Novel slurry containing graphene oxide-grafted microencapsulated phase change material with enhanced thermo-physical properties and photo-thermal performance

In this work, a new microencapsulated phase change material, paraffin@ silica (SiO2)/graphene oxide (GO), is prepared by two steps: engulfing paraffin with silica by in situ hydrolysis and poly condensation of tetraethoxysilane and the modification of the SiO2 shell with GO. The paraffin@SiO2/GO composite is composed of spherical capsules with diameters of ~20 um. Raman spectrometer analysis verifies the embedding of GO in the SiO2 shell. The melting and freezing temperatures of the composite are very close to those of paraffin. Based on the melting and freezing enthalpy of the composite, the encapsulation ratio of paraffin is calculated to be 50.8% in the paraffin@SiO2 composite and 49.6% in the paraffin@SiO2/GO composite. It is shown that the paraffin@SiO2/GO composite exhibits enhanced thermal stability and excellent thermal reliability. The phase change slurry prepared by dispersing the paraffin@SiO2/GO composite in water shows higher thermal conductivity and heat capacity along with remarkable photo-thermal conversion performance, making it potential for use as the heat transfer fluid in direct absorption solar collectors. The high heat storage capability and excellent photo-thermal conversion performance of the paraffin@SiO2/GO composite enable it to be a potential material to store solar energy in practical applications.