A series of ceramic composites containing Si 3 N 4 , SiC, ZrO 2 , Al 2 O 3 and nano-sized h-BN was prepared. Boric acid and urea were ball-milled with these ceramic powders and then in-situ reduced into nano-sized BN coated on the surface of ceramic particles. The reaction processes and the microstructure characteristics of BN nanocomposite powders were analyzed by SEM, TEM, XRD and IR methods. t-BN first appeared as semifinished product during reduction and then turned into h-BN after reheated at higher temperature. Finally hot-pressing was applied to prepare ceramic composites. A drill test was also undertaken to evaluate the machinability. The results showed that all these materials containing more than 20wt% BN exhibit a combination of high strength and excellent machinability, which can be attributed to nano-sized h-BN particles dispersed in ceramic grain boundaries uniformly.

N-doped mesoporous TiO2 with high surface area and crystallinity were synthesized by sol-gel method using polyacrylamide (PAM) and polyethylene glycol (PEG) as the complex templates. The resulting materials were characterized by XRD, TEM, N2 adsorption-desorption, and UV-Vis spectroscopy. It is found that when the weight ratio of PAM and PEG is 1:4, the sample, prepared at 600 °C in nitrogen and at 500 °C in air, is anatase phase and has high surface area and crystallinity. The particle size and pore size of the sample are about 10 nm and 17 nm respectively. Compared with that of the undoped mesoporous TiO2, the absorption band edges of N-doped samples exhibit an evident red-shift. The results of the photocatalytic degradation of methyl orange (MO) show that N-doped sample appears to have higher photocatalytic activity under visible light than undoped sample.

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Porous silicon nitride ceramics with various amounts (25, 35, and 45 vol %) of hexagonal boron nitride (h-BN) were fabricated at 1800°C for 2h by the pressureless sintering process. With FESEM and TEM, the effects of h-BN on the microstructure and mechanical properties of Si3N4 ceramics were investigated. Results of the microstructure and mechanical properties of Si3N4/BN composites showed that the growth of the elongated β-Si3N4 were hindered by h-BN additive, which resulted in the decrease of fracture toughness of Si3N4/BN ceramics with increasing h-BN content. The morphologies of the fracture surfaces by FESEM revealed the fracture mode for Si3N4/BN composites to be intergranular. However, phase analysis by XRD indicated that the effect of h-BN on the α- to β- Si3N4 phase transformation of Si3N4/BN composites was negligible.

Nano-TiO2 powders were synthesized by a sol-gel method using tetrabutyl titanate as the precursor, and then the composites of ACF(activated carbon fiber) supported nano-TiO2 was prepared by impregnating method. Tests of the amount of loaded TiO2 showed that three impregnating times was adequate. The Nano-TiO2 powders and composites were characterized by XRD, SEM, and BET surface area method. XRD tests showed that nano-TiO2 powders prepared by this way are anatase phase, and the mean size of the particles is about 11.5nm, when the calcination temperature is 673K. BET results showed that compared with original ACF, the surface area of the composites decreased slightly, indicating the impregnating process did not change the porous structure of original ACF. SEM result indicated that most of the nano-TiO2 particles as the size of 10-20nm were homogeneously dispersed on the surface of ACF.