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Kimoto, Kazushi*; Kawamura, Katsuyuki*; Makino, Hitoshi; Takayama, Yusuke
no journal, ,
Bentonite is being considered as a buffer material for the geological disposal of high-level radioactive waste. To ensure the long-term reliability of the buffer material, the properties of hydrated montmorillonite, the main component of bentonite, must be well understood. However, the deformation and mass transport properties of bentonite are affected by the nanoscale porous structure created by the aggregation system of hydrated montmorillonite. Therefore, it is important to know not only the properties of montmorillonite on a single crystal scale, but also the microstructure formed by the aggregate system. In this presentation, we will report on a method for modeling the microstructure based on coarse-grained molecular dynamics (coarse-grained MD), which has been developed based on this perspective.
Hamamoto, Takafumi*; Ishidera, Takamitsu; Matsubara, Ryuta*
no journal, ,
no abstracts in English
Sugita, Tsuyoshi; Mori, Masanobu*; Shimoyama, Iwao
no journal, ,
This study investigates the conversion of biotite, a subgroup of clay minerals, into photocatalysts through heat treatment with CaCl
. The resulting reaction products were analyzed in terms of their composition, structure, optical properties, and photocatalytic activity against Cr(VI) and salicylic acid (SA). Biotite and CaCl mixtures could be heated to 600
C while retaining the biotite crystal structure, whereas heating to 700C resulted in transformation to octahedral wadalite crystals. The band gap of the wadalite obtained after heat treatment was approximately 3.10 eV. The photocatalytic reduction rate per unit surface area increased markedly with increasing heat-treatment temperature, and the Cr(VI) reduction and SA degradation rates of the sample calcined at 800C were approximately 18 and 9 times greater, respectively, than those of the sample calcined at 500C. Leaching tests of the reaction products revealed that the elution of Ca
and Cl
was particularly significant. Even the samples that retained the biotite structure after heat treatment displayed some photocatalytic activity, indicating that this method may be applicable to preparing photocatalysts from mica and related minerals with similar structures.