863results about "Silicon carbide" patented technology

The invention relates to a nano silicon-carbon composite negative material for lithium ion batteries and a preparation method thereof. A porous electrode composed of silica and carbon is taken as a raw material, and a nano silicon-carbon composite material of carbon-loaded nano silicon is formed by a molten salt electrolysis method in a manner of silica in-situ electrochemical reduction. Silicon and carbon of the material are connected by nano silicon carbide, and are metallurgical-grade combination, so that the electrochemical cycle stability of the nano silicon-carbon composite material is improved. The preparation method of the nano silicon-carbon composite material provided by the invention comprises the following steps: compounding a porous block composed of carbon and silica powder with a conductive cathode collector as a cathode; using graphite or an inert anode as an anode, and putting the cathode and anode into CaCl₂ electrolyte or mixed salt melt electrolyte containing CaCl₂ to form an electrolytic cell; applying voltage between the cathode and the anode; controlling the electrolytic voltage, the electrolytic current density and the electrolytic quantity, so that silica in the porous block is deoxidized into nano silicon by electrolytic reduction, and the nano silicon-carbon composite material for lithium ion batteries is prepared at the cathode.

A nanoparticle reactor comprises a nucleation and core growth region providing a laminar flow of reactants in which the reactants thermally decompose to produce a supersaturated vapor that nucleates aerosol particles into particle cores. Nozzle(s) turbulently mix a preheated diluent into the heated reactants. The mixed preheated diluent and heated reactants flow into a core densification region where particle growth is quenched, coagulation limited and sufficient thermal energy for densification of the cores of the particles is provided. Nozzles turbulently mix a preheated additional reactant. A jet and chemical injection and layer formation region is used to develop the particle cores.

A method is disclosed whereby a functional nanomaterial such as a monolayer carbon nanotube, a monolayer boron nitride nanotube, a monolayer silicon carbide nanotube, a multilayer carbon nanotube with the number of layers controlled, a multilayer boron nitride nanotube with the number of layers controlled, a multilayer silicon carbide nanotube with the number of layers controlled, a metal containing fullerene, and a metal containing fullerene with the number of layers controlled is produced at a high yield. According to the method, when a multilayer carbon nanotube (3) is formed by a chemical vapor deposition or a liquid phase growth process, an endothermic reaction aid (H₂S) is introduced in addition to a primary reactant (CH₄, H₂) in the process to form a monolayer carbon nanotube (4).

A method and apparatus for forming a plurality of fibers from (e.g., CVD) precursors, including a reactor adapted to grow a plurality of individual fibers; and a plurality of independently controllable lasers, each laser of the plurality of lasers growing a respective fiber. A high performance fiber (HPF) structure, including a plurality of fibers arranged in the structure; a matrix disposed between the fibers; wherein a multilayer coating is provided along the surfaces of at least some of the fibers with an inner layer region having a sheet-like strength; and an outer layer region, having a particle-like strength, such that any cracks propagating toward the outer layer from the matrix propagate along the outer layer and back into the matrix, thereby preventing the cracks from approaching the fibers. A method of forming an interphase in a ceramic matrix composite material having a plurality of SiC fibers, which maximizes toughness by minimizing fiber to fiber bridging, including arranging a plurality of SiC fibers into a preform; selectively removing (e.g., etching) silicon out of the surface of the fibers resulting in a porous carbon layer on the fibers; and replacing the porous carbon layer with an interphase layer (e.g., Boron Nitride), which coats the fibers to thereby minimize fiber to fiber bridging in the preform.

A superabrasive fracture resistant compact is formed by depositing successive layers of ceramic throughout the network of open pores in a thermally stable self-bonded polycrystalline diamond or cubic boron nitride preform. The void volume in the preform is from approximately 2 to 10 percent of the volume of the preform, and the average pore size is below approximately 3000 nanometers. The preform is evacuated and infiltrated under at least about 1500 pounds per square inch pressure with a liquid pre-ceramic polymerizable precursor. The precursor is infiltrated into the preform at or below the boiling point of the precursor. The precursor is polymerized into a solid phase material. The excess is removed from the outside of the preform, and the polymer is pyrolized to form a ceramic. The process is repeated at least once more so as to achieve upwards of 90 percent filling of the original void volume. When the remaining void volume drops below about 1 percent the physical properties of the compact, such as fracture resistance, improve substantially. Multiple infiltration cycles result in the deposition of sufficient ceramic to reduce the void volume to below 0.5 percent. The fracture resistance of the compacts in which the poes are lined with formed in situ ceramic is generally at least one and one-half times that of the starting preforms.

The production of ultrafine metal carbide powders from polymeric powder and metallic precursor powder starting materials is disclosed. In certain embodiments, the polymeric powder may comprise polypropylene, polyethylene, polystyrene, polyester, polybutylene, nylon, polymethylpentene and the like. The metal precursor powder may comprise pure metals, metal alloys, intermetallics and/or metal-containing compounds such as metal oxides and nitrides. In one embodiment, the metal precursor powder comprises a silicon-containing material, and the ultrafine powders comprise SiC. The polymeric and metal precursor powders are fed together or separately to a plasma system where the feed materials react to form metal carbides in the form of ultrafine particles.

Silicon-containing products, such as silicon, silicon carbide and silicon nitride, containing less than 0.01 weight percent total mineral impurities and selectively determined carbon-to-silicon ratios. The products are derived from plant matter, such as rice hulls and rice straw, containing at least three weight percent silica. Methods are provided for making such high purity silicon-containing products by leaching silica-containing plant matter with aqueous sulfuric acid under controlled temperatures, pressures and reaction times to remove minerals and metals while adjusting the mole ratio of fixed carbon to silica, and then thermally treating under controlled conditions to produce the desired product.

A method for producing ultrafine metal carbide particles and hydrogen is disclosed. The method includes introducing a metal-containing precursor and a carbon-containing precursor into a thermal reaction chamber, heating the precursors in the thermal reaction chamber to form the ultrafine metal carbide particles from the precursors and to form carbon monoxide and hydrogen, collecting the ultrafine doped metal carbide particles, converting at least a portion of the carbon monoxide to carbon dioxide and generating additional hydrogen, and recovering at least a portion of the hydrogen.

Embodiments of the invention described herein include metamaterials that exhibit negative permittivity and negative permeability at optical frequencies, methods for preparing such materials, and devices prepared from same.

A method for producing carbon-silica products from silica-containing plant matter such as rice hulls or straw by leaching with sulfuric acid to remove non-silica minerals and metal while adjusting the mole ratio of fixed carbon to silica in the resultant product. The carbon and silica are intimately mixed on a micron or submicron scale and are characterized by high purity and reactivity, small particle size, high porosity, and contain volatile carbon that can be used as a source of energy for the production of silicon-containing products from the carbon-silica products. High purity silicon-containing products made from the carbon-silica products of the invention are also disclosed.

The invention discloses a preparation method of a silicon carbide aerogel on the basis of a SiO2 aerogel as a template. The method is characterized in that the method comprises the following steps: preparing the SiO2 aerogel, adding a carbon material or a carbonaceous compound into the pores of the SiO2 aerogel, preparing and preparing a silicon carbide aerogel through a carbon thermal reduction process, or adding the prepared SiO2 aerogel into the carbon material to prepare a SiO2 aerogel composite material, and preparing the silicon carbide aerogel through carbon thermal reduction; removing residual impurities in the silicon carbide aerogel by using a nitric acid and sulfuric acid mixed liquid; and removing superfluous SiO2 by using sodium hydroxide, and removing silicon by using hydrofluoric acid.

The invention discloses a preparation method of fibrous nano silicon carbide. The preparation method is characterized by comprising the following steps: taking a carbon source and chrysotile asbestos of which the main chemical ingredient is silicon dioxide according to the molar ratio of carbon to silicon dioxide being (0.3-3):1; separately grinding the carbon source and chrysotile asbestos, evenly mixing to obtain a mixture; putting the mixture into a reaction device, vacuumizing, and continuously introducing argon in the reaction device; heating to 1350-2500 DEG C and carrying out thermal reaction for 0.2-6 hours; cooling to room temperature, stopping introduction of argon; collecting the reduction product, and grinding into fine powder which is the fibrous nano silicon carbide powder product. The preparation method has the advantages that raw materials are easily availably and equipment and technology are simple; moreover, the preparation method is friendly to environment and high in productivity. The prepared fibrous nano silicon carbide has good performances, can be widely applied to high-tech equipments such as nose cones of space shuttles, brakes of airplanes and racing bicycles, rocket nozzles, satellite antennas, guided missiles and the like, and also has broad use in nanometer microsystems.

Methods are described that have the capability of producing submicron/nanoscale particles, in some embodiments dispersible, at high production rates. In some embodiments, the methods result in the production of particles with an average diameter less than about 75 nanometers that are produced at a rate of at least about 35 grams per hour. In other embodiments, the particles are highly uniform. These methods can be used to form particle collections and/or powder coatings. Powder coatings and corresponding methods are described based on the deposition of highly uniform submicron/nanoscale particles.

A novel polycrystalline stoichiometric fine SiC fiber substantially free of impurities is produced using a novel pre-ceramic polymer. The pre-ceramic polymer is prepared by reacting a mixture of chlorodisilane, boron trichloride, and a vinyl chlorodisilane with an excess of hexamethyldisilazane to form the pre-ceramic polymer resin, which may then be melt-spun, cured, pyrolyzed and heat-treated to obtain the finished SiC fiber. The manufacturing process for the production of the fine SiC ceramic fiber allows for flexibility with respect to cross-linking, in that low-cost thermal treatments may replace more complex methods, while obtaining fibers with improved materials properties as compared to currently available SiC fibers.

This invention relates to a method for preparing nanometer SiC material using nanometer-grade or micron-grade commercial SiC with different shapes, sizes as raw material. The raw materials and catalysts are put into heating device, which is pumped beforehand. Inert gas is let into the heating device as protective gas. The materials and catalysts then will be heated to temperature of 1300~2000° C., and the temperature preserved for a certain period. The nanorod or nanowire produced can be used in the research and development for SiC photoelectric devices, especially for nanometer photoelectric devices and field emission electron sources. This method features simple operation, low cost, and high yield.

A negative active material for a rechargeable lithium battery and a rechargeable lithium battery including the same. The active material includes a silicon-containing compound represented by the following Chemical Formula 1 where Si exists with a concentration gradient from the surface to the center of the negative active material:

SiC_x  [Chemical Formula 1]

• • where 1, 0.05≦x≦1.5.

In SiC sublimation crystal growth, a crucible is charged with SiC source material and SiC seed crystal in spaced relation and a baffle is disposed in the growth crucible around the seed crystal. A first side of the baffle in the growth crucible defines a growth zone where a SiC single crystal grows on the SiC seed crystal. A second side of the baffle in the growth crucible defines a vapor-capture trap around the SiC seed crystal. The growth crucible is heated to a SiC growth temperature whereupon the SiC source material sublimates and forms a vapor which is transported to the growth zone where the SiC crystal grows by precipitation of the vapor on the SiC seed crystal. A fraction of this vapor enters the vapor-capture trap where it is removed from the growth zone during growth of the SiC crystal.

A novel top-down procedure for synthesis of stable passivated nanoparticles uses a one-step mechanochemical process to form and passivate the nanoparticles. High-energy ball milling (HEBM) can advantageously be used to mechanically reduce the size of material to nanoparticles. When the reduction of size occurs in a reactive medium, the passivation of the nanoparticles occurs as the nanoparticles are formed. This results in stable passivated silicon nanoparticles. This procedure can be used, for example in the synthesis of stable alkyl- or alkenyl-passivated silicon and germanium nanoparticles. The covalent bonds between the silicon or germanium and the carbon in the reactive medium create very stable nanoparticles.