A cubic boron nitride (cBN)-based composite including about 30-65 vol. % cBN, about 15-45 vol. % titanium (Ti)-containing binders, about 2-20 vol. % zirconium dioxide (ZrO.sub.2), about 3-15 vol. % cobalt-tungsten-borides (Co.sub.xW.sub.yB.sub.z), and about 2-15 vol. % aluminum oxide (Al.sub.2O.sub.3).

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).

A method for manufacturing a part made of composite material includes forming a ceramic matrix phase in pores of a fibrous preform by pyrolysis of a cross-linked copolymer ceramic precursor, the cross-linked copolymer including a first precursor macromolecular chain of a first ceramic having free carbon, and a second precursor macromolecular chain of a second ceramic having free silicon, the first macromolecular chain being bonded to the second macromolecular chain by cross-linking bridges including a bonding structure of formula *.sup.1—X—*.sup.2; in this formula, X designates boron or aluminium, -*.sup.1 designates the bond to the first macromolecular chain and -*.sup.2 the bond to the second macromolecular chain.

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.

One aspect of the present disclosure provides a composite sheet including a porous sintered ceramic component having a thickness of less than 2 mm and a resin filled into pores of the sintered ceramic component, wherein the curing rate of the resin is 10 to 70%.

Provided is a method for continuously producing a silicon nitride sintered compact for enabling a continuous production of silicon nitride sintered compacts by sintering using a silicon nitride powder having a high β-phase rate. A fired compact 1 housed in a firing jig 2 contains a silicon nitride powder having at least 80% of β-transition rate and 7 to 20 m.sup.2/g of specific surface area together with a sintering additive, where the total content of aluminum element is adjusted not to exceed 800 ppm. The firing jig 2 is supplied into a continuous firing furnace equipped with a closed-type firing container 5 having at its end portions a supplying openable door 3 and a discharging openable door 4 for supplying and discharging the firing jig, a heating mechanism 6 provided on the body periphery of the firing container 5, a conveyance mechanism for supplying/discharging the firing jig into/from the firing container, and a gas-supplying mechanism for supplying an inert gas into the firing container, so that the silicon nitride is heated to a temperature in the range of 1200 to 1800° C. in an inert gas atmosphere and at a pressure of not less than 0 MPa.Math.G and less than 0.1 MPa.Math.G so as to be sintered.

One aspect of the present disclosure provides a composite sheet including a porous sintered ceramic component having a thickness of less than 2 mm and a resin filled into pores of the sintered ceramic component, wherein the resin is a semi-cured product of a resin composition including a compound having a cyanate group and the content of triazine rings in the resin is 0.6 to 4.0 mass %.

A cutting tool including a substrate and a coating film disposed on the substrate, wherein the cutting tool includes: a rake face; a flank face contiguous to the rake face; and a cutting edge region composed of a boundary part between the rake face and the flank face, wherein the coating film includes a TiSiCN layer, the TiSiCN layer has: a first TiSiCN layer positioned in the rake face; and a second TiSiCN layer positioned in the cutting edge region, the first TiSiCN layer has a composition of Ti.sub.(1-Xr)Si.sub.XrCN, the second TiSiCN layer has a composition of Ti.sub.(1-Xe)Si.sub.XeCN, and the Xr and the Xe each represent 0.010 or more and 0.100 or less, and satisfy a relationship of Xe-Xr≥0.003.

A composite sheet includes porous a nitride sintered body having a thickness of less than 2 mm and resins filled in pores of the nitride sintered body, and has a main surface having a maximum height roughness Rz of less than 20 μm. A method for manufacturing the composite sheet includes an impregnating step of impregnating pores of a porous the nitride sintered body having a thickness of less than 2 mm with a resin composition, a smoothing step of smoothing the resin composition attached to a main surface of the nitride sintered body to obtain a resin-impregnated body in which a part of the main surface is exposed, and a curing step of heating the resin-impregnated body to cure or semi-cure the resin composition impregnated in the pores to obtain the composite sheet.

Provided is a boron nitride sintered body in which an average number of lump particles having a particle size of 30 μm or more formed by aggregation of primary particles of boron nitride is 3 or less in a cross-sectional image including 100 or more particles observed at a magnification of 500 times with a scanning electron microscope. A method of manufacturing a boron nitride sintered body includes a nitriding step of sintering a raw material powder containing boron carbide in a nitrogen-containing atmosphere to obtain a fired product containing boron carbonitride, a pulverizing step of pulverizing the fired product to obtain a boron carbonitride powder having a specific surface area of 12 m.sup.2/g or more, and a firing step of molding and heating a blend containing the boron carbonitride powder and a sintering aid to obtain a boron nitride sintered body.