Phase-change gradient composites for variable thermal management

Phase-change composites attracted much attention on thermal management due to their excellent temperature-control capabilities based on reversible latent heat storage and release. However, current research mostly focuses on the uniform composite filled with individual phase-change molecule, which are subject to a limited temperature adjustment range and thus cannot meet the required variable heat flux. Herein, we fabricated a phase-change gradient composite by one-step incorporating either tetracosane or octacosane into graphene aerogel via followed by graphene-interfacial welding. The one-step preparation enhances the dispersion uniformity of phase-change in aerogel compared with traditional two-step loading. The phase-change process and thermodynamic properties of the gradient and uniform composite were investigated at different heating temperatures. According to simulation and experimental results, the temperature control capability of the gradient phase-change composite is much superior to that of the uniform composite due to the tunable heat storage at a temperature gradient. At a heating temperature of 86 °C, the gradient phase-change composite could maintain a temperature below 60 °C up to 1580 s, extending 306 and 112 s longer than that of uniform composite filled only with tetracosane or octacosane, respectively. Thus, gradient phase-change composite offers tailored solutions for tunable temperature control for high- and variable-power devices.