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.

1 . A process of making continuous nanofibers comprising the steps of: 
 providing seed-nanostructures in a reactor capable of maintaining a positive internal pressure; applying a static electric charge to an assembly of said seed-nanostructures in said reactor by means of a static electric charge generator sufficiently so that said seed-nanostructures become aligned relative to each other; removing oxygen and water and injecting inert gas in said reactor with said seed-nanostructures; heating each lower tip of at least one filament by focusing at least one laser light beam on said tip by means of at least one laser until said tip becomes molten hot; moving said tip of said filament out of a path of said beam toward said seed-nanostructures such that said seed-nanostructures become attached to said tip of said filament; providing feed-material comprised of all atomic elements from which new nanofibers are built; making a vapor from said feed-material by heating said feed-material; heating said vapor to a temperature sufficient to cause new nanofiber growth and gathering atoms of said vapor together in a local region of said laser light beam by focusing said beam from said laser; raising said tip of said filament to a position just above said beam such that said new nanofibers form from said vapor in a continuous structure with said seed-nanostructures; pulling out said filament with attached said new nanofibers at a rate controlled to match a rate of new nanofiber growth; providing tension on said new nanofibers as they grow by at least one tensioning means; and constraining said new nanofibers to grow substantially parallel to each other by said tensioning means.    
   
   
       2 . The process of  claim 1  wherein said process is a continuous-flow process such that said feed-material is continuously provided as required to allow continuous growth of said new nanofibers.  
   
   
       3 . The process of  claim 2  wherein the step of providing said feed-material further comprises including in said feed-material a total of at most 5 atom % of at least one transition element selected from the group consisting of all transition elements.  
   
   
       4 . The process of  claim 3  wherein the step of providing tension further comprises converging said laser light beam such that a photon density gradient is provided having a toroidal shape, said laser being a visible light laser, and the step of constraining said new nanofibers to grow substantially parallel to each other further comprises constraining said new nanofibers to assemble into a cylindrical shape by means of said photon density gradient.  
   
   
       5 . The process of  claim 4  wherein the step of providing tension further comprises applying an electrical field to said new nanofibers by means of an electric field generator.  
   
   
       6 . The process of  claim 4  wherein the step of providing feed-material further comprises providing carbon feed-material, including in said feed-material a total of at most 3 atom % of at least three transition elements selected from the group consisting of all transition elements, and said new nanofibers are carbon nanofibers.  
   
   
       7 . The process of  claim 5  wherein the step of providing feed-material further comprises providing carbon feed-material, including in said feed-material a total of at most 3 atom % of at least three transition elements selected from the group consisting of all transition elements, and said new nanofibers are carbon nanofibers.  
   
   
       8 . The process of  claim 6  wherein the step of pulling up said filament further comprises winding said filament together with attached said new nanofibers, and the step of heating said feed-material further comprises heating said feed-material by means of an infrared laser.  
   
   
       9 . The process of  claim 7  wherein the step of pulling out said filament further comprises winding said filament together with attached said new nanofibers, and the step of heating said feed-material further comprises heating said feed-material by means of at least one infrared laser.  
   
   
       10 . The process of  claim 5  wherein the step of providing feed-material further comprises providing boron nitride in said feed-material.  
   
   
       11 . The process of  claim 5  wherein the step of providing feed-material further comprises providing silicon carbide in said feed-material.  
   
   
       12 . The process of  claim 5  wherein the step of providing feed-material further comprises providing aluminum nitride in said feed-material.  
   
   
       13 . A process of making continuous nanofibers comprising the steps of: 
 providing seed-nanotubes in a reactor; applying a static charge to at least one filament in said reactor by means of a static charge generator sufficiently so that said seed-nanotubes become aligned relative to each other; removing oxygen and water and injecting inert gas in said reactor; heating each lower tip of said at least one filament by focusing at least one laser light beam on said tip by means of at least one laser until said tip becomes molten hot; moving said tip of said filament out of a path of said beam toward said seed-nanotubes such that said seed-nanotubes become attached to said tip of said filament; providing feed-material including all elements from which new nanofibers are built; making a vapor from said feed-material by heating said feed-material by at least one heating means; heating said vapor to a temperature sufficient to cause new nanofiber growth and gathering atoms of said vapor together in a local region of said laser light beam by focusing said beam from said laser; raising said tip of said filament to a position just above said beam such that new nanofibers form from said vapor in a continuous structure with said seed-nanotubes; pulling out said filament with attached said new nanofibers at a rate controlled to match a rate of new nanofiber growth; providing tension on said new nanofibers as they grow by converging said laser light beam such that a photon density gradient is provided having a toroidal shape; and constraining said new nanofibers to grow substantially parallel to each other in a substantially cylindrical shape by means of said photon density gradient.    
   
   
       14 . The process of  claim 13  wherein said process is a continuous-flow process such that said feed-material is continuously provided as required to allow continuous growth of said new nanofibers.  
   
   
       15 . The process of  claim 14  wherein the step of providing tension further comprises applying an electric field to said new nanofibers by means of an electric field generator.  
   
   
       16 . The process of  claim 15  wherein the step of pulling out said filament further comprises winding said filament together with attached said new nanofibers, and the step of heating said feed-material further comprises heating said feed-material by means of an infrared laser.  
   
   
       17 . The process of  claim 13  wherein the step of providing feed-material further comprises providing feed-material that comprises a carbon material selected from the group consisting of carbon, and silicon carbide, and any combination of these.  
   
   
       18 . The process of  claim 16  wherein the step of providing feed-material further comprises providing feed-material that comprises a carbon material selected from the group consisting of carbon, silicon carbide, and any combination of these.  
   
   
       19 . The process of  claim 13  wherein the step of providing feed-material further comprises providing feed-material that comprises a nitride selected from the group consisting of boron nitride, and aluminum nitride, and any combination of these.  
   
   
       20 . The process of  claim 16  wherein the step of providing feed-material further comprises providing feed-material that comprises a nitride selected from the group consisting of boron nitride, and aluminum nitride, and any combination of these.