bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nacritic Clay Associated with the Jiangshan-Shaoxing Deep Fault in Zhejiang Province, China
Authors: Shen Z. Y. , Wilson M. J. , Fraser A. R. , Pearson M. J. 
Published: August 2006

AbstractA kaolin clay occurring in Carboniferous mudstone near the Jiangshan-Shaoxing deep fault in Zhejiang Province, eastern China was characterized by XRD and IR. Although the dominant mineral appeared to be kaolinite, IR also suggested the possible occurrence of nacrite. This was confirmed by forming intercalation complexes with potassium acetate and with hydrazine hydrate, both water complexes having the same characteristic spacing at 8.35 Â. Different particle size fractions of the kaolin clay were studied and the results indicated that nacrite content increased with increasing particle size. This occurrence of nacrite is consistent with previous findings of the polytype in high temperature and pressure environments.
Redox Treatment of an Fe/Al Pillared Montmorillonite. A Mössbauer Study
Authors: Bakas T. , Moukarika A. , Papaefthymiou V. , Ladavos A. 
Published: August 2006

AbstractPillared structures with an interlayer opening of ∼0.3 nm were obtained after successive heat treatments of the PILC precursor in reducing and oxidizing conditions. This precursor was prepared by reacting a Na+-montmorillonite with an intercalant containing Al and Fe oxo-hydroxides (Al/Fe = 1). Powder X-ray diffraction, elemental analysis, 57Fe Mössbauer spectroscopy, catalytic activity measurements and surface area data were used to characterize the samples. On the basis of Mössbauer spectra taken at temperatures between 4.2 and 300 K, it is deduced that oxidizing steps produce Al substituted maghemite which converts into Al substituted magnetite upon reducing heat treatment. Firing the precursor in oxidizing atmosphere forms pillars of few nm in diameter. However, heating under reducing conditions yields pillars of smaller diameter. This later behaviour is maintained even after reheating the material in oxidizing atmosphere. From the temperature dependence of Mössbauer spectra it is deduced that the diameter of the Fe oxide particles in the pillars is smaller than 10 nm.
Electrochemical Coagulation of Clay Suspensions
Authors: Szynkarczuk J. , Kan J. , Hassan T. A. T. , Donini J. C. 
Published: August 2006

AbstractIn the electrocoagulation process a suspension of kaolinite and bentonite is coagulated by electrochemical treatment where aluminum anodes are dissolved and aluminum ions react with clay particles, forming flocs which precipitate. Several factors affecting the efficiency of electrocoagulation are investigated. They include NaCl concentration, voltage, and flow conditions within the cell. Increased NaCl concentration led to lower electric resistance and cleaner running electrodes. Enhanced shear associated with recirculation resulted in clear supernatant and more compact floes. While increasing the feed rate, which was equivalent to decreasing aluminum concentration through the system, reduced cake height but increased turbidity.
Formation of Smectite Crystals at High Pressures and Temperatures
Authors: Yamada Hirohisa , Nakazawa Hiromoto , Hashizume Hideo 
Published: August 2006

AbstractSmectite single crystals of superior quality were synthesized at high pressures and temperatures using a modified belt type high pressure apparatus. Pressure-temperature conditions were established for smectite formation by quenching experiments in the pressure range from 2–5.5 GPa and temperatures of 700°–1000°C. Smectite crystals with extraordinary quality were formed beyond 3 GPa and 1000°C with coexisting phases of coesite, kyanite, jadeite, and in some cases with mica and glass. Smectite was confirmed from the XRD taken after intercalation of ethylene glycol. The smectite crystals were considered to be quenched crystals metastably from the hydrous silicate melts formed at high pressures and temperatures.
Sorption of Cesium on Compacted Bentonite
Authors: Oscarson Dennis W. , Hume Harold B. , King Fraser 
Published: August 2006

AbstractSorption parameters are important components of models used to predict mass transport through dense or compacted earthen materials. These parameters are, however, generally determined in batch tests with loose, unconsolidated materials. Here we directly measure, using a specially designed cell, the extent of Cs+ sorption on bentonite compacted to a series of densities ranging from 0.50 to 1.50 Mg/m3, and compare the results with those obtained from batch tests with loose bentonite. The clay was saturated with a Na-Ca-Cl-dominated solution with an effective ionic strength of 220 mol/m3. The sorption data were expressed as distribution coefficients, Kd. Over the clay density range examined, Kd values for Cs+ with compacted clay are about one-half to one-third the value of those with loose clay. The lower sorption on compacted clay is attributed to small and occluded pores that Cs+ cannot enter; thus it cannot access the entire volume, or all the sorption sites, of compacted clay. The data suggest that reasonable estimates of Kd with compacted clay can be obtained by scaling down the Kd values measured on loose clay by a factor na/n, where na is the accessible porosity and n the total porosity of compacted clay.
Particle Morphological Evolution During the Conversion of I/S to Illite in Lower Cretaceous Shales from Sergipe-Alagoas Basin, Brazil
Authors: Varajão Angélica , Meunier Alain 
Published: August 2006

AbstractThe illitic end of mixed-layer illite-smectite series (I/S) in shales from Lower Cretaceous Barra de Itiúba Formation, Sergipe-Alagoas basin, was examined with X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). A mathematical decomposition of XRD patterns shows different I/S and illite populations. All the samples contain ordered (R = 1) I/S, poorly crystallized illite (PCI) and well crystallized illite (WCI). A randomly interstratified (R = 0) I/S was also identified in a fractured zone at 1020 m. The percentage of expandable layers in ordered I/S decrease progressively from 20% to 10%. TEM observations show a continuous change in morphology between two basic particle shapes: elongated (lath) and isometric. The size and morphology of particles change with increasing depth. The proportion of laths decreases while isometric particles become predominant. However, both particle types continuously grow and enrich the larger size fraction. The growth process is driven by a mass transfer from the dissolving small particles of predominantly I/S (R = 1) composition to the larger (more illitic) lath and isometric ones. The proportion of lath-shaped particles decreases with depth indicating that the more stable population upon increased burial is the isometric well crystallized illite (WCI) particles. Very large laths are observed in the fault zone where conditions may favor faster growth processes.
A Technique for Maintaining Texture and Permanent Expansion of Smectite Interlayers for TEM Observations
Authors: Kim Jin-Wook , Peacor Donald R. , Tessier Daniel , Elsass Francoise 
Published: August 2006

AbstractA process for treating smectite-bearing rock samples that utilizes LR White resin; allows TEM observation of expanded smectite interlayers and therefore preservation of original rock textures. Examples of several lattice fringe images are shown, including: (1) Dioctahedral smectite layers from a shale (1388.9 meter depth, Texas Gulf Coast) give fringes that consistently have spacings of 1.2–1.3 nm, yet duplicate other features previously observed in collapsed samples. (2) Packets of illite layers give fringes with 1.0-nm spacings coexisting with packets of (dominantly) R1 I/S having 2.1-nm lattice fringe spacings in a Gulf Coast shale from 4742.1 m. (3) Rectorite from Garland Co., Arkansas gives 2.3-nm lattice fringes. Samples with wide ranges of I/S ratios and lithologies have been found to be permanently expanded with retention of original textures, commonly leading to unambiguous identification of illite and smectite interlayers in lattice fringe images.
Layer Charge Characteristics of Smectites in Salt-Affected Soils in Alberta, Canada
Authors: Kohut Connie K. , Dudas M. J. 
Published: August 2006

AbstractThe layer charge characteristics of expanding phyllosilicates in four salt-affected soils in Alberta, Canada were investigated using X-ray diffraction analysis of alkylammonium saturated samples. The layer charge was found to be lower and more heterogeneous than previously reported for non-saline Alberta soils, with the mean layer charge ranging between 0.261 to 0.339 tool (—)/O10(OH)2. Layer charge characteristics varied inconsistently with location, depth and particle size, likely the result of both different origins and weathering processes. Different degrees of K depletion from the micaceous component after equilibration with alkylammonium compounds may also account for some variability between samples. Extreme broadening and essential disappearance of smectite diffraction maxima was noted for some samples after intercalation with alkylammonium cations of all carbon chain lengths, indicating unusual alteration of the layer charge characteristics in some salt-affected soils.
Separation of Sub-Micron Particles from Soils and Sediments without Mechanical Disturbance
Authors: Churchman G. J. , Weissmann D. A. 
Published: August 2006

AbstractA method is described for the separation of the finest particles from soils and sediments without mechanical disturbance. Particles are separated through the induction of osmotic stress. Generally, samples are treated with a concentrated sodium salt solution and then exposed to water by diffusion. Naturally sodic samples are simply exposed to water. Solid samples and the swollen and dispersed material they produce are confined by dialysis tubing. Examples show that the method gives a size gradient of particles in a vertical column of suspension. The compositions of particles can vary with size. The method can be used to show the effects on separated particles of ions other than Na+ and also of other physicochemical treatments of soils and sediments. It is inexpensive and requires little labor.
Layer Charge of the Expandable Component of Illite/Smectite in K-Bentonite as Determined by Alkylammonium Ion Exchange
Authors: Cetin Kenan , Huff Warren D. 
Published: August 2006

Abstract—The charge of the expandable interlayers in a series of fourteen diagenetic illite/smectites (I/S) from lower Paleozoic K-bentonites was determined by the alkylammonium ion exchange method. The magnitude (<0.50 equivalents per half formula unit) and characteristic heterogeneous distribution of interlayer charges in eight samples with expandabilities from 70% to about 15% confirm the smectitic character of the expandable interlayers in this range. This result coupled with the lack of a correlation between expandability and interlayer charge is consistent with the hypothesis of a layer-by-layer transformation from a precursor smectite to highly illitic I/S clays during K-bentonite diagenesis. The charge of the expandable interlayers in I/S samples with about 10% or less expandabilities have been inferred to be vermiculitic rather than smectitic. The K-fixed interlayers and expandable interlayers in these samples appear to be similar in charge. The significantly higher charges inferred for the highly illitic samples can be consistent both with a layer-by-layer transformation and the neoformation mechanisms proposed in the literature for the formation of illite.
Dehydroxylation of Aluminous Goethite: Unit Cell Dimensions, Crystal Size and Surface Area
Authors: Ruan H. D. , Gilkes R. J. 
Published: August 2006

AbstractThis work investigates unit cell dimensions, crystal size and specific surface area of aluminous goethite that was progressively dehydroxylated to form hematite. Goethite synthesized from the ferrous system altered to hematite with DTGA maximum increasing from 236° to 273°C for 0 to 30.1 mole % Al-substitution. Unit cell dimensions of goethite and hematite decreased as Al-substitution increased and increased as excess OH increased. The crystallographically equivalent a axis of goethite and c axis of hematite were more sensitive than other axes to the presence of excess structural OH associated with Al-substitution. Specific surface area increased from 147 to 288 m2/g for goethite and from 171 to 230 m2/g for hematite as Al-substitution increased. An increase in specific surface area on heating goethite at temperatures between 200° and 240°C is related to a decrease in the size of coherently diffracting domains of goethite crystals and to the development of pore and structural defects associated with the formation of hematite. The decrease in specific surface area for heating temperatures above 240°C is attributed to the growth of hematite crystals by diffusion.
Quantification Curves for XRD Analysis of Mixed-Layer 14Å/10Å Clay Minerals
Authors: Pons C. H. , de la Calle C. , Martin de Vidales J. L. 
Published: August 2006

AbstractUsing theoretical profiles of diffracted X-ray intensity for interstratification between layers having d-spacings around 14.3 Å and 10.1 Å, a series of diagrams was derived from which the proportion of 14.3 Å layers (W14) and the probability of passing from a 14.3 Å layer to a 10.1 Å layer (P14/10) can be derived. W14 can be derived independently of P14/10 using the angular distance between reflections situated at 18.2° and 25.4° 2θ (CuKα). Once W14 is determined, P14/10 may be obtained using the angular width of the diffuse reflections between 27° and 34° 2θ. In this case, two different diagrams are proposed for P14/10 determination because experimental X-ray patterns show either one or two diffuse reflections. Comparison of five experimental patterns with theoretical patterns calculated using W14 and P14/10 obtained using these diagrams indicates that the method can be useful for determining W14 and P14/10 in unknown samples. Moreover, the method described is independent of the Lorentz polarization factor and the layer type. The d-spacings associated with the two kinds of layers, however, should be similar (± 1%) to those for which the determinative diagrams were calculated.
Monte Carlo Simulation of Interlayer Molecular Structure in Swelling Clay Minerals. 1. Methodology
Authors: Skipper N. T. , Chang Fang-Ru Chou , Sposito Garrison 
Published: August 2006

AbstractMonte Carlo (MC) simulations of molecular structure in the interlayers of 2:1 Na-saturated clay minerals were performed to address several important simulation methodological issues. Investigation was focused on monolayer hydrates of the clay minerals because these systems provide a severe test of the quality and sensitivity of MC interlayer simulations. Comparisons were made between two leading models of the water-water interaction in condensed phases, and the sensitivity of the simulations to the size or shape of the periodically-repeated simulation cell was determined. The results indicated that model potential functions permitting significant deviations from the molecular environment in bulk liquid water are superior to those calibrated to mimic the bulk water structure closely. Increasing the simulation cell size or altering its shape from a rectangular 21.12 Å × 18.28 Å × 6.54 Å cell (about eight clay mineral unit cells) had no significant effect on the calculated interlayer properties.
Model Calculation of Sepiolite Surface Areas
Authors: Hibino Toshiyuki , Tsunashima Atsumu , Yamazaki Atsushi , Otsuka Ryohei 
Published: August 2006

AbstractIn general, the N2-BET surface areas of sepiolite samples range from 95 to 400 m2/g depending on deposits.The surface areas of five sepiolites, all varying in crystallite size, were measured on heating, and were compared with a model calculation. A sharp decrease in the surface area, due to crystal folding, was observed between 200° and 400°C. Both before and after the folding, each sepiolite sample had peculiar values. Our model sufficiently explains this difference in surface areas among the samples. In the model, which is based on the Brauner-Preisinger structural model, surface area is a function of the crystallite size and the ratios of the coverage for nitrogen adsorption on both the internal and external surfaces. These ratios of the coverage can be inversely estimated from the model. The ratios of the coverage on the internal surface are less than 0.19, and that on the external surface between 0.7 and 1.0.
Low-Charge to High-Charge Beidellite Conversion in a Vertisol from South Italy
Authors: Righi Dominique , Terribile Fabio , Petit Sabine 
Published: August 2006

AbstractThe fine silt (2–5 μm) coarse clay (0.1–2 μm) and fine clay (<0.1 μm) fractions of a Vertisol from South Italy were studied with X-ray diffraction. The most reactive fine clay (<0.1 μm) fraction was investigated in detail using a curve decomposition method analysis of X-ray diffraction diagrams, FTIR spectroscopy and chemical analysis. In the soil parent material, the fine clay fraction was dominated by low-charge smectites (beidellite and montmorillonite) whereas, high-charge beidellite was the dominant clay mineral in the fine clay from the upper soil horizons. This suggested that high-charge beidellite was produced through alteration of the preexisting low-charge smectites and was the stable clay phase in this soil environment, characterized by high pH (>8.0). After K-saturation and 25 wetting and drying cycles, the high-charge beidellite from the soil horizons lost expandability far more than the original low-charge smectites.
Synthesis and Catalytic Properties of Silicate-Intercalated Layered Double Hydroxides Formed by Intragallery Hydrolysis of Tetraethylorthosilicate
Authors: Yun Sang Kyeong , Constantino Vera R. L. , Pinnavaia Thomas J. 
Published: August 2006

AbstractLayered double hydroxides (LDH's) interlayered with silicate anions were prepared by reaction of tetraethylorthosilicate (TEOS) with synthetic meixnerite-like precursors of the type [Mg1−xAlx(OH)2][OH−]x·zH2O, where (1 − x)/x ≈ 2, 3, or 4. TEOS hydrolysis at ambient temperature occurred readily in the galleries of the hydroxide precursors with (1 − x)/x ≈ 3 or 4, but a temperature of ∼100°C was required to achieve silicate intercalation for the LDH composition with (1 − x)/x ≈ 2. On the basis of the observed gallery heights (∼7.0−∼7.2 Å) and 29Si MAS NMR spectra that indicated the presence of Q2, Q3, and Q4SiO4 sites, the intercalated silicate anions, which are formed by condensation reactions of silanol groups and partial neutralization of SiOH groups with gallery hydroxide ions, are assigned short chain structures. Also, some O3SiOH groups become grafted to the LDH layers by condensation with MOH groups on the gallery surfaces. The LDH-silicates exhibited comparable non-microporous N2 BET surface areas in the range 59–85 m2/g, but they differed substantially in acid/base reactivities, as judged by their relative activities for the catalytic dehydration/disproportionation of 2-methyl-3-butyn-2-ol (MBOH). Under reaction conditions where the LDH structure is retained (150°C), all the silicate intercalates showed mainly basic reactivities for the disproportionation of MBOH to acetone and acetylene. However, all the LDH silicates were less reactive than the corresponding LDH carbonates. Conversion of the LDH silicates to metal oxides at 450°C introduced acidic activity for MBOH dehydration, whereas the metal oxides formed by LDH carbonate decomposition were exclusivity basic under analogous conditions.
Variable-Temperature Mössbauer Spectroscopy of Nano-Sized Maghemite and Al-Substituted Maghemites
Authors: Da Costa G. M. , De Grave E. , Bowen L. H. , De Barker P. M. A. , Vandenberghe R. E. 
Published: August 2006

AbstractSynthetic aluminum-substituted maghemite samples, γ-(Fe1-xAlx)2O3, have been prepared by thermal decomposition of Al-lepidocrocite (γ-Fe1-xAlxOOH), with × = 0, 0.04, 0.06, 0.14 and 0.18. The particles are needle-shaped and the mean crystallite diameter along the [311] crystallographic direction was found to be between 2.0 and 5.0 nm. Mössbauer spectra were collected at 6 K and from 80 K up to 475 K at steps of 25 K. In a wide range of temperatures the spectra of the non-substituted sample consist of a superposition of a broad sextet and a superparamagnetic doublet, whereas for the Al-maghemites this range is much smaller. From the temperature variation of the fractional doublet area two different parameters were defined: the temperature corresponding to a 50/50 doublet-sextet spectrum (T1/2), and the temperature below which the doublet ceases to exist (T0). These two parameters (T1/2 and T0) decrease from 390 K and 92 K (Al-free sample), to 118 K and 64 K (4 mole % Al) and to 100 K and 48 K (18 mole % Al), respectively. The average hyperfine fields at 6 K undergo a steep drop in going from the Al-free sample (Hhf = 506 kOe) to the sample with 4 mole % Al (Hhf = 498 kOe), but for higher substitutions the effect is much smaller. The A- and B-site quadrupole splittings, obtained from the data between 220 K and 475 K, were found as: ΔEQ,A = 0.86 ± 0.04 mm/s and ΔEQ,B = 0.65 ± 0.04 mm/s for the 4 mole % Al sample. The characteristic Mössbauer temperature, determined from the temperature dependence of the average isomer shift, was found to be in the range of 500–600 K.
Mechanism of Illitization of Bentonites in the Geothermal Field of Milos Island Greece: Evidence Based on Mineralogy, Chemistry, Particle Thickness and Morphology
Authors: Christidis George E. 
Published: August 2006

AbstractHydrothermal alteration has caused illitization along a 40m vertical profile in the Tsantilis bentonite deposit, Eastern Milos, Greece which consists principally of a Wyoming-type montmorillonite and authigenic K-feldspar. The product K-bentonite which contains illite/smectite, kaolinite, K-feldspar, quartz, sulphates and sulphides exhibits an unusual tendency for increase of expandability with depth.Mineralogy and I/S textures were determined with X-ray diffraction and SEM and TEM methods respectively and chemistry using X-ray fluorescence. Illitization is characterized by a 5- to 6-fold increase of K and release of Si, Fe, Mg Na, and Ca from the parent rock, indicating a K-influx (K-metasomatism) in the system.The I/S particle morphology is characterized by both flaky and lath-like particles, the former dominating in the range 100-50% expandable layers (R0 ordering) and the latter in the range 50-10% expandable layers (R1 and R > 1 ordering). Flaky particles are also abundant in samples with R1 ordering and abundant kaolinite, indicating that the latter might affect illitization. The I/S particles are classified in populations with thickness multiples of 10 A, their thickness being probably smaller than the coherent XRD domain. As the reaction proceeds, particles grow thicker and more equant. The distribution of I/S particle dimensions forms steady state profiles showing log-normal distribution; however, sensu stricto Ostwald ripening is unlikely. It seems that the reaction proceeds toward minimization of the surface free energy of I/S, being affected principally by temperature and K-availability. The spatial distribution of expandability implies that the heating source was probably a mineralized vein with T < 200°C, directed away from the bentonite, suggesting that illitization might be used as an exploration guide for mineral deposits.