Method for producing nano-structured materials

Abstract

A method for synthesizing a nano-structured material, including four primary steps: (A) providing a reaction chamber wherein the nano-structured material is generated from at least a starting material selected from the group consisting of a metal, a metal alloy, a metal compound, and a ceramic; (B) operating a twin-wire arc nozzle, comprising two wires and a working gas being controllably fed into the chamber, to form an arc between two converging leading tips of the two wires to heat and melt the starting material at the leading tips for providing a stream of liquid droplets traveling in a predetermined direction (preferably vertically downward); (C) operating at least a second high energy source for producing a vaporizing zone adjacent to the arc and inside the chamber wherein the liquid droplets are vaporized to form vapor species; and (D) cooling the vapor species for forming the nano-structured material. The second high energy source is selected from the group consisting of a laser beam, an electron beam, an ion beam, a flame, an induction plasma, and combinations thereof. The second high energy source may also be a plurality of arc plasmas. The nano-structured material produced can be in the form of a nanometer-sized powder particles or a coating (or thin film) containing nanometer-sized phases deposited on a substrate.

What is claimed:  
     
         1 . A method for synthesizing a nano-structured material, comprising: 
 (A) providing a chamber wherein said nano-structured material is generated from at least a starting material selected from the group consisting of a metal, a metal alloy, a metal compound, and a ceramic;    (B) operating a twin-wire arc nozzle, comprising two wires and a working gas being controllably fed into said chamber, to form an arc between two converging leading tips of the two wires to heat and melt said at least a starting material at said leading tips for providing a stream of liquid droplets traveling in a predetermined direction;    (C) operating at least a second high energy source for producing a vaporizing zone adjacent to said arc and inside said chamber with said liquid droplets traveling into said vaporizing zone and being vaporized therein to form vapor species; and    (D) operating heat treatment means to cool said vapor species for forming said nano-structured material.    
     
     
         2 . The method as defined in  claim 1 , wherein said second high energy source is selected from the group consisting of a laser beam, an electron beam, an ion beam, a flame, a high-frequency induction plasma, and combinations thereof.  
     
     
         3 . The method as defined in  claim 1 , wherein said nano-structured material comprises nanometer-sized powder particles.  
     
     
         4 . The method as defined in  claim 1 , wherein step (D) comprises a sub-step of directing said vapor species to impinge upon a substrate and deposit thereon to form said nano-structured material that is characterized by a coating containing nanometer-sized phases deposited on said substrate.  
     
     
         5 . The method as defined in  claim 1 , wherein said second high energy source comprises a plurality of arc plasmas.  
     
     
         6 . The method as defined in  claim 1 , further comprising an additional step (E), after step (C) and before step (D), said step (E) comprises introducing a stream of reactive gas into said chamber to impinge upon said vapor species and exothermically react therewith to produce said nano-structured material.  
     
     
         7 . The method as defined in  claim 1 , wherein step (B) includes: 
 operating wire feeding and control means to either continuously or intermittently feed said two wires into said chamber in such a fashion that the two leading tips are maintained at a desired separation; and    operating power supply means to provide currents through said two wires to form said arc with a temperature sufficient for melting said at least a starting material at said leading tips.    
     
     
         8 . The method as defined in  claim 6 , wherein step (E) includes operating means for controlling the flow rate of the reactive gas, thereby enabling change of particle size of the nanometer-scaled powder material.  
     
     
         9 . The method as defined in  claim 6 , wherein said reactive gas is selected from the group consisting of nitrogen, phosphorus, arsenic, oxygen, sulfur, selenium, tellurium, fluorine, chlorine, bromine, iodine, a carbon-containing gas, and mixtures thereof.  
     
     
         10 . The method as defined in  claim 1 , wherein said working gas is selected from the group consisting of nitrogen, hydrogen, noble gases and mixtures thereof.  
     
     
         11 . The method as defined in  claim 1 , wherein said vapor species are cooled in step (D) to become nanometer-sized powder particles and step (D) is followed by a step (F) which comprises operating a powder collector for collecting said powder particles.  
     
     
         12 . The method as defined in  claim 3 , wherein said step (D) includes a sub-step of operating means for injecting a cooling gas into said vapor species, thereby minimizing agglomeration of said nanometer-sized powder material.  
     
     
         13 . The method as defined in  claim 1 , wherein said working gas flow direction is arranged to be approximately vertically downward.  
     
     
         14 . The method as defined in  claim 1 , wherein said at least a starting material comprises two different materials.  
     
     
         15 . The method as defined in  claim 14 , wherein said two different materials make up the two wires in such a manner that the two wires have different material compositions.  
     
     
         16 . The method as defined in  claim 14 , wherein said two different materials include indium and tin.  
     
     
         17 . The method as defined in  claim 14 , wherein said two different materials include antimony and tin.  
     
     
         18 . The method as defined in  claim 1 , further including a step of positioning a reservoir at the bottom portion of said twin-wire arc or a distance below said twin-wire arc in such a fashion that said reservoir receives said stream of liquid droplets from the wires and exposes said liquid to said second energy source to vaporize at least a portion of said liquid.  
     
     
         19 . The method of  claim 1 , wherein said step (D) includes a sub-step of passivating said vapor species to stabilize said nano-structured material.