Mise au point de l'analyse des surfaces de silice par ablation : ionisation couplée à la spectrométrie de masse

Abstract : Many techniques such as vibrational spectroscopy (Raman of infrared), nulcear magnetic resonance, small angle scattering, thermogravimetric analysis, specific surface area measurements has been used for decades to study silica compounds. Mass spectrometry techniques have not been used much to characterize such compounds up until now. The aim of this work was to determine the contribution of this technique in the analysis of varied silicas. After arriving at the optimal experimental parameters relative to the FTMS 2000 laser microprobe, correlations were extracted from the obtained mass spectra. A relation between the mass of detected clusters and specific surface area of the analysed samples was established. The more important the specific surface area, the larger the clusters induced by laser irradiation. Moreover, we have demonstrated a correlation between the ratio of the intensities of the clusters SiO(2n+1)H-/SinO(2n+1)- and the concentration of hydroxyl groups of the analysed silica. The greater ratio, the larger the concentration of OH groups. This relation has been confirmed by the study of the thermal treatment of a stober's silica. Finally, grafted samples were analysed in order to identify the corresponding grafts. It has been achieved with styrene grafts. As for the aftermath of this research, the structure's modelisation of the detected clusters will be undertaken, with the aim of better understanding formation mechanisms of these species. Additionnaly, the extraction of different grafts without any fragmentation by laser irradiation would be best done by using a matrix, which absorbs part of the laser beam energy
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Paul-Eric Lafargue. Mise au point de l'analyse des surfaces de silice par ablation : ionisation couplée à la spectrométrie de masse. Autre. Université Paul Verlaine - Metz, 1997. Français. ⟨NNT : 1997METZ035S⟩. ⟨tel-01777218⟩

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