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1.
Mg–20 wt% Ni–Y composite was successfully prepared by reactive mechanical alloying (RMA). X-ray diffraction (XRD) measurement showed that both MgH2 and Mg2NiH4 co-exist in the milled composite. The composite exhibits excellent hydrogen sorption kinetics and does not need activation on the first hydrogen storage process. It can absorb 3.92 and 5.59 wt% hydrogen under 3.0 MPa hydrogen pressure at 293 and 473 K in 10 min, respectively, and desorb 4.67wt% hydrogen at 523 K in 30 min under 0.02 MPa hydrogen pressure. The equilibrium desorption pressure of the composite are 0.142, 0.051 and 0.025 MPa at 573, 543 and 523 K, respectively. The differential scanning calorimetry (DSC) measurement showed that dehydrogenation of Mg–20 wt% Ni–Y composite was depressed about 100 K comparing to that of milled pure MgH2. It is deduced that both the catalysis effect of Mg2Ni and YH3 distributed in Mg substrate and the crystal defects formed by RMA are the main reason for improving hydrogen sorption kinetics of the Mg–20 wt% Ni–Y composite. 相似文献
2.
Federico Cova Pierre Arneodo LarochetteFabiana Gennari 《International Journal of Hydrogen Energy》2012
In the present work we investigate the hydrogen sorption properties of composites in the MgH2–Ni, MgH2–Ni–LiH and MgH2–Ni–LiBH4 systems and analyze why Ni addition improve hydrogen sorption rates while LiBH4 enhance the hydrogen storage capacity. Although all composites with Ni addition showed significantly improved hydrogen storage kinetics compared with the pure MgH2, the fastest hydrogen sorption kinetics is obtained for Ni-doped MgH2. The formation of Mg2Ni/Mg2NiH4 in Ni-doped MgH2 composite and its microstructure allows to uptake 5.0 wt% of hydrogen in 25 s and to release it in 8 min at 275 °C. In the MgH2–Ni–LiBH4 composite, decomposition of LiBH4 occurs during the first dehydriding leading to the formation of diborane, which has a Ni catalyst poison effect via the formation of a passivating boron layer. A combination of FTIR, XRD and volumetric measurements demonstrate that the formation of MgNi3B2 in the MgH2–Ni–LiBH4 composite happens in the subsequent hydriding cycle from the reaction between Mg2Ni/Mg2NiH4 and B. Activation energy analysis demonstrates that the presence of Ni particles has a catalytic effect in MgH2–Ni and MgH2–Ni–LiH systems, but it is practically nullified by the addition of LiBH4. The beneficial role of LiBH4 on the hydrogen storage capacity of the MgH2–Ni–LiBH4 composite is discussed. 相似文献
3.
Amorphous-crystalline composite ribbons of quaternary Mg–Ni–(Y,La)–Pd alloys are produced via rapidly solidification and used as precursors for creating nanocrystalline hydrogen storage materials. The resulting materials demonstrate relatively high hydrogen capacity of around 4.5 mass% H and excellent absorption/desorption kinetics at 573 K. Additionally, the alloys demonstrate reversible hydrogen storage at 473 K. A composition of Mg85Ni10Y2.5Pd2.5 fully absorbs and desorbs 4.6 mass% H in 90 min. The cyclability of the quaternary alloys demonstrates good stability, with little loss in maximum capacity through 8–10 cycles. This has been attributed to the improved stability of the nanocrystalline structure attained via the Y and La additions. Thermodynamically, the enthalpy of the hydrogen absorption reaction is reduced by 5 kJ/mol in the quaternary alloys, compared to Mg-MgH2; while the entropy of reaction is also reduced. 相似文献
4.
Yang-huan Zhang Bao-wei Li Hui-ping Ren Shi-hai Guo Zhong-wang Wu Xin-lin Wang 《International Journal of Hydrogen Energy》2009
In order to improve the hydriding and dehydriding performances of the Mg2Ni-type alloys, Ni in the alloy was partially substituted by element Co, and melt-spinning technology was used for the preparation of the Mg20Ni10−xCox (x = 0–4) hydrogen storage alloys. The structures of the as-cast and spun alloys were studied by XRD, SEM and HRTEM. Thermal stability of the as-spun alloys was researched by DSC. The hydrogen absorption and desorption kinetics of the alloys were measured using an automatically controlled Sieverts apparatus. The results showed that no amorphous phase formed in the as-spun Co-free alloy, but the as-spun alloys containing Co showed certain amount of amorphous phase. The hydrogen absorption capacities of the as-cast alloys first increase and then decrease with the variety of Co content. The hydrogen desorption capacities of as-cast and spun alloys rise with increasing Co content. The rapid quenching significantly improved the hydrogenation and dehydrogenation capacities and the kinetics of the alloys. When the quenching rate increased from 0 (as-cast was defined as spinning rate of 0 m/s) to 30 m/s, the hydrogen absorption capacity of the alloys (x = 0) at 200 °C and 1.5 MPa in 20 min rose from 1.39 to 3.12 wt%, and from 1.91 to 2.96 wt% for the alloy (x = 4). The hydrogen desorption capacity of the alloy (x = 0) in 20 min increased from 0.19 to 0.89 wt%, and from 1.39 to 2.15 wt% for the alloy (x = 4). 相似文献
5.
The evolution of crystal structure and chemical state of Mg1.9Al0.1Ni alloy during hydrogen absorption–desorption cycling was examined by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). We research the hydrogen storage capacity of the Mg1.9Al0.1Ni by the H/D kinetic curves. The H/D kinetic curves indicate that the hydrogen storage capacity increased with the increased cycles and the samples were activated after 10 cycles have the maximum hydrogen storage capacity. The local structure of Ni atoms was studied by extended X-ray absorption fine structure (EXAFS). The EXAFS results indicate the Ni–Ni bonds distance has no obviously change with the cycles increasing, whereas the Ni–Mg bond lengths increase, and the Ni–Mg bond lengths are longer obviously than before 10 cycles whereas it has no obviously change after 10 cycles. 相似文献
6.
MgH2 is a perspective hydrogen storage material whose main advantage is a relatively high hydrogen storage capacity (theoretically, 7.6 wt.% H2). This compound, however, shows poor hydrogen desorption kinetics. Much effort was devoted in the past to finding possible ways of enhancing hydrogen desorption rate from MgH2, which would bring this material closer to technical applications. One possible way is catalysis of hydrogen desorption. This paper investigates separate catalytic effects of Ni, Mg2Ni and Mg2NiH4 on the hydrogen desorption characteristics of MgH2. It was observed that the catalytic efficiency of Mg2NiH4 was considerably higher than that of pure Ni and non-hydrated intermetallic Mg2Ni. The Mg2NiH4 phase has two low-temperature modifications below 508 K: un-twinned phase LT1 and micro-twinned phase LT2. LT1 was observed to have significantly higher catalytic efficiency than LT2. 相似文献
7.
Myoung Youp Song Young Jun Kwak Byung-Soo Lee Hye Ryoung Park Byoung-Goan Kim 《International Journal of Hydrogen Energy》2012
Ni, Fe2O3, and CNT were added to Mg. The content of the additives was about 20 wt % with that of Fe2O3 6 wt%. The contents of about 20 wt % additives and 6 wt% Fe2O3 are known optimum ones to improve the reaction rates of Mg with H2. Samples with compositions of 80 wt% Mg–14 wt% Ni–6 wt% Fe2O3 (named as Mg–14Ni–6Fe2O3), and 78 wt% Mg–14 wt% Ni–6 wt% Fe2O3–2 wt% CNT (named as Mg–14Ni–6Fe2O3–2CNT) were prepared by reactive mechanical grinding. The hydriding and dehydriding properties of these samples were then measured, and the effects of Ni, Fe2O3, and CNT addition on the hydriding and dehydriding rates of Mg-based alloys were investigated by comparing their hydrogen-storage properties with those of pure Mg and Mg–10 wt% Fe2O3. 相似文献
8.
Henrietta W. Langmi G. Sean McGrady Rebecca Newhouse Ewa Rönnebro 《International Journal of Hydrogen Energy》2012
Two composite hydrogen storage materials based on Mg2FeH6 were investigated for the first time. The Mg2FeH6–LiBH4 composite of molar ratio 1:5 showed a hydrogen desorption capacity of 5.6 wt.% at 370 °C, and could be rehydrogenated to 3.6 wt.% with the formation of MgH2, as the material was heated to 445 °C and held at this temperature. The Mg2FeH6–LiNH2 composite of 3:10 molar ratio exhibited a hydrogen desorption capacity of 4.3 wt.% and released hydrogen at 100 °C lower then the Mg2FeH6–LiBH4 composite, but this mixture could not be rehydrogenated. Compared to neat Mg2FeH6, both composites show enhanced hydrogen storage properties in terms of desorption kinetics and capacity at these low temperatures. In particular, Mg2FeH6–LiNH2 exhibits a much lower desorption temperature than neat Mg2FeH6, but only Mg2FeH6–LiBH4 re-absorbs hydrogen. 相似文献
9.
H.J. Lin L.Z. Ouyang H. Wang D.Q. Zhao W.H. Wang D.L. Sun M. Zhu 《International Journal of Hydrogen Energy》2012
The effect of Ce and Ni contents on the glass-forming ability (GFA) of Mg–Ce–Ni system in the Mg-rich corner of Mg–Ce–Ni system is revealed. Ce is more advantageous for the GFA of Mg-rich Mg–Ce–Ni system than Ni, and the lowest Ce content is ∼5 at.% to obtain the fully amorphous alloy. Amorphous alloy with the highest Mg content, Mg90Ce5Ni5, was obtained by melt-spinning. With the amorphous alloy as precursor, nanostructure multi-phases compositae was prepared by crystallizing it in hydrogenation process. The compositae with reversible hydrogen storage capacity of 5.3 wt.% shows much faster kinetics and lower MgH2 desorption activation energy than those of induction-melt Mg90Ce5Ni5 alloy. Both in situ formed nanosized Mg2Ni and CeH2.73 act as effective catalysts and significantly improve the hydrogen storage properties of MgH2. 相似文献
10.
Muralidhar Chourashiya Dong-Cheol Yang Choong-Nyeon ParkChan-Jin Park 《International Journal of Hydrogen Energy》2012
Magnesium may be the most promising solid-state hydrogen storage material owing to its high storage capacity (7.6 wt%) and highest volumetric density (2 times of liquid H2). On the other hand, suffers from its sluggish absorption/desorption characteristics. In the present study, the simple/cost-effective hydriding combustion synthesis (HCS) was used to prepare highly-active Mg-based-samples. The preparative parameters of HCS were varied, and its effects on the micro-structural and hydrogen storage properties were determined. The results and its analysis showed that the simple HCS process possesses a multifaceted dependence on a range of experimental factors and affect the final product. The estimated dependence enabled us to explain the combined effect of individual experimental factors on the prepared samples. The Mg–Ni–C sample prepared at 610 °C with 6%wt-nano-Ni and 4 wt%-multi-walled-CNTs as reactants, resulted in sample with a surface area as high as 19.01 m2/g and a desorption capacity of 5.77 wt%, highlighting the promising characteristics of HCS to prepare highly-active Mg-based-materials. 相似文献
11.
This work deals with the assessment of the thermo-kinetic properties of Mg–Fe based materials for hydrogen storage. Samples are prepared from MgxFe (x: 2, 3 and 15) elemental powder mixtures via low energy ball milling under hydrogen atmosphere at room temperature. The highest yield is obtained with Mg15Fe after 150 h of milling (90 wt% of MgH2). The thermodynamic characterization carried out between 523 and 673 K shows that the obtained Mg–Fe–H hydride systems have similar thermodynamic parameters, i.e. enthalpy and entropy. However, in equilibrium conditions, Mg15Fe has higher hydrogen capacity and small hysteresis. In dynamic conditions, Mg15Fe also shows better hydrogen capacity (4.85 wt% at 623 K absorbed in less than 10 min and after 100 absorption/desorption cycles), reasonably good absorption/desorption times and cycling stability in comparison to the other studied compositions. From hydrogen uptake rate measurements performed at 573 and 623 K, the rate-limiting step of the hydrogen uptake reaction is determined by fitting particle kinetic models. According to our results, the hydrogen uptake is diffusion controlled, and this mechanism does not change with the Mg–Fe proportion and temperature. 相似文献
12.
Mg (200 nm) and LaNi5 (25 nm) nanoparticles were produced by the hydrogen plasma-metal reaction (HPMR) method, respectively. Mg–5 wt.% LaNi5 nanocomposite was prepared by mixing these nanoparticles ultrasonically. During the hydrogenation/dehydrogenation cycle, Mg–LaNi5 transformed into Mg–Mg2Ni–LaH3 nanocomposite. Mg particles broke into smaller particles of about 80 nm due to the formation of Mg2Ni. The nanocomposite showed superior hydrogen sorption kinetics. It could absorb 3.5 wt.% H2 in less than 5 min at 473 K, and the storage capacity was as high as 6.7 wt.% at 673 K. The nanocomposite could release 5.8 wt.% H2 in less than 10 min at 623 K and 3.0 wt.% H2 in 16 min at 573 K. The apparent activation energy for hydrogenation was calculated to be 26.3 kJ mol−1. The high sorption kinetics was explained by the nanostructure, catalysis of Mg2Ni and LaH3 nanoparticles, and the size reduction effect of Mg2Ni formation. 相似文献
13.
Liuting Zhang Lixin ChenZhiwen Chen Shunkui WangXiulin Fan Shouquan LiHongwei Ge Qidong Wang 《International Journal of Hydrogen Energy》2014
A significant enhancement in the dehydrogenation performance of LiBH4 is achieved by modifying with fluorographite (FGi). In-depth investigations show that the dehydrogenation thermodynamics and kinetics of LiBH4 are strongly improved by ball milling LiBH4 with FGi. The ball-milled LiBH4–FGi (mass ratio of 1:1) composite starts to release hydrogen without impurity gas at around 180 °C, and obtains a hydrogen desorption capacity of 7.2 wt% below 200 °C in seconds, which is improved dramatically compared with pristine ball-milled LiBH4. Microscopic morphology indicates that numerous ∼90 nm spots formed on the surface of FGi. Based on the microstructure analyses combined with hydrogen storage performances, the prominent effect of FGi is largely attributed to the nano-modifying effect and the exothermic reaction between LiBH4 and FGi during the dehydrogenation process. Furthermore, partial reversibility of the LiBH4–FGi composite has been demonstrated and the mechanism underlying the cycling capacity loss is discussed. The use of FGi may shed light on future study on searching for new strategies to improve both the thermodynamics and kinetics of light-metal complex hydrides. 相似文献
14.
Jianxin Zou Hao Guo Xiaoqin Zeng Si Zhou Xi Chen Wenjiang Ding 《International Journal of Hydrogen Energy》2013
For the first time, Mg based Mg–Transition metal (TM) –La (TM = Ti, Fe, Ni) ternary composite powders were prepared directly through arc plasma evaporation of Mg–TM–La precursor mixtures followed by passivation in air. The composition, phase components, microstructure and hydrogen sorption properties of the composite powders were carefully investigated. Composition analyses revealed a reduction in TM and La contents for all powders when compared with the compositions of their precursors. It is observed that the composites are all mainly composed of ultrafine Mg covered by nano La2O3 introduced during passivation. Based on the Pressure–Composition–Temperature measurements, the hydrogenation enthalpies of Mg are determined to be −68.7 kJ/mol H2 for Mg–Ti–La powder, −72.9 kJ/mol H2 for Mg–Fe–La powder and −82.1 kJ/mol H2 for Mg–Ni–La powder. Meantime, the hydrogen absorption kinetics can be significantly improved and the hydrogen desorption temperature can be reduced in the hydrogenated ternary Mg–TM–La composites when compared to those in the binary Mg–TM or Mg–RE composites. This is especially true for the Mg–Ni–La composite powder, which can absorb 1.5 wt% of hydrogen at 303 K after 3.5 h. Such rapid absorption kinetics at low temperatures can be attributed to the catalytic effects from both Mg2Ni and La2O3. The results gathered in this study showed that simultaneous addition of 3d transition metals and 4f rare earth metals to Mg through the arc plasma method can effectively alter both the thermodynamic and kinetic properties of Mg ultrafine powders for hydrogen storage. 相似文献
15.
Won Ha Ho-Shin Lee Jeong-Il Youn Tae-Whan Hong Young-Jig Kim 《International Journal of Hydrogen Energy》2007
Hydrogenation and degradation properties of Mg–10 wt% Ni hydrogen storage alloys were investigated by cyclic hydriding–dehydriding tests. Mg–10 wt% Ni alloy was synthesized by rotation-cylinder method (RCM) under 0.3% HFC-134a/air atmosphere and their hydrogenation and degradation properties were evaluated by pressure-composition-isotherm (PCI) measurement. Hydrogen storage capacities gradually increased following 160 hydriding–dehydriding cycles and thereafter started to decrease. Measured maximum hydrogen capacity of Mg–10 wt% Ni alloy is 6.97 wt% at 623 K. Hydriding and dehydriding plateau pressure were kept constant for whole cycles. Reversible hydrogen capacity started to descend after 280 hydriding–dehydriding cycles. The lamellar eutectic structure of Mg–Ni alloy consists of Mg-rich α-phase and β-Mg2Ni. It is assumed that the lamellar eutectic structure enhances hydrogenation properties. 相似文献
16.
Myoung Youp Song Sung Nam Kwon Jong-Soo Bae Seong-Hyeon Hong 《International Journal of Hydrogen Energy》2008
Mg–23.5 wt% Ni and Mg–23.5 wt% Ni–5 wt% Cu alloys for hydrogen storage were prepared by melt spinning and crystallization heat treatment. The alloys were ground by a planetary ball mill for 2 h in order to obtain a fine powder. The activated Mg–23.5Ni and Mg–23.5Ni–5Cu alloys absorbed 4.34 and 4.84 wt% H, respectively, at 573 K under 12 bar H2 for 60 min. The activated Mg–23.5Ni and Mg–23.5Ni–5Cu alloys desorbed 4.27 and 4.81 wt% H, respectively, at 573 K under 1.0 bar H2 for 30 min. The hydriding rates of the alloys are quite high, even at 473 K, while the dehydriding rates of the samples at 473 K are nearly zero. 相似文献
17.
Kinetic properties of La2Mg17–x wt.% Ni (x = 0–200) hydrogen storage alloys prepared by ball milling
Xia Li Tai Yang Yanghuan Zhang Dongliang Zhao Huiping Ren 《International Journal of Hydrogen Energy》2014
The as-cast La2Mg17 with different amount of Ni powders were mixed through ball milling to produce a new type of La2Mg17–x wt.% Ni (x = 50, 100, 150, 200) alloy. The microstructures of the alloys were characterized by XRD technique, the results show that the crystal structure transfers to amorphous one with the increasing amount of Ni powders. La2Mg17–50 wt.% Ni alloy reaches the highest hydrogen absorption capacity of 5.13 wt.% at 300 °C under 2 MPa hydrogen pressure due to its amorphous structure. Furthermore, La2Mg17–50 wt.% Ni alloy expresses fast hydriding kinetics and absorbs 4.99 wt.% hydrogen gas in 200 s. The hydrogen desorption ability described as discharge capacity during electrochemical reaction is fade next to La2Mg17–200 wt.% Ni alloy, attributed to the less Mg2NiH4 with lower enthalpies and easier to release H2. The maximum discharge capacity of La2Mg17–200 wt.% Ni alloy reaches to exciting 980.90 mAh/g, while the La2Mg17 alloy is only 18.10 mAh/g with inconspicuous improvement of cycle stability. These dramatic difference in electrochemical performance reflect the consequence of sluggish dehydriding process of La2Mg17–50 and 100 wt.% Ni alloys again. Whereas La2Mg17–200 wt.% Ni alloy has lower resistance both on alloy surface and in the bulk. 相似文献
18.
The structure stability of nanometric-Ni (n-Ni) produced by Vale Inco Ltd. Canada as a catalytic additive for MgH2 has been investigated. Each n-Ni filament is composed of nearly spherical interconnected particles having a mean diameter of 42 ± 16 nm. After ball milling of the MgH2 + 5 wt.%n-Ni mixture for 15 min the n-Ni particles are found to be uniformly embedded within the particles of MgH2 and at their surfaces. Neither during ball milling of the MgH2 + 5 wt.%n-Ni mixture nor its first decomposition at temperatures of 300, 325, 350 and 375 °C the elemental n-Ni reacts with the elemental Mg to form the Mg2Ni intermetallic phase (and eventually the Mg2NiH4 hydride). The n-Ni additive acts as a strong catalyst accelerating the kinetics of desorption. From the Arrhenius and Johnson–Mehl–Avrami–Kolmogorov theory the activation energy for the first desorption is determined to be ∼94 kJ/mol. After cycling at 300 °C the activation energy for desorption is determined to be ∼99 kJ/mol. This is much lower than ∼160 kJ/mol observed for the undoped and ball milled MgH2. During cycling at 275 and 300 °C the n-Ni additive is converted into Mg2Ni (Mg2NiH4). The newly formed Mg2NiH4 has a nanosized grain on the order of 20 nm. Its catalytic potency seems to be similar to its n-Ni precursor. The formation of Mg2Ni (Mg2NiH4) may be one of the factors responsible for the systematic decrease of hydrogen capacity observed upon cycling at 275 and 300 °C. 相似文献
19.
Yanghuan Zhang Haitao Wang Tingting Zhai Tai Yang Yan Qi Dongliang Zhao 《International Journal of Hydrogen Energy》2014
Nanocrystalline and amorphous Mg–Nd–Ni–Cu-based (Mg24Ni10Cu2)100−xNdx (x = 0–20) alloys were prepared by melt spinning and their structures as well as hydrogen storage characteristics were investigated. The analysis of XRD, TEM and SEM linked with EDS reveal that all the as-cast alloys hold a multiphase structure, containing Mg2Ni-type major phase as well as some secondary phases Mg6Ni, Nd5Mg41 and NdNi, whose amounts clearly grow with Nd content rising. Furthermore, the as-spun Nd-free alloy displays an entire nanocrystalline structure whereas the as-spun Nd-added alloys have a mixed structure of nanocrystalline and amorphous, moreover, the amorphization degree of the alloys visibly increases with Nd content rising, implying that the addition of Nd facilitates the glass forming in the Mg2Ni-type alloy. The addition of Nd results in a slight decrease in the hydrogen absorption capacity of the as-cast and spun alloys, but it significantly enhances their hydrogen storage kinetics and hydriding/dehydriding cycle stability of the alloy. In order to reveal the capacity degradation mechanism of the as-spun alloy, the structure evolution of the nanocrystalline and amorphous alloys during the hydriding–dehydriding cycles was investigated. It is found that the root causes of leading to the capacity degradation of the nanocrystalline and amorphous alloys are nanocrystalline coarsening, crystal defect decreasing and amorphous phase crystallizing. 相似文献
20.
Hydrogen storage materials research is entered to a new and exciting period with the advance of the nanocrystalline alloys, which show substantially enhanced absorption/desorption kinetics, even at room temperatures. In this work, hydrogen storage capacities and the electrochemical discharge capacities of the Mg2(Ni, Cu)-, LaNi5-, ZrV2-type nanocrystalline alloys and Mg2Ni/LaNi5-, Mg2Ni/ZrV2-type nanocomposites have been measured. The electronic properties of the Mg2Ni1-xCux, LaNi5 and ZrV2 alloys were calculated. The nanocomposite structure reduced hydriding temperature and enhanced hydrogen storage capacity of Mg-based materials. The nanocomposites (Mg,Mn)2Ni (50 wt%)-La(Ni,Mn,Al,Co)5 (50 wt%) and (Mg,Mn)2Ni (75 wt%)-(Zr,Ti)(V,Cr,Ni)2.4 (25 wt%) materials releases 1.65 wt% and 1.38 wt% hydrogen at 25 °C, respectively. The strong modifications of the electronic structure of the nanocrystalline alloys could significantly influence hydrogenation properties of Mg-based nanocomposities. 相似文献