Processing and structure of nanoparticles: Characterization and modeling

Around 1992 scientist make the visionary argument that materials, if made nanocrystalline, would have a number of appealing new physical characteristics of potential significance for structural and functional applications. These provocative thoughts stimulated wide¬spread interest in the materials properties and novel mechanisms of nanostructured materials over the past two decades. In a flashback we must say that unfortunately most of the experimental findings documented in this period of two decades were not representative of intrinsic material response, due to the problems and difficulties associated with preparing and controlling nanocrystalline samples.

The objectives of our work are aimed at manufacturing and characterizing both theoretically and experimentally nanoparticles. The thesis describes the theoretical framework from which size and size distributions of metallic nanoparticles can be predicted. Our novel theoretical approach was successfully confronted to experiments using transmission electron microscopy dealing with nano-materials based on magnetron sputtering.

Also the kinetics of formation of silica fractal-like aggregates during combustion of a stoichiometric methane/air mixture with the hexamethyldisiloxane admixture was studied. Today the production of nanoparticles in a flame is used in the gas phase combustion synthesis of a variety of inorganic oxides. However, in many combustion applications, such as in domestic boilers or gas engines the formation of particles during combustion is undesirable. When using biogas as an energy source, during combustion, siloxanes are converted into silica particles which deposit onto internal parts of the equipment and are emitted into the environment. In this thesis work transmission electron microscopy is combined with the theoretical analysis to find conditions for formation of silica fractal-like aggregates.