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采用新的合成方法制备了一类新的化合物LaSr2-xCaxV3O9±y, X射线粉末衍射分析证实它们是单一化合物。利用计算机及自编软件对其进行了指标化并计算了它们的晶胞常数。结构数据表明, 随钙含量的增加, LaSr2-xCaxV3O9±y发生了从立方到正交到立方的相转变。热重和光电子能谱表明, 新化合物中的钒是以V^3^+和V^4^+的低价态形式存在, 它们具有较低的电阻率。 相似文献
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在MgO·nB_2O_3-18%MgSO_4-H_2O体系0 ℃结晶过程的动力学研究、用物理方 法和化学分析确定析出固相的组成和测定固相共饱和点的基础上,给出了该体系0 ℃时的热力学非平衡态液固相关系图。该相图存在四个相区,分别与H_3BO_3, MgO·3B_2O_3·7.5H_2O,MgO·2B_2O_3·9H_2O和2MgO·3B_2O_3·15H_2O(多水 硼镁石)相对应。结果表明MgCl_2和MgSO_4介质对镁硼酸盐的析出有不同的影响。 相似文献
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本文测定了278.2~318.2K间的五个温度下七种浓度的NaOAc分别在10, 20,30, 40, 50, 60, 70, 80, 90及100%MeOH-H~2O体系中的摩尔电导Λ, 并应用FOS,Pitts, L-W, F-78等四个电导方程对实验数据进行了拟合处理, 得到了三个拟合参数Λ~O, K~Λ及R(或α)。最后, 对四个方程与实验的吻合程度, 温度、溶剂组成等对Λ~O、K~Λ的影响规律及溶质-溶剂相互作用进行了讨论。 相似文献
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Jingfei Luan Zhigang Zou Minghui Lu Guoyou Luan Yanfeng Chen 《Research on Chemical Intermediates》2006,32(1):31-42
In2BiTaO7 was synthesized using the solid-state reaction method and its photocatalytic properties were investigated. The results of
powder X-ray diffraction (XRD) indicated that the compound crystallizes in the pyrochlore-type structure, cubic system with
space group Fd-3m. The lattice parameter is 10.6972(1) ?. In addition, the compound shows strong optical absorption in the
visible region (λ > 420 nm) and the band gap of In2BiTaO7 was estimated to be about 2.47 eV. For the photocatalytic reaction, H2 or O2 evolution was observed from CH3OH/H2O or AgNO3 solution respectively with In2BiTaO7 as the photocatalyst under visible light irradiation, indicating that In2BiTaO7 is responsive to visible light for splitting water. Furthermore, the catalyst remained photoactive in the wavelength range
up to 510 nm. Photocatalytic degradation of methylene blue (MB) dye over the compound was further investigated under visible
light irradiation. The results showed that complete removal of aqueous MB could be achieved after irradiation for 135 min
over In2BiTaO7. Furthermore, under visible light irradiation In2BiTaO7 showed markedly higher catalytic activity compared to P-25 for MB photocatalytic degradation. 相似文献
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《Composite Interfaces》2013,20(3-4):169-176
The water sorption properties of Precipitated Calcium Carbonate (PCC) formulations have been studied in relation to the rheological behaviour. Uncoated mineral fillers (median diameter 0.85 μm) have been dispersed in an organic liquid used as plasticizer, a dioctylphthalate (DOP), at a concentration of 25% by weight (volume fraction of about 11%). Water sorption isotherms onto PCC in air and in the organic matrix have been constructed. Measurement of water concentration in the DOP permits a complete evaluation of water exchanges at the inorganic (mineral)/organic (plasticizer) interface. Evolutions of yield stress, storage modulus and loss modulus have been determined as functions of the water activity in the system. A drastic change of rheological properties has been observed for water activities above 0.3. 相似文献
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《Composite Interfaces》2013,20(7):647-655
Composites based on the blends of polyurethane and poly(methyl methacrylate) of various composition were synthesized in situ in the presence of various amounts of nanoparticles (fumed silica). From thermophysical measurements it was found that, during reaction, phase separation and evolution of two phases occur. The temperature transitions in the systems and their positions depend on the blend composition and on various amounts of nanoparticles. Using scanning differential calorimetry from the changing of heat capacity increments the fraction of an intermediate region between two main phases has been estimated. For the first time it was observed that in nanocomposites in the temperature region between two main relaxation transitions, there appears a third transition, which was related to the adsorption layers formed by both components at the interface of the nanoparticles. The appearance of such intermediate regions increases essentially the fraction of an interfacial region in the system. 相似文献
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《Composite Interfaces》2013,20(3):185-236
The peculiarities of reaction-induced phase separation and the structure formation in semi- and full interpenetrating polymer networks and in the blends of linear polymers formed in situ are analyzed. It is shown that for most of these systems phase separation proceeds viathe spinodal decomposition mechanism resulting in the formation of interconnected spatially periodic structures. The possible ways for the structure regulation of the composites produced are considered. 相似文献
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《Composite Interfaces》2013,20(2-3):281-299
Nowadays, utilisation of biodegradable materials has become necessary in order to maintain global environmental and ecological balance. Fully biodegradable nano 'Green' textile composites have been prepared from cellulose nanofibers reinforced corn starch resin and ramie fabric. Nanofibers having dimensions of approximately 1 μm long and 20–30 nm in diameter are used in the study. The nanofibers were incorporated in corn starch resin via ball mill mixing using ceramic balls. Textile composites were fabricated by pasting the reinforced resin onto the ramie fabric and by hot compression molding technique. Interactions at the fiber–matrix interface and the compatibility between cellulose and corn starch resin molecules will affect the properties of the system. The well dispersed cellulose nanofibers contribute higher interfacial area and good fiber networking within the matrix resin. This will lead to better barrier properties. Sorption characteristics of water, oil and diesel in the textile composites were analysed and the influence of nano fibers and macro fibers on the transport phenomena was investigated. The kinetics of sorption-diffusion process was investigated. Kinetic parameters such as n, k, diffusion coefficient, permeability, solubility parameter, % swelling index, etc., were analysed. The presence of cellulose nanofibers influences the sorption mechanism. The water sorption mechanism in the nanocomposites was found to exhibit slight deviation from Fickian mode. Structure–property relationships of the nanocomposites were evaluated. 相似文献
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《Composite Interfaces》2013,20(3-4):167-186
A study of the microstructure developing at the surface of glass fibers in a poly(vinyl acetate) (PVAc)/polyester blend is presented. Three different experimental methods are used: a technique based on the Wilhelmy method to measure the wettability of the fibers before curing, and both optical microscopy and atomic force microscopy in the pulsed-force mode to characterize potential phases splitting at the fiber–matrix interface after curing. It was found that, depending on the curing conditions and the concentration in PVAc, the surface treatment of the fiber could have a significant influence on the microstructure. For a concentration in PVAc lower than 5 wt% and a curing temperature of 80°C, extreme cases, such as the development of layers of one of the phases at the surface or the formation of lenses of one phase, were observed. In other cases, in particular for elevated temperatures and higher concentrations in PVAc, the fibers did not exert a significant influence on the morphology. It was also found that in such a reactive system, surface tension considerations alone are insufficient to explain the configuration of the phases at the surface of the fibers. 相似文献