A method for manufacturing a silicon nitride substrate is provided. The method comprises the steps of: preparing a ceramic composition containing a metal silicon powder and a crystalline phase control powder containing a rare earth element-containing compound and a magnesium-containing compound; manufacturing a sheet-shaped molded body of a slurry prepared by mixing a solvent and an organic binder with the ceramic composition; and performing heat treatment including a nitrification section where heat treatment is performed at a first temperature in the range of 1300-1500? C. together with the application of nitrogen gas to the molded body at a predetermined pressure and a sintering section where heat treatment is performed at a second temperature in the range of 1700-1900? C.

A system and method for forming a porous ceramic preform is provided. The method may include forming a stacked powder structure including a binder layer and a powder layer on the binder layer. The binder layer may be formed by depositing a binder with a spray nozzle on a substrate. The powder layer may be formed by depositing a powder on the binder layer. The porous ceramic preform may be formed by heating the stacked powder structure to pyrolyze the binder. The porous ceramic preform is configured to be infiltrated by a molten material. The substrate may comprise a ceramic fiber preform. After melt infiltration of the porous ceramic preform and the ceramic fiber preform, a densified ceramic feature having a predetermined geometry may be formed on a ceramic matrix composite (CMC) component.

When a large-sized silicon nitride substrate having high thermal conductivity is produced, a portion where the thermal conductivity is low is generated, which causes reduction in yield (pass rate). Provided is a silicon nitride substrate in which ?e/?c, which is a ratio of a thermal conductivity ?c at a center portion of the substrate to a thermal conductivity ?e at an end portion of the substrate, is 0.85 to 1.15. Preferably, the silicon nitride substrate has a size of 150 mm?150 mm or more. In the silicon nitride substrate, the ?c and the ?e each are preferably 100 W/m.Math.K or more.

Disclosed is a composition having nanoparticles or particles of a refractory metal, a refractory metal hydride, a refractory metal carbide, a refractory metal nitride, or a refractory metal boride, an organic compound consisting of carbon and hydrogen, and a nitrogenous compound consisting of carbon, nitrogen, and hydrogen. The composition, optionally containing the nitrogenous compound, is milled, cured to form a thermoset, compacted into a geometric shape, and heated in a nitrogen atmosphere at a temperature that forms a nanoparticle composition comprising nanoparticles of metal nitride and optionally metal carbide. The nanoparticles have a uniform distribution of the nitride or carbide.

An electrostatic chuck is provided. An electrostatic chuck is implemented by comprising a silicon nitride sintered body and an electrostatic electrode embedded in the silicon nitride sintered body. Therefore, the electrostatic chuck includes a ceramic sintered body, which is silicon nitride, to have excellent plasma resistance, chemical resistance and thermal shock resistance while exhibiting heat dissipation performance of a level equivalent or similar to that of an aluminum nitride ceramic sintered body, which has been conventionally and widely used, and thus can be widely used in a semiconductor process.

An electrostatic chuck is provided. An electrostatic chuck is implemented by comprising a silicon nitride sintered body and an electrostatic electrode embedded in the silicon nitride sintered body. Therefore, the electrostatic chuck includes a ceramic sintered body, which is silicon nitride, to have excellent plasma resistance, chemical resistance and thermal shock resistance while exhibiting heat dissipation performance of a level equivalent or similar to that of an aluminum nitride ceramic sintered body, which has been conventionally and widely used, and thus can be widely used in a semiconductor process.

A method is disclosed for forming a blended phosphor composition. The method includes the steps of firing precursor compositions that include europium and nitrides of at least calcium, strontium and aluminum, in a refractory metal crucible and in the presence of a gas that precludes the formation of nitride compositions between the nitride starting materials and the refractory metal that forms the crucible. The resulting compositions can include phosphors that convert frequencies in the blue portion of the visible spectrum into frequencies in the red portion of the visible spectrum.

An apparatus and a method for producing fine particles capable of increasing the production and producing fine particles at low costs by feeding a large quantity of material efficiently into the plasma. The apparatus includes a vacuum chamber, a material feeding device connected to the vacuum chamber and feeding material particles into the vacuum chamber from material feeding ports, a plurality of electrodes connected to the vacuum chamber, tip ends of which protrude into the vacuum chamber to generate plasma and a collecting device connected to the vacuum chamber and collecting fine particles, which generates discharge inside the vacuum chamber and produces the fine particles from the material, in which the material feeding ports of the material feeding device are arranged in a lower side than the plural electrodes in the vertical direction in the vacuum chamber.

An apparatus and a method for producing fine particles capable of increasing the production and producing fine particles at low costs by feeding a large quantity of material efficiently into the plasma. The apparatus includes a vacuum chamber, a material feeding device connected to the vacuum chamber and feeding material particles into the vacuum chamber from material feeding ports, a plurality of electrodes connected to the vacuum chamber, tip ends of which protrude into the vacuum chamber to generate plasma and a collecting device connected to the vacuum chamber and collecting fine particles, which generates discharge inside the vacuum chamber and produces the fine particles from the material, in which the material feeding ports of the material feeding device are arranged in a lower side than the plural electrodes in the vertical direction in the vacuum chamber.

A method is provided for producing a pulverulent precursor material of the general formula M1.sub.xM2.sub.y(Si,Al).sub.12(O,N).sub.16 or M1.sub.2-zM2.sub.zSi.sub.8Al.sub.4N.sub.16 having the method steps A) producing a pulverulent mixture of starting materials, B) calcining the mixture under a protective gas atmosphere and subsequent grinding, wherein in method step A) at least one nitride with a specific surface area of greater than 2 m.sup.2/g is selected as starting material. A pulverulent precursor material and the use thereof are additionally provided.