Stable Colloidal Dispersions of Highly Concentrated Thermo-efficient Nanomaterials

Abstract

Phase change materials (PCM) were utilized as solvents to synthesize small particles and stabilize them in those media in order to determine time independent thermal properties of nanostructure-enhanced phase change materials (NePCM). Spherical Ag particles in poly (ethylene glycol), PEG, and CuO rods in dodecane were achieved at high concentrations, these concentrated colloids exhibited a significant stability against precipitation at room temperature. The resulting nanoparticles and nanorods were characterized using UV-Visible spectrophotometry; transmission electron microscopy (TEM); Cytoviva optical microscopy; X-ray diffraction (XRD) and Fourier transform infrared spectroscopy, FTIR. Thermal conductivity enhancements were determined at different concentrations of particles as well as at different temperatures by using thermal analyzers (TPS 500 and KD2 Pro). Moreover, metallic Ag clusters were formed during illumination of organometallic Ag precursors in alkanes containing oleoyl sarcosine. Clusters were detected by UV-Vis and fluoresence spectroscopies and their concentrations were estimated from titration experiments. A novel feature of the clusters was their long lifetime even under air in non-polar solvents.