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WO1992009540A1 - Procede de preparation de matieres en ceramique - Google Patents

Procede de preparation de matieres en ceramique Download PDF

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Publication number
WO1992009540A1
WO1992009540A1 PCT/US1991/008981 US9108981W WO9209540A1 WO 1992009540 A1 WO1992009540 A1 WO 1992009540A1 US 9108981 W US9108981 W US 9108981W WO 9209540 A1 WO9209540 A1 WO 9209540A1
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Prior art keywords
metal oxide
composition
silicon
fibers
ceramic
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Application number
PCT/US1991/008981
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English (en)
Inventor
Sivananda S. Jada
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Manville Corporation
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Publication date
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Publication of WO1992009540A1 publication Critical patent/WO1992009540A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/48—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C13/00—Fibre or filament compositions
    • C03C13/06—Mineral fibres, e.g. slag wool, mineral wool, rock wool
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/16—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay
    • C04B35/18—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay rich in aluminium oxide
    • C04B35/185—Mullite 3Al2O3-2SiO2
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/62227—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products obtaining fibres
    • C04B35/62231—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products obtaining fibres based on oxide ceramics
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/624—Sol-gel processing

Definitions

  • the present invention is concerned with the manufacture of ceramic silicon metal oxide materials utilizing sol-gel technology.
  • U.S. Patent No. 3,709,706 describes refractory aggregates and shaped articles such as fibers, films, flakes and microspheres of zirconia and silica mixtures. Fibers were spun from an aqueous colloidal dispersion of silica and aqueous solution of zirconium diacetate.
  • U.S. Patent No. 4,349,456 describes shaped and fired porous or impermeable non-vitreous ceramic microcapsules of metal oxide made by a non-melt process comprising the liquid extraction of aqueous metal oxide precursor with a dehydrating liquid having a limited water solubility and drying and firing the resulting gelled microcapsules.
  • U.S. Patent No. 4,931,414 describes solid transparent non-vitreous microspheres (zirconia-silica) are formed by a extractive gelation (extracting carboxylic acid away from zirconyl carboxylate) of a sol in liquid medium such as hot peanut oil.
  • Alumino-silicate gels (containing 63-80 weight percent Al 2 O 3 ) were obtained from hydrolysis of silicon tetraethoxide and aluminum isopropoxide.
  • Mullite is the metal oxide system which corresponds to three moles of Al 2 O 3 to two moles of SiO 2 .
  • Japanese patent application No. 58-112309, laid open publication No. 60-5022, F. Hashimi et al discloses a process of preparing alumina fibers by forming a spinning dope containing aluminum oxychloride, a silicon compound and urea and calcining the fibers at more than 500oCentigrade. The mixture was concentrated under reduced pressure at 50oCentigrade to provide a spinning dope.
  • Japanese patent application No. 58-231012 laid open publication No. 60-122777 published on July l, 1985, T. Ando et al describes a process for preparing a refractory insulating board precursor which comprising kneading aluminum material fibers with an alumina content of 75% by weight or more with silica-alumina mixed sol, then molding the mixture by filtration, drying the molded product to prepare a precursor for a refractory insulating board to be used at a temperature of 950oCentigrade or higher.
  • FIGURE 1 is a schematic diagram of the overall process of the present invention to produce the spherical particles;
  • FIGURE 2 shows zircon hollow spheres at 1000 magnification;
  • FIGURE 3 is an X-ray diffraction pattern of zircon hollow particles calcined at 1100oC.
  • FIGURE 4 is a scanning electron microscope (SEM) micrograph of precursor mullite granules at 3500 magnification.
  • the present invention is concerned with obtaining ceramic materials.
  • the present invention is also concerned with obtaining mullite compositions in various forms, e.g., discrete particles, hollow particles, refractory fibers, flakes and the like.
  • the silicon that may be employed can generally be characterized as silicon oxides or alkoxides.
  • the silicon oxides can be silicon dioxide or polymers thereof.
  • the silicon alkoxides can be those comprised of the silicon containing materials further comprising hydrocarbyl containing lower alkyl radicals from 1 to 6 carbon atoms, preferably ethyl.
  • Illustrative materials are tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, ethyltriethoxysilane and amyltriethoxysilane, and the like.
  • the silicon material be colloidal silica which has an acidic ph, preferably a ph of 3-5.
  • the colloidal silica is preferably in an aqueous state with a particle size less than 50 nanometers, preferably 0.5-25 nanometers.
  • the ph is adjusted from the normal ph of colloidal silica which is basic, usually about 8 to 10 by the use of acidic materials. Any acidic material that does not interfere with subsequent processing steps may be employed whether it be organic or inorganic, although preferably organic acids of less than 6 carbon atoms and even more preferably acetic acid is employed.
  • acidic material that does not interfere with subsequent processing steps may be employed whether it be organic or inorganic, although preferably organic acids of less than 6 carbon atoms and even more preferably acetic acid is employed.
  • To the aqueous colloidal silica solution is added the metal oxide precursor solution. Alternatively, the metal oxide can be placed into an aqueous solution and then the two solutions blended to give a homogeneous solution.
  • the metal oxide can be a dispersion or solution of one or more ceramic metal oxide which include zirconium oxide, TiO 2 , Cr 2 O 3 , WO 3 , ThO 2 , Fe 2 O 3 , MgO, Y 2 O 3 , ZrO 2 , HfO 2 , V 2 O 5 , Nb 2 O 5 , UO 2 , BeO, CoO, NiO, CuO, ZnO, ln 2 O 3 , Sb 2 O 3 , Al 2 O 3 , SnO 2 , and mixtures thereof such as ZnO ⁇ TiO 2 , TiO 2 ⁇ Fe 2 O 3 , SnO 2 ⁇ TiO 2 , Nd 2 O 3 --TiO 2 , Al 2 O 3 ⁇ Cr 2 O 3 , MgO ⁇ Al 2 O 3 , MgO ⁇ TiO 2 , MgO ⁇ ZrO 2 , ThO 2 --UO 2 , ThO 2 ⁇ CeO 2 ,
  • dispersion or sols of said ceramic metal oxides in combination or admixture with dispersions or sols of one or more metal oxides which are unstable in normal air environment (such as Li 2 O, Na 2 O, K 2 O, CaO, SrO, and BaO) and/or ceramic nonmetal oxides having an atomic number of 14 or greater (such as SiO 2 , As 2 O 3 , and P 2 O 5 ) , representative combinations including A1 2 O 3 ⁇ Li 2 O, TiO 2 --K 2 O, ZrO 2 ⁇ CaO, ZrO 2 ⁇ A1 2 O 3 ⁇ CaO, ZrO 2 ⁇ SrO, TiO 2 ⁇ BaO, TiO 2 ⁇ ZrO 2 ⁇ BaO, Al 2 O 3 ⁇ Na 2 O, MgO ⁇ SiO 2 , Fe 2 O 3 ⁇ BaO, ZrO 2 - -SiO 2 , Al 2 O 3 ⁇ AS 2
  • the metal oxide is selected from Periodic Table Group II or Group III metals.
  • a number of the above-described oxides useful in this invention are commercially available in the form of aqueous sols, salts or dry powders which can be readily dispersed in water to form sols, such as Al 2 O 3 , Cr 2 O 3 and Fe 2 O 3 sols sold under the trademark "Nalco”, silica sols sold under the trademarks “Nalco,” “Ludox,” “Syton” and “Nyacol,” and Al 2 O 3 colloidal powder sold under the trademark “Dispal”, aluminum oxychloride power is sold under the trademark "Chlorhydrol Micro-Dry.”
  • the precursor material in the form of dispersion or sols of said oxides it is within the scope of this invention to use the precursor material in the form of water soluble or dispersible inorganic or organic compounds which are calcinable to the corresponding oxide.
  • These compounds representatively include many carboxylates and alcoholates, e.g. acetates, formates, oxalates, lactates, propylates, citrates, and acetylacetonates, and salts of mineral acids, e.g., bromides, chlorides, chlorates, nitrates, sulfates, and phosphates, and oxysalts of mineral and organic acids, e.g., oxybromides, oxychlorides, oxychlorides, oxychlorates, oxynitrates, and oxyacetates, selection of the particular precursor compound being dictated by availability and ease of handling.
  • mineral acids e.g., bromides, chlorides, chlorates, nitrates, sulfates, and phosphates
  • oxysalts of mineral and organic acids e.g., oxybromides, oxychlorides, oxychlorides, oxychlorates, oxynitrates
  • Representative precursor compounds useful in this invention include ferric chloride or nitrate, chromium chloride, cobalt nitrate, nickel chloride, copper nitrate, zinc chloride or carbonate, lithium propylate, sodium carbonate or oxalate, potassium chloride, beryllium chloride, magnesium acetate, calcium lactate, strontium nitrate, barius acetate, yttrium bromide, zirconium acetate, hafnium oxychloride, vanadium chloride, ammonium tungstate, aluminum chloride, indium iodide, titanium acetylacetonate, stannic sulfate, lead formate, antimony chloride, bismuth nitrate, neodymium chloride, phosphoric acid, cerium nitrate, uranium nitrate, and thorium .nitrate.
  • Representative precursor compounds are aluminum oxychloride, aluminum oxynitrate, oxyacetates and
  • the Al 2 O 3 precursor can be aluminum alkoxide.
  • the aluminum alkoxides can be those of the aluminum containing materials further comprising hydrocarbyl containing lower alkyl radicals from 1 to 15 carbon atoms, preferably isopropyl.
  • Illustrative materials are aluminum tri-sec-butoxide, aluminum tri-tert-butoxide, aluminum triethoxide, aluminum n-butoxide, aluminum secbutoxide stearate, aluminum t-butoxide, aluminum di(sec-butoxide) acetoacetic esterchelate, aluminum di(iso-propoxide, aluminum phenoxide, and the like.
  • the most preferred material is aluminum oxychloride which on sintering gives the aluminum oxide.
  • Controlled amounts of additives and/or mineralizers are added as sintering aids to reduce the higher temperatures required for mullite formation and also as grain- growth inhibitors and mullite toughening agents.
  • the additives added most frequently include Fe 2 O 3 , Cr 2 O 3 , TiO 2 , ZrO 2 , Ga 2 O 3 , MgO, Na 2 O, K 2 O, B 2 O 3 and V 2 O 3 .
  • ZrO 2 increases the toughness of mullite by a grain-boundarystrengthening mechanism by adding up to 0.05 wt% ZrO 2 .
  • the Na 2 O, Fe 2 O 3 and B 2 O 3 reduce the temperature of mullite formation and crystallization.
  • B 2 O 3 is a preferred mineralizer (concentrations ⁇ 2%) added to the precursor solution in the form of boric acid.
  • the colloidal silica be a very fine particle size.
  • the silica concentration should be less than 50% and preferably approximately 10-30%, and even more preferably, about 20% by weight.
  • the purpose in adding the acidic material is to produce a negative electrostatic charge on the silica particles.
  • Colloidal silica particles exhibit a significant negative electrostatic charge in the ph range of from 3 to 5 and a value within this range is selected for matching with the ph of the aqueous metal oxide precursor solution.
  • the ph adjusted colloidal silica solution are added to the slurry containing the desired metal oxide precursor solution and the mixture is stirred, preferably in the presence of ultrasonic treatment to facilitate the reaction.
  • the colloidal silica particles with a negative electrostatic charge are attracted to the positively charged metal ion (for example the zeta potential for zirconia at a ph of 3-5 is approximately 58-64 millivolts and for alumina at ph 3-5 is about 45-50 millivolts).
  • the ratio of silicon material to metal oxide is from 0.5 to 1.1 (silicon calculated as silicon dioxide) to l (metal oxide calcu lated as metal dioxide) mole ratio. Most preferably, the mole ratio is 1:1.
  • mullite composition i.e., a metal oxide system that corresponds to three moles of Al 2 O 3 to two moles of SiO 2 .
  • ultrasonic treatment may be utilized.
  • the processing parameters are at ambient temperature and pressure and that the frequency of kilohertz ranges from 0.01 to 1 kilohertz, preferably less than 0.1 kilohertz, e.g. 0.05 to 0.07 kilohertz.
  • the concentration ranges from 10 to 80 wt%.
  • the viscosity of the composition ranges from 1 to 40 Centipoise (CPS).
  • One technique would be merely to allow the mixture to evaporate to dryness.
  • the evaporation can be accelerated by heating at a temperature from ambient to 100"Centigrade. In this fashion, the water and other volatile components can be readily removed therefrom.
  • the dried material could be flakes or other particulate to form. It may be ground to a desired size.
  • the mullite precursor composition can also be spray-dried using the apparatus described in Figure 1.
  • the particles are subjected to a sintering or calcining treatment to obtain the desired ceramic particles.
  • the sintering temperature is at least 250° to 1500o, and even more preferably, about 900o to 1200oCentigrade.
  • a description of the equipment utilized is as follows:
  • FIG. 1 shows the schematic diagram of the apparatus useful in the present invention.
  • a tank 10 is a reservoir of the aqueous liquid 12.
  • the tank is open to the atmosphere at the top as indicated by arrows 14.
  • the tank is operated at ambient pressure.
  • a second tank 16 is one that likewise contains liquid 12 which passes from the tank 10 to the tank 16 by pipe 17.
  • the cavity 20 is one that is exposed to atmospheric pressure, for it is the cavity above the reservoir in the tank 10.
  • a similar cavity 22 is atop the reservoir 12 above the level 24 of the fluid in the reservoir 16.
  • the lower tank 16 likewise is open to the atmosphere as is indicated by arrow 26.
  • Line 18 maintains equal pressure in tanks 10 and 16.
  • the liquid transfer tube 28 is attached to nozzle means generally shown as reference numeral 30.
  • the inlet 32 for the liquid is placed adjacent to the air inlet 34 which is connected to an air pump generally expressed as 36.
  • the nozzle 30 is generally available from Spraying Systems, Inc. of Wheaton, Illinois, and is utilized in this invention as follows. When air from pump 36 passes through conduit 34 and air outlet 38, the liquid composition from reservoirs 12 and 24 pass through conduit 32 and is atomized into heated chamber 40. The spray nozzle 30 is locked in position by lock nut 42 onto an appropriately configured vessel 44. The top portion 46 of the nozzle is appropriately configured to lock in place at position 48 which is at the bottom of container 40.
  • the spray 50 from the air pump is schematically shown in Figure 1.
  • an atomized spray occurs whereby particulates are formed and subsequently become hollow spheres as the aqueous portion of the mixture is volatilized off in the heated chamber 40.
  • the particles are subsequently collected at a trough at the bottom (not shown) and the volatilized portion of the aqueous material is disposed of (apparatus not shown).
  • the reservoir level 24 drops.
  • the liquid 12 flows through pipe 17 into container 16 thereby increasing the level 24 to the point that it is just at the exit 52 of conduit 18.
  • the orifice 38 is preferably 0.016 inches in diameter and the orifice 33 of conduit 32, ranges from 0.05 inches for the inner diameter to 0.064 inches for the outer diameter or .007 inches.
  • the air is fed through conduit 34 at a range of 5 to 100 pounds per square inch gauge (psig), and even more preferably, 10 to 70 psig, most preferably, 15 to 30 psig.
  • psig pounds per square inch gauge
  • Two of the interior walls of heat chamber 40 have four 500 watt strip heaters attached to black painted aluminum plates attached to the interior of the walls of the reservoir 40. The heating of the chamber preferably exceeds 250°F, and even more preferably, 400° - 1000oF.
  • the microspheres or particles that are produced preferably have a size less than 75 microns with a lower limit of approximately l micron.
  • the size range is preferably 10 to 60 microns, and even more preferably, 15 to 50 microns.
  • particles that are not hollow may be produced. This may be accomplished by modifying the processing conditions such as a lower drying temperature and a higher viscosity homogeneous solution that is spray-dried.
  • an alternative particle collection device can be anything commercially available such as a cyclone collection system with a separate system for separating and collating the particulates depending upon the sizes desired for particles.
  • the microspheres preferably will have a surface area greater than 75 square meters (m 2 ) per gram, preferably 150 square meters per gram and upwards of 250 square meters per gram.
  • Another alternative to form the desired physical mullite composition is to spin fibers from the concentrated dope. In this fashion, the composition that is spun can be quite high in concentration of the mullite composition, preferably greater than 55% by weight mullite precursor, and even more preferably, greater than 60% by weight up to approximately 75% by weight. The most, preferred is having at least 65% solids of the spinning composition. In the spinning of the mullite composition, optionally it may be desirable to add organic polymers such as natural or synthetic polymers having fiberforming ability.
  • soluble derivatives of starch or cellulose such as starch acetate, hydroxyethyl starch, methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxypropyl cellulose, and the like may be employed.
  • Other materials may be synthetic polymeric materials such as polyvinyl alcohol, polyethylene glycol, polyacrylamide and the like.
  • polyethylene oxide having a molecular weight of 1,000 to 600,000 may also be employed.
  • the amount of polymeric material is an effective amount which ranges from l to 20% by weight of mullite.
  • the most preferred physical form of the mullite is fibrous.
  • the fibers may be formed from any general fiber forming technique. The most preferred is to feed viscous precursor material through a spinnerette which output is then subjected to forced air to form long strands of fibers. The fibers are subsequently collected and calcined.
  • the physical materials are subjected to a sintering or a calcining treatment to obtain the desired crystalline composition.
  • the sintering temperature is at least 250 - 1500oCentigrade, and even more preferably, about 900 - 1200°Centigrade.
  • the fibers formed will have lengths that range from 0.5 to 20 centimeters and diameters in the range of 0.05 to 10 microns with an average fiber diameter being the range of 1.5 to 5 microns, preferably less than 3 microns.
  • any process of manufacturing the fiber may be utilized as in the making of fiberglass from a melt can be applicable.
  • the dope that is utilized is a highly viscous dope. Therefore, the steam blown process would be applicable, namely, that the dope is forced through jets and is subjected to air from jets to volatilize the aqueous or other organic portion of the precursor mullite composition.
  • Forcing the dope through rotating spinnerettes likewise can be used as a technique for forming fibers.
  • the fiber may be fed to a continuous belt where it could be lead to be ovencured and subsequently to the calcining as indicated previously.
  • the spinnerette can be rotating thereby forcing the dope through the holes in the spinnerette.
  • the ceramic materials could then subsequently be formed into products as desired by forming a roving or board for insulation purposes.
  • the ceramic materials e.g. mullite compositions, can be utilized for refractory purposes such as insulation of heated products or in appliances such as ovens, microwaves and the like.
  • Other end uses are thermal shields used in space exploration equipment, missiles, rockets and in commercial and military aircraft for heat and/or fire protection in voice record box, engine parts, fuselage.
  • Colloidal silica (Ludox TM , trademark of E.I. DuPont Company) having an average particle diameter 7 nanometers with a ph of 9.9 is diluted with water to make a 21% by weight percent silica in the mixture. After dilution and stirring of the mixture, the ph of the solution is adjusted to a ph in range of 3 to 5 by the addition of acetic acid. A second slurry was prepared of zirconium acetate (21% by weight) which is stirred. The ph adjusted colloidal silica solution is then added to the slurry containing zirconium acetate and stirred in the presence of ultrasonic equipment operating at 60 - hertz.
  • Lidox TM trademark of E.I. DuPont Company
  • the SiO 2 :ZrO 2 is a 1:1 mole ratio. After a period of time, the viscosity of the mixture was 4-5 CPS. The mixture was then placed in a piece of equipment comparable to that shown in Figure 1. Air was pumped through nozzle 34 with the aqueous liquid being sucked through conduit 32 and likewise through conduit 28 from reservoir 12 and vessels 16 and 18. The temperature of the vessel 40 was initially 400°F and during spraying decreased to approximately 275° to 300"F. The particles were collected at the bottom and were subjected to sintering or drying. The particles were dried for 2 hours at 250° then at 650o for 2-4 hours until the powder is colorless and then for 2 hours at 1100oCentigrade.
  • the X-ray diffractogram of the sample calcined to 1100oC is shown in Figure 3.
  • X-ray diffraction pattern of zirconium silicate, zircon, (ZrSiO 4 ) matches standard pattern PDF file No. 6-266, JCPDS International Center for Powder Diffraction Data except for two weak diffraction peaks.
  • Figures 2-3 clearly demonstrate that pure zircon hollow particles have been produced.
  • the hollow spheres approximately 10-20 microns in diameter, are tough, dimensionally stable over a range of temperatures up to 2500°C.
  • the sample produced was tested at 500oF using the guarded hot plate method where the density was 75 pounds per cubic foot having a thermal conductivity of 1.86 (btu-inches per hour - per square foot per degree Fahrenheit). Comparable experiments were conducted according to ASTM-C 177 for different temperatures ranging from 600°F to 1400oF.
  • the zircon samples were prepared by pouring the zircon material into Ceraboard (trademark of Manville Sales Corporation) rings with a glass cloth top and bottom. After the samples were tested, physical cracks with depths of 0.25+ inches were observed. The results are tabulated below.
  • Colloidal silica having an average particle diameter of 12 nanometers with a ph of 8.9 is diluted with water to a solution that is 21% by weight percent silica. After dilution and stirring of the mixture, the ph of the solution is adjusted to a ph in range of 3 to 5.
  • a second slurry was prepared of zirconium oxychloride (Magnesium Elektron Co.), 21% by weight, which is stirred.
  • the ph adjusted colloidal silica solution is then added to the slurry containing zirconium oxychloride and stirred with a mechanical mixture.
  • the SiO 2 :ZrO 2 is a 1:1 mole ratio.
  • the viscosity of the mixture was 3-5 CPS.
  • the mixture was spray-dried and calcined the precursor hollow microspheres as described in Example 1.
  • Example 3 Hollow microspheres were prepared in the same manner as in Example 1 except that zirconyl oxynitrate [ZrO(NO 3 ) 2 ] is used.
  • Hollow microspheres were prepared in the same manner as in Example 1 except that 2% w/w of B 2 O 3 by the weight of zircon was added as boric acid to the precursor solution.
  • Ludox TM 180g In a separate beaker, take Ludox TM 180g and to that add 180g (equal amount) of water. Then add 4-5g of acetic acid. Add this ph adjusted Ludox TM to a solution of 558.1g aluminum oxychloride (50% by wt) in 500 ml ethanol. Mix thoroughly. The solution was combined up to make approximately 5 gallons of precursor solution.
  • the solution was spray-dried using the apparatus of Figure 1.
  • the spray-dried material was sintered at 250°C for 1 hour; 650oC for 1 hour and finally at 1000°C for 48 hours.
  • the oven was cooled to room temperature.
  • the products were tested by spectroscopic and X-ray diffraction tests for composition were determined to be mullite particles.
  • Hollow mullite particles were prepared in the same manner as in Example 5 except that % w/w of B 2 O 3 by the weight of mullite was added as boric acid to the precursor solution.
  • Example 7
  • a poly(tetraethylorthosilicate) solution was prepared as follows:
  • the silica content in the condensed solution was 57.68% (calculated).
  • the polymeric solution had a viscosity of 9-11 cps (by Brookfield Viscometer). The ph was 2-3.
  • a mullite composition was formed from disperal (trademark of Condea for Al 2 O 3 sol powder - 60% Al 2 O 3 ) by adding 101.96g of Al 2 O 3 sol dissolved in 900g of water with 2g of acetic acid. Small portions of Al 2 O 3 powder were added with vigorous agitation. SiO 2 sol, (Ludox brand) having 3.5-4.0 ph (adjusted from 9.9 by adding acetic acid 5g, to 80.11g Ludox) was added into middle of the Al 2 O 3 powder addition. Then, 3.64g of PEO (polyethyleneoxide from Polysciences, Inc.) (MW 300,000) dissolved in 50g of hot water was added; PEO should be completely dissolved in hot water. The mullite composition could be formed by evaporating to dryness the aqueous composition.
  • Example 9 Mullite fiber could be formed from the following composition:
  • Aluminum acetate dibasic Al(OH) 2 CH 3 COO; Mol. wt. : 120.0412 from Niacet Corp:
  • LudoxTM 400.57g of LudoxTM is required for 2 moles g SiO 2
  • the actual amount utilized is:
  • Example 10 In a beaker, 250 ml of water was preheated to 60oC; Small amounts totaling 84.97g of aluminum acetate was added. When the solution was clear, LudoxTM, (40.06g + 0.64g acetic adjusted to ph 5.5-6) was added; 0.43g of PEO (polyethyleneoxide from Polysciences, Inc.) MW 300,000 dissolved in 10g of hot water and the resulting viscous solution was formed into fiber by rotary fiberization process.
  • LudoxTM (40.06g + 0.64g acetic adjusted to ph 5.5-6) was added; 0.43g of PEO (polyethyleneoxide from Polysciences, Inc.) MW 300,000 dissolved in 10g of hot water and the resulting viscous solution was formed into fiber by rotary fiberization process.
  • PEO polyethyleneoxide from Polysciences, Inc.
  • LudoxTM 40.06g
  • PEO polyethyleneoxide from Polysciences, Inc.
  • Azeotropic mixture was made by adding an equal amount (250 ml) of ethanol. The mixture was subjected to a rotary evaporation to remove 400 ml of ethanol + water giving 163.0g of residue. The residue was further diluted with ethanol and a few drops of antifoaming agent (AF-10-IND, A-82723B Thompson-Hayward Chemical Company having a concentration of 100 ml water to 1 drop of antifoaming agent). The product was vacuum distilled on a rotary evaporator. The viscous material was tested for viscosity on Brookfield Viscometer, LV Series, and was found to be 58,000 - 59,000 cps and shear rate was 3.96. Formation Of Fibers
  • the fibers were formed by feeding a viscous mass of 8,000 to 60,000 centipoise to a centrifugal spinning machine with a 5 3/8" diameter disk having multiple holes of 0.012" in their smallest dimension. Air ring pressure was maintained at 7 psig. The ambient relative humidity was maintained and the ambient temperature between 80 and 100oF. The mullite fiber precursor temperature at the beginning of the run was between 25 and 70°F and the disc temperature was between 80 and 100°F.
  • Fibers formed by above step were spread on a stainless steel tray and subjected to a heat treat cycle as follows:

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  • General Chemical & Material Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Dispersion Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Composite Materials (AREA)
  • Silicates, Zeolites, And Molecular Sieves (AREA)
  • Compositions Of Oxide Ceramics (AREA)

Abstract

Procédé de préparation de matières en céramique comprenant les étapes consistant à former une composition de matière contenant du silicium à un pH acide; à former une composition précurseur aqueuse de céramique et d'oxyde de métal, à former un mélange homogène du silicium et des compositions précurseurs de céramique et d'oxyde de métal, à solidifer la céramique et l'oxyde de métal au silicium précurseur à partir de la composition homogène, à fritter la céramique et l'oxyde de métal au silicium solidifié et à récupérer les matières d'oxyde de métal au silicium.
PCT/US1991/008981 1990-12-03 1991-12-02 Procede de preparation de matieres en ceramique WO1992009540A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US62131890A 1990-12-03 1990-12-03
US621,318 1990-12-03

Publications (1)

Publication Number Publication Date
WO1992009540A1 true WO1992009540A1 (fr) 1992-06-11

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PCT/US1991/008981 WO1992009540A1 (fr) 1990-12-03 1991-12-02 Procede de preparation de matieres en ceramique

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Country Link
WO (1) WO1992009540A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007104477A1 (fr) * 2006-03-10 2007-09-20 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Barbotines et matériau composite céramique qu'elles permettent de produire
RU2530033C1 (ru) * 2013-07-26 2014-10-10 Федеральное государственное унитарное предприятие "Всероссийский научно-исследовательский институт авиационных материалов (ФГУП "ВИАМ") СПОСОБ ПОЛУЧЕНИЯ КЕРАМИЧЕСКОГО ВОЛОКНА НА ОСНОВЕ ZrO2 И SiO2

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3709706A (en) * 1969-05-16 1973-01-09 Minnesota Mining & Mfg Refractory fibers and other articles of zirconia and silica mixtures
WO1990003955A1 (fr) * 1988-10-14 1990-04-19 Raychem Corporation Corps denses dielectriques en oxyde metallique, poudres de precurseur relatives et procedes de preparation

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3709706A (en) * 1969-05-16 1973-01-09 Minnesota Mining & Mfg Refractory fibers and other articles of zirconia and silica mixtures
WO1990003955A1 (fr) * 1988-10-14 1990-04-19 Raychem Corporation Corps denses dielectriques en oxyde metallique, poudres de precurseur relatives et procedes de preparation

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007104477A1 (fr) * 2006-03-10 2007-09-20 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Barbotines et matériau composite céramique qu'elles permettent de produire
RU2530033C1 (ru) * 2013-07-26 2014-10-10 Федеральное государственное унитарное предприятие "Всероссийский научно-исследовательский институт авиационных материалов (ФГУП "ВИАМ") СПОСОБ ПОЛУЧЕНИЯ КЕРАМИЧЕСКОГО ВОЛОКНА НА ОСНОВЕ ZrO2 И SiO2

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