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WO1992014576A1 - Production plasmatique de carbures ceramiques ultrafins - Google Patents

Production plasmatique de carbures ceramiques ultrafins Download PDF

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Publication number
WO1992014576A1
WO1992014576A1 PCT/US1992/001064 US9201064W WO9214576A1 WO 1992014576 A1 WO1992014576 A1 WO 1992014576A1 US 9201064 W US9201064 W US 9201064W WO 9214576 A1 WO9214576 A1 WO 9214576A1
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WIPO (PCT)
Prior art keywords
reactor
reactants
temperature
zone
reaction
Prior art date
Application number
PCT/US1992/001064
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English (en)
Inventor
Patrick R. Taylor
Shahid A. Pirzada
Original Assignee
Idaho Research Foundation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US07/782,790 external-priority patent/US5182606A/en
Application filed by Idaho Research Foundation filed Critical Idaho Research Foundation
Publication of WO1992014576A1 publication Critical patent/WO1992014576A1/fr

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J19/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J19/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J19/087—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy
    • B01J19/088—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor employing electric or magnetic energy giving rise to electric discharges
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/956—Silicon carbide
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/956—Silicon carbide
    • C01B32/963—Preparation from compounds containing silicon
    • C01B32/97—Preparation from SiO or SiO2
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/90—Carbides
    • C01B32/914—Carbides of single elements
    • C01B32/991—Boron carbide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/00049—Controlling or regulating processes
    • B01J2219/00243—Mathematical modelling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J2219/0871—Heating or cooling of the reactor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J2219/0873—Materials to be treated
    • B01J2219/0881—Two or more materials
    • B01J2219/0886—Gas-solid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2219/00—Chemical, physical or physico-chemical processes in general; Their relevant apparatus
    • B01J2219/08—Processes employing the direct application of electric or wave energy, or particle radiation; Apparatus therefor
    • B01J2219/0894—Processes carried out in the presence of a plasma
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/01—Particle morphology depicted by an image
    • C01P2004/03—Particle morphology depicted by an image obtained by SEM
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/51—Particles with a specific particle size distribution
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer

Definitions

  • This invention relates to a method and apparatus for the production of ceramic carbides to be used in the development and manufacturing of high value materials.
  • the method and apparatus comprise a plasma torch, a reaction chamber and a rapid quenching chamber.
  • the relatively new trend in silicon carbide formation is to make it by thermal plasma processes.
  • the high temperatures available in the plasma increase the reaction kinetics by several orders of magnitude and fast quenching rates produce very small particles at high conversion rates, thus providing a number of advantages over older methods for producing very fine, submicron powders of SiC.
  • the gas phase synthesis conducted in a pure and controlled atmosphere at a high temperature gives the powder which is produced properties which are very desirable in subsequent fabrication. These properties include high sphericity, a small diameter and a narrow size distribution.
  • Plasma processing has a wide range of potential applications, ranging from coating of thin layers on substrates to the destruction of toxic wastes.
  • One of the many promising areas of plasma processing is the production of ultra-fine (submicron size) powders of high-value materials (such as carbides and nitrides). Powders produced in a pure and controlled atmosphere may be essential for subsequent fabrication of advanced materials.
  • Silicon carbide has many eminent properties, such as: high refractoriness, high oxidation resistance and high hardness. It also has a thermal conductivity comparable to the metals, and its thermal expansion coefficient is relatively low compared with other ceramics. Because of these properties, silicon carbide can be effectively used for high temperature mechanical applications. The products obtained by the present invention can be employed for those purposes for which ceramic carbides are presently used.
  • SiC powders A fundamental prerequisite for producing such structural ceramics depends on the availability of relatively inexpensive, high purity, reproducibly- sinterable SiC powders.
  • One of the more important problems in the application of SiC is its poor sinterability, which is due to strong covalent bonds between molecules.
  • the silicon carbide powder In order to enhance sintering characteristics, the silicon carbide powder must have a uniform particle size distribution and a submicron mean particle size.
  • SiC powder there have been a number of investigations concerning the production of SiC powder in plasma reactors.
  • the reactants used e.g., silane
  • These reactants are used because they are easily vaporized and therefore easily converted.
  • Silicon carbide has been produced using inexpensive reactants, such as silica and hydrocarbons, with an RF plasma.
  • RF plasmas may present a thermal efficiency problem when scaled up to an industrial size.
  • SiO 2 (s) + 3C (s) SiC (s) + 2CO (g)
  • the reaction is very slow even under plasma reactor conditions; so the reaction rates must be increased by the formation of gaseous intermediaries.
  • the reactants for the SiC formation are silica and methane. When silica is exposed to high temperature (>2839°C), it disassociates into silicon monoxide and oxygen, i.e.,
  • SiO 2 (s) SiO(g) + O(g)
  • methane When methane is exposed to high temperature, it decomposes into different species depending upon the temperature.
  • the important reactions for the methane decomposition are as follows:
  • the formation of acetylene by the thermal decomposition of methane is explained by the theory of free radicals and has been observed by a number of investigators, including the work reported here.
  • the primary species formed when methane is exposed to high temperatures are: Hj, C 2 H 2 , H and C.
  • the purpose of the present invention is to design, build and operate a plasma reactor to synthesize ultra-fine SiC in a non-transferred arc plasma system using inexpensive reactants such as silica and methane.
  • a new method and apparatus for producing pure, ultra-fine uniform sized ceramic carbides has been developed which comprises a non-transferred arc plasma torch as a heat source, a tubular reactor as a reaction chamber, and a quench chamber for rapidly quenching products to minimize their re-oxidation.
  • the process uses the high temperatures of the plasma torch to vaporize oxides and to make gaseous suboxides of SiO 2 , B 2 O 3 and TiO 2 (such as silica, Boron oxide and Titanium oxide) and to thermally decompose methane (to form acetylene, carbon and hydrogen).
  • the tubular reactor allows sufficient residence time (under the proper reaction conditions of temperature and partial pressures) for the formation of the ceramic carbides.
  • the powders are collected, treated by roasting to remove excess carbon, and leached to remove excess metals and oxides.
  • the product is pure, ultra-fine (0.2-0.4 micron) ceramic carbide.
  • FIG. 1 is a schematic diagram of a plasma reactor system incorporating the reactor of the present invention.
  • FIG. 2 is a sectional view of an embodiment of the reactor according to the invention.
  • FIG. 3 is a graph of typical temperature profiles at the outlet end of the reaction chamber.
  • FIG. 4 is a graph of the average temperature profile in the reactor.
  • FIG. 5 is a size distribution bar chart of the silica powder used in the system.
  • FIG. 6 is a bar chart showing SiC yield as a function of the methane/silica molar ratio.
  • HG. 7 is a photomicrograph of an SiC powder produced in the system shown in FIG. 1.
  • FIG. 8 is a bar chart of the particle size distribution of SiC powder.
  • FIG. 9 is a photograph of the plasma reactor system according to the invention.
  • FIG. 10 is a schematic of the model for the laminar flow reactor zone.
  • FIG. 11 is the free energy in kcal/mole versus temperature in kelvin for temperatures above 3000 degrees kelvin.
  • FIG. 12 is the free energy in kcal/mole versus temperature in kelvin in the temperature range above 2000 degrees kelvin but below 3000 degrees kelvin.
  • FIG. 13 is the free energy in kcal/mole versus temperature in kelvin for temperatures below 2000 degrees kelvin.
  • Other features would include the formation of pure, fine tungsten carbide powders using tungstic acid or tungsten oxide and methane; formation of pure, fine titanium carbide powders using titanium oxide and methane; thermal decomposition of methane to form acetylene and carbon; formation of fine silicon monoxide powder using silica; formation of fine silicon powder; formation of fine boron powder; and destruction of hazardous waste.
  • the reactor is divided into three zones. These zones are based on temperatures.
  • the first zone 1 is the plasma jet or vaporization zone, where the temperature is considered to be above 3000°K.
  • the second zone 3 is the reaction zone, where the temperature is between 2000°K and 3000°K.
  • the third zone 5 is the re-oxidation or quenching zone, where the temperature is less than 2000°K.
  • SiC + 2CO SiO 2 + 3C (22)
  • the free energy diagram for the above reactions is shown in FIG. 13.
  • This region can be considered a re-oxidation zone. If the quenching is sufficiently rapid (>10 4o k sec) and the gaseous atmosphere remains reducing, the re-oxidation reactions do not happen to any appreciable extent.
  • FIG. 1 A photograph of the system is shown in FIG. 9.
  • the central part of the system comprises a tubular, water cooled, stainless steel reactor 7 constructed of 316 stainless steel; the reactor 7 design accommodates the high temperatures associated with the plasma torch 17.
  • Theoretical calculations (see page 14, lines 8-12) are used to determine the temperature and velocity profiles expected in the reactor 7.
  • the appropriate reactor diameter is estimated and the condensating rate control strategies of the particles present in the stream determined (the relationship between the internal diameter 57 of the reactor and the energy density at various power levels of the plasma torch 17 are taken into account).
  • the time to complete the reaction is calculated using assumed kinetic equations. Having calculated the estimated reaction time, the length of the reaction chamber can be determined which will provide the reactants enough residence time in the reaction chamber to react (elutriation velocities for particles of different sizes were taken into account in determining the reactor 7 length).
  • a graphite tube 9 serves as the refractory lining of the reactor 7, protecting it from the high temperatures associated with the plasma torch. Because the graphite lining has high heat conductivity, to minimize heat loss it is necessary to insulate the graphite tube 9 with graphite felt 11, or zirconia felt but because of their low thermal conductivity and high refractoriness, several layers (5-6) of felt must be applied. The felt is placed between the graphite refractory 61 lining and the reactor inner wall 59.
  • the collection chamber 15 acts as a quenching chamber for the incoming gases, both by expansion and intensive water cooling.
  • the chamber 15 resembles a rectangular box with a periphery water-cooled jacket.
  • the collection chamber is constructed of 316 stainless steel.
  • water is circulated as a coolant.
  • the incoming reactants encounter an intensively water-cooled quenching barrier which minimizes or prevents re- oxidization.
  • a copper cooling coil is provided oppositely disposed from the collection chamber entrance which provides further cooling to the incoming reactants. Once the gas stream passes the copper coil and exits the collection chamber, it has cooled to a temperature of approximately 150-160°C. Teflon seals are provided on the cover to avoid any leakage from the collection chamber 5.
  • the reactor 7 and the quenching section 15 are shown in FIG. 2.
  • a non-transferred arc plasma torch 17 (Model PT50 from Plasma Energy
  • the front electrode connected to the negative terminal, serves as the cathode and the rear electrode, connected to the positive terminal, serves as the anode. Both electrodes are constructed of a copper chrome alloy and are intensively water cooled. A mixture of argon 19 and helium 21 is used as the plasma gas, the flow rates of the individual gases being adjusted and recorded separately.
  • the torch is attached to a 96 KW D.C. power supply.
  • the plasma torch 17 is attached to the front portion 23 of the reactor 7 using a stainless steel coupling 25 in combination with an injection ring or other feeding arrangement which is used to feed the reactants; the connecting system is fabricated from 316 stainless steel.
  • the stainless steel coupler serves to prevent leakage around the insertion area and permits easy removal of the plasma torch 17 for inspection or replacement. Insulating felt is used between the front portion 23 and the injection ring to minimize the heat losses from the front section.
  • a Metco powder feeder 29 (Model 3MP) comprising a hopper for powder storage, an adjustable speed rotating wheel and a vibrating system to prevent clogging feeds the powders combined with the gas stream into the reactor 7 through a copper tube.
  • a graphite disc Using a graphite disc, reactants are radially fed into the reaction chamber 1 at three points. The reactants pass through the reactor, enter the collection chamber, are cooled, and subsequently exit the collection chamber; the exit gas temperature is approximately 150-160°C.
  • the exiting gas stream contains fine particles, it is necessary to pass the stream through a stainless steel tubular filter 31.
  • Various filtering materials can be used but preferably 0.5 micron size "Nomex" cloth filter with a folded periphery filter bag. Maximum efficiency was obtained using filter bags with as large of surface area as possible.
  • the off gases are passed over a burner 33 for further combustion. This ensures full burning of the outgoing gases and converts the carbon monoxide present in the gases to carbon dioxide; the hazardous effects of the outgoing gases are minimized.
  • the gases are then vented to a stack. Alternatively, the off gases can be recycled to increase the overall efficiency of the reactor, decrease production costs and reduce the hazardous effects of the off gases.
  • the reactor chamber includes multiple ports 37, 39, 41, 43 along the reactor 7 and the collection chamber. These ports are used to take samples of the gases and the solid species as they transition the reactor and collection chamber, and to monitor temperatures at various intervals in the reactor and the collection chamber; both "C” and "K” type thermocouples are used. (A two color pyrometer was used to measure the temperature of graphite lining (9) in the reaction zone. Temperatures in the first half of the reactor could not be measured by thermocouples because of the high temperatures associated with the plasma torch but could be estimated theoretically.)
  • Each sampling line is mounted at different positions along the length of the reactor 7, each line comprising a 0.25 inch graphite tube inserted into the chamber, a microfilter, and a shut off valve.
  • the lines are connected to a Varian gas chromatograph 45 (Model 3300) via a vacuum pump.
  • the filter separates the solid species from the gaseous stream.
  • the gas chromatograph removes the samples using a vacuum pump placed at the end of the sampling lines and has an air actuated auto-sampling valve which takes samples at specified times.
  • the information from the system is interfaced with a data acquisition system.
  • the data system comprises an IBM personal computer (Model 30) coupled with a "Metrabyte" analog and digital conversion boards.
  • the conversion boards are connected to the thermocouple, flow sensors, pressure transducers and power supply parameters.
  • silica powder and technical grade (about 97% minimum purity) methane 28 are the primary reactants for the synthesis of ultra- fine silicon carbide in the plasma reactor.
  • the silica powder size distribution is shown in FIG. 5 and primarily it comprises 6 to 40 micron particles.
  • the methane 28 is combined with the silica powder at the powder feeder and used as the carrier gas along the powder feeder and to feed the powder into the reaction chamber.
  • a mixture of methane and argon can be used as the carrier gas where argon is simply added to maintain a fixed flow rate of the carrier gas. Flow rates for both gases are monitored using a mass flow meter and maintained at a delivery pressure for both gases of approximately 50 PSI.
  • the silica powder is dried in an oven before each run to remove moisture and ensure proper feeding. Moisture in the system could disrupt the chemical balance of the system and induce clogging prior to the reactants entering the reaction chamber, thereby devoiding the system of all uniformity.
  • the silica feed rate is maintained at about 5.0 g min.
  • the plasma torch is operated using argon and helium as plasma gases filtered through a 15 micron filter.
  • the plasma torch 17 is started with argon 19, but after about 10 minutes, helium 21 is added to enhance its power. Since helium has a higher ionization energy, the voltage across the electrodes is increased depending upon its flow rate and subsequently the power of the torch is increased.
  • the argon and helium are maintained at a delivery pressure of 130 PSI at the source, however, due to many restrictions in the gas lines, the delivery pressure drops to 30 PSI at the torch.
  • the flow rates for the argon and helium range between 3.5 to 4.0 SCFM (STP).
  • STP SCFM
  • Temperatures are measured in the second section 3 of the reactor 7 using "C” type thermocouples.
  • Example temperature profiles at the end of the reaction chamber versus time are given in FIG. 3.
  • Curve “A” is the centerline temperature at the discharge end of the reactor, while curves “B” and “C” are the temperatures at the half radius 49 and the wall 9, respectively. As shown in the figure, the temperatures rise sharply in the beginning; this is a result of pre ⁇ heating the reactor without any reactants. After some minutes, the reactor attains a thermal equilibrium at which point the feed is started into the reactor; this is represented in FIG. 3 as a sudden drop in temperature.
  • the powders produced are analyzed by chemical and physical characterization. Chemical quantitative analysis is performed for all the species present in the product. Physical characterization includes size, mo ⁇ hology, and size distribution of the powder.
  • Qualitative analysis of the powder produced is performed by x-ray diffraction at two stages: first, it is analyzed in the as-produced form, and second, it is analyzed after chemical treatment.
  • Chemical treatment consists of roasting the powders in air followed by leaching with HF acid and then a mixture of HF and HNO 3 acids.
  • the as-produced powder shows free carbon, silicon, silicon monoxide, silicon dioxide, and beta-silicon carbide.
  • the chemically treated powder only shows beta-silicon carbide.
  • Free carbon in the sample is determined by oxidizing the sample in a tube furnace at a temperature of 650°C. The sample is placed in a ceramic boat in the furnace. A pre-adjusted air stream is passed through the tube. All free carbon present in the sample is oxidized to CO 2 (using copper oxide wire in air). Carbon dioxide present in the outgoing gas stream is trapped by Ba(OH), solution which converts the CO 2 to BaC0 3 . The remaining solution is titrated with HC1 and the absorbed quantity of CO 2 is determined. Free Silicon and Silica
  • silicon If free silicon is in amo ⁇ hous form, it will be dissolved in hydrofluoric acid. If the silicon is in metallic form, it will not be dissolved in HF, but it can be dissolved in a mixture of IHF + 3HNO 3 . Silicon monoxide is also soluble in HF + HN0 3 solution. Silica is soluble in HF acid.
  • Samples are analyzed in two ways. First, a sample is roasted in the tube furnace to determine the free carbon and then it is treated with hydrofluoric acid and a mixture of hydrofluoric and nitric acids. The residue is pure silicon carbide. The solution after dissolution is analyzed for silicon content by atomic abso ⁇ tion (for the complete mass balance). A similar sample from the same experiment is analyzed in a reverse way. That is, the treatment with the acids comes first and then roasting is performed in the tube furnace.
  • Powders produced from each experiment are studied for particle size and mo ⁇ hology using a scanning electron microscope.
  • a photomicrograph of an SiC product sample is shown in FIG. 7. Most of the particles in the micrograph are 0.2-0.4 microns in size.
  • Particle size distribution is also very important in the subsequent treatment of the powder.
  • Coulter counter and Horiba particle analyzers are used to study the particle size distribution in this work.
  • the size distribution of the silicon carbide powder from T-31 is shown in FIG. 8. It mainly consists of particles ranging in size from 0.2 to 0.4 micron. Reaction Mechanisms
  • SiO(g) and Si(g) react with H ⁇ g) and C 2 H(g) to form SiC(s). These are gas-gas reactions and require the formation of critical nuclei.
  • the yield of silicon carbide could be increased by extending this reaction zone.
  • Models for the heat transfer and fluid flow in the reactor 7 have been developed and evaluated experimentally. The models assume steady state behavior and neglect the flame zone except as a heat and vaporization source.
  • FIG. 10 A schematic of the model for the laminar flow reactor zone is presented in FIG. 10.
  • An energy balance equation in dimensionless form is:
  • Heat convected and radiated to the walls 51 of the reactor is equal to the heat taken away through the walls 51 by cooling water.
  • it can be represented as follows:
  • SiO(g) reacts with C 2 H 2 (g) to form SiC.
  • concentration of SiO(g) and temperature act as the driving force for the reaction, assuming C 2 H 2 is in abundance.
  • the model is the subject of the paper "Fundamentals of Silicon Carbide Synthesis in a Thermal Plasma," by P. R. Taylor and S. A. Pirzada. More detailed models, including heterogeneous kinetics and nucleation and growth kinetics, are the subject of further investigation.
  • the powders that are being produced are suitable for ceramic application by consolidation and sintering.
  • Carbide powders produced pursuant to the present invention can be employed in applications where prior silicon carbide powders, including abrasives, have been used. Nomenclature
  • T w wall temperature (°K)

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Carbon And Carbon Compounds (AREA)

Abstract

Appareil et procédé de synthèse de carbures céramiques ultrafins (inférieur au micron) dans un réacteur thermique à torches à plasma (7) à partir essentiellement de silice, d'oxyde de bore, de dioxyde de titane ou d'autres oxydes, comme sources de métal, et de métane comme réducteur. Une torche à plasma (17) fonctionnant à la fois avec de l'argon et de l'hélium comme un gaz plasmatiques et employant comme principal gaz porteur le méthane, est relié à un réacteur à plasma (7) pour fournir la chaleur nécessaire au déclenchement de la réaction. Une chambre collectrice (5) dotée d'un refroidissement intérieur et extérieur est reliée au réacteur pour refroidir les réactants. Le refroidissement de la torche (17), du réacteur (7) et la chambre collectrice (5) est réalisée par des serpentins, des déflecteurs et des chemises.
PCT/US1992/001064 1991-02-22 1992-02-14 Production plasmatique de carbures ceramiques ultrafins WO1992014576A1 (fr)

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Application Number Priority Date Filing Date Title
US65864991A 1991-02-22 1991-02-22
US658,649 1991-02-22
US07/782,790 US5182606A (en) 1989-06-22 1991-11-15 Image fixing apparatus

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Cited By (6)

* Cited by examiner, † Cited by third party
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WO1996006700A3 (fr) * 1994-08-25 1996-03-28 Qqc Inc Particules nanometriques et leurs utilisations
WO2000010756A1 (fr) * 1998-08-18 2000-03-02 Noranda Inc. Procede et systeme de plasma a arc transfere pour la production de poudres fines et ultra-fines
FR2787676A1 (fr) * 1998-12-18 2000-06-23 Soudure Autogene Francaise Piece d'usure pour torche de travail a l'arc realisee en cuivre allie
SG111177A1 (en) * 2004-02-28 2005-05-30 Wira Kurnia Fine particle powder production
RU2359905C1 (ru) * 2008-05-19 2009-06-27 Государственное образовательное учреждение высшего профессионального образования "Сибирский государственный индустриальный университет" Способ получения шихты для производства карбидокремниевой керамики твердофазным спеканием
CN111867973A (zh) * 2018-03-23 2020-10-30 日清工程株式会社 复合粒子及复合粒子的制造方法

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US3340020A (en) * 1963-08-13 1967-09-05 Ciba Ltd Finely dispersed carbides and process for their production
GB1093443A (en) * 1965-02-15 1967-12-06 British Titan Products Silicon carbine
USRE28570E (en) * 1971-02-16 1975-10-14 High temperature treatment of materials
USRE32908E (en) * 1984-09-27 1989-04-18 Regents Of The University Of Minnesota Method of utilizing a plasma column

Patent Citations (4)

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Publication number Priority date Publication date Assignee Title
US3340020A (en) * 1963-08-13 1967-09-05 Ciba Ltd Finely dispersed carbides and process for their production
GB1093443A (en) * 1965-02-15 1967-12-06 British Titan Products Silicon carbine
USRE28570E (en) * 1971-02-16 1975-10-14 High temperature treatment of materials
USRE32908E (en) * 1984-09-27 1989-04-18 Regents Of The University Of Minnesota Method of utilizing a plasma column

Cited By (6)

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CN111867973A (zh) * 2018-03-23 2020-10-30 日清工程株式会社 复合粒子及复合粒子的制造方法

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