articles+ search results

General chemistry, physical chemistry, Chimie générale, chimie physique, Environment, Environnement, Metrology and instrumentation, Métrologie et instrumentation, Climatology, meteorology, Climatologie, météorologie, Pneumology, Pneumologie, Pollution, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Etat colloïdal et états dispersés, Colloidal state and disperse state, Aérosols, Aerosols, Sciences appliquees, Applied sciences, Pollution, Pollution atmosphérique, Atmospheric pollution, Aérosol, Aerosols, Aerosol, Milieu urbain, Urban environment, Medio urbano, Métropole, Metropolitan area, Metrópolis, Aerosol direct radiative forcing, Aerosol optical depth (AOD), Angström exponent, Beijing metropolitan area, and Single scattering albedo (SSA)

Ground-based and satellite observations indicated heavy anthropogenic aerosol loading over the Beijing metropolitan area from 2004 to 2011. The aerosol optical properties and radiative forcing had strong seasonal variations and large differences in the city, the suburban and the regional background. The annual means of the aerosol optical depth (AOD) at 550 nm wavelength were 0.40 ± 0.04 in the Beijing City, 0.51 ± 0.05 in the Xianghe suburban and 0.20 ± 0.02 in the background, while the annual means of Angstrom exponent were 1.28 ± 0.07,1.16 ± 0.06 and 0.99 ± 0.05, respectively. The annual means of single scattering albedo (SSA) and aerosol direct radiative forcing at the top of atmosphere (TOA) at 550 nm wavelength were 0.89 ± 0.09 and -0.013 ± 0.002 W/m2 in the Beijing City, 0.87 ± 0.09 and -0.004 ± 0.003 W/m2 in the Xianghe suburban, and 0.88 ± 0.08 and 0.002 ± 0.001 W/m2 in the background. The seasonal maximums of TOA were -0.007 ± 0.001 W/m2, 0.012 ± 0.003 W/m2 and 0.013 ± 0.003 W/m2 in Beijing City, the suburb and the background in spring, respectively. The seasonal minimums of TOA were -0.022 ± 0.003 W/m2, -0.014 ±0.001 W/m2 and -0.010 ± 0.002 W/m2 in winter. There were no significant weakening trend of the aerosol direct radiative forcing in the large urban area in the period. .

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Atmosphère, atmosphere, Atmósfera, Chargement, loading, Cargamento, Déformation, deformation, Fissure, fissures, Fisura, Infiltration, infiltration, Infiltración, Pluie, rainfall, Lluvia, Précision, accuracy, Precisión, Radon, radon, Radón, Rayon X, X-rays, Rayos X, Remblaiement, landfills, Terraplenado, Sol, soils, Suelo, Stockage, storage, Almacenamiento, Tassement différentiel, differential settlement, Cap cover, Compacted clay liner, Crack, Differential settlement, Landfill, and X-ray CT scanner

In Japan, surface facilities are being considered, as is already the case in France, for the storage of low-activity nuclear wastes. At these sites, a compacted clay liner (CCL) in combination with different soil and geosynthetic layers is generally used as a cap barrier. The aim of the CCL is to limit the infiltration of moisture, especially that due to rainfall, through the barrier into the waste body and to inhibit the possible release of radon gas into the atmosphere. However, the cap cover may be subjected to differential settlement that could induce cracking and consequently cause loss of fluid toughness, namely; greenhouse gas emission. Indirect tensile tests, such as punching and bending tests, are carried out on the CCL to characterize its sensitivity to cracking. In this study, a method based on the use of an X-ray CT scanner is presented for determining the deformation field of the specimen. This paper first describes the X-ray CT scanner and then discusses the improved facility developed for the new device used for the bending test. It is demonstrated that this method is suitable for determining the evolution of cracking in the clay specimen. To improve the observation accuracy of the CCL due to loading, a bending apparatus is newly developed for an X-ray CT scanner. This allows the inner conditions of CCL, especially cracks, due to loading to be observed and evaluated with little disruption of the specimen behavior.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Argile minéral, clay minerals, Arcilla mineral, Phyllosilicate, sheet silicates, Filosilicato, Silicate, silicates, Silicato, Smectite, smectite, Esmectita, Chargement, loading, Cargamento, Consommation, consumption, Consumo, Contrainte, stress, Coacción, Localisation, localization, Localización, Matériau armé, reinforced materials, Modèle, models, Modelo, Montmorillonite, montmorillonite, Montmorilonita, Performance, performances, Polymère, polymers, Technologie, technology, Tecnología, Température, temperature, Temperatura, Viscosité, viscosity, Viscosidad, Immiscible rubber blends, Natural rubber, Nitrile rubber, Organically modified montmorillonite, Stress relaxation, and Stretched-exponential relaxation

To reduce material consumption, it is important to have reinforced material with longer life time. Incorporation of nanoparticles to reinforce and compatibilize polymer blends is one of the widely undergoing research areas in polymer science technology. A series of natural rubber and nitrile rubber (NR/NBR) nanocomposite vulcanazite, reinforced with two different organically modified clay (OMt) were prepared. To predict the performance of a material over long periods of time, stress relaxation studies with both the reinforced systems were done. The effects of loading, blend composition, filler polarity and temperature on stress relaxation of OMt reinforced NR/NBR nanocomposites were carefully measured. Based on the stress relaxation measurements, it was observed that due to its polarity difference, 01 Mt (Mt modified with dimethyl, benzyl, HT modification provided by Southern Clay Products) was preferentially located at the NBR phase while 02Mt (Mt modified with mercapto silane provided by English India Clay) had more affinity with natural rubber in the NR/NBR nanocomposites. The preferential localization of OMt has been analyzed by HRTEM. The nature of interaction of the nanoclay was found to influence the stress relaxation rate. NR/NBR nanocomposites with higher filler loading showed higher rates of relaxation rate due to the presence of more filler-filler interactions. At 70°C, the viscosity ratio was found to influence the reinforcement, and consequently relaxation rate of the 50/50 NR/NBR nanocomposites. It was found that the rearrangements of the polymer chains are dependent on the blend composition, temperature, filler/polymer interactions etc. To explain and predict observed phenomena, the stretched-exponential Kohlrausch equation and Maxwell-Weichert model were used. For both models, the experimental curve fitted well with the theoretical models.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Electrotechnique. Electroenergetique, Electrical engineering. Electrical power engineering, Electroénergétique, Electrical power engineering, Centrales électriques, Electric power plants, Divers, Miscellaneous, Conversion directe et accumulation d'énergie, Direct energy conversion and energy accumulation, Conversion photoélectrique, Photoelectric conversion, Energie, Energy, Energie naturelle, Natural energy, Energie solaire, Solar energy, Conversion photovoltaïque, Photovoltaic conversion, Cellules solaires. Cellules photoélectrochimiques, Solar cells. Photoelectrochemical cells, Cellule solaire, Solar cell, Célula solar, Composé ternaire, Ternary compound, Compuesto ternario, Condition météorologique, Atmospheric condition, Condición meteorológica, Evaluation performance, Performance evaluation, Evaluación prestación, Germanium, Germanio, Norme, Standards, Norma, Phosphure d'indium, Indium phosphide, Indio fosfuro, Phosphure de gallium, Gallium phosphide, Galio fosfuro, Porteur chaud, Hot carrier, Portador caliente, Production énergie électrique, Electric power production, Producción energía eléctrica, Production énergie, Power production, Producción energía, Rendement énergétique, Energetic efficiency, Rendimiento energético, Sensibilité spectrale, Spectral sensitivity, Sensibilidad espectral, Simulation système, System simulation, Simulación sistema, Spectre solaire, Solar spectrum, Espectro solar, Village, Pueblo, InGaP, Concentrator photovoltaics, and Hot carrier solar cell

In this paper we present detailed balance simulations which determine the material parameters required to produce hot carrier solar cell (HCSC) annual energy yields comparable with that of multi-junction (MJ) systems. We demonstrate that HCSCs are less spectrally sensitive than equivalent MJ devices providing significant motivation for pursuing their development. Spectral variation in a given location over the course of the day and throughout the year means that the HCSC provides more consistent power production. The HCSC can also be developed for a standard reference spectrum and still perform optimally in a variety of locations with different atmospheric conditions, unlike the location sensitive performance of MJ devices. We show that an ideal hot carrier solar cell with bandgap 0.69 eV under 2000 x concentration would require a thermalization coefficient <0.1 W K-1 cm-2 to produce more power over the course of the year than an InGaP/GaAs/Ge triple junction device located at Solar Village in Saudi Arabia. The lowest experimentally demonstrated thermalization coefficient is 9.5 W K-1 cm-2 indicating that further materials development is required to achieve this target.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Argile minéral, clay minerals, Arcilla mineral, Halogénure, halides, Haluro, Phyllosilicate, sheet silicates, Filosilicato, Silicate, silicates, Silicato, Smectite, smectite, Esmectita, Alcool, alcohols, Alcohol, Ammonium, ammonium, Amonio, Analyse diffraction RX, X-ray diffraction analysis, Bromure, bromides, Bromuro, Coût, cost, Costo, Echange ion, ion exchange, Cambio iónico, Ecoulement, flow, Energie, energy, Energía, Epuration, purification, Depuración, Flottation, flotation, Flotación, Gonflement, swelling, Inflamiento, Montmorillonite, montmorillonite, Montmorilonita, Séparation, separation, Separación, HTAB, Modification, Na-Bentonite, and Purification

Bentonites are commonly subjected to a water and energy intensive purification process in order to obtain high-grade montmorillonite, prior to modification to suit technological needs. In this study, the purification and modification processes were combined in order to minimize costs. A method for the production of organobentonite from roughly purified Na-bentonite from Reşadiye, Turkey, was proposed with a quaternary alkylammonium salt, hexadecyl trimethyl ammonium bromide. Further purification and ion exchange reactions were simultaneous within a centrifugal separation process, followed by the removal of excess modifier agent using the flotation method. The parameters of centrifugal force, feed solid content for Falcon concentrator and modification time, and the amount of alcohol for ion exchange reactions were optimized. Ammonium intercalated organoclays were characterized by X-ray diffraction analysis, thermogravimetric analysis, and swelling tests in organic liquids. An optimum flow sheet for the simultaneous purification and modification process yielding a 97% pure organobentonite with a 2.02 nm basal spacing was developed.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Electrotechnique. Electroenergetique, Electrical engineering. Electrical power engineering, Electroénergétique, Electrical power engineering, Conversion directe et accumulation d'énergie, Direct energy conversion and energy accumulation, Conversion photoélectrique, Photoelectric conversion, Energie, Energy, Energie naturelle, Natural energy, Energie solaire, Solar energy, Rayonnement solaire, Solar radiation, Conversion photovoltaïque, Photovoltaic conversion, Cellules solaires. Cellules photoélectrochimiques, Solar cells. Photoelectrochemical cells, Cellule solaire silicium, Silicon solar cells, Cellule solaire à colorant, Dye-sensitized solar cell, Célula solar sensibilizada tinte, Cellule solaire, Solar cell, Célula solar, Circuit additionneur, Summing circuits, Dégradation, Degradation, Degradación, Dépendance température, Temperature dependence, Eclairement énergétique, Irradiance, Aclaramiento energético, Electrolyte, Electrólito, Endommagement, Damaging, Deterioración, Essai longue durée, Long term test, Ensayo larga duración, Etude comparative, Comparative study, Estudio comparativo, Etude en condition extérieure, Outdoor study, Estudio en condición exterior, Evaluation performance, Performance evaluation, Evaluación prestación, Haute température, High temperature, Alta temperatura, Liquide ionique, Ionic liquid, Líquido iónico, Long terme, Long term, Largo plazo, Polycristal, Polycrystal, Policristal, Rendement énergétique, Energetic efficiency, Rendimiento energético, Ressort, Spring, Resorte, DSSC, Field testing, and Lifetime

This paper reports on the long-term testing of Dye-Sensitized Solar Cells (DSSCs) compared with a polycrystalline Si solar cell under the outdoor conditions of Abu Dhabi, UAE. A comparison of the temperature and irradiance dependence of both types of solar cells shows that DSSCs has relatively better performance than the polycrystalline Si solar cell under low irradiance levels and high temperatures. The monthly energy yields reveal that DSSCs produce about 20% higher energy during the spring months and about 30% higher energy during the summer months. The long-term stability of different DSSCs has been monitored under real outdoor conditions for over six months and degradation mechanisms have been proposed. Ionic liquid based DSSCs were significantly more stable when compared to devices based on other electrolyte solvents. However, the efficiency of all the experimental DSSCs degraded over time due to several factors outlined in the paper. This paper further outlines the advantages of DSSCs for their potential use in buildings in warm regions such as the Middle East and North Africa.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Argile minéral, clay minerals, Arcilla mineral, Carbonate, carbonates, Carbonato, Phosphate, phosphates, Fosfato, Phyllosilicate, sheet silicates, Filosilicato, Silicate, silicates, Silicato, Altération, alteration, Alteración, Aluminium, aluminum, Aluminio, Analyse chimique, chemical analysis, Análisis químico, Apatite, apatite, Apatito, Calcite, calcite, Calcita, Chrome, chromium, Cromo, Combustion, combustion, Combustión, Croissance, growth, Elément trace, trace elements, Formule structurale, structural formula, Fracture, fractures, Fractura, Lessivage, leaching, Lavado con lejía, Litage, bedding, Estratificación fina, Matière organique, organic materials, Materia orgánica, Microscopie électronique balayage, scanning electron microscopy, PH, pH, Panache, plumes, Penacho, SPOT, Spot, Smectite, smectite, Esmectita, Substitution, substitution, Substitución, Cr-smectite, Jordan, Natural analogues, Suweileh, Varicolored marble, and Volkonskoite

Unique green earthy clay occurs as thin layers along bedding planes, and in cavities and fractures in Suweileh area, Jordan. The collected green earthy samples were subjected to microscopic, chemical, thermal, infrared, XRD, SEM and EDX analyses. The source of Cr3+ is the varicolored marble of upper Cretaceous age in Suweileh area (dominated by recrystalline calcite and apatite). These rocks are equivalent to the varicolored marble in central (Daba Siwaqa) and north Jordan (Maqarin). Currently, hyperalkaline circulating waters (pH ∼12.7) are active in Maqarin area, north Jordan. Combustion of the organic matter in the bituminous phosphatic marl has accelerated the leaching of Cr3+ among other redox sensitive trace elements. Cr-smectite has precipitated from the alkaline circulating water enriched with Cr3+. The uninterrupted continuous flaky growth of the smectite suggests its chemical origin. Smectites are expected to be a sink of alteration products in the late stage evolution of a high pH plume. Chromium substitution for aluminum in a pre-existing smectite is also indicated in the same area. The spot chemical analysis of Suweileh smectite has indicated the following structural formula: Ca0.30Na0.23(Al0.47Cr0.63Fe0.13Mg0.66Zn0.06Ti0.03)(Si3.88 Al0.12)O10(OH)2. The formula indicates that Cr3+ is immobilized in the octahedral layer of smectite.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Oxyde, oxides, Óxido, Acide, acids, Acido, Air, air, Aluminium, aluminum, Aluminio, Atmosphère, atmosphere, Atmósfera, Azote, nitrogen, Nitrógeno, Calorimétrie, calorimetry, Calorimetría, Chromatographie, chromatography, Cromatografía, Combustion, combustion, Combustión, Cristallinité, crystallinity, Cristalinidad, Dégradation, degradation, Fusion, melting, Fusión, Hydroxyde, hydroxides, Hidróxido, Morphologie, morphology, Morfología, Propriété thermique, thermal properties, Propiedad térmica, Proton, protons, Protón, Réduction, reduction, Résonance magnétique nucléaire, nuclear magnetic resonance, Resonancia magnética nuclear, Solution, solution, Stabilité, stability, Estabilidad, Température, temperature, Temperatura, Crystallinity, Flame retardancy, LDH, Nanocomposite, and Polyamide

New long aliphatic chain polyamide/Mg-Al layered double hydroxide (LDH) nanocomposites were successfully prepared via a solution intercalation technique under ambient condition in N,N-dimethylacetamide as solvent. The polyamide was synthesized using direct polycondensation reaction from an oleic acid based monomer which was characterized by proton nuclear magnetic resonance and size exclusion chromatography. The polyamide showed a semi-crystalline structure with melting temperature of 223 °C. Organo-modified Mg-Al LDH was produced by one-step method and used to improve properties of the polyamide. Thermal properties and flame retardancy of the nanocomposites were studied by thermogravimetric analysis, differential scanning calorimetry and microscale combustion calorimeter. The thermal degradation results in both air and nitrogen atmospheres showed that the addition of organo-modified LDH resulted in a substantial increase in the thermal stability and char yields of the nanocomposites as compared to the neat polyamide. The flammability tests revealed that incorporation of the organo-modified LDH in the polyamide resulted in a reduction of the heat release rate, heat release capacity and total heat release.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Energie, Energy, Combustibles, Fuels, Combustibles de remplacement. Production et utilisation, Alternative fuels. Production and utilization, Hydrogène, Hydrogen, Evaluation, Evaluación, Hydrogène, Hydrogen, Hidrógeno, Processus hiérarchie analytique, Analytic hierarchy process, Proceso jerarquía analítico, Stockage hydrogène, Hydrogen storage, Fuzzy theory, Hydrogen storage systems for automobiles, and Multi-criteria evaluation

In this paper, five hydrogen storage systems for automobiles are evaluated using the fuzzy analytic hierarchy process (AHP) in respect to eight criteria. The hydrogen storage systems for automobiles to be evaluated are 350 bar compressed gas hydrogen, 700 bar compressed gas hydrogen, liquefied hydrogen, metal hydride and chemical hydride. The selected criteria used in the evaluation of five hydrogen storage systems are weight efficiency, volume efficiency, system cost, energy efficiency, cycle life, refueling time, safety and infrastructure. According to the evaluation, compressed gas hydrogen ranks the highest in classification in Korea. Liquefied hydrogen ranks higher than metal hydride and chemical hydride. If the infrastructure for liquefied hydrogen were good in Korea, liquefied hydrogen may rank the highest in classification. Also, it should be noted that the rank of hydrogen storage systems can be changed according to the future technological developments.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Argile minéral, clay minerals, Arcilla mineral, Inosilicate, chain silicates, Oxyde, oxides, Óxido, Phyllosilicate, sheet silicates, Filosilicato, Aluminosilicate, aluminosilicates, Aluminosilicato, Calcium, calcium, Calcio, Chaux, lime, Cal, Concentration, concentration, Concentración, Densité, density, Densidad, Diffraction RX, X-ray diffraction, Difracción RX, Gel, gels, Hydrate, hydrates, Hydroxyde, hydroxides, Hidróxido, Kaolinite, kaolinite, Caolinita, Résistance compression, compressive strength, Resistencia compresión, Silicate, silicates, Silicato, Sodium, sodium, Sodio, Spectrométrie IR, infrared spectroscopy, Espectrometría IR, Tobermorite, tobermorite, Tobermorita, Transformation Fourier, Fourier transformation, Zone transition, transition zones, Zona transición, Alkali activated lime pozzolan, Metakaolin, and Pozzolanic reaction

The research aim was to investigate phase development and reaction transition zone of alkaline activated lime-calcined clay materials. Locally available china clay mainly supplied metakaolin (MK) after calcination. MK and calcium hydroxide (CH) were used to supply SiO2 and CaO, respectively. The CH to MK ratio of 0.4 with CaO/SiO2 of 1.18 was selected to coincide with the theoretical CaO/SiO2 of calcium silicate hydrate in tobermorite group (Ca5Si6O16(OH)2). Phase development was investigated using X-ray diffraction and Fourier transform infrared spectroscopy. Compressive strength and density were also investigated to confirm binding properties of the pozzolanic reaction products. The reaction of mixture was dependent on the NaOH concentration. At low concentration of NaOH (<1 M), the pozzolanic reaction was dominant while the zeolitic reaction and geopolymerization became dominant at medium NaOH concentration (> 1 M) and at high NaOH concentration, respectively. The activations of CH:MK mixtures with 0.01 and 0.1 M NaOH promoted semicrystalline calcium silicate hydrate (CSH (I)) and crystalline calcium aluminosilicate hydrate (CASH) formations. The mixture with 0.01 M NaOH gave the highest compressive strength of 19.0 MPa. With 3 and 5 M NaOH activations, sodium aluminosilicate hydrate (NASH) and sodium calcium silicate hydrate (NCSH) compounds were formed instead of CSH (I) gel and crystalline CASH phase. At 10 M NaOH, NCSH disappeared and only NASH was formed and resulted in a relatively low compressive strength of 6.7 MPa.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Argile minéral, clay minerals, Arcilla mineral, Phyllosilicate, sheet silicates, Filosilicato, Silicate, silicates, Silicato, Acier, steel, Acero, Colmatage, clogging, Taponamiento, Conductivité hydraulique, hydraulic conductivity, Conductividad hidráulica, Densité, density, Densidad, Eau salée, salt water, Agua salada, Expérimentation, testing, Gel, gels, Gonflement, swelling, Inflamiento, Hydraulique, hydraulics, Hidraúlica, Modèle, models, Modelo, Particule, particles, Porosité, porosity, Porosidad, Pression, pressure, Presión, Précision, accuracy, Precisión, Sable, sand, Arena, Silt, silt, Limo, Smectite, smectite, Esmectita, Clay gel, Clogging, Filter porosity, Hydraulic conductivity, and Hydraulic gradient

The common practice in geotechnical laboratories is to apply high hydraulic gradients for getting results in reasonable time but this can jeopardize the accuracy. In this paper, the hydraulic conductivity of a smectite rich clay from Iraq was determined under different hydraulic gradients (5 to 10.000 m/m) using several densities and two permeants. Also, two types of filters were used, ordinary stainless steel sintered filter and sand/silt filter, in order to examine the possible effect of clogging by dragged clay gel particles. It was concluded that the outflow filter can affect the evaluated conductivity especially when applying high hydraulic gradients. For sintered filters the hydraulic conductivity was reduced as the gradient increased, while the conductivity increased as the hydraulic gradient increased when using sand/silt filters. For salt water the impact of the gradient was less obvious than for distilled water. A theoretical model was derived for selecting safe hydraulic gradients as a function of dry density, swelling pressure and permeant type. A major conclusion was that the gradient in laboratory testing should not exceed 100 m/m.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Argile minéral, clay minerals, Arcilla mineral, Nésosilicate, nesosilicates, Phyllosilicate, sheet silicates, Filosilicato, Silicate, silicates, Silicato, Adsorption, adsorption, Adsorción, Alunitisation, alunitization, Alunitización, Ammonium, ammonium, Amonio, Diffraction RX, X-ray diffraction, Difracción RX, Dispersion, dispersion, Dispersión, Distribution dimension, size distribution, Déshydratation, dehydration, Deshidratación, Désorption, desorption, Desorción, Halloysite, halloysite, Halloysita, Haute température, high temperature, Alta temperatura, Isotherme, isotherms, Isothermo, Microscopie électronique transmission, transmission electron microscopy, Morphologie, morphology, Morfología, Mullite, mullite, Mullita, Particule, particles, Silice, silica, Sílice, Stabilité, stability, Estabilidad, Sulfate, sulfates, Sulfato, Surface spécifique, specific surface, Ségrégation, segregation, Traitement thermique, heat treatment, Tratamiento térmico, Transformation, transformations, Transformación, Transition phase, phase transitions, Transición fase, Phase transition, Thermal treatment, and Tubular morphology

Halloysite is one of the nanoscale tubular minerals in nature. This article reports the mineralogical character, dispersion treatment, structural, and morphological stabilities of a 10 A-type halloysite mineral from Hunan, China. X-ray diffraction (XRD), transmission electron microscopy (TEM), particle-size distribution and N2 adsorption-desorption isotherms were adopted to characterize the raw and calcined minerals. Ammonium lauryl sulfate was used as the surfactant to obtain mono-dispersed halloysite nanotubes. The raw mineral is a kind of tubular nanotube with a hollow interior channel, the specific surface area is 56.7 m2/g. Alunitization occurred in the impure mineral. Thermal treatment to the mineral induced shrinkage of the c-axis and yielded a 7 A-type structure. The tube wall was transformed to an amorphous structure in the dehydration process at 450 °C. Phase segregation occurred to yield amorphous SiO2 and γ-Al2O3 at around 1000 °C. The tubular morphology can be maintained even after it is calcined at 1100 °C for 6 h, and the specific surface area is enlarged slightly to 65.7 m2/g. While after being calcined to 1300 °C, the mineral will generate mullite and silica, accompanied with collapse of the tubular walls. A schematic diagram is proposed to illustrate the structural transformation procedure. The results provide assurance to the use of halloysite in high temperature circumstances, such as three-way catalysts.

General chemistry, physical chemistry, Chimie générale, chimie physique, Condensed state physics, Physique de l'état condensé, Sciences exactes et technologie, Exact sciences and technology, Chimie, Chemistry, Chimie generale et chimie physique, General and physical chemistry, Physicochimie de surface, Surface physical chemistry, Etat colloïdal et états dispersés, Colloidal state and disperse state, Matériaux poreux, Porous materials, Adsorption liquide solide, Liquid solid adsorption, Adsorción líquido sólido, Analyse thermodynamique, Thermodynamic analysis, Análisis termodinámico, Caractérisation, Characterization, Caracterización, Composé de métal de transition, Transition element compounds, Eau, Water, Agua, Isotherme adsorption, Adsorption isotherm, Isotermo adsorción, Matériau poreux, Porous material, Material poroso, Oxyde de titane, Titanium oxide, Titanio óxido, Phosphate, Phosphates, Fosfato, Préparation, Preparation, Preparación, Thermodynamique, Thermodynamics, Termodinámica, Zéolite naturelle, Natural zeolite, Adsorption isotherms, Natural Yemeni zeolite, Phosphate adsorption, and Titania_dioxide

In order to develop an effective technique for enhancing the efficiency of phosphate ion (PO3-4) removal, a novel composition of TiO2/Zeolite (TZ) adsorbent was prepared and investigated systematically. The characteristics of TZ and its mechanism for PO3-4 removal were investigated and compared with that of natural zeolite (NZ). Important parameters which affect adsorption, such as contact time, pH, dosage, temperature, initial PO3-4 concentration and the presence of competing anions were investigated. Almost 100% removal efficiency was achieved by the TZ composite at low initial PO3-4 concentrations. The specific surface area and PO3-4 adsorption capacity of the composite material reached 166.5 m2/g and 37.6 mg/g, respectively. Moreover, Maximum adsorption occurred at around pH 2-4 and 35 °C. The results of zeta potential, FTIR, XRF and EDS analyses indicated that electrostatic attraction and replacement of surface hydroxyl groups (T/OH) by phosphate were the main adsorption mechanism. Arsenate and silicate markedly decreased the removal of PO3-4 whereas the effect of other anions was insignificant. The adsorption isotherm results illustrated that Freundlich model (FM) provided the best fit for the equilibrium data. In addition to that, the change in free energy (AGO), enthalpy (AHO) and entropy (ASO) revealed that the adsorption of PO3-4 ion by zeolite is spontaneous and endothermic at 25 and 35 °C. It was concluded that a TiO2/Zeolite composite is a highly efficient and economic adsorbent material with good regeneration and can be utilized in the remediation of environmental pollution.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Argile minéral, clay minerals, Arcilla mineral, Phyllosilicate, sheet silicates, Filosilicato, Silicate, silicates, Silicato, Air, air, Climat, climate, Clima, Conductivité hydraulique, hydraulic conductivity, Conductividad hidráulica, Densité, density, Densidad, Déchet dangereux, hazardous wastes, Residuo peligroso, Désert, deserts, Desierto, Fluage, creep, Fluencia, Gonflement, swelling, Inflamiento, Matériau, materials, Pression, pressure, Presión, Propriété géotechnique, engineering properties, Propiedad geotécnica, Résistance cisaillement, shear strength, Resistencia cizallamiento, Sable, sand, Arena, Saturation, saturation, Saturación, Smectite, smectite, Esmectita, Sol, soils, Suelo, Stabilité versant, slope stability, Estabilidad vertiente, Teneur eau, water content, Contenido en agua, Uranium, uranium, Uranio, Compacted clay liner, Design, Hydraulic conductivity, Shear strength, and Swelling pressure

Compacted clay liners (CCL) can be used to isolate hazardous wastes like the soil and military scrap contaminated with depleted uranium that emanated from the Iraqi wars in 1991 and 2003. Near-surface repositories for such dangerous waste can preferably be located in the Iraqi deserts, which make up 60% of the territory of Iraq. CCLs are usually constructed using a mixture of clayey soil and coarse material compacted in air-dry form or suitably wetted. In the present study, two smectitic soils from Iraq, termed green and red clays, were investigated for potential use in CCLs. The shear strength, swelling pressure, hydraulic conductivity and creep properties were determined and used for preliminary design of top and bottom-liners. The engineering properties were determined for various dry densities and water contents ranging from air-dry to fully saturated conditions. The results showed that mixtures of sand and 30%-50% green clay and mixtures of sand and 40%-60% red clay are suitable for constructing top-liners with a hydraulic conductivity between 1 x 10-10 and 1 x 10-9 m/s. For bottom-liners, mixtures of sand and 70% green clay and mixtures of sand and 80% red clay can be considered. They were found to have a hydraulic conductivity of 1 x 10-11 m/s for a density at saturation of 2.1 g/cm3 (dry density, 1.7 g/cm3).As to the slope stability of top-liners, the shear strength for different clay percentages was found to guarantee slope stability for 18° inclination under both air-dry and water saturated conditions.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Energie, Energy, Combustibles, Fuels, Combustibles de remplacement. Production et utilisation, Alternative fuels. Production and utilization, Hydrogène, Hydrogen, Etude comparative, Comparative study, Estudio comparativo, Hydrogène, Hydrogen, Hidrógeno, Sécurité énergétique, Energy security, China, Denmark, and Hydrogen pathway

When designed and built properly, hydrogen energy systems can enhance energy security through technological diversification and minimizing dependence on foreign imports of energy fuels. However, hydrogen can be produced from different feedstocks according to separate pathways, and these different pathways create particular consequences on a nation's overall energy security. The objective of this study is to investigate the superiorities and inferiorities of hydrogen pathways from the perspective of China and Denmark, and to determine which pathways best contribute to national energy security objectives. The results are useful for stakeholders and energy analysts so that they can correctly plan and research the most socially optimal portfolio of hydrogen technologies.

General chemistry, physical chemistry, Chimie générale, chimie physique, Energy, Énergie, Sciences exactes et technologie, Exact sciences and technology, Sciences appliquees, Applied sciences, Energie, Energy, Combustibles, Fuels, Combustibles de remplacement. Production et utilisation, Alternative fuels. Production and utilization, Hydrogène, Hydrogen, Hydrogène, Hydrogen, Hidrógeno, Vecteur énergie, Energy carrier, Vector energía, Exogenous, Hydrogen energy, Input-output analysis, and Korea

Korea has been developing hydrogen energy technology to enhance its energy security. The Hydrogen Energy R&D Center established by the Korean government invested about 100 billion Korean won (KRW) into the development of hydrogen energy technology from 2003 to 2012. This study uses input-output (I-O) analysis, along with the scenario-based exogenous specification method, to investigate the effect of hydrogen energy technology investment on the Korean economy for the period 2020-2040. We focus on two perspectives: (1) the sectoral linkage effect and (2) the sectoral impacts of hydrogen energy supply investments. The overall results reveal that the hydrogen sector can be characterized as intermediate primary production because of its high backward and forward linkage effects. By 2040, total production in the hydrogen sector under two scenarios will be 13,484 and 2979 billion KRW, respectively. This study is a pioneering study into the assessment of the economy-wide effects of Korea's hydrogen energy industries.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Argile minéral, clay minerals, Arcilla mineral, Phyllosilicate, sheet silicates, Filosilicato, Silicate, silicates, Silicato, Smectite, smectite, Esmectita, Aquifère, aquifers, Ciment roche, cement, Cemento roca, Conductivité hydraulique, hydraulic conductivity, Conductividad hidráulica, Diffraction RX, X-ray diffraction, Difracción RX, Dissolution, dissolution, Disolución, Dégradation, degradation, Eau souterraine, ground water, Agua subterránea, Gonflement, swelling, Inflamiento, Matériau remblai, backfill, Minéralogie, mineralogy, Mineralogía, Montmorillonite, montmorillonite, Montmorilonita, PH, pH, Pression, pressure, Presión, Prospection, exploration, Prospección, Solution, solution, Tampon, buffers, Tampón, Température, temperature, Temperatura, Gaomiaozi (GMZ01) bentonite, Hydraulic conductivity, NaOH solution, Swelling pressure, Temperature, and pH value

Gaomiaozi (GMZ) bentonite has been recognized as the first choice for using as buffer/backfill materials in deep geological repository for the disposal of high-level nuclear waste (HLW) in China. Groundwater in Beishan area, which has been considered as a potential site for the construction of Chinese deep geological repository, may reach a high pH value because of its chemical background and possible cement degradation during the operation of the repository. Meanwhile, temperature may increase with decay heat released from the waste in the canister. Investigation of pH value of alkaline-solutions and temperature effects on the behavior of compacted GMZ01 bentonite is of great importance for the Chinese deep geological repository program. For this purpose, a series of swelling pressure and hydraulic conductivity tests with various pHs of NaOH solutions were conducted at different temperatures. The X-ray diffraction (XRD) exploration was performed on the GMZ01 bentonite specimens before and after experiencing the swelling pressure and hydraulic conductivity tests, in order to find out the influences of temperature and pHs on the mineralogy of GMZ01 bentonite. Results show that the swelling pressure of GMZ01 bentonite decreases as the pH value of NaOH solutions increases, while the decreasing rate significantly depends on temperature. The swelling pressure evolution curve was double-peak structured, which faded with the increases of pH and temperature. The hydraulic conductivity of GMZ01 bentonite increases with the increase of the pH value of NaOH solutions and the rise of temperature. All these observations were consistent with the XRD test results: the dissolution of montmorillonite in GMZ01 bentonite increases with the pH increases. This process was accelerated by the temperature rise.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Phyllosilicate, sheet silicates, Filosilicato, Silicate, silicates, Silicato, Anisotropie, anisotropy, Anisotropía, Argile minéral, clay minerals, Arcilla mineral, BASIC, Concentration, concentration, Concentración, Excavation, excavations, Excavación, Gonflement, swelling, Inflamiento, Houle, swells, Oleaje, Microscopie électronique balayage, scanning electron microscopy, Propriété chimique, chemical properties, Propiedad química, Solution aqueuse, aqueous solutions, Solución acuosa, Stabilité, stability, Estabilidad, Variabilité, variability, Aqueous solution chemistry, Clayey rock, SEM-EDS, Swelling anisotropy coefficient, and Swelling ratio

Clayey rock has a large clay mineral content. When in contact with aqueous solutions with different chemical properties, the rock expands considerably and presents a significant hazard to the stability of underground excavations. The swelling behaviour of Cenozoic clayey rock from Shandong Province, China, was investigated when subjected to various aqueous chemical solutions, using the free swell test method. The influence of different chemical paths on the swelling of clayey rock was analysed, and the basic mechanisms of the swelling and shrinkage variability of clayey rock were analysed by SEM-EDS. The results demonstrated that the swelling of clayey rock was clearly anisotropic, quantified by the swelling anisotropy coefficient. Swelling was independent of the chemical path, but dependent on the concentration of the aqueous solution. The more concentrated the solution, the weaker the swelling.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Argile minéral, clay minerals, Arcilla mineral, Phyllosilicate, sheet silicates, Filosilicato, Silicate, silicates, Silicato, Smectite, smectite, Esmectita, Cellulose, cellulose, Celulosa, Concentration, concentration, Concentración, Densité, density, Densidad, Energie nucléaire, nuclear energy, Energía nuclear, Excavation, excavations, Excavación, Exposition, exhibits, Expérimentation, testing, Filtration, filtration, Filtración, Forage, drilling, Sondeo, Humate, humates, Minerai uranium, uranium ores, Montmorillonite, montmorillonite, Montmorilonita, Optimisation, optimization, Optimización, Performance, performances, Potassium, potassium, Potasio, Pression, pressure, Presión, Protection, protection, Sodium, sodium, Sodio, Uranium, uranium, Uranio, Viscosité, viscosity, Viscosidad, Carboxymethyl cellulose, Double protection drilling fluid, Orthogonal testing, Potassium humate, Sandstone-like uranium formation, and Vegetable gum

Nuclear energy, an alternative for fossil fuel, is accompanied by the excavation of uranium ores and in turn the use of drilling fluids. Thus, the objective of this study was to optimize the formula of drilling fluid for sandstone-like uranium formation representing the Xinjiang's Yili Basin uranium formation in China. Additives such as Na2CO3, potassium humate (KHM), sodium carboxymethyl cellulose (Na-CMC), and vegetable gum (VG) were introduced to montmorillonite (Mt) slurry to maximize the performance of drilling fluid in terms of rheological behavior and filtration characteristics. Orthogonal testing, soaking test, and pressure-bearing test were conducted to find the optimum formula of drilling fluid. The maximized performance was achieved with a drilling fluid consisting of 4% Mt, 1.6% Na2CO3, 0.1% KHM, 1.5% Na-CMC, and 0.5% VG. The lowest density and water loss, with a sufficiently high viscosity were achieved with this concentration combination of each additive. Soaking and pressure-bearing tests exhibited no visual changes of a specimen treated with the drilling fluid, which confirmed the result of optimization.

General chemistry, physical chemistry, Chimie générale, chimie physique, Geology, Géologie, Chemical industry parachemical industry, Industrie chimique et parachimique, Sciences exactes et technologie, Exact sciences and technology, Terre, ocean, espace, Earth, ocean, space, Sciences de la terre, Earth sciences, Minéralogie, Mineralogy, Silicates, Expansion, expansion, Expansión, Granulat, aggregate, Agregado, Industrie, industry, Industria, Optimisation, optimization, Optimización, Pelote, pellets, Bolas, Programme ordinateur, computer programs, Programa computador, Température, temperature, Temperatura, Expandability, Expanded clay aggregates, Lightweight aggregate, Optimization, and Working parameters

The main aim of this study is to establish optimum working conditions and to propose expandability charts for Kalecik Clay using expansion ratio versus unit volume weight values via a statistical computer program (Design Expert 7.0). First of all, some suitable samples were collected from the Kalecik County (Ankara, Turkey). Later, the samples were crushed and milled up to 200 μm clay size in the laboratory. Then, pellets with a 10 mm diameter were dried in ovens and heated inside a furnace to expand in different temperatures. One heating operation began with 900 °C and ended with 1200 °C. In addition to that, the holding time periods were selected as 5, 10, 15 or 20 min for each operation. In the final stage, the unit volume weight and expansion ratio of the produced aggregates were determined. As results of this study, both the optimum furnace holding time and furnace temperature values for the samples were determined in order to maximize the expansion ratio values and minimize the unit volume weight for Kalecik Clays. Some expandability charts were proposed for Kalecik Clay by using the findings. The charts allow one to assign expansion ratio and unit volume weight values in different working conditions including holding time inside the furnace and furnace temperature. The proposed charts are expected to be quite useful for more efficient production of expanded clay aggregates in construction industry.