Chemical vapor deposition and powder formation using thermal spray

Abstract

A method for chemical vapor deposition using a very fine atomization or vaporization of a reagent containing liquid or liquid-like fluid near its supercritical temperature, where the resulting atomized or vaporized solution is entered into a flame or a plasma torch, and a powder is formed or a coating is deposited onto a substrate. The combustion flame can be stable from 10 torr to multiple atmospheres, and provides the energetic environment in which the reagent contained within the fluid can be reacted to form the desired powder or coating material on a substrate. The plasma torch likewise produces the required energy environment, but, unlike the flame, no oxidizer is needed so materials stable in only very low oxygen partial pressures can be formed. Using either the plasma torch or the combustion plasma, coatings can be deposited and powders formed in the open atmosphere without the necessity of a reaction chamber, but a chamber may be used for various reasons including process separation from the environment and pressure regulation.

We claim:  
     
         1 . Apparatus for producing an atomized spray of a formative fluid capable of forming a selected material in a formation region, said apparatus comprising: 
 a. reservoir means for containing said formative fluid at a first selected temperature and a first selected pressure;    b. means for pressurizing said formative fluid to a second selected pressure;    c. a fluid conduit formed of metal, said metal conduit having an input end in fluid communication with said reservoir and an opposed outlet end having an outlet port oriented to direct the formative fluid passing through said fluid conduit to said formation region; and    d. temperature regulating means positioned in thermal connection with said fluid conduit means for regulating the temperature of said formative solution at said outlet end at a second temperature below the supercritical temperature of said formative fluid, said second temperature being selectable such that said fluid is in liquid state when passing through said fluid conduit and such that atomization of said formative fluid is promoted or controlled upon said formative fluid exiting said outlet end of said fluid conduit.    
     
     
         2 . Apparatus according to    claim 1    further comprising a gas supply means for admixing at least one gas with the atomized formative fluid which exits said outlet end of said fluid conduit.  
     
     
         3 . Apparatus according to    claim 1    further comprising an energy source for providing energy to the atomized formative fluid which exits said outlet end of said fluid conduit so as to promote formation of said material.  
     
     
         4 . Apparatus according to    claim 3    comprising means to provide said energy as a flame source that causes combustion of at least one component of said formative fluid.  
     
     
         5 . Apparatus according to    claim 1    including means to position a substrate such that said material is deposited as a film or coating on said substrate  
     
     
         6 . Apparatus according to    claim 1    comprising means to raise said third selected pressure above ambient pressure.  
     
     
         7 . Apparatus according to    claim 1    comprising means to lower said third selected pressure below ambient pressure.