Hydrogen storage properties of mechanically milled La2Mg17-x wt.% Ni （x=0, 50, 100, 150 and 200） composites

Melting method was used to obtain La2Mg17 alloy,and then Ni powder was added by mechanical alloying method.The kinetics of hydriding process and electrochemical properties of La2Mg17-x wt.%Ni(x=0,50,100,150,200) composites were investigated.X-ray diffraction(XRD) and scanning electron microscopy(SEM) analyses showed that the crystal structure of composite alloy gradually transformed into amorphous phase by the effect of ball milling and Ni powders.The research of hydrogen absorption properties found that La2Mg 17-50 wt.%Ni reached the highest hydrogen absorption than other alloys with more addition of Ni content,reached to 5.796 wt.% at 3 MPa,and up to 5.229 wt.% merely in 2 min,which revealed that the amorphous phase reduced the H occupation of the lattice clearance,resulting in the decline of hydrogen absorption capacity.The electrochemical tests indicated that the maximum discharge capacity increased to 353.1 mAh/g at 30 oC,however,the cycle stability decreased considerably.A series of kinetic measurements demonstrated that the controlling steps of electrochemical process of La 2 Mg 17-x wt.%Ni alloys transferred from hydrogen diffusion on alloy bulk(x=50,100) to hydrogen diffusion on both alloy bulk and surface(x=150,200).     

Electrochemical hydrogen storage performances of the nanocrystalline and amorphous（Mg24 Ni10 Cu2）100-x Ndx（x=0–20） alloys applied to Ni-MH battery

Melt spinning technology was used to prepare the Mg2 Ni-type（Mg24 Ni10 Cu2）100–x Ndx（x=0,5,10,15,20） alloys in order to obtain a nanocrystalline and amorphous structure.The effects of Nd content and spinning rate on the structures and electrochemical hydrogen storage performances of the alloys were investigated.The structure characterizations of X-ray diffraction（XRD）,transmission electron microscopy（TEM） and scanning electron microscopy（SEM） linked with energy dispersive spectroscopy（EDS） revealed that the as-spun Nd-free alloy displayed an entire nanocrystalline structure,whereas the as-spun Nd-added alloys held a nanocrystalline and amorphous structure and the degree of amorphization visibly increased with the rising of Nd content and spinning rate,suggesting that the addition of Nd facilitated the glass forming of the Mg2 Ni-type alloy.The electrochemical measurements indicated that the addition of Nd and melt spinning improved the electrochemical hydrogen storage performances of the alloys significantly.The discharge capacities of the as-cast and spun alloys exhibited maximum values when Nd content was x=10,which were 86.4,200.5,266.3,402.5 and 452.8 mAh/g corresponding to the spinning rate of 0（As-cast was defined as the spinning rate of 0 m/s）,10,20,30 and 40 m/s,respectively.The cycle stability（S20,the capacity maintain rate at 20thcycle） of the as-cast alloy always rose with the increasing of Nd content,and those of the as-spun alloys exhibited the maximum values for Nd content x=10,which were 77.9%,83.4% 89.2% and 89.7%,corresponding to the spinning rate of 10,20,30 and 40 m/s,respectively.     

快淬工艺对低钴AB5型贮氢合金电化学性能的影响

研究了快淬工艺对稀土基低钴AB5型LaxMm1-x（NiMnSiAlFe）4．7Co0．2（x=0、01）贮氢合金的电化学性能及其微观结构的影响。研究结果表明,快淬改善了两种合金的循环稳定性,其主要原因是快淬使合金的晶胞体积增大,且使合金的晶粒细化;快淬对La含量x=0合金的循环寿命的增加幅度尤其明显,主要是因为快淬使该合金的晶粒更为细小。La替代Mm使合金的放电容量提高,其原因是La替代Mm抑制了第二相Ce2Ni7相的形成,并使合金的晶胞体积增大。     

快淬工艺对Mg2Ni型合金气态及电化学贮氢动力学的影响

用铸造及快淬工艺制备Mg2Ni型Mg2-xLaxNi(x=0,0.2,0.4,0.6)贮氢合金。用XRD、SEM、HRTEM分析铸态及快淬态合金的微观结构,合金的气态贮氢动力学性能用自动控制的Sieverts设备测试,并用程控电池测试仪测试合金的电化学贮氢动力学。结果发现,La替代Mg明显地改变Mg2Ni型合金的相组成。当x≤0.2时,La替代Mg不改变合金的主相Mg2Ni,但出现少量的LaMg3及La2Mg17相。当La替代量x≥0.4时,合金的主相改变为(La,Mg)Ni3+LaMg3。快淬含La合金显示了以非晶相为主的结构,表明La替代Mg提高了Mg2Ni型合金的非晶形成能力。合金的气态及电化学吸放氢动力学对La含量及快淬工艺敏感,适当的快淬处理可以提高合金的气态及电化学贮氢动力学,但获得最佳贮氢动力学的快淬工艺与合金的成分密切相关。     

热处理对FeCuNbSiB单层膜磁性能的影响

本文研究了热处理对FeCuNbSiB薄膜结构及磁性能的影响。XRD分析表明制备态的FeCuNbSiB为非晶态,并且在300℃热处理仍然保持非晶态。300℃热处理后,薄膜释放应力,软磁性能有所提高。热处理温度进一步升高,薄膜由非晶态转化为纳米晶,矫顽力及饱和磁化场明显增加,磁矩向垂直膜面方向转动,软磁性能下降。     

Fe81Ga19磁致伸缩合金的动态磁导率研究

研究了Fe81Ga19磁致伸缩合金在不同的偏置磁场和频率下的动态磁导率。在低频或准静态下,该合金的磁导率能够达到160以上,但随频率增加,磁导率逐渐下降,频率大于6 KHz时,磁导率的下降减缓,并逐渐趋于稳定。当施加平行偏置磁场时,磁导率明显降低,而施加垂直偏置磁场时,与零偏置磁场相比,磁导率除较低频率段有少量的下降外,基本保持不变。     

MnO_2包覆Co纳米颗粒的制备与表征

采用化学还原方法制备出具有纳米尺度的Co颗粒,并在其表面包覆1层MnO2膜,从而制备出具有核/壳结构的Co/MnO2颗粒。应用热处理手段,制备出3种不同类型的核/壳样品,分别通过XRD、TEM、SEM测量手段,对它们进行结构分析。并同时对这种铁磁/反铁磁的核壳结构样品进行磁性研究,发现包覆热处理后的Co颗粒具有可观的交换偏置现象。     

熔体快淬对La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0～0.2)电极合金循环稳定性的影响

为了改善La-Mg-Ni系A287型电极合金的电化学循环稳定性,用Zr部分替代合金中的La,并用熔体快淬工艺制备了La0.75-xZrxMg0.25Ni3.2Co0.2Al0.1(x=0、0.05、0.1、0.15、0.2)电极合金.用XRD、SEM、TEM分析了铸态及快淬态合金的微观结构,测试了铸态及快淬态合金的电化学循环稳定性,研究了快淬工艺及Zr替代La对合金循环稳定性的影响,探讨了电极合金的失效机理.结果表明,铸态及快淬态合金均具有多相结构,包括两个主相(La,Mg)Ni3及LaNi5和一个残余相LaNi2.快淬处理及Zr替代La可以显著的改善舍金的电化学循环稳定性.导致合金失效的主要原因是电极表面被电解液剧烈腐蚀以及合金电极在电化学循环过程中的粉化.     

蒸发波导模型与微波超视距传播试验对比

海洋蒸发波导是实现近海面超视距电波传播的重要环境,利用蒸发波导模型和电波传播数值算法是获取路径损耗的主要途径.基于海上平台约7个月测量的水文气象参数,对比了Paulus提出的PJ模型和美国海军研究生院(Naval Postgraduate School,NPS)提出的NPS模型,同时利用约1个月的海上超视距传播测试数据...     

知识管理在磁性材料行业的应用

为了对磁性材料行业的材料配方和性能配方之间的知识进行有效管理,和准确预测材料配方和性能之间的变化趋势,提出了一个基于神经网络的磁性材料设计方法,并在此基础上实现了磁性材料设计专家系统.首先对配方和性能的基础数据进行了管理,然后通过生产实验数据训练神经网络,实现了性能和配方的相互推导,最后对配方或性能的变化趋势进行了准确预测.实验结果表明,专家设计系统的趋势预测具有极高的精确性.企业实施该系统后较大幅度的提高了新产品的开发速度,提高了企业的市场竞争力.