Showing papers on "Silicon carbide published in 1983"

Silicon carbide, a high temperature semiconductor

Abstract: Electronic applications are described that would benefit from the availability of high temperature semiconductor devices. Comparisons are made among potential materials for these devices and the problems of each are discussed. Recent progress in developing silicon carbide as a high temperature semiconductor is described.

Single crystal growth of SiC substrate material for blue light emitting diodes

Abstract: The fabrication of 6H-SiC ingot single crystals with up to 20-mm diam and 24-mm length is described. Crystal growth was realized with a modified Lely method using a suitable seed crystal. The growth temperature was 2200°C to obtain preferential growth of the 6H-modification with 2.9-eV bandgap useful for blue light emitting silicon carbide diodes. It is the first time that 6H-SiC ingot crystals yielding substrates for the industrial production of devices based on this compound were obtained. With controlled Al doping of the crystal it was possible to fabricate blue light diodes with the highest quantum efficiency reported so far.

Method for providing a coating layer of silicon carbide on the surface of a substrate

Abstract: The invention provides a novel method for providing the surface of various kinds of substrate articles, e.g. sapphire, quartz, alumina, metals, glass, plastics and the like with a coating layer of an amorphous silicon carbide of the formula Si x C 1-x , in which x is a positive number of 0.2 to 0.9, by exposing the surface of the substrate article to an atmosphere of plasma generated in a gaseous atmosphere of an organosilicon compound having no halogen or oxygen atom directly bonded to the silicon atom, such as hexamethyl disilane, optionally admixed with a vapor or gas of a hydrocarbon compound, e.g. methane, benzene and the like.

Abrasive product and method for manufacturing

Abstract: An abrasive body is provided which has high strength and an ability to withstand high temperatures making it suitable as a tool insert for dressing tools and surface set drill bits. The body comprises a mass of diamond particles present in an amount of 80 to 90 percent by volume of the body and a second phase present in an amount of 10 to 20 percent by volume of the body, the mass of diamond particles containing substantial diamond-to-diamond bonding to form a coherent skeletal mass and the second phase containing nickel and silicon, the nickel being in the form of nickel and/or nickel silicide and the silicon being in the form of silicon, silicon carbide and/or nickel silicide. The abrasive bodies are made under conditions of elevated temperature and pressure suitable for diamond compact manufacture.

Thermal ink jet printhead

Abstract: A protective passivation structure is provided for a thermal ink jet printing head which employs a resistive heating element formed of phosphorus-diffused silicon. The passivation structure includes a layer of silicon nitride over the heating element with a layer of silicon carbide over the silicon nitride layer. The nitride exhibits good adhesion to the underlying silicon as well as good thermal conductivity. The carbide has exceptionally good wear and hardness qualities against ink bubble cavitation as well as adhering well to the nitride.

R.F.-plasma system for the production of ultrafine, ultrapure silicon carbide powder

Abstract: A new high-temperature plasma tube has been developed that overcomes the meltdown problem of the conventional water- and gas-cooled quartz plasma tubes commonly used. The key feature of this system is the placement of several heavy-walled, water-cooled copper fingers inside a quartz mantle to shield the mantle from the intense radiation of the plasma. The copper fingers act as transformers to couple the plasma to the field of the coil. This new stystem has been used to produce ultrafine, ultrapure silicon carbide powder.

Randomly-oriented polycrystalline silicon carbide coatings for abrasive grains

Abstract: Disclosed is a composite abrasive particle comprising a core abrasive crystal and a silicon carbide coating inherently bonded to substantially all of the exterior surfaces of said core crystal, said silicon carbide coating characterized by silicon carbide crystals having a random orientation substantially independent of the structure of the core crystal, the outer surface of the coating being conformationally irregular Aggregates of the composite abrasive particles are interconnected by a matrix of silicon carbide which has an open structure Preferred core abrasive crystals are diamond or cubic boron nitride The composite abrasive particles preferably are made by infiltrating core crystals coated with non-diamond carbonaceous material with fluid silicon to produce a mass of core crystals bonded together by silicon carbide and elemental silicon, leaching substantially all of the silicon from the bonded mass with a silicon leaching agent, sub-dividing the resulting leached mass, and recovering the composite abrasive particles

Silicon carbide materials

Abstract: Silicon carbide material retains the hardness, wear and resistance properties and can be rendered electrically conductive by the incorporation of germanium in the range 0.01 to 0.03 percent therein. The material is very hard, is electrically conductive in the 2x104 Ωcm range and is useful in highly corrosive and abrasive applications. A process for producing said material by pyrolytically dissociating an organic silicon and carbon bearing gas like triethylsilane and tetraethylgermanium over a substrate taken from the group of quartz, sapphire, ceramic alumina, silicon carbide, gallium arsenide and metals melting above 800°C, is also described.

Titanium metal-matrix composites

Abstract: Titanium alloy composites having substantially reduced reaction zones are provided which comprise a high strength/high stiffness filament such as silicon carbide, silicon carbide-coated boron, boron carbide-coated boron and silicon-coated silicon carbide, embedded in a fine-grained titanium alloy containing at least 40 percent beta phase, less than 7 percent Al and having a beta-transus temperature below 1750° F. (955° C.). Also provided is a method for fabricating titanium composites which comprises mechanically working a desired titanium alloy to obtain sheetstock in a desired thickness and having a relatively fine grain size, laying up a preform and consolidating the preform under increased temperature and pressure, wherein consolidation is carried out at a temperature below the beta-transus temperature of the alloy, thereby reducing the amount of reaction zone between the filament and the alloy matrix.

Ceramics containing fibers of silicon carbide

Abstract: Ceramics incorporating fibrous crystals of silicon carbide, optionally, in combination with an electroconductive substance have high electroconductivity and are amenable to electric discharge machining.

Diffusion of Silver and Cesium in Silicon-Carbide Coatings of Fuel Particles for High-Temperature Gas-Cooled Reactors

Abstract: Fractional releases of silver and cesium from irradiated silicon-carbide-layered coated particles have been measured during isothermal anneals in the temperature range between 1273 and 1773 K. The release rates measured have been evaluated with the aid of a statistical numerical treatment based on a simple diffusion model in multizone geometry. The resulting diffusion coefficients are described for silver and for cesium. A statistical treatment of the data gives corresponding 95% confidence limits. It is argued that the pathway of cesium and silver transport in silicon-carbide layers is grain boundary diffusion. This explains the large scatter found in the data for coating layers because the defect structure depends on the individual manufacturing conditions and varies from coating to coating. Comparison with data from the literature shows the superiority of silicon carbide with respect to silver retention relative to diffusion rates in pyrocarbons, while cesium data indicate no distinct improvement.

Substantially pore-free sintered polycrystalline articles of α-silicon carbide, boron carbide and free carbon and process for their manufacture

Abstract: The invention provides substantially pore-free sintered polycrystalline articles comprising α-silicon carbide, boron carbide and free carbon, the quantitative proportions of which, in percent by weight, are defined by the trapezoidal area having, in the ternary system B/Si/C of FIG. 1 the corner points a=89.0% B 4 C, 9.9% α-Sic, 1.1% C b=9.9% B 4 C, 89.0% α-SiC, 1.1% C c=9.0% B 4 C, 81.0% α-Sic, 10.0% C d=81.0% B 4 C, 9.0% α-SiC, 10.0% C The articles have a density of at least 99% of the theoretical density, an average structural grain size of less than 20 μm and a 4-point flexural strength of at least 400 N/mm 2 . They are manufactured from fine-grained mixtures of α-silicon carbide, boron carbide, carbon and/or material that can be coked to form carbon, in a two-stage sintering process. In the first stage, green bodies preshaped from the powder are subjected to pressureless sintering to a density of at least 95% TD at from 1950° to 2150° C. In the second stage, the sintered articles are subjected to a post-densification to a density of at least 99% TD, by isostatic hot pressing, without encapsulating, at from 1850° to 2150° C. in a high-pressure autoclave under a gas pressure of at least 10 MPa.

Lithium-containing neutron target particle

Abstract: To provide a lithium-containing neutron target particle for breeding tritium within the core of a nuclear reactor, including a central core formed of a stable lithium-containing compound, a surrounding buffer layer, and an outer tritium-impermeable silicon carbide coating, the core is initially sealed with an inner sealing layer of pyrolytic carbon and an outer sealing layer of stoichiometric zirconium carbide. The pyrocarbon seal protects the lithium within the core from attack from the zirconium carbide coating atmosphere, and the zirconium carbide layer prevents loss of lithium from the core when the silicon carbide coating is deposited at elevated temperatures.

Composite silicon carbide sintered shapes and its manufacture

Abstract: A composite silicon carbide sintered shape is provided in two forms in which the former form includes rare earth oxides as a sintering assist, and the latter form includes rare earth oxides and/or aluminum oxide or boron oxide as a sintering assist, characterized in that both forms have a surface layer abundant in rare earth oxides. Methods for manufacturing such sintered shapes are also provided.

Electrically conductive sintered ceramics and ceramic heaters

Abstract: An electrically conductive sintered ceramics of the present invention comprises, as the main ingredients thereof, (a) silicon carbide, (b) an inorganic compound which exhibits a positive resistance-temperature coefficient, and preferably (c) a sintering assistant. The electrically conductive sintered ceramics obtained exhibits a positive resistance-temperature coefficient as a whole. A ceramic heater of the invention makes use of the electrically conductive sintered ceramics in an electrically conductive portion thereof. A sintered product which exhibits a positive resistance-temperature coefficient helps to prevent the occurrence of thermal runaway or thermal destruction.

Fiber reinforced glass matrix composites

Abstract: What is disclosed is a method of preparing fiber reinforced glass composites from high modulus fibers, such as carbon fibers and silicon carbide fibers, and silazane polymers. The composites are obtained by heating a pressed and post-cured prepreg to an elevated temperature in an inert atmosphere. Prepregs containing silicon carbide fibers can be fired in air. A simple, low temperature laminating procedure is used in the preparation of these composites in place of the standard hot pressing technique.

Ultrafine powder of silicon carbide, a method for the preparation thereof and a sintered body therefrom

Abstract: The invention provides a method for the preparation of an ultrafine powder of silicon carbide having an extremely fine and uniform particle size distribution of spherical agglomerate particles each formed of crystallites of 5 nm or smaller in size. The silicon carbide powder is prepared by the vapor phase pyrolysis of a specified methyl hydrogen(poly)silane as diluted with a carrier gas, e.g. hydrogen, to give a concentration of 40% by volume or lower at a temperature of 750° to 1600° C. The silicon carbide powder can readily be sintered at a temperature of 1750° to 2500° C. even without addition of a sintering aid to give a sintered body of extremely high density reaching 80% or larger of the theoretical value which can never be obtained of the conventional silicon carbide powders.

Photosensitive member for electrophotography comprises inorganic layers

Abstract: Disclosed is a photosensitive member, or an electrophotographic photosensitive member, characterised by having a photoconductive layer comprising at least one of an amorphous hydrogenated and/or fluorinated silicon germanium and an amorphous hydrogenated and/or fluorinated silicon germanium carbide, a first amorphous hydrogenated and/or fluorinated silicon carbide layer formed on the photoconductive layer and a second amorphous hydrogenated and/or fluorinated silicon carbide layer formed beneath said photoconductive layer.

Method for forming fibrous silicon carbide insulating material

Abstract: A method whereby silicon carbide-bonded SiC fiber composites are prepared from carbon-bonded C fiber composites is disclosed. Carbon-bonded C fiber composite material is treated with gaseous silicon monoxide generated from the reaction of a mixture of colloidal silica and carbon black at an elevated temperature in an argon atmosphere. The carbon in the carbon bond and fiber is thus chemically converted to SiC resulting in a silicon carbide-bonded SiC fiber composite that can be used for fabricating dense, high-strength high-toughness SiC composites or as thermal insulating materials in oxidizing environments.

Electromagnetic wave absorbers

Abstract: of the disclosure: An electromagnetic wave absorber comprising an electromagnetic wave absorbing layer consisting essentially of silicon carbide fibers, which layer may be applied to a metal plate. The wave absorber comprising the absorbing layer-applied metal plate exerts wave absorption expressed in terms of a wave attenuation which is at least 10 dB higher than the inherent attenuation caused by reflection of the wave by the absorbing layer-free original metal plate, the wave used being one which has a frequency of 8-16 GHz.Further, the silicon carbide fibers may be made into woven cloths, mat felts or the like which are laminated together and then composited with a synthetic resin or ceramics to prepare the wave absorbing layer.

Process for producing ultrafine silicon carbide powder

Abstract: A process for producing an ultrafine silicon carbide powder by passing a granulated blend of silica powder, carbon powder and a carbonaceous binder downwardly through a vertical indirect heating reactor, wherein means are provided for increasing the bulk density of the carbon powder for preventing the disintegration of the blend during the reaction which might result from the use of ultrafine powder as the carbon powder in the blend.

Alumina silicon carbide, and silicon primary protective coatings for carbon-carbon substrates

Abstract: In accordance with the invention, a composition of matter is provided for forming a coating for protecting carbonaceous substrates from degradation at elevated temperatures. The composition of matter is a mixture of particulate silicon, silicon carbide and alumina. The mixture contains between about 40% and 50% silicon by weight of the total composition, between about 30% and 50% silicon carbide by weight of the total composition and between about 20% and 30% alumina by weight of the total composition. A method is provided for forming a primary protective coating on carbonaceous substrates utilizing the aforesaid mixture. An enhancement coating is provided for sealing the primary coating in applications where the substrate will be subjected to elevated temperatures and temperature cycling.

Process for preparing silicon carbide whiskers

Abstract: The process according to the present invention involves mixing 100 parts by weight of a silica gel, containing 60 to 250% by weight with respect to a silicon of a water-soluble compound of at least one metal selected from the group consisting of iron, nickel and cobalt, with 110 to 400 parts by weight of furnace carbon black having a structure indicated by a DBP absorption number of 50 ml/100 g or higher, and then reacting the mixture under a non-oxidative atmosphere at a temperature of 1,300° to 1,700° C to produce silicon carbide whiskers

Preparation of Silicon Nitride Powder from Silica

Abstract: Although thermodynamic data predict the difficulty in advancing the reaction, 3SiO2(S) + 6C(S) + 2N2(G) = Si3N4(S) + 6CO(G), in a closed system, it has been proved that heating fine powder mixtures of silica and carbon in nitrogen gas flow results in sufficient formation of silicon nitride powder, without detectable coexisting silicon carbide. Apparent activation energy (≃163 kcal/mol) on the reaction approximates to the value of ∆Hr (≃l60 kcal/mol at 1700 K) calculated on the elementary reaction, SiO2(S) + C(S) = SiO(G) + CO(G), which therefore seems to be a rate-determining one. The observation of fibrous silicon nitride growing out into gaps among aggregated powder lumps and that of weight losses of samples larger than expected suggest that SiO gas should be generated as an intermediate product. Silicon nitride powder prepared from silica through the improved reaction process possesses excellent characteristics such as high α-phase content, homogeneous shape and size, and very low content of metallic impurities.

Production of reaction-bonded silicon carbide bodies

Abstract: The production of a reaction-bonded silicon carbide artefact by siliconizing a green body comprising a coherent mixture of carbon and silicon carbide particles includes the step of forming a layer of carbon of open cellular structure on the green body by carbonization of a sleeve or tube on the green body by carbonization of a sleeve or tube of carbonaceous material in contact with the body. This material may be impregnated with particulate silicon suspended in water or a paste. The material may be a quilted or woven fabric of fibrous material or it may be in the form of paper. The material is in a flexible strip or sheet form to enable it to be wrapped around the green body or a former about which the green body is to be formed.

Sic sintered body having metallized layer and production method therefor

Abstract: high density and electrically insulating sintered body 11 has SiC as its principal component and as an electro-conductive thin layer 17 on a desired surface thereof. To achieve good bonding the electro-conductive thin layer is a metallized layer containing at least one metal selected from Group Ib and VIII metals and their alloys and a binder forming a vitreous matter with a silicon oxide, and is bonded to said sintered body via a fused layer formed between a silicon oxide film formed on the surface of said sintered body 11 and the oxide of said binder. The invention can be applied to a semiconductor device using an electrically insulating silicon carbide sintered body as the substrate.

Light emitting diode having silicon carbide layers

Abstract: A light emitting diode has a substrate body consisting of silicon carbide, which is transmissive for the luminescent radiation generated by the diode. The diode has a first epitaxially deposited layer, consisting of silicon carbide of a first conductivity type, disposed on the substrate body, and a second epitaxially deposited layer of silicon carbide of a second conductivity type disposed on the first layer. The diode has one electrode connected to the second layer and another electrode connected to an exposed portion of the first layer.

Method of manufacturing crystalline silicon carbide

Abstract: A method of manufacturing silicon carbide whiskers in which a carbon and silicon containing material having a thin configuration and sufficient porosity to permit both the passage of a gas therethrough and to provide spaces for growing whiskers therein is charged on a gas-permeable tray, and heated in a furnace of non-oxidizing atmosphere. The tray is moved intermittently through a series of temperature zones, increasing stage-by-stage from about 400° C. to 1,300° C., while a non-oxidizing gas is circulated through the porous material to remove any impurities. Thereafter, the heated tray is intermittently moved through a series of increasing temperature stages from about 1,350° C. to 1,450° C. to effect whisker growth. The treated silicon carbide-containing material is dispersed in a two-phase mixture of a hydrophobic organic liquid and water. The desired silicon carbide whiskers can be isolated from the aqueous phase.