Study on the nucleating agents for gallium to reduce its supercooling. (February 2020) - Zhang, Chenglin
Highlights: This work reduced the supercooling of gallium by adding nucleating agents. TeO2, CaO, MgO, iron, and copper particles were selected as nucleating agents and compared. The nucleating agent that has similar lattice content with α-Ga and relatively good wettability with gallium shows better performance in reducing the supercooling of gallium. The influence of thermal history and the size of nucleating agent on the supercooling of gallium were investigated. The proportion of nucleating agents in the mixture was optimized. Abstract: Gallium, a typical room temperature liquid metal, has high thermal conductivity and large volume fusion enthalpy. These characteristics make it a promising phase change material (PCM). However, the significant supercooling of gallium has obstructed its wide application. Adding nucleating agents is a commonly adopted method to reduce supercooling, while the study of nucleating agents for liquid metal is rarely reported so far. In this paper, the influences of the thermal history and the particle size of nucleating agents on the supercooling of gallium were systematically investigated. After that, several particles, such as TeO2, CaO, MgO, iron, and copper were selected as nucleating agents for experiments. The lattice constant was found as one of the most important parameters when selecting nucleating agents. In addition, a more favorable wettability of the nucleating agents with gallium also contributed to the restraint of supercooling. The experimental result showed that the addition of TeO2, whose lattice constant appears as the most similar to that of α-Ga, had the best effect for reducing the supercooling of gallium. The largest reduction of supercooling occurred when 0.5 wt.% TeO2 was added, and more additions resulted in particle agglomeration and a lower nucleation effect. This paper provides important routes for the selection of nucleating agents for gallium, which will benefit for future applications of liquid metal in building heat storage, thermal comfort maintenance and thermal management.