Alignment of carbon nanotubes comprising magnetically sensitive metal oxides in nanofluids

Patent metadata

Field	Value
Publication number	US-9396853-B2
Application number	US-201314143453-A
Country	US
Kind code	B2
Filing date	Dec 30, 2013
Priority date	Sep 16, 2010
Publication date	Jul 19, 2016
Grant date	Jul 19, 2016

Abstract

The present invention is a nanoparticle mixture or suspension or nanofluid comprising nonmagnetically sensitive nanoparticles, magnetically sensitive nanoparticles, and surfactant(s). The present invention also relates to methods of preparing and using the same.

First claim

We claim:

1. A nanoparticle composition comprising:
one or more nonmagnetically sensitive nanoparticles, one or more magnetically sensitive nanoparticles, and one or more surfactants; wherein the one or more surfactants are selected from the group consisting of an ampholytic surfactant, an amphoteric surfactant, an anionic surfactant, a cationic surfactant, a zwitterionic surfactant, and combinations thereof; wherein the one or more surfactants are attached to the one or more nonmagnetically sensitive nanoparticles forming a surfactant and nonmagnetically sensitive particle complex (S/NSP) by electrostatic attraction; wherein the S/NSP complex is attached to the one or more magnetically sensitive nanoparticles by electrostatic attraction; and wherein at least a portion of the nonmagnetically sensitive nanoparticles are magnetically aligned.

2. The nanoparticle composition of claim 1 further comprising a fluid, wherein the fluid has a dipole moment greater than about zero.

3. The nanoparticle composition of claim 2 , wherein the fluid has a pH greater than about 5 and the surfactants have a net negative charge, or the fluid has a pH less than about 9 and the surfactants have a net positive charge.

4. The nanoparticle composition of claim 1 , wherein the magnetically sensitive particles are magnetically sensitive metals, metal oxides, or combinations thereof.

5. The nanoparticle composition of claim 4 , wherein the magnetically sensitive metal oxide is selected from the group consisting of Fe, Co, Fe 2 O 3 , and Fe 3 O 4 .

6. The nanoparticle composition of claim 1 , wherein the magnetically sensitive particles comprise Fe 2 O 3 .

7. The nanoparticle composition of claim 1 , wherein the nonmagnetically sensitive nanoparticles are carbon nanotubes.

8. The nanoparticle composition of claim 1 , wherein the surfactants are selected from the group a consisting of a betain, a carboxylate, a quaternary amine, a quaternary ammonium, a sulfate, a sulfonate, a sultaine, and combination thereof.

9. The nanoparticle composition of claim 8 , wherein the sulfonate is sodium dodecylbenzene sulfonate, the quaternary ammonium is a heterocyclic quaternary ammonium, and the quaternary amine is trimethylammonium bromide.

10. The nanoparticle composition of claim 1 , wherein the one or more nonmagnetically sensitive nanoparticles comprise SWNT, DWNT, MWNT, graphite, graphene, modified carbon nanotubes, or functionalized carbon nanotubes; and wherein substantially all of the nonmagnetically sensitive nanoparticles are magnetically aligned.

11. A nanofluid comprising:
one or more nonmagnetically sensitive nanoparticles comprising carbon nanoparticles, one or more magnetically sensitive nanoparticles, and one or more surfactants;
wherein the nonmagnetically sensitive nanoparticles, magnetically sensitive nanoparticles, and one or more surfactants are dispersed in a fluid;
wherein the fluid has a pH greater than about 5 and the surfactants have a net negative charge, or the fluid has a pH less than about 9 and the surfactants have a net positive charge;
wherein the one or more surfactants are selected from the group consisting of a betaine, a carboxylate, a quaternary amine, a quaternary ammonium, a sulfate, a sulfonate, a sultaine, and combinations thereof;
wherein the one or more surfactants are attached to the one or more nonmagnetically sensitive nanoparticles forming a S/NSP complex by electrostatic attraction; wherein the S/NSP complex is attached to the one or more magnetically sensitive nanoparticles by electrostatic attraction; wherein at least a portion of the nonmagnetically sensitive nanoparticles are magnetically aligned; and wherein the nanofluid exhibits an increase of thermal conductivity of at least about 10%.

12. The nanofluid composition of claim 11 , wherein the fluid has a dipole moment greater than about zero.

13. The nanofluid composition of claim 11 , wherein the magnetically sensitive nanoparticles have a positive charge and the surfactants have a net negative charge, or wherein the magnetically sensitive nanoparticles have a negative charge and the surfactants have a net positive charge.

14. The nanofluid composition of claim 11 , wherein the surfactants have a pH that imparts or maintains a net negative or positive charge.

15. The nanofluid composition of claim 11 , wherein the nanofluid exhibits an increase of thermal conductivity of at least about 50%.

16. The nanofluid composition of claim 11 , wherein the one or more magnetically sensitive nanoparticles comprise metals, metal oxides or combinations thereof; and wherein substantially all of the nonmagnetically sensitive nanoparticles are magnetically aligned.

17. A nanoparticle composition prepared by the process comprising:
combining one or more nonmagnetically sensitive nanoparticles, one or more magnetically sensitive nanoparticles, and one or more surfactants;
dispersing one or more nonmagnetically sensitive nanoparticles, one or more magnetically sensitive nanoparticles, and one or more surfactants in a dispersion; and
exposing the dispersion and its contents to a magnetic field, wherein the nanoparticle composition exhibits an increase of thermal conductivity of at least about 10%; wherein the one or more surfactants are selected from the group consisting of a cationic surfactant, an anionic surfactant, a zwitterionic surfactant, and combinations thereof; wherein the one or more surfactants are attached to the one or more nonmagnetically sensitive nanoparticles forming a S/NSP complex by electrostatic attraction; wherein the S/NSP complex is attached to the one or more magnetically sensitive nanoparticles by electrostatic attraction; and wherein at least a portion of the nonmagnetically sensitive nanoparticles are magnetically aligned.

18. The nanoparticle composition of claim 17 , wherein the S/NSP complex is formed prior to the dispersing step.

19. The nanoparticle composition of claim 17 , wherein the combining step further comprises combining the one or more nonmagnetically sensitive nanoparticles, one or more magnetically sensitive nanoparticles, and one or more surfactants in a fluid, and wherein the process further comprises attaching one or more magnetically sensitive particles to one or more S/NSP complexes, one or more nonmagnetically sensitive nanoparticles and one or more magnetically sensitive nanoparticles in the fluid.

20. The nanoparticle composition of claim 19 , wherein the attaching one or more magnetically sensitive particles to one or more S/NSP complexes occurs prior to dispersing the one or more surfactants; or wherein the attaching one or more magnetically sensitive particles to one or more S/NSP complexes occurs after dispersing the one or more surfactants.

Assignees

• Georgia Tech Res Inst
• South Dakota Board Of Regents

Inventors

• Hong Haiping
• Peterson G P “Bud”

Classifications

• H01F1/44 Primary

  of magnetic liquids, e.g. ferrofluids (particles in a bonding agent H01F1/28, H01F1/36, {H01F1/37}) · CPC title

• C08K2003/2275

  Ferroso-ferric oxide (Fe3O4) · CPC title

• Y10S977/742

  Carbon nanotubes, CNTs · CPC title

• C08K3/04

  Carbon · CPC title

• B82Y30/00

  Nanotechnology for materials or surface science, e.g. nanocomposites · CPC title