@article {146, title = {Investigating carbon materials nanostructure using image orientation statistics}, journal = {Carbon}, volume = {84}, year = {2015}, month = {Apr-2015}, pages = {160 - 173}, abstract = {

A new characterization method of the lattice fringe images of turbostratic carbons is proposed. This method is based on the computation of their orientation field without explicit detection of fringes. It allows meaningful insights into the material nanostructure and nanotexture at several scales, either qualitatively or quantitatively. The calculation of pairwise spatial statistics of the orientation field at short distance provides measurements of the coherence lengths along any direction, in particular along and orthogonally to the layers. These statistics also allow representing orientation coherence patterns typical of the observed nanostructure. At larger distances, the mean disorientation of the fringes is computed and information about the homogeneity of the sample is obtained. An experimental validation is carried out on various artificial images and an application to the characterization of four bulk turbostratic carbons is provided.

}, issn = {00086223}, doi = {10.1016/j.carbon.2014.11.048}, author = {J. Philippe Da-Costa and Weisbecker, P. and Baptiste Farbos and Jean-Marc Leyssale and G{\'e}rard L. Vignoles and Germain, C.} } @article {143, title = {Nanoscale elasticity of highly anisotropic pyrocarbons}, journal = {Carbon}, volume = {94}, year = {2015}, month = {Nov-2015}, pages = {285 - 294}, abstract = {

We report on the elastic properties of high-textured laminar pyrocarbons (PyCs) as obtained at the nanoscale using atomistic simulations on realistic models of the rough laminar (RL) PyC, the regenerative laminar (ReL) PyC, and the ReL PyC heat treated at temperatures up to 1700 \°C. The purely longitudinal ( and ) and transverse ( and ) elastic properties of such materials have values of around 50\–75\% of those found for graphite. Conversely, cross longitudinal-transverse properties ( and ) are much larger in PyCs than in graphite (up to around one order of magnitude for ). Our results also show that stiffness decreases with the hydrogen content, that longitudinal properties increase with the extent of graphene domains and decrease with the misorientation of the layers, and that transverse and cross properties significantly increase with the amount of interlayer cross-links present in the materials. Comparison to known experimental data indicates that texture effect at superior scales play an important role in the effective macroscopic elasticity constants. Finally, from a materials perspective and in agreement with the structural evolution, the elastic properties of the ReL PyC evolve with heat treatment towards those of the RL PyC.

}, issn = {00086223}, doi = {10.1016/j.carbon.2015.06.060}, author = {Baptiste Farbos and J. Philippe Da-Costa and G{\'e}rard L. Vignoles and Jean-Marc Leyssale} } @article {89, title = {Effect of Gas Adsorption on Acoustic Wave Propagation in MFI Zeolite Membrane Materials: Experiment and Molecular Simulation}, journal = {Langmuir}, volume = {30}, year = {2014}, month = {Aug-04-2014}, pages = {10336-10343}, type = {Article}, abstract = {
Abstract Image

The present study reports on the development of a characterization method of porous membrane materials which consists of considering their acoustic properties upon gas adsorption. Using acoustic microscopy experiments and atomistic molecular simulations for helium adsorbed in a silicalite-1 zeolite membrane layer, we showed that acoustic wave propagation could be used, in principle, for controlling the membranes operando. Molecular simulations, which were found to fit experimental data, showed that the compressional modulus of the composite system consisting of silicalite-1 with adsorbed He increases linearly with the He adsorbed amount while its shear modulus remains constant in a large range of applied pressures. These results suggest that the longitudinal and Rayleigh wave velocities (VL and VR) depend on the He adsorbed amount whereas the transverse wave velocity VT remains constant.

}, issn = {0743-7463}, doi = {10.1021/la502182k}, author = {Manga, Etoungh D. and Blasco, Hugues and J. Philippe Da-Costa and Drobek, Martin and Ayral, Andre and Le Clezio, Emmanuel and Despaux, Gilles and Benoit A. Coasne and Julbe, Anne} }