First-principles calculations of LaNi5-xSnxHy intermetallics and intermediate phase

The crystal and electronic structures of LaNi_4.75Sn_0.25 intermetallics and LaNi_4.5Sn_0.5H_y (y=2.0, 2.5) intermediate phase have been investigated by the full-potential linearized augmented plane wave (FP-LAPW) method. Hydrogen occupation sites in LaNi_4.5Sn_0.5H_y have been determined based on Westlake$'$s criterions: (1) the minimum hole radius is 0.04~nm; (2) the minimum H-H distance is 0.21~nm; as well as geometry optimizations and internal coordinates optimizations. We find that hydrogen atoms prefer to occupy the 12n^*, 6m, 12o, 6m^* sites in LaNi_4.5Sn_0.5H_2.0 and the 6m^*, 4h, 6m, 12o, 12n^* sites in LaNi_4.5Sn_0.5H_2.5. The specific coordinates of hydrogen atoms in LaNi_4.5Sn_0.5H_y are also determined. The results show that hydrogen atoms tend to keep away from tin atoms. The maximum hydrogen content decreases compared with LaNi₅. The interactions between Sn and Ni with H play a dominate role in the stability of LaNi_4.5Sn_0.5-H system. Lattice expansion and increment of Fermi energy E _F show that both Sn and H atoms decrease structural stability of these alloys.     

LaNi4.7Al0.3和MlNi4.5Al0.5合金在H2-CO系统中贮氢性能下降的研究

研究了贮氢合金LaNi4.7Al0 .3和MlNi4.5Al0 .5在纯氢 ( 99.999% )及氢中含CO气体杂质条件下的 p c t特性及循环性能。结果表明 ,合金经CO毒化后 ,平台压升高 ,平台倾斜加剧 ,平台宽度缩小 ,饱和吸氢量减小。毒化后两种贮氢合金的循环性能衰退 ,而且随着循环次数的增加吸氢量减少 ,增加CO的浓度 ,吸氢量减少更加明显。合金贮氢性能下降的原因可能是由于表面生成了氧化物及新相 ,阻止了氢的吸附与扩散。     

Hydrogen-induced Amorphization in LaNi2.5M0.5 (M=Ni, Fe, Mn, Si) Alloys

采用XRD和电化学测试的方法研究了Fe、Mn、Si部分替代Ni对LaNi3型贮氢合金氢致非晶化的影响.结果表明:LaNi2.5M0.5(M=Ni,Fe,Mn,Si)贮氢合金的主相均为LaNi3相;在第一次充电后,合金均有一定程度的氢致非晶化现象;LaNi3和LaNi2.5Fe0.5合金的放电曲线没有放电平台,表明合金充电后为非晶态;LaNi2.5Mn0.5和LaNi2.5Si0.5合金的放电曲线有一个倾斜的平台,这表明少量的Mn和Si可以在一定程度上抑制LaNi3型贮氢合金的氢致非晶反应.     

LaNi4.75Al0.25储氢材料的密度泛函理论研究

在全电子水平上，基于广义梯度近似（GGA）密度泛函和全势能线性缀加平面波方法（FLAPW），研究了LaNi4.75Al0.25的晶体结构。采用GGA Perdew96交换相关泛函，计算给出了LaNi4.75Al0.25的晶胞参数为a=b=0．5033nm、c=0．4018nm、a／c=1．252，Al原子最可能占据的3g格位的等效位置（0．75，0，0．5），计算还给出了合金的能带结构、态密度（DOS）和电荷密度图，计算结果与实验值符合得相当好。     

Effects of rapid quenching on structure and electrochemical characteristics of La0.5Ce0.2Mg0.3Co0.4Ni2.6-xMnx （x=0-0.4） electrode alloys

The La-Mg-Ni system PuNi3-type La0.5Ce0.2Mg0.3Co0.4Ni2.6-xMnx (x=0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by casting and rapid quenching. The effects of the rapid quenching on the structure and electrochemical characteristics of the alloys were studied. The results obtained by XRD, SEM and TEM indicate that the as-cast and quenched alloys mainly consist of two major phases, (La,Mg)Ni3 and LaNi5, as well as a residual phase LaNi. The rapid quenching does not exert an obvious influence on the phase composition of the alloys, but it leads to an increase of the LaNi5 phase and a decrease of the (La, Mg)Ni3 phase. The as-quenched alloys have a nano-crystalline structure, and the grain sizes of the alloys are in the range of 20-30 nm. The results by the electrochemical measurements indicate that both the discharge capacity and the high rate discharge(HRD) ability of the alloy first increase and then decrease with the variety of quenching rate and obtain the maximum values at the special quenching rate which is changeable with the variety of Mn content. The rapid quenching significantly improves the cycle stabilities of the alloys, but it slightly impairs the activation capabilities of the alloys.     

工业纯Sn和Sn-3Ag-0.5Cu合金在沈阳大气环境下自然暴露的初期腐蚀行为

通过沈阳大气环境下的自然暴露实验研究工业纯Sn和Sn-3Ag-0.5Cu合金的早期大气腐蚀行为。采用扫描电子显微镜(SEM)和X射线光电子能谱仪(XPS)分析了表面腐蚀产物的形貌与成分。结果表明:工业纯Sn与Sn-3Ag-0.5Cu合金在沈阳工业大气环境下自然暴露后都很快发生了表面腐蚀并失泽,早期腐蚀产物疏松、龟裂并易于剥落。XPS深度分析表明:自然条件下暴露18 d后,表面腐蚀产物层厚度约为400 nm。工业大气中的悬浮物颗粒对腐蚀的形核和扩展起重要作用,Sn-3Ag-0.5Cu合金中的第二相Ag3Sn和Cu6Sn5作为阴极存在,但对大气腐蚀的加速影响不大。     

Sn-Ag-Cu-Ce无铅钎料合金体系的热力学计算及预测

利用周模型对Sn—Ag—Cu—Ce无铅钎料合金体系进行了热力学计算预测。热力学计算结果表明，Ag、Cu含量(质量分数)分别为0．5％-4．5％时，当Ce的含量(质量分数)超过0．05％时，体系达到化学平衡状态；当Ce的含量(质量分数)达到0．6％左右时，Sn、Ag、Cu分别都出现了“等活度系数”现象。这一研究结果可为无铅钎料合金的成分设计提供理论指导。     

Anodic behaviour of amorphous NiP/tin multilayers in an acidic chloride solution

The anodic behaviour of electrodeposited NiP/Sn multilayers with submicron sublayers (0.1-0.5 μm) was tested in acidic (pH 4.5) NaCl aqueous solutions by voltammetric and potentiostatic techniques. A significant decrease of the passivation currents was observed especially when the Sn sublayers are very thin (∼0.1 μm). A compositional (EDX), structural (XRD) and morphological (SEM) characterisation of the electrodeposited multilayers was performed. Evidence for the formation of a protective layer at the NiP/Sn interface consisting of corrosion products of both NiP and Sn was obtained by XPS and electrochemical measurements.     

Effects of Co Substitution for Ni on Microstructures and Electrochemical Properties of LaNi3.8 Hydrogen Storage Alloys

系统研究了Co替代Ni对LaNi3.8型LaNi3.8-xCox(x=0.0,0.2,0.4,0.6)贮氢合金组织结构和电化学性能的影响。研究表明,所有合金都由LaNi5、Ce5Co19和Pr5Co19相组成。随着Co含量的增加,3个相的相丰度发生变化,而且单胞体积也相应的增加,这使得合金的放氢平台压降低到镍氢电池需要的范围(0.01~0.1 MPa)。与LaNi3.8相比,含Co合金的循环性能得到改善。LaNi3.4Co0.4具有最大的放电容量,这一点与固态放氢量一致。LaNi3.6Co0.2倍率放电性能最好,具有最大的交换电流密度(Io)和最小的电荷转移电阻(Rct)。     

Investigation Of Stability And Hydrogen Storage Properties Of LaNi5-XMx（M=Al, Mn) Alloys

通过对LaNi5-xAlx和LaNi5-xMnx两个合金系的晶胞参数、热力学性能、吸氢量、平衡氢压等储氢性能进行对比和分析，建立了LaNi5-xMx(M=Al，Mn)合金系中的x与平台压力以及温度间的对应关系，探讨了晶格常数和晶胞体积及合金稳定性的变化对合金系储氢性能的影响．结果表明，与LaNi5-xAlx相比较，LaNi5-xMnx合金的晶胞体积较大，使其平衡氢压降得更低；随x的增加，LaNi5-xMnx合金晶胞体积膨胀的各向异性程度(即晶轴比变化)较小，且合金稳定性的变化较小，随z增加吸氢量衰减不明显．     

La_(0.7)Mg_(0.3)Ni_(2.8)Co_(0.5-x)Fe_x系列合金的制备及其储氢性能

在制备La-Ni-Co-Fe中间合金的基础上,采用机械合金化方法制备La0.7Mg0.3Ni2.8Co0.5-xFex(x=0,0.1,0.2,0.3,0.4,0.5)系列储氢合金,研究在不同球磨时间下储氢合金的物相、微观形貌和电化学性能及元素置换对其储氢性能的影响。结果表明:La0.7Mg0.3Ni2.8Co0.5合金的主相为LaNi5相,La0.7Mg0.3Ni2.8Co0.5-xFex系列储氢合金球磨40 h和80 h后,主相为LaNi5相和少量LaMg2Ni9相;且随着球磨时间的增加,合金晶粒变细小,La0.7Mg0.3Ni2.8Co0.5合金的最大放电容量呈变大的趋势,从142.4 mA.h/g增加到157.5 mA.h/g,La0.7Mg0.3Ni2.8Co0.2Fe0.3合金的最大放电容量从150.7mA.h/g增加到162.1mA.h/g,合金具有较好的循环稳定性能。     

Preparation and characterization of nanostructured Bi_2Se_3 and Sn_(0.5)-Bi_2Se_3

Nanostructured Bi2Se3 and Sn0.5·Bi2Se3 were successfully synthesized by hydrothermal coreduction from SnCl2-H2O and the oxides of Bi and Se. The products were characterized by X-ray diffraction (XRD),transmission electron microscopy (TEM),and field emission scanning electron microscope (FESEM). Bi2Se3 powders obtained at 180°C and 150°C consist of hexagonal flakes of 50-150 nm in side length and nanorods of 30-100 nm in diameter and more than 1 μm in length. The product obtained at 120°C is composed of thin...     

ELECTRONIC STRUCTURE OF THE LaNi5-xGax INTERMETALLIC COMPOUNDS

The equilibrium structures and electronic structure of LaNi5-xGax （x=0, 0.5, 1.0） compounds have been investigated by all-electron calculations. Based on the full geometry optimization, the densities of states and electron densities of LaNi5-xGax are plotted and analyzed. It is clear that the substitution of Ga at the Ni site leads to a progressive filling of the Ni-d bands, the ionic interaction between Ni and Ni, with Ga plays a dominant role in the stability of LaNi5-xGax compounds. The smaller the shift of EF toward higher energy region, the more stable the compounds will be. The increased contribution of the Ni-d-Ga-d interactions near EF and the low energy metal-gallium bonding bands indicate that the compounds become more stable. The results are compared with experimental data and discussed in light of previous studies.     

LaNixSny金属氢化物电极的制备及性能

从电化学角度研究了含锡贮氢合金的贮氢性能，并对金属氢化物电极制作技术进行了探索。结果表明，用这种贮氢合金制成的电极容量达到３４０ｍＡｈ／ｇ以上，而且容易活化。采用颗粒细小的镍粉较粒径较大的铜粉好，导电剂用量１０％；采用混合粘结剂ＣＭＣ和ＰＴＦＥ，ＣＭＣ用量为０．４％，ＰＴＦＥ用量为１０％。     

Valence electron structure and hydrogen storage property of LaNi_-4Co

In the present study, two models of atom occupation in 4 Co were put forward and corresponding valence electron structures(VESs) of these two models were investigated according to empirical electron theory(EET) of solids and molecules. Results demonstrate that the VES-concerned hardness factor(FH) of LaNi4 Co is lower than that of LaNi5, so LaNi4 Co has lower hardness,higher plasticity and improved anti-pulverization ability. In the mean time, the difference of the equilibrium hydrogen pressure between LaNi4 Co and LaNi5 was analyzed in the electronic level. The analysis shows that the strength of the weakest bond net in octahedron lattice interstices of LaNi4 Co is much lower than that in LaNi5; consequently,LaNi4Co’s bond net easily deforms to accommodate hydrogen so that LaNi4 Co has lower equilibrium hydrogen pressure in comparison with LaNi5. The results can provide some theory guide on the design of hydrogen storage alloys.     

碳纳米管对LaNi5稀土合金电化学性能的影响

采用LaNi5稀土合金作为催化剂，用化学气相沉积法(CVD)制备了碳纳米管。研究了含有5％碳纳米管的LaNi5稀土合金电极样品的电化学性能。测定了碳纳米管电极的电化学储氢性能。实验发现：含有碳纳米管的LaNi5稀土合金的电化学放电容量更高，当放电电流密度为100mA／g时，其电化学储氢量高达385mAh／g。其循环寿命也得到了较大改善。循环100次，放电容量仅下降15％。     

Electrochemical and mechanical behaviour of Sn‐2.5Ag‐0.5Cu and Sn‐48Bi‐2Zn solders

In this paper, two tin‐based alloys (Sn‐2.5Ag‐0.5Cu and Sn‐48Bi‐2Zn) are proposed as new lead‐free solders. Alloys have been developed by melting pure elements. Samples have been evaluated in terms of microstructure, corrosion resistance and mechanical features. Corrosion tests have been performed in 3% NaCl solution by polarization curves and electrochemical impedance spectroscopy (EIS). SEM observations and EDS analysis were carried out on samples before and after corrosion tests. Static monotonic tensile tests have been performed on three specimens for each alloy. SEM and EDS analysis revealed the presence of Sn‐Ag and Sn‐Cu intermetallic compounds within the Sn‐Ag‐Cu alloy. As a result of corrosion test, the Sn‐Ag‐Cu alloy showed a better corrosion resistance with respect to Sn‐Bi‐Zn. Both alloys evidenced good mechanical properties higher than the traditional Sn‐Pb system. Sn‐Ag‐Cu seems to be a suitable soldering material.     

TbMn6—xCoxSn6赝三元化合物的结构和磁性

本文研究了ＴｂＭｎ６－ｘＣｏｘＳｎ和赝三元化合物的结构和磁性，结果表明：用Ｃｏ部分取代ＴｂＭｎ６Ｓｎ６中的Ｍｎ不改变其晶体结构，但随Ｃｏ含量的增加晶格常数和单胞体积单调减小；居里温度随Ｃｏ含昨增大而降低；自旋重取向温度也随Ｃｏ含量增大而降低，但Ｃｏ含≥０．６时自旋重取向消失；     

Effect of Manganese substitution on hydrogen storage properties of LaNi4.25-xAl0.75Mnx alloy

The effect of Mn substitution on phase structure, hydrogen hydriding/dehydriding properties (plateau pressure and slope) and reaction heat enthalpy of LaNi4.25-xAl0.75Mnx alloys (x=0, 0.25, 0.35, 0.45, 0.55 and 0.65) were studied.The experimental results show that all LaNi4.25-xAl0.75Mnx alloys have single phase and have the same hexagonal structure as that of LaNi5 alloy (CaCu5 type, P6/mmm).With increasing Mn substitution content, the cell parameters of LaNi4.25-xAl0.75Mnx alloy greatly increase, but the maximum hydrogen storage capacity and the equilibrium absorption pressure of LaNi4.25-xAl0.75Mnx alloy decrease from 1.38 wt.% to 1.18 wt.% and from 1.61 to 0.0712 MPa, respectively.Moreover, the hydrogen pressure plateau slope factor σ increases from 0.014 to 0.18, but the hysteresis factor is nearly constant.The heat enthalpy absolute value |ΔHplat| increases from 46.7 kJ·mol-1 H2 to 56.1 kJ·mol-1 H2 as the Mn content x increases from 0 to 0.65.     

~(199)Sn AND ~(57)Fe MOSSBAUER SPECTROSCOPIC STUDY OF THE MECHANICALLY ALLOYED Fe-Sn ALLOYS

1.IntroductionMechanicalalloyinghasbeenwelldevelopedasapowerfultechniqueofsolidstatere-artiontosynthesizealloysfarfromequilibrium,suchasamorphous,quasicrystajlineandnanocrystajlinealloys,etc.II--3].InFe-Snsystem,alltheiron-stannidesareferromagneticatroomtemperatureI4],thereforetheevolutionofmechanicalalloyinganddetailedchemicaldrirmationcanbeobtainedfromboththe57Feand119SnMossbauerspectraandcorre-spondinghyperfineparameters.The57Feand119SnMossbauerstudyofFe3Snpowdersbailaflledfor400hshowe…