Microstructure Studies of Polycrystalline Refractory Oxides
Summary rept. 29 Mar 1972-28 Apr 1973
AVCO CORP LOWELL MA SYSTEMS DIV
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The program was divided into three tasks within the general topic of microstructure effects on the properties of polycrystalline oxides. The press forging process was advanced to the point where a three-inch Al2O3 hemisphere of prescribed dimensions could be forged. The product had high transmissivity and a strong crystallographic texture. Initial experiments on press forging Si3N4 are reported. Three grades of powder used in the fabrication of hot pressed 99. 9 Al2O3 were found to contain particulate impurities which lead to inclusions andor flaws in the product. Fracture origins were correlated with such flaws or other flawed features of structure in over 70 of the specimens tested. A study of gassolid interactions in Al2O3 showed that CO was the major species evolved from material hot pressed in graphite.
- Ceramics, Refractories and Glass