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1.
Siarhei Kalinichenka Lars Röntzsch Thomas RiedlThomas Weißgärber Bernd Kieback 《International Journal of Hydrogen Energy》2011,36(17):10808-10815
For hydrogen storage applications a nanocrystalline Mg90Ni8RE2 alloy (RE = Y, Nd, Gd) was produced by melt spinning. The microstructure in the as-cast, melt-spun and hydrogenated state was characterized by X-ray diffraction and electron microscopy. Its activation, hydrogenation/dehydrogenation properties and cycle stability were examined by thermogravimetry in the temperature range from 50 °C to 385 °C and pressures up to 30 bar H2. It was found that the activated alloy can reach a reversible gravimetric hydrogen storage density of up to 5.6 wt.%-H. Furthermore, the reversible gravimetric hydrogen storage density increases with the number of hydrogenation/dehydrogenation cycles, while the dehydrogenation rate remained unchanged. This observation was attributed to the increase of the specific surface area of the ribbon due to cracking during repeated cycling. However, the microstructure of the hydrogenated alloy remained nanocrystalline throughout cycling. 相似文献
2.
The hydrogenation/dehydrogenation characteristics and hydrogen storage properties of nominal Mg3Ag and Mg3Y alloys prepared by induction melting were investigated. The as-melted Mg3Ag alloy was composed of Mg54Ag17 phase, while Mg3Y consisted of Mg24Y5 and Mg2Y phases. Mg54Ag17 transformed into MgAg and MgH2 during the first hydrogenation, and the phase transition of the following hy/dehydrogenation cycles was Mg3Ag + 2H2 ↔ MgAg + 2MgH2. Both Mg24Y5 and Mg2Y undertook disproportion reactions and decomposed into MgH2 and YH3. Experimental and calculated results demonstrated that there was no necessary relation between the thermodynamic stabilities and the size interstices in these alloys. The dehydrogenation enthalpy change (ΔH) and entropy change (ΔS) of Mg3Ag were calculated and compared with that of pure Mg, which indicated that the increase of ΔS could counteract the stabilization effect of ΔH, which offered a method for tuning the thermodynamic properties of Mg-based alloys. 相似文献
3.
Siarhei KalinichenkaLars Röntzsch Thomas RiedlThomas Gemming Thomas WeißgärberBernd Kieback 《International Journal of Hydrogen Energy》2011,36(2):1592-1600
Microstructural and hydrogen storage properties of three nanocrystalline melt-spun Mg-base alloys (Mg90Cu2.5Ni2.5Y5, Mg85Cu5Ni5Y5 and Mg80Cu5Ni5Y10) have been investigated in view of their application as reversible hydrogen storage materials. The activation procedure and the hydrogen sorption kinetics of these alloys were studied by thermogravimetry at different temperatures in the range from 100 °C to 380 °C. It has been found that these alloys can reach reversible gravimetric hydrogen storage densities of up to 4.8 wt.%-H2. Even at a low temperature of 100 °C, the hydrogenation kinetics of the investigated alloys is rather high in the range of 1.5 wt.%-H2 per hour. In the hydrogenated state, these alloys consist of MgH2, high temperature Mg2NiH4, Mg2NiH0.3, YH2, YH3 as well as MgCu2. The presence of MgCu2 indicates the reaction of Mg2Cu with hydrogen. After repeated hydrogenation/dehydrogenation the preservation of a nanocrystalline grain structure has been confirmed by scanning electron microscopy, energy-filtered and conventional transmission electron microscopy. Additionally, the distribution of hydrogen in the hydrogenated sample was mapped by means of electron energy loss spectroscopy. 相似文献
4.
Siarhei Kalinichenka Lars Rntzsch Bernd Kieback 《International Journal of Hydrogen Energy》2009,34(18):7749-7755
Nanocrystalline magnesium-rich Mg–Ni–Y alloys were produced by melt-spinning. They were characterized regarding their microstructure, crystallization behaviour, and cyclic hydrogenation/dehydrogenation properties in view of their application as reversible hydrogen storage materials. Transmission electron microscopy reveals that these alloys consist in the as-spun state of mixtures of nanocrystalline Mg(Ni;Y) grains that are embedded in an amorphous matrix. Differential scanning calorimetry and X-ray diffraction analysis show that these alloys undergo several crystallization steps in the temperature range between 180 and 370 °C. It was found that only a few thermal activation cycles of the as-quenched ribbons are required in order to reach excellent hydrogenation/dehydrogenation properties of these alloys. In thermogravimetric analyses using a magnetic suspension balance it could be shown that these alloys can reach reversible gravimetric hydrogen storage densities of up to 5.3 wt.%-H with hydrogenation and dehydrogenation rates of up to 1 wt.%-H/min even at temperatures of 250 °C. The structure of the alloys remains nanocrystalline even after several hydrogenation/dehydrogenation cycles. 相似文献
5.
《International Journal of Hydrogen Energy》2020,45(41):21588-21599
Element substitution is an effective strategy for improving Mg-based alloys in their hydrogenation/dehydrogenation property. Thereby, in this paper, Sm was selected to partially replace La in a La–Mg-based alloy for improving its hydriding and dehydriding performance. The alloys with the compositions of Mg80Ni10La10-xSmx (x = 0–4) were manufactured through vacuum induction melting. Their microstructures and phase compositions were measured by XRD, SEM and HRTEM. The isothermal hydrogen storage property was tested through an automatic Sieverts apparatus. Non-isothermal hydrogen desorption performance was measured through TGA and DSC. Arrhenius and Kissinger methods were adopted to calculate the dehydrogenation activation energy of alloys. The results reveal that all of the experimental alloys can reversibly absorb and release a large amount of H2 at appropriate temperatures. The substitution of Sm for La ameliorates the hydriding and dehydriding kinetics, but it results in an undesired reduction of hydrogen absorption and desorption capacities. Substituting La by Sm decreases the initial hydrogen release temperature of the hydride visibly. Furthermore, substituting Sm for La engenders the dehydrogenation activation energy decline clearly, which is considered as the main reason for the improved hydrogen desorption kinetics resulted from Sm replacing La. 相似文献
6.
Zhenwei Dong Liqun Ma Yaoming WuLimin Wang Xiaodong Shen 《International Journal of Hydrogen Energy》2011,36(4):3016-3021
The microstructure and electrochemical hydrogen storage characteristics of (La0.7Mg0.3)1−xCexNi2.8Co0.5 (x = 0, 0.05, 0.10, 0.15 and 0.20) alloys have been investigated. The results show that all alloys consist of (La, Mg)Ni3 and LaNi5 phases. The cyclic stability (S100) of the alloy electrodes increases from 58.7% (x = 0) to 69.8% (x = 0.20) after 100 charge/discharge cycles. The high rate dischargeability (HRD) increases from 66.8% (x = 0) to 69.6% (x = 0.10), then decreases to 65.1% (x = 0.20) at the discharge current density of 1200 mA/g. Moreover, the electrochemical kinetic characteristics of the alloy electrodes are also improved by increasing Ce content. 相似文献
7.
The effect of Mg content on the structural characteristics and hydrogen storage properties of the Ca3.0−xMgxNi9 (x = 0.5, 1.0, 1.5 and 2.0) alloys was investigated. The lattice parameters and unit cell volume of the PuNi3-type (Ca, Mg)Ni3 main phase decreased with increasing Mg content. The 6c site of PuNi3-type structure was occupied by both Ca and Mg atoms. Moreover, the occupation factor of Ca on the 6c site decreased with the increase of Mg content. The hydrogen absorption capacity of the alloys decreased due to higher Mg content. However, the thermodynamic properties of hydrogen absorption and desorption were improved and the plateau pressures were increased. When x = 1.5–2.0, the Ca3.0−xMgxNi9 alloys had favorable enthalpy (ΔH) and entropy (ΔS) of hydride formation. 相似文献
8.
The hydrogen absorption properties of LaNi4.8T0.2 (T = Mg, Bi and Sb) alloys are reported. The effects of the substitution of Ni in the LaNi5 compound with Mg, Bi and Sb are investigated. The ability of alloys to absorb hydrogen is characterized by the pressure–composition (p–c) isotherms. The p–c isotherms allow the determining thermodynamic parameters enthalpy (ΔHdes) and entropy (ΔSdes) of the dehydrogenation processes. The calculated ΔHdes and ΔSdes data helps to explain the decrease of hydrogen equilibrium pressure in alloys doped with Al, Mg and Bi and its increase in the Sb-doped LaNi5 compound. Generally, partial substitution of Ni in LaNi5 compound with Mg, Bi and Sb cause insignificant changes of hydrogen storage capacity compared to the hydrogen content in the initial LaNi5H6 hydride phase. However, it is worth to stress that, in the case of LaNi4.8Bi0.2, a small increase of H/f.u. up to 6.8 is observed. The obtained results in these investigations indicate that the LaNi4.8T0.2 (T = Al, Mg and Bi) alloys can be very attractive materials dedicated for negative electrodes in Ni/MH batteries. 相似文献
9.
Weiqing Jiang Zhiqiang Lan Wei Wenlou Liu Yixin Jin Guo 《International Journal of Hydrogen Energy》2010
La2−xTixMgNi9 (x = 0.2, 0.3) alloys have been prepared by magnetic levitation melting under an Argon atmosphere, and the as-cast alloys were annealed at 800 °C, 900 °C for 10 h under vacuum. The effects of annealing on the hydrogen storage properties of the alloys were investigated systematically by XRD, PCT and electrochemical measurements. For the La2−xTixMgNi9 (x = 0.2, 0.3) alloys, LaNi5, LaMg2Ni9 and LaNi3 are the main phases and a Ti2Ni phase appears at 900 °C. The effective hydrogen storage capacity increases from 1.10, 1.10 wt.% (as-cast) to 1.22, 1.16 wt.% (annealed 800 °C) and 1.31, 1.27 wt.% (annealed 900 °C), respectively. The annealing not only improves the hydrogen absorption/desorption kinetics but also increases the maximum discharge capacity and enhances the cycling stability. The La1.8Ti0.2MgNi9 alloy annealed at 900 °C exhibits good electrochemical properties, and the discharge capacities decrease from 366.1 mA h/g to 219.6 mA h/g after 177 charge-discharge cycles. 相似文献
10.
The catalytic effects of rare earth fluoride REF3 (RE = Y, La, Ce) additives on the dehydrogenation properties of LiAlH4 were carefully investigated in the present work. The results showed that the dehydrogenation behaviors of LiAlH4 were significantly altered by the addition of 5 mol% REF3 through ball milling. The destabilization ability of these catalysts on LiAlH4 has the order: CeF3>LaF3>YF3. For instance, the temperature programmed desorption (TPD) analyses showed that the onset dehydrogenation temperature of CeF3 doped LiAlH4 was sharply reduced by 90 °C compared to that of pristine LiAlH4. Based on differential scanning calorimetry (DSC) analyses, the dehydriding activation energies of the CeF3 doped LiAlH4 sample were 40.9 kJ/mol H2 and 77.2 kJ/mol H2 for the first and second dehydrogenation stages, respectively, which decreased about 40.0 kJ/mol H2 and 60.3 kJ/mol H2 compared with those of pure LiAlH4. In addition, the sample doped with CeF3 showed the fastest dehydrogenation rate among the REF3 doped LiAlH4 samples at both 125 °C and 150 °C during the isothermal desorption. The phase changes in REF3 doped LiAlH4 samples during ball milling and dehydrogenation were examined using X-ray diffraction and the mechanisms related to the catalytic effects of REF3 were proposed. 相似文献
11.
In this paper, the hydrogen storage properties and reaction mechanism of the 4MgH2 + LiAlH4 composite system with the addition of Fe2O3 nanopowder were investigated. Temperature-programmed-desorption results show that the addition of 5 wt.% Fe2O3 to the 4MgH2 + LiAlH4 composite system improves the onset desorption temperature to 95 °C and 270 °C for the first two dehydrogenation stage, which is lower 40 °C and 10 °C than the undoped composite. The dehydrogenation and rehydrogenation kinetics of 5 wt.% Fe2O3-doped 4MgH2 + LiAlH4 composite were also improved significantly as compared to the undoped composite. Differential scanning calorimetry measurements indicate that the enthalpy change in the 4MgH2–LiAlH4 composite system was unaffected by the addition of Fe2O3 nanopowder. The Kissinger analysis demonstrated that the apparent activation energy of the 4MgH2 + LiAlH4 composite (125.6 kJ/mol) was reduced to 117.1 kJ/mol after doping with 5 wt.% Fe2O3. Meanwhile, the X-ray diffraction analysis shows the formation of a new phase of Li2Fe3O4 in the doped composite after the dehydrogenation and rehydrogenation process. It is believed that Li2Fe3O4 acts as an actual catalyst in the 4MgH2 + LiAlH4 + 5 wt.% Fe2O3 composite which may promote the interaction of MgH2 and LiAlH4 and thus accelerate the hydrogen sorption performance of the MgH2 + LiAlH4 composite system. 相似文献
12.
J. Zhang Y.N. HuangC. Mao P. PengY.M. Shao D.W. Zhou 《International Journal of Hydrogen Energy》2011,36(22):14477-14483
Mg3MNi2 (M = Al, Ti, Mn) ternary intermetallic compounds with cubic structure are a new type of potential hydrogen storage alloys. Using ab initio density functional theory (DFT) calculations, the energetics and electronic structures of Mg3MNi2 (M = Al, Ti, Mn) compounds are systematically investigated. The optimized structural parameters including lattice constants and internal atomic positions are close to experimental data determined from X-ray powder diffraction. The calculated results of formation enthalpy ΔHform show that the stabilities of cubic Mg3MNi2 (M = Al, Ti, Mn) compound, compared with hexagonal Mg2Ni, increase in the order of Mg3MnNi2, Mg2Ni, Mg3TiNi2 and Mg3AlNi2, whereas the stabilities of their saturated Mg3MNi2H3 (M = Al, Ti, Mn) hydrides, compared with monoclinic Mg2NiH4, decrease in the order of Mg2NiH4, Mg3AlNi2H3, Mg3TiNi2H3 and Mg3MnNi2H3. Further calculations of hydrogen desorption enthalpy ΔHdes indicate that these cubic Mg3MNi2 (M = Al, Ti, Mn) compounds possess promising dehydrogenation properties for their relatively lower ΔHdes values. Among of them, the dehydrogenation ability of Mg3TiNi2 is the most pronounced. Analysis of electronic structures suggests that the strong covalent bonding interactions between Ni and M within cubic Mg3MNi2 (M = Al, Ti, Mn) are dominant and directly control the structural stabilities of these compounds. 相似文献
13.
The present study compares the dehydrogenation kinetics of (2LiNH2+MgH2) and (LiNH2+LiH) systems and their vulnerabilities to the NH3 emission problem. The (2LiNH2+MgH2) and (LiNH2+LiH) mixtures with different degrees of mechanical activation are investigated in order to evaluate the effect of mechanical activation on the dehydrogenation kinetics and NH3 emission rate. The activation energy for dehydrogenation, the phase changes at different stages of dehydrogenation, and the level of NH3 emission during the dehydrogenation process are studied. It is found that the (2LiNH2+MgH2) mixture has a higher rate for hydrogen release, slower rate for approaching a certain percentage of its equilibrium pressure, higher activation energy, and more NH3 emission than the (LiNH2+LiH) mixture. On the basis of the phenomena observed, the reaction mechanism for the dehydrogenation of the (2LiNH2+MgH2) system has been proposed for the first time. Approaches for further improving the hydrogen storage behavior of the (2LiNH2+MgH2) system are discussed in light of the newly proposed reaction mechanism. 相似文献
14.
《International Journal of Hydrogen Energy》2019,44(58):30574-30582
In this paper, the best performance of the MgH2 destabilized system with different ratios of Cd (1:1, 2:1, 3:1 and 4:1) have been studied for the first time. Remarkable enhancements on the onset dehydrogenation temperature, as well as the isothermal de/rehydrogenation kinetics were shown by the 4MgH2 + Cd composite. In order to improve the hydrogen storage properties of the 4MgH2 + Cd, TiF3 was added and its catalytic effects were investigated. Temperature programmed dehydrogenation result had revealed that the onset dehydrogenation temperature was improved once the 10 wt% TiF3 was incorporated into the 4MgH2 + Cd system. The absorption and desorption kinetics were also improved compared to the un-doped 4MgH2 + Cd composite system. The scanning electron microscope result had displayed that the 4MgH2 + Cd + 10 wt% TiF3 had the smallest particle size compared to the pure and the ball-milled MgH2, as well as the 4MgH2 + Cd composite system. The X-ray diffraction results had demonstrated the formation of an intermediate compound, Mg3Cd, which was formed during the heating process. For the TiF3-doped sample, it is reasonable to conclude that the in-situ formed TiH2 and F-containing species play a synergetic role to encourage interactions between the MgH2 and the Cd and thus further ameliorate the performances of the hydrogen storage of 4MgH2 + Cd composite system. 相似文献
15.
《International Journal of Hydrogen Energy》2022,47(81):34545-34554
In this work, three different states of Mg-9.1Y-1.8Zn alloys including as-cast, extruded and swaged were prepared by semi-continuous casting, extrusion and swaging processes, respectively. Their compositions, microstructures and hydrogen storage properties were investigated. The results show that Mg-9.1Y-1.8Zn alloys in three different states are all composed of Mg and long-period stacking ordered (LPSO) phases. The LPSO phases occurs to break and decompose after hydrogenation and in-situ forms the YHχ(χ = 2,3) nano-hydrides. The nano-hydrides can be used as in-situ catalysts to improve the hydrogen storage properties of alloys. Meanwhile, many nanocrystalline grains appear in the core of alloy after swaging, and the average grain size ranges from 80 to 200 nm. The presence of nanocrystals may increase the specific surface area of alloy, facilitating the diffusion and absorption of hydrogen. Comparatively, the swaged alloy exhibits the largest hydrogen storage capacity and excellent hydrogen sorption kinetics relative to other states of alloys. 相似文献
16.
Zhenggan Pu Yunfeng ZhuJinyu Zhu Jianguang YuanJiguang Zhang Wei ChenJiaojiao Fang Liquan Li 《International Journal of Hydrogen Energy》2014
The structure, kinetics and electrochemical characteristics of Mg2NiH4-x wt.% MmNi3.8Co0.75Mn0.4Al0.2 (x = 5, 10, 20, 40) composites prepared by mechanical milling have been investigated in this paper. XRD results indicate that the as-milled Mg2NiH4 shows nanocrystalline or amorphous-like structure, and it does not react with MmNi3.8Co0.75Mn0.4Al0.2 during mechanical milling. As the amount of MmNi3.8Co0.75Mn0.4Al0.2 increases, the maximum discharge capacity decreases initially from 508 mAh/g (x = 5) to 440 mAh/g (x = 10) and then increases to 509 mAh/g (x = 40). Meanwhile, the capacity retention (R10) increases from 12.8% (x = 5) to 23.4% (x = 40), and the corrosion potential of electrode (Ecorr) increases from −0.930 V to −0.884 V (vs. Hg/HgO). Especially, the more MmNi3.8Co0.75Mn0.4Al0.2 content the composite contains, the higher high rate dischargeability (HRD) the electrode exhibits, which could be attributed to the catalytic reaction and reduction of the Mg2NiH4 grain size brought by MmNi3.8Co0.75Mn0.4Al0.2. The improvement in electrode kinetics has been depicted from the bulk hydrogen diffusion coefficient (D), the exchange current density (I0) and the charge transfer resistance (Rct) on the alloy surface. 相似文献
17.
Mg2CoH5 was synthesized by reactive mechanical milling (RMM) under hydrogen atmosphere (0.5 MPa) from 2MgH2–Co and 3MgH2–Co mixtures, with a yield >80%. The microstructure, structure and thermal behavior of the phases formed during the processing were investigated by transmission electron microscopy, X-ray diffraction and differential scanning calorimetry. Kinetic properties of the reaction with hydrogen of the 2MgH2–Co and 3MgH2–Co mixtures after RMM were evaluated using modified Sieverts-type equipment. The 3MgH2–Co mixture showed better properties for storage applications, with its highest rate of hydrogen absorption and desorption at 300 °C, its storage capacity of about 3.7 wt% in less than 100 s, and good stability after cycling. Although the starting material presents Mg2CoH5 as majority phase, the cycling leads to disproportion between Mg and Co. We obtained a mixture of Mg2CoH5, Mg6Co2H11 and MgH2 hydrides, as well as other phases such as Co and/or Mg, depending on experimental conditions. 相似文献
18.
The effect of transition metal fluorides on the dehydrogenation and hydrogenation of MgH2 has been investigated. Many of the fluorides show a considerable catalytic effect on both the dehydrogenation temperature and hydrogenation kinetics of MgH2. Among them, NbF5 and TiF3 most significantly enhance the hydrogenation kinetics of MgH2. It is suggested that hydride phases formed by the reaction between MgH2 and these transition metal fluorides during milling and/or hydrogenation play a key role in improving the hydrogenation kinetics of MgH2. 相似文献
19.
Claudio Pistidda Daphiny Pottmaier Fahim Karimi Sebastiano Garroni Agnieszka Rzeszutek Martin Tolkiehn Maximilian Fichtner Wiebke Lohstroh Marcello Baricco Thomas Klassen Martin Dornheim 《International Journal of Hydrogen Energy》2014
In this work the effect of the ratio of starting reactants on the hydrogen absorption reaction of the system xNaH + MgB2 is investigated. At a constant hydrogen pressure of 50 bar, depending on the amount of NaH present in the system NaH + MgB2, different hydrogen absorption behaviors are observed. For two system compositions: NaH + MgB2 and 0.5NaH + MgB2, the formation of NaBH4 and MgH2 as only crystalline hydrogenation products is achieved. The relation between the ratio of the starting reactants and the obtained hydrogenation products is discussed in detail. 相似文献
20.
Jiguang Zhang Yunfeng ZhuYicun Wang Zhenggan PuLiquan Li 《International Journal of Hydrogen Energy》2012
Mg2−xAlxNi (x = 0, 0.3, 0.5, 0.7) hydrogen storage alloys used as the negative electrode in a nickel–metal hydride (Ni–MH) battery were successfully prepared by means of hydriding combustion synthesis (HCS) and the selected alloy Mg1.5Al0.5Ni was further modified by mechanical milling (MM). The structural and electrochemical hydrogen storage properties of Mg2−xAlxNi alloys have been investigated in detail. XRD results show that a new phase Mg3AlNi2 that possesses an excellent cycling stability is observed with the substitution of Al for Mg. A short-time mechanical milling has a significant effect on improving the discharge capacity of the HCS product of Mg1.5Al0.5Ni. The maximum discharge capacity of Mg1.5Al0.5Ni ascends with increasing mechanical milling time and reaches the maximum 245.5 mAh/g when milled for 10 h. The alloy milled for 5 h shows the best electrochemical kinetics, which is due to its smaller mean particle size and uniform distribution of the particles. Further increasing in mechanical milling time could not bring about better electrochemical kinetics, which might be attributed to the agglomeration of the alloy particles and thus the charge-transfer reaction and hydrogen diffusion are restrained. It is suggested that the novel method of HCS + MM is promising to prepare ternary Mg-based intermetallic compound for electrochemical hydrogen storage. 相似文献