Bound water of sepiolite dehydrates in two steps in the temperature range of 250-650°C, as shown in the TG-curve. These steps are described here as steps II and III. At step II, half of the bound water is removed; other half at step III. From step II to III, discontinuous changes are confirmed in such properties as activation energy of dehydration, a-dimension, axial ratio, and intensities and spacings of X-ray powder reflections. A structural state at step II may be recognized as a distinct phase in the dehydration process.

MoS2(1-x)Te2x, the alloy of MoS2 and MoTe2 was fabricated with just co-sputtering and the combination of co-sputtering with following thermal treatment in chalcogen ambient. Phase separation, where MoTe2 was segregated rather than S and Te being uniformly distributed, was observed for some samples. From the physical structure evaluation using XRD, it was shown that the samples that was sulfurized after unintentional oxidation during shelf time exhibited no phase separation. It was suggested that oxidation of Mo or amorphous nature of the film at the chalcogenization stage may prevent the phase separation. In addition, some samples were stored in desiccator for stability evaluation. It was revealed that the samples undergo oxidation to different extent depending on the carrier gas used in tellurization. Finally, the bandgap and band structure was evaluated for samples with different Te concentration. The bandgap showed bowing behavior for different Te concentration with the bowing parameter b = -1.21 eV. Combined with the bandgap evaluation, the valence analysis with XPS showed that the band structure shifted according to the Te concentration. The shift in bandgap allows flexible band alignment which is expected to expand the materials applicability.

There are faint contaminants near primary stars in the direct imaging of exoplanets. Our goal is to estimate statistically the ratio of exoplanets in the detected batch of point sources by calculating the fraction of contamination. In this study, we compared the detected number of stars with the number of contaminants predicted by our model. We found that the observed number of faint stars were fewer than the predicted results towards the Pleiades and GOODS-South field when the parameters of the conventional stellar distribution models were employed. We thus estimated new model parameters in correspondence to the results of the observations.

Association of minerals such as zincblende, galena, chalcopyrite, pyrite, quartz, illite and chlorite (magnesium-rich type) has been observed in ores and also in the alteration zone adjacent to ore bodies of “Kurokō” (the black ore) deposits in Japan. Recently, in some ore bodies, detailed mineralogical studies have shown that non-metallic minerals in ores and the adjacent alteration zone are those poor in magnesium, iron and potassium, such as pyrophyllite, kaolinite, diaspore, quartz, 26 Å- and 30 Å-clay minerals. The 26 Å-clay mineral is a mixed-layer mineral of illite and its hydrated form. The 30 Å-clay mineral is a regularly interstratified montmorillonite-(aluminous) chlorite clay mineral. The presence of brucite is also usually suggested. An environmental condition to form ore deposits with such a mineral association may be a leaching condition, under which ions such as magnesium, iron and potassium were liable to be partially leached away or to precipitate as hydroxides rather than to form silicates such as illite or chlorite.

Hydrated halloysite clays altered from glassy tuff during weathering were examined in detail by x-ray, thermal, and electron micrographic methods. The electron micrographs show fibrous crystals of hydrated halloysite associated with many rounded grains, the former frequently jutting out from the latter. X-ray powder diffraction data and thermal curves show clearly the presence of hydrated halloysite, and on closer examination dehydrated halloysite and a small amount of montmorillonite can be detected. The presence of allophane as an accessory mineral is suggested in certain specimens. Furthermore the degree of crystallinity of hydrated halloysite varies slightly from specimen to specimen. The variation of the degree of crystallinity of the hydrated halloysite and of the kinds and amounts of accessory clay minerals, and the variation of the shapes of the particles observed in the electron micrographs are generally related to each other. Hydrated halloysite of a relatively well-crystallized sort generally co-exists with halloysite (dehydrated) and consists of elongated crystals having sharp edges; rounded grains are composed entirely of these fibrous crystals. On the other hand, a poorly crystallized sort tends to be associated with allophane and to show extremely fine hairlike, twisted fibers; these are associated with well-defined rounded grains. A genetic process of clay-mineral formation from volcanic glass is considered.