Although metal-organic frameworks (MOFs) have been extensively investigated for many applications including adsorbents, some MOFs suffer from poor chemical stability lower than other microporous materials like zeolites. Here, we report the hybridization of a prototype MOF, MOF-5 composed of Zn₄O units and benzene linkers, with a layered titanate, K₂Ti₄O₉. The reaction of K₂Ti₄O₉ having zinc acetylacetonate complexes in the interlayer space with MOF-5 precursors including zinc acetate and benzene-1,4-dicarboxylic acid gave the product showing the basal spacing of 2.0 nm in the powder X-ray diffraction pattern, which was larger than that of the starting K₂Ti₄O₉ (0.87 nm). This product, in contrast to the starting K₂Ti₄O₉, had micropores, revealed by the N₂ adsorption isotherm. Scanning electron microscopy showed that the product was composed of belt-like particles with the length of ca. 1 µm like the starting K₂Ti₄O₉ and nanoparticles deposited on the belt-like particles assignable to MOF-5 nanocrystals. The N₂ adsorption isotherms of the products after the exposures of water vapor with different humidities showed that the bare MOF-5 underwent the structural collapse when treated with 10%-water vapor whereas the product retained the structure even after the treatment with 30%-water vapor. These results suggested that unit-cell-thick MOF-5 was immobilized in the interlayer space of K₂Ti₄O₉.

Although DSSC using quasi-solid electrolytes have been developed to stabilize electrolyte systems, their ionic conductivity is lower than that of liquid systems. Therefore, in this study, organic-modified clay was added to quasi-solid electrolytes to improve the ion conductivity. We found that the effect of adding clay on the ion diffusion coefficient (D) differed depending on the ion species used in the electrolyte. The D of triiodide with Li⁺ increased approximately 3.1 times with adding clay, whereas that with imidazolium ions decreased by approximately 0.38 times. The photoelectric conversion efficiency (η) of DSSC with the prepared quasi-solid electrolytes was measured and, similar to the change in D, it increased from 0.22 to 0.87% with Li⁺ and decreased from 1.4 to 1.1% with imidazolium ions. From this study, it was found that the addition of clay can be expected to improve the function of quasi-solid electrolytes by using appropriate ionic species.

The cations in the octahedral sheet of montmorillonite (usually composed of Al, Fe and Mg) occasionally exceed 2 mols of charge per mole of formula unit [mol/mol_FU] when analyzed by the conventional structural formula method (SFM) consisting of di-octahedral region from chemical analysis of refined clay samples exchanged with ions other than Mg. To correct this deviation, this paper proposes an improved structural formula method (iSFM) that places the excess amount of Mg (mMg) into the vacancy of the octahedral sheet to become m(Mg₂Al) in the tri-octahedral region. The iSFM is applied to five clay samples, and the results show that the clays, mainly containing montmorillonite, can be appropriately evaluated as bleaching earth or bentonite, regardless of their pH values or amorphous hydrated silica contents.

Irradiating kaolinite crystals with electron beams is known to cause radiation damage and result in amorphization. For this study, we irradiated radiation to kaolinite with a high Hinckley index and investigated the increase in plasticity-imparting capacity. For the first experiment, samples of two types were prepared: a dried coarse sample with a Hinckley index of 1.41 and a 7.66 µm median particle diameter. The slip sample made by adding water to the same sample. These samples were irradiated with ⁶⁰Co-γ rays at two levels: 50 kGy and 100 kGy. The hygroscopicity rate was investigated as an indicator of plasticity-imparting capacity, the peak-to-background ratio and crystallinity in X-ray diffraction as indicators of amorphization, and the Hinckley index and S-Hinckley index as indicators of stacking fault. The results suggest that radiation damage caused amorphization and a decrease in plasticity-imparting capacity. The slip sample irradiated with ⁶⁰Co-γ rays at 100 kGy showed a diffraction peak at 1.43 nm, which subsequently disappeared. For the next experiment, we used a fine-grained sample obtained by wet grinding the above kaolin in a ball mill. The Hinckley index of the fine-grained sample was 1.05. The median particle diameter was 4.25 µm. In this experiment, the slip samples were irradiated with ⁶⁰Co-γ rays at a dose of 100 kGy. The hygroscopicity rates were 0.95% for the non-irradiated sample and 0.87% for the irradiated sample. The peak-to-background ratio changed from 45.40 for the non-irradiated sample to 42.35 for the irradiated sample. Through two experiments, amorphization caused by radiation exposure differs from the amorphization of secondary clay, suggesting reduction in its plasticity-imparting capacity.