The United States of America As Represented by the Secretary of

Government of the United States of America, As Represented by the Secretary of Commerce

Gasper J Piermarini

Alexander N Pechenik

Stanley Block

A method of producing a dense compact of ultra-fine powder employs low temperatures and high pressures to produce a very dense, nearly ideally packed compact from a starting nano-sized powder. The final product is capable of being easily hot-pressed or sintered to full density.

Method for fabrication of dense compacts from nano-sized particles using

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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McLean, VA, United States of America

Gasper J Piermarini