Solidification and Super-cooling Behaviors of Silica Nanofluids based on the Molten Eutectic Nitrate Salt

Abstract SiO2 nano-powders with different particle sizes were used to fabricate nitrate-based nanofluids with the nano-particle concentration arranged from 0.5-4.0 wt.%. The crystallization process of the as-prepared composite and the influence of nanoparticles on the cooling kinetics was analyzed based on experimental data. The research results show that Johnson-Mehl-Avrami equation can be only used to describe the crystallization process of pure eutectic salt, but not suit for nanofluids since the nanoparticles addition can alter the crystallization kinetics of the composites. Depending on the particle size and concentration, nanoparticles addition was found to be able to improve the degree of supercooling and reduce the crystallization completion time by varying degrees. Further verification by a modified JMAK equation shows that with the nanoparticle addition, the component ‘n’ would fluctuate within a certain range, which indicates that the nanoparticles can improve the crystallization process by altering the nucleation mechanism and adjusting the cooling rate resulted from the increased thermal conductivities of the nano-fluids.