Fundamental Investigation on Processing of High Performance Covalent Ceramic Nanocomposites by Polymer Precursor Pyrolysis

摘要

Alumina based ceramic nanocomposites were investigated with the objective of improving fracture toughness. Specific focus during processing was directed at the retention of nanocrystalline microstructures in the matrix of the composites while still achieving full density. Second phases were added to the alumina matrix to investigate the applicability of toughening mechanisms that have been developed earlier for microcrystalline ceramics. The use of spark plasma sintering technique allowed the retention of ultrafine grain size of alumina due to lowered sintering temperatures and shorter sintering times. Very attractive improvements in fracture toughness were noted in Al2O3/Nb, Al2O3/ carbon nanotube, Al2O3/SiC whisker, and Al2O3/Nb/carbon nanotube composites. The results were analyzed in the context of effective toughening mechanisms in these nanocrystalline matrices.