Diagnostics of plasma-liquid interactions in suspension and solution precursor plasma spraying

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This research program focuses on the diagnostics and fundamentals of plasma-liquid interactions in suspension plasma spraying (SPS) and in solution precursor plasma spraying (SPPS). The acquired knowledge will be applied to the synthesis of nanostructured cathodes for lithium-ion batteries and to the deposition of piezoelectric sensors for structural health monitoring.Nanostructured materials and advanced coatings are key assets for the energy, sensors, aerospace, biomedical and microelectronics industries, all prominently contributing to Canada’s economy. These materials and coatings can be obtained from several processing routes, including thermal plasma i) synthesis and ii) deposition, both having proven scalability and industrial processing rates. In these two technologies, feedstock materials are injected into high enthalpy, high temperature plasma jets to be i) melted, vaporized and rapidly quenched to form powders or ii) heated, melted and accelerated towards a substrate to form coatings. To obtain nanostructured powders and coatings, nanoparticle suspensions or solutions of precursors are generally selected as feedstock; the corresponding processes are named SPS and SPPS, respectively. SPS and SPPS processes share a common characteristic: a liquid carries the nanoparticles or the precursors into the plasma jet, as opposed to an inert gas carrying micro-sized particles in conventional plasma spray.The availability of data acquired in-situ is paramount to the understanding and optimization of SPS and SPPS, just as the introduction of optical sensors helped in understanding and transferring micro-sized particle plasma spray processes to the production floor. Still, commercially available plasma spray sensors are inefficient in diagnosing nano-sized particles and plasma-liquid interactions are far more complex than plasma-gas interactions. As such, further efforts are required to develop sophisticated measurement devices to characterize the plasma-liquid interactions in SPS and SPPS, and to diagnose the velocity, size, heating and composition of nanoparticles in-flight.This research program will address this need by pursuing five research objectives:1. To adapt sophisticated data analysis methods and diagnostics tools to characterize SPS and SPPS;2. To understand how atomized liquid droplets interact with the plasma jet, mapping the dispersion and size distribution of the droplets within the plasma jet;3. To investigate the plasma-liquid interactions, explaining the influence of the liquid droplets on the plasma properties in controlled-atmospheres;4. To study the relations between the plasma-liquid interactions and the microstructural properties of the synthesized nanomaterials;5. To apply the acquired knowledge in SPS and SPPS to the synthesis of nanostructured cathodes for lithium-ion batteries and of piezoelectric sensors for structural health monitoring.This research will contribute to maintain Canada’s leadership in thermal plasma and thermal spray processes. Efficient diagnostics in SPS and SPPS will help transferring such synthesis processes to the worldwide thermal spray industry, which accounts for $10 billion nowadays, the market share of Canada and USA being 37.5%. The training of graduate students in SPS, SPPS and plasma diagnostics is thus a good investment for Canada. Employers will be seeking highly qualified personnel (HQP) with skills that will not only enable them to synthesize nanoparticles and nanostructured coatings, but that will also enable them to engineer and optimize materials for specific applications.