US Government As Represented by the Secretary of the Army

James W McCauley

Frederick Schmid

Dennis J Viechnicki

Gary A Gilde

Parimal J Patel

Charles P Gazzara

Jarda L Caslavsky

Normand D Corbin

A transparent aluminum oxynitride product is produced by a first heat treating step wherein a combination of AlOand AlN at a temperature within the solid-liquid phase and a second step of sintering the heat treated combination at a temperature at least 50&#xb0; C. less than the heat treating temperature. The method introduces a small fraction of liquid that aids in pore elimination and densification. In a single step, the material is shifted from the liquid/solid region into a solid AlON solution region, wherein the liquid is fully reacted with the solid AlON phase, with further sintering occurring. The procedure is sufficient to eliminate voids and other imperfections which often result in a reduction in optical clarity.

Transient liquid phase reactive sintering of aluminum oxynitride (AlON)

A structural ceramic material comprising single phase polycrystalline cubic aluminum oxynitride preferably with at least 97% of theoretical density which displays transparency and isotropic optical, thermal and electrical properties, an infrared cutoff at about 5.2 microns wavelength, and which shows no chemical or physical property change after heating in air (atmosphere) at 1100.degree. C.

Process for producing polycrystalline cubic aluminum oxynitride

A method for the production of improved, transparent single crystals having a corundum structure under conditions of minimum thermal strain, comprising the optimum orientation of growth planes of a seed crystal in a melt substantially parallel to the vertical side wall means of a crucible, and heating and subsequent cooling the melt, thereby nucleating on the seed crystal.

Method of orienting seed crystals in a melt, and product obtained thereby

The unidirectional solidification of a metal-ceramic composite in a system omprising the positioning of a seed crystal in a crucible, adding a portion of premelted ceramic material, a metallic material, and the remainder of the premelted ceramic. The temperature of the ceramic material is raised to about 50.degree.C above its melting point and then slowly decreased with a corresponding increase in the flow of an inert coolant gas through the system thereby unidirectionally solidifying the material to produce a single crystal having the orientation of the seed.

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Wakefield, MA, United States of America

James W McCauley