Gte Laboratories Incorporated

Other

United States of America As Represented by the Secretary of the Air Force

Gte Products Corporation

J Thomas Smith

Carr L Quackenbush

Helmut Lingertat

Anthony P Moschetti

Vincent W Nehring

Jeffrey T Neil

F Joseph Reid

Kenneth W French

Kenneth H Shaner

Alfred Piorkow

Robert C Kocher

An improved cooled high power laser mirror system is described which uses a ilicon mirror face with an attached silicon nitride based heat exchanger assembly. The silicon nitride provides a high strength, high toughness, and stiff backup assembly. The particular silicon nitride system is microstructurally engineered to provide a thermal expansion match to silicon designed to insure high quality bonding and minimum mirror distortion.

Cooled laser mirror materials

A method of preparing fully dense silicon nitride based ceramic articles comprises the steps of blending a metal oxide component and silicon nitride, wherein a portion of the silicon nitride comprises acicular crystals; comminuting the powder mixture to reduce the aspect ratio of the acicular crystals to an average of less than about 3; pressing the comminuted powder to form a compact; and pressureless sintering the compact to a fully dense ceramic body. Powder mixtures and powder compacts for forming fully dense silicon nitride based ceramic bodies are also disclosed.

Silicon nitride based ceramics and method

Apparatus for automatically measuring aperture size of apertured material includes a means for supporting and transporting the apertured material and a light source providing a light beam directed for passage through the apertured material to a light detector and is characterized by a comparator mask of alternate light transparent and opaque sectors of a given dimension and means for overlaying the apertured material with the comparator mask to provide a given length of light transparent slot and responsive to signals representing light transmitted through the given length of slot for deriving a signal representing the width of the slots of the slotted material. Also, a process for automatically measuring aperture size includes the steps of overlaying the slotted material with the comparator mask and utilizing a signal from the light detector representing light transmission of the slots of a given length to derive a signal representative of the slot width.

Apparatus and process for automatically measuring aperture size of

Sintered silicon nitride-silica-yttria ceramic articles having silica-rich or yttria-rich casing layers are disclosed. The surface layers are formed by sintering pre-compacted bodies in a powder setter bed to produce unitary sintered bodies having surface layers in which the atom ratio of yttrium to silicon has a smooth gradient from the surface of the article to the interior body of the article.

Sintered silicon nitride ceramic articles having surface layers of

Dense, composite, polycrystalline ceramic articles comprising silicon nitride, silicon dioxide, and yttrium oxide and having thin surface layers of controlled composition are formed by sintering pre-pressed compacts embedded in setter bed powder mixtures having compositions of silicon nitride, silicon dioxide, and yttrium oxide which differ from that of the pressed compact. Employing the method of this invention, articles are produced which have surface layers in which the minor phase of the article is enriched with either yttrium or silicon.

Method of producing dense silicon nitride ceramic articles having

Si.sub.3 N.sub.4 polycrystalline ceramic bodies formed from starting materials containing about 2 to 4 weight percent SiO.sub.2, less than 0.1 weight percent cation impurities and Y.sub.2 O.sub.3 in critical amounts exhibit optimum oxidation resistance. Such bodies are useful as engine parts or components or as regenerator structures for waste heat recovery.

Oxidation resistant silicon nitride containing rare earth oxide

An electrical power generation system includes a waterwheel contained within a housing enclosure above a water collection compartment, a water discharge nozzle in alignment with said waterwheel, means for delivering water to said discharge nozzle including a pump for returning water from the collection compartment, a portion of the output of the waterwheel being used to drive the pump, wherein the waterwheel includes fin elements having inclined water entrapping flange portions and is supported by means of an adjustable support to maintain the waterwheel dynamically balanced and in alignment with the discharge nozzle.

Waterwheel power generator

Polycrystalline ceramic bodies of Si.sub.3 N.sub.4 when prepared to obtain an intergranular phase which is substantially crystalline, exhibits significantly improved mechanical strength at elevated temperatures above 1,000.degree. C. up to 1600.degree. C. over bodies having glass-containing intergranular phases.

Growing community of inventors

Acton, MA, United States of America

J Thomas Smith