M Liu
,
XM Zhang
,
M.Z. Liu
,
X.M. Mengand Y Y Li(Institute of Metal Research
,
Chinese Academy of Sciences
,
Shenyang 110015
,
China)(Metal Material Department
,
Sichuan Union University
,
Chengdu 610065
,
China)
金属学报(英文版)
In this paper by means of TEM and HREM, we found that the presence of r-phase plays the most important role in enabling two way shape memory effect (TWME) to be obtained by the stabilization of stress induced martensite variants (SSIM). This idea is different from the traditional suggestion that strain fields developed by dislocation produced TWME. With prolonged isothermal ageing time, the bainitic tronsforma-tion product α1 precipitated, the amount of γ-phase increased, while the martensite was retained and became less ondered. These factors all reduced TWME. During age-ing, the stacking faults in bainitic product α1 disappeared, which indicated that the bainitic product α1 is a sub-equilibrium phase. The interfaces of α-plates also lost straightness step by step, some plates twisted, bronched and overlapped. Its formation is irreversible in tnorphology and reduces the quantities of martensite. Although the precipitation of r may stabilize some martensite or oppose its growth,α may hinder nucleation of martensite. Thus, it was considered that α-plates were the worst de- stroyed element. These suggestions agreed well with our performance test results in that the transformation temperntures and the amount of TWME changed in the same way with prolonged ageing, firstly increasing and then decreasing after reaching an optimal maximum value.
关键词:
precipitate
,
null
,
null
,
null
Journal of Physical Chemistry C
We report the electrical, thermal, magnetic, and thermoelectric properties of Y-doped Ca(3)Co(4)O(9) from 300 down to 5 K. The results indicate that with Y doping, the increase of resistivity originates from the decreases of carrier concentration and mobility, while the increase of Seebeck coefficient is caused by the reduction of carrier concentration together with the enhanced electronic correlation. Point-defect scattering, is the dominant thermal transport mechanism in this system. Due to the considerable difference in mass between Y(3+) and Ca(2+), thermal conductivity is observably suppressed by doping. The substitution of Y also disturbs the interlayer ferrimagnetic coupling. The ground state of this System converts front ferrimagnetism to paramagnetism gradually. The alteration of transport properties of Ca(3-x)Y(x)Co(4)O(9) reveals two Crossovers: the transition from Fermi-liquid-like metal to thermally activated semiconductor occuring at x approximate to 0.25, and the transition from thermally activated semiconductor to two-dimensional variable range hopping semiconductor occurring at x approximate to 0.5. The optimal thermoelectric response In Ca(3-x)Y(x)Co(4)O(9) is found to exist only at the critical state after which the doping-induced metal-insulator transition takes place. Oil the basis of these experimental results, a possible phase diagram for Ca(3-x)Y(x)Co(4)O(9) is proposed.
关键词:
temperature thermoelectric properties;giant magnetoresistance;solid-solutions;conductivity;electron;system;ca3co4o9+delta;thermopower;crystals;behavior
王龙章
,
黄克雄
,
骆如铁
,
姚渝
,
叶大陆
,
陈新民
金属学报
本文讨论了双金属共存体系M_1-M_2-x-y,当两种金属的化合物相互作用生成多金属化合物时,优势区相图的绘制原理、方法及计算机程序。通过绘制Zn-Fe-SO系的优势区相图,分析了ZnO·Fe_2O_3的生成及稳定条件,并说明了其在硫化锌矿焙烧中的指导作用。
关键词:
M_1-M_2-x-y体系
,
predominance diagram
,
roasting
,
zinc sulfide ore
Applied Physics Letters
The effect of nonmagnetic Y partial substitution at the Dy site in Dy(1-x)Y(x)MnO(3) up to x=0.2 on magnetism, specific heat, and ferroelectricity is investigated, which resulted in a preliminary multiferroic phase diagram. It is revealed that the Y partial substitution suppresses the Dy-spin ordering point (T(Dy)) and ferroelectric ordering point (T(FE)) but enhances the Mn-spin ordering point (T(N)). The interaction between the spins of Dy and Mn is remarkably affected by Y substitution. The measured electrical polarization depends on the Y substitution in a complex way because the ferroelectricity is sensitive to the interaction between the spins of Dy and Mn. (c) 2011 American Institute of Physics. [doi: 10.1063/1.3536506]
关键词:
ferroelectricity;polarization
王秋艳
,
徐连义
,
付煜
,
张艳丽
,
谢嫚
稀有金属材料与工程
采用低温共沉淀-水热-煅烧法合成了锂离子电池Fe-Ni-Mn体系正极材料Li1+x(Fey/2Niy/2Mn1-y)1-xO2,并用XRD、SEM、ICP光谱和电化学性能测试对材料进行了表征.XRD测试和ICP分析表明,Fe、Ni取代Li2MnO3中的部分Mn,形成很好的固溶结构yLiFe1/2Ni1/2O2-(1-y)Li2MnO3 (y=0.l,0.2,0.3,0.4,0.5).SEM测试表明,取代量y不同,材料的表观形貌有所不同,y=0.4时材料的颗粒粒径均匀、较小,呈类球形结构.电化学性能测试表明,当y=0.4时,循环稳定性最好,充放电50次后放电比容量仍可维持在195.0 mAh/g,放电中值电压为3.5 V,y=0.4时样品在大倍率放电下的电化学性能表现良好.
关键词:
锂离子电池
,
正极材料
,
Li1+x(Fey/2Niy/2Mn1-y)1-xO2
,
离子掺杂
Journal of Physics and Chemistry of Solids
The changes of Mn-Y (Y = S, Se, Te) bond lengths R with the Mn composition x in the diluted magnetic semiconductors Zn1-xMnxY are calculated from the optical spectra and their pressure shifts. The calculated results suggest that the Mn-Y bond lengths change little with the Mn composition x-much less than expected from lattice parameters as determined by X-ray diffraction. These results are also in good agreement with the observed values obtained from the EXAFS measurements. It appears that for ternary A(1-x)M(x)Y (M denotes the divalent transition-metal ion) alloys the changes of M-Y bond lengths R with the M composition x can be studied from their optical spectrum data. (C) 2000 Elsevier Science Ltd. All rights reserved.
关键词:
semiconductors;high pressure;crystal fields;luminescence;light;properties;absorption fine-structure;local-structure;dependence;pressure;exafs
Physica Status Solidi a-Applied Research
Amorphization behavior is studied for several Y-based binary metal systems by room temperature 360 keV xenon ion mixing of multiple metal films to doses ranging from 7 x 10(14) to 1 X 10(16) Xe/cm2. In all systems studied, amorphization is achieved after ion mixing to the relevant doses. Interesting results are observed in the Ti-Y system, having rather positive heat of formation, i.e. 16 kJ/mol. A metastable crystalline Ti-Y phase is formed, for the first time, at medium dose ion mixing, and complete amorphous phase is formed in a narrow composition range, i.e. around Ti45Y55. Recrystallization temperatures of all formed amorphous alloys are determined by both, in-situ transmission electron microscopy annealing and confined furnace annealing. Possible interpretation is given to the observations by comparing with those proposed models for predicting glass forming ability.
关键词:
amorphous alloy formation;phase formation;thin-films;prediction
张志纯
,
龙志林
,
危洪清
,
李乡安
,
彭建
,
唐平
稀有金属材料与工程
采用单辊法和铜模铸造法制备了Fe75-xMxHf3Y2B20(M=Co,Nb;x=0,4 at%)合金系的非晶薄带和非晶棒样品,并测试了该非晶合金系的差示扫描量热曲线、X射线衍射图谱和软磁性能.结果表明:少量的Nb或Co替代Fe75Hf3Y2B20中的Fe元素,合金的热稳定性和玻璃形成能力可得到明显的提高;其中Fe71Nb4Hf3Y2820的过冷液相区宽度△Tx高达75 K,约化玻璃转变温度Trg为0.58,直径达4 mm,饱和磁感应强度为0.97～1.08 T,该非晶合金同时具有较大的热稳定性、较强的玻璃形成能力和较好的软磁性能.
关键词:
铁基块体非晶合金
,
过冷液相区
,
玻璃形成能力
,
软磁性能
