Dehydration and rehydration of vermiculites: I. Phlogopitic Mg-vermiculite

Abstract

Dehydration and rehydration of a phlogopitic Mg-vermiculite were studied by thermo-analysis (TG, DSC) and in situ X-ray powder diffractometry. A detailed analysis of the relation between temperature and state of hydration of the vermiculite was rendered possible by use of slow heating rates in combination with a fast-recording position-sensitive detector. The results confirm the existence of a number of definite states of hydration characterized by basal spacings of 1.441,1.429,1.376, 1.165, 1.151,1.002 and 0.926 nm, all of which have already been described in the literature. In addition, so far undetected regular 1 : 1 interstratifications have been found. They formed during those transformations which lead to a change in the number of sheets of interlayer water molecules. These structures exhibit integral series of 00l reflections and d(001) spacings of 2.54 and 2.15 nm for the 2 : 1 and 1 : 0 transitions in the ratio of molecular layers of water, respectively.

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

“…Similar heating procedures at 250~ produced an irrational series of basal maxima (Figure 2). These results generally agreed with Mg-exchanged vermiculite behavior under heating (cf Collins et al 1992;Reichenbach and Beyer, 1994;Ruiz-Conde et al, 1996). Figure 3 shows X-ray patterns of different size-fractions of the studied sample.…”

Interstratified vermiculite–mica in the gneiss–metapelite–serpentinite rocks at Hafafit area, Southern Eastern Desert, Egypt: From metasomatism to weathering

“…In all Hafafit vermiculite samples, the 0 0 2 reflection with a dspacing of 10.20 Å corresponding to the 1-WLHS and the reflections at 7.45-8.45 Å, 3.56, 3.54, 3.36, 3.15, 3.08, 2.79 and 2.52 Å may point to dehydration of the vermiculite (Collins et al, 1992;Reichenbach and Beyer, 1994;Marcos et al, 2003). The processes of dehydration-hydration depend on temperature, pressure, chemical composition, particle size and relative humidity (Marcos et al, 2003(Marcos et al, , 2009.…”

Ion Exchanged Vermiculites with Lower Expansion Onset Temperatures

“…Some ion exchanged vermiculites, with less well defined water layer hydration states (WLHS), are less thermally stable than Mg-vermiculite [23]. Compared to pure vermiculite, vermiculite-mica interstratified materials feature higher expansion ratios with the thermal exfoliation also commencing at lower temperatures [21,[24][25][26][27].…”