CA2246870C - Method for producing engineered materials from salt/polymer aqueous solutions - Google Patents
Method for producing engineered materials from salt/polymer aqueous solutions Download PDFInfo
- Publication number
- CA2246870C CA2246870C CA 2246870 CA2246870A CA2246870C CA 2246870 C CA2246870 C CA 2246870C CA 2246870 CA2246870 CA 2246870 CA 2246870 A CA2246870 A CA 2246870A CA 2246870 C CA2246870 C CA 2246870C
- Authority
- CA
- Canada
- Prior art keywords
- metal cation
- accordance
- porous preform
- structural mass
- heating
- Prior art date
- Legal status (The legal status 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 status listed.)
- Expired - Fee Related
Links
- 229920000642 polymer Polymers 0.000 title claims abstract description 42
- 239000000463 material Substances 0.000 title claims abstract description 24
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 8
- 150000003839 salts Chemical class 0.000 title claims abstract description 7
- 239000007864 aqueous solution Substances 0.000 title claims abstract description 6
- 229910052751 metal Inorganic materials 0.000 claims abstract description 56
- 239000002184 metal Substances 0.000 claims abstract description 56
- 150000001768 cations Chemical class 0.000 claims abstract description 36
- 239000002243 precursor Substances 0.000 claims abstract description 18
- -1 cation salt Chemical class 0.000 claims abstract description 12
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 5
- 238000000034 method Methods 0.000 claims description 42
- 239000000243 solution Substances 0.000 claims description 25
- 239000000919 ceramic Substances 0.000 claims description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- 238000010438 heat treatment Methods 0.000 claims description 16
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 13
- 239000002202 Polyethylene glycol Substances 0.000 claims description 12
- 229920001223 polyethylene glycol Polymers 0.000 claims description 12
- 239000008187 granular material Substances 0.000 claims description 11
- 239000000203 mixture Substances 0.000 claims description 10
- 239000011368 organic material Substances 0.000 claims description 10
- 239000000725 suspension Substances 0.000 claims description 8
- 229920006395 saturated elastomer Polymers 0.000 claims description 7
- 239000000758 substrate Substances 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 4
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical class CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 3
- 150000001242 acetic acid derivatives Chemical class 0.000 claims description 3
- 229910052768 actinide Inorganic materials 0.000 claims description 3
- 150000001255 actinides Chemical class 0.000 claims description 3
- 150000001720 carbohydrates Chemical class 0.000 claims description 3
- 235000014633 carbohydrates Nutrition 0.000 claims description 3
- 150000004649 carbonic acid derivatives Chemical class 0.000 claims description 3
- 150000003841 chloride salts Chemical class 0.000 claims description 3
- 229920000159 gelatin Polymers 0.000 claims description 3
- 150000004679 hydroxides Chemical class 0.000 claims description 3
- 229910052747 lanthanoid Inorganic materials 0.000 claims description 3
- 150000002602 lanthanoids Chemical class 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 150000002823 nitrates Chemical class 0.000 claims description 3
- 150000003891 oxalate salts Chemical class 0.000 claims description 3
- 239000000123 paper Substances 0.000 claims description 3
- 230000000737 periodic effect Effects 0.000 claims description 3
- 108090000623 proteins and genes Proteins 0.000 claims description 3
- 102000004169 proteins and genes Human genes 0.000 claims description 3
- 239000002131 composite material Substances 0.000 claims description 2
- 150000001875 compounds Chemical class 0.000 claims description 2
- 239000004744 fabric Substances 0.000 claims description 2
- 239000006260 foam Substances 0.000 claims description 2
- 108010010803 Gelatin Proteins 0.000 claims 2
- 235000021120 animal protein Nutrition 0.000 claims 2
- 150000002118 epoxides Chemical class 0.000 claims 2
- 235000019322 gelatine Nutrition 0.000 claims 2
- 235000011852 gelatine desserts Nutrition 0.000 claims 2
- 235000018102 proteins Nutrition 0.000 claims 2
- 230000001131 transforming effect Effects 0.000 claims 1
- 239000000843 powder Substances 0.000 description 9
- 239000010408 film Substances 0.000 description 8
- 239000011148 porous material Substances 0.000 description 7
- 239000000126 substance Substances 0.000 description 7
- 239000000047 product Substances 0.000 description 6
- 239000010409 thin film Substances 0.000 description 6
- 239000012266 salt solution Substances 0.000 description 5
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- 239000002594 sorbent Substances 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- 239000007795 chemical reaction product Substances 0.000 description 3
- 239000011521 glass Substances 0.000 description 3
- 229920001477 hydrophilic polymer Polymers 0.000 description 3
- 239000012528 membrane Substances 0.000 description 3
- 229920000620 organic polymer Polymers 0.000 description 3
- 229910002651 NO3 Inorganic materials 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 239000004931 filters and membranes Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000012263 liquid product Substances 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 2
- 239000000049 pigment Substances 0.000 description 2
- 229920002635 polyurethane Polymers 0.000 description 2
- 239000004814 polyurethane Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000003825 pressing Methods 0.000 description 2
- 239000000376 reactant Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- BNGXYYYYKUGPPF-UHFFFAOYSA-M (3-methylphenyl)methyl-triphenylphosphanium;chloride Chemical compound [Cl-].CC1=CC=CC(C[P+](C=2C=CC=CC=2)(C=2C=CC=CC=2)C=2C=CC=CC=2)=C1 BNGXYYYYKUGPPF-UHFFFAOYSA-M 0.000 description 1
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 description 1
- IAYPIBMASNFSPL-UHFFFAOYSA-N Ethylene oxide Chemical compound C1CO1 IAYPIBMASNFSPL-UHFFFAOYSA-N 0.000 description 1
- 229910000608 Fe(NO3)3.9H2O Inorganic materials 0.000 description 1
- WHNWPMSKXPGLAX-UHFFFAOYSA-N N-Vinyl-2-pyrrolidone Chemical compound C=CN1CCCC1=O WHNWPMSKXPGLAX-UHFFFAOYSA-N 0.000 description 1
- 241000282320 Panthera leo Species 0.000 description 1
- 229920002472 Starch Polymers 0.000 description 1
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 description 1
- 229930006000 Sucrose Natural products 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- JLDSOYXADOWAKB-UHFFFAOYSA-N aluminium nitrate Chemical compound [Al+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O JLDSOYXADOWAKB-UHFFFAOYSA-N 0.000 description 1
- 150000001719 carbohydrate derivatives Chemical class 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 239000001913 cellulose Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000003517 fume Substances 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 230000036571 hydration Effects 0.000 description 1
- 238000006703 hydration reaction Methods 0.000 description 1
- 238000010335 hydrothermal treatment Methods 0.000 description 1
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical class [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- GWUSZQUVEVMBPI-UHFFFAOYSA-N nimetazepam Chemical compound N=1CC(=O)N(C)C2=CC=C([N+]([O-])=O)C=C2C=1C1=CC=CC=C1 GWUSZQUVEVMBPI-UHFFFAOYSA-N 0.000 description 1
- 239000006259 organic additive Substances 0.000 description 1
- 150000002924 oxiranes Chemical class 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 235000019698 starch Nutrition 0.000 description 1
- 239000005720 sucrose Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
Landscapes
- Processes Of Treating Macromolecular Substances (AREA)
- Oxygen, Ozone, And Oxides In General (AREA)
Abstract
A method for producing engineered materials from salt/polymer aqueous solutions in which an aqueous continuous phase having at least one metal cation salt is mixed with a hydrophilic organic polymeric disperse phase so as to form a metal cation/polymer gel. The metal cation/polymer gel is then treated to form a structural mass precursor, which structural mass precursor is heated, resulting in formation of a structural mass having predetermined characteristics based upon the intended application of the structural mass.
Description
BACKGROUND OF THE INVENTION
Field of the Invention This invention relates to a low-cost method for the production of engineered materials from salt/polymer aqueous solutions by which method engineered structures having a broad range of features and properties can be prepared, which features and properties can be preset for a wide range of applications. For example, the method of this invention is suitable for producing continuous thin films which can be utilized as surface protection against harsh environments (temperature, chemical, friction and grinding, etc.), as an electrochemical component, such as for solid oxide fuel cells and electroceramic membranes, porous filters and membranes, and as a surface with desired optical or decorative properties. The method of this invention may also be used to produce spherical granules of polycrystalline materials having good flowability and packing properties, and which are suitable for use as pigments, sorbents, catalysts, or as powders for efficient pressing and sintpring into dense materials. The method of this invention may also be used to prepare materials having an engineered pore structure, for example porous ceramics having wide applications as filters, membranes, and chemical sorbents or reactants.
High technology ceramics are known for possessing a combination of good thermal, chemical, mechanical and electronic properties, making them unique for certain technical applications. Their usefulness, however, depends upon the manner in which they are produced, including the characteristics of the ceramic powders used as starting powders which are sintered to produce the ceramic product. In addition, methods for producing such high technology ceramics are generally of high cost due, in part, to the expense and difficulty associated with preparing suitable ceramic powders in large quantities.
SUMMARY OF THE INVENTION
Accordingly, it is one object of this invention to provide a method for producing engineered materials, including thin films, spherical granules, and porous ceramics, which is considerably less expensive than conventional methods.
It is another object of this invention to provide a method for producing engineered materials, including high technology ceramics, which elimin~tes the need for producing ceramic powders used as starting powders.
These and other objects of this invention are achieved by a method for producing engineered materials from salt/polymer aqueous solutions in which an aqueous continuous phase comprising at least one metal cation salt is mixed with a hydrophilic organic polymeric disperse phase, resulting in formation of a metal cation/polymer gel. The metal cation/polymer gel is then processed in a manner which produces a structural mass precursor. The structural mass precursor is then heated, forming a structural mass having predetermined characteristics based upon the intended application or applications of the structural mass. Structural masses which can be produced in accordance with the method of this invention include, but are not limited to, thin films, spherical granules, and porous ceramics.
Thin films produced in accordance with the method of this invention can be used for surface protection against harsh environments, as electrochemical components, as porous filters and membranes, and as a surface having desired optical or decorative properties. Spherical granules produced in accordance with the method of this invention may be used as pigments, sorbents, catalysts, or as powders for efficient pressing and sintering into dense materials. By the term "spherical granules," we mean polycrystalline structures having a generally spherical shape.
Porous ceramics produced in accordance with the method of this invention may be used as filters, membranes, and chemical sorbents or reactants.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features and objects of this invention will be better understood from the following detailed description taken in conjunction with the drawings wherein:
Fig. 1 is an SEM picture of a fractured cross section of a film coated glass showing a thin iron oxide film of uniform thickness produced in accordance with one embodiment of the method of this invention; and Fig. 2 is an SEM picture of a dried material of spherical granules 2-3 microns in diameter of aluminum oxide produced in accordance with one embodiment of the method of this invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
My earlier filed U.S. patent application, Serial No. 08/406,173 teaches the pl~a~lion of fine grained high surface area powders starting with an aqueous salt solution with a hydrophilic organic additive that forms a gelatinous intermediate liquid product which is then dried and calcined to form the powder.
The method of the present invention provides an alternative treatment of the gelatinous intermediate liquid product to produce materials with structures and properties which can be engineered for a wide range of applications.
In accordance with each embodiment of the method of this invention, an aqueous continuous phase comprising at least one metal cation salt is mixed with a hydrophilic organic polymeric disperse phase, resulting in formation of a metal cation/polymer gel. The metal cation/polymer gel is then treated so as to produce a structural mass precursor of the structural mass end product, which structural mass precursor is then heated to form the end product structural mass having characteristics predetermined based upon the specific application of the end product structural mass.
By the term "gel" as used throughout the specification and claims, I
mean a colloid in which a disperse phase is combined with a continuous phase to produce a viscous gel-like product. In the gel formed in accordance with the method of this invention, the disperse or colloidal phase is the hydrophilic organic polymer and the continuous phase is water. The metal cation sait is dissolved in the water. When the hydrophilic organic polymer is added to the aqueous metal salt solution, a gel is formed by virtue of the gelling property of the polymer. In this process, the hydrophilic organic polymer absorbs the liquid onto its structure due to chemical affinity. The amount and nature of the water absorbed depends on the chemical composition of the polymer. The hydrophilic absorption of the water causes the polymer to swell. This action is distinguishable from a sponge which, for example, absorbs water due to capillarity, although it may also absorb water by chemical absorption as in the method of this invention.
I have determined that hydrophilic organic materials serve as good media for uniformly absorbing the metal ions of aqueous soluble salts. Hydrophilic polymers, such as polyethylene glycol and some polyurethanes, have high capacities for ~ ing water. When a hydrophilic polymer is added to an aqueous metal salt solution, it swells as it absorbs the solution into its structure. The product is a gel with the metal salt solution "frozen" within the dispersed polymeric network. If the metal salt solution is dilute and the polymer added is not enough to gel the mixture, excess water may be dried off until the mixture is thick enough to form a gel. All hydrophilic organic material such as carbohydrates (sucrose, starches and cellulose) and carbohydrate derivatives; hydrophilic homopolymer and copolymers of ethylene oxide, 2-hydroxethylenemethacrylate, hydroxyalkyl-methacrylates, hydroxyalkylacrylates, acrylamide, and n-vinylpyrrolidone, hydrophilic polymer such as polyurethanes, polyurethane-acrylic, and polyurethane-methacrylic copolymers and interpenetrating polymer networks, and proteins derived from animal-protein-gelatins, are suitable for use in the method of this invention. In accordance with a particularly preferred embodiment, said organic material is polyethylene glycol.
Metal cation salts suitable for use in accordance with the method of this invention are selected from the group consisting of chlorides, carbonates, hydroxides, isopropoxides, nitrates, acetates, epoxides, oxalates, and mi~Lules thereof. Metal cations suitable for use in accordance with the method of this invention are selected from the group consisting of at least one metal from Group IA, IIA, IIIA, IVA, VA, VIA, IB, IIB, IIIB, IVB, VB, VIB, VIIB, and VIII of the Periodic Table of the Elements, lanthanides, actinides, and mixtures thereof.
Thin continuous films are produced in accordance with one embodiment of the method of this invention by applying a metal cation/polymer gel formed by mixing an aqueous continuous phase comprising at least one metal cation salt with a hydrophilic organic polymeric disperse phase to a substrate surface, forming a continuous thin film thereon. Upon drying and heat treatment, the continuous thin film forms a continuous ceramic layer over the substrate surface.
EXAMPLE I
A hydrated ferric nitrate salt was dissolved in water to form a solution. Polyethylene glycol was also dissolved in the solution. The solution was stirred over a hot plate to thicken, thickening occurring as a result of evaporation of free water. If the solution is too thick, the resulting continuous film is also thick and flakes off the substrate surface after drying. I found that a solution containing 6.45 grams of polyethylene glycol, 13.49% Fe(NO3)3.9H20 with the balance being H20, was thin enough to form a continuous reddish brown film on a glass slide.
After heating to 500~C, the film remained continuous, transparent, and reddish brown. An SE~I picture of a fractured cross section of the film coated glass is shown in Fig. 1, in which can be seen a thin iron oxide film of substantially uniform thickness.
In accordance with another preferred embodiment of the method of this invention, the structural mass precursor formed from the metal cation/polymer gel is formed by placing the metal cation/polymer gel in a hydrothermal reaction vessel and increasing the pressure inside the hydrothermal reaction vessel by heating, thereby forming a colloidal suspension therein. The colloidal suspension is then removed from the hydrothermal reaction vessel and heated, resulting in formation of a plurality of substantially spherical granules.
EXAMPLE II
To produce spherical granules in accordance with one embodiment of the method of this invention, an aluminum nitrate salt was dissolved in water after which polyethylene glycol was dissolved therein. The clear solution, containing 10.7% Al(NO3)3.9H2O, 17.9% polyethylene glycol, and 71.4% water was contained in a Teflon~ cup that had a cover. This, in turn, was placed in a hydrothermal reaction vessel which was placed in an oven at 150~C for 20 hours.
During this treatment, pressure in the hydrothermal reaction vessel increased due to the vapors or gaseous products from the thermal process. At the end of the hydrothermal treatment, the solution remained clear, but a white colloidal suspension settled at the bottom of the reaction vessel. The white colloidal suspension was filtered out and dried at about 100~C. Fig. 2 is an SEM picture of the dried material and shows spherical granules 2-3 microns in diameter of aluminum oxide.
Porous ceramics are produced in accordance with one embodiment of this invention wherein the structural mass precursor is formed by dissolving the metal cation/polymer gel in water to form a metal cation/polymer solution. A
porous preform is immersed in the metal cation/polymer solution resulting in absorption of at least a portion of the metal cation/polymer solution into the porous preform. The saturated porous preform is then dried after which it is heated to a temperature suitable for burning out at least a portion of the porous preform, leaving behind a porous structure having a shape and porosity corresponding to the porous preform.
The preparation of porous bodies whose pore structures are replicas of the skeletal structures of porous preforms in accordance with this embodiment of this invention allows the preparation of a wide range of materials with pre-designed pore structures. Porous materials such as papers, fabrics, threads, foams or monoliths, whether natural or synthetic, having random or ordered structure, can all be replicated by impregn~ting them with the metal cation/polymer solution which is subsequently converted to an oxide phase. If the preform is organic, it can be burned off in air, creating a pore structure in the oxide product that is a replica of its skeletal structure. Some organic preforms may also be pyrolyzed, leaving a fibrous m~tt ri~l that may act as a reinforcement for the ceramic product.
In accordance with another embodiment, if the porous preform is a metal or ceramics, upon heat treatment, it may form a compound or a composite with the salt material in the liquid.
EXAMPLE III
A solution was prepared by dissolving 40 grams of Al(NO3)3.9H2O
in 25 grams of water. One gram of polyethylene glycol was dissolved in the solution. The solution was stirred over a hot plate during which it was allowed to thicken and fume. The combined weight reduced to just 30 grams, indicating that the aluminum salt had lost some of its water of hydration. Ten grams of water were added to the dried materials which dissolved the fumed solid to a clear solution again. The final solution, therefore, weighed 40 grams, and contained 0.107 moles of aluminum nitrate and 1 gram of polyethylene glycol. A Fisher brand filter paper, rated 7-790A, was saturated with this solution and allowed to dry to a tacky sheet by h~rl~ng it in air. The tacky, saturated sheet was placed on an alumina plate and heated in air at a rate of 2~C per minute up to a temperature of about 450~C. The material remained as a continuous sheet, mostly white, with brown specks. Under a microscope, the brown specks were determined to be fibers, presumably incompletely burned fibers of the filter material. The white material appeared as a continuous glassy phase with pores, which presumably were spaces originally occupied by the filter material that had burned off. There was no evidence of cracks in the resulting structure. The material was further treated by heating in air at a rate of about 2~C per minute to 900~C and held at this temperature for 5 hours. At the conclusion of this period, the sheet structure was retained, but had turned completely white. The pore openings, as well as its glassy appearance, also remained. The sheet structure was handleable, in spite of being only 7 mils thick with a density of 0.58 grams/cm3, or 15% of the theoretical density of alumina.
While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.
Field of the Invention This invention relates to a low-cost method for the production of engineered materials from salt/polymer aqueous solutions by which method engineered structures having a broad range of features and properties can be prepared, which features and properties can be preset for a wide range of applications. For example, the method of this invention is suitable for producing continuous thin films which can be utilized as surface protection against harsh environments (temperature, chemical, friction and grinding, etc.), as an electrochemical component, such as for solid oxide fuel cells and electroceramic membranes, porous filters and membranes, and as a surface with desired optical or decorative properties. The method of this invention may also be used to produce spherical granules of polycrystalline materials having good flowability and packing properties, and which are suitable for use as pigments, sorbents, catalysts, or as powders for efficient pressing and sintpring into dense materials. The method of this invention may also be used to prepare materials having an engineered pore structure, for example porous ceramics having wide applications as filters, membranes, and chemical sorbents or reactants.
High technology ceramics are known for possessing a combination of good thermal, chemical, mechanical and electronic properties, making them unique for certain technical applications. Their usefulness, however, depends upon the manner in which they are produced, including the characteristics of the ceramic powders used as starting powders which are sintered to produce the ceramic product. In addition, methods for producing such high technology ceramics are generally of high cost due, in part, to the expense and difficulty associated with preparing suitable ceramic powders in large quantities.
SUMMARY OF THE INVENTION
Accordingly, it is one object of this invention to provide a method for producing engineered materials, including thin films, spherical granules, and porous ceramics, which is considerably less expensive than conventional methods.
It is another object of this invention to provide a method for producing engineered materials, including high technology ceramics, which elimin~tes the need for producing ceramic powders used as starting powders.
These and other objects of this invention are achieved by a method for producing engineered materials from salt/polymer aqueous solutions in which an aqueous continuous phase comprising at least one metal cation salt is mixed with a hydrophilic organic polymeric disperse phase, resulting in formation of a metal cation/polymer gel. The metal cation/polymer gel is then processed in a manner which produces a structural mass precursor. The structural mass precursor is then heated, forming a structural mass having predetermined characteristics based upon the intended application or applications of the structural mass. Structural masses which can be produced in accordance with the method of this invention include, but are not limited to, thin films, spherical granules, and porous ceramics.
Thin films produced in accordance with the method of this invention can be used for surface protection against harsh environments, as electrochemical components, as porous filters and membranes, and as a surface having desired optical or decorative properties. Spherical granules produced in accordance with the method of this invention may be used as pigments, sorbents, catalysts, or as powders for efficient pressing and sintering into dense materials. By the term "spherical granules," we mean polycrystalline structures having a generally spherical shape.
Porous ceramics produced in accordance with the method of this invention may be used as filters, membranes, and chemical sorbents or reactants.
BRIEF DESCRIPTION OF THE DRAWINGS
The above-mentioned and other features and objects of this invention will be better understood from the following detailed description taken in conjunction with the drawings wherein:
Fig. 1 is an SEM picture of a fractured cross section of a film coated glass showing a thin iron oxide film of uniform thickness produced in accordance with one embodiment of the method of this invention; and Fig. 2 is an SEM picture of a dried material of spherical granules 2-3 microns in diameter of aluminum oxide produced in accordance with one embodiment of the method of this invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
My earlier filed U.S. patent application, Serial No. 08/406,173 teaches the pl~a~lion of fine grained high surface area powders starting with an aqueous salt solution with a hydrophilic organic additive that forms a gelatinous intermediate liquid product which is then dried and calcined to form the powder.
The method of the present invention provides an alternative treatment of the gelatinous intermediate liquid product to produce materials with structures and properties which can be engineered for a wide range of applications.
In accordance with each embodiment of the method of this invention, an aqueous continuous phase comprising at least one metal cation salt is mixed with a hydrophilic organic polymeric disperse phase, resulting in formation of a metal cation/polymer gel. The metal cation/polymer gel is then treated so as to produce a structural mass precursor of the structural mass end product, which structural mass precursor is then heated to form the end product structural mass having characteristics predetermined based upon the specific application of the end product structural mass.
By the term "gel" as used throughout the specification and claims, I
mean a colloid in which a disperse phase is combined with a continuous phase to produce a viscous gel-like product. In the gel formed in accordance with the method of this invention, the disperse or colloidal phase is the hydrophilic organic polymer and the continuous phase is water. The metal cation sait is dissolved in the water. When the hydrophilic organic polymer is added to the aqueous metal salt solution, a gel is formed by virtue of the gelling property of the polymer. In this process, the hydrophilic organic polymer absorbs the liquid onto its structure due to chemical affinity. The amount and nature of the water absorbed depends on the chemical composition of the polymer. The hydrophilic absorption of the water causes the polymer to swell. This action is distinguishable from a sponge which, for example, absorbs water due to capillarity, although it may also absorb water by chemical absorption as in the method of this invention.
I have determined that hydrophilic organic materials serve as good media for uniformly absorbing the metal ions of aqueous soluble salts. Hydrophilic polymers, such as polyethylene glycol and some polyurethanes, have high capacities for ~ ing water. When a hydrophilic polymer is added to an aqueous metal salt solution, it swells as it absorbs the solution into its structure. The product is a gel with the metal salt solution "frozen" within the dispersed polymeric network. If the metal salt solution is dilute and the polymer added is not enough to gel the mixture, excess water may be dried off until the mixture is thick enough to form a gel. All hydrophilic organic material such as carbohydrates (sucrose, starches and cellulose) and carbohydrate derivatives; hydrophilic homopolymer and copolymers of ethylene oxide, 2-hydroxethylenemethacrylate, hydroxyalkyl-methacrylates, hydroxyalkylacrylates, acrylamide, and n-vinylpyrrolidone, hydrophilic polymer such as polyurethanes, polyurethane-acrylic, and polyurethane-methacrylic copolymers and interpenetrating polymer networks, and proteins derived from animal-protein-gelatins, are suitable for use in the method of this invention. In accordance with a particularly preferred embodiment, said organic material is polyethylene glycol.
Metal cation salts suitable for use in accordance with the method of this invention are selected from the group consisting of chlorides, carbonates, hydroxides, isopropoxides, nitrates, acetates, epoxides, oxalates, and mi~Lules thereof. Metal cations suitable for use in accordance with the method of this invention are selected from the group consisting of at least one metal from Group IA, IIA, IIIA, IVA, VA, VIA, IB, IIB, IIIB, IVB, VB, VIB, VIIB, and VIII of the Periodic Table of the Elements, lanthanides, actinides, and mixtures thereof.
Thin continuous films are produced in accordance with one embodiment of the method of this invention by applying a metal cation/polymer gel formed by mixing an aqueous continuous phase comprising at least one metal cation salt with a hydrophilic organic polymeric disperse phase to a substrate surface, forming a continuous thin film thereon. Upon drying and heat treatment, the continuous thin film forms a continuous ceramic layer over the substrate surface.
EXAMPLE I
A hydrated ferric nitrate salt was dissolved in water to form a solution. Polyethylene glycol was also dissolved in the solution. The solution was stirred over a hot plate to thicken, thickening occurring as a result of evaporation of free water. If the solution is too thick, the resulting continuous film is also thick and flakes off the substrate surface after drying. I found that a solution containing 6.45 grams of polyethylene glycol, 13.49% Fe(NO3)3.9H20 with the balance being H20, was thin enough to form a continuous reddish brown film on a glass slide.
After heating to 500~C, the film remained continuous, transparent, and reddish brown. An SE~I picture of a fractured cross section of the film coated glass is shown in Fig. 1, in which can be seen a thin iron oxide film of substantially uniform thickness.
In accordance with another preferred embodiment of the method of this invention, the structural mass precursor formed from the metal cation/polymer gel is formed by placing the metal cation/polymer gel in a hydrothermal reaction vessel and increasing the pressure inside the hydrothermal reaction vessel by heating, thereby forming a colloidal suspension therein. The colloidal suspension is then removed from the hydrothermal reaction vessel and heated, resulting in formation of a plurality of substantially spherical granules.
EXAMPLE II
To produce spherical granules in accordance with one embodiment of the method of this invention, an aluminum nitrate salt was dissolved in water after which polyethylene glycol was dissolved therein. The clear solution, containing 10.7% Al(NO3)3.9H2O, 17.9% polyethylene glycol, and 71.4% water was contained in a Teflon~ cup that had a cover. This, in turn, was placed in a hydrothermal reaction vessel which was placed in an oven at 150~C for 20 hours.
During this treatment, pressure in the hydrothermal reaction vessel increased due to the vapors or gaseous products from the thermal process. At the end of the hydrothermal treatment, the solution remained clear, but a white colloidal suspension settled at the bottom of the reaction vessel. The white colloidal suspension was filtered out and dried at about 100~C. Fig. 2 is an SEM picture of the dried material and shows spherical granules 2-3 microns in diameter of aluminum oxide.
Porous ceramics are produced in accordance with one embodiment of this invention wherein the structural mass precursor is formed by dissolving the metal cation/polymer gel in water to form a metal cation/polymer solution. A
porous preform is immersed in the metal cation/polymer solution resulting in absorption of at least a portion of the metal cation/polymer solution into the porous preform. The saturated porous preform is then dried after which it is heated to a temperature suitable for burning out at least a portion of the porous preform, leaving behind a porous structure having a shape and porosity corresponding to the porous preform.
The preparation of porous bodies whose pore structures are replicas of the skeletal structures of porous preforms in accordance with this embodiment of this invention allows the preparation of a wide range of materials with pre-designed pore structures. Porous materials such as papers, fabrics, threads, foams or monoliths, whether natural or synthetic, having random or ordered structure, can all be replicated by impregn~ting them with the metal cation/polymer solution which is subsequently converted to an oxide phase. If the preform is organic, it can be burned off in air, creating a pore structure in the oxide product that is a replica of its skeletal structure. Some organic preforms may also be pyrolyzed, leaving a fibrous m~tt ri~l that may act as a reinforcement for the ceramic product.
In accordance with another embodiment, if the porous preform is a metal or ceramics, upon heat treatment, it may form a compound or a composite with the salt material in the liquid.
EXAMPLE III
A solution was prepared by dissolving 40 grams of Al(NO3)3.9H2O
in 25 grams of water. One gram of polyethylene glycol was dissolved in the solution. The solution was stirred over a hot plate during which it was allowed to thicken and fume. The combined weight reduced to just 30 grams, indicating that the aluminum salt had lost some of its water of hydration. Ten grams of water were added to the dried materials which dissolved the fumed solid to a clear solution again. The final solution, therefore, weighed 40 grams, and contained 0.107 moles of aluminum nitrate and 1 gram of polyethylene glycol. A Fisher brand filter paper, rated 7-790A, was saturated with this solution and allowed to dry to a tacky sheet by h~rl~ng it in air. The tacky, saturated sheet was placed on an alumina plate and heated in air at a rate of 2~C per minute up to a temperature of about 450~C. The material remained as a continuous sheet, mostly white, with brown specks. Under a microscope, the brown specks were determined to be fibers, presumably incompletely burned fibers of the filter material. The white material appeared as a continuous glassy phase with pores, which presumably were spaces originally occupied by the filter material that had burned off. There was no evidence of cracks in the resulting structure. The material was further treated by heating in air at a rate of about 2~C per minute to 900~C and held at this temperature for 5 hours. At the conclusion of this period, the sheet structure was retained, but had turned completely white. The pore openings, as well as its glassy appearance, also remained. The sheet structure was handleable, in spite of being only 7 mils thick with a density of 0.58 grams/cm3, or 15% of the theoretical density of alumina.
While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.
Claims (20)
1. A method for producing engineered materials from salt/polymer aqueous solutions comprising:
mixing an aqueous continuous phase comprising at least one metal cation salt with a hydrophilic organic polymeric disperse phase, forming a metal cation/polymer gel;
forming a structural mass precursor using said metal cation/polymer gel; and heating said structural mass precursor, forming a structural mass having predetermined characteristics.
mixing an aqueous continuous phase comprising at least one metal cation salt with a hydrophilic organic polymeric disperse phase, forming a metal cation/polymer gel;
forming a structural mass precursor using said metal cation/polymer gel; and heating said structural mass precursor, forming a structural mass having predetermined characteristics.
2. A method in accordance with Claim 1, wherein said hydrophilic organic polymeric disperse phase comprises an organic material selected from the group consisting of carbohydrates, polymers, proteins derived from animal protein gelatins, and mixtures thereof.
3. A method in accordance with Claim 1, wherein said at least one metal cation salt is selected from the group consisting of chlorides, carbonates, hydroxides, isopropoxides, nitrates, acetates, epoxides, oxalates, and mixtures thereof.
4. A method in accordance with Claim 1, wherein said metal cations are selected from the group consisting of at least one metal from Group 1A, 2A, 3A, 4A, 5A, 6A, 1B, 2B, 3B, 4B, 5B, 6B, 7B, and 8 of the Periodic Table, lanthanides, actinides, and mixtures thereof.
5. A method in accordance with Claim 1, wherein said structural mass precursor is formed by applying said metal cation/polymer gel to a substrate surface, forming a continuous film, and said continuous film is dried, whereby said heating of said dried continuous film forms a continuous ceramic layer on said substrate surface.
6. A method in accordance with Claim 1, wherein said structural mass precursor is formed by placing said metal cation/polymer gel in a hydrothermal reaction vessel and increasing a pressure inside said hydrothermal reaction vessel by heating said hydrothermal reaction vessel, forming a colloidal suspension which is removed from said hydrothermal reaction vessel, whereby said heating of said colloidal suspension forms a plurality of substantially spherical granules.
7. A method in accordance with Claim 1, wherein said structural mass precursor is formed by dissolving said metal cation/gel in water, forming a metal cation/polymer solution, immersing a porous preform in said metal cation/polymer solution, absorbing at least a portion of said metal cation/polymer solution into said porous preform, and drying said saturated porous preform, whereby said heating of said dried, saturated porous preform burns out at least a portion of said porous preform, leaving behind a porous structure having a shape and porosity corresponding to said porous preform.
8. A method in accordance with Claim 5, wherein said organic material is polyethylene glycol.
9. A method in accordance with Claim 6, wherein said organic material is polyethylene glycol.
10. A method in accordance with Claim 7, wherein said organic material is polyethylene glycol.
11. A method in accordance with Claim 7, wherein said porous preform is one of a metal and a ceramic whereby, upon heating, said one of said metal and said ceramic forms one of a compound and a composite with said at least one metal cation salt in said metal cation/polymer solution.
12. A method in accordance with Claim 7, wherein said porous preform is a material selected from the group consisting of paper, fabric, foam, and monoliths.
13. A method for producing engineered structural materials comprising the steps of:
mixing an aqueous solution comprising at least one metal cation salt with a hydrophilic organic material, forming a metal cation/polymer gel;
transforming said metal cation/polymer gel into a structural mass precursor form; and heating said structural mass precursor form of said metal cation/polymer gel, resulting in formation of a structural mass having predetermined characteristics.
mixing an aqueous solution comprising at least one metal cation salt with a hydrophilic organic material, forming a metal cation/polymer gel;
transforming said metal cation/polymer gel into a structural mass precursor form; and heating said structural mass precursor form of said metal cation/polymer gel, resulting in formation of a structural mass having predetermined characteristics.
14. A method in accordance with Claim 13, wherein said hydrophilic organic material is selected from the group consisting of carbohydrates, polymers, proteins derived from animal protein gelatins, and mixtures thereof.
15. A method in accordance with Claim 14, wherein said organic material is polyethylene glycol.
16. A method in accordance with Claim 13, wherein said at least one metal cation salt is selected from the group consisting of chlorides, carbonates, hydroxides, isopropoxides, nitrates, acetates, epoxides, oxalates, and mixtures thereof.
17. A method in accordance with Claim 13, wherein said metal cations are selected from the group consisting of at least one metal from Group 1A, 2A, 3A, 4A, 5A, 6A, 1B, 2B, 3B, 4B, 5B, 6B, 7B, and 8 of the Periodic Table, lanthanides, actinides, and mixtures thereof.
18. A method in accordance with Claim 13, wherein said structural mass precursor is formed by applying said metal cation/polymer gel to a substrate surface, forming a continuous film, and said continuous film is dried, whereby said heating of said dried continuous film forms a continuous ceramic layer on said substrate surface.
19. A method in accordance with Claim 13, wherein said structural mass precursor is formed by placing said metal cation/polymer gel in a hydrothermal reaction vessel and increasing a pressure inside said hydrothermal reaction vessel by heating said hydrothermal reaction vessel, forming a colloidal suspension which is removed from said hydrothermal reaction vessel, whereby said heating of said colloidal suspension forms a plurality of substantially spherical granules.
20. A method in accordance with Claim 13, wherein said structural mass precursor is formed by dissolving said metal cation/gel in water, forming a metal cation/polymer solution, immersing a porous preform in said metal cation/polymer solution, absorbing at least a portion of said metal cation/polymer solution into said porous preform, and drying said saturated porous preform, whereby said heating of said dried, saturated porous preform burns out at least a portion of said porous preform, leaving behind a porous structure having a shape and porosity corresponding to said porous preform.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US925,581 | 1997-09-08 | ||
| US08/925,581 US5874374A (en) | 1995-03-17 | 1997-09-08 | Method for producing engineered materials from salt/polymer aqueous solutions |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2246870A1 CA2246870A1 (en) | 1999-03-08 |
| CA2246870C true CA2246870C (en) | 2002-03-26 |
Family
ID=25451952
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2246870 Expired - Fee Related CA2246870C (en) | 1997-09-08 | 1998-09-08 | Method for producing engineered materials from salt/polymer aqueous solutions |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2246870C (en) |
-
1998
- 1998-09-08 CA CA 2246870 patent/CA2246870C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| CA2246870A1 (en) | 1999-03-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5171720A (en) | Porous ceramic sinter and process for producing same | |
| US4518704A (en) | Activated carbon formed body and method of producing the same | |
| CN110183244B (en) | Hollow mullite spherical material and preparation method thereof | |
| CA2190280C (en) | Nano powder synthesis using hydrophilic organic media | |
| Alves et al. | Processing of porous cordierite bodies by starch consolidation | |
| US4971697A (en) | Thin silica flakes and method of making | |
| US5712037A (en) | Substituted silica gel | |
| US6620458B2 (en) | Method to produce alumina aerogels having porosities greater than 80 percent | |
| US5030396A (en) | Process for production of porous ceramic article | |
| US5104632A (en) | Method of making thin silica flakes | |
| US5983488A (en) | Sol-casting of molten carbonate fuel cell matrices | |
| Sokolov et al. | Preparation and characterization of macroporous α‐alumina | |
| EP0479553B1 (en) | Production of porous ceramics | |
| US5874374A (en) | Method for producing engineered materials from salt/polymer aqueous solutions | |
| CA1036623A (en) | Compositions comprising inorganic metal compounds and water-soluble organic silicone compounds | |
| JPH04228476A (en) | Preparation of ceramic fiber/matrix composite material and composite material obtained by this method | |
| CA2246870C (en) | Method for producing engineered materials from salt/polymer aqueous solutions | |
| CN120379701A (en) | Slurry for low-temperature hardening of ceramic porous body and method for producing ceramic porous body using same | |
| WO2005033042A1 (en) | Manufacturing method of ceramic body with excellent adiabatic capacity | |
| JPS62202880A (en) | Manufacture of porous ceramic body | |
| JPH04202069A (en) | Laminated ceramic porous body | |
| JPS62186921A (en) | Porous zirconia composite filter and its production | |
| JP4260067B2 (en) | Method for producing alumina fiber | |
| JP3654085B2 (en) | Polyvinyl alcohol resin porous body and porous structure coated with the porous body | |
| JPS5939765A (en) | Method for manufacturing porous alumina sintered body |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |
Effective date: 20160908 |