W掺杂对Nb固溶体抗氢脆及透氢性能的改性研究

元素掺杂是消除Nb金属氢脆问题的有效方法。本文制备了W掺杂的Nb100-xWx (x=2,5,8,10,16)合金，采用XRD、SEM、Sieverts 气体吸附技术、电化学方法和三点弯曲试验研究了掺杂量对合金结构、氢化物形成焓、氢扩散系数和抗氢脆机械力学性能的影响。研究证实，熔炼制备Nb100-xWx为Nb-bcc结构的固溶体合金，W掺杂引起晶体结构畸变收缩，其畸变行为随掺杂量增大更为明显。Nb基固溶体在匀晶转变时存在非平衡转变，形成富W和贫W区相间分散的枝状结晶形貌。随W掺杂量增大，其枝状结构趋于更加细化和致密、分界明显。W掺杂引起合金的氢化物形成焓增大、有利于H原子的释放，Nb84W16合金样品具有最大的氢扩散系数（1.66×10-9 cm2·s-1），约是Nb98W2合金的1.8倍。W掺杂提高Nb100-xWx固溶体合金的抗氢脆性能，Nb84W16合金膜有最大的临界载荷值（78.4N）和最大位移量（0.83mm），分别是Nb98W2合金膜的1.9倍和1.8倍，力学性能的改善与其枝状结晶结构有关。     

Investigation of the isothermal section of the Ce-Co-Al ternary system at 573 K

The isothermal section of the Ce-Co-Al ternary system at 573 K was investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques. It consisted of 19 single-phase regions, 46 two-phase regions and 25 three-phase regions. Four ternary compounds, namely CeCoAl, Ce2Co15Al2, CeCoAl4, CeCo2Al8, were confirmed in this system. At 573 K, the maximum solid solubilities of Co in CeAl2 and Al in CeCo2 were about 10.4 at.% and 10.0 at.%, resp...     

锂离子电池负极材料 Na2Li2Ti6O14的嵌脱锂过程动力学研究

为了研究钛酸钠锂(Na2Li2Ti6O14)负极材料嵌脱锂的动力学行为,用溶胶-凝胶法合成 Na2Li2Ti6O14负极材料,采用 X 射线衍射法(XRD)和电子显微镜(SEM)分别对材料进行物相分析和微观形貌的观察.采用恒流充放电测试、循环伏安法(CV)和恒电流间歇滴定法(GITT)研究了 Na2Li2Ti6O14的电化学性能和嵌脱锂过程动力学.研究结果表明,制备的 Na2Li2Ti6O14材料纯度高,结晶度良好,循环稳定性好;由不同扫描速率的循环伏安法测出的 Na2Li2Ti6O14中锂离子在氧化、还原峰对应的化学扩散系数 Da和 Dc分别为7.3×10-11和7.8×10-11cm2/s;由恒电流间歇滴定技术测得的锂离子在 Na2Li2Ti6O14电极中的扩散系数为10-11~10-8cm2/s.     

Effect of rapid solidification treatment on structure and electrochemical performance of low-Co AB5-type hydrogen storage alloy

The effect of rapid solidification on structure and electrochemical performance of the LaNi4.5Co0.25Al0.25 hydrogen storage alloy was investigated by X-ray powder diffraction and a simulated battery test, including maximum capacity, cycling stability, self-discharge, and high-rate discharge ability （HRD）. All the melt-spun alloys were single-phase with the CaCu5-type structure （space groupP6/mmm）. In comparison to the as-cast alloy, the rapidly quenched alloys manifested an improved homogeneity of com-position and expanded lattice parameters. The electrochemical measurements showed that the activation property, cycling stability and self-discharge of the alloy electrodes were also improved for the rapid solidified alloys. The HRDof the as-cast alloy was better than those of all the rapidly solidified alloys. As the quenching rate increased, the HRD and exchange current density first decreased and then increased.     

基于DFTB法的碳纳米管(CNT)储氢机理的探讨

碳纳米结构材料(C60,CNT)被认为是氢能的主要载体而备受关注,但近几年来的报道不尽一致.基于DFTB分析法,结合相关的研究成果,从氢与碳纳米结构的原子相互作用入手,探讨CNT储氢的可行性,并介绍了氢化的C60-H 和CNT-H 结构和电化学特性.理论分析表明,H2分子直接穿透碳结构网进入内部(C60笼,碳纳米管)的趋势受到来自碳纳米结构本身势垒的抑制,而通过转换极性,利用电化学的方式储存与释放氢气是可行的.     

Nb90W5M5三元固溶体合金的结构和氢渗透性能

合金化是改善Nb金属氢脆问题的有效途径。本文制备了Nb90W5M5三元(M=Co,Ni,Mo,Ti)合金,利用XRD、SEM、PCT、电化学测试和三点弯曲试验研究其相结构、氢化物形成焓、氢扩散系数和机械力学性能。研究证实,Nb90W5M5(M=Co,Ni,Mo,Ti)均为Nb基固溶体结构(Nb-bcc),受原子半径的影响,Nb90W5M5三元合金均有不同程度的晶格畸变现象。Nb90W5Co5合金的晶胞体积畸变收缩明显、晶格点阵常数最小,在Nb基固溶体的晶界和晶内缺陷处有富Co的NbCo化合物固溶组织析出。Nb90W5Co5合金具有低的氢化物形成焓绝对值(-22.3 kJ/mol)、高的氢扩散系数(1.57×10-9 cm^2/s)、高临界载荷(78.4 N),表现出良好的抗弯力学性能和氢渗透性能,这与其多元掺杂导致的微观结构特征有关。     

不同放电深度下LaNi3.8Co0.6Mn0.3Al0.3合金的电化学行为研究

为了分析储氢合金放电过程中的电化学反应与动力学变化规律,采用电化学交流阻抗分析方法研究 La-Ni3.8Co0.6Mn0.3Al0.3合金电极在不同放电深度下的电化学行为.结果表明:随着放电深度的增加,电极表面活性氢覆盖面积S 及内部金属颗粒间接触电阻Rpp逐渐降低,即电极的导电性增加;此外,交换电流密度Io也随放电深度增加而增大,意味着电极表面反应速率加快,同时氢扩散系数 DH 明显降低;合金电极动力学在放电前期主要由电极表面反应速率控制,后期由电极中氢原子在合金颗粒内部的氢扩散系数控制.     

Isothermal section of Gd-Sm-Co ternary system at 773 K

The isothermal section of the phase diagram of the Gd-Sm-Co ternary system at 773K was investigated by X-ray powder diffraction(XRD),differential thermal analysis(DTA),optical microscopy and scanning electron microscopy(SEM) techniques.The result shows that the isothermal section consists of 12 single-phase regions,16 two-phase regions and 5 three-phase regions.Five pairs of corresponding compounds of Gd-Co and Sm-Co systems,i.e.,Gd2Co17 and Sm2Co17,Gd2Co7 and Sm2Co7,GdCo3 and SmCo3,GdCo2 and SmCo2,Gd3Co and SmCo form continuous series of solid solutions.The maximum solid solubility of Sm in Gd 4Co3 and Gd12Co7 were about 7.2 at.% and 47.8 at.% Sm,respectively.The maximum solid solubility of Gd in Sm5Co19 and Sm5Co2 were about 4.7 at.% and 7.6 at.% Gd,respectively.The binary compounds Sm9Co4,GdCo5 and SmCo5 were not observed at 773K.No ternary compound was found.     

Crystal structure and magnetic behavior of the La0.1Bi0.9FeO3 compound

The nano-crystalline La_(0.1)Bi_(0.9)FeO_3 compound was successfully synthesized by starch-based combustion method. The crystal structure and magnetic behavior were studied by temperature-dependent X-ray diffraction(XRD), scanning electron microscopy(SEM), differential scanning calorimetry(DSC) and magnetic measurements. The La_(0.1)Bi_(0.9)FeO_3 compounds crystallized in a rhombohedrally distorted perovskite structure with space group R3 c. The substitution of La for Bi reduced the rhombohedral distortion. The structural phase transitions in La_(0.1)Bi_(0.9)FeO_3 driven by temperature showed that the extraordinary two-phase coexistence state of BiF eO 3 and LaF eO 3 was observed in a narrow temperature range of 630–700 oC. The magnetization of the La_(0.1)Bi_(0.9)FeO_3 sample was improved by heat treatment in the temperature range. When the heat treatment temperatures rose from 25 to 600 oC, the remanence(Mr) and coercivity(Hc) of the La_(0.1)Bi_(0.9)FeO_3 compound almost remained the same, and increased rapidly to 0.134 emu/g and 7.1 KOe on further increasing the heat treatment temperature to 650 oC.     

高能球磨处理的NdMgNi4金属间化合物的储氢特性

用高能球磨法处理单相NdMgNi4金属间化合物,研究了球磨时间对化合物结构和储氢特性的影响。XRD、SEM等分析证实,单相NdMgNi4金属间化合物在球磨过程中发生了由晶态到非晶态的转变。经20 h的球磨处理后基本转变为非晶态的NdMgNi4金属间化合物。电极测试结果表明,球磨NdMgNi4金属间化合物的电极性能(放电容量、循环稳定性)与球磨引起的晶态转变程度密切相关。非晶态NdMgNi4金属间化合物优于晶态NdMgNi4金属间化合物。与相同球磨条件处理的Mg2Ni化合物相比,虽二者初始放电容量相当(约380 mAh/g),但前者循环性能得到明显改善。