The thermal decomposition of commercial silicone grease was carried out in a closed reactor (Swagelok) that was heated at 800 degrees C for 3 h, yielding a SiO2-carbon composite with a BET surface area of 369 m2/g. The bulk conductivity (5.72 x 10(-6) S x cm(-2)) of the SiO2-carbon composite was determined by impedance measurements. The as-prepared SiO2-carbon composite was further annealed at 500 degrees C in air for 2 h, which led to the formation of white paramagnetic silica particles (confirmed by ESR), possessing a surface area of 111 m2/g. The present synthetic technique requires unsophisticated equipment and a low-cost commercial precursor, and the reaction is carried out without a solvent, surfactant, or catalyst. The mechanism for the formation of a porous SiO2-carbon composite from the silicone grease is also presented.

Novel Ta2O5 nanobars anchored on micron-sized carbon spheres were synthesized by the thermal decomposition of pentaethoxy tantalate, Ta(OEt)5. This one-step reaction was carried out using the RAPET (Reaction Under Autogenic Pressure at Elevated Temperature) method by dissociating Ta(OEt)5 at 800 degrees C for 3 h. The as-prepared Ta2O5/C nanobar-composite was annealed under air at 500 degrees C for 3 h (eliminating the carbon spheres), resulting in neat Ta2O5 nanobars. The products, Ta2O5/C and Ta2O5 nanobars, were characterized using methods such as electron microscopy (SEM, TEM, HRTEM, SAEDS, EA, EDX) and Powder-XRD. Transmission electron microscope (TEM) images indicated the particle size of the Ta2O5 nanobars coated on 40-60 nm carbon spheres. The optical properties of the Ta2O5/C nanobar-composite and the neat Ta2O5 nanobars were determined by UV-vis absorption spectrometry and their band gaps were found at 265 (4.7 eV) and 260 nm (4.8 eV), respectively. A PL band was also observed for a Ta2O5/C nanobar-composite and Ta2O5 nanobars. The above results indicate that Ta2O5 nanobars have a promising application in optical devices.