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41.
Jean Ravez Re´gnault Von Der Mu¨hll Paul Hagenmuller 《Journal of solid state chemistry》1975,14(1):20-24
Au sein d'un re´seau de type BaFeF5 des chai?nes d'octae`dres fluore´sa`sommets communs peuvent disparai?tre en donnant naissance a des canaux dont l'occupation partielle ou totale par des files de cations Sr2+ et de couples d'anions F?, conduit respectivement aux phases Sr3(FeF6)2 ou Sr5T3F19 (T = Cr, Co, Ga). Une discussion cristallochimique permet d'expliquer l'existence d'un domaine de solutions solides au sein du diagramme ternaire SrF2BaF2FeF3. 相似文献
42.
A. González Arias C. Torres C. de
Francisco J. M. Muñoz P. Hernández
Gómez O. Alejos O. Montero J. I. Iñiguez 《Journal of Thermal Analysis and Calorimetry》2006,86(1):195-198
The article discusses theory and experiment about the measurement of
defect concentration in Ti-substituted yttrium iron garnet by means of thermogravimetry
techniques. The two possible cases arising from oxygen interchange with atmosphere,
oxygen vacancies and interstitial cations, may be analyzed quantitatively
from the derived expressions. The possibility of another type of defects being
present in the samples, not associated to oxygen evolution, is not excluded.
Measurements were carried out in air and CO2 for different
Ti contents. The substitution tends to increase slightly the defect parameter
θ in YIG, while a CO2 reducing atmosphere is
much more effective than the Ti substitution for increasing θ. Calculations
for a given single-phased sample sintered in air show two possibilities: a
deficit of one oxygen atom for every 2.5 unit cells of 96 atoms, or one excess
cation for every 3.5 cells. Other samples show very similar results. The accuracy
involved in the measurements is about 2–3%. 相似文献
43.
44.
del Mar Graciani M Rodríguez A Muñoz M Moyá ML 《Langmuir : the ACS journal of surfaces and colloids》2005,21(16):7161-7169
Micellization in water-ethylene glycol (EG) N-dodecyl, N-tetradecyl, and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SB3-12, SB3-14, and SB3-16, respectively) micellar solutions, with the weight percent of EG changing within the range 0-40, was studied by means of surface tension measurements. Information about the influence of the added EG on the aggregation number of the sulfobetaine micelles and on the polarity of the interfacial region of micelles was obtained through fluorescence and spectroscopic measurements. Surface tension measurements also provide information about the dependence of the surface excess concentration, the minimum area per surfactant molecule, the surface pressure at the cmc, and the standard Gibbs energy of adsorption on the added weight percent of the organic solvent. The Gordon parameter of the water-EG mixtures was also estimated by means of surface tension measurements. The thermodynamic and structural changes originated by the presence of EG control the micellar kinetic effects observed in the reaction methyl 4-nitrobenzenesulfonate + Br(-) occurring in the water-EG sulfobetaine micellar solutions. Information about the distribution of bromide ions between the bulk and micellar pseudophases was obtained through conductivity measurements. The kinetic micellar effects were quantitatively explained by using the pseudophase kinetic model. 相似文献
45.
本文将3-三氰基乙烯基-N-十六烷基吲哚与花生酸混合制成单分子膜。不同摩尔比混合膜的π-A曲线均出现平台,表明膜压缩过程中分子排列相态发生变化。混合LB膜的紫外吸收光谱证明吲哚分子形成聚集体,X-射线衍射结果说明这种聚集体被夹带在花生酸的框架结构中。 相似文献
46.
Host-guest complexes of cucubit[8]uril with phenanthrolines and some methyl derivatives 总被引:1,自引:0,他引:1
DAY Anthony I 《中国科学B辑(英文版)》2005,48(4):305-314
Cucurbituril a molecular container (or host) has a rigid hollow interior cavity which is large enough to accommodate, one or more, smaller molecules (or guests). The cavity is accessible through two carbonyl portal openings. Molecules or guests enter the … 相似文献
47.
A simple method has been developed for the simultaneous determination of N-butylscopolamine bromide and oxazepam in pharmaceutical formulations using first-order digital derivative spectrophotometry. Acetonitrile was selected as the solvent in which both compounds showed well-defined bands. Both analytes showed good stability in this solvent when solutions of the analytes were exposed to light and temperatures between 20 degrees and 80 degrees C. The simultaneous determination of both drugs was performed by the zero-crossing method at 226.0 and 257.0 nm for N-butylscopolamine and oxazepam, respectively. The linear range of determination was found to be 2.5 x 10(-7) to 8.0 x 10(-5) mol/L for N-butylscopolamine and 7.1 x 10(-8) to 8.0 x 10(-5) mol/L for oxazepam. A very good level of repeatability (relative standard deviation) of 0.2% was observed for N-butylscopolamine and oxazepam. The ingredients commonly found in pharmaceutical formulations do not interfere. The proposed method was applied to the determination of these drugs in pharmaceutical formulations (capsules). 相似文献
48.
Bitao Su Ke Wang Jie Bai Hongmei Mu Yongchun Tong Shixiong Min Shixiong She Ziqiang Lei 《Frontiers of Chemistry in China》2007,2(4):364-368
Fe3+-doped TiO2 composite nanoparticles with different doping amounts were successfully synthesized using sol-gel method and characterized
by X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultravioletvisible spectroscopy (UV-Vis) diffuse reflectance
spectra (DRS). The photocatalytic degradation of methylene blue was used as a model reaction to evaluate the photocatalytic
activity of Fe3+/TiO2 nanoparticles under visible light irradiation. The influence of doping amount of Fe3+ (ω: 0.00%–3.00%) on photocatalytic activities of TiO2 was investigated. Results show that the size of Fe3+/TiO2 particles decreases with the increase of the amount of Fe3+ and their absorption spectra are broaden and absorption intensities are also increased. Doping Fe3+ can control the conversion of TiO2 from anatase to rutile. The doping amount of Fe3+ remarkably affects the activity of the catalyst, and the optimum efficiency occurs at about the doping amount of 0.3%. The
appropriate doping of Fe3+ can markedly increase the catalytic activity of TiO2 under visible light irradiation.
__________
Translated from Journal of Northwest Normal University (Natural Science), 2006, 42(6): 55–56 [译自: 西北师范大学学报(自然科学版)] 相似文献
49.
50.
铜在HOPG上电沉积过程的现场ECSTM研究 总被引:3,自引:1,他引:3
用自制的电化学扫描隧道显微镜(ECSTM)现场研究Cu在HOPG上的电沉积过程.结果表明Cu在HOPG上的电沉积为三维成核的过程.当电位较低或Cu2+离子浓度较低时,铜在本体金属生长主要沿着台阶方向.过电位较高时,铜的成核数目增加,沉积层的晶粒有所细化.同时,非现场ECSTM比较研究表明,STM针尖对针尖局部区域的电沉积起屏蔽作用,针尖所在区域Cu的沉积速度比其它区域明显减小 相似文献