Showing papers on "Silicon carbide published in 1980"

High-strength silicon carbide fibre-reinforced glass-matrix composites

Abstract: Silicon carbide fibre-reinforced glass-matrix composites have been fabricated and tested. Two fibre forms, a 140 μm diameter monofilament and a 10 μm diameter filamentary yarn, were incorporated into a matrix of borosilicate glass. The hot-pressing fabrication procedure resulted in fully dense unidirectionally reinforced specimens with excellent flexural strength and fracture toughness over the temperature range 22 to 700° C. In addition, composite thermal expansion was found to be nearly independent of fibre orientation indicating that multiaxially reinforced composites should be readily fabricable without the occurrence of extensive cracking.

Synthesis of continuous silicon carbide fibre: Part 2 Conversion of polycarbosilane fibre into silicon carbide fibres

Abstract: The polycarbosilane (PC-470) synthesized by thermal decomposition of polydimethylsilane was melt-spun. The conversion process of the fibre into silicon carbide fibre was investigated by chemical analysis, TG-DTA and infra-red spectrum analysis, and measurements of the mechanical properties and densities. The conversion process of polycarbosilane (PC-TMS) synthesized by Fritz was examined and compared with the conversion process of PC-470. It is shown that the process is divided into three stages; condensation at the first stage, thermal decomposition at the second stage and crystallization at the third stage. The mechanical properties and density of the SiC fibre obtained by heattreatment were affected by the molecular weight and structure of the polycarbosilane of the starting material.

High-temperature structural ceramics.

Abstract: The unique properties of ceramics based on silicon carbide and silicon nitride make them prime candidates for use in advanced energy conversion systems. These compounds are the bases for broad families of engineering materials, whose properties are reviewed. The relationships between processing, microstructure, and properties are discussed. A review and assessment of recent progress in the use of these materials in high-temperature engineering systems, and vehicular engines in particular, is presented.

Method of making a shaped silicon carbide-silicon matrix composite and articles made thereby

Abstract: A method is described for making a shaped silicon carbide-silicon matrix composite. A confined carbon fiber preform is infiltrated with sufficient molten silicon metal at a temperature in the range of from about 1400° C. to about 1800° C. in an inert atmosphere or vacuum. Silicon carbide powder can also be incorporated in the preform structure.

High yield silicon carbide pre-ceramic polymers

Abstract: Pre-polymers which are alkoxylated or phenoxylated methylpolysilanes are useful for the preparation of fine grained silicon carbide ceramic materials and silicon carbide-containing ceramics. The pre-polymers exhibit ease of handling and their use to obtain silicon carbide ceramic materials results in high yields.

Internal combustion engine and composite parts formed from silicon carbide fiber-reinforced ceramic or glass matrices

Abstract: A high strength, fracture tough, high temperature oxidatively stable, heat insulating internal combustion engine combustion chamber component is described made of a silicon carbide fiber reinforced ceramic matrix or a silicon carbide fiber reinforced glass matrix material. An internal combustion engine containing combustion chamber components as above described is also disclosed.

Continuous length silicon carbide fiber reinforced ceramic composites

Abstract: A silicon carbide fiber reinforced ceramic matrix composite is disclosed having high strength, fracture toughness, and oxidative stability even at high temperature use. The composite is made up of a plurality of ceramic layers, each layer reinforced with a plurality of unidirectional continuous length silicon carbide fibers, each layer having an axial flexural strength greater than 70,000 psi and a high fracture toughness, exemplified by a critical stress intensity factor greater than 10×103 psi (inch)1/2. The composite is formed by starting with the ceramic matrix material in the glassy state and converting it from the glassy state to the ceramic state after densification of the composite.

Silicon carbide fiber reinforced glass composites

Abstract: Silicon carbide fiber reinforced glass composites are disclosed having high strength, fracture toughness, and oxidative stability, even in high temperature use environments. Disclosed composites include silicon carbide fiber reinforced borosilicate glass, high silica content glass, and aluminosilicate glass. Flexural strengths in excess of 40,000 psi up to temperatures as high as 1150° C. are attained with such composites.

Method for preparing silicon carbide

Abstract: What is disclosed is an improved method of preparing silicon carbide which is characterized by the preparation of a specific pre-silicon carbide polymer. The method allows the preparation of silicon carbide from specific polysilane polymers without the cumbersome extractions and purifications found in the newer methods of silicon carbide preparation.

Sintered silicon carbide-titanium diboride mixtures and articles thereof

Abstract: Sintered articles made from binary compositions of silicon carbide and titanium diboride are described. The articles may be prepared by initially mixing finely-divided silicon carbide, carbon or a carbon source material, a densification or sintering aid, and finely-divided titanium diboride, forming the mixture into a desired shape and subsequently heating at temperatures sufficiently high to form a sintered ceramic article of silicon carbide and titanium diboride. When the present sintered ceramic articles contain high amounts of titanium diboride, generally between about 65 and about 95 percent, and more preferably, between about 80 and about 95 percent, by weight, they are quite electrically conductive, generally having less than 0.2 ohm-cm electrical resistivity, and are useful as electrical ignitors. Such articles are also extremely resistant to corrosion by molten aluminum and aluminum alloys; thus, they are aptly suited to use as electrodes in aluminum refining processes. When the present sintered ceramic articles contain high amounts of silicon carbide, generally between about 50 and about 95 percent by weight, they are characterized by high densities and high strengths, typically having MOR above 50,000 psi, and an extraordinary resistance to thermal shock. Such articles are particularly useful in the fabrication of diesel engine precombustion chambers and as honeycomb structures, such as those utilized in automobile emission control units.

High yield silicon carbide from alkylated or arylated pre-ceramic polymers

Abstract: Pre-polymers which are alkylated or arylated methylpolysilanes are useful for the preparation of silicon carbide ceramic materials. The pre-polymers exhibit ease of handling and their use to obtain silicon carbide ceramic materials results in high yields.

Blue-Emitting Diodes of 6H-SiC Prepared by Chemical Vapor Deposition

Abstract: Silicon carbide (SiC) blue-light-emitting diodes with an external quantum efficiency of 2×10-5 photons/electron were prepared by the chemical vapor deposition method. Epitaxial growth of 6H-SiC has been carried out at 1800°C on a 6H-SiC substrate using the SiCl4-C3H8-H2 system. Epitaxial layers of the n and p types with appropriate carrier concentrations were obtained by doping N from NH3 and Al from AlCl3, respectively. A pn junction was prepared in one growth run by a double epitaxial process. The peak wavelength of the electroluminescence spectrum was 495 nm.

Process for producing silicon carbide heating elements

Abstract: A process for producing a silicon carbide heating element is disclosed comprising: adding boron or a boron compound in an amount corresponding to from 0.3 to 3.0% by weight as boron, and carbon or a carbon compound in an amount corresponding to from 0.1 to 6.0% by weight as carbon, to a SiC powder having an average particle size of 1.0μ or less; blending and molding the mixture; conducting a primary sintering in vacuum or in an inert atmosphere, except nitrogen; and thereafter conducting a secondary sintering at from 1500° to 2300° C. in a pressurized nitrogen atmosphere to produce a silicon carbide heating element having a density of at least 80% based on the theoretical density and an electrical resistivity of 1.0 Ω-cm or less.

Semiconductor device using SiC as supporter of a semiconductor element

Abstract: In a semiconductor device, an active element is mounted on a supporter made of silicon carbide SiC. Since the thermal expansion coefficient of SiC is nearly equal to that of the semiconductor element, the integration of the element and the supporter will not give rise to thermal stresses in the element. Since silicon carbide has high degrees of thermal dissipation and conduction, the supporter of SiC can effectively dissipate heat generated in the semiconductor element. And since SiC has a high electrical conductivity and a high mechanical strength and is also light, it can be used as electrodes for the semiconductor element.

Silicon coated silicon carbide filaments and method

Abstract: Silicon carbide filament is produced by overcoating a carbon monofilament core using continuous process vapor deposition. The deposition takes place by passing the carbon monofilament through a reactor into which gaseous sources of silicon and carbon are injected. At a deposition temperature of about 1300 C., a deposit of fine grained beta crystals of silicon carbide are formed. Application of a thin coating of silicon-rich silicon carbide on the surface of the filament both adds strength and provides a surface which is readily bonded to metals, glass and resin matrix materials during the forming of composite structures.

Coated stoichiometric silicon carbide

Abstract: The invention relates to a surface treatment for stoichiometric silicon carbide. A carbon-rich silicon carbide layer is applied over the silicon carbide. In the case of the silicon carbide surface, the ratio of silicon to carbon in the carbon-rich layer varies from one at the silicon carbide interface to near zero in the interior of the carbon-rich layer to greater than zero and preferably 0.3 to 0.5 on the surface of the carbon-rich layer remote from the interface. A preferred method of making the silicon carbide layer is also presented.

Electrically insulating substrate and a method of making such a substrate

Abstract: From 0.1 to 3.5% by weight of beryllium oxide powder, calculated as beryllium, is added to silicon carbide powder containing up to 0.1% by weight of aluminum, up to 0.1% by weight of boron and up to 0.4% by weight of free carbon, and the mixed powder is pressure-molded. The resulting molded article is heated to a temperature of 1,850° C. to 2,500° C. till there is obtained a sintered body having at least 90% relative density of silicon carbide. Thus, the sintered body having thermal conductivity of at least 0.4 cal/cm.sec.° C. at 25° C., electrical resistivity of at least 10 7 Ohm.cm at 25° C. and coefficient of thermal expansion of 3.3˜4×10 -6 /°C. at 25° C. to 300° C. can be obtained.

High yield silicon carbide pre-polymers

Abstract: Novel, high yielding prepolymers are prepared by reducing chloropolysilanes with lithium aluminum hydride. These prepolymers exhibit good handling properties and are useful for preparing ceramics, silicon carbide ceramic materials and articles containing silicon carbide.

Sintered silicon carbide - aluminum nitride articles and method of making such articles

Abstract: Sintered ceramic products comprised of from about 55 to about 99.5 percent by weight of silicon carbide co-sintered with from about 0.5 to about 45 percent by weight aluminum nitride containing a dispersion of free carbon in amounts between about 0.5 and about 4.0 percent by weight of the product are described. The sintered products have a bulk density of at least 75 percent of the theoretical density of silicon carbide. The products are produced by sintering, under substantially pressureless conditions, mixtures of silicon carbide, carbon, or a carbon source material, and aluminum nitride. The aluminum nitride component, in ranges of from about 3.0 to about 45 percent, may be initially mixed with the silicon carbide and carbon or carbon source material. In ranges of from about 0.5 to about 3.0 percent, the aluminum nitride component may be added to the mixture in vapor form during sintering.

Article coated with beta silicon carbide and silicon

Abstract: This application discloses a new powder composition which may be plasma sprayed onto the surface of an article to provide a protective coating therefor. The protective coating may be resistant to heat, wear, and corrosion. The coating may also provide a thermal or radiation barrier. In particular, the coating composition for arc plasma spraying consists of finely divided silicon carbide mixed with finely divided silicon. This coating composition is applied to a substrate by developing a plasma spray, feeding the coating composition to the plasma spray and directing the plasma spray at an exposed surface of the substrate so that the exposed substrate is coated with a coating which consists essentially of beta silicon carbide and silicon. The new article of manufacture disclosed in this application, is a substrate with a tightly adherent coating thereon consisting essentially of beta silicon carbide and silicon. The substrate may be any material, either metallic or non-metallic, to which the coating adheres. The coating may provide the substrate with wear resistant characteristics as, for example, if the substrate is to be used for machining metals or as a valve seat in an aluminum engine. The substrate, with the coating thereon, may be used to withstand severe temperatures as, for example, in rocket nozzles and other areas where a substrate would be subjected to extreme temperatures.

Anomalous Solid-Particle Erosion Rate of Hot-Pressed Silicon Carbide

Abstract: The steady-state erosion rate of a commercial hot-pressed SiC was investigated using angular Al/sub 2/O/sub 3/ particles. An anomalous size dependence was observed which may be due to grain boundries. (DLC)

Dynamic modulus and damping of boron, silicon carbide, and alumina fibers

Abstract: The dynamic modulus and damping capacity for boron, silicon carbide, and silicon carbide coated boron fibers were measured from-190 to 800 C. The single fiber vibration test also allowed measurement of transverse thermal conductivity for the silicon carbide fibers. Temperature dependent damping capacity data for alumina fibers were calculated from axial damping results for alumina-aluminum composites. The dynamics fiber data indicate essentially elastic behavior for both the silicon carbide and alumina fibers. In contrast, the boron based fibers are strongly anelastic, displaying frequency dependent moduli and very high microstructural damping. Ths single fiber damping results were compared with composite damping data in order to investigate the practical and basic effects of employing the four fiber types as reinforcement for aluminum and titanium matrices.

A process for the preparation of silicon or ferrosilicon

Abstract: A process for the production of silicon or ferrosilicon by reduction of silicon oxide, optionally in the presence of iron or iron oxide, using a carbonaceous reducing agent, in a reduction furnace. The yield is improved without harmful temperature rises if the ratio of the amount of thermal energy supplied to the furnace to the amount of silicon oxide supplied to the furnace is made adjustable in such a manner that a value for the ratio can be set within an interval, which interval in its lower end is limited by the lowest value permitting constant reduction of the silicon monoxide and silicon directly with a certain part of the reducing agent which is supplied at the top of the furnace, because the amount of produced silicon monoxide is insufficient for complete conversion of all the carbonaceous reducing agent to silicon carbide at the top of the furnace, and in its upper end is limited by the highest value permitting constant reduction of the silicon oxide raw material to silicon monoxide and silicon di- retcly with silicon carbide, because the amount of produced silicon monoxide is sufficient for conversion of the carbonaceous reducing agent to silicon carbide at the top of the furnace, and that a sufficient content of reducing agent is maintained in the lower, hotter, parts of the furnace so that reduction to some extent can take place directly with the reducing agent.

Dense shaped articles of polycrystalline β-silicon carbide and process for the manufacture thereof by hot-pressing

Abstract: The invention relates to dense shaped articles of polycrystalline α-silicon carbide containing from 0.1 to 0.4%, by weight, of aluminum and optionally, a small amount of nitrogen and/or phosphorus, having a homogeneous virtually single-phase microstructure. The additional constituents are substantially in the form of a solid solution in the α-SiC lattice. The shaped articles are distinguished by flexural strength of at least 600 N/mm2 up to 1450° C. and low subcritical crack propagation under mechanical stress. The fracture mechanism is trans granular up to at least 1450° C. The shaped articles are manufactured by simultaneously shaping and hot pressing pulverulent α-silicon carbide containing a small amount of an aluminum-containing additive, such as aluminum powder, aluminum nitride and/or aluminum phosphide, at temperatures between 1850° C. and 2300° C. under a pressure of at least 100 bar (10 MPa).

Process for producing beta -silicon carbide fine powder

Abstract: A process for producing a beta -silicon carbide powder is disclosed wherein a ternary mixture of carbon, silicon and silica powders mixed in amounts falling within the region defined by the points O, P, Q and R in the FIGURE are reacted in an oxidizing atmosphere.