Preparation of stable carbon nanotube dispersions in liquids

Abstract

The introduction of nanotubes in a liquid provides a means for changing the physical and / or chemical properties of the liquid. Improvements in heat transfer, electrical properties, viscosity, and lubricity can be realized upon dispersion of nanotubes in liquids; however, nanotubes behave like hydrophobic particles and tend to clump together in liquids. Methods of preparing stable dispersions of nanotubes are described and surfactants / dispersants are identified which can disperse carbon nanotubes in aqueous and petroleum liquid medium. The appropriate dispersant is chosen for the carbon nanotube and the water or oil based medium and the dispersant is dissolved into the liquid medium to form a solution. The carbon nanotube is added to the dispersant containing the solution with agitation, ultrasonication, and / or combinations thereof.

Description

[0001] This application claims priority from U.S. Provisional application Ser. No. 60 / 254,959 filed on Dec. 12, 2000 entitled “Methods of Dispersing Carbon Nanotubes in Liquids” and is hereby incorporated by reference herein.BACKGROUND OF THE INVENTION [0002] 1. Technical Field [0003] Methods are described and surfactants are identified which can disperse carbon nanotubes in aqueous and petroleum liquid medium utilizing selected dispersants and mixing methods to form stable carbon nanotube dispersions. [0004] 2. Description of the Prior Art [0005] Carbon nanotubes are a new form of the material formed by elemental carbon, which possess different properties than the other forms of the carbon materials. They have unique atomic structure, very high aspect ratio, and extraordinary mechanical properties (strength and flexibility), making them ideal reinforcing fibers in composites and other structural materials. [0006] Carbon nanotubes are characterized as generally to rigid porous carbo...

AI Technical Summary

Benefits of technology

[0026] It is an object of the present invention to provide a method of preparing a stable dispersion of the carbon nanotube in a liquid medium with the combined use of dispersants and physical agitation.

[0028] It is another object of the present invention to utilize carbon nanotubes which may optionally be surface treated to be hydrophilic at surface for ease of dispersing into the aqueous medium.

[0040] It is another object of the present invention to form a uniform and stable dispersion of carbon nanotubes containing dissolved non-dispersing, “other” compounds in the liquid oil based medium.

Problems solved by technology

Differences in degree of graphitization, orientation and crystallinity of graphite planes, if they are present, the potential presence of heteroatoms and even the absolute difference in substrate diameter make experience with continuous fibers poor predictors of nanofiber chemistry.

Dispersing the nanotubes into organic and aqueous medium has been a serious challenge.

Moreover, the surfactants don't include the dispersants typically utilized in the lubricant industry.

U.S. Pat. No. 5,853,877 by Shibuta teaches dispersing disentangled nanotubes in a polar solvent and forming a coating composition with additives such as dispersing agents; however, a method of obtaining a stable dispersion is not taught.