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Nanomatériaux
(18) Production(s) de l'année 2020
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Topological Study of Phase-Separated Ag-Conducting Chalcogenide Glasses Using Peak Force Quantitative Nano-Mechanical Characterization
Auteur(s): Piarristeguy Andrea, Le Parc R., Ramonda Michel, Escalier Raphaël, Pradel Annie
(Article) Publié:
-Frontiers In Materials. Computational Materials Science Section, vol. 6 p. (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02434357_v1
DOI: 10.3389/fmats.2019.00340
WoS: 000509310000001
Exporter : BibTex | endNote
Résumé: Carefully read the entire proof and mark all corrections in the appropriate place, using the Adobe Reader commenting tools (Adobe Help). Do not forget to reply to the queries. We do not accept corrections in the form of edited manuscripts. In order to ensure the timely publication of your article, please submit the corrections within 48 hours.
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Zeolite Structure Direction: Identification, Strength and Involvement of Weak CH⋅⋅⋅O Hydrogen Bonds
Auteur(s): Mineva Tzonka, Dib Eddy, Gaje Arnold, Petitjean Hugo, Bantignies J.-L., Alonso Bruno
(Article) Publié:
Chemphyschem, vol. 27 p.149-153 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02405117_v1
DOI: 10.1002/cphc.201900953
WoS: 000507998800003
Exporter : BibTex | endNote
Résumé: We demonstrate that weak CH⋅⋅⋅O hydrogen bonds (HBs) are important host−guest interactions in zeolite assemblies involving structure directing organocations. This type of HB is identified between alkyl groups of the organic structure directing agent (OSDA) and the silica framework in as‐synthesized silicalite‐1 of complex topology (MFI) using a combination of experimental and theoretical data obtained at low and room temperatures. The 28 weak CH⋅⋅⋅O HBs, evidenced along dynamics simulation at room temperature, represent 30 % of the energy of the Coulomb electrostatic interaction between OSDA and the zeolite framework. The strongest and most stable HB found here connects the OSDA to the [415262] cage containing F atoms and should contribute to preserve zeolite topology during crystal growth. An inspection of other as‐synthesized zeolites of very different framework topology indicates that the directional CH⋅⋅⋅O HBs have to be considered when discussing zeolite structure directing phenomena.
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Effect of low frequency phonons on structural properties of ZIFs with SOD topology
Auteur(s): Formalik F., Fischer Michael, Rogacka J., Firlej L., Kuchta Bogdan
(Article) Publié:
Microporous And Mesoporous Materials, vol. 304 p.109132 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02116566_v1
DOI: 10.1016/j.micromeso.2018.09.033
WoS: WOS:000546913300003
Exporter : BibTex | endNote
3 Citations
Résumé: The structural transformations of periodic structures are very often initiated by the dynamicalfluctuation of theequilibrium structure. The natural mechanical excitations in crystals are called phonons. If the energy of thesefluctuations is low, they can easily be transformed into static deformations which define new structural prop-erties of the materials. This is the case in so called gate opening transformations which modify the structure andthe adsorptive properties of porous solids. Using the example of three SOD-type zeolitic imidazolate frameworks(ZIFs) containing linker molecules with different substituents, we show that analysis of low-frequency phononsobtained from density-functional theory (DFT) calculations allows one to model the observed gate opening andto understand the microscopic mechanism of this structural transformation.
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How dense is the gas adsorbed in nanopores?
Auteur(s): Firlej L., Rogacka J., Formalik F., Kuchta Bogdan
(Article) Publié:
Microporous And Mesoporous Materials, vol. 304 p.109240 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02116565_v1
DOI: 10.1016/j.micromeso.2018.12.024
WoS: WOS:000546913300007
Exporter : BibTex | endNote
1 Citation
Résumé: Unlike macroscopic objects, any system of nanometric size shows characteristics that strongly depend on its sizeand geometric form. It is mainly because the major part of atoms (or molecules) of nano-object is located at itssurface, and their cohesive energy is smaller than for the atoms in the bulk. Here we show that when a fluid isconfined in nano-volume, delimited by non-attractive pore walls, its density is heterogeneous, in particular closeto the pore wall, and, on average, smaller than the density of bulk fluid. This effect progressively weakens whenthe pore size increases, and totally disappears for pores larger than 5 nm. The reported observation has nontrivialinfluence on evaluation of total and excess amount of fluid adsorbed in nanopores, as these quantities aretraditionally calculated assuming the known – and homogeneous –density of the bulk fluid. Additionally, wepropose a new method of the estimations of the accessible pore volume, based on the analysis of the density ofconfined fluid. The right estimation of both: pore volume and gas density is essential for quantitative interpretationof experimental adsorption isotherms: evaluation of pore size distribution and of the adsorbed amount.Although we analyze these problems taking an example of hydrogen at 77 K, our conclusions are general andapply to any fluid confined in nanopores.
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