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Showing papers on "Silicon carbide published in 1979"


Journal ArticleDOI
TL;DR: In this article, thermal conductivity measurements of 6H SiC crystals were done in the 300-500 K range by means of radiation thermometry, and it was found that the thermal conductivities normal to the c axis is proportional to T−1.49, the room temperature value being 3.87 W/cm
Abstract: Thermal conductivity measurements of 6H SiC crystals were done in the 300–500 K range by means of radiation thermometry. Both p‐ and n‐type crystals with carrier concentrations in the 8×1015 to 1020 cm−3 range were used. For the purest samples it was found that the thermal conductivity normal to the c axis is proportional to T−1.49, the room‐temperature value being 3.87 W/cm deg. It was also found that the thermal conductivity parallel to the c axis is about 30% lower than that normal to the c axis. Electrical data in the 100–1000 K range are also presented.

145 citations


Journal ArticleDOI
TL;DR: In the presence of carbon or silicon carbide, silica can be reacted to form a vapor of silicon monoxide and the rates of these reactions were explored at 1300° to 1550°C as mentioned in this paper.
Abstract: In the presence of carbon or silicon carbide, silica can be reacted to form a vapor of silicon monoxide. The rates of these reactions were explored at 1300° to 1550°C. For mixtures of carbon and silica, evidence supported a two-step reaction: silicon carbide formed prior to reaction between silicon carbide and silica.

94 citations


Journal ArticleDOI
TL;DR: In this article, the growth kinetics of SiC epitaxial layers have been investigated by sublimation sandwich-method in vacuum at temperature range from 1600 to 2100°C, and the limiting stages of the crystallization process have been determined.
Abstract: The growth kinetics of SiC epitaxial layers has been investigated by sublimation sandwich-method in vacuum at temperature range from 1600 to 2100°C. The limiting stages of the crystallization process have been determined. Silicon deficit in the growth cell was shown to result in the great retarding of SiC epitaxial layers growth due to the decreasing of evaporation coefficient by a factor of 101–102 and more. The impurities introduced into the system at low supersaturations and temperatures, especially rare-earth elements, Al, B, Cr reduce as a rule evaporation and condensation coefficients and therefore the growth rate of epitaxial layers. [Russian Text Ignored].

87 citations


Patent
21 May 1979
TL;DR: Disclosed is an improved abrasive material particularly useful as a dispersoid in metal matrices to provide articles of use having superior abrasive properties, especially at elevated temperatures as mentioned in this paper.
Abstract: Disclosed is an improved abrasive material particularly useful as a dispersoid in metal matrices to provide articles of use having superior abrasive properties, especially at elevated temperatures The improved abrasive material typically comprises silicon carbide particulate, the individual particles of which have a predominantly alumina coating thereon to inhibit dissolution of the particles in the metal matrix at high temperatures The invention finds special application in abrasive blade tips for service in gas turbine engines, the tips comprising a nickel base or cobalt base superalloy having the alumina coated silicon carbide particles dispersed therein

77 citations


Patent
26 Mar 1979
TL;DR: In this paper, pressureless sintered silicon carbide ceramic bodies, having an equiaxed microstructure and an alpha crystalline habit, were produced by firing shaped bodies, containing finely divided silicon carbides, boron source such as BORON carbide, carbon source, phenolic resin and a temporary binder, at a sintering temperature of from about 1900° C to about 2250° C.
Abstract: Pressureless sintered silicon carbide ceramic bodies, having an equiaxed microstructure and an alpha crystalline habit can be produced by firing shaped bodies, containing finely divided silicon carbide, boron source such as boron carbide, carbon source such as phenolic resin and a temporary binder, at a sintering temperature of from about 1900° C. to about 2250° C., depending on the sintering atmosphere, under conditions such that a coating of carbon source is maintained on the finely divided silicon carbide, and sufficient boron is maintained within the shaped body during firing. Boron can be maintained within the shaped body by various techniques, such as the use of a "seasoned boat" or graphite container for the body being sintered, which has been saturated with boron by exposure to boron at or about the temperature of sintering. There is also disclosed a process for producing a sintered silicon carbide ceramic body, with or without the equiaxed crystal microstructure, from silicon carbide powders of alpha or beta crystal structure, or amorphous noncrystalline silicon carbide, or mixtures thereof.

76 citations


Patent
09 Feb 1979
TL;DR: A mass of diamond crystals in contact with a mass of eutectiferous silicon-rich alloy and a silicon carbide ceramic substrate are disposed in a container and placed within a pressure transmitting powder medium.
Abstract: A mass of diamond crystals in contact with a mass of eutectiferous silicon-rich alloy and a silicon carbide ceramic substrate are disposed in a container and placed within a pressure transmitting powder medium. Pressure is applied to the powder medium resulting in substantially isostatic pressure being applied to the container and its contents sufficient to dimensionally stabilize the container and its contents. The resulting shaped substantially isostatic system of powder-enveloped container is hot-pressed whereby fluid eutectiferous silicon-rich alloy is produced and infiltrated through the interstices between the diamond crystals and contacts the contacting face of the silicon carbide substrate sufficiently producing, upon cooling, an adherently bonded integral composite.

68 citations


Journal ArticleDOI
TL;DR: In this article, sliding friction experiments were conducted with single-crystal silicon carbide in contact with various metals and it was shown that the coefficient of friction is related to the relative chemical activity of the metals.
Abstract: Sliding friction experiments were conducted with single-crystal silicon carbide in contact with various metals. Results indicate the coefficient of friction is related to the relative chemical activity of the metals. The more active the metal, the higher the coefficient of friction. All the metals examined transferred to silicon carbide. The chemical activity of the metal and its shear modulus may play important roles in metal-transfer, the form of the wear debris and the surface roughness of the metal wear scar. The more active the metal, and the less resistance to shear, the greater the transfer to silicon carbide and the rougher the wear scar on the surface of the metal. Hexagon-shaped cracking and fracturing formed by cleavage of both prismatic and basal planes is observed on the silicon carbide surface. Presented at the 33rd Annual Meeting in Dearborn, Michigan, April 17–20, 1978

54 citations


Journal ArticleDOI
TL;DR: In this paper, the formation of silicon carbide powders by the vapor phase reaction of SiCl4 + CH4 (1400-1500°C), CH3SiCl3 (800-1400°C) and (CH3)4Si (800 − 1400 °C) was studied.
Abstract: The formation of silicon carbide powders by the vapor phase reaction of SiCl4 + CH4 (1400–1500°C), CH3SiCl3 (800–1400°C) and (CH3)4Si (800–1400°C) was studied. The effectiveness of the silicon sources was in the sequence (CH3)4Si > CH3SiCl3 > SiCl4, in accordance with the thermodynamic parameters. Fine β-SiC powders were produced by the pyrolysis of (CH3)4Si in hydrogen above 900°C. The crystallinity of the products increased with increasing reaction temperature. The particles were spherical and had average sizes of 0.02–0.12μm which decreased with increasing reaction temperature and with decreasing (CH3)4Si concentration. A reaction process consisting of the formation of particles of organosilicon polymers and their subsequent decomposition was proposed for the formation of SiC particles by the pyrolysis of (CH3)4Si.

51 citations


Patent
30 Mar 1979
TL;DR: Silicon carbide coated carbon fibers and composite materials incorporating these fibers are disclosed in this paper, where the silicon carbide coating provides electrical insulation and improved resistance to environmental degradation, and the coated fibers may be embedded in organic, metal or glass matrices to form useful composite materials.
Abstract: Silicon carbide coated carbon fibers and composite materials incorporating these fibers are disclosed. The silicon carbide coating provides electrical insulation and improved resistance to environmental degradation. The coated fibers may be embedded in organic, metal or glass matrices to form useful composite materials.

50 citations


Patent
02 Jan 1979
TL;DR: In this paper, a shape confined structure composed of a mass of diamond and/or cubic boron nitride crystals coated with elemental non-diamond carbon in contact with a supporting silicon carbide substrate is infiltrated by fluid silicon producing a like-shaped composite of a polycrystalline body component integrally bonded to the substrate.
Abstract: A shaped confined structure composed of a mass of diamond and/or cubic boron nitride crystals coated with elemental non-diamond carbon in contact with a supporting silicon carbide substrate is infiltrated by fluid silicon producing a like-shaped composite of a polycrystalline body component integrally bonded to the supporting silicon carbide substrate.

49 citations


Patent
31 Aug 1979
TL;DR: In this article, a process is described for the production of dense metastable phases of carbon which have characteristics similar to diamond, which are applied to substrates to produce hard and impermeable surfaces thereby producing cutting elements, styli, etc.
Abstract: A process is described for the production of dense metastable phases of carbon which have characteristics similar to diamond. Particulates of the metastable carbon are produced by reacting silicon carbide or a silicon carbide precursor, such as a silane or silicon metal, with a fluorocarbon, such as carbon tetrafluoride at a temperature greater than about 800° C. A preferred range is from about 900° C. to 1200° C. The reaction may be carried out in a high voltage electrical diacharge, or other plasma, or in a furnace. The presence of a "promoter" metal, such as nickel and iron, increases the reaction rate and the quantity of the metastable carbon phases. Relatively large quantities of these diamond-like particulates are produced, and their properties are such as to make them useful for many of the same applications for which commercial diamonds are utilized. They are also useful in numerous high temperature applications. Layers of the metastable carbon phases may be applied to substrates to produce hard and impermeable surfaces thereby producing cutting elements, styli, etc.

Patent
26 Feb 1979
TL;DR: In this article, the authors provided shaped polycrystalline silicon carbide having densities of at least 97% and improved mechanical properties particularly at high temperatures, said articles consisting of at at least 95.4% by weight of.alpha.-silicon carbide, about 0.1 to 2.0% of additional carbon, about 2.2 to 3.5% of nitrogen, and about 0 to 0.9% of oxygen.
Abstract: OF THE DISCLOSURE There are provided shaped articles of polycrystalline silicon carbide having densities of at least 97% and improved mechanical properties particularly at high temperatures, said articles consisting of at least 95.4% by weight of .alpha.-silicon carbide, about 0.1 to 2.0% by weight of additional carbon, about 0.2 to 2.0% by weight of aluminium, about 0 to 0.5% by weight of nitrogen, and about 0 to 0.1% by weight of oxygen, the .alpha.-silicon carbide being in the form of a homogeneous micro-structure with an average grain size of less than 10 µm. There is also provided a process for the preparation of such articles by pressureless sintering submicron powder compacts consisting of .alpha.-silicon carbide and aluminium- and carbon containing additives as sintering aids.

Journal ArticleDOI
TL;DR: In this article, an investigation was conducted to determine the nature of the deformation and fracture of silicon carbide and its effects on friction properties, and the results indicated that, when deformation is primarily elastic, the friction does not depend on crystallographic orientation and there is no detectable fracture or crocking.
Abstract: An investigation was conducted to determine the nature of the deformation and fracture of silicon carbide and its effects on friction properties. Friction experiments were conducted with hemispherical and conical diamond riders sliding on the basal plane of silicon carbide. The results indicate that, when deformation is primarily elastic, the friction does not depend on crystallographic orientation and there is no detectable fracture or crocking. When, however, plastic deformation occurs, silicon carbide exhibits anisotropic friction and deformation behavior. Surface fracture crack patterns surrounding wear tracks are observed to be or three types. The crack-geometries of two types are generally independent of orientation, the third crack, however, depends on the orientation. All surface cracks extend into subsurface. Anisotropic friction, deformation and fracture on the basal plane are primary controlled by the slip system {101¯0} ⟨112¯0⟩ and a cleavage of {101¯0}. Presented as an American Society of Lub...

Journal ArticleDOI
TL;DR: In this article, a study was made of changes in fracture strength, Weibull modulus and electrical resistivity of silicon carbide and graphite materials exposed to fast neutron fluences of 2 × 1023 to 2 × 1024n/m2 (E > 1 MeV).

Journal ArticleDOI
TL;DR: In this paper, the reaction of hot-pressed SiC and a nickel-based superalloy at temperatures between 700 and 1150°C was studied and some degree of reaction was observed in both metal and ceramic at all temperatures studied.
Abstract: A study has been made of the reaction of hot-pressed SiC and a nickel-based superalloy at temperatures between 700 and 1150° C. Under conditions of reduced oxygen pressure at the reaction interface, obtained by applying pressure to the couple, some degree of reaction was observed in both metal and ceramic at all temperatures studied. Preliminary studies utilizing the same techniques at 1000° C with a Si-SiC ceramic composite, Si3N4, MgO, Al2O3, and SiO2 also indicated some degree of reaction in the metal for all ceramics examined.

Patent
09 Feb 1979
TL;DR: In this paper, a silicon carbide sintered body exhibiting N-type semiconductivity is produced by shaping a mixture of β-silicon carbide, boron additive and a carbonaceous additive into a green body and sintering the body in an atmosphere containing nitrogen.
Abstract: A silicon carbide sintered body exhibiting N-type semiconductivity is produced by shaping a mixture of β-silicon carbide, boron additive and a carbonaceous additive into a green body and sintering the body in an atmosphere containing nitrogen to produce a sintered body having a density of at least about 90% and pores which are substantially non-interconnecting.

Journal ArticleDOI
TL;DR: In this article, high-resolution transmission electron microscopy, utilizing tilted illumination lattice imaging techniques, has been used to examine the structure of interfaces between transforming polytypes in cubic silicon carbide samples subsequent to annealing heat treatments.
Abstract: SUMMARY High resolution transmission electron microscopy, utilizing tilted illumination lattice imaging techniques, has been used to examine the structure of interfaces between transforming polytypes in cubic silicon carbide samples subsequent to annealing heat treatments. Though structure projection images have not been possible, detailed observation of the twinned cubic, 3C/6H and 3C/4H interfaces have been made including stacking sequence information observed with ∼ 0·25 nm lattice fringes. In contrast to the apparently strain-free coherent conditions found at twinned cubic and 3C/6H interfaces, 3C/4H interfaces were observed to be coherent but with a short-range strain field periodic over every twelve layers of the cubic structure. The 3C/6H transformation has been clearly observed to initiate at twin interfaces and to proceed by the propagation of steps of unit-cell height along the coherent interface. The implications of these observations for phase transformations in silicon carbide, together with the necessary associated structural rearrangements, are discussed. Finally, some preliminary observations (utilizing impurity-sensitive SEM contrast, together with the optical examination of thin foils in polarized light) concerning possible impurity redistributions and anomalous grain growth effects during polytypic phase transformations are presented.

Patent
03 Dec 1979
TL;DR: In this paper, a carbon-containing preform (body of the desired shape) is contacted with elemental silicon powder at a temperature of 1400° C to 1500° C. and the silicon-contacted carboncontaining body is thereafter treated at aperature of 1800°C. to 2000°C to transform at least the major part of the carbon into silicon carbide.
Abstract: In the production of shaped silicon-carbide bodies, especially tubes whichonsist predominantly of silicon carbide throughout their thickness for use in nuclear-reactor technology, a carbon-containing preform (body of the desired shape) is contacted with elemental silicon powder at a temperature of 1400° C. to 1500° C. and the silicon-contacted carbon-containing body is thereafter treated at a temperature of 1800° C. to 2000° C. to transform at least the major part of the carbon into silicon carbide.


Book ChapterDOI
TL;DR: In this paper, a high-velocity sandblast-type erosion test was performed on 200 materials to determine their suitability for application in coal gasifier valves, and it was shown that cermet binder content and porosity are related to erosion resistance.
Abstract: Over 200 materials were screened by a high-velocity sandblast-type erosion test to determine their suitability for application in coal gasifier valves. Most metals had relatively similar and low erosion resistances. Ceramics and cermets such as boron carbide (B 4 C), tungsten carbide (WC), silicon carbide (SiC), silicon nitride (Si 3 N 4 ), and titanium diboride (TiB 2 ), if manufactured to minimize porosity, had more than four times the erosion resistance of metals. Several coatings such as boronized molybdenum and tungsten carbide, chemical vapor-deposited titanium carbon nitride (TiCN), and electrodeposited TiB 2 also proved highly erosion resistant when applied in sufficient thicknesses. Additional findings confirmed that cermet binder content and ceramic porosity are related to erosion resistance.

Patent
02 Feb 1979
TL;DR: In this article, a method of producing a silicon carbide sintered body having a density of at least 2.4 g/cm3 is described, which is obtained by preparing a mixture consisting mainly of silicon carbides with an average particle size of not more than 3.0 microns and a temporary binder, shaping the mixture into a green body and sintering the green body at a temperature of 1,750° C-2,100° C.
Abstract: A method of producing a silicon carbide sintered body is disclosed. The sintered body having a density of at least 2.4 g/cm3 is produced by preparing a mixture consisting mainly of silicon carbide with an average particle size of not more than 3.0 microns and a temporary binder, shaping the mixture into a green body and sintering the green body at a temperature of 1,750° C.-2,100° C. Before the sintering, silicon carbide is contacted with either hydrofluoric acid or anhydrous hydrofluoric acid and an atmosphere is held in a non-oxidizing state after the contact treatment up to the completion of the sintering.

Patent
07 Mar 1979
TL;DR: In this article, a method of producing a silicon carbide powder consisting of fine particles of uniform shape and size, comprising baking at 1,350° to 1,850° C.
Abstract: A method of producing a silicon carbide powder consisting of fine particles of uniform shape and size, comprising baking at 1,350° to 1,850° C. under a non-oxidizing atmosphere a powdery mixture consisting of 1 part by weight of silica powder or a compound forming silica powder at high temperatures, carbon powder or a compound forming carbon powder at high temperatures, and silicon carbide or a substance forming silicon carbide at high temperatures, the amounts of the silica powder-forming compounds, the carbon powder-forming compounds and the silicon carbide powder-forming substance being determined such that the amounts of the formed powders are equal to those specified above.

Patent
09 Jul 1979
TL;DR: In this article, a method of etching surfaces such as silicon dioxide, silicon nitride and silicon carbide by exposing the surface simultaneously to a noble gas halide such as fluorinated xenon compound and radiation such as electron beam radiation was described.
Abstract: The invention relates to a method of etching surfaces such as silicon dioxide, silicon nitride and silicon carbide by exposing the surface simultaneously to a noble gas halide such as fluorinated xenon compound and radiation such as electron beam radiation. The etch rate of silicon dioxide achieved by the present invention, as illustrated in Figure 1, is about 200 angstroms per minute.

Patent
08 Mar 1979
TL;DR: In this article, a composition is provided for use in forming varistor blocks containing mostly zinc oxide together with other impurities, including significant amounts of silicon carbide to a concentration of less than one molar percent of the total varistor composition.
Abstract: A composition is provided for use in forming varistor blocks containing mostly zinc oxide together with other impurities, including significant amounts of silicon carbide to a concentration of less than one molar percent of the total varistor composition The method of forming varistor blocks according to the invention includes mixing zinc oxide powder together with the silicon carbide and other impurities, and then sintering the mixture at a temperature in the range of from approximately 1100° C to approximately 1250° C

Journal ArticleDOI
TL;DR: In this article, the friction properties and mechanical behavior of single-crystal silicon carbide (0001) surface sliding against itself and against polycrystalline titanium are examined. And the results indicate hexagon-shaped pits of silicon carbides and the formation of platelet hexagonshaped wear debris of silicon carbonide due to cleavages of both prismatic and basal planes as a result of sliding against themselves.
Abstract: An investigation was conducted to examine the friction properties and mechanical behavior of single-crystal silicon carbide (0001) surface sliding against itself and against polycrystalline titanium. The results indicate hexagon-shaped pits of silicon carbide and the formation of platelet hexagon-shaped wear debris of silicon carbide due to cleavages of both prismatic and basal planes as a result of silicon carbide sliding against itself. The fracturing of silicon carbide also occurs near the adhesive bond to titanium. The wear debris produced by brittle fracture plows the titanium and transfers to it. Further, the silicon carbide wear debris, which adhered and transferred to titanium, plows the silicon carbide surface and transfers back to it

Journal ArticleDOI
TL;DR: In this paper, a silicon carbide film was chemically vaporized on molybdenum in the temperature range of 1050-1300°C by reaction of hydrogen and ethyltrichlorosilane as an application of a low-Z material to fusion reactor protective plates.

Patent
09 Mar 1979
TL;DR: In this paper, an apparatus for producing silicon carbide consisting mainly of β-type crystal is described, in which the starting material of silica and carbon with a mole ratio of C/SiO2 of 3.2-5.0 is charged by electrically indirect heating in horizontal direction to effect the formation of SiC, cooling the resulting reaction product in the cooling zone under a nonoxidizing atmosphere, and recovering the cooled product from the bottom portion of the reaction vessel to obtain a product having a composition ratio by weight of silicon carbides, free carbon which lies
Abstract: An apparatus for producing silicon carbide consisting mainly of β-type crystal are disclosed. The fine silicon carbide consisting mainly of β-type crystal is produced by charging the starting material of silica and carbon with a mole ratio of C/SiO2 of 3.2-5.0 into a top portion of a vertical-type reaction vessel having a preheating zone, a heating zone and a cooling zone in this order, descending the starting material by gravity through the reaction vessel, heating the starting material in the heating zone at a temperature of 1,600°-2,100° C. by electrically indirect heating in horizontal direction to effect the formation of SiC, cooling the resulting reaction product in the cooling zone under a non-oxidizing atmosphere, and recovering the cooled product from the bottom portion of the reaction vessel to obtain a product having a composition ratio by weight of silicon carbide, silica and free carbon which lies within the area represented by the area ABCD shown in Fig. 1 of the accompanying drawings.

Patent
02 Jul 1979
TL;DR: In this article, a mixture of silicon carbide whiskers and carbon dioxide was used to recover a carbon dioxide-based particle product from the mixture of carbon dioxide and silicon carbides, which was then combined with an immiscible organic solvent.
Abstract: The present invention is directed to silicon carbide whisker recovery from a mixture of silicon carbide whiskers and carbonaceous silicon carbide particles. The invention involves shredding the mixture down to a specified size, dispersing the mixture in water to form an aqueous mixture, agitating the aqueous mixture, mixing the aqueous mixture with an immiscible organic solvent which is lighter than water, agitating the resulting water-organic solvent mixture, allowing the organic solvent and its contents to rise above the water and its contents, separating the two liquid phases into an organic solvent phase and an aqueous phase and, lastly, performing a solid-liquid separation on each of the two phases, thereby obtaining from the aqueous solution the desired silicon carbide whiskers and obtaining from the organic solvent solution a carbonaceous silicon carbide particle product.

Patent
17 Aug 1979
TL;DR: In this paper, a graphite protector is divided into at least two parts to prevent the occurrence of cracks due to a difference between the protector and its coat in thermal expansion coefficient, and the whole surface of the protector is covered with a silicon carbide film or a silicon nitride film.
Abstract: PURPOSE: To manufacture a high purity silicon single crystal by dividing a graphite protector holding a quartz crucible into at least two parts and by covering the whole surface of the protector with a silicon carbide film or a silicon nitride film CONSTITUTION: A graphite protector is divided into a least two parts to prevent the occurrence of cracks due to a difference between the protector and its coat in thermal expansion coefficient For example, the outside of quartz crucible body 4 in chamber 1 is enclosed with graphite protector 6 set on fixed ring 7 on rotating support rod 3 Protector 6 is divided inot two parts in the longitudinal direction, and the whole surface is covered with ≥10μm thick silicon carbide film 5 Starting material charged into crucible 2 and heated with heater 8 Rod 3 is rotated Seed crystal 14 attached to the lower end of pulling chain 15 is dipped in molten silicon 16 in crucible 2 and pulled up while being rotated to obtain a silicon single crystal Crucible 2 is heated to 1,300W1,500°C and protector 6 is thermally expanded, yet the expansion is absorbed in the divided and joined portion Accordingly, no crack occurs and the generation of CO and SiO is prevented to inhibit carbon and oxygen from mixing into silicon 16 COPYRIGHT: (C)1981,JPO&Japio

Journal ArticleDOI
TL;DR: In this article, the sputtering yield of silicon carbide with hydrogen, helium and argon ions was measured by a volumetric method as a function of target temperature, and it was found to have a maximum at around 700°C for hydrogen ions, while it increased monotonically with temperature for helium ion.