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Studies of the g factors for the tetragonally elongated and compressed CuIIN6 octahedra in image omitted (MI = K, Rb, Cs; MII = Ca, Sr, Ba, Pb) crystals

Philosophical Magazine

The EPR g factors, g// and g perpendicular to, of tetragonally elongated and compressed CuIIN6 octahedral clusters (with the ground states |dx2 - y2 > and |dz2 >, respectively) in [image omitted] (MI = K, Rb, Cs; MII = Ca, Sr, Ba, Pb) crystals were calculated using a two-mechanism model. In the model, the contributions to the g-shifts, gi (= gi - gs, where i = // or perpendicular to; gs approximate to 2.0023 is the free-ion g value), from both the crystal-field (CF) mechanism related to CF excited states and the charge-transfer (CT) mechanism related to CT excited states, which is neglected in the widely-used CF theory, were considered. For the CF mechanism, two theoretical methods, the perturbation theory method (PTM) and the complete diagonalization (of energy matrix) method (CDM), were applied. The CF parameters used were calculated from the superposition model, in which the structural data for CuIIN6 clusters in [image omitted] crystals were measured exactly by X-ray diffraction. The calculated g factors for both the tetragonally elongated and compressed CuIIN6 octahedra are in reasonable agreement with the experimental values. For the strongly covalent CuIIN6 clusters in crystals with different ground states, both the PTM and CDM can be applied to calculate the g-shifts, [image omitted], arising from the CF mechanism, but exact and reasonable calculations of g factors should take both CF and CT mechanisms into account.

关键词: crystal field;electron paramagnetic resonance;octahedral cluster;charge transfer;spin-hamiltonian parameters;atomic screening constants;jahn-teller;distortion;temperature-dependence;lead hexanitrocuprate(ii);2-mechanism model;scf functions;br crystals;complexes;bands

Cu对MI(NiAlMnCoCu)5.1贮氢合金电化学性能的影响

林玉芳 , 李蓉 , 张羊换 , 陈梅艳 , 王新林

功能材料

研究了Cu含量对MINi3.9-xCoo.4 Al0.2 Mno.6Cux贮氢合金的电化学性能的影响.实验发现:随着Cu含量x从0增加至0.3,合金的活化性能仍保持在2~3次;但合金的最大放电容量从344mAh/g下降到310mAh/g;高倍率放电性能均在81%以上;合金的循环寿命随着Cu含量的增加而有所提高的.实验表明,合金中加入适量的Cu,可有效的改善舍金的循环寿命.

关键词: 贮氢合金 , Cu含量 , 电化学性能

Ni52MI24Ga24金属间化合物的单晶生长和磁性功能

陈京兰 , 胡凤霞 , 高书侠 , 王中 , 高智勇 , 赵连城 , 宫声凯 , 徐惠彬

金属学报

研究了Ni52Mn24Ga24合金单晶在磁场作用下能产生的目前最大的磁致伸缩应变.发现了该材料的双向相变应变效应以及磁场对此的增强现象在1.2 T磁场的作用下,可逆的相变应变达4%以上.实现这一结果的关键条件是马氏体变体的择优取向报道了获得马氏体变体的择优取向样品的单晶生长特性和后处理方法.根据前人报道的理论模型分析了实验结果,指出磁感生应变的物理机制是磁场提供的Zeeman能驱动变体间孪晶界的移动.

关键词: Ni52Mn24Ga24 , null , null

Effect of Pr content in Ml on the electrochemical properties of Ml(Ni-Co-Mn-Al)(5) alloys

Journal of Alloys and Compounds

The electrochemical properties of MINi(3.5)Co(0.8)Mn(0.4)Al(0.3) alloys with various Pr contents in MI were studied in this work, It was found that the Pr content in MI obviously affected the electrochemical properties of MI(Ni-Co-Mn-Al)(5) alloys. The electrochemical properties were greatly improved if the electrode alloy contained about 20 at.% Pr in MI. The electrode made from this alloy has a higher capacity, better discharge rate characteristics and longer cycle life than that from alloy with less than 10 at.% Pr in MI, as in common misch metal. The AA size cells in which electrode alloy contains about 17 at% Pr in MI are also studied. It was found that these cells have a very long cycle life (1400 cycles) with reasonable capacity (1250 mA h) and rate capability (1100 mAh) when discharged at 5 C). In particular, they have a very superior low temperature capability. For example, their capacity was higher than 1050 mA h when discharged at 1C and -18 degrees C.

关键词: Pr;Ml;electrochemical properties;Ml-Ni alloys;hydrogen batteries;electrodes;hydrides;storage;lani5

On the Indeterminacy in Hardness of Shape Memory Alloys

F.T.Cheng

材料科学技术(英)

The present communication addresses an interesting problem related to the indeterminacy in hardness of superelastic NiTi reported by Xu et al. The origin of the indeterminacy is attributed to the inadequacy of the conventional Vickers hardness testing measurement which does not record elastic deformation, and thus the indeterminacy may be removed with suitable techniques. Concepts of hardness in relation to deformation are clarified. Recommendations for measuring the hardness of NiTi and other elastic-plastic materials are suggested, together with comments on the advantages and disadvantages of each of these methods.

关键词: Hardness , null , null , null , null , null

Thermodynamic analyses of strain-induced martensite transformation in Fe-7Mn-1.2C alloy

Jingpei XIE , Yaomin ZHU , Xiaoping WANG

材料科学技术(英)

The M-s temperature, Delta G(gamma-->alpha), Delta G(gamma-->M) and mechanical energy under a non-severe impact loading in a medium manganese steel (Fe-7Mn-1.2C) have been calculated by means of Xu's Fe-X-C model. The relation between the yield strength of austenite and the driving force for martensite transformation has been established. It is proved that the martensite transformation can take place in a medium manganese steel (Fe-7Mn-1.2C alloy) under a non-severe impact loading.

关键词:

磷在12Cr1MoV钢中非平衡晶界偏聚动力学的实验研究

李莉 , 李庆芬 , 郑磊 , 徐庭栋 , 杜善义

钢铁研究学报

以工业用12Cr1MoV钢为研究对象,通过俄歇电子能谱分析方法(AES),对磷在恒温过程中的非平衡晶界偏聚浓度进行了测定.获得的磷在钢中的非平衡晶界偏聚动力学曲线直接验证了非平衡晶界偏聚动力学理论中的Xu-Song模型.

关键词: 晶界偏聚 , 临界时间 , 扩散 ,

试验因素对LDPE熔融接枝AA影响的灰色系统分析

刘朝宗 , 任露泉 , 蒋蔓

高分子材料科学与工程

研究了丙烯酸(AA)作为接枝单体,过氧化二异丙苯(DCP)作为引发剂,与低密度聚乙烯(LDPE)混合,在单螺杆挤出机中进行熔融接枝反应,测定了LDPE-g-AA的熔融指数(MI)和表征接枝率的吸光比(R).用灰色系统理论的方法分析了试验因素,如AA、DCP及螺杆转速(r/min)对MI和R的关联度.结果表明,各因素对MI和R的影响程度是不同的,AA掺入量与MI有密切关系,而DCP加入量对MI影响程度较小.所考查的3个因素对接枝率的影响无明显差异,所得结果对高聚物的接枝改性有一定的指导意义.

关键词: 低密度聚乙烯 , 接枝 , 灰色系统

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