Elaboration and characterization of materials obtained by pressing of vermiculite without binder addition
Résumé
Vermiculite materials were obtained by uniaxial pressing of potassic vermiculite powders obtained by sonication without any binder addition. The vermiculite powders, made of aggregates of particles with nanometric thick-ness and micrometric in plane dimension, were pressed in the range 17.7–80 MPa at room temperature and 200 °C, and further annealed in the range 400–800 °C. Pressing powders at 200 °C instead of 25 °C allowed the slight increase of the density of the formed materials (from 1.9 to 2 g·cm −3) due to the desorption of the water molecules from the interaggregate and interparticle spaces, allowing a higher densification. The density was also increased by tailoring the particle size distribution. The pressed materials were formed of oriented arrangement of vermiculite aggregates. The porous structure, characterized by mercury porosimetry, scanning electron microscopy, and small angle X-ray scattering, was modelled by oriented oblate spheroidal pores formed in the voids between the stacked aggregates organized in a structure possessing a cylindrical symmetry. The porous structure was found to vary with the pressure and the annealing temperature.