| 摘要 |
786,951. Glass manufacture. CORNING GLASS WORKS. May 23, 1956 [July 6, 1955], No. 15976/56. Class 56. A glass article has on at least a portion of its surface a compressional layer which contains a lower weight percentage of Na 2 O and/or K 2 O and a higher weight percentage of LiO 2 than the interior of the article. The article while at a temperature between the strain point and softening point is held in contact with a lithium salt, which is molten but not decomposed at that temperature, for a time sufficient to permit lithium ions to diffuse into the surface of the glass in exchange for alkali metal ions of the glass, to increase the tensile strength of the article. A number of examples of suitable glasses are given including in percentages SiO 2 55-66 ; Al 2 O 3 10-20; Na 2 O and/or K 2 O 10-13; TiO 2 8-12; ZrO 2 2-5; B 2 O 3 less than 2. Where the glass contains sufficient Al 2 O 3 , beta-spodumene is formed to give an opaque surface, the formation being assisted by the presence of TiO 2 and if sufficient TiO 2 is present, the inner glass may become translucent when reheated. The lithium salt used may be pure or diluted with other salts such as sulphates, chlorides and nitrates of calcium and magnesium. Colouring oxides of U, Cr, Ma, Fe, Co and Ni may be present in the glass. |
