A cBN sintered compact comprising a cubic boron nitride and a ceramic binder phase, wherein a cubic C-containing Ta compound in an amount of 1.0 to 15.0 vol % is dispersed in the ceramic binder phase and has a mean particle diameter of 50 to 500 nm.

The invention relates to nickel-coated hexagonal boron nitride nanosheet composite powder, its preparation and high-performance composite ceramic cutting tool material. The composite powder has a core-shell structure with BNNS as the core and Ni as the shell. The self-lubricating ceramic cutting tool material is prepared by wet ball milling mixing and vacuum hot-pressing sintering with a phase alumina as the matrix, tungsten-titanium carbide as the reinforcing phase, nickel-coated hexagonal boron nitride nanosheet composite powder as the solid lubricant and magnesium oxide and yttrium oxide as the sintering aids. The invention also provides preparation methods of the nickel-coated hexagonal boron nitride nanosheet composite powder and the self-lubricating ceramic cutting tool material.

A method for the preparation of a dense HfC(Si)—HfB.sub.2 composite ceramic. hafnium oxide powders, nano-sized carbon black and silicon hexaboride powders are mixed in a molar ratio of (1-10):(1-20):(1-5) to obtain a powder mixture. The powder mixture is subjected to ball milling, dried and transferred to a graphite mold for spark plasma sintering. In this way, an in-situ carbon-boron reduction reaction and the sintering densification are completed in one step, and the obtained HfC(Si)—HfB.sub.2 composite ceramic has a density of 94.0%-100% and uniformly dispersed grains.

A film is formed by use of a composition containing (A) a binder resin, (B) a hard particle, and (C) a solid lubricant selected from the group containing molybdenum disulfide and graphite, wherein the composition contains tungsten carbide as the hard particle, and wherein weight ratio of (B) the hard particles and (C) the solid lubricant, (B)/(C), is in the range of 1 to 3.

A long-term ablation-resistant nitrogen-containing carbide ultra-high temperature ceramic with an ultra-high melting point is prepared as follows: preparing the HfC powder and the HfN powder according to a mass ratio of HfC:HfN=(1-7):1; uniformly mixing the HfC powder and the HfN powder with the carbon powder and the carbon nitride powder to obtain a mixed powder, wherein the amount of the carbon powder and the amount of the carbon nitride powder do not exceed 8.0 wt. % and 5.0 wt. %, respectively, of the mixed powder mass; and performing spark plasma sintering on the mixed powder to produce the ceramic with the ultra-high melting point, a density ≥98%, and a uniform C/N content distribution. The ultra-high temperature ceramic is suitable for ultra-high temperature ablation-resistant protection at ≥3000° C. The ceramic maintains a close to zero ablation rate and a continuously stable oxidation-resistant protective structure after ablation for 300 s.

The present invention relates to a process for preparing a composite, ultra-refractory, fibre-reinforced ceramic material obtained through the infiltration of carbon and/or silicon carbide fibres with a ceramic suspension comprising yttrium, lanthanum and/or scandium compounds, and the subsequent densification of the composite. The fibre-reinforced UHTC compounds obtained by the process can be used for making items intended for use in extreme temperature and pressure conditions.

The invention relates to an item made of a material consisting of a plurality of ceramic phases, said material including: a majority ceramic phase comprising nitrides and/or carbonitrides of one or more element(s) selected from among Ti, Zr, Hf, V, Nb, and Ta, said majority ceramic phase being present in a percentage by weight comprised between 60 and 98%, at least one minority ceramic phase, with either one single minority ceramic phase formed of zirconium and/or aluminium silicide, or several minority ceramic phases formed respectively of carbides of one or more element(s) selected from among Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W and of zirconium oxides and/or aluminium oxides, said at least one minority ceramic phase being present in its entirety in a percentage by weight comprised between 2 and 40%.

The present invention also relates to the method for manufacturing this item.

A preceramic resin formulation comprising a polycarbosilane preceramic polymer, an organically modified silicon dioxide preceramic polymer, and, optionally, at least one filler. The preceramic resin formulation is formulated to exhibit a viscosity of from about 1,000 cP at about 25° C. to about 5,000 cP at a temperature of about 25° C. The at least one filler comprises first particles having an average mean diameter of less than about 1.0 μm and second particles having an average mean diameter of from about 1.5 μm to about 5 μm. Impregnated fibers comprising the preceramic resin formulation are also disclosed, as is a composite material comprising a reaction product of the polycarbosilane preceramic polymer, organically modified silicon dioxide preceramic polymer, and the at least one filler. Methods of forming a ceramic matrix composite are also disclosed.

A cubic boron nitride (cBN)-based composite including about 30-65 vol. % cBN, about 3-30 vol. % zirconium (Zr)-containing compounds, about 0-10 vol. % cobalt-tungsten-borides (Co.sub.xW.sub.yB.sub.z), about 2-30 vol. % aluminum oxide (Al.sub.2O.sub.3), about 0.5-10 vol. % tungsten borides, and less than or equal to about 5 vol. % aluminum nitride (AlN).

The cubic boron nitride sintered material is a cubic boron nitride sintered material comprising: cubic boron nitride particles in an amount of 70 vol % or more and less than 100 vol %, and a bonding material, wherein the bonding material includes an aluminum compound, and includes cobalt as a constituent element; the cubic boron nitride sintered material has a first region in which a space between adjacent cubic boron nitride particles is 0.1 nm or more and 10 nm or less; and when the first region is analyzed by using an energy dispersive X-ray analyzer equipped with a transmission electron microscope, the atom % of aluminum in the first region is 0.1 or more.