Applied Mechanics and Materials Vols. 423-426

Abstract: PAN/POSS nanofibers membrane with different content POSS have been prepared by electrospinning. The morphology and thermal properties of PAN/POSS nanofibers are characterized by SEM and DSC, respectively. The addition of different content of POSS into PAN matrix have a slight effect on the diameter of nanofibers. Compared to pure PAN fibers, the exothermic peak shift to higher temperatures by 6.8°C when POSS loading is 3wt%, and the corresponding Tg have increased 17.3°C.

Abstract: Waterbased phenolic resin/silica hybrid material was prepared by situ polymerization using TEOS (tetraethyl orthosilicate) as precursor. Effects of pre-hydrolysis condition of TEOS and TEOS content on the formation and stabilization of the hybrid material were studied. The flammability of the prepared composite material was studied by TGA (Thermo gravimetric analysis), LOI (limited oxygen index) and UL-94 test. The results show that stable waterbased hybrid material can be prepared when the amount of ammonia is 0.020g. TGA, LIO and UL-94 test result show that the hybrid material presents better flame retardancy.

Abstract: The single and synergism effect of SiC and ZrO₂ nanoparticles on low temperature oxidation resistance of MoSi₂ were investigated by thermo-gravimetric analysis (TGA), phase and micrograph analysis of surface film. The results show that at the oxidation temperature of 600°C, the addition of 10%ZrO₂ results in obvious oxidation mass gain of MoSi_2, and discontinuous protective film forming on the surfaces, which makes “pesting” phenomenon still occur. The addition of 10%SiC accelerates the oxidation of MoSi₂, but compact SiO₂ protective film formed on the surface after some time of oxidation, avoiding the occurrence of large scope of “pesting” phenomenon. The synergism of 10%ZrO₂ and 10%SiC promotes the formation of compact, even silicate glass film on the surface of MoSi₂, as a result, significantly improves the low temperature oxidation resistance of MoSi₂.

Abstract: In order to study the physical nature and basic rule of diamond wire saw slicing SiCp-Al composites, the slicing mechanism was studied in theory first. There are different ways of slicing Al and SiC particles respectively: Al is sliced in plastic way and SiC particles are sliced in brittle ways such as being cut off or pulled out or pressed into matrix or burst. Then based on the finite element software Abaqus, the process of diamond wire saw slicing SiCp-Al composites was simulated. The distribution of internal stress and surface topography was discussed: The internal stress in SiC particles is far high than that in Al. The surface topography of sliced SiCp-Al composites is determined by SiC particles states mainly. The research results provide reference and guidance to the optimization of actual process of diamond wire saw slicing SiCp-Al composites.

Abstract: Porous peanut-like Sm-doped BiVO₄ sub-microstructures were synthesized via a hydrothermal process with bismuth nitrate, ammonium metavanadate and Sm (NO₃)₃ as raw materials. The crystal structures, morphologies, and optical properties of the as-prepared samples were characterized by X-ray powder diffraction, transmission electron microscope, scanning electron microscopy, and UV-visible absorption spectra. Simulated solar light induced photocatalytic degradation of Rhodamine B by porous peanut-like Sm-doped BiVO₄ sub-microstructures have been investigated, and results show the 2% Sm-doped BiVO₄ porous sub-microstructures with higher photocatalytic activity than other samples.

Abstract: Sliding wear behavior of the (NbSe₂+SiC)/Cu composite was studied on a pin-on-disc wear tester under various electrical currents and applied loads. The worn surfaces were characterized using scanning electron microscopy and energy dispersive spectroscopy to probe the wear mechanisms. Experiment results show that the friction coefficient and wear rate of (NbSe₂+SiC)/Cu composite increased with increasing of the normal load. Adhesive wear, abrasive wear and fatigue wear were the main wear mechanism during the sliding process.

Abstract: Effects of atomic oxygen (AO) irradiation on the structural and tribological behaviors of MoS₂ filled polyimide (PI) composites were studied by using ball-on-disc tribometer, infrared spectra, X-ray photoelectron spectroscopy and scanning electron microscopy. It was found that the irradiation of AO induced the destruction of polymer molecular structures and formation of volatile products which induced the change of the structure, morphology and tribological properties of samples. The addition of MoS₂ filler significantly increased the AO resistance of PI composites due to the formation of MoO₃-rich skin layers during AO process. The addition of MoS₂ improved the tribological properties of PI before and after AO irradiation.

Abstract: A diamond-structure alumina photonic crystal with a rectangle cavity defect has been fabricated combining stereolithography (SL) and gel-casting. In transmission spectra a resonance peak of transmission of 70% is observed in the band gap of 10.48Ghz-12.21Ghz, by comparing with the measured result of the perfect structure and theoretical calculations. Experimental results showed that the peak of photonic band gap was caused by the rectangle cavity defect of the diamond structural photonic crystal. The method provides us with a novel approach to fabricate ceramic microwave photonic crystals with point defect.

Abstract: Carbon nanotubes/zirconia/hydroxyapatite biocomposites was prepared by hot-pressing sintering under Ar atmosphere. The influence of sintering temperature on the mechanical properties and microstructure of carbon nanotube/zirconia/hydroxyapatite biocomposites was studied. We tested the bending strength and fracture toughness by universal electronic materials testing machine. The component of the composites was tested by XRD. The fracture surface of the composites was observed by SEM. The results indicate that the bending strength and fracture toughness of the composites is lower when the sintering temperature is lower than 1200°C. The difference of bending strength and fracture toughness at 1200°C and 1300°C is little. The number of them has risen markedly than the low temperature which reached to189.2MPa and 1.8MPa·m^-1/2 respectively. The composition of the composites is mainly of hydroxyapatite, zirconia, carbon nanotubes, and a small amount of calcium phosphate, which indicated that part of the hydroxyapatite has decomposed. SEM photographs show that the fracture surface of the composites sintered at 1200 °C and 1300 °C is ductile fracture status and has bigger density.