水熱合成へクトライト無機層間化合物の熱分析

抄録

Hectorite-inorganic interlayer complexes, hydrothermally synthesized from precursory Si-Mg hydrous oxide at 125°-300°C in 2h, were studied by thermal analyses. DTA detected a broad low-temperature endotherm corresponding to a loss of loosely bound interlayer water, a small endotherm associated with dehydroxylation (ca. 700°C), and immediately followed by the two sharp exotherms corresponding to enstatite formation. The peak temperatures of two exotherms decrease drastically with increasing Li content. The peak temperature of the first exotherm correlates well with interlayer Li content (r=-0.92) and is affected by the excess amount of Na and/or Mg. Moreover, peak area of the first exotherm correlates well with the specific surface area (r=0.94). Thus, these results suggest that the first exotherm corresponds to early enstatite recrystallization of inorganic materials which exist between silicate layers and act as pillars on dehydration. As the peak temperature of the second exotherm is affected significantly by the Li content in octahedral sheet (r=-0.91), it is assumed that the second exotherm is associated with enstatite recrystallization of hectorite silicate layers. Results of DTG indicate that there are three types of water in the complexes; interlayer water (RT-300°C), less tightly bound structural water (300°-650°C) and structural water in silicate layer (650°-850°C). The amount of the structural water which is released at low temperature correlates with specific surface area (r=0.99) very well and the amount of the silicate structural water correlates well with the methylene blue adsorbed (r=0.96).