V对贮氢合金微观结构和电化学性能的影响

为了开发AB5型稀土系低Co贮氢合金，研究了加V低Co贮氢合金M／Ni3．55Co0.3Mn0.4Al0．25Cu0．15Fe0.1Cr0.1Zn0.13Vx（x=0．02，0．05，0．08）V含量变化对放电容量、循环稳定性的影响机理。结果表明，加V低钴贮氢合金可以获得良好的综合电化学性能，但V的加入应严格控制。在本研究范围内，x=0．02的加V低钴贮氢合金具有最佳的综合电化学性能。     

Al对无钴AB5型贮氢合金微观结构和电化学性能的影响

采用单辊快凝方法制备了过化学计量比稀土贮氢合金La(NiMn)α-xAlx(5<α<6,x为0~0.5),研究了Al含量及淬速对合金电极性能及微观结构的影响。结果表明:快淬过化学计量比合金相结构均为过饱和CaCu5型单相,且随Al含量的增加,合金晶胞体积呈线性增大;不同淬速条件下合金凝固组织的形貌和晶态存在明显差别。随Al含量的增加,合金电极的放电容量有所降低,但电极循环寿命得到极大改善。当x=0.3和淬速为10~15 m/s时,合金电极的最大放电容量为322和309 mA.h/g,经150次循环后,电极容量保持率分别为93.5%和95.5%。低温(400℃)退火对合金电极活化性能有所改善,但并未影响合金的循环寿命。     

贮氢合金制备工艺对其电化学性能的影响

AB5型贮氢合金是目前国内外MH／Ni电池生产中是耿广泛的负极材料，而贮氢合金的电化学性能是由合金的成分，微观结构和表面状态决定的，本文综述了AB5型贮氢合金制备工艺－熔炼，热处理以及制粉工艺对其化学性能的影响，指出制备工艺对贮氢合金的成分均匀性和微观结构影响很大，而提高贮氢合金电化学性能最有效的方法是通过合金成分优化和采用较优的制备工艺，来获得高容量，长寿命，低价格的贮氢合金。     

Fe替代Co对AB5型贮氢合金电化学性能和相结构的影响

研究了Fe替代C0对Mm（NiMnSiAl）4.3Co0.6-xFex（x=0，0．2，0．4，0．6）贮氢合金电化学性能和相结构的影响。研究结果表明：Fe替代Co使合金的放电容量降低，但使合金的循环稳定性得到改善；合金具有双相结构，主相为CaCu5型相，还有少量的第二相Ce2Ni7相，随着Fc替代量的增加，第二相没有明显变化，但合金的点阵常数和晶胞体积略有增加，这是Fe替代Co使合金循环稳定性得以改善的一个主要原因。     

钐对无钴AB5型稀土贮氢合金微观结构和电化学性能的影响

用真空感应熔炼铸锭以及快淬工艺制备过化学计量比无钴AB5型稀土贮氢合金La0.85-xCe0.15 SmxNi4.55 Mn0.40Al0.30和La0.69Ce0.31-xSmxNi4.55Mn0.40Al0.30(x=0,0.08,0.16).研究了钐含量及快淬对无钴AB5型稀土贮氢合金的微观结构、吸放氢性能、电化...     

冷却速度时Ml（NiCoMoTi）5贮氢合金电化学性能的影响

对不同冷却速度下制成的具有同一成分的贮氢合金做了电化学充放电循环实验,比较了它们的容量、电化学循环稳定性及放电电压性能。高的冷却速度导致放电容量的特别是大电流放电容量较大幅度下降,活化困难,放电电压也有所降低,但改善了合金的循环稳定性及放电电压平台特性。     

热处理温度对AB5型MlNi3.60Co0.85Mn0.40Al0.15贮氢电极合金的微结构和电化学性能

研究了铸态及经加热温度为1273－1373K、保温时间8h和水冷处理后AB5型MlNi3.60Co0.85Mn0.40Al0.15贮氢电极合金的微结构和电化学性能。结果表明：铸态合金的显微组织是典型的树枝晶结构,经1273K处理后合金的显微组织仍为树枝晶,但树枝结构不明显,经1373K处理后合金的显微组织为柱状晶;与铸态合金相比,经1273K处理后合金的活化性能降低,电化学容量和高倍率放电性能基本保护不变,循环寿命改善;经1373K处理的合金活化性能降低,电化学容量明显减上,高倍率放电性能降低,循环寿命显著改善。热处理引起合金电化学性能的变化与合金的微结构的改变有关。     

稀土氧化物对贮氢合金电极电化学性能的影响

研究了稀土氧化物La_2O3_,CeO_2,Nd_2O_3和Y_2O_3对AB_5型贮氢电极电化学性能的影响。研究表明,除Y2_O3_外,其余的稀土氧化物可提高贮氢电极的1C放电容量和放电电压,延长贮氢电极的循环寿命,且对贮氢电极性能有利的顺序为:La2_O3_>CeO2_>Nd2_O3_;稀土氧化物添加量越多,贮氢电极的循环稳定性越好,但对贮氢电极的1C放电容量和放电电压的影响存在最佳值。造成这些结果的原因是:稀土氧化物增大贮氢合金颗粒间的接触电阻;稀土氧化物的催化作用;稀土氧化物对镍催化剂的稳定作用及抑制贮氢合金进一步氧化的作用。     

高性能AB5型贮氢合金的成分设计

贮氢合金是MH-Ni电池技术的核心，则其化学成分是决定贮氢合金性能的主要因素，在分析MH-Ni电池对负极材料的性能要求及电极失效机理的基础上，详细讨论了AB5型贮氢合金的主要电化学性能与各种合金元素之间的关系，提出了高性能AB5型贮氢合金成分设计的总体思路和应考虑的各种因素。     

稀土钐对AZ61合金组织和性能的影响

采用XRD、OM和SEM等手段研究了稀土钐(0~2.0wt%)对AZ61合金显微组织和力学性能的影响。结果表明,稀土Sm可以显著提高时效态合金从室温至175℃区间的抗拉强度和屈服强度。在AZ61合金中加入0.5wt%~2.0wt%的Sm后,合金的显微组织得到细化,Sm优先与A1形成高熔点Al2Sm弥散相。在研究范围内,加入1.5wt%Sm的合金从组织到各项力学性能最优。     

Effects of Sm addition on microstructure and mechanical properties of a Mg-10Y alloy简

To further increase the mechanical properties, 0.5wt.% Sm was introduced to a Mg-10Y alloy in this study. The effects of Sm addition on the microstructures and mechanical properties of the Mg-10Y alloy, especially the aged Mg-10Y alloy, were investigated. The microstructure observation and tensile tests were performed by using an optical microscopy, a scanning electron microscopy and a universal material testing machine, respectively. The phase analysis was performed using X-ray diffractometer. The results show that the 0.5wt.% Sm addition can not only promote the formation of fine and dispersed Mg24Y5 phases, but also improve their morphology and distribution; it also increases the thermal stability of Mg24Y5 phases. Sm addition is seen to increase the ultimate tensile strength of Mg-10Y alloy at elevated temperatures(200, 250, 300 and 350 ℃), while decrease the elongation. But the elongation is still up to 7.5% even at 350 ℃. In the range of 250 ℃ to 300℃, the ultimate tensile strength of the alloy reaches its maximum(with a range average of 235 MPa) and is not sensitive to the temperature change, which is very useful to the application of heat-resistant magnesium alloys. Even at 350 ℃, the ultimate tensile strength of Mg-10Y-0.5Sm is still up to 155 MPa. Considering both of the ultimate tensile strength and elongation, the maximum application temperature of the Mg-10Y-0.5Sm alloy can be up to 300 ℃. The strengthening mechanisms of Mg-10Y-0.5Sm alloy are mainly attributed to dispersion strengthening of Mg24Y5 phase particles with a certain solubility of Sm and grain refinement strengthening of α-Mg matrix.     

Effects of annealing treatment on the microstructure and electrochemical properties of low-Co hydrogen storage alloys containing Cu and Fe

The effects of annealing treatment on the microstructure and electrochemical properties of low-Co LaNi_3.55Mn_0.35Co_0.20Al_0.20Cu_0.75Fe_0.10 hydrogen storage alloys were investigated. X-ray diffraction (XRD) analysis indicated that annealing treatment remarkably reduced the lattice strain and defects, and increased the unit-cell volume. The optical microscope analysis showed that the as-cast alloy had a crass dendrite microstructure with noticeable composition segregation, which gradually disappeared with increasing annealing temperature, and the microstructure changed to an equiaxed structure after annealing the alloy at 1233 K. The electrochemical tests indicated that the annealed alloys demonstrated much better cycling stability compared with the as-cast one. The capacity retention at the 100th cycle increased from 90.0% (as-cast) to 94.7% (1273 K). The annealing treatment also improved the discharge capacity. However, the high rate dischargeability (HRD) value of the annealed alloy slightly dropped, which was believed to be ascribed to the decreased exchange current density and the hydrogen diffusion coefficient in alloy bulk.     

Effects of annealing treatment on the microstructure and electrochemical properties of low-Co hydrogen storage alloys containing Cu and Fe

The effects of annealing treatment on the microstructure and electrochemical properties of low-Co LaNi3.55Mno.35Co0.20Al0.20Cuo.75Fe0.10 hydrogen storage alloys were investigated.X-ray diffraction (XRD) analysis indicated that annealing treatment remarkably reduced the lattice strain and defects,and increased the unit-cell volume.The optical microscope analysis showed that the as-cast alloy had a crass dendrite microstructure with noticeable composition segregation,which gradually disappeared with increasing annealing temperature,and the microstructure changed to an equiaxed structure after annealing the alloy at 1233 K.The electrochemical tests indicated that the annealed alloys demonstrated much better cycling stability compared with the as-cast one.The capacity retention at the 100th cycle increased from 90.0％(as-cast) to 94.7％ (1273 K).The annealing treatment also improved the discharge capacity.However,the high rate dischargeability (HRD)value of the annealed alloy slightly dropped,which was believed to be ascribed to the decreased exchange current density and the hydrogen diffusion coefficient in alloy bulk.     

Effect of Dy addition on microstructure and mechanical properties of Mg-4Y-3Nd-0.4Zr alloy

Minor Dy element was added into a Mg-4Y-3Nd-0.4Zr alloy, and its effects on the microstructure and the mechanical properties at elevated temperatures were investigated. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to observe the microstructures. The results indicated that the as-cast eutectic and isolated cuboid-shaped Mg-RE phases were Mg₅RE and Mg₃RE₁₇, respectively, and distributed mainly along grain boundaries. After a solution treatment, the eutectic Mg₅RE phases were dissolved into the matrix, whereas the Mg₃RE₁₇ compound still remained. After peak aging, fine Mg-RE phases were precipitated homogeneously within the matrix of the alloys containing Dy. Dy addition can result in a significant improvement in the tensile strength at both room and elevated temperatures, and a slight decrease in the elongation.     

Sm、Sb合金化对AZ61组织和性能影响的研究

研究了铸态AZ61-1Sm-xSb合金,并对其进行了热挤压和时效处理（T5）。结果表明,AZ61-1Sm-xSb合金的主要合金相为β-Mg17Al12、Al2Sm、Al3Sm及SbSm。与AZ61相比,AZ61-1Sm中的Mg17Al12相呈现不连续分布的特征;而在AZ61-1Sm中添加Sb,Mg17Al12不连续分布特征更加明显,并且出现针状SbSm相,当 Sb添加量为1.5wt%时出现大块状SbSm相,而β-Mg17Al12、Al2Sm、Al3Sm均为颗粒状并呈弥散分布。Sm和Sb的添加能提高AZ61合金挤压和时效态合金力学性能,而在AZ61-1Sm合金中添加Sb元素能显著提高合金的高温强度。     

Effect of commercial AB5 alloy addition on the electrochemical properties of Ml-Mg-Ni-based hydrogen storage alloys

A commercial AB5 hydrogen storage alloy was used as an additive to improve the electrochemical properties of Ml-Mg-Ni-based hydrogen storage alloys.The effect of AB5 alloy addition on the phase structure,charge/discharge characteristics,and electrochemical kinetics of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 alloy was investigated.The maximum discharge capacity of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 + 4 wt.% AB5 electrode reaches 406 mAh/g.The anodic polarization,cyclic voltammetry,and potential step discharge experiments show that the electrochemical kinetics of the electrode with additives was promoted,with the LaNi5 phase of AB5 alloy acting as electro-catalytic sites in the electrode alloy.The high-rate dischargeability of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 + 4 wt.% AB5 alloy electrode at 1100 mA/g reaches 60.9%,which is 9.4% higher than that of Ml0.90Mg0.10Ni3.08Mn0.13Co0.63Al0.14 alloy electrode.The cycling stability of the electrode with 4 wt.% AB5 alloy has also been improved.     

Sm和Sb对时效态Mg-12Gd-2Y-0.5Zr合金组织与力学性能的影响

通过SF6+CO2气体保护,在大气环境下制备了Mg-12Gd-2Y-(0.5Sm,0.5Sb)-0.5Zr镁合金,采用OM、SEM、XRD和TEM等手段研究了20～300℃下时效态合金的显微组织和力学性能。结果表明:随Sm、Sb的加入,试验合金晶粒细化,合金屈服强度提高。随实验温度升高,屈服强度略微降低,抗拉强度提高。该合金具有抗拉强度的温度效应。断口分析表明,合金具有沿晶断裂+局部解理断裂的混合断口特征。