Sintered ceramic electrical insulators - made from inexpensive mixt. of natural olivine and alumina-silica clay and having magnesium-ferro-cordierite crystal phase

摘要

Sintered ceramic mouldings, esp. insulators for the electric industry are based on olivine, and with compsn. by wt. after sintering:- 10-30% MgO+FeO, 15-40% Al2O3, 40-65% SiO2, 3-7% FeO; and the crystal phase obtd. is magnesium-ferro-cordierite. The FeO is pref. present at 5%, and the wt. ratio MgO:FeO pref. 90:10. The moulding may also contain =4% alkali oxides, esp. K2O. In the pref. mfr., a mixt. of olivine plus natural alumina-silica cpds., esp. clay or kaolin is moulded, dried and sintered at 1100-1280 degrees C. The mixt. may also contain feldspar, porcelain flour, mullite, sillimanite, chamotte and/or steatite. An abundant, naturally-occurring, and inexpensive material, viz. olivine, is used with natural clays to obtain insulators with good mechanical strength, high insulation resistance and high resistance to thermal shock.