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KNO3/Al2O3和K2CO3/Al2O3的强碱性研究 总被引:4,自引:0,他引:4
采用CO2-TPD及Hammett批示剂法测定了KNO3/Al2O3及K2CO3/Al2O3样品的碱量和碱强度。当KNO3,K2CO3的负载量低于其单层分散阈值时,能在AlO3均匀分布并产生强度为18.4的强碱位;高于其单层分散阈值后则能生成强度为27.0的超强碱位。 相似文献
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用多组态HFR方法系统地计算了高剥离粪钠CrⅩⅣ-FmXC离子(Z=24-100)单电子组态的能级,相应谱线的跃迁波长,跃迁概率和振子强度,在已有实验的基础上,用自编的Fortran程序对HF计算的3p^2P1/2,3/2能级结果进行了最小二乘拟合计算,从而预测计算了CrⅩⅣ-FmXC离子3s^2S1/2-3p^2P1/2,3/2跃迁的谱线波长。计算结果与已有的实验值均符舍得很好,尤其是与最近测量的实验值相当一致:而与其他理论预测值也基本吻合。 相似文献
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《中国物理》2003,12(9):792-795
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实验上探讨了Y3+离子掺杂对La2/3-xYxCa1/3MnO3(0<x<0.2)单相样品的结构及其输运性质的影响.结果表明,随着Y的掺杂,晶胞参数收缩,从顺磁性半导体到铁磁性金属的转变温度Tc明显降低,而巨磁阻效应却大大提高.为了探讨其物理起因,我们对Tc温度以上的导电机理通过定量分析电阻随温度的变化而得以研究,结果表明,载流子的迁移遵从跳跃方式而不是热激活形式,在此基础上对Y掺杂作用进行了讨论. 相似文献
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Electrical Transport and Low—Field Magnetoresistance in La2/3Ca1/3MnO3/YSZ Composites 总被引:2,自引:0,他引:2 下载免费PDF全文
《中国物理快报》2002,19(8):1168-1171
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XUZhao-Xin ZHANGJun YINGHe-Ping 《理论物理通讯》2003,40(5):623-630
The ground-state and thermodynamic properties of quantum mixed-spin chains of 1/2-1/2-1-1 and 3/2-3/2-1-1 are investigated by a quantum Monte Carlo simulation with the loop-cluster algorithm. For 1/2-1/2-1-1 chain, we find it hastwo phases separated by an energy-gap vanishing point in the ground-state. For 3/2-3/2-1-1 chain,the numerical results show two energy-gap vanishing points isolated by different phases in its ground-state. Our calculations indicate that all these ground state phases can be understood by means of valence-bond-solid picture, and the thermodynamic behavior at finite temperatures is continuous as a function of parameter α=J2/J1. 相似文献
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采用固态反应法制备了(La2/3Ca1/3)(Mn(3-x)/3Gax/3)O3(x=0.00,0.10,0.15,0.20,0.30)体系的系列样品。通过系统地测量其零场和1.6特斯拉(T)磁场下样品的电阻率-温度关系以及一定温度下磁电阻率与磁场的关系,发现随Ga^3+替代量的增加其磁电阻率峰和电阻率峰均向低温方向移动,磁电阻率峰值增大,并伴生磁电阻率峰展宽效应。作者认为,上述结果是由于Ga^3 相似文献
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采用磁控溅射方法在(100)YSZ基底上沉积了YBa2Cu3O7/SrTiO3/YBa2Cu3O7异质外延三层膜。利用交流磁化率和四引线电阻测量的方法确定了三层膜的超导性能,利用X射线衍射和透射电子显微镜研究了三层膜的结构特征。研究结果表明,膜层的结晶质量较好,临界转变温度Tc在83.5K和86.7K之间。YBCO膜层中的绝大多数甚至全部)晶粒为c取向,在有些膜中只存在少量的a或b取向的YBCO晶 相似文献
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We utilize the random network model based on phase separation scenario to simulate the conductive behaviour and anisotropic characteristics of resistivity for La2/3Ca1/3MnO3 (LCMO) thin films. The simulated results agree well with our experimental data, showing a metal-to-insulator transition from a high-T paramagnetic (PM) insulating phase to a low-T ferromagnetic (FM) metallic phase in both the untilted film deposited on a (001) SrTiO3 (STO) substrate and the tilted film grown on a vicinal cut STO substrate. It is found that the resistivity of the tilted sample is higher than that of the untilted one, displaying prominent anisotropic characteristics. The studies reveal that the tilting not only decreases the conduction of the FM domains, but also increases the activation energy of the PM regions, inducing the enhancement of resistivity. All those results suggest that the intrinsic inhomogeneity in the phase separation system plays a significant role in the electrical conductivity and the resistive anisotropy is related to the structure of the crystal lattice. 相似文献
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A series of (La_{1-x}Tb_x)_{2/3}Sr_{1/3}MnO_3 polycrystalline samples has been studied by means of x-ray diffraction, magnetostriction, and thermal expansion measurements. It has been found that this series undergoes a phase transition from a rhombohedral to an orthorhombic form at the doping level x≈0.20 at room temperature accompanied by an anisotropic magnetostriction up to -50×10^{-6} under a magnetic field of 1T. The linear and volume magnetostrictions vary with chemical composition, even change sign. At T=80K, the magnetostrictions for the samples of x=0.20 and 0.40 exhibit different behaviours. The sample of x=0.20 has positive volume and linear magnetostrictions and a negative anisotropic magnetostriction, while the sample of x=0.40 has an opposite behaviour. The magnitude of volume magnetostriction for both the samples is essential (~10^{-4}) at T=80K under a magnetic field of 4T. We conclude that these anomalous effects are due to the charge delocalization and the structural phase transition between orthorhombic and rhombohedral forms induced by the applied magnetic field. 相似文献
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Oscillation conditions of cw simultaneous dual-wavelength Nd:YAG laser for transitions 4F3/2-4I9/2 and 4F3/2-4I11/2 下载免费PDF全文
The operating condition of a cw simultaneous dual-wavelength Nd:YAG laser for both {}^4F_{3/2}-{}^4I_{9/2} (quasi-three-level system) and {}^4F_{3/2}-{}^4I_{11/2}(four-level system) transitions is studied. According to this condition, the cw simultaneous dual-wavelength at 1.06μm and 946 nm in Nd:YAG crystal has been realized experimentally through an adaptive coating design of the cavity mirrors. A total power output of 2.5W of the dual-wavelength at 946nm and 1.06μm has been achieved with an optical conversion efficiency 14.3%. The experimental results are in good agreement with the theoretical analysis. 相似文献
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本文用米氏方法导出了三种组分构成的均匀球形复合微粒子光学散射截面的计算公式,并计算了复合微粒子Al2O3/MgO/C在特定红外光波波长下的光学散射截面。给出了复合微粒子中不同组分的介质层厚度与散射截面的关系曲线,最后对结果作了简单讨论。 相似文献
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溶胶—凝胶法制备CH3SiO3/2—SiO2孤立膜 总被引:2,自引:0,他引:2
采用溶胶凝胶法,以20%正硅酸乙酯/80%甲基三乙氧基硅烷为先驱体,通过控制溶胶过程及选择合适的成膜参数,并以一种疏不性膜为可分离载体,制备得到了大尺寸的,厚度可达50 ̄1000μm的无支撑孤立膜。研究了制膜过程中正硅酸乙酯对抑制结晶沉淀及成膜行为的影响。采用AFM观察了膜的表面形貌,采用XRD对结晶沉淀进行了结构分析。 相似文献
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Ni/Al2O3催化剂上CH4/CO2重整反应积碳的研究 总被引:1,自引:0,他引:1
采用X光电子能谱(XPS)和脉冲反应技术考察了973K下经不同方法处理后的Ni/Al2O3催化剂表面的积碳,单独用CH4或CO处理后的催化剂在283.6eV左右出现了一个新的Cls峰,可归属为金属碳化物,对CH4,CO处理过的催化剂用CO2处理后发现,结合能约为283.6eV的Cls峰强度明显降低,但由CO处理的催化剂的积碳的活性不如由甲烷生成的积碳活性好,CO歧化反应可能是导致镍催化剂失活的主要 相似文献
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p=2U/3V系统的态函数形式 总被引:2,自引:0,他引:2
给出了压强p、内能U和体积V满足p=2U/3V的系统的态函数形式。并据此讨论了理想 玻色气体、理想费米气体和通常的理想气体的状太民方程不同的热力学原因。 相似文献