Abstract: This invention involves a new type of feedthrough-plug member for metal halide HID lamp using PCA envelopes. The construction of the lamp housing consists of a PCA envelope and specially designed axially graded alumina-metal cermet multi-layers to eliminate cracking in cermet or PCA due to thermal stresses arising from thermal expansion mismatch. The fills are metal halides such as Na--Sc--I, rare earth halides, Hg, Sn, and inert gases. The PCA vessel and directly sealed cermet-feedthrough assemblies allow the metal halide lamps to operate at high wall temperatures with better lumen output, color temperature, and CRI.

Abstract: An arc tube for an electrodeless metal halide discharge lamp has an arc chamber fabricated from a material selected from the group consisting of magnesia-doped polycrystalline alumina, silicon dioxide doped polycrystalline alumina and monocrystalline alumina. The arc chamber is tubular and has at least one end and has a given outside diameter. At least one end cap closes the at least one end of the arc chamber, the end cap being formed from magnesia-doped polycrystalline alumina and comprising a substantially cup-shaped member having an inside diameter which is sealed to the outside diameter of the arc chamber by a shrink-fit.

Abstract: An arc tube for an electrodeless metal halide discharge lamp has an arc chamber fabricated from a material selected from the group consisting of magnesia-doped polycrystalline alumina, silicon dioxide doped polycrystalline alumina and mono-crystalline alumina. The arc chamber is tubular and has at least one end and has a given outside diameter. At least one end cap closes the at least one end of the arc chamber, the end cap being formed from magnesia-doped polycrystalline alumina and comprising a substantially cup-shaped member having an inside diameter which is sealed to the outside diameter of the arc chamber by a shrink-fit.

Abstract: Electrodeless arc tubes for high pressure sodium discharge lamps comprise a substantially tubular, translucent body formed from a material comprising sintered polycrystalline alumina. The body has an inside diameter and an outside diameter and a given length. A fill comprising sodium and xenon are loaded within the body. At least one end-seal is provided for the body, the end-seal comprising a first alumina disc sealed within the inside diameter by compression, the first disc being spaced inwardly from an end of the body and having a substantially centrally located aperture therein. A second alumina disc seals the aperture, the second disc being bonded to the first disc and to the inner wall of the body by a sealing frit.

Abstract: A method of making a sintered ceramic body for applications such as wear resistant parts and cutting tools. A green body is prepared from a powder mixture including alumina, TiC or (Ti(C,N)), a densification aid, and TiO.sub.2. The weight ratio of alumina to TiC in the body is about 40:60 to about 95:5; that of TiO.sub.2 to alumina plus TiC is 0:100 to about 2:98. The green body is rapid sintered by heating in a sintering atmosphere to about 1800.degree.-1920.degree. C. for a time sufficient to achieve a density of at least about 4.20 g/cc. The heating rate above about 800.degree. C. is between about 120.degree. C./min and the rate at which the green body experiences thermal shock. The sintering atmosphere is Ar-H.sub.2 or N.sub.2 -H.sub.2 in a molar ratio of Ar or N.sub.2 to H.sub.2 of about 92:8 to 100:0. Carbon monoxide is introduced to the sintering atmosphere only after the sintering temperature exceeds about 1400.degree. C.

Abstract: A new and improved bonded ceramic-metal article and the method of making the article is described. The ceramic-metal article comprises a ceramic article, such as a lanthana-strengthened yttria article, bonded to a metal article, such as niobium, by a layer of a brazing material to form a bonded ceramic-metal article. The method of bonding the ceramic article to the metal article comprises placing the brazing alloy, such as a brazing alloy consisting essentially of 63% by weight silver, 35.25% by weight copper, and 1.75% by weight titanium, between the lanthana-strengthened yttria article and the niobium article and heating the layered structure in vacuum at about 50 degrees centigrade above the liquidus temperature of the brazing alloy for a period of about 5 minutes.

Abstract: A method of making a translucent alumina article is described. The method comprises the following steps:Step 1 - An alumina powder and a sintering aid are mixed in a liquid for a period sufficient to form a homogeneous slurry.Step 2 - The homogeneous slurry from Step 1 is dried remove the liquid to form a dried powder.Step 3 - The dried powder is shaped to form a compacted green body.Step 4 - The compacted green body from Step 3 is heated at a temperature equal to or less than 500.degree. C. and for a period sufficient to form a compacted green body having a density of at least 30% of theoretical density.Step 5 - The compacted green body having a density of at least 30% of theoretical density from Step 4 is heated at a temperature from about 800.degree. C. to about 1300.degree. C. in an oxygen containing atmosphere for a period sufficient to impart green strength to said compacted green body to form a prefired compacted green body.

Abstract: A new and improved method of brazing a ceramic-metal article is described. The ceramic-metal article comprises a ceramic article, such as a lanthana-strengthened yttria article, bonded to a metal article, such as niobium, by a layer of a brazing material, such as brazing alloy consisting essentially of 72% by weight silver, 28% by weight copper to form a joined ceramic-metal article. The method of brazing the ceramic article comprises coating a surface of the lanthana-strengthened yttria article with a group IVB metal, such as titanium, hafnium, and zirconium then placing a brazing alloy, such as a brazing alloy consisting essentially of 72% by weight silver and 28% by weight copper or a brazing alloy consisting essentially of 82% by weight gold and 18% by weight nickel, between the coated lanthana-strengthened yttria article and the niobium article and heating the layered structure in vacuum at about 50 degrees centrigrade above the liquidus temperature of the brazing alloy for a period of about 5 minutes.

Abstract: A new and improved method of bonding a bonded ceramic-metal article is described. The ceramic-metal article comprises a ceramic article, such as a lanthana-strengthened yttria article, bonded to a metal article, such as niobium, by a layer of a brazing material, such as a brazing alloy consisting essentially of 63% by weight silver, 35.25% by weight copper, and 1.75% by weight titanium to form a bonded ceramic-metal article. The method of bonding the ceramic article to the metal article comprises placing the brazing alloy between the lanthana-strengthened yttria article and the niobium article and heating the layered structure in vacuum at about 50 degrees centigrade above the liquids temperature of the brazing alloy for a period of about 5 minutes.

Abstract: An improved process for producing a translucent polycrystalline alumina body comprising rapid-sintering a prefired compacted green body of alumina of predetermined shape is disclosed. The green body of alumina includes alumina doped with one or more sintering aids. Rapid sintering in accordance with the method of the present invention comprises the steps of raising the temperature of the prefired compacted green body of predetermined shape up to maximum sintering temperature at a heating rate greater than or equal to about 0.1.degree. C./second and less than the rate at which the green body experiences thermal shock; and heating the green body at the maximum sintering temperature for a period of time sufficient to produce a translucent polycrystalline alumina body. The rapid sintering is carried out under a flowing gas mixture of nitrogen and at least about 2.5 volume percent hydrogen.

Abstract: A thermal shock apparatus comprises a hot gas stream impinging means, a hot gas stream impinging control means, a positioning means for the hot gas stream impinging means, and a sample holding means. A sample is subjected to an essentially instantaneous impingement of a hot gas stream upon a predetermined area of the sample when a heat gun is moved past heat deflection foils and positioned above the sample causing a thermal shock within the sample.

Abstract: An improved process for producing a translucent polycrystalline alumina body comprising sintering a prefired compacted green body of alumina of predetermined shape is disclosed. The green body of alumina includes alumina doped with one or more sintering aids. The method of the present invention comprises sintering the prefired compacted green body of predetermined shape at a maximum sintering temperature in an atmosphere containing nitrogen and an amount of hydrogen greater than or equal to about 2.5 volume percent and less than 75 volume percent for a period of time sufficient to produce a translucent polycrystalline alumina body.

Abstract: The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

Abstract: A method whereby silicon carbide-bonded SiC fiber composites are prepared from carbon-bonded C fiber composites is disclosed. Carbon-bonded C fiber composite material is treated with gaseous silicon monoxide generated from the reaction of a mixture of colloidal silica and carbon black at an elevated temperature in an argon atmosphere. The carbon in the carbon bond and fiber is thus chemically converted to SiC resulting in a silicon carbide-bonded SiC fiber composite that can be used for fabricating dense, high-strength high-toughness SiC composites or as thermal insulating materials in oxidizing environments.

Abstract: The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MP.am.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

Abstract: The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.075 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.