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961.
针对混合溶液中重金属元素的激光诱导击穿光谱(LIBS)测量系统,为提高测量系统的检测灵敏度,以提高混合溶液中Ca和Cr金属元素LIBS光谱线强度的信噪比为目标,对LIBS测量系统中的激光脉冲能量、液相样品流速、ICCD门宽、延时等实验参数进行了优化,得到最优化参数激光脉冲能量、样品流速、ICCD门宽、延时分别为35 m J、30 ml/min、1400 ns和2400 ns,为降低LIBS技术应用于混合溶液中痕量重金属元素的检出限提供了实验参数支撑. 相似文献
962.
The aim of this work is to study the effects of duty ratio on the growth mechanism of the ceramic coatings on Ti-6Al-4V alloy prepared by pulsed single-polar MPO at 50 Hz in NaAlO2 solution. The phase composition of the coatings was studied by X-ray diffraction, and the morphology and the element distribution in the coating were examined through scanning electron microscopy and energy dispersive spectroscopy. The thickness of the coatings was measured by eddy current coating thickness gauge. The corrosion resistance of the coated samples was examined by linear sweep voltammetry technique in 3.5% NaCl solution. The changes of the duty ratio (D) of the anode process led to the changes of the mode of the spark discharge during the pulsed single-polar MPO process, which further influenced the structure and the morphology of the ceramic coatings. The coatings prepared at D = 10% were composed of a large amount of Al2TiO5 and a little γ-Al2O3 while the coatings prepared at D = 45% were mainly composed of α-Al2O3 and γ-Al2O3. The coating thickness and the roughness were both increased with the increasing D due to the formation of Al2O3. The formation of Al2TiO5 resulted from the spark discharge due to the breakdown of the oxide film, while the formation of Al2O3 resulted from the spark discharge due to the breakdown of the vapor envelope. The ceramic coatings improved the corrosion resistance of Ti-6Al-4V alloy. And the surface morphology and the coating thickness determined the corrosion resistance of the coated samples prepared at D = 45% was better than that of the coated samples prepared at D = 10%. 相似文献
963.
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
964.
A green-emitting phosphor of hexagonal BaZnSiO4:Eu2+ was prepared by a combustion-assisted synthesis method and an efficient green emission from ultraviolet to visible light was observed. The luminescence and crystallinity were investigated by using luminescence spectrometry and X-ray diffractometry. In the hexagonal structure of BaZnSiO4:Eu2+ phosphor, Eu2+ ions occupy three different lattice sites by substitution for Ba2+ ions. Eu2+ ions on Ba (1) and Ba (2) sites gave emissions at about 505 nm while Eu2+ ions on Ba (3) sites showed an emission band at 403 nm. The excitation spectrum is a broad band extending from 260 to 465 nm, which matches the emission of ultraviolet light-emitting diodes. The critical quenching concentration of Eu2+ in BaZnSiO4:Eu2+ phosphor is about 0.05 mol. The value of the critical transfer distance is calculated as 10.97 Å. The corresponding concentration quenching mechanism is verified to be the electric multipole–multipole interaction. The CIE coordinates of the optimized sample $\mathrm{Ba}_{0.95}\mathrm{ZnSiO}_{4}{:}\mathrm{Eu}_{0.05}^{2+}$ were calculated as (x,y)=(0.172,0.463). 相似文献
965.
966.
967.
968.
基于ANSYS对CFETR真空室简化模型进行了2D/3D电磁分析,得到了真空室磁场强度以及电磁力的分布。分析结果显示2D/3D真空室的磁场强度及电磁力分布基本一致,这表明了可以使用2D模型替代3D模型对未来真空室简化模型进行电磁分析。 相似文献
969.
A new green phosphor Ca12Al14O32Cl2: Tb3+ derived from Tb-doped Ca-Al layered double hydroxide (Tb-doped CaAl-LDH) was prepared through phase transition route. The X-ray diffraction measurement results revealed that the Tb-doped CaAl-LDH transformed into Ca12Al14O32Cl2:Tb3+ phase at 600 °C. With temperature varying from 600, 800–1000 °C, the crystallinity of the Ca12Al14O32Cl2:Tb3+ phase gradually improved. Compositional analyses suggested the chemical formula of the Ca12Al14O32Cl2:Tb3+ phase estimated to be Ca12Al13.52Tb0.48O32Cl2. The Ca12Al13.52Tb0.48O32Cl2 phase can be efficiently excited by near ultraviolet light and show strong green emissions attributed to 5D4→7FJ (J = 5, 6) transition of Tb3+. The present Ca12Al13.52Tb0.48O32Cl2 may be a promising candidate for green phosphor applied in LED. 相似文献
970.
Xin?Qin Penghui?ShiEmail author Haolin?Liu Jinchen?Fan Yulin?Min Qunjie?XuEmail author Weifeng?Yao 《Journal of nanoparticle research》2017,19(6):225
Metal nanoparticles have been combined with magnet metal–organic frameworks (MOFs) to afford new materials that demonstrate an efficient catalytic degradation, high stability, and excellent reusability in areas of catalysis because of their exceptionally high surface areas and structural diversity. Magnetic M x O y @N-C (M = Fe, Co, Mn) nanocrystals were formed on nitrogen-doped carbon surface by using 8-hydroxyquinoline as a C/N precursor. The Co@N-C, MnO@N-C, and Fe/Fe2O3@N-C catalysts were characterized by X-ray diffraction (XRD), Raman, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), N2 adsorption/desorption, and X-ray photoelectron spectroscopy (XPS). The catalytic performances of catalysts were thoroughly investigated in the oxidation of aniline solution based on sulfate radicals (SO4 ?.) toward Fenton-like reaction. Magnetic M x O y @N-C exhibits an unexpectedly high catalytic activity in the degradation of aniline in water. A high magnetic M x O y @N-C catalytic activity was observed after the evaluation by aniline degradation in water. Aniline degradation was found to follow the first-order kinetics, and as a result, various metals significantly affected the structures and performances of the catalysts, and their catalytic activity followed the order of Co > Mn > Fe. The nanoparticles displayed good magnetic separation under the magnetic field. 相似文献