Highly chemically and thermally resistant borosilicate glass whi

Details Highly chemically and thermally resistant borosilicate glass whi Highly chemically and thermally resistant borosilicate glass whi

1993-09-10

1995-10-17

Bell, Mark I.

Compositions: ceramic

Ceramic compositions

Glass compositions, compositions containing glass other than...

501 70, C03C 3093

Patent

active

054591104

ABSTRACT:
A highly chemically resistant borosilicate glass which is capable of forming a seal with tungsten and has a glass transition temperature T.sub.g >570.degree. C., a coefficient of thermal expansion of between 3.95 and 4.5.times.10.sup.-6 K.sup.-1, a hydrolytic resistance in accordance with DIN 12111 in class one and a TK.sub.100 value in accordance with DIN 52326 of at least 240.degree. C. is described which has the composition (in % by weight, based on oxide) of SiO.sub.2 70 to 78, B.sub.2 O.sub.3 9 to 12, Al.sub.2 O.sub.3 1.5 to 4, Li.sub.2 O 0 to 4, Na.sub.2 O 1 to 5, K.sub.2 O 1 to 5, total of alkali metal oxides 5 to 7, MgO 0 to 3, CaO 1 to 3, BaO 0 to 2, ZnO 0 to 2, ZrO.sub.2 0.5 to 3, total of MgO+CaO+BaO+ZnO+ZrO.sub.2 6 to 10, and optionally conventional refining agents. It is preferred that the K.sub.2 O:Na.sub.2 O ratio be greater than 1 and that alkaline earth metal oxides, except for CaO, be omitted. In order to reduce the UV transparency, the glass is particularly suitable for use as a lamp glass in lamps which are subjected to very high temperatures, and as a flame-resistant safety glass.

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Chemical Abstract, vol. 106, No. 24, 200 648, Jun. 1987.
Translation of JP 4-33741 (Abstract), Jun. 1992.
Hienz G. Pfaender, Schott Guide To Glass, p. 110, 1983 (no month).
Doremus Glass Science 1973 (no month) John Wiley & Sons, Inc. pp. 160-163.

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