Influence of Pyridine–Borane on the Sintering Behavior and Properties of α-Silicon Carbide

In the present study, α-SiC powder is coated with pyridineborane (BH₃·C₅H₅N), a liquid molecular compound, which forms a boron carbonitride (BC_3.5N) layer by heat treatment at 1000°C under argon. The precipitation method leads to an improved chemical homogeneity in the compacted powder resulting in enhanced densification and significant reduction in grain growth during subsequent sintering at temperatures exceeding 2070°C. Thus, small average grain sizes of d ₅₀= 1.3 μm and a narrow grain size distribution ( d ₁₀= 0.6 μm, d ₉₀= 2.2 μm) are detected in the liquid-phase-processed sample sintered at 2200°C for 0.5 h in argon. Final densities of at least 98% of theoretical could be obtained by pressureless sintering at 2100°C. These results as well as the microstructural distribution of the sintering aids in the densified samples are discussed.