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

本研究项目的重点是悬浮等离子喷涂（SPS）和溶液前驱体等离子喷涂（SPPS）中等离子体-液体相互作用的诊断和基本原理。所获得的知识将应用于锂离子电池纳米结构阴极的合成，以及用于结构健康监测的压电传感器的沉积。纳米结构材料和先进涂层是能源、传感器、航空航天、生物医学和微电子行业的关键资产，所有这些都为加拿大经济做出了突出贡献。这些材料和涂层可以从几种加工路线获得，包括热等离子体i）合成和ii）沉积，两者都具有经证实的可扩展性和工业加工速率。在这两种技术中，原料材料被注入到高焓、高温等离子体射流中，以i）熔化、蒸发和快速淬火以形成粉末，或ii）加热、熔化并朝向基底加速以形成涂层。为了获得纳米结构粉末和涂层，通常选择纳米颗粒悬浮液或前体溶液作为原料;相应的工艺分别称为SPS和SPPS。SPS和SPPS工艺有一个共同的特点：液体携带纳米颗粒或前体进入等离子体射流，而不是传统等离子体喷涂中携带微米颗粒的惰性气体。**现场采集数据的可用性对于了解和优化SPS和SPPS至关重要，正如光学传感器的引入有助于了解和将微米颗粒等离子喷涂工艺转移到生产车间一样。尽管如此，商业上可用的等离子体喷雾传感器在诊断纳米尺寸的颗粒方面效率低下，并且等离子体-液体相互作用比等离子体-气体相互作用复杂得多。因此，需要进一步努力开发复杂的测量设备，以表征SPS和SPPS中的等离子体-液体相互作用，并诊断飞行中纳米颗粒的速度，尺寸，加热和成分。本研究计划将通过追求五个研究目标来满足这一需求：*1.采用先进的数据分析方法和诊断工具来表征SPS和SPPS;*2.了解雾化液滴如何与等离子体射流相互作用，绘制等离子体射流中液滴的分散和尺寸分布;*3.研究等离子体-液体相互作用，解释受控气氛下液滴对等离子体性质的影响;*4.研究等离子体-液体相互作用与合成纳米材料的微观结构性质之间的关系;将在SPS和SPPS中获得的知识应用于锂离子电池纳米结构阴极的合成和用于结构健康监测的压电传感器的合成。这项研究将有助于保持加拿大在热等离子体和热喷涂工艺方面的领导地位。SPS和SPPS中的高效诊断将有助于将此类合成工艺转移到全球热喷涂行业，该行业目前占100亿美元，加拿大和美国的市场份额为37.5%。因此，培训SPS、SPPS和血浆诊断学的研究生对加拿大来说是一项很好的投资。雇主将寻求高素质的人才（HQP），他们的技能不仅使他们能够合成纳米颗粒和纳米结构涂层，而且还使他们能够为特定应用设计和优化材料。

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.