IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0800730
(2007-05-08)
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등록번호 |
US-8691129
(2014-04-08)
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발명자
/ 주소 |
- Zhamu, Aruna
- Shi, Jinjun
- Guo, Jiusheng
- Jang, Bor Z.
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출원인 / 주소 |
- Nanotek Instruments, Inc.
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대리인 / 주소 |
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인용정보 |
피인용 횟수 :
0 인용 특허 :
18 |
초록
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A method of producing an electrically conductive composite composition, which is particularly useful for fuel cell bipolar plate applications. The method comprises: (a) providing a supply of expandable graphite powder; (b) providing a supply of a non-expandable powder component comprising a binder o
A method of producing an electrically conductive composite composition, which is particularly useful for fuel cell bipolar plate applications. The method comprises: (a) providing a supply of expandable graphite powder; (b) providing a supply of a non-expandable powder component comprising a binder or matrix material; (c) blending the expandable graphite with the non-expandable powder component to form a powder mixture wherein the non-expandable powder component is in the amount of between 3% and 60% by weight based on the total weight of the powder mixture; (d) exposing the powder mixture to a temperature sufficient for exfoliating the expandable graphite to obtain a compressible mixture comprising expanded graphite worms and the non-expandable component; (e) compressing the compressible mixture at a pressure within the range of from about 5 psi to about 50,000 psi in predetermined directions into predetermined forms of cohered graphite composite compact; and (f) treating the so-formed cohered graphite composite to activate the binder or matrix material thereby promoting adhesion within the compact to produce the desired composite composition. Preferably, the non-expandable powder component further comprises an isotropy-promoting agent such as non-expandable graphite particles. Further preferably, step (e) comprises compressing the mixture in at least two directions. The method leads to composite plates with exceptionally high thickness-direction electrical conductivity.
대표청구항
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1. A method of producing an electrically conductive composite composition, said method comprising: a) providing a supply of expandable graphite powder;b) providing a supply of a non-expandable powder isotropy-promoting agent that enhances isotropy and reduces anisotropy and a binder or matrix, the b
1. A method of producing an electrically conductive composite composition, said method comprising: a) providing a supply of expandable graphite powder;b) providing a supply of a non-expandable powder isotropy-promoting agent that enhances isotropy and reduces anisotropy and a binder or matrix, the binder or matrix being a powder and being present in an amount between 3 and 60% by weight;c) blending said expandable graphite with said non-expandable powder component to form a powder mixture wherein said non-expandable powder component is in the amount of between 3% and 60% by weight based on the total weight of the powder mixture;d) exposing said powder mixture to a temperature sufficient for exfoliating the expandable graphite to obtain a compressible mixture comprising expanded graphite worms and said non-expandable component;e) without activating the binder or matrix material, compressing said compressible mixture at a pressure within the range of from about 5 psi to about 50,000 psi in a uniaxial, biaxial, triaxial or isostatic compression into predetermined forms of cohered graphite composite compact such that the isotropy promoting agent changes the orientation of the expandable graphite to a more isotropic orientation upon compression; andf) treating the so-formed cohered graphite composite to activate the binder or matrix material thereby promoting adhesion within the compact; wherein the method produces a composite compact having a thickness direction conductivity greater than 50 S/cm, the thickness direction conductivity also being greater than the thickness-direction conductivity when the isotropy promoting agent is not present, and having an in-plane conductivity of the composite compact that is less than the in-plane conductivity of the composite compact when the isotropy promoting agent is not present. 2. The method as defined in claim 1, wherein said binder or matrix material comprises a polymer, ceramic, glass, metal, carbon, polymeric carbon, asphalt, tar, coal tar pitch, petroleum pitch, mesophase pitch, or a combination thereof. 3. The method as defined in claim 1, wherein said binder or matrix material comprises a polymer selected from the group consisting of polyethylene, polypropylene, nylon, polyesters, polytetrafluoroethylene, polyvinylidene fluoride, fluoro polymers, polyacrylonitrile, acrylic resins, epoxides, polyimide, phenol formaldehydes, vinyl ester, isocyanate resins, and combinations thereof. 4. The method as defined in claim 3, wherein said binder or matrix material comprises a char-yielding material and the method further comprises a step of baking or pyrolizing said composite at a temperature for a period of time sufficient to convert said char-yielding material into carbon or graphite. 5. The method as defined in claim 4, wherein said char-yielding material is selected from the group consisting of asphalt, tar, sugars, phenolic resins, coal tar pitches, petroleum pitches, mesophase pitches, saccharides, organic polymers, and combinations thereof. 6. The method as defined in claim 2, wherein said binder or matrix material comprises an inorganic vitreous glass-forming material which contains at least one of the compounds selected from the group consisting of boric oxide, silica, phosphorous pentaoxide, germanium oxides, vanadium pentoxides, and beryllium fluoride. 7. The method as defined in claim 6, wherein said binder or matrix material comprises a glass-forming composition containing at least two oxides selected from the group consisting of silica, aluminum oxide, sodium oxide, potassium oxide, magnesium oxide, cuprous oxide, barium oxide, lead oxide, and boric oxide. 8. The method as defined in claim 1, wherein said isotropy-promoting agent is selected from the group consisting of non-expandable graphite particles, carbon blacks, graphite or carbon fibers, graphite or carbon nano-fibers, nano-tubes, glass fibers, ceramic fibers, polymer fibers, metal fibers, metal particles, polymer particles, organic particles, inorganic particles, and combinations thereof. 9. The method as defined in claim 8, wherein said biaxial compression comprises a uniaxial compression in a first direction, which is followed by a compression in a second direction. 10. The method as defined in claim 1, wherein biaxial, triaxial, or isostatic compression is followed by a shaping operation. 11. The method as defined in claim 10, wherein said shaping operation comprises an uniaxial compression, shearing, impression, embossing, compression molding, or a combination thereof. 12. A method of producing an electrically conductive composite composition, said method comprising: a) providing a supply of expandable graphite powder;b) providing a supply of an isotropy-promoting, non-expandable powder component that enhances isotropy and reduces anisotropy;c) blending said expandable graphite with said non-expandable powder component that enhances isotropy and reduces anisotropy to form a powder mixture wherein said non-expandable powder component is between 3% and 60% by weight based on the total weight of the powder mixture;d) exposing said powder mixture to a temperature sufficient for exfoliating the expandable graphite to obtain a compressible mixture comprising expanded graphite worms and said non-expandable component;e) impregnating said compressible mixture with a binder or matrix material, wherein said binder or matrix material is between 3% and 60% by weight based on the total weight of the composite composition;f) compressing said impregnated compressible mixture at a pressure within the range of from about 5 psi to about 50,000 psi in at least two directions into predetermined forms of cohered graphite composite compact such that the isotropy promoting agent changes the orientation of the expandable graphite to a more isotropic orientation upon compression; andg) treating the so-formed cohered graphite composite to activate the binder or matrix material thereby promoting adhesion within the compact; wherein the method produces a composite compact having a thickness direction conductivity greater than 50 S/cm, the thickness direction conductivity also being greater than the thickness-direction conductivity when the isotropy promoting agent is not present, and having an in-plane conductivity of the composite compact that is less than the in-plane conductivity of the composite compact when the isotropy promoting agent is not present. 13. The method as defined in claim 12, wherein said non-expandable powder component comprises a graphite particle, carbon black, graphite or carbon fiber, graphite or carbon nano-fiber, nano-tube, glass fiber, ceramic fiber, polymer fiber, metal fiber, metal particle, polymer particle, organic particle, inorganic particle, or a combination thereof. 14. The method as defined in claim 13, wherein said binder or matrix material comprises a polymer, ceramic, glass, metal, carbon, polymeric carbon, asphalt, tar, coal tar pitch, petroleum pitch, mesophase pitch, or a combination thereof. 15. The method as defined in claim 13, wherein said binder or matrix material comprises a polymer selected from the group consisting of polyethylene, polypropylene, nylon, polyesters, polytetrafluoroethylene, polyvinylidene fluoride, fluoro polymers, polyacrylonitrile, acrylic resins, epoxides, polyimide, bismaleimide, phenol formaldehydes, vinyl ester, isocyanate resins, and combinations thereof. 16. The method as defined in claim 13, wherein said binder or matrix material comprises an inorganic vitreous glass-forming material which contains at least one of the compounds selected from the group consisting of boric oxide, silica, phosphorous pentaoxide, germanium oxides, vanadium pentoxides, and beryllium fluoride. 17. The method as defined in claim 13, wherein said binder or matrix material comprises a glass-forming composition containing at least two oxides selected from the group consisting of silica, aluminum oxide, sodium oxide, potassium oxide, magnesium oxide, cuprous oxide, barium oxide, lead oxide, and boric oxide. 18. The method as defined in claim 12, wherein said step of compressing in at least two directions comprises a biaxial, triaxial, or isostatic compression to produce a composite with reduced anisotropy. 19. The method as defined in claim 12, wherein said step of compressing in at least two directions comprises a biaxial, triaxial, or isostatic compression, which is followed by a shaping operation. 20. The method as defined in claim 19, wherein said shaping operation comprises an uniaxial compression, shearing, impression, embossing, compression molding, or a combination thereof. 21. The method as defined in claim 12, wherein said step of compressing in at least two directions comprises an uniaxial compression in a first direction, which is followed by a compression in a second direction, or comprises a biaxial compression in first and second directions, followed by a compression in a third direction. 22. The method as defined in claim 12, wherein said binder or matrix material comprises a char-yielding material and the method further comprises a step of baking or pyrolizing said composite at a temperature for a period of time sufficient to convert said char-yielding material into carbon or graphite. 23. The method as defined in claim 22, wherein said char-yielding material is selected from the group consisting of asphalt, tar, sugars, phenolic resins, coal tar pitches, petroleum pitches, mesophase pitches, saccharides, organic polymers, and combinations thereof 24. The method as defined in claim 12, wherein step (e) comprises impregnating said compressible mixture with a first component of a two-component or multiple-component thermosetting or polymerizing resin and then impregnating said compressible mixture with a second component of said resin. 25. The method as defined in claim 12, wherein step (e) comprises impregnating said compressible mixture with a mixture of a volatile diluent and a first component of a two-component or multiple-component thermosetting or polymerizing resin, removing said volatile diluent, and then impregnating said compressible mixture with a second component of said resin. 26. The method as defined in claim 25, wherein said resin comprises epoxy resin and said first component comprises a curing agent or hardener. 27. A method of producing an electrically conductive composite composition, said method comprising: a) providing a supply of exfoliated graphite that enhances isotropy and reduces anisotropy;b) providing a supply of an isotropy-promoting, non-expandable powder component, wherein said non-expandable powder component is between 3% and 60% by weight based on the total weight of the exfoliated graphite and the non-expandable powder component;c) providing a supply of a binder material, wherein said binder material is a powder and is between 3% and 60% by weight based on the total weight of the final composite composition;d) blending said exfoliated graphite, said non-expandable powder component, and said binder material to form a compressible mixture;e) without activating the binder material compressing said compressible mixture at a pressure within the range of from about 5 psi to about 50,000 psi in at least two direction into predetermined forms of cohered graphite composite compact such that the isotropy promoting agent changes the orientation of the expandable graphite to a more isotropic orientation upon compression; andf) treating the so-formed cohered graphite composite to activate the binder material thereby promoting adhesion within the compact; wherein the method produces a composite compact having a thickness direction conductivity greater than 50 S/cm, the thickness direction conductivity also being greater than the thickness-direction conductivity when the isotropy promoting agent is not present, and having an in-plane conductivity of the composite compact that is less than the in-plane conductivity of the composite compact when the isotropy promoting agent is not present. 28. The method as defined in claim 27 wherein said non-expandable powder has a size smaller than a particle size of the exfoliated graphite. 29. The method as defined in claim 27, wherein said non-expandable powder component comprises a graphite particle, carbon black, graphite or carbon fiber, graphite or carbon nano-fiber, nano-tube, glass fiber, ceramic fiber, polymer fiber, metal fiber, metal particle, polymer particle, organic particle, inorganic particle, or a combination thereof. 30. The method as defined in claim 27, wherein said step of compressing in at least two directions comprises a biaxial, triaxial, or isostatic compression to produce a composite with reduced anisotropy. 31. The method as defined in claim 27, wherein said step of compressing in at least two directions comprises a biaxial, triaxial, or isostatic compression, which is followed by a shaping operation. 32. The method as defined in claim 27, wherein said step of compressing in at least two directions comprises an uniaxial compression in a first direction, which is followed by a compression in a second direction, or comprises a biaxial compression in first and second directions, followed by a compression in a third direction.
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