Fig xA XRD patterns of NiO
MgH2 (99.5% pure, 50 nm), CoFe2O4, ZnFe2O4, MnFe2O4 Mn0.5Zn0.5Fe2O4 (?99% pure, 40 nm) powders, MgO (99.5% pure, 50 nm) and Co (?99.5% pure, 50 nm) powders were purchased from Sigma Aldrich Co., and all raw materials were used as-received state without further purification. All operations were performed in a glove box filled with a high purity argon AZD2932 in order to avoid oxidation and humidity. The MgH2 powder was ball milled with 3 mol%, 5 mol%, 7 mol% and 9 mol% of the total substance amount of CoFe2O4, ZnFe2O4, MnFe2O4 and Mn0.5Zn0.5Fe2O4 ferrites nanoparticles, respectively. Then the mixture was loaded into a cast stainless steel milling vial with a ball to powder weight ratio of 20:1. Subsequently, the samples were ball-milled for 30 min by using a high-energy Spex mill (QM-3B) at a rotating rate of 1200 rpm. After each 10 min of the ball milling, the steel vial was rested for 5 min to cool down it. 10 g CoFe2O4 nanoparticle was put in a ceramic boat and annealed at 500 °C for 2 h at a hydrogen flow rate of 50 ml min−1 in the tube furnace.