Laboratoire Charles Coulomb UMR 5221 CNRS/UM2 (L2C)

français

Nos tutelles

CNRS

Nos partenaires

Rechercher





Accueil > Colloïdes, Verres et Nanomatériaux > Equipe : Physique des Verres > Thème : Structure, vibration, relaxations dans les systèmes désordonnés

Thème : Structure, vibration, relaxations dans les systèmes désordonnés

Présentation

In the last years important progress has been made on long-standing fundamental questions such as those related to sound properties in glasses and their relation with the universal low-temperature anomalies. A comprehensive picture of the nontrivial frequency dependence of sound attenuation in oxide glasses can now be proposed. It is controlled by three processes which in increasing order of the frequency at which they dominate are : the thermal relaxation of defects, relaxation via anharmonic interactions with the thermal bath, and a remarkably rapid increase (α Ω4) towards a Ioffe-Regel crossover at THz frequencies which we have evidenced in two oxide glasses. The latter mechanism relates to the boson peak and the low temperature plateau generally observed in the thermal conductivity. The close relation between the Ioffe-Regel crossover and the boson peak implies a resonance of these rather local low-lying optic modes with acoustic modes near the Ioffe-Regel limit.

Current researches

'

Membres

PERMANENTS NON PERMANENTS

Page(s) : < | 1 | 2 |

Hypersound damping in vitreous silica measured by a picosecond optical technique

Involved researchers : M. Foret, S. Ayrinhac (PhD), B. Rufflé
(Collaboration A. Devos, IEMN, Université Lille)
The attenuation of longitudinal acoustic phonons up to frequencies nearing 250 GHz (...)

Lire la suite

The boson peak and its relation with acoustic attenuation in glasses

Involved researchers : B. Rufflé, E. Courtens and R. Vacher
(Collaboration D.A. Parshin Université Saint Petersbourg Russie)
Experimental results on the density of states and on the acoustic (...)

Lire la suite

Glass-specific behavior in the damping of acousticlike vibrations

Involved researchers : B. Rufflé, G. Guimbretière (PhD), E. Courtens, and R. Vacher
(Collaboration G. Monaco, ESRF, Grenoble)
High frequency sound is observed in lithium diborate glass, (...)

Lire la suite

Anharmonic vs. relaxational sound damping in silica glasses

Involved researchers : M. Foret, R. Vacher, E. Courtens
The temperature dependence of the frequency dispersion in the sound velocity and damping of vitreous silica is reanalyzed. Thermally (...)

Lire la suite

Hyper-Raman scattering analysis of the vibrations in borate glasses

Involved researchers : B. Hehlen, G. Simon, E. Courtens, R. Vacher
Hyper-Raman scattering has been measured on vitreous boron oxide, v-B2O3. This spectroscopy, complemented with Raman scattering (...)

Lire la suite

Small ring density and inter-tetrahedra bond angle of permanently densified silicas : Femtosecond and Raman spectroscopy study

Involved researchers : B. Hehlen, M. Foret
(Collaboration with P. Langot, J. Burgin, and F. Vallée, CPMOH-Bordeaux)
Normal and permanently densified silica glasses (SiO2) have been investigated (...)

Lire la suite

Glass and environment

In the forthcoming ecological era, new European environmental regulations (horizon 2020) will impose the design of new “green” materials with lower energetic production costs. In this context, the (...)

Lire la suite

Structure and Dynamics in Nanoconfined Self-Assembled Polymers

Involved researchers : A.C. Genix (collaboration : J. Colmenero, A. Arbe, San Sebastian –SPAIN)
We are exploiting the selectivity of neutron scattering combined with isotopic substitution to (...)

Lire la suite

Investigation of the polymer dynamics in silica/polymer nanocomposites

Involved researchers : A.C. Genix, J. Oberdisse, C. Dupas (collaboration : F. Ganachaud, Ecole de Chimie – Montpellier / M. Tyagi, NIST – USA / J. Colmenero, A. Arbe, San Sebastian – SPAIN)
We are (...)

Lire la suite

Ferroelectric relaxors

Collaboration with J. Hlinka, Academy of Sciences of the Czech Republic Praha) (P. Papet, J. Rouquette, and J. Haines, Institut Charles Gehrardt, Montpellier)
One major interest of Hyper-Raman (...)

Lire la suite

Page(s) : < | 1 | 2 |


AIGLe

MathJax