Ceramic-glass composites for electrical insulation - made by mixing corundum and glass of controlled particle size, pressing and sintering at low temp

摘要

Non-porous ceramic elements capable of accepting a glaze and made of a mixt. of 36-60% corundum and 64-40% gloss by sintering at a temp. 1050 degrees C the particle size of the corundum being 85 wt. % 20 mu and 3 wt. % 2 mu, and the glass compsn. comprising 52-65 mol. % SiO2, 7-18% Al2O3, 1-10% B2O3, 5-26% CaO, 0-20% MgO, 0-4% BaO, 0-3% ZnO, 0-2% F2O5, 0-1.5% F, with 1.5 mole % alkali metal oxides. The glass a vitreous transition temp. of 640-750 degrees C and a softening temp. of 800-1000 degrees C, while the temp. for which the specific electrical conductivity reaches 100 x 10-10 mho/cm, (tk100) is 500 degrees C, the elastic modulus is 0.75 x 106 kg/cm2, and the linear expansion coefft. is 7.5 x 10-6/degree C (20-400 degrees C). The glass is used in a particle size range of 80 (95) wt. % 20 mu, 45 (75) wt. % 6.3 mu and 15 (25) wt. % 2 mu. Used for electric insulation of the KER 200 class. Lower sintering temps. are employed than for prior art materials having this class of electrical properties (1350 degrees C).