FABRICATION OF UNDERCOOLED BISMUTH TIN LIQUID METAL PARTICLES WITH HIGH YIELD

Abstract

Despite increasing attention to the liquid metals, most of the studies in this field have focused on the gallium-based alloys due to their low melting points. The examples of metastable undercooled liquid metal particles are rare due to the thermodynamic challenges in achieving significant level of undercooling. In this study, the fabrication of undercooled bismuth-tin (BiSn) liquid metal micro- /nano-particles at eutectic composition was studied. The droplet emulsion technique was used for particle formation in broad size range. The effects of the particle size and the shell formation reactions on the yield of undercooled particles were investigated. The fabricated particles were characterized using back- scattered scanning electron microscopy (BSE-SEM) and differential scanning calorimetry (DSC). The particle size distribution and the ratio of undercooled particles were statistically analyzed. Optimization of the processing conditions and the successful selection of oxidants enabled undercooling of BiSn liquid metal particles. In doing so, both micro- and nano-size particles could be fabricated with high yield (≥ 97%). The crystallization temperature was measured to be 0.37 Tm and the particles could preserve their liquid state at room temperatures for months.