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101.
The temperature programmed (palladium) hydride decomposition appeared very effective method for diagnosing the extent of alloying in Pd-Pt/SiO2 catalysts. Introduction of Pt to Pd catalysts moves the TPHD peak gradually towards lower temperatures and the shift in hydride decomposition peak is accompanied by a decrease in the amount of released hydrogen. The catalysts prepared the direct redox method showed much better alloy homogeneity than the samples prepared by coimpregnation. The results of probing with other techniques, i.e. catalytic probing with hydrodechlorination of CCl2F2 and XRD, were in line with TPHD data. The catalytic probing showed the presence of synergistic effect, a clear indication of Pd-Pt mixing. XRD data of post-reaction samples showed carbon incorporation into Pd-rich phase, whereas separate Pt-rich phase did not experience any bulk carbiding. 相似文献
102.
化学镀Ni—P镀层的X射线衍射研究 总被引:2,自引:0,他引:2
根据X射线衍射分析结果,对化学镀高P(含P>11wt%或19at%)Ni-P镀层加热时效时,镀层成分和加热温度对结构转变的影响作了研究,结果表明,高P共晶、过共晶(含P>11wt%或19at%)合金的结构转变有如下特征:(1)相同加热时效条件下,Ni-P合金的结构转变与成分有密切关系:(2)对同一成分的过共晶合金,Ni-P合金的结构转变与时效温度密切相关;(3)过共晶合金在290~360℃温度范围内时效处理,出现Ni_xP_y介稳相,X射线衍射分析认为Ni_xP_y为Ni_(12)P_5。 相似文献
103.
Viscose-based activated carbon fibers (VACFs) were treated by a dielectric-barrier discharge plasma at different conditions. Nitrogen was used as the feed gas to create nitrogen radicals. The textural characteristics were analyzed by SEM, BET and XRD. The surface chemical functional groups were analyzed by XPS. The results show that after nitrogen plasma modification (NPM), the external surface of the VACFs was etched and became rougher, the surface area and pore volume decreased, the average micropore width barely changed, the PSD of the VACF became narrower and the graphitic crystallites of VACF had been destroyed slightly. XPS revealed that NPM could remarkably change the distribution of the oxygen functional groups on the VACFs surface and there were more nitrogen atoms incorporated into the aromatic ring. A tentative explanation for the modification process is proposed. 相似文献
104.
Polypyrrole (PPy) doped with dodecylsulfate (DS) and an organic dye (indigo carmine, IC) was electrochemically prepared and characterized by Raman spectroscopy and X-ray diffraction (XRD). The photoelectrochemical properties of PPy-DS and PPy-DS-IC in contact with an electrolytic solution containing a redox couple were studied using the theories for the semiconductor ∣ electrolyte interface. Results indicate that the system containing IC presents a higher photocurrent density under polychromatic illumination and faster response time when compared with PPy-DS. This fact was assigned to the formation of molecular-scale paths in PPy-DS-IC. The IC molecules lying perpendicularly between PPy chains, as confirmed by the X-ray analysis, could facilitate the mass transport at the interface and increase the ordering degree to provide better electronic charge transfer in the bulk. Although the photoelectrochemical devices presented here do not present all the properties of inorganic-based devices, we discuss some strategies to enhance the photoelectrochemical properties and response time of conducting polymers used in these type of systems. 相似文献
105.
L. FAN‡ D. PATERSON† I. McNULTY‡ M. M. J. TREACY & J. M. GIBSON‡ 《Journal of microscopy》2007,225(1):41-48
Measuring medium‐range order is a challenging and important problem in the structural study of disordered materials. We have developed a new technique, fluctuation x‐ray microscopy, that offers quantitative insight into medium‐range correlations in disordered materials at nanometre and larger length scales.In this technique, which requires a spatially coherent x‐ray beam, a series of speckle patterns are measured at a large number of locations in a sample using various illumination sizes. Examination of the speckle variance as a function of the illumination spot size allows the structural correlation length to be measured. To demonstrate this technique we have studied polystyrene latex spheres, which serve as a model for a dense random‐packed glass, and for the first time have measured the correlation length in a disordered system by fluctuation X‐ray microscopy. We discuss data analysis and procedures to correct for shot noise and detector noise. This approach could be used to explore medium‐range order and subtle spatial structural changes in a wide range of disordered materials, from soft matter to nanowire arrays, semiconductor quantum dot arrays and magnetic materials. 相似文献
106.
Structural and electrical measurements of CdZnSe composite 总被引:1,自引:0,他引:1
V. Kishore Vibhav K. Saraswat N. S. Saxena T. P. Sharma 《Bulletin of Materials Science》2005,28(5):431-436
TheI—Vcharacterization and the electrical resistivity of selenium rich Se85Cd15-xZnx (x = 0, 3, 7, 11 and 15) system at room temperature have been studied. Samples were obtained using melt cooling technique. So
prepared samples were then characterized in terms of their crystal structure and lattice parameter using X-ray diffraction
method. The materials were found to be poly crystalline in nature, having zinc blend structure over the whole range of zinc
concentration. The measurements ofI—V bdcharacteristics have been carried out at different temperatures from room to 140°C. The electrical resistivity of the samples
with composition at room temperature has been found to vary between maximum 2.7 x 108 Ωm and minimum 7.3 x 105 Ωm and shows a maximum at 3 at. wt.% of Zn. The carrier activation energy of the samples with composition has also been determined
and found to vary from 0.026 eV to 0.111 eV. 相似文献
107.
双能X射线骨密度仪测定技术研究 总被引:6,自引:0,他引:6
以Lunar公司DPX-L型双能X射线骨密度仪为例,研究引起测量误差的主要因素并提出质控措施。用自检模块、腰椎体膜评定仪器的体外测量精度好于1%。对10位志愿者重复2次测量,体内精度对腰椎,MPD(平均百分差)为0.46,CV(变异系数)为0.75;对股骨颈,MPD为1.26、CV为0.47;Ward’s三角区MPD为2.01、CV为1.14;大转子MPD为1.66、CV为0.72。扫描图像由2位 相似文献
108.
The twinning of YBa2Cu3O7 (YBCO) thin films with c-axis orientation on (001) MgO, (001) SrTiO3, (012) LaAlO3, (110) NdGaO3 and (001) NdGaO3 substrates, prepared by laser ablation, has been examined using a combination of and θ/2θ scans at a four-circle diffractometer. On all substrates, except for (001) NdGaO3, the tetragonal to orthorhombal phase transition results in four different orientations of YBCO twins relating to the substrate. On (001) NdGaO3 only two different twin orientations, accompanied by a slight lattice monoclinization, has been observed. 相似文献
109.
A review is proposed of different techniques available today for the characterization of the atomic structure of carbon nanotubes. This review covers the electron microscopies, various diffraction techniques, scanning probe microscopies, and optical spectroscopies, including Raman scattering. The advantages and limitations of the characterization techniques are discussed. 相似文献
110.