Abstract: A polycrystalline diamond (PCD) body with improved thermal stability is disclosed which comprises a PCD body which has had at least one of its previously empty pores infiltrated by a silicon containing alloy. According to the process of the invention, a porous PCD body is obtained, preferably by acid leaching a PCD body which was formed in the presence of a metal catalyst such as cobalt. The porous PCD body is then surrounded by either the desired silicon containing alloy, or by the constituents of that alloy, each preferably in powdered form. The PCD body with its surrounding material is then heated and pressed to temperatures sufficient to melt the surrounding material (thereby forming the silicon alloy if not already formed) and to cause it to infiltrate into the pores. After the infiltration, it is preferred to remove the excess silicon containing alloy from the external surfaces of the PCD body, such as by an acid bath. It is also preferred to include several porous PCD bodies per process cycle.

Abstract: A novel method of making a refractory material is disclosed comprising the steps of providing an electrical arc metal furnace, charging that furnace with a charge of refractory oxide, and selecting voltage, amperage and electrode spacings to create novel "hum and scum" melt conditions. This hum and scum condition is maintained until said charge is substantially melted. The described technique is particularly useful for melting magnesia chrome materials to produce fusion cast refractory products which are highly reduced and quite dense. The elaboration of this product requires higher energy input per pound concurrent with an increased consumption of reducing materials compared with standard preparation conditions. The resulting product exhibits higher oxidation weight gains, higher densities, lower porosities, high cold crush strengths, more thermal shock resistance, and better corrosion-erosion resistance than similar magnesia chrome refractory products fused using prior "arc and bark" processes.

Abstract: Fine alumina powders for making alumina bodies are produced by seeding of a non-alpha alumina with submicron alpha alumina particles, firing, and crushing and milling the fired product to a fine powder. The powder so produced may be formed by conventional techniques such as pressing, granulating, slip casting, tape casting, and extrusion, and sintered to produce the desired fired product.

Abstract: A system to prevent, retard or reverse the decomposition of silicon carbide articles during high temperature plasma sintering. Preferably, the system comprises sintering a silicon carbide refractory or ceramic green body in a closed sintering environment, such as a covered crucible, with strategic placement of the plasma torch or torches, exhaust outlet and crucibles. As sintering proceeds, a silicon vapor pressure builds up within the crucible, retarding the decomposition of the silicon carbide body. The plasma torch, exhaust outlet, and crucibles are positioned so that buoyant convective flow is maximized to increase the heat transfer and energy efficiency. In another embodiment, a "sacrificial" source of silicon carbide is placed into the sintering furnace. The silicon carbide in the sacrificial source starts to decompose before the silicon carbide refractory or ceramic article, creating a supersaturated atmosphere of silicon vapor species in the furnace.

Abstract: Particulate material is poured into a container which is decay and heat resistant, the container is sealed and subjected to axial compression at elevated temperature to cause densification of the material, there being an arrangement for preventing substantial radially outward deformation of the container during compression. An important application is to immobilization of nuclear reactor waste in a synthetic rock structure formed during the high temperature compression step, and advantageously the containers are secured within an outer metal cannister for subsequent safe handling and disposal. An important embodiment includes a bellows container which advantageously is upwardly pressed into an inverted metal cannister restrained by an upper abutment, the bellows container becoming an interference fit within the metal cannister during the final portion of compression, but the bellows container wall itself being substantially sufficient to prevent gross outward deformation of the bellows container.

Abstract: A process for producing fine non-oxide powder from an alkoxide selected from the group consisting of a silicon alkoxide and an aluminum alkoxide, which comprises dispersing carbon powder in the alkoxide, hydrolyzing the dispersion, and heating the hydrolyzate mixture thereby obtained, in a nitrogen atmosphere at a temperature of from 1350.degree. C. to 1650.degree. C. for from 30 minutes to 30 hours.

Abstract: A method of containing radioactive or other dangerous material separately or intermixed with a bonding compound of a material, resistant to leaching by water, in a gas-tight container and of converting the material by hot isostatic pressing (HIP) into a dense body. The material is filled into a cylindrical container having a corrugated bellows-like wall. The dangerous material is prevented from filling up the annular spaces formed by the corrugations, by means of a barrier means placed inside the container. A metallic netting combined with a paper-like sheet of ceramic material makes a suitable barrier means.

Abstract: A method for producing high technology ceramics with minimal porosity comsing the steps of filling a can with a constituent powder of a ceramic, creating a vacuum in the can and maintaining the vacuum throughout the entire process; outgassing the powder in the can by placing a furnace around the area of the can that encloses the powder and heating the furnace to at least 100.degree. C.; removing the furnace after a minimum of five minutes of heating; cold rolling the can in a rolling system; igniting the powder so a localized propagation reaction front is created; and hot rolling the can in the rolling system so the propagation reaction front is maintained between the rolls of the rolling system.

Abstract: The method of consolidating a metallic, metallic and ceramic, or ceramic body in any of initially powdered, sintered, fibrous, sponge, or other form capable of compaction, includes the steps:(a) providing a bed of flowable particles within a contained zone, said particulate primarily including flowable and resiliently compressible carbonaceous particles,(b) positioning said body in said bed,(c) and effecting pressurization of said bed to cause pressure transmission via said particles to said body, thereby to compact the body into desired shaped, increasing its density,(d) said body and bed being at elevated temperatures prior to said pressurization step.

Abstract: A refractory article for casting of liquid melts, especially steel, fabricated from a mixture of Al.sub.2 O.sub.3, graphite, a flux component, a synthetic resin binder and a metallic powder. The flux component contains a first flux with a melting point from 550.degree. to 900.degree. C. and a second flux that becomes active in the mixture in a temperature ranging from 1350.degree. and 1550.degree. C. The refractory article need not be heated before use, and the carbon contained therein, which determines the strength of the article, is retained for a much longer period during use, so that the article will have a long service life.

Abstract: A method is disclosed of making a plurality of dimensionally accurate hot pressed ceramic bodies. A plurality of Si.sub.3 N.sub.4 plates having a thickness to width ratio of 1:3 to 1:40 are stacked in a hot pressing assembly (40-41-42-43). The plates are arranged in groups of progressively decreasing number so that (a) for a plate group (10-11-12-13-14) residing in a zone of compression (15) that will experience the least movement along the pressing direction the stacked number of plates is greatest within such group, and (b) for a plate group residing in a zone of compression (22) that will experience the most movement along the pressure direction the stacked number of plates (21) within such group is the lowest, each group being separated from adjacent groups by an inert rigid spacer.

Abstract: A sintered material based on silicon nitride for use in preparing cutting tools is provided. This material is prepared by sintering a mixture of silicon nitride containing 2-10 percent by weight of yttrium oxide, 1-5 percent by weight of aluminium oxide and 10-40 percent by weight of titanium carbide coated with titanium nitride under hot pressing or sintering followed by hot isostatic pressing at an elevated temperature ranging from 1600.degree. C. to 1800.degree. C. The coated titanium carbide in the form of powder can be formed by depositing a film of titanium nitride on the surface of titanium carbide in the presence of gaseous titanium tetrachloride, hydrogen and nitrogen under the partial pressure of 0.1 to 0.5 atmosphere at 1000.degree. C. to 1500.degree. C. The material can endow the cutting tools with higher toughness and strength and longer life.

Abstract: In order to facilitate a shape-keeping compression in a process of fabricating an elongated glass-body, particularly a preform for optical waveguides on the basis of SiO.sub.2 in which, from a powdery glass starting material a porous body is formed and sintered into a glass body, there is provided a process in which the filling of the powdery glass starting material into the compression mold is carried out by simultaneously effecting a precompaction and in which, following the fill-in operation, the pre-compacted powdery material is compressed to obtain the porous body. Steps and measures are proposed for stabilizing the flexible hose which is preferably used as a compression mold, in its shape during the fill-in process. For the filling-in of the material there is used a screw conveyor or an arrangement of several screw conveyors arranged coaxially or next to each other, in order to form a porous body having the desired radial material composition.

Abstract: Silicon nitride sintered bodies which contain no more than 15% by weight metallic non-oxide compounds as silicon nitride high temperature grain growth inhibitors and total amount of 4-25% of MgO and Al.sub.2 O.sub.3 as densifying aids in MgO/Al.sub.2 O.sub.3 weight ratio being 19 to 2.

Abstract: A process for producing readily sinterable aluminum nitride powder, which comprises mixing(i) alumina powder and/or powder of a compound capable of forming alumina by heat treatment,(ii) carbon powder and/or powder of a compound capable of forming carbon by heat treatment, and(iii) powder of at least one compound selected from the group consisting of alkaline earth metal oxides, compounds capable of forming said alkaline earth metal oxides by heat treatment, rare earth element oxides and compounds capable of forming said rare earth element oxides by heat treatment,and calcining the resulting mixture in a nitrogen-containing non-oxidative atmosphere, provides an aluminum nitride powder which is readily sinterable without further mixing with a sintering aid.

Abstract: The invention relates to polycrystalline sintered compact based on europium hexaboride having a density of at least 85% of the theoretical density. The compacts comprise EuB.sub.6, from about 0.1 to 10% by weight of B.sub.4 C and, optionally, amorphous carbon, and have a total of Eu+B+C of at least 98.5% by weight. They have a homogeneous microstructure with mean grain sizes of less than 20 .mu.m, in which, in addition to the crystalline phase EuB.sub.6-x C.sub.x, in which x has values of from 0 to 0.25, B.sub.4 C can be detected as a separate, finely divided, crystalline phase.The sintered compacts can be manufactured from powder mixtures comprising europium hexaboride of stoichiometric composition and additions of boron carbide and/or mixtures of a carbon-containing material and a boron component by means of hot pressing in graphite moulds, by means of isostatic hot pressing in casings that can be sealed so that they are gas-impermeable, or by means of pressureless sintering.

Abstract: The present invention discloses a method of making fiber reinforced glass, glass-ceramic or ceramic matrix composite articles. The method comprises forming the matrix material into fibers and then into yarn which is woven or knitted into cloth. The matrix cloth is then cut into preformed shapes and interleaved with preformed pieces of fabric which have been woven or knitted from yarn containing the fiber reinforcement. The interleaved preformed structure is then placed in a die and densified under pressure and temperature to form the composite article. Also disclosed is a method wherein the yarn of reinforcing fiber and matrix fibers is woven or knitted together to form a hybrid cloth. This hybrid cloth is then cut into predetermined forms and placed in a die and densified under heat and pressure to form the composite article.

Abstract: A ceramic preform is coated with a layer of amorphous carbon and is then hot-isostatically compressed to form the desired ceramic part. The layer of carbon can then be removed.

Abstract: A high toughness silicon nitride sintered body comprises silicon nitride as a main component and at least one member selected from the group consisting of silicides and carbides in the form of plate particles, of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W. In the sintered body, the longer diameter d.sub.1 of principal plane of plate of the plate particles and the shorter diameter d.sub.2 of the same plane has a relation of d.sub.1 /d.sub.2 <10, and the thickness of plate of the plate particles is 1/5 or below of d.sub.2.

Abstract: The specification discloses a powder process in which metal or ceramic particles are mixed with a binder such as ultra high molecular weight polyethylene powder and are compacted. The compacted shape is heated to a temperature near the melting point of the binder to consolidate the binder and produce a green shape. The green shape is formed and the binder is removed. Thereafter, the shape is sintered to form a final part.

Abstract: A method for manufacturing a metal sintered body disclosed herein is characterized by the use of steps of: mixing 70 to 90 weight % of self-fluxing alloy powder and 10 to 30 weight % of metal powder of high melting point having a higher melting point than that of the self-soluble metal powder and in which the self-fluxing alloy powder is liable to be deposited thereon to obtain a metal powder having a sintering property; using a material in which 1 to 10 weight % of plastic binder is kneaded with the metal powder having a sintering property to obtain a molded body having a predetermined shape; and sintering the molded body at a temperature in excess of a liquid phase line of the self-fluxing alloy powder.

Abstract: Method and apparatus for producing multi-layer, thin-film flexible photovoltaic cells with front and rear junction regions electrically in series and formed of ceramic glass semi-conductor alloys of silicon laminated with an intervening semi-conducting layer less than 60 Angstroms thick or an insulating layer less than 20 Angstroms thick. The respective spectral sensitivities of front and rear junction regions are in different frequency ranges. The method and apparatus include providing two ribbons of the silicon alloy in a molten state, passing the molten ribbons between respective first pairs of opposed rollers in first rolling stations, cooling the first pairs of rollers for rapidly cooling the molten ribbons to semi-solidus condition, then passing them between other pairs of opposed rollers in other rolling stations at a ribbon temperature in the range from 740.degree. C. to 1130.degree. C. for promoting crystal growth in the ribbons while being rolled.

Abstract: The disclosure relates to a feedstock of particulate material for use in formation of articles therefrom, the feedstock including a homogeneous combination of large particles, small particles and a binder. The large particles comprise less than about 60% by volume of the feedstock and are defined as particles having a diameter greater than their diffusion length. The fine particles and binder combined comprise more than about 40% by volume of the feedstock, the fine particles being defined as particles having a diameter less than their diffusion length.

Abstract: A composite material sensitive to weak variations of oxygen pressure at a low temperature, of the type containing microscopic particles of an ionic conductor of oxygen ions contained in a solid solution, in tetravalent metal oxides, oxides of other metals with a valence less than four, other than the said of such a solid solution, the material contains discrete microscopic particles of an electronic conductor.

Abstract: A flash compression process for the manufacture of photovoltaic cells wherein a powder of photovoltaic material is compressed under high pressure between upper and lower compression members and is simultaneously melted in place by means of an electric discharge supplied through the compression members. The photovoltaic material is subjected to a controlled solidification process by which impurities are confined to one side of the photovoltaic cell. The photovoltaic cell may be formed directly on a substrate and may be surface doped during the formation process.

Abstract: A green compact (17) preheated to a predetermined temperature in a heating furnace (16) is inserted into a container comprising a press table (20) and a hollow cylinder (25), and molten glass (33) is then placed into the container. The green compact (17) is uniformly pressed by a press rod (29) through the molten glass (33). The molten glass (33) is cooled by a coolant flowing through channels (22) and (26) formed in the press table (20) and the cylinder (25), whereby a solidified shell (34) is formed at the outer peripheral portion of the mass of glass. Finally, the shell (34) is taken out from the container, and the molten portion of glass (33) is transferred into a ladle (31) through a grating (30), leaving the compressed sintered product on the grating (30).

Abstract: A method of manufacturing ceramic sintered bodies. A basic starting material corresponding to the sintered body is mixed with compounds which form a melting phase with the starting material during sintering. Prior to the sintering, presintered starting material nuclei having an average crystallite size which corresponds at least three times the average crystallite size of the basic starting material are added to the basic material and melt-forming compounds. The nuclei are added in a quantity of at least 0.1% by weight of the starting material to be sintered. By this addition the grain size and grain distribution in the ceramic sintered body of materials with discontinuous grain growth can be effectively checked and controlled.

Abstract: A method of producing a composite compact of cBN and WC-Co, comprising: mixing fine particles of cBN with a minor part of titanium carbide, the former being in an amount of 60-80% and the latter 40-20%, correspondingly, of the combined volume, putting the mixture in an intimate contact with a composite of WC-Co, heating the whole to a temperature high enough to cause an outflow of a liquid phase from said composite and infiltration thereof into said mixture under a pressure-temperature condition where cubic boron nitride is crystallographically stable, interjoining adjacent particles of cBN and titanium carbide, and as a whole to the composite of WC-Co, and recovering the integrated product of cBN, titanium carbide and WC-Co.

Abstract: Fine spherical amorphous powder represented by the general formula:SiCxNyHzwherein 0.1<x<2.0, 0.1<y<1.5 and 0<z<4, is prepared by vapor phase oxidation of organosilicon compound substantially free from halogen atoms and oxygen atoms. An ultimately crystalline, uniform and fine powder of silicon nitride and silicon carbide is prepared by heat treatment of the fine spherical amorphous powder. The powder and the crystalline uniform, and fine powder are used as raw materials for composite ceramics and as functional materials for solar cell.

Abstract: A method for producing .alpha.-silicon nitride whiskers. Silicon is blended with amorphous silicon nitride and a pore-forming composition particles able to be removed without leaving a residue, such as naphthalene particles. The mixture is compacted to a desired shape, after which the pore-forming particles are removed from the mixture to form a porous silicon precursor compact having the desired shape. The silicon precursor is reacted with a substance that releases free nitrogen, such as nitrogen or dry ammonia. The reaction is carried out at a temperature sufficiently high to form an identically shaped porous compact of .alpha.-silicon nitride whiskers but sufficiently low to avoid subliming substantially all of the formed whiskers. Preferably, the reaction is carried out in a range between about 1100.degree. C. and 1500.degree. C. The shaped porous compact of .alpha.

Abstract: In the manufacture of an article of ceramic material, for example a bladed turbine wheel of silicon nitride, there is first formed a plurality of article parts, at least one of which is a shaped powder body formed from powder of ceramic material mixed with a plasticizer, after which the plasticizer is driven off by a suitable heating operation. The article parts are then assembled together into a configuration conforming to that of the article to be manufactured, and the assembled article parts are surrounded with a gas-impermeable layer, for example a layer of glass. Finally, the assembled parts are isostatically pressed at elevated temperature to form the assembled article parts into a dense, homogeneous article.

Abstract: The present invention discloses a method for densifying previously sintered parts constructed of powdered metals, ceramics or the like to nearly 100% theoretical density. The method of the present invention comprises heating the parts containing binder and hard phase above their liquid phase temperature and then applying a pressure in a predetermined range to the parts for a predetermined period of time and simultaneously maintaining the parts at or above their liquid phase temperature. This pressure range is set so that the pressure is below the pressure necessary to overcome the capillary force acting on the binder to keep the binder from entering the voids but above the pressure necessary to physically move or collapse themicrostructure inwardly, thus filling the voids with a homogeneous mixture of binder and hard phase. The method of the present invention achieves complete closure of even large voids and the elimination of substantially all porosity within the part.

Abstract: The invention provides a method for the preparation of an ultrafine powder of silicon carbide having an extremely fine and uniform particle size distribution of spherical agglomerate particles each formed of crystallites of 5 nm or smaller in size. The silicon carbide powder is prepared by the vapor phase pyrolysis of a specified methyl hydrogen(poly)silane as diluted with a carrier gas, e.g. hydrogen, to give a concentration of 40% by volume or lower at a temperature of 750.degree. to 1600.degree. C. The silicon carbide powder can readily be sintered at a temperature of 1750.degree. to 2500.degree. C. even without addition of a sintering aid to give a sintered body of extremely high density reaching 80% or larger of the theoretical value which can never be obtained of the conventional silicon carbide powders.

Abstract: An object is manufactured from a powdered material by isostatic pressing of a body, preformed from the powdered material, with a pressure medium, whereby the preformed body, in which at least the surface layer consists of a ceramic material in the form of a nitride, is surrounded by a casing which is rendered impenetrable to the pressure medium, before the isostatic pressing is carried out and the powder sintered. As the material in the casing there is used boron oxide or a glass containing boron oxide or a material forming glass while being heated, in which the content of boron oxide is sufficiently high for the glass--or the glass formed during heating--to be removable by water. The preformed body surrounded by the casing is subjected to a heat treatment for the formation of boron nitride on the surface of the preformed body, before the isostatic pressing is carried out. The casing is removed from the finished product by means of water or water vapor.

Abstract: A series of sintered shapes of silicon carbide of high strength comprising 0.027 to 11.300 atomic percent of one or more members of rare earth oxides and the balance of silicon carbide are disclosed. Method of making such silicon carbide shapes is also disclosed.

Abstract: A method is disclosed for simultaneously and uniformly densifying a plurality of semidense ceramic powder bodies. The bodies are hinged together with a uniform space therebetween to form a cluster. The spaces in each cluster are filled with an isostatic pressure medium and then the clusters are stacked in a predetermined alignment along a pressing axis and hot pressed to substantially full density. The bodies are then ruptured from said clusters so as to be in a condition for use as a tool.

Abstract: A process is disclosed for reacting oxides of yttrium and aluminum.

Abstract: Process of hot isostatic pressing of MnZn ferrite material for producing ferrite close to theoretical density without a significant increase in grain size. Permeability is increased with the increase in theoretical density. The process includes the steps of pressurizing an entire ferrite sample which is surrounded by pieces of similar composition while in alumina crucibles with fused alumina grain there between and an optional oxygen getter on top of the grain, introducing an inert atmosphere, elevating pressure and temperature, the temperature elevated to a value below that previously used for sintering or hot pressing, and maintaining temperature to optimize density without excess grain growth. Density is thereby optimized without excess grain growth, while maintaining or improving the magnetic properties.

Abstract: A quantity of material (10), which is at less than a predetermined density, is disposed within a sealed container (12) which is, in turn, encapsulated in a pressure-transmitting (18) medium which is, in turn, placed within a pot die (20) of a press where it is restrained as a ram (24) enters the pot die (20) and applies a force to the pressure-transmitting medium (18) to densify the material within the container into a compact (10') of predetermined density. The pressure-transmitting medium (18) is characterized by a rigid interconnected ceramic skeleton structure (26) which is collapsible in response to a predetermined force and fluidizing glass (28) capable of fluidity and supported by and retained within the skeleton structure (26). The glass (28) becomes fluidic and capable of plastic flow at temperatures utilized for compaction whereas the ceramic skeleton (26) retains its configuration and acts as a carrier for the fluidic glass (28).

Abstract: Hot pressed refractory boride shapes are treated with molten alkali metal hydroxide such as by immersion in a bath of the molten hydroxide. The treatment cleans and removes residual carbon from the surface layer of the shapes.

Abstract: A cermet electrode assembly for use in an electrolytic cell is produced by the process of hot isostatic molding a cermet material onto a metal current member. The electrode assembly has long service life and can be joined to an electrical current source by conventional metal joining techniques.

Abstract: A silicon carbide-silicon matrix composite incorporates unreacted coarse carbon particles (e.g. graphite particles) dispersed throughout the composite. The coarse particles are incorporated in a coherent mixture of carbon and silicon carbide powders which, after compaction, is infiltrated with molten silicon to form a matrix of reaction bonded silicon carbide in a substantially continuous free silicon carbide phase. By using coarse carbon particles of density of at least 0.963 g/ml, the molten silicon reacts only with the surfaces of those particles which may as a result remain unreacted and dispersed throughout the composite.

Abstract: A cathodic element for a Hall-Heroult aluminum reduction cell is formed from a refractory hard metal, preferably TiB.sub.2, in a generally mushroom-shaped configuration. The element is economical of raw materials and has improved thermal endurance when compared to a right cylinder or other element of uniform cross-section.

Abstract: In a process for making refractory articles, such as cores and moulds for use in casting metals, the articles are formed from dies using a refractory material mixed with a thermosetting resin. The articles are formed with the mixture heated to a softened state and the resin is cured. Thereafter the article has to be fired and problems have arisen with deformation of the articles during the firing process.With the present invention, the articles, 8, which as can be seen in FIG. 2 are mould segments, are bound into an assembly with a flexible refractory tape (15) which shrinks on firing to a greater extent than the articles, and thus pulls the assembly tightly together whereby each article provides support for the adjacent article and prevents distortion. The joint faces between the mould segments are thus held in tight abutment and for pouring metal into the mould, the firing cup is fitted and a coating of refractory slurry is brushed on without removing the tape to seal the assembly.

Abstract: A method of overlaying sulphur concrete is adapted for use in placing sulphur concrete against or over an existing solid surface such as the exterior surface of a wall, floor, or column base. The existing surface, which typically is a portland cement concrete surface, is prepared by first applying a layer of a bituminous material containing a bitumen which liquifies at temperatures corresponding to the pour temperatures of the sulphur concrete. The sulphur concrete is poured against or over the bitumen-containing surface so that the bitumen therein melts to form a liquid slip plane. The shrinkage of the sulphur concrete which occurs during its temperature-reduction setting occurs without producing cracks because of the relative slippage permitted between the existing wall surface and the sulphur concrete.

Abstract: A particulate mixture of ceramic powder, free carbon and a hydride of a metal selected from the group consisting of hafnium, niobium, tantalum, titanium, vanadium, zirconium and mixtures thereof is hot pressed decomposing the hydride and reacting the resulting metal with carbon producing a polycrystalline microcomposite comprised of a continuous phase of the carbide of the metal which encapsulates at least about 20% by volume of the ceramic particles and which either encapsulates or is intermixed with the balance of said ceramic particles.

Abstract: A method and apparatus for the production of a transversely corrugated or serrated interior pipe of a double walled special gas discharge pipe with high angle selectivity, especially to the production of such pipe from silicate materials, preferably for CO.sub.2 laser with axial gas discharge with high amplification, the method and apparatus providing for the economic production of such pipes from silicate materials, with defined sharp-edged corrugations, in the required accuracy and quality. This is accomplished by forming an interior pipe from a smooth cylindrical glass pipe, which has been heated by means of suitable heat sources, until the material can be plastically formed.

Abstract: A process for improving the high temperature flexural strength of titanium diboride-boron nitride (TiB.sub.2 -BN) intermetallic compositions which comprises reheating hot pressed TiB.sub.2 -BN stock to about 2000.degree. C. for about four hours in an inert atmosphere.

Abstract: A particulate mixture of ceramic powder, boron and a hydride of a metal selected from the group consisting of hafnium, niobium, tantalum, titanium, vanadium, zirconium and mixtures thereof is hot pressed decomposing the hydride and reacting the resulting metal with boron producing a polycrystalline microcomposite comprised of a continuous phase of the boride of the metal which encapsulates at least about 20% by volume of the ceramic particles and which either encapsulates or is intermixed with the balance of said ceramic particles.

Abstract: A mixture containing 35 to 65% by weight of Al.sub.2 O.sub.3, 30 to 60% by weight of SiO.sub.2, 1.5 to 4% by weight of Cr.sub.2 O.sub.3, and 0.01 to 0.1% by weight of carbon, the balance being unavoidable impurities, is melted, and amorphous fibers are formed from said molten material by blowing or spinning. The fibers are heated rapidly to a temperature of 950.degree. C. to 1,150.degree. C., held at that temperature for several to about a dozen minutes, and cooled rapidly to ordinary room temperature.