Advanced Materials Research Vol. 66

Abstract: SR/Al2O3 composites were fabricated from different heat treatment temperatures of alumina. The results show that the relative density is over 94% and flexural strength is 66.5MPa when silicone content is 33wt.%. The flexural strength of the obtained SR/Al2O3 composites is decreased when increasing the heat treatment temperature of sandy alumina, indicating that the surface hydroxyl groups directly influence the flexural strength of SR/Al2O3 composites.

Abstract: Co3O4 microspheres were synthesized by hydrothermal-precipitation method using NH3•H2O, H2O2, n-butanol and polyethylene glycol as precipitator, oxidant, assistant solvent and dispersant respectively. The products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical properties of the Co3O4 electrode were performed by cyclic voltammetry (CV) and galvanostaitc charge/discharge methods. The results exhibited that the Co3O4 single electrode had excellent stability, cyclic performance and high specific capacitance in KOH electrolyte. The specific capacitance as a single electrode was up to 653.74 F/g in the 6mol/L KOH solution with 0-0.4V potential at 2mA/cm2 current density. The effects of electrolyte concentrations and current densities on its capacitive performance were investigated. The Co3O4 prepared material is potential candidate for the preparation of power source devices.

Abstract: Low density syntactic foam monolayer slices, which were made of epoxy resin matrix and plastic microballoons (MB), were fabricated by rolling process with thickness controlled at 200μm. Density of monolayer slice ranges from 0.500g/cm3 to 0.996g/cm3 and it is designed to fit power law equation. The volume percentage of plastic microballoons in the monolayer pellets varies from 16.61% to 58.06%. The slices were characterized by optical and scanning electron microscopy, and measurement of density and sound wave velocity. The density, glass transition temperature and acoustic impedance were observed to vary with the volume percentage of plastic microballoons in the composite. Graded syntactic foams were fabricated by stacking slices of different density in a sequence of density gradient and the slices were bound together with adhesive made of epoxy resin-hardener under the pressure of 5MPa.

Abstract: Carbon nanotubes reinforced alumina was fabricated by spark plasma sintering method. When adding 0.2wt% nanotubes, the fracture toughness of the composites prepared increases 19% compared with the pure alumina ceramics. The effect of sintering schedule on microstructure and mechanical properties is investigated systematically. Microstructure studies reveal that at high sintering temperature, the nanotubes tend to gather in the gaps surrounded by three or more grains in a flocculent state, which leads to poor mechanical properties. Raman spectrum indicates that long sintering duration may cause serious nanotubes destruction and lower the mechanical properties.