Laser fabrication of continuous nanofibers

Abstract

This invention provides a continuous process of making continuous nanofibers of all kinds, such as SiC, BN, AlN, and C. Laser heating a vapor of feed-material made of all atomic elements needed to grow chosen nanofibers results in growth of nanofibers onto seed-nanostructures attached to a filament, which is then pulled up continuously at a rate controlled by a rate of growth of the nanofibers. More feed-material is supplied at a rate sufficient to enable the nanofibers to grow longer continuously without limit. Laser light focused into a doughnut shape provides a photon density gradient, which constrains the nanofibers to grow parallel to each other and in the form of cylinders, so that industrially useful structures like cables and cylinders can be made in one low cost operation and in large quantities.

Description

BACKGROUND OF THE INVENTION [0001] This invention relates to a continuous-flow process of making continuous-length nanofibers by laser vaporization. [0002] The fantastic properties and applications of nanotubes have been described in a presentation of a new field called “Fractal Tube Reinforcement Microengineering” by Russell in 32nd International SAMPE Technical Conference, p. 224 (Nov. 5-9, 2000). There has been great interest in using nanotubes as building blocks to construct all kinds of products with superior performance, but nanotubes have been far too costly and of insufficient length and quantity to be useful for most industrial applications. Smalley, et al. in U.S. Pat. No. 6,183,714 disclose pulse laser vaporization of carbon mixed with one or more Group VIII transition metals to make a carbon nanotube. They then use a second laser pulse to maintain this nanotube end in an annealing zone, which allows growth of ropes of nanotubes. These ropes, however, are not continuous-l...

AI Technical Summary

Benefits of technology

[0006] Another object is to provide a process of controlling the growth of new nanofibers in order to make useful structures like cables and cylinders in one continuous operation. This is accomplished herein by applying tension to the growing nanofibers by focusing at least one laser light beam into the shape of a doughnut at a vapor of feed-material in a reaction zone. This provides a photon density gradient, which gathers atoms of the vapor together and constrains the growth of new nanofibers to be parallel to each other and to assume a cylindrical form. In another aspect an electrical field is applied to align the new nanofibers and constrain them into chosen shapes and useful structures.

Problems solved by technology

There has been great interest in using nanotubes as building blocks to construct all kinds of products with superior performance, but nanotubes have been far too costly and of insufficient length and quantity to be useful for most industrial applications.

These ropes, however, are not continuous-length ropes and not attached to anything that can be pulled or wound.

So, this process is not continuous and must be stopped to recover nanotube ropes from condensed vapor.

However, they do not disclose any way to apply tension to the nanofibers to constrain them to grow parallel to each other with controlled geometry to form useful structures.

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