Integrated Calorimetry and Vibrational Spectroscopies
Zusammenfassung der Projektergebnisse
The Associated RAman BrIllouin CAlorimeter, called by the acronym ARABICA is a unique and very versatile equipment. It is possible to study simultaneously the structure, the elastic properties and the energetics of matter in relation with temperature and time. This particularity makes that no offset of temperature or time is possible insuring a very accurate recording of all data during a transformation. The setup can be used in a full or partial associated configuration. The equipment in is total integrated configuration can be operated from -50°C to 750°C and with heating and cooling rates between 0.5 and 300 °C/min. The alfa - beta transition of quartz was revisited and the high precision results obtained with a significant lower reduce uncertainties confirm the possibility to interpret this transition as a first order Landau transition. The dynamic of the glass transition was recorded for four different types of glasses: phosphates, tellurites, borosilicates and sodo lime silicates. In all cases the structural modifications, observed by the Raman spectrometry, showed significant modifications a lot before any noticeable enthalpic effects (DSC measurement). These structural reorganizations below the glass transition are associated with local atomic relaxations. This mismatch between structural and enthalpic signature increases with the cooling rate hat which was submitted the glass i.e. the fictive temperature. In parallel it was observed that the modifications of the elastic properties recorded from the Brillouin spectroscopy were concomitant to the structural modifications. Relaxations of different densified glasses were observed. Depending of the mode of densification, cold or hot compression, as well as their chemical composition it was observed that this process is more or less related with the glass transition. The energy stored by the densification can be release way below the glass transition in the case of cold compression of highly polymerized glasses or during the glass transition for hot compression of more depolymerized glasses. The DSC calorimeter can be shifted and replaced by a displacement stage. In this configuration mapping of heterogeneous samples can be realized. And other sample environments can also be achieved. Temperatures up to 1100 and 1500°C were reached by using respectively a hot stage and a heating wire. Tensile and compression stages can be also mounted on the displacement stage to observe modification of matter (Raman) and their mechanical properties (Brillouin) with stress. With these different environments crystallization of glasses at high temperature and pressure induce phase transitions of perovskite type compound were studied. Combining these different investigations, evolutions of the glass structure and of their elastic properties can be correlated to Pressure and Temperature. Calibration curves were established and applied to reconstruct the thermal and pressure history of modified glasses. This methodology was applied to a large set of phenomena: Fiber drawing, Laser modified regions, Indented deformation, Densification, Cation exchange. The Brillouin spectrometer can be also used alone in a macro configuration. In such a way all the elastic modulus of matter can be determined very precisely. Different glass series were investigated in the following compositional systems: tin-tellurites, titano-silicates, alumino-borosilicates, alumino-phosphates, alumino-silicates. A very good agreement was found between the data obtained here optically and conventional macroscopic measurements.
Projektbezogene Publikationen (Auswahl)
-
Combined Differential scanning calorimetry, Raman and Brillouin. Analytica Chimica Acta, 2018,998, 37-44
Veber, A, Cicconi, MR, Reinfelder, H, de Ligny, D
-
Effect of thermally induced structural disorder on the chemical durability of International Simple Glass. npj Materials Degradation, 2018, 2:31
Angeli, F., T. Charpentier, P. Jollivet, D. de Ligny, M. Bergler, A. Veber, S. Gin, and H. Li
