Showing papers in "Clay science in 2010"

Preparation and properties of exfoliated vermiculite-polyamide 6 nanocomposite

Abstract: Ion-exchange treatment of natural vermiculite (VER) with dodecylammonium (DDA) ions and subsequent preparation of a polyamide 6 (PA6) based nanocomposite was conducted to investigate the potential suitability of VER for use in polymer nanocomposites. In order to investigate the ion-exchange behavior, ground VER powder and DDA were treated at 60°C for 12 h, in which time the intercalation reaction was completed. DDA intercalation was rapid and complete for VER even in dilute DDA solution (0.5 mass%) at a low suspension VER concentration of 1 mass%. The VER-PA6 nanocomposite was formed via exfoliation of a DDA modified VER (DDAVER) layer. DDAVER was melt-kneaded with PA6 in a twin-screw extruder at 260°C. The morphology of the nanocomposite was characterized using X-ray diffraction and transmission electron microscopy. Measurements of the mechanical properties and methanol permeability were also carried out. The DDAVER-PA6 nanocomposite exhibits a high degree of VER exfoliation and the rigidity and gas barrier properties also appear to reflect the nanocomposite morphology. Addition of a small amount of DDAVER with 3 mass% sili- cate was sufficient to improve the rigidity, heat resistance and barrier properties of the nanocomposite.

Determination of carbonate content of soils and clays by using co_2 detector tube : improvement of the method and some applications

Abstract: We improved the method for determination of carbonate in soils and clays (Wada (1997) Soil Sci. Plant Nutr., 43, 45-50). A sample was placed in a flexible gas-tight plastic bag attached with stopcock and heat-sealed. The carbonate in the sample was decomposed by addition of HCl and the generated CO 2 was diluted by injecting a known amount of air followed by determination of the CO 2 concentration of the gas in the bag. The carbonate content of the sample was calculated by summing the amount of gaseous and dissolved CO 2 , the latter of which was estimated with the aid of Henry's law. A series of test using standard carbonate minerals showed a 20 min of digestion was sufficient for complete dissolution. The improved method was applied to some clays and soil samples. Some Japanese soils from greenhouses contained about 0.08 to 0.35 mol kg -1 of carbonate, while their soil pH values were significantly lower than those expected from carbonate equilibrium.

SYNTHESIS AND CELLULAR UPTAKE OF FLUORESCEIN INTERCALATED LAYERED DOUBLE HYDROXIDE(2010 TMC Special Paper)

Abstract: Layered double hydroxidc (LDH) is widety known as anionic clay and has an anion exchange property. The cellular uptake of LDH has received considcrabte attention in recent yeais in view oftheir potential technological irr]portance as materials for drug delivery due to low cytotoxicity, good biocompatibility and controlled release of drug. Tb investigate th ccllular uptake beh avjour of LDH, the stable and labeled highly fiuorescent might be required. In this paper, we focused on fiuorescein disodium sa]t (Fluo), as a guest in fiuorescence dye, thc intercalation fFluo into Mg-Al LDH by coprecipitation method has been investigated. To define the abilities ofLDH as materials for drug delivery, the cellular uptake ofthe FluofLDH for the marnrnalian cells, L929 and HeLa, has also bccn studied. The characterization ofthe F]uofLDH was canied out by using XRD, FT-TR and clement chcmicaL ana]ysis. The FluofLDH had a ]ayered strLtcture, which the two kinds ofbasal spacing (O03) was 1.58 nm and O.77 nm. These values indicated that hc interlayer placc ofFluo anion changed for horizontal orientation to vertical orientatien with increasing Fluo contcllt, According to the fiuorescence, confocal and TEM images of cells, the fiuorescence of ccllular cytoplasm and the internalized FluolLDH particles were observed. Witi demonstrated that thc FluofLDH was internalized into the mamrnalian cclls by the cellular endocytosis.

The occurrence and structure of vermiform chlorite

Abstract: To understand the origin of its unique morphology, the structure of vermiform chlorite has been investigated Two chlorite specimens (magnesian chamosite) were analyzed: vermicular aggregates in quartz-feldspar veins in a pelitic schist, and those grown on a quartz single-crystal surface Both specimens show very similar textures; they are composed of pseudohexagonal chlorite plates of several tens μm in lateral size and several hundreds nm in packet thickness, stacked to form long vermicular aggregates up to several hundreds μm Chemical analyses indicated that the two specimens have similar compositions with IV Al 12∼13 per 40 sites and Fe/(Mg + Fe) ratio of ∼055 XRD and EBSD indicate IIbb semi-random stacking HRTEM shows that the stacking is considerably disordered in terms both of the layer orientation and direction of the interlayer dis- placement The vermicular morphology of chlorite is probably originated from a relatively faster spiral growth along the stacking in hydrothermal fluid