Methods and devices for electrophoretic deposition of a uniform carbon nanotube composite film

• US 7,850,874 B2
• Filed: 09/20/2007
• Issued: 12/14/2010
• Est. Priority Date: 09/20/2007
• Status: Active Grant

• Current Assignee: NuRay Technology Co., Ltd.
• Original Assignee: Xintek, Inc.
• Inventors: Gao, Bo, Geng, Huaizhi, Lu, Mei, Liu, Jie
• Primary Examiner(s): MC GINTY, DOUGLAS J
• Application Number:
  US11/903,194
• Publication Number:
  US 20090078914A1
• Time in Patent Office: 1,181 Days
• Field of Search: 252/510, 252/511, 252/502, 977/742, 977/745, 977/748, 977/746, 977/749
• US Class Current: 252/510
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: C01B 2202/28 Solid content in solvents
• CPC Class Codes: C01B 32/174 Derivatisation; Solubilisation; Dispersion in solvents
• CPC Class Codes: C25D 13/02 with inorganic material
• CPC Class Codes: H01J 1/304 Field-emissive cathodes
• CPC Class Codes: H01J 2201/30469 Carbon nanotubes (CNTs)
• CPC Class Codes: H01J 9/025 of field emission cathodes
• CPC Class Codes: Y10S 977/742 Carbon nanotubes, CNTs
• CPC Class Codes: Y10S 977/745 having a modified surface
• CPC Class Codes: Y10S 977/746 Modified with biological, organic, or hydrocarbon material
• CPC Class Codes: Y10S 977/748 Modified with atoms or molecules bonded to the surface
• CPC Class Codes: Y10S 977/749 Modified with dissimilar atoms or molecules substituted for carbon atoms of the cnt, e.g. impurity doping or compositional substitution

Abstract

Methods and devices are provided relating to the homogeneous deposition of a composite film of carbon nanotubes by electrophoresis. The methods comprise linking carbon nanotubes to matrix particles prior to electrophoretic deposition. The methods improve the adhesion of the composite film to the substrate and reduce the surface roughness. Carbon nanotube films and electron field emission cathodes fabricated by this process demonstrate enhanced electron field emission characteristics.

Claims

1. A method of preparing a carbon nanotube-matrix particle complex, comprising:

providing at least one carbon nanotube;

providing at least one matrix particle;

providing at least one linker molecule having at least two functional groups; and

dispersing the at least one carbon nanotube, the at least one matrix particle, and the at least one linker molecule together simultaneously in a liquid medium to form a stable suspension thereof, wherein the liquid medium is selected from water, methanol, ethanol, isopropanol, butanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO) or a combination thereof, and wherein a first functional group of the at least one linker molecule binds to a surface of the at least one matrix particle thereby forming a coated surface, and a second functional group of the at least one linker molecule binds to the at least one carbon nanotube to thereby form a carbon nanotube-matrix particle complex.

3. The method of claim 1, wherein the matrix particle is a glass particle.

4. The method of claim 3, wherein the glass particle has a diameter of 300 nm to 3 μ

m.

5. The method of claim 1, wherein the linker molecule is an aminosilane molecule.

6. The method of claim 5, wherein the aminosilane molecule is selected from the group consisting of (3-aminopropyl) triethoxysilane (APS), (3-aminopropyl) trimethoxysilane, (3-aminopropyl)methyldiethoxysilane, (3-aminopropyl)methyldimethoxysilane, (2-aminoethyl-3-aminopropyl) triethoxysilane, (2-aminoethyl-3-aminopropyl) trimethoxysilane, and (2-aminoethyl-3-aminopropyl)methyldimethoxysilane.

7. The method of claim 5, wherein the binding of the first functional group of the aminosilane molecule to the surface of the matrix particle is through a chemical reaction between one or more alkoxy groups of the aminosilane molecule and one or more hydroxyl groups of the matrix particle.

8. The method of claim 7, wherein the matrix particle is a glass particle.

9. The method of claim 5, wherein the binding of the second functional group of the aminosilane molecule to the carbon nanotube is through an electrostatic interaction between an amino group of the aminosilane molecule and one or more oxygen-containing groups of the carbon nanotube.

10. The method of claim 1, further comprising adding dispersant to the liquid medium, wherein the dispersant is selected from the group consisting of polyvinyl pyrrolidone (PVP), polyvinyl butyral (PVB) and ethyl cellulose.

11. The method of claim 1, further comprising treating the at least one carbon nanotube with acid to impart a negative charge to the at least one carbon nanotube prior to dispersion into the liquid medium.

12. A carbon nanotube-matrix particle complex made from the method of claim 1.

26. The method of claim 1, wherein the linker molecule and the matrix particle are dispersed in the liquid medium at a ratio of 1:

800 mL/mg.

27. The method of claim 1, further comprising dispersing the carbon nanotube-matrix particle complex in a suspension wherein agglomeration is substantially reduced in comparison to agglomeration in a suspension of carbon nanotubes and matrix particles.

28. The method of claim 1, further comprising adding carboxyl or other oxygen-containing groups to the surface of the carbon nanotube prior to dispersion in the liquid medium.

37. The method according to claim 1, wherein the at least one carbon nanotube links to and protrudes from the coated surface of the at least one matrix particle.

2. A method of preparing a carbon nanotube-matrix particle complex comprising a matrix particle with a carbon nanotube linked to and protruding from a coated surface of said matrix particle, the method comprising:

providing at least one carbon nanotube;

providing at least one matrix particle;

providing at least one linker molecule; and

dispersing the at least one carbon nanotube, the at least one matrix particle, and the at least one linker molecule together simultaneously in a liquid medium to form a stable suspension thereof, wherein a first functional group of the at least one linker molecule binds to the surface of the at least one matrix particle thereby forming the coated surface, and a second functional group binds to the at least one carbon nanotube such that a carbon nanotube-matrix particle complex is formed wherein the carbon nanotube protrudes from the coated surface of the matrix particle.

13. A method of preparing a carbon nanotube-matrix particle complex, comprising:

providing at least one carbon nanotube;

providing at least one matrix particle;

providing at least one linker molecule dispersing the at least one linker molecule and the at least one matrix particle in an alcohol solution wherein the linker molecule binds to a surface of the matrix particle thereby initially forming a functionalized matrix, particle, and wherein the alcohol comprises an alcohol selected from the group consisting of methanol, ethanol, isopropanol, and butanol; and

subsequently dispersing the at least one functionalized matrix particle in a liquid medium with at least one carbon nanotube to form a stable suspension thereof, wherein the liquid medium is selected from water, methanol, ethanol, isopropanol, butanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO) or a combination thereof, and wherein the at least one functionalized matrix particle binds to the at least one carbon nanotube to form a carbon nanotube-matrix particle complex.

14. The method of claim 13, further comprising sonicating or stirring the alcohol solution comprising the at least one linker molecule and the at least one matrix particle to form the at least one functionalized matrix particle.

15. The method of claim 13, further comprising cross-linking the at least one functionalized matrix particle by applying heat.

16. The method of claim 13, wherein the at least one matrix particle is a glass particle.

17. The method of claim 16, wherein the glass particle has a diameter of 300 nm to 3 μ

m.

18. The method of claim 13, wherein the at least one linker molecule is an aminosilane molecule.

19. The method of claim 18, wherein the aminosilane molecule is selected from the group consisting of (3-aminopropyl) triethoxysilane (APS), (3-aminopropyl) trimethoxysilane, (3-aminopropyl)methyldiethoxysilane, (3-aminopropyl)methyldimethoxysilane, (2-aminoethyl-3-aminopropyl) triethoxysilane, (2-aminoethyl-3-aminopropyl) trimethoxysilane, and (2-aminoethyl-3-aminopropyl)methyldimethoxysilane.

20. The method of claim 18, wherein the binding of the first functional group of the aminosilane molecule to the surface of the at least one matrix particle is through a chemical reaction between one or more alkoxy groups of the aminosiloxane molecule and one or more hydroxyl groups of the matrix particle.

21. The method of claim 20, wherein the at least one matrix particle is a glass particle.

22. The method of claim 18, wherein the binding of the second functional group of the aminosilane molecule to the at least one carbon nanotube is through an electrostatic interaction between an amino group of the aminosiloxane molecule and one or more oxygen-containing groups of the carbon nanotube.

23. The method of claim 13, further comprising adding dispersant to the liquid medium, wherein the dispersant is selected from the group consisting of polyvinyl pyrrolidone (PVP), polyvinyl butyral (PVB) and ethyl cellulose.

24. The method of claim 13, further comprising treating the carbon nanotubes with acid to impart a negative charge to the at least one carbon nanotube prior to dispersion into the liquid medium.

25. A carbon nanotube-matrix particle complex made from the method of claim 13.

29. The method of claim 13, wherein the linker molecule and the matrix particle are dispersed in the alcohol solution at a ratio of 1:

800 mL/mg.

30. The method of claim 13, wherein the functionalized matrix particle is dispersed in the liquid medium at 400 wt % of total carbon nanotubes.

31. The method of claim 13, further comprising dispersing the carbon nanotube-matrix particle complex in a suspension wherein agglomeration is substantially reduced in comparison to agglomeration in a suspension of carbon nanotubes and matrix particles.

32. The method of claim 13, further comprising adding carboxyl or other oxygen-containing groups to the surface of the carbon nanotube prior to dispersion into the liquid medium.

33. A method of preparing a carbon nanotube-matrix particle complex, comprising:

providing at least one carbon nanotube;

providing at least one matrix particle having a diameter of 300 nm to 3 μ

m;

providing at least one linker molecule having at least two functional groups; and

dispersing the at least one carbon nanotube, the at least one matrix particle, and the at least one linker molecule in a liquid medium to form a stable suspension thereof, wherein a first functional group of the at least one linker molecule binds to a surface of the at least one matrix particle thereby forming a coated surface, and a second functional group of the at least one linker molecule binds to the at least one carbon nanotube to thereby form a carbon nanotube-matrix particle complex.

34. The method according to claim 33, wherein the at least one carbon nanotube links to and protrudes from the coated surface of the at least one matrix particle.

35. The method according to claim 34, wherein the matrix particle is a glass particle.

36. The method according to claim 33, further comprising sonicating or stirring the suspension comprising the at least one carbon nanotube, the at least one linker molecule and the at least one matrix particle.