Nanocrystalline and amorphous NdMg12-type NdMg11Ni+x wt%Ni(x=100,200)alloys were successfully prepared through ball milling(BM).The microstructures and electrochemical properties were systematically studied to get a m...Nanocrystalline and amorphous NdMg12-type NdMg11Ni+x wt%Ni(x=100,200)alloys were successfully prepared through ball milling(BM).The microstructures and electrochemical properties were systematically studied to get a more comprehensive understanding of the sample alloys.The maximum discharging capacity could be obtained at only two cycles,indicating that as-milled alloys have superior activation capability.The more the Ni content,the better the electrochemical properties of the as-milled samples.To be specific,the discharge capacities of x=100 and x=200(BM 20 h)samples are 128.2 and 1030.6 mAh/g at 60 mAh/g current density,respectively,revealing that enhancement of Ni content could significantly improve the discharging capacities of the samples.Additionally,milling duration obviously influences the electrochemical properties of the samples.The discharging capacity always rises with milling duration prolonging for the x=100 sample,but that of the(x=200)sample shows a trend of first augment and then decrease.The cycling stability of the(x=100)alloy clearly decreases with extending milling duration,whereas that of the(x=200)alloy first declines and then augments under the same conditions.In addition,the high rate discharge(HRD)abilities of the sample display the maximal values as milling duration changes.The HRD(HRD=C300/C60×100%)values of the as-milled alloys(x=100,200)are 80.24%and 85.17%,respectively.展开更多
To improve the hydrogenation and dehydrogenation dynamics of NdMg12-type alloy,we replaced part of Mg with Ni in thesamples and used the ball milling method to prepare NdMg11Ni+x wt.%Ni(x=100,200)samples.The infuences...To improve the hydrogenation and dehydrogenation dynamics of NdMg12-type alloy,we replaced part of Mg with Ni in thesamples and used the ball milling method to prepare NdMg11Ni+x wt.%Ni(x=100,200)samples.The infuences of millingduration and Ni content on the electrochemical and gascous dynamics of the samples were studied in detail.Dehydrogena-tion activation cnergies of samples were calculated by using Kissinger and Arrhenius methods.The conclusions show thatthe dynamic properties of samples are significantly enhanced with the increase in Ni content.With the change of the miling duration,the gaseous hydrogenation rate and high rate discharging capability reach the maximal values.However,thedehydrogenation dynamics of sample alloys are always enhanced with the prolonging of milling duration.More concretely,prolonging milling duration from 5 to 60 h improves the dehydrogenation ratio of NdMgNi+100 wt.%Ni alloy from58.03%to 64.81%and that of NdMgNi+200 wt.%Ni alloy from 62.20%to 71.59%.Besides,the enhancement of gaseoushydrogen storage dynamics of the samples is believed to be the result of the declined dehydrogenation activation energyresulted from the increase in milling duration and Ni content.展开更多
Nanocrystalline and amorphous Nd Mg_（12^-）type Nd Mg_（11）Ni＋ x wt% Ni（x=100, 200） hydrogen storage alloys were synthesized by mechanical milling. The effects of Ni content and milling time on hydrogen storage t...Nanocrystalline and amorphous Nd Mg_（12^-）type Nd Mg_（11）Ni＋ x wt% Ni（x=100, 200） hydrogen storage alloys were synthesized by mechanical milling. The effects of Ni content and milling time on hydrogen storage thermodynamics and dynamics of the alloys were systematically investigated. The gaseous hydrogen absorption and desorption properties were investigated by Sieverts apparatus and differential scanning calorimeter connected with a H_2 detector. Results show that increasing Ni content significantly improves hydrogen absorption and desorption kinetics of the alloys. Furthermore,varying milling time has an obvious effect on the hydrogen storage properties of the alloys. Hydrogen absorption saturation ratio（R^a_（10）; a ratio of the hydrogen absorption capacity in 10 min to the saturated hydrogen absorption capacity） of the alloys obtains the maximum value with varying milling time. Hydrogen desorption ratio（R^d_（20）, a ratio of the hydrogen desorption capacity in 20 min to the saturated hydrogen absorption capacity） of the alloys always increases with extending milling time. The improved hydrogen desorption kinetics of the alloys are considered to be ascribed to the decreased hydrogen desorption activation energy caused by increasing Ni content and milling time.展开更多
基金financially supported by the National Natural Science Foundations of China (Nos. 51761032, 51871125 and 51471054)
文摘Nanocrystalline and amorphous NdMg12-type NdMg11Ni+x wt%Ni(x=100,200)alloys were successfully prepared through ball milling(BM).The microstructures and electrochemical properties were systematically studied to get a more comprehensive understanding of the sample alloys.The maximum discharging capacity could be obtained at only two cycles,indicating that as-milled alloys have superior activation capability.The more the Ni content,the better the electrochemical properties of the as-milled samples.To be specific,the discharge capacities of x=100 and x=200(BM 20 h)samples are 128.2 and 1030.6 mAh/g at 60 mAh/g current density,respectively,revealing that enhancement of Ni content could significantly improve the discharging capacities of the samples.Additionally,milling duration obviously influences the electrochemical properties of the samples.The discharging capacity always rises with milling duration prolonging for the x=100 sample,but that of the(x=200)sample shows a trend of first augment and then decrease.The cycling stability of the(x=100)alloy clearly decreases with extending milling duration,whereas that of the(x=200)alloy first declines and then augments under the same conditions.In addition,the high rate discharge(HRD)abilities of the sample display the maximal values as milling duration changes.The HRD(HRD=C300/C60×100%)values of the as-milled alloys(x=100,200)are 80.24%and 85.17%,respectively.
基金It is sincere thanks to the National Natural Science Foundation of China(Nos.51871125 and 51761032)the MajorScience and Technology Innovation Projects in Shandong Province(2019JZZYO10320)for the financial support of this work.
文摘To improve the hydrogenation and dehydrogenation dynamics of NdMg12-type alloy,we replaced part of Mg with Ni in thesamples and used the ball milling method to prepare NdMg11Ni+x wt.%Ni(x=100,200)samples.The infuences of millingduration and Ni content on the electrochemical and gascous dynamics of the samples were studied in detail.Dehydrogena-tion activation cnergies of samples were calculated by using Kissinger and Arrhenius methods.The conclusions show thatthe dynamic properties of samples are significantly enhanced with the increase in Ni content.With the change of the miling duration,the gaseous hydrogenation rate and high rate discharging capability reach the maximal values.However,thedehydrogenation dynamics of sample alloys are always enhanced with the prolonging of milling duration.More concretely,prolonging milling duration from 5 to 60 h improves the dehydrogenation ratio of NdMgNi+100 wt.%Ni alloy from58.03%to 64.81%and that of NdMgNi+200 wt.%Ni alloy from 62.20%to 71.59%.Besides,the enhancement of gaseoushydrogen storage dynamics of the samples is believed to be the result of the declined dehydrogenation activation energyresulted from the increase in milling duration and Ni content.
基金financially supported by the National Natural Science Foundation of China(Nos.51371094 and 51471054)
文摘Nanocrystalline and amorphous Nd Mg_（12^-）type Nd Mg_（11）Ni＋ x wt% Ni（x=100, 200） hydrogen storage alloys were synthesized by mechanical milling. The effects of Ni content and milling time on hydrogen storage thermodynamics and dynamics of the alloys were systematically investigated. The gaseous hydrogen absorption and desorption properties were investigated by Sieverts apparatus and differential scanning calorimeter connected with a H_2 detector. Results show that increasing Ni content significantly improves hydrogen absorption and desorption kinetics of the alloys. Furthermore,varying milling time has an obvious effect on the hydrogen storage properties of the alloys. Hydrogen absorption saturation ratio（R^a_（10）; a ratio of the hydrogen absorption capacity in 10 min to the saturated hydrogen absorption capacity） of the alloys obtains the maximum value with varying milling time. Hydrogen desorption ratio（R^d_（20）, a ratio of the hydrogen desorption capacity in 20 min to the saturated hydrogen absorption capacity） of the alloys always increases with extending milling time. The improved hydrogen desorption kinetics of the alloys are considered to be ascribed to the decreased hydrogen desorption activation energy caused by increasing Ni content and milling time.
