Structural alteration of sepiolite by dry grinding

The effects of dry grinding on the structure of sepiolite were studied by XRD, surface area measurement, TG-DTA and IR spectroscopy techniques. The results show that the sepiolite framework is rather resistant to mechanical stress and its alteration by dry grinding occurs through three successive, overlapping processes: (i) thinning of the fibrous particles without structural alteration; (ii) distortion of the parallel units of sepiolite fibres, affecting essentially the particle surface which transforms into an amorphous protective coating; (iii) disruption of the inner structure and a prototropy effect, producing an amorphous phase with some residual order.