Gallium-in-glycerol phase change material emulsions (PCMEs) with superior latent heat capacity and thermal conductivity

Abstract

In this study, we demonstrate a phase change material emulsion (PCME) with high thermal conductivity and latent heat capacity, produced by emulsifying Ga in glycerol as a flowable, electrically insulating liquid matrix. Polyvinylpyrrolidone (PVP) was employed as an emulsifier to achieve high Ga loadings (50–80 vol%) with stable dispersion, leveraging the strong binding affinity of PVP to Ga and the increased matrix viscosity. The Ga-in-glycerol emulsions retained solid–liquid phase transition temperatures near those of bulk Ga, melting at approximately 30 °C and crystallizing between −30 °C and −40 °C, unlike previous nano-sized dispersions that exhibited substantial depression of the phase transition temperatures. These PCMEs displayed significantly enhanced thermal properties compared to conventional emulsions with organic PCMs, with thermal conductivities reaching up to 4.85 W m⁻¹ K⁻¹ and latent heat capacities up to 241.52–262.91 J cm⁻³ at 80 vol% Ga loading. Despite the high Ga loading, the emulsions maintained electrical insulation. Additionally, these emulsions exhibited viscoelasticity, which confers them with high sedimentation stability and structure integrity while enabling their fluidic processing under shear. The unique combination of high thermal conductivity, substantial latent heat capacity, electrical insulation, and excellent rheological processability of these Ga-in-glycerol emulsions demonstrates their potential for advanced thermal management and energy storage applications, including electronics cooling and renewable energy systems.