Methods for coating surfaces with magnetic composites exhibiting distinct flux properties

• US 6,375,885 B1
• Filed: 07/27/1998
• Issued: 04/23/2002
• Est. Priority Date: 08/25/1994
• Status: Expired due to Fees

• Current Assignee: University of Iowa Research Foundation
• Original Assignee: University of Iowa Research Foundation
• Inventors: Leddy, Johna, Amarasinghe, Sudath
• Primary Examiner(s): Silbaugh, Jan H.
• Assistant Examiner(s): Lee, Edmund H.
• Application Number:
  US09/122,861
• Time in Patent Office: 1,366 Days
• Field of Search: 264/308, 264/309, 264/113, 264/437, 264/427, 264/250, 264/216, 264/310, 264/311, 264/255, 264/428, 427/131, 427/132, 427/407.1
• US Class Current: 264/427
• CPC Class Codes: B03C 1/01 by addition of magnetic adjuvants
• CPC Class Codes: B03C 1/025 High gradient magnetic separators
• CPC Class Codes: B03C 1/034 characterised by the matrix elements
• CPC Class Codes: B03C 1/035 Open gradient magnetic separators, i.e. separators in which the gap is unobstructed, characterised by the configuration of the gap
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C23C 24/08 by application of heat or pressure and heat C23C24/04 takes precedence
• CPC Class Codes: C23C 30/00 Coating with metallic material characterised only by the composition of the metallic material, i.e. not characterised by the coating process C23C26/00, C23C28/00 take precedence
• CPC Class Codes: C23C 6/00 Coating by casting molten material on the substrate
• CPC Class Codes: C25B 11/00 Electrodes; Manufacture thereof not otherwise provided for
• CPC Class Codes: C25D 3/54 of metals not provided for in groups C25D3/04 - C25D3/50
• CPC Class Codes: G21F 9/12 by absorption; by adsorption; by ion-exchange
• CPC Class Codes: H01F 1/0027 Thick magnetic films forming thick magnetic films H01F41/16
• CPC Class Codes: H01F 1/0054 Coated nanoparticles, e.g. nanoparticles coated with organic surfactant
• CPC Class Codes: H01F 1/009 bidimensional, e.g. nanoscale period nanomagnet arrays H01F10/007 takes precedence
• CPC Class Codes: H01F 10/007 ultrathin or granular films H01F10/005 and H01F10/3227 take precedence; applying ultrathin or granular layers to substrates H01F41/301
• CPC Class Codes: H01F 41/24 from liquids
• CPC Class Codes: H01F 41/26 using electric currents , e.g. electroplating
• CPC Class Codes: H01F 41/301 for applying ultrathin or granular layers ultrathin or granular layers H01F10/007
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: H01M 2300/0082 : Organic polymers
• CPC Class Codes: H01M 4/02 : Electrodes composed of, or comprising, active material
• CPC Class Codes: H01M 4/86 : Inert electrodes with catalytic activity, e.g. for fuel cells
• CPC Class Codes: H01M 4/8605 : Porous electrodes
• CPC Class Codes: H01M 4/8857 : Casting, e.g. tape casting, vacuum slip casting
• CPC Class Codes: H01M 4/8882 : Heat treatment, e.g. drying, baking
• CPC Class Codes: H01M 4/9083 : on carbon or graphite
• CPC Class Codes: H01M 4/926 : on carbon or graphite
• CPC Class Codes: H01M 8/1004 : characterised by membrane-electrode assemblies [MEA] H01M8/12 takes precedence
• CPC Class Codes: H01M 8/1009 : with one of the reactants being liquid, solid or liquid-charged H01M8/12 takes precedence
• CPC Class Codes: H01M 8/249 : comprising two or more groupings of fuel cells, e.g. modular assemblies
• CPC Class Codes: Y02E 60/10 : Energy storage using batteries
• CPC Class Codes: Y02E 60/50 : Fuel cells
• CPC Class Codes: Y10T 428/32 : Composite [nonstructural laminate] of inorganic material having metal-compound-containing layer and having defined magnetic layer

Abstract

A method for coating a surface with a magnetic composite material exhibiting distinct flux properties due to gradient interfaces within the composite. Surfaces coated with such a composite can be used to improve fuel cells and to effect improved transport and separation of different species of materials. A wide variety of devices can incorporate such composite-coated surfaces, including separators, fuel cells, electrochemical cells, and electrodes for channeling flux of, or for effecting electrolysis of, magnetic species.

Claims

1. A method for forming a graded density magnetic composite, comprising:

contacting a surface with a composition comprising a magnetic material to form a magnetic material coated surface;

applying to the magnetic material coated surface at least a first polymer solution comprising at least one polymer, having a first concentration, and a first solvent, and evaporating the first solvent to form a first polymer coating on said magnetic material coated surface;

applying to the first polymer coating a second polymer solution comprising at least one polymer, having a second concentration different from the first polymer solution concentration, and a second solvent, and evaporating the second solvent to form a second polymer coating on the first polymer coating, and thereby yield the graded density magnetic composite.

2. The method of claim 1, further comprising:

applying to the second polymer coating a third polymer solution comprising at least one polymer, having a third concentration different from at least one of the first and second polymer solution concentrations, and a third solvent, and

evaporating the third solvent to form a third polymer coating on the second polymer coating, and thereby yield the graded density magnetic composite.

3. The method of claim 2, further comprising:

applying to the third polymer coating a fourth polymer solution comprising at least one polymer, having a fourth concentration different from at least one of the first, second and third polymer solution concentrations, and a fourth solvent, and

evaporating the fourth solvent to form a fourth polymer coating on the third polymer coating, and thereby yield the graded density magnetic composite.

4. The method of claim 1 wherein the at least one polymer comprises one of a density gradient polymer and an ion exchange polymer.

5. The method of claim 1 wherein the first polymer concentration ranges from about 2% by weight to about 50% by weight and the second polymer concentration ranges from about 2% by weight to about 50% by weight.

6. The method of claim 1 wherein applying at least one of the first and second polymer solutions comprises spin casting.

7. The method of claim 1 wherein the graded density magnetic composite includes a graded parallel to the surface.

8. The method of claim 1 further comprising removing the graded density magnetic composite from the surface to yield a free-standing composite.

9. The method of claim 1 further comprising arranging the surface in an external magnetic field.

10. The method of claim 9 wherein the magnetic field is non-uniform.

11. The method of claim 9 further comprising removing the magnetic field after applying the at least first and second polymer solutions.

12. The method of claim 9 wherein the at least first and second polymer solutions are applied and the magnetic field is applied such that the magnetic composite includes a magnetic gradient in a first coordinate and a density gradient in a second coordinate.

13. The method of claim 1 wherein the at least first polymer solution comprises a mixture of an ion-exchange polymer and a density gradient polymer.

14. The method of claim 1 wherein the at least first polymer solution comprises a density gradient polymer, and further comprising the step of adsorbing an ion exchange polymer into the density gradient polymer.

15. The method of claim 8, wherein said free-standing composite comprises a film.

16. A method of making a graded density magnetic composite, comprising:

forming a magnetic material coated surface; and

applying to the magnetic material coated surface a plurality of successively formed coatings, each being formed by;

applying a respective polymer solution comprising at least one polymer, having a respective polymer concentration, and a respective solvent, and

evaporating the respective solvent,

wherein said respective polymer concentrations are not all identical, thereby yielding the graded density magnetic composite.

17. The method of claim 16, wherein said respective polymer concentrations are varied to form a monotonic graded density on said magnetic material coated surface with respect to said at least one polymer.

18. The method of claim 16, wherein said respective polymer concentrations are varied to form an approximately discontinuously graded, density on said magnetic material coated surface with respect to said at least one polymer.

19. The method of claim 16, wherein said at least one polymer comprises at least one of a density gradient polymer and an ion exchange polymer.

20. The method of claim 16, wherein said respective polymer concentration ranges from about 2% to about 50% by weight.

21. The method of claim 16, wherein said successively applying said respective polymer solution comprises spin casting.

22. The method of claim 16, wherein said graded density magnetic composite comprises a graded density parallel to the surface.

23. The method of claim 16, further comprising removing said graded density magnetic composite from said magnetic material coated surface to yield a free-standing composite film.

24. The method of claim 16, further comprising forming said magnetic material coated surface in an external magnetic field.

25. The method of claim 24, wherein said magnetic field is non-uniform.

26. The method of claim 24, further comprising removing said magnetic field after said successively applying said respective polymer solution.

27. The method of claim 24, wherein said respective polymer solution is successively applied, and the magnetic field is applied such that the magnetic composite includes a magnetic gradient in a first coordinate, and a density gradient in a second coordinate.

28. The method of claim 17, wherein said respective polymer solution comprises a mixture of an ion exchange polymer and a density gradient polymer.

29. The method of claim 17, wherein said respective polymer solution comprises a density gradient polymer, and further comprising the step of adsorbing an ion exchange polymer into the layer formed by the density gradient polymer.