Browsing by Author "Yang, W"
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- ItemAtomistic 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, GHThe 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.
- ItemExperimental 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, PNumerical 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.
- ItemStudy 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, GHMXene 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.