Morphology of Phase Separation in AlN--Al sub 2 OC and SiC--AlN Ceramics

Solid solutions in the AlN--Al sub 2 OC and SiC--AlN systems were fabricated by hot-pressing powder mixtures in graphite dies. X-ray diffraction showed the samples to be single phases of 2H structure. The samples were annealed between 1600-1900 deg C for up to 1000 h. In the SiC--AlN system, optical...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 1990-09, Vol.73 (9), p.2640-2646
Main Authors: Kuo, S-Y, Virkar, A V
Format: Article
Language:English
Subjects:
360201 - Ceramics, Cermets, & Refractories- Preparation & Fabrication
360202 - Ceramics, Cermets, & Refractories- Structure & Phase Studies
400101 - Activation, Nuclear Reaction, Radiometric & Radiochemical Procedures
656002 - Condensed Matter Physics- General Techniques in Condensed Matter- (1987-)
ALUMINIUM COMPOUNDS
ALUMINIUM NITRIDES
ALUMINIUM OXIDES
CARBIDES
CARBON
CARBON COMPOUNDS
CHALCOGENIDES
COHERENT SCATTERING
CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
CRYSTALLOGRAPHY
DIFFRACTION
DISPERSIONS
ELECTRON MICROSCOPY
ELEMENTAL MINERALS
ELEMENTS
FABRICATION
GRAPHITE
HOT PRESSING
INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
MATERIALS SCIENCE
MATERIALS WORKING
MICROSCOPY
MINERALS
MIXTURES
MORPHOLOGY
NITRIDES
NITROGEN COMPOUNDS
NONMETALS
OPTICAL MICROSCOPY
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PNICTIDES
POWDERS
PRESSING
SCATTERING
SILICON CARBIDES
SILICON COMPOUNDS
SOLID SOLUTIONS
SOLUTIONS
X-RAY DIFFRACTION
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Summary:Solid solutions in the AlN--Al sub 2 OC and SiC--AlN systems were fabricated by hot-pressing powder mixtures in graphite dies. X-ray diffraction showed the samples to be single phases of 2H structure. The samples were annealed between 1600-1900 deg C for up to 1000 h. In the SiC--AlN system, optical microscopy and X-ray diffraction failed to reveal microstructural or phase changes. However, electron microscopy showed that samples had decomposed. Streaking of diffraction spots occurred along directions orthogonal to {012} planes ( approx 43 deg off the c axis), which is approximately the direction along which the elastic energy function is a minimum. The orientation-dependent Young's modulus was also a minimum along this direction. In AlN--Al sub 2 OC, optical microscopy and X-ray diffraction indicated the occurrence of decomposition. The precipitates were disk-shaped with (001) orthogonal to the disks. The occurrence of decomposition along the (001) direction suggests that it is the elastically soft direction. Graphs, Photomicrographs, Diffraction patterns. 22 ref.--AA
ISSN:0002-7820
1551-2916