Abstract: A process of obtaining silicon nitride (Si3N4) surface coatings on ceramic pieces and components by impregnation of the surfaces of the ceramic pieces with silicon powder suspensions with a particle size preferably less than 200 ?m. The thickness of the coatings depends on the impregnation time and on the properties of the slip and the ceramic piece. The subsequent nitridation of the coating by thermal treatment at temperatures between 1300° C. and 1500° C. in N2 atmospheres leads to a continuous Si3N4 coating. The chemical stability and compatibility between Si3N4 and molten silicon enables its application in silicon metallurgy, in manufacturing crucibles for silicon fusion or for housing said molten silicon, in manufacturing pipes and chutes for its transport or in manufacturing different components for its subsequent purification.

Abstract: The invention relates to a method for obtaining ?-alumina crystals or fibers using the vapor-liquid-solid (VLS) mechanism, by controlling the slightly oxidizing atmospheres in systems that contain metal Al and SiO2. The inventive method consists of growing ?-alumina fibers using the growth of alumina fibers via VLS from Al and SiO2, and controlling the partial pressure of the different oxidizing agents, in the area known as active oxidation of Al with formation of corundum fume and active oxidation of Si with formation of silica fume in accordance with the respective Si—SiO2 and Al—Al2O3 volatility diagrams.

Abstract: A process of obtaining silicon nitride (Si3N4) surface coatings on ceramic pieces and components by impregnation of the surfaces of the ceramic pieces with silicon powder suspensions with a particle size preferably less than 200 ?m. The thickness of the coatings depends on the impregnation time and on the properties of the slip and the ceramic piece. The subsequent nitridation of the coating by thermal treatment at temperatures between 1300° C. and 1500° C. in N2 atmospheres leads to a continuous Si3N4 coating. The chemical stability and compatibility between Si3N4 and molten silicon enables its application in silicon metallurgy, in manufacturing crucibles for silicon fusion or for housing said molten silicon, in manufacturing pipes and chutes for its transport or in manufacturing different components for its subsequent purification.