Nanocrystalline/amorphous La Mg11Ni+x Ni(x=100%, 200%, mass fraction) composite hydrogen storage alloys were synthesized by ball milling technology. The effects of Ni content and milling time on the gaseous hydrogen s...Nanocrystalline/amorphous La Mg11Ni+x Ni(x=100%, 200%, mass fraction) composite hydrogen storage alloys were synthesized by ball milling technology. The effects of Ni content and milling time on the gaseous hydrogen storage thermodynamics and dynamics of the alloys were systematically investigated. The hydrogen desorption properties were studied by Sievert's apparatus and a differential scanning calorimeter(DSC) connected with a H2 detector. The thermodynamic parameters(ΔH and ΔS) for the hydrogen absorption and desorption of the alloys were calculated by Van't Hoff equation. The hydrogen desorption activation energy of the alloy hydride was estimated using Arrhenius and Kissinger methods. The results indicate that a variation in the Ni content has a slight effect on the thermodynamic properties of the alloys, but it significantly improves their absorption and desorption kinetics performances. Furthermore, varying milling time clearly affects the hydrogen storage properties of the alloys. All the as-milled alloys show so fast hydrogen absorption rate that the absorbed amount in 10 min reaches to at least more than 95% of the saturated hydrogen absorption capacity. Moreover, the improvement of the gaseous hydrogen storage kinetics of the alloys is found to be ascribed to a decrease in the hydrogen desorption activation energy caused by increasing Ni content and prolong milling time.展开更多
As the alloy with the most suitable Ni/（La＋Mg） ratio has higher capacity and good cycle stability,the effects of Ni/（La＋Mg） ratios on the electrochemical performances of the La0.80Mg0.20Nix （x=3.5 to 5.0） allo...As the alloy with the most suitable Ni/（La＋Mg） ratio has higher capacity and good cycle stability,the effects of Ni/（La＋Mg） ratios on the electrochemical performances of the La0.80Mg0.20Nix （x=3.5 to 5.0） alloys have been investigated to find the most suitable Ni/（La＋Mg） ratio. The results of XRD and SEM observations show that the phase composition of the alloys varies with different Ni/（La＋Mg） ratios. When Ni/（La＋Mg） is not more than 4.25,all the alloys contain LaNi5 and （La,Mg）2Ni7 phases,in addition,the LaMg and （La,Mg）Ni3 phases exist in the x=3.5 and 3.75 alloys,respectively. The LaMg2Ni9 phase exists in the x=4.25 alloy. There are the LaNi5 and LaMg2Ni9 phases in the x=4.5,4.75,and 5.0 alloys. The phase abundance and cell volume change with different Ni content. When the Ni/（La＋Mg） ratio is not more than 4.25,the alloys possess excellent activation capability,however,the activation capabilities of the alloys decrease with a further increase in the Ni/（La＋Mg） ratio. With increasing the Ni/（La＋Mg） ratio,the maximum discharge capacities,the medium voltages,and the cycle stabilities of the alloys first increase and then decrease. When the Ni/（La＋Mg） ratio is 3.75,the corresponding alloy has the maximum discharge capacity among all the alloys. However,the cycle stability of the Ni/（La＋Mg）=4.0 alloy is better than that of the others.展开更多
基金Projects(51161015,51371094,51471054)supported by the National Natural Science Foundation of China
文摘Nanocrystalline/amorphous La Mg11Ni+x Ni(x=100%, 200%, mass fraction) composite hydrogen storage alloys were synthesized by ball milling technology. The effects of Ni content and milling time on the gaseous hydrogen storage thermodynamics and dynamics of the alloys were systematically investigated. The hydrogen desorption properties were studied by Sievert's apparatus and a differential scanning calorimeter(DSC) connected with a H2 detector. The thermodynamic parameters(ΔH and ΔS) for the hydrogen absorption and desorption of the alloys were calculated by Van't Hoff equation. The hydrogen desorption activation energy of the alloy hydride was estimated using Arrhenius and Kissinger methods. The results indicate that a variation in the Ni content has a slight effect on the thermodynamic properties of the alloys, but it significantly improves their absorption and desorption kinetics performances. Furthermore, varying milling time clearly affects the hydrogen storage properties of the alloys. All the as-milled alloys show so fast hydrogen absorption rate that the absorbed amount in 10 min reaches to at least more than 95% of the saturated hydrogen absorption capacity. Moreover, the improvement of the gaseous hydrogen storage kinetics of the alloys is found to be ascribed to a decrease in the hydrogen desorption activation energy caused by increasing Ni content and prolong milling time.
基金Sponsored by National Natural Science Foundation of China (50642033) Natural Science Foundation of Inner Mongolia of China (200711020703) Science and Technology Planned Project of Inner Mongolia of China (20050205)
文摘As the alloy with the most suitable Ni/（La＋Mg） ratio has higher capacity and good cycle stability,the effects of Ni/（La＋Mg） ratios on the electrochemical performances of the La0.80Mg0.20Nix （x=3.5 to 5.0） alloys have been investigated to find the most suitable Ni/（La＋Mg） ratio. The results of XRD and SEM observations show that the phase composition of the alloys varies with different Ni/（La＋Mg） ratios. When Ni/（La＋Mg） is not more than 4.25,all the alloys contain LaNi5 and （La,Mg）2Ni7 phases,in addition,the LaMg and （La,Mg）Ni3 phases exist in the x=3.5 and 3.75 alloys,respectively. The LaMg2Ni9 phase exists in the x=4.25 alloy. There are the LaNi5 and LaMg2Ni9 phases in the x=4.5,4.75,and 5.0 alloys. The phase abundance and cell volume change with different Ni content. When the Ni/（La＋Mg） ratio is not more than 4.25,the alloys possess excellent activation capability,however,the activation capabilities of the alloys decrease with a further increase in the Ni/（La＋Mg） ratio. With increasing the Ni/（La＋Mg） ratio,the maximum discharge capacities,the medium voltages,and the cycle stabilities of the alloys first increase and then decrease. When the Ni/（La＋Mg） ratio is 3.75,the corresponding alloy has the maximum discharge capacity among all the alloys. However,the cycle stability of the Ni/（La＋Mg）=4.0 alloy is better than that of the others.
