Accession Number : AD0463287

Title :   CHEMICAL STRENGTHENING OF CERAMIC MATERIALS.

Descriptive Note : Summary rept., 7 Apr 64-6 Apr 65,

Corporate Author : LINDEN LABS INC STATE COLLEGE PA

Personal Author(s) : Kirchner, Henry P. ; Gruver, Robert M.

Report Date : 07 MAY 1965

Pagination or Media Count : 68

Abstract : An investigation of the effect of compressive surface layers on the strength of polycrystalline ceramic bodies is d5scribed. The feasibility of chemically strengthening polycrystalline ceramics by formation of low-expansion, solid-solution surface layers has been established. During cooling after sintering at high temperatures, the main body tends to contract more than the surface layers resulting in compressive stresses in the surfaces. The existence of these stresses has been demonstrated by ring tests. Failure by shearing off of the surface layers is prevented by establishing gradual variations in composition within the body. These variations in compositions result in variations in thermal expansion coefficient which, in turn, result in gradual variations in stresses and reduction of the maximum shear stress. The compressive stresses may be acting to reduce the contribution of surface flaws to the structural failure of these bodies. The thermal expansion properties of a wide variety of oxide solid solution compositions in phases having the spinel, periclase and corundum structures were measured. Some of these materials have lower thermal expansion coefficients than the bodies on which they would be placed. (Author)

Descriptors :   (*CERAMIC MATERIALS, MECHANICAL PROPERTIES), SURFACES, COMPRESSIVE PROPERTIES, THERMAL EXPANSION, SOLID SOLUTIONS, SPINEL, TITANIUM COMPOUNDS, ALUMINUM COMPOUNDS, MAGNESIUM COMPOUNDS, CHROMIUM COMPOUNDS, GALLIUM COMPOUNDS, COBALT COMPOUNDS, NICKEL COMPOUNDS, TIN COMPOUNDS, OXIDES, CERAMIC COATINGS, X RAY DIFFRACTION, STRUCTURAL PROPERTIES, CRYSTALS.

Distribution Statement : APPROVED FOR PUBLIC RELEASE