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 fabricating a ceramic material, the method including forming a ceramic material by performing a first chemical reaction at least between a first powder of an intermetallic compound and a reactive gas phase, a liquid phase being present around the grains of the first powder during the first chemical reaction, the liquid gas phase being obtained from a second powder of a metallic compound by melting the second powder or as a result of a second chemical reaction between at least one element of the first powder and at least one metallic element of the second powder, a working temperature being imposed during the formation of the ceramic material, which temperature is low enough to avoid melting the first powder.

A method of forming a moisture-tolerant coating on a silicon carbide fiber includes exposing a silicon carbide fiber to a gaseous N precursor comprising nitrogen at an elevated temperature, thereby introducing nitrogen into a surface region of the silicon carbide fiber, and exposing the silicon carbide fiber to a gaseous B precursor comprising boron at an elevated temperature, thereby introducing boron into the surface region of the silicon carbide fiber. Silicon-doped boron nitride is formed at the surface region of the silicon carbide fiber without exposing the silicon carbide fiber to a gaseous Si precursor comprising Si. Thus, a moisture-tolerant coating comprising the silicon-doped boron nitride is grown in-situ on the silicon carbide fiber.

A process for producing an ordered martensitic iron nitride powder that is suitable for use as a permanent magnetic material is provided. The process includes fabricating an iron alloy powder having a desired composition and uniformity; nitriding the iron alloy powder by contacting the material with a nitrogen source in a fluidized bed reactor to produce a nitride iron powder; transforming the nitride iron powder to a disordered martensitic phase; annealing the disordered martensitic phase to an ordered martensitic phase; and separating the ordered martensitic phase from the iron nitride powder to yield an ordered martensitic iron nitride powder.

The present invention relates to a process for producing a silicon carbide-containing body (100), characterized in that the process has the following process steps: a) providing a mixture (16) comprising a silicon source and a carbon source, the silicon source and the carbon source being present together in particles of a solid granular material; b) arranging a layer of the mixture (16) provided in process step a) on a carrier (12), the layer of the mixture (16) having a predefined thickness; and c) treating the mixture (16) arranged in process step b) over a locally limited area with a temperature within a range from 1400 C. to 2000 C. according to a predetermined three-dimensional pattern, the predetermined three-dimensional pattern being selected on the basis of the three-dimensional configuration of the body (100) to be produced. Such a process allows simple and inexpensive production even of complex structures from silicon carbide.

A process for producing an ordered martensitic iron nitride powder that is suitable for use as a permanent magnetic material is provided. The process includes fabricating an iron alloy powder having a desired composition and uniformity; nitriding the iron alloy powder by contacting the material with a nitrogen source in a fluidized bed reactor to produce a nitride iron powder; transforming the nitride iron powder to a disordered martensitic phase; annealing the disordered martensitic phase to an ordered martensitic phase; and separating the ordered martensitic phase from the iron nitride powder to yield an ordered martensitic iron nitride powder.

Embodiments of disclosure may provide a method for forming an aluminum-containing nitride ceramic matrix composite, comprising heating a green body, an aluminum-containing composition, ammonia and a mineralizer composition in a sealable container to a temperature between about 400 degrees Celsius and about 800 degrees Celsius and a pressure between about 10 MPa and about 1000 MPa, to form an aluminum-containing nitride ceramic matrix composite characterized by a phosphor-to-aluminum nitride (AlN) ratio, by volume, between about 1% and about 99%, by a porosity between about 1% and about 50%, and by a thermal conductivity between about 1 watt per meter-Kelvin and about 320 watts per meter-Kelvin. The green body comprises a phosphor powder comprising at least one phosphor composition, wherein the phosphor powder particles are characterized by a D50 diameter between about 100 nanometers and about 500 micrometers, and the green body has a porosity between about 10% and about 80%. The aluminum-containing composition has a purity, on a metals basis, between about 90% and about 99.9999%. The fraction of free volume within the sealable container contains between about 10% and about 95% of liquid ammonia prior to heating the green body, the aluminum-containing composition, ammonia and the mineralizer composition in the sealable container.

The present disclosure relates to the formation of polycrystalline diamond materials with fine diamond grains and nano-sized particles of a grain growth inhibitor. In one embodiment, a method of fabricating a polycrystalline diamond material is provided. The method includes providing a mixture of diamond particles with an average particle size of about 1 micron or less, distributing a plurality of nano-sized titanium-containing particles with the diamond mixture, to act as a grain growth inhibitor, and sintering the mixture of diamond particles and titanium-containing particles at high pressure and high temperature to create a polycrystalline structure of sintered diamond grains. The sintered diamond grains have an average size of about 1 micron or less.

Embodiments of disclosure may provide a method for forming an aluminum-containing nitride ceramic matrix composite, comprising heating a green body, an aluminum-containing composition, ammonia and a mineralizer composition in a sealable container to a temperature between about 400 degrees Celsius and about 800 degrees Celsius and a pressure between about 10 MPa and about 1000 MPa, to form an aluminum-containing nitride ceramic matrix composite characterized by a phosphor-to-aluminum nitride (AlN) ratio, by volume, between about 1% and about 99%, by a porosity between about 1% and about 50%, and by a thermal conductivity between about 1 watt per meter-Kelvin and about 320 watts per meter-Kelvin. The green body comprises a phosphor powder comprising at least one phosphor composition, wherein the phosphor powder particles are characterized by a D50 diameter between about 100 nanometers and about 500 micrometers, and the green body has a porosity between about 10% and about 80%. The aluminum-containing composition has a purity, on a metals basis, between about 90% and about 99.9999%. The fraction of free volume within the sealable container contains between about 10% and about 95% of liquid ammonia prior to heating the green body, the aluminum-containing composition, ammonia and the mineralizer composition in the sealable container.

A method of manufacturing polycrystalline abrasive elements consisting of micron, sub-micron or nano-sized ultrahard abrasives dispersed in micron, sub-micron or nano-sized matrix materials. A plurality of ultrahard abrasive particles having vitreophilic surfaces are coated with a matrix precursor material and then treated to render them suitable for sintering. The matrix precursor material can be converted to an oxide, nitride, carbide, oxynitride, oxycarbide, or carbonitride, or an elemental form thereof. The coated ultrahard abrasive particles are consolidated and sintered at a pressure and temperature at which they are crystallographically or thermodynamically stable.