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Preparation and Evaluation of Si-Al-O-N.
Final rept. 1 Jan-31 Dec 73,
IIT RESEARCH INST CHICAGO ILL
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The purpose of this program was to prepare specimens of Si-Al-O-N compositions of adequate intrinsic i.e., pore-free, high single phase constitution and size to permit evaluation of chemical, physical, and mechanical properties. A wide variety of processing techniques, including hot pressing, pseudoisostatic hot pressing, cold pressing and sintering, and combinations of these techniques, using beta silicon nitride, alpha silicon nitride, alpha alumina, active alumina, silicon, aluminum nitride, magnesia, and other materials as precursors were employed. Modulus of rupture and elasticity measurements made on representative samples give low strength values compared with Arrols data 120,000 psi. An explanation for the low strength data may be found in the type of fracture obtained. The scanning electron microscope reveals a fine grain intergranular failure. Further evidence suggests liquid phase sintering at high temperature, which could produce a glassy grain boundary.
APPROVED FOR PUBLIC RELEASE