Browsing by Author "Yang, W"

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    Atomistic characterisation of graphite oxidation and thermal decomposition mechanism under isothermal and non-isothermal heating scheme
    (Elsevier B. V., 2022-07) Cordeiro, IMDC; Yuen, ACY; Wang, W; Yang, W; Chan, QN; Yeoh, GH
    The oxidation of graphene-based material (i.e. graphite, graphene) is a reaction of immense importance owing to its extensive industrial application (i.e. nanocomposites, flame retardants, energy storage). Although immense experimental works were carried out for identifying the thermal degradation and oxidation process of graphene, they generally lack atomistic-level observation of the surface reactions, thermal formation pathways from solid to product volatiles and structural evolutions during oxidation. To analyse the favourable properties of graphene from its carbon-chain molecular structure viewpoint, it is essential to investigate graphene-based materials at an atomic level. This study bridges the missing knowledge by performing quantitative reactive forcefield coupled molecular dynamics simulation (MD-ReaxFF) to determine the oxidation kinetics of graphite under computational characterisation schemes with temperatures ranging from 4000 K to 6000 K. The kinetics parameters (i.e. activation energy) were extracted through proposed numerical characterisation methods and demonstrated good agreement with the thermogravimetric analysis experiments and other literature. Activation energy at 193.84 kJ/mol and 224.26 kJ/mol were extracted under the isothermal scheme by two distinct characterisation methods, achieving an average relative error of 11.3 % and 2.5 % compared to the experiment data, which is 218.60 kJ/mol. In comparison, the non-isothermal simulations yielded 214.53 kJ/mol, with a significant improvement on the average relative error of 1.86 %. © 2022 Elsevier B.V.
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    Controlling spin orientation and metamagnetic transitions in anisotropic van der Waals antiferromagnet CrPS4 by hydrostatic pressure
    (Wiley, 2022-02) Peng, Y; Lin, Z; Tian, G; Yang, J; Zhang, P; Wang, F; Gu, P; Liu, X; Wang, CW; Avdeev, M; Liu, F; Zhou, D; Han, R; Shen, P; Yang, W; Liu, S; Ye, Y; Yang, J
    Controlling the phases of matter is a central task in condensed matter physics and materials science. In 2D magnets, manipulating spin orientation is of great significance in the context of the Mermin–Wagner theorem. Herein, a systematic study of temperature‐ and pressure‐dependent magnetic properties up to 1 GPa in van der Waals CrPS4 is reported. Owing to the temperature‐dependent change of the magnetic anisotropy energy, the material undergoes a first‐order spin reorientation transition with magnetic moments realigning from being almost parallel with the c axis in the ac plane to the quasi‐1D chains of CrS6 octahedra along the b axis upon heating. The spin reorientation temperature is suppressed after applying pressure, shifting the high‐temperature phase to lower temperatures with the emergence of spin‐flop transitions under magnetic fields applied along the b axis. The saturation field increases with pressure, indicating the enhancement of interlayer antiferromagnetic coupling. However, the Néel temperature is slightly reduced, which is ascribed to the suppression of intralayer ferromagnetic coupling. The work demonstrates the control of spin orientation and metamagnetic transitions in layered antiferromagnets, which may provide new perspectives for exploring 2D magnetism and related spintronic devices. © 2021 Wiley-VCH GmbH.
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    Experimental and numerical study on the hemodynamics of stenosed carotid bifurcation.
    (Springer, 2010-12-01) Cheung, SCP; Wong, KKL; Yeoh, GH; Yang, W; Tu, JY; Beare, R; Thanh, P
    Numerical simulation is performed to demonstrate that hemodynamic factors are significant determinants for the development of a vascular pathology. Experimental measurements by particle image velocimetry are carried out to validate the credibility of the computational approach. We present a study for determining complex flow structures using the case of an anatomically realistic carotid bifurcation model that is reconstructed from medical imaging. A transparent silicone replica of the artery is developed for invitro flow measurement. The dynamic behaviours of blood through the vascular structure based on the numerical and experimental approaches show good agreement. © 2010, Springer.
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    Study of structure morphology and layer thickness of Ti3C2 MXene with small-angle neutron scattering (SANS)
    (Elsevier B. V., 2021-07-05) Yuen, ACY; Chen, TBY; Lin, B; Yang, W; Kabir, II; Cordeiro, IMDC; Whitten, AE; Mata, JP; Yu, B; Lu, HD; Yeoh, GH
    MXene is a class of 2D materials exfoliated from ternary carbide and nitride ceramics. During synthesis, etching and delamination conditions affect the quality, overall crystallinity, defects and surface functionalization of MXene flakes. In this article, the morphological structure of MXene (Ti3C2) nanosheets under temperature between 20 °C and 60 °C were investigated with the application of Small-Angle Neutron Scattering (SANS) combined with several complementary techniques, such as Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The SANS analysis enabled structural information to be obtained about the Ti3C2 nanosheets, which consists of layers of transition metal carbides in a multilayer lamella morphology. The results showed that a single Ti3C2 layer is approximately 11.4 – 11.8 Å (1.14 – 1.18 nm) in thickness with a 20.3 – 21.5 Å (2.03 – 2.15 nm) interstacking layer gaps. This results in a total thickness of approximately 32 Å (3.2 nm), which was consistent with the model-dependent lamella model analysis. Furthermore, the thickness of the Ti3C2 layer increased by approximately ~2 Å (0.2 nm) when the temperature increased from 20 - 40 to 50 - 60 °C. © 2021 The Author(s). Published by Elsevier B.V.