ORCID Profile
0000-0002-0031-6190
Current Organisation
University of Sydney
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: Elsevier BV
Date: 07-2020
Publisher: American Chemical Society (ACS)
Date: 10-11-2017
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.MICRON.2017.06.001
Abstract: Quantification of microstructure, especially grain size, in polycrystalline materials is a vital aspect to understand the structure-property relationships in these materials. In this paper, representative characterization techniques for determining the grain size, including optical microscopy (OM), electron backscatter diffraction (EBSD) in the scanning electron microscopy (SEM), and atomic force microscopy/magnetic force microscopy (AFM/MFM), are thoroughly evaluated in comparison, illustrated by rare-earth sintered Nd-Fe-B permanent magnets. Potential applications and additional information achieved by using aforementioned characterization techniques have been discussed and summarized.
Publisher: Springer Science and Business Media LLC
Date: 05-2022
DOI: 10.1007/S10853-022-07227-3
Abstract: A series of novel CoCrFeNi-based high-entropy alloys containing Sc and C were designed. These HEAs exhibited hardness, fracture toughness and wear resistance comparable or better than a range of selected benchmark systems. Microstructurally, we observed composite microstructures comprising variously a Sc-rich intermetallic phase, a sigma phase and an FCC solid solution phase within which precipitated M 23 C 6 carbides. The Sc-rich intermetallic phase possessed a stoichiometry close to (Co, M) 2 (Sc, M), where M = Ni and Fe. As the carbon content increased, the hardness levels ‘softened’ from 799 VHN (C-free) to 674 VHN (C = 4 at.%), though the fracture toughness was increased ~ 112%. At the same time, the specific wear rate was enhanced from 0.33 × 10 −3 to 0.14 × 10 −3 mm 3 ·(N m) −1 . The effectiveness of these microstructures in balancing high hardness, crack deflection and a relatively low wear rate was attributed to the enhanced stability of the FCC solid phase as the C content was increased. Graphical abstract
Publisher: Springer Science and Business Media LLC
Date: 28-03-2022
DOI: 10.1007/S40192-022-00257-4
Abstract: Two methods used to construct a microstructural representative volume element (RVE) were evaluated for their accuracy when used in a crystal plasticity-based finite element (CP-FE) model. The RVE-based CP-FE model has been shown to accurately predict the complete tensile stress–strain response of a Ti–6Al–4V alloy manufactured by laser powder bed fusion. Each method utilized a different image-based technique to create a three-dimensional (3D) RVE from electron backscatter diffraction (EBSD) images. The first method, referred to as the realistic RVE (R-RVE), reconstructed a physical 3D microstructure of the alloy from a series of parallel EBSD images obtained using serial-sectioning (or slicing). The second method captures key information from three orthogonal EBSD images to create a statistically equivalent microstructural RVE (SERVE). Based on the R-RVEs and SERVEs, the CP-FE model was then used to predict the complete tensile stress–strain response of the alloy, including the post-necking damage progression. The accuracy of the predicted stress–strain responses using the R-RVEs and SERVEs was assessed, including the effects of each microstructure descriptor. The results show that the R-RVE and the SERVE offer comparable accuracy for the CP-FE purposes of this study.
Publisher: Springer Science and Business Media LLC
Date: 31-05-2023
DOI: 10.1038/S41586-023-05952-6
Abstract: Titanium alloys are advanced lightweight materials, indispensable for many critical applications 1,2 . The mainstay of the titanium industry is the α–β titanium alloys, which are formulated through alloying additions that stabilize the α and β phases 3–5 . Our work focuses on harnessing two of the most powerful stabilizing elements and strengtheners for α–β titanium alloys, oxygen and iron 1–5 , which are readily abundant. However, the embrittling effect of oxygen 6,7 , described colloquially as ‘the kryptonite to titanium’ 8 , and the microsegregation of iron 9 have hindered their combination for the development of strong and ductile α–β titanium–oxygen–iron alloys. Here we integrate alloy design with additive manufacturing (AM) process design to demonstrate a series of titanium–oxygen–iron compositions that exhibit outstanding tensile properties. We explain the atomic-scale origins of these properties using various characterization techniques. The abundance of oxygen and iron and the process simplicity for net-shape or near-net-shape manufacturing by AM make these α–β titanium–oxygen–iron alloys attractive for a erse range of applications. Furthermore, they offer promise for industrial-scale use of off-grade sponge titanium or sponge titanium–oxygen–iron 10,11 , an industrial waste product at present. The economic and environmental potential to reduce the carbon footprint of the energy-intensive sponge titanium production 12 is substantial.
Publisher: Elsevier BV
Date: 12-2021
Publisher: Elsevier BV
Date: 09-2020
Publisher: Elsevier BV
Date: 02-2022
Publisher: Elsevier BV
Date: 12-2022
Publisher: Elsevier BV
Date: 02-2020
Publisher: American Physical Society (APS)
Date: 14-05-2018
Publisher: American Chemical Society (ACS)
Date: 27-09-2016
Abstract: Intentional and unintentional doping in semiconductor nanowires undoubtedly have significant impact on the device performance. However, spatially resolved precise determination of dopant concentration is challenging due to insufficient sensitivity and resolution of conventional techniques. In this paper, quantitative 3D distribution of Si and Zn dopants in planar GaAs nanowires and their interface with AlGaAs film underneath are obtained by using a unique atom probe tomography technique, providing critical insights for the growth and potential applications of these nanowires.
Publisher: Elsevier BV
Date: 10-2021
Publisher: Elsevier BV
Date: 09-2021
Publisher: Elsevier BV
Date: 10-2022
Publisher: Wiley
Date: 24-06-2019
Publisher: Elsevier BV
Date: 12-2023
Publisher: Elsevier BV
Date: 08-2022
Publisher: Elsevier BV
Date: 06-2022
Publisher: Elsevier BV
Date: 12-2020
Publisher: Elsevier BV
Date: 08-2021
Publisher: Wiley
Date: 19-06-2017
Abstract: III–V ternary InGaAs nanowires have great potential for electronic and optoelectronic device applications however, the 3D structure and chemistry at the atomic‐scale inside the nanowires remain unclear, which hinders tailoring the nanowires for specific applications. Here, atom probe tomography is used in conjunction with a first‐principles simulation to investigate the 3D structure and chemistry of InGaAs nanowires, and reveals i) the nanowires form a spontaneous core–shell structure with a Ga‐enriched core and an In‐enriched shell, due to different growth mechanisms in the axial and lateral directions ii) the shape of the core evolves from hexagon into Reuleaux triangle and grows larger, which results from In outward and Ga inward interdiffusion occurring at the core–shell interface and iii) the irregular hexagonal shell manifests an anisotropic growth rate on {112}A and {112}B facets. Accordingly, a model in terms of the core–shell shape and chemistry evolution is proposed, which provides fresh insights into the growth of these nanowires.
Publisher: American Astronomical Society
Date: 28-12-2017
Publisher: Oxford University Press (OUP)
Date: 18-02-2019
DOI: 10.1017/S1431927619000114
Abstract: Covering a broad optical spectrum, ternary In x Ga 1− x As nanowires, grown by bottom-up methods, have been receiving increasing attention due to the tunability of the bandgap via In composition modulation. However, inadequate knowledge about the correlation between growth and properties restricts our ability to take advantage of this phenomenon for optoelectronic applications. Here, three different InGaAs nanowires were grown under different experimental conditions and atom probe tomography was used to quantify their composition, allowing the direct observation of the nanowire composition associated with the different growth conditions.
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.ULTRAMIC.2018.09.003
Abstract: In this work, the nano-textured surface of a GaN-based vertical light emitting diode (VLED) is characterized using a unified framework of non-destructive techniques (NDT) incorporating scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy, Photoluminescence (PL), and X-ray diffraction (XRD) to optimize the light output efficiency. The surface roughness of ∼300 nm is revealed by AFM. Compressive stress-state of 0.667 GPa in the GaN surface is indicated by the E
Publisher: Elsevier BV
Date: 03-2020
Publisher: Elsevier BV
Date: 02-2019
Publisher: American Chemical Society (ACS)
Date: 27-07-2021
Publisher: Springer Science and Business Media LLC
Date: 10-06-2020
Publisher: American Chemical Society (ACS)
Date: 10-07-2017
Abstract: In this work, Ag as a highly reflective mirror layer of gallium nitride (GaN)-based blue vertical light-emitting diodes (VLEDs) has been systematically investigated by correlating scanning electron microscopy/energy dispersive X-ray spectroscopy/transmission Kikuchi diffraction/electron backscatter diffraction, aberration-corrected scanning transmission electron microscopy, and atomic force microscopy techniques. In the context of high-efficiency lighting, three critical aspects have been scrutinized on the nanoscale: (1) chemical diffusion, (2) grain morphology, and (3) surface topography of the Ag layer. We found that nanoscale inhomogeneous distribution of In in InGaN/GaN quantum wells (QWs), interfacial diffusion (In/Ga out-diffusion into the Ag layer and diffusion of Ag into p-GaN and QWs), and Ag agglomeration deteriorate the light reflectivity, which account for the decreased luminous efficiency in VLEDs. Meanwhile, the surface morphology and topographical analyses revealed the nanomorphology of the Ag layer, where a nanograin size of ∼300 nm with special nanotwinned boundaries and an extremely smooth surface of ∼3-4 nm are strongly desired for better reflectivity. Further, on the basis of these microscopy results, suggestions on light extraction optimization are given to improve the performance of GaN-based blue VLEDs. Our findings enable fresh and deep understanding of performance-microstructure correlation of LEDs on the nanoscale, providing guidance to the design and manufacture of high-performance LED devices.
Publisher: Elsevier BV
Date: 03-2020
DOI: 10.1016/J.BIOMATERIALS.2019.119748
Abstract: Understanding the pathways and mechanisms of human tooth decay is central to the development of both prophylaxes and treatments, but only limited information is presently available about the initiation of caries at the nanoscale. By combining atom probe tomography and high-resolution electron microscopy, we have found three distinct initial sites for human dental enamel dissolution: a) along the central dark line (CDL) within carbonated apatite nanocrystals, b) at organic-rich precipitates and c) along high-angle grain boundaries. 3D maps of the atoms within hydroxyapatite nanocrystallites in sound and naturally-decayed human dental enamel reveal a higher concentration of Mg and Na in the CDL. The CDL is therefore thought to provide a pathway for the exchange of ions during demineralization and remineralization. Mg and Na enrichment of the CDL also suggests that it is associated with the ribbon-like organic-rich precursor in amelogenesis. Organic-rich precipitates and high-angle grain boundaries were also shown to be more vulnerable to corrosion while low-angle grain boundaries remained intact. This is attributed to the lower crystallinity in these regions.
Publisher: Elsevier BV
Date: 11-2022
Publisher: Elsevier BV
Date: 12-2020
No related grants have been discovered for Hansheng Chen.