The present invention provides a gallium nitride sintered body and a gallium nitride molded article which have high density and low oxygen content without using a special apparatus. According to the first embodiment, a gallium nitride sintered body, which is characterized by having density of 2.5 g/cm.sup.3 to less than 5.0 g/cm.sup.3 and an intensity ratio of the gallium oxide peak of the (002) plane to the gallium nitride peak of the (002) plane of less than 3%, which is determined by X-ray diffraction analysis, can be obtained. According to the second embodiment, a metal gallium-impregnated gallium nitride molded article, which is characterized by comprising a gallium nitride phase and a metal gallium phase that exist as separate phases and having a molar ratio, Ga/(Ga+N), of 55% to 80%, can be obtained.

The present invention provides a gallium nitride sintered body and a gallium nitride molded article which have high density and low oxygen content without using a special apparatus. According to the first embodiment, a gallium nitride sintered body, which is characterized by having density of 2.5 g/cm.sup.3 to less than 5.0 g/cm.sup.3 and an intensity ratio of the gallium oxide peak of the (002) plane to the gallium nitride peak of the (002) plane of less than 3%, which is determined by X-ray diffraction analysis, can be obtained. According to the second embodiment, a metal gallium-impregnated gallium nitride molded article, which is characterized by comprising a gallium nitride phase and a metal gallium phase that exist as separate phases and having a molar ratio, Ga/(Ga+N), of 55% to 80%, can be obtained.

A method of forming a doped substrate comprises heating a substrate comprising a layer of a dopant on at least one surface to a predetermined temperature; applying a predetermined degree of isostatic external pressure on the surface of said substrate at said predetermined temperature for a time sufficient to induce thermal migration of the dopant into the substrate to provide a doped substrate; and removing the isostatic pressure and cooling the doped substrate to about room temperature. The substrate is a glass material, a single crystal material, a poly-crystalline material, a ceramic material, or a semiconductor material, and the substrate may be optically transparent. The dopant comprises one or more transition metals, one or more rare earth elements, or a combination of both. The layer of a dopant comprises one or more segregated layers of distinct chemical species. The isostatic pressure and elevated temperature may be applied simultaneously or sequentially.

A method of forming a doped substrate comprises heating a substrate comprising a layer of a dopant on at least one surface to a predetermined temperature; applying a predetermined degree of isostatic external pressure on the surface of said substrate at said predetermined temperature for a time sufficient to induce thermal migration of the dopant into the substrate to provide a doped substrate; and removing the isostatic pressure and cooling the doped substrate to about room temperature. The substrate is a glass material, a single crystal material, a poly-crystalline material, a ceramic material, or a semiconductor material, and the substrate may be optically transparent. The dopant comprises one or more transition metals, one or more rare earth elements, or a combination of both. The layer of a dopant comprises one or more segregated layers of distinct chemical species. The isostatic pressure and elevated temperature may be applied simultaneously or sequentially.

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%.

The invention relates to a method for treating magnesia-carbon products.

The invention relates to a method for treating magnesia-carbon products.

One aspect of the present invention is a method for producing a composite, including a step of placing a porous boron nitride sintered body immersed in a resin composition under a pressurized condition and then placing the boron nitride sintered body immersed in the resin composition under a pressure condition lower than the pressurized condition, wherein the step is repeated a plurality of times.

One aspect of the present invention is a method for producing a composite, including a step of placing a porous boron nitride sintered body immersed in a resin composition under a pressurized condition and then placing the boron nitride sintered body immersed in the resin composition under a pressure condition lower than the pressurized condition, wherein the step is repeated a plurality of times.

A plate-shaped heat dissipation member includes a metal-silicon carbide composite containing aluminum or magnesium, in which at least one of two main surfaces of the heat dissipation member is curved to be convex in an outward direction of the heat dissipation member, and when a flatness of the one main surface defined by JIS B 0621 is represented by f.sub.1 and a flatness of the other main surface different from the one main surface defined by JIS B 0621 is represented by f.sub.2, f.sub.2 is less than f.sub.1 by 10 μm or more.