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ALL-CELLULOSE COMPOSITES: COMPOSITES LIKE NO OTHER
No full textInternational audienceAll-cellulose composites are a type of single-polymer composite materials in which the matrix and the reinforcing fibers are same matter, leading to a perfect adhesion between both. It is inspired by "all-polymer composite" approach developed in the past century for thermoplastic polymers. All-cellulose composites can be based on a wide range of lignocellulosic materials. As cellulose does not melt, the approach is based on cellulose fiber incomplete dissolution; fibers can be natural or artificial, as paper sheets or textile, aligned or not 1 . The continuous phase is made either by partially dissolved fibers themselves or by adding a cellulose solution. The dissolved cellulose is then coagulated, and the solvent is removed by washing it out. Depending on drying conditions, materials of different density and morphology can be obtained. In our work we used two types of solvents: 8% NaOH-water and ionic liquids. To control the properties of all-cellulose composites, we monitored the kinetics of fiber dissolution 2 . The rheological properties of cellulose-NaOH-water solutions in the presence of non-dissolved fibers were investigated 3 . The morphology and mechanical properties of all-cellulose composites were correlated with the type of starting cellulose material, degree of fibers' dissolution and processing conditions 4-7 . .</div
Upcycling Orange Waste into Bio-Based Aerogels
No full textInternational audienceThe orange juice industry produces large amounts of by-products. This work introduces new materials based on orange juice side streams�lightweight and high-surface-area aerogels. Orange waste and its fractions (peels, bagasse, and pulp) were first subjected to citric acid hydrolysis, a "green" waterbased pre-treatment. Processing parameters (washing with water, biomass fraction, and biomass and citric acid concentrations) were tuned to maximize suspensions' kinetic stability and produce homogenous aerogels. Soluble sugars removal during biomass washing, along with increased biomass and citric acid concentrations led to higher stability of the suspensions, bearing a pectinrich liquid phase with a dispersed swollen insoluble fraction. Suspensions' rheological properties, insoluble contents, and insoluble fractions' swelling capacities were evaluated. The prepared suspensions were subjected to non-solvent-induced phase separation and solvent exchange with ethanol, followed by drying with supercritical carbon dioxide. Obtained aerogels possessed low densities (<0.1 g/cm 3 ) and high specific surface areas (190-235 m 2 /g). The insoluble swollen fibers were partially porous and embedded in an open-pore nanostructured network.</div
Increasing Inter-Fiber Contact in the Altendorf-Jeulin Model
No full textInternational audienceIn fields such as material design or biomedicine, fiber materials play an importantrole. Fiber simulations, also called digital twins, provide a basis for testing andoptimizing the material’s physical behavior digitally. Inter-fiber contacts caninfluence the thermal and mechanical behavior of a fiber system; to our knowledge,however, there exist no parametric fiber models allowing for explicit modeling ofthe number of inter-fiber contacts. Therefore, this paper proposes an extension ofthe iterative force-biased fiber packing by Altendorf & Jeulin. In this extension,we model the inter-fiber contacts explicitly and add another force to the force-biased packing to increase the number of contacts. We successfully validate thepacking with respect to its parameter accuracy. Moreover, we show that theextension indeed increases the number of contacts, even exceeding theoreticalvalues. Hence, this packing scheme has the potential to achieve higher accuracyin physical simulations
GWTC-4.0: An Introduction to Version 4.0 of the Gravitational-Wave Transient Catalog
No full textInternational audienceThe Gravitational-Wave Transient Catalog (GWTC) is a collection of short-duration (transient) gravitational wave signals identified by the LIGO-Virgo-KAGRA Collaboration in gravitational-wave data produced by the eponymous detectors. The catalog provides information about the identified candidates, such as the arrival time and amplitude of the signal and properties of the signal's source as inferred from the observational data. GWTC is the data release of this dataset and version 4.0 extends the catalog to include observations made during the first part of the fourth LIGO-Virgo-KAGRA observing run up until 2024 January 31. This paper marks an introduction to a collection of articles related to this version of the catalog, GWTC-4.0. The collection of articles accompanying the catalog provides documentation of the methods used to analyze the data, summaries of the catalog of events, observational measurements drawn from the population, and detailed discussions of selected candidate
Numerical investigation of coupled thermo-hydro-mechanical subsurface processes: importance of thermal effects and pressure diffusivity on post-injection seismic events
No full textInternational audienceEnhanced Geothermal Systems (EGS) extract energy from deep hot dry rocks (HDR) by artificially stimulating reservoirs through hydraulic fracturing, acid injection, CO₂ injection, and similar methods. Their effectiveness depends on Thermo-Hydro-Mechanical (THM) coupling processes particularly within fracture networks. A key challenge is induced seismicity, especially delayed post-injection events that can exceed those during injection. Since earlier models based only on injected fluid volume fail to capture the underlying mechanisms, advancing THM understanding is essential for predicting and managing these risks.This study develops coupled THM models in COMSOL Multiphysics to investigate pressure and temperature diffusivity in HDR and their interaction with stress fields and fractures. Realistic fracture networks are statistically generated to capture their influence on fluid flow, heat transport, and stress redistribution. The modeling progresses from thermo-hydraulic (TH) validation with analytical solutions, to hydro-mechanical (HM) validation with field data, and finally to a fully coupled THM model. Results indicate that fracture configuration strongly controls the distribution and propagation rate of pressure and temperature within the target layer, yet this influence is highly dependent on the thermophysical properties of the chosen working fluid (water or supercritical CO2). The integrated framework thus provides insight into the mechanisms driving delayed seismicity and supports safer, more efficient EGS operations
Detailed and simplified parameterized LCA models for Early-Stage Energy Projects: A Microalgae-Based Biogas Case
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A unique solution to overcome the barriers to planetesimal formation at low dust-to-gas ratio
No full textNational audienceIn the incremental growth model, planetesimal formation constitutes the least understood step in the process of planetary formation. The two main difficulties in this regard are the collision/fragmentation and the drift barriers. Numerous solutions have been proposed to overcome these barriers, but often need a conjunction of processes to reach the conditions for planetesimal formation. We present numerical simulations, in which the protoplanetary disk turbulence is fully captured rather than modeled with a turbulent diffusion or turbulent viscosity parameter. When the turbulent cascade is taken into account, and in the case of weakly turbulent disks, not only can solid grains be highly concentrated in clusters, but their radial drift can also be slowed or even halted. These results open a unique path to planetesimal formation starting at disk canonical dust-to-gas ratio, namely Keplerian turbulence
Déterritorialiser l’euro. La Banque centrale européenne à l’épreuve de l’harmonisation des circuits de crédit nationaux
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Thermohydraulic modelling of the WLAM process – Application to the prediction of grain structure development on Inconel alloys
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3D Scanning of Celtic Coins and Deep Learning to Identify Monetary Dies
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