Rheological properties of calcium carbonate self-setting injectable paste

With the development of minimally invasive surgical techniques, there is growing interest in the research and development of injectable biomaterials with controlled rheological properties. In this context, the rheological properties and injectability characteristics of an original CaCO3 self-setting paste have been investigated. Two complementary rheometrical procedures have been established using a controlled stress rheometer to follow the structure build-up at rest or during gentle mixing and/or handling on the one hand, and the likely shear-induced breakdown of this structure at 25 or 35 C on the other. The data obtained clearly show the influence of temperature on the development of a cement microstructure during setting, in all cases leading to a microporous cement made of an entangled network of aragonite-CaCO3 needle-like crystals. Linear viscoelastic measurements arriving from an oscillatory shear at low deformation showed a progressive increase in the viscous modulus (G0 0) during paste setting, which is enhanced by an increase in temperature. In addition, steady shear measurements revealed the shear-thinning behaviour of this self-setting paste over an extended period after paste preparation and its ability to re-build through progressive paste setting at rest. The shear-thinning behaviour of this self-setting system was confirmed using the injectability system and a procedure we designed. The force needed to extrude a homogeneous and continuous column of paste decreases strongly upon injection and reaches a weight level to apply on the syringe piston around 2.5 kg, revealing the ease of injection of this CaCO3 self-setting paste

Use of Carbon Additives towards Rechargeable Zinc Slurry Air Flow Batteries

The performance of redox flow batteries is notably influenced by the electrolyte, especially in slurry-based flow batteries, as it serves as both an ionic conductive electrolyte and a flowing electrode. In this study, carbon additives were introduced to achieve a rechargeable zinc slurry flow battery by minimizing the zinc plating on the bipolar plate that occurs during charging. When no carbon additive was present in the zinc slurry, the discharge current density was 24 mA∙cm$^{-2}$ at 0.6 V, while the use of carbon additives increased it to up to 38 mA∙cm$^{-2}$. The maximum power density was also increased from 16 mW∙cm$^{-2}$ to 23 mW∙cm$^{-2}$. Moreover, the amount of zinc plated on the bipolar plate during charging decreased with increasing carbon content in the slurry. Rheological investigation revealed that the elastic modulus and yield stress are directly proportional to the carbon content in the slurry, which is beneficial for redox flow battery applications, but comes at the expense of an increase in viscosity (two-fold increase at 100 s$^{-1}$). These results show how the use of conductive additives can enhance the energy density of slurry-based flow batteries

Pristine and modified porous membranes for zinc slurry–air flow battery

The membrane is a crucial component of Zn slurry–air flow battery since it provides ionic conductivity between the electrodes while avoiding the mixing of the two compartments. Herein, six commercial membranes (Cellophane™ 350PØØ, Zirfon®, Fumatech® PBI, Celgard® 3501, 3401 and 5550) were first characterized in terms of electrolyte uptake, ion conductivity and zincate ion crossover, and tested in Zn slurry–air flow battery. The peak power density of the battery employing the membranes was found to depend on the in-situ cell resistance. Among them, the cell using Celgard® 3501 membrane, with in-situ area resistance of 2 Ω cm$^{2}$ at room temperature displayed the highest peak power density (90 mW cm−2). However, due to the porous nature of most of these membranes, a significant crossover of zincate ions was observed. To address this issue, an ion-selective ionomer containing modified poly(phenylene oxide) (PPO) and N-spirocyclic quaternary ammonium monomer was coated on a Celgard® 3501 membrane and crosslinked via UV irradiation (PPO-3.45 + 3501). Moreover, commercial FAA-3 solutions (FAA, Fumatech) were coated for comparison purpose. The successful impregnation of the membrane with the anion-exchange polymers was confirmed by SEM, FTIR and Hg porosimetry. The PPO-3.45 + 3501 membrane exhibited 18 times lower zincate ions crossover compared to that of the pristine membrane (5.2 × 10$^{-13}$ vs. 9.2 × 10$^{-12}$ m$^{2}$ s$^{-1}$). With low zincate ions crossover and a peak power density of 66 mW cm$^{-2}$, the prepared membrane is a suitable candidate for rechargeable Zn slurry–air flow batteries

Development of an injectable composite for bone regeneration

With the development of minimally invasive surgical techniques, there is a growing interest in the research and development of injectable biomaterials especially for orthopedic applications. In a view to enhance the overall surgery benefits for the patient, the BIOSINJECT project aims at preparing a new generation of mineral-organic composites for bone regeneration exhibiting bioactivity, therapeutic activity and easiness of use to broaden the application domains of the actual bone mineral cements and propose an alternative strategy with regard to their poor resorbability, injectability difficulties and risk of infection. First, a physical-chemical study demonstrated the feasibility of self-setting injectable composites associating calcium carbonate-calcium phosphate cement and polysaccharides (tailor-made or commercial polymer) in the presence or not of an antibacterial agent within the composite formulation. Then, bone cell response and antimicrobial activity of the composite have been evaluated in vitro. Finally, in order to evaluate resorption rate and bone tissue response an animal study has been performed and the histological analysis is still in progress. These multidisciplinary and complementary studies led to promising results in a view of the industrial development of such composite for dental and orthopaedic applications

INSTABILITES EN EXTRUSION DE POLYMERES FONDUS ATTENUATION, ELIMINATION, MECANISMES

CES TRAVAUX PORTENT SUR LA STABILITE EN EXTRUSION DES POLYMERES FONDUS EN ECOULEMENT EN CONTRACTION BRUSQUE. LES PHENOMENES OBSERVES SONT LA FISSURATION EN SORTIE DE FILIERE, LE GLISSEMENT A LA PAROI ET LES INSTABILITES. ON A UTILISE DES POLYDIMETHYLSILOXANES ET DIFFERENTS TYPES DE POLYETHYLENE, DONT LES STRUCTURES MOLECULAIRES (QUANTITE ET REPARTITION DES RAMIFICATIONS) ONT ETE CARACTERISEES. CHAQUE ECOULEMENT A ETE VISUALISE EN SORTIE DE FILIERE ; DES MESURES DE VITESSES ONT ETE FAITES DANS LE CAPILLAIRE, A SA PAROI ET EN AMONT DE LA CONTRACTION. LE DEVELOPPEMENT DU PHENOMENE DE FISSURATION EN SORTIE DE FILIERE A ETE OBSERVE : LE SCENARIO SUIVI SE GENERALISE A L'ENSEMBLE DES POLYMERES FONDUS. LES RAMIFICATIONS LONGUES PERMETTENT D'ATTENUER LEUR PROFONDEUR. LES ECOULEMENTS A DEBIT IMPOSE PEUVENT PRESENTER DES REGIMES AVEC OSCILLATIONS INSTANTANEES DE LA PRESSION. L'AUGMENTATION DE LA COMPRESSIBILITE EN AUGMENTANT LE NOMBRE DE RAMIFICATIONS PERMET DE LES ATTENUER, PARFOIS DE LES ELIMINER. UN MILIEU POREUX PLACE EN ENTREE DE FILIERE LES ELIMINE TOTALEMENT. EN EXTRUSION DE POLYMERES FONDUS, IL EXISTE DEUX TYPES DE GLISSEMENT A LA PAROI. LE PREMIER S'OBSERVE DANS DES FILIERES DE FAIBLE ENERGIE DE SURFACE EN ECOULEMENT STABLE. LA CONTRIBUTION DU GLISSEMENT AU DEBIT N'EVOLUE ALORS PAS. LE SECOND, GLISSEMENT MACROSCOPIQUE DE NATURE COHESIVE, NE DEPEND PAS DE LA NATURE DE LA SURFACE DE LA FILIERE ET EST GERE PAR DES EFFETS DE VOLUME EN ECOULEMENT INSTABLE. LA CONTRIBUTION DU GLISSEMENT AU DEBIT AUGMENTE AVEC LE REGIME D'EXTRUSION ; ON TEND VERS UN ECOULEMENT EN BLOC. EN TERME DE RENTABILITE EN EXTRUSION, L'INTRODUCTION DE RAMIFICATIONS LONGUES PERMET DE REPOUSSER L'APPARITION DES INSTABILITES MAIS LE GAIN EST NON REPRODUCTIBLE. PAR CONTRE, UN MILIEU POREUX DE FORT POUVOIR FILTRANT PLACE EN AMONT DE LA CONTRACTION REPOUSSE CETTE APPARITION D'UN FACTEUR 2 AU MOINS. CES INSTABILITES S'INITIENT EN AMONT DE LA CONTRACTION SUR L'AXE DE L'ECOULEMENT, LA OU L'ELONGATION EST MAXIMALE ET ELLES GENERENT DES ECOULEMENTS INSTATIONNAIRES EN VOLUME. ELLES ONT AU MOINS UNE FREQUENCE PROPRE QUI EST LA MEME QUE CELLE MESUREE EN AMONT DE LA CONTRACTION LE LONG DES LIGNES DE COURANT ET EN SORTIE DE FILIERE. MEME SI LES VARIATIONS INSTANTANEES LOCALES DE LA VITESSE PEUVENT ETRE IMPORTANTES, CELLES DE LA VITESSE SUR L'AXE ET CELLES DU DEBIT SONT FAIBLES.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Cellulose nanocrystal reinforced oxidized natural rubber nanocomposites

International audienc

Glissement et Rhéométrie

International audienc

Modélisation de la microstructuration dans les polymères chargés. Application à la mise en forme.

Cette thèse étudie la possibilité de simuler des écoulements complexes (polymères chargés, suspensions de fibres courtes, polymères) en prenant en compte la structure à l échelle microscopique dans le cadre de la théorie cinétique. Il y a un couplage fort entre la structure microscopique et la cinématique à l échelle macroscopique. Le caractère multidimensionnel de l équation de Fokker-Planck décrivant la microstructure du fluide rend la simulation difficile avec des approches déterministes classiques. Pour palier ce problème, plusieurs méthodes visant à réduire les dimensions sont développées et testées. Ces méthodes sont appliquées en particulier dans le cas des écoulements recirculants. Le cas d une recirculation ajoute une difficulté supplémentaire car nous ne connaissons ni les conditions initiales, ni les conditions aux limites. Or les recirculations se trouvent dans beaucoup d écoulements industriels, lors de la mise en forme des matériaux. Pour cette raison nous avons développé des méthodes numériques spécifiques à ce type d écoulement.Finalement, une partie de la thèse est dédiée à une étude expérimentale permettant de valider les résultats numériques obtenus et d étudier les phénomènes physiques entrant en jeu dans la mise en forme des polymères chargés.This document deal with the possibility to perform a simulation of a complex fluid flow (short fibres suspension, viscoelastic flow, short fibres reinforced polymer) taking into account the microstructural state in the kinetic theory background. There is a strong coupling effect between the microstructural state and the kinematics at the macroscopic scale. Classical deterministic approaches fail to solve the Fokker-Planck equation describing the fluid microstructure because of the high degree of freedom involved. To overcome this difficulty, this work present and test some techniques of dimensional reduction. These methods are applied to recirculating flows. The recirculation add a difficulty because nor initial conditions nor boundary conditions are known. And some recirculating areas appear in many industrial flows during the materials forming. That is why we have developed some numerical methods dealing with these kinds of flows. Finally, a part of this work is dedicated to an experimental study allowing to validate the numerical results and to focus on some physical phenomenons that occur during the material forming.GRENOBLE1-BU Sciences (384212103) / SudocSudocFranceF

Cellulose nanomaterials: size and surface influence on the thermal and rheological behavior

International audienc

Melt processing of cellulose nanocrystal reinforced polycarbonate from a masterbatch process

International audienc