On the processing of nanocrystalline and nanocomposite ceramics

Two methods are being developed for the production of nanostructured bulk ceramics. The first method utilizes hot pressing to consolidate a flame-synthesized metastablc nanopowder, taking advantage of a pressure-induced phase transformation to suppress grain growth during consolidalion. This process, called Transformation Assisted Consolidation (TAC), is being used to prepare test samples of single-phase nanoceramics-nanocrystalline ceramics. The second method utilizes plasma spraying of an aggregated powder feed to generate a splat-quenched metastable phase with extended solid solubility. In this case, TAC processing promotes co-nucleation of two or more nanophases from the rapidly quenched material, which provides an additional mechanism to limit grain growth during sintering. This variant on TAC processing is being used to prepare test samples of multiphase nanoceramics-nanocomposite ceramics. (Author)