Microstructures and densification of MoSi2–SiC composite by field-activated and pressure-assisted combustion synthesis

Abstract

Abstract Using Mo, Si, and C element powders as starting materials, a field-activated and pressure-assisted combustion synthesis (FAPACS) was employed to synthesize high-density bulk MoSi2–SiC composite in one step. Effects of sintering temperatures (1100, 1200, 1400 and 1600 °C) on microstructures and densification were investigated. With the exception of 1100 °C, at which synthesis was incomplete, the FAPACS was characterized by the four stages, i.e. initial expansion, slight shrinkage, abrupt shrinkage and slight expansion. The study shows that the sintering ability at the higher temperature is better than that at the relatively lower temperature. When the sintering temperature reaches 1400 or 1600 °C with holding time of 10 min, the high-temperature transitional phases, i.e. Mo4.8Si3C0.6, were presented and the produced SiC particles are agglomerate. The relative density of the products (holding time: 10 min) was improved tremendously from 59% to 96.0% over the range 1100–1400 °C, and a smaller enhancement in densification up to 98.5% was achieved between 1400 and 1600 °C. Moreover, an extended holding time (up to 20 min) at 1600 °C resulted in nearly Mo4.8Si3C0.6-free and dense MoSi2–SiC products with the relative density of 99.0%. Simultaneously, a locally uniform distribution of SiC in the synthesized MoSi2 matrix was achieved. And the interfaces between the synthesized phases are clean without impurities (e.g. SiO2) and porosities. Thereby, in order to pursue an equilibrium among densification, microstructural uniformity and formation of transitional phases, the most suitable sintering temperature and holding time for fabrication of MoSi2–SiC by FAPACS are recommended to be 1600 °C and 20 min in the present work.