Abstract: A method is described for the production of porous bodies from vitreous silica without the use of tools. Vitreous silica wool and/or threads are wound in layers on a form. After the coil has attained a certain minimum thickness, the threads of each succeeding layer are permanently bonded by heating the threads of the preceding layer at the points where the threads cross. The form is removed, and then the threads on the inside of the body are bonded together.The bodies are used for the production of high-purity blocks of silicon for solar cells.

Abstract: A dielectric material having a high dielectric constant, very low high-frequency losses and very high temperature stability is prepared in particular by sintering previously ground raw materials in an oxidizing atmosphere at 1450.degree. C. The molar composition of the raw materials is as follows: t, TiO.sub.2 ; x, SnO.sub.2 ; y, ZrO.sub.2 ; a, NiO; b, La.sub.2 O.sub.3 ; where t is between 0.9 and 1.1, x is between 0.1 and 0.4 moles, y is between 0.6 and 0.9, a is between 0.015 and 0.06 moles, b is between 0.01 and 0.1 moles with an addition of iron of 0.0035 mole in respect of one mole of TiO.sub.2 obtained, for example, from the use of steel equipment for the grinding operation. When x is in the vicinity of 0.35, the coefficient of thermal variation .tau..sub.f is reduced to zero and the quality criterion Q.f is high.

Abstract: A process for producing a sintered ceramic body, which comprises heating a semi-inorganic block copolymer at a temperature of from 500.degree. to 2300.degree. C. in an environment of vacuum or inert gases, reducing gases or hydrocarbon gases, said copolymer comprising polycarbosilane blocks, having a main-chain skeleton composed mainly of carbosilane units of the formula --Si--CH.sub.2 -- and titanoxane units of the formula --Ti--O--; and shaping the heated product, and simultaneously with, or after, the shaping of the heated product, sintering the shaped product at a temperature of from 800.degree. C. to 2300.degree. C. in an environment of vacuum or inert gases, reducing gases or hydrocarbon gases; and a sintered ceramic body consisting substantially of Si, Ti and C and optionally of O, said sintered by being composed substantially of(1) an amorphous material consisting substantially of Si, Ti and C and optionally of O, or(2) an aggregate consisting substantially of ultrafine crystalline particles of .beta.

Abstract: A process of producing a sintered compact comprises filling a cup with a powdered material to be sintered, putting on an opening of the cup a covering member consisting of a lid and solder so as to permit ventilation between the interior and exterior of the cup to form a cup assembly, applying heat as well as vacuum to the cup assembly to degas the powdered material, melting the solder by the continuation of heat to air-tightly seal the cup with the lid to obtain a closed cup compressible under high pressure at high temperature while maintaining the air-tight seal, and hot-pressing the closed cup to obtain a sintered compact.The covering member may include a porous lid closing the cup and a solder put on the porous lid.

Abstract: A process for producing an alumina sintered product is disclosed wherein the starting alumina mixture contains about 0.01 to 0.55% by weight of MgO and 0.5 to 5.5% by weight of Y.sub.2 O.sub.3. The process yields a sintered product having a porosity on the order of less than 0.1% by volume and an average crystal grain size of about 2 microns or less and is particularly suitable for use in high speed microfinish cutting.

Abstract: A method of bonding at least two types of refractory ceramic materials, a first material being, for example, fireclay and a second material being, for example, alumina, to each other in order to enhance both the abrasion and corrosion resistances of heat resistant plates for valve closures of foundry ladles. The second, thermally more resistive material, which is applied to the first material in the form of relatively small particles, is preheated on at least the outer surface layers of the particles, the entire volume of the particles usually being preheated or even molten. The bonding of the two preheated materials occurs in such a way that minute particles up to drops of the second, thermally more resistive material are thrown at high speed (with high kinetic energy) onto the preheated surface of the first material. The source of such a relatively high kinetic energy can be constituted by either an explosion or a plasma beam ejected at a high outlet velocity out of the mouth of a plasma torch.

Abstract: In a process for the production of dispersion ceramics by sintering or hot pressing of a mixture of a matrix-forming ceramic material and of at least one ceramic embedment material dispersible therein which at the sintering temperature of the ceramic and at room temperature is present in different enantiotropic solid modifications of different densities, a ceramic embedment material is employed which is divided into at least two groups of different, substantially uniform particle sizes, each group having different lower phase-transition temperatures.

Abstract: A method for producing silica glass wherein a dry silica gel subjected to a water desorption treatment and a carbon removal treatment is heated and has its temperature raised in an atmosphere containing chlorine, to perform a hydroxyl group removal treatment, the resultant silica gel is thereafter heated to a temperature of approximately 1,000.degree. C.-1,100.degree. C. in an atmosphere containing at least 1% of oxygen, to perform a chlorine removal treatment, and the resultant silica gel is further heated to a temperature of 1,050.degree. C.-1,300.degree. C. in He or in vacuum, to perform a sintering treatment. The silica glass thus produced does not form bubbles even when heated to high temperatures of or above 1,300.degree. C. Therefore, it is easily worked and it is free from the lowering of transparency attributed to the bubble formation.

Abstract: This disclosure relates to an improved method for achieving the best bond strength and for minimizing distortion and cracking of hot pressed articles. In particular, in a method for hot press forming both an outer facing circumferential surface of and an inner portion of a hub, and of bonding that so-formed outer facing circumferential surface to an inner facing circumferential surface of a pre-formed ring thereby to form an article, the following improvement is made.Normally, in this method, the outside ring is restrained by a restraining sleeve of ring-shaped cross-section having an inside diameter. A die member, used to hot press form the hub, is so-formed as to have an outside diameter sized to engage the inside diameter of the restraining sleeve in a manner permitting relative movement therebetween. The improved method is one in which several pairs of matched restraining sleeve and die member are formed with each matched pair having a predetermined diameter.

Abstract: The present invention is directed to a method for hot pressing irregularly haped refractory articles with these articles of varying thickness being provided with high uniform density and dimensional accuracy. Two partially pressed compacts of the refractory material are placed in a die cavity between displaceable die punches having compact-contacting surfaces of the desired article configuration. A floating, rotatable block is disposed between the compacts. The displacement of the die punches towards one another causes the block to rotate about an axis normal to the direction of movement of the die punches to uniformly distribute the pressure loading upon the compacts for maintaining substantially equal volume displacement of the powder material during the hot pressing operation.

Abstract: A process is disclosed for producing a non-woven boron nitride (BN) fiber felt. Boron nitride fibers are blended with a lesser amount of boron oxide fibers and a nondissolving, anhydrous liquid medium to form a homogeneous slurry. The slurry is deposited on the moving screen of a Fourdrinier machine where the liquid content is gradually reduced until sufficient fiber to fiber contact is made to provide internal cohesiveness, to form a felt. The felt may be further treated by heating it in an anhydrous gas atmosphere at a sufficient temperature to soften the boron oxide binder to fuse the BN fibers together, and then converting the interstitial boron oxide into boron nitride. The resulting boron nitride-bonded boron nitride felt may be used as an electric cell separator in a lithium sulfide battery.

Abstract: A process is disclosed for producing a non-woven, boron nitride-bonded boron nitride fiber mat, suitable for use as an electric cell separator in a lithium-sulfide battery. A web having a combination of structural boron nitride (BN) fibers and interstitial, thermally bondable boron oxide (B.sub.2 O.sub.3) fibers is passed through the nip of a pair of cooperating calender rolls at an appropriate temperature and pressure to soften the boron oxide binder throughout the web to fuse the BN fibers together. The interstitial boron oxide then is heated in an anhydrous ammonia atmosphere to convert it into boron nitride.

Abstract: The present invention relates to a composition particularly suitable for as structural components subject to high-temperature environments containing gaseous hydrogen and fluorine. The composition of the present invention consists essentially of lanthanum hexaboride-molybdenum diboride with dispersed silicon. The composition is formed by hot pressing a powder mixture of lanthanum hexaboride as the major constituent and molybdenum disilicide. This composition exhibits substantial resistance to thermal shock and corrosion in environments containing hydrogen and fluorine gases at material surface temperatures up to about 1850.degree. K. Upon exposure of the hot-pressed composition to high-temperature environments containing fluorine gases, a highly protective layer of lanthanum trifluoride containing dispersed molybdenum is formed on exposed surfaces of the composition.

Abstract: A method of producing ceramic articles having a density substantially equal to the theoretical density comprises heating a highly porous preliminary molding made of a ceramic powder to obtain a preliminarily sintered molding of a porosity below 30%, followed by sintering the preliminarily sintered molding under a uniform pressure by the use of a powder acting as a pressure transmitting medium. This method permits producing a ceramic article having a desired shape, and no deformation in it.

Abstract: A ceramic tubesheet pierced by a plurality of hollow, glass fibers and consisting of sintered particles is rendered essentially impermeable by selectively fusing the portion of the tubesheet subjacent to and defining one of its surfaces. The fiber lengths extending from the opposite surface of the tubesheet are freer to flex and less likely to be broken than if the entire tubesheet were fused.

Abstract: Stabilized zirconia refractories comprising fine block crystals of zirconia, having a high bulk density due to their dense texture and a higher bending strength than the conventional calcined zirconia refractories are disclosed. The stabilized electrocast zirconia refractories are obtained by pouring an electrofused melt of a blend of a zirconia-base material and a stabilizing agent into a mold and solidifying the poured melt from its lower portion by cooling the bottom part of the mold forcibly. Also the method for producing the stabilized electrocast zirconia refractories is disclosed.

Abstract: A method is described for making a shaped silicon carbide-silicon matrix composite. A confined carbon fiber preform is infiltrated with sufficient molten silicon metal at a temperature in the range of from about 1400.degree. C. to about 1800.degree. C. in an inert atmosphere or vacuum. Silicon carbide powder can also be incorporated in the preform structure.

Abstract: The subject invention is related to the preparation of ceramic bodies wherein the crystal phase consists essentially of cesium-stuffed, hexagonal cordierite. The bodies are capable of use temperatures up to 1600.degree. C., exhibit nearly isotropic axial thermal expansions, and consist essentially, expressed in weight percent on the oxide basis, of about 11-13% MgO, 34-36% Al.sub.2 O.sub.3, 33-42% SiO.sub.2, and 10-22% Cs.sub.2 O.

Abstract: A method of making a multi-layer ceramic substrate for an integrated circuit device package having internal circuitry by forming a plurality of porous ceramic bisque sheets, impregnating the pores of the bisque sheets with an organic binder material, forming openings through the impregnated bisque sheets, filling the openings with conductive material and imprinting conductive circuitry patterns on the surface of the impregnated bisque sheets of a conductive material, assembling the plurality of apertured printed impregnated bisque sheets into a laminated unit, and sintering the laminated unit to form a unitary laminated structure having an interconnected internal circuitry system.

Abstract: This invention relates to a process for producing crystallized glass having superior mechanical properties and thermal properties, which comprises (1) coating glass in the form of a powder or molded article with an organometallic polymer, said polymer being soluble in an organic solvent and having a skeleton comprising (a) titanoxane linkages --Ti--O-- or zirconoxane linkages --Zr--O-- or both and (b) siloxane linkages --Si--O-- in which most of the silicon atoms have as a side chain at least one organic group selected from alkyl and phenyl groups, and optionally (c) boroxane linkages --B--O-- or aluminoxane linkages --Al--O-- or both; and (2) firing the resulting polymer-coated glass in an oxidizing atmosphere to crystallize at least a part of the glass. This invention also pertains to a process for producing a ceramics-crystallized glass composite article using the aforesaid crystallized glass.

Abstract: Fusion cast refractories are formed by first displacing the air from the mold cavity with an inert, heavy gas, preferably argon. The molten fusion cast refractory is then poured into the mold cavity and allowed to solidify. This procedure minimizes the evolution of gases from molds which have an organic binder and thus reduces the formation of pores in the solidified refractory.

Abstract: A hot pressed, biaxially oriented, alumina fiber reinforced, ceramic composite having alternate layers of parallel running alumina fibers within a glass matrix such that the fibers of one layer are positioned at right angles to the fibers of any adjoining layer.

Abstract: In one embodiment, a compact for tools, such as cutting, drilling, wire drawing and shaping tools, consists essentially of a porous mass of self-bonded, boron-doped diamond particles and a catalyst-solvent material. The method for making such a compact comprises the steps of bonding a mass of boron-doped diamond particles, aided by a catalyst-solvent material, under high temperatures and high pressures (HP/HT).In another embodiment, a composite compact, which is made in a similar manner to the first embodiment, consists essentially of (i) a layer of a porous mass of self-bonded, boron-doped diamond particles and catalyst-solvent material; and (ii) a substrate layer of cemented carbide bonded to the diamond layer.

Abstract: Improvements in molded articles from sinterable particulate solids, improvements in method for making such articles, and novel sacrificial binders for use in making such articles are disclosed. The sacrificial binders used in this invention comprise block polymers having the structural formulaAB--AB--.eta. Awherein ".eta." is 0 or a positive integer, "A" is a linear or branched polymer that is glassy or crystalline at room temperature and has its softening point in the range of about 80.degree. C. to about 250.degree. C. and "B" is a polymer different from A that behaves as an elastomer at processing temperatures, a plasticizer which may be oil, wax, or oil and wax, and optionally other components.

Abstract: Method and apparatus for producing silicon nitride molded bodies by means of a pseudoisostatic hot pressing process. Silicon nitride is initially ground in a grinding vessel with grinding elements wherein the vessel is lined with the same material from which the grinding elements are made, e.g., hot pressed silicon nitride. Grinding is continued until a specific surface area greater than 15 m.sup.2 is obtained. The grinding takes place in the presence of a grinding liquid to prevent oxidation of the freshly ground silicon nitride. The silicon nitride suspension is then treated in a pressure vessel to remove the grinding liquid therefrom and form a blank. The blank is thereafter embedded within a pressure transfer medium, e.g., boron nitride, and inserted into the die of a hot pressing furnace to obtain the desired hot pressed silicon nitride.

Abstract: A method of making a unitary silicon nitride comprising object and tool is disclosed. A uniform powder mixture of Si.sub.3 N.sub.4 containing SiO.sub.2 as an oxide coating, 4-12% by weight Y.sub.2 O.sub.3, and 0.50-2.5 Al.sub.2 O.sub.3 is prepared. The mixture is hot pressed at a temperature of 1,680.degree.-1,750.degree. C. under a pressure and for a period of time sufficient to produce at least 99.0% (preferably at least 99.5%) of full theoretical density in the mixture to form a pressed object. The heating and pressure is then relieved and the object cooled. The object is heat treated by holding at a temperature in the range of 1,000.degree.-1,400.degree. C. without mechanical pressure for at least 5 minutes but for a time sufficient to provide a nucleating reaction in secondary phases formed as a result of hot pressing. The heat treatment can take place either as an interruption of the cooling cycle or as a subsequent reheat cycle after cooling to room temperature.

Abstract: A method of making a unitary silicon nitride comprising object is disclosed. A uniform powder mixture is prepared of Si.sub.3 N.sub.4 containing SiO.sub.2 as an oxide surface coating, 4-12% by weight Y.sub.2 O.sub.3, and 0.50-2.5% Al.sub.2 O.sub.3. The mixture is heated to 1000.degree.-1400.degree. C. under a pressure of at least 2,000 psi for a time of at least one minute but sufficient to permit a nucleating reaction to take place in secondary phases. Heating is then increased to a temperature of 1680.degree.-1750.degree. C. under a pressure and for a period of time sufficient to produce 99.0% or more of full theoretical density in the pressed object.

Abstract: A method of producing semicrystalline silicon by heating the silicon to a molten state and gradually cooling the silicon to mitigate disruptions in the silicon continuum and promote semicrystalline growth. The product formed is a silicon body, which may be sliced into wafers having highly ordered grains of a mean diameter of at least about one mm.

Abstract: Disclosed is an improved method for manufacturing an object of silicon nitride. In the method, a body preformed from silicon nitride powder and enclosed in a casing of glass is isostatically pressed with a gaseous pressure medium in a pressure vessel at a temperature required for sintering of silicon nitride. After pressing and sintering are completed, the pressure and the temperature in the pressure vessel are adjusted such that the temperature maintains the glass in a plastic state and the pressure in the pressure vessel is below the partial pressure of nitrogen gas for silicon nitride at that temperature so that the glass casing is blown up around the body and the body is freed from or can easily be freed from the glass casing.

Abstract: A sintered, polycrystalline and fully dense chromium oxide body is prepared by heating a Cr.sub.2 O.sub.3 powder compact at relatively low temperature on condition that a liquid of low-melting chromium oxide compound is formed partially in the compact during heating. In practice the compact buried in carbon powder is heated above 1350.degree. C. The porosity of the sintered body is controlled by changing the proportion of the amount of coarse particles and fine particles in the starting Cr.sub.2 O.sub.3 powder. A sintered and crack-free body with uniform microstructure and without abnormal grain growth of Cr.sub.2 O.sub.3 is obtained by the sintering of Cr.sub.2 O.sub.3 powder compact with Cr metal powder.

Abstract: An improved nozzle for use with abrasive and/or corrosive materials is formed of sintered ceramic compositions having high temperature oxidation resistance, high hardness and high abrasion and corrosion resistance. The ceramic may be a binary solid solution of a ceramic oxide and silicon nitride, and preferably a ternary solid solution of a ceramic oxide, silicon nitride and aluminum nitride. The ceramic oxide is selected from a group consisting of Al.sub.2 O.sub.3, Y.sub.2 O.sub.3 and Cr.sub.2 O.sub.3, or mixtures thereof. Titanium carbide particles are dispersed in the ceramic mixture before sintering. The nozzles are encased for protection from external forces while in use by a metal or plastic casing.

Abstract: A shaped confined structure composed of a mass of diamond and/or cubic boron nitride crystals coated with elemental non-diamond carbon in contact with a carbonaceous substrate is infiltrated by fluid silicon producing a like-shaped composite of a polycrystalline body phase integrally bonded to a substrate supporting phase.

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: Embodiments of a method are disclosed for producing large size cadmium mercury telluride (CMT) sputtering targets of a homogeneous composition. Sputtering targets of CMT having a general formula Cd.sub.x Hg.sub.1-x Te wherein x has values in the range of about 0.14 to 0.60 are prepared by compacting finely divided CMT of a particle size smaller than 150.mu. in a die into a coherent compact having a density of at least 97% theoretical density. CMT with an x value of about 0.14 to about 0.20 preferably is compacted at a die preheat temperature of about 100 to 300.degree. C. and at a compacting pressure of at least about 400 MPa. CMT having an x value of about 0.20 to about 0.60 preferably is compacted at a die preheat temperature of about 300.degree. C. and a compacting pressure of about 160 to 275 MPa. The die may be evacuated to a pressure of less than about 133 Pa absolute prior to compacting.

Abstract: A piezoelectric ceramic elements obtained by hot-press sintering a composition expressed by the formula:(1-w)PbTi.sub.1-z Zr.sub.z O.sub.3 +wMnO.sub.2at a temperature of 1050.degree. to 1300.degree. C. under a pressure of 100 to 500 Kg/cm.sup.2 for 0.5 to 24 hours shows a mechanical quality factor of 200 or more and a Poisson's ratio of more than 1/3 and gives a piezoelectric material having a large coupling coefficient which can be processed into a thin sheet having a thickness of 30 .mu.m and is especially suitable as a material for resonators and filters by utilizing its thickness extensional vibration.

Abstract: A shaped confined mass of diamond and/or cubic boron nitride crystals coated with elemental non-diamond carbon, under a partial vacuum, is infiltrated by fluid silicon producing a like-shaped product wherein the crystals are bonded together by a medium comprised of silicon carbide and elemental silicon.

Abstract: A photoflash lamp in which the combustible material within the lamp envelope comprises a plurality of filaments released from the periphery of a rotating heat-extracting disk in contact with a melt of suitable combustible material, such as hafnium, zirconium or magnesium. Filament configurations are determined to a large degree by the peripheral geometry of the rotating disk. In one embodiment, the filaments have unequal lengths, while in another arrangement, filaments having unequal cross-sections are arranged in a substantially homogeneous mass. In yet another embodiment, each of the filaments has periodic notches along the length thereof.

Abstract: The present invention is directed to the fabrication of boron carbide articles having length-to-diameter or width ratios greater than 2 to 1. The process of the present invention is practiced by the steps comprising hot pressing boron carbide powder into article segments or portions in which the segments have a length-to-diameter or width ratio less than 1.5, aligning a plurality of the initially hot-pressed segments in a hot-pressing die with the end surfaces of the segments placed in intimate contact with one another, and then hot pressing the aligned segments into an article of the desired configuration. The resulting article exhibits essentially uniform density throughout the structure with the bonds between the segments being equivalent in hardness, strength, and density to the remainder of the article.

Abstract: A compact is surrounded by a compatible, nonsinterable powder within a container with a layer of sinterable powder disposed on top of the nonsinterable powder and placed in a sintering oven. During sintering, the sinterable powder forms a cover that retards decomposition of the compact and serves to enhance densification of the compact.

Abstract: A method of containing spent nuclear fuel or high-level nuclear fuel waste in a resistant material for isolating the fuel or the waste from the environment, includes the provision of an open container and a cover fitting the container opening, with both the container and cover being made of a ceramic material which is given a high density by isostatic hot pressing. The nuclear fuel or the waste is placed in the container, the cover is placed over the opening of the container, and the container with the cover is contained in a gas-tight casing, whereupon the opened container and the cover are joined by isostatic hot pressing into a homogeneous monolithic body within a completely closed space.

Abstract: A process for producing a compact silicon nitride ceramic product which comprises molding a powder mixture of Si.sub.3 N.sub.4, Ta.sub.2 O.sub.5 and Al.sub.2 O.sub.3 in proportions defined by the region A, B, C, D in the FIGURE within the ranges of 65.0 to 96.0% by volume Si.sub.3 N.sub.4, 1.0 to 32.0% by volume Ta.sub.2 O.sub.5 and 3.0 to 20.0% by volume Al.sub.2 O.sub.3, and then firing the powder mixture in a non-oxidizing atmosphere containing a carbon compound; or hot-pressing the powder mixture; in a graphite mold.

Abstract: A method of producing dense shaped articles of pure boron carbide that optionally contain 0.1 to 8% by weight of free carbon in the form of graphite is disclosed involving the steps of homogeneously mixing boron carbide in submicron powder form with small quantities of a carbon containing additive, forming the powder mixture into a shaped green body and then sintering the body in a controlled atmosphere and in the absence of external pressure at a temperature of about 2100.degree.-2200.degree. C. The shaped articles thus obtained are polycrystalline and, insofar as they correspond to the stoichiometric composition B.sub.4 C, single-phase; they have an average grain size of not more than 10 .mu.m, a density of at least 90% of the theoretical density of boron carbide and a flexural strength of at least 300 N/mm.sup.2. The fracture mode of the sintered articles is completely transcrystalline.

Abstract: A composite solid electrolyte material for use in oxygen sensors, which comprises a mixture of at least two ceramic constituents, one of which is a good oxygen ion conductor and the other a non-electrolyte, is useful for oxygen sensor fabrication. Particularly, it enables gas analysis oxygen sensors to be produced by conventional techniques because the coefficient of thermal expansion of the composite electrolyte material can be closely matched to the material of a supporting sensor body. The closeness of thermal expansion coefficients means that oxygen sensors can now be formed in the "green" state, then fired.

Abstract: Highly densified, polycrystalline photoconductors can be produced by hot-pressing various materials, such as powdered lead monoxide. The powdered material is subjected to a temperature and pressure for a length of time sufficient to form a photoconductive element having a density of at least 85% and up to and including the theoretical density of the material. Such formed photoconductive element or material can be utilized in electro-photographic applications and, with the exception of such material in its single crystal form, will exhibit increased absorption of activating radiation, increased signal-to-noise ratios, and improved spatial frequency response in comparison with presently known photoconductive elements or materials.

Abstract: An improved method for producing a ceramic insulator is disclosed. The method comprises the steps of charging ceramic batch into a longitudinally extending die in which stepped arbors are supported by a plunger, forming a blank by pressing the batch between the arbor plunger and an opposing plunger, ejecting the blank and removing the arbors therefrom, contouring the blank to a desired shape, and firing the contoured blank. The insulator has a length-to-diameter ratio greater than 3:1 but not greater than 8:1; the improvement constitutes controlling the relative movements of the opposing plungers with respect to the longitudinal wall of the die during pressing of the blank so that at least 80 percent of the total plunger movement is in the direction of decreasing arbor diameter whereby variations in the end-to-end density of the insulator are minimized.

Abstract: Zinc oxide powder and a single phase mixed oxide glass powder including bismuth oxide are mixed and then simultaneously heated and pressed to form a consolidated ceramic body of linear electrical characteristics. Subsequent annealing transforms the body to one of non-linear characteristics.

Abstract: A composition comprising .alpha.-alumina in a concentration of at least 99.95 weight percent and process for producing such .alpha.-alumina wherein alumina having an alkali metal content between 0.05 and 0.60 weight percent and Al.sub.2 O.sub.3 content of more than 95 weight percent is electrically fused with silica and additional alkali, if desired, in an electric arc furnace, the heated composition is cooled, comminuted and the so-formed glass phase is removed from an alumina containing phase by mechanical or chemical means.

Abstract: A mass of diamond crystals in contact with a mass of eutectiferous silicon-rich alloy and a silicon nitride ceramic substrate are disposed in a container and placed within a pressure transmitting powder medium. Pressure is applied to the powder medium resulting in substantially isostatic pressure being applied to the container and its contents sufficient to dimensionally stabilize the container and its contents. The resulting shaped substantially isostatic system of powder-enveloped container is hot-pressed whereby fluid eutectiferous silicon-rich alloy is produced and infiltrated through the interstices between the diamond crystals and contacts the contacting face of the silicon nitride substrate sufficiently producing, upon cooling, an adherently bonded integral composite.

Abstract: Composite ceramic articles formed by integrally assembling a plurality of previously molded constituent members without applying an adhesive to their joints and designed to have a density higher than 98% of the theoretical value, and a flexural strength greater than 50 kg/cm.sup.2 at 1200.degree. C., and a method of producing ceramic articles of particularly complex shape which comprises the steps of previously molding a plurality of constituent members of complex shape and later integrally assembling said constituent members without applying an adhesive to their joints.

Abstract: Disclosure is made of a high-density, high-strength silicon carbide ceramic material that is produced using a silicon carbide powder containing boron or boron-containing compound as a densification additive by the utilization of boron in the sintering atmosphere.