Mg-based alloys must be dehydrogenated at high pressure and temperatures, limiting their practical application. In this paper, Nd_(5)Mg_(41)Ni alloy was prepared by vacuum melting, and the as-cast alloy was ball mille...Mg-based alloys must be dehydrogenated at high pressure and temperatures, limiting their practical application. In this paper, Nd_(5)Mg_(41)Ni alloy was prepared by vacuum melting, and the as-cast alloy was ball milled for 5 h, 10 h, 15 h, and 20 h. The effect of ball milling time on the microstructure and hydrogen storage properties of the alloy was systematically studied. The alloy comprises Nd_(5)Mg_(41), NdMg_(12), NdMg_(3), and Mg_(2)Ni phases. The Nd_(5)Mg_(41)Ni alloy milling for 10 h can reach 95% of the saturated hydrogen absorption at 553 K by 40 s, and the alloy can desorb hydrogen only by 20 min. The dehydrogenation activation energy is only 99.9 kJ/mol H_(2). Ball milling makes the alloy produce many nanocrystalline and amorphous structures. The nano-grain boundary provides a channel for the diffusion of hydrogen atoms, and the high energy at the grain boundary provides energy for the phase deformation nucleus. Ball milling leads to the refinement of alloy particles and shortens the diffusion distance of hydrogen atoms to the interior of alloy particles. Defects such as twins and dislocations generated by milling provide energy for the phase deformation nucleus during the hydrogen absorption and desorption.展开更多
Mg-based hydrides are too stable and the kinetics of hydrogen absorption and desorption is not satisfactory.An efficient way to improve these shortcomings is to employ reactive ball milling to synthesize the nanocompo...Mg-based hydrides are too stable and the kinetics of hydrogen absorption and desorption is not satisfactory.An efficient way to improve these shortcomings is to employ reactive ball milling to synthesize the nanocomposite materials of Mg and additives.In this experiment,TiF_(3)was selected as an additive,and the mechanical milling method was employed to prepare the experimental alloys.The alloys used in this experiment were the as-cast Ce_(5)Mg_(85)Ni_(10),as-milled Ce_(5)Mg_(85)Ni_(10)and Ce_(5)Mg_(85)Ni_(10)+3 wt.%TiF3.The phase transformation,structural evolution,isothermal and non-isothermal hydrogenation and dehydrogenation performances of the alloys were inspected by XRD,SEM,TEM,Sievert apparatus,DSC and TGA.It revealed that nanocrystalline appeared in the as-milled samples.Compared with the as-cast alloy,ball milling made the particle dimension and grain size decrease dramatically and the defect density increase significantly.The addition of TiF_(3)made the surface of ball milling alloy particles markedly coarser and more irregular.Ball milling and adding TiF_(3)distinctly improved the activation and kinetics of the alloys.Moreover,ball milling along with TiF_(3)can decrease the onset dehydrogenation temperature of Mg-based hydrides and slightly ameliorate their thermodynamics.展开更多
The Mg90Ce5 RE5(RE=La,Ce,Nd)alloys were prepared by a vacuum induction furnace and their micro structure,phase transformation,thermodynamics and kinetics property were systematically studied by XRD,SEM,TEM,and PCT cha...The Mg90Ce5 RE5(RE=La,Ce,Nd)alloys were prepared by a vacuum induction furnace and their micro structure,phase transformation,thermodynamics and kinetics property were systematically studied by XRD,SEM,TEM,and PCT characterization methods.The result shows that the activated alloys are composed of Mg/MgH2 and corresponding REH2+x with nanoscale.The REH2+x grain with Ce and La or Nd functional group have lower nucleation potential barriers than CeH2+x grains as the nucleation location,thus improve the hydrogen absorption kinetics of these alloys among which the Mg90Ce5Nd5 alloy can absorb 90%of the hydrogen within 2 min at 320℃.In addition,the Mg90Ce10 alloy has the lowest activation energy with 103.2 kJ mol-1 and the fastest desorption kinetics,which can release 5 wt%of the hydrogen within 20 min at 320℃.This is a correlation with grain size and the in-suit formed CeH2.73/CeO2 interface.Moreover,the co-doping Ce and La or Nd can effectively disorganize the thermodynamic stability of Mg-based hydrogen storage alloys to a certain degree,but the dehydrogenation kinetics of that still is restricted by the recombination energy of hydrogen ions on the surface.展开更多
Greatly stable thermodynamics and sluggish kinetics impede the practical application of Mg-based hydrogen storage alloys.The modifications of composition and structure are important strategies in turning these hydroge...Greatly stable thermodynamics and sluggish kinetics impede the practical application of Mg-based hydrogen storage alloys.The modifications of composition and structure are important strategies in turning these hydrogen storage properties.In this study,Mg-based Mg90Ce5 Sm5 ternary alloy fabricated by vacuum induction melting was investigated to explore the performance and the reaction mechanism as hydrogen storage material by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscopy(TEM) and pressure-composition isotherms(PCI) measurements.The results indicate that the Mg-based Mg90Ce5 Sm5 ternary alloy consists of two solid solution phases,including the major phases(Ce,Sm)5 Mg41 and the minor phases(Ce,Sm)Mg12.After hydrogen absorption,these phases transform into the MgH2 and(Ce,Sm)H2.73 phase,while after hydrogen desorption,the MgH2 transforms into the Mg phase,but the(Ce,Sm)H2.73 phases are not changed.The alloy has a reversible hydrogen capacity of about 5.5 wt% H2 and exhibits well isothermal hydrogen absorption kinetics.Activation energy of 106 kJ/mol was obtained from the hydrogen desorption data between 573 and 633 K,which also exhibits the enhanced kinetics compared with the pure MgH2 sample,as a result of bimetallic synergy catalysis function of(Ce,Sm)H2.73 phases.The rate of hydrogen desorption is controlled by the release and recombination of H2 from the Mg surface.Furthermore,the changes of enthalpy and entropy of hydrogen absorption/desorption were calculated to be-80.0 kJ/mol H2,-137.5 J/K/mol H2 and 81.2 kJ/mol H2,139.2 J/K/mol H2,respectively.展开更多
The composites comprised of Co nanoparticle and C nanosheet were prepared though a high-temperature carbonization reaction.The catalysis of Co@C composites on the hydrogen storage behavior of Mg_(90)Ce_(5)Y_(5)alloy w...The composites comprised of Co nanoparticle and C nanosheet were prepared though a high-temperature carbonization reaction.The catalysis of Co@C composites on the hydrogen storage behavior of Mg_(90)Ce_(5)Y_(5)alloy was investigated in detail by XRD,SEM,TEM,PCI,and DSC method.Because of the synergistic catalytic function of C and Co in C@Co nanocomposites,the Mg_(90)Ce_(5)Y_(5)alloy with 10 wt.%C@Co shows the excellent hydrogen absorption and desorption performances.Time for releasing hydrogen reduces from 150 min to 11 min with the addition of the C@Co composites at the temperature of 300℃.Meanwhile,the dehydrogenation activation energy also declines from 130.3 to 81.9 kJ mol^(-1)H_(2)after the addition of the C@Co composites.This positive effect attributes to the C layer with the high defect density and the Co nanoparticles,which reduces the energy barriers for the nucleation of Mg/MgH_(2)phase and the recombination of hydrogen molecule.Besides,the C@Co composites also improve the activation property of the Mg_(90)Ce_(5)Y_(5)alloy which was folly activated in the first cycle.Moreover,the temperature for initial dehydrogenation and the endothermic peak of the alloy hydride were also decreased.Although the addition of the C@Co composites increases the plateau pressures and decreases the value of the decomposition enthalpy,these differences are so small that the improvement on thermodynamics can hardly be seen.展开更多
For purpose of promoting the hydrogen absorption and desorption thermodynamics and kinetics properties of Mg-Ni-based alloys, partially substituting Y and Cu for Mg and Ni respectively and melt spinning technique were...For purpose of promoting the hydrogen absorption and desorption thermodynamics and kinetics properties of Mg-Ni-based alloys, partially substituting Y and Cu for Mg and Ni respectively and melt spinning technique were applied for getting Mg25-xYxNi9 Cu(χ = 0-7) alloys. Their microstructures and phases were characterized with the help of X-ray diffraction and transmission electron microscopy. Their hydrogen absorbing and desorbing properties were tested by a Sievert apparatus, DSC, and TGA, which were connected with a H2 detector. In order to estimate the dehydrogenation activation energy of alloy hydride, both Arrhenius and Kissinger methods were applied for calculation. It is found that their hydriding kinetics notably declines, however, their hydrogen desorption kinetics conspicuously improves, with spinning rate and Y content increasing. Their hydrogen desorption activation energy markedly decreases under the same constraint, and it is found that melt spinning and Y substituting Mg improve the real driving force for dehydrogenation. As for the tendency of hydrogen absorption capacity,it presents an elevation firstly and soon after a decline with the rising of spinning rate, however, it always lowers with Y content growing. With Y content and spinning rate increasing, their thermodynamic parameters(△H and △S absolute values) visibly decrease, and the starting hydrogen desorption temperatures of alloy hydrides obviously lower.展开更多
In this paper,the as-cast Mg85Cu5Ni10 alloy and Mg85Cu5Ni10-x wt%CeO2(x=0,4,8)alloys were prepared successfully by vacuum induction smelting and ball milling.The microstructure,hydrogen absorption/desorption kinetics ...In this paper,the as-cast Mg85Cu5Ni10 alloy and Mg85Cu5Ni10-x wt%CeO2(x=0,4,8)alloys were prepared successfully by vacuum induction smelting and ball milling.The microstructure,hydrogen absorption/desorption kinetics and thermodynamics performances of the alloys were studied in detail.The results show that the Mg85Cu5Ni10 alloys with CeO2 additive have faster hydrogenation/dehydrogenation kinetics and better thermodynamic properties.The dehydrogenation activation energy is reduced to 81.211 kJ/mol from 119.142 by adding 8 wt%CeO2.CeO2 contributes to producing structural defects,nanocrystallines,grain boundaries,partial amorphous,lattice dislocations and cracks which are favorable to provide more hydrogen diffusion channels during hydriding/dehydriding process.Meanwhile,CeO2 additive weakens the bond energy of Mg-H.These micro structural changes caused by CeO2 additive improve the hydrogen storage performance of Mg85Cu5Ni10 markedly.展开更多
Experimental alloys with compositions of Mg(25-x)YxNi9Cu(x=0,1,3,5,7)have been successfully prepared through melt spinning method.The phase compositions and microstructures were measured by X-Ray diffraction(XRD)and h...Experimental alloys with compositions of Mg(25-x)YxNi9Cu(x=0,1,3,5,7)have been successfully prepared through melt spinning method.The phase compositions and microstructures were measured by X-Ray diffraction(XRD)and high-resolution transmission electron microscopy(HRTEM).The de-/hydrogenation properties were measured by utilizing Sievert apparatus,differential scanning calorimetry(DSC)and thermal gravimetric analyzer(TGA)connected with a H2 detector.The Arrhenius and Kissinger methods were adopted to calculate their dehydrogenation activation energies.The results show that hydrogen absorption kinetics of the alloys notably decline while their hydrogen desorption kinetics conspicuously improve with spinning rate increasing.The dehydrogenation activation energy markedly decreases with spinning rate increasing,which makes the hydrogen desorption kinetics improve.The thermodynamic parameters(H and S absolute values)clearly decrease with spinning rate increasing.The hydrogen absorption capacity exhibits different trends with spinning rate rising.Specifically,hydrogen absorption capacity increases at the beginning and declines later for Y1 alloy,but that of Y7 alloy always decreases with spinning rate growing.展开更多
In this investigation,mechanical grinding was applied to fabricating the Mg-based alloys La_(7)Sm_(3)Mg_(80)Ni_(10)+5 wt.%M(M=None,TiO_(2),La_(2)O_(3))(named La_(7)Sm_(3)Mg_(80)Ni_(10)-5 M(M=None,TiO_(2),La_(2)O_(3)))...In this investigation,mechanical grinding was applied to fabricating the Mg-based alloys La_(7)Sm_(3)Mg_(80)Ni_(10)+5 wt.%M(M=None,TiO_(2),La_(2)O_(3))(named La_(7)Sm_(3)Mg_(80)Ni_(10)-5 M(M=None,TiO_(2),La_(2)O_(3))).The result reveals that the structures of as-milled alloys consist of amorphous and nanocrystalline.The particle sizes of the added M(M=TiO_(2),La_(2)O_(3))alloys obviously diminish in comparison with the M=None specimen,suggesting that the catalysts TiO_(2)and La_(2)O_(3)can enhance the grinding efficiency.What’s more,the additives TiO_(2)and La_(2)O_(3)observably improve the activation performance and reaction kinetics of the composite.The time required by releasing 3 wt.%hydrogen at553,573 and 593 K is 988,553 and 419 s for the M=None sample,and 578,352 and 286 s for the M=TiO_(2)composite,and 594,366,301 s for the La_(2)O_(3)containing alloy,respectively.The absolute value of hydrogenation enthalpy change|△H|of the M(M=None,TiO_(2),La_(2)O_(3))alloys is 77.13,74.28 and 75.28 kJ/mol.Furthermore,the addition of catalysts reduces the hydrogen desorption activation energy(E_(a)^(de)).展开更多
The influences of the catalysts of CoS2 and MoB2 nano-particles on microstructure and hydrogen stor-age behaviors of as-milled SmsMg41 alloy have been compared in this work. The SmsMg41 ＋ 5 wt.% M （M = COS2, MoS2） ...The influences of the catalysts of CoS2 and MoB2 nano-particles on microstructure and hydrogen stor-age behaviors of as-milled SmsMg41 alloy have been compared in this work. The SmsMg41 ＋ 5 wt.% M （M = COS2, MoS2） alloys were prepared by milling the mechanical ground as-cast SmsMg41 alloy powders （particle size ≤75 μm） with 5 wt.% CoS2 or MoS2 nano-particles （particle size ≤ 30 nm）, respectively. The results demonstrate that the CoS2 and MoS2 nanoparticles are embedded into the alloy surface, which is nanostructure containing some crystal defects, such as dislocation, grain boundary and twin etc. Those microstructures play a beneficial role in reducing the total potential barrier that the hydrogen absorption or desorption reactions must overcome, hence improving the hydrogen storage kinetics of the alloys. The as-milled alloys are composed of SmsMg41 and SmMg3 phases, and ball milling refines their crys-tal grains. The MgH2 and Sm3H7 phases appear after hydrogenation, while Mg and Sm3H7 phases exist after dehydrogenation. The dehydriding activation energy of M = CoS2 and MoS2 alloys are 101.67 and 68.25 kJ/mol H2 respectively. The initial hydrogen desorption of M = CoS2 and MoS2 alloys are 252.9 ℃ and 247.8 ℃.The hydrogenation and dehydrogenation enthalpy changes of M = MoS2 alloy are a little smaller than that of MzCoS2 alloy. Therefore, the catalyst MoS2 can improve the as-milled SmsMg41 alloy in hydrogen storage property more effectively than C0S2.展开更多
Nanocrystalline and amorphous Mg2Ni-type（Mg24Ni10Cu2）100–xNdx（x = 0, 5, 10, 15, 20） alloys were prepared by melt-spinning technology. The structures of as-cast and spun alloys were characterised by X-ray diffract...Nanocrystalline and amorphous Mg2Ni-type（Mg24Ni10Cu2）100–xNdx（x = 0, 5, 10, 15, 20） alloys were prepared by melt-spinning technology. The structures of as-cast and spun alloys were characterised by X-ray diffraction,scanning electron microscopy and transmission electron microscopy. Electrochemical performance of the alloy electrodes was measured using an automatic galvanostatic system. The electrochemical impedance spectra and Tafel polarisation curves of the alloy electrodes were plotted using an electrochemical work station. The hydrogen diffusion coefficients were calculated using the potential step method. Results indicate that all the as-cast alloys present a multiphase structure with Mg2 Ni type as the major phase with Mg6 Ni, Nd5Mg41 and Nd Ni as secondary phases. The secondary phases increased with the increasing Nd content. The as-spun Nd-free alloy exhibited nanocrystalline structure, whereas the as-spun Nd-doped alloys exhibited nanocrystalline and amorphous structures. These results suggest that adding Nd facilitates glass formation of Mg2Ni-type alloys. Melt spinning and Nd addition improved alloy electrochemical performance, which includes discharge potential characteristics, discharge capacity, electrochemical cycle stability and high-rate discharge ability.展开更多
The melt spinning（MS） and ball milling（BM） technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologi...The melt spinning（MS） and ball milling（BM） technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologies, viz. melt spinning and ball milling, were employed to fabricate the SmMg_（11）Ni alloy. The structure and hydrogen storage performance of these two kinds of alloys were researched in detail. The results reveal that the as-spun and milled alloys both contain nanocrystalline and amorphous structures. By means of the measurement of PCT curves, the thermodynamic parameters of the alloys prepared by MS and BM are ΔN_（Ms）（des） = 82.51 kJ/mol and ΔH_（BM）（des） = 81.68 kJ/mol, respectively, viz.ΔH_（MS）（des） 〉 ΔH_（BM）（des）. The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun one. The as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one. As to the as-milled and spun alloys, the onset hydrogen desorption temperatures are557.6 and 565.3 K, respectively. Additionally, the as-milled alloy shows a superior hydrogen desorption property than the as-spun one. On the basis of time that required by desorbing hydrogen of 3 wt% H_2, the as-milled alloy needs 1488.574,390 and 192 s corresponding to hydrogen desorption temperatures 593,613,633 and 653 K, while the as-spun alloy needs 3600,1020,778 and 306 s corresponding to the same temperatures. The dehydrogenation activation energies of the as-milled and spun alloys are 100.31 and105.56 kJ/mol, respectively, the difference of which is responsible for the much faster dehydriding rate of the as-milled alloy.展开更多
基金supported by the Program for the Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(No.NJYT24006)the National Natural Science Foundation of China(Nos.51901105 and 51871125)+1 种基金the Natural Science Foundation of Inner Mongolia,China(Nos.2019BS05005 and 2021MS05064)the Inner Mongolia University of Science and Technology Innovation Fund(No.2019QDL-B11).
文摘Mg-based alloys must be dehydrogenated at high pressure and temperatures, limiting their practical application. In this paper, Nd_(5)Mg_(41)Ni alloy was prepared by vacuum melting, and the as-cast alloy was ball milled for 5 h, 10 h, 15 h, and 20 h. The effect of ball milling time on the microstructure and hydrogen storage properties of the alloy was systematically studied. The alloy comprises Nd_(5)Mg_(41), NdMg_(12), NdMg_(3), and Mg_(2)Ni phases. The Nd_(5)Mg_(41)Ni alloy milling for 10 h can reach 95% of the saturated hydrogen absorption at 553 K by 40 s, and the alloy can desorb hydrogen only by 20 min. The dehydrogenation activation energy is only 99.9 kJ/mol H_(2). Ball milling makes the alloy produce many nanocrystalline and amorphous structures. The nano-grain boundary provides a channel for the diffusion of hydrogen atoms, and the high energy at the grain boundary provides energy for the phase deformation nucleus. Ball milling leads to the refinement of alloy particles and shortens the diffusion distance of hydrogen atoms to the interior of alloy particles. Defects such as twins and dislocations generated by milling provide energy for the phase deformation nucleus during the hydrogen absorption and desorption.
基金the National Natural Science Foundation of China(Nos.51871125,51761032,52001005 and 51731002)Major Science and Technology Innovation Projects in Shandong Province(No.2019JZZY010320)for financial support of the work.
文摘Mg-based hydrides are too stable and the kinetics of hydrogen absorption and desorption is not satisfactory.An efficient way to improve these shortcomings is to employ reactive ball milling to synthesize the nanocomposite materials of Mg and additives.In this experiment,TiF_(3)was selected as an additive,and the mechanical milling method was employed to prepare the experimental alloys.The alloys used in this experiment were the as-cast Ce_(5)Mg_(85)Ni_(10),as-milled Ce_(5)Mg_(85)Ni_(10)and Ce_(5)Mg_(85)Ni_(10)+3 wt.%TiF3.The phase transformation,structural evolution,isothermal and non-isothermal hydrogenation and dehydrogenation performances of the alloys were inspected by XRD,SEM,TEM,Sievert apparatus,DSC and TGA.It revealed that nanocrystalline appeared in the as-milled samples.Compared with the as-cast alloy,ball milling made the particle dimension and grain size decrease dramatically and the defect density increase significantly.The addition of TiF_(3)made the surface of ball milling alloy particles markedly coarser and more irregular.Ball milling and adding TiF_(3)distinctly improved the activation and kinetics of the alloys.Moreover,ball milling along with TiF_(3)can decrease the onset dehydrogenation temperature of Mg-based hydrides and slightly ameliorate their thermodynamics.
基金supported financially by the National Natural Science Foundations of China(Nos.51901105,51761032 and 51871125)the Natural Science Foundation of Inner Mongolia,China(No.2019BS05005)the Inner Mongolia University of Science and Technology Innovation Fund(2019QDL-B11)。
文摘The Mg90Ce5 RE5(RE=La,Ce,Nd)alloys were prepared by a vacuum induction furnace and their micro structure,phase transformation,thermodynamics and kinetics property were systematically studied by XRD,SEM,TEM,and PCT characterization methods.The result shows that the activated alloys are composed of Mg/MgH2 and corresponding REH2+x with nanoscale.The REH2+x grain with Ce and La or Nd functional group have lower nucleation potential barriers than CeH2+x grains as the nucleation location,thus improve the hydrogen absorption kinetics of these alloys among which the Mg90Ce5Nd5 alloy can absorb 90%of the hydrogen within 2 min at 320℃.In addition,the Mg90Ce10 alloy has the lowest activation energy with 103.2 kJ mol-1 and the fastest desorption kinetics,which can release 5 wt%of the hydrogen within 20 min at 320℃.This is a correlation with grain size and the in-suit formed CeH2.73/CeO2 interface.Moreover,the co-doping Ce and La or Nd can effectively disorganize the thermodynamic stability of Mg-based hydrogen storage alloys to a certain degree,but the dehydrogenation kinetics of that still is restricted by the recombination energy of hydrogen ions on the surface.
基金the National Natural Science Foundation of China(51901105,51871125,51761032)Natural Science Foundation of Inner Mongolia,China(2019BS05005)。
文摘Greatly stable thermodynamics and sluggish kinetics impede the practical application of Mg-based hydrogen storage alloys.The modifications of composition and structure are important strategies in turning these hydrogen storage properties.In this study,Mg-based Mg90Ce5 Sm5 ternary alloy fabricated by vacuum induction melting was investigated to explore the performance and the reaction mechanism as hydrogen storage material by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscopy(TEM) and pressure-composition isotherms(PCI) measurements.The results indicate that the Mg-based Mg90Ce5 Sm5 ternary alloy consists of two solid solution phases,including the major phases(Ce,Sm)5 Mg41 and the minor phases(Ce,Sm)Mg12.After hydrogen absorption,these phases transform into the MgH2 and(Ce,Sm)H2.73 phase,while after hydrogen desorption,the MgH2 transforms into the Mg phase,but the(Ce,Sm)H2.73 phases are not changed.The alloy has a reversible hydrogen capacity of about 5.5 wt% H2 and exhibits well isothermal hydrogen absorption kinetics.Activation energy of 106 kJ/mol was obtained from the hydrogen desorption data between 573 and 633 K,which also exhibits the enhanced kinetics compared with the pure MgH2 sample,as a result of bimetallic synergy catalysis function of(Ce,Sm)H2.73 phases.The rate of hydrogen desorption is controlled by the release and recombination of H2 from the Mg surface.Furthermore,the changes of enthalpy and entropy of hydrogen absorption/desorption were calculated to be-80.0 kJ/mol H2,-137.5 J/K/mol H2 and 81.2 kJ/mol H2,139.2 J/K/mol H2,respectively.
基金financially supported by the National Natural Science Foundations of China(51761032 and 51871125)the Natural Science Foundations of Inner Mongolia,China(No.2019BS05005)the Scientific Research Staring Foundation of Taiyuan University of Science and Technology(20202040)
文摘The composites comprised of Co nanoparticle and C nanosheet were prepared though a high-temperature carbonization reaction.The catalysis of Co@C composites on the hydrogen storage behavior of Mg_(90)Ce_(5)Y_(5)alloy was investigated in detail by XRD,SEM,TEM,PCI,and DSC method.Because of the synergistic catalytic function of C and Co in C@Co nanocomposites,the Mg_(90)Ce_(5)Y_(5)alloy with 10 wt.%C@Co shows the excellent hydrogen absorption and desorption performances.Time for releasing hydrogen reduces from 150 min to 11 min with the addition of the C@Co composites at the temperature of 300℃.Meanwhile,the dehydrogenation activation energy also declines from 130.3 to 81.9 kJ mol^(-1)H_(2)after the addition of the C@Co composites.This positive effect attributes to the C layer with the high defect density and the Co nanoparticles,which reduces the energy barriers for the nucleation of Mg/MgH_(2)phase and the recombination of hydrogen molecule.Besides,the C@Co composites also improve the activation property of the Mg_(90)Ce_(5)Y_(5)alloy which was folly activated in the first cycle.Moreover,the temperature for initial dehydrogenation and the endothermic peak of the alloy hydride were also decreased.Although the addition of the C@Co composites increases the plateau pressures and decreases the value of the decomposition enthalpy,these differences are so small that the improvement on thermodynamics can hardly be seen.
基金Project supported by the National Natural Science Foundation of China(51761032,51471054,51871125)
文摘For purpose of promoting the hydrogen absorption and desorption thermodynamics and kinetics properties of Mg-Ni-based alloys, partially substituting Y and Cu for Mg and Ni respectively and melt spinning technique were applied for getting Mg25-xYxNi9 Cu(χ = 0-7) alloys. Their microstructures and phases were characterized with the help of X-ray diffraction and transmission electron microscopy. Their hydrogen absorbing and desorbing properties were tested by a Sievert apparatus, DSC, and TGA, which were connected with a H2 detector. In order to estimate the dehydrogenation activation energy of alloy hydride, both Arrhenius and Kissinger methods were applied for calculation. It is found that their hydriding kinetics notably declines, however, their hydrogen desorption kinetics conspicuously improves, with spinning rate and Y content increasing. Their hydrogen desorption activation energy markedly decreases under the same constraint, and it is found that melt spinning and Y substituting Mg improve the real driving force for dehydrogenation. As for the tendency of hydrogen absorption capacity,it presents an elevation firstly and soon after a decline with the rising of spinning rate, however, it always lowers with Y content growing. With Y content and spinning rate increasing, their thermodynamic parameters(△H and △S absolute values) visibly decrease, and the starting hydrogen desorption temperatures of alloy hydrides obviously lower.
基金Project supported by the National Natural Science Foundation of China(51761032,51901105,51871125)。
文摘In this paper,the as-cast Mg85Cu5Ni10 alloy and Mg85Cu5Ni10-x wt%CeO2(x=0,4,8)alloys were prepared successfully by vacuum induction smelting and ball milling.The microstructure,hydrogen absorption/desorption kinetics and thermodynamics performances of the alloys were studied in detail.The results show that the Mg85Cu5Ni10 alloys with CeO2 additive have faster hydrogenation/dehydrogenation kinetics and better thermodynamic properties.The dehydrogenation activation energy is reduced to 81.211 kJ/mol from 119.142 by adding 8 wt%CeO2.CeO2 contributes to producing structural defects,nanocrystallines,grain boundaries,partial amorphous,lattice dislocations and cracks which are favorable to provide more hydrogen diffusion channels during hydriding/dehydriding process.Meanwhile,CeO2 additive weakens the bond energy of Mg-H.These micro structural changes caused by CeO2 additive improve the hydrogen storage performance of Mg85Cu5Ni10 markedly.
基金the National Natural Science Foundations of China (Nos. 51761032, 51871125 and 51471054) for financial support of the work
文摘Experimental alloys with compositions of Mg(25-x)YxNi9Cu(x=0,1,3,5,7)have been successfully prepared through melt spinning method.The phase compositions and microstructures were measured by X-Ray diffraction(XRD)and high-resolution transmission electron microscopy(HRTEM).The de-/hydrogenation properties were measured by utilizing Sievert apparatus,differential scanning calorimetry(DSC)and thermal gravimetric analyzer(TGA)connected with a H2 detector.The Arrhenius and Kissinger methods were adopted to calculate their dehydrogenation activation energies.The results show that hydrogen absorption kinetics of the alloys notably decline while their hydrogen desorption kinetics conspicuously improve with spinning rate increasing.The dehydrogenation activation energy markedly decreases with spinning rate increasing,which makes the hydrogen desorption kinetics improve.The thermodynamic parameters(H and S absolute values)clearly decrease with spinning rate increasing.The hydrogen absorption capacity exhibits different trends with spinning rate rising.Specifically,hydrogen absorption capacity increases at the beginning and declines later for Y1 alloy,but that of Y7 alloy always decreases with spinning rate growing.
基金financially supported by the National Natural Science Foundation of China(Nos.51901105,51871125,and 51761032)Natural Science Foundation of Inner Mongolia,China(2019BS05005)+1 种基金Inner Mongolia University of Science and Technology Innovation Fund(2019QDL-B11)Major Science and Technology Innovation Projects in Shandong Province(2019JZZY010320)
文摘In this investigation,mechanical grinding was applied to fabricating the Mg-based alloys La_(7)Sm_(3)Mg_(80)Ni_(10)+5 wt.%M(M=None,TiO_(2),La_(2)O_(3))(named La_(7)Sm_(3)Mg_(80)Ni_(10)-5 M(M=None,TiO_(2),La_(2)O_(3))).The result reveals that the structures of as-milled alloys consist of amorphous and nanocrystalline.The particle sizes of the added M(M=TiO_(2),La_(2)O_(3))alloys obviously diminish in comparison with the M=None specimen,suggesting that the catalysts TiO_(2)and La_(2)O_(3)can enhance the grinding efficiency.What’s more,the additives TiO_(2)and La_(2)O_(3)observably improve the activation performance and reaction kinetics of the composite.The time required by releasing 3 wt.%hydrogen at553,573 and 593 K is 988,553 and 419 s for the M=None sample,and 578,352 and 286 s for the M=TiO_(2)composite,and 594,366,301 s for the La_(2)O_(3)containing alloy,respectively.The absolute value of hydrogenation enthalpy change|△H|of the M(M=None,TiO_(2),La_(2)O_(3))alloys is 77.13,74.28 and 75.28 kJ/mol.Furthermore,the addition of catalysts reduces the hydrogen desorption activation energy(E_(a)^(de)).
基金financially supported by the National Natural Science Foundations of China(51471054,51761032 and51371094)Natural Science Foundation of Inner Mongolia,China(2015MS0558)
文摘The influences of the catalysts of CoS2 and MoB2 nano-particles on microstructure and hydrogen stor-age behaviors of as-milled SmsMg41 alloy have been compared in this work. The SmsMg41 ＋ 5 wt.% M （M = COS2, MoS2） alloys were prepared by milling the mechanical ground as-cast SmsMg41 alloy powders （particle size ≤75 μm） with 5 wt.% CoS2 or MoS2 nano-particles （particle size ≤ 30 nm）, respectively. The results demonstrate that the CoS2 and MoS2 nanoparticles are embedded into the alloy surface, which is nanostructure containing some crystal defects, such as dislocation, grain boundary and twin etc. Those microstructures play a beneficial role in reducing the total potential barrier that the hydrogen absorption or desorption reactions must overcome, hence improving the hydrogen storage kinetics of the alloys. The as-milled alloys are composed of SmsMg41 and SmMg3 phases, and ball milling refines their crys-tal grains. The MgH2 and Sm3H7 phases appear after hydrogenation, while Mg and Sm3H7 phases exist after dehydrogenation. The dehydriding activation energy of M = CoS2 and MoS2 alloys are 101.67 and 68.25 kJ/mol H2 respectively. The initial hydrogen desorption of M = CoS2 and MoS2 alloys are 252.9 ℃ and 247.8 ℃.The hydrogenation and dehydrogenation enthalpy changes of M = MoS2 alloy are a little smaller than that of MzCoS2 alloy. Therefore, the catalyst MoS2 can improve the as-milled SmsMg41 alloy in hydrogen storage property more effectively than C0S2.
基金financially supported by the National Natural Science Foundation of China (Nos. 51161015 and 51371094)Natural Science Foundation of Inner Mongolia, China (No. 2011ZD10)
文摘Nanocrystalline and amorphous Mg2Ni-type（Mg24Ni10Cu2）100–xNdx（x = 0, 5, 10, 15, 20） alloys were prepared by melt-spinning technology. The structures of as-cast and spun alloys were characterised by X-ray diffraction,scanning electron microscopy and transmission electron microscopy. Electrochemical performance of the alloy electrodes was measured using an automatic galvanostatic system. The electrochemical impedance spectra and Tafel polarisation curves of the alloy electrodes were plotted using an electrochemical work station. The hydrogen diffusion coefficients were calculated using the potential step method. Results indicate that all the as-cast alloys present a multiphase structure with Mg2 Ni type as the major phase with Mg6 Ni, Nd5Mg41 and Nd Ni as secondary phases. The secondary phases increased with the increasing Nd content. The as-spun Nd-free alloy exhibited nanocrystalline structure, whereas the as-spun Nd-doped alloys exhibited nanocrystalline and amorphous structures. These results suggest that adding Nd facilitates glass formation of Mg2Ni-type alloys. Melt spinning and Nd addition improved alloy electrochemical performance, which includes discharge potential characteristics, discharge capacity, electrochemical cycle stability and high-rate discharge ability.
基金Project supported by the National Natural Science Foundations of China(51761032,51371094 and 51471054)Natural Science Foundation of Inner Mongolia,China(2015MS0558)
文摘The melt spinning（MS） and ball milling（BM） technologies are thought to be efficient to prepare nanostructured Mg and Mg-based alloys for improving their hydrogen storage performances. In this paper, two technologies, viz. melt spinning and ball milling, were employed to fabricate the SmMg_（11）Ni alloy. The structure and hydrogen storage performance of these two kinds of alloys were researched in detail. The results reveal that the as-spun and milled alloys both contain nanocrystalline and amorphous structures. By means of the measurement of PCT curves, the thermodynamic parameters of the alloys prepared by MS and BM are ΔN_（Ms）（des） = 82.51 kJ/mol and ΔH_（BM）（des） = 81.68 kJ/mol, respectively, viz.ΔH_（MS）（des） 〉 ΔH_（BM）（des）. The as-milled alloy shows a larger hydrogen absorption capacity as compared with the as-spun one. The as-milled alloy exhibits lower onset hydrogen desorption temperature than the as-spun one. As to the as-milled and spun alloys, the onset hydrogen desorption temperatures are557.6 and 565.3 K, respectively. Additionally, the as-milled alloy shows a superior hydrogen desorption property than the as-spun one. On the basis of time that required by desorbing hydrogen of 3 wt% H_2, the as-milled alloy needs 1488.574,390 and 192 s corresponding to hydrogen desorption temperatures 593,613,633 and 653 K, while the as-spun alloy needs 3600,1020,778 and 306 s corresponding to the same temperatures. The dehydrogenation activation energies of the as-milled and spun alloys are 100.31 and105.56 kJ/mol, respectively, the difference of which is responsible for the much faster dehydriding rate of the as-milled alloy.
