Fabrication of High-Performance Thermally Conductive Phase Change Material Composites with 2D Boron Nitride Based Porous Ceramic Network for Efficient Thermal Management

A Phase change material (PCM) has a great potential for heat energy storage and efficient heat management. However, achieving high performance PCM composites is still challenging because of its low thermal conductivity and weak mechanical properties. In particular, to improve the properties of PCM composite with preserving intrinsic latent heat is most important. In this work, we first simply synthesized a PCM matrix with the highly improved mechanical property, fabricated two kinds of porous ceramic fillers (boron nitride (BN)-cellulose nanofiber (CNF), aluminum nitride (AlN)-CNF) through freeze-casting and carbonization of CNF to form porous structured ceramic filler, and fabricated PCM composites using three kinds of method to maximize the properties of fabricated composites. These strategies resulted in synergistic effects that highly improved the thermal and mechanical properties of the PCM composites.<br/>(i) We synthesized erythritol (ET) grafted bisphenol A (ETBPA) through esterification. The ET grafted on the BPA addressed phase separation between BPA and ET and reinforced the mechanical properties of matrix. The latent heat and mechanical properties were measured according to ratios of ETBPA and leakage test also performed to confirm enhanced thermal stability. As a result, the ETBPA (1.5:1 ratio) showed the latent heat of 297.36 J/g (76% of pure paraffin), the enhanced tensile stress and strain of 241 and 247% comparing pure ET, and no leakage at the melting point of the ET.<br/>(ii) Fabrication of porous ceramic fillers was carried out using BN and AlN through freeze-casting and carbonization of CNF. After that, hybridization of porous ceramic filler (BNCNF, AlNCNF) and raw ceramic filler (BN, AlN) was conducted. The hydrophilic functional group derived from carbonized CNF on ceramic filler improved interfacial interaction between ETBPA and fillers. Moreover, the porous ceramic filler and impregnation of raw ceramic filler formed efficient heat conduction paths along through plane direction in the matrix.<br/>(iii) The PCM composites (ETBPA/BNCNF/BN, ETBPA/AlNCNF/AlN) was fabricated by three kinds of methods: mixing, hot-pressing, and injection molding. To confirm the effect of our new strategies, we measured thermal, mechanical properties, and heat management performance of composites. As a result, the composite showed ultra-high through-plane thermal conductivity of 13.09 W/mK (2,518% enhancement comparing paraffin), tensile strength of 3.2 MPa (300% enhancement comparing paraffin), and elongation at break of 4.55% (37% enhancement comparing paraffin). Therefore, the new attempts of this study will contribute to the research of thermal conductive PCM composites afterwards.<br/>This newly developed PCM composites with superior thermal and mechanical properties than existing PCM composites would suggest a new insight to study of multifunctional PCM composites.