Synthesis and Monte Carlo simulation of metallic nanoparticles and thermophysical property studies of nanofluids.

摘要

Nanostructured materials, including versatile nano-objects such as nanoparticles, nanotubes, nanowires, quantum dots and other nano-units as the building blocks for new bottom-up approaches to device and system assembly, are at the leading edge of the rapid developing field of nanoscience and nanotechnology. Metallic nanoparticles have captivated scientists' enduring attention and passion for their novel physical and chemical properties and promising application in numerous areas.;In this work, we present for the first time, a whole new metallic nanoparticles synthetic strategy based on a heterogeneous metal displacement reduction mechanism. In association with this underlying principle, we developed hydrodynamically and mechanically-assisted, and ultrasonication-assisted displacement reduction methods to successfully prepare a series of silver, copper, iron oxide, gold and platinum nanoparticles. By controlling reactant concentration and particle average residence time, we achieve size selectivity and size distribution control, which provides the possibility for exploitable scalability in commercial production.;Based on our experimental system, we established a kinetic model using a Monte Carlo stochastic algorithm and FORTRAN programming to explain the formation of dispersions of various sizes and size distributions. The model was tested with parameters of our real system of silver nanoparticles formation with a variety of mean size and size distribution. The simulated average size, size distribution and the time scale of the process agree reasonably well with the experimental values. Thus the established theoretical model was proven to simulate and predict the practical system adequately and effectively.;Thermophysical property of copper nanofluids we produced was studied, and the effective thermal conductivity of nanofluids at room temperature enhances with increased nanoparticles volume fraction; a 7.4% of enhancement was obtained with 1% volume fraction.