Influence of Sintering Conditions and Nanosilicon Carbide Concentration on the Mechanical and Thermal Properties of Si3N4-Based Materials

In the work, silicon nitride ceramics (Si3N4) and silicon nitride reinforced by nano silicon carbide particles (Si3N4-nSiC) in amounts of 1–10 wt.% were investigated. The materials were obtained using two sintering regimes: under conditions of ambient and high isostatic pressure. The influence of the sintering conditions and the concentration of nanosilicon carbide particles on the thermal and mechanical properties was studied. The presence of highly conductive silicon carbide particles caused an increase in thermal conductivity only in the case of the composites containing 1 wt.% of the carbide phase (15.6 W·m−1·K−1) in comparison with silicon nitride ceramics (11.4 W·m−1·K−1) obtained under the same conditions. With the increase in the carbide phase, a decrease in the densification efficiency during sintering was observed, which caused a decrease in thermal and mechanical performance. The sintering performed using a hot isostatic press (HIP) proved to be beneficial in terms of mechanical properties. The one-step high-pressure assisted sintering process in the HIP minimizes the formation of defects at the sample surface.