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61.
Partitioning adsorption properties of palladium cations on composite supports of MgO/-Al2O3 were explored by IR, TPR and catalytic performance tests for CO oxidation. The experimental results revealed that palladium cations in conventional impregnation was dispersed completely on -Al2O3, when the amount of MgO in the samples was lower than 5%. For the catalysts prepared by double impregnation, part of palladium dispersed on MgO phase due to the complexing action of EDTA. Pd–MgO interaction suppressed the reaction of CO oxidation. 相似文献
62.
以碳纳米管(CNT)作为低铂载量膜电极(CCM)催化层(0.1 mgPt·cm-2)添加剂,研究了CNT的添加方式对催化层微观结构以及膜电极性能的影响.结果表明,与常规低铂载量催化层相比,在其表面喷涂一层CNT或将CNT均匀分散到Pt/C催化层中均有利于提升低铂载量膜电极的输出性能,在70℃和100%相对湿度条件下最高输出功率比常规低铂载量膜电极的0.522 W·cm-2分别提升了22.4%和60.0%,并且均匀分散添加方式优于分层添加方式.其原因在于分层添加CNT后改善了低铂催化层和气体扩散层之间的接触界面,降低了催化层与扩散层间的接触电阻,而均匀分散添加方式除了可降低界面接触电阻外,还显著改善了低铂催化层中的气体传输,大幅提升了Pt催化剂的利用效率,使得膜电极电化学反应电阻明显降低.进一步对均匀分散添加方式中CNT的载量进行优化,表明CNT添加量为37.5 μg·cm-2时电池输出性能最佳,70℃和100%相对湿度条件下的最大输出功率达到0.91 W·cm-2.本研究工作表明,将CNT均匀分散添加到催化层中是一种有效提升低铂载量膜电极性能的方法. 相似文献
63.
Guadalupe Fortuño 《Plasma Chemistry and Plasma Processing》1988,8(1):19-34
A parametric study of the etching of Si and SiO2 by reactive ion etching (RIE) was carried out to gain a better understanding of the etching mechanisms. The following fluorocarbons (FCs) were used in order to study the effect of the F-to-Cl atom ratio in the parent molecule to the plasma and the etching properties: CF4, CF3Cl, CF2Cl2, and CFCl3 (FC-14, FC-13, FC-12, and FC-11 respectively). The Si etch rate uniformity across the wafer as a function of the temperature of the wafer and the Si load, the optical emission as a function of the temperature of the load, the etch rate of SiO2 as a function of the sheath voltage, and the mass spectra for each of the FCs were measured. The temperature of the wafer and that of the surrounding Si load strongly influence the etch rate of Si, the uniformity of etching, and the optical emission of F, Cl, and CF2. The activation energy for the etching reaction of Si during CF4 RIE was measured. The etch rate of Si depends more strongly on the gas composition than on the sheath voltage; it seems to be dominated by ion-assisted chemical etching. The etching of photoresist shifted from chemical etching to ion-assisted chemical etching as a function of the F-to-Cl ratio and the sheath voltage. The etch rate of SiO2 depended more strongly on the sheath voltage than on the F-to-Cl ratio. 相似文献
64.
BAO Ren-lie KONG Zu-ping GU Min YUE Bin WENG Lin-hong HE He-yong 《高等学校化学研究》2006,22(6):679-683
IntroductionSynthesis of natural minerals is helpful for tracingthe geological origin of mineral formation and forverifying the quality of minerals. The investigations onthe conditions for mineral formation, such as pressure,temperature, and starting mate… 相似文献
65.
Xiao Lian Zhang Joseph T. Hupp Gerald D. Danzer 《Journal of Electroanalytical Chemistry》1995,380(1-2)
The comparative interfacial oxidation kinetics of the approximate structural isomers trans-(O)2ReV(py)+4 and cis-(O)2ReV(bpy)(py)+2 (py, pyridine; bpy, 2,2′-bipyridine) have been assessed in aqueous solution via conventional cyclic voltammetry at a highly ordered pyrolytic graphite (HOPG) electrode. HOPG was employed because of its known propensity to diminish interfacial electron transfer (ET) rates (by ca. three to four orders of magnitude) and because of a probable lack of importance of kinetic work terms (diffuse double-layer corrections). Measured rates for the trans complex exceed those for the cis by about a factor of 3. Expressed as an effective activation Gibbs energy difference ΔG*, this corresponds to a cis-trans difference of ca. 3 kJ mol−1. The actual vibrational barriers to ET have determined from a combination of published X-ray structural results (trans complex) and new resonance Raman results (cis complex). The values are 0.6 kJ mol −1 for the trans oxidation and 4.4 kJ mol−1 for the cis oxidation (i.e. close to the barrier difference inferred from rate measurements). Further analysis shows that most of the barrier difference is associated with displacement of a (predominantly) Re-N(bpy) stretching mode found only in the cis system. Differences in metal-oxo displacements (cis > trans) are also implicated. 相似文献
66.
Structural tuning of coordination polymers by 4-connecting metal node and secondary building process
Due to variation in ligand's conformation, metal node's connecting geometry, and secondary building process by anions, bat-like, dumbell-like, diamondoid, or pillar-layer topologies are achieved. 相似文献
67.
A Pluta polarizing interference microscope with a fibre stretching device attached was used to detect the changes in molecular structure that occur during the fibre cold drawing process. Fibres drawn with low draw ratios show different types of deformation mechanisms. The interference patterns recorded at different draw ratios are used to relate the deformation mechanisms with the measured structural parameters. Some optical parameters are measured such as; refractive indices nand n birefringence n, the polarizability per unit volume , the orientation distribution function f(θ), the angle θ between the stretching direction and the chain axis, and the angle θm which the transition dipole moment of the molecular species makes with the molecular axis (chain axis). Three polymeric fibres (Polyethylene terephthalate PET, Polypropylene PP and Polyamide PA) were used in this study and their interferograms are illustrated. 相似文献
68.
稀土氨基酸固体络合物的合成及结构分析进展 总被引:16,自引:2,他引:16
本文综述了稀土氨基酸络合物的合成,以及应用红外、核磁、X-射线衍射、热分析等方法进行结构分析研究的进展情况。 相似文献
69.
W. Ryba-Romanowski S. Go
b G. Dominiak-Dzik W. A. Pisarski D. Podsiada Z. Czapla 《Journal of Molecular Structure》1998,450(1-3):219-222
Chromium doped (CH3)2NH2Al(SO4)2·6H2O (DMAAlS) and (CH3)2NH2Ga(SO4)2·6H2O (DMAGaS) single crystals were grown and investigated using the methods of optical spectroscopy. It was found that the Cr3+ ions in the two crystals are situated in a strong crystal field in which the 2E state is the lowest. The single narrow R-line associated with the 2E–4A2 phosphorescence of Cr3+ in DMAAlS in a ferroelectric phase indicates an undistorted octahedral site, whereas important distortion of Oh symmetry and structural disorder was inferred from spectral data obtained with DMAGaS:Cr3+ in a low temperature phase. Results of optical investigation are discussed taking into account the structural data. 相似文献
70.
Layered compounds have been synthesized and structurally characterized for the n=5 and 6 members of the perovskite-related family La4Srn−4TinO3n+2 by combining X-ray diffraction and transmission electron microscopy. Their structure can be regarded as comprising [(La,Sr)5Ti5O17] and [(La,Sr)6Ti6O20] perovskite blocks joined by crystallographic shears along the a-axis, with consecutive blocks shifted by 1/2 [100]p. The n=5 member is similar to the previously reported n=5 member of other AnBnO3n+2-related series. The n=6 member, which has only been briefly reported in other systems previously, is also a well-behaved member of this AnBnO3n+2 series. 相似文献