Silicon nitride/silicon carbide nanocomposites and alumina-based nanocomposites were investigated in an effort to produce materials with high structural integrity and service properties. Bulk nano-nano composites of silicon nitride and silicon carbide were processed by crystallization of amorphous Si-C-N ceramics that were consolidated in-situ during pyrolysis of a polymer precursor. This material was developed for the purpose of examining the creep behavior of covalent ceramics when there is no oxide glassy phase at grain boundaries. Si3N4/SiC micro-nano composites were sintered by spark plasma sintering (SPS), aiming at better microstructural control and improved creep resistance. Composites of alumina with diamond, silicon carbide and metal (Nb) were developed by high pressure sintering and SPS. These composites maintain microstructures with a nanometric alumina matrix and are targeted for studying the toughening mechanisms and superplastic deformation mechanisms.