Methods to Generate Size- and Composition Controlled Aerosol Nanoparticles
Abstract: This thesis describes experiments performed using different methods to produce aerosol nanoparticles with control over size and composition. The process included differential mobility analyzers (DMAs) as size-selecting instruments and tube furnaces for particle synthesis. A method to estimate the degradation of the DMA performance from the ideal case for individual DMAs was proposed and tested experimentally. Using this method, the size dependence of the DMA performance was predicted from measurements at a single particle size. Size- and composition controlled binary alloy aerosol nanoparticles were generated. Core particles were formed by the evaporation/condensation method, and alloy particles were created by the subsequent condensation of another material. The Au-Ga system was used as a test system. Generation processes were investigated by studying deposition patterns inside a horizontal evaporation/condensation nanoparticle generator. Comparison to estimates calculated from a one-dimensional monodisperse aerosol formation model indicates the presence of non-uniform flow inside the generator. Aerosol nanoparticles were created from the vapor emanating from the thermal decomposition of iron pentacarbonyl. The size, morphology, composition and structure of the generated iron-containing particles were investigated. The sintering behavior of agglomerated aerosol nanoparticles was investigated. When comparing the relative compaction temperature for different nanoparticles produced in different laboratories deviations in the sintering behavior were found. These could be associated to the different particle compositions. Individual nanoparticles were generated from monodisperse colloidal suspensions by the use of an electrospray method. Deposition of single particles could be achieved and controlled by deposition time and dilution ratio. The method was found to be independent of particle material.
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