Glass for seals

Water glass asbestos joints, 5, g, 8, 46 Water glass, for sealing, 5, 7 Williamson reaction, 6, 48 Wool, 5, 40... 

Made by Plowden Thompson Ltd. Dial 36 is a borosilicate glass for sealing to timgsten. The linear expansion coefficient (20-300°Q is 3-6 X 10 . 

A borosilicate glass for sealing to alloys of the Kovar type (p. Ill) l Clso seals to some electrical porcelains. It is made by the British phomson Houston Co., and is often referred to as BTH C,40 or as The linear expansion coefficient is 4-85 x 10 from 50 to... 

Pids is a soda glass for sealing to platinum, and is made by Plowden b Thompson Ltd. The linear expansion coefficient (20-300°C) is pi K 10-. ... 

Sealing glass for seals to NiFe45 (DIN 17745) and compression seals... 

Thermal Properties. Many commercial glass-ceramics have capitalized on thek superior thermal properties, particularly low or zero thermal expansion coupled with high thermal stabiUty and thermal shock resistance properties that are not readily achievable in glasses or ceramics. Linear thermal expansion coefficients ranging from —60 to 200 x 10 j° C can be obtained. Near-zero expansion materials are used in apphcations such as telescope mirror blanks, cookware, and stove cooktops, while high expansion frits are used for sealing metals. 

The thermal expansivity of Ni—Fe alloys vary from ca 0 at ca 36 wt % Ni (Invar [12683-18-OJ) to ca 13 x 10 / C for Ni. Hence, a number of compositions, which are available commercially, match the thermal expansivities of glasses and ceramics for sealing electron tubes, lamps, and bushings. In addition, the thermal expansion characteristic is utilized ia temperature controls, thermostats, measuriag iastmments, and condensers. 

Fig. 7. Comparison of the thermal stabihty, ie, formation of monomer and loss of of FRPS and APS upon heating for 2.5 h at 285°C in glass tubes sealed at 0.67 or 13.3 kPa. A is FRPS residual styrene formed B, FRPS loss C, APS loss and D, APS residual styrene formed. To convert kPa to...

Tubes for sealed tube reactions, such as the Carius determination of halogens and sulphur, can be made from Pyrex, Monax or soda glass. The mechanical strength of the glasses is about the same, but a soda Carius tube is much more likely to crack as a result of thermal strain than a Pyrex or Monax one. The Carius tubes are usually made from tubing of approximately 20-25 mm diameter and 3 mm wall thickness—Pyrex extra heavy tubing of external diameter 22 mm has a wall thickness of 2-5-4 mm and can be used up to 600°C. 

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