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Showing papers on "Silicon carbide published in 1984"


Journal ArticleDOI
TL;DR: In this paper, an investigation was undertaken to determine the magnitude of the strengthening effect of fiber and platelet silicon carbide in an aluminum alloy 6061 matrix in addition to a series of tensile tests.

303 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructure, texture, and whisker orientations in 6061 Al-20 wt pct SiC whisker composites have been examined using transmission electron microscopy and X-ray diffraction.
Abstract: The microstructure, texture, and whisker orientations in 6061 Al-20 wt pct SiC whisker composites have been examined using transmission electron microscopy and X-ray diffraction. Tension creep tests of the composite material have also been conducted in the temperature range 505 to 644 K (450 to 700 F). The steady state creep rate of the composite depends strongly on the temperature and applied stress. The stress exponent for the steady state creep rate of the composite is approximately 20.5 and remains essentially constant within the range of test temperatures. The activation energy is calculated to be 390 kJ/mol, nearly three times as high as the activation energy for self-diffusion of aluminum. No threshold stress was observed. Fracture surface examination using scanning electron microscopy shows that the composite fails by coalescence of voids in the aluminum matrix which originate at the aluminum-SiC interface. It is demonstrated that SiC paniculate composites are less creep resistant than SiC whisker composites.

270 citations


Journal ArticleDOI
TL;DR: In this paper, the authors analyse the FM interaction zone composition, its kinetics of growth in the 700 to 1100°C temperature range, and the growth mechanism of the FM reaction zone.
Abstract: It is generally accepted that silicon carbide CVD-filaments are more suitable than the related boron filaments for reinforcing titanium alloys at medium temperatures Silicon carbide has a higher refractoriness and chemical inertia than boron Moreover, the SiC CVD-filaments retain a much higher fraction of their room temperature mechanical performances up to about 800 to 1000° C and could be produced in the future at a lower price Despite the fact that SiC seems to be less reactive than boron towards most metals, it nevertheless reacts with titanium and its alloys at rather low temperatures (700 to 800° C) Furthermore, silicon carbide when deposited from a gas phase (eg methyl chlorosilane and hydrogen mixtures) often contains small amounts of more reactive species such as elemental silicon or carbon In the same manner, coatings containing elemental carbon have been applied to SiC CVD-filaments in order to reduce their sensitivity to surface abrasion effects Therefore, SiC filament-titanium matrix composites must be regarded as non-equilibrium systems when they are heated at medium or high temperatures The occurrence of chemical interactions between SiC and titanium in the solid state, controlled by diffusion, has already been established either from experiments performed on diffusion couples with a plane interface [1, 2] or on fibrous composite samples [3–12] However, the nature of the phases and the growth mechanism of the filament-matrix (FM) reaction zone remains a subject of controversy The aim of the present contribution is to analyse, for various well characterized SiC-based CVD-filaments (stoichiometric SiC, SiC with a pyrocarbon coating, SiC with a SiC + C coating) and titanium matrices (unalloyed titanium or Ti-6Al-4V): (a) the FM interaction zone composition, (b) its kinetics of growth in the 700 to 1100° C temperature range, and (c) the growth mechanism The filaments which have been used here have been carefully analysed previously on a chemical, microstructural and mechanical point of view in Part 1 In the same manner, the results of the present study on FM chemical interaction will be later correlated with those of different mechanical characterizations [13, 14]

240 citations


Journal ArticleDOI
TL;DR: In this article, the chemical properties of silicon carbide fibres relevant to the use of SiC fibres as a reinforcement in metal matrix composite materials are reviewed, with particular attention paid to the oxidation properties and interaction with metals and alloys with respect to chemical interactions and fibre/matrix bonding.

162 citations



Journal ArticleDOI
TL;DR: In this article, a silicon carbide whisker-reinforced aluminum alloy (20% SiC fibers in 2024 aluminum) is shown to exhibit tensile ductilities in the order of 300% when deformed under thermal cycling conditions (100 ⇇ 450° C ) and at low stresses ( σ ⋍ 20 MPa ).

114 citations


Patent
27 Jun 1984
TL;DR: Improved granular abrasive material comprises silicon carbide particles at least partially coated with an integral, durable surface layer of a hard refractory material comprising metal nitride or carbide.
Abstract: Improved granular abrasive material comprises silicon carbide particles at least partially coated with an integral, durable surface layer of a hard refractory material comprising metal nitride or carbide. Hard refractory materials which provide a useful coating include, for example, silicon nitride or carbide, titanium nitride or carbide, sialon, and others. The surface layer is preferably provided by chemical vapor deposition, most preferably utilizing a fluidized bed. The improved granular abrasive material is particularly useful in various abrasive products such as coated abrasive products, nonwoven abrasive products and abrasive grinding wheels.

95 citations


Journal ArticleDOI
TL;DR: In this article, the authors studied the thermal oxidation of 3C SiC layers on silicon substrates and found that the oxide growth followed a linear parabolic relationship with time, and the activation energy of the parabolic rate constant was 50 kcal/mole.
Abstract: Thermal oxidation of thick single-crystal 3C SiC layers on silicon substrates was studied. The oxidations were conducted in a wet O2 atmosphere at temperatures from 1000 to 1250 C for times from 0.1 to 50 h. Ellipsometry was used to determine the thickness and index of refraction of the oxide films. Auger analysis showed them to be homogeneous with near stoichiometric composition. The oxide growth followed a linear parabolic relationship with time. Activation energy of the parabolic rate constant was found to be 50 kcal/mole, while the linear rate constant was 74 kcal/mole. The latter value corresponds approximately to the energy required to break a Si-C bond. Electrical measurements show an effective density of 4-6 x 10 to the 11th per sq cm for fixed oxide charges at the oxide-carbide interface, and the dielectric strength of the oxide film is aproximately 6 x 10 to the 6th V/cm.

78 citations


Patent
18 Jan 1984
TL;DR: In this article, a gas turbine engine containing core engine components made of silicon carbide fiber reinforced glass matrix material is described, which is a high strength, fracture-tough, high temperature oxidatively stable, core engine component.
Abstract: High strength, fracture tough, high temperature oxidatively stable, gas turbine engine core engine components are described made of silicon carbide fiber reinforced ceramic matrix or silicon carbide fiber reinforced glass matrix material. A gas turbine engine containing core engine components as above described is also disclosed.

61 citations



Patent
25 Jun 1984
TL;DR: In this paper, a combination of sintering, plasma arc spraying, hot isostatic pressing and chemical milling is used to form an abrasive surface on an article.
Abstract: A combination of sintering, plasma arc spraying, hot isostatic pressing and chemical milling is used to form an abrasive surface on an article. Alumina coated silicon carbide particulates are clad with nickel and sinter bonded to the surface of a superalloy turbine blade tip. An impermeable layer of plasma arc sprayed superalloy matrix is deposited over the particulates and then has its inherent voids eliminated by hot isostatic pressing. The abrasive material so formed on the surface is then machined to expose the particulates. Next, a portion of the matrix is removed so that the machined particulates project into space and are thus best enabled to interact with abradable ceramic air seals in a gas turbine engine. The ceramic particulates are sized so they are larger than the finished thickness of the abrasive and they have small aspect ratios. Thus, a high density spacing can be achieved while at the same time it is insured that matrix adequately surrounds the particles and holds them in place during use.

Journal ArticleDOI
TL;DR: In this paper, a silicon carbide single crystal has been studied using x-ray photoelectron spectroscopy and x−ray and electron excited Auger spectroscopic techniques, and a procedure for producing atomically clean SiC crystal surface has been perfected.
Abstract: A silicon carbide single crystal has been studied using x‐ray photoelectron spectroscopy and x‐ray and electron excited Auger spectroscopy. A procedure for producing an atomically clean SiC crystal surface has been perfected. The SiC exhibits prominent bulk plasmon loss features associated with Si and C photoelectrons. This loss, at 22.5 eV, agrees well with optical data establishing the bulk plasmon energy.

Patent
Raymond V. Sara1
27 Jul 1984
TL;DR: In this paper, a carbon or graphite mold is provided with an oxidation prohibitive coating comprising a rigid, glassy, ceramic, refractory material containing mullite and silicon carbide or boron carbide.
Abstract: A carbonaceous article, e.g., a carbon or graphite crucible or mold, is provided with an oxidation prohibitive coating comprising a rigid, glassy, ceramic, refractory material containing mullite and silicon carbide or boron carbide or both. The carbonaceous article has a coefficient of thermal expansion which is greater than about 1.5 x 10 -6 inch/inch/ °C.

Patent
13 Dec 1984
TL;DR: Sintered silicon carbide/graphite/carbon composite ceramic body having a homogeneous fine grain microstructure with at least 50 percent of its graphite grains having a size not exceeding about 8 microns and an aspect ratio less than about 3, with graphite grain having an average size exceeding that of the silicon-carbide grains, and having a density of at least 75 percent of theoretical can be made by firing of a shaped green body with a sintering aid selected from the group consisting of aluminum, beryllium or boron or compounds containing
Abstract: Sintered silicon carbide/graphite/carbon composite ceramic body having a homogeneous fine grain microstructure with at least 50 percent of its silicon carbide grains having a size not exceeding about 8 microns and an aspect ratio less than about 3, with graphite grains having an average size not exceeding that of the silicon carbide grains microns uniformly dispersed throughout the matrix of silicon carbide and having a density of at least 75 percent of theoretical can be made by firing of a shaped green body having a density of at least about 45 percent of theoretical, the shaped green body containing graphite of fine particle size, a sintering aid selected from the group consisting of aluminum, beryllium or boron or compounds containing any one or more of these or a mixture of any of the foregoing elements or compounds, silicon carbide having a surface area of from about 5 to about 100 square meters/gram and, optionally, a temporary binder at a sintering temperature of from about 1900° C. to about 2300° C. in an inert atmosphere or vacuum. The process for making such pressureless-sintered composite bodies is relatively undemanding of exact temperature/time control during sintering. Contain embodiments of such composite sintered bodies may electrical-discharge machined.

Journal ArticleDOI
TL;DR: In this article, the interactions of several high-yield fission products with the SiC coating were studied in laboratory experiments by doping simulated fuel kernels with selected fission product elements before Triso coating.

Journal ArticleDOI
TL;DR: The physical properties and oxidation behavior of silicon carbide thin films were reported in this article, where these films were RF sputtered from a composite target of stoichiometric proportion onto thermally oxidized silicon substrates.
Abstract: The physical properties and oxidation behavior of silicon carbide thin films are reported. These films were RF sputtered from a composite target of stoichiometric proportion onto thermally oxidized silicon substrates. The refractive index of the carbide films, after annealing at 1100°C in hydrogen, was very close to the bulk value of 2.65. Structural and compositional properties were studied by Rutherford backscattering spectrometry, secondary ion mass spectrometry, and x‐ray diffraction techniques. Thermal oxidation was carried out in wet and dry oxygen at 900°–1100°C for a period of up to 16h. Depending on the temperature and time period, the oxidation rate of silicon carbide was about 2–11 times slower than that of single‐crystal (100) Si. The oxide layer grown out of the carbide films was determined to be silicon oxide. The average activation energy for wet and dry oxidation was calculated to be 50 and 43.5 kcal/mol, respectively. The patterning of the films was investigated using and plasmas. "Bird's beak" profiles, obtained upon field oxidation of structures, were studied.

Patent
11 Apr 1984
TL;DR: In this article, spherical particles of polycrystalline silicon carbide having a density greater than 80% of the theoretical density for silicon carbides and having an average diameter ranging from about 10 microns to about 5000 microns are produced by forming spherical agglomerates of a sinterable silicon carbonide powder.
Abstract: Spherical particles of polycrystalline silicon carbide having a density greater than 80% of the theoretical density for silicon carbide and having an average diameter ranging from about 10 microns to about 5000 microns are produced by forming spherical agglomerates of a sinterable silicon carbide powder and sintering the agglomerates at a temperature ranging from about 1900° C. to about 2300° C.

Patent
06 Apr 1984
TL;DR: The N-methylhydridosilazanes are a convenient source of silicon nitride by chemical vapor deposition to form films for masking layers and dielectric coatings with reduced levels of silicon carbide contamination in the silicon oxide as mentioned in this paper.
Abstract: Cyclic silazanes which are particularly useful for the formation of silicon nitrides have the general formula: ##STR1## wherein Me represents methyl (CH3), n=3-6, x=0-1 and y=0.25-1. These N-methylhydridosilazanes are a convenient source of silicon nitride by chemical vapor deposition to form films for masking layers and dielectric coatings with reduced levels of silicon carbide contamination in the silicon nitride. Low molecular weight, linear polymers of the N-methylhydridosilazanes are also useful in the preparation of silicon nitrides by evaporation from liquid solutions and subsequent pyrolysis and are particularly useful for infiltration of refractories. Particularly preferred compounds of the invention are 2,6 di-N-methyl-1,3,5,7-tetramethylcyclotetrasilazane; 2,4,6,8-tetra-N-methyl-1,5-dimethylcyclotetrasilazane and their polymeric derivatives.

Patent
Mark P. Taylor1
09 Aug 1984
TL;DR: A fiber-reinforced composite having a high degree of fracture toughness and being composed of a glass-ceramic matrix reinforced with silicon carbide or graphite type fibers is described in this paper.
Abstract: There is disclosed a fiber-reinforced composite having a high degree of fracture toughness and being composed of a glass-ceramic matrix reinforced with silicon carbide or graphite type fibers, the predominant crystal phase of the matrix glass-ceramic being canasite, and/or agrellite, and/or fedorite.

Journal ArticleDOI
TL;DR: In this article, the authors investigated ion-beam and laser mixing of Ni overlayers on silicon carbide substrates using cross-section and analytical techniques of electron microscopy, and ion scattering and channeling techniques.
Abstract: We have investigated ion‐beam and laser mixing of Ni overlayers on silicon carbide substrates using cross‐section and analytical techniques of electron microscopy, and ion scattering and channeling techniques. The thickness of the overlayers was varied from 200 to 500 A on both crystalline and polycrystalline substrates of silicon carbide. The thickness of the ion‐beam mixed region was found to increase with increasing dose of the implanted ions. The laser mixing was obtained only within a critical window of the pulse energy density (1.15±1.25 J cm−2) of a ruby laser (wavelength 0.693 μm, and pulse duration 28×10−9 s). The structure of the mixed region was found to be amorphous, with occasional presence of crystalline nickel silicide (Ni2Si) islands. The laser‐mixed SiC specimens showed a considerable improvement (>35%) in their fracture strength.

Patent
31 May 1984
TL;DR: An abrasive product and process for grinding titanium metal and its alloy is described in this article, where the product used to grind the titanium consists of a grinding wheel wherein the abrasive grains are aggregates of silicon carbide particles bonded together with a refractory bond such as silicon oxynitride or a silicate based material.
Abstract: An abrasive product and process is disclosed, for grinding titanium metal and its alloy. The product used to grind the titanium consists of a grinding wheel wherein the abrasive grains are aggregates of silicon carbide particles bonded together with a refractory bond such as silicon oxynitride or a silicate based material.

Journal ArticleDOI
TL;DR: In this article, pressureless sintering of commercially available alpha-SiC powders at temperatures between 1900 and 2150 C for periods of 10 to 240 min under one atmosphere of argon pressure was investigated.
Abstract: An investigation is made of pressureless sintering of commercially available alpha-SiC powders at temperatures between 1900 and 2150 C for periods of 10 to 240 min under one atmosphere of argon pressure. It is found that alpha-SiC powder containing boron and carbon sintering aids is sinterable at 2150 C for a period of 30 min to a high final density (greater than 96 percent of theoretical). In alpha-SiC powder containing aluminum and carbon sintering aids, the final density achieved is only about 80 percent of theoretical. Determinations are made of room temperature and high temperature (1370 C) flexure strength and oxidation resistance on sintered high density (more than 96 percent of theoretical) alpha-SiC (boron, carbon) material. It is found that both the strength and the resistance to oxidation are equivalent and comparable to those of the sintered alpha-SiC which represents the state of the art.

Journal ArticleDOI
TL;DR: In this paper, structural ceramics based on silicon nitride, silicon carbide, and transformation-toughened zirconium oxide are proposed for advanced heat engines.
Abstract: Structural ceramics based on silicon nitride, silicon carbide, and transformation-toughened zirconium oxide are potential candidates for advanced heat engines. Flaw populations, introduced during processing, currently limit their reliability. Processing steps responsible for common flaw populations will be discussed. It will be shown that new processing steps, based on colloidal powder treatments, combined with second phase engineering can increase fabrication reliability.

Patent
24 Sep 1984
TL;DR: In this paper, a semiconductor substrate or layer formed principally of silicon or silicon carbide is selectively or nonselectively etched by using a hydrogen fluoride gas plasma as a reactive gas plasma.
Abstract: A semiconductor substrate or layer formed principally of silicon or silicon carbide is selectively or nonselectively etched by using a hydrogen fluoride gas plasma as a reactive gas plasma. In the case of nonselectively etching the semiconductor substrate or layer, a mask layer of silicon oxide, silicon nitride, metal such as aluminum, chrominum, nickel, cobalt, tantalum, tungsten or molybdenum, or photoresist is preformed into a required pattern on the semiconductor substrate or layer.

Patent
01 Jun 1984
TL;DR: In this article, a series of sintered shapes of silicon carbide of high strength comprising 0.027 to 11.300 atomic percent of one or more members of rare earth oxides and the balance of silicon carbonide are disclosed.
Abstract: A series of sintered shapes of silicon carbide of high strength comprising 0.027 to 11.300 atomic percent of one or more members of rare earth oxides and the balance of silicon carbide are disclosed. Method of making such silicon carbide shapes is also disclosed.

Patent
27 Aug 1984
TL;DR: In this article, a silicon carbide-silicon matrix composite incorporating unreacted coarse carbon particles (e.g. graphite particles) dispersed throughout the composite is described, and the coarse particles are incorporated in a coherent mixture of carbon and silicon carbides powders which, after compaction, is infiltrated with molten silicon to form a matrix of reaction bonded silicon carbon.
Abstract: A silicon carbide-silicon matrix composite incorporates unreacted coarse carbon particles (e.g. graphite particles) dispersed throughout the composite. The coarse particles are incorporated in a coherent mixture of carbon and silicon carbide powders which, after compaction, is infiltrated with molten silicon to form a matrix of reaction bonded silicon carbide in a substantially continuous free silicon carbide phase. By using coarse carbon particles of density of at least 0.963 g/ml, the molten silicon reacts only with the surfaces of those particles which may as a result remain unreacted and dispersed throughout the composite.

Patent
22 May 1984
TL;DR: In this article, the authors proposed a composite magnetic disk for magnetic recording, which consists of an annular core of polymeric material to which is bonded at least one disk of reaction-bonded silicon carbide with a magnetic recording layer on its outer surface.
Abstract: The invention relates to a composite magnetic disk for magnetic recording, which consists of an annular core of polymeric material to which is bonded at least one disk of reaction-bonded silicon carbide with a magnetic recording layer on its outer surface. After its processing, the SiSiC disk surface shows optimum planarity and smoothness so that it can be used as a magnetic disk substrate. Furthermore, the material has a low density and an extremely high specific modulus of elasticity so that numbers of revolution higher than obtainable with formerly known AlMg5 disk substrates can be reached.

Patent
Tetsuo Kosugi1
25 Jul 1984
TL;DR: In this paper, a sinter consisting of a boride, nitride or carbide of the element of Group IIIa, IVa, Va or VIa of the Periodic Table and retaining a high strength at a temperature of up to 1,100° C is dispersed in sintered ceramics comprising at least one of silicon carbide, silicon nitride and sialon as its principal component.
Abstract: A ceramic structure whose portion exposed to a heat cycle, as a high-temperature gas turbine blade, a turbo charger or the like, is coated with ceramics having a construction wherein a sinter mainly comprising a boride, nitride or carbide of the element of Group IIIa, IVa, Va or VIa of the Periodic Table and retaining a high strength at a temperature of up to 1,100° C is dispersed in sintered ceramics comprising at least one of silicon carbide, silicon nitride and sialon as its principal component A ceramic structure having a thermal shock resistance, high versatility and reliability can be obtained

Patent
27 Jul 1984
TL;DR: In this article, a siliconizing apparatus consisting of a graphite plate with boron nitride, a porous silicon carbide plate with a layer of carbon and a lumpy metallic silicon inserted between the two plates is described.
Abstract: Silicon-infiltrated, reaction-bonded silicon carbide molded bodies for application in machine building are produced by means of a siliconizing apparatus, comprising a graphite plate coated with boron nitride, a porous silicon carbide plate coated with a layer of boron nitride, silicon carbide and carbon and a layer of lumpy metallic silicon inserted between the two plates. Furthermore, following the heating and solidification of the liquid silicon, wherein due to the increase in volume of the silicon, beads of silicon appear at the surface of the molded body, these may be easily removed when the infiltrated silicon carbide molded bodies are cooled in a nitrogen atmosphere.

Patent
08 Jun 1984
TL;DR: In this article, a silicon carbide-coated nuclear reactor is described for continuous production of solar grade purity elemental silicon by thermal reaction of a suitable precursor gas, such as silane (SiH4).
Abstract: A reactor apparatus (10) adapted for continuously producing molten, solar grade purity elemental silicon by thermal reaction of a suitable precursor gas, such as silane (SiH4), is disclosed. The reactor apparatus (10) includes an elongated reactor body (32) having graphite or carbon walls which are heated to a temperature exceeding the melting temperature of silicon. The precursor gas enters the reactor body (32) through an efficiently cooled inlet tube assembly (22) and a relatively thin carbon or graphite septum (44). The septum (44), being in contact on one side with the cooled inlet (22) and the heated interior of the reactor (32) on the other side, provides a sharp temperature gradient for the precursor gas entering the reactor (32) and renders the operation of the inlet tube assembly (22) substantially free of clogging. The precursor gas flows in the reactor (32) in a substantially smooth, substantially axial manner. Liquid silicon formed in the initial stages of the thermal reaction reacts with the graphite or carbon walls to provide a silicon carbide coating on the walls. The silicon carbide coated reactor is highly adapted for prolonged use for production of highly pure solar grade silicon. Liquid silicon (20) produced in the reactor apparatus (10) may be used directly in a Czochralski or other crystal shaping equipment.