FUNCTIONAL PARTICLE GENERATION BY AEROSOL-ASSISTED PROCESSES
Ehrman, Sheryl H
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Aerosol-assisted processes are continuous with short residence times, simple operating procedures, and facile equipment requirements. They are scalable and promising for fabrication of functional particles as conductive pastes in solar cell metallization and interference packaging, electrode materials in energy storage devices, and photocatalysts in energy conversion. Although aerosol-assisted processes have long been used in manufacturing and their fundamentals have been intensively explored, further investigation is still required to better understand the particle formation mechanisms of different aerosol-assisted processes. In this dissertation, three different aerosol-assisted processes are investigated, spray pyrolysis, colloidal spray pyrolysis (CSP), and spray drying. These processes can be conducted under mild reaction conditions with simple operation procedures. The product particles are controllable. The effects of process variables on the product particles are studied. Furthermore, the prospects of applying these three aerosol-assisted processes in generating functional particles in applications, including solar cell metallization, battery, and photocatalysis are assessed. Part 1) includes Chapters 3-5. I first present Cu-Sn binary particle generation by spray pyrolysis. Through studying the particle oxidation behaviors under different reaction conditions, the Cu-Sn binary particles exhibit high oxidation-resistance. The one-dimensional and two-dimensional structures fabricated by direct printing inks containing Cu-Sn powders display low resistivity. They all suggest that Cu-Sn binary particles produced by spray pyrolysis are promising materials in the inks in printed electronics and in the conductive pastes in solar cell metallization and interference packaging. In Part 2), Chapters 6, a novel aerosol-assisted process, CSP, is developed. This process addresses one restriction of conventional spray pyrolysis which can only be used to fabricate particles from precursor solutions containing high-solubility salts. By applying CSP, tin@carbon (Sn@C) composite particles are produced with controllable interior structures. These composite particles exhibit high-performance as the anode materials for Li-ion and Na-ion batteries. In Part 3), Chapter 7, spray drying is utilized to fabricate photocatalysts from precursor solutions containing SnO2 colloids and edge-oxidized graphene oxide (eo-GO) sheets. The particle morphology, element distribution, and band structures were investigated by various tools. The photocatalytic activity of the composite particles is five times that of commercialized TiO2 (P25) in reducing CO2 into CH4.