Hydration Behavior of Na-Smectite Crystals Synthesized at High Pressure and High Temperature

Hirohisa Yamada1, Hiromoto Nakazawa1, Hideo Hashizume1, Shuichi Shimomura1 and Takashi Watanabe2
1 National Institute for Research in Inorganic Materials Namiki 1, Tsukuba, Ibaraki, 305 Japan
2 Department of Geoscience, Joetsu University of Education Yamayashiki, Joetsu, Niigata, 943 Japan

Abstract: Hydration behavior of Na-smectite crystals synthesized at a pressure of 5.5 GPa and temperatures of 1400°–1500°C was examined by X-ray powder diffraction at various relative humidities (RH) in the range of 0–100%. The basal spacing of the Na-smectite crystal increased stepwise with increase in RH. The reflections observed were only normal reflections of a single or dual hydration states of smectite. No irrational, intermediate, or asymmetrical reflections were observed. The simple hydration behavior, not known for natural smectite with fine particle sizes and low crystallinity, indicates that the Na-smectite crystals are as perfect as common inorganic crystals with an ordered structure.

Key Words: High-pressure experiment • Hydration • Relative humidity • Smectite crystal

Clays and Clay Minerals; February 1994 v. 42; no. 1; p. 77-80; DOI: 10.1346/CCMN.1994.0420110
© 1994, The Clay Minerals Society
Clay Minerals Society (www.clays.org)