Tribological properties of low-temperature graphite fluorides. Influence of the structure on the lubricating performances

International audienceThe present work is concerned with the study of the tribological properties of various fluorinated carbon phases obtained at room temperature and then post-treated under fluorine atmosphere at different temperatures. The tribological tests evidence good intrinsic properties for all the compounds (friction coefficient in the range 0.07-0.09). Differences appear after few cycles. Friction measurements after 100 cycles and complementary Raman analyses of the tribofilm remaining in the wear scar point out that long term tribologic properties of the fluorinated compounds strongly depend on the evolution undergone by the materials under friction. The release of HF molecules, the loss of fluorine and partial rebuilding of graphitic phases are at the origin of the degradation of the friction properties. The good properties of the compounds post-treated at temperature in the range 150-300 °C are attributed to the chemical and structural stability of these compounds under friction

Etude de la synthèse et du traitement thermique sous fluor de fluorures de graphite préparés à température ambiamte (Applications au stockage électrochimique de l'énergie)

Des fluorures de graphite ont été préparés à température ambiante en présence de F2-HF-MFn, MFn étant BF3 ou un fluorure de chlore préparé à partir de Cl2 ou de KCl, puis traités thermiquement sous fluor. La synthèse a également été réalisée sur un micropilote en vue d'une industrialisation. Afin de mieux comprendre le comportement des matériaux lors d'utilisations comme lubrifiant solide et comme cathode dans des piles au lithium, ces composés ont été caractérisés. La DRX a permis de déterminer la structure des composés. L'identification et la quantification des espèces intercalées ont été réalisées par RMN 19F, 11B et 1H, et par RPE. La covalence de la liaison C-F a été évaluée par RMN 13C et InfraRouge. Ce travail a permis d'obtenir une large gamme de matériaux aussi compétitifs que ceux déja connus et commercialisés pour les applications citéesCLERMONT FD-BCIU Sci.et Tech. (630142101) / SudocSudocFranceF

Comparative performances for primary lithium batteries of some covalent and semi-covalent graphite fluorides

Different graphite fluorides were prepared by three different synthesis ways: fluorination at room temperature, at 600 °C, and refluorination at 400 and 530 °C of a fluorinated graphite prepared at room temperature. All the samples have been characterized by 19F MAS NMR and FT-IR spectroscopies. Their electrochemical performances as cathode materials in primary lithium batteries have been investigated at room temperature and at 60 °C and as a function of the current density. Ageing behavior has been also studied using some liquid electrolytes. Refluorinated sample at 400 °C exhibits the best performances because of both its good average discharge potential and its discharge capacity, i.e. 2.54 V and 848 Ah kg-1, respectively. For this sample, the best specific energy density and specific power density are 2149 Wh kg-1 and 902 W kg-1, respectively.info:eu-repo/semantics/publishe

Solid-state NMR study of the post-fluorination of (C2.5F) n fluorine - GIC

The conversion of (C2.5F)n fluorine-graphite intercalation compounds (GIC) into covalent graphite fluoride during a post-treatment in pure F2 gas is studied by solid-state NMR. First, a careful characterization of the starting material is performed; in particular, for the first time for fluorinated carbons, two-dimensional 19F- →13C cross-polarization wide-line separation (CP-WISE) experiments were carried out. This completes the classical NMR data such as 19F and 13C chemical shifts, quantitative 13C solid echo, and C-F bond length measurements, which were estimated by dipolar recoupling using inverse CP MAS. The data of the raw (C2.5F) n and of the samples post-fluorinated at 350, 450, and 550°C were compared to investigate the C-F bonding as a function of the treatment temperature. The C-F bonding is discussed taking into account a hyperconjugation of the C-F bonds with neighboring unfluorinated carbon atoms. © 2007 American Chemical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Lubricating performances of room temperature highly fluorinated f-graphite heat-treated under fluorine atmosphere

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