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(41) Production(s) de WEIGEL C.
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Atomic-Spring-like Effect in Glassy Silica-Helium Composites br 
Auteur(s): Bowron Daniel T., Keen David A., Kint M., Weigel C., Ruffle B., Konczewicz L., Contreras S., Coasne Benoit, Garbarino Gaston, Beaudhuin Mickael, Haines Julien, Rouquette Jerome
(Article) Publié:
The Journal Of Physical Chemistry C, vol. 126 p.5722-5727 (2022)
Ref HAL: hal-03669554_v1
DOI: 10.1021/acs.jpcc.2c00026
WoS: WOS:000783122600037
Exporter : BibTex | endNote
Résumé: We determine the structural origin of an “atomic-spring-like effect”in a glassy silica-helium composite, which exhibits this mechanical property thatreversibly accumulates and restores energy at the subnanoscale based on a high-pressure experimental pair distribution function study combined with atom-scalemolecular simulations. These unexpected experimental results were obtained byusing a 3 μm spot size 61 keV X-ray beam and large area detector and bysubtracting the scattered intensity due to helium outside the sample from the silicasignal at the same focal point for each pressure point. The compression behavior ofthe glassy silica-helium composite is characterized on a structural level by the change from a uni- to bimodal distribution in the inter- tetrahedral distances in the amorphous isotropic structure of silica. We propose a simple characterization of this atomic-spring-like glass property using impedance spectroscopy measurements.
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Raman resonance tuning of quaterthiophene in filled carbon nanotubes at high pressures
Auteur(s): Alencar R. S., Aguiar A. L., Ferreira R. S., Chambard R., Jousselme B., Bantignies J.-L., Weigel C., Clement S., Aznar R., Machon D., Souza Filho A. G., San-Miguel A., Alvarez L.
(Article) Publié:
Carbon, vol. 173 p.163-173 (2021)
Texte intégral en Openaccess : 
Ref HAL: hal-03163018_v1
DOI: 10.1016/j.carbon.2020.10.083
WoS: WOS:000613132200003
Exporter : BibTex | endNote
Résumé: Filling carbon nanotubes with molecules is a route for the development of electronically modified one-dimensional hybrid structures for which the interplay between the electronic structure of molecules and nanotubes is a key factor. Tuning these energy levels with external parameters is an interesting strategy for the engineering of new devices and materials. Here we show that the hybrid system composed by quaterthiophene (4T) molecules confined in single-walled carbon nanotubes, presents a piezo-Raman-resonance of the molecule vibrational pattern. This behavior manifests as a rapid pressure induced enhancement of the 4T Raman mode intensities compared to the tubes G-band Raman modes. Density functional theory calculations allow to explain the spectral behaviour through the pressure-enhanced quaterthiophene resonance evolution. By increasing pressure, the tube cross-section deformation leads to a reduction of the intermolecular distance, to the splitting of the molecular levels and then to an increase of resonance channels. Calculations and experiments converge to the 4T piezo-resonance scenario associated with the pressure-induced nanotube radial collapse observed at about 0.8 GPa. Our findings offer possibilities for the development of pressure transducers based on molecule-filled carbon nanotubes.
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Elastic and plastic transformations of vitreous silica underpressure
Auteur(s): Foret M. , Ruffle B., Weigel C., Vacher R.
Conférence invité: Journées de la Matière Condensée, 2018 (Grenoble, FR, 2018-08-27)
Ref HAL: hal-01940534_v1
Exporter : BibTex | endNote
Résumé: The talk focuses on the thermodynamical properties of vitreous silica submitted to high pressures in a diamond anvil cell as obtained directly from Brillouin Light Scattering experiments or indirectly from standard relations. The analysis reveals non-negligible differences between static and dynamic compressibilities which are mostly related to the existence of thermally activated relaxational processes. Estimate of the residual densifications after complete cycles of compression/decompression is discussed.
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