Phase structure and electrochemical properties of melt-spinning alloy Zr(MnVNi)_(2.4)

1　INTRODUCTIONItiswellknownthatZr basedAB2 LavesphasealloyelectrodeshavehigherdischargecapacityandmuchbettercyclingstabilitythanthatofAB5alloysalthoughitisexpensivecomparedtoAB5alloys .HowtofurtherimprovetheratioofpropertiesandpriceofAB2 alloyshasbeendrawingtheinterestofmanyin vestigators .Someinvestigationsrevealedthatover stoichiometricAB5typealloyshadbettercharge dis chargecyclingstabilitythanstoichiometricalloys[15] ,andsomeover stoichiometricAB2 typealloysshowedhigherdischargec…     

Effect of La on the crystalline and electrochemical properties of Ti-Zr-Ni melt-spun alloys

Ti45Zr30Ni25 and Ti45Zr30Ni25La alloys were prepared by melt-spinning, and the phase structure and electrochemical performances of the melt-spun alloys were investigated. The results showed that the Ti45Zr30Ni25 alloy was composed of the quasicrystalline phase, amorphous phase and Laves phase. The Ti445Zr30Ni25La alloy contained quasicrystalline and amorphous phases. The maximum discharge capacity was 111 mAh/g for the Ti45Zr30Ni25 alloy electrode, and 124 mAh/g for the Ti45Zr30Ni25La alloy electrode. The Ti45Zr30Ni25La alloy electrode ex-hibited a better high-rate dischargeability and cycling stability than the Ti45Zr30Ni25 alloy electrode. The improvement of electrochemical properties was mainly ascribed to the increase in the amorphous phase due to the addition of La.     

元素Ti对贮氢合金ZrMn0．7V0．2CO0．1Ni1．2相结构和电化学性能的影响

研究了元素Ti对贮氢电极合金ZrMn0.7V0.2Co0.1Ni1.2的相结构、相组成以及电化学性能的影响。结果表明，对于合金Zr1-xTix(Mn0.7V0.2Co0.1Ni1.2)，其母体合金的主相为C15型Laves相，并含有少量的非Laves相Zr7M10；但随着掺Ti量的增加，合金中出现C14型Laves相，而且其含量逐渐增加；在x=0．1～0．2时，合金中还出现少量的TiNi相，而在x=0．4～0．5时，非Laves相Zr7M10和TiNi相全部消失，说明元素Ti大量的掺杂抑制了第二相的产生：而且随着Ti含量的增加，合金中的C15型和C14型Laves相的晶格常数逐渐减小。电化学测试结果发现，当含Ti量x=0．2时，合金有最大放电容量Cmax为354mAh／g，在放电电流为300mAh／g条件下，高倍率放电性能比母体合金提高了15％。     

Electrochemical Properties and Reaction Mechanism of Ti-V Multiphase Alloy at High Temperature

研究333 K时Ti0.17Zr0.08V0.35Cr0.1Ni0.3 合金的循环稳定性和高温倍率放电性能。333 K时,当放电电流密度为60 mA/g时,Ti0.17Zr0.08V0.35Cr0.1Ni0.3合金第1次放电容量为450 mAh/g。随着充放电循环的进行,放电容量迅速降低。当放电电流密度为2400 mA/g,截止电压为0.6 V时,Ti0.17Zr0.08V0.35Cr0.1Ni0.3合金的放电容量仍达到160 mAh/g。并详细探讨影响以上合金电化学性能的因素     

Zr系贮氢合金晶体结构与电极特性间关系

ＡＢ２型Ｌａｖｅｓ相ＺｒＣｒ（０．４）Ｍｎ（０．２）Ｖ（０．１）Ｎｉ（１．３）贮氢合金经球磨非晶化处理后，相同化学成分的贮氢合金电极容量锐减，合金的晶体结构与其电化学放电容量密切相关．在晶态合金中，主要是Ｚｒ２Ｂ２（Ｂ＝Ｃｒ，Ｍｎ，Ｖ，Ｎｉ）四面体间隙的氢对电化学放电容量作出贡献，而在非晶态合金中，则是Ｚｒ３Ｂ，Ｚｒ４四面体间隙的氢．由于静电作用，都只有一半的间隙位置能容纳氢原子．非晶化处理导入额外的能量，以致降低合金中氢的电化学反应激活能．     

Ti对Zr—Mn—V—Ni系合金的微结构和电化学性能的影响

Ｚｒ－Ｍｎ－Ｖ－Ｎｉ合金中Ｚｒ－Ｎｉ金属间化合物与Ｌａｖｅｓ相共存,Ｚｒ０．５Ｔｉ０．５Ｍｎ０．２Ｖ０．６Ｎｉ１．２合金内形成了含Ｔｉ的ｂｃｃ相,选区电子衍射和ＥＤＳ能谱分析结果表明,ｂｃｃ相为Ｂ２型Ｒ相（Ｔｉ０．５Ｚｒ０．２）Ｎｉ,Ｔｉ取代部分Ｚｒ,改变了四元合金中Ｌａｖｅｓ相的晶胞参数和亚结构,非Ｌａｖｅｓ相的形成导致合金元素在各相间的重新分配,多相合金内Ｌａｖｅｓ相的晶胞参数合金的名义成分。     

Improvement in the electrochemical properties of ZrMn2 hydrides by substitution of elements

The hydrogen-storage properties and the electrochemical properties are investigated for the alloys ZrMn₂Ni_x, ZrMnNi_1+x, Zr_0.5Ti_0.5Mn_0.4V_0.6Ni_1−xFe_x and Zr_0.5Ti_0.5Mn_0.4V_0.6Ni_0.85M_0.15. The C14 Laves phase forms in all the alloys ZrMn₂Ni_x (x=0.0, 0.3, 0.6, 0.9 and 1.2). Among the alloys ZrMn₂Ni_x, ZrMn₂Ni_0.6 has the largest discharge capacity (29 mAh/g) and a relatively good cycling performance, and shows a relatively easy activation. The C14 Laves phase also forms in all the alloys ZrMnNi_1+x (x=0.0, 0.1, 0.2, 0.3 and 0.4). Among the alloys ZrMnNi_1+x, ZrMnNi_1.0 has the largest discharge capacity (42 mAh/g) and a relatively good cycling performance, and shows the easiest activation. Zr_0.5Ti_0.5Mn_0.4V_0.6Ni_1−xFe_x (x=0.00, 0.15, 0.30, 0.45 and 0.60) has the C14 Laves phase hexagonal structure. Their hydrogen storage capacities do not show significant differences. The discharge capacity just after activation decreases with an increase in the amount of the substituted Fe but the cycling performance is improved. The discharge capacity after activation of the alloy with x=0.00 is about 240 mAh/g at the current density 60 mA/g. Zr_0.5Ti_0.5Mn_0.4V_0.6Ni_0.85Fe_0.15 is the best composition with a relatively large discharge capacity and a good cycling performance. The increase in the discharge capacity of Zr_0.5Ti_0.5Mn_0.4V_0.6Ni_0.85Fe_0.15 with the increase in the current density (from 60 mA/g to 125 mA/g) is considered to result from the self-discharge property of the electrode. Zr_0.5Ti_0.5Mn_0.4V_0.6Ni_0.85M_0.15 (M=Fe, Co, Cu, Mo and Al) alloys also have the C14 Laves phase hexagonal structure. The alloys with M=Co and Fe have relatively larger hydrogen storage capacities. The discharge capacities just after activation are relatively large in the case of the alloys with M=Co and Fe. The Zr_0.5Ti_0.5Mn_0.4V_0.6Ni_0.85Co_0.15 alloy is best with a relatively large discharge capacity (257 mAh/g at the current density 250 mA/g for the 12^th cycle) and a good cycling performance. During activation form Ni-rich and Fe-rich regions on the surface of the Zr_0.5Ti_0.5Mn_0.4V_0.6 Ni_0.85Fe_0.15 alloy. They may act as the active sites for the electrochemical reaction. With the increase in the number of charge-discharge cycles for the Zr_0.5Ti_0.5Mn_0.4V_0.6Ni_0.85Fe_0.15 alloy, the quantities of the Zr and Fe dissolved in the electrolyte solution increase. This article is based on a presentation made in “The 2nd KIM-JIM Joint Symposium: Hydrogen Absorbing Materials”, held at Hanyang University, Seoul, Korea, October 27–28, 2000 under the auspices of The Korean Institute of Metals and Materials and The Japan Institute of Metals.     

快速凝固钛钒系贮氢合金电化学性能研究

研究了快速凝固处理对钛钒系贮氢电极合金Ti0.8Zr0．2V2．4Mn0．48Cr0．72Ni0．9的相结构、特别是电化学性能的影响规律。XRD研究表明：合金主要由六方结构的C14 Laves相和体心立方结构的钒基固溶体相所组成，快速凝固减少了合金中C14 Laves相的含量。电化学性能分析表明：快速凝固降低了合金电极的最大放电容量，增加了电极的活化次数，提高了电极表面的反应阻抗，恶化了电极的动力学性能，但是却大大改善了合金电极的循环稳定性。     

Crystallographic and electrochemical characteristics of melt-spun Ti-Zr-Ni-Cu alloys

Ti44Zr32Ni22Cu2 and Ti41Zr29Ni28Cu2 alloys were prepared by the melt-spinning method. The phase structure was analyzed by X-ray diffraction,and the electrochemical performances of the melt-spun alloys were investigated. The results indicated that the Ti44Zr32Ni22Cu2 alloy was composed of the icosahedral quasicrystals and amorphous phases,and the Ti41Zr29Ni28Cu2 alloy comprised icosahedral quasicrystals,amorphous,and Laves phases. The maximum discharge capacity was 141 mAh/g for the Ti44Zr32Ni22Cu2 alloy and 181 mAh/g for the Ti41Zr29Ni28Cu2 alloy,respectively. The Ti41Zr29Ni28Cu2 alloy also showed a better high-rate dischargeability and cycling stability. The better electrochemical properties should be ascribed to the high content of Ni,which was beneficial to the electrochemical kinetic properties and made the alloy more resistant to oxidation,as well as to the Laves phase in the Ti41Zr29Ni28Cu2 alloy,which could work as the electro-catalyst and the micro-current collector.     

Ti基贮氢合金Ti0．3Zr0．225V0．25Mn0．3-xNi0．45＋x（x=0-0．25）的显微组织及电化学性能

为了改善Ti基贮氢合金的电化学性能，采用XRD，SEM及EDS分析了Ti0．3Zr0．225V0．25Mn0．3-xNi0．45＋x（x=，0．05，0．10，0．15，0．20，0．25）贮氢合金的相结构及相成分，并研究了合金的电化学性能。结果表明，合金均由六方结构的C14型Laves主相和立方结构的C15型Laves第二相构成；随着Ni替代量x的增大，合金的活化性能降低，而循环稳定性得到一定程度的改善。当Ni替代量x=0．05时，合金的放电容量达到最大，为426mAh／g，显示出很大的应用潜力.     

热处理对包含正二十面体准晶相Ti1.4V0.6Ni合金电极的电化学性能的影响（英文）

研究了热处理前后Ti1.4V0.6Ni合金的结构和电化学性能。采用X射线粉末衍射(XRD)方法分析合金的结构。电化学特性包括放电容量、循环稳定性和高倍率放电性能等。XRD衍射分析表明,在590°C热处理30min的合金,主要包含正二十面体准晶相、Ti2Ni(FCC)相、V基固溶相(BCC)和C14Laves相(Hex)。电化学测试显示,热处理后在30°C和放电电流密度为30mA/g的条件下,合金电极的最大放电容量可达330.9mA·h/g,并且循环稳定性和高倍率放电性能也得到改善。此外,通过电化学阻抗和合金内部氢的扩散系数研究了合金电极的动力学性能。     

（Zr,Ti）（V,Mn,Pd,Ni,Fe）2系贮氢电极合金的循环稳定性

（Ｚｒ，Ｔｉ（Ｖ，Ｍｎ，Ｐｄ，Ｎｉ，Ｆｅ）２系贮氢电极合金具有较高的电化学容量。在充放电循环过程中，发生合金组元有选择地溶了，致使合金Ｃ１４７主相结构严重畸变，逐渐丧失了可逆贮氢能力。     

Ti对Ml(NiCoMnTi)_5合金相结构和充放电循环性能的影响

研究了微量 Ｔｉ在 Ｍｌ（ＮｉＣｏＭｎＴｉ）５合金中的作用．结果表明,在铸态条件下,Ｔｉ几乎全部以 ＴｉＮｉ３第二相的形式在晶界析出,退火处理后 ＴｉＮｉ３相消失,但 ＳＥＭ和 ＥＤＳ表明 Ｔｉ取代了 ＡＢ５型化合物中 Ａ侧的稀土 Ｍｌ;而不是 Ｂ侧的 Ｎｉ．Ｔｉ在 Ａ侧的取代量以 ５％为宜．此时合金在铸态和退火态的放电容量都在 ３１０ ｍＡ·ｈ／ｇ以上．进一步提高取代量虽然会改善循环稳定性,但大大降低了放电容量．     

Cobalt-free over-stoichiometric Laves phase alloys for Ni–MH batteries

The charge–discharge cycling behavior of the over-stoichiometric Laves phase alloy Zr_0.75Ti_0.25V_0.9Mn_0.4Cr_0.3Ni_1.4 as hydride electrode has been studied in a negative electrode-limited sealed cell. This cobalt-free alloy shows a maximum discharge capacity C_max=373 mAh g⁻¹ at 160 mA g⁻¹ discharge current and a high rate dischargeability of 285 mAh g⁻¹ at 1500 mA g⁻¹ discharge rate. After 600 cycles the discharge capacity is 81% of the C_max; the alloy also shows good charging efficiency (98%) and low temperature discharge rate.     

合金元素掺杂对TiV_(2.1)Ni_(0.4)合金相结构及电化学性能的影响

研究了合金元素掺杂对TiV2.1Ni0.4系列合金的相结构及电化学性能的影响。XRD分析表明,该合金由V基固溶体主相和以网状分布于主相晶界的Ti2Ni第二相和C15型Laves第三相组成。BEI、EDS和电化学测试表明,Zr、Cu合金元素进入第二相晶格而使合金的电化学容量略降,但提高了合金的循环性能;Cr元素由于大部分进入到主相晶格而使合金的电化学循环性能大幅度提高,经40次循环后容量保持率仍达88.4%,但最大放电容量有所降低。     

Pulverization mechanism of the multiphase Ti–V-based hydrogen storage electrode alloy during charge/discharge cycling

Pulverization is an important key factor for the electrochemical cycle stability of many hydrogen storage alloys. In this paper, the pulverization mechanism of the multiphase Ti–V-based hydrogen storage alloy which mainly consists of a V-based solid solution phase with the BCC structure and a C14 Laves phase is studied based on a sample material of the Ti_0.8Zr_0.2V_2.7Mn_0.5Cr_0.6Ni_1.25Fe_0.2 alloy. The microstructure of the alloy and the morphology change of the alloy electrode during the charge/discharge process were observed by transmission electron microscope, scanning electron microscope and atomic force microscope, etc. The effect of mechanical properties of the V-based phase and the C14 Laves phase on the pulverization behavior of the Ti–V-based alloy is discussed. The results show that microcracks initially occur at the phase boundary of the V-based phase and the C14 Laves phase and then extend to the C14 Laves phase in the charge/discharge process. The phase boundary is composed of a Ti segregated amorphous layer with a thickness of about 90 nm, mismatching with the crystallized V-base phase and C14 Laves phase. The toughness of the C14 Laves phase is much lower and the hardness is higher than that of the V-based phase. The weak bonding strength of the phase boundary, the lower toughness of the C14 Laves phase and the large volume expansion/contraction of the C14 Laves phase during charge/discharge cycling are the main factors that cause the pulverization of the Ti–V-based alloy.     

Ti_（0.10）Zr_（0.15）V_（0.35）Cr_（0.10）Ni_（0.30）-10% LaNi_3复合物的电化学储氢特性及协同效应

为了改善钛钒基固溶体合金的电催化活性和动力学性能,采用两步电弧熔炼法制备储氢复合合金Ti0.10Zr0.15V0.35Cr0.10Ni0.30–10%LaNi3,利用X-射线衍射、场发射扫描电镜-能谱、电化学阻抗谱和恒流充放电测试技术系统研究该储氢复合合金电极的电化学性能与协同效应。结果表明：该复合合金的主相是BCC结构的钒基固溶体相和六方结构的C14Laves相,在复合过程中生成了第二相;复合合金电极的综合电化学性能较母体合金有显著改善;复合合金电极的活化周期为5周,最大放电容量为362.5mA·h/g,在233K时放电能力为65.84%;在活化、复合、任意循环及高、低温和高倍率放电过程中,该储氢复合合金电极的放电容量均存在协同效应;该复合合金电极的电荷转移电阻和交换电流密度均存在协同效应。     

熔体旋淬Ml（NiCoMnAl）5贮氢合金的微结构与电化学行为

研究了熔体旋淬和常规熔铸Ml(NiCoMnAl)5贮氢合金的微结构和电化学行为。SEM和XRD分析表明,熔体旋淬合金由细小的柱状晶组成,它们的晶体结构与铸态一样,都为CaCu5型六方晶休结构。电化学测试表明,旋淬态合金电极初始容量较高（＞210mA.h/g)经1－2次循环就可达到最大放电容量。旋淬速度为10m/s的合金电极的放电容量（294mA.h/g)稍高于铸态合金电极的容量。所有旋淬态合金电极充放电循环稳定性皆优于铸态合金,在600mA/g电流质量密度下,旋流速度为10m/s的合金电极具有较好的高倍率充放电能力,但随着循环次数的增加,其容量稳定性稍次于旋淬速度为25m/s和40m/s的合金电极。     

新型钛钒系贮氢电极合金

研究了新型钛钒系贮氢电极合金Ti0.8Zr0.2V2.665Mn0.535Cr0.8Ni的相结构、微观组织及电化学性能。XRD及EDS分析表明：铸态合金主要由C14 Laves相母体和树枝晶的钒基固溶体相组成，同时由于成分偏析的缘故，合金中还存在少量的TiNi基的第三相。热处理使得合金中C14 Laves相及钒基固溶体相的晶胞参数和晶胞体积增大，促进合金成分的均匀化，同时极大地改善了合金电极的综合电化学性能。     

快凝合金Zr（Ni0.55Mn0.3V0.1Cr0.05）2.1的相结构与储氢性能

在快冷（冷却速度１０＾５－１０＾６Ｋ／ｓ）Ｚｒ（Ｎｉ０．５５Ｍｎ０．３Ｖ０．１Ｃｒ０．０５）２．１合金中观察到一种高温条件下丰碑 纳米晶Ｃ１４Ｌａｖｅｓ相,其丰度随冷凝速度下降明显减少。