Abstract: The invention relates to corrosion-resistant, temperature-stable, durable mould release layers, suitable for the die casting of non-ferrous metals, comprising boron nitride and slips for production thereof, a method for production of the slips, a method for production of the mould release layers and the use of the mould release layers.

Abstract: The invention relates to the reprocessing of used evaporation boats. This is done by a method which comprises comminuting used, aluminum-contaminated evaporation boats and roasting them in a nitrogen-containing atmosphere.

Abstract: Stable slip casting composition having a total solids content of from 50 to 80 percent by weight on a base of finely divided, AlN-containing powders. It contains as liquid dispersion medium, water mixed with a water-soluble, aliphatic, polyvalent alcohol and admixtures for adjusting the viscosity required for slip casting. The liquid dispersion medium can contain, for instance, from 1 to 20 percent by weight of an alcohol such as glycerin calculated on the total weight of water and alcohol.

Abstract: The invention is a process for the manufacture of sinterable silicon carbide and/or boron carbide powders having a maximum particle size of 1 .mu.m and finer. The process is carried out by wet grinding in aqueous suspension using mills charged with a grinding medium and with the addition of antioxidants in the presence of surfactants and subsequent wet chemical treatment with an aqueous potassium hydroxide solution. The wet grinding can be carried out, for example, with the addition of hydroquinone in the presence of quaternary ammonium salts and the wet chemical treatment with a 5-50% by weight aqueous potassium hydroxide solution under normal pressure at temperatures in the range of from room temperature to the boiling temperature of the reaction mixture or under elevated pressure at temperatures of up to 300.degree. C.