| 摘要 |
<p>1408210 Semi-conducting glaze composition O NIGOL 26 Oct. 1973 [27 Oct 1972] 50030/73 Heading C1M A semi-conducting glaze composition comprises a base glaze to which are added tin oxide (SnO 2 ), antimony trioxide (Sb 2 O 3 ) and zinc oxide (ZnO), the tin oxide and antimony trioxide being present in an amount 3-12À5% by weight of the total solids of the composition, and the zinc oxide being present in an amount 0À5-3% by weight of the total solids of the composition. The weight ratio of SnO 2 to Sb 2 O 3 is preferably in the range 4 : 1-50 : 1. The mean particle size of the base glaze is preferably less than 10 microns whilst the mean particle size of the SnO 2 and Sb 2 O 3 may be less than 0À5 microns. In a "one-step" glaze the SnO 2 , Sb 2 O 3 and ZnO are mixed with the base glaze materials and water to produce a glazing slip whilst in a "two-step" glaze the ZnO and a pre-calcined ground mixture of SnO 2 and Sb 2 O 3 are mixed with the base glaze materials and water to form the slip. The slurry may be applied to unfired dry porcelain insulators or to pre-fired porcelain insulators, by dipping, flooding or spraying. Firing may be at 2300‹ F. for six hours. Preferred base glaze compositions contain, in per cent by weight: (a) 70À75% SiO 2 , 11À64% Al 2 O 3 , 13À91% CaO, 2À50% K 2 O, 0À68% Na 2 O, 0À18% TiO 2 , 0À28% Fe 2 O 3 , 0À06% MgO; and (b) 70À0% SiO 2 , 13À66% Al 2 O 3 , 11À84% CaO, 2À71% K 2 O, 0À76% Na 2 O, 0À34% Ti 2 O, 0À30% Fe 2 O 3 and 0À09% MgO. Surface resistivities of 40-400 megohms per square may be obtained.</p> |
