共查询到20条相似文献,搜索用时 15 毫秒
1.
Ashish Bhatnagar Sunita K. Pandey Viney Dixit Vivek Shukla Rohit R. Shahi M.A. Shaz O.N. Srivastava 《International Journal of Hydrogen Energy》2014
The present investigation describes the hydrogen storage properties of 2:1 molar ratio of MgH2–NaAlH4 composite. De/rehydrogenation study reveals that MgH2–NaAlH4 composite offers beneficial hydrogen storage characteristics as compared to pristine NaAlH4 and MgH2. To investigate the effect of carbon nanostructures (CNS) on the de/rehydrogenation behavior of MgH2–NaAlH4 composite, we have employed 2 wt.% CNS namely, single wall carbon nanotubes (SWCNT) and graphene nano sheets (GNS). It is found that the hydrogen storage behavior of composite gets improved by the addition of 2 wt.% CNS. In particular, catalytic effect of GNS + SWCNT improves the hydrogen storage behavior and cyclability of the composite. De/rehydrogenation experiments performed up to six cycles show loss of 1.50 wt.% and 0.84 wt.% hydrogen capacity in MgH2–NaAlH4 catalyzed with 2 wt.% SWCNT and 2 wt.% GNS respectively. On the other hand, the loss of hydrogen capacity after six rehydrogenation cycles in GNS + SWCNT (1.5 + 0.5) wt.% catalyzed MgH2–NaAlH4 is diminished to 0.45 wt.%. 相似文献
2.
Pei-Jun Wang Zhan-Zhao FangLai-Peng Ma Xiang-Dong KangPing Wang 《International Journal of Hydrogen Energy》2008
Single-walled carbon nanotubes (SWNTs) were mechanically milled with LiBH4/MgH2 mixture, and examined with respect to its effect on the reversible dehydrogenation properties of the Li–Mg–B–H system. Experimental results show that the addition of SWNTs results in an enhanced dehydriding rate and improved cyclic stability of the LiBH4/MgH2 composite. For example, the LiBH4/MgH2 composite with 10 wt% purified SWNTs additive can release nearly 10 wt% hydrogen within 20 min at 450 °C, with an average dehydriding rate over 2 times faster than that of the neat LiBH4/MgH2 sample. Based on the results of phase analysis and a series of designed experiments, the mechanism underlying the observed property improvement was discussed. 相似文献
3.
In this paper, we report the hydrogen storage properties and reaction mechanism of NaAlH4–MgH2–LiBH4 (1:1:1) ternary-hydride system prepared by ball milling. It was found that during ball milling, the NaAlH4/MgH2/LiBH4 combination converted readily to the mixture of LiAlH4/MgH2/NaBH4 and there is a mutual destabilization among the hydrides. Three major dehydrogenation steps were observed in the system, which corresponds to the decomposition of LiAlH4, MgH2, and NaBH4, respectively. The onset dehydrogenation temperature of MgH2 in this system is observed at around 275 °C, which is over 55 °C lower from that of as-milled MgH2. Meanwhile, NaBH4-relevant decomposition showed significant improvement, starts to release hydrogen at 370 °C, which is reduced by about 110 °C compared to the as-milled NaBH4. The second and third steps decomposition enthalpy of the system were determined by differential scanning calorimetry measurements and the enthalpies were changed to be 61 and 100 kJ mol−1 H2 respectively, which are smaller than that of MgH2 and NaBH4 alone. From the Kissinger plot, the apparent activation energy, EA, for the decomposition of MgH2 and NaBH4 in the composite was reduced to 96.85 and 111.74 kJ mol−1 respectively. It is believed that the enhancement of the dehydrogenation properties was attributed to the formation of intermediate compounds, including Li–Mg, Mg–Al, and Mg–Al–B alloys, upon dehydrogenation, which change the thermodynamics of the reactions through altering the de/rehydrogenation pathway. 相似文献
4.
A novel hydrogen storage composite system, MgH2–Na3AlH6 (4:1), was prepared by mechanochemical milling, and its hydrogen storage properties and reaction mechanism were studied. Temperature-programmed desorption results showed that a mutual destabilization effect exists between the components. First, Na3AlH6 reacts with MgH2 to form a perovskite-type hydride, NaMgH3, Al, and H2 at a temperature of about 170 °C, which is about 55 °C lower than the decomposition temperature of as-milled Na3AlH6. Then, at a temperature of about 275 °C, the as-formed Al can destabilize MgH2 to form the intermetallic compound Mg17Al12, which is accompanied by the self-decomposition of the residual MgH2. This temperature is about 55 °C lower than the decomposition temperature for as-milled MgH2. Furthermore, when heated up to 345 °C, NaMgH3 starts to decompose into NaH, Mg, and H2, which is followed by the decomposition of NaH at a temperature of about 370 °C. Rehydrogenation processes show that Mg17Al12 and NaMgH3 are fully reversible. It is believed that the Mg17Al12 and NaMgH3 formed in situ provide synergetic thermodynamic and kinetic destabilization, leading to the dehydrogenation of MgH2, which is responsible for the distinct reduction in the operating temperatures of the as-prepared MgH2–Na3AlH6 (4:1) composite system. 相似文献
5.
Remarkable improvement of hydrogen sorption properties of Li–N–H system has been obtained by doping with a small amount of LiBH4. The starting and ending temperatures of hydrogen desorption shift to lower temperatures and the release of NH3 is obviously restrained by 10 mol% LiBH4 doping. The kinetics of hydrogen desorption and absorption of Li–N–H system became faster by the addition of LiBH4. About 4 wt.% H2 can be released within 30 min and ∼4.8 wt.% H2 can be reabsorbed within 2 min by LiBH4 doped sample at 250 °C, while only 1.44 wt.% H2 is released and 2.1 wt.% is reabsorbed for pure Li–N–H system. The quaternary hydride (LiNH2)x(LiBH4)(1−x) formed by the reaction between LiBH4 and LiNH2 may contribute to the enhancement of the hydrogen sorption performances by yielding a ionic liquid phase and transferring LiNH2 from solid state to molten state with a weakened N–H bond. 相似文献
6.
Jiasheng Wang Shumin Han Wei Zhang Dan Liang Yuan Li Xin Zhao Ruibing Wang 《International Journal of Hydrogen Energy》2013
A 2LiBH4–MgH2–MoS2 composite was prepared by solid-state ball milling, and the effects of MoS2 as an additive on the hydrogen storage properties of 2LiBH4–MgH2 system together with the corresponding mechanism were investigated. As shown in the TG–DSC and MS results, with the addition of 20 wt.% of MoS2, the onset dehydrogenation temperature is reduced to 206 °C, which is 113 °C lower than that of the pristine 2LiBH4–MgH2 system. Meanwhile, the total dehydrogenation amount can be increased from 9.26 wt.% to 10.47 wt.%, and no gas impurities such as B2H6 and H2S are released. Furthermore, MoS2 improves the dehydrogenation kinetics, and lowers the activation energy (Ea) 34.49 kJ mol−1 of the dehydrogenation reaction between Mg and LiBH4 to a value lower than that of the pristine 2LiBH4–MgH2 sample. According to the XRD test, Li2S and MoB2 are formed by the reaction between LiBH4 and MoS2, which act as catalysts and are responsible for the improved hydrogen storage properties of the 2LiBH4–MgH2 system. 相似文献
7.
Shu-Sheng Liu Li-Xian Sun Jian Zhang Yao Zhang Fen Xu Yong-Heng Xing Fen Li Jijun Zhao Yong Du Wang-Yu Hu Hui-Qiu Deng 《International Journal of Hydrogen Energy》2010
To improve the dehydrogenation properties of MgH2, a novel hydrogen storage system, MgH2–Li3AlH6, is prepared by mechanochemical milling. Three physical mixtures containing different mole ratios (1:4, 1:1 and 4:1) of MgH2 and Li3AlH6 are studied and there exists a mutual destabilization effect between the components. The last mixture shows a capacity of 6.5 wt% H2 with the lowest starting temperature of dehydrogenation (170 °C). First, Li3AlH6 decomposes into Al, LiH and H2, and then the as-formed Al can easily destabilize MgH2 to form the intermetallic compound Mg17Al12 at a temperature of 235 °C, which is about 180 °C lower than the decomposition temperature of pristine MgH2. Finally, the residual MgH2 undergoes a self-decomposition whose apparent activation energy has been reduced by about 22 kJ mol−1 compared with pristine MgH2. At a constant temperature of 250 °C, the mixture can dehydrogenate completely under an initial vacuum and rehydrogenate to form MgH2 under 2 MPa H2, showing good cycle stability after the first cycle with a capacity of 4.5 wt% H2. The comparison between 4 MgH2 + Li3AlH6 and 4 MgH2 + LiAlH4 mixtures is also investigated. 相似文献
8.
Michael U. Niemann Sesha S. Srinivasan Ashok Kumar Elias K. Stefanakos D. Yogi Goswami Kimberly McGrath 《International Journal of Hydrogen Energy》2009
In this article, we investigate the ternary LiNH2–MgH2–LiBH4 hydrogen storage system by adopting various processing reaction pathways. The stoichiometric ratio of LiNH2:MgH2:LiBH4 is kept constant with a 2:1:1 molar ratio. All samples are prepared using solid-state mechano-chemical synthesis with a constant rotational speed, but with varying milling duration. Furthermore, the order of addition of parent compounds as well as the crystallite size of MgH2 are varied before milling. All samples are intimate mixtures of Li–B–N–H quaternary hydride phase with MgH2, as evidenced by XRD and FTIR measurements. It is found that the samples with MgH2 crystallite sizes of approximately 10 nm exhibit lower initial hydrogen release at a temperature of 150 °C. Furthermore, it is observed that the crystallite size of Li–B–N–H has a significant effect on the amount of hydrogen release with an optimum size of 28 nm. The as-synthesized hydrides exhibit two main hydrogen release temperatures, one around 160 °C and the other around 300 °C. The main hydrogen release temperature is reduced from 310 °C to 270 °C, while hydrogen is first reversibly released at temperatures as low as 150 °C with a total hydrogen capacity of ∼6 wt.%. Detailed thermal, capacity, structural and microstructural properties are discussed and correlated with the activation energies of these materials. 相似文献
9.
Li Li Fangyuan QiuYijing Wang Yanan XuCuihua An Guang LiuLifang Jiao Huatang Yuan 《International Journal of Hydrogen Energy》2013
The hydrogen storage properties of LiAlH4 doped efficient TiN catalyst were systematically investigated. We observe that TiN catalyst enhances the dehydrogenation kinetics and decreases the dehydrogenation temperature of LiAlH4. The dehydrogenation behaviors of 2%TiN–LiAlH4 are investigated using temperature programmed desorption (TPD), differential scanning calorimetry (DSC) and fourier transform infrared spectroscopy (FTIR). Interestingly, the onset hydrogen desorption temperature of 2%TiN–LiAlH4 sample gets lowered from 151.0 °C to 90.0 °C with a faster kinetics, and the dehydrogenation rate reached a maximum value at 137.2 °C. By adding a small amount of as-prepared TiN, approximately 7.1 wt% of hydrogen can be released from the LiAlH4 at 130 °C. Interestingly, the result of the FTIR indicates that the 2%TiN–LiAlH4 maybe restore hydrogen under 5.5 MPa hydrogen. Moreover, 2%TiN–LiAlH4 displayed a substantially reduced activation energy for LiAlH4 dehydrogenation. 相似文献
10.
Xugang Zhang Zhinian LiFang Lv Hualing LiJing Mi Shumao WangXiaopeng Liu Lijun Jiang 《International Journal of Hydrogen Energy》2010
Significant improvements in the hydrogen absorption/desorption properties of the 2LiNH2–1.1MgH2–0.1LiBH4 composite have been achieved by adding 3wt% ZrCo hydride. The composite can absorb 5.3wt% hydrogen under 7.0 MPa hydrogen pressure in 10 min and desorb 3.75wt% hydrogen under 0.1 MPa H2 pressure in 60 min at 150 °C, compared with 2.75wt% and 1.67wt% hydrogen under the same hydrogenation/dehydrogenation conditions without the ZrCo hydride addition, respectively. TPD measurements showed that the dehydrogenation temperature of the ZrCo hydride-doped sample was decreased about 10 °C compared to that of the pristine sample. It is concluded that both the homogeneous distribution of ZrCo particles in the matrix observed by SEM and EDS and the destabilized N–H bonds detected by IR spectrum are the main reasons for the improvement of H-cycling kinetics of the 2LiNH2–1.1MgH2–0.1LiBH4 system. 相似文献
11.
In the present study, we employed a multi-component combination strategy to constitute an AB/LiNH2/LiBH4 composite system. Our study found that mechanically milling the AB/LiNH2/LiBH4 mixture in a 1:1:1 molar ratio resulted in the formation of LiNH2BH3 (LiAB) and new crystalline phase(s). A spectral study of the post-milled and the relevant samples suggests that the new phase(s) is likely ammoniate(s) with a formula of Li2−x(NH3)(NH2BH3)1−x(BH4) (0 < x < 1). The decomposition behaviors of the Li2−x(NH3)(NH2BH3)1−x(BH4)/xLiAB composite were examined using thermal analysis and volumetric method in a wide temperature range. It was found that the composite exhibited advantageous dehydrogenation properties over LiAB and LiAB·NH3 at moderate temperatures. For example, it can release ∼7.1 wt% H2 of purity at temperature as low as 60 °C, with both the dehydrogenation rate and extent far exceeding that of LiAB and LiAB·NH3. A selectively deuterated composite sample has been prepared and examined to gain insight into the dehydrogenation mechanism of the Li2−x(NH3)(NH2BH3)1−x(BH4)/xLiAB composite. It was found that the LiBH4 component does not participate in the dehydrogenation reaction at moderate temperatures, but plays a key role in strengthening the coordination of NH3. This is believed to be a major mechanistic reason for the favorable dehydrogenation property of the composite at moderate temperatures. 相似文献
12.
Huaqin Kou Ge Sang Zhiyong Huang Wenhua Luo Lixin Chen Xuezhang Xiao Changwen Hu Yuanlin Zhou 《International Journal of Hydrogen Energy》2014
In the present work, the role of NbF5 addition amount in affecting the comprehensive hydrogen storage properties (dehydrogenation, rehydrogenation, cycling performance, hydrogen capacity) of 2LiBH4–MgH2 system as well as the catalytic mechanism of NbF5 have been systematically studied. It is found that increasing the addition amount of NbF5 to the 2LiBH4–MgH2 system not only results in dehydrogenation temperature reduction and hydriding–dehydriding kinetics enhancement but also leads to the de/rehydrogenation capacity loss. Compared with other samples, 2LiBH4–MgH2 doping with NbF5 in weight ratios of 40:4 exhibits superior comprehensive hydrogen storage properties, which can stably release ∼8.31 wt.% hydrogen within 2.5 h under 4 bar H2 and absorb ∼8.79 wt.% hydrogen within 10 min under 65 bar H2 at 400 °C even up to 20 cycling. As far as we know, this is the first time that excellent reversibility as high as 20 cycles without obvious degradation tendency in both of hydrogen capacity and reaction rate has been achieved in the 2LiBH4–MgH2 system. The further experimental study reveals that the highly catalytic effects of NbF5 on the 2LiBH4–MgH2 system are derived from the reaction between NbF5 and LiBH4, which provides a fundamental insight into the catalytic mechanism of NbF5. 相似文献
13.
Jie Meng Yan-Biao Pan Qun Luo Xue-Hui An Yang Liu Qian Li Kuo-Chih Chou 《International Journal of Hydrogen Energy》2010
The hydrogen storage samples of Nd–Mg–Ni–Fe3O4 alloy were prepared by microwave sintering (MS) and conventional sintering (CS) methods, respectively. Their phase structures, morphologies, hydrogen storage properties were intensively studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and pressure–composition–temperature (PCT). XRD and SEM analysis results show that the microwave sintered Nd–Mg–Ni–Fe3O4 alloy has multiphase structure involving Mg and homogeneous grains, whereas the alloy prepared by CS has Mg41Nd5 phase and coarse grains. The alloy prepared by MS can release 85% of the saturated hydrogen capacity at 573 K in 600 s and its characteristic reaction time (tc) is less than 2900 s, while the alloy prepared by CS releases less than 70% of the absorbed hydrogen at 573 K within 1300 s and its tc is more than 3000 s. It is found that the alloy prepared by MS not only has high hydrogen capacity, but also better dehydriding kinetic property than the alloy prepared by CS. 相似文献
14.
Julian Jepsen Chiara Milanese Alessandro Girella Gustavo A. Lozano Claudio Pistidda José M. Bellosta von Colbe Amedeo Marini Thomas Klassen Martin Dornheim 《International Journal of Hydrogen Energy》2013
Among different Reactive Hydride Composites (RHCs), the combination of LiBH4 and MgH2 is a promising one for hydrogen storage, providing a high reversible storage capacity. During desorption of both LiBH4 and MgH2, the formation of MgB2 lowers the overall reaction enthalpy. In this work, the material was compacted to pellets for further improvement of the volumetric hydrogen capacity. The influence of compaction pressure on the apparent density, thermal conductivity and sorption behaviour for the Li-based RHC during cycling was investigated for the first time. Although LiBH4 melts during cycling, decrepitation or disaggregation of the pellets is not observed for any of the investigated compaction pressures. However, a strong influence of the compaction pressure on the apparent hydrogen storage capacity is detected. The influence on the reaction kinetics is rather low. To provide explanations for the observed correlations, SEM analysis before and after each sorption step was performed for different compaction pressures. Thus, the low hydrogen sorption in the first cycles and the continuously improving sorption for low pressure compacted pellets with cycling may be explained by some surface observations, along with the form stability of the pellets. 相似文献
15.
N.S. Mustafa F.A. Halim Yap M.S. Yahya M. Ismail 《International Journal of Hydrogen Energy》2018,43(24):11132-11140
The hydrogen storage properties and reaction mechanism of the combined NaAlH4 + Ca(BH4)2 (2:1) composite system was investigated in the present study. Analyses show that after 6 h of milling, the NaAlH4 + Ca(BH4)2 combination fully converted to the mixture of Ca(AlH4)2 + NaBH4, and a metathesis reaction occurred between the hydrides. Four major dehydrogenation stages were observed in the system, which corresponds to the decomposition of Ca(AlH4)2, CaAlH5, CaH2 and NaBH4, respectively. The onset desorption temperature of the composite system is reduced to 125 °C, which is much lower than a unary component of NaAlH4 and Ca(BH4)2. The de/rehydrogenation kinetics of the composite system had improve at a higher temperature. From the Kissinger plot, the apparent activation energies for the decomposition of CaAlH5 and NaBH4 in the composite system were reduced to 142.9 and 146.5 kJ/mol, respectively. It is believed that the formation of AlCa, AlB and CaB alloys during the dehydrogenation process is responsible for the distinct reduction in the onset desorption temperature and kinetics enhancement of the 2NaAlH4 + Ca(BH4)2 composite system. 相似文献
16.
In a previous paper, it was demonstrated that a MgH2–NaAlH4 composite system had improved dehydrogenation performance compared with as-milled pure NaAlH4 and pure MgH2 alone. The purpose of the present study was to investigate the hydrogen storage properties of the MgH2–NaAlH4 composite in the presence of TiF3. 10 wt.% TiF3 was added to the MgH2–NaAlH4 mixture, and its catalytic effects were investigated. The reaction mechanism and the hydrogen storage properties were studied by X-ray diffraction, thermogravimetric analysis, differential scanning calorimetry (DSC), temperature-programmed-desorption and isothermal sorption measurements. The DSC results show that MgH2–NaAlH4 composite milled with 10 wt.% TiF3 had lower dehydrogenation temperatures, by 100, 73, 30, and 25 °C, respectively, for each step in the four-step dehydrogenation process compared to the neat MgH2–NaAlH4 composite. Kinetic desorption results show that the MgH2–NaAlH4–TiF3 composite released about 2.4 wt.% hydrogen within 10 min at 300 °C, while the neat MgH2–NaAlH4 sample only released less than 1.0 wt.% hydrogen under the same conditions. From the Kissinger plot, the apparent activation energy, EA, for the decomposition of MgH2, NaMgH3, and NaH in the MgH2–NaAlH4–TiF3 composite was reduced to 71, 104, and 124 kJ/mol, respectively, compared with 148, 142, and 138 kJ/mol in the neat MgH2–NaAlH4 composite. The high catalytic activity of TiF3 is associated with in situ formation of a microcrystalline intermetallic Ti–Al phase from TiF3 and NaAlH4 during ball milling or the dehydrogenation process. Once formed, the Ti–Al phase acts as a real catalyst in the MgH2–NaAlH4–TiF3 composite system. 相似文献
17.
Yongfeng Liu Yu ZhangHai Zhou Yi ZhangMingxia Gao Hongge Pan 《International Journal of Hydrogen Energy》2014
The dehydrogenation/hydrogenation properties of LiBH4-xMg(OH)2 were systematically investigated. The results show that the LiBH4-0.3Mg(OH)2 composite possesses optimal dehydrogenation properties: approximately 9.6 wt% of hydrogen is released via a stepwise reaction with an onset temperature of 100 °C. In the range of 100–250 °C, a chemical reaction between LiBH4 and Mg(OH)2 first occurs to give rise to the generation of LiMgBO3, MgO and H2. From 250 to 390 °C, the newly developed LiMgBO3 reacts with LiBH4 to form MgO, Li3BO3, LiH, B2O3 and Li2B12H12 with hydrogen release. From 390 to 450 °C, the decomposition of LiBH4 and Li2B12H12 proceeds to release additional hydrogen and to form LiH and B. A further hydrogenation experiment indicates that the dehydrogenated LiBH4-0.3Mg(OH)2 sample can take up 4.7 wt% of hydrogen at 450 °C and 100 bar of hydrogen with good cycling stability, which is superior to the pristine LiBH4. 相似文献
18.
Xiantun Huang Anpeng Tao Jiong Guo Wenlou Wei Jin Guo Zhiqiang Lan 《International Journal of Hydrogen Energy》2018,43(3):1651-1657
Mg–Al alloy was prepared by sintering and mechanical alloying, and the effects of graphene (Gp), TiF3 and Gp/titanium (III) fluoride (TiF3) on the hydrogen storage properties of the Mg–Al alloy were studied. The results show that Gp and TiF3 could improve the hydrogen storage properties of Mg–Al alloy. In particular, Gp and TiF3 showed good synergistic effect for enhancing the hydrogen storage properties of Mg–Al alloy. For example, when 1.0 wt% of H2 was absorbed/desorbed, the hydrogen adsorption/desorption temperature of the Mg–Al alloy and Mg–Al-M (M = Gp, TiF3, and TiF3@Gp) composites were 241/343 °C, 185/310 °C, 229/292 °C and 159/280 °C, respectively. For the Mg–Al alloy, the apparent activation energy was 176.5 kJ mol?1, and it decreased to 139.8 kJ mol?1, 171.6 kJ mol?1, and 94.3 kJ mol?1, with the addition of Gp, TiF3 and TiF3@Gp composites, respectively. Evidently, the comprehensive hydrogen storage properties of Mg–Al alloy were improved remarkably under the synergistic effect of Gp and TiF3. 相似文献
19.
Rapee Gosalawit-Utke Chiara Milanese Payam Javadian Julian Jepsen Daniel Laipple Fahim Karmi Julián Puszkiel Torben R. Jensen Amedeo Marini Thomas Klassen Martin Dornheim 《International Journal of Hydrogen Energy》2013
Nanoconfinement of 2LiBH4–MgH2–TiCl3 in resorcinol–formaldehyde carbon aerogel scaffold (RF–CAS) for reversible hydrogen storage applications is proposed. RF–CAS is encapsulated with approximately 1.6 wt. % TiCl3 by solution impregnation technique, and it is further nanoconfined with bulk 2LiBH4–MgH2 via melt infiltration. Faster dehydrogenation kinetics is obtained after TiCl3 impregnation, for example, nanoconfined 2LiBH4–MgH2–TiCl3 requires ∼1 and 4.5 h, respectively, to release 95% of the total hydrogen content during the 1st and 2nd cycles, while nanoconfined 2LiBH4–MgH2 (∼2.5 and 7 h, respectively) and bulk material (∼23 and 22 h, respectively) take considerably longer. Moreover, 95–98.6% of the theoretical H2 storage capacity (3.6–3.75 wt. % H2) is reproduced after four hydrogen release and uptake cycles of the nanoconfined 2LiBH4–MgH2–TiCl3. The reversibility of this hydrogen storage material is confirmed by the formation of LiBH4 and MgH2 after rehydrogenation using FTIR and SR-PXD techniques, respectively. 相似文献
20.
Yongfeng Liu Yanjing YangYifan Zhou Yu ZhangMingxia Gao Hongge Pan 《International Journal of Hydrogen Energy》2012
Hydrogen storage properties and mechanisms of the combined Mg(BH4)2–NaAlH4 system were investigated systematically. It was found that during ball milling, the Mg(BH4)2–xNaAlH4 combination converted readily to the mixture of NaBH4 and Mg(AlH4)2 with a metathesis reaction. The post-milled samples exhibited an apparent discrepancy in the hydrogen desorption behavior with respect to the pristine Mg(BH4)2 and NaAlH4. Approximately 9.1 wt% of hydrogen was released from the Mg(BH4)2–2NaAlH4 composite milled for 24 h with an onset temperature of 101 °C, which is lowered by 105 and 139 °C than that of NaAlH4 and Mg(BH4)2, respectively. At initial heating stage, Mg(AlH4)2 decomposed first to produce MgH2 and Al with hydrogen release. Further elevating operation temperatures gave rise to the reaction between MgH2 and Al and the self-decomposition of MgH2 to release more hydrogen and form the Al0.9Mg0.1 solid solution and Mg. Finally, NaBH4 reacted with Mg and partial Al0.9Mg0.1 to liberate all of hydrogen and yield the resultant products of MgAlB4, Al3Mg2 and Na. The dehydrogenated sample could take up ∼6.5 wt% of hydrogen at 400 °C and 100 atm of hydrogen pressure through a more complicated reaction process. The hydrogenated products consisted of NaBH4, MgH2 and Al, indicating that the presence of Mg(AlH4)2 is significantly favorable for reversible hydrogen storage in NaBH4 at moderate temperature and hydrogen pressure. 相似文献