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981.
A simple thermodynamic model, originally developed for metals based on the Gibbs–Thomson equation and related considerations for homogeneous nucleation, has been extended to predict the solid–liquid interface energy γsl of organic crystals. The model predictions correspond to available experimental and other theoretical results for 38 organic crystals. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
982.
The influences of boron addition on the phase formation, Curie temperature and magnetic entropy change of the NaZn13-type La(Fe0.9Si0.1)13 compound have been investigated. Eight boron containing La(Fe0.9Si0.1)13Bx samples were prepared with x=0, 0.03, 0.06, 0.1, 0.2, 0.3, 0.5 and 0.6, respectively. Experimental results show that a small amount of B addition in La(Fe0.9Si0.1)13 forms the solid solution NaZn13-type structure phase by substituting B for Si or doping B into interstitial position of the lattice, preserves its giant magnetocaloric effects due to their first-order structural/magnetic transition, as well as increase its Curie temperature Tc slightly. The maximum magnetic entropy changes in the magnetic field change of 0–1.6 T are around 20 J kg–1 K–1 for the samples with Boron addition less than 0.3, while improving the Curie temperatures by 2 K. 相似文献
983.
X.J. Liu Z.Q. Li A. Yu M.L. Liu W.R. Li B.L. Li P. Wu H.L. Bai E.Y. Jiang 《Journal of magnetism and magnetic materials》2007
We have investigated the magnetic, electrical transport and electron spin resonance (ESR) properties of polycrystalline Fe-doped manganite LaMn0.7Fe0.3O3+δ prepared by sol–gel method. A typical cluster-glass feature is presented by DC magnetization and AC susceptibility measurements and a sharp but shallow memory effect was observed. Symmetrical Lorentzian lines of the Mn/Fe spectra were detected above 120 K, where the sample is a paramagnetic (PM) insulator. When the temperature decreases from 120 K, magnetic clusters contributed from ferromagnetic (FM) interaction between Mn3+ and Mn3+/Fe3+ ions develop and coexist with PM phase. At lower temperature, these FM clusters compete with antiferromagnetic (AFM) ones between Fe3+ ions, which are associated with a distinct field-cooled (FC) effect in characteristic of cluster-glass state. 相似文献
984.
The polycrystalline Ti/TiNx multilayer films were deposited by magnetron sputtering, and the as-deposited multilayer coatings were annealed at 500-800 °C for 2-4 h in vacuum. We investigated the effects of annealing temperature and annealing time on the microstructural, interfacial, and mechanical properties of the polycrystalline Ti/TiNx multilayer films. It was found that the hardness increased with annealing temperature. This hardness enhancement was probably caused by the preferred crystalline orientation TiN(1 1 1). The X-ray reflectivity measurements showed that the layer structure of the coatings could be maintained after annealing at 500 °C and the addition of the Si3N4 interlayer to Ti/TiNx multilayer could improve the thermal stability to 800 °C. 相似文献
985.
The oxidation kinetics of MgNd alloys oxidized in pure O2 at high temperatures has been investigated. The results revealed two stages of the reaction: A fast initial oxidation was followed by a slow oxide growth with a parabolic kinetics. For MgNd alloys (Nd = 25 wt.%), the oxidation rate increased with the enhancement of the oxidation temperature. A sudden ignition was found for this alloys oxidized at 873 K up to about 80 min. Moreover, the increase of the Nd content would harm the oxidation resistance of the MgNd alloys. By Auger electron spectroscopy (AES), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, it was found that a triplex structure of oxide film formed. The outer layer was composed of MgO, Nd2O3 and Nd(OH)3, the middle layer mainly consisted of MgO and Nd2O3, and the inner layer was the transitional layer made of MgO, Nd2O3 and the content of the substrate. The protective oxidation was associated with the formation of the dense Nd2O3/MgO layer during isothermal oxidation process. The oxidation mechanisms for the formation of oxide film are discussed. 相似文献
986.
In this article, we present studies on therahertz (THz) wave generation and frequency up-conversion in a periodically poled lithium niobate (PPLN) crystal. A frequency at 1.37 THz was generated as femtosecond pump pulses passed through a PPLN crystal with grating periods of 30 μm. The pump-induced THz wave interacts with the probe wave in the crystal by frequency mixing. The frequency up-converted THz wave is easily detected by a normal photodiode. A new scheme for generation and detection of THz wave in one non-linear crystal was proposed. 相似文献
987.
We have investigated the threshold properties of Rubidium blue bronze Rb0.3MoO3 under high dc electric field in a large temperature range 20-150 K. The second threshold fields have been observed at temperature up to 102.4 K, and have quasi-linear relationships with temperatures 20-45 K and 55-100 K, respectively. A novel crossover platform has been found firstly in the temperature dependence of the second threshold field ET2 at about 45-55 K. The results indicate that the dynamical behavior of the second threshold effects may originate from different mechanisms. We suggest that the highly conducting state at 20-45 K and 55-100 K result from the undamped sliding motion of rigid CDW and current inhomogeneity, respectively. 相似文献
988.
Z.M. Tian J.H. He Y.Q. Wang P. Li H.Y. Xie L. Liu S.Y. Yin 《Solid State Communications》2007,142(9):545-549
Magnetic properties have been investigated on Mn doped TiO2(Ti0.98Mn0.02O2) bulk samples prepared by solid state reaction, which were sintered at different temperature ranging from 450 °C to 900 °C in air and argon atmosphere, respectively. The results show that the magnetic properties were strongly dependent on the sintering temperature and atmosphere. For samples sintered in air, the magnetization initially increase with the increase of sintering temperature up to 600 °C and thereafter it decrease. While the magnetization of samples sintered in argon atmosphere decreases monotonically with the increase of sintering temperature. Furthermore, for samples sintered at 600 °C in air, the magnetic susceptibility exhibits a dominant Curie-Weiss behaviour and no magnetic transition is observed over the temperature range from 10 to 300 K. In contrast, for samples sintered in argon atmosphere, besides the magnetic transition near 45 K perhaps caused by Mn3O4, another magnetic transition appears near room temperature. 相似文献
989.
When a particle is bounded in a central force field, the only nonvanishing component of the mean value for current density
is along the azimuthal direction; and the total current can therefore be defined. It is found that the total current is in
fact a mean value of a newly defined total current operator in the quantum mechanical state. Not only the total current operator
itself but also the mean total current has exact classical correspondence. 相似文献
990.
Using Co2O3 as the Co source, doped cerium oxide thin films with the composition of Ce0.97C00.03O2-δ (CCO) are deposited on Si(111) and glass substrates by pulse laser deposition technique. X-ray diffraction reveals that CCO films with (111) preferential orientation are grown on Si, while the fihn on glass is polycrystalline with nanocrystal. X-ray photoelectron spectroscopy shows that the (Jo displaces the (;e atom and exists in high spin state rather than low spin state, which contributes to the room-temperature ferromagnetism confirmed by vibration sample magnetometer. I~ilms on Si and glass are different in ferromagnetism, which is believed to be induced by different film microstructures. Based on these results, the possible ferromagnetism in this insulating film is discussed. Anyway, successful fabrication of CCO films with room-temperature ferromagnetism on Si substrates is of great importance in both technological and theoretical aspects. 相似文献