Annick Hubin - Academia.edu (original) (raw)

Papers by Annick Hubin

2018 Joint Thermophysics and Heat Transfer Conference

Due to their small size and tremendous speeds, meteoroids often burn up at high altitudes, above ... more Due to their small size and tremendous speeds, meteoroids often burn up at high altitudes, above 80 km, where the atmosphere is rarefied. Ground radio stations are able to detect the free electrons concentration in the meteoroid wake, which is produced by hyperthermal collisions of the ablated species with the free-stream. The interpretation of radio data, however, currently relies on phenomenological methods, derived under the assumption of free molecular flow, hence, poorly accounts for the dynamics of the vapour, chemistry, and diffusion in the meteor trail. In this work, we aim to provide a detailed description of the flowfield around a meteoroid by means of Direct Simulation Monte Carlo and to obtain the evolution of the free electrons in the meteor wake via an extended trail simulation. An evaporation boundary condition is developed in the framework of an open source DSMC software. The material is assumed to be composed by a mixture of metal oxides which are typically present in ordinary chondritic meteorites. The transport properties of the ablated vapour are computed following the Chapman-Enskog theory and the DSMC phenomenological parameters are retrieved by fitting the collision integrals over a wide range of temperatures. As a last step, chemical and diffusion processes in the trail are computed. Starting from the baseline DSMC solution, our approach marches in time along the precomputed streamlines, calculating chemistry and radial diffusion for metals and free electrons. As study case, the flow around a 1 mm evaporating meteoroid is analysed at different altitudes. A high level of thermal nonequilibrium is appreciated in the head of the meteor, whereas in the trail, after a few diameters, the flow equilibrates. At lower densities, the vapour can travel upstream without interacting much with the incoming jet. On the other hand, at lower altitudes, re-condensation plays a significant role in the stagnation region. Finally, a trail, several meters long and formed by metallic species, generates behind the body. Ionization of sodium turns out to be the dominant process in the production of free electrons, whereas radial diffusion seems to prevail over recombination as depletion mechanism.

World Electric Vehicle Journal

Battery performance and lifetime constitute a bottleneck for electric vehicles and stationary ele... more Battery performance and lifetime constitute a bottleneck for electric vehicles and stationary electric energy storage systems to penetrate the market. Electrochemical or physics based battery models are one of the engineering tools to enhance their performance. These models should enable us to optimize the cell design and the battery management system. In this study we evaluate the ability of the much used Porous Electrode Model (PEM) to predict the effect of changing cathode density in the overall performance of a Li-Ion cell. We conclude that the PEM is well capable of predicting battery discharge capacities for cells with changing cathode density.

XXXVI Reunión del grupo de electroquímica RSEQ // XVII Encontro Ibérico de Electroquímica

Libro de abstracts

Journal of The Electrochemical Society, 2021

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Journal of Electroanalytical Chemistry, 2020

, T. (2020). Effect of excess hydrogen bond donors on the electrode-electrolyte interface between... more , T. (2020). Effect of excess hydrogen bond donors on the electrode-electrolyte interface between choline chloride-ethylene glycol based solvents and coppe.

Monthly Notices of the Royal Astronomical Society, 2019

Due to their small size and tremendous speeds, meteoroids often burn up at high altitudes above 8... more Due to their small size and tremendous speeds, meteoroids often burn up at high altitudes above 80 km, where the atmosphere is rarefied. Ground radio stations allow us to detect the concentration of electrons in the meteoroid trail, which are produced by hyperthermal collisions of ablated species with the freestream. The interpretation of these data currently relies on phenomenological methods, derived under the assumption of free molecular flow, that poorly accounts for the detailed chemistry, diffusion in the vapour phase, and rarefied gas effects. In this work, we employ the direct simulation Monte Carlo (DSMC) method to analyse the detailed flowfield structure in the surroundings of a 1 mm meteoroid at different conditions, spanning a broad spectrum of Knudsen and Mach numbers, and we extract resulting ionization efficiencies. For this purpose, we couple the DSMC method with a kinetic boundary condition which models evaporation and condensation processes in a silicate material. ...

Electrochimica Acta, 2019

Electrochimica Acta, 2018

A comprehensive electrochemical impedance study is conducted on LiNi 0.80 Co 0.15 Al 0.05 O 2 ele... more A comprehensive electrochemical impedance study is conducted on LiNi 0.80 Co 0.15 Al 0.05 O 2 electrode material as a function of state-of-charge and aging. Electrodes are harvested from four commercial batteries with different state-of-health conditions. Odd random phase electrochemical impedance spectroscopy and the symmetric cell approach are applied in this work in order to obtain reliable impedance results. An equivalent electrical circuit model is constructed. The parameters related to the generalized finite-space Warburg element, the CPE element and the charge transfer resistance are further interpreted. Valuable information is obtained and closely linked to the physical phenomena. The charge transfer resistance has been proved to be the most reliable parameter for the estimation of state-of-health.

Electrochemistry Communications, 2018

The Journal of Physical Chemistry C, 2018

Odd Random Phase Electrochemical Impedance Spectroscopy to Study the Corrosion Behavior of Hot Dip Zn and Zn-Alloy Coated Steel Wires in Sodium Chloride Solution

Journal of The Electrochemical Society, 2018

Journal of Visualized Experiments, 2016

Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from... more Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties. The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale, results from a post-test microscopy analysis are presented.

Gas/Surface Interaction Study of Low-Density Ablators in Sub- and Supersonic Plasmas

11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference, 2014

2013 World Electric Vehicle Symposium and Exhibition (EVS27), 2013

Battery performance and safety constitute a bottleneck for electric vehicles to penetrate the car... more Battery performance and safety constitute a bottleneck for electric vehicles to penetrate the car market. Online battery models are one of the engineering tools to enhance their performance. Empirical battery models form the subject of many scientific publications. In this paper a study, is performed of the usefulness of the first order impedance model through the consistency of the parameters under changes in the calibration signal, i.e. the current pulse. It can be concluded that simple first order models show little potential to really increase battery performance. Only the equivalent series resistance of the first order impedance model is insensitive to small variations of the calibration signal.

Towards a Nano-Scale Electrochemical and Spectroscopic Characterization of Organic Layers on Oxide Surfaces

ECS Transactions, 2007

Journal of Electroanalytical Chemistry, 2021

Sustainable Energy & Fuels, 2020

Nickel-containing N-doped carbons were synthesized and analyzed for the electrochemical reduction... more Nickel-containing N-doped carbons were synthesized and analyzed for the electrochemical reduction of CO2 to CO under industrially relevant conditions.

Applied Catalysis B: Environmental, 2018

Take-down policy If you believe that this document breaches copyright please contact us providing... more Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Journal of Electroanalytical Chemistry, 2018

Chemical Engineering Research and Design, 2018

The chemical and electrochemical performance of a microfluidic reactor for the cogeneration of ni... more The chemical and electrochemical performance of a microfluidic reactor for the cogeneration of nitrobenzene derivatives and electricity has been analysed. Reactor operation has been tested using loads of 100Ω and 1000Ω, allowing an in-depth characterisation replicating the circumstances of actual chemical production. Conversion rates of up to 64% and power densities of up to 0.299mW cm −2 have been attained. The main products obtained using this cogeneration co-laminar flow cell (CLFC) are aniline and nitrosobenzene. Nitrosobenzene is identified as a product generated by cogeneration while aniline is established to be an unwanted side-product at the anode due to oxidant crossover, which reduces the cogeneration efficiency. Reactor stability has been determined by monitoring of the anode, cathode and cell potentials. Self-poisoning of the anode reaction leads to loss in electrical performance. Due to its ability to self-regenerate, the power density shows an oscillating behaviour over time. Results in this paper reveal that the concept of a cogeneration microreactor is promising, although the anode reaction and the mass transfer in the reactor can still be optimised further for actual applications.