Metallic tin powder with diameter less than 50 nm was synthesized by inert gas condensation method and subsequently oxidized to tin oxide () along the two heat-treatment routes. The powder of single phase with a tetragonal structure was obtained by the heat-treatment route with intermediate annealing step-wise oxidation, whereas the powder with mixture of orthorhombic and tetragonal phases was obtained by the heat-treatment route without intermediate annealing (direct oxidation). gas sensors fabricated from the nano-phase powders were investigated by structural observations as well as measurement of electrical resistance. The gas sensors fabricated from the mixed-phase powder exhibited much lower sensitivity against gas than those fabricated from the powder of tetragonal phase. Reduced sensitivity of gas sensors with the new orthorhombic phase was attributed to detrimental effects of phase boundaries between orthorhombic and tetragonal phases and many twin boundaries on the charge mobility.

A radically new approach to the in situ synthesis of the consituent phases of a composite structure has enabled the production of a new WC/Co materials with an ultrafine microstructure. The process for synthesizing nanophase WC/Co powders consists of spray drying from solution to form a homogeneous precursor powder, and thermochemical conversion of the precursor powder to the nanophase WC/Co powder. Near theoretical density of pure nanophase WC-10 wt%Co has been obtained in only 30 sec at 140. But WC particles were grown up very rapidly with longer sintering time to get full density. To overcome coarsening of WC particle during sintering, VC, TaC and VC/TaC were used as the grain growth inhibitor with different amount respectively. VC/TaC doped WC-10 wt%Co was shown superior hardness and TRS and microstructure was maintained ultrafine scale (average WC size is less than 0.1 ).