Chinese Physics Letters
The magnetic properties of 1 T-TaS2 and 1 T-Fe-0.07 Ta-0.93 S-2 have been studied, Experimental results show that the phase transition temperature of 1 T-TaS2 is a function of the magnetic field, At low temperatures, both compounds are in a mixed state of charge density wave -spin density wave due to the coherent superposition of antiferromagnetic coupling.
关键词:
density
Physica B-Condensed Matter
The magnetic properties and magnetocaloric effect of Tb(1-x)Y(x)CoC(2) (x = 0, 0.1, 0.2, 0.3, 0.4) compounds have been investigated systematically. All the compounds undergo second-order transitions from paramagnetic to ferromagnetic states without thermal and magnetic hysteresis. With increasing Y content from 0 to 0.4, the Curie temperatures decrease nearly linearly from 28 to 18 K. The nature of the second-order phase transitions can be confirmed by Arrott plots. For Tb(0.6)Y(0.4)CoC(2) compound, the maximum value of the magnetic entropy change -Delta S(M) at 20 K is 9.35 J kg(-1) K(-1) for an external field change of 5T (5.14 J kg(-1) K(-1) for 2T). The large reversible magnetic entropy change makes Tb(0.6)Y(04)CoC(2) compound an attractive candidate for the application at hydrogen liquefaction temperature. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Curie temperature;Magnetocaloric effect;Magnetic properties;ac susceptibility
Physical Review B
The magnetic properties and phase transitions of 1T-TaS2 and 1T-Fe0.07Ta0.93S2 have been studied in the interval of 1.5-300 K and over the range of 100 Oe-60 kOe. Experimental results show that at high temperatures the compounds are in a diamagnetic state and the commensurate-charge-density-wave-triclinic-nearly-commensurate transition temperature of 1T-TaS2 decreases with increasing magnetic field. The amount of variation is a function of the magnetic field. At low temperatures both 1T-TaS2 and 1T-Fe0.07Ta0.93S2 are in a paramagnetic state owing to the localized moments that come from the single Anderson-Mott localization state. The curves of magnetization versus temperature do not follow the Curie law or Curie-Weiss law, but can be described fairly well as M = M(0) + gamma T--n. The fitting parameters of experimental curves show that a part of the neighboring moment appears as antiferromagnetic coupling due to exchange interaction between the moments. The magnetic-field dependence of magnetization exhibits a complicated feature at low temperature. It shows that the compounds may undergo a phase transition at the maximum value of magnetization and then they are probably in a mixed charge-density-wave-spin-density-wave (CDW-SDW) state or SDW state due to the coherent superposition of the antiferromagnetic coupling.
关键词:
metal-insulator-transition;density-wave domains;high magnetic-fields;charge-density;doped 1t-tas2;coexistence;microscopy;systems;silicon;2h-tas2
孙建春
,
盛光敏
,
陈登明
,
周安若
,
朱光俊
功能材料
1J50软磁合金的性能主要是通过H_2热处理获得的,在1130℃和H2气氛保护下对冷轧态1J50软磁合金进行了热处理.运用MATS-2010SA软磁测试仪对处理前后1J50软磁合金的磁性能进行了检测,运用金相显微镜、XRD等手段对处理前后1J50软磁合金的组织结构进行了分析.结果表明,通过H_2热处理,1J50软磁合金的矫顽力显著降低,起始磁导率和最大磁导率提高;组织结构发生明显变化,冷轧态1J50软磁合金组织为孪晶奥氏体,平均晶粒尺寸为200μm,处理过后,晶粒显著长大,平均晶粒尺寸为100μm;由于在600℃时采取了快冷,处理后1J50软磁合金中未出现大量FeNi相和FeNi_3相.
关键词:
H2热处理
,
1J50
,
组织结构
,
性能
罗广圣
,
李小怡
,
周正有
,
刘光华
,
熊惟皓
,
吴小山
中国有色金属学报
采用固相反应法制备La(1.x)2/3Ca1/3MnO3(x=0.0,0.04)和(La0.7Y0.3)2/3Ca1/3MnO3系列样品,测量不同温度下的磁化强度-磁场曲线,计算样品的磁熵变,研究La空位掺杂和Y3+离子掺杂对磁热效应的影响.结果表明,La空位掺杂(x=0.04)的样品在居里温度附近磁熵变最大值为6.22 J/(kg.K),这比La2/3Ca1/3MnO3磁熵变最大值(6.26 J/(kg.K))稍有降低;而Y3+离子掺杂的样品在温度60 K时和磁场强度2 T下,其磁熵变最大值为0.568 J/(kg.K),并且磁熵变随温度变化有继续增大的趋势.这表明(La0.7Y0.3)2/3Ca1/3MnO3可以作为一定温区的磁致冷材料.
关键词:
(La(1-x-y)Yy)2/3Ca1/3MnO3化合物
,
固相反应
,
磁热效应
,
磁熵变
,
空位掺杂
刘叔仪
金属学报
<正> 作为固体脆性断裂判据的J积分,其数值与其积分路径无关,这在文献中叫“守恒性”。这个守恒性已被推广到塑性断裂,这到底有否根据?本文目的是作这个问题的证明。未用原作者的方法,但由两个旋度判据得到应力应变函数行列式给出的一些否定结论,希望这对J积分应用条件的了解有所助益。1.弹塑性J积分守恒的条件 J积分
关键词:
Communications in Theoretical Physics
For the first time, by taking into account all the irreducible representations and their components in the electron-phonon interaction (EPI) as well as all the levels and the admixtures of wavefunctions within d(3) electronic configuration, the values of parameters in expressions of Raman and optical-branch terms of thermal shifts (TS) due to EPI for three levels, T-4(2) band and T-4(1) band of ruby have been evaluated; the contributions to TS of T-4(2) and T-4(1) broad bands from thermal expansion have also been. calculated; and then, the TS of the peak energies of 'T2 and 4 Ti broad bands have been calculated. The results are in satisfactory agreement with observed data. The values of single-electron reduced matrix elements representing the strengths of EPI of T-4(2) and T-4(1) bands have respectively been determined. For TS of the peak energies of T-4(2) and T-4(1) bands, it is found that the contribution to TS from the second-order term in EPI Hamiltonian is dominant; TS due to EPI of acoustic branches are over two times as much as those of optical branches, and both of them increase rapidly with temperature; the neighbor-level term is insignificant; the contribution to TS from thermal expansion is specially important, and all the three terms of TS of T-4(2) or T-4(1) band axe red shifts.
关键词:
crystal fields;optical spectral bands;electron-phonon interaction;thermal expansion;thermal shift;theoretical calculations;high-pressure;field;spectroscopy;spectra
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
Materials Science & Engineering C-Biomimetic Materials Sensors and Systems
Micropits surrounded by coloured halos were observed under incident-light microscope on 1Cr18Ni9Ti stainless steel surface after "ennoblement" in seawater. Ennoblement has been attributed to biofilm formation on stainless steel surface in seawater. In this study. the environment in biofilm for ennoblement was simulated by adding H(2)O(2) into seawater at concentrations that were reported to detect in marine biofilm [N. Washizu, Y. Katada, T. Kodama, Corros. Sci.46 (2004)1291.]. H(2)O(2) increased the passivity of stainless steel in seawater, but this passivation was not uniform. The probability of pitting corrosion was increased after ennoblement. Equal thickness interference on the deposition film around the pits was believed to be the reason for the coloured fringes. It is conceivable that haloed pits on the stainless steel surface are the characteristic morphological indications for pitting corrosion formed under ennoblement condition in seawater. Examinations on the microbial and structural effects of the biofilm were not included in this study. (C) 2008 Elsevier B.V. All rights reserved.
关键词:
Haloed pits;Pitting corrosion;Stainless steel;Ennoblement;Seawater;triangular current scan;oxygen reduction;films;biofilm;growth
李国华
,
马淳安
,
郑遗凡
,
徐铸德
无机材料学报
无机类富勒烯纳米粒子具有良好的润滑性能. 宏量制备高纯度的样品以满足性能测试的要求, 是目前面临的主要技术难题. 本文采用剥离-掺杂-水热处理这一工艺流程制备了多元金
属二硫化物纳米粒子, 应用XRD、TEM、HRTEM和EDS等分析手段对其形貌、晶相组成、结构和化学组成进行了表征. 实验结果表明, 多元金属二硫化物纳米颗粒具有管状形貌,管壁为
多层状结构, 化学组成为NiX(WYMo1-Y)1-XS2, 同时, 样品中具有类富勒烯结构的纳米粒子大幅度提高; 并依据实验结果对多元金属二硫化物纳米管的形成机理进行了探讨.
关键词:
剥离-掺杂-水热处理
,
multi-metal disulfide
