Advanced Materials Research Vols. 399-401

Abstract: The emphasis of this study was surface modification on MWNTs by dielectric barrier discharge plasma at atmospheric pressure. The effects of the plasma treatment on the MWNTs were characterized by SEM, XRD and FT-IR. The results show that surface of carbon nanotubes (CNTs) emerge carboxyl group, and the plasma modified CNTs by a physico chemical adsorption without structural damage. Modified CNTs/ferrite/polyimide nanocomposites, were prepared and mechanical test demonstrate the low temperature plasma treatment is an effective way to improve interfical bonding bewteen CNTs and polyimide (PI) matrix.

Abstract: Mo₂FeB₂ cermets were prepared by in-situ reaction and vacuum liquid phase sintering technology which used Mo powder, Fe powder and FeB powder as raw materials. Added with the different content of Cr, Ni, the influence on microstructure and properties of the alloy were studied, and the distribution and phase of the alloy was investigated by SEM, EDS, XRD. The results show that Ni only exists in the binder of the cermets, Cr exists in both hard phase and binder and produces the particles of Mo₂FeB₂ fine grain size, With 10%wt of Cr, 2%wt of Ni added, comprehensive mechanics performance of the material is best and the bending strength was highest with high hardness.

Abstract: The polyacrylonitrile short fibers/ room temperature vulcanizing silicone rubber (PAN/RTV silicone) composites were prepared by mechanical mixing method and vulcanization at room temperature for 7 days as internal insulator. The effects of the content of fiber on the mechanical and ablative performances for the composites were investigated. The results show that with increasing content of PAN fiber filled, the tensile strength increases, the break elongation decreases, and the ablation rate(Rt) of PAN/silicone composites decreases rapidly at first, then increases. When PAN fiber content is 10phr, the ablation rate(Rt) is 0.06mm/s.

Abstract: Zinc Oxide (ZnO) nanoparticles were firstly synthesized by the hydration of alkoxide. The as-synthesized ZnO were dispersed in the polyvinylpyrrolidone (PVP) solution. PVP/ZnO composite nanofibers were prepared via electrospinning the PVP/ZnO mixed solution. The morphology of ZnO nanoparticles and as-spun nanofibers was measured by scanning electron microscopy (SEM). The as-synthesized ZnO nanoparticles were homogeneous and stable, and their size ranged from 30 to 40 nm. The composite nanofibers showed a uniform and continuous morphology. With the increase of the ZnO content in the composite nanofibers, the diameter distribution of the composite nanofibers became wider. Transmission electron microscopy (TEM) images clearly showed that ZnO nanoparticles were distributed uniformly in the PVP/ZnO composite nanofibers without any aggregation, although the ZnO content reached as highly as 6 wt. %. The structures and properties of the composite nanofibers were investigated using X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and Combined Stead State Fluorescence and Phosphorescence Lifetime Spectrometer (FLSP).

Abstract: Calcium carbonate (CaCO₃) whiskers were firstly treated by sodium stearate, and then blended with polypropylene (PP) to prepare the composites by a closely intermeshing co-rotating twin-screw extruder at 200°C. The performance of the composites, such as thermal behavior, microstructure and mechanical properties, were analyzed with differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and mechanical testing. The results showed that CaCO₃ whisker influenced the crystalline behavior of PP phase in the blends because of its intervening. Moreover, thermo-decomposing temperature, tensile and bending strengths of the blends all increased with increasing whisker content. CaCO₃ whiskers had good reinforcing and toughening effects on PP.

Abstract: The microstructure evolution and mechanical properties of Mg₂B₂O₅ whiskers reinforced AZ31B magnesium composite during extruded were investigated using optical microscope and scanning electron microscope. Mg₂B₂O₅w/AZ31B was fabricated by stir-casting and the as-cast ingot was machined into cylindrical billets. Then the hot extrusion was carried out at 350°C at a constant speed of 10 mm/s with extrusion ratio of 6.25:1. The mechanical properties (strength, ductility and hardness) were tested by tensile tests and hardness tests at room temperature. Typical microstructures of different positions of extruded stock showed the microstructure evolution law during extrusion processing. It was found that DRX took place and whiskers accelerated DRX during hot extrusion. The whisker distribution in the composites was improved by hot extrusion. Additionally, the vickers microhardness of the composites increased first, and then decreased with deformation degree increased.

Abstract: Vanadium and chromium-carbide particulates reinforced iron matrix surface composite was produced by cast technique and in-situ synthesis technique. The microstructure of the surface composite was studied by scanning electron microscope(SEM) and X-ray diffraction(XRD). The results show that the production of an iron matrix surface composite reinforced by vanadium and chromium-carbide particulates using the process is feasible. Spherical VC particles and strip-chunky Cr7C3 are generated in the surface composite. An excellent metallurgy-bond is observed between the surface composite and the mater-steel.

Abstract: Abstract. Adding dispersants like surfactants and polymers to modify nanoparticles surface is an effective way to enhance the dispersion stability of nanoparticles in refrigeration oil. In this paper, many groups of nano-CoFe₂O₄ refrigeration oil were prepared. In order to obtain the most effective kind of dispersant and the optimum additive amount, sedimentation observation method was employed for evaluation of the dispersion stability of CoFe₂O₄ nanoparticles in 3GS mineral lubricant. The spectral behavior of the surface modified nano-CoFe₂O₄ was studied by Fourier transform infrared (FT-IR) spectrometer. It was revealed that the optimized mass ratio between nano-CoFe₂O₄ and dispersant ratio is 2 to 5; a relatively appropriate dispersant for nano-CoFe₂O₄ would be Tween40, Tween60, Span80, Span80; Tween60 was the best. It was also illustrated in the infrared spectrum that nano-CoFe₂O₄ particles surface modified by Tween60 was connected by organic groups in Tween60. Thus, the particles changed from hydrophilic to lipophilic and performed good dispersity and high stability when dispersed in mineral refrigeration oil.

Abstract: In this paper, the single ply fiber breakage model is established based on the distribution function of fiber static strength, and on this basis, the acting process of fiber breakage in FRP laminate is analyzed in detail. According to the experiment data, a method is devised to identify the parameters of the static strength distribution function. Through the references to the classical laminate theory, a computation model of the laminate stiffness degradation process is developed which takes the fiber breakage damage into consideration. The analysis of the results shows that this model can employ only several parameters to describe very well the laminate stiffness degradation process under different stresses.

Abstract: In this paper, a novel flame retarded MCA-PA6 (PA6 incorporated with melamine cyanurate) resin was synthesized by in-situ polymerization. The synthetic product was characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), Fourier transform infrared spectroscope (FTIR), thermogravimetry analysis (TG), differential scanning calorimetry (DSC) and elemental analysis. The result showed that good dispersability were obtained in MCA-based PA6 prepared successfully. Meanwhile, the maximum mass loss rate appeared at about 450 °C and the residual char increased from 1.2 wt% to 3.2 wt% at 500 °C due to the existence of MCA.This research revealed MCA-PA6 owned a good thermal stability, hence there was potential flame retardance.