All recovered samples were observed by back-scattering Etazolate images, obtained with a JEOL 840 scanning electron microscope (SEM) at the CLYM laboratory (Lyon, France). Microstructural observations allowed characterizing the different stages of the reaction progress and nucleation-growth mechanism. Considering the potentially strong catalytic effects of even small amount of H2O in the sample charges, water content of the samples was determined from Fourier transform infrared spectroscopy (FTIR) using a Vertex 70 Bruker spectrometer coupled to a Hyperion microscope (at Institut de Planétologie et Astrophysique, Grenoble, France). Details of FTIR measurements are described elsewhere (Perrillat et al., 2013). The OH content of the samples, as calculated using the calibration by Libowitzky and Rossman (1997), varies from 154 to 603 wt.ppm H2O with an average value of 436 wt.ppm H2O (Fig. 2).
Fig. 2. Unpolarized IR spectrum of recovered sample Fa52k in the region of the OH stretching modes. All the samples exhibit a broad absorption band in the range 3000 to 4000 cm−1, attributable to the presence of molecular H2O at grain boundaries. The hydroxyl content is calculated from the integrated area of this broad absorption band after background baseline correction and thickness normalization using the general calibration of Libowitzky and Rossman (1997). The bands located near 2900 cm−1 are characteristic of C–H bending of the epoxy glue and are disregarded for the determination of OH contents.Figure optionsDownload full-size imageDownload high-quality image (50 K)Download as PowerPoint slide
Fig. 2. Unpolarized IR spectrum of recovered sample Fa52k in the region of the OH stretching modes. All the samples exhibit a broad absorption band in the range 3000 to 4000 cm−1, attributable to the presence of molecular H2O at grain boundaries. The hydroxyl content is calculated from the integrated area of this broad absorption band after background baseline correction and thickness normalization using the general calibration of Libowitzky and Rossman (1997). The bands located near 2900 cm−1 are characteristic of C–H bending of the epoxy glue and are disregarded for the determination of OH contents.Figure optionsDownload full-size imageDownload high-quality image (50 K)Download as PowerPoint slide