Dual-plasma synthesis of coated metal nanoparticles with controlled surface properties

There are many fluid based heat transfer processes that could benefit from an increase in efficiency. Recently a process has emerged that allows the improvement of the thermal conductivity of existing heat transfer fluids. This increase is achieved when particles with at least one dimension less than 100 nm (i.e. nanoparticles) are dispersed into the heat transfer fluid to create a so-called "nanofluid".;In this work, a novel dual-plasma reactor using a low-pressure pulsed DC arc system for the synthesis of metal nanoparticles coupled with an in-flight RF plasma polymerization system was designed to synthesize coated and functionalized metal nanoparticles. The reactor geometry takes into account the initial nanoparticle trajectory in order to optimize the nanoparticle collection efficiency. It was found that microdroplets also produced in the pulsed DC arc system could be effectively filtered out through strategic collection of the nanoparticles. The plasma polymer coatings produced range from slightly non-polar to polar, based on contact angle measurements. The hydrophilicity of the surface depends strongly on the gas species present in the plasma environment.;Nanofluids are not free of problems, unfortunately. The dispersed nanoparticles are not stable and tend to form agglomerates that settle out of suspension. The conventional method for combating this involves the use of surfactants, but these tend to loose effectiveness at moderate temperatures. Another more permanent and reliable method for stabilizing these nanofluids is to functionalize their surface in an effort to create a more favorable interaction between the particle surface and the host fluid.