| 摘要 |
1,157,587. Glazing. SIGRI ELEKTROGRAPHIT G.m.b.H. 8 March, 1968 [10 March, 1967], No. 11554/68. Heading C1M. [Also in Division H5] A porous element is protectively glazed by impregnation with an aqueous solution of an Al salt and a salt of an alkaline-earth metal e.g., Ca, Mg, or Ba, drying, and firing at 1100- 1650‹ C. in an oxidizing atmosphere, e.g. air. The element may be a SiC heating element. The solution may be acidic; it may also contain salts of Zr, Ti, rare earths, or alkali metals, e.g., Na or K. The salts may be chlorides, hydroxychlorides, oxychlorides, nitrates, or sulphates. The solution may contain a total of 15-35% wt. of the salts, e.g. 2-15%Al<SP>+ +</SP> +, 0À3-6% Mg+ + and/or Ca<SP>++</SP>, and 0-1À5% Na<SP>+</SP> or K<SP>+</SP>. To the glazed element a further surfacing layer may be applied, by application of a suspension which, in dry weight per cent, consists of SiO 2 , 6-85; A1 2 0 3 , 12-33À9; alkaline earth oxide(s), 0-4; alkali metal oxide(s), 0À1-1; boron oxide(s), 0-0À5; Zr or Ti oxide(s), 0-6; rare earth oxide(s), 0-10; methyl cellulose, e.g. 0À7%. After drying, the suspension is fired at 1300- 1600‹ C. in an oxidizing atmosphere. |
