A study of metal hydride as novel thermal energy storage material by using rapid solidification

Cast and rapid solidification Ce2Mg17 alloy are synthesized by induction furnace melting and single roll rapid solidification method. The effects of rapid solidification rate on kinetics, thermodynamics and cycling stability of Ce2Mg17 alloy and the thermal storage mechanism are investigated by XRD (X-ray diffraction), SEM (Scanning electron microscope) and TEM (Transmission electron microscope). The reaction enthalpy of Ce2Mg17 is 75.5 kJ mol−1 H2 and equilibrium pressure is 0.91 MPa at 400 °C, which are lower than pure MgH2's and Mg2FeH6's. The results also show that rapid solidified Ce2Mg17 alloy shows a better kinetics performance, comparing to those of casted samples. XRD results show that during hydrogenation, Ce2Mg17 forms CeHx and Mg, and Mg is hydrogenated after the formation of CeHx. This disproportionation reaction is irreversible, but the Ce2Mg17 alloy after disproportionation reaction is still reversible. The amorphous structure formed in rapid solidification is in favor of CeHx decomposition. The disproportionation reaction improves anti-sintering properties and cycling stability. Rapid solidification Ce2Mg17 alloy shows promise to solar power thermal energy storage.