Grenoble Institute of Technology

About: Grenoble Institute of Technology is a education organization based out in Grenoble, France. It is known for research contribution in the topics: Hyperspectral imaging & Geology. The organization has 3427 authors who have published 5345 publications receiving 137158 citations. The organization is also known as: Grenoble INP.

Infrared and terahertz studies of polar phonons and magnetodielectric effect in multiferroic Bi Fe O 3 ceramics

Abstract: $\mathrm{Bi}\mathrm{Fe}{\mathrm{O}}_{3}$ ceramics were investigated by means of infrared reflectivity and time domain terahertz transmission spectroscopy at temperatures $20\char21{}950\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, and the magnetodielectric effect was studied at $10\char21{}300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ with the magnetic field up to $9\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. Below $175\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the sum of polar phonon contributions to the permittivity corresponds to the value of measured permittivity below $1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$. At higher temperatures, a giant low-frequency permittivity was observed, obviously due to the enhanced conductivity and possible Maxwell-Wagner contribution. Above $200\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ the observed magnetodielectric effect is caused essentially through the combination of magnetoresistance and the Maxwell-Wagner effect, as recently predicted by Catalan [Appl. Phys. Lett. 88, 102902 (2006)]. Since the magnetodielectric effect does not occur due to a coupling of polarization and magnetization as expected in magnetoferroelectrics, we call it an improper magnetodielectric effect. Below $175\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ the magnetodielectric effect is by several orders of magnitude lower due to the decreased conductivity. Several phonons exhibit gradual softening with increasing temperature, which explains the previously observed high-frequency permittivity increase on heating. The observed noncomplete phonon softening seems to be the consequence of the first-order nature of the ferroelectric transition.

Implications of CO2 Contamination in Rechargeable Nonaqueous Li-O2 Batteries.

Abstract: In this Letter, the effect of CO2 contamination on nonaqueous Li-O2 battery rechargeability is explored. Although CO2 contamination was found to increase the cell's discharge capacity, it also spontaneously reacts with Li2O2 (the primary discharge product of a nonaqueous Li-O2 battery) to form Li2CO3. CO2 evolution from Li2CO3 during battery charging was found to occur only at very high potentials (>4 V) compared to O2 evolution from Li2O2 (∼3-3.5 V), and as a result, the presence of CO2 during discharge dramatically reduced the voltaic efficiency of the discharge-charge cycle. These results emphasize the importance of not only completely removing CO2 from air fed to a Li-air battery, but also developing stable cathodes and electrolytes that will not decompose during battery operation to form carbonate deposits.

Metallic additive manufacturing: state-of-the-art review and prospects

Abstract: Additive manufacturing processes, used for more than 25 years, are no longer confined to rapid prototyping applications. Mostly used nowadays in niche markets (medical applications, aerospace...) to manufacture metallic parts, they should provide improvements in terms of time-to-market, ecological impact and design compared to traditional industrial processes. Current metallic additive manufacturing studied in this paper are Selective Laser Sintering, Direct Metal Laser Sintering, Selective Laser Melting, Electron Beam Melting and Direct Metal Deposition. The performances of these processes are investigated through criteria derived from the time cost quality triangle and some prospects concerning these processes are given.

All you need is shape: Predicting shear banding in sand with LS-DEM

Abstract: This paper presents discrete element method (DEM) simulations with experimental comparisons at multiple length scales—underscoring the crucial role of particle shape. The simulations build on technological advances in the DEM furnished by level sets (LS-DEM), which enable the mathematical representation of the surface of arbitrarily-shaped particles such as grains of sand. We show that this ability to model shape enables unprecedented capture of the mechanics of granular materials across scales ranging from macroscopic behavior to local behavior to particle behavior. Specifically, the model is able to predict the onset and evolution of shear banding in sands, replicating the most advanced high-fidelity experiments in triaxial compression equipped with sequential X-ray tomography imaging. We present comparisons of the model and experiment at an unprecedented level of quantitative agreement—building a one-to-one model where every particle in the more than 53,000-particle array has its own avatar or numerical twin. Furthermore, the boundary conditions of the experiment are faithfully captured by modeling the membrane effect as well as the platen displacement and tilting. The results show a computational tool that can give insight into the physics and mechanics of granular materials undergoing shear deformation and failure, with computational times comparable to those of the experiment. One quantitative measure that is extracted from the LS-DEM simulations that is currently not available experimentally is the evolution of three dimensional force chains inside and outside of the shear band. We show that the rotations on the force chains are correlated to the rotations in stress principal directions.