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: 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: Apparatus and method for sensing the state of electrodes during baking to obtain an indication of the internal condition of the electrodes where changes of phase are being produced. The apparatus includes a conductor disposed within the electode material during baking, an external, low power, variable frequency electric generator connected to the conductor, and means for analyzing a response signal, especially impedance of the response signal upon changing the frequency of the electric current, to determine the condition of the electrode along its height.

Abstract: Apparatus and method for sensing the state of electrodes during baking to obtain an indication of the internal condition of the electrodes where changes of phase are being produced. The apparatus includes a conductor disposed within the electode material during baking, an external, low power, variable frequency electric generator connected to the conductor, and means for analyzing a response signal, especially impedance of the response signal upon changing the frequency of the electric current, to determine the condition of the electrode along its height.