Showing papers in "Clay science in 2014"

Preparation of large-area reduced graphene oxide-smectite composite film and its electromagnetic shielding effectiveness

Abstract: The objective of this research was to prepare a clay film with electromagnetic shielding properties by making a clay film electrically conductive. To achieve this goal, we attempted to intercalate graphene into smectite clay and to prepare a graphene-smectite composite film with dimensions corresponding to those of A4 paper. The composite film was prepared by mixing graphene oxide and smectite in water, drying the solid, and annealing at 250°C for 30 min in an air atmosphere. The film was characterized by X-ray diffraction anal - ysis, Fourier transform infrared spectroscopy, thermogravimetry, differential thermal analysis, and scanning electron microscopy. Conductivity and electromagnetic shielding were measured with a linear, 4-pin electrode method and the KEC method, respectively. The characterizations indicated that the reduced graphene oxide compounded with the smectite clay at the nanometer scale. The obtained composite film contained 33 wt% carbon, and the sheet resistance was 1036 Ω·cm −2 . The shielding effectiveness of the composite film was 67% at electromagnetic frequencies less than 100 MHz. At frequencies less than 10 MHz, the shielding effective- ness of the film exceeded 97%. We have therefore succeeded in developing a clay film with electromagnetic shielding properties by addition of reduced graphene oxide to smectite clay.

Local structure around cesium in montmorillonite, vermiculite and zeolite under wet condition

Abstract: We have observed the local stmcture around cesium in silicate minerals under wet and dry conditions by using X-ray absorption fine stmcture (XAFS) technique at Cs KLedge. The measurements under wet and dry conditions simulated changes of the actual environment, High transmission ability at Cs KLedge provides XAFS measurement under various conditions. Montmori11onite, verrniculite, and zeolite were employed for the study. Vermiculite was obtained by wet classification of the actual soil at Fukushima. The result ofXAFS measurement shows that water molecules in interlayer position are remoyed by cesium adsorption in the interlayer site of verrniculite. Cesium ion was adsorbed on one side of the interlayer site of swelled montmorillonite under wet condition. On the other hand, water molecules were not coordinated with cesium ion in the zeolite even in the case ofwet condition.

Caryopilite and greenalite from the manganese deposits in shikoku, southwest japan

Abstract: Caryopilite, Mn2'-rich serpentine group mineral, is a major constituent of the manganese ores in the North Chichibu belt in the Shikoku region, SW Japan, The Nomh Chichibu belt is thc Jurassic accretionary complex containing abundant chert beds of Permian-1[tiassic age and has been subjected to low-grade metamorphism of the prehnite-pumpellyite to pumpellyite-actinolite facies. Caryopilite close to Mn end-member in composition and having IMpolytype commonly occur in the chert-hosted manganese deposits. Greenalite, the Fe2' analogue of caryopilite, has 1T polytype and rarely occurs in some chert-hosted deposits. Fe-rich caryopilite having intermediate composition between caryopilite and greenalite and having IMpolytype occurs in an iron-manganese d posit and a manganese deposit associated with basalt. Manganoan chlorites also eccur in these deposits,

Observation of the intercalation process of a tetra-cationic porphyrin achieving high molecular density without aggregation into an anionic clay film by an immersion method

Abstract: Several remarkable organic-inorganic multilayer hybrids, which include extremely high-density photosensitizer dyes, without aggregation have been produced using a method based on tCsize-matching intercalation\" with a simple immersion technique. This study focuses on the intercalation process. kmporal progress ofthe intercalation of the +4-charged cationic porphyrin molecules in the interlaycrs of the anionic synthetic clay particles, which were fabricated into a thin transparent film, was observed by a spectroscopic method at various temperatures. The distance between the adjacent cations in the cationic porphyrin molecule was designed to be close to the average distance between the clay anionic sites, which is called the size-matching condition. When the leading amount of the porphyrin corresponded to 30% versus the cation exchange capacity (CEC) of the clay in a film, almost all the porphyrin molecules were intercalated into the clay film during a 10 h immersion. No aggregated species were observed at any time during the immersion. After the immersion, the average eccupied area of one porphyrin molecule was estimated to be 8,3 nm2. The time course of the intercalation was well simulated by a simple exponential function with a single time rate constant for each temperature condition. The Arrhenius plot ofthe rate was linear, and the Arrhenius activation energy estimated from the rate constants was 26.8 kJ rnol'i.