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991.
W.Y. Zhang C.H. Chiu L.C. Zhang K. Biswas H. Ehrenberg W.C. Chang J. Eckert 《Journal of magnetism and magnetic materials》2007
The effect of refractory element addition on phase transformation, crystallization behavior and magnetic properties of Pr8.5Fe81.5B10 (addition-free) and Pr8.5Fe81.5M2B10 (M=V, Cr, Nb, Zr, Ti) ribbons has been investigated. The annealed addition-free ribbon as well as the samples with V or Cr additions are mainly composed of the metastable Pr2Fe23B3 phase, whereas annealed ribbons with Nb, Zr or Ti additions primarily consist of Pr2Fe14B and a minor amount of Fe3B/boride. The complete suppression of the metastable Pr2Fe23B3 phase due to Nb, Zr or Ti additions leads to a significant enhancement of the magnetic properties. For example, the remanence, the coercivity and the energy product are remarkably increased from 2.5 kG, 0.4 kOe and 0.2 MG Oe for the addition-free material to 9.2 kG, 4.7 kOe and 7.6 MG Oe for the specimens with Nb addition. The successful elimination of the metastable Pr2Fe23B3 phase is believed to profit from two factors: (a) Nb, Zr or Ti atoms substitute the Pr site, comparatively increase the Pr content, and thus inhibit the nucleation of Pr-lean Pr2Fe23B3 phases, and (b) the formation of Nb, Zr, or Ti borides consumes some part of B, which hinders the generation of the B-rich Pr2Fe23B3 phase. 相似文献
992.
Composite coating of Ni-Co/Al2O3 was deposited in Ce2(SO4)3 containing electrolyte by pulse reverse current (PRC) method. The effect of Ce2(SO4)3 in electrolyte on morphology, microstructure, composition, micro-hardness and residual macrostress of composite coating was investigated. The results indicates that with addition of Ce2(SO4)3 in electrolyte, the composite coating becomes uniform, compact and possesses finer grains, the composite content of Al2O3 is enhanced, the micro-hardness of composite coating is improved, while the residual macrostress is decreased. 相似文献
993.
Surface status and size influences of nickel nanoparticles on sulfur compound adsorption 总被引:1,自引:0,他引:1
Metallic nickel nanoparticles were incorporated on mesoporous silica to remove sulfur compounds in diesel selectively. In the first method, nickel nanoparticles were formed on mesoporous silica SBA-15 by impregnation and subsequent reduction of nickel nitrate. The sulfur adsorption capacity was strongly dependent on the nickel loading and the average nickel particle size. In the second method, nickel nanoparticles were synthesized in solution in the presence of a capping agent and then incorporated in mesoporous silica MCF by sonication. Although these particles maintain their sizes on the MCF surface after heat treatment, capping agent remaining on the Ni particle surface might interfere the adsorption of sulfur compounds. 相似文献
994.
In this report, we demonstrate the efficient generation of collinearly propagating photon pairs in a bulk periodically poled potassium titanyl phosphate pumped by a cw laser. The detected coincidence counts are more than 7400/s with 3.58 mW pump power in a Hanbury-Brown-Twiss-type experiment. The estimated photon pair production rate is about 0.73 MHz/mW. This is very promising for some applications, such as quantum key distribution, proof of the Bell-inequality, preparation of single photon states in broadband wave packets, Franson-type interference and so on. 相似文献
995.
Al-doped ZnO (AZO) transparent conductive thin films were grown by magnetron sputtering with AZO (98 wt.% ZnO, 2 wt.% Al2O3) ceramic target in Ar + H2 ambient at a relatively low temperature of 100 °C. To investigate the dependence of crystalline and properties of as-grown AZO films on the H2-flux, X-ray diffraction (XRD), X-ray photoemission spectrometer (XPS), Hall and transmittance spectra measurements were employed to analyze the AZO samples deposited with different H2-flux. The results indicate that H2-flux has a considerable influence on the transparent conductive properties of AZO films. The resistivity of 4.15 × 10−4 Ω cm and the average transmittance of more than 94% in the visible range were obtained with the optimal H2-flux of 1.0 sccm. Such a low temperature growing method present here may be especially useful for some low-melting point photoelectric devices and substrates. 相似文献
996.
Electrodynamic Analysis of Dissipative Electromagnetic Materials Based on Fractional Derivative
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The generalized Lagrangian is defined in a dissipative electromagnetic medium on the basis of the combination of dynamical analysis and fractional derivative. Lorentz medium models are obtained by formulating relevant Euler-Lagrange equations. The invariance is obtained subsequently by investigating the invariance of time variation in the system, and then the relation between the related Hamiltonian and electromagnetic energy density is investigated. Canonical equations are obtained eventually. The electrodynamic interpretation on dissipative electromagnetic systems is revealed. 相似文献
997.
Kyung Ah Jeon Hyo Jeong Son Chang Eun Kim Jong Hoon Kim Sang Yeol Lee 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):222
ZnO nanowires were fabricated on c-plane (0 0 0 1), a-plane (1 1 2¯ 0) sapphire, and boron doped p-type (1 0 0) Si substrates in vacuum furnace by simple physical vapor deposition. Room temperature photoluminescence spectra of the nanowires show the near band-edge emission and the deep-level green light emission. The ZnO nanowires formed on sapphire (1 1 2¯ 0) substrates exhibited enhancement on optical properties and better crystalline structures than those of nanowires grown on other substrates. The formation mechanism and the effect of substrate direction on structural and optical properties of the nanowires are discussed. 相似文献
998.
Yu-Lin Tsai Cheng-Chung Chang Chi-Chih Kang Ta-Chau Chang 《Journal of luminescence》2007,127(1):41-47
We have previously illustrated that the electron donor of carbazole moiety and the electron acceptor of methyl pyridinium cation in 3,6-bis(1-methyl-4-vinylpyridinium) carbazole diiodide (BMVC) molecule could form an intramolecular charge-transfer state. The intramolecular twist of the vinyl group in bridging the donor and acceptor plays an important role in the BMVC fluorescence. Here, we have synthesized three 9-aryl-substituted BMVC derivatives with different electronic properties for the design of the second generation of fluorescence probes. The steady-state solvatochromic studies show no appreciable change to the charge transfer of BMVC by substituting an anisole electron-donating group at 9-position of BMVC. However, substituting a 9-nitrobenzyl electron-withdrawing group in BMVC could restrict the charge transfer in the excited state. Moreover, the increase of the fluorescence yields of 9-anisole BMVC and 9-phenyl BMVC upon interaction with DNA is even higher than that in glycerol, while the fluorescence yield of 9-nitrobenzyl BMVC upon interaction with DNA is much lower than that in glycerol. Although 9-nitrobenzyl BMVC is a good G-quadruplex stabilizer, substituting an electron-withdrawing group at 9-position of BMVC is not recommended for the design of fluorescence probes. On the other hand, co-localization between 9-phenyl BMVC and MitoTracker Red in the merged image of cells indicates that the 9-phenyl BMVC is a potential fluorescent mitochondrial probe. 相似文献
999.
Geometries, relative energies, and stabilities of endo- and exohedral complexes, X@Si20H20 and XSi20H20, (X = H+, H, N, P, C?, and Si?) are calculated at B3LYP/6-31G* level. The energy minimum structure of Si20H21 + shows that the proton cannot be positioned in the Si20H20 centre, but prefers attach to Si20H20 exohedrally with C2v symmetry. Most investigated Ih endohedral complexes X@Si20H20 (X = H, N, P, C?, and Si?) are local minima, except for 2N@Si20H20, which is a high-order saddle point. Inclusions energies of the endohedral complexes are calculated, and it reveals that energy penalties caused by encapsulation are rather small. Exohedral complexes XSi20H20 (X = H, N, P, C?, and Si?) have C2v or Cs local minima, and most of them are more stable than their endohedral isomers with the exception of C2v 4PSi20H20 and 4Si?Si20H20. 相似文献
1000.