30 research outputs found
Design, Characterization and Investigation of Heavy Metal Ions Removal by New Cellulose-Ether Based adsorbent
The present investigation deals with the elaboration in homogenous conditions of new cross-linked, hydroxyl cellulose (HEC) based material. Further, its application as a new eco-friendly low-cost efficient adsorbent of hazardous metal ions from an aquatic environment is treated. In this respect, the functionalization of HEC has been carried out using EDTA as a cross-linking agent exploiting its high capacity to chelate heavy metal ions in aqueous solutions. The proposed structure of the new crosslinked material (HECD) was investigated using structural analyses (FTIR-ATR vibrational spectroscopy and CP/MAS 13C NMR Spectroscopy). Also, the thermal and crystalline behaviours of unmodified and modified HEC were studied using thermogravimetric (TG and DTG) and DRX patterns. In addition, SEM images were recorded to demonstrate the changes expected at the morphological and textural level. Furthermore, the adsorption capacity of Pb (II), Cu (II), Cd (II) and Zn (II) ions from aqueous solutions by HECD was investigated using batch technique and optimized according to metal concentration, pH, contact time, ionic selectivity and regenerability. The maximum metal uptakes under optimum conditions were of 1.96, 4.18, 1.81 and 1.66 mmol/g for Pb (II), Cu (II), Cd (II) and Zn (II), respectively. Thus, to examine the mechanism of adsorption, the experimental data is fitted to kinetic, isothermal, and thermodynamic modelling
Crossover in the nature of the metallic phases in the perovskite-type RNiO_3
We have measured the photoemission spectra of NdSmNiO,
where the metal-insulator transition and the N\'{e}el ordering occur at the
same temperature for and the metal-insulator transition
temperature () is higher than the N\'{e}el temperature for . For , the spectral intensity at the Fermi level is high in the
metallic phase above and gradually decreases with cooling in the
insulating phase below while for it shows a pseudogap-like
behavior above and further diminishes below . The results
clearly establish that there is a sharp change in the nature of the electronic
correlations in the middle () of the metallic phase of the
NiO system.Comment: 4 pages, 4 figure, submitted to Phys. Rev.
Reply to: Ultrafast evolution and transient phases of a prototype out-of-equilibrium Mott-Hubbard material
International audienceReplying to D. Moreno-MencÃa et al. Nature Communicationshttps://doi.org/10.1038/s41467-019-11743-3 (2019)
Probing symmetry-breaking defects in polished graphitizable s p 2 carbons using angle-resolved polarized Raman scattering
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Effect of reducing gas on the hydrogen production by thermo-oxidation of water over 1%Rh/Ce0.6Zr0.4O2
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High-Temperature Lattice-Dynamics Evolution of YMnO3 and YbMnO3
International audienceThe exact mechanism responsible for the ferroelectricity in hexagonal manganite has been the subject of intense debate. Whether ferroelectricity and ferroelastic order appear at the same temperature and the role of covalency in the ferroelectric order are still discussed. High-temperature phase transitions are here investigated through the prism of lattice-dynamics evolution with temperature. Comparison is made between the YMnO3 and YbMnO3 behavior using polarized Raman spectroscopy. While YMnO3 shows two phase transitions (isosymetric at about 900 K and ferroelastic at 1200 K) YbMnO3 presents no lattice instability up to 1350 K. Phonons involved in the lattice instability and the zone tripling transition are identified. Moreover, peculiar hardening on heating of some YbMnO3 phonons is revealed and discussed, which further highlights the dynamical difference between these two hexagonal manganites
Local symmetry breaking and spin–phonon coupling in SmCrO3 orthochromite
Raman scattering and infrared reflectivity performed on polycrystalline SmCrO3 support stronginfluence of the antiferromagnetic order on phononmodes. Both measurements show softening of some modes below TN. Such a behavior is explained by spin–phonon coupling in this compound. Furthermore, temperature dependence of the infrared spectra has demonstrated important changes compared to the Raman spectra, suggesting strong structural modifications due to the cation displacements rather to those of the oxygenions. Our results reveal that polar distortions originating in local symmetry breaking, i.e. local non-centrosymmetry, resulting in Cr off-centring.Fil: El Amrania, M.. Université F. Rabelais; FranciaFil: Zaghrioui, M.. Université F. Rabelais; FranciaFil: Ta Phuoc, V.. Université F. Rabelais; FranciaFil: Gervais, F.. Université F. Rabelais; FranciaFil: Massa, Nestor Emilio. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Centro de QuÃmica Inorgánica "Dr. Pedro J. Aymonino". Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Centro de QuÃmica Inorgánica "Dr. Pedro J. Aymonino"; Argentin
Thermochromic effect in NdNiO 3−δ thin films annealed in ambient air
International audienceThe synthesis of NdNiO3 perovskite structure was achieved by soft post deposition annealing of initially amorphous thin films reactively sputter deposited on silicon substrates. The physical measurements were fully consistent with the properties expected for the thermochromic NdNiO3 phase. Upon heating, the optical transmission that was correlated with the electrical properties decreased in the infrared domain showing a thermochromic effect in this optical region. The metal–insulator transition temperature was found to be −68 °C for the specimen tested and the jump in resistance at the transition was 1.4 orders of magnitude. The state-of-the-art methods that normally involve an annealing at a high oxygen pressure (200 × 105 Pa) or epitaxial stabilization were considerably improved in this work by the use of dc sputtering and the optimization of the deposition conditions. Therefore, the novel soft process proposed here opens up numerous research possibilities
Structural modifications of disordered YMn1-xInxO3 solid solutions evidenced by infrared and Raman spectroscopies
International audiencePolycrystalline YMn1−xInxO3 compounds were obtained by solid state reaction and found to present a blue color for high substitution rate. X-ray diffraction analyses reveal the formation of solid solutions and the increase of cell parameters following Vegard's law. Far infrared reflectivity and Raman scattering spectra show the presence of random disorder and structural modifications without phase transition. A detailed analysis of some phonon modes allows to explain the structural changes upon doping. It was found that monocaping YO7 antiprisms are almost unaffected by substitution. However, results reveal the existence of two different MO5 (M = In, Mn) trigonal bipyramids. Their apical Mn–O distances are shorter than In–O bonds and both distances increase with the substitution rate, which is consistent with the evolution of the cell parameters