Conductive High-Toughness Oxides

Oxide coatings have been used in thermal and environmental barrier layers for coatings for hot section turbine applications, among other uses. With the PS-PVD method, Glenn researchers observed the formation of a minority phase of a metastable oxide (zirconium oxide) that is usually found only in a vapor state. They found that the high temperatures and fast deposition process of the PS-PVD system incorporated nonequilibrium phases in the coating and retained them at room temperature as well as at high temperature in the absence of oxygen. The material is vaporized and condensed on the surface via a rapid quenching, essentially &#34trapping&#34 this phase in the deposited coating. The coating microstructure and composition can also be manipulated by changing the processing parameters, allowing the thickness of the coating to be tailored to a given application. Since this metastable phase is conductive, this coating can be used as (for example) an extremely sensitive (thermal or temperature) sensor. It also has very good durability and erosion resistance, making it useful as a protective and conductive coating for electronics and microelectronics. This is an early-stage technology requiring additional development, and Glenn welcomes co-development opportunities. Innovators at NASA's Glenn Research Center have developed a novel method for making oxide coatings that have excellent mechanical strength and electronic conductivity at room temperature. Using the Plasma Spray-Physical Vapor Deposition (PS-PVD) processing methodology, Glenn researchers have been able to produce a coating containing a metastable phase that no other method can achieve. Upon exposing the material to moderate temperatures (greater than 300°C) in the presence of oxygen, the metastable phase is further oxidized, and the material becomes insulating while retaining its high toughness and microstructure. With this innovation, a coating can be created from any metal oxide, including rare earth oxides, zirconium oxide, hafnium oxide, titanium oxide, or any combination of two or more oxides. Glenn's innovation has great potential for industries that require increasingly tough ceramic coatings, such as electronics, chemical and petroleum refineries, the aerospace industry, and automotive and aeronautics manufacturing.