Low-temperature sintering of silicon carbide with Li 2O-Al 2O 3-SiO 2 melts as sintering aids

Abstract

With reference to sintering of SiC with Li 2O-Al 2O 3-SiO 2 (LAS) melts, equilibrium partial pressures of SiO, CO and Al 2O resulting from reactions of SiC and LAS have been thermodynamically estimated by taking carbon activity and temperature into account. Experimental work involving various LAS compositions and different powder beds showed that SiC/40 v% LAS (65·2 wt% SiO 2, 15·0 wt% Al 2O 3, 19·8 wt% Li 2O or 55·0 wt% SiO 2, 22·5 wt% Al 2O 3, 22·5 wt% Li 2O) can be densified in carbon rich powder bed to above 95%. The sintering temperature (100 °C above m.p. of LAS) of these were the lowest of all. Thermodynamic estimations were used to explain the results. XRD, optical microscopy and SEM studies also supported the explanation.