General Electric Company

Svante Prochazka

Charles D Greskovich

Frederic Joseph Klug

Robert Arthur Giddings

Richard J Charles

Curtis Alan Johnson

Wayne D Pasco

Chester R O'Clair

John A Palm

Thomas Bert Gorczyca

Fred F Holub

Krishan Lal Luthra

Minyoung Lee

Curtis E Scott

Milivoj Konstantin Brun

Dominic A Cusano

Samson Hettiarachchi

Young Jin Kim

D Sangeeta

Gary M Renlund

Harald L Witting

Hsueh-Rong Chang

Jennifer L Myers

William J Dondalski

William S Coblenz

Charles E Van Buren

An electrochemical corrosion potential sensor is fabricated by initially joining an electrical conductor to a sensor tip. An electrical cable is joined to the tip conductor. Ceramic powder is fused under heat around the tip conductor to form an integral annular electrically insulating band therearound to insulate the tip from the cable. The band may be formed by plasma spraying, or it may be molded and sintered to seal it to the tip and conductor without brazing. In a preferred embodiment, the band is formed of yttria-stabilized-zirconia or magnesia-stabilized-zirconia.

Brazeless electrochemical corrosion potential sensor

Sodium loss, free halide build-up, devitrification and wall etching of the arc chamber are substantially reduced in an electrodeless HID metal halide arc discharge lamp by a protective metal silicate coating present only on the interior, equatorial portion of the arc chamber wall which is closest to the arc plasma. Suitable coatings include a metal silicate of a metal selected from the group consisting essentially of scandium, yttrium, beryllium, rare earth metal and mixture thereof.

Protective metal silicate coating for electrodeless HID lamps

A method for refined silicon carbide powder comprises attrition milling silicon carbide material in a liquid medium with a milling media to obtain refined silicon carbide particles having a specific surface area of at least 15 m.sup.2 /g, and preferably 20 m.sup.2 /g, with a median particle size of less than 0.5 microns, and preferably 0.25 microns. The invention includes the finished powder.

Sintered silicon carbide and method of making

A method for making a composite ceramic article by infiltration of a sintered ceramic preform with an infiltrate phase. The ceramic preform is made by directionally solidifying a liquid medium containing a dispersion of ceramic particles to produce a green, porous ceramic preform a plurality of interconnected lamelli that are partially separated from one another by complementary interlamellar regions, removing the solidified liquid medium and sintering the ceramic preform. This method may be used to make silicon carbide composites where a silicon carbide preform is first infiltrated with carbon to coat the lamelli of the preform, followed by infiltration of the carbon coated preform with molten silicon, whereby the molten silicon and carbon react to form silicon carbide in the interlamellar regions. The ceramic preform may also be coated with a thin, diffusion-inhibiting ceramic layer prior to infiltration in order to prevent interdiffusion between the lamelli of the preform and the infiltrate phase, and provide a plurality of mechanically weak, crack deflecting interfaces within the composite article.

Method of making a ceramic composite by infiltration of a ceramic preform

Fibers having reduced surface roughness have a continuous coating of a silicone resin that undergoes pyrolysis in hydrogen or helium to form a hard, amorphous solid coat containing silicon, oxygen, and carbon. This silicon oxycarbide glass coating has exceptional high temperature strength and chemical stability compared to even vitreous silica. The coating is resistant to crystallization and oxidation at temperatures above 1000.degree. C.

Amorphous silicon oxycarbide coated silicon carbide or carbon fibers

A composite is comprised of reinforcement fibers having a continuous coating of a metal diboride form the group consisting of titanium diboride, zirconium diboride, hafnium diboride, aluminum diboride, and mixtures thereof, and a molten silicon infiltration formed silicon carbide matrix. The reinforcement fibers are fibers from the group consisting of elemental carbon, silicon carbide, and mixtures thereof. A method for forming the fiber reinforced composite comprises depositing a continuous coating of the metal diboride on the fibers. A carbonaceous material is admixed with the coated fibers so that at least 5 volume percent of the mixture is the fibers. The mixture is formed into a preform having an open porosity ranging from about 25 volume percent to about 90 volume percent of the preform. The preform is heated in an inert atmosphere or partial vacuum, and infiltrated with molten silicon to produce an infiltrated product having the composition of the composite.

Silicon carbide composite with metal boride coated fiber reinforcement

A protective coating of suitable composition and thickness is applied to the inner surface of the arc tube of a high-intensity, metal halide discharge lamp in order to avoid a substantial loss of the metallic component of the metal halide fill and hence a substantial buildup of free halogen, thereby extending the useful life of the lamp. A preferred lamp structure includes a fused silica arc tube with a silicon coating. The silicon coating is preferably applied to the arc tube using a chemical vapor deposition process.

Protective coating for high-intensity metal halide discharge lamps

Spherical particles of polycrystalline silicon carbide having a density greater than 80% of the theoretical density for silicon carbide and having an average diameter ranging from about 10 microns to about 5000 microns are produced by forming spherical agglomerates of a sinterable silicon carbide powder and sintering the agglomerates at a temperature ranging from about 1900.degree. C. to about 2300.degree. C.

Fabrication of small dense silicon carbide spheres

A silicon carbide sintered body characterized by its microstructural stability at high temperatures is produced by forming a mixture of .beta.-silicon carbide powder, .alpha.-silicon carbide seeding powder, boron additive and a carbonaceous additive into a green body and sintering it to produce a sintered body with a density of at least 80% wherein at least 70% by weight of the silicon carbide is .alpha.-silicon carbide.

Silicon carbide sintered body

Optically translucent theoretically dense body of mullite is produced by pressing an amorphous mixed oxide powder composition of from about 72.5 weight % to about 76.5 weight % Al.sub.2 O.sub.3 /balance SiO.sub.2 into a compact of density of at least 1.0 g/cc, sintering the compact in oxygen or a vacuum of 0.05 torr to 1 torr producing a gas-impermeable compact, hot isostatically pressing the gas-impermeable compact to theoretical density, and with respect to compositions ranging from higher than about 74 wt % Al.sub.2 O.sub.3 /balance SiO.sub.2, annealing the theoretically dense body.

Optically translucent ceramic

Amorphous mixed oxide powder composed of from about 74 weight % to about 76.5 weight % Al.sub.2 O.sub.3 balance SiO.sub.2 is pressed into a compact with a density of at least 1 g/cc, fired in oxygen or vacuum of 0.05 to 1 torr producing a gas-impermeable compact, and sintered in air, argon, helium, nitrogen or mixtures thereof producing an optically translucent theoretically dense body of mullite.

Process for producing optically translucent ceramic

Amorphous mixed oxide powder composed of from about 74 weight % to about 76.5 weight % Al.sub.2 O.sub.3 balance SiO.sub.2 is pressed into a compact with a density of at least 1 g/cc and sintered in oxygen producing an optically translucent theoretically dense body of mullite.

Process for producing optically translucent mullite ceramic

A silicon nitride compact with a density of 95% to 100% is produced by forming a particulate dispersion of silicon nitride and beryllium additive into a compact, firstly sintering the compact from about 1900.degree. C. to about 2200.degree. C. in nitrogen at superatmospheric pressure sufficient to prevent thermal decomposition of the silicon nitride until the entire outside surface of the compact becomes impermeable to nitrogen gas, and then secondly sintering the compact from about 1800.degree. C. to about 2200.degree. C. under a nitrogen pressure having a value at least twice the first nitrogen sintering pressure.

Sintering of silicon nitride to high density

A compact composed of a mixture of silicon nitride with less than about 0.5 weight % cation impurities and containing beryllium additive, and having an oxygen content of at least about 1.4 weight %, is sintered from 1900.degree. C. to 2200.degree. C. in nitrogen at superatmospheric pressure producing a sintered compact of at least about 80% density.

Sintering of silicon nitride with Be additive

A particulate dispersion of .alpha.-alumina, magnesium oxide and an additive selected from the group consisting of zirconium oxide, hafnium oxide and mixtures thereof, is formed into a green body and sintered in hydrogen producing a theoretically dense ceramic with improved optical transmission properties.

Growing community of inventors

Ballston Lake, NY, United States of America

Svante Prochazka