Low melting point liquid metal as a new class of phase change material: An emerging frontier in energy area

The application of phase change materials (PCMs) grew rapidly in the last few years, especially in those areas like solar energy, thermal comfort control, green building, environmental conservation and electronic cooling etc. Tremendous efforts have therefore been made on finding new powerful PCMs or improving performance of the currently available PCMs which generally subject to inherent defects, such as low thermal conductivity, poor stability after millions of repeated solidifying and melting processes, easy phase separation during transition and narrow temperature span between the melting point and the evaporation state. To better serve for the stringent request from many emerging utilization situations, this article is dedicated to systematically present a new class of high performance PCM, the low melting point liquid metals or their alloys, which were seldom addressed before. The unique merits, application features and potential values of these highly conductive liquid like materials were summarized with their basic properties interpreted. Some latest advancement made in the area was discussed for illustration purpose. Comparative evaluation on the fundamental mechanisms and practical issues between conventional PCMs and the low melting point metal PCM was carried out. Further, some involved scientific and technical challenges were raised. The present work is expected to incubate an emerging frontier towards studying and utilizing metal PCMs in the coming time, which is rather useful for a broad range of energy areas.