Spheroidal aggregates comprising single-wall carbon nanotubes and method for making the same

Abstract

A method for separating single-wall carbon nanotubes from an aqueous slurry comprises adding a water-immiscible organic solvent to an aqueous slurry comprising single-wall carbon nanotubes, isolating at least some of the single-wall carbon nanotubes in the solvent, and removing the solvent from the single-wall carbon nanotubes to form dried single-wall carbon nanotubes. A spheroidal aggregate of single-wall carbon nanotubes is formed wherein the aggregate is approximately spherical and has a diameter in a range of about 0.1 and about 5 mm, and wherein the aggregate contains at least about 80 wt % single-wall carbon nanotubes. The spheroidal aggregates of single-wall carbon nanotubes are easily handled in industrial processes and are redispersable to single-wall carbon nanotubes and / or ropes of single-wall carbon nanotubes. This invention can also be applied to multi-wall carbon nanotubes.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims priority from U.S. provisional application Ser. No. 60 / 369,387, filed Apr. 2, 2002, which application is incorporated herein by reference.FIELD OF THE INVENTION[0002]This invention relates generally to carbon nanotubes, more particularly to single-wall carbon nanotubes, and more particularly to a form of single-wall carbon nanotubes convenient for handling and processing, and method for making the same.BACKGROUND OF THE INVENTION[0003]Single-wall carbon nanotubes (SWNT), commonly known as “buckytubes,” have unique properties, including high strength, stiffness, thermal and electrical conductivity. SWNT are hollow, tubular fullerene molecules consisting essentially of sp2-hybridized carbon atoms typically arranged in hexagons and pentagons. Single-wall carbon nanotubes typically have diameters in the range of about 0.5 nanometers (nm) and about 3.5 nm, and lengths usually greater than about 50 nm. Background informat...

AI Technical Summary

Benefits of technology

[0010]In one embodiment, the invention relates to an aggregate comprising single-wall carbon nanotubes wherein the aggregate is spheroidal and has a diameter in a range of about 0.5 and about 2 mm, and wherein the aggregate contains at least about 80 wt % single-wall carbon nanotubes. In another embodiment, the invention relates to a method for efficiently and quickly separating single-wall carbon nanotubes from an aqueous slurry, comprising adding a water-immiscible organic solvent to an aqueous slurry comprising single-wall carbon nanotubes, isolating at least some of the single-wall carbon nanotubes in the solvent, and removing the solvent from the single-wall carbon nanotubes to form dried single-wall carbon nanotubes. In yet another embodiment, the invention relates to a method for forming spheroidal aggregates of single-wall carbon nanotubes comprising adding a water-immiscible organic solvent to an aqueous slurry comprising single-wall carbon nanotubes, forming aggregates of single-wall carbon nanotubes in the solvent, and removing the solvent from the aggregates to form spheroidal aggregates of dried single-wall carbon nanotubes. Note “dried” carbon nanotubes shall mean nanotubes containing not more than about 20 wt % solvent.

[0011]In another embodiment, the invention relates to an aggregate comprising multi-wall carbon nanotubes wherein the aggregate is spheroidal and has a diameter in a range of about 0.5 and about 2 mm, and wherein the aggregate contains at least about 80 wt % multi-wall carbon nanotubes. In another embodiment, the invention also relates to a method for efficiently and quickly separating multi-wall carbon nanotubes from an aqueous slurry, comprising adding a water-immiscible organic solvent to an aqueous slurry comprising multi-wall carbon nanotubes, isolating at least some of the carbon nanotubes in the solvent, and removing the solvent from the carbon nanotubes to form dried multi-wall carbon nanotubes. Yet another embodiment of the invention relates to a method for forming spheroidal aggregates of multi-wall carbon nanotubes comprising adding a water-immiscible organic solvent to an aqueous slurry comprising multi-wall carbon nanotubes, forming aggregates of multi-wall carbon nanotubes in the solvent, and removing the solvent from the aggregates to form spheroidal aggregates of dried multi-wall carbon nanotubes.

[0012]The spheroidal aggregates of single-wall carbon nanotubes are easily handled in industrial processes and are redispersable to single-wall carbon nanotubes and / or ropes of single-wall carbon nanotubes. The spheroidal aggregates of multi-wall carbon nanotubes are also easily handled in industrial processes and are redispersible to individual multi-wall carbon nanotubes.

Problems solved by technology

Fine and fluffy powders can easily become airborne and can often be difficult to handle in industrial processes.

Although wet and dry purification procedures can yield purified single-wall carbon nanotubes, the resulting form of the single-wall carbon nanotubes can be difficult to handle in industrial processes.

Separation of the purified single-wall carbon nanotubes from the aqueous phase, often done by filtration or centrifugation, is typically slow and tedious, and often results in matted, compressed and dense forms of single-wall carbon nanotubes, such as mats, papers and chunks, that are difficult to redisperse in subsequent processes.