008
Publisher: Elsevier BV
Date: 09-2018
Publisher: Elsevier BV
Date: 03-2021
Publisher: Springer Science and Business Media LLC
Date: 06-08-2019
DOI: 10.1038/S41467-019-11506-0
Abstract: Doping is indispensable to tailor phase-change materials (PCM) in optical and electronic data storage. Very few experimental studies, however, have provided quantitative information on the distribution of dopants on the atomic-scale. Here, we present atom-resolved images of Ag and In dopants in Sb 2 Te-based (AIST) PCM using electron microscopy and atom-probe tomography. Combing these with DFT calculations and chemical-bonding analysis, we unambiguously determine the dopants’ role upon recrystallization. Composition profiles corroborate the substitution of Sb by In and Ag, and the segregation of excessive Ag into grain boundaries. While In is bonded covalently to neighboring Te, Ag binds ionically. Moreover, In doping accelerates the crystallization and hence operation while Ag doping limits the random diffusion of In atoms and enhances the thermal stability of the amorphous phase.
Publisher: Elsevier BV
Date: 12-2023
Publisher: IOP Publishing
Date: 04-2007
Publisher: Research Square Platform LLC
Date: 19-02-2021
DOI: 10.21203/RS.3.RS-245717/V1
Abstract: Atom Probe Tomography (APT) is currently a well-established technique to analyse the composition of solid materials including metals, semiconductors and ceramics with up to near-atomic resolution. Using an aqueous glucose solution, we now extended the technique to frozen solutions. While the mass signals of the common glucose fragments CxHy and CxOyHz overlap with (H2O)nH from water, we achieved stoichiometrically correct values via signal deconvolution. Density functional theory (DFT) calculations were performed to investigate the stability of the detected pyranose fragments. This paper demonstrates APT’s capabilities to achieve sub-nanometre resolution in tracing whole glucose molecules in a frozen solution by using cryogenic workflows. We use a solution of defined concentration to investigate the chemical and spatial resolution capabilities as a step toward the measurement of biological molecules in solution in 3D with sub-nanometre resolution by using cryo-APT. Our analyses take analytical techniques to a new level, since chemical characterization methods for cryogenically-frozen solutions or biological materials are limited.
Publisher: Springer Science and Business Media LLC
Date: 28-04-2022
DOI: 10.1038/S41467-022-30019-X
Abstract: The enormous magnitude of 2 billion tons of alloys produced per year demands a change in design philosophy to make materials environmentally, economically, and socially more sustainable. This disqualifies the use of critical elements that are rare or have questionable origin. Amongst the major alloy strengthening mechanisms, a high-dispersion of second-phase precipitates with sizes in the nanometre range is particularly effective for achieving ultra-high strength. Here, we propose an alternative segregation-based strategy for sustainable steels, free of critical elements, which are rendered ultrastrong by second-phase nano-precipitation. We increase the Mn-content in a supersaturated, metastable Fe-Mn solid solution to trigger compositional fluctuations and nano-segregation in the bulk. These fluctuations act as precursors for the nucleation of an unexpected α-Mn phase, which impedes dislocation motion, thus enabling precipitation strengthening. Our steel outperforms most common commercial alloys, yet it is free of critical elements, making it a new platform for sustainable alloy design.
Publisher: Elsevier BV
Date: 02-2019
Publisher: Elsevier BV
Date: 06-2018
DOI: 10.1016/J.ULTRAMIC.2018.03.018
Abstract: In atom probe tomography (APT), multiple events can arise as a consequence of e.g. correlated field evaporation and molecular ion dissociation. They represent challenging cases for single-particle detectors and can cause compositional as well as spatial inaccuracies. Here, two state-of-the-art atom probe microscopes (Cameca LEAP 5000 XS and 5000 XR) were used to investigate cemented tungsten carbide, which exhibits high amounts of multiple events. By advanced data analysis methods, the natural character of the multiple events, as well as the performance of the APT detectors, are assessed. Accordingly, possible signal loss mechanisms are discussed.
Publisher: Oxford University Press (OUP)
Date: 08-03-2011
DOI: 10.1017/S1431927610094535
Abstract: Atom probe tomography (APT) represents a significant step toward atomic resolution microscopy, analytically imaging in idual atoms with highly accurate, though imperfect, chemical identity and three-dimensional (3D) positional information. Here, a technique to retrieve crystallographic information from raw APT data and restore the lattice-specific atomic configuration of the original specimen is presented. This lattice rectification technique has been applied to a pure metal, W, and then to the analysis of a multicomponent Al alloy. Significantly, the atoms are located to their true lattice sites not by an averaging, but by triangulation of each particular atom detected in the 3D atom-by-atom reconstruction. Lattice rectification of raw APT reconstruction provides unprecedented detail as to the fundamental solute hierarchy of the solid solution. Atomic clustering has been recognized as important in affecting alloy behavior, such as for the Al-1.1Cu-1.7Mg (at. %) investigated here, which exhibits a remarkable rapid hardening reaction during the early stages of aging, linked to clustering of solutes. The technique has enabled lattice-site and species-specific radial distribution functions, nearest-neighbor analyses, and short-range order parameters, and we demonstrate a characterization of solute-clustering with unmatched sensitivity and precision.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9TA10818A
Abstract: Elucidating the atomic structure and chemistry of catalysts by correlative scanning photoemission electron microscopy and atom probe tomography.
Publisher: Elsevier BV
Date: 06-2018
Publisher: Oxford University Press (OUP)
Date: 03-02-2012
DOI: 10.1017/S1431927611012530
Abstract: Atom probe tomography (APT) provides three-dimensional analytical imaging of materials with near-atomic resolution using pulsed field evaporation. The processes of field evaporation can cause atoms to be placed at positions in the APT reconstruction that can deviate slightly from their original site in the material. Here, we describe and model one such process—that of preferential retention of solute atoms in multicomponent systems. Based on relative field evaporation probabilities, we calculate the point spread function for the solute atom distribution in the “ z ,” or in-depth direction, and use this to extract more accurate solute concentration profiles.
Publisher: Oxford University Press (OUP)
Date: 10-04-2023
Abstract: The developing flexible ultrathin glass for use in foldable displays has attracted widespread attention as an alternative to rigid electronic smartphones. However, the detailed compositional effects of chemically strengthened glass are not well understood. Moreover, the spatially resolved chemistry and depth of the compression layer of tempered glass are far from clear. In this study, commonly used X-ray spectroscopy techniques and atom probe tomography (APT) were used comparatively to investigate the distribution of constituent elements in two representative smartphone glass s les: non- and chemically tempered. APT has enabled sub-nanoscale analyses of alkali metals (Li, Na, K, and Ca) and this demonstrates that APT can be considered as an alternative technique for imaging the chemical distribution in glass for mobile applications.
Publisher: Elsevier BV
Date: 06-2012
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 04-2009
Publisher: Elsevier BV
Date: 12-2018
Publisher: Wiley
Date: 18-09-2018
Publisher: Research Square Platform LLC
Date: 10-02-2022
DOI: 10.21203/RS.3.RS-1212931/V1
Abstract: Nanocrystalline (NC) metals are attractive due to their outstanding mechanical, physical and chemical properties. However, they are generally metastable and prone to undergo grain coarsening, which severely impedes their engineering application, particularly at elevated temperatures. A strategy to counteract this phenomenon lies in decreasing the energetic driving force for grain growth, through grain boundary segregation according to the Gibbs adsorption isotherm. The natural thought of ‘more segregation is better’, which was exercised over decades to solve this problem, however, does not work because interfaces themselves are thermodynamic entities, with only limited solute decoration tolerance. Herein, we propose to solve this long-standing problem via introducing multi-component co-segregated interfaces. This concept allows us to maximize the solute decoration of interfaces and minimize their energy, without triggering formation of new phases. This is enabled by extending the high entropy alloy (HEA) concept from the bulk to interfaces, a strategy we refer to as interfaces with higher entropy. This design concept is not transferred one-to-one but constrained by a few rules that reflect the nature of interfaces: use of several co-segregating elements with high mixing entropy segregation remains in the dilute limit and use of elements with high segregation coefficient. The latter criterion marks an important difference to the HEA concept as a high segregation coefficient guarantees that alloying elements are deposited only to those locations where they are needed, namely, to the interfaces, thus drastically reducing alloying costs. We applied this new design approach to NC-Nb and show that we can increase its stability from 873 to 1023 K with as little alloying as only 1 at.% of Ti, Ni, Co and Hf with equal fractions. The material maintains its nanocrystalline structure even after 2200 h at 973 K. This work thus offers a new paradigm for designing stable dilute NC materials for advanced engineering application.
Publisher: Elsevier BV
Date: 05-2011
DOI: 10.1016/J.ULTRAMIC.2010.11.007
Abstract: Atom probe tomography uses time-of-flight mass spectrometry to identify the chemical nature of atoms from their mass-to-charge-state ratios. Within a mass spectrum, ranges are defined so as to attribute a chemical identity to each peak. The accuracy of atom probe microanalysis relies on the definition of these ranges. Here we propose and compare several automated ranging techniques, tested against simulated mass spectra. The performance of these metrics compare favourably with a trial of users asked to manually range a simplified simulated dataset. The optimised automated ranging procedure was then used to precisely evaluate the very low iron concentration (0.003-0.018 at%) in a zirconium alloy to reveal its behaviour in the matrix during corrosion oxygen is injected into solution and has the effect of increasing the local iron concentration near the oxide-metal interface, which in turn affects the corrosion properties of the metal substrate.
Publisher: Wiley
Date: 07-02-2020
Publisher: Elsevier BV
Date: 02-2023
Publisher: Elsevier BV
Date: 05-2014
Publisher: Springer Science and Business Media LLC
Date: 12-11-2021
DOI: 10.1038/S41467-021-26858-9
Abstract: Introducing regions of looser atomic packing in bulk metallic glasses (BMGs) was reported to facilitate plastic deformation, rendering BMGs more ductile at room temperature. Here, we present a different alloy design approach, namely, doping the nonmetallic elements to form densely packed motifs. The enhanced structural fluctuations in Ti-, Zr- and Cu-based BMG systems leads to improved strength and renders these solutes’ atomic neighborhoods more prone to plastic deformation at an increased critical stress. As a result, we simultaneously increased the compressive plasticity (from ∼8% to unfractured), strength (from ∼1725 to 1925 MPa) and toughness (from 87 ± 10 to 165 ± 15 MPa√m), as exemplarily demonstrated for the Zr 20 Cu 20 Hf 20 Ti 20 Ni 20 BMG. Our study advances the understanding of the atomic-scale origin of structure-property relationships in amorphous solids and provides a new strategy for ductilizing BMG without sacrificing strength.
Publisher: AIP Publishing
Date: 15-08-2010
DOI: 10.1063/1.3462399
Abstract: The impact of laser pulsing on the field evaporation process is investigated for Al and W by pulsed laser atom probe tomography. Quantitative analysis reveals the influence on the spatial resolution of the peak temperature reached by the specimen following light absorption from the laser pulse. It is concluded that surface migration processes induce significant degradation of the lateral resolution, changing by 100% and 20%, respectively, for Al and W when the specimen temperature is increased from 4% to 7% of the material’s melting point, while the in-depth resolution is shown to remain nearly constant for both materials.
Publisher: The Electrochemical Society
Date: 23-11-2020
DOI: 10.1149/MA2020-02623154MTGABS
Abstract: Increasing concerns regarding the environmental impact of power generation and the reduction of carbon emissions have become a major motivation for the use of sustainable electrical power. In this perspective, renewable energy sources are expected to take up an important part of electric energy produced in the near future. Since renewable sources such as wind and solar are intermittent in nature, their increased installation will result in either excessive or insufficient power generation at times. A large variety of concepts for using this surplus power is currently under development. Acidic water electrolysis is an attractive environmentally-safe solution for the conversion and storage of excess electricity into hydrogen and oxygen. The large scale application of water electrolysis systems is currently hindered by low efficiency and instability of catalysts during long term operation [1]. This is especially crucial for the anodic oxygen evolution reaction (OER) which catalyzed by Iridium based alloys and oxides making the issues related to efficiency of catalyst utilization and durability even more critical. The development of catalyst materials with superior performance demands a deep understanding of the OER itself as well as electrocatalysts degradation mechanisms. Although a large number of possible OER mechanisms have been proposed [2], the topic remains a subject of intensive debates across the scientific literature, since the intermediates and their possible interrelations are in most cases unknown. Additional challenges in mechanistic studies are related to the changes in the composition of the catalyst and its degradation triggered by OER. Though the existence of experimental correlation between the structure, activity of OER catalyst and its dissolution was numerously reported and discussed [2,3], reports addressing all these aspects in one study are rare. This indicates that further research efforts are required to reveal reaction intermediates and products by means, for instance, of mass spectrometry at the atomic scale by atom probe tomography, that complement spectroscopic insight from synchrotron-based experiments, ideally in operando conditions. In this presentation, the main fundamental limitations that hinder the current understanding of the reactions mechanisms occurring in water electrolysis will be discussed. It will be stressed that only the combination of insights enables the establishing of reliable structure-function relationships in electrocatalyst materials. We present our approach to investigate complex processes in electrocatalysis with a combination of independent methods like online electrochemical mass spectrometry, atom probe tomography and synchrotron-based spectroscopy [4,5]. In particular, we discuss approaches to resolving the reaction mechanism on constantly evolving surfaces present our recent results on the interplay between the nature of the active sites in Ir-based oxides and their stability towards the OER and establish structure–function relationships between the reactivity and the atomic-scale surface structure [5]. Finally, using the new insights gained in our recent studies [4-6], we discuss potential design strategy for Ir-based OER catalysts with high catalytic activity and long-term stable performance. [1] S. Cherevko et al., Catalysis Today 2016, 262, 170-180 [2] T. Reier, H.N. Nong, D. Teschner, R. Schlögl, P. Strasser, Adv. Energy Mater. 2017, 7(1), 1601275. [3] O. Kasian, J.P. Grote, S. Geiger, S. Cherevko, K.J.J. Mayrhofer, Angew. Chem. Int. Ed. 2018, 57, 2488 –2491. [4] K. Schweinar, R.L. Nicholls, C.R. Rajamathi, P. Zeller, M. Amati, L. Gregoratti, D. Raabe, M. Greiner, B. Gault, O. Kasian, J. Mater. Chem. A 2020, 8(1), 388-400. [5] O. Kasian, S. Geiger, T. Li, J-P. Grote, K. Schweinar, S. Zhang, C. Scheu, D. Raabe, S. Cherevko, B. Gault, K. Mayrhofer, Energy Environ. Sci. 2019, 12(12), 3548-3555. [6] K. Schweinar, I. Mouton, B. Gault, O. Kasian, J. Phys. Chem. Lett. 2020, submitted.
Publisher: Springer Science and Business Media LLC
Date: 17-09-2021
DOI: 10.1038/S41467-021-25778-Y
Abstract: Wear-related energy and material loss cost over 2500 Billion Euro per year. Traditional wisdom suggests that high-strength materials reveal low wear rates, yet, their plastic deformation mechanisms also influence their wear performance. High strength and homogeneous deformation behavior, which allow accommodating plastic strain without cracking or localized brittle fracture, are crucial for developing wear-resistant metals. Here, we present an approach to achieve superior wear resistance via in-situ formation of a strong and deformable oxide nanocomposite surface during wear, by reaction of the metal surface with its oxidative environment, a principle that we refer to as ‘reactive wear protection’. We design a TiNbZr-Ag alloy that forms an amorphous-crystalline oxidic nanocomposite surface layer upon dry sliding. The strong (2.4 GPa yield strength) and deformable (homogeneous deformation to 20% strain) nanocomposite surface reduces the wear rate of the TiNbZr-Ag alloy by an order of magnitude. The reactive wear protection strategy offers a pathway for designing ultra-wear resistant alloys, where otherwise brittle oxides are turned to be strong and deformable for improving wear resistance.
Publisher: Elsevier BV
Date: 09-2023
Publisher: Elsevier BV
Date: 07-2015
Publisher: Elsevier BV
Date: 05-2021
Publisher: Oxford University Press (OUP)
Date: 23-03-2023
Abstract: Measuring local chemistry of specific crystallographic features by atom probe tomography (APT) is facilitated by using transmission Kikuchi diffraction (TKD) to help position them sufficiently close to the apex of the needle-shaped specimen. However, possible structural damage associated to the energetic electrons used to perform TKD is rarely considered and is hence not well-understood. Here, in two case studies, we evidence damage in APT specimens from TKD mapping. First, we analyze a solid solution, metastable β-Ti-12Mo alloy, in which the Mo is expected to be homogenously distributed. Following TKD, APT reveals a planar segregation of Mo among other elements. Second, specimens were prepared near Σ3 twin boundaries in a high manganese twinning-induced plasticity steel, and subsequently charged with deuterium gas. Beyond a similar planar segregation, voids containing a high concentration of deuterium, i.e., bubbles, are detected in the specimen on which TKD was performed. Both ex les showcase damage from TKD mapping leading to artefacts in the distribution of solutes. We propose that the structural damage is created by surface species, including H and C, subjected to recoil from incoming energetic electrons during mapping, thereby getting implanted and causing cascades of structural damage in the s le.
Publisher: Elsevier BV
Date: 02-2017
Publisher: Elsevier BV
Date: 10-2022
Publisher: No publisher found
Date: 2022
Publisher: Elsevier BV
Date: 05-2010
DOI: 10.1016/J.ULTRAMIC.2010.11.019
Abstract: In-depth analysis of pulsed laser atom probe tomography (APT) data on the field evaporation of the III-V semiconductor material GaSb reveals strong variations in charge states, relative abundances of different cluster ions, multiplicity of detector events and spatial correlation of evaporation events, as a function of the effective electric field at the specimen surface. These variations are discussed in comparison with the behaviour of two different metallic specimen materials, an Al-6XXX series alloy and pure W, studied under closely related experimental conditions in the same atom probe instrument. It is proposed that the complex behaviour of GaSb originates from a combination of spatially correlated evaporation events and the subsequent field induced dissociation of cluster ions, the latter contributing to inaccuracies in the overall atom probe composition determination for this material.
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.ULTRAMIC.2015.04.005
Abstract: Artefacts in atom probe tomography can impact the compositional analysis of microstructure in atom probe studies. To determine the integrity of information obtained, it is essential to understand how the positioning of features influences compositional analysis. By investigating the influence of feature orientation within atom probe data on measured composition in microstructural features within an AA2198 Al alloy, this study shows differences in the composition of T1 (Al2CuLi) plates that indicates imperfections in atom probe reconstructions. The data fits a model of an exponentially-modified Gaussian that scales with the difference in evaporation field between solutes and matrix. This information provides a guide for obtaining the most accurate information possible.
Publisher: Elsevier BV
Date: 05-2022
Publisher: American Association for the Advancement of Science (AAAS)
Date: 19-06-2020
Abstract: We developed high-temperature high-d ing high-entropy alloys with superior mechanical properties via Snoek relaxation.
Publisher: Elsevier BV
Date: 05-2011
DOI: 10.1016/J.ULTRAMIC.2010.11.014
Abstract: Spatial Distribution Maps (SDM) in their various forms have previously been used to identify and characterize crystallographic structure within APT reconstructions. Importantly, it has been shown that such SDM analyses can also provide the crystallographic orientation of the specimen with respect to the direction of the detector in the original experiment. In this study, we investigate the application of SDMs to the analysis of APT reconstruction of a nanocrystalline Al film. We demonstrate that significant intra-granular crystallographic information is retained in the reconstruction, even in the x-y plane perpendicular to the direction of the detector. Further, the crystallographic orientation of the grains can be characterized highly accurately not only with respect to the bulk specimen but also their misorientation with respect to neighbouring grains.
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 05-2011
DOI: 10.1016/J.ULTRAMIC.2010.11.016
Abstract: Key to the integrity of atom probe microanalysis, the tomographic reconstruction is built atom by atom following a simplistic protocol established for previous generations of instruments. In this paper, after a short review of the main reconstruction protocols, we describe recent improvements originating from the use of exact formulae enabling significant reduction of spatial distortions, especially near the edges of the reconstruction. We also show how predictive values for the reconstruction parameters can be derived from electrostatic simulations, and finally introduce parameters varying throughout the analysis.
Publisher: Springer Science and Business Media LLC
Date: 18-06-2021
Publisher: Wiley
Date: 07-02-2020
Publisher: Oxford University Press (OUP)
Date: 08-2022
DOI: 10.1017/S1431927621012381
Abstract: Atom probe tomography (APT) helps elucidate the link between the nanoscale chemical variations and physical properties, but it has a limited structural resolution. Field ion microscopy (FIM), a predecessor technique to APT, is capable of attaining atomic resolution along certain sets of crystallographic planes albeit at the expense of elemental identification. We demonstrate how two commercially available atom probe instruments, one with a straight flight path and one fitted with a reflectron lens, can be used to acquire time-of-flight mass spectrometry data concomitant with a FIM experiment. We outline various experimental protocols making the use of temporal and spatial correlations to best discriminate field-evaporated signals from the large field-ionized background signal, demonstrating an unsophisticated yet efficient data mining strategy to provide this discrimination. We discuss the remaining experimental challenges that need to be addressed, notably concerned with accurate detection and identification of in idual field-evaporated ions contained within the high field-ionized flux that contributes to a FIM image. Our hybrid experimental approach can, in principle, exhibit true atomic resolution with elemental discrimination capabilities, neither of which atom probe nor FIM can in idually fully deliver—thereby making this new approach, here broadly termed analytical field ion microscopy (aFIM), unique.
Publisher: Springer Science and Business Media LLC
Date: 08-07-2021
Publisher: Springer Science and Business Media LLC
Date: 03-2022
DOI: 10.1038/S41467-022-28706-W
Abstract: Interstitials, e.g., C, N, and O, are attractive alloying elements as small atoms on interstitial sites create strong lattice distortions and hence substantially strengthen metals. However, brittle ceramics such as oxides and carbides usually form, instead of solid solutions, when the interstitial content exceeds a critical yet low value (e.g., 2 at.%). Here we introduce a class of massive interstitial solid solution (MISS) alloys by using a highly distorted substitutional host lattice, which enables solution of massive amounts of interstitials as an additional principal element class, without forming ceramic phases. For a TiNbZr-O-C-N MISS model system, the content of interstitial O reaches 12 at.%, with no oxides formed. The alloy reveals an ultrahigh compressive yield strength of 4.2 GPa, approaching the theoretical limit, and large deformability (65% strain) at ambient temperature, without localized shear deformation. The MISS concept thus offers a new avenue in the development of metallic materials with excellent mechanical properties.
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 09-2018
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 06-2021
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2017
Publisher: Elsevier BV
Date: 09-2007
DOI: 10.1016/J.ULTRAMIC.2007.02.004
Abstract: In the interaction between ultrafast laser pulses and a field emitter both optical and thermal processes are involved. In this paper, these physical process, and their timescales, are experimentally explored. Simple models are proposed to explain the observed experimental behaviour, and the influence of various parameters are investigated. In the case of optical processes, it is shown that the optical field is greatly enhanced at the tip apex, and that field evaporation could be induced by an optical non-linear effect called optical rectification. In the case of thermal processes, it is shown that the temperature rise because of light absorption can be determined and that the cooling process of the tip surface can be studied by pump probe measurements.
Publisher: Elsevier BV
Date: 12-2018
Publisher: No publisher found
Date: 2023
Publisher: IOP Publishing
Date: 2022
Abstract: Atom probe tomography (APT) analysis is being actively used to provide near-atomic-scale information on the composition of complex materials in three-dimensions. In recent years, there has been a surge of interest in the technique to investigate the distribution of hydrogen in metals. However, the presence of hydrogen in the analysis of almost all specimens from nearly all material systems has caused numerous debates as to its origins and impact on the quantitativeness of the measurement. It is often perceived that most H arises from residual gas ionization, therefore affecting primarily materials with a relatively low evaporation field. In this work, we perform systematic investigations to identify the origin of H residuals in APT experiments by combining density-functional theory (DFT) calculations and APT measurements on an alkali and a noble metal, namely Na and Pt, respectively. We report that no H residual is found in Na metal s les, but in Pt, which has a higher evaporation field, a relatively high signal of H is detected. These results contradict the hypothesis of the H signal being due to direct ionization of residual H 2 without much interaction with the specimen’s surface. Based on DFT, we demonstrate that alkali metals are thermodynamically less likely to be subject to H contamination under APT-operating conditions compared to transition or noble metals. These insights indicate that the detected H-signal is not only from ionization of residual gaseous H 2 alone, but is strongly influenced by material-specific physical properties. The origin of H residuals is elucidated by considering different conditions encountered during APT experiments, specifically, specimen-preparation, transportation, and APT-operating conditions by taking thermodynamic and kinetic aspects into account.
Publisher: American Physical Society (APS)
Date: 15-06-2011
Publisher: Elsevier BV
Date: 10-2021
Publisher: Springer Science and Business Media LLC
Date: 22-07-2021
Publisher: Elsevier BV
Date: 05-2020
Publisher: Research Square Platform LLC
Date: 07-01-2022
DOI: 10.21203/RS.3.RS-1092384/V1
Abstract: Chemical short-range order (CSRO) refers to atoms of specific elements self-organising within a disordered crystalline matrix. These particular atomic neighbourhoods can modify the mechanical and functional performances of materials 1-6. CSRO is typically characterized indirectly, using volume-averaged (e.g. X-ray/neutron scattering) 2,7,8 or through projection (i.e. two-dimensional) microscopy techniques 5,6,9,10 that fail to capture the complex, three-dimensional atomistic architectures. Quantitative assessment of CSRO and concrete structure-property relationships remain unachievable. Here, we present a machine-learning enhanced approach to break the inherent resolution limits of atom probe tomography to reveal three-dimensional analytical imaging of the size and morphology of multiple CSRO. We showcase our approach by addressing a long-standing question encountered in a body-centred-cubic Fe-18Al (at.%) solid solution alloy that sees anomalous property changes upon heat treatment 2. After validating our method against artificial data for ground truth, we unearth non-statistical B2-CSRO (FeAl) instead of the generally-expected D03-CSRO (Fe3Al) 11,12. We propose quantitative correlations among annealing temperature, CSRO, and the nano-hardness and electrical resistivity, supported by atomistic simulations. The proposed strategy can be generally employed to investigate short/medium/long-range ordering phenomena in a vast array of materials and help design future high-performance materials.
Publisher: Elsevier BV
Date: 05-2017
Publisher: MDPI AG
Date: 27-11-2020
DOI: 10.3390/NANO10122362
Abstract: This study focuses on the synthesis of FeRh nanoparticles via pulsed laser ablation in liquid and on controlling the oxidation of the synthesized nanoparticles. Formation of monomodal γ-FeRh nanoparticles was confirmed by transmission electron microscopy (TEM) and their composition confirmed by atom probe tomography (APT). For these particles, three major contributors to oxidation were analysed: (1) dissolved oxygen in the organic solvents, (2) the bound oxygen in the solvent and (3) oxygen in the atmosphere above the solvent. The decrease of oxidation for optimized ablation conditions was confirmed through energy-dispersive X-ray (EDX) and Mössbauer spectroscopy. Furthermore, the time dependence of oxidation was monitored for dried FeRh nanoparticles powders using ferromagnetic resonance spectroscopy (FMR). By magnetophoretic separation, B2-FeRh nanoparticles could be extracted from the solution and characteristic differences of nanostrand formation between γ-FeRh and B2-FeRh nanoparticles were observed.
Publisher: Oxford University Press (OUP)
Date: 04-02-2019
DOI: 10.1017/S1431927618016161
Abstract: Although atom probe tomography (APT) reconstructions do not directly influence the local elemental analysis, any structural inferences from APT volumes demand a reliable reconstruction of the point cloud. Accurate estimation of the reconstruction parameters is crucial to obtain reliable spatial scaling. In the current work, a new automated approach of calibrating atom probe reconstructions is developed using only one correlative projection electron microscopy (EM) image. We employed an algorithm that implements a 2D cross-correlation of microstructural features observed in both the APT reconstructions and the corresponding EM image. We apply this protocol to calibrate reconstructions in a Cu(In,Ga)Se 2 -based semiconductor and in a Co-based superalloy. This work enables us to couple chemical precision to structural information with relative ease.
Publisher: Oxford University Press (OUP)
Date: 08-2022
DOI: 10.1017/S1431927621012952
Abstract: Atom probe tomography (APT) is often introduced as providing “atomic-scale” mapping of the composition of materials and as such is often exploited to analyze atomic neighborhoods within a material. Yet quantifying the actual spatial performance of the technique in a general case remains challenging, as it depends on the material system being investigated as well as on the specimen's geometry. Here, by using comparisons with field-ion microscopy experiments, field-ion imaging and field evaporation simulations, we provide the basis for a critical reflection on the spatial performance of APT in the analysis of pure metals, low alloyed systems and concentrated solid solutions (i.e., akin to high-entropy alloys). The spatial resolution imposes strong limitations on the possible interpretation of measured atomic neighborhoods, and directional neighborhood analyses restricted to the depth are expected to be more robust. We hope this work gets the community to reflect on its practices, in the same way, it got us to reflect on our work.
Publisher: Springer Science and Business Media LLC
Date: 19-11-2014
DOI: 10.1038/NCOMMS6501
Abstract: Microscopy encompasses a wide variety of forms and scales. So too does the array of simulation techniques developed that correlate to and build upon microstructural information. Nevertheless, a true nexus between microscopy and atomistic simulations is lacking. Atom probe has emerged as a potential means of achieving this goal. Atom probe generates three-dimensional atomistic images in a format almost identical to many atomistic simulations. However, this data is imperfect, preventing input into computational algorithms to predict material properties. Here we describe a methodology to overcome these limitations, based on a hybrid data format, blending atom probe and predictive Monte Carlo simulations. We create atomically complete and lattice-bound models of material specimens. This hybrid data can then be used as direct input into density functional theory simulations to calculate local energetics and elastic properties. This research demonstrates the role that atom probe combined with theoretical approaches can play in modern materials engineering.
Publisher: Maney Publishing
Date: 11-02-2016
Publisher: Oxford University Press (OUP)
Date: 11-03-2019
DOI: 10.1017/S143192761801615X
Abstract: Analysis and understanding of the role of hydrogen in metals is a significant challenge for the future of materials science, and this is a clear objective of recent work in the atom probe tomography (APT) community. Isotopic marking by deuteration has often been proposed as the preferred route to enable quantification of hydrogen by APT. Zircaloy-4 was charged electrochemically with hydrogen and deuterium under the same conditions to form large hydrides and deuterides. Our results from a Zr hydride and a Zr deuteride highlight the challenges associated with accurate quantification of hydrogen and deuterium, in particular associated with the overlap of peaks at a low mass-to-charge ratio and of hydrogen/deuterium containing molecular ions. We discuss possible ways to ensure that appropriate information is extracted from APT analysis of hydrogen in zirconium alloy systems that are important for nuclear power applications.
Publisher: Elsevier BV
Date: 06-2018
Publisher: Elsevier BV
Date: 10-2017
Publisher: Wiley
Date: 12-06-2023
DOI: 10.1111/JOCN.16792
Abstract: To examine the association between nursing unit safety culture, quality of care, missed care and nurse staffing levels, and inpatient falls using two data sources: incidence of falls and nurses' perceptions of fall frequency in their units. The study explores the association between the two sources of patient falls and identifies if nurses' perceptions of patient fall frequency reflect the actual patient falls recorded in the incident management system. Inpatient falls are associated with severe complications that result in extended hospitalisation and increased financial consequences for patients and healthcare services. A multi‐source cross‐sectional study guided by the STROBE guidelines. A purposive s le of 33 nursing units (619 nurses) from five hospitals completed an online survey from August to November 2021. The survey measured safety culture, quality of care, missed care, nurse staffing levels and nurses' perceptions of patient fall frequency. In addition, secondary data on falls from participating units between 2018 and 2021 were also collected. Generalised linear models were fitted to examine the association between study variables. Nursing units with strong safety climate and working conditions and lower missed care were associated with lower rates of falls using both data sources. Nurses' perceptions of the frequency of falls in their units were reflective of the actual incidence rate of falls, but the association was not statistically significant. Nursing units with a strong safety climate and better collaborations between nurses and other professionals, including physicians and pharmacists, were associated with lower incidents of patient falls. This study provided evidence for healthcare services and hospital managers to minimise patient falls. Patients who had experienced a fall, which was reported in the incident management system, from the included units in the five hospitals were part of this study.
Publisher: IEEE
Date: 12-2012
Publisher: Informa UK Limited
Date: 05-2013
Publisher: Wiley
Date: 28-12-2018
Abstract: Severe lattice distortion is a core effect in the design of multiprincipal element alloys with the aim to enhance yield strength, a key indicator in structural engineering. Yet, the yield strength values of medium- and high-entropy alloys investigated so far do not substantially exceed those of conventional alloys owing to the insufficient utilization of lattice distortion. Here it is shown that a simple VCoNi equiatomic medium-entropy alloy exhibits a near 1 GPa yield strength and good ductility, outperforming conventional solid-solution alloys. It is demonstrated that a wide fluctuation of the atomic bond distances in such alloys, i.e., severe lattice distortion, improves both yield stress and its sensitivity to grain size. In addition, the dislocation-mediated plasticity effectively enhances the strength-ductility relationship by generating nanosized dislocation substructures due to massive pinning. The results demonstrate that severe lattice distortion is a key property for identifying extra-strong materials for structural engineering applications.
Publisher: Elsevier BV
Date: 12-2015
Publisher: Springer Science and Business Media LLC
Date: 11-2018
DOI: 10.1038/S41586-018-0685-Y
Abstract: Oxygen, one of the most abundant elements on Earth, often forms an undesired interstitial impurity or ceramic phase (such as an oxide particle) in metallic materials. Even when it adds strength, oxygen doping renders metals brittle
Publisher: Elsevier BV
Date: 05-2020
Publisher: Springer Science and Business Media LLC
Date: 19-03-2018
DOI: 10.1038/S41467-018-03591-4
Abstract: Analysis and design of materials and fluids requires understanding of the fundamental relationships between structure, composition, and properties. Dislocations and grain boundaries influence microstructure evolution through the enhancement of diffusion and by facilitating heterogeneous nucleation, where atoms must overcome a potential barrier to enable the early stage of formation of a phase. Adsorption and spinodal decomposition are known precursor states to nucleation and phase transition however, nucleation remains the less well-understood step in the complete thermodynamic sequence that shapes a microstructure. Here, we report near-atomic-scale observations of a phase transition mechanism that consists in solute adsorption to crystalline defects followed by linear and planar spinodal fluctuations in an Fe-Mn model alloy. These fluctuations provide a pathway for austenite nucleation due to the higher driving force for phase transition in the solute-rich regions. Our observations are supported by thermodynamic calculations, which predict the possibility of spinodal decomposition due to magnetic ordering.
Publisher: Elsevier BV
Date: 11-2017
Publisher: Trans Tech Publications, Ltd.
Date: 06-2010
DOI: 10.4028/WWW.SCIENTIFIC.NET/MSF.654-656.2366
Abstract: Atom probe tomography provides compositional information in three dimensions at the atomic scale, and is therefore extremely suited to the study of nanocrystalline materials. In this paper we present atom probe results from the investigation of nanocomposite TiSi¬Nx coatings and nanocrystalline Al. We address some of the major challenges associated with the study of nanocrystalline materials, including specimen preparation, visualisation, common artefacts in the data and approaches to quantitative analysis. We also discuss the potential for the technique to relate crystallographic information to the compositional maps.
Publisher: Springer Science and Business Media LLC
Date: 14-10-2021
DOI: 10.1038/S41467-021-26197-9
Abstract: The local variation of grain boundary atomic structure and chemistry caused by segregation of impurities influences the macroscopic properties of polycrystalline materials. Here, the effect of co-segregation of carbon and boron on the depletion of aluminum at a Σ5 (3 1 0 )[0 0 1] tilt grain boundary in a α − Fe-4 at%Al bicrystal is studied by combining atomic resolution scanning transmission electron microscopy, atom probe tomography and density functional theory calculations. The atomic grain boundary structural units mostly resemble kite-type motifs and the structure appears disrupted by atomic scale defects. Atom probe tomography reveals that carbon and boron impurities are co-segregating to the grain boundary reaching levels of .5 at%, whereas aluminum is locally depleted by approx. 2 at.%. First-principles calculations indicate that carbon and boron exhibit the strongest segregation tendency and their repulsive interaction with aluminum promotes its depletion from the grain boundary. It is also predicted that substitutional segregation of boron atoms may contribute to local distortions of the kite-type structural units. These results suggest that the co-segregation and interaction of interstitial impurities with substitutional solutes strongly influences grain boundary composition and with this the properties of the interface.
Publisher: Elsevier BV
Date: 08-2020
Publisher: Elsevier BV
Date: 08-2018
Publisher: Elsevier BV
Date: 08-2023
Publisher: Elsevier BV
Date: 03-2019
Publisher: American Association for the Advancement of Science (AAAS)
Date: 04-12-2020
Abstract: We propose a protocol for near-atomic–scale analysis of frozen water and embedded nanostructures by cryo–atom probe tomography.
Publisher: Oxford University Press (OUP)
Date: 18-01-2010
DOI: 10.1017/S1431927609991267
Abstract: This article addresses gaps in definitions and a lack of standard measurement techniques to assess the spatial resolution in atom probe tomography. This resolution is known to be anisotropic, being better in-depth than laterally. Generally the presence of atomic planes in the tomographic reconstruction is considered as being a sufficient proof of the quality of the spatial resolution of the instrument. Based on advanced spatial distribution maps, an analysis methodology that interrogates the local neighborhood of the atoms within the tomographic reconstruction, it is shown how both the in-depth and the lateral resolution can be quantified. The influences of the crystallography and the temperature are investigated, and models are proposed to explain the observed results. We demonstrate that the absolute value of resolution is specimen specific.
Publisher: Springer Science and Business Media LLC
Date: 04-12-2018
DOI: 10.1038/S41598-018-36110-Y
Abstract: Amyloid-beta (Ab) proteins play an important role in a number of neurodegenerative diseases. Ab is found in senile plaques in brains of Alzeimer’s disease patients. The 42 residues of the monomer form dimers which stack to fibrils gaining several micrometers in length. Using Ab fibrils with 13 C and 15 N marker substitution, we developed an innovative approach to obtain insights to structural and chemical information of the protein. We deposited the modified protein fibrils to pre-sharped aluminium needles with -nm apex diameters and, using the position-sensitive mass-to-charge spectrometry technique of atom probe tomography, we acquired the chemically-resolved three dimensional information for every detected ion evaporated in small fragments from the protein. We also discuss the influence of experimental parameters such as pulse energy and pulse frequency of the used Laser beam which lead to differences in the size of the gained fragments, developing the capability of localising metal atom within Ab plaques.
Publisher: Oxford University Press (OUP)
Date: 02-02-2017
DOI: 10.1017/S1431927616012721
Abstract: There are two main projections used to transform, and reconstruct, field ion micrographs or atom probe tomography data into atomic coordinates at the specimen surface and, subsequently, in three dimensions. In this article, we present a perspective on the strength of the azimuthal equidistant projection in comparison with the more widely used and well-established point projection (or pseudo-stereographic projection), which underpins data reconstruction in most software packages currently in use across the community. After an overview of the reconstruction methodology, we demonstrate that the azimuthal equidistant is more robust with regards to errors on the parameters used to perform the reconstruction and is therefore more likely to yield more accurate tomographic reconstructions.
Publisher: Oxford University Press (OUP)
Date: 18-03-2020
DOI: 10.1017/S1431927620000197
Abstract: Interfaces play critical roles in materials and are usually both structurally and compositionally complex microstructural features. The precise characterization of their nature in three-dimensions at the atomic scale is one of the grand challenges for microscopy and microanalysis, as this information is crucial to establish structure–property relationships. Atom probe tomography is well suited to analyzing the chemistry of interfaces at the nanoscale. However, optimizing such microanalysis of interfaces requires great care in the implementation across all aspects of the technique from specimen preparation to data analysis and ultimately the interpretation of this information. This article provides critical perspectives on key aspects pertaining to spatial resolution limits and the issues with the compositional analysis that can limit the quantification of interface measurements. Here, we use the ex le of grain boundaries in steels however, the results are applicable for the characterization of grain boundaries and transformation interfaces in a very wide range of industrially relevant engineering materials.
Publisher: Public Library of Science (PLoS)
Date: 16-01-2020
Publisher: Oxford University Press (OUP)
Date: 08-2022
DOI: 10.1017/S1431927621012964
Abstract: Analyzing porous (nano)materials via atom probe tomography has been notoriously difficult. Voids and pores act as concentrators of the electrostatic pressure, which results in premature specimen failure, and the electrostatic field distribution near voids leads to aberrations that are difficult to predict. In this study, we propose a new encapsulating method for porous s les using a low melting point Bi–In–Sn alloy, known as Field's metal. As a model material, we used porous iron made by direct-hydrogen reduction of single-crystalline wüstite. The complete encapsulation was performed using in situ heating on the stage of a scanning electron microscope. No visible corrosion nor dissolution of the s le occurred. Subsequently, specimens were shaped by focused ion-beam milling under cryogenic conditions at −190°C. The proposed approach is versatile and can be applied to provide good quality atom probe datasets from micro/nanoporous materials.
Publisher: Elsevier BV
Date: 12-2023
Publisher: American Chemical Society (ACS)
Date: 16-01-2018
Abstract: Dislocations have been considered to be an efficient source for scattering midfrequency phonons, contributing to the enhancement of thermoelectric performance. The structure of dislocations can be resolved by electron microscopy whereas their chemical composition and decoration state are scarcely known. Here, we correlate transmission Kikuchi diffraction and (scanning) transmission electron microscopy in conjunction with atom probe tomography to investigate the local structure and chemical composition of dislocations in a thermoelectric Ag-doped PbTe compound. Our investigations indicate that Ag atoms segregate to dislocations with a 10-fold excess of Ag compared with its average concentration in the matrix. Yet the Ag concentration along the dislocation line is not constant but fluctuates from ∼0.8 to ∼10 atom % with a period of about 5 nm. Thermal conductivity is evaluated applying laser flash analysis, and is correlated with theoretical calculations based on the Debye-Callaway model, demonstrating that these Ag-decorated dislocations yield stronger phonon scatterings. These findings reduce the knowledge gap regarding the composition of dislocations needed for theoretical calculations of phonon scattering and pave the way for extending the concept of defect engineering to thermoelectric materials.
Publisher: Springer Science and Business Media LLC
Date: 31-05-2018
Publisher: Oxford University Press (OUP)
Date: 07-2009
DOI: 10.1017/S1431927609092988
Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009
Publisher: Informa UK Limited
Date: 03-2013
Publisher: Elsevier BV
Date: 08-2010
DOI: 10.1016/J.ULTRAMIC.2010.04.017
Abstract: The implementation of fast pulsed laser has significantly improved the performance of the atom probe technique by enabling near-atomic-scale three-dimensional analysis of poorly conducting materials. This has broadened the range of applications for the atom probe, addressing a major limitation of the technique. Despite this, the implications of lasing on the tomographic reconstruction of atom probe data have yet to be fully characterised. Here, we demonstrate how changes in the shape of the specimen surface, induced by laser pulsing, affect the ion trajectories, and hence the projection parameters used to build the three-dimensional map.
Publisher: Springer Science and Business Media LLC
Date: 16-03-2018
Publisher: International Union of Crystallography (IUCr)
Date: 10-2021
DOI: 10.1107/S1600576721008578
Abstract: Volumetric crystal structure indexing and orientation mapping are key data processing steps for virtually any quantitative study of spatial correlations between the local chemical composition features and the microstructure of a material. For electron and X-ray diffraction methods it is possible to develop indexing tools which compare measured and analytically computed patterns to decode the structure and relative orientation within local regions of interest. Consequently, a number of numerically efficient and automated software tools exist to solve the above characterization tasks. For atom-probe tomography (APT) experiments, however, the strategy of making comparisons between measured and analytically computed patterns is less robust because many APT data sets contain substantial noise. Given that sufficiently general predictive models for such noise remain elusive, crystallography tools for APT face several limitations: their robustness to noise is limited, and therefore so too is their capability to identify and distinguish different crystal structures and orientations. In addition, the tools are sequential and demand substantial manual interaction. In combination, this makes robust uncertainty quantification with automated high-throughput studies of the latent crystallographic information a difficult task with APT data. To improve the situation, the existing methods are reviewed and how they link to the methods currently used by the electron and X-ray diffraction communities is discussed. As a result of this, some of the APT methods are modified to yield more robust descriptors of the atomic arrangement. Also reported is how this enables the development of an open-source software tool for strong scaling and automated identification of a crystal structure, and the mapping of crystal orientation in nanocrystalline APT data sets with multiple phases.
Publisher: Elsevier BV
Date: 12-2022
Publisher: Elsevier BV
Date: 04-2020
Publisher: AIP Publishing
Date: 27-02-2006
DOI: 10.1063/1.2181654
Abstract: The temperature evolution at the apex of a sharply pointed needle submitted to ultrafast pulsed-laser irradiation was determined using a pump-probe method. The laser pulse acts as a pump pulse whereas the probe pulse is a fast high-voltage pulse. Then cooling times are consistent with a heating zone of a few microns with a laser beam polarized along the tip axis and a spot size of 0.8mm.
Publisher: Elsevier BV
Date: 10-2019
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2009
Publisher: Elsevier BV
Date: 11-2020
Publisher: Springer Science and Business Media LLC
Date: 26-02-2018
DOI: 10.1038/S41467-018-03115-0
Abstract: Copper indium gallium diselenide-based technology provides the most efficient solar energy conversion among all thin-film photovoltaic devices. This is possible due to engineered gallium depth gradients and alkali extrinsic doping. Sodium is well known to impede interdiffusion of indium and gallium in polycrystalline Cu(In,Ga)Se 2 films, thus influencing the gallium depth distribution. Here, however, sodium is shown to have the opposite effect in monocrystalline gallium-free CuInSe 2 grown on GaAs substrates. Gallium in-diffusion from the substrates is enhanced when sodium is incorporated into the film, leading to Cu(In,Ga)Se 2 and Cu(In,Ga) 3 Se 5 phase formation. These results show that sodium does not decrease per se indium and gallium interdiffusion. Instead, it is suggested that sodium promotes indium and gallium intragrain diffusion, while it hinders intergrain diffusion by segregating at grain boundaries. The deeper understanding of dopant-mediated atomic diffusion mechanisms should lead to more effective chemical and electrical passivation strategies, and more efficient solar cells.
Publisher: Springer Science and Business Media LLC
Date: 26-03-2022
DOI: 10.1186/S12913-022-07717-9
Abstract: There are significant challenges in ensuring sufficient clinician participation in quality improvement training. Clinician capability has been identified as a barrier to the delivery of evidence-based care. Clinician training is an effective strategy to address this barrier, however, there are significant challenges in ensuring adequate clinician participation in training. This study aimed to assess the extent of participation by antenatal clinicians in evidence-based training to address alcohol consumption during pregnancy, and to assess differences in participation by profession. A 7-month training initiative based on six evidence-based principles was implemented in a maternity service in New South Wales, Australia. Descriptive statistics described participation in training (% attending: any training six evidence-based principles of training all principles). Regression analyses examined differences by profession. Almost all antenatal clinicians participated in some training (182/186 98%) 69% participated in ≥1 h of training (μ = 88.2mins, SD:56.56). The proportion of clinicians participating in training that satisfied each of the six principles ranged from 35% (training from peers and experts) to 82% (training was educational and instructional). Only 7% participated in training that satisfied all principles. A significantly higher proportion of midwifery compared to medical clinicians participated in training satisfying five of the six training principles. A training initiative based on evidence-based principles resulted in almost all clinicians receiving some training and 69% participating in at least 1 h of training. Variability between professions suggests training needs to be tailored to such groups. Further research is required to determine possible associations with care delivery outcomes. Australian and New Zealand Clinical Trials Registry, No. ACTRN12617000882325 (date registered: 16/06/2017).
Publisher: Elsevier BV
Date: 06-2010
DOI: 10.1016/J.ULTRAMIC.2010.03.003
Abstract: Laser-assisted atom probe tomography was used to investigate the nanostructure and composition of high-performance, ultra-hard Ti-Si-N nanocomposite films. However, the quality of data is heavily dependent on analysis conditions. In order to obtain reliable data from these, and other 'less conducting' specimens, the analysis parameter space was thoroughly investigated to optimize the mass resolution and hit multiplicity obtained in atom probe tomography. Geometric factors including tip radius and shank angle were found to play a significant role in mass resolution but had no apparent effect on the number of multiple hits observed. Increased laser energy led to a gradual increase in the number of single hits, but a modest improvement in mass resolution. The influence of other instrumental factors including detection rate and base temperature was investigated separately. Preliminary PLAP results are presented, and correlated with TEM analysis of the microstructure of the film.
Publisher: Oxford University Press (OUP)
Date: 31-01-2017
DOI: 10.1017/S1431927616012757
Abstract: The functional properties of the high-temperature superconductor Y 1 Ba 2 Cu 3 O 7− δ (Y-123) are closely correlated to the exact stoichiometry and oxygen content. Exceeding the critical value of 1 oxygen vacancy for every five unit cells ( δ .2, which translates to a 1.5 at% deviation from the nominal oxygen stoichiometry of Y 7.7 Ba 15.3 Cu 23 O 54− δ ) is sufficient to alter the superconducting properties. Stoichiometry at the nanometer scale, particularly of oxygen and other lighter elements, is extremely difficult to quantify in complex functional ceramics by most currently available analytical techniques. The present study is an analysis and optimization of the experimental conditions required to quantify the local nanoscale stoichiometry of single crystal yttrium barium copper oxide (YBCO) s les in three dimensions by atom probe tomography (APT). APT analysis required systematic exploration of a wide range of data acquisition and processing conditions to calibrate the measurements. Laser pulse energy, ion identification, and the choice of range widths were all found to influence composition measurements. The final composition obtained from melt-grown crystals with optimized superconducting properties was Y 7.9 Ba 10.4 Cu 24.4 O 57.2 .
Publisher: Springer Science and Business Media LLC
Date: 24-02-2020
DOI: 10.1038/S41467-020-14832-W
Abstract: Quantifying chemical compositions around nanovoids is a fundamental task for research and development of various materials. Atom probe tomography (APT) and scanning transmission electron microscopy (STEM) are currently the most suitable tools because of their ability to probe materials at the nanoscale. Both techniques have limitations, particularly APT, because of insufficient understanding of void imaging. Here, we employ a correlative APT and STEM approach to investigate the APT imaging process and reveal that voids can lead to either an increase or a decrease in local atomic densities in the APT reconstruction. Simulated APT experiments demonstrate the local density variations near voids are controlled by the unique ring structures as voids open and the different evaporation fields of the surrounding atoms. We provide a general approach for quantifying chemical segregations near voids within an APT dataset, in which the composition can be directly determined with a higher accuracy than STEM-based techniques.
Publisher: Springer Science and Business Media LLC
Date: 26-03-2018
Publisher: American Physical Society (APS)
Date: 29-08-2022
Publisher: Elsevier BV
Date: 2016
Publisher: Elsevier BV
Date: 04-2018
Publisher: Springer Science and Business Media LLC
Date: 21-02-2020
DOI: 10.1038/S41467-020-14820-0
Abstract: An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Publisher: Wiley
Date: 23-01-2007
DOI: 10.1002/SIA.2491
Abstract: This paper reports preliminary results showing that the use of femtosecond laser pulses enables the field evaporation of single atoms, from specimens with a tip‐like shape, without significant specimen heating. It is shown that the field evaporation is assisted by the laser field, which is enhanced by the sub wavelength dimensions of the tip. It is also shown that laser pulsing leads to a high mass resolution, making the use of energy compensating devices in a wide‐angle three‐dimensional atom‐probe ineffectual. In addition, the performances of a position‐sensitive detector that fulfills the wide‐angle 3DAP requirements are presented. The emergence of the third generation of tomographic atom‐probe with (i) wide‐angle analysis capabilities and (ii) a field of application that is extended to poor conductive or insulating materials is then discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 03-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9EE01872G
Abstract: Combination of atom probe tomography, isotope-labelling and online electrochemical mass spectrometry provides direct correlation of atomic scale structure of Ir oxide catalysts with the mechanism of oxygen formation from the lattice atoms.
Publisher: Elsevier BV
Date: 09-2022
Publisher: Elsevier BV
Date: 10-2013
Publisher: Springer Science and Business Media LLC
Date: 06-11-2018
DOI: 10.1557/JMR.2018.375
Publisher: Oxford University Press (OUP)
Date: 28-08-2023
Abstract: Atom probe tomography (APT) is ideally suited to characterize and understand the interplay of segregation and microstructure in modern multi-component materials. Yet, the quantitative analysis typically relies on human expertise to define regions of interest. We introduce a computationally efficient, multi-stage machine learning strategy to identify compositionally distinct domains in a semi-automated way, and subsequently quantify their geometric and compositional characteristics. In our algorithmic pipeline, we first coarse-grain the APT data into voxels, collect the composition statistics, and decompose it via clustering in composition space. The composition classification then enables the real-space segmentation via a density-based clustering algorithm, thus revealing the microstructure at voxel resolution. Our approach is demonstrated for a Sm–(Co,Fe)–Zr–Cu alloy. The alloy exhibits two precipitate phases with a plate-like, but intertwined morphology. The primary segmentation is further refined to disentangle these geometrically complex precipitates into in idual plate-like parts by an unsupervised approach based on principle component analysis, or a U-Net-based semantic segmentation trained on the former. Following the composition and geometric analysis, detailed composition distribution and segregation effects relative to the predominant plate-like geometry can be readily mapped from the point cloud, without resorting to the voxel compositions.
Publisher: Oxford University Press (OUP)
Date: 08-2022
DOI: 10.1017/S1431927621012629
Abstract: Three-dimensional field ion microscopy is a powerful technique to analyze material at a truly atomic scale. Most previous studies have been made on pure, crystalline materials such as tungsten or iron. In this article, we study more complex materials, and we present the first images of an amorphous s le, showing the capability to visualize the compositional fluctuations compatible with theoretical medium order in a metallic glass (FeBSi), which is extremely challenging to observe directly using other microscopy techniques. The intensity of the spots of the atoms at the moment of field evaporation in a field ion micrograph can be used as a proxy for identifying the elemental identity of the imaged atoms. By exploiting the elemental identification and positioning information from field ion images, we show the capability of this technique to provide imaging of recrystallized phases in the annealed s le with a superior spatial resolution compared with atom probe tomography.
Publisher: Elsevier BV
Date: 10-2013
Publisher: Springer Science and Business Media LLC
Date: 10-05-2023
DOI: 10.1038/S42005-023-01203-2
Abstract: Retrieving information on the chemical and bonding states of atoms in a material in three-dimensions is challenging even for the most advanced imaging techniques. Here, we demonstrate that this information is accessible via straight-flight-path atom probe tomography experimental data, however it requires additional processing. Using an activation energy model that involves linear field dependance, and complementing it with DFT simulations, we extract the ion energy loss related to the kinetics of the field evaporation process from the mass peak shape. In turn, we reconstruct how evaporated atoms were originally bound to the surface. We name our data processing approach evaporation energy loss spectroscopy (FEELS), and showcase its application by analyzing microstructural features and defects in an array of metallic materials. Finally, we discuss the general applicability of FEELS to any atom probe data set.
Publisher: American Physical Society (APS)
Date: 09-03-2020
Publisher: Springer Science and Business Media LLC
Date: 25-07-2022
DOI: 10.1038/S41467-022-31964-3
Abstract: The high-strength 7xxx series aluminium alloys can fulfil the need for light, high strength materials necessary to reduce carbon-emissions, and are extensively used in aerospace for weight reduction purposes. However, as all major high-strength materials, these alloys can be sensitive to stress-corrosion cracking (SCC) through anodic dissolution and hydrogen embrittlement (HE). Here, we study at the near-atomic-scale the intra- and inter-granular microstructure ahead and in the wake of a propagating SCC crack. Moving away from model alloys and non-industry standard tests, we perform a double cantilever beam (DCB) crack growth test on an engineering 7xxx Al-alloy. H is found segregated to planar arrays of dislocations and to grain boundaries that we can associate to the combined effects of hydrogen-enhanced localised plasticity (HELP) and hydrogen-enhanced decohesion (HEDE) mechanisms. We report on a Mg-rich amorphous hydroxide on the corroded crack surface and evidence of Mg-related diffusional processes leading to dissolution of the strengthening η-phase precipitates ahead of the crack.
Publisher: IOP Publishing
Date: 18-03-2016
Publisher: Springer New York
Date: 2012
Publisher: Elsevier BV
Date: 06-2012
Publisher: Elsevier BV
Date: 06-2012
Publisher: Elsevier BV
Date: 08-2020
Publisher: Elsevier BV
Date: 04-2018
Publisher: Elsevier BV
Date: 04-2017
Publisher: AIP Publishing
Date: 15-10-2008
DOI: 10.1063/1.3006017
Abstract: The method suggested by Kellogg [J. Appl. Phys. 52, 5320 (1981)] to estimate the temperature of a field emitter under laser pulsing irradiation is reconsidered in the case of a W-Re alloy. It is shown that the temperature obtained using this method is not the absolute temperature, but, if properly calibrated, a value that could be considered as a good approximation of the average temperature reached by the tip when illuminated by picosecond laser pulses.
Publisher: Elsevier BV
Date: 03-2021
Publisher: Wiley
Date: 03-09-2020
Publisher: Oxford University Press (OUP)
Date: 07-2009
DOI: 10.1017/S143192760909881X
Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009
Publisher: Elsevier BV
Date: 12-2018
Publisher: Elsevier BV
Date: 09-2023
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Baptiste Gault.