Preparation of graphite nanoparticles-modified phase change microcapsules and their dispersed slurry for direct absorption solar collectors

A microencapsulated phase change composite, in which paraffin as the core and graphite nanoparticles embedded melamine-formaldehyde (MF) as the shell, has been prepared and characterized. The paraffin@MF/graphite composite is composed of spherical particles with diameters ranging from hundreds of nanometers to several micrometers. Raman spectroscopy analyses confirm the existence of graphite on the shell of the paraffin@MF/graphite composite. DSC results indicate that the melting temperature and latent heat of the paraffin@MF/graphite composite are 50.5 degrees C and 90.8 J g(-1), respectively, in which the mass ratio of paraffin is calculated to be 51.1%. The paraffin@MF/graphite composite can be dispersed into the ionic liquid to form a novel latent functional thermal fluid (LFTF). It is found that the temperature of the LFTF can increase from 30 to 113 degrees C under irradiation, indicating its remarkable photo-thermal conversion performance. The thermal storage capacity of this new kind of heat transfer fluid (HTF) is twice larger than pure ionic liquid. The high heat storage capability and excellent photo-thermal conversion performance enable the paraffin@MF/graphite composite as a potential material for solar energy utilization. (C) 2016 Elsevier B.V. All rights reserved.