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11.
Magnus Rnning Florian Huber Hilde Meland Hilde Venvik De Chen Anders Holmen 《Catalysis Today》2005,100(3-4):249-254
In order to investigate the effect of cerium oxide on Cu–Zn-based mixed-oxide catalysts four catalyst samples were characterized by means of XRD, in situ XANES and thermogravimetric analysis. The activity of the catalyst samples was tested for the forward water–gas shift reaction. Cerium oxide was found to increase the crystallinity of the ZnO phase indicating a segregation of the Cu and ZnO phases. The TOF of the water–gas shift reaction based on chemisorption data was found to be independent of composition and preparation conditions of the four catalyst samples. In contrast, the catalyst stability depends on composition and preparation conditions. Cerium oxide impregnated before calcination of the hydrotalcite-based Cu–Zn precursors leads to a more stable water–gas shift catalyst. 相似文献
12.
Maria Chiara Dalconi Giuseppe Cruciani Alberto Alberti Paolo Ciambelli 《Catalysis Today》2005,110(3-4):345-350
High-silica zeolites exchanged with transition metal ions (TMIs) are the subject of great interest for their unusual catalytic activity and selectivity. Structural information like coordination and accessibility of TMIs in zeolites are important factors for understanding their catalytic activity. Siting of TMIs in zeolites is typically obtained by spectroscopic (EXAFS, EPR, UV–vis and IR) and computational methods, as in the case of Co-ferrierite. However, some controversy exists in the literature concerning the model for incorporation of bare Co ions in ferrierite. We show here that the results of our synchrotron X-ray powder diffraction studies on Co- and Ni-exchanged ferrierite (Si/Al = 8.5) are in a good agreement with the model of Co siting based on an indirect spectroscopic approach and help to validate this model. By direct structural evidences, a possible explanation for the larger catalytic activity of Co sites in the main channels of ferrierite can be inferred. A combination of data from in situ XRD continuous monitoring of the Co ion migration during calcination and crystal-chemical considerations allows to device a strategy for the design of optimised co-cations containing Co-ferrierite catalysts. 相似文献
13.
In this paper we show that by the analysis of 2D images collected with a laboratory X-ray microdiffractometer it is possible to non-destructively evaluate the structure, the microstructure, and the preferred orientation of films. In particular, the structural analysis of Co/Au multilayers on Si(1 0 0) deposited at different Ar pressures are reported and discussed. 相似文献
14.
Hun Xue 《Materials Letters》2007,61(2):347-350
Macroporous nanocrystalline zinc ferrite with single spinel-phase was prepared by a facile self-propagating combustion method using zinc nitrate, iron nitrate and glycine. The as-prepared ZnFe2O4 were characterized by X-ray diffraction (XRD) analysis, N2 adsorption, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and energy dispersive X-ray spectrum (EDS). The magnetic properties of the prepared ZnFe2O4 were also studied. 相似文献
15.
TiO2 andCeO2 aresemiconductormaterials .TiO2hasthepropertiesofphoto catalysis[1] whileCeO2 hastheabilityofoxygenstorageandcanpromotethedispersionofprecionsmetalsonthesupporter[2 ] .CeO2 TiO2 com plexcompoundwasusedascatalystandspecialfunction almaterial[3~ 5] .ThetraditionalsynthesisofCeO2 TiO2complexcompoundisbyceramicmethodthatusesoxidesasrawmaterialsanditiscalcinedabove 130 0℃[6~ 8] .However ,thestructureandmicrostructureofthecomplexcompoundarenotsuitableforcatalystandfunctionalm… 相似文献
16.
This paper presents the current understanding of the flame retardant mechanism of Casico?. The study includes the flame retardant effect of each individual component: ethylene–acrylate copolymer, chalk and silicone elastomer, as well as the formation of an intumescent structure during heating. The flame retardant properties were investigated by cone calorimetry and oxygen index tests. To obtain insight into the flame retardant mechanism, heat treatment under different conditions has also been performed. The results indicate that the flame retardant mechanism of Casico is complex and is related to a number of reactions, e.g. ester pyrolysis of acrylate groups, formation of carbon dioxide by reaction between carboxylic acid and chalk, ionomer formation and formation of an intumescent structure stabilized by a protecting char. Special emphasis is given to the formation of the intumescent structure and its molecular structure as evaluated from 13C MAS‐NMR and 29Si MAS‐NMR, ESCA and XRD analysis. After treatment at 500°C the intumescent structure consists mainly of silicon oxides and calcium carbonate and after treatment at 1000°C the intumescent structure consists of calcium silicate, calcium oxide and calcium hydroxide. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
17.
Development of nano indium tin oxide (ITO) grains by alkaline hydrolysis of In(III) and Sn(IV) salts
Indium tin oxide (ITO) nano powders of different compositions (In: Sn = 90: 10, 70: 30 and 50: 50) were prepared by heat treatment
(300-450°C) of mixed hydroxides of In(III) and Sn(IV). The hydroxides were obtained by the reaction of aq. NH3 with mixed aq. solutions of In(NO3)3 and SnCl4. FTIR and TG/DTA studies revealed that powders existed as In(OH)3H2O—SnO3H2H2O in the solid state and then they transformed to In2O3—SnO2 via some metastable intermediates after 300°C. Cubic phase of In2O3 was identified by XRD for the oxides up to 30% of Sn. Particle size measurements of the solid dispersed in acetone and SEM
study for microstructure showed that the oxides were in the nano range (55-75 nm) whereas the size range determined from Debye-Scherrer
equation were 11–24 nm. 相似文献
18.
Travis Blalock 《Surface & coatings technology》2007,201(12):5850-5858
In this study a set of thin Hydroxyapatite (HA) [Ca10(PO4)6(OH)2] coatings was deposited on heated silicon and titanium substrates using Ion Beam Assisted Deposition (IBAD). The effects of substrate temperature and processing parameters on the microstructural properties and composition of the coatings are being studied. Analytical techniques include transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) with an energy dispersive X-ray spectroscopy (EDS), as well as scanning electron microscopy (SEM) with EDX, X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR). The current results indicate that as substrate temperature increases the Ca/P ratio of the coatings both on titanium and silicon substrates increases. The crystallinity of the coatings and the number of calcium phosphate compounds within the coating including HA also increases. STEM-EDS revealed an atomically diffused intermediate layer at the interface between the coating and substrate. XRD results along with TEM selected area diffraction (SAD) revealed that the coatings are composed of HA, other calcium phosphate, and calcium oxide compounds. 相似文献
19.
缓冲层对氮化镓二维生长的影响 总被引:1,自引:0,他引:1
报道了在射频等离子体(RF-Plasma)辅助的分子束外延(MBE)技术中,使用白宝石(0001)衬底,采用低温缓冲层工艺外延氮化镓(GaN)。通过原子力显微镜(AFM)的表面形貌比较及X射线双晶衍射(XRD)ω扫描摇摆曲线的分析,讨论了低温缓冲层成核机理及缓冲层生长温度与形成准二维生长的关系,确立了缓冲层的三维成核,准二维生长的生长机理,并在此基础上实现了氮化镓外延层更好地二维生长,进一步提高了氮化镓外延层的晶体质量。 相似文献
20.
Sodium‐ion conducting polymer electrolytes based on poly(vinyl alcohol) complexed with sodium bromide were prepared with a solution‐casting technique. The structure of these films was determined with X‐ray diffraction, and the complexation of the salt with the polymer was confirmed with Fourier transform infrared spectroscopy studies. Electrical conductivity was measured with an alternating‐current impedance analyzer in the frequency range of 100 Hz to 1 MHz and in the temperature range of 303–373 K. It was observed that the magnitude of conductivity increased with the increase in the salt concentration as well as the temperature. The nature of the charge transport in these polymer electrolyte films was determined with both Wagner's polarization technique and the Watanabe technique. The dominant conducting species were found to be ions, particularly anions. Optical absorption studies were performed in the wavelength range of 200–600 nm, and the absorption edge, direct band gap, and indirect band gap values were evaluated. Electrochemical cells were fabricated, and their discharge characteristics were studied. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献