Fluorine micas were synthesized using talc and K₂SiF₆ at 900°C for 1 hour in an electric furnace. With increasing K₂SiF₆/talc ratio, b and c unit cell parameters of synthetic fluorine micas were decreased. This result may be interpreted in terms of the shrinkage of the octahedral sheet by the loss of Mg²⁺ from the octahedral site. Infrared absorption spectra of synthetic micas showed the splitting of the absorption band of Si-O stretching, which indicates that some alkali ions migrate into the interlayer site of silicate skeleton. The one dimensional Fourier synthesis showed that with the increase of K₂SiF₆/talc ratio the electron density of K⁺ in the interlayer site of synthetic micas increased and that of Mg²⁺ from the octahedral site decreased. These analytical data indicate that fluorine micas are mainly formed by the transformation from talc without entire disruption of the original atomic arrangement by the intercalation process of alkali ion into the interlayer site of talc and partially formed by solid state reactions. The negative zeta potential of synthetic fluorine micas decreased in magnitude as with increasing K₂SiF₆/talc ratio. It indicates that the zeta potential of synthetic fluorine micas is closely connected with their net layer charge.

View full abstract

The removal of acetaldehyde by sepiolite combined with 2-aminobenzoic acid (OABA)(sepiolite-OABA complex) from ambient air was studied in comparison with that of the aldehyde by sepiolite, coconut-shell active carbon (carbon), 5A-zeolite, 13X-zeolite, diatomaceous earth, as well as these porous material-OABA complexes. Experiments were done at 25°C in ambient air. The removal rate of the aldehyde by these porous material-OABA (10%) complexes followed the order of sepiolite->>carbon->13X-zeolite->5A-zeolite->diatomaceous earth-OABA (10%) complexes. The amount of the aldehyde removed by the sepiolite-OABA complex was much larger than that by OABA and that by sepiolite itself. The larger removal rate of the aldehyde by the sepiolite-OABA complex was thought to be caused through the reaction between the aldehyde and OABA which is activated by sepiolite. The removal of the aldehyde by the sepiolite-OABA complex was particularly remarkable when the aldehyde concentration was low, e. g., such as 1-10 ppm. This complex was thought to be very useful as the deodorant for acetaldehyde.

View full abstract

The formation process of kaolinite from the amorphous mixture of silica and alumina by hydrothermal reaction was studied by XRD, IR, DTA-TG, TEM, and high-resolution solid state ²⁹Si-and ²⁷Al-MAS/NMR. The amorphous mixture of the starting material prepared with commercially available silica-sol and alumina-sol was hydrothermally treated with distilled water in a Teflon pressure vessel at 220°C for a reaction time varying from 1 to 144 hours. The Q⁴ state component of the amorphous starting material changed into an intermediate amorphous Q³ state. The intermediate amorphous phase converted into crystalline kaolinite with spherical shape (Q³ state). The yield and crystallinity of kaolinite increased with an increase in the reaction time. On the other hand, the coordination number of aluminum converted from a mixture of six-and four-coordinations to six-coordination. In the earlier stages of crystallization of kaolinite, spherical kaolinite is more abundant than platy kaolinite, and the spherical kaolinite changes into platy one with increasing hydrothermal reaction time.

View full abstract

The gold decoration technique of electron microscopy was applied to natural (001) surfaces of two kinds of pyrophyllite crystals (green and white colored specimens) collected from “Roseki” deposits distributed in the Shokozan area, Chugoku province, southwest Japan. The specimens are characterized by some parallel steps of malformed circular or polygonal forms with varying step separations. Crystals exhibit paired and single steps which may be correlated to 2M or 1T polytypes, respectively. The paired steps take place normally by the interlacing process on their crystal growth. The different surface microtopographs on both green and white colored crystals are explained based on the understanding on spiral morphology.

View full abstract

Hydrothermal experiments have been carried out to find the equilibrium conditions for the reactions:
2kaolinite=pyrophyllite+2diaspore+2water (1)
kaolinite+2quartz=pyrophyllite+water (2) As starting materials, a natural mixture of kaolinite-pyrophyllite-boehmite was used for the experiments. Determination of reaction direction was based upon X-ray diffraction patterns.
It has been confirmed that the equilibrium curve for the reaction (1) passes through the points 325 ± 10°C at 1kb and 330 ± 10°C at 2kb, and the curve for the reaction (2) passes through 250 ± 10°C at 1kb and 260 ± 10°C at 2kb. The present temperatures for the reaction (2) are lower than any other one reported so far.

View full abstract

Anion exchanged hydrotalcites have been characterized by means of X-ray, thermal and infrared spectroscopic methods. The sample has been treated in the solution containing various anions such as S^2-, SO₄^2-, SO₃^2-, HSO₃^-, S₂O₃^2-, S₂O₄^2-, S₂O₅^2-, SCN^-. The dehydration temperature of structural OH as well as the CO₃ remarkably shifts from 400 to 480°C in the samples exchanged with anions such as SO₄^2-, HSO₃^2-, S₂O₅^2-, which suggests the presence of some interactions between the anions and the structural OH. All the sulfur atoms exchanged are retained in the temperature up to 980°C. Infrared spectroscopic and thermogravimetric data show that the exchanged SO₄ occupy the site of CO₃.

View full abstract