The Possibility of Dense Materials Based on Obtaining an AlN–SiC Solid Solution by Self-Propagating High-Temperature Synthesis Gasostating

Abstract

The synthesis and sintering of the (AlN)x(SiC)1 – x solid solution have been studied under conditions of self-propagating high-temperature synthesis (SHS) gasostating at high nitrogen gas pressures (up to 110 MPa). The phase formation during the combustion of mixtures of aluminum and silicon carbide with a different amount of Al (from 35 to 60 wt %) is studied. It is shown that the optimal amount of aluminum mixed with silicon carbide to obtain a single-phase solid solution (with the complete conversion of aluminum to aluminum nitride, and also without the dissociation of silicon carbide) is 45–50 wt %. Using a mixture with 55–60 wt % Al leads to excessively high temperatures, which in turn leads to the decomposition of silicon carbide to Si + C elements. The optimal parameters for obtaining dense material in one stage are determined. The measured porosity and density of the samples allow us to establish that, for samples with 50 wt % of the aluminum content, prepressing is essential for the final density. It is found that the additive of 5 wt % yttrium oxide increases the density of the material by almost 10%. A similar effect is also exerted by an increase in the initial gas pressure from 80 to 110 MPa. The maximum density that is achieved is 2.7 g/cm3, which is 83% of the theoretical density. The total volumetric shrinkage of the material is 10% ± 0.5, which can be almost completely leveled by the addition of 3 wt % boron. The hardness of the samples reaches up to 2000 kg/mm2.