The initial and thermally treated composites based on SnOx/MWCNT have been studied by the XANES and XPS methods using the equipment of the BESSY II Russian-German beamline of synchrotron radiation and by the AES and HRTEM methods. The characteristic mechanisms of chemical and structural transformations in the SnOx phase have been determined depending on the vacuum annealing temperature. It has been found that the basic process in the metal-oxide component at annealing temperatures not exceeding 500°C is the tin monoxide SnO disproportionation reaction with the formation of the dioxide SnO2 phase and metallic tin. An increase in the annealing temperature to 800°C results in the activation of carbothermal reduction of metallic tin in contact areas of oxide clusters and MWCNT, as well as in the formation of nanocrystalline structures in the metal-oxide component of composite. 相似文献
Layers of por-Si/SnOx nanocomposite formed by high-power ion beam irradiation with nanosecond duration have been studied. The results of structural
and elemental analyses of these layers are presented. The high sensitivity of this nanocomposite to low NO2 concentrations at room temperature has been revealed. 相似文献
Using the methods of X-ray photoelectron (XPS) and X-ray absorption near edge structure (XANES) spectroscopies with synchrotron radiation, data on changes in the electronic structure and chemical composition of nitrogen-containing multiwalled carbon nanotubes (N-MWCNTs) upon their exposure to the radiation of argon ions with an energy of 5 keV are obtained. It is found that the exposure leads to an increase in the degree of defectiveness of the N-MWCNTs structure and to the carbon oxidation with formation of various oxygen-containing groups (C–OH, C=O/COOH, C–O–C/O–C–O, and CO3). The presence of carbon–oxygen bonds on the surface of carbon nanotubes is associated with the formation of radiation defects. It is shown that an increase in the fraction of nitrogen atoms present in the substituting configuration in the N-MWCNTs wall structure due to the irradiation does not give rise to an increase in the density of the occupied states near the Fermi level against the background of an increase in the degree of structure defectiveness, carbon oxidation, and a decrease in the total nitrogen concentration. The obtained results show that the irradiation of N-MWCNTs with argon ions allows one to successfully functionalize their surface.
Physics of the Solid State - Changes in the local atomic and electronic structure and the chemical state of the surface of multiwalled carbon nanotubes (MWCNTs) irradiated with continuous and... 相似文献
The changes in the electronic structure and phase composition of porous silicon under action of pulsed ionic beams have been studied by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES) using synchrotron radiation. The Si 2p and O 1s core photoemission spectra for different photoelectron collection angles, valence band photoemission spectra, and X-ray absorption near-edge fine structure spectrain the region of Si L2,3 edges of the initial and irradiated samples have been analyzed. It has been found that, as a result of the irradiation, a thin oxide film consisting predominantly of higher oxide SiO2 is formed on the porous silicon surface, which increases the energy gap of the silicon oxide. Such film exhibits passivation properties preventing the degradation of the composition and properties of porous silicon in contact with the environment. 相似文献
The specific features of changes in the electronic structure of multi-walled carbon nanotubes (MWCNTs) due to the interaction with an amorphous tin oxide in the SnOx/MWCNT composite formed by magnetron sputtering have been investigated using X-ray spectroscopy. It has been shown that the formation of chemical bonds responsible for significant changes in the local and electronic structures of the outer layers of MWCNTs occurs at the boundaries of the “amorphous oxide/MWCNT” contacts. The vacuum annealing of the composite leads to the disturbance of the chemical interaction at interfaces of the composite and to a partial recovery of the local structure of the outer layers of MWCNTs. A decrease in the amount of oxygen in the tin oxide under vacuum annealing conditions causes an increase in the number of unpaired Sn 5s electrons, which, in turn, enhances the charge transfer through the interfaces in the composite and leads to a splitting of the π*-subsystem of the outer layers of MWCNTs. 相似文献
Nanocomposite layers based on multiwalled carbon nanotubes (MWCNTs) and non-stoichiometric tin oxide (SnOx) have been grown by magnetron deposition and CVD methods. In the case of the CVD method, the study of the structure and phase
composition of obtained nanocomposite layers has shown that a tin oxide “superlattice” is formed in the MWCNT layer volume,
fixed by SnOx islands on the MWCNT surface. During magnetron deposition, the MWCNT surface is uniformly coated with tin oxide islands,
which causes a change in properties of individual nanotubes. Electrical measurements have revealed the sensitivity of nanocomposite
layers to (NO2)− molecule adsorption, which is qualitatively explained by a change in the conductivity of the semiconductor fraction of p-type MWCNTs. 相似文献
The transformation of the structural phase state and the electronic structure of the SnO2 ? x/MWCNT composite has been studied using X-ray spectroscopy and high-resolution transmission electron microscopy. It has been shown that the character of the interaction of the metal-oxide component of the composite with the array of carbon nanotubes depends on the structural state of tin oxide in globules of the metal-oxide component. In the initial composite with a large content of amorphous tin oxide, covalent functionalization of the MWCNT surface occurs. High-vacuum annealing results in the formation of a nanocrystalline structure in globules of the metal-oxide component and is accompanied by changes in the character of its interaction with carbon tubes. 相似文献
Data on the distribution of iron in nitrogen-containing multiwall carbon nanotubes (N-MWCNTs) and changes in its chemical state and concentration under different parameters of irradiation by a pulsed ion beam are obtained by methods of transmission electron microscopy, X-ray photoelectron spectroscopy, and energy dispersion analysis. It is shown that the irradiation of N-MWCNTs with an energy density of 0.5 J/cm2 lead to the formation, on their lateral surfaces, of structures with a size of 2–10 nm, consisting of metallic iron encapsulated in a carbon shell. An increase in the energy density to 1–1.5 J/cm2 leads to a substantial removal of iron clusters from the tips of carbon nanotubes and a reduction in the amount of iron in the bulk of the N-MWCNT layer.
The origin of the low-frequency band (250–300 cm?1) in the Raman spectra of multi-walled carbon nanotubes (MWCNTs) produced by the CVD method has been studied. The studies performed by Raman spectroscopy, transmission electron microscopy, Auger spectroscopy, and X-ray photoelectron spectroscopy after chemical and thermal treatments allow the assumption that this band belongs to radial vibrations of carbon atoms in internal walls of MWCNTs. 相似文献