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应用X射线异常散射技术研究了[Ni70Co30(25A)/Cu(20A)]20多层膜的界面结构, 结果表明, 退火前后Cu/Ni70Co30和Ni70Co30/Cu界面的温度行为不同.对于制备态样品, 界面结构是非对称的, 在Cu/Ni70Co30界面, 存在一个8A厚的CuNi3过渡层和一个4A厚的NiCo层. 然而, Ni70Co30/Cu界面却不存在任何扩散. 285\textcelsius 2h退火后,Ni70Co30/Cu界面开始发生扩散, 产生了一个12A厚的CuNi2Co过渡层. X射线能量分别在Co, Ni, Cu K吸收边附近的X射线漫散射实验, 揭示了在Ni70Co30/Cu多层膜的界面处,
Cu与Ni和Co具有不同的横向关联长度, 显示了不均匀的横向分布. 相似文献
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将Zr55Al10Ni5Cu30块体非晶合金在715 K等温退火30 min, 引入少量纳米晶, 然后于室温以不同的应变速率进行轧制, 用差示扫描量热仪考察不同应变量样品的热稳定性和自由体积演化. 结果表明:即使轧制到95%的最大应变量, 样品的热稳定性也几乎没有发生改变. 在各种应变速率下, 随着应变量的增加, 自由体积含量持续上升. 但随着应变速率的增加, 相同应变量下自由体积的含量先上升后降低, 该规律与单一非晶态结构合金在塑性变形过程中自由体积的变化情况截然不同. 相似文献
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进行了10—27 GPa应力范围内Zr51Ti5Ni10Cu25Al9金属玻璃的平面冲击实验以研究其高压-高应变率加载下的塑性行为.由样品自由面粒子速度剖面的分析获得了冲击加载过程的轴向应力,并通过轴向应力与静水压线的比较获得剪应力.实验结果表明,尽管存在明显的松弛效应,但Zr基金属玻璃的Hugoniot弹性极限随着冲击应力的增加而增加.然而,塑性波阵面上的剪应力则显示先硬化而后软化现象,而且软化的幅度随冲击应力的增加而增加.冲击加载下Zr基金属玻璃的上述剪应力变化特征与分子动力学模拟结果比较一致,但与压剪实验结果和一维应力冲击实验结果明显不同. 相似文献
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采用分子动力学方法对Ca70Mg30合金快速凝固玻璃形成过程进行了计算机模拟, 深入分析了液-固玻璃转变过程热力学、 动力学和结构特性的转变机理, 对不同方法所确立的玻璃转变温度之间的关系进行了探讨. 结果表明: 本模拟计算所获得的Ca70Mg30金属玻璃的结构因子和玻璃转变温度均与实验结果符合, 而且二十面体局域结构对Ca70Mg30金属玻璃的形成起决定性作用. 由于周围原子形成的瞬时"笼子效应", 过冷液体动力学特性逐渐偏离Arrhenius规律而满足模态耦合理论的幂指数规律. 动力学玻璃转变温度接近于微观结构玻璃转变温度, 但高于热力学玻璃转变温度; 而且它们与理想动力学玻璃转变温度之间满足Odagaki关系. 相似文献
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James R. Stevens 《固体与材料科学评论》1984,12(4):297-328
The viscosity of an amorphous polymeric solid above its glass transition [T g (T,P)] increases as the temperature of the solid is decreased or the pressure is increased. Under changes in temperature or pressure, molecular subunits in the polymeric solid undergo configurational changes. Such changes or relaxations have a distribution of relaxation strengths and times. As the solid is cooled or as the hydrostatic pressure on the solid is increased, the relaxation strengths increase and the relaxation times increase. These changes in relaxation or dynamic properties are very dramatic as the empirical T g is approached. Near T g the polymeric solid is no longer in volume equilibrium; continued cooling or pressuring at a time rate faster than the average relaxation time will produce a polymeric glass. This glass is a nonequilibrium, amorphous solid. If the glass is held at a fixed temperature and pressure very close to, but below, T g , the volume of the glass will be observed to relax to its equilibrium value. For temperatures and pressures well below T g , equilibrium is a much more conjectural concept since the relaxation times become extremely long. It has been proposed1,2 that there is a characteristic temperature T g at which an amorphous polymer undergoes a second-order transition to an equilibrium glass with zero configurational entropy (i.e., a noncrystallizable solid). 相似文献
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Elena Fertman Sergiy Dolya Vladimir Desnenko Anatoly Beznosov Marcela Kajňaková Alexander Feher 《Journal of magnetism and magnetic materials》2012
A detailed study of the low-temperature magnetic state and the relaxation in the phase-separated colossal magnetoresistance Nd2/3Ca1/3MnO3 perovskite has been carried out. Clear experimental evidence of the cluster-glass magnetic behavior of this compound has been revealed. Well defined maxima in the in-phase linear ac susceptibility χ′(T) were observed, indicative of the magnetic glass transition at Tg∼60 K. Strongly divergent zero-field-cooled and field-cooled static magnetizations and frequency dependent ac susceptibility are evident of the glassy-like magnetic state of the compound at low temperatures. The frequency dependence of the cusp temperature Tmax of the χ′(T) susceptibility was found to follow the critical slowing down mechanism. The Cole–Cole analysis of the dynamic susceptibility at low temperature has shown extremely broad distribution of relaxation times, indicating that spins are frozen at “macroscopic” time scale. Slow relaxation in the zero-field-cooled magnetization has been experimentally revealed. The obtained results do not agree with a canonical spin-glass state and indicate a cluster glass magnetic state of the compound below Tg, associated with its antiferromagnetic–ferromagnetic nano-phase segregated state. It was found that the relaxation mechanisms below the cluster glass freezing temperature Tg and above it are strongly different. Magnetic field up to about μ0H∼0.4 T suppresses the glassy magnetic state of the compound. 相似文献
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Seyed Ali Salehizadeh Dariush Souri 《Journal of Physics and Chemistry of Solids》2011,72(11):1381-1385
The glass transition temperature dependence to heating rate and therefore the activation energy (ΔH?) of the glass transition of (60-x)V2O5–xNiO–40TeO2 oxide glasses with 0≤x≤20 (in mol%) were investigated at heating rates φ (=3 6, 9, 10 and 12 K/min) using differential scanning calorimetry (DSC). The heating rate dependence of Tg was used to investigate the applicability of different theoretical models describing the glass transition. Using the application of Moynihan and Kissinger et al. models to the present data, different values of (ΔH?) at each different heating-rate regions were obtained. The fragility parameter (m=ΔH?/R Tg) was ∼24.98 for x=10 mol%, suggesting that this glass may be considered as a rather strong glass (fragility index m∼>20 is an indication of fragile glass). Also the compositional dependence of Tg and ΔH? was investigated. 相似文献
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Thin films of (111)-oriented spinel ferrite Al0.5Fe2.5O4 have been prepared by a pulsed-laser deposition (PLD) technique on α-Al2O3 (0001) substrates. The films exhibit cluster-glass behaviors with a spin-freezing temperature, Tg, near or above room temperature. The magnetization was found to increase following light irradiation below Tg, which indicates the photoinduced melting of cluster-glass states. An analysis comparing the dynamic behavior of magnetic response to light irradiation between zero-field-cooled (ZFC) states and field-cooled (FC) states at 10 K under various light intensities, I, revealed that the direct photoexcitation of spins occurs when I≤0.78 mW/mm2, while the thermal heating effect following the light absorption of the samples also contributes to the enhancement of magnetization when I≥1.22 mW/mm2. The magnetization of the films could be controlled by light irradiation even at room temperature. This suggests the possibility of utilizing these films in the development of novel magneto-optical memory devices. 相似文献
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N. Guskos J. Typek M. Wabia V. Likodimos H. Fuks I. Rychlowska-Himmel J. Walczak 《Applied magnetic resonance》1998,14(2-3):397-402
The temperature dependence of the EPR spectrum for the α-phase of iron tungstate has been investigated in the temperature range of 40–260 K. At temperatures betweenT 1 ≈ 250 K andT 2 ≈ 205 K where the antiferromagnetic phase transition occurs, a relatively narrow EPR line arising from the dominant iron(III) species has emerged, gaining intensity with the temperature increase. Its linewidth temperature evolution could be described by Huber equation, with TN = 200 K, which is consistent with the peak seen in magnetic susceptibility measurements, while the correspondingg-factor shifts to higher fields reflecting the build-up of internal field emerging from increasing shortrange order in the spin system. At temperatures lower than T2, a very broad and distorted EPR line with temperature dependentg-factor and linewidth has been observed reflecting the corresponding rise of the magnetic susceptibility below the antiferromagnetic phase transition, presumably arising from magnetic clusters embedded in the antiferromagnetic background. 相似文献
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Differential scanning calorimetry (DSC) under non-isothermal conditions is used to study the crystallization kinetics of Sb14As29Se52Te5 chalcogenide glass. In addition, two approaches are used to analyze the dependence of glass transition temperature (Tg) on the heating rate (α). One is empirical linear relationship between (Tg) and ln(α). The second approach is the use of straight line vs. 1/Tg for the evaluation of the activation energy for glass transition. The phases at which the alloy crystallizes after the thermal treatment have been identified by using X-ray diffraction. The diffractogram of the transformed material shows the presence of some crystallites of As, Te, AsSb, As2Se3, Sb2Se3 and AsSe.5Te.5 in the residual amorphous matrix. 相似文献
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Annealing temperature dependence of the stress-induced magnetic anisotropy in Co73Mo2Si15B10 (λs < 0) and (Co0.89Fe0.11) 72Mo3Si15B10 (λ > 0) metallic glass ribbons has been studied experimentally. The room temperature values of the induced anisotropy constants K depend strongly on the annealing conditions, and reveal a change of sign at annealing temperatures well below Tcryst. It is concluded that transient creep and steady-state creep at the elevated temperature give rise to compressive and tensile stresses, respectively, in the expression for the magnetoelastic coupling energy at room temperature. 相似文献
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利用正电子湮没寿命谱实验手段研究了22Na放射源的e+自辐射对三 嵌段共聚物SEBS的正电子湮没参数的影响,而后结合Eldrup的经典模型,研究了SEBS的自由体积孔尺寸和自由体积分数随着温度的变化关系,给出了自由体积分数在Tg以上和在Tg以下各自区域内分别与温度呈线性关系,最后结合Williams-Landel-Ferry(WLF)自由体积理论和Eldrup的经典模型讨论了热膨胀系数和自由体积分数中的A常数.
关键词:
正电子湮没技术
嵌段共聚物
自辐射
热膨胀 相似文献
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The temperature dependence of the 17O NQR spectra of the O-H---O bonded oxygens in PbHPO4 have been studied using a proton-17O double resonance technique. The results show that the protons move between two off-centre sites above Tc and freeze into one of the possible equilibrium sites below Tc. 相似文献
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The temperature dependence of the 17O NQR spectra in KH2PO4 has been measured using a proton-17O double resonance technique in the laboratory frame. The spectra are consistent with a model where the protons rapidly move above Tc between the two equilibrium sites in the O-H--O bonds, whereas the motion freezes in below Tc. 相似文献