Application of Improved Aerosol Deposition to Deposit Functional Films and Atomistic Investigation of Dynamic Response of Particle During Ballistic Impact
2023-01
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Application of Improved Aerosol Deposition to Deposit Functional Films and Atomistic Investigation of Dynamic Response of Particle During Ballistic Impact
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2023-01
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Aerosol deposition (AD) is a novel approach to producing robust nanocrystalline thin films or thick ceramic coatings at room temperature. It is hence applicable to variable substrates from low-melting metal substrates to refractory ceramic substrates. Aerosolizing precursor powder into appropriate size distribution and concentration is crucial to making films with good adhesion. The fluidized bed is a common approach, which is driven by a pressure difference for aerosol generation. Nonetheless, this method often fails to make aerosol flow with proper size distribution without pre-treatment on precursor powder.Furthermore, owing to its solid-state deposition property, particle-substrate interaction plays an essential role in AD, especially in making thin films with nanoparticles. Numerous experimental and simulation studies have been investigated to physically and theoretically understand events of particle-substrate interaction in AD. However, thermal energy evolution and structural transformation in nanoparticles have so far not been fully elucidated. Therefore, the purpose of the studies proposed here is to develop different methods for generating aerosol flow, subject to the type of as-deposited coatings, and to perform simulation studies focusing on nanoparticle-substrate interaction at an atomistic scale. The first portion of my dissertation will focus on combining the spray pyrolysis technique with aerosol deposition (AD) for producing Yttria-stabilized zirconia (YSZ) based thermal barrier coatings (TBCs). The desired outcome of this study is to achieve an in-flight synthesis of applied particles in AD and deposit synthesized YSZ particles into layers. We additionally investigate the effect of operating conditions of spray pyrolysis on the size distribution of synthesized particles, the impact of substrate hardness on the coatings growth rate, and the influence of solute composition in precursor liquid on the thermal performance of as-deposited YSZ coatings. The second portion of my dissertation will develop a voice-coil-based powder dispensing system for aerosol generation, coupling it with conventional aerosol deposition (AD) and co-deposit thermoelectric coatings with variable elements ratio by this improved AD setup. Transport properties of as-deposited samples with different amounts of the doped element will be measured to know the dopant effect on the thermoelectric performance of as-deposited coatings. The third portion of my dissertation will focus on elucidating nanoparticle-substrate interaction in aerosol deposition at an atomistic scale via molecular dynamics (MD) simulations. Yttria-stabilized zirconia (YSZ) is selected as the material for both impacting nanoparticles and substrates. The simulations that will be performed can be categorized into cold impact and thermal impaction simulations. In cold impact simulations, we will study the influence of impact speeds on thermal energy evolution, structural transformation, and mechanical deformation in nanoparticles and substrates. In thermal impact simulations, we will investigate the role that ratio of translational kinetic energy and thermal energy in nanoparticles plays and demonstrate the influence of this ratio on nanoparticle behavior during the collision process. The final section of my dissertation focuses on investigating the effects of particle grain size on its plasticity, deformation mechanism, and dislocation propagation during the ballistic impact. By using molecular dynamics simulation, we can study the microstructure transformation and dislocation interactions in the particle over the compressive strains. The results indicate that impact velocity adversely affects the dislocation mobility in the particle, and there is increased dislocation density in the particle with a larger initial grain size.
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University of Minnesota Ph.D. dissertation.January 2023. Major: Mechanical Engineering. Advisor: Christopher Hogan. 1 computer file (PDF); xii, 166 pages + 1 supplementary file.
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Song, Guanyu. (2023). Application of Improved Aerosol Deposition to Deposit Functional Films and Atomistic Investigation of Dynamic Response of Particle During Ballistic Impact. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/262886.
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