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En l’absence de traitements de protection, de nombreux objets et éléments patrimoniaux en attente de restauration se dégradent sous l’effet de la corrosion atmosphérique. Ainsi les témoignages de notre histoire disparaissent lentement. Il est nécessaire de développer des traitements de protection temporaires, peu coûteux, réversibles et répondant aux normes environnementales actuelles, afin d’enrichir le panel de solutions dont disposent les professionnels de la conservation restauration. Ces recherches sont également motivées par les conservateurs du patrimoine qui souhaitent éviter des travaux de restauration complexes et onéreux sur des collections importantes. L’enjeu de cette étude est in fine de pouvoir proposer un traitement alternatif pour la protection du patrimoine ferreux soumis à la corrosion atmosphérique sous abri. Les molécules choisies pour réaliser ces nouveaux traitements sont des acides carboxyliques. Ces composés sont mis en œuvre dans différents types de solutions, dont les performances anti-corrosion sont prouvées par des mesures électrochimiques et des tests de vieillissement artificiels et naturels. Parallèlement à ce travail, le carboxylate de fer, responsable de l’inhibition de la corrosion est étudié aux points de vue morphologique, thermique, chimique et structural grâce à la combinaison de plusieurs techniques d’analyses. Ces travaux permettent de proposer des traitements protecteurs, adaptés à l’état de surface de l’élément à protéger, au type d’intervention envisagée (dépendant notamment de l’urgence de l’intervention, et des moyens humains et financiers à disposition), et aux conditions de conservation de l’élément. / Without any protection treatment, lots of artefacts or elements from our cultural heritage slowly decay because of atmospheric corrosion. Therefore there is a need for temporary, cheap, easy-to-use and non-toxic protection systems, fitting to the actual environmental laws. These treatments could give new solutions to the conservators for protecting the artefacts and sometimes avoid them complex and expensive restoration works. Long chain carboxylic acids have been chosen for this purpose, and used in different kinds of treatments. Their good performances are proved by electrochemical measurements and artificial and natural ageing tests. In parallel with this work, the iron (III) carboxylate, which is the compound responsible for the inhibition properties, has been studied in term of morphology, structure, and chemical properties, thanks to many analytical techniques. This work finally leads to propose a specific and adapted solution for each element or artefact that has to be treated- depending on its surface, its environmental conditions of exposure, the emergency of its treatment, and the financial and human means available.

Abstract A theoretical study of the Kolbe-Schmitt reaction mechanism, performed using a DFT method, reveals that the reaction between sodium phenoxide and carbon dioxide proceedswith the formation of three transition states and three intermediates. In the first step of the reaction, a polarized ONa bond of sodium phenoxide is attacked by the carbon dioxide molecule, and the intermediate NaPh-CO2 complex is formed. In the next step of the reaction the electrophilic carbon atom attacks the ring primarily at the ortho position, thus forming two new intermediates. The final product, sodium salicylate, is formed by a 1,3-proton shift from C to O atom. The mechanism agrees with the experimental data related to the Kolbe-Schmitt reaction.

Compared to SO42-(H2O)n, the solute-solvent interaction is favorable by C2O4 2- (H2O)n, n = 6∼12, due to two charges separation and more space in C2O42-. Because of the extensive hydration bonds, the stepwise solvation energy is around 15 kcal/mol even for larger clusters. The solvation dynamics for C 2O42-(H2O)n is influenced by the coupling between torsional movement along C-C bond and solute-solvent interaction. / For Na(H2O)n, the "constant IP" observed experimentally for Na(H2O)n is due to autoionization through Rydberg transition induced by the release of large relaxation energy after the removal of unpaired electron. In contrast, the reorganization is less extensive in Na(NH3)n, as both the electron-NH3 and NH 3-NH3 interactions are weaker, and the structure of Na(NH 3)n is determined by the maximization of Na+-NH 3 interaction. The autoinization is no important and the threshold measured in experiment is indeed for ionization of Na(NH3)n. / In the size-dependant charge separation of SO42-(H 2O)n with n = 3∼7, the key factor governing the charge separation is the difference in the strength of solvation interaction: while interaction with water is strong for SO42- and OH-, it is relatively weak for HSO4-. It gives rise to a barrier for charge separation as SO42- is transformed into HSO4- and OH-, although the overall reaction energy is exothermic. The barrier is high when more than two H2O are left to solvate HSO4-. The entropy is another important factor, which leads to the eventual switch-off of charge separation as cluster size increases. / The equilibrium structures of SO42-(H 2O)n with n = 6∼12 are determined by the competition between the solute-solvent and solvent-solvent interactions. Facilitated by SO42- in symmetry, the extensive hydrogen bonds are formed. The stepwise solvation energy is quite large (often exceeding 15 kcal/mol). AIMD simulation shows "crowding" effects in the first solvation of SO42-(H2O)12 at raised temperature. / The structure and solvation of hydrated di-anion (SO4 2-, C2O42-) clusters and solvated Na clusters are explored computationally by the quantum chemical calculation using Gaussian programme, and by the density functional theory based ab initio molecular dynamics (AIMD) method using Vienna Ab Initio Simulation Package (VASP). / Gao Bing. / "May 2006." / Adviser: Zhi-feng Liu. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6420. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 131-139). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.