High pressure process for producing transformation toughened cer

Details High pressure process for producing transformation toughened cer High pressure process for producing transformation toughened cer

1987-02-18

1988-09-13

Dixon, Jr., William R.

Compositions: ceramic

Ceramic compositions

Refractory

501 1, 501 87, 501 96, 501105, 501151, 264 65, C04B 3548

Patent

active

047710225

ABSTRACT:
Toughening agents are produced by the application of high pressure, sufficient to transform a powder material into a denser high pressure polymorph. When the pressure is released, the high pressure phase is retrieved metastably at ambient conditions of pressure and temperature. The amount of high pressure phase retained at ambient conditions depends on the relative hydrostaticity of the pressurized environment and particle size of the powder. The high pressure phase is almost completely retained in a hydrostatic environment. One embodiment of the process of the present invention produces pressure transformation toughened zirconia comprising a high pressure phase having a symmetry no greater than tetragonal (defined as tetragonal II) dispersed within a matrix of a less dense monoclinic phase.

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patent: 4506024 (1985-03-01), Claussen et al.
CA 74(22):6664u, Weir et al., "Compressability of Inorganic Oxides", 1971.
CA 103(20):170176z, Syssan, "Pressure Induced Structural Transition in Sttium Sulfide", 1985.
Stevens, "An Introduction to Zirconia", Magnesium Elektron Ltd., Jun. 1983.
Kulcinski, G. L., "High-Pressure Induced Phase Transition in ZrO.sub.2 ", Journal of American Ceramic Society, vol. 51, No. 10, Oct. 1968.
daJornada, J. A. H., et al., "Phase Transition and Compression of LiNbO.sub.3 Under Static High Pressure," Journal of Applied Physics, vol. 57, No. 3, Feb. 1, 1985, 842-844.
Block, S., et al., "Pressure-Temperature Phase Diagram of Zirconia," Journal of the American Ceramic Society, vol. 68, No. 9, Sep. 1985, 497-499.

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