GB1216986A - Glazed ciramic article - Google Patents

Abstract

1,216,986. Glazed ceramic article. WISSENSCHAFTLICH - TECHNISCHER BETRIEB KERAMIK. 4 June, 1970, No. 48543/67. Heading C1M. In a glazed ceramic article, the ceramic is composed by wt. of: SiO 2 , 35-60%; Al 2 O 3 , 25-40%; K 2 O or Na 2 O, 2-10%; with or without compatible ingredient(s) or impurity; and the glaze is composed by wt. of: SiO 2 , 55-69%; Al 2 O 3 , 20-25%; MgO, 6-10%; K 2 O of Na 2 O, 2-5%; B 2 O 3 , 3-5%; Ca 5 (PO 4 ) 3 - OH, 0-0À5%; with or without compatible ingredients or impurity. The coefficient of thermal expansion of the glaze is preferably 1À5-2À0 x 10<SP>-6</SP>. The burning temperature of the glaze, i.e. the temperature at which the glaze becomes capable of flowing smoothly, is preferably 1370-1390‹ C. The article may be a briquette and may be coated by dipping or spraying with a slip of the glaze-forming mixture. Before coating, article may be a fired or unfired body of the above composition. 'The ceramic may be prepared from a batch of: clay 14%; kaolin, 39%; alumina, 10%; talcum, 22%; orthoclase, 15%. The glaze may be prepared from: ceramic fragments, 50%; talcum, 10%; orthoclase, 5%; Al 2 O 3 , 5%; kaolin, 5%; borosilicate frit, 24À5%; Ca 5 (PO 4 ) 3 - OH, 0À5%; the borosilicate frit is SiO 2 , 79À5%; Al 2 O 3 , 4%; K 2 O, 5%; B 2 O 3 , 11À5%. The glaze is wet-ground till only 0À05% of the mixture has grain size > 63 Ám. On firing, a pronounced crystal phase is present in the glaze, in which cordierite, corundum, mullite, and protoenstatite are detectable. The intermediate layer mullitized from the porcelain is built up from solid cordierite crystals in close contact.