Advanced Materials Research Vols. 557-559

Abstract: Silane coupling agent KH-570 was applied to modify the surface capability of the alumina (Al₂O₃). The modified Al₂O₃ were dispersed in styrene. The in-situ polymerization was used to prepare the polystyrene/alumina (PS/Al₂O₃) composites, in which azodiisobutyronitrile (AIBN) was used as initiator. FTIR, DSC and TG were applied to characterize the prepared composites. The solvent resistance, thermal resistance of the composites and the average molecular weight of PS in PS/Al₂O₃ nanocomposites were studied. The experimental results demonstrated that the solvent resistance of PS/Al₂O₃ nanocomposites was improved by the adding of Al₂O₃ nanoparticles. The thermal resistance of the composites increased with the increasing of the Al₂O₃ content. Meanwhile, the molecular weight of PS in the composites increased with the increasing of the Al₂O₃ content.

Abstract: In this study, germanium nanowires (GeNWs) were grown directly on gold-evaporated germanium substrates by a solid-liquid-solid (SLS) mechanism in the temperature range 550°C- 650°C. The growth of GeNWs is very sensitive to the growth temperature and only in a limited temperature range (575°C-625°C) can GeNWs having excellent morphology and high surface density be successfully grown. These long, thin, and straight GeNWs have a high aspect ratio and are surrounded by an oxide layer. The composition of corresponding oxide layers is GeO_x (x<2). As the thickness of Au film is decreased from 9 nm to 1 nm, the average diameter of GeNWs decreases from 119.3 nm to 38.5 nm. Our experimental results demonstrate that the diameter of germanium nano¬wires can be controlled by the thickness of Au metal film.

Abstract: This perspective reviews recent developments in the adsorption behavior and the adsorption kinetics of gold nanoparticles(AuNPs),with emphasis on papers initiating the developments and with an eye to their consequences. The aspect adsorption behavior of organic molecules on AuNPs have included the adsorption pattern of thionine, 1,4-PDI , 4-Methoxypyr-idine, 1,2,3-triazole and SH-PEG5K and the influence of adsorption. The aspect adsorption characteristics of biomolecules on AuNPs have included the adsorption kinetics of single-stranded DNA and proteins on the AuNPs. The last key aspect adsorption AuNPs on self-assembled monolayers have included the adsorption kinetics of AuNPs on different SAMs and semiconductor crystals.

Abstract: Polytetrafluoroethylene (PTFE) nanocomposites filled with alumina nanoparticles were prepared by compression molding and follow-up sintering. The tribological behaviors of PTFE nanocomposites sliding against GCr15 steel were evaluated using ball-on-disk tribology test rig. The worn surfaces of the unfilled and filled PTFE nanocomposite were investigated using a scanning electron microscope (SEM). The wear behavior of the PTFE nanocomposites was explained in terms of the topography of worn surfaces. It was found that the addition of alumina nanoparticles was effective in enhancing the wear resistance of the PTFE nanocomposite.

Abstract: UV resistance of hybrid nanocomposite films of γ-Glycidoxypropyltrimethoxysilane (GPTMS)/TiO₂-ZrO₂ prepared by Tetrabutoxytitanate, Zirconium n-tetrabutanoxide and GPTMS via sol-gel method were analyzed by observation of the film appearance, thermal gravimetric analysis (TGA), UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR) before and after UV irradiation. It was found that cracks on the hybrid films increase with irradiation time, total inorganic content and the content of TiO₂. The transmittance of the hybrid film increased with the increase of ZrO₂ content, which blocks part of the photo catalysis effect of TiO₂. When the ZrO₂ content increased to equal with TiO2, UV resistance of the hybrid film approaches that of pure ZrO2. The irregular behavior of yellow index data indicates that the deterioration in transmittance is caused by cracks mainly. FTIR results show that the hybrid film of TiO₂/ZrO₂(3/1) (T₃Z) still retains a stronger photo catalysis effect, after UV irradiation, the peak indicating the concentration of –OH enlarged greatly, while that of the pure ZrO₂ hybrid film remains unchanged.

Abstract: Carbon nanotube (CNT) is one of the most attractive materials for the potential applications of nanotechnology due to its excellent mechanical, thermal, electrical and optical properties. We demonstrated the fabrication of carbon nanotube and carbon nanofiber (CNF) inside the pore and at the surface of anodic aluminum oxide (AAO) membrane by chemical vapor deposition method at atmospheric pressure. Ethanol was used as a hydrocarbon source and Co–Mo as catalyst. CNT was synthesized at different temperature. High graphitic multiwall carbon nanotube (MWCNT) was found at 750°C, while CNF was found at 800°C and above temperature analyzing by Raman spectroscopy.

Abstract: CeO₂ hollow nanospheres with average diameter of 500 nm have been fabricated through a template-assisted approach at 200 °C. A possible formation mechanism has been briefly discussed.

Abstract: A novel ultrafine polyethylene/silica composite particle with core-shell structure was prepared by the sol-gel method in the presence of the melt polyethylene emulsion. A series of samples with different polyethylene content were prepared to investigate the unique characteristics of this original composite particle. The core-shell structure and composition of the composite particle was proved by the transmission electron microscopy observation and Fourier transform infrared spectra. The composite particles possess a spherical morphology and the mean size is about 160nm, presented by the scanning electronic microscope observation and nanoparticle tracking analysis, respectively.

Abstract: A relative standard deviation (RSD) method has been developed to evaluate the nanocatalyst dispersibility in an energetic polymer. The dispersibility of nanocatalyst and thermal characteristics of the polymer exhibits high dependence on the RSD of the concentration distributions of nanocatalyst. The improvement of the dispersibility of nanocatalyst, which is dependent on kneading time, can be presented by a decrease in the RSD of the concentration distributions. Moreover, the decomposition temperature and the combustion heat of the polymer is reduced gradually and enhanced distinctly, respectively, with the decrease of the RSD of the nanocatalyst distributions. However, over-kneading may lead to a reunion of nanocatalyst and a decline of thermal characteristics of the energetic polymer, and presented with an increasing of the RSD of the concentrations of nanocatalyst. The optimal kneading time is 3 h and an acceptable value of the RSD is approximately 1% of the concentration distributions of nanocatalyst for the energetic polymer with nanometer copper oxide catalyst.

Abstract: Green copolymers as phase change material were prepared by grafting polyethylene glycol(PEG) onto a rigid molecular skeleton of cellulose nanocrystals (CNs), and their thermal properties were studied by thermal delay method and differential scanning calorimetry. The influences of the CNs on the thermal conductivity behavior and thermal energy storage capacity of the copolymers were evaluated. As expected, a great enhancement on thermal conduction can be achieved by introducing CNs.