Chemical synthesis of nanoparticles and electrohydrodynamic manipulation of nanoparticulate suspensions

This research concerns the study of nanoparticle synthesis methods and the influence that nanoparticles can have on the physical and electrical properties of non-polar fluids. In this study it is demonstrated that a very small volume fraction of nanoparticles can have a very large effect on the macroscopic properties of fluids. Characterization of nanoparticles and nanofluids has led to the creation of new techniques for controlled deployment of nanoparticles within larger structures. A new dielectrophoretic technique can be used for (1) uniformly sized droplet generation and manipulation with controllable droplet size, (2) oil-in-water emulsion creation in unique way, (3) recycling nanoparticles from nanoparticulate suspensions and (4) creation of core-shell structures. Different types, sizes and morphologies of nanoparticles have been made successfully by chemical synthesis and new synthesis routes have been created. A new wet chemical route has been devised to synthesise nickel nanoparticles with controllable size and different morphology including new shapes such as micro-flower and nano-stars. PZT nanoparticles have been synthesized hydrothermally with controllable size and new morphologies created such as nearly spherical nanoparticles and pellets. A novel wet chemical synthesis method was developed to produce core-shell structures of Ni- and also Fe3O4 - coated SiO2, BT, and PZT particles. The characterization of non-polar fluid-based nanofluids included a sedimentation study, studies of the fluidic properties (viscosity and surface tension) and electrical properties such as DC conductivity and dielectric permittivity. The results clearly show that the macroscopic properties of base fluids (silicone oil and perfluorinated oil) were changed even with a very low concentration (< 0.6 vol %) of nanoparticles added. The properties of nanofluids are found to depend on the properties of the base fluid and also on the properties of the dispersed nanoparticles. Importantly, the properties are demonstrated to depend on the fluid-particle interaction.