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991.
A phosphate post-treatment process for Ce conversion film on aluminum was studied. SEM (scanning electronic microscope), XPS (X-ray photoelectron spectroscopy) and electrochemical measurements were used to characterize the properties of the films. After the post-treatment the micro-cracks on the film surface obviously diminished, and corrosion resistance of the conversion film in NaCl solution increased. The conversion film, without post-treatment, was mainly composed of hydrated cerium oxides, and the dehydration of the film may cause cracking of the films. After phosphate treatment, stable cerium phosphate CePO4 was formed on the surface, and the content of crystal water decreased greatly, leading to improvement of the film performance with less micro-cracks. 相似文献
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995.
The excitation-power dependence of the near-band-edge emission in ZnO inverse opals and nanocrystal films has been studied. The dependence of the photoluminescence intensity I on the excitation power L can be described by a power law, i.e., I∼Lα, where α is an exponent that is often used to identify the origin of the near-band-edge emission from semiconductors in previous models. However, in this work, it was found that the values of α show a strong variation between ZnO inverse opals and nanocrystal films. And our results show that the change of α is mainly caused by the laser heating effects. Therefore, the value of α could not be simply employed to unequivocally evaluate the origin of the near-band-edge emission in complex nanostructures. 相似文献
996.
The effect of a small amount Fe2O3 (0.1-2 mol%) doping on the electrical properties of (Na0.5K0.5)0.96Li0.04Nb0.86Ta0.1Sb0.04O3 (NKLNTS) ceramics was investigated. It was found that the B-site substitution of Fe3+ does not change the crystal structure within the studied doping level and all modified ceramics have a pure tetragonal perovskite structure at room temperature. The addition of Fe2O3 can promote the sintering of NKLNTS ceramics, and simultaneously cause the grain growth so that Fe3+-doped NKLNTS compositions show degraded densification at higher doping level. Furthermore, the dielectric properties of the NKLNTS ceramics do not show a significant change by Fe2O3 doping. However, the addition of Fe2O3 was found to have a significant influence on the electric fatigue resistance and the durability against water. The presence of oxygen vacancies caused by the replacement of Fe3+ for B-site ions makes the NKLNTS ceramics harder. 相似文献
997.
We had prepared Mn-doped ZnO and Li, Mn codoped-ZnO films with different concentrations using spin coating method. Crystal structure and magnetic measurements demonstrate that the impurity phases (ZnMnO3) are not contributed to room temperature ferromagnetism and the ferromagnetism in Mn-doped ZnO film is intrinsic. Interesting, saturated magnetization decreases with Mn or Li concentration increase, showing that some antiferromagnetism exists in the samples with high Mn or Li concentration. In addition, Mn0.05Zn0.95O film annealed in vaccum shows larger ferromagnetism than the as-prepared sample and more oxygen vacancies induced by annealing in reducing atmosphere enhance ferromagnetism, which supports the bound magnetic polaron model on the origin of room temperature ferromagnetism. 相似文献
998.
Dependence of Crystal Quality and β Value on Synthesis Temperature in Growing Gem Diamond Crystals 总被引:3,自引:0,他引:3
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High quality Ib gem diamond single crystals were synthesized in cubic anvil high-pressure apparatus (SPD- 6 × 1200) under 5.4GPa and 1230℃-1280℃. The (100) face of seed crystal was used as growth face, and Ni70Mn25Co5 alloy was used as solvent/catalyst. The dependence of crystal quality andβ value (the ratio of height to diameter of diamond crystal) on synthesis temperature was studied. When the synthesis temperature is between 1230℃ and 1280℃, theβ value of the synthetic high-quality gem diamond crystals is between 0.4 and 0.6. The results show that when theβ value is between 0.4 and O. 45, the synthetic diamonds are sheet-shape crystals; however, when theβ value is between 0.45 and 0.6, the synthetic diamonds are tower-shape crystals. In addition, when theβ value is less than 0.4, skeleton crystals will appear. When theβ value is more than 0.6, most of the synthetic diamond crystals are inferior crystals. 相似文献
999.
Fibre Optical Parametric Amplification in Defect Bragg Fibres with Zero Dispersion Slow Light Effect
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Nonlinearity enhancement by slow light effect and strong light confinement in defect Bragg fibres is demonstrated and anMysed in applications of fibre optical parametric amplifiers. Broadband low group velocity and zero dispersion as well as the strong light confinement by band gap enhances the nonlinear coefficient up to more than one order than the conventional high nonlinear fibres. Moreover, the zero dispersion wavelength of coupled core mode can be designed arbitrarily, under which the phase-matching bandwidth of the nonlinear process can be extended. 相似文献
1000.
To assess the reproducibility of quantitative measurements of cartilage morphology and trabecular bone structure of the knee at 7 T, high-resolution sagittal spoiled gradient-echo images and high-resolution axial fully refocused steady-state free-precession (SSFP) images from six healthy volunteers were acquired with a 7-T scanner. The subjects were repositioned between repeated scans to test the reproducibility of the measurements. The reproducibility of each measurement was evaluated using the coefficient(s) of variation (CV). The computed CV were 1.13% and 1.55% for cartilage thickness and cartilage volume, respectively, and were 2.86%, 1.07%, 2.27% and 3.30% for apparent bone volume over total volume fraction (app.BV/TV), apparent trabecular number (app.Tb.N), apparent trabecular separation (app.Tb.Sp) and apparent trabecular thickness (app.Tb.Th), respectively. The results demonstrate that quantitative assessment of cartilage morphology and trabecular bone structure is reproducible at 7 T and motivates future musculoskeletal applications seeking the high-field strength's superior signal-to-noise ratio. 相似文献