The features of spark plasma sintering of submicron Al2O3 powders with different contents (0, 0.5, 1.5, 5 vol.%) of -SiC nanoparticles have been studied. The microstructure and hardness of Al2O3 + 5 vol.% SiC ceramics obtained by sintering Al2O3 powders with -SiC particles of various types (nanoparticles, submicron particles, fibers) have been studied. Sintering was carried out at heating rates (Vh) from 10 to 700 °C/min. The sintering process of Al2O3 + SiC ceramics with low heating rates (Vh = 10–50 °C/min) has a complex three-stage character, with a flat area in the temperature range of 1200–1300 °C. At high heating rates (Vh > 250 °C /min), the usual three-stage character of sintering is observed. The analysis of temperature dependences of compaction was carried out using the Young-Cutler model; It was found that the kinetics of powder sintering is limited by the intensity of grain boundary diffusion. It is shown that the dependence of the hardness of Al2O3 + SiC ceramics on Vh has a nonmonotonic character, with a maximum. In the case of pure alumina, an increase in Vh leads to a monotonic decrease in hardness.

The effect of an additive of 0.5 wt. % of zirconium oxide on the spark plasma sintering (SPS) kinetics of alumina powders has been studied. Ceramics were obtained by mixing alumina powders in a planetary mill with grinding media from stabilized zirconium oxide. The activation energy of SPS was estimated using the Young-Cutler model. It has been shown that the density and average grain size in ceramics obtained from submicron alumina powders are significantly affected by the nonequilibrium state of the interfaces formed as a result of the transformation of the amorphous phase present on the alumina powder particle surface. The grain size and density of ceramics obtained from fine powders are significantly affected by the coalescence of ZrO2 particles.