Effect of pH on the fabrication of lauric acid/Ag phase change nanocapsules via liquid-phase reduction

Abstract

Phase change nanocapsules can be dispersed in fluids to form latant functional thermal fluids (LFTFs), which can serve as effective coolants for extending the lifespan of electronic devices. For this purpose, it is significant to prepare phase change capsules that possess excellent heat storage capacity, thermal conductivity, and suspension stability. In this paper, lauric acid/silver composite phase change nanocapsules were prepared by liquid-phase reduction method. To investigate the effect of pH value on capsule synthesis, six phase change capsule samples were prepared between pH values of 2.6–4.6. The results indicate that the prepared nanocapsules exhibited good heat storage capacity and thermal conductivity under different pH values. However, as pH increases, the silver shell thickness on the nanocapsule surface initially decreases and subsequently increases. The silver shell thickness of L3 is the thinnest, measuring 12.5 nm. Correspondingly, the enthalpy and volume encapsulation rate of the phase change capsules first increase and then decrease. The lauric acid/Ag nanocapsules possess a thermal conductivity in the 1.77–4.32 W/(m∙K) range. Further, it is found that pH affects the formation of silver shell on the surface of lauric acid/Ag phase change nanocapsules by influencing the electrostatic interactions between particles, and diffusion in the system, which explains the variation of silver shell thickness with pH value for the six capsule samples. We also found that the thinner the silver shell of the nanocapsules, the more advantageous it is to reduce the density of the capsules, thereby improving their suspension. Therefore, controlling the pH value during the preparation to obtain lauric acid/Ag phase change nanocapsules with thin silver shell thickness plays an important role in improving the overall performance of phase change nanocapsules used for preparing latent functionally thermal fluid.