Abstract: The present invention provides a fibre-strengthened ceramic formed body with improved mechanical strength, wherein it contains at least 15% by volume of zirconium dioxide, hafnium dioxide or zirconium dioxide/hafnium dioxide composition in the form of monoclinic crystals and an amount of inorganic fibres sufficient for increasing the strength, which is obtainable by hot pressing a mixture of ceramic matrix materials, at least 15% by volume of tetragonal zirconium dioxide, hafnium dioxide or zirconium dioxide/hafnium dioxide composition particles and the fibres at a temperature above the tetragonal.fwdarw.monoclinic transition temperature.The present invention also provides a process for the production of such a ceramic formed body.

Abstract: Sintered bodies of silicon carbide having remarkably increased volume resistivity and thermal conductivity can be obtained by heating a green body shaped of a fine silicon carbide powder admixed with boron or a boron compound, e.g. boron carbide, titanium boride and boron oxide, as a sintering aid at 1800.degree. to 2200.degree. C. in the presence of or in the vicinity of a shaped body of a powdery mixture of a fine silicon carbide powder admixed with boron nitride in the same furnace. The improvements in the volume resistivity and thermal conductivity of the sintered body are particularly remarkable when the fine silicon carbide powder is a pyrolysis product of a methyl hydrogen silane compound such as tetramethyl disilane.

Abstract: A silicon carbide sintered body suitable for electrical discharge machining and a method for its manufacture are disclosed. The silicon carbide sintered body comprises 0.5-5% by weight of AlN, 0.5-3% by weight (as Ti) of a Ti compound, 0.5-8% by weight of C, 0-3% by weight (as B) of B or a B compound, and a remainder of substantially SiC. It has a volume resistivity at room temperature of not greater than 10 ohm-cm and a density of at least 90% of the theoretical density of SiC. The manufacturing method comprises shaping a mixture of the raw materials and sintering the shaped green body in a non-oxidizing atmosphere at a temperature of 2000.degree.-2300.degree. C.

Abstract: A neutron-absorbing material is formed by a process which includes the steps of: mixing an absorptive material having a high thermal neutron capture cross-section (e.g., B.sub.4 C), a neutron-moderating material (e.g., graphite) and a binder (e.g., a phenol formaldehyde resin); shaping such mixture; curing such shaped mixture (e.g., to complete polymerization of the resin and to have only a carbon residue); and siliconizing such shaped and cured mixture. The resulting product has been formed to be denser and stronger, and more oxidation- and abrasion-resistant than prior art compositions.

Abstract: The present invention relates to a sintered product containing silicon carbide as a main component which comprises a phase(a) containing at least one metal selected from among Al, Sc, Y and rare earth elements and oxygen, a particle phase(b) comprising at least one metal carbide selected from among carbides of Ti, Zr, Hf, Va, Nb, Ta, W and the like, a composite particle phase(c) comprising said phase(a) and said phase(b) surrounding the phase(a) and silicon carbide matrix(d) in which the above phase(a), (b) and (c) are dispersed.The silicon carbide sintered product of the present invention exhibits a remarkably high strength and a remarkably high toughness which have not been attained up to this time, so that it can form various heat-resistant structural materials having a high reliability.

Abstract: A ceramic structure whose portion exposed to a heat cycle, as a high-temperature gas turbine blade, a turbo charger or the like, is coated with ceramics having a construction wherein a sinter mainly comprising a boride, nitride or carbide of the element of Group IIIa, IVa, Va or VIa of the Periodic Table and retaining a high strength at a temperature of up to 1,100.degree. C. is dispersed in sintered ceramics comprising at least one of silicon carbide, silicon nitride and sialon as its principal component. A ceramic structure having a thermal shock resistance, high versatility and reliability can be obtained.

Abstract: Sintered silicon carbide body having a D.C. electrical resistivity of at least 10.sup.8 Ohm cm at 25.degree. C., a density of at least 2.95 g/cm.sup.3 is formed upon sintering in a nitrogenous atmosphere at a temperature of about 2250.degree. C. or greater, a shaped body composed essentially of carbon or carbon source material in amount sufficient to provide up to 2.5 percent uncombined carbon; from about 0.4 to about 2.0 percent boron carbide; up to 25 percent of temporary binder and a balance of silicon carbide which is predominantly alpha-phase. The shaped body may additionally include other sintering aids such as BN or Al without destruction of desired high electrical resistivity.

Abstract: The invention is a ceramically-bonded large-area neutron absorber articles of low density having a space filling ofabout 40 to 60% by volume boron carbide+silicon carbide in a B.sub.4 C:SiC ratio of about 9:1 to 1:9 andabout 10 to 20% by volume of free carbon, the remainder pores.They have a density of from about 1.5 to 2.2 g/cm.sup.3 and a flexural strength of from about 20 to 50 N/mm.sup.2 at room temperature measured according to the 3-point method, which strength after the corrosion test of immersion for about 3000 hours in boiling water, drops by less than about 40% of the initial value. Graphite powder may optionally be included with a pulverulent organic resin binder and a wetting agent, molding the mixture under pressure at about room temperature, curing the resin binder at temperatures of up to about 180.degree. C. and then coking the molded plates in the absence of air at temperatures of up to about 1000.degree. C. under a controlled temperature program.

Abstract: A silicon carbide powder consisting of an aluminum component such as aluminum nitride and aluminum oxide and a chromium component such as chromium carbide as essential ingredients and if desired, a rare earth element such as yttria is sintered into an integrated molded article. This sintered article has excellent strength and toughness and a markedly reduced tendency to undergo corrosion when brought into contact with iron at high temperatures.

Abstract: Vinyl-containing polysilanes of the average formula[R.sub.2 Si][RSi][R.sub.d '(CH.sub.2 .dbd.CH)Si]where R is an alkyl radical containing 1 to 4 carbon atoms, R' is an alkyl radical containing 1 to 4 carbon atoms, a vinyl radical, or a phenyl radical, d is 1 or 2 and where the polysilane contains 0 to 60 mole percent [R.sub.2 Si] units, 30 to 99.5 mole percent [RSi] units, and 0.5 to 15 mole percent [R.sub.d '(CH.sub.2 .dbd.CH)Si] units are disclosed. The vinyl-containing polysilanes may be converted to silicon carbide-containing ceramics by pyrolysis in an inert atmosphere or in a vacuum at temperatures greater than 800.degree. C. Shaped articles prepared from the vinyl-containing polysilanes may be rendered infusible prior to pyrolysis by exposure to air or ultraviolet light.

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 zirconoxane units of the formula (Zr--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, Zr and C and optionally of O, said sintered body being composed substantially of(1) an amorphous material consisting substantially of Si, Zr and C and optionally of O, or(2) an aggregate consisting subtantially of ultrafine crystalline particles of .beta.

Abstract: An electrically conductive sintered ceramics of the present invention comprises, as the main ingredients thereof, (a) silicon carbide, (b) an inorganic compound which exhibits a positive resistance-temperature coefficient, and preferably (c) a sintering assistant. The electrically conductive sintered ceramics obtained exhibits a positive resistance-temperature coefficient as a whole.A ceramic heater of the invention makes use of the electrically conductive sintered ceramics in an electrically conductive portion thereof.A sintered product which exhibits a positive resistance-temperature coefficient helps to prevent the occurrence of thermal runaway or thermal destruction.

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: The invention provides substantially pore-free sintered polycrystalline articles comprising .alpha.-silicon carbide, boron carbide and free carbon, the quantitative proportions of which, in percent by weight, are defined by the trapezoidal area having, in the ternary system B/Si/C of FIG. 1 the corner pointsa=89.0% B.sub.4 C, 9.9% .alpha.-Sic, 1.1% Cb=9.9% B.sub.4 C, 89.0% .alpha.-SiC, 1.1% Cc=9.0% B.sub.4 C, 81.0% .alpha.-Sic, 10.0% Cd=81.0% B.sub.4 C, 9.0% .alpha.-SiC, 10.0% CThe articles have a density of at least 99% of the theoretical density, an average structural grain size of less than 20 .mu.m and a 4-point flexural strength of at least 400 N/mm.sup.2. They are manufactured from fine-grained mixtures of .alpha.-silicon carbide, boron carbide, carbon and/or material that can be coked to form carbon, in a two-stage sintering process. In the first stage, green bodies preshaped from the powder are subjected to pressureless sintering to a density of at least 95% TD at from 1950.degree. to 2150.degree. C.

Abstract: The carbonaceous body of the invention is prepared by shaping and sintering uniform powdery mixture composed of a powder of a low-temperature coke, a powder of boron carbide and a powder of silicon carbide in such a proportion that the weight proportion of the boron carbide and the silicon carbide is in the range from 2:98 to 80:20 and the volume proportion of the coke powder and the combination of the boron carbide and silicon carbide is in the range from 50:50 to 95:5. The carbonaceous body thus obtained is highly resistant against air oxidation even at a temperature of 1400.degree. C. in addition to the outstandingly high mechanical strengths in comparison with conventional carbonaceous shaped materials such as artificial graphite.

Abstract: Finely divided silicon carbide containing at least 10% by weight of 2H-type silicon carbide is very easily sinterable and can be sintered into a sintered body having a density of at least 85% of the theoretical density by sintering or a hot pressing at a temperature lower than the sintering temperature of ordinary .beta.-type submicron silicon carbide.

Abstract: Non-oxide powders such as carbides, nitrides, carbides/nitrides and borides are obtained by reducing an oxide powder in a reducing atmosphere, and after or concurrently with the reduction, treating the reduced powder in a carbonizing atmosphere, a nitrogenizing atmosphere, a carbonizing and nitrogenizing atmosphere, or a boronizing atmosphere. As the above oxide powder, there is used a brittle material obtained by rapid cooling of a melted oxide. The non-oxide powders obtained are utilized as a hard component of cemented carbides and cermet. These powders are fine particles having a particle size of 1.0 .mu.m or smaller and a high purity.

Abstract: In accord with the present invention, a composite ceramic article may be produced by joining separate components of ceramic materials with a cement or brazing compound of finely-divided metal borides, such as Mo.sub.2 B.sub.5, MoB.sub.2, TiB.sub.2, GeB.sub.2, ZrB.sub.2, SmB.sub.6, NbB.sub.2, HfB, VB.sub.2, WB.sub.2 or TaB.sub.2. A particularly useful metal boride for use with silicon carbide is Mo.sub.2 B.sub.5.If the metal carbide parts or components to be joined are sintered, the metal boride cement is selected to have a melting point within 150.degree. C., but less than the sintering temperature of the metal carbide.If the metal carbide parts or components to be joined are unsintered, or an unsintered component is to be joined to a sintered component, the metal boride cement is selected to have a melting point slightly higher than the sintering temperature of the metal carbide components to be joined.

Abstract: Continuous inorganic fibers consisting substantially of Si, Ti and C and optionally of O, said fibers being composed 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.-SiC, TiC, a solid solution of .beta.-SiC and TiC and TiC.sub.1-x wherein 0<x<1 and having a particle diameter of not more than 500 A, in which amorphous SiO.sub.2 and TiO.sub.2 sometimes exist in the neighborhood of these ultrafine crystalline particles, or (3) a mixture of said amorphous material (1) and said aggregate (2) of ultrafine crystalline particles. The aforesaid continuous inorganic fibers can be produced by the following steps: a first step of preparing a semi-inorganic block copolymer comprising polycarbosilane blocks having a main chain skeleton composed mainly of carbosilane units of the formula --Si-CH.sub.

Abstract: What is disclosed is a process for preparing polysilazane polymers by contacting and reacting chlorine-containing disilanes with ammonia. The polysilazane polymers are useful as chemical intermediates to produce silicon-containing chemical compounds. They are also useful in the formation of silicon carbide-containing ceramic materials.

Abstract: Flaky .beta.-SiC mainly composed of .beta.-SiC which is obtained from an organic silicon polymer containing the carbon and silicon atoms as the major skeletal component and the method for producing such flaky .beta.-SiC are disclosed. Such .beta.-SiC is especially utilized as the starting material for ceramics having a laminar structure as well as for the refractories. The ceramics and refractories provided with such .beta.-SiC have excellent resistance to thermal shock, to thermal fatigue as well as to oxidation.

Abstract: The invention provides a novel highly refractory sintered body based on a tal diboride such as TiB.sub.2 or Mo.sub.2 B.sub.5 and W.sub.2 B.sub.5 containing a binder ingredient. The high-temperature performance of the sintered body is further improved by including an auxiliary additive ingredient selected from several carbides, nitrides, silicides and oxides such as WC, TiC, TaN, TiN, MoSi.sub.2, TiO.sub.2, Al.sub.2 O.sub.3, B.sub.2 O.sub.3 and the like in a limited amount.

Abstract: A process for producing silicon carbide heating elements is described comprising:a primary sintering wherein a mixture including SiC powder, boron or a boron compound, and carbon or a carbon compound in specific proportions, is molded and sintered to obtain a sintered product having from 70 to 95% of the theoretical density; anda secondary sintering wherein the sintered product obtained in the primary sintering is further sintered at each temperature from 1,600.degree. C. to 2,200.degree. C. to obtain a sintered product having a density of at least 80% of the theoretical density and a specific resistivity of not more than 1.0 .OMEGA.-cm.

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: High density, sintered refractory articles composed of: 60 to 98% by weight of boron carbide and 2 to 40% by weight of silicon carbide, and 0 to 10% by weight of aluminum. As a result of the composition, products with densities in excess of 94% of theoretical can be produced by cold pressing followed by a pressureless heat treatment.

Abstract: A reaction bonded silicon carbide body in which there is included in the free silicon phase of the body to modify the electrical resistivity of the body, at least one of the Group III elements boron and indium or at least one of the Group V elements antimony and tantalum. The element may be added in compound form and may be included in the green body prior to reaction bonding or in the silicon with which it is reaction bonded.

Abstract: Shaped silicon carbide ceramic articles of high density, e.g., at least 90 percent of theoretical, are produced by cold pressing and sintering boron-containing high purity, submicron beta silicon carbide powder. The silicon carbide powder is produced preferably by gas phase reaction of silicon halide, e.g., silicon tetrachloride, carbon source reactant, e.g., halogenated hydrocarbon, and boron source reactant, e.g., boron trichloride, with a hydrogen plasma.

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.