Conventional and microwave sintering of condensed silica fume

Condensed silica fume, a by-product from the production of silicon alloys, was sintered by (i) conventional heating in a dilatometric furnace, both at constant heating rate and isothermal heating, and (ii) by the microwave heating. The dense products with relative density up to 95% of theoretical can be obtained only by short runs at high heating rates, preferentially accomplished by the microwave treatment. Prolonged heating leads to the devitrification of the original glassy phase to cristobalite, accompanied by an arrest of densification.