Production of Energy Saving Materials from the Waste Mixtures of REEs

This work details the procedures and steps for the synthesis of new magnetocaloric materials starting from the outputs generated by recycling for re-use in magnetic refrigeration application. The outputs utilized were a rare earth element-rich product obtained during the hydrometallurgical processing of nickel–metal hydride (NiMH) batteries. This stream contained a mix of rare earth elements (REEs), mainly lanthanum and cerium. After removing some impurities from this feed, especially aluminium, we have used the obtained product in the manufacturing of advanced REEs-based magnetocaloric materials, especially manganites-, orthoferrites-, and REEs-based alloys. The composition of the output from hydrometallurgical processing of NiMH batteries and typical compositions of magnetocaloric materials was determined using inductively coupled plasma-optical emission spectroscopy. The magnetocaloric oxides were successfully synthesized by using conventional solid-state reaction method. Carbothermic and calciothermic reduction methods were used for the synthesis of the as-cast alloy. The X-ray diffraction analysis shows that the magnetocaloric oxides are well crystallized with presence of secondary phases. The effect of temperature on the crystal structure is briefly described.