Abstract: A process for producing a silicon carbide sintered body is disclosed, which comprises the steps of charging a sintering raw material consisting mainly of silicon carbide fine powder and sintering aid into a dispersion medium together with, if necessary, at least one substance of a molding assistant and a deflocculating agent to form such a uniform suspension that a volume ratio of solid content composed of said silicon carbide fine powder and sintering aid in said suspension is not more than 15%; spray freezing said suspension in an atmosphere held at a temperature lower than a melting point of said dispersion medium to obtain a granular frozen body; freeze drying said granular frozen body for sublimation of said dispersion medium to obtain a powdery dried mixture; shaping said powdery dried mixture into a green body of an optional form; and sintering said green body without pressing.

Abstract: .beta.-type silicon carbide having exceedingly high purity is stably and continuously produced in an apparatus comprising a vertical type reaction vessel having an inlet, a preheating zone, a heating zone, a cooling zone and a closable outlet which are sequentially communicated in this order in vertical direction, and a heat insulating layer composed essentially of fine powders of graphite and carbonaceous materials arranged on at least outside of the heating zone, the heating zone of the reaction vessel being made of graphite and having a heating means to indirectly and electrically heat charged materials, the preheating zone having a horizontal cross-sectional area larger than that of the heating zone at any level above an arbitrary position of the preheating zone.

Abstract: Metal carbide powders containing free carbon which have heretofore been difficult to refine can be refined excellently by charging the metal carbide powders in a fluidizing bed consisting of fluidized heat-resistant particles and having a temperature of a determined range to burn and remove the free carbon contained therein, and by subsequently discharging refined metal carbide powders and combustion gas from an upper part of the fluidizing bed for recovery of the refined metal carbide powders.

Abstract: An apparatus for producing silicon carbide consisting mainly of .beta.-type crystal are disclosed. The fine silicon carbide consisting mainly of .beta.-type crystal is produced by charging the starting material of silica and carbon with a mole ratio of C/SiO.sub.2 of 3.2-5.0 into a top portion of a vertical-type reaction vessel having a preheating zone, a heating zone and a cooling zone in this order, descending the starting material by gravity through the reaction vessel, heating the starting material in the heating zone at a temperature of 1,600.degree.-2,100.degree. C. by electrically indirect heating in horizontal direction to effect the formation of SiC, cooling the resulting reaction product in the cooling zone under a non-oxidizing atmosphere, and recovering the cooled product from the bottom portion of the reaction vessel to obtain a product having a composition ratio by weight of silicon carbide, silica and free carbon which lies within the area represented by the area ABCD shown in Fig.

Abstract: A method of producing a silicon carbide sintered body is disclosed. The sintered body having a density of at least 2.4 g/cm.sup.3 is produced by preparing a mixture consisting mainly of silicon carbide with an average particle size of not more than 3.0 microns and a temporary binder, shaping the mixture into a green body and sintering the green body at a temperature of 1,750.degree. C.-2,100.degree. C. Before the sintering, silicon carbide is contacted with either hydrofluoric acid or anhydrous hydrofluoric acid and an atmosphere is held in a non-oxidizing state after the contact treatment up to the completion of the sintering.

Abstract: A process and an apparatus for producing silicon carbide consisting mainly of .beta.-type crystal are disclosed. The fine silicon carbide consisting mainly of .beta.-type crystal is produced by charging the starting material of silica and carbon with a mole ratio of C/SiO.sub.2 of 3.2-5.0 into a top portion of a vertical-type reaction vessel having a preheating zone, a heating zone and a cooling zone in this order, descending the starting material by gravity through the reaction vessel, heating the starting material in the heating zone at a temperature of 1,600.degree.-2,100.degree. C.