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Port Kembla, Australia

Ley K.J.,RMIT University | Shaw L.A.,RMIT University | Yiapanis G.,RMIT University | Yiapanis G.,IBM | And 4 more authors.
Molecular Simulation | Year: 2016

Responsive surfaces have been suggested to enhance longevity and antifouling performance of materials in many applications from industrial coatings to tissue engineering and drug delivery. We present a molecular dynamics study investigating de-swelling and swelling of some of the most commonly used responsive materials - PEG-functionalised silica and polymer surfaces - as a function of hydration and temperature. We show that PEG chains grafted onto the hard silica substrates exhibit a dehydration-induced collapse that is far more pronounced compared to chains grafted onto the soft polyester surface. The difference between the hard and soft substrates is particularly notable at low coverage densities where the chains are sufficiently separated from one another. We also show that inter-molecular hydrogen bonding responsible for the conformational state of the tethered chains in water can be temperature controlled. It can be suggested that the hard substrates with the intermediate-to-high coverage densities of low molecular weight hydrophilic grafts may be more appropriate for anti-fouling applications due to their ability to trap greater amount of water molecules. Soft substrates may be detrimental for the efficient response of the functionalised surfaces to changes in hydration and enhancement of the surface hardness must be considered when designing responsive surfaces for solution-based applications, such as antimicrobial coatings for industry and biomedicine. © 2015 Taylor & Francis.

de Ryck A.,Albi-Carmaux School of Engineering | Zhu H.P.,University of New South Wales | Zhu H.P.,University of Western Sydney | Wu S.M.,University of New South Wales | And 2 more authors.
Powder Technology | Year: 2010

Flows of granular material on 'non-frozen' and 'frozen' heaps are considered numerically and theoretically in this work. The surface flow on a 'non-frozen' heap is first investigated numerically using the discrete element method. The flow profiles of the surface granular flow and the creep motion of particles in the heap are studied. It is shown that the mean velocity of the surface flow exhibits a linear relationship with the distance from the heap surface, while that of the particles in the heap decays exponentially with the distance. The existence of such a creep motion may be attributed to the variation of the porosity distribution of the heap. The granular flow on a 'frozen' static heap is also simulated, and compared with the one on the corresponding 'non-frozen' heap. The results show that the surface conditions of the heap, to some extent, affect the flow upon it. The surface flow on a static heap is then theoretically examined in detail by using a recently developed continuum model. The depth of the steady-state surface flow and its dependence on wall friction and heap width are investigated. In addition, the theoretical results are compared with the DEM simulation results and the experimental ones in the literature, and qualitatively good agreements are observed. © 2010 Elsevier B.V.

Rahman M.,University of New South Wales | Rahman M.,University of Western Sydney | Shinohara K.,Research Laboratory of Particulate Chemical Engineering | Zhu H.P.,University of Western Sydney | And 2 more authors.
Chemical Engineering Science | Year: 2011

The mechanism of particle segregation in forming a conical pile or centrally filling a cylindrical vessel is investigated by applying a Shinohara et al.'s Screening Layer model (1972, 1984 and 1990), where the segregation patterns were measured by a tube-sampling experiment and a DEM simulation. The distribution of mixing ratio of a segregating component of different sizes can be drawn along the pile surface and well correlated with each other for the first time. As a result, the zone, where the segregating component of smaller particle is contained around a central feed point, was found to expand by an increment of the initial mixing ratio, the volumetric feed rate and the flow length of the pile surface. These characteristics are governed by flowability parameters such as velocity ratio, penetration rate and packing rate of the segregating component, which are affected by operating conditions besides particle properties and are to be delved into further. In spite of complicated avalanche phenomena of particles exhibited around the flowing head along the conical pile surface, the present model description consisting of the material balance within the flowing layer was found to be satisfactory in practice with the verifications from the experiments and the microscopic DEM simulation. © 2011 Elsevier Ltd.

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