Advanced Materials Research Vols. 284-286

Abstract: Poly(lactic acid) (PLA)/graphene nanocomposites were prepared by solution blending using chloroform as a mutual solvent. Transmission electron microscopy (TEM) was used to examine the quality of the dispersion of graphene in the PLA matrix. The isothermal crystallization behaviors of PLA and PLA/graphene nanocomposites were investigated by differential scanning calorimetry (DSC). The isothermal crystallization kinetics were analyzed by Avrami model based on the DSC data. The results showed that the well dispersed graphene nanosheets could act as a heterogeneous nucleating agent and lead to an acceleration of crystallization during the PLA isothermal crystallization process. According to the Arrhenius equation, the activation energies were found to be -106.9 and -46.6 kJ/mol for pure PLA and PLA/0.1 wt % graphene nanocomposite, respectively. The crystal morphology were characterized with polarizing optical microscope (POM).

Abstract: The polyaniline(PANI)-poly(vinyl alcoho1)(PVA) composite film doped with HC1 was prepared with PVA as matrix. Effects of PVA content, film drying temperature on properties of PANI-PVA composite film were studied. Tensile strength, elasticity, conductivity and thermal stability of PVA, HC1-PANI or PANI-PVA were compared. Tensile strength and elasticity of PVA film were the largest, its conductivity was the least. The conductivity of PANI-PVA was the largest, tensile strength and elasticity of PANI-PVA are bigger than those of HC1-PANI. The order of their thermal stability is PVA> HC1-PANI > PANI-PVA before 260°C, the order of their thermal stability is HC1-PANI>PANI-PVA> PVA after 260°C.

Abstract: The magnesium hydroxide (MH) whiskers were modified with 3-(trimethoxysilyl) propyl methacrylate (γ-MPS) followed by in situ copolymerization of styrene. The high impact polystyrene (HIPS)/MH composites were prepared by melt compounding of HIPS with untreated MH whiskers and modified MH whiskers (MMH), respectively. Their morphological structure and rheological properties were characterized by scanning electron microscopy and capillary rheometer. The results show that the HIPS/MH composites are a shear-thinning non-Newtonian, its apparent viscosities are bigger than those of the HIPS melt. With increasing MH loading, apparent viscosity of HIPS/MH composites increase. The PS encapsulated on MH whiskers surface enhanced the interface adhesion between inorganic particles and HIPS matrix and improved the flow abilities of the HIPS/MH composites melts.

Abstract: Reference to traditional optimization methods, neural network based on improved genetic algorithm is used in optimization of reversed phase chromatography pluralistic isocratic mobile phase separation conditions. With detailing the combination of the improved genetic algorithm and neural network theory, the optimization process for the liquid chromatography conditions is introduced in details. Used this method to small peptide RP chromatography optimization, after searching operation, the establishment of an effective separation of forecast model receives satisfactory predictive value, which can prove that this method can be used in optimization of drug liquid chromatography conditions.

Abstract: An in-situ synthesis process combining an infiltration casting with a subsequent heat treatment was applied to fabricate special tungsten carbide (WC) bundles-reinforced iron matrix composites in this work. The microstructure and wear-resistance of the tungsten carbide bundles reinforced iron matrix composites were studied by using scanning electron microscopy, X-ray diffraction and wear tester. Results showed that the tungsten carbide bundles distributed in the matrix with the center-to-center spacing 2.2 mm, and the diameter of each tungsten carbide bundle is about 1 mm. Most of the tungsten carbides agglomerated, but still there were tungsten carbide particles and the size of tungsten carbide particle was about 10—15 μm. The weight loss of the tungsten carbides bundle reinforced iron matrix composites increased with the increase of the loads and the weight loss of the composites is much less than those of the gray cast iron under the same condition. The wear mechanism of tungsten carbide bundles-reinforced iron matrix composites appears as: micro-cutting, micro-ploughing, broken tungsten carbide and broken particles re-embedded in the matrix.

Abstract: Niobium carbide (NbC) particulates -reinforced iron matrix composites were prepared by in- situ fabrication method combining an infiltration casting with a subsequent heat treatment. The microstructure and wear-resistance of NbC particulate-reinforced iron matrix composites were studied using scanning electron microscopy, X-ray diffraction, and wear testing. The results indicate that at 1172 °C for 3 hours NbC particulate-reinforced iron matrix composites were fabricated, and the size of NbC reinforcement was 0.3–3.5 μm. The relative wear resistance of the composites was 5.4 times higher than that of gray cast iron under a 20 N load. This was achieved at 22 % NbC volume fraction. Wear of the composites manifests as grooves, broken carbide particulates and some micro-cracks.

Abstract: The method of infiltration casting plus heat treatment process employing chromium wires and cast iron applied to in-situ synthesized (Fe,Cr)₇C₃ particulates bundle reinforced iron matrix composites. The phase analysis, microstructure, microhardness and wear-resistance of composite were observed and measured. The results show that it is possible to fabricate (Fe,Cr)₇C₃ particulates bundle reinforced iron matrix composite produced by this technology, and a special structure which called particulates bundle was fabricated. (Fe,Cr)₇C₃ particulates bundle were distributed in the forms of granular, lath-shaped and hexagon-shaped in the particulates bundle. The macrohardness of particulates bundle was 52 HRC, and the relative wear resistance of the composites is 2.3—23 times higher than that of the cast iron.

Abstract: Surfaces of jute fiber needled mats were treated by alkali, potassium permanganate and A-151 silane coupling respectively, and those reinforced vinyl resin composites were made by VARTM method . The changes of the surface energy of the jute fiber mats were analyzed basing on the dynamic contact angle, and the surface of the jute fiber and the interface morphology of the composites were observed by SEM. The results showed that interface compatibility and the comprehensive properties of the composites were improved evidently, because the surface energy of the jute fiber was lowered and the surface micro-structures of the fiber were changed. Especially, the tensile strength and flexural strength of the composites treated by A-151 silane coupling increased by 63.08% and 94.79% respectively.

Abstract: In locally long fiber reinforced aluminum parts two types residual stresses exist. They are the microscopic residual stress between fiber and matrix and the macroscopic residual stress between reinforced and unreinforced zones. The residual stresses between fiber and matrix in γ-Al₂O₃ long fiber reinforced aluminum alloy Al-6-1-1 were measured with X-ray Diffraction process as well as simulated with FEM method. The results indicated that the residual stresses in both fiber and matrix were distributed very unequally. The maximum tensile residual stress occurred at the boundary in the matrix and the maximum compressive residual stresses occurred near the boundary in the fiber. The macroscopic residual stresses between the reinforced and unreinforced zones were also measured with borehole method as well as simulated with FEM. It was found that the macroscopic residual stresses at most locations in both the reinforced and unreinforced zones were not harmfully high. However in both reinforced and unreinforced zones there were small sub-zones of very large tensile residual stresses.

Abstract: 2-propylamino-4,6-(O,O’-dibuthyldithiophosphate)-s-1,3,5-triazine(DPOB)was synthesized and it’s tribological behavior as lubricant in rapeseed oil (RSO) were evaluated using a four-ball tester. The lubrication mechanism was investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The results indicate that the compound possess excellent load-carrying capacity and antiwear ability, and has some friction-reducing property only under the low load condition. Based on the results of XPS and SEM analysis, it can be seen that tribochemical reaction occurred between the synthesized compounds and metal surfaces during the sliding process, to form a complex film which has excellent load-carrying capacity and antiwear ability.