Abstract: Mg-5wt.%Al alloy based composites reinforced with 0wt.%, 1wt.%, 2wt.% silicon carbon (SiC) particles (average particle size about 3.5µm) were prepared under flux protection conditions. The microstructures, textures, components and hardness of the above composites were investigated through optical microscope, scanning electron microscope, X-ray diffraction and sclerometer. The results indicate that SiC particles are distributed along grain boundaries, limiting grain growth and conducing to the refinement of the matrix. The hardness of composites increases with the increase of SiC particles addition amount. The presences of Mg2Si and the binary carbide Al4C3 were observed in the composites. The Al4C3 phase has a crystal structure closer to that of Mg than to that of SiC, which can be act as a potential nucleant for Mg-5wt.%Al alloy.
Abstract: A low-viscosity and solvent-free polyurethane adhesive was prepared with mixed polyester, polyether and IPDI as main raw materials. The influences of different moral ratios of polyester and polyether on reaction time, viscosity and water resistance, adhesive strength were researched. The effects of catalysts to adhesive were well discussed. The experimental results showed that polyurethane adhesives composed by mixed polyester and polyether had low viscosity and had better waterproof quality. The adhesives showed the best comprehensive properties when the mole ratio of OHs of polyether to OHs of polyester was 0.3/0.7. Catalysts added to this adhesive could speed the curing reaction, but it reduced the peel strength of the adhesives.
Abstract: Attapulgite fiber-aerogel composite was synthesized using sol-gel technology combining with surface modification and conventional drying to overcome the brittle disadvantage of traditional aerogel. Attapulgite fiber was added in the process of sol into gel, in order to enhance the mechanical property of SiO2 aerogel. Hydrophobic and low density fiber-aerogel composites were obtained in this experiment. Investigation of the removal of attapulgite reinforced SiO2 aerogel to TPH in water under low temperature was also carried out. The results showed that the attapulgite fiber-aerogel composites we obtained in this study had good performances of mechanical and hydrophobic properties; the removal rate of aerogel to TPH was 91.02% under the temperature of 10°C.
Abstract: The experiments were carried out in a horizontal tube furnace using Al and NH3 as the source materials. The structure and morphology of the as-synthesized AlN nanowires are characterized by X-ray diffraction, scanning electron microscopies and Raman spectrum. The results indicated that the structure of synthesized AlN nanowire is hexagonal wurtzite structure, the length of the AlN nanowire is between several micrometers and the the average diameter is about 100 nm.The growth of the AlN nanowires can be expelained by vapor–liquid-solid mechanism.
Abstract: The effects of functional groups and degree of functionalization on the young modulus of carbon nanotubes (CNTs) are investigated through molecular dynamics and molecular mechanics simulations. It is found that young’s modulus depends greatly on the functional groups and degree of functionalization. The results show that the fluorine (-F) can replace the hydrogen, and young modulus of sing-walled CNTs (SWNT) modified by -F functional group can inherit the mechanical properties of intrinsic SWNT. The binding energy between functional groups and SWNT, and electrostatic energy among the functional groups are mainly responsible for these findings. These characteristics rival those of SWNT modified by hydrogen allow one to consider SWNT modified by -F functional group for a range of technologies, in particular require better inertness and stability than unachievable for the compound.
Abstract: Ni60 superhard alloy with the additions of graphite solid lubricants was successfully prepared on 45 carbon steel substrate by means of laser cladding. The quality of coating was relatively high and had metallurgical bonding with the substrate. The morphology of laser cladding layer was observed by SEM, composition analysis was applied by EDS. Elevated temperature frictional behaviors of graphite/Ni60 composites coatings were investigated on MMG-10 wear machine. The results showed that the friction coefficient of graphite/Ni60 composite coating was obviously decreased from 0.55 to 0.20 with increasing temperature. The wear mechanism transformed from adhesion to oxidation with the increase of temperature. The graphite/Ni60 composite coating material showed the optimum self-lubricating property at 500°C.
Abstract: The thermoplastic processing and mechanical properties of starch and polyvinyl alcohol (PVA) composites reinforced with microcrystal cellulose (MCC) were investigated. Glycerol with 30 wt% was chosen as the plasticizer for starch and PVA, respectively. MCC with 2 wt% was used to reinforce the starch/PVA composite. The results showed that the mechanical properties of the obtained starch/PVA blend were best when the glycerol content was 30% of starch and 20% of PVA, and the weight ratio of PVA and starch was 4/6 (wPVA/wstarch). After the addition of MCC, the mechanical properties of the starch/PVA blends were improved, and the tensile strength was increased by 52%. Moreover, it was confirmed by rheological measurements that MCC could interact with the composite materials, which results in the improvement of the mechanical strength of the starch/PVA composites.
Abstract: The electrical resistivity is studied when B4C modified phenol-formaldehyde (PF) resin is heat-treated at temperatures of 300-1500 °C, and then the X-ray diffraction (XRD) spectra are also investigated. The results indicate that the electrical resistivity is elevated with the increase of pyrolytic temperature of PF resin. The addition of B4C decreases the electrical resistivity efficiently when the temperature is range of 700-1000 °C. Especially the composite is treated at tmperatures of 1000-1500 °C. The analysis of XRD spectra suggests that the addition of B4C promotes the arrangement of residue at high temperature. The arrangement reaction has not a direct effect on the electrical resistivity.
Abstract: Triacetin (TAC) was used as plasticizer to improve the ductile of polylactic acid (PLA). A composite film composed of PLA and TCA was therefore Paraed, and the packaging properties of this film were tested including the elongation, tensile strength, tear strength, Transparency and permeability. The results suggest that the film owns superior synthetically packaging properties when the proportion of TAC is 30 % (mass ratio). At the same time, this film has a low gas barrier which is especially for the package of the novel vegetable and fruits.