| abstract |
Micaceous glass ceramics are obtd. from glass comprising (by wt.) 35-69% SiO2, 12-35% Al2O3, 3-25% MgO, 2-30 % CaO, 3-25% R2O, 2-12% F, 0-5% Cl. 0-10% BaO and 0-5% ZnO; the R2O comprises 0-20% K2/ and 0-20% Na2O. By controlled crystallisation it is converted to ceramic contg. >=25 vol.% mica. The glass may also contain small amts. (15 wt.% total) of CoO, CuO, NiO, Fe, FeO, Cr2O3, Fe2O3, B2O3, As2O3, Sb2O3, MnO2, TiO2, ZrO2, P2O5 or V2O5. The glass melt may first be cooled or may be treated directly at 750-1100 degrees C to convert it to a glass ceramic contg. fluorphlogopite crystals. The prod. has high bending strength and temp. resistance making it suitable for a wide range of applications. |