Methods for coating surfaces with magnetic composites exhibiting distinct flux properties

• US 5,786,040 A
• Filed: 04/01/1996
• Issued: 07/28/1998
• Est. Priority Date: 08/25/1994
• Status: Expired due to Term

• Current Assignee: University of Iowa Research Foundation
• Original Assignee: University of Iowa Research Foundation
• Inventors: Leddy, Johna, Amarasinghe, Sudath
• Primary Examiner(s): TUNG, TA HSUNG
• Application Number:
  US08/626,082
• Time in Patent Office: 848 Days
• Field of Search: 204/290 R, 204/291, 204/292, 204/293, 427/598, 427/599, 427/547, 427/548, 427/549, 427/128, 427/58
• US Class Current: 427/598
• 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 of making an electrode with a surface coated with a magnetic composite with a plurality of boundary regions with magnetic gradients having paths to the surface of said electrode, comprising the steps of:

mixing a first mixture of at least approximately 1 percent by weight of inert polymer coated magnetic microbeads containing at least approximately 10 percent by weight of magnetizable material having diameters of at least approximately 0.11 micrometer in a first solvent with a second mixture comprising at least approximately 2% by weight of an ion exchange polymer in a second solvent to yield a mixed suspension;

applying said mixed suspension to the surface of the electrode, said electrode being arranged in a magnetic field of at least approximately 0.05 Tesla which has a component oriented approximately along the normal of said electrode surface; and

evaporating said first solvent and said second solvent to yield the electrode with a surface coated with the magnetic composite having a plurality of boundary regions with magnetic gradients having paths to the surface of the electrode.

2. The method as claimed in claim 1, wherein said mixing steps comprises mixing a first mixture of at least approximately 5 percent by weight of inert polymer coated magnetic microbeads containing between approximately 10 percent and approximately 90 percent magnetizable material having diameters ranging between approximately 0.5 micrometer and approximately 12 micrometers with the second mixture.

3. The method as claimed in claim 1, wherein said applying step comprises applying said mixed suspension to the surface of the electrode, said electrode being arranged in a magnetic field of between approximately 0.05 Tesla and approximately 2 Tesla.

4. The method as claimed in claim 1, wherein said mixing step comprises mixing a first mixture of at least approximately 5 percent by weight of inert polymer coated magnetic microbeads containing between approximately 10 percent and approximately 90 percent by weight of magnetizable polymer material having diameters of at least approximately 0.5 micrometer in a first solvent with a second mixture comprising at least approximately 5 percent by weight of a perfluorinated sulfonic acid polymer in a second solvent to yield said mixed suspension.

5. The method as claimed in claim 1, wherein said mixing step comprises mixing a first mixture of at least approximately 5 percent by weight of inert polymer coated magnetic microbeads containing between approximately 10 percent and approximately 90 percent by weight organo-Fe material having diameters of at least 0.5 micrometer in a first solvent with a second mixture comprising at least approximately 5 percent by weight of an ion exchange polymer in a second solvent to yield said mixed suspension.

6. A method of making an electrode with a surface coated with a composite with a plurality of boundary regions with magnetic gradients having paths to the surface of said electrode when an external magnetic field is applied to the electrode, comprising the steps of:

mixing a first mixture of at least 5 percent by weight of inert polymer coated microbeads containing between 10 percent and 90 percent magnetizable non-permanent magnetic material and having diameters of at least 0.5 micrometer in a first solvent with a second solution of at least 5 percent of ion exchange polymers in a second solvent to yield a mixed suspension;

applying said mixed suspension to the surface of the electrode; and

evaporating said first solvent and said second solvent to yield the electrode with a surface coated with the composite having a plurality of boundary regions with magnetic gradients having paths to the surface of the electrode when an external magnet is applied.

7. The method as claimed in claim 6, wherein said magnetizable non-permanent magnet material comprises Fe/Fe oxide material.

8. A method of coating a surface with a magnetic composite material, comprising the steps of:

applying to the surface a composition comprising an inert polymer coated magnetic microbeads, an ion exchange polymer, and a solvent as a mixed suspension;

arranging the surface in a magnetic field; and

evaporating the solvent to form a coating of the magnetic composite on the surface.

9. The method of claim 8, wherein said applying step comprises applying to the surface a composition comprising a first mixture of at least approximately 1% by weight of inert polymer coated magnetic microbeads in a first solvent mixed with a second mixture of at least approximately 2% by weight of ion exchange polymer in a second solvent.

10. The method of claim 8, wherein said arranging step comprises arranging the surface in a magnetic field of at least approximately 0.05 Tesla having a component oriented approximately along the normal of the surface.

11. The method of claim 8, wherein said applying step comprises applying to the surface a composition comprising a first mixture of at least approximately 1% by weight inert polymer coated magnetic microbeads in a first solvent mixed with a second mixture of at least approximately 2% by weight of ion exchange polymer in a second solvent, wherein said magnetic microbeads comprise at least about 10% by weight of magnetizable material and have a diameter of at least approximately 0.11 micrometer, and said ion exchange polymer comprises a perfluorinated sulfonic acid polymer.

12. The method of claim 11, wherein said evaporating step yields a surface coating with a magnetic composite having magnetic microbeads trapped in a perfluorinated sulfonic acid polymer and the magnetic microbeads are stacked in pillars substantially normal to the electrode surface.

13. The method of claim 11, wherein said evaporating step comprises evaporating the solvent to form a coating of the magnetic composite on the surface, the magnetic composite comprising perfluorinated sulfonic acid polymer in the range of from 10 percent to 90 percent by volume, and the ratio of the surface area of the magnetic microbeads to the volume of perfluorinated sulfonic acid polymer is in the range of from 10⁴ cm^-1 to 10⁶ cm^-1.

14. The method of claim 8, wherein said applying step comprises spin casting said mixed suspension on the surface.