Ceramic structural material

A method of forming an integral structure of a low expansion glass-ceramic material having one or more coherent solid, reinforced portion and a gas conducting portion which comprises

• (a) bundling together in a desired configuration to define said solid, reinforced portion a plurality of axially elongated individual sinterable rods with their axes parallel and in wall-to-wall contact with each other, said rods being comprised of a thermally crystallizable glass composition of weight percent in the range:
• SiO.sub.2 68.6 - 75.8
• Al.sub.2 O.sub.3 16.8 - 21.3
• Li.sub.2 O 3.7 - 4.44
• NaO.sub.2 0.1 - 0.55
• K.sub.2 o 0 - 0.2
• mgO 0 - 0.1
• ZnO 0 - 1.7
• TiO.sub.2 1.4 - 2.0
• ZrO.sub.2 1.17 - 1.6
• Cl.sub.2 0 - 0.1
• Sb.sub.2 O.sub.3 0.3 - 0.5
• F.sub.2 0 - 0.1
• (b) filling the interstices between adjacent rods of said portion with additional sinterable glass of the composition set forth in step (a) and having substantially the same thermal expansion characteristics as the sinterable rods when both are subjected to a thermal treatment suitable for converting such glass to glass-ceramic,
• (c) tightly packing together a plurality of axially elongated tubes of thermally crystallizable glass of a composition within the range of glass of step (a) in a desired matrix configuration and corresponding to said gas conducting portion of the structure, said tubes being adjacent to and against at least one side of said rod-frit structure portion, each of said tubes being sealed at its opposite ends and containing a heat expansible fluid medium and the tubes being essentially parallel to other tubes of the gas conducting portion and to the rods of the reinforced portion of the structure, the glass of said tubes having substantially the same thermal expansion characteristics as said rods and interstitially disposed glass when all are subjected to a thermal treatment for converting them to glass-ceramic,
• (d) constraining the tubes of said configuration in their position adjacent and against said rod configuration and against substantial movement in a direction normal to their parallel tube alignment,
• (e) subjecting said constrained rods, interstitial glass and tubes to a temperature sufficient to soften said rods, said interstitial glass and said tubes and cause said fluid medium in said end sealed tubes to expand the tubes into tight contact with adjacent tubes and said adjacent rod-interstitial glass structure bonding such tubes of the gas conducting portion to each other and to said solid portion as an integral structure, said temperature being in the range of 50.degree. to 250.degree. F. above the annealing point of the glass of the said constituents of said integral structure in which temperature range the glass thereof nucleates during said fusion,
• (f) jointly heating said fused integral glass structure to a higher temperature than the temperature in step (e) in the range of 200.degree. to 500.degree. F. above the said original annealing point of the glass,
• (g) finally heating said fused structure in a temperature range from 1800.degree.-2300.degree. F. for completing crystallization thereof to a glass-ceramic having an average coefficient of lineal thermal expansion of about -18 to +15 .times. 10.sup..sup.-7 /.degree. C. over the range of 0.degree.-300.degree. C., and thereafter cooling said structure, and
• (h) opening the opposite sealed ends of the tubes at a time subsequent to performing step (e), thereby providing the gas conducting portion of said integral structure.