| 摘要 |
1,255,942. Porcelain. NATIONAL RESEARCH DEVELOPMENT CORP. 19 May, 1969 [20 Feb., 1968], No. 8320/68. Heading CIJ. Porcelainarticles are toughened by immersion for 5 to 200 minutes in a bath of molten halide of K, Pb or Cs. In examples, molten baths of KBr, RbCl, GsBr and a mixture of KBr and K 2 SO 4 are used. As a comparison porcelain shapes are treated by immersion in melts of (a) NaNO 3 containing 20 wt. per cent NaBF 4 and 1% 4g, (b) KNO 3 containing 10 wt. per cent KBF 4 and 1% Ag, (c) NaI. The articles can be preheated to the temperature of the bath, e.g. 700-900‹ C. before immersion. Porcelain shapes are made by settling an aqueous slurry of porcelain powder in a mould under vibration, air drying, firing at 875-880‹C. and annealing at 400‹ C. An industrial porcelain is formed from 27% feldspar, 27À5% quartz and 45% kaolin and a dental porcelain is formed from 70-90% feldspar,1-18% quartz and 1-10% kaolin. A porcelain article analyses, before treatment, 69À36 wt. per cent SiO 2 , 8À11% Al 2 O 3 , 7À35% B 2 O 3 , 8À53% K 2 O and 4À81% Na 2 O. |
