The nanostructure, physical properties and mechanical performance of C-S-H, 1.4 nm tobermorite, jennite, and ettringite were studied. C-S-H of variable stoichiometries was examined as a model system in comparison with that produced in the hydration of Portland cement. The current Master’s thesis is comprised of four research papers designed to improve the current understanding of the nanostructure and engineering properties of C-S-H systems and modified C-S-H systems. Many of the controversial issues in cement science were identified and were addressed in a comprehensive research study, which examined the key features of the C-S-H systems at the nano-structure level. In Chapter 4, each paper presented new evidence for a number of mechanical aspects of C-S-H materials. Numerous advanced analytical tools were used in order to verify the observations made in each section. The major achievements of the current work are mentioned briefly as follows: 1. It was determined that microindentation is a useful method for determining the creep behavior of C-S-H of various stoichiometries, 1.4 tobermorite, jennite, and ettringite. 2. Microindentation parameters i.e. creep modulus, indentation modulus and indentation hardness are porosity dependent. 3. Microindentation creep measurements on C-S-H (C/S = 0.80 and 1.20) demonstrated that creep modulus, indentation modulus, and indentation hardness are all dependent on mass-loss from the 11%RH condition. 4. Evidence was presented that the nanostructural role of interlayer water in C-S-H has a significant influence on the creep process.

La disparition attendue des combustibles fossiles dans un avenir proche est l'un des grands défis de ce siècle auquel nous devons faire face. Pour cela, il serait judicieux de transférer l’énergie primaire utilisée aujourd'hui en énergies renouvelables. Le secteur des transports est l'un des plus concernés par cette problématique. Une application dans ce secteur nécessite de nombreux travaux de recherche et c'est dans ce contexte que le stockage de l'hydrogène à l'intérieur des clathrate hydrates a été entrepris au cours de mon programme de recherche doctoral. Cette étude avait pour objectif d’étudier les interactions hôte-invité (dynamique) dans les clathrates hydrates et s’est étendue de la synthèse de clathrates hydrates jusque l’insertion de l'hydrogène en leur sein. Cette étude a été faite à la fois d’un point de vue expérimental et théorique : des simulations de Dynamique Moléculaire (MD) ont été utilisées afin de guider l’interprétation d’expériences de Diffusion incohérente Quasi Elastique des Neutrons (QENS). Dans un premier temps, nous avons développé cette approche méthodologique en étudiant la dynamique du clathrate hydrate de bromométhane, système prototype. Dans un deuxième temps, nous avons appliqué cette approche multi-technique à l'étude de clathrate hydrates impliqués dans la problématique du stockage d'hydrogène. Pour cela, nous avons étudié le clathrate hydrate de tétrahydrofurane (THF), utilisé comme sous-structure hôte au stockage d'hydrogène. Un dispositif expérimental original a été développé pour la préparation d'un hydrate clathrate binaires H2-THF. L’analyse des expériences de diffusion neutronique effectuée sur ce clathrate binaire a révélé l’existence de mouvements diffusifs localisés des molécules d’hydrogène à l’intérieur des cages. / The expected disappearance of fossil fuels in the near future is one of the major challenges of this century which we need to face up and it is necessary to anticipate it. For that, it will be convenient that we have begun the primary energy transfer used today to renewable energy. The sector of transport is one of the most concerned by these renewable energies. An application in this sector would require numerous research works and it is in this context that the hydrogen storage inside the clathrate hydrates has been undertaken during my PhD. This work aimed at investigating the host-guest interactions (dynamics) of clathrate hydrates and ranged from the synthesis of clathrate hydrates to the insertion of hydrogen within them. This study has been done both from experimental and theoretical point of view. Molecular Dynamics (MD) simulations were used to guide the interpretation of incoherent Quasi-Elastic Neutron Scattering (QENS) experiments. At first, we developed a methodology combining MD and QENS to investigate the dynamics of bromomethane clathrate hydrate, a prototypical system. Having validated the multi-technique approach, the methodology has been applied to investigate clathrate hydrates involved in the hydrogen storage problematic. In this issue, the tetrahydrofuran (THF) clathrate hydrate, used as host sub-structure for storing hydrogen, has been studied. An original experimental set-up has been developed for the preparation of a binary H2-THF clathrate hydrate. The analysis of QENS experiments performed on this binary clathrate hydrate revealed the existence of localized translational motion of hydrogen molecules within the clathrate cages.

Les piles à combustible (PAC) utilisant l’hydrogène comme vecteur, possèdent de bons rendements énergétiques et ne produisent aucun gaz à effet de serre. Elles se présentent donc aujourd’hui comme une solution propre et efficace. Cette alternative pourrait ainsi devenir un substitut possible aux hydrocarbures et pallier l’intermittence de certaines énergies renouvelables.Il existe différents types de PAC se distinguant principalement par la nature de l’électrolyte qui compose leur membrane échangeuse de protons. Utiliser les clathratehydrates d’acide fort comme électrolyte solide représente une alternative peu explorée à ce jour. Ces systèmes sont des solides cristallins nanoporeux constitués d’un réseau hôte de molécules d’eau formant des cavités nanométriques et encapsulant des molécules invitées.Dans le cas de clathrate hydrates d’acide fort, le confinement d’acides au sein des cages aqueuses génère des excès de protons délocalisés le long de leur réseau aqueux. A température ambiante, ces clathrate hydrates présentent alors une excellente conductivité protonique, plus élevée que celle des membranes de PACs actuellement utilisées. L’objectif de ce doctorat a été d’élaborer un électrolyte à base de clathrate hydrate d’acide hexafluorophosphorique (un des meilleurs conducteurs connus de cette classe de systèmes)sur la base d’une approche physico-chimique fondamentale, et de développer un montage miniaturisé de PAC intégrant ce nouvel électrolyte.A un niveau fondamental, il a été nécessaire de comprendre les facteurs régissant la conductivité protonique élevée de ces systèmes et en particulier, le lien existant entre la conductivité et le nombre d’hydratation (rapport molaire eau/acide dans le clathrate). Les mécanismes microscopiques mis en jeu ont été étudiés en s’appuyant sur la spectroscopie et l’imagerie Raman, complétées par des expériences de résonance magnétique nucléaire, de diffraction des rayons X et de spectroscopie d’impédance électrochimique. Un ensemble d’informations structurales (type de clathrate formé, transition de phase et stabilité thermodynamique), dynamiques (modes de vibration, diffusion des protons et cinétique) et chimiques (inclusion d’impuretés fluorées) a ainsi été obtenu. En tant que sonde sélective et locale, la technique de diffusion Raman a apporté des informations uniques. Elle a permis de sonder les interactions acides-cages, de proposer un protocole expérimental permettant de contrôler le nombre d’hydratation et également, de révéler pour la première fois une microstructuration du clathrate hydrate observée uniquement au-dessus d’un seuil d’hydratation. Ces propriétés physico-chimiques ont été corrélées aux mesures de conductivité, permettant de comprendre l’impact du nombre d’hydratation et des impuretés chimiques sur les performances de l’électrolyte solide. L’ensemble de ces résultats a permis d’aboutir à un développement technologique original. Une nouvelle micropile à combustible utilisant des clathrate hydrates d’acide hexafluorophosphorique comme électrolyte a été conçue. Ce développement offre ainsi une PAC aux performances comparables aux PACs actuellement disponibles et fonctionnant de la température ambiante à des températures négatives. / Fuel cells (FC) using hydrogen possess very good energy performance and produce no greenhouse gases. It presents itself today as a clean and efficient solution. This alternative could then become a possible substitute for fossil fuels and palliate for the intermittency ofcertain renewable energies.There are various types of FC, mainly distinguished by the nature of the electrolyte that composes their proton exchange membrane. Using strong acid clathrate hydrates as solid electrolyte represents an alternative for which very little is known nowadays. These systems are nanoporous crystalline solids consisting of a water host network forming nanometric cavities encapsulating guest molecules. In the case of strong acid clathrate hydrates, the confinement of acidic species within the aqueous cages generates proton excess that isdelocalized along their aqueous network. At room temperature, these clathrate hydrates have then excellent proton conductivity, which is higher than that of the FCs membranes currently used. The objective of this PhD was to develop an electrolyte based on hexafluorophosphoricacid clathrate hydrate (one of the best-known conductors of this class of system) on the basisof a fundamental physico-chemical approach, and to develop a miniaturized FC assemblyincorporating this new electrolyte.At a fundamental level, it was necessary to understand the driving factors responsible for the super-protonic conductivity of these systems and in particular, the relationship between the conductivity and the hydration number (i.e. water to acid molar ratio in the clathrate). The microscopic mechanisms have been studied by means of Raman spectroscopy and imaging, supplemented by nuclear magnetic resonance, X-ray diffraction and electrochemical impedance spectroscopy experiments. A set of results concerning the structure (clathrate type, phase transition and thermodynamic stability), the dynamics (vibrational modes, proton diffusion and kinetics) and the chemistry (inclusion of fluorinated impurities) has thus been obtained. As a selective and microscopic probe, the Raman scattering technique provided unique information. It allowed to probe the acid-cages interactions, to propose an experimental protocol monitoring the hydration number and also,to reveal, for the first time, a microstructuration of the clathrate hydrate only observed abovea hydration threshold. These physico-chemical properties have been correlated with the conductivity measurements, making it possible to understand the impact of the hydration number and of the chemical impurities onto the electrochemical performances of the solid electrolyte. All these results led to an original technological development. A new micro-fuel cell using hexafluorophosphoric acid hydrates as the electrolyte has been designed. This development offers a FC with performances comparable to the FCs currently available and operating from room temperature to negative temperatures.

Anorganische Salzhydrate sind aufgrund ihrer hohen spezifischen Schmelzwärmen als Phase-Change-Materials(PCM) für Latentwärmespeicher favorisiert. Die Unterkühlung der Salzhydratschmelzen stellt oftmals ein besonderes Problem bei technischen Anwendungen dar. Erstmalig wurden kombinatorische Methoden zur strukturell unspezifischen Suche nach Keimbildnern genutzt. Das hier entwickelte Verfahren erlaubt es, thermische Kristallisationseffekte zwischen 10°C und 170°C zu untersuchen. Bis zu 2025 Materialkombinationen können sowohl parallel synthetisiert als auch analysiert werden. Die Synthese der Keimbildner erfolgte durch Verhältnisvariation gelöster Salze mittels automatisierter Dosierung auf Trägerplatten und anschließendem Tempern. Die aktiven Kombinationen wurden durch zeitaufgelöste Thermographie identifiziert. Die Schlüssigkeit des gesamten Verfahrens konnte durch das erfolgreiche Screening zweier PCM mit unterschiedlichen Schalttemperaturen (NaCH3COO*3H2O; Fp=58°C und LiNO3*3H2O; Fp=29°C) nachgewiesen werden.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19695号 / 工博第4150号 / 新制||工||1640(附属図書館) / 32731 / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 小池 克明, 教授 高岡 昌輝, 准教授 村田 澄彦 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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The system H₂O-CH₄ is found in a variety of geological environments in the earth’s crust, from sedimentary basins to low grade metamorphic terrains. Knowledge of the PressureVolume-Temperature-Composition (PVTX) properties of the H₂O-CH₄ system is necessary to understand the role that these fluids play in different geological environments. In this study the properties of the H₂O-CH₄ fluid system at elevated temperatures and pressures has been investigated experimentally to determine the PVTX properties of H₂O-CH₄ fluids in the P-T range equivalent to late diagenetic to low grade metamorphic environments, and XCH₄≤4mol%. A study has also been conducted to determine methane hydrate stability over the temperature range of -40~20°C. Synthetic fluid inclusions were employed in both studies as miniature autoclaves. Experimental data for the PVTX properties of H₂O-CH₄ fluids under late diagenetic to low grade metamorphic conditions was used to calculate the slopes of isoTh lines (the line connecting the P-T conditions of the inclusions at formation and at homogenization) at different PTX conditions. An empirical equation to describe the slope of iso-Th line as a function of homogenization temperature and fluid composition was developed. The equation is applicable to natural H₂O-CH₄ fluid inclusions up to 500°C and 3 kilobars, for fluid compositions ≤4 mol% CH₄. The Raman peak position of CH₄ gas is a function of the pressure and temperature. This relationship was used to determine the pressure along the methane hydrate stability curve in the H₂O-CH₄ system. The combined synthetic fluid inclusion, microthermometry and Raman spectroscopy method is a novel experimental approach to determine the P-T stability conditions of methane hydrates. The method is fast compared to conventional methods, and has the potential to be applied to study other gas hydrate systems. / Ph. D.

No / Solvent influences on the crystallization of polymorph and hydrate forms of the nootropic drug piracetam (2-oxo-pyrrolidineacetamide) were investigated from water, methanol, 2-propanol, isobutanol, and nitromethane. Crystal growth profiles of piracetam polymorphs were constructed using time-resolved diffraction snapshots collected for each solvent system. Measurements were performed by in situ energy dispersive X-ray diffraction recorded in Station 16.4 at the synchrotron radiation source (SRS) at Daresbury Laboratory, CCLRC UK. Crystallizations from methanol, 2-propanol, isobutanol, and nitromethane progressed in a similar fashion with the initial formation of form I which then converted relatively quickly to form II with form III being generated upon further cooling. However, considerable differences were observed for the polymorphs lifetime and both the rate and temperature of conversion using the different solvents. The thermodynamically unstable form I was kinetically favored in isobutanol and nitromethane where traces of this polymorph were observed below 10°C. In contrast, the transformation of form II and subsequent growth of form III were inhibited in 2-propanol and nitromethane solutions. Aqueous solutions produced hydrate forms of piracetam which are different from the reported monohydrate; this crystallization evolved through successive generation of transient structures which transformed upon exchange of intramolecular water between the liquid and crystalline phases

No / The surface energy of a-lactose monohydrate measured by inverse gas chromatography (IGC) is reported along with a dynamic molecular modelling study of the interaction of the various molecular probes with different surfaces of a-lactose monohydrate. The IGC results show that a-lactose monohydrate is acidic in nature. Using quantitative calculations of the energy of adsorption, the acidic nature of the surface is confirmed and the calculated values agree closely with the experimentally measured values. Along with the acidic nature, dynamic molecular modelling also reveals that the presence of a channel and water molecules on a surface affects the surface energetics of that face. The presence of water on the surface can decrease or increase the surface energy by either blocking or attracting a probe molecule, respectively. This property of water depends on its position and association with other functional groups present on the surface. The effect of a channel or cavity on the surface energy is shown to depend on its size, which determines whether the functional groups in the channel are assessable by probe molecules or not. Overall molecular modelling explains, at the molecular level, the effect of different factors affecting the surface energy of individual faces of the crystal.