Fast Solidification of Pure Gallium at Room Temperature and its Micromechanical Properties

Abstract

lent fluidity at room temperature, electrical and thermal conductivity, deformability in response to various stimuli, etc. Thus it has been intensively investigated in the field of thermal management, [1,2] flexible electronics and devices, [3][4][5][6][7] additive manufacture, [8,9] medical therapies, [10][11][12] soft robotics, [13,14] etc. Among the applications, the solid-liquid phase transition of gallium can enable diverse and specific functions beyond the single liquid-state metal behaviors. For instance, the phase transition of gallium-based polymer can achieve reversible transitional insulator and conductor, which can be applied as temperature-controlled electrical switches and circuits. [15] Taking advantage of the mechanical strength of solid gallium, the mechanically transformative electronics, sensors, and implantable devices can be also realized by solid-phase phase transition. [10,16] Moreover, phase transition of the liquid gallium or its alloy composite can generate reversible and strong adhesion to different surfaces, which can be used as transformable grippers for various objects. [14,13,17] During the solid-liquid phase transition, the melting process is relatively quick as temperature rises above the melting point. However, the solidification of gallium usually requires a much lower temperature than the melting point as well much longer time due to the significant supercooling effect (the With excellent electrical conductivity, fluidity, rheological property, and biocompatibility, gallium has been intensively studied in the fields of flexible electronics and devices, thermal management, and soft robotics. However, the large degree of supercooling of gallium presents a large limitation for phase transition-related applications such as the very low temperature required for solidification, the impurities, and side effects brought in by nucleating agents. In this study, solidification process of liquid gallium by using solid gallium as a nucleating agent is discovered to be fast and facile at room temperature compared with other agent materials including copper, iron, and nickel. Quantificationally, solidified gallium as a nucleating agent, can effectively reduce the supercooling degree from about 66.3 to 14.8 °C. The freezing velocity can reach to 200 mm 3 min −1 . The possible mechanism is reducing the energy barrier via adding nucleation site, allowing rapid solidification at room temperature accompanying heat dissipation. Moreover, micromechanical properties are compared between raw solid Ga and the solidified Ga induced by Ga agent, which suggests a slight decrease in mechanical strength at room temperature with the nucleating agent. It will be beneficial to understand the phase change and also provide guidance for the application of gallium regarding its mechanical properties.

Sustainable Thermal Regulation of Electronics via Mitigated Supercooling of Porous Gallium‐Based Phase Change Materials

“…At room temperature, thin wires (Ga, Cu, Ni, Fe) with a diameter of 300 µm were investigated as nucleating agents. [ 22 ] Among them, solid Ga wire demonstrated a reduction in supercooling of ≈77.7% compared to pristine Ga, owing to its similar crystal structure with liquid Ga, which promotes heterogeneous nucleation.…”