M. Abbate

Polyaniline/lignin blends: thermal analysis and XPS

Polyaniline (Pani) base and Kraft lignin (Lig) blend films have been prepared using the solvent evaporation method. The highest lignin concentration used was of 36% (m/m). The thermal behaviour of free standing Pani and of Pani/Lig blends was characterized using thermogravimetric analysis (TGA) and DMTA techniques. The TGA results indicate that Pani/Lig blends have greater thermal stability than the pure polymers. The dynamic mechanical analysis (DMA) experiments indicated that the addition of lignin in the blend occur an impairment of rotation of part of the Pani chain. The possibility of interactions between Pani and lignin is discussed through X-ray photoelectron spectroscopy and DMA measuring. These interactions can occur between Pani chain amine nitrogen and carbonyl group present in the lignin and also between imine nitrogen and hydroxyl groups of lignin.

Changes in the Electronic Structure of Chemically Deintercalated LiCoO2

We studied the changes in the electronic structure of induced by deintercalation using and X‐ray absorption spectroscopy. The mean probing depth of this technique is . The results were analyzed using atomic multiplet and band structure calculations. The spectrum shows that the ions in are in a trivalent low‐spin state. The spectra of deintercalated show only minor changes as a function of concentration. The absence of changes indicates that the ions remain mostly unaffected by deintercalation. In particular, the ions in deintercalated are not oxidized to a tetravalent state as normally assumed. The spectra of deintercalated show an increase in the absorption intensity below threshold; this absorption increase indicates that the ions in are reduced upon deintercalation. ©2000 The Electrochemical Society

Preparation and characterization of TiO2 and V2O5 nanoparticles produced by ball-milling

Abstract We studied the crystalline and electronic structure of TiO 2 and V 2 O 5 nanoparticles produced by ball-milling. The experimental techniques used here were X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The XRD diagrams show that ball-milling preserves the crystalline structure of the bulk TiO 2 and V 2 O 5 materials. The particle size estimated with the Scherrer formula after 24 h of ball-milling is 6 nm for TiO 2 and 13 nm for V 2 O 5 . The XPS spectra exclude the possibility of impurity contamination and confirm the composition of the nanoparticles. A chemical shift in the Ti 2p XPS spectrum indicates a slight reduction of the Ti ions in the TiO 2 nanoparticles. The analysis of the Ti 2p satellites shows that the O 2p–Ti 3d covalence decreases in the TiO 2 nanoparticles. These effects are attributed to a reduced O coordination of the Ti ions at the surface of the TiO 2 nanoparticles. The effects are less evident in the case of the larger V 2 O 5 nanoparticles because the surface/volume ratio is smaller.

The Electronic-Structure of Zro2 - Band-Structure Calculations Compared to Electron and X-Ray-Spectra

Abstract We present and discuss band-structure calculations of ZrO2 in the cubic phase calculated by means of the Localized-Spherical-Waves (LSW) method with an extended basis set. The results obtained are in agreement with previous calculations and confirm a large covalent contribution to the bonding in ZrO2. The results are also compared to x-ray and electron spectra showing an overall good agreement between theory and experiment. In particular, the calculations reproduce well the distribution of the spectral weight and the magnitude of the band gap and the crystal-field splitting.

Structural and Morphological Characterization of the PP-0559 Kaolinite from the Brazilian Amazon Region

We report a structural and morphological characterization of the natural kaolinite PP-0559, from the Brazilian Amazon region, with the aim to contribute to the understanding of this clay mineral in environmental redox reactions. The triclinic structure was confirmed by transmission electron microscopy and electron diffraction studies. It exhibits oriented crystals, with diameters between 0.2 and 2 mm and about 50 nm of thickness. The anisotropic crystals after orientation were studied by electron paramagnetic resonance as a function of the applied magnetic field. The main EPR absorption lines of the substitutional Fe+3 impurity and radiation induced paramagnetic centers were studied as possible oxidizing centers of kaolinite.

Anisotropy of Magnetization and Nanocrystalline Texture in Electrodeposited CeO2 Films

Anisotropy of Magnetization and Nanocrystalline Texture in Electrodeposited CeO2 Films V. Fernandes, P. Schio, R. J. O. Mossanek, A. J. A. de Oliveira, W. A. Ortiz, D. Demaille, F. Vidal, Y. Zheng, P. Fichtner,* L. Amaral, M. Abbate, J. Varalda, W. H. Schreiner, and D. H. Mosca Departamento de Fisica, Universidade Federal do Parana, 81531-990 Curitiba PR, Brazil Departamento de Fisica, Universidade Federal de Sao Carlos, 13565-905, S. Carlos SP, Brazil Institut des NanoSciences de Paris, UPMC-Paris 6, CNRS UMR 7588, 75252 Paris Cedex 05, France Escola de Engenharia and Instituto de Fisica, Universidade Federal do Rio Grande do Sul, 91501-970 Porto Alegre, Brazil

Effects of Ni vacancies and crystallite size on the O 1s and Ni 2p x-ray absorption spectra of nanocrystalline NiO

We have studied the electronic structure of nanocrystalline NiO thin films, grown by radio-frequency magnetron sputtering under different experimental conditions, using x-ray absorption spectroscopy. The O 1s and Ni 2p spectra showed distinct changes as a function of O2 content in the plasma, which were reproduced with cluster model calculations. These changes are attributed to the incrementing of the surface contribution due to a decrease of the crystallite size as the O2 content in the plasma increases, and to the presence of induced nickel vacancies. Thus, the changes in the electronic structure can be related to the modification of structural and transport properties of these nanocrystalline films.

Mn-2p XPS spectra of differently hole-doped Mn perovskites

Abstract We have measured Mn-2p photoemission spectra in Mn perovskites doped by two methods: La1−xCaxMnO3 and LaMnO3+δ. Intra- and inter-series comparisons reveal that the position and intensity of the Mn-2p satellite depend only on the level of doping, and that it can always be decomposed into the satellites of the end members LaMnO3 and CaMnO3. We have fitted the spectra of the end members with the configuration–interaction cluster model and show that the linear combinations of these calculated spectra reproduce correctly all the details of the spectra of the doped compounds.

Evidence of chemical bonding in the electronic structure of a metastable Fe80Cu20 alloy

We studied the electronic structure of a metastable Fe80Cu20 alloy using x-ray photoelectron spectroscopy (XPS). The sample was produced by ball-milling, giving single-phase (BCC) nanoparticles with a diameter of about 10 nm. The core level Fe 2p and Cu 2p spectra of the alloy are rather similar to those of the individual Fe and Cu constituents; the absence of chemical shifts in these spectra indicates that the charge transfer between the Fe and Cu is negligible. On the other hand, the valence band spectrum of the alloy deviates from a linear combination of the corresponding Fe and Cu bands. The difference in the valence band of the alloy is attributed to bonding interactions between the Fe 3d and Cu 3d states. This illustrates the presence of chemical bonding between the valence electrons in a metastable alloy made of immiscible elements.

Cluster model calculations with nonlocal screening channels of metallic and insulating V O 2

We studied the changes in the electronic structure of