1979 Volume 87 Issue 1011 Pages 576-582
Metallic Al or Al compound was added to the reactants in the process of synthesizing submicron powder of silicon carbide (SiC) by reaction of carbon black with Si, SiO or SiO2. Effect of Al addition was studied by measuring various properties of SiC powder prepared.
Results obtained are as follows:
(1) When SiO or SiO2 was used as silicon source, an addition of Al resulted in the increase of specific surface area and the formation of 2H polytype, whereas those of Siderived powder were not significantly influenced by the Al addition.
(2) By adding 1wt% of B and of C as densification aids, both SiO- and SiO2-derived powders could be sintered to ≥90% TD below 1900°C, which was lower than sintering temperature (≈2100°C) of SiC powder prepared without Al additive by 200° to 400°C.
(3) Improved sinterability of the SiC powder prepared in this experiment might be caused by the enhancement of atomic mobility resulted from solid-solid transformation of 2H polytype (Hedvall effect) or by the presence of liquid phase.
(4) A characteristic of low-temperature sintered specimens was the fact that they consisted of both polytypes of 3C (≈50%) and 4H (≈50%).
