Advanced Materials Research Vols. 881-883

Abstract: The composites of tetrafluoroethylene-propylene copolymer (TFE-P copolymer)/N, N'-metaphenylene-bis-maleimide (MPBM)/DCP were prepared by mill. The effects of MPBM on the crosslinking density and mechanical properties of TFE-P copolymer were investigated by equilibrium swelling method, MDR rheometer and electric tensile testing machine. The results show that MPBM can efficiently increase the crosslinking density of TFE-P copolymer cured with peroxide. There is a linear relationship between MPBM and the crosslinking density while MPBM is less than 5 phr.; due to the resinification and reinforcing effect of micro-zone of MPBM resin, the crosslinking degree and the modulus of the composite increase faster while MPBM is used more than 5 phr. Perfect network and mechanical properties could be obtained by regulating the amount of MPBM in peroxide curing system.

Abstract: WO₃ doping TiO₂ composites with nanocarbon are prepared by sol-gel and hydrothermal, and the composites are studied by X-ray diffraction (XRD), UV-visible light scanning. The photocatalytic degradation effects of different conditions on the direct scarlet 4BS solution has been Investigated. The results show that doped WO₃ does not change the main structure of TiO₂, but affect its crystalline properties. When WO₃ doping amount is 3.0 mol%, the crystallinity of composite reaches maximum value. The introduction of nanocarbon can improve the crystallinity of composite when the molar ratio of WO₃ doping is 3.0%, the photocatalytic activity is the highest, nanocarbon as a carrier can increase the photocatalyst adsorption capacity to achieve the objective of improving the photocatalytic efficiency when WO₃ and nanocarbon doped TiO₂, the stability of the composite about catalytic activity is excellent.

Abstract: The cross-linking kinetics of an epoxy/amine resin system was studied using the conventional DSC and FTIR spectroscopy, respectively. Conventional DSC was modified to accommodate two fibre optic probes which could be used to monitor the spectra of epoxy/amine resin system during cure. The cross-linking kinetics for the epoxy/amine resin system obtained via the conventional DSC and FTIR and simultaneous DSC/FTIR were similar. The feasibility of using a simple bifurcated fibre optic probe to link the DSC to the FTIR spectrometer was demonstrated.

Abstract: The ZnS-ZnO composite film was successfully prepared by sulfidation of the as-electrodeposited ZnO film in the aqueous solution of zinc nitrate and hexamethylenetetramine. The ZnO film was electrodeposited on the substrate of indium-tin oxide (ITO) glass, and then the sodium sulfide solution was used to convert the ZnO film into the ZnS-ZnO composite film. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectrometer (EDS) and UVvisible absorption. The experimental results show that the composite film on ITO glass still retained the morphology of as-electrodeposited ZnO coating, and is composed of ZnS with cubic structure and ZnO with hexagonal structure.

Abstract: In this paper, the phase compositions and microstructure of MgO-C samples containing Si powder in N₂ sintered at 1350-1500°C were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The α-Si₃N₄, β-Si₃N₄, MgSiN₂ and SiC phases have formed together with MgO and C phases in the sintered samples. The morphologies of β-Si₃N₄ crystals were almost in the shape of rod-like through the α-β phase transformation of Si₃N₄ by Mg-Si-O-N and silicon liquid. The morphologies of α-Si₃N₄ crystals were in the shape of equiaxed. The morphology of MgSiN₂ crystals was in the shape of polyhedron with the size of 5 μm.

Abstract: Abstract: In this study we present a method for the determination of free polyethylene glycol in a gel. We detect the PEG residues of cross-linked sodium hyaluronate gel by spectrophotometry. The pretreatment of cross-linked sodium hyaluronate gel is special and the plot of working curve is unconventional. The precision, the recovery rate with marker, the reliability and repeatability of this method are tested and verified. The results indicated that the method has an excellent linear relationship in the range of 0-40.5µg mL^-1. The regression equation is Y=0.0108X+0.2047 (R2=0.9994). The standard deviation of the detection method is 1.10% (n=9). The recovery rate with marker is 97.8% and the repeatability is perfect. In conclusion, the method possesses the properties of simple operation, quickness, excellent stability. Moreover this method can be applied for the quality control of gel products cross-linked by PEG and liquid samples containing PEG.

Abstract: The in-situ synthesized TiB reinforced titanium matrix composites have been prepared by spark plasma sintering technique at 950–1250°C, using mixtures of 10wt% TiB2 and 90wt% Ti powders. The effects of the sintering temperature on the mechanical properties (Vickers microhardness, yield strength and Young`s modulus) of the composites were investigated. SEM was used to analyze the reaction process and the microstructure of the compacts synthesized at different sintering temperatures. The results indicated that the in situ synthesized TiB grow rapidly with increasing sintering temperature. The composite sintered at 1250°C have the highest relative density of 99.2%. However, the composite sintered at 950°C exhibits the best Vickers microhardness of 4.64GPa and yield strength of 989MPa, respectively.

Abstract: PTFE/Nafion (PN) membranes were fabricated for the application of moderate and high temperature proton exchange membrane fuel cells (PEMFCs), respectively. Membrane electrode assemblies (MEAs) were fabricated by PTFE/Nafion membranes with commercially available low and high temperature gas diffusion electrodes (GDEs).The influence of [ZrOCl₂]/[Nafio wt. ratio of Nafion/ZrOCl₂ solution on the membrane morphology of NFZrP and PEMFCs performance was investigated. And the influence of hybridizing silicate into the PN membranes on their direct methanol fuel cell (DMFC) performance and methanol crossover was investigated. Silicate in PN membranes causes reduction both in proton conductivity and methanol crossover of membranes. Due to the low conductivity of PTFE and silicate, PNS had a higher proton resistance than Nafion-112.The effects of introducing sub-μm porous PTFE film and ZrP particles into Nafion membranes on the DMFC performance were investigated. The influence of ZrP hybridizing process into NF membranes on the morphology of NFZrP composite membranes and thus on the DMFC performance was also discussed.

Abstract: ZrO₂ nano-crystals have been prepared through the integrated process of high-gravity field and hydrothermal crystallization by using ZrOCl_2•8H₂O solution added scale 3mol% yttrium nitrate and precipitator ammonia. Precursor of ZrO₂ powders was prepared by high-gravity field co-precipitation reaction. Then, the precursor crystallized by the hydrothermal method to obtain ZrO₂ powders. The influence of hydrothermal crystallization temperature and hydrothermal crystallization time on crystal structure, morphology and grain size has been investigated. The structure, morphology and grain size of ZrO₂ were characterized by X-ray diffraction(XRD) , transmission electron microscopy( TEM).The sizes of pure tetragonal ZrO₂ nano-crystallites prepared by hydrothermal crystallizing at 175°C-200°C for 1-8h are observed to be typically in the rang of 4-10nm. What’s more, ZrO₂ powders prepared from crystallizing at 200°C for 6h shows great crystallinity , uniformly particle size and low aggregate.

Abstract: Polyvinylpyrrolidone (PVP) has been used to control size and shape of metal nanoparticles in aqueous solution, where PVP plays the dual role of protective and reducing agent. The influence of PVP with different molecular weight on the aspect ratio of nanorods and nanowires during a classical polyol process was studied. Nanowires with higher aspect ratio were obtained by using PVP with higher molecular weight. It is suggested that the reduction rate is decreased with an increase of the molecular weight of PVP, leading to the growth of nanowires with higher aspect ratio.