Tools for vapor phase processing of refractory metals.
Abstract
This grant is to upgrade an existing, electron beam directed vapor deposition (EB-DVD) system that has shown promise for the deposition of complex chemistry coatings and as a tool for discovery of new materials via the synthesis of combinatorial libraries. Vapor phase processing is widely used during the manufacture of many DOD systems, and by research communities who design new materials, develop novel device concepts and explore future coatings. It is indispensable for the fabrication of microelectronic and quantum devices, it is widely used to control the spectral reflectance and transmittance of optical components, and vapor phase coatings greatly extend the operational lifeof materials in extreme environments such as gas turbine engines or the leading edges of hypersonic vercapacitors and integrated functional materials havealso all benefited from the capabilities of continually upgraded EB-DVD processing tools. This vapor phase synthesis and processing technique is currently used for the exploration of multiple principle element (MPE) alloys containing five or more elements with approximately equal molarfractions. However, the chemical complexity requires tens of millions of unique compositions (for five and 6-component systems) to be evaluated. Until computationally efficient simulation and modeling tools emerge, the approach that most quickly converges on promising materials is combinatorial synthesis combined with high throughput screening.Efforts to use the EB-DVD technique for the processing of the most refractory metallic alloy libraries, and for the deposition of complex chemistry metallic coatings for hot corrosion and oxidation protection, have exposed several issues with existing plasma assistance techniques used to create defect free coatings. In the technology upgrade proposed here, we seek to use the high thermionic current density emitted from electron beam heated evaporating surfaces to create an intense (more than 50% ionized) evaporant plasma that can be deposited on electrically bia approach, a ring anode positioned several centimeters from the electron beam impingement point on the vapor source is connected to a powersupply and a positive potential of 10-80 V used to accelerate the thermionic electrons, raising their kinetic energy into the 10-20 eV range. Their subsequent impact with vapor atoms then has a high probability of causing their ionization. The vapor emitted from the surface is therefore ionized by collisions with these thermionic electrons during its transport to a substrate for deposition. In thiselegant approach, the electron beam simultaneously creates and ionizes the vapor (and combinations of inert and reactant gases that can be added to the process).The proposed technology upgrade increases the rate and cleanliness of evaporation of refractory metals and high temperature ceramics by increasing the EB gun power from 10 to 17 kW, and implements this novel, low cost approach for plasma-assisted deposition. Together with a new source crucible, these upgrades have the potential to accelerate the discovery of refractory metal MPEs, transform the deposition of metallic coatings such as the bond coats used to extend the life of marine gas turbine engines, provide new options for ceramic environmental, thermal barrier and erosion protection coatings, and lead to new ablation resistant coatings for hypersonic vehicle leading edges. The EB-DVD tool supports many DOD funded and proposed efforts in these areas, while continuing to provide a training environment for graduate students, many of whom transition to positions supporting defense community needs.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 08, 2020
- Source ID
- N000142012331
Entities
People
- H.N.G. Wadley
Organizations
- Office of Naval Research
- United States Navy
- University of Virginia