Rare earth elements and transition metals have been found to improve the hydrogen storage characteristics of magnesium-based alloys.This study investigated the Mg-Ho-Fe(MHF) ternary alloy prepared using the vacuum ind...Rare earth elements and transition metals have been found to improve the hydrogen storage characteristics of magnesium-based alloys.This study investigated the Mg-Ho-Fe(MHF) ternary alloy prepared using the vacuum induction melting technique.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),pressure-composition-temperature(PCT),and differential scanning calorimetry(DSC) were used to analyze the alloy's phase transitions,microstructure,thermodynamics,and kinetic properties.The results reveal that the Mg_(98)Ho_(1.5)Fe_(0.5) alloy forms a solid solution with Ho and Fe in the magnesium matrix.Upon hydrogen absorption,the activated alloy transforms into a mixture of Mg/MgH_(2) phases and nanoscale HoH_(2) phases.Notably,only the MgH_(2) phase decomposes during hydrogen desorption,while the HoH_(2) phase remains unchanged,exhibiting a positive catalytic effect.The alloy demonstrates excellent hydrogen absorption kinetics,achieving a capacity of 5.56 wt% H_(2) within 10 min at 360℃,owing to the combined catalytic effects of Ho and Fe.The activation energy for hydrogen desorption is found to be 135.87 kJ/mol,which is lower than that of the activation energies of pure MgH_(2) and MgFe alloys,indicating an enhancement in desorption kinetics.Moreover,the enthalpy and entropy changes for hydrogen absorption and desorption are determined to be-70.51 kJ/mol H_(2),-125.62 J/(K·mol) H_(2),72.83 kJ/mol H_(2),and 128.95 J/(K·mol) H_(2),respectively.Furthermore,it is worth noting that the thermodynamic properties of the alloy are improved due to the catalytic effect of Ho and Fe.展开更多
基金Project supported by the Fundamental Research Program of Shanxi Province (202203021211193,202203021211190)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(2022L291,2022L274)+1 种基金the National Natural Science Foundation of China (51761032,51871125,52071227)the Key Scientific Research Project in Shanxi Province(202102050201003)。
文摘Rare earth elements and transition metals have been found to improve the hydrogen storage characteristics of magnesium-based alloys.This study investigated the Mg-Ho-Fe(MHF) ternary alloy prepared using the vacuum induction melting technique.X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),pressure-composition-temperature(PCT),and differential scanning calorimetry(DSC) were used to analyze the alloy's phase transitions,microstructure,thermodynamics,and kinetic properties.The results reveal that the Mg_(98)Ho_(1.5)Fe_(0.5) alloy forms a solid solution with Ho and Fe in the magnesium matrix.Upon hydrogen absorption,the activated alloy transforms into a mixture of Mg/MgH_(2) phases and nanoscale HoH_(2) phases.Notably,only the MgH_(2) phase decomposes during hydrogen desorption,while the HoH_(2) phase remains unchanged,exhibiting a positive catalytic effect.The alloy demonstrates excellent hydrogen absorption kinetics,achieving a capacity of 5.56 wt% H_(2) within 10 min at 360℃,owing to the combined catalytic effects of Ho and Fe.The activation energy for hydrogen desorption is found to be 135.87 kJ/mol,which is lower than that of the activation energies of pure MgH_(2) and MgFe alloys,indicating an enhancement in desorption kinetics.Moreover,the enthalpy and entropy changes for hydrogen absorption and desorption are determined to be-70.51 kJ/mol H_(2),-125.62 J/(K·mol) H_(2),72.83 kJ/mol H_(2),and 128.95 J/(K·mol) H_(2),respectively.Furthermore,it is worth noting that the thermodynamic properties of the alloy are improved due to the catalytic effect of Ho and Fe.
