Disclosed in the present invention are a method for water-repellent coating treatment of a boron nitride powders and water-repellent treated boron nitride, the method comprising producing a water-repellent coating layer on the surface of the boron nitride powders by plasma treatment using a silicon-containing organic compound containing silicone, wherein the water-repellent coating layer remains on the boron nitride through chemical binding with the boron nitride even after ultrasonic water washing.

A method of forming a water resistant boundary on a fissile material for use in a water cooled nuclear reactor is described. The method comprises mixing a powdered fissile material selected from the group consisting of UN and U.sub.3Si.sub.2 with an additive selected from oxidation resistant materials having a melting or softening point lower than the sintering temperature of the fissile material, pressing the mixed fissile and additive materials into a pellet, sintering the pellet to a temperature greater than the melting point of the additive. Alternatively, if the melting point of the oxidation resistant particles is greater than the sintering temperature of UN or U.sub.3Si.sub.2, then the oxidation resistant particles can have a particle size distribution less than that of the UN or U.sub.3Si.sub.2

A method of forming a water resistant boundary on a fissile material for use in a water cooled nuclear reactor is described. The method comprises mixing a powdered fissile material selected from the group consisting of UN and U.sub.3Si.sub.2 with an additive selected from oxidation resistant materials having a melting or softening point lower than the sintering temperature of the fissile material, pressing the mixed fissile and additive materials into a pellet, sintering the pellet to a temperature greater than the melting point of the additive. Alternatively, if the melting point of the oxidation resistant particles is greater than the sintering temperature of UN or U.sub.3Si.sub.2, then the oxidation resistant particles can have a particle size distribution less than that of the UN or U.sub.3Si.sub.2.

A method of forming a high purity granular material, such as silicon carbide powder. Precursors are added to a reactor; at least part of a fiber is formed in the reactor from the precursors using chemical deposition interacting with said precursors; and the granular material is then formed from the fiber. In one aspect, the chemical deposition may include laser induced chemical vapor deposition. The granular material may be formed by grinding or milling the fiber into the granular material, e.g., ball milling the fiber. In one example, silicon carbide powder having greater than 90% beta crystalline phase purity and less than 0.25% oxygen contamination can be obtained.

A thermally conductive composite particle, including: a core portion including an inorganic particle; and a shell portion including a nitride particle and covering the core portion, is provided. The thermally conductive composite particle is a sintered body.

A super hard polycrystalline construction includes a first region having a body of thermally stable polycrystalline super hard material with an exposed surface forming a working surface, and a peripheral side edge. The polycrystalline super hard material has a plurality of intergrown grains of super hard material, a second region forming a substrate to the first region, and a third region interposed between the first and second regions. The third region extends across a surface of the second region along an interface, the third region having a composite material having a first phase comprising a plurality of non-intergrown diamond grains, the majority of said diamond grains having a coating comprising nano-sized cBN particles. There is also disclosed a method of forming such a construction.

A super hard polycrystalline construction has a first region having a body of thermally stable polycrystalline super hard material with an exposed surface forming a working surface, and a peripheral side edge, a second region forming a substrate to the first region and a third region interposed between the first and second regions. The third region extends across a surface of the second region along an interface and has a composite material having a first phase comprising a plurality of non-intergrown diamond grains, the majority of the diamond grains having a coating comprising nano-sized BN particles. There is also disclosed a method of making such a construction.

This invention provides resin formulations which may be used for 3D printing and pyrolyzing to produce a ceramic matrix composite. The resin formulations contain a solid-phase filler, to provide high thermal stability and mechanical strength (e.g., fracture toughness) in the final ceramic material. The invention provides direct, free-form 3D printing of a preceramic polymer loaded with a solid-phase filler, followed by converting the preceramic polymer to a 3D-printed ceramic matrix composite with potentially complex 3D shapes or in the form of large parts. Other variations provide active solid-phase functional additives as solid-phase fillers, to perform or enhance at least one chemical, physical, mechanical, or electrical function within the ceramic structure as it is being formed as well as in the final structure. Solid-phase functional additives actively improve the final ceramic structure through one or more changes actively induced by the additives during pyrolysis or other thermal treatment.

A method of manufacturing a polycrystalline abrasive construction comprises providing a plurality of particles of a superhard material, the particles coated with a first matrix precursor material, providing a plurality of second matrix precursor particles having an average size less than 2 micron, the second matrix precursor particles including a liquid phase sintering agent, mixing together the plurality of particles of superhard material with particles of the second matrix precursor material and consolidating and sintering the particles of superhard material and the particles of matrix precursor material. A polycrystalline abrasive construction comprises a particles of a superhard material dispersed in a matrix material comprising a material derived from a liquid phase sintering aid and chemical barrier particles having an average particle size of less than 100 nm dispersed in the matrix. Greater than 50% of the chemical barrier particles are located substantially at boundaries between superhard particles and the matrix.

A 3D printing method includes mixing a sintered component which is selected from the group comprising ceramic materials, ceramic material combinations, metal materials, metal material combinations and metal alloys, with at least one surface coating component which is selected from the group comprising boron nitride, graphene, carbon nanotubes, tungsten sulfide, tungsten carbide, molybdenum sulfide, molybdenum carbide, calcium fluoride, caesium molybdenum oxide sulfide, titanium silicon carbide and cerium fluoride, in a powder mixture; and laser sintering or laser melting the powder mixture in a selective laser sintering method or a selective laser melting method.