Advanced Materials Research Vol. 32

Abstract: This paper aims to provide an understanding of the intrinsic frictional behaviour of CNTs under contact sliding by eliminating the possible effects of CNT rolling and slipping. Two critical steps towards the mechanism exploration were carried out: (1) the development of a new deposition method for CNT film fabrication, which allows the manufacture of densely packed, highly entangled CNT films to be firmly bonded on solid substrates for contact sliding testing; and (2) the theoretical understanding of the frictional behaviour of CNTs using the molecular dynamics analysis. The investigation clarified the controversial arguments in the literature and concluded that CNT films can be used as a superior solid lubricant with an ultra-low coefficient of friction of around 0.01.

Abstract: This paper presents the effects of incorporating carbon nanotubes (CNT) into nylon 6 on thermal properties and fire performance of woven glass reinforced CNT/nylon 6 nanocomposite laminates. Incorporation of CNT in nylon 6 improved the thermal stabilities, thermal conductivity and fire performance of laminates without compromising their mechanical properties. The thermal conductivity of laminates with 2 wt% CNT increased up to 42% compared to that without CNT. The ignition time and peak HRR time was delayed approx. 31% and 118%, respectively, in laminates with 4 wt% CNT in nylon 6 over that without CNT.

Abstract: In this paper, TiO2 nanopowders are produced by gas-phase detonation method. The powders are analyzed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and specific surface area determination. The results indicate that the powders are mixed crystal of rutile and anatase, and have good dispersibility and high specific surface area. Also, the particle sizes of powders are between 40 to 200 nm which are spheroid and cube. The measurement data of detonation pressures shows that the reaction took place under a deflagration to detonation transition (DDT).

Abstract: The paper is a short review of the fabrication, wet and dry corrosion, as well as plasma nitridation of novel Ni-Cr nanocomposites. The nanocomposites, fabricated by co-electrodeposition of Ni and nanometer-sized Cr particles, have the nanocrystalline Ni matrix dispersing the second phase of nanoparticles. They, compared to conventionally coarse-grained Ni-Cr alloys, exhibit dramatically increased resistance to liquid corrosion in a 3.5% NaCl solution, and to hot corrosion under molten salt of Na2SO4-Na2SO4-NaCl at 700oC. The reason for these is correlated with the unique structure of the nanocomposite, which guarantees the fast diffusion of chromium from the composite interior to the corrosion front for the formation of a continuous, protective layer of chromium oxide-rich films severing the composites from environmental corrosive species. During plasma nitridation at 560oC the Ni-Cr nanocomposite forms a thick nitriding layer which cannot be achieved on the conventional alloy counterpart with a comparable composition, due to enhanced nitridation kinetics.

Abstract: Reduced gravity experimentation is important to many research groups working in various fields investigating both fundamental and applied aspects of diverse physical phenomena. Very few terrestrial or extra-terrestrial experimental facilities are currently available that allow researchers access to reduced gravity environments. The Queensland University of Technology’s has recently fabricated a purpose built, stand alone 2.0 second drop tower specifically to accommodate reduced gravity experimentation. The specifications and operational procedures of this new research facility are presented. Information concerning current and future areas of research is also presented and discussed. These research areas include: 1) cellular biology, 2) fluid dynamics and multiphase flow, 3) nanomaterial production including silica sol-gels and carbon nanotubes, and 4) heterogeneous combustion with a focus on bulk metallic materials burning in oxygen enriched atmospheres performed in collaboration with NASA and industry partners. Discussion on the use of the new research facility in the production of advanced materials for earth-based applications will be presented. Opportunities will also be discussed regarding both collaborative research and the provision of reduced gravity test services.

Abstract: It is well known that environmental conditions impact the performance of thermoplastic articles, therefore requiring selection of appropriate raw materials. Nevertheless, frequently due to business reasons, when selecting a material, the rigor of understanding the fundamental physical events responsible for the desired performance is shortchanged. In this study, we investigate the effects of cyclic heat history on the dimensional stability of articles made with commercial grade rigid thermoplastic resins, particularly, in the temperature range close to the material’s glass transition temperature, as more materials are used in hot & arid environments. The two physical events identified as most relevant to desired article performance are the relaxation of the processinduced residual stresses within the material and the dynamic phenomena brought about by the material’s coefficient of thermal expansion, CTE. We find that the periodic development of convexconcave surfaces on an article matches the periodic development of a non-uniform temperature gradient within the article. We demonstrate that this periodic heat exposure leads to an irreversible concave deformation of the article’s exposed surface. Moreover, articles exhibit this deformation phenomenon regardless of the level of the initial process-induced stresses. We offer explanations of these behaviors and discuss their practical implications.

Abstract: Carbon nanotube (CNT) can be thought of as a hexagonal network of carbon atoms that has been rolled up to make a seamless cylinder. If they are consisting of one layer, they are termed singled-walled CNTs (SWNTs) while if there are multiple walls, they are called multi-walled CNTs (MWNTs). For most functional devices application, an aligned arrangement of CNTs is desired. Aligned multiwalled carbon nanotubes (MWNTs) have been successfully grown by the inclusion of a buffer layer of oxidized Al. An Al2O3 layer has been proven to be an important contributing factor towards obtaining good quality aligned CNTs. In this work, Al is deposited onto the Si wafer using electron beam evaporation and later oxidized by heating in air. A thin layer of iron catalyst is then deposited on top of the oxidized Al layer and annealed at 400oC. The result shows an improvement in the intensity of the graphitization peak (G-band) in the Raman spectra and aligned MWNTs is observed in these samples compared to the ones that have undergone the same process parameter except the Al2O3 layer.