Liquid Metal-Based Magnetorheological Fluid with a Large Magnetocaloric Effect

Herein, liquid metal and Mn0.6Fe0.4NiGe0.54Si0.46 particles with a large magnetocaloric effect are adopted to prepare a novel magnetocaloric suspension named liquid metal-based magnetorheological fluid (LM2RF), which can well solve the problems of brittleness, low thermal conductivity, and poor machinability in classical magnetocaloric materials. The low melting point and high boiling point of liquid metal could significantly widen the operating temperature range of such a fluid. As a carrier, the high thermal conductivity, low viscosity, and large density of liquid metal display advantageous to heat transfer. The maximum loading fraction is 19.5 wt %, while LM2RF features the liquid state. A series of tests are conducted to investigate the alloying behavior in LM2RF. It is found that galinstan will react with Mn0.6Fe0.4NiGe0.54Si0.46 particles and form MnGa alloy. However, the reaction rate is very slow and the generated MnGa alloy is passivating. Consequently, the quantity of MnGa alloy is too sparse to affect the magnetocaloric performance of LM2RF. Overall, the LM2RF exhibits a large MCE at around room temperature with a lower magnetic hysteresis loss, and the transition temperature (Tm) remains constant in 60 days. This work demonstrates the outstanding performance of LM2RF and provides a promising alternative to MCE materials for practical magnetic refrigeration.