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Jakse N.,CNRS Materials Science and Engineering | Bouhadja M.,CNRS Materials Science and Engineering | Kozaily J.,Conditions Extremes et Materiaux Haute Temperature et Irradiation CEMHTI | Kozaily J.,Laue Langevin Institute | And 7 more authors.
Applied Physics Letters | Year: 2012

In the present work the structural properties of low silica content calcium aluminosilicate melts with concentration ratio CaO/Al2O3 1 are investigated in the liquid and undercooled states by neutron diffraction experiments and ab initio molecular dynamics simulations. The results show the presence of AlO5 units and triclusters as well as non-bridging oxygen in the fully charge balanced compositions. Moreover, our findings allow us to identify a possible interplay between these structural units. Finally, we discuss the influence of these defective structural units on the properties of tetrahedral network and more particularly their implication on the evolution of the viscosity and the fragility. © 2012 American Institute of Physics.

Dupleix A.,Arts et Metiers ParisTech | Dupleix A.,Aalto University | De Sousa Meneses D.,Conditions Extremes et Materiaux Haute Temperature et Irradiation CEMHTI | Hughes M.,Aalto University | Marchal R.,Arts et Metiers ParisTech
Wood Science and Technology | Year: 2013

There is a lack of quantitative data on the penetration depth and the amount of energy absorbed by green wood under infrared (IR) radiation. This lack of knowledge is a potential barrier to the development of IR heating as an alternative to soaking as a means of warming logs prior to peeling in the manufacture of plywood. Experimental measurements of normal hemispherical spectral reflectance and transmittance over the range 550-5,500 cm-1 wavenumbers on four wood species, beech, birch, Douglas-fir and spruce have brought new knowledge on mid-infrared absorption properties of green wood and removed some uncertainties. For instance, it is not possible to deliver energy deeper than up to 0.3 mm below the wood surface because 70-90 % of all incident IR radiation on the wood surface is absorbed in this layer. Some wood features, such as surface quality, the presence of knots and of free water in wood (the latter two having a more significant effect) influence the amount of energy absorbed. These results illustrate that IR radiation can heat the surface layers, but then heat penetrates deeper into the inside layers of wood by conduction. © 2013 Springer-Verlag Berlin Heidelberg.

Bytchkov A.,Conditions Extremes et Materiaux Haute Temperature et Irradiation CEMHTI | Bytchkov A.,University of Orléans | Bytchkov A.,European Synchrotron Radiation Facility | Fayon F.,Conditions Extremes et Materiaux Haute Temperature et Irradiation CEMHTI | And 7 more authors.
Physical Chemistry Chemical Physics | Year: 2010

The local structure of P-rich and Se-rich phosphorus-selenium glasses was studied using high-resolution 31P solid-state MAS NMR. Two-dimensional 31P homonuclear through-bond correlation MAS experiments and 2D homonuclear J-resolved MAS measurements were performed at high spinning frequency to probe P-P and P-Se-P connectivities between the different P sites for the compounds in two glass-forming regions, P 2.5Se97.5-P50Se50 and P 67Se33-P84Se16. Amorphous phosphorus and crystalline α-P4Se3 and β-P 4Se3 were also studied as reference materials. Glasses from the Se-rich region contain mainly three- and four-coordinated P sites linked together by Sen chains, whereas P-rich glasses contain a mixture of P4Se3 molecular units and possibly other structural units embedded in a red-phosphorus-like polymeric network. © the Owner Societies 2010.

Massa N.E.,National University of La Plata | Del Campo L.,Conditions Extremes et Materiaux Haute Temperature et Irradiation CEMHTI | Del Campo L.,University of Orléans | De Sousa Meneses D.,Conditions Extremes et Materiaux Haute Temperature et Irradiation CEMHTI | And 4 more authors.
Journal of Physics Condensed Matter | Year: 2013

We report on near normal far- and mid-infrared emission and reflectivity of NdMnO3 perovskite from room temperature to sample decomposition above 1800 K. At 300 K the number of infrared active phonons is in close agreement with the 25 calculated for the orthorhombic -Pbnm (Z = 4) space group. Their number gradually decreases as we approach the temperature of orbital disorder at ∼1023 K where the orthorhombic O′ lower temperature cooperative phase coexists with the cubic orthorhombic O. At above ∼1200 K, the three infrared active phonons coincide with that expected for cubic Pm-3m (Z = 1) in the high temperature insulating regime. Heating samples in dry air triggers double exchange conductivity by Mn3+ and Mn4+ ions and a small polaron mid-infrared band. Fits to the optical conductivity single out the octahedral antisymmetric and symmetric vibrational modes as the main phonons in the electron-phonon interactions at 875 K. For 1745 K, it is enough to consider the symmetric stretching internal mode. An overdamped defect induced Drude component is clearly outlined at the highest temperatures. We conclude that rare earth manganite eg electrons are prone to spin, charge, orbital, and lattice couplings in an intrinsic orbital distorted perovskite lattice, favoring embryonic low energy collective excitations. © 2013 IOP Publishing Ltd.

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