Provided is a member for optical glass manufacturing apparatus. The member is used for optical glass manufacturing apparatus and exposed to a gas containing a halogen element in a high temperature environment of 1100° C. or higher. The member includes dense ceramics containing silicon nitride as a main component, and a porosity of a surface layer of the member is smaller than a porosity of the inside of the member.

The present invention relates to a method for producing a metal nitride by igniting a raw material powder containing a metal powder filled in a reaction vessel under a nitrogen atmosphere and propagating nitriding combustion heat generated by a nitriding reaction of the metal to the whole raw material powder, the method including forming a heat insulating layer made of a material having nitrogen permeability and inert to the nitriding reaction on an upper surface of a layer made of the raw material powder. According to the present invention, it is possible to provide a method for reducing the amount of unreacted metal powder when producing a metal nitride by a combustion synthesis method.

The present invention is directed to a method for producing a silicon nitride sintered material, the method including heating a molded article, which contains a silicon nitride powder having a β phase ratio of 80% or more, a dissolved oxygen content of 0.2% by mass or less, and a specific surface area of 5 to 20 m.sup.2/g, and a sintering auxiliary containing a compound having no oxygen bond, and which has an overall oxygen content controlled to be 1 to 15% by mass and an aluminum element overall content controlled to be 800 ppm or less, to a temperature of 1,200 to 1,800° C. in an inert gas atmosphere under a pressure of 0 MPa.Math.G or more and less than 0.1 MPa.Math.G to sinter the silicon nitride.

In the present invention, there can be provided a method for producing a silicon nitride sintered material, which method is advantageous in that a silicon nitride sintered material having high thermal conductivity can be obtained even when using a silicon nitride powder having a high β phase ratio and conducting calcination under normal pressure or substantially normal pressure.

A member for optical glass production apparatus is a member exposed to a gas containing a halogen element in a high temperature environment; the member includes a first member (4) directly or indirectly supporting an optical glass (10) and a second member (5) supporting the first member (4).

A silicon nitride powder for sintering which, despite of its fine powdery form, shows a very small increase in the oxygen concentration with time and features excellent storage stability. The silicon nitride powder for sintering has a specific surface area of 5 to 30 m.sup.2/g, and is characterized by having a hydrophobicity (M value) of 30 or more and an increase in the oxygen concentration of 0.30% by mass or less after left to stand in the air of a humidity of 90% and 20° C. for 48 hours. The silicon nitride powder for sintering can be obtained by dry-pulverizing aggregated masses of the silicon nitride in an inert atmosphere in the presence of a silane coupling agent.

A honeycomb structure according to at least one embodiment of the present invention includes: a honeycomb structure portion having: an outer peripheral wall; and a partition wall arranged inside the outer peripheral wall to define a plurality of cells each extending from a first end surface of the honeycomb structure portion to a second end surface thereof to form a flow path; and a pair of electrode portions arranged on an outer peripheral surface of the outer peripheral wall of the honeycomb structure portion. The electrode portions are each a porous body in which particles of silicon carbide are bound by a binding material, the silicon carbide contains α-type silicon carbide and β-type silicon carbide, and the silicon carbide has a D50 in a volume-based cumulative particle size distribution of 25 μm or less.

Provided is a method for producing a silicon nitride sintered body including: a step of molding and firing a raw material powder containing silicon nitride, in which an α-conversion rate of the silicon nitride contained in the raw material powder is less than or equal to 30 mass %. A thermal conductivity (at 20° C.) of the silicon nitride sintered body exceeds 100 W/m.Math.K and a fracture toughness (K.sub.IC) is greater than or equal to 7.4 MPa.Math.m.sup.1/2.

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.

A cubic boron nitride sintered material comprises cubic boron nitride particles, a binding phase, and an interfacial phase. The interfacial phase intervenes between the cubic boron nitride particles and the binding phase. The interfacial phase includes aluminum, nitrogen, boron, and oxygen. A total of an average value of the atomic concentrations of aluminum included in the interfacial phase and an average value of the atomic concentrations of nitrogen included in the interfacial phase is 50.0 at % or more. A ratio of an average value of the atomic concentrations of nitrogen included in the interfacial phase to an average value of the atomic concentrations of boron included in the interfacial phase is more than 1.00.

In one aspect, ceramic bodies are described herein exhibiting composite architecture. Briefly, a composite ceramic body comprises a bulk region including a mixture of alpha-SiAlON and beta-SiAlON, and a surface region covering the bulk region, the surface region having a residual stress of −500 MPa to 500 MPa and a thickness of at least 5 μm.