Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A polycrystalline silicon nitride body having a density of at least 99.5% of the theoretical density of silicon nitride, a thickness ranging from about 0.15 mm up to but less than 0.4 mm, a minimum in-line transmission of about 5% of radiant energy at wavelengths ranging from about 0.9 micron to about 2.5 microns, and a minimum in-line transmission of about 10% at wavelengths ranging from about 2.5 microns to about 4.5 microns.

Abstract: A non-aqueous gel of at least two metal oxides which is a precursor for glassy amorphous or crystalline mixed oxides is produced by reacting an alkoxide of one metal and a halide of another metal producing a low molecular weight polymeric reaction product, heating the reaction product to produce a polymeric product of substantially higher molecular weight, and heating the higher molecular weight polymeric product in air to remove its carbonaceous content.

Abstract: Scintillator bodies comprising fluorescent materials and having high optical translucency with low light absorption and methods of making the scintillator bodies are disclosed. In accordance with one embodiment of the invention, the scintillator bodies are formed by a hot-pressing process. In another embodiment, cold-pressing followed by sintering is employed. Another embodiment employs controlled cooling. Another embodiment employs hot-forging. The scintillator bodies that result are easily machined to desired shapes and sizes.

Abstract: A particulate dispersion of silicon nitride and beryllium additive is formed into a green body and sintered at a temperature ranging from about 1900.degree. C. to about 2200.degree. C. in a sintering atmosphere of nitrogen at superatmospheric pressure producing a sintered body with a density ranging from about 80% to about 100%.

Abstract: A silicon carbide sintered body exhibiting N-type semiconductivity is produced by shaping a mixture of .beta.-silicon carbide, boron additive and a carbonaceous additive into a green body and sintering the body in an atmosphere containing nitrogen to produce a sintered body having a density of at least about 90% and pores which are substantially non-interconnecting.