Unusual X-Ray Characteristics of Vermiculite from Wiry, Lower Silesia, Poland

Abstract

Coarse-grained vermiculite from a serpentinite-pegmafite thermal zone displays a rational series of narrow 14.4 A basal reflections and an unusual broad 28 A peak. X-ray diffraction simulations and fitting techniques show that the 28 ,~ peak is related to 28 .~ domains consisting of elongated 2:1 layers of different lengths. The domains are located at the crystal edges of the vermiculite.

Influence of crystal structure defects on the small-angle neutron scattering/diffraction patterns of clay-rich porous media

“…A complete statistical analysis regarding the overall content of defects cannot be achieved because of the segregated nature of defects in different zones. Nevertheless, TEM observations obtained in the present study seem to corroborate the interpretation of Sakharov et al (2001). The layer-termination defects in Fig.…”

“…Its position systematically corresponded to twice the position of the 001 reflection, which gradually shifted from $15 to $12.2 Å and finally to $10 Å (Hubert et al, 2013), clearly indicating that this additional reflection is related to the presence of layers with swelling properties. Similar structure analysis on a fine fraction of another type of natural vermiculite by Sakharov et al (2001) also showed the presence of a similar reflection at 2d 001 . These latter authors demonstrated that this diffraction feature could not be reproduced by considering ordered successions of layers with different chemistry.…”

“…These latter authors demonstrated that this diffraction feature could not be reproduced by considering ordered successions of layers with different chemistry. Sakharov et al (2001) assigned this reflection to the presence of domains located at the edges of the crystal, consisting of elongated layers of various lengths. Such a model considering the succession of a layer and a missing neighbouring layer at the same layer-to-layer distance in a single crystal is consistent with the observation made by Hubert et al (2013) regarding the position at 2d 001 upon dehydration.…”

“…One way to test the influence of the local layer-termination defects described by Sakharov et al (2001) on calculated ND patterns is to consider two kinds of unit cells along the c* axis, referred to as A and B. The A unit cell is characterized by the stacking of two original unit cells with random AEa/3 and AEb/3 displacements and by a total d 001 value of 29.7 Å .…”