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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Cristallochimie des phases AFm hybrides : interactions entre les hydrates cimentiers lamellaires et les adjuvants organiques / Crystal-chemistry of hybrid AFm phases : Interactions between lamellar cement hydrates and organic admixtures

Wang, Qirong 01 December 2016 (has links)
Dix molécules organiques modèles simulant les fonctions chimiques des superplastifiants utilisés dans la formulation des bétons ont été intercalées dans les hydrates cimentiers lamellaires conduisant à la formation de phases AFm hybrides. Les interfaces entre les deux sous-réseaux organiques et inorganiques de ces composés hybrides ont été étudiées afin de caractériser les interactions entre hydrates cimentiers et adjuvants organiques lors de la prise du béton. Les affinités de ces molécules vis-à-vis du feuillet minéral ont pu être comparées et il en ressort les deux séries suivantes : -PO32- > -SO3- > -CO2- pour les parties hydrophiles et C7-R > Φ-R > C5-R > C2-R pour les parties hydrophobes. L’interface organique-inorganique i.e. le mode d’accrochage et l’orientation de la molécule organique au sein de l’espace interlamellaire ont principalement été caractérisés par DRX sur poudre et spectroscopie infrarouge. Différents modes de connexion ont pu être identifiés par intercalation et par greffage. Les molécules organiques examinées sont ainsi orientées soit perpendiculairement, soit parallèlement aux feuillets associés à différents mode d’accroche. Différents taux d’hydratation de ces hydrants hybrides ont ensuite été identifiés et un travail de résolution structurale sur la phase insérant l’anion C6H5SO3- a permis de préciser l’organisation structurale de l’espace interlamellaire. Finalement, une étude sur l’intercalation de quelques superplastifiants commerciaux a mis en évidence un phénomène d’exfoliation de ces hydrates lamellaires. L’étude préalablement réalisée sur des molécules modèles permet alors de mieux comprendre les interactions se produisant au sein du milieu complexe que constitue un béton frais. / Ten organic molecules models simulating the chemical functions of superplasticizers used in concretes formulation were intercalated into lamellar cement hydrates to synthesize hybrid AFm phases. The interfaces between the organic and inorganic networks of these hybrid compounds have been studied to characterize the interactions between cementitious hydrates and organic additives in concrete. The affinities of these molecules toward the mineral layers have been compared and display the following tendencies : -PO32- > -SO3- > -CO2- for the hydrophilic parts and C7-R > Φ-R > C5-R > C2-R for the hydrophobic parts. The organic-inorganic interface (connection mode and orientation of the organic molecule) of the hybrid AFm phases was characterized by powder WRD and infrared spectroscopy. Organic molecules are oriented either perpendicular or parallel to the sheets resulting from different connection modes mainly intercalation and also grafting. The various hydration levels of these hybrids hydrates were then determined, and a structural resolution was attempted on AFm inserting C6H5SO3- anion allowing a description of its interlayer structure. Finally, a study on the intercalation of some commercial superplasticizers highlighted the exfoliation phenomenon for these lamellar hydrates.The present study on model molecules leads to a better understanding of the interactions occuring in complex fresh concrete environment.
2

Multifunctional Molecule-Grafted V₂C MXene as High-Kinetics Potassium-Ion-Intercalation Anodes for Dual-Ion Energy Storage Devices

Sabaghi, Davood, Polčák, Josef, Yang, Hyejung, Li, Xiaodong, Morag, Ahiud, Li, Dongqi, Shaygan Nia, Ali, Khosravi H, Saman, Šikola, Tomáš, Feng, Xinliang, Yu, Minghao 23 May 2024 (has links)
Constructing dual-ion energy storage devices using anion-intercalation graphite cathodes offers the unique opportunity to simultaneously achieve high energy density and output power density. However, a critical challenge remains in the lack of proper anodes that match with graphite cathodes, particularly in sustainable electrolyte systems using abundant potassium. Here, a surface grafting approach utilizing multifunctional azobenzene sulfonic acid is reported, which transforms V2C MXene into a high-kinetics K+-intercalation anode (denoted ASA-V2C) for dual-ion energy storage devices. Importantly, the grafted azobenzene sulfonic acid offers extra K+-storage centers and fast K+-hopping sites, while concurrently acting as a buffer between V2C layers to mitigate the structural distortion during K+ intercalation/de-intercalation. These functionalities enable the V2C electrode with significantly enhanced specific capacity (173.9 mAh g−1 vs 121.5 mAh g−1 at 0.05 A g−1), rate capability (43.1% vs 12.0% at 20 A g−1), and cycling stability (80.3% vs 45.2% after 900 cycles at 0.05 A g−1). When coupled with an anion-intercalation graphite cathode, the ASA-V2C anode demonstrates its potential in a dual-ion energy storage device. Notably, the device depicts a maximum energy density of 175 Wh kg−1 and a supercapacitor-comparable power density of 6.5 kW kg−1, outperforming recently reported Li+-, Na+-, and K+-based dual-ion devices.

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