新型稀土镁基贮氢电极合金的结构与性能

系统研究了La0．7Mg0．3(Ni0．85Co0.15)x(x=2．5，3．0，3．5，4．0，4．5，5．0)贮氢电极合金的结构和储氢性能．该类型合金由(La，Mg)Ni3相(PuNi3型结构)和LaNi5相(CaCu5型结构)组成，两相的a轴参数和晶胞体积都随着x值的增大而减小．(La，Mg)Ni3相的丰度先从x=2．5时的48．4％增加到x=3．5时的78．2％，然后又减小到x=5．0时的12．2％，而LaNi5相的丰度在x=2．5-3．5时基本保持不变(-20％)，在x=4．0时突然增加到71.9％．合金的吸氢量从x=2．5时的0．86％(质量分数)增加到x=3．5时的1．50％然后又减小到x=5．0时的1．19％．合金的放氢平台压力在x=2．5-3．5时保持基本不变(-65．9kPa)，然后逐渐增加到x=5．0时的0．30MPa．随着x的增加，吸放氢过程的滞后效应先增大后减小，而合金的放氢平台变得更加平坦．     

球磨La2Mg17与Ni复合合金的电化学贮氢性能研究

利用机械合金化法制备了La2Mg17+200%(质量分数)Ni复合储氢合金,并对不同球磨时间时合金的微观结构和电化学性能进行研究。结果发现,在球磨过程中Ni粉诱导了La-Mg-Ni非晶/纳米晶结构的形成。XRD和HRTEM结果共同表征了球磨80h时,合金中有Ni金属的存在,且XRD衍射峰强度较低,宽化严重,SAD为宽化的多环,表明形成非晶结构。电化学及其反应动力学测试结果发现,不同球磨时间的电化学反应的动力学控制机理是不同的。球磨60和80h后合金中不仅存在La-Mg-Ni非晶相,同时也有催化剂金属Ni,使合金的表面电荷转移反应电阻较小,氢在合金体相内的扩散系数D和极限电流密度I L均最大,最终导致80h的放电容量为最大值948.3mAh/g。然而,当合金的球磨时间为100和120h时,合金粉化到纳米级,100h的电荷转移反应电阻R ct最大,合金表面电化学反应缓慢,且合金体相内的极限电流密度和氢扩散系数均最小,属于合金电解液表面间的电荷转移和氢向体相内扩散联合控制的过程,必然导致其放电比容量较小。     

ZrTi-V-Mn-Ni系贮氢合金的相结构与电化学性能研究*

优化合金组成,设计六种锆基AB2型贮氢合金材料。XRD分析表明,当0≤x≤0.5时,Zr1-xTix(NiCoMnV)2.1贮氢合金的主相都是Laves C15,但随Ti含量的增加,Laves C14相含量增多;当用V-Fe(85.6%)合金代替Zr0.6Ti0.4(NiCoMn-VFeCr)1.7中的V时,贮氢合金中Laves C14相的含量几乎可与Laves C15相当。电化学测试表明：Zr0.9Ti0.1(NiCoMnV)2.1贮氢电极的放电容量可达340mAh/g左右,但是随着Ti含量的逐渐增加,合金电极的放电容量降低很快。以适量的（V－Fe)合金取代Zr0.6Ti0.4(NiCoMnVFeCr)1.7合金中的V和Fe,发现合金电极的第一次放电容量就能达到200mAh/g左右,并且其容量稍高于含纯V的合金电极,容量可达315mAh/g左右。     

Mo对A2B7型La-Mg-Ni贮氢电极合金相结构及电化学性能的影响

采用X射线衍射技术(XRD)、电池程控测试仪和电化学工作站等技术手段,研究了少量Mo替换Ni对La0.75-Mg0.25Ni3.5-xMox(x=0~0.5,原子分数/%,下同)贮氢电极合金相结构及电化学性能的影响。结果表明:La0.75Mg0.25-Ni3.5-xMox合金具有多相结构,主相由Gd2Ni7型结构的La2Ni7和CaCu5型结构的LaNi5构成,合金活化性能良好,经过4次充放电过程基本都能达到活化状态。当Mo的加入量达到0.3%时,合金中出现MoNi4,且La2Ni7和LaNi5的点阵参数随之增大;合金的高倍率放电(HRD)性能显著提高,HRDI=900mA/g由82.58%(x=0)增加到86.72%(x=0.5);循环稳定性能(S100)也得到较大改善,呈现先增加后降低的变化趋势,x=0.3时循环稳定性能最好,S100达到76.61%,但合金的最大放电比容量(Cmax)逐渐降低。     

La0.67Mg0.33Ni3.0-xAlx(x=0～0.3)贮氢合金的相结构及电化学性能的研究

研究了Al元素对合金La0．67Mg0．33Ni3．0中Ni的替代对舍金的微观组织结构及电化学性能的影响。X射线衍射(XRD)分析结果表明La0．67Mg0．33Ni3．0合金由PuNi3型(La，Mg)Ni3相和Ce2Ni2型(La，Mg)2Ni7相组成，Al元素加入后，开始出现CaCu5型LaNi5相，随着Al含量的增加，LaNi5相逐渐增多，当x=0．3时，LaNi5相成为合金的主相，合金La0．67Mg0．33Ni3．0中Al的X荧光元素面分布图像表明了Al元素主要进入LaNi5相中，说明Al是一种LaNi5相形成元素；电化学测试表明，随着Al含量的增加，合金的最大放电容量依次下降，4种合金的最大放电量分别为392、324、267和252mAh／g，活化次数变化不大(2～3次即可活化)，循环稳定性先增加后下降。     

快淬对AB2型贮氢合金电化学性能与微观结构的影响

为了改善AB2型Laves相贮氢合金的电化学性能,对AB2型Ti基及Ti-Zr基贮氢合金进行快淬处理。用XRD和SEM分析了铸态及快淬态合金的相结构,并观察了合金的微观组织形貌。研究了快淬工艺参数对AB2型Laves相贮氢合金的电化学性能及微观结构的影响。研究的结果表明快淬对AB2型Laves相贮氢合金电化学性能的影响与合金的成分密切相关。对Ti基合金,随淬速的增加,合金的容量显著提高,在一定淬速下出现极大值。快淬对合金的活化性能基本没有影响,合金的循环稳定性有所改善但不显著;对Ti-Zr基合金,随淬速增加,合金的循环稳定性得到大幅度提高,而合金的容量及活化性能明显降低。快淬使AB2型贮氢合金电化学性能发生变化的根本原因是合金的微观结构发生了变化。     

机械合金化制备Mg76-xTi12Ni12Mnx（x=2,4,6,8）合金及其贮氢性能研究

利用机械合金化法制备了Mg76-xTi12Ni12Mnx(x=2,4,6,8)合金,并研究了Mn添加量对合金贮氢性能的影响。结果表明,在Mg76-xTi12Ni12Mnx(x=2,4,6,8)合金中合金相主要由Mg2Ni和Ti2Ni相组成,合金最大贮氢量分别为3.47%、3.32%、3.60%和3.11%(质量分数,下同),合金氢化物的分解热依次为-79.2kJ/mol、-78.0kJ/mol、-73.7kJ/mol和-73.6kJ/mol,添加Mn可降低合金氢化物的稳定性,改善其热力学性能,非晶化不利于提高合金的贮氢性能。     

La2Mg4-xCaxNi13贮氢合金的相结构与电化学性能

以La2Mg4-xCaxNi13合金为基础，研究了Ca部分替代Mg对合金相结构和电化学性能的影响。XRD和Rietveld分析表明，随ca替代量的增加，合金中MgNi2相含量逐渐减少，（La，Ca，Mg）Ni3相含量则先增加后减少；同时，ca的添加改变了La2Mg4-xCaxNi13合金中主相的晶格常数。电化学测试表明，ca部分替代Mg能够大幅提高合金电极的放电容量，其中La2Mg4-xCaxNi13合金具有最大的放电容量350．5mAh／g。     

La1.5Mg0.5Ni7-xCox(x=0～1.8)贮氢合金结构和电化学性能研究

La1.5Mg0.5Ni7-xCox(x=0～1.8)贮氢合金电极由高频感应熔炼加热处理制备得到.合金结构分析表明,合金主相为Ce2Ni7型结构,Mg原子分布在Ce2Ni7型单胞结构的Laves相单元中,而Co原子则分布在CaCu5单元中.随着合金中Co含量的增多,点阵参数和单胞体积呈增大趋势,氢化物变的更加稳定.合金的吸放氢平台在298K条件下介于1.01×103～1.01×104Pa之间,吸放氢滞后效应较小.合金电极的电化学分析表明合金具有390mAh/g以上的放电容量和良好的活化特性,Co元素不利于合金电极循环稳定性的改善,氢在合金中的扩散是电极反应的控制步骤.La1.5Mg0.5Ni7.0合金电极表现出较好的综合电化学性能.     

烧结工艺对贮氢合金La0.67Mg0.33Ni2.5Co0.5的微观组织结构及电化学性能影响的研究

系统研究了固相反应烧结方法制备La0.67Mg0.33Ni2.5Co0.5贮氢合金的烧结工艺对该合金的微观组织结构及电化学性能的影响规律.分析和研究了合金的微观组织结构、电化学放电性能及Mg含量的挥发损失问题.XRD和SEM及EPMA分析结果表明,在不同烧结条件下合金均由不合Mg的LaNi5相、富Mg的LaNi3相及一个贫Mg的LaNix(x=3.0～3.8)相三相组成.当烧结温度不超过1203k时合金主相为LaNi3相,当烧结温度超过1203K,LaNi5相逐步成为主相.原子吸收光谱分析结果表明,烧结温度不超过1203K,Mg元素没有明显损失;当烧结温度超过1203K,会引起Mg的大量挥发损失.电化学性能分析结果表明,烧结温度不超过1203K,合金放电能力主要受合金组织形成与均匀性影响;而烧结温度超过1203K,Mg元素挥发损失成为影响合金放电能力的决定因素.烧结条件为873～1123k保持24h、1203k保持2h,是制备La0.67Mg0.33Ni2 5Co0.5贮氢合金的适宜工艺.用该工艺制备的La0 67Mg0.33Ni2.5Co0.5贮氢合金Mg含量稳定(2.92%质量分数)、微观组织均匀、放电容量高(395mAh/g)、活化性能好(2个循环).     

Anomalous isotope effect for hydrogen absorption in La0.4Ce0.6Ni5

An anomalously large isotope effect associated with the absorption of hydrogen and deuterium was observed in La_.4Ce_.6Ni₅. The isotope effect is strongly temperature dependent with a cross-over occurring below room temperature.     

Dielectric Properties of Ba0.6Sr0.4TiO3-La(B0.5Ti0.5)O3 (B=Mg, Zn) Ceramics

Ba_0.6Sr_0.4TiO₃-La(B_0.5Ti_0.5)O₃ (B = Mg, Zn) ceramics were prepared by a solid-state reaction method, and their microwave dielectric characteristics and tunability were investigated. The ferroelectric-dielectric solid solutions with cubic perovskite structures were obtained for compositions of 10 to 60 mol% La(Mg_0.5Ti_0.5)O₃ and 10 to 50 mol% La(Zn_0.5Ti_0.5)O₃. With the increase of linear oxide dielectric content, the dielectric constant and tunability were decreased and Qf was increased. Ba_0.6Sr_0.4TiO₃-La(Mg_0.5Ti_0.5)O₃ has better dielectric properties than Ba_0.6Sr_0.4TiO₃-La(Zn_0.5Ti_0.5)O₃. 0.9Ba_0.6Sr_0.4TiO₃-0.1La(Mg_0.5Ti_0.5)O₃ has a dielectric constant ε = 338.2, Qf = 979 GHz and a tunability of was 3.7% at 100 kHz under 1.67 kV/mm. The Qf value of 0.5Ba_0.6Sr_0.4TiO₃- 0.5La(Mg_0.5Ti_0.5)O₃ reached 9367 GHz, but the tunable properties were lost.     

Dielectric properties of Ba0.6Sr0.4TiO3-Sr(Ga0.5Ta0.5)O3 solid solutions

Ba_0.6Sr_0.4TiO₃-Sr(Ga_0.5Ta,sub>0.5)O₃ solid solutions are prepared by a solid-state reaction method, and their dielectric and tunable characteristics are investigated. The solid solutions with cubic perovskite structures are obtained for compositions of 10-50 mol% Sr(Ga_0.5Ta_0.5)O₃. It is observed that the addition of Sr(Ga_0.5Ta_0.5)O₃ into Ba_0.6Sr,sub>0.4TiO₃ causes a shift in the phase transition peak to a lower temperature. Ba_0.6Sr_0.4TiO₃-Sr(Ga_0.5Ta,sub>0.5)O₃ solid solutions exhibit depressed and broadened phase transition peaks, resulting in decreased dielectric constants and dielectric losses at room temperature. With the increase of Sr(Ga_0.5Ta_0.5)O₃ content, the dielectric constant, loss tangent, and tunability are decreased. 0.9Ba_0.6Sr_0.4TiO₃-0.1Sr(Ga_0.5Ta,sub>0.5)O₃ has a dielectric constant ϵ = 534 and a tunability of 16% at 100 kHz under 2.63 kV/mm. The dielectric characteristics of Ba_0.6Sr_0.4TiO₃-Sr(Ga_0.5Ta,sub>0.5)O₃ ceramics at microwave frequencies are also evaluated.     

Sol-gel synthesis of lead-free (K0.5Bi0.5)0.4Ba0.6TiO3 nanorods

A kind of lead-free ferroelectric nanorods, (K_0.5Bi_0.5)_0.4Ba_0.6TiO₃, has been prepared by the sol-gel process. The phase formation, structure and morphological analyses of (K_0.5Bi_0.5)_0.4Ba_0.6TiO₃ were investigated by XRD, FTIR, Raman and TEM. The results revealed that single-crystalline (K_0.5Bi_0.5)_0.4Ba_0.6TiO₃ nanorods with width around 80 to 120 nm, and length around 200-300 nm were obtained by calcining dried gels at 800 °C for 2 h. Raman analysis of (K_0.5Bi_0.5)_0.4Ba_0.6TiO₃ nanorods indicated that A₁(TO₂) and E(TO) mode incorporated into one broad peak at around 285 cm^− 1, which can be attributed to the cation disorder (Bi, K, Ba) on the 12-fold coordinated A site of ABO₃ structure.     

Thermal, spectroscopic and magnetic properties of the CoxNi1−x(SeO3)·2H2O (x = 0, 0.4, 1) phases: Crystal structure of Co0.4Ni0.6(SeO3)·2H2O

The Co_xNi_1−x(SeO₃)·2H₂O (x = 0, 0.4, 1) family of compounds has been hydrothermally synthesized under autogeneous pressure and characterized by elemental analysis, infrared and UV-vis spectroscopies and thermogravimetric and thermodiffractometric techniques. The crystal structure of Co_0.4Ni_0.6(SeO₃)·2H₂O has been solved from single-crystal X-ray diffraction data. This phase is isostructural with the M(SeO₃)·2H₂O (M = Co and Ni) minerals and crystallizes in the P2₁/n space group, with a = 6.4681(7), b = 8.7816(7), c = 7.5668(7) Å, β = 98.927(9)° and Z = 4. The crystal structure of this series of compounds consists of a three-dimensional framework formed by (SeO₃)²⁻ selenite oxoanions and edge-sharing M₂O₁₀ dimeric octahedra in which the metallic cations are coordinated by the oxygens belonging to both the selenite groups and water molecules. The diffuse reflectance spectra show the essential characteristics of Co(II) and Ni(II) cations in slightly distorted octahedral environments. The calculated values of the Dq and Racah (B and C) parameters are those habitually found for the 3d⁷ and 3d⁸ cations in octahedral coordination. The magnetic measurements indicate the existence of antiferromagnetic interactions in all the compounds. The magnetic exchange pathways involve the metal orbitals from edge-sharing dimeric octahedra and the (SeO₃)²⁻ anions which are linked to the M₂O₁₀ polyhedra in three dimensions.     

La0.67Mg0.33Ni3合金的活化性能与吸放氢动力学研究

以磁场辅助烧结法(MASS)制备的La0.67Mg0.33Ni3合金为对象,采用XRD、SEM及定容法研究了合金的相结构、微观形貌、活化能力及吸放氢动力学性能。结果显示,MASS制备的合金主相为PuNi3型结构的(La,Mg)Ni3。合金颗粒表面粗糙,呈现多孔结构。1T磁场下合成的合金经过3个循环就可完全活化,最大吸氢量达到1.47%(质量分数)。动力学测试表明,该合金在室温、1MPa氢气下50s内吸氢达到饱和;在333K、0.001MPa氢气下400s内可完成放氢,具有最佳的动力学性能,但合金可逆放氢量较低。     

Co0.5TiOPO4: Crystal structure, magnetic and electrochemical properties

The new titanium oxyphosphate Co_0.5TiPO₅ has been prepared by solid state reaction. Its structure has been determined by single crystal X-ray diffraction and was further investigated by FT-IR spectroscopy and magnetic measurements. The compound crystallizes in the monoclinic system, S.G: P2₁/c [a = 7.358(1) Å, b = 7.378(2) Å, c = 7.383(3) Å, β = 119.66(3)°, Z = 4, R₁ = 0.0142, wR₂ = 0.0429]. The structure can be described as a network of very distorted TiO₆ octahedra, in which the Ti⁴⁺ ions are displaced from the centres of the octahedra, and slightly distorted PO₄ tetrahedra. Half of the octahedral cavities are occupied by Co atoms. The other half of octahedral sites is vacant and favourable for the electrochemical insertion of lithium. The insertion of lithium was studied by galvanostatic charging and discharging between different voltage limits.     

Structure and magnetostriction of (Dy0.7Tb0.3)(0.5)Pr0.5Fex alloys (1.10 <= x <= 1.85)

The structure and magnetostriction of R0.5Pr0.5Fex, (R = Dy0.7Tb0.3, 1.10 less than or equal to x less than or equal to 1.85) alloys were investigated. It was found that the matrix of are-melting R0.5Pr0.5Fex, alloys is the (Dy, Tb, Pr) Fe-2 phase with the MgCu2-type cubic structure and the second phase is rare earth-rich phase when x<1.25. In the range of 1.40 less than or equal to x<1.55, the second phase is (Dy, Tb, Pr)Fe-3 and it becomes the main phase when x >1.55. The crystalline structure of mechanically grinding R0.5Pr0.5Fex, alloys is similar to that of the are-melted alloys. The magnetostriction of the alloys increases with increasing Fe content when x less than or equal to 1.25 and decreases when x>1.25.     

Microstructure, domain structures and ferroelectric properties in (Pb0.8,La0.1,Ca0.1)TiO3/Pb(Zr0.2,Ti0.8)O3 bilayered thin film

Ferroelectric (Pb_0.8,La_0.1,Ca_0.1)TiO₃/Pb(Zr_0.2,Ti_0.8)O₃ (PLCT/PZT) bilayered thin film was prepared on Pt(111)/Ti/SiO₂/Si(100) substrate by RF magnetron sputtering technique. Pure perovskite crystalline phase, determined by X-ray diffraction, was formed in the PLCT/PZT bilayer. The bilayered film exhibited a very dense and smooth surface morphology with a uniform grain size distribution. The ferroelectric domain structures were investigated by a combination of vertical and lateral piezoresponse force microscopy (VPFM and LPFM, respectively). It is demonstrated by both VPFM and LPFM observations that out-of-plane and in-plane lamellar ferroelectric domains coexist in the bilayered thin film. The PLCT/PZT bilayered film possesses good ferroelectric properties with relatively high spontaneous polarization (2P_s = 82 µC/cm²) and remnant polarization (2P_r = 26.2 µC/cm²).