Preparation and characterization of lauric acid-stearic acid/fumed silica/expanded graphite thermally conductive enhanced composites

Abstract

Fatty acid and fatty acid blend phase change materials (PCM) have issues with easy leakage and low thermal conductivity in thermal storage and exothermic processes. To overcome this issue, a novel low-temperature composite material, Lauric acid - stearic acid - fumed silica - expanded graphite (LA-SA-FS-EG), was fabricated by vacuum impregnation technique using lauric acid-stearic acid (LA-SA) as the phase change material (PCM), fumed silica (FS) as the support material, and expanded graphite (EG) as the thermal conductive material. Leakage tests indicated that the maximum adsorption of LA-SA by fumed silica was 75 wt%. Scanning electron microscopy (SEM) was employed to observe the microscopic morphology of the composites. The crystal structure and chemical composition of the composites were analyzed by X-ray diffraction (XRD) and Fourier infrared spectroscopy (FT-IR). The differential scanning calorimeter (DSC) data indicates that the melting temperatures of LA-SA-FS-EG 3 %, 5 % and 7 % were 33.38 °C, 33.32 °C and 33.13 °C respectively, with melting latent heats of 110.8 J/g, 114.3 J/g and 119.9 J/g, respectively. The thermal conductivity of LA-SA-FS-EG 7 % is improved by 454 % compared to the LA-SA-FS composite without the addition of EG. LA-SA-FS-EG7% composite showed excellent heat storage capacity. LA-SA-FS-EG7% has a 46.1 % increase in heat storage rate and a 59.4 % increase in thermal release rate compared to LA-SA-FS composite. Notably, the LA-SA-FS-EG7% composite retains good thermal properties even after 1000 heating and cooling cycles. Consequently, the LA-SA-FS-EG7% composites produced have potential applications in thermal energy storage and building energy efficiency.