Spring 2019 - Seminar Series
Dr. Ranga Gopalakrishnan - University of Memphis
Room temperature, solvent-free processing of ceramic coatings using Aerosol Deposition method
Abstract
Aerosol Deposition (AD) method is a scalable, room temperature and solvent-free route for processing dense ceramic coatings in which sub-10 mm aerosol particles are impacted at speeds 300 – 1000 m/s on diverse substrates (metal/ceramic/glass/plastic) at reduced pressures (~500 Pa). The mechanism of coating formation, termed as room temperature impact consolidation (RTIC), involves the conversion of the kinetic energy of impacting particles to compressive strain energy in the deposited particle fragments, subsequently compacting them into a dense layer for coating to build up at a high rate ~ microns per minute. This method is particularly suitable for producing thin coatings of ceramic materials. The adherence, thickness, porosity, and surface area per unit mass of the produced thin film ceramics are highly sensitive to the morphology and extent of agglomeration of the particles used and their kinetic energy at impact. The design and quality control of industrial scale coating processes require strict control of the morphology and extent of agglomeration of impacting particles. Challenges in scaling AD to industrial scale include the creation of steady source of micron-sized aerosol particles, design of supersonic nozzles to achieve desired impact velocity of particles and pre-treatment of powders to generate particles that will maximize the efficiency of deposition. In this presentation, I will present the current work in our lab to create coatings of ceramic materials such as titanium dioxide, hydroxyapatite on diverse substrates motivated by energy and biomedical applications. The realization of highly adherent coatings using AD method has been demonstrated in our lab that opens up the scope for processing ceramic coatings at low cost and without the use of toxic solvents and/or heat.
About the Speaker
Dr. Ranga Gopalakrishnan obtained his PhD from the University of Minnesota – Twin Cities in 2013 specializing in aerosol transport processes. He has published several articles on aerosol transport modeling and experimental studies probing momentum and charge transfer onto particles in the non-continuum transport regimes. He has done postdoctoral stints at the California Institute of Technology where he worked on aerosol detachment processes from surfaces and at the University of California at Berkeley working on plasma-liquid interactions. He is currently an Assistant Professor at the University of Memphis. His current research is focused on the application of aerosol science fundamentals to additive manufacturing applications. Specifically, his group is working on scaling up the Aerosol Deposition method for use as a sustainable, room temperature processing method for coatings of ceramics and polymeric materials. His research interests also include modeling of aerosol and plasma transport processes using Langevin Dynamics methods.