Accession Number : ADA300648

Title :   Control of Texture in Monolithic Alumina.

Descriptive Note : Final rept.,

Corporate Author : BALDWIN ELECTRONICS INC LITTLE ROCK AR

Personal Author(s) : Brandon, David ; Chen, Dezhou ; Chan, Helen

PDF Url : ADA300648

Report Date : SEP 1995

Pagination or Media Count : 23

Abstract : Conventional ceramic powder slips seeded with alpha-Al2O3 platelets were rheologically processed to align the seed crystals. An aqueous-based gel reaction was used to ensure that alignment was retained in the green body and throughout the drying procedure. Bulk samples were produced by laying-up the cast tapes, filter pressing to form a green compact, and then drying and sintering. The degree of preferred orientation in the sintered samples was characterieed by X-ray diffraction. It was found that the degree of texture was significantly enhanced relative to samples processed in the same manner, but with no platelet additions. SEM study of the final microstructures showed that the grain size and grain morphology was sensitive to the initial distribution of platelets within the green tape, which in turn was dependent on the volume fraction and size of the platelets. Further, it was demonstrated that using this technique it is possible to achieve a specimen which exhibits an equiaxed grain structure, and yet has a strong degree of preferred orientation. Finally, studies of indentation cracking showed that a pronounced texture inhibited long range crack propagation, and instead promoted localized cracking.

Descriptors :   *ALUMINUM OXIDES, *TEXTURE, CONTROL, MICROSTRUCTURE, DISTRIBUTION, POWDERS, CRACKS, MORPHOLOGY, X RAY DIFFRACTION, GRAIN SIZE, CRYSTALS, CERAMIC MATERIALS, CHEMICAL REACTIONS, SAMPLING, TAPES, RHEOLOGY, FILTERS, MONOLITHIC STRUCTURES(ELECTRONICS), GELS, GREEN(COLOR), GRAIN STRUCTURES(METALLURGY), DRYING, CASTINGS, SINTERING, PRESSING(FORMING), SEEDING.

Subject Categories : Inorganic Chemistry
      Physical Chemistry
      Ceramics, Refractories and Glass
      Fabrication Metallurgy

Distribution Statement : APPROVED FOR PUBLIC RELEASE