Showing papers on "Silicon carbide published in 1970"

ESR in irradiated silicon carbide

Abstract: Thirty samples of n- and p-type 6H and n-type 3C silicon carbide single crystals were irradiated at room temperature with either 0.8 or 1.0 MeV electrons or reactor neutrons. Seven different radiation- induced e.s.r. spectra were found. Some of these have been described before, but further investigations of production rates and annealing behaviour have necessitated changes in the previously proposed models. The e.s.r. parameters of these centres are given. Three of the spectra are tentatively ascribed to (1) the uncharged carbon vacancy, (2) the negatively charged carbon divacancy, and (3) the uncharged silicon vacancy trapped at a boron site. Tentative models for three other centres are discussed.

Production of silicon carbide from rice hulls

Abstract: THIS INVEENTION DISCLOSES THE PRODUCTION OF SILICON CARBIDE FROM THE SILICA AND CARBON PRESENT IN RICE HULLS.

Energy Band Structures of Four Polytypes of Silicon Carbide Calculated with the Empirical Pseudopotential Method

Abstract: The electronic band structures of four polytypes of silicon carbide (3C, 2H, 4H, 6H) are calculated with the aid of local atomic pseudopotentials for carbon and silicon. The same pseudopotentials are used in all four polytypes. A description is given of the basic assumptions in the empirical pseudopotential method. A computer program is used which is able for symmetric k-values to reduce the dimensionality of matrices. The calculated energy band structures are in satisfactory agreement with well-established experimental data. D ie elektronischen Bandstrukturen von vier Polytypen des Siliziumkarbids(3C, 2H, 4H, 6H) werden mit lokalen atomaren Pseudopotentialen fur Kohlenstoff und Silizium berechnet, die in allen vier Polytypen gleich gewahlt werden. Die Grundlagen und die Anwendungsmoglichkeiten der empirischen Pseudopotentialmethode werden beschrieben. Ein Computerprogramm wird benutzt, in das eine Symmetrisierungsprozedur zur Verringerung der Dimensionalitat der Matrizen bei symmetrischen k-Punkten eingearbeitet ist. Die berechneten Bandstrukturen stimmen mit wohlbekannten experimentellen Daten gut uberein.

Surface Aspects of New Fibers, Boron, Silicon Carbide, and Graphite

Abstract: A review of the literature for surface characteristics of boron, silicon carbide and graphite fibers was made. Some of the physical and chemical characteristics of the surfaces of these fibers are described. Surface properties that are unique as well as common to each fiber are discussed. Comparisons of these fiber surface properties to those of glass fibers are made in efforts to bring out differences and similarities. This report is an attempt to summarize the strength of the “bond” at the fiber-resin interface in high modulus fiber reinforced composites. The problems associated with defining the chemical and physical nature of the fiber surfaces which are most relevant to the development of composites with optimum mechanical properties are pointed out.

Method for making abrasive articles

Abstract: DEPOSITING ABRASIVE PARTICLES, SUCH AS DIAMONDS, SILICON CARBIDE, TITANIUM CARBIDE, ALUMINUM OXIDE, OR MIXTURES THEREOF, IN A MATRIX OF ELECTROCHEMICALLY DEPOSITED METALS ON THE OUTER PERIPHERY AND/OR THE ADJACENT MARGINAL SIDE PORTIONS OF METAL (OR NON-METALS) BLANKS OR WHEELS.

Silicon carbide semiconductor device with heavily doped silicon carbide ohmic contacts

Abstract: This disclosure relates to a semiconductor device comprised of a body of silicon carbide. The body of silicon carbide has at least two regions of opposite type semiconductivity with a pin junction between the regions of opposite type semiconductivity. An electrical contact consisting of silicon carbide is affixed to each region.

Procedures for coating substrates with silicon carbide

Abstract: Thin, adherent oxidation and corrosion resistant silicon carbide coatings are provided on filamentary base materials by continuously passing a hot surface of the filamentary material through a liquid organo silicon halide, wherein the temperature of the hot surface is high enough to cause the organo silicon halide immediately surrounding the hot surface to film boil, decompose, and deposit the silicon carbide coating The filamentary base material has a melting point which exceeds the formation temperature of silicon carbide The base material may be tungsten, tantalum, columbium, or alloys thereof The base material may also be glass or alumina When the base material is glass, the glass filaments may be coated directly after forming All of the substrates may be preheated to the required temperature and the substrates which are electrically conductive may be heated by electrical resistance heating

Growth of β-silicon carbide on silicon

Abstract: The structure and topography have been examined of β-SiC layers formed on silicon heated in a low pressure of ethylene in an ultra-high vacuum system. Particulate epitaxic growth has been observed on substrates of various low-index orientations and an unusual double epitaxic relationship on (110) substrates noted.

Method of making aluminum-silicon alloys

Abstract: A method of making aluminum-silicon alloy in a blast furnace utilizing substantially pure oxygen, wherein lumps of silicon carbide comprise all or part of the furnace bed.

Field emission from silicon carbide whiskers.

Abstract: IT is thought that most of the silicon carbide whiskers grown by the E.R.D.E. process do so by the vapour–liquid–solid (VLS) mechanism1 where a metal is the principal “activator” in the process. Often a globule of frozen eutectic can be seen on the ends of the whiskers. Further, it has been observed that in many cases smaller whiskers had grown out from these balls. Some of the specimens, however, did not show such a eutectic residue on their ends and it is these that have been studied here.

Ohmic Contacts to Silicon Carbide

Abstract: We have studied a number of metal alloys in a search for improved ohmic contacts to SiC. A Cu–Ti eutectic alloy wets SiC at 880°C forming a shallow contact which is ohmic on p‐type SiC. An Al–Si eutectic wets SiC at 900° to 1000°C giving a contact which is ohmic on p‐type SiC; the penetration is 300 to 500 A.

Ionization Gauge Using a SiC p-n Junction Electron Emitter

Abstract: Ionization gage with reverse biased silicon carbide p-n junction hot electron emitter as source

Composite materials with flake reinforcement

Abstract: Silicon carbide or boron carbide flakes are floated on a liquid bath, fixed into a sheet and formed into sheet laminates useful as high modulus structural composites. This assures a planar orientation and high packing factor of the reinforcing flake in the composite.

Cordierite binder composition

Abstract: Lightning arrester resistance material is composed of silicon carbide particles and a binder therefor composed of cordierite formed of a fired mixture of cordierite-forming glass material and cordierite-forming crystalline material.

High temperature low ohmic contact to silicon

Abstract: A high temperature low ohmic electrical contact is made to a silicon body by forming a very thin layer of silicon carbide over the silicon body and then forming a metallic layer, such as a refractory metal, over the silicon carbide to form a high quality low ohmic contact to the surface of the silicon body.

Investigation of the interaction of silicon carbide with refractory metals and oxides

Abstract: This paper describes the results of a study of the interaction of silicon carbides with refractory metals (Nb, Ta, Mo, W) and oxides (BeO, MgO, ZrO2, ThO2) held in contact for 2 hr in vacuum at 1200–2000°C.

Method of making silicon carbide junction diodes

Abstract: THE PRODUCTION OF ELECTROLUMINESCENT SILICON CARBIDE JUNCTION DIODES IS DESCRIBED. THESE DIODES ARE PREFERABLE PRODUCED BY GROWTH FROM A SILICON CARBIDE OR CARBON SOLUTION IN SILICON FORMED BETWEEN A SURFACE OF A P OR N-TYPE SILICON CARBIDE BASE CRYSTAL AND A SOURCE OF CARBON ATOMS SUCH AS A BLOCK OF SOLID CARBON. THE SILICON CONTAINS ONE OR MORE P OR N-TYPE IMPURITIES SO THAT A P-N JUNTION IS FORMED ON THE CRYSTAL. A MULTISTRATUM EPITAXIAL LAYER IS GROWN ON THE BASE CRYSTAL BY PROVIDING IMMEDIATELY ADJACENT THE BASE CRYSTAL A LAYER OF SILICON HAVING ONE IMPURITY CONCENTRATION AND PROVIDING AT A REMOTE SPOT IN THE REACTION ZONE ANOTHER MASS OF SILICON HAVING A DIFFERENT IMPURITY CONCENTRATION. THE INITIAL STRATUM IS GROWN AT A RELATIVELY LOW TEMPERATURE AND THE SECOND STRATUM IS GROWN AT A HIGHER TEMPERATURE. THE INITIAL STRATUM CAN BE VERY THIN (LESS THAN .0005 INCH) AND TRANSPARENT AND THE SECOND STRATUM CAN BE OPAQUE AND OF LOW RESISTANCE DUT TO CODOPING WITH BORON AND ALUMINUM.

Improvements in or relating to the Manufacture of Dense Bodies of Silicon Carbide.

Abstract: 1,180,918. Silicon carbide. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. 1 June, 1967 [10 June, 1966], No. 26094/66. Heading C1A. A porous body comprising a coherent mixture of finely divided SiC and C, which is to be processed by infiltration with molten Si, is heated in the presence of SiO vapour which reacts with the C in the surface layers of the body thereby increasing the porosity of the said layers. The body may be heated at 1600‹ to 1700‹ C. and the SiO vapour is preferably produced by the addition of 15 gm. SiO2 to 200 to 300 gm. of the Si to be infiltrated into the body.

Method of manufacturing silicon carbide whiskers

Abstract: WHISKERS OF APPROXIMATE DESIRED DIAMETER ARE GROWN ON A UNIFORM ROUGH SURFACE OF A SUBSTRATE BY MEANS OF A NUCLEATING SUBSTANCE DUE TO THE PRESENCE OF CRYSTALLITES PROJECTING FROM THE SURFACE THE LATRAL DIMENSIONS OF WHICH AT THE SURFACE APPROXIMATELY CORRESPOND IN SIZE TO THE THICKNESS OF THE CRYSTALS TO BE GROWN.

Electronic structure of isolated single vacancy centres in silicon carbide

Abstract: The lowest electronic levels of the various charged states of the isolated carbon and silicon single vacancies in silicon carbide have been calculated using the defect molecule approach with lattice distortion.

Fracture of Silicon Carbide Fibre

Abstract: SILICON carbide fibre in the form of a 100 µm diameter polycrystalline coating on a 12 µm tungsten wire substrate is now commercially available. The short term strength of this material has been shown1 to be essentially constant to 1,100° C, but creep rupture results (unpublished work of K. F. A. Walles) have shown that over a longer period there is a considerable loss of strength at 850°, and that at 1,100° C the strength after ten hours is only 10 per cent of that at room temperature. This behaviour is in marked contrast to bulk silicon carbide in either single crystal or polycrystalline form, where the strength has been shown to increase with temperature2, and to reach values as high as 4,500 MN/m2 (650 k.s.i.) at 1,750° for single crystals3. In view of this discrepancy, it seemed worthwhile to try to establish the cause of this loss of strength at temperatures in the region of 1,000° C.