| 摘要 |
Shaped refractory ceramic and refractory ceramic composite objects are made from corresponding shaped, oxidation-resistant-metal-bearing objects through exposure to an oxidizing environment without substantial changes in dimensions by providing in the shaped metal-bearing objects a combination of a) metals which when oxidized form a ceramic compound with a larger molar volume than the molar volume of the metals consumed to make the ceramic compound with b) metals which when oxidized form a ceramic compound with a smaller molar volume than the molar volume of the metals consumed to make the ceramic compound. Metal-bearing objects, containing metals such as silicon or aluminum, which when oxidized form ceramic or ceramic-composite objects containing refractory ceramic compounds of desired properties, such as compounds containing silicon oxide or aluminum oxide, for which the ceramic compounds have a molar volume that is greater than the molar volumes of the metals consumed to make the ceramic compounds, expand upon oxidation, thereby having an adverse effect on the properties of the resulting ceramic and preventing the maintenance of the dimensions of the metal-bearing objects. The present invention is the discovery that when alkali or alkaline earth metals, which when oxidized have molar volumes that are less than such metals, are alloyed with or otherwise combined with oxidation-resistant metals that are formed into the metal-bearing objects and converted into desired refractory ceramics, swelling, resulting loss of mechanical properties, and dimensional changes are reduced or eliminated. Further, such combination of a) metals that after oxidation form ceramic compounds having a molar volume greater than the molar volumes of the metals consumed to make the ceramic compound with b) alkali or alkaline earth metals that after oxidation form ceramic compounds having a molar volume less than the molar volume of the alkali or alkaline earth metals consumed to make the ceramic compounds provides an unexpectedly advantageous brazing alloy for joining ceramic-bearing bodies.
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