ABSTRACT Timothy Ward CTS-9509394 The objectives of this research are: (1) to advance the understanding of the physical and chemical processes which govern the particle morphology (e.g. dense, hollow particles or porous) and microstructure (e.g. find-grained or single crystal) of inorganic (ceramic or metal) powders produced by spray processes, and (2) to utilize that understanding to develop and test strategies for producing desired, or avoiding undesired, morphologies for several representative materials and precursor types. The basic experimental approach will be to utilize an electrodynamic balance to levitate individual solution precursor particles, and then observe the morphology evolution of the individual particle as the temperature and/or humidity are changed in a controlled fashion. As the temperature is changed (up to 800{SYMBOL 176 f "Symbol"}C or higher in some cases), solvent evaporation, precursor decomposition, gas evolution, melting, sintering, evaporation/condensation and other processes contribute to the final morphology and microstructure. Morphology evolution will be followed visually using a video camera and light scattering, and mass changes will be monitored using a video camera and light scattering, and mass changes will be monitored using the particle levitation voltage. Both single-phase and multicomponent/multiphase particles will be investigated utilizing precursors which have been reported to yield different particle morphologies in powder synthesis by spray pyrolysis. Specifically, metallic Ag and zirconia will be studied using nitrate, chloride, organometallic and colloidal precursors. Metal/ceramic composite particles (zirconia/silver) and multicomponent mixtures containing a volatile component (PbO) will be investigated. The results of this project will enable better control over particle characteristics in materials produced by spray processes. Inorganic materials which might be good candidates for production by spray processes include: elec tronic ceramics such as superconductors and ferroelectrics, fullerenes, nanophase materials and composites, and metal powders. ***
