Search results for "electron spectroscopy"
showing 10 items of 525 documents
Effect of antisite defects on the magnetic properties of ZnFe2 O4
2013
Magnetic zinc ferrite (ZnFe2O4) nanopowders were synthesized using the sol–gel autocombustion method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements demonstrated that thermal decomposition of the 1-mm-thick xerogel layers in air formed monophasic spinel ferrite nanopowders with a particle size less than 30 nm. X-ray photoelectron spectroscopy (XPS) showed that the obtained reaction product contained antisite defects, with zinc ions occurring at the octahedral sites of the spinel structure. The concentration of antisite defects or inversion degree decreased when the relatively low annealing temperature was increased from 150 to 500 °C. Overall, the obtained ZnFe2…
Facile synthesis of magnetically separable CoFe2O4/Ag2O/Ag2CO3 nanoheterostructures with high photocatalytic performance under visible light and enha…
2017
Riga Technical University supported the preparation of this manuscript from the Scientific Research Project Competition for Young Researchers No. ZP-2016/7. The authors wish to kindly acknowledge the financial support of HZB, Estonian Research Council (PUT1096, PUT735 and IUT2-25) and Estonian Centre of Excellence in Research Project “Advanced materials and high-technology devices for sustain-able energetics, sensorics and nanoelectronics” TK141 (2014–2020.4.01.15-0011).
Soft X-ray photoelectron microscopy used for the characterization of diamond, a-C and CN , thin films
2002
Abstract This article gives an overview about the application of X-ray photoemission electron microscopy (X-PEEM) used for the analysis of carbon thin films. We present the results of an X-ray absorption near edge structure (XANES) study of CVD diamond, a-C and CNx films on Si (100) as well as a defect analysis of a hard disc scratch test. The sp2/sp3 ratio of the carbon films was determined and mapped in the electron micrographs, which show localized defects in the surface.
Scale composition and oxidation mechanism of the Ti–46Al–8Nb alloy in air at 700 and 800 °C
2011
It is known that the oxide scale formed on TiAl alloys is generally composed of a mixture of alumina (Al2O3) and titania (TiO2). The presence of niobium changes the activities of Ti and Al and influences the kinetics of oxidation and oxide layer composition. In this work, the Tie46Ale8Nb alloy was subjected to cyclic oxidation in air at 700 � C (for 2 and 24 h) and 800 � C (for 300 h). Scale composition was analyzed by means of different techniques including X-ray photoelectron spectroscopy, X-ray diffraction and secondary ion mass spectroscopy. The scale consisted of several layers. The outer layer was built of alumina (amorphous or with very fine grains), whereas the inner layer e mainly …
Synthesis and characterization of mesoporous Mn-MCM-41 materials
2011
Si { 1 H} CP-MAS NMR X-ray photo-emission spectroscopy a b s t r a c t MCM-41 has been synthesized at two different pH using cetyl-trimethylammonium bromide (CTAB) surfactant as template and adding the silica precursor to aqueous solutions containing CTAB. The obtained solids were calcined at 600 ◦ C for 4 h. Mn-MCM-41 powders with different Mn/Si molar ratios were prepared using the incipient wetness method, followed by calcination at 550 ◦C for 5 h. At the end of the impregnation process the powders colour changed from white to brown whose intensity depends on manganese quantity. The materials characterization was performed by X-ray diffraction, N2 adsorption, 29 Si Cross Polarization–Mag…
SEM and XPS studies of titanium dioxide thin films grown by MOCVD
1998
Abstract The metal organic chemical vapour deposition (MOCVD) method was used to prepare titanium dioxide thin films. Thin films of TiO2, about 100 nm thick, were deposited on (100)Si and (1102)Al2O3 sapphire substrates using titanium isopropoxide (Ti(OC3H7)4) as metal organic precursor. The morphology of the films and the presence of impurities on the thin films surfaces were studied using respectively, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The influence of the growth parameters such as the deposition temperature, the carrier gas (nitrogen) flow rate and the presence of an additional oxygen flow on the characteristics of the titanium dioxide films h…
Selective hydrogenation of nitroderivatives over Au/TiO2/UVM-7 composite catalyst
2020
Abstract Hydrogenation of nitroderivatives (4-nitrostyrene or 7-nitro-1-tetralone) was performed using as support a silica mesoporous material with high specific surface area (1091 m2/g) and a bimodal pore size distribution (UVM-7). Gold and/or TiO2 were deposited inside the pores of this support with the aim to achieve high activity and selectivity for this reaction. The morphology and structure of the powders have been characterized by adsorption-desorption isotherms, XRD, TEM, STEM-HAADF, XPS and ATR-FTIR. Structural characterizations shown differences between the catalysts with and without titania. The presence of TiO2 provides a better size distribution of the spherical gold nanopartic…
N-TiO2 Photocatalysts highly active under visible irradiation for NOX abatement and 2-propanol oxidation
2013
N-doped TiO2 powders were prepared by two different sol-gel methods. Samples were characterised by X-ray diffraction (XRD), BET specific surface area measurements (SSA), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and Electron Paramagnetic Resonance (EPR). XPS measurements revealed a signal at 400 eV assignable to nitrogen in the form of Ti-N-O. EPR signals are attributed to molecular NO trapped with cavities/defects possibly interacting with oxygen vacancies. The photocatalytic activity under UV and visible light was determined following the abatement of NOx and the photodegradation of 2-propanol in gas-solid systems. N…
Graphene oxide-silica nanohybrids as fillers for PA6 based nanocomposites
2014
Graphene oxide (GO) was prepared by oxidation of graphite flakes by a mixture of H2SO4/H3PO4 and KMnO4 based on Marcano's method. Two different masterbatches containing GO (33.3%) and polyamide-6 (PA6) (66.7%) were prepared both via solvent casting in formic acid and by melt mixing in a mini-extruder (Haake). The two masterbatches were then used to prepare PA6-based nanocomposites with a content of 2% in GO. For comparison, a nanocomposite by direct mixing of PA6 and GO (2%) and PA6/graphite nanocomposites were prepared, too. The oxidation of graphite into GO was assessed by X-ray diffraction (XRD), Micro-Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectrosco…
In-situ study of multi-phase indium nanoparticle growth on/into CuPcF4 organic thin film in ultra-high vacuum conditions
2021
Abstract We study the in-situ growth of a nanocomposite material consisting of a thin CuPcF4 film and multiphase/multidimensional indium nanoparticles, self-organizing on the surface and in the bulk, at various stages of thermal deposition of metal on an organic film under ultrahigh vacuum conditions. The analysis of high-resolution transmission electron microscopy (HR-TEM) images provided valuable information about the evolution of morphology, size, density, and distribution of indium nanoparticles upon indium deposition. These 2D/3D ultra-small nano-objects turned out to have not only body-centered tetragonal (bct) crystal structure, typical for bulk indium, but also unusual face-centered…