Liquid phase sintering and characterization of SiC ceramics

The present study focuses on the sintering of silicon carbide-based ceramics (SiC) by liquid phase sintering (LPS) followed by characterization of the produced ceramics AlN/Re2O3 mixtures were used as additives in the LPS process. In the first step, the LPS-SiC materials were produced in a graphite resistance furnace in the form of discs at different temperatures. The conditions with the best results regarding real density and relative density were taken as reference for sintering in the form of prismatic bars. In the second step, these samples were evaluated regarding fracture toughness (K-IC), by the Single Edge V Notch Beam - SEVNB - method, and flexural strength. K-IC behavior was evaluated according to the depth and curvature radius of the notches. Reliable K-IC values were presented when the ceramic displayed a small curvature radius at the notch tip. When the radius was large, it did not maintain the square root singularity of the notch tip. Tests were carried out to determine K-IC values in atmospheric air and water. K-IC results were lower in water than air, with a decrease ranging between 2.56% and 11.26% The observations indicated a direct gram size correlation between K-IC values and fracture strength of the SiC ceramics.