SGER/GOALI: Electrostatic-Force-Assisted Cold Gas Dynamic Spray of Nanoparticles-A New Low Temperature Process for Producing Nanostructured Coatings and Bulk Materials

University Of Wisconsin-Milwaukee, Milwaukee WI

Investigators

Abstract

Nanostructured coatings and bulk materials have become increasingly important in developing new structural surfaces and bulk components. For instance, sprayed coatings using nanocrystalline metallic stainless steel powders exhibit superior hardness compared to conventional coatings, and nanostructured Al-based bulk alloy exhibits tensile strength about twice that of the commercial counterparts. Various methods, such as laser deposition, thermal spray, and plasma spray, have been developed in the laboratory to obtain nanostructured coatings. However, to date no nanoscale powder coating technologies for industrial applications are commercially available yet. The research being conducted is focused on a new and innovative electrostatic-force-assisted cold gas dynamic spray (ECGDS) technique for producing nanostructured coatings at low temperature with low cost and high throughput. The intellectual merit of the work involves the extension of the conventional CGDS system for micro-sized particles to the nanoscale particle size spectrum. It combines the electrostatic field with the supersonic gas-particle two-phase dynamic flow field to provide sufficient momentum for nanoparticles to penetrate through the bow shock and then deposit on the target surface with sufficient kinetic energy. The objectives of the research effort are to investigate the feasibility of the ECGDS, to understand the transport process of nanoparticles in the supersonic flow, and to correlate the spray parameters, including nanoparticle size, carrier gas, gas pressure, and gas temperature, with the density and the structure of the resulted coating through intensive numerical simulations and experimental studies. Innovations of the proposal include use of electrostatic force to assist nanoparticle acceleration to penetrate the bow shocks, techniques to prevent agglomeration of nanoparticles, and a new charger to charge nanoparticles to high levels. This SGER-GOALI project is expected to have a significant and broad impact on research and education at UWM as well as in the Great Milwaukee Area. The ECGDS system is an essential tool for the development of new low temperature coating technology, which will directly impact many industrial applications, such as fuel cells. Results on the nanoparticle production, dispersion, and charging will significantly contribute to the general area of nanoparticle-based nanomanufacturing and nanofabrication. This GOALI project will be co-developed with International Thermal Systems (ITS, GOALI partner), and this technology, if successful, will be transferred directly to industry. The project promotes further educational efforts at UWM through the participation of undergraduates, graduates and K-12 teachers, particularly underrepresented minorities. The work is also impacting the curriculum at UWM.