Microstructure and Mechanical Properties of Polymer‐Derived Al 2 o 3 ‐SiC Micro‐Nano Composites

Abstract

A set of Al 2 O 3 -SiC nanocomposites containing 3 - 8 vol. % SiC was prepared by the infiltration of a pre-sintered alumina matrix with a SiC forming preceramic polymer, poly(allyl)carbosilane, with high ceramic yield (75 % by weight). The volume fraction, and grain size of the SiC particles were influenced by the volume fraction of open pores in the pre-sintered alumina matrix, by the concentration of the solution of the polymer used for the infiltration, and by the conditions of sintering. The specimens were densified by pressureless sintering at temperatures between 1750 and 1850 °C. The microstructural characteristics (grain size and grain size distribution of Al 2 O 3 matrix grains and SiC particles, fraction of inter- and intragranular SiC particles, presence of defects) were determined, and the mechanical properties (hardness, and fracture toughness) were measured by indentation method in the materials with residual porosity less than 2 vol. %. The influence of the processing parameters (way of preparation, concentration of the polymer, conditions of sintering) on the microstructure of the composite is discussed with implications to the composites' mechanical properties.