Abstract: A duplex eutectic silicon alloy including 30-70 weight % silicon, 10-45 weight % nitrogen, 1-40 weight % aluminum, and 1-40 weight % oxygen has a eutectic structure comprising a ??-sialon phase and an ??-sialon phase. The alloy is produced by controlling cooling at a rate of 50° C. or less per minute in combustion synthesis. A ductile sintered product capable of replacing steel in various applications can be produced by placing a compact composed of a powder of the alloy in a sintering furnace which can supply a heat quantity at least ten times the heat capacity of the compact; and sintering the compact at a pressure at least as great as atmospheric pressure, within a nitrogen atmosphere in which the silicon gas mole fraction is 10% or more, and at a temperature within the range from 1400° C. to 1700° C.

Abstract: A controlled combustion synthesis apparatus comprises an ignition system, a pressure sensor for detecting internal pressure, a nitrogen supply, a gas pressure control valve for feeding nitrogen and exhausting reaction gas, means for detecting the internal temperature of the reaction container, a water cooled jacket, and a cooling plate. A temperature control system controls the temperature of the reaction container by controlling the flow of cooling water supplied to the jacket and the cooling plate in response to the detected temperature. By combustion synthesizing, while controlling the internal pressure and temperature, the apparatus can synthesize a silicon alloy including 30-70 wt. % silicon, 10-45 wt. % nitrogen, 1-40 wt. % aluminum, and 1-40 wt % oxygen.