| 摘要 |
885,618. Glass. CORNING GLASS WORKS. June 21, 1960 [July 1, 1959], No. 21712/60. Class 56. A glass article made from a composition in which at least 100 parts out of a total of not more than 110 comprise 65-72 parts by weight of SiO 2 , not less than 4 parts Li 2 O and 22.5-30 parts Al 2 O 3 , the weight ratio of Li 2 O/Al 2 O 3 being not more than 0.3/1, the article being provided with a thin semi-crystalline surface layer in which there is a compressive stress by heating to a temperature at which its viscosity is between 10<SP>7</SP> and 10<SP>10</SP> poises for from 1 to 40 hours until miscroscopic and sub-miscroscopic crystals of beta-eucryptite are formed within its surface, the formation being promoted by the presence in the original composition of either 0.1-3.5 parts TiO 2 , 0.1-5 parts B 2 O 3 , 0.4-2 parts Na 2 O or 0.5-10 parts PbO. AS 2 O 3 may be added as a fining agent. Specification 885,619 is referred to. |
