Crystallization kinetics of （Ni0.75Fe0.25）78-xNbxSi10B12 （x = 0, 5） amorphous alloys

Amorphous ribbons of （Ni0.75Fe0.25）78-xNbxSi10B12 （x = 0, 5） were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuous heating, and the activation energies of the alloys were calculated using Kissinger plot method and Ozawa plot method on the basis of differential thermal analysis data. The crystallization products were analyzed by X-ray diffraction. After the （Ni0.75Fe0.25）78Si10B12 amorphous alloy was annealed at the temperatures 715 and 745 K, a single phase of γ-（Fe, Ni） solid solution with grain sizes of about 10.3 and 18.5 nm, respectively, precipitates in the amorphous matrix. The crystallized phases are γ-（Fe, Ni） solid solution, Fe2Si, Ni2Si, and Fe3B after annealing at 765 K. The （Ni0.75Fe0.25）73NbsSi10 B12 amorphous alloy was annealed at 720, 750, and 800 K; and the crystallization phases, γ（Fe, Ni） solid solution, （Fe, Ni）23B6. Ni31Si12 and Nb2NiB0.16 form simultaneously.     

Effects of Pd substitution for Ni on corrosion performances of Mg0.9Ti0.1Nil-xPdx hydrogen storage alloys

The Mg0.9Ti0.1Ni1-xPdx （x= 0, 0.05, 0.1, 0.15） hydrogen storage electrode alloys were prepared by mechanical alloying. The main phases of the alloys were determined as amorphous by X-ray diffraction（XRD）. The corrosion potentials of the alloys were measured by open circuit potential measurements and the values are -0.478, -0.473, -0.473 and -0.471 V （vs Hg/HgO electrode） for x=0, 0.05, 0.1, 0.15, respectively. The corrosion currents of the studied alloys were obtained by non-linear fitting of the anodic polarization curve using Bulter-Volmer equation and Levenberg-Marquardt algorithm, which were obtained after different cycles. The initial corrosion currents of the alloys are decreased with the increasing of Pd content. The increasing of Pd content in the alloys inhibits the corrosion rates of the electrode alloys with the progress of cycle number. The electrochemical impedance spectroscopy（EIS） was conducted after open circuit potential of the alloys stabilizing. The impedance data fit well with the theoretical values obtained by the proposed equivalent circuit model. The corrosion resistances and the thickness of surface passive film of the alloys, which were deduced by the analyses of EIS, are enhanced with the increasing of Pd content in the alloys, which are consistent with the results of corrosion rates obtained from anodic polarization measurements.     

Fe0.85Mn0.15Ti0.9M0.1（M=Zr,V,Ca）合金的贮氢性能

系统地研究了Ｆｅ０．８５Ｍｎ０．１５Ｔｉ０．９Ｍ０．１（Ｍ＝Ｚｒ,Ｖ,Ｃａ）合金的贮氢性能。研究结果表明：Ｆｅ０．８５Ｍｎ０．１５Ｔｉ０．９Ｚｒ０．１合金在室温下经几分钟的孕育期就可吸氢,但合金在氢化过程中形成了氢含量很高的α相,导致合金的贮氢量降低,同时还使ｐ－ｃ－Ｔ曲线的平台特性变差;Ｆｅ０．８５Ｍｎ０１５Ｔｉ０．９Ｖ０．１合金的活化性能进上步得到改善,在室温下几乎不需要孕育期就可以吸氢,但同     

Electrochemical characteristics of amorphous MgTixNi （x = 0,0.1, and 0.2） hydrogen storage alloys

MgTi _x Ni (x = 0, 0.1, and 0.2) alloys were successfully prepared by mechanical alloying (MA), and the influence of milling time on the electrochemical characteristics of the electrodes was discussed. MgTi _x Ni alloys after 90 h milling displayed the best electrochemical performance. The X-ray diffraction patterns showed that the alloy ball-milled for 90 h was amorphous with a widened diffraction peak. The charge-discharge tests indicated that these alloys had good electrochemical activation properties, and the MgTi_0.2Ni alloy electrode exhibited the best cycle performance. The initial discharge capacity of the MgTi_0.2Ni alloy reached up to 401.1 mAh·g⁻¹, and the retention rate of capacity was 31.0% after 30 cycles, much higher than that of MgNi (17.3%). The Tafel polarization curves revealed that Ti addition could enhance the anticorrosion performance of these alloys in alkali solution, which was responsible for the ameliorated cyclic stability of these alloy electrodes.     

Ti0.9Zr0.2Mn（1.8—x）MxV0.2（M=Ni,Cr;x=0,0.2）合金的贮氢性能

研究了Ti0.9Zr0.2Mn(1.8-x)MxV0.2(M=Ni,Cr;x=0,0.2)合金的晶体结构与贮氢性能。结果表明,Ti0.9Zr0.2Mn1.6Ni0.2V0.2和Ti0.9Zr0.2Mn1.6Cr0.2V0.2的贮氢量达到240mL/g。合金的主相均为C14 Laves相,镍,铬的取代使点阵常数和晶胞体积增大,P－C－T曲线的滞后降低,压力平台的倾斜度增加。     

Influences of Ti substitution on the structure and electrochemical properties of Mg1-xTixNi（x=0,0.1, 0.2, and 0.3） hydrogen storage alloys

MgNi-based hydrogen storage alloys Mg_1−x Ti _x Ni (x = 0, 0.1, 0.2, and 0.3) were prepared by means of mechanical alloying. Mg in the alloy was partially substituted by Ti to improve the cycle stability of the alloys. The effects of the substitution of Ti for Mg on the microstructure and electrochemical performances of the alloys were investigated in detail. The results indicate that the substitution of Ti for Mg obviously decreases the discharge capacity, but it significantly improves their cycle stabilities. The microstructure of the alloys analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) shows that the alloys have a dominatingly amorphous structure. The substitution of Ti for Mg helps to improve the anti-oxidation/corrosion ability of the MgNi alloy but demolishes the electrochemical kinetics of hydrogenation/dehydrogenation. The Mg_0.9Ti_0.1Ni alloy electrode milled for 80 h exhibits the best integrative capability, which has the maximal discharge capacity of 331.66 mAh/g and the C ₃₀/C _max of 63.65%.     

Stability of amorphous Al90TMxCe10—x（TM=Fe or Ni） alloys

X-ray diffraction(XRD) and differential scanning calorimetry(DSC) were used to investigate the crystallization process of amorphous Al90TMxCe10-x (atom fraction in%;TM=Fe or Ni;x=3,5)alloys,Aging effects were examined by X-ray diffraction,The structure corresponding to the prepeak for the amorphous Al90Fe5Ce5 alloy is more stble than the amorphous matrix,but it is not stable for amorphous Al90Ni5Ce5 alloy during the first crystallization stage and even decomposes at room temperature,Although both Al-Ni and Al-Fe have strong chemical bonding,the cyrstallization onset temperature of amorphous Al-Fe-Ce alloys is much higher than that of amorphous Al-Ni-Ce alloys,which is likely caused by the different stability of the structure corresponding to the prepeak.The crystallization onset temperature increases as Ce/Ni ratio increases in amporphous Al90NixCe10-x alloys,whereas it decreases as Ce/Fe ratio increases in amorphous Al90FexCe10-x alloys.A better atomic packing produces as Ce content increases because of the size mismatch in Al-Ni-Ce systems and as Fe content increases because of the increasing Fe central structural units.     

La（0.67-x）（Ti/Zr）xMg0.33Ni2.5Co0.5（x=0～0.15）贮氢合金结构和电化学性能

采用感应熔铸＋热处理的方法制备了La（0.67-x）（Ti/Zr）xMg0.33Ni2.5Co0.5合金.结构分析表明,合金由PuNi3型相、Ce2Ni7型相、MgCu4Sn型相和Ti-Ni或Zr-Ni合金相等组成;Ti/Zr元素在PuNi3型物相和Ce2Ni7型物相中没有固溶,而是单独以Ti-Ni和Zr-Ni合金的形式存在;随Ti和Zr含量的增多,合金中PuNi3型物相的单胞体积呈线性减小趋势.Ti和Zr元素的掺入提高了合金的吸放氢平台,降低了合金的贮氢量.电化学研究表明,Ti/Zr元素显著提高了合金电极的高倍率放电性能,但过量的Zr元素会恶化合金电极的电催化活性;Ti/Zr元素的掺入对合金电极循环稳定性有一定改善,但同时会降低合金电极的电化学放电容量.     

球磨Mg50Ni50＋x wt%Ti（x=0,1,3,5）合金的贮氢性能

为了改善镁基贮氢合金的贮氢性能,在合金中加入不同量的Ti作为催化剂,用机械球磨法制备出Mg50Ni50＋x wt%Ti（x=0,1,3,5）合金粉末。用XRD、SEM分析了合金的微观结构,研究了Ti含量的变化对合金气态吸氢动力学及电化学性能的影响。结果表明：随着Ti含量的增加,合金相中出现了TiNi2相,TiNi2相不利于气态吸氢及电化学贮氢性能,但对合金的容量保持率及高倍率放电性能有很好的促进作用。     

新型复合贮氢合金Zr0.9Ti0.1（Ni,Co,Mn,V）2.1的制备与电化学性能

采用熔铸方法制备母合金Zr0.9Ti0.1(Ni,Co,Mn,V)2.1,进而在母合金基础上添加吸氢剂B,利用球磨制得4种复合贮氢合金,X射线衍射结果表明,随着球磨时间的增加,复合合金由晶态转化为非晶态;电化学测试结果表明,复合合金经过1-2次球磨就能完全活化,具有很好的活化性能;在60mA/g电流下,复合贮氢合金C和D的稳定容量均可达到440mA.h/g左右,比母复金高出80mA.h/g;但随着球磨时间的延长,所得的复合金容量比铸态母合金的还低;在300mA/g电流下,复合合金D具有较好的循环稳定性,经过200次循环后其容量仅衰减3%。     

Effects of Pd substitution for Ni on corrosion performances of Mg_(0.9)Ti_(0.1)Ni_(1-x)Pd_x hydrogen storage alloys

1 Introduction MgNi-based amorphous hydrogen storage alloys have drawn much attention in the last ten years. Compared with AB5 or AB2 type electrode alloys, the alloy candidates for the negative electrode of Ni-MH batteries possess several advantages, su…     

（Ti0.1V0.9）100-xFex（x=0～6）储氢合金的微观结构及储氢特性

研究了（Ti0.1V0.9）100-xFex（x=0～6）合金的微观结构及其吸放氢特性。微结构分析表明，合金均由单一的体心立方（bcc）结构的钒基固溶体相组成；合金的点阵常数随着Fe含量的增加呈线性递减，晶胞体积也随之逐渐降低。储氢性能测试表明，所有合金的动力学性能均比较好，在10℃和4MPa初始氢压条件下，合金无需氢化孕育期就能吸氢。随着Fe含量从x=0增加至x=6，合金的活化性能得到改善；10℃最大吸氢量从509．5ml／g逐渐降至424．8ml／g；50℃有效放氢量先升后降，并在x=4时达到最高值255．6ml／g。在所研究的合金中，Ti9.6V86.4Fe4合金具有最佳综合性能，经2次吸放氢循环即可活化，10℃最大吸氢量为494．5ml／g，50℃有效放氢量达到255．6ml／g。     

Fe_(0.85)Mn_(0.15)Ti_(0.9)M_(0.1)(M=Zr,V,Ca)合金的贮氢性能

系统地研究了 Fe0 .85 Mn0 .1 5 Ti0 .9M0 .1 (M=Zr,V,Ca)合金的贮氢性能。研究结果表明 :Fe0 .85 Mn0 .1 5 Ti0 .9Zr0 .1 合金在室温下经几分钟的孕育期就可吸氢 ,但合金在氢化过程中形成了氢含量很高的α相 ,导致合金的贮氢量降低 ,同时还使 p- c- T曲线的平台特性变差 ;Fe0 .85 Mn0 .1 5 Ti0 .9V0 .1 合金的活化性能进一步得到改善 ,在室温下几乎不需要孕育期就可以吸氢 ,但同时要降低合金的贮氢量 ,而对合金的 p- c- T曲线平台特性影响不明显 ;用 Ca取代 Fe0 .85 Mn0 .1 5 Ti合金中的部分 Ti则对合金的贮氢性能影响不明显。通过 XRD分析认为 ,上述性能的变化主要与合金中出现第二相有关     

Mg2Ni1-xCux (x=0, 0.2, 0.4)合金熔炼法加球磨处理后的储氢性能

采用熔炼法加球磨处理制备Mg2Ni1-xCux(x=0,0.2,0.4)合金。通过XRD和SEM/EDX对合金的相成分和微观组织进行分析。研究表明,3种合金中都有Mg2Ni相形成。随着Cu含量的增加,合金分别形成Mg2Cu相和Cu11Mg10Ni9相。PCT测量结果表明,Cu的添加可以改善合金的吸放氢性能。     

熔体快淬Zr(V1-xFex)2 (x=0.15)合金的贮氢性能

采用非自耗真空电弧炉熔炼制备Zr(V1-xFex)2(x=0.15)母合金锭,利用单辊旋淬设备制得不同淬速的合金薄带。X射线衍射结果表明,不同淬速Zr(V1-xFex)2(x=0.15)合金均为近乎单相的C15型Laves相,熔体快淬工艺可消除铸态合金中的包晶反应残留相和枝晶偏析,得到均匀细晶组织。快淬Zr(V1-xFex)2(x=0.15)合金吸氢后的晶体结构未发生改变,饱和吸氢后的体胀率约20%,根据V’antHoff关系外推出室温下快淬合金的平衡压力低于10-5Pa量级。     

Ti1.2Fe＋x%Mg（x=1,3,5）合金的贮氢特性

在TiFe合金中添加少量的IIA族轻金属元素Mg，并且使Ti侧过化学计量，组织Ti1.2F3 x%（质量分数，下同）Mg（x=1,3,5)试验合金，研究了该系列合金的储氢特性。结果表明，Ti1.2F3 3%Mg和Ti1.2F3 5%Mg合金在室温下，经2次吸放氢操作即能完全活化，前者的储氢量为213ml/g，且具有较小的压力滞后和平台斜率，适合作为内氢燃料电池氢源储氢材料。X射线分析发现，所有试验合金的主相均为TiFe相，而合金显微组织显示，Mg以弥散颗粒分布于合金基体，并讨论了Mg的添加和Ti过量对合金活化性能和储氢容量的影响机制。