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.

Description

RELATED CASES [0001] This application is a continuation of U.S. patent application Ser. No. 09 / 921,437 filed Mar. 8, 2001, which is a divisional of U.S. patent application Ser. No. 09 / 293,867 filed Apr. 16, 1999, (now abandoned), which is a divisional of U.S. patent application Ser. No. 08 / 691,853, filed Aug. 2, 1996, now U.S. Pat. No. 5,997,956, which claims the benefit of U.S. Provisional Application Ser. No. 60 / 002,084, filed Aug. 4, 1995, the contents of all of which are hereby incorporated in their entirety by this reference.II. FIELD OF THE INVENTION [0002] This invention relates to methods of powder formation and thin film deposition from reagents contained in liquid or liquid-like fluid solutions, whereby the fluid solution, near its supercritical point temperature, is released into a region of lower pressure causing a superior, very fine atomization or vaporization of the solution. Gasses are entrained or fed into the dispersed solution and rapidly flow into a flame or plas...

AI Technical Summary

Benefits of technology

"The present invention provides a method and apparatus for depositing coatings and nanophase materials using plasma torch and CCVD techniques. The method involves using a solution fluid near or above its critical pressure and temperature, which is then heated just prior to being released through a nozzle or restriction. This results in a very fine atomization of the solution, with the precursor molecules reacting or dissolving prior to the atomization process. The method can be used to deposit coatings from various metalorganics and inorganic precursors. The resulting powder size can be decreased by decreasing the concentration of the initial solution, decreasing the time in the hot gases, decreasing the size of the droplets formed, and increasing the vapor pressure of the reagent. The method also allows for the formation of high-speed gas-vapor streams, improving film quality and deposition efficiency. The noncombustible fluids can be used as the solvent for the precursors, and the deposition can be performed at reduced pressures or in a controlled atmosphere. The technical effects of the invention include improved deposition efficiency, reduced powder size, and improved film quality."

Problems solved by technology

Many of these fluids are not stable as liquids at STP, and must be combined in a pressure cylinder or at a low temperature.

Conversely, if in-line filters become clogged or precipitant is found remaining in the main container, an incompatibility under those conditions may have occurred.

Images