Hydrogen storage properties of (Ti0.85Zr0.15)1.05Mn1.2Cr0.6V0.1M0.1 (M=Ni, Fe, Cu) alloys easily activated at room temperature

The(Ti_(0.85)Zr_(0.15))_(1.05)Mn_(1.2)Cr_(0.6)V_(0.1)M_(0.1)(M=Ni, Fe, Cu) alloys with a single C14-type Laves phase have been fabricated by arc melting. They are able to be easily activated by one hydrogen absorption and desorption cycle under 4 MPa hydrogen pressure and vacuum at room temperature. Partial substitution of M for Mn results in the increase of hydrogenation and dehydrogenation capacities in an order of Ni Fe Cu. M elements increase the absorption and desorption plateau pressure in an order of(Ti_(0.85)Zr_(0.15))_(1.05)Mn_(1.2)Cr_(0.6)V_(0.1)Cu_(0.1)(Ti_(0.85)Zr_(0.15))_(1.05)Mn_(1.2)Cr_(0.6)V_(0.1)Fe_(0.1)(Ti_(0.85)Zr_(0.15))_(1.05)Mn_(1.2)Cr_(0.6)V_(0.1)Ni_(0.1). The(Ti_(0.85)Zr_(0.15))_(1.05)Mn_(1.2)Cr_(0.6)V_(0.1)Cu_(0.1) alloy has reversible hydrogen capacities of 1.81 wt% at 273 K and 1.58 wt% at 318 K with formation enthalpy(ΔH_(ab)) of-20.66 kJ mol~(-1) and decomposition enthalpy(ΔH_(de)) of 27.37 kJ mol~(-1). The differences in the hydrogen storage properties can be attributed to the increase of the interstitial size for hydrogen accommodation caused by the increase of unit cell volumes in the order of(Ti_(0.85)Zr_(0.15))_(1.05)Mn_(1.2)Cr_(0.6)V_(0.1)Ni_(0.1)(Ti_(0.85)Zr_(0.15))_(1.05)Mn_(1.2)Cr_(0.6)V_(0.1)Fe_(0.1)(Ti_(0.85)Zr_(0.15))_(1.05)Mn_(1.2)Cr_(0.6)V_(0.1)Cu_(0.1).     

Mg0.9M0.1Ni(M=Cr,Al,Ti,Zr)三元镁基储氢合金的制备及其电化学性能的研究

用机械合金化法成功地合成了Mg1.9M0.1Ni(M=Cr,Al,Ti,Zr),XRD结果表明,球磨80h后,Mg0.9M—Ni和Mg0.9Al0.1Ni合金已经完全非晶化．对此三元合金体系进行了电化学容量及循环寿命测试以及电化学交流阻抗(mS)测试．结果表明用这几种元素替代Mg后,合金电极的循环寿命有了明显的提高,但是其最高放电容易有所降低,抗腐蚀性能增强;该系列合金电极反应的速度控制步骤是由合金电解液界面间的电荷迁移和氢的扩散联合控制的．     

Effect of Mg substitution for La on microstructure, hydrogen storage and electrochemical properties of La1−xMgxNi3.5 (x=0.20, 0.23, 0.25 at%) alloys

The effect of Mg substitution for La on microstructure, hydrogen storage and electrochemical properties of the annealed La_(1-x) Mg_x Ni_3.5(x=0.20, 0.23, 0.25 at%) alloys have been studied. All the samples were mainly composed of(LaMg)_2Ni_7,(LaMg)Ni_3, and LaNi_5 phases. Mg substitution for La changed the phase abundance, but did not change the constitution of all phases, which is con fi rmed by the results of backscattered SEM images and EDS analysis. The P–C isotherms indicated that the La_(1-x) Mg_x Ni_3.5alloys reversibly absorbed and desorbed hydrogen smoothly at 298 K. The hydrogen absorption cyclic stabilities of La_(1-x) Mg_x Ni_3.5alloy after 5 hydrogen absorption/desorption cycles reached the maximum values of91.9% and 96.0% at 298 K and 323 K, respectively. The hydrogen desorption capacity and plateau pressure for the La_(1-x) Mg_x Ni_3.5alloy reached the maximum values of 1.055 H/M and 0.074 MPa, respectively. The desorption capacities of La_(1-x) Mg_x Ni_3.5reached 0.193 H/M and 0.565 H/M in the fi rst minute at 298 K and 323 K, respectively. Electrochemical property measurement indicated that La_(1-x) Mg_x Ni_3.5(x=0.20,0.23, 0.25 at%) alloys possessed excellent activation capability and were completely activated within3 cycles. Discharge capacities of La_(1-x) Mg_x Ni_3.5alloys reached 378.2 m A h/g(x = 0.20 at%), 342.7 m A h/g(x = 0.23 at%), and 369.6 m A h/g(x = 0.25 at%), respectively. Moreover, energy density of La_(1-x) Mg_x Ni_3.5alloy was much larger than that of La_0.80Mg_0.20Ni_3.5 alloy and nearly approaches the maximum value of La0.75Mg0.25Ni3.5. Thus, the La_(1-x) Mg_x Ni_3.5alloy exhibits optimum comprehensive properties of hydrogen storage and electrochemistry.     

Hydrogen storage performances of the as-milled REMg11Ni (RE = Sm, Y) alloys catalyzed by CeO2

The addition of catalysts and rare earth elements is considered to be very effective methods to enhance the hydrogenation/dehydrogenation properties of Mg and Mg-based hydrides. In this paper, the REMg11 Ni+ 5 wt%CeO_2(RE = Sm, Y)(named REMg11 Ni-5 CeO_2(RE = Sm, Y)) alloys were fabricated through ball milling. The phase composition and structure of the as-milled alloys were investigated in detail. The isothermal hydrogen storage thermodynamics and kinetics of the as-milled alloys were measured by using an automatically Sievert apparatus. Non-isothermal dehydrogenation performance of the alloys was investigated by thermogravimetry(TG) and differential scanning calorimetry(DSC) at different heating rates. The results revealed that all the asmilled alloys were the nanocrystalline and amorphous structure. The RE = Y alloy had a faster hydriding rate and a lower onset hydrogen desorption temperature than the RE = Sm alloy. The superior property of the RE= Y alloy depended on the decrease of the dehydrogenation activation energy. By means of the measurement of Pressure-Composition-Isotherm(P-C-T) curves, the thermodynamic parameters of the REMg11 Ni-5 CeO_2(RE =Sm, Y) alloys were calculated, and the dehydrogenation enthalpy change was 74.86 k J/mol for the RE = Sm alloy and 73.75 k J/mol for the RE = Y alloy, respectively.     

Effect of heat treatment on hydrogen storage properties and thermal stability of V68Ti20Cr12 alloy

Effect of heat treatment on the crystal structure, microstructure, hydrogen storage properties and thermal stability of V68Ti20Cr12 alloy prepared by arc-melting was studied in this work. It was found that both the as-cast and annealed (973 K/72 h) V68Ti20Cr12 alloys consisted of a single body-centered cubic (bcc) phase. After heat treatment, the hydrogen absorption/desorption kinetic characteristics of the as-cast alloy was improved greatly due to the homogeneous composition and perfect structure. The mechanism of hydrogen absorption/desorption process in the as-cast and annealed alloys was further investigated according to the Johnson-Mehl-Avrami (JMA) equation. The hydrogen absorption process of the as-cast and annealed alloys would be controlled by the one-dimensional diffusion process, while the hydrogen desorption process in the as-cast and annealed alloys was dominated by the geometrical contraction model. The pressure-composition-temperature (PCT) measurements show that the plateau pressure of the annealed alloy becomes comparatively flat. Furthermore, the activation energies of the dehydrogenation in the as-cast and annealed alloys were calculated using the Kissinger method, indicating that heat treatment is a very beneficial way to improve hydrogen absorption/desorption kinetics of the alloy.     

元素掺杂对镁基储氢合金电化学性能的影响

利用氢化燃烧合成复合高能球磨法制备镁基储氢电极合金Mg2NiH4,并对合金进行不同元素(Cr、Co、Nb、Ti和V)掺杂处理。使用X线衍射仪(XRD)和电化学工作站对材料结构性能进行表征,并考察不同元素掺杂对电极合金的结构和电化学性能的影响。结果表明:少量金属元素掺杂处理并没有改变合金的主相结构。元素掺杂降低了合金电极的最大放电容量和动力学性能,但是合金电极的电化学循环稳定性均得到不同程度的提高,其中Ti掺杂处理对于改善合金电极电化学循环性能最为明显。     

高能球磨制备MgxTi100-x合金的微观组织及储氢性能

应用振动高能球磨机械合金化方法制备MgxTi100-x(x=35,50,65,80)系列合金,采用XRD、SEM、TEM以及吸放氢测试等手段分析研究Mg含量与球磨时间对MgxTi100-x球磨产物微观组织演化规律、相结构和吸氢行为的影响.结果表明:在相同球磨时间(20 h)下,球磨合金MgxTi100-x微观组织的相组...     

Recent progress on the hydrogen storage properties of ZrCo-based alloys applied in International Thermonuclear Experimental Reactor (ITER)

Under the development of International Thermonuclear Experimental Reactor (ITER) system aimed at realizing the controllable fusion reaction to solve the energy crisis fundamentally, there is an urgent need to find an appropriate material for tritium handling. ZrCo alloy is considered to be a promising candidate for the storage and delivery of hydrogen isotopes due to the favorable characteristics such as low plateau pressure for absorption, high dissociation pressure at moderate temperature and better ability of trapping 3He. However, the hydrogen induced disproportionation and the slower recovery/deliverty rate of ZrCo-based alloys have limited their further application in ITER system. This review summarizes the efforts towards enhancing the hydrogen storage properties of ZrCo-based alloys including element substitution, surface modification, disproportionation mechanism investigation and the isotope effect study. Element substitution and surface modification play positive role to improve the anti-disproportionation ability and kinetic property of the alloys. However, the ZrCo-based alloys require to be further modified by more attempts such as new composition, novelty modification method or catalyst addition in order to better satisfy the application demands for tritium handling. Moreover, new insight for further understanding the inner disproportionation mechanisms of this material is needed by combining the advance characterization and theoretical analysis, which is in favor of addressing the disproportionation problem of the ZrCo-based alloys essentially.     

铸态Mm(NiCoMnAlB)5+χ储氢合金的电化学性能

主要研究了硼对低钴(质量分数小于5%)储氢合金电化学性能的影响,并设计了Mm(NiCoMnAlB)5 χ(χ=0.02,0.03,0.05,0.1,0.2,0.3)一系列非化学配分铸态合金成分.结果表明,硼的加入可以提高活性和高倍率性能,但降低合金的放电容量.微观分析可知,加入硼可形成第二相,提高活性和高倍率性能.同时利用MASTER软件对合金成分进行了优化,得出最佳合金成分Mm(NiCoMnAlB)5.1,预测出新合金成分Mm(NiCoMnAlB)5.08,并用实验方法验证了性能结果.     

Mg2Ni+x0.5 wt% V2O5+y0.5 wt Ni(x,y=0,1)复合体系的贮氢和电化学性能研究

用球磨方法制备Mg2Ni x0.5 wt%V2O5 y0.5 wt Ni(x,y=0,1)复合贮氢合金,并进行气态吸放氢变温动力学与电化学充放电实验.结果表明,x,y=1时体系的气态吸放氢和放电容量效果最好,多元复合的放电容量超过单一化合物的放电容量的总和.     

Crystal structure and hydrogen storage properties of(La,Ce)Ni_(5-x)M_x(M = Al,Fe, or Co) alloys

The effects of partial substitution of La by Ce and Ni by Al, Fe, or Co in LaNi_5-based alloys on hydrogen storage performance were systematically studied. All samples were prepared using vacuum arc melting in an argon atmosphere. The results showed that for LaNi_(5-x)M_x(M = Al, Fe, or Co) alloys, the lattice constants and unit cell volumes increased with an increasing amount of Al and Fe. On the other hand, these parameters decreased upon partial substitution of La by Ce. In addition, the lattice constant remained almost constant in the La_(0.6)Ce_(0.4)Ni_(5–x)Cox alloys regardless of the value of x(x = 0.3, 0.6, or 0.9), as Ce might enhance the homogeneity of the CaCu_5-type phase in Co-containing alloys. The hydrogen storage properties of the alloys were investigated using pressure, composition, and temperature isotherms. The experimental results showed that the plateau pressure decreased with an increasing content of Al, Fe, or Co, but it increased with Ce addition. Furthermore, the plateau pressures of all Co-containing alloys were almost identical upon substitution with Ce. Finally, the enthalpy(ΔH) and entropy(ΔS) values for all alloys were calculated using van't Hoff plots. The relationship between the lattice parameters and enthalpy changes for hydrogenation will be discussed.     

LaNi_（5－x）Al_x贮氢合金的研究

用Ａｌ置换ＬａＮｉ５贮氢合金中部分Ｎｉ，得到一系列ＬａＮｉ（５－ｘ）Ａｌｘ（ｘ＝０．１，０．３，０．５）贮氢合金．通过对合金的热力学性能的测试可知：随着Ａｌ的加入及其含量的增加，贮氢合金的平台氢压降低，吸氢量有所减少，而吸氢速度有所增加．通过对合金及吸氢后氢化物品体结构的Ｘ射线衍射分析，发现Ａｌ的加入并未使晶体结构类型发生变化，只是晶格常数略有增加；同时还证明了ＬａＮｉ（５－ｘ）Ａｌｘ合金吸氢后其晶体结构也未发生变化，但晶格常数增加较大．     

Significantly enhanced hydrogen desorption properties of Mg(AlH4)2 nanoparticles synthesized using solvent free strategy

Mg(AlH_4)_2 nanoparticles with a particle size less than 10 nm have been successfully synthesized by mechanochemical method using LiAlH_4 and MgCl_2 as raw materials together with Li Cl buffering additive. In comparison to Mg(AlH_4)_2 microparticles, Mg(AlH_4)_2 nanoparticles exhibit a faster hydrogen desorption kinetics and lower desorption temperature. The hydrogen desorption temperatures of the first and second dehydrogenation steps are 80 and 220 °C for the Mg(AlH_4)_2 nanoparticles, which are about 65 and 60 °C, respectively, lower than those of Mg(AlH_4)_2 microparticles. The decomposition activation energy is reduced from 135 k J/mol for Mg(AlH_4)_2 microparticles to 105.3 k J/mol for Mg(AlH_4)_2 nanoparticles. It is proposed that the shortened diffusion distance and enhanced diffusivity of Mg(AlH_4)_2/MgH_2 nanoparticles provide an energy destabilization for lowering the dehydrogenation temperature, and thus being the key factor for promoting the hydrogen desorption kinetics. More importantly, it is demonstrated that the dehydrided nano MgH_2 hydride with a particle size below 10 nm can be formed after rehydrogenation process, resulting in the good cycling hydrogen desorption performance of nano MgH_2.     

储氢合金Mg2Ni的制备及其储氢性能分析

Mg-Ni基储氢合金以其比容量高、成本低而倍受关注.采用感应熔炼法,在不高于900 ℃的温度下成功制备出Mg2Ni合金,X射线衍射及金相组织分析表明,合金中主相为Mg2Ni.对制备出的Mg2Ni合金进行气态吸放氢性能测试,结果表明,经粉碎后的合金粉体经第1次活化,吸氢量为3.15 wt%,2次活化后吸氢量达到3.49 wt%,接近其理论值,而合金块体在第2次活化后的吸氢量远小于合金粉体的吸氢量,且第3次活化后未见明显增大.     

Effect of stoichiometry and Cu-substitution on the phase structure and hydrogen storage properties of Ml-Mg-Ni-based alloys

To improve the electrochemical properties of rare-earth-Mg-Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the alloys were studied. Nonsubstituted Ml_0.80Mg_0.20(Ni_2.90Co_0.50-Mn_0.30Al_0.30)_x (x=0.68, 0.70, 0.72, 0.74, 0.76) alloys and Cu-substituted Ml_0.80Mg_0.20(Ni_2.90Co_0.50-y Cu_y Mn_0.30Al_0.30)_0.70 (y=0, 0.10, 0.30, 0.50) alloys were prepared by induction melting. Phase structure analysis shows that the nonsubstituted alloys consist of a LaNi₅ phase, a LaNi₃ phase, and a minor La₂Ni₇ phase; in addition, in the case of Cu-substitution, the Nd₂Ni₇ phase appears and the LaNi₃ phase vanishes. Thermodynamic tests show that the enthalpy change in the dehydriding process decreases, indicating that hydride stability decreases with increasing stoichiometry and increasing Cu content. The maximum discharge capacity, kinetic properties, and cycling stability of the alloy electrodes all increase and then decrease with increasing stoichiometry or increasing Cu content. Furthermore, Cu substitution for Co ameliorates the discharge capacity, kinetics, and cycling stability of the alloy electrodes.     

La0.7Mg0.3-xTixNi2.8Co0.3(x=0.03,0.06,0.09,0.12)合金的储氢与电化学性能研究

用高频感应熔炼方法制备了La0.7Mg0.3-xTixNi2.8Co0.3(x=0.03,0.06,0.09,0.12)系列合金,并对其储氢和电化学性能进行测试.结果表明x=0.06时,合金储氢性能最好,气态储氢容量达1.2wt%,放电容量和比容量分别为336 mA.h.g-1,70.0%.     

Microstructural evolution and performance of hydrogen storage and electrochemistry of Co-added La0.75Mg0.25Ni3.5−xCox (x = 0, 0.2, 0.5 at%) alloys

Microstructure, hydrogen storage and electrochemical performances of Co-added La_(0.75)Mg_(0.25)Ni_(3.5_x)Co_x(x = 0,0.2, 0.5 at%) alloys are studied. XRD and rietveld refinement results suggest that the samples are mainly composed of(LaMg)Ni_3,(LaMg)_2Ni_7 and LaNi_5 phases, Co substitution for Ni changes the phase abundance,but not the phase composition. With the rising of Co content, the amount of(LaMg)_2 Ni_7 phase decreases, but the amount of LaNi_5 phase increases, while the amount of(LaMg)Ni_3 phase firstly increases and then decreases.The alloys reversibly absorb and desorb hydrogen at 298 K smoothly. When Co content is 0.2 at%, the hydrogen absorption capacity reaches the maximum value of 1.14 H/M, and the absorption capacities reach 1.09 H/M and 1.03 H/M in the first minute at 298 K and 323 K, respectively. Electrochemical performance measurement results show that La_(0.75)Mg_(0.25)Ni_(3.5-x)Co_x alloys are completely activated within 2 cycles, and the cyclic stability of La_(0.75)Mg_(0.25)Ni_(3.3)Co_(0.2) alloy approaches 63.7% after 100 charge/discharge cycles, which is higher than that(S_(100) = 60%) of La_(0.75)Mg_(0.25)Ni_(3.0)Co_(0.5) alloy. Thus, the La_(0.75)Mg_(0.25)Ni_(3.3)Co_(0.2) alloy exhibits optimum comprehensive properties of hydrogen storage and electrochemistry.     

快淬Mg2Ni型合金的结构及贮氢动力学

用快淬技术制备Mg2-xLaxNi(x=0,0.2,0.4,0.6)贮氢合金,用XRD,SEM和HRTEM分析合金的微观组织结构;测试合金的气态及电化学贮氢动力学。结果表明:快淬二元Mg2Ni合金具有典型的纳米晶结构,而快淬La替代合金明显地具有非晶结构,La替代Mg提高Mg2Ni型合金的非晶形成能力。La替代Mg明显地改变Mg2Ni型合金的相组成,当x=0.4时,合金的主相改变为(La,Mg)Ni3+LaMg3。快淬及La替代明显影响合金的气态及电化学贮氢动力学,La替代使合金的吸氢动力学先降低后增加,但使合金的气态脱氢及电化学贮氢动力学先增加后降低。快淬对合金气态及电化学贮氢动力学的影响与合金的成分相关,对于La0.4合金,合金的气态吸氢动力学随淬速的增加先增加后减小,其放氢动力学随淬速的增加而增加。     

Fabrication and characterization of nanocrystalline Al/Al12（Fe,V）3Si alloys by consolidation of mechanically alloyed powders

The aim of this study was to produce bulk nanocrystalline Al/Al12（Fe,V）3Si alloys by mechanical alloying （MA） and subsequent hot pressing （HP） of elemental powders. A nanostructured Al-based solid solution was formed by MA of elemental powders for 60 h. After HP of the as-milled powders at 550℃ for 20 min, the Al12（Fe,V）3Si phase was precipitated in a nanocrystalline Al matrix. Scanning electron microscopy （SEM） images of the bulk samples represented a homogeneous and uniform microstructure that was superior to those previously obtained by rapid solidification-powder metallurgy （RS-PM）. Nanostructured Al-8.5Fe-1.3V-1.7Si and Al-11.6Fe-1.3V-2.3Si alloys ex-hibited high HV hardness values of～205 and～254, respectively, which are significantly higher than those reported for the RS-PM counter-parts.     

La3-xYxMgNi14(x=0～2)贮氢合金的相结构与电化学性能研究

系统研究了La3-xYxMgNi14(x=0,1.0,1.5,2.0)贮氢合金的相结构和电化学性能.结构分析表明,合金均由Gd2Co7和Ce2Ni7型结构相组成.随Y含量值x的增加,Gd2Co7型相的丰度增加,Ce2Ni7型相的丰度减少.合金各相的晶胞参数(a,c)和晶胞体积(V)均随x的增加而线性减小.电化学研究表明,随着Y含量的增加,合金电极最大放电容量减小,活化性能显著降低.合金随x的增加,HRD值减小与合金电极电催化活性及氢在合金相中的扩散速率的减小有关.