W.C. Williams, I.C. Bang, E. Forrest, L.W. Hu and J. Buongiorno
nanofluids, preparation, characterization, quality control
As part of an effort to evaluate water-based nanofluids for nuclear applications, preparation and characterization has been performed for nanofluids being considered for MIT’s nanofluid heat transfer experiments. Three methods of generating these nanofluids are available: creating them from chemical precipitation, purchasing the nanoparticles in powder form and mixing them with the base fluid, and direct purchase of prepared nanofluids. Characterization of nanofluids includes colloidal stability, size distribution, concentration, and elemental composition. Quality control of the nanofluids to be used for heat transfer testing is crucial; an exact knowledge of the fluid constituents is a key to uncovering mechanisms responsible for heat transport enhancement. Testing indicates that nanofluids created by mixed liquid with nanoparticles in powder form are often not stable, although some degree of stabilization is obtainable with pH control and/or surfactant addition. Some commercially available prepared nanofluids have been found to contain unacceptable levels of impurities and included a different weight percent of desired metal compared to vendor specifications. Tools utilized to characterize and qualify nanofluids for this study include neutron activation analysis, inductively-coupled plasma spectroscopy (ICP), TEM imaging, and dynamic light scattering. Preparation procedures and characterization results for selected nanofluids will be discussed in detail.