B4C and B4C-W2B5 composite ceramics are prepared via hot pressing. The composition and microstructure of the ceramics are characterized by means of X-ray diffraction (XRD), electron probe microanalysis (EPMA) and transmission electron microscope (TEM). Their electrical conductivity and Seebeck coe

Ultra long SiC core and SiO2 shell nanocables have been prepared by pyrolysis of poly (dimethyl siloxane) at 1050℃ in flowing Argon. The longest nanocable can be up to at least 6mm. Transmission electron microscopy observations indicate that the diameter of the cores varies from about 3 to 18nm, and the thickness of the outer sheaths varies from about 6 to 45nm and that the cores are crystalline and the sheaths are amorphous. The growth of the nanocables may be governed by a chemical vapor solid process. The nanocables exhibit good photoluminescence property.

A B4C ceramic doped with 0.2 at% Si is prepared via hot pressing. The composition and microstructure of the ceramic are characterized by means of X-ray diffraction (XRD) and electron probe microanalysis (EPMA). The electrical conductivity and Seebeck coefficient of the ceramic samples are measured from room temperature up to 1500 K. The electrical conductivity increases with temperature; the Seebeck coefficient also increases with temperature and rises to a value of about 320μV K-1 at 1500K. The value of the figure of merit of 0.2 at% Si-doped B4C is higher than that of undoped B4C and rises to about 1×10-4K-1 at 1500K. The reason for enhancement in the figure of merit of Si-doped B4C is discussed.

TiB2/B4C composite ceramics are prepared via hot pressing, in which the TiB2 particles are formed by introducing TiC0.78 and through the reaction between B4C and TiC0.78. The electrical and thermal conductivities and Seebeck coefficient of samples containing 0, 12.5 and 25.4 vol% TiB2 are measured from room temperature up to 1200K. The results show that the transport properties of the samples vary with the TiB2 content. The transport properties of a 12.5 vol% TiB2/B4C sample are dominated by the B4C matrix as in undoped B4C ceramics, whilst the transport properties of a 25.4 vol% TiB2/B4C sample are dominated by TiB2 particles. The figure of merit of the 25.4 vol% TiB2/B4C sample is higher than that of the undoped B4C ceramic sample between room temperature and about 700K, which indicates that it is possible to improve the thermoelectric properties by selecting an optimum combination of different materials.