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Publication numberUS20030138673 A1
Publication typeApplication
Application numberUS 10/266,832
Publication dateJul 24, 2003
Filing dateOct 8, 2002
Priority dateAug 23, 2000
Also published asCA2420057A1, CA2420057C, CN1289389C, CN1455756A, EP1315673A1, EP1315673A4, US6461415, US20040011245, US20090064893, WO2002016263A1
Publication number10266832, 266832, US 2003/0138673 A1, US 2003/138673 A1, US 20030138673 A1, US 20030138673A1, US 2003138673 A1, US 2003138673A1, US-A1-20030138673, US-A1-2003138673, US2003/0138673A1, US2003/138673A1, US20030138673 A1, US20030138673A1, US2003138673 A1, US2003138673A1
InventorsSankar Sambasivan, Kimberly Steiner
Original AssigneeSankar Sambasivan, Steiner Kimberly A.
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
High temperature amorphous composition based on aluminum phosphate
US 20030138673 A1
Abstract
A composition providing thermal, corrosion, and oxidation protection at high temperatures is based on a synthetic aluminum phosphate, in which the molar content of aluminum is greater than phosphorous. The composition is annealed and is metastable at temperatures up to 1400 C.
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Claims(8)
1. A high temperature stable composition comprising aluminum phosphate wherein the ratio of aluminum to phosphorous is greater than one-to-one, said composition being annealed and characterized by containing at least 50 percent by weight of an amorphous content, said composition being metastable of temperatures from ambient up to 1400 C.
2. The composition of claim 1 additionally comprising a substrate, said composition being a coating on said substrate.
3. The composition of claim 1 wherein said composition is in the form of a fiber.
4. The composition of claim 2 wherein said coating protects said substrate from oxidation at elevated temperatures.
5. The composition of claim 2 wherein said coating protects said substrate from corrosion at elevated temperatures.
6. The composition of claim 1 comprising an additional metal.
7. An aluminum phosphate composition, said composition comprising aluminum phosphate wherein the amount of aluminum relative to phosphorous in said composition exceeds five percent, said composition being metastable at temperatures up to 1400 C.
8. A method for protecting a substrate from corrosion and oxidation at elevated temperatures, said method comprising the steps of applying a precursor solution to said substrate, said precursor solution comprising phosphorous pentoxide and an aluminum salt, wherein the ratio of aluminum to phosphorous is greater than one to one, and thereafter drying annealing said solution on said substrate.
Description
    BACKGROUND OF THE INVENTION
  • [0001]
    This invention relates to synthetic inorganic compositions which remain metastable and possess other desired properties at mid and high temperature, for example, from 800 C. to 1400 C. and greater.
  • [0002]
    It is known to use metal oxide coatings for high temperature protection of substrates or other surfaces. Up to the present time, however, there are no known synthetic oxides which can remain amorphous and metastable at temperatures up to 1400 C. or greater. Silica, for example, is known to devitrify/crystallize at temperatures slightly greater than 850 C. other non-oxide materials, such as silicon oxy-carbide and silicon oxy-nitride rapidly oxidize and fort crystalline phases at high temperatures in air.
  • [0003]
    Aluminum phosphate is a well known inorganic material that has found many uses in applications including catalysts, refractories, composites, phosphate bonded ceramics, and many others. Aluminum phosphate has a low density (d=2.56 g/cm3). It is chemically inert and stable at high temperatures, as well as being chemically compatible with many metals and with most widely used ceramic materials including silicon carbide, alumina, and silica over a moderate range of temperatures.
  • [0004]
    Aluminum phosphate, however, is unsuitable for use as a high temperature ceramic material because it undergoes polymorphic transformations (quartz-type, tridymite and cristobalite) with corresponding large molar volume changes. Thus, it would be desirable to provide a synthetic form of aluminum phosphate which is metastable and remains substantially amorphous at increasing temperatures, or during heating and cooling cycles. Another desirable property would be to provide an aluminum phosphate composition having a low oxygen diffusivity at high temperatures or in harsh environments, in order to provide oxidation protection and corrosion resistance to substrates such as metals and ceramics.
  • [0005]
    U.S. Pat. No. 6,036,762 describes a precursor solution for producing metal phosphates using metal salts and phosphorous pentoxide dissolved in a common organic solvent. The preparation of aluminum phosphate is described.
  • SUMMARY OF THE INVENTION
  • [0006]
    The present invention contemplates a new class of aluminum phosphate compounds which are formulated to contain an excess amount of aluminum species in the composition, that is, the aluminum atoms exceed the number found in stoichiometric aluminum phosphate, or the number of phosphorous atoms. The composition may be made by the solvent method described in the aforesaid U.S. Pat. No. 6,036,762, incorporated herein by references, with an excess of aluminum salt being incorporated into the mixture in comparison to the phosphorous, with the excess being more than one percent and preferably greater than five percent. The solution is dried and then annealed, for example, at temperatures of 800 C. or greater, in air until the composition attains a dark color. The annealing step is believed to cause a transformation of the molecular structure, with the final product being more than 50% amorphous in content, and with the amorphous nature being sustained for long periods at temperatures up to 1400 C. or greater without oxidation. Depending on the synthetic procedure and presence of other additives, the composition may also contain small crystalline inclusions which can impact other desirable properties, such as toughness and optical activity. The composition exhibits other desirable properties, such as very low oxygen diffusivity, low thermal conductivity and high emissivity. Thus, a particularly suitable application is to use the composition as a coating on a substrate to minimize oxidation of the substrate at high temperatures.
  • [0007]
    The initially formed organic solution can be converted into any desired form. For example, the solution may be applied to a metal, ceramic or other substrate, such as ceramic composites and then annealed, or it may be converted into any desired shape, such as fibers or filaments or in any other desired molded form, or may be converted into a powder for application to substrates using a suitable spray technique. Various particular potential end use applications will be listed herein.
  • DETAILED DESCRIPTION
  • [0008]
    The preferred method for making the composition of the present invention is described in U.S. Pat. No. 6,036,762. An aluminum salt, such as aluminum nitrate having water of hydration is dissolved in an organic solvent, preferably an alcohol such as ethanol. A quantity of phosphorus pentoxide (P2O5) is dissolved in a separate container in the same solvent. The molar ratio of Al to P in the Al solution is greater than a one-to-one ratio with phosphorous and is preferably at least 1% and most preferably at least 5% greater. The upper practical limit of excess aluminum has not been determined, but compositions containing ten times excess aluminum have been prepared, and a 1.5 to 3.5 excess molar ratio appears to be most promising in terms of retaining the amorphous content at high temperatures.
  • [0009]
    The two solutions are mixed together. There is a controlled reactivity between the alcohol and (P2O5) in which phosphate esters are produced. With sufficient aging, the solution becomes sufficiently polymeric to provide good film forming properties.
  • [0010]
    It is contemplated that additional metals or metallic compounds could be either dissolved in the precursor or added as nano-sized crystals, such as calcium tungstate, erbium phosphate or other phosphates.
  • [0011]
    The precursor liquid can be coated onto a suitable substrate, such as a metal or alloy or ceramic or mixed with particles of ceramic material requiring oxidation and/or corrosion protection. In addition, the liquid can be drawn into fibers, placed in a mold, or used alone.
  • [0012]
    The liquid is converted into solid, stable form by annealing or pyrolysis in air. Typically, this requires heating to temperatures normally above 750 C. for a period of time, for example, for one hour, or at higher temperatures. Complete annealing becomes evident when the composition assumes a black or dark grey color.
  • [0013]
    It is believed that the decomposition behavior of organic based precursor at least partially controls the molecular events leading to a unique inorganic compound. The material contains in excess of 50% of an amorphous compound and may also contain nanocrystals. The material remains amorphous and metastable when heated to temperatures from ambient and up to 1400 C. or greater for extended period of time. It is believed that increased storage time of the precursor solution increases amorphous content.
  • [0014]
    Based on initial observations, it has been found that the amorphous content of the annealed composition of the present invention may be influenced by at least two factors, namely, the chemistry of the substrate to which the precursor solution.
  • [0015]
    As an example of the first effect, coatings of solution on fibrous substrates appear to be substantially completely amorphous even after annealing at 1200 C. for two hours. This has been initially confirmed by TEM analysis of solution coated and annealed on mallite-alumina fibers with an overcoat of alumina. On the other hand, powders synthesized in alumina crucibles at 1000 C. for 30 minutes contain a significant fraction of AIPO4 crystallites.
  • [0016]
    Aging of the precursor solution appears to have a significant effect on the phosphorous environment in the precursor as well as the amorphous content in the pyrolyzed product. Storage of the solution in a refrigerator for a period of up to two years or at room temperature for over one month tends to yield more pure amorphous content.
  • [0017]
    Of the samples tested, the material had a low density in the order of 1.99 to 2.25 g/cm3, in comparison with 3.96 g/cm3 for alumina. The composition exhibits low oxygen diffusivity; in samples conducted containing 75% excess aluminum the chemical diffusivity was in the order of 110−12 cm2/sec at 1400 C. The material also exhibits a high emissivity, potentially useful in thermal protection systems, such as space applications. Thermal conducivity has been measured at 1 to 1.5 W/m.k. The material is inert in various harsh environments, and has a non-wetting character to most materials, including molten aluminum and solid oxides. Coatings as thin as 0.25 microns are capable of protecting metallic and other surfaces.
  • [0018]
    Potential applications include thermal, corrosion and oxidation protection for metals and metal/ceramic-based thermal protection systems, high emissivity coatings, interface coatings for silicon carbide and oxide based ceramic matrix systems, environmental barrier coatings for metal and ceramic based systems, fibers for composites and fiber lasers, corrosion protection in molten metal processing, monolithic materials for thermal insulation, catalyst supports, as well as many others. The material may also possess a low dielectric constant, making it useful in Radome applications.
  • EXAMPLE I
  • [0019]
    To make 850 ml of 75.46 g/L a precursor solution to synthesize the amorphous aluminum phosphate material with a 1.75:1 Al:P ratio (0.375 molar excess Al2O3), 408.90 g Al (NO3)39H2O was dissolved in 382 ml ethanol to make 500 ml of solution. In a separate container in an inert atmosphere, 25.23 g P2O5 was dissolved in 300 ml ethanol. After the P2O5 is dissolved, the two solutions were mixed together and allowed to stir for several minutes. After the solution was thoroughly mixed, it was placed in a large container in an oven at 150C for one or more hours. After the resulting powder is completely dried, it was annealed in air to 1100 C. for one hour to form amorphous aluminum phosphate powder with 0.75 moles excess aluminum per mole aluminum phosphate.
  • EXAMPLE II
  • [0020]
    To form an oxidation resistant amorphous aluminum phosphate coating on a rectangular coupon of 304 stainless steel, the piece was dipped in the precursor solution of Example 1, diluted to a certain concentration and removed. The sample was dried in flowing air to remove the solvent. The sample was dried more thoroughly in an oven at 65 C. The piece was annealed in air to 1000 C. (at a ramp rate of 10C/minute) for 100 hours and cooled to room temperature at 10C/minute, along with an uncoated piece of 304 stainless steel of the same size and shape. The weight of each uncoated piece was measured prior to anneal. The weight was measured again after coating and anneal. The amorphous aluminum phosphate coated piece showed remarkably less weight gain. The weight gain data is given in the table below.
    TABLE 1
    Weiqht gain of uncoated, and C-1.75 coated stainless
    steel coupons annealed to 1000 C. in air. The weight
    gain is related to the weight of the annealed, uncoated
    coupon.
    Original Weight after Weight % Weight
    Sample weight (g) anneal (g) gained (g) gained
    Amorphous 20.3727 20.4207 0.048 0.24%
    aluminum
    phosphate
    (incl. coating)
    Uncoated 20.6303 22.4123 1.782 8.64%
  • EXAMPLE III
  • [0021]
    To form an amorphous aluminum phosphate coating on a solid substrate by plasma spray, amorphous aluminum phosphate-powder made in Example I is milled to a small and uniform size (around 20 microns) in a ball mill. The powder is then deposited using the small particle plasma spray process (U.S. Pat. No. 5,744,777).
  • EXAMPLE IV
  • [0022]
    Bulk amorphous aluminum phosphate is formed by electroconsolidation (U.S. Pat. No. 5,348,694). Finely ground amorphous aluminum phosphate powder was mixed with a binder (1 wt % PEG 8000 and 2 wt % 20M) and then pressed into a pellet. This pellet was pre-sintered at 1200 C. for five hours. The pellet was then electroconsolidated at 1300 C. for 30 minutes. The final pellet had a density of 1.99 g/cm3.
  • EXAMPLE V
  • [0023]
    Amorphous aluminum phosphate fibers were made from viscous polymer formed from the precursor solution of Example I. The AlPO4 solution was dried at 50-65C until 40-30% of the weight is retained. The residue had a mainly clear, glassy appearance with a high viscosity. Green fibers were pulled with a needle, inserted into the viscous residue and quickly removed. The fibers were dried immediately in flowing air at 650 F. The green fibers were then annealed to at least 1000 C. to form amorphous aluminum phosphate fibers.
  • EXAMPLE VI
  • [0024]
    Rare earth and other metal ions can be incorporated into the amorphous aluminum phosphate structure. An erbium doped precursor solution with 0.75 moles excess metal (aluminum and erbium) of which 5 mol % is erbium was synthesized in a manner similar to the amorphous aluminum phosphate solution of Example I. 31.2 g Al (NO3)39H2O was dissolved in 75 ml ethanol. In an inert atmosphere glove box in a separate container, 1.94 g Er(NO3)3 5H2O was dissolved in 20 ml ethanol. The erbium nitrate solution was added to the aluminum nitrate solution and left to stir for several minutes. In a separate container in an inert atmosphere glove box, 3.55 g P2O5 was dissolved in 40 mL ethanol. After the P2O5 was dissolved, the aluminum nitrate and erbium solution was added and left to stir for several minutes. The solution was then dried at 150 C. for about an hour and annealed to 1000 C. for one hour. X-ray diffraction of this material annealed to 1000 C. for one hour confirms the amorphous structure, with no erbium phosphate crystalline.
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2165819 *May 24, 1935Jul 11, 1939Steatit Magnesia AgElectric insulator and method of making same
US3176933 *May 3, 1963Apr 6, 1965Jr Dewey L ClemmonsThermal control of space vehicles
US3323889 *Mar 27, 1964Jun 6, 1967Owens Illinois IncMethod for increasing scratch resistance of a glass surface with a pyrolyzing treatment and a coating of an olefin polymer
US3450574 *Nov 14, 1966Jun 17, 1969Northern Electric CoMethod of coating refractory wares with magnesia
US3516811 *Oct 4, 1966Jun 23, 1970Indian Head IncMethod of and apparatus for coating glassware retaining its heat of formation
US3694299 *May 27, 1971Sep 26, 1972Ppg Industries IncMultiple glazed unit and method of manufacture
US3711322 *Jul 6, 1970Jan 16, 1973Nippon Sheet Glass Co LtdGlass having semitransparent colored coating
US3793105 *Dec 10, 1971Feb 19, 1974Ici LtdGlass laminates
US3847583 *May 2, 1973Nov 12, 1974Jenaer Glaswerk Schott & GenProcess for the manufacture of multi-component substances
US3870737 *Jul 25, 1972Mar 11, 1975Ici LtdPhosphates
US3926103 *Dec 6, 1973Dec 16, 1975American Glass ResRecovery system for spraying apparatus
US3943231 *Jun 18, 1973Mar 9, 1976Hoechst AktiengesellschaftProcess for making condensed aluminum phosphates
US3960592 *Oct 21, 1974Jun 1, 1976Imperial Chemical Industries LimitedPhosphates
US3984591 *Dec 19, 1973Oct 5, 1976Glaverbel-Mecaniver S.A.Process for forming a metallic oxide coating
US4005172 *Oct 21, 1974Jan 25, 1977Imperial Chemical Industries LimitedSolid complex phosphate of aluminum
US4005232 *Feb 25, 1975Jan 25, 1977Imperial Chemical Industries LimitedCoatings of metal phosphates on metals or glass
US4008299 *Oct 21, 1974Feb 15, 1977James Derek BirchallMethod of making a fibre of aluminium phosphate
US4289863 *Apr 4, 1980Sep 15, 1981Gulf Oil CorporationEthylene polymerization process
US4551652 *Jun 1, 1982Nov 5, 1985U.S. Philips CorporationDisplay screen having aluminum phosphate barrier layer and method of manufacture
US5030431 *Jun 7, 1989Jul 9, 1991W. R. Grace & Co.-Conn.High pore volume and pore diameter aluminum phosphate
US5146743 *Oct 25, 1990Sep 15, 1992Emitec Gesellschaft Fur Emissionstechnologie MbhProcess for accelerating the response of an exhaust gas catalyst, and apparatus and electrically heatable carrier bodies for performing the method
US5208069 *Oct 28, 1991May 4, 1993Istituto Guido Donegani S.P.A.Method for passivating the inner surface by deposition of a ceramic coating of an apparatus subject to coking, apparatus prepared thereby, and method of utilizing apparatus prepared thereby
US5223336 *Sep 30, 1991Jun 29, 1993Monsanto CompanyGlass fiber insulation
US5292701 *May 10, 1991Mar 8, 1994W. R. Grace & Co.-Conn.High pore volume and pore diameter aluminum phosphate and method of making the same
US5348694 *Mar 17, 1993Sep 20, 1994Superior Graphite Co.Method for electroconsolidation of a preformed particulate workpiece
US5411711 *Feb 1, 1993May 2, 1995Emitec Gesellschaft Fuer Emissionstechnologie MbhElectrically heatable honeycomb body, in particular catalyst carrier body, with internal support structures
US5496529 *Mar 17, 1994Mar 5, 1996Rhone-Poulenc ChimieAluminum phosphates and binder compositions/ceramic materials comprised thereof
US5552361 *Nov 4, 1993Sep 3, 1996W. R. Grace & Co.-Conn.Aluminum phosphate composition with high pore volume and large pore diameter, process for its production and use thereof
US5665463 *Jan 26, 1996Sep 9, 1997Rockwell International CorporationFibrous composites including monazites and xenotimes
US5698758 *May 22, 1995Dec 16, 1997W. R. Grace & Co.-Conn.Aluminum phosphate composition with high pore volume and large pore diameter, process for its production and use thereof
US5707442 *Nov 15, 1995Jan 13, 1998Rhone-Poulenc ChimieAluminum phosphates and binder compositions/ceramic materials comprised thereof
US5744777 *May 31, 1996Apr 28, 1998Northwestern UniversitySmall particle plasma spray apparatus, method and coated article
US5856027 *Mar 31, 1997Jan 5, 1999Howmet Research CorporationThermal barrier coating system with intermediate phase bondcoat
US6022513 *Oct 31, 1996Feb 8, 2000Pecoraro; Theresa A.Aluminophosphates and their method of preparation
US6036762 *Jan 5, 1999Mar 14, 2000Sambasivan; SankarAlcohol-based precursor solutions for producing metal phosphate materials and coating
US6140410 *Jul 13, 1998Oct 31, 2000E. I. Du Pont De Nemours And CompanyFluoropolymer composition
US6162498 *Apr 9, 1998Dec 19, 2000Institut Fur Neue Materialien Gemeinnutzige GmbhMethod for providing a metal surface with a vitreous layer
US6221955 *Dec 9, 1998Apr 24, 2001Dekro Paints (Proprietary) LimitedPolyurethane resins
US6312819 *May 26, 1999Nov 6, 2001The Regents Of The University Of CaliforniaOriented conductive oxide electrodes on SiO2/Si and glass
US6379746 *Jan 31, 2000Apr 30, 2002Corning IncorporatedMethod for temporarily protecting glass articles
US6383989 *May 29, 2001May 7, 2002The Regents Of The University Of CaliforniaArchitecture for high critical current superconducting tapes
US6461415 *Aug 23, 2000Oct 8, 2002Applied Thin Films, Inc.High temperature amorphous composition based on aluminum phosphate
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US6884527Jul 21, 2003Apr 26, 2005The Regents Of The University Of CaliforniaBiaxially textured composite substrates
US7727497 *Aug 9, 2006Jun 1, 2010Hoya CorporationMethod for producing particles, particles, and sintered body
US7887917 *Jun 30, 2006Feb 15, 2011Unifrax I LlcInorganic fiber
US8551897Jan 24, 2011Oct 8, 2013Unifrax I LlcInorganic fiber
US9005355Oct 15, 2010Apr 14, 2015Bunge Amorphic Solutions LlcCoating compositions with anticorrosion properties
US9023145Feb 10, 2009May 5, 2015Bunge Amorphic Solutions LlcAluminum phosphate or polyphosphate compositions
US9078445Apr 16, 2012Jul 14, 2015Bunge Amorphic Solutions LlcAntimicrobial chemical compositions
US9155311Mar 15, 2013Oct 13, 2015Bunge Amorphic Solutions LlcAntimicrobial chemical compositions
US9169120Feb 12, 2010Oct 27, 2015Bunge Amorphic Solutions LlcAluminum phosphate or polyphosphate particles for use as pigments in paints and method of making same
US9187653Jul 27, 2010Nov 17, 2015Bunge Amorphic Solutions LlcAluminum phosphate, polyphosphate, and metaphosphate particles and their use as pigments in paints and method of making same
US20070020454 *Jun 30, 2006Jan 25, 2007Unifrax CorporationInorganic fiber
US20070053814 *Aug 9, 2006Mar 8, 2007Pentax CorporationMethod for producing particles, particles, and sintered body
US20070057391 *Aug 3, 2006Mar 15, 2007Den-Mat CorporationMethod for forming ceramic ingot
US20070298277 *Jun 21, 2006Dec 27, 2007General Electric CompanyMetal phosphate coating for oxidation resistance
US20110118102 *May 19, 2011Zoitos Bruce KInorganic fiber
CN102500533A *Nov 3, 2011Jun 20, 2012昆明理工大学Method for coating corrosion-resistant paint on surface of steel
CN102500533BNov 3, 2011Jul 2, 2014昆明理工大学Method for coating corrosion-resistant paint on surface of steel
Classifications
U.S. Classification428/702, 501/153, 252/397, 252/387, 427/427, 423/305, 106/14.05, 427/443.2, 106/14.21, 427/435, 501/95.1, 428/704, 501/127
International ClassificationC01B25/36, C23C4/12, C09D5/08, C23C30/00, C23C4/10, C23C2/04, C09D1/00, C09D7/12, C04B41/45, C23C22/74, C04B35/447, C03C17/02, C03C10/00, C03C3/17, C04B33/14, C04B35/628
Cooperative ClassificationC09D7/1216, C04B41/009, C04B35/63488, C03C3/17, C08K7/04, C23C2/04, C03C10/00, C04B2235/77, C04B35/62268, C01B25/36, C04B2235/3224, C04B2235/3217, C23C22/74, C04B2235/3418, C04B2235/721, C03C17/02, C04B2235/5228, C04B33/30, C04B2235/3227, C04B2235/44, C04B2235/402, C04B35/62881, C08K3/32, C04B35/6303, C04B2235/9607, C04B33/14, C04B35/62655, C04B35/62873, C04B33/36, C04B41/4584, C23C4/134, C04B35/447, C23C30/00, C04B2235/5436, C04B2235/3232, C08K3/22, C23C4/11
European ClassificationC04B41/00V, C23C4/10B, C23C4/12L, C23C30/00, C23C2/04, C01B25/36, C03C10/00, C23C22/74, C03C17/02, C04B41/45P, C04B35/447, C09D7/12D2, C03C3/17, C04B33/30, C04B33/14, C04B35/63B, C04B33/36, C04B35/634D14, C04B35/628F8R, C04B35/628F14, C04B35/626A16F, C04B35/622F2P
Legal Events
DateCodeEventDescription
Jan 13, 2003ASAssignment
Owner name: APPLIED THIN FILMS, INC., ILLINOIS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SAMBASIVAN, SANKAR;STEINER, KIMBERLY A.;REEL/FRAME:013656/0951
Effective date: 20021213