Abstract: Cutting tools and cutting tool inserts having improved mechanical and chemical wear resistance under demanding conditions of machining speed, temperature, or workpiece hardness comprise a silicon nitride substrate body having at least one hard, adherent coating layer of a refractory metal carbide. The silicon nitride substrate body consists essentially of a first phase of silicon nitride and a refractory second phase comprising silicon nitride and an effective amount of a densification aid selected from the group consisting of silicon dioxide, aluminum oxide, magnesium oxide, yttrium oxide, hafnium oxide, zirconium oxide, the lanthanide rare earth oxides, and mixtures thereof.

Abstract: Coated abrasion resistant composite ceramic cutting tools comprise a composite substrate body consisting essentially of a particulate material selected from the group consisting of the refractory metal carbides, nitrides, carbonitrides and combinations thereof uniformly distributed in a matrix, coated with at least one adherent coating layer comprising a refractory metal carbide. The particulate material is of an average particle size ranging between about 0.5 microns to about 20 microns and comprises from about 5 to about 60 volume percent of the composite cutting tool. The matrix consists essentially of a modified silicon aluminum oxynitride having about 2 to about 25 volume percent of a modifier selected from the oxides of silicon, yttrium, magnesium, hafnium, zirconium, beryllium, the lanthanides and combinations thereof.

Abstract: Abrasion resistant composite cutting tools comprise a particulate material selected from the group consisting of the refractory metal carbides, nitrides, carbonitrides and combinations thereof uniformly distributed in a matrix. The particulate material is of an average particle size ranging between about 0.5 microns to about 20 microns and comprises from about 5 to about 60 volume percent of the composite cutting tool. The matrix consists essentially of a modified silicon aluminum oxynitride having about 2 to about 25 volume percent of a modifier selected from the oxides of silicon, yttrium, magnesium, hafnium, zirconium, beryllium, the lanthanides and combinations thereof.

Abstract: Coated abrasion resistant composite ceramic cutting tools comprise a composite substrate body consisting essentially of a particulate material selected from the group consisting of the refractory metal carbides, nitrides, carbonitrides and combinations thereof uniformly distributed in a matrix, coated with at least one adherent coating layer of alumina. The particulate material is of an average particle size ranging between about 0.5 microns to about 20 microns and comprises from about 5 to about 60 volume percent of the composite cutting tool. The matrix consists essentially of a modified silicon aluminum oxynitride having about 2 to about 25 volume percent of a modifier selected from the oxides of silicon, yttrium, magnesium, hafnium, zirconium, beryllium, the lanthanides and combinations thereof.

Abstract: An improved modified silicon aluminum oxynitride based composite cutting tool is made by forming a homogeneous matrix of a modified silicon aluminum oxynitride prior to uniformly dispersing a hard refractory material throughout the homogeneous matrix, then densifying the combined materials to form a composite cutting tool having a density greater than 98 percent of the theoretical density of the combined materials.

Abstract: Coated composite ceramic cutting tools and cutting tool inserts having improved mechanical and chemical wear resistance under demanding conditions of machining speed, temperature, or workpiece hardness comprise a composite silicon nitride substrate having at least one hard adherent coating of alumina. The composite silicon nitride substrate consists essentially of a first phase of silicon nitride and a refractory second phase comprising silicon nitride and an effective amount of a densification aid selected from yttrium oxide, zirconium oxide, hafnium oxide, the lanthanide rare earth oxides, and mixtures thereof.

Abstract: An arc limiting refractory resistive element is fabricated from aluminum oxide, carbon black and a sintering aid. The fabricating process includes compacting a mixture of the materials, sintering the compact in an inert atmosphere, then oxidizing the outer region of the sintered compact to form a non-conductive sheath around the electrically conductive material.

Abstract: Cutting tools and cutting tool inserts having improved mechanical and chemical wear resistance under demanding conditions of machining speed, temperature, or workpiece hardness comprise a composite silicon nitride substrate having at least one hard adherent coating layer of a refractory metal carbide. The composite silicon nitride substrate body consists essentially of particles of a refractory material uniformly distributed in a matrix consisting essentially of a first phase of silicon nitride and a refractory second phase comprising silicon nitride and an effective amount of a densification aid selected from the group consisting of yttrium oxide, hafnium oxide, the lanthanide rare earth oxides, and mixtures thereof.

Abstract: Cutting tools and cutting tool inserts having improved mechanical and chemical wear resistance under demanding conditions of machining speed, temperature, or workpiece hardness comprise a composite silicon nitride substrate having at least one hard adherent coating layer of a refractory metal carbonitride. The composite silicon nitride substrate body consists essentially of particles of a refractory material uniformly distributed in a matrix consisting essentially of a first phase of silicon nitride and a refractory second phase comprising silicon nitride and an effective amount of a densification aid selected from the group consisting of yttrium oxide, hafnium oxide, the lanthanide rare earth oxides, and mixtures thereof.

Abstract: Cutting tools and cutting tool inserts having improved mechanical and chemical wear resistance under demanding conditions of machining speed, temperature, or workpiece hardness comprise a silicon nitride substrate body having at least one hard, adherent coating layer of a refractory metal carbonitride. The silicon nitride substrate body consists essentially of a first phase of silicon nitride and a refractory second phase comprising silicon nitride and an effective amount of a densification aid selected from the group consisting of silicon dioxide, aluminum oxide, magnesium oxide, yttrium oxide, hafnium oxide, zirconium oxide, the lanthanide rare earth oxides, and mixtures thereof.

Abstract: Coated abrasion resistant composite ceramic cutting tools comprise a composite substrate body consisting essentially of a particulate material selected from the group consisting of the refractory metal carbides, nitrides, carbonitrides and combinations thereof uniformly distributed in a matrix, coated with at least one adherent coating layer comprising a refractory metal carbonitride. The particulate material is of an average particle size ranging between about 0.5 microns to about 20 microns and comprises from about 5 to about 60 volume percent of the composite cutting tool. The matrix consists essentially of a modified silicon aluminum oxynitride having about 2 to about 25 volume percent of a modifier selected from the oxides of silicon, yttrium, magnesium, hafnium, zirconium, beryllium, the lanthanides and combinations thereof.

Abstract: Cutting tools and cutting tool inserts having improved mechanical and chemical wear resistance under demanding conditions of machining speed, temperature, or workpiece hardness comprise a composite silicon nitride substrate having at least one hard adherent coating layer of a refractory metal nitride. The composite silicon nitride substrate body consists essentially of particles of a refractory material uniformly distributed in a matrix consisting essentially of a first phase of silicon nitride and a refractory second phase comprising silicon nitride and an effective amount of a densification aid selected from the group consisting of yttrium oxide, hafnium oxide, the lanthanide rare earth oxides, and mixtures thereof.

Abstract: Coated abrasion resistant composite ceramic cutting tools comprise a composite substrate body consisting essentially of a particulate material selected from the group consisting of the refractory metal carbides, nitrides, carbonitrides and combinations thereof uniformly distributed in a matrix, coated with at least one adherent coating layer comprising a refractory metal nitride. The particulate material is of an average particle size ranging between about 0.5 microns to about 20 microns and comprises from about 5 to about 60 volume percent of the composite cutting tool. The matrix consists essentially of a modified silicon aluminum oxynitride having about 2 to about 25 volume percent of a modifier selected from the oxides of silicon, yttrium, magnesium, hafnium, zirconium, beryllium, the lanthanides and combinations thereof, and a silicon aluminum oxynitride.

Abstract: Cutting tools and cutting tool inserts having improved mechanical and chemical wear resistance under demanding conditions of machining speed, temperature, or workpiece hardness comprise a silicon nitride substrate body having at least one hard, adherent coating layer of a refractory metal nitride. The silicon nitride substrate body consists essentially of a first phase of silicon nitride and a refractory second phase comprising silicon nitride and an effective amount of a densification aid selected from the group consisting of silicon dioxide, aluminum oxide, magnesium oxide, yttrium oxide, hafnium oxide, zirconium oxide, the lanthanide rare earth oxides, and mixtures thereof.

Abstract: Molybdenum is removed from an aqueous solution containing tungsten and molybdenum by extracting the molybdenum from the aqueous solution having a pH greater than 8.5 with a liquid organic extractant containing a preferred complexing agent, 3,4-dimercaptotoluene.

Abstract: A vacuum-tight assembly, such as a discharge tube for a sodium vapor arc lamp, includes a high density polycrystalline ceramic body, such as alumina or yttria, having a cavity and at least one closure member and a sealing material for sealing the cavity from the atmosphere. The closure member is formed from a molybdenum alloy containing titanium, vanadium, chromium or mixtures thereof. The closure member and the sealing material have thermal coefficients of expansion closely matched to the thermal coefficient of expansion of the ceramic body over a wide temperature range. In a preferred embodiment, an alumina discharge tube is sealed by a closure member formed from a molybdenum alloy containing 50 atom percent titanium.

Abstract: Coarse particle size zinc sulfide is treated with a solution of alkali metal halide to make it adaptable for hot-pressing into shaped, polycrystalline windows which is more transparent in the visible to near visible and infrared spectral regions than untreated coarse particle size zinc sulfide.

Abstract: A vacuum-tight assembly, such as a discharge tube for a sodium vapor arc lamp, includes a high density polycrystalline ceramic body, such as alumina or yttria, having a cavity, at least one closure member, and a sealing material. The closure member is formed from a molybdenum-titanium alloy containing a small amount of nickel, cobalt, or copper. The nickel, cobalt, or copper forms a relatively low melting eutectic with titanium, thereby facilitating fabrication of closure members by sintering. The closure member and the sealing material have thermal coefficients of expansion closely matched to the thermal coefficient of expansion of the ceramic body over a wide temperature range.