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    Applied Clay Science

  • 中文名称: 应用黏土科学
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  • ISSN: 0169-1317
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  • 机译 在瓷砖生产中使用的白垩纪粘土的燃烧转化
    摘要:Mineralogical transformations caused by firing, of five different compositions used in the formulation of ceramic pastes have been studied. Test samples have been prepared by extrusion and fired in the range of 900--ll50deg.C. Analysis of the fired samples was carried out by optical microscopy. The presence of enstatite, gehlenite, hercynite and mullite and abundant vitreous phase showed neomineralization. A fluid texture was present in all the samples and phenocrysts occurred in the partially microcrystalline matrix. In this way, the ceramic ware was analogous to porhyritic type rocks, with quartz phenocrystals and a typical undulating liquidation, opaque minerals such as hematites and crystalloelastic quartz structures on grains of orthoclase. The samples with low carbonate contents were composed of bulky particles, predominantly of quartz and hematites, which are agglomerated in a vitreous matrix.
  • 机译 粘土和催化作用:有希望的未来
    • 作者:A. Vaccari;
    • 刊名:Applied Clay Science
    • 1999年第4期
    摘要:The main properties of cationic and anionic clays as well as their role in catalysis are discussed in light of the versatility and potential of these materials. Clays exhibit specific features such as high versatility, wide range of preparation variables, use in catalytic amounts, ease of set-up and work--up, mild experimental conditions, gain in yield and/or selectivity, low cost, etc., which may be very useful tools in the move towards establishing environmentally friendly technologies. Furthermore, the possibility of upgrading these materials by the pillaring process opens new and interesting perspectives, also considering possible shape selective advantages. Recent catalytic applications of cationic and anionic clays in organic or fine chemistry (acid- or base--catalyzed reactions, Diels--Alder reactions, reactions using metallic nitrates, etc.), environmental catalysis (DeSOx, DeNOx or contaminant oxidation) and energy exploitation (partial oxidation of methane) are discussed as very promising research subjects with a wide range of possible future developments.
  • 机译 定量分析粘土土工材料织物取向的扫描电镜图像处理方法
    摘要:A novel computerized procedure is presented for processing scanning electron (SEM) micro- graphs of argillaceous geomaterials in order to quantify the clay particle orientation. An index of fabric orientation is extrapolated from the pixels (5l2 X 5l2) with maximum brightness intensity, through an iteration 'thinning' process. A binary map of lines (vectors) is obtained which allows the determination of the clay particle orientation applying a line-following algorithm. The results are represented by a histogram (direction ranges at intervals of l0deg).
  • 机译 物理,化学和矿物学对重塑的低活性敏感性海洋黏土流变学的影响
    摘要:The rheological response of remoulded Leda clay from the South Nation River landslide (l97l) site has been investigated using a coaxial viscometer. The yield stress at constant water content was found to: decrease as the pore-water salinity decreased, with the decrease occurring at much lower salinity when Ca-saturated than when Na--saturated; decrease as the clay content of the soil was decreased; decrease upon the extraction of oxide minerals by dithionite--citlate--bi- carbonate; decrease when the phyllosilicate content of the soil was depleted by a severe alternating acid/base extraction procedure; increase as the pH of the marine clay, whether carbonate-containing or carbonate-free, was lowered by acid addition. The effects are in agreement with expectations based on electrical double-layer theory. The relative effects of the various pretreatments are qualitatively discussed. Viscoplastic-shear-thinning and Bingham plastic response most commonly occurred, although at low salinities viscoplastic-shear-thickening response was exhibited for materials with high silt contents and after phyllosilicate-depletion. No relationship between flow type and the tendency to exhibiting quick clay behaviour is apparent.
  • 机译 铁铝比对无定形铁铝氧化物对铅和铜的保留率的影响
    摘要:Results are presented from a study on the influence of pH on the retention of Pb and Cu by amorphous iron, aluminium and mixed iron--aluminium oxides, plus kaolinite clay. The composition (Fe/Al molar ratio) of the oxides significantly affects their surface properties. increasing the Fe/Al ratio generally enhances the surface area a1though the maximum surface area is found at Fe/Al = l. The cation exchange capacity (CEC) was dependent upon pH and Fe/Al ratio, decreasing in order Fe > 3FeAl > Al > Fe3Al > FeAl >> kaolinite at pH 6.3--7. The oxide points of zero charge could be divided into two groups: Fe/Al 5(Al, Fe3Al, FeAl; pH_zPc = 6.2--6.4) and Fe/Al > l (3FeAl, Fe; pH_ZPc = 5.3--5.8). Batch equilibrium suspension tests were conducted with Pb and Cu (single metal solutions) to assess contaminant retention capability of each oxide and kaolinite. Pb retention by mixed oxides at a particular pH increases with Fe/Al ratio in the order Fe > 3FeAl > FeAl > Fe3Al > Al. The same order is observed at low to medium Cu concentrations (0.5, 2.5, 5 mmol/l) but at higher metal loading (25 mmol/l), only Fe oxide has a clearly greater retention capacity. Oxides with Fe/Al < l (Al, Fe3Al) retain more Cu than Pb in single contaminant tests at equal metal concentration. Bulk precipitation tests (no oxides or kaolinite) combined with surface charge measurements suggest that adsorption is the dominant retention mechanism, particularly at less than pH 6. Amorphous oxides demonstrate considerably greater heavy metal accumulation capacity, specific surface area, and surface charge than kaolinite.
  • 机译 酸处理海泡石的结构:小角度X射线散射和多MAS-NMR研究
    摘要:Structural changes in the chain silicate sepiolite brought about by acid treatment were studied by X--ray diffraction, gas adsorption and MAS-NMR methods. It was established that as the amount of iron and aluminum extracted from the mineral is increased, the specific surface area of the sample is also increased (from l95.2 to 306.6 m~2/g) and the originally microporous structure is transformed into a mesoporous one. The ion exchange capacity of sepio1ite (0.486 mequ/g) may be completely eliminated by acid treatment. The changes in the surface fractal dimension D_s (from 2.35 to 2.03) and the correlation length l_c (from 24.9 nm to l7.6 nm) were followed bV SAXS measurements. 29_Si -- and 27_Al -- MAS -- NMR studies yield information on changes occurring in the structure of the mineral, i.e., on the arrangement of Si and Al atoms in the lattice. During acid treatment the clay structure is progressively transformed into amorphous silica- alumina.
  • 机译 减少有机粘土配方中除草剂的光降解和挥发
    摘要:The use of commercially available emulsifiable concentrate (EC) formulations of alachlor and metolachlor may be an environmental hazard because of their volatilization to the atmosphere and photodecomposition, which requires increased applied amounts. The objectives of this study were to develop organo--clay based formulations which would be less volatile and better protected from photodegradation. Bioassays have shown that the use of organo--clay formulations improves photoprotection, reduces volatilization and maintains herbicidal activity in the soil under labora- tory and field conditions. Largest adsorption of herbicides by organo--clays correlates with an optimal reduction of photodecomposition and volatilization. It appears that the role of the organic cation, e.g., benzyltrimethylammonium (BTMA) is to enhance the adsorption of the non-polar herbicides to the organo-clay complex, whereas the actual photoprotection is mainly provided by the clay.
  • 机译 某些西班牙粘土(海泡石,坡缕石,膨润土)的制药应用:一些预配制研究
    摘要:ln this work, a pharmaceutical preformulation study of four Spanish clays (two sepiolites, one palygorskite and one bentonite) is presented, comparing the results obtained with those of three mineral products currently used in pharmaceutical technology. The results showed that the mineralogical and chemical purity of these clays is similar and even higher than that of the three commercial products. The microorganism content is inside the range required for non-sterile pharmaceutical forms. We also determined two parameters concerning the clays' suitability for use in tablet manufacture (colour and water content) and one indicating appropriateness as an antidiarrheic product (adsorption capacity of methylene blue). The clays are yellowish white in colour, although correction does not seem necessary; water content varies according to the structure of the clay and storage conditions. Adsorption capacity of methylene blue is affected by the amount of hydration water present, dehydration temperature and the type of interchangeable cation found in the clay.
  • 机译 激发回波l_H核磁共振成像技术测量水在污染物中的自扩散系数
    摘要:l_H nuclear magnetic resonance (NMR) imaging was performed for the measurement of self diffusion coefficients of water molecules (l_H_2O) in smectite. We measured two smectite samples (saponite and montmorillonite) with 96.6 wt./100 of water at 23.8deg.C. A stimulated echo imaging sequence with magnetic field gradient pulses for the diffusion measurement was applied to the samples at a static magnetic field of 2.35 T. Eight NMR images were obtained with systematically changing the strength of field gradient pulses. The statistics of 225 diffusion data for each sample showed that the average diffusion coefficient was 2.06 X l0~-9 m~2/s for saponite and l.52 X l0~-9 m~2/s tbr montmorillonite. The standard deviation was 0.02 X I0~-9 m~2/s for saponite and 0.05 X l0~-9m~2/s for montmorillonite. The measurement time for the eight NMR images was 2.8 h, which is much shorter than that fro conventional methods. Therefore, NMR imaging is suitable for the quick measurement of water dit1usion in clay.
  • 机译 一价和二价金属硫酸盐对石灰稳定高岭石稠度和压实度的影响
    摘要:The factors influencing the durability of compacted lime--stabilised clay soils depend in part on the short-term material properties that emanate from the immediate changes that occur (within a few hours) during the initial part of the stabilisation process. The long-term properties take a much longer period to develop and small changes are still occurrent after several years. In both cases, the genesis of the properties may be directly linked to the properties of the parent soil and the cationic process that takes place as soon as the mix materials are in contact with water. Thus, the significance of the constitution of the parent material and the factors influencing the cationic exchange process cannot be overemphasised. Both these factors are affected by the presence of sulphates in the soil. This paper shows how the commonly occurring monovalent metal sulphates of sodium and potassium, and the divalent ones of calcium (gypsum) and magnesium, affect the consistency and dynamic compaction properties of an industrial kaolinitic clay soil of high purity, to which sulphates have been artitlcially introduced. The results clearly illustrate that the effects of the presence of sulphate depend strongly on the sulphate cation type. Some cations (Ca~2+ and Mg~2+ ) enhance the effects of lime addition while others have the tendency to reverse these effects (Na+ and K~+).
  • 机译 蒙脱石作为乳液的胶体稳定剂I.蒙脱石和非离子表面活性剂乳液的制备和性能
    摘要:Bentonites, montmorillonites, and hectorites were used as colloidal stabilizers of oil--in-water (O/W) emulsions. The enrichment of the solid particles on the oil--water interface was attained by the addition of nonionic coemulsifiers (glycerol monostearate (GMS), deca(ethylene glycol) hexadecyl ether, alkyl polyglucoside, and lecithin). The clay mineral content of the aqueous dispersion was 2/100 (w/w). Stable emulsions required amounts of 0.5--l.5 g coemulsifier per l00 ml aqueous dispersion. Oil volume fraction was varied between φ= 0.l7 and φ= 0.50. At φ> 0.50 the O/W emulsions changed into water-in-oil (W/O) emulsions. The number average diameter of the droplets was about 25 nm. The volume average diameter (50--100 nm) more strongly depended on the clay mineral/coemulsifier combinations. Wyoming bentonite and the corresponding delaminated sodium montmorillonite were useful stabilizers; technical, soda- activated bentonites yielded unstable emulsions, or emulsification was not successful. A synthetic hectorite which caused pronounced thickening of the coherent phase was an effective stabilizer. Creaming was often observed because of the buoyancy of the large droplets. Most of the creamed emulsions were stable over long periods and did not separate an oil phase. The resistance against creaming increased with the oil volume fraction. An increase of the solid content had to be accompanied by an increase of the coemulsifier concentration to reduce the rate of creasing.
  • 机译 X射线,EPMA和氧同位素研究了希腊马其顿Askos的超镁铁质岩石中的ver云母
    摘要:Extensive metasomatic zones of vermiculite-, tremolite--, chlorite-, and talc-rich rocks have been developed at the contacts of serpentinized ultramafic bodies and surrounding two-mica gneisses in the Askos area, Macedonia, Greece. These zones are probably related to the intrusion of acid magmatic bodies in the area. X-ray and EPMA studies confirmed the formation of vermiculite through a layer-by-layer transformation of original micas. In decreasing abundance, the following mixed--layer and discrete phases were identifiedf biotite/trioctahedral vermiculite (hydrobiotite), biotite/smectite, trioctahedral chlorite/trioctahedral vermicuIite (corrensite), vermiculite/smectite and discrete biotite, vermiculite, chlorite and talc. The 2--20 μm fraction of the vermiculitic samples consists mostly of biotite/vermiculite (> 40/100) with the biotite percentage dominating in the mixed phase. Lower abundances (20--40/100) of biotite/smectite and chlorite/vermiculite occur in both finer fractions (2--20 and < 2 pm) of all vermiculitic samples. Vermiculite/smectite is very abundant in the < 2 μm fractions of most vermiculitic samples. The DTA curves of the samples analyzed are characteristic of Mg-vermiculites. The electron micro- probe analyses show a gradual K leaching from precursor mica with increasing degree of weathering. Oxygen isotope results confirm this assumption. Initially, hydrothermal fluids derived from the neighboring granitic intrusions, were responsible for the micatization of the primary minerals of the ultramafic bodies. Hydrothermal activity was also responsible for the partial formation of corrensite. Consequently, water moving downwards was very important for the formation of the vermiculite and other clay mineral mixed-layer phases through the alteration of micas and chlorite. The low relief and the long-lasting tectonic stability of the area were essential
  • 机译 温度对压实膨润土水力传导率的影响
    摘要:The hydraulic conductivities of water saturated Ca--bentonite with dry densities of l .4, l.6, and l .8 Mg/m~3 were measured within the temperature range of 20 to 80deg.C. The hydraulic conductivities of all the compacted bentonites are lower than l0~-11 m/s, and the relationship between the logarithm of the hydraulic conductivity and the bentonite dry density can be fitted to a straight line. The hydraulic conductivities of bentonites increase with increasing temperature, and the hydraulic conductivities at 80deg.C increase up to about three times those at 20deg.C. The measured values are in agreement with those predicted from the hydraulic conductivities at 20deg.C assuming that only fluid properties are changed with changing temperature. The change in viscosity of water with increasing temperature contributes greatly to the increase of hydraulic conductivity.
  • 机译 绿土作为乳液的胶体稳定剂。蒙皂石乳液的流变性能
    摘要:Oil-in-water emulsions were prepared by dispersing aqueous dispersions of several bentonites, montmorillonites, and hectorites (2/100 solid content) in paraffn oil which contained l00 mg/25 ml of a coemulsifier (alkyl polyglucoside, glycerol monostearate, lecithin, tetra-and deca(ethylene oxide) hexadecyl ethers). The colloidal stabilizers were sodium montmorillonite from Wyodring (USA), sodium bentonite from Kimolos (Greece), soda-activated bentonite from Milos (Greece) and Kimolos, also after decomposition of the carbonate. Three samples of synthetic hectorites (as synthesized, after washing, and after impregnation with sodium polyphosphate) were also used as colloidal stabilizers. The processing steps had strong effects on the rheological properties of the clay mineral dispersions. The rheological behavior of emulsions reflected these properties of the dispersions. Due to the presence of the dispersed oil droplets, the shear stresses of the emulsions were distinctly higher than the corresponding values of the dispersions and increased with the oil volume fraction. Their behavior changed from antithixotropic to thixotropic with increasing oil volume fraction. The storage modulus G' of the emulsions with alkyl polyglucoside and glycerol monostearate showed no linear viscoelastic regions indicating the destructive character of the oscillation experiments even at the smallest deformation and the lowest frequencies. The structure of the emulsion was more stable in the presence of lecithin and ethylene oxide ethers and resisted to the shearing forces during the oscillation experiments as indicated by the observation of linear viscoelastic regions.
  • 机译 电解质浓度和pH值对原始和Na_2CO_3活化的KUtahya膨润土流变性能的影响
    摘要:The effect of the Na_2CO_3 activation on the rheological properties of a bentonite from Kiltahya (Turkey) was investigated. The bentonite was activated with Na_2CO_3 at different dosages (1-15 g Na_2CO_3/100 g bentonite). The activated samples were examined by chemical and X-ray diffraction analysis. The calcium bentonite was completely converted to sodium bentonite when the Na_2CO_3/bentonite ratio was 2.5/100. The rheological values showed a maximum after addition of 2.5/100 Na_2CO_3 (bentonite concentrations 2-6/100 w/w). At 2.5 g Na_2CO_3/100 g bentonite, the shear stress was also measured at several NaCl and Na-hexametaphosphatC concentrations. NaCl addition decreased the rheological properties up to NaCl concentrations of 0.005 moll~-l. Further addition of NaCl increased the rheological properties again. The addition of Na-hexa- metaphosphate caused a decrease in the rheological properties to a constant value higher phosphate concentrations. The lowest yield stress was obtained around pH 7.
  • 机译 有机物对硬质土壤物理和理化性质的影响
    摘要:The main thrust of this study is to investigate the effects of organic matter on the physical and the physicochemical properties of illitic soils. For this purpose, organic matter (peat) was added to inorganic illitic clayey soil at eight levels (0/100, 5/100, l0/100, l2.5/100, l5/100, l7.5/100, 20/100, and 30/100 by weight). The physicochemical properties of the resulting soils were determined using a Grain Size Analyzer (GSA) with specific surface area measurement, Scanning Electron Microscopy (SEM), and Infrared Spectroscopy (lR). The physical properties of the mixtures were determined by conducting a series of laboratory tests including Atterberg limits, compaction, unconfined compressive strength, and swell characteristics tests. The results showed that at low organic contents (in general less than 15/100) the soil particles tend to aggregate, whereas at higher organic contents the soil particles tend to disperse. Also, the IR tests showed that direct chemical interactions took place between the organic and the inorganic fractions of the mixtures. The tests on the physical properties showed that at low organic content (up to l0/100) the plasticity index slightly increased then after, the plasticity index decreased with increasing organic content. Organic matter has shown to decrease the maximum dry density and increase the optimum water content, nevertheless, although organic matter decreased the soils compactability, the feasibility of compaction of slightly organic content soils still exists. Moreover, it was shown that organic matter decreased the peak strength values and increased the water contents at these peak strengths. The final free swell for illitic soils increased with increasing levels of added organic matter.
  • 机译 加热期间形成硫酸钙:一些基本参数
    摘要:The appearance of white deposits on some ceramic products is known as efflorescence. In this study, efflorescence is principally made up of hydrated calcium sulphate. This salt is mainly formed during the firing of the material and is affected by various parameters f firing cycle, material texture and mineralogical and chemical composition of the raw materials. Evidence for this formation is found by analyzing gases evolved during firing. SO_2 (from pyrite oxidation) and CO_2 (from decomposition of CaCO_3). The retention of SO_2 is essential in the CaSO_4 formation. Fourier transform infrared (riIR) analysis of CaCO_3 reacting with SO_2, as a function of time and temperature, has allowed to determine the formation mechanism. Determination of the pore size distribution of the ware during the firing has revealed that porosity is a crucial property for the oxidation of pyrite. This detailed analysis has finally led to recommendations to limit the formation of CaSO_4 during the firing cycle.
  • 机译 无机材料(SiO_2纳米颗粒,蒙脱石微孔板和氧化钼)的超薄膜,通过与有机聚离子的逐层交替组装制备
    摘要:We have been investigating alternate assembling of inorganic materials, SiO_2 nanopafticles, clay microplate, and polyoxometalates with oppositely-charged polyions. In this paper, previously reported results are summarized and compared in order to establish a unified interpretation. Reproducible film growth is observed in assembly of anionic SiO_2 particles and cationic poly(diallyldimethylammon ium chloride) (PDDA). The adsorption time required for successful assembly of SiO_2 nanoparticles is only 2 s. Scanning electron microscopic (SEM) observation shows that the obtained film has a surprisingly flat surface. Similarly montmorillonite clay microplate is successfully assembled with cationic PDDA and poly(ethyleneimine) (PEI), but its adsorption required 5--6 min. These adsorption kinetics are interpreted based on the nature of the adsorbent. Adsorption of rigid and spherical SiO_2 particles is diffusion-limited and very fast,
  • 机译 过渡金属交换锂蒙脱石上聚甲基丙烯酸甲酯的形成
    摘要:Hectorite clay films exchanged with Cu~2+ or Fe~3+ react with methyl--methacrylate monomer in a solventless process to form poly(methyl-methacrylate) (PMMA). Scanning force microscopy (SFM), electron spin resonance (ESR), and X--ray diffraction (XRD) are useful in studying the resulting clay/polymer composite. SFM shows that PMMA forms on the surface of both the Cu~2+ - and Fe~3+--exchanged forms. In addition, XRD shows PMMA formation in the interlayer region of the Fe~3+ -exchanged hectorite but not the interlayer region of Cu~2+--exchanged hectorite. SFM shows that the morphology of the polymer formed on the film surface depends on: (1) the type of transition metal exchanged into the interlayer region. (2) The mode of delivery (vapor vs. liquid) of methyl-methacrylate monomer to the surface of the clay. PMMA does not form to a significant extent on or within Ca~2+--exchanged hectorite, and ESR shows no evidence of free radical formation or reduction of the transition metals during any of the polymerization reactions. The results suggest the possibility of an unusual cationic polymerization of methyl-methacrylate to tbrm PMMA with organic cations being stabilized by interaction with the silicate surface. The experimental results have implications for ''solventless synthesis'' of PMMA and other polymers.
  • 机译 聚亚苯基亚乙烯基/蒙莫层状纳米复合材料的合成与发光性能
    摘要:A layered nanocomposite of poly(p--phenylenevinylene) (PPV) with montmorillonite clay is prepared at ambient temperature by incorporation of poly(p--xylylenedimethylsulfonium) (PXDMS) into the montmorillonite galleries, followed by the base--mediated elimination of dimethylsulfide. Powder X--ray diffraction on the intermediate and final product show gallery expansions of 5.5 and 4.6 A, respectively, indicating the nanoscale ordering of polymer and montmorillonite layers. Thermogravimetric analyses of the products indicates the loss of approximately 75/100 of the sulfonium groups by reaction with base. Luminescence measurements show a shili in emission peak intensities indicating the conversion of PXDMS to PPV within the montmorillonite galleries.
  • 机译 甲硅烷基化辉石的制备与表征
    摘要:Organic modification of a layered silicate, magadiite (the ideal formula is Na_2Si_14O_29' nH_2O), was conducted by the reaction between the interlayer hydroxyl groups of magadiite and organochlorosilanes (trimethylchrolosilane triethylchlorosilane, triisopropylchlorosilane, butyldimethy hlorosilane, octyldimethylchlorosilane, and octadecyldimethylchlorosilane). By uti- lizing the dodecyltrimethylammonium-exchanged magadiite as the intermediate, bulky organosilyl groups have successfully been introduced into the interlayer space of magadiite. The silylation of the interlayer silanol groups of layered silicates may lead to novel functional inorganic--organic supramolecular systems alternative to the intercalation compounds formed by ion exchange reactions.
  • 机译 液晶/粘土矿物复合材料
    摘要:Novel liquid crystalline composites composed of a nematic two--frequency addressing liquid crystal (TFALC) and a few percents of various types of organized clay minerals (LCC) have been prepared. The affinity of the organized clay minerals for the liquid crystal, which was evaluated by measuring their contact angles, was highly dependent on the kind of organic ammonium cations used tbr the organization of the clay. In the case of an organized clay having good affinity for the liquid crystal, the organized clay was dispersed homogeneously in the liquid crystal in the size of several micron meters. Also, the LCCs were stable enough against sedimentation or aggregation under an electric field. The LCCs were sandwiched between transparent conductive In/SnO_2 (ITO)--coated glasses with l2 ym polymer beads as a spacer and their electro--optical properties were measured. The LCC cells exhibited a bistable and reversible electro--optical effect between a light scattering state and transparent state. The contrast between the light scattering and transparent memory states is highly dependent on the kind of the organized clays. The LCCs based on the organized clays with better affinity for the liquid crystal exhibited relatively higher contrast. The memory effect exhibited by the LCCs is rather unusual since most of conventional nematic liquid crystals do not exhibit such a memory effect due to their low viscosity. Their memory mechanism was proposed.
  • 机译 简介:从粘土矿物-聚合物相互作用到粘土矿物-聚合物纳米复合材料
    摘要:Clay mineral--polymer nanocomposites are hybrids which exhibit a change in composition and structure over the scale of nanometers. Because of their high aspect ratio layered silicates such as 2:1 clay minerals, hydrous alkali silicates and crystalline silicic acids are the most important reinforcing phases for engineering polymers. Clay mineral--polymer complexes can be prepared in several ways. However, true nanocomposites are only obtained by methods which overcome the tendency of the silicate layers to form the--face aggregates. A serious obstacle in reinforcing engineering polymers by delaminated silicates is the incompatibility between the silicate layers and many polymers. A decisive step is, therefore, the appropriate modification of the external and internal surfaces of the silicates. Processing of clay minerals with melted polymers and intercalative polymerization are the most promising ways to prepare nanocomposites.
  • 机译 聚合物层状硅酸盐(粘土)纳米复合材料的可燃性和热稳定性研究
    摘要:ln the pursuit of improved approaches to fire retarding polymers, a wide variety of concerns must be addressed in addition to the flammability issues. For commodity polymers, their low cost requires that the fire retardant (FR) approach also be of low cost. This limits solutions primary to additive type approaches. These additives must be inexpensive and easily processed with the polymer. In addition, the additive must not excessively degrade the other performance properties of the polymer, and it must not create environmental problems when recycling or at the time of its final disposal. We have recently found that polymer layered--silicate (clay) nanocomposites have the unique combination of reduced flammability and improved physical properties. This paper is intended as an overview of the research to date, by our group and others, on the use of clays, dispersed at the nanometer level, in polymers for improving thermal stability and flammability.
  • 机译 薄粘土膜中的扩散控制:通过控制水性电解质来调整层状粘土膜结构
    摘要:Clay--modified electrodes have been used to investigate the effects of varying anions and cations in the bathing solution and clay film history on the transport of probe molecules as controlled by the swelling properties of Wyoming montmorillonite. The cations K~+ and Ca~2+ have been shown to restrict swelling in clays exposed to mixtures of NaCl and KCl or CaCl_2. In dilute NaCl/KCl or NaCl/CaCl_2 mixtures, the K~+ and Ca~2+ appeared to be exchangeable, however in more concentrated mixtures attenuation of the swelling due to K~+ or Ca~2+ was more persistent. Trivalent anions were more readily incorporated in the interlayer than quadravalent anions in well swollen clay films. However, the opposite trend was observed in films formed with smaller interlayer spacing via bathing in higher concentration electrolytes. Divalent electrolyte anions also affected larger probe molecule transport than monovalent anions in these less-swollen times.
  • 机译 层状氢氧化铜Cu_2(OH)_3X(X =羧酸盐)的可控磁性
    摘要:Physical and chemical properties of organic/inorganic hybrid nanocomposites are attractive, because they are potential materials yielding new functionality, such as a cooperative phenomenon, multi-functional property and so on. Layered copper hydroxides, Cu_2(OH)_3X (X = carboxylate anions), are two dimensional magnetic materials whose structures consist of alternating stacking of the magnetic copper hydroxides layer and the carboxylate layer. In this paper we report the preparations, structures and magnetic properties of various copper hydroxides. In the series of Cu_2(OH)_3(n-C_mH_(2m+1COO), the carboxylate anions form an interdigitated monolayer in the m = 0 and l materials, while those do a bilayer in the m = 6--ll materials. The intermediate materials (m = 2-5) exhibit both mono-- and bi-layer structures, which are governed by the condition at their preparations. The temperature dependence of the paramagnetic susceptibilities of the m = 0 and l materials suggests an intralayer ferromagnetic interaction, while that of the m = 6-ll materials does an antiferromagnetic interaction. Further, the longer alkyl chain materials show a divergence of the ac magnetic susceptibility at 22 K, indicating a ferromagnetic order. It is found that the materials show a drastic change in magnetism, depending on the molecular orientation of the carboxylate anions. The Cu K-edge EXAFS spectroscopy at 20 K indicates a characteristic difference in local structure between the shorter and the longer alkyl chain materials, they are large enough to explain the drastic magnetic change. In this report, we also show controllable magnetic properties of Cu_2(OH)_3(8-(p-(phenylazo)phenyl)oxy)octanoate), derived from cooperation between the inorganic layer carrying magnetism and the organic layer playing a role of sensor. A reversible structural transformation occurs as a result of soaking in hot
  • 机译 蒙脱石层间空间中二元液体中生长的CdS,TiO_2和Pd〜o纳米粒子
    摘要:The interfacial layers on the clay mineral/liquid interface usually range from 0.5 to 5 nm. When clay mineral particles are dispersed in binary textures (ethanol--cyclohexane and ethanol- toluene), an adsorption layer evolves on their surface which may function as a nanophase reactor for the synthesis of nanocrystalline materials. In the adsorption layer on the surface of montmoril- lonite CdS, TiO_2 and metallic palladium nanoparticles with a diameter of 5--l5 nm were grown. The appearance of semiconductor particles and the dependence of particle size upon the Cd~2+ precursor concentration were followed by determination of the band gap energy. The rheological characteristics of suspensions containing nanopaticles are basically different from those of the original suspension. Solid powder samples obtained from the suspensions were studied by small-angle X-ray scattering (SAXS) measurements; the size of nanoparticles located on the clay mineral surfaces was determined and changes in the structure of the support were monitored.
  • 机译 聚合物插层的双氢氧化物纳米复合材料的表面和界面性能
    摘要:The surface and interfacial properties of the layered double hydroxide (LDH) phase Mg_6Al_2(OH)_16CO_3 4H_2O (LDHCO3) and its nanocomposites with poly(styrenesultbnate) (LDHPSS) and poly(vinylsulfonate) (LDHPVS) were characterized by X--ray diffraction, thermo- gravimetric analysis, Fourier transform infrared spectroscopy, transmission electron microscopy, He pycnometry, and electrophoretic light scattering. Polymer incorporation within the inter--gallery space resulted in a shift of the d_003 reflection from 7.7 A (LDHCO3) to 12.7 A (LDHPVS) and 21 A (LDHPSS). This increase in basal plane spacing caused the density of the LDH samples to decrease from 2.05 g/cm~3 (LDHCO3) to 1.83 and l.4l g/cm~3 for LDHPVS and LDHPSS nanocomposites, respectively. LDHCO3 exhibited a positive electrophoretic mobility over the pH range from 4-ll with an isoelectric point (iep) at pH ll. However, the LDH nanocomposites displayed a negative electrophoretic mobility over the measured pH range, indicating that the
  • 机译 聚阳离子交换膨润土的表征与用途
    摘要:The interaction of polymers with clays is considered with particular emphasis on the adsorption of polycations of the type [CH_2CHOHCH_2N(CH_3)_2]~n+_n onto a low iron Texas bentonite, Westone--L (WL). The influence of clay type, particle size and resident cation on the amount of adsorbed polycation is reported along with variable temperature X-ray diffraction of the resulting complexes. The information obtained from Cs~+- and Na~+--WL suspensions using 133_(cs) and 23(Na) solution phase NMR is summarised and used to show that this technique can provide quantitative information regarding the displacement of Cs~+-ions from the exchange sites by polycation in suspension and reflect subtle in-situ changes intimated from Zeta potential measurements. The use of polycation-exchanged clays as scavengers of p-nitrophenol from water is described as is the significant activity of acid-treated polycation--exchanged clays for the catalytic isomersion of ∝-pinene to camphene and limonene.
  • 机译 聚合物层状硅酸盐纳米复合材料:概述
    摘要:An overview of polymer--clay hybrid nanocomposites is provided with emphasis placed on the use of alkylammonium exchanged smectite clays as the reinforcement phase in selected polymer matrices. A few weight percent loading of organoclay in nylon 6 boosts the heat distortion temperature by 80dej.C, making possible structural applications under conditions where the pristine pormer word normally fail .A similar loading of clay nanolayers in elastomeric epoxy and polyurethane matrices dramatically improves both the toughness and the tensile properties of these thermoset systems. Glassy epoxy nanocomposites exhibit substantial improvement in yield strength and modulus under compressive stress-strain conditions. The latest development in polypropylene hybrids have yielded nanocomposites with improved storage moduli. Polyimide hybrids in thin-film form display a l0-fbld decrease in permeability toward water vapor at 2 wt./100 clay loading. In situ and melt intercalation processing methods are effective in producing reinforced polystyrene hybrids. Nitrile rubber hybrids show improved storage moduli and reduced permeabilities even toward gases as small as hydrogen. Poly(ε -caprolactone)welay nanocomposites prepared by in situ polymerization of scaprolactone in organoclay galleries show a substantial reduction in water adsorPtion. Polysiloxane nanocomposites produced from poly(di- methylsiloxane) and organoclay mixtures have improved in tensile properties, thermal stability and resistance to swelling solvents. Organoclay-poly(l-lactide) composite film was obtained by solvent casting technique. Clay nanolayers dispersed in liquid crystals act as structure directors and form hybrids composites that can be switched from being highly opaque to highly transparent by applying an electric tleld of short duration.
  • 机译 聚合物/层状硅酸盐纳米复合材料作为高性能烧蚀材料
    摘要:The ablative performance of poly(caprolactam) (nylon 6) nanocomposites is examined. A relatively tough, inorganic char forms during the ablation of these nanocomposites resulting in at least an order--of magnitude decrease in the mass loss (erosion) rate relative to the neat polymer. This occurs for as little as 2 wt./100 (~ 0.8 vol./100) exfoliated mica-type layered silicate. The presence of the layers does not alter the first--order decomposition kinetics of the polymer matrix. Instead, the nanoscopic distribution of silicate layers leads to a uniform char layer that enhances the ablative performance. The formation of this char is only minutely influenced by the type of organic modification on the silicate surface or specific interactions between the polymer and the aluminosilicate surface, such as end-tethering of a fraction of the polymer chains through ionic interaction to the layer surface. Thus, the enhancement in ablative performance should be general for the class of exfoliated layered silicate/polymer nanocomposites.
  • 机译 聚环氧乙烷/ NH〜+ _4-蒙脱土纳米复合材料
    摘要:New materials based on the intercalation of poly(ethylene oxide), PEO, into homoionic NH~+_4-smectites (montmorillonite and hectorite) have been synthesised and characterised. IR spectroscopy of the resultant nanocomposites shows changes in the polymer helical conformation of PEO as well as in the T_d symmetry of the ammonium ion. Intercalation of PEO into NH~+_4-hectorite produces a material with regular stacking of the clay layers, but in PEO/NH~+_4 montmorillonite, the layers appear to be irregularly stacked with PEO chains arranged in double layers. However, by exchanging NH~+_4 with Na~+ ions, the layer stacking becomes ordered. Ionic conductivity of these materials is lower than that of analogous materials containing alkali metal cations. Typical conductivity values measured in a direction parallel to the silicate layers at 200dej.C are in the order of l0~-7 S/cm.
  • 机译 以甲醇高岭石为中间体,将烷基胺和水嵌入高岭石
    摘要:Alkykamines and water were intercalated between the layers of kaolinite by utilizing a kaolinite/methanol intercalation compound as an intermediate. A kaolinite/methanol intercalation compound was synthesized by guest displacement reaction of a kaolinite/Nmethylfor- mamide intercalation compound with methanol. The basal spacing increased up to 5.75 nm when octadecylamine was used. It increased linearly with the length of alkyl chains by 0.255 nm per carbon atom, suggesting that the alkylamine molecules in the interlayer space of kaolinite take a bilayer arrangement with their alkyl chains almost perpendicular to the layers of kaolinite. Water molecules were also intercalated into kaolinite by displacement of methanol. The basal spacing of the product was l.00 nm under wet conditions and 0.85 nm after drying. By using hydrated kaolinite as an intermediate, pyridine molecules were intercalated into kaolinite, thus, the hydrated kaolinite also shows the ability as an intermediate for displacement reactions. These results demonstrate that kaolinite has higher intercalation ability for a wider variety of guest species than previously accepted if appropriate intermediates are used.
  • 机译 层状粘土矿物上阳离子花青染料的吸附和聚集
    摘要:The adsorption and aggregation of a cationic cyanine dye, l,l'-diethyl-2,2'-cyanine (pseudoiso- cyanine; abbreviated as PIC), on various clays have been investigated. The PIC formed J-aggre- gates on Na-montmorillonite and synthetic Na--tluor-tetrasilicic mica (TSM), while they distributed molecularly on synthetic Na--saponite and synthetic Na-hectorites. The particle size of the clays was considered to be a dominant factor to control the aggregation of PIC. The J-aggregate formation was suppressed when tetramethylammonium--montmorillonite was employed as a host material. Ethylene glycol in the suspension was also responsible for the suppression of J-aggregate formation of PlC. Thus, the aggregation of PlC was effectively controlled by the species surrounding the PIC cations as well as the nature of clays.
  • 机译 粘土和粘土-橡胶复合材料的表面改性
    摘要:The nature of clay fines influences the characteristics of clay--rubber composites. This paper discusses the improvement of properties of clay--rubber composites by acid activation and surface modification of the clay. Acid-treated clays show a higher surface activity and a stronger combining ability with silane coupling agents. The silane modified clay fines rein1brce the rubber by increasing the compatibility between rubber and clay.
  • 机译 粘土烧成动力学的一种方法
    摘要:Results of a detailed study on microtextural and microchemical characteristics of pottery obtained during different experimental firing runs carried out at different temperature under oxidising conditions are reported. During firing, the reaction behaviour of temper grains and clay matrix is dominated by disequilibrium conditions and characterised by the presence of different reacting sub-systems. Each one of them is compositionally well established and corresponds to different mineral phases in mutual contact. Reactions occur following the two main mechanisms: (i) reactions leading to nucleation and growth of new mineral phases (modal reactions) and (ii) reactions producing only compositional variations of phases (cryptic reactions). Modal reactions are given by new phases rimming the temper grains, whereas the cryptic reactions may develop during the partial transformation of a single phase, producing compositional zonings. Kinetic aspects are also considered in order to asses the role exerted by temperature, by bulk and mineral compositions and by fluid phase on the attainment of modal or cryptic reactions during firing.
  • 机译 被液体淹没的砂-膨润土混合物的膨胀和压缩特性
    摘要:The swell behavior of expansive soils may be desirable as in many hydraulic containment applications or unfavourable and may cause major deterioration and distresses in many geotechnical applications such as highways and shallow foundations on expansive formations. In this study, the role of liquid chemistry on the swell and compressibility characteristics is investigated. Two types of bentonites are mixed with pure silica sand. Mixtures of 20/100 bentonite are compacted to l8 kN m~-3 dry density at 8/100 water content. Swell and compressibility are evaluated by oedometer test using various concentrations (0.0, 0.l, 0.5, l.0, 4.0 N) of Ca(NO_3)_2 and NaNO_3. Results indicate that swell potential (SP), swell time, swell pressure, and volume compressibility decreases with increase of chemical concentrations for the two types of mixtures. Therefore, degradation in the efficiency of high quality bentonite (HQB) in containment applications should be considered. Pr-wetting or grouting with NaNO_3 and Ca(NO_3)_2 concentrations (0.5--l N) could be practical alternative to control swell in foundation and highway engineering.
  • 机译 高锰酸盐介导的蒙脱土中羟基-Cr中间层的溶解
    摘要:Expandable layer silicates may be intercalated with a variety of hydrolyzed metal cations. Chromium is among those metals that have received the most attention, due to its presence in many polluted environments and toxicity when present as Cr(VI). of all potential oxidants of Cr(III), high-valence Mn remains one of the most potent. Manganese(VII) species were, therefore, introduced to suspensions of hydroxy--Cr(III) interlayered montmorillonite to: (i) establish the role that Mn(VII) plays ill the oxidation of intercalated Cr(III) and, (ii) attempt to intercalate Mn species that would impart catalytic activity to the montmorillonite. The oxidation of intercalated hydroxy-Cr(IlI) polymers by Mn(VII) was rapid initially then decreased sharply due, in part, to accumulation of residual Mn within the interlayer. As this intercalated Mn was present as Mn(II), the oxidative capacity of the clay was not enhanced. Furthermore, the hydroxy-Cr(III) pillars readily collapsed upon oxidation, eliminating much of the gallery space required for effective catalysis. However, the intercalation of Mn onto montmorillonite by means of reduction, described for the first time in this paper, may find application in the synthesis of related pillared clay catalysts.
  • 机译 天然海泡石和热处理海泡石在环境空气中的吸附-解吸水蒸气
    摘要:A sepiolite from Yunclillos (Spain) has been heat--treated in air in the temperature range of 110--500deg.C. The heat treatment up to 200deg.C does not modify the volume of dricropores or the non-microporous surface area of the original sepiolite. As the temperature of the heat treatment increases to 500deg.C there is a decrease in the non-microporous surface area and a loss of microporosity, the original structure not being restored after rehydration for sepiolite heat-treated at 400 and 500deg.C. In order to analyze the behavior of sepiolite as controller of humidity, worlding cycles of 24 h with variable temperature and relative humidity (RH) have been simulated and the experimental results have been compared with the adsorption isotherms of water vapor in air. These isotherms are a very good guide to predict the amount of water that the sepiolite can retain--liberate when the RH of the air is modified. Considering the shape of the isotherms, showing a faster increase in the amount of water retained at RH > 50/100, it is possible to deduce that sepiolite will be especially useful as controller of humidity in environments where the RH is usually very high (80--90/100) and sporadically is considerably decreased (below 60/100). On the other hand, the thermal treatment of sepiolite at 500deg.C does not improve the capacity to control the humidity of the environment.
  • 机译 珍珠岩细粉的沸石化:最终产品的矿物学特征和化学元素的迁移
    摘要:This study examines the synthetic zeolites produced from perlite waste. Zeolitisation was carred out in autoclaves with NaOH solutions at l00deg--l40deg.C. The volcanic glass was converted to zeolite-P_c, zeolite--V and hydroxysodalite. The rate of conversion of the glass and the transformation of zeolites depended on temperature, time and NaOH concentration. The principal chemical changes observed between the initial glass and the end product involved the removal of Si and K and the uptake of Na. The amount of Si and K released increased with increasing alkalinity, reaching a steady state in the whole temperature range. The amount of Si at the steady state decreased with increasing temperature, while that of K followed an opposite trend. Therefore, the SiO_2fAI_2O_3 ratio of the solid phase at steady state increased with increasing temperature. The amount of Na taken up increased with increasing alkalinity, increasing the Na_2O:Al_2O_3 ratio and decreasing the SiO_2:Na_2O ratio of the solid phase, as reaction progresses. The crystallinity of zeolite--P_c increased with the amount of Na_2O present in solution up to a maximum value, then decreased rapidly. The zeolite-P_c initially formed had a high SiO_2:Al_2O_3 ratio, which then decreased gradually until zeolite-V was formed. Both zeolites were replaced by hydroxysodalite at higher alkalinity. Zeolite--V was metastable and converted to zeolite-P_c after prolonged exposure to the atmosphere. The average cation exchange capacity (CEC) of the zcolite products is 3.0 meq/g and equilibrium was attained very fast, suggesting that the products can be
  • 机译 埃及高岭土:新投资环境下的前景
    摘要:Egypt has large reserves of kaolin in many localities in Sinai, Red Sea coast and Kalabsha near Aswan. These kaolins can satisfy the local demand for tiller, paper and ceramic industries l0 times for at least 50 years, in comparison to the current demand. However, the Egyptian kaolin is hard and massive. It is also low grade so that it needs beneficiation to be suitable for paper and ceramic industries, which import their needs at the present time. Beneficiation of the Egyptian kaolin from different localities indicated their technical viability for ceramic production and as paper filler. In the meantime, the Egyptian government has created a new healthy climate to encourage investment in Egypt. For example, the government provided many facilities to investors in the new cities, increased the period of free taxes to l0--20 years (depending on the project site) and reduced the interest of borrowing money from banks. All these facilities, among others, will have a positive impact on the economic viability of projects. This paper evaluates the situation of Egyptian kaolins, their methods of beneficiation and the domestic market. A summary for the economic pre--feasibility study was presented. The new laws of investment make such economic pre-feasibility more profitable in terms of return on investment (ROI) and pay back period (PBP).
  • 机译 萨索洛区(意大利北亚平宁山脉)的瓷砖粘土材料。地质,组成和技术特性
    • 作者:Michele Dondi;
    • 刊名:Applied Clay Science
    • 1999年第3/4期
    摘要:In the Sassuolo area (northern Italy) there is the largest tilemaking district in the world, which has practically served over the past years as an industrial scale laboratory for assessing the technological properties of clays and their suitability for the production of wall and floor tiles. The local clays are recovered from different geological units and distinguished in two principal types, with clearly differentiated compositions and technological properties: "marly clays" and "red shales". These local clays, which 20 years ago constituted the sole mineral resource of the Sassuolo District, now supply only 40/100 of the demand. This trend is largely connected with both process innovation (wet grinding, fast firing, etc.) and product changes (from red to white bodies). Overall, approximately 2 million tpa of clay materials are used in coloured bodies f marly clays for wall tiles (majolica, "birapida", "monoporosa' ') and red shales for both floor tiles (glazed red stoneware) and wall tiles (''monoporosa'').
  • 机译 三核醋酸铁络合物插层蒙脱石的热转变
    摘要:Fe(III) pillared montmorillonite was prepared using trinuclear acetato complex of Fe(III) as the pillaring agent and the resulted material was characterised by different analytical techniques. Basal spacing of the material is found to be l8 A even after calcination at 500deg.C indicating the formation of stable pillars. Thermal analysis indicate that the complex decomposes slowly from the silicate layer at higher temperature to form metal oxyhydroxide pillars. Sample calcined at 500deg.C shows the highest surface area of 284 m~2/g. Mbssbauer analysis was carried to identify the exact phase of Fe(III) formed during thermal treatment. From the Mossbauer spectra recorded at 298 and 77 K, it is observed that the species formed from the decomposition of the acetyl group of the complex is γ-FeOOH even at 500deg.C; whereas, the pure complex decomposed directly to ∝-Fe_2O_3 at 300deg.C. This confirmed the role played by the silicate 1ayer in directing the phase formation of Fe(III) during the heat treatment.
  • 机译 适用于医疗用途的两种泥炭的地球化学特征及其在浸出过程中的行为
    摘要:The compositional characteristics of two peats, from Austria and Italy, have been studied. The Massaciuccoli peat shows a high quantity of trace elements (Br, Cd, Mo, Se, U, As and Sb) with respect to the average shale, whereas the Neydheding peat contains more Br, Se and U. Since the therapeutic properties of peats are broad and interesting, the mobility of trace elements (As, Cd, Hg, Pb, Sb, Se, Te and Tl) used for pelotherapy, during water leaching and after Na exchange, have been checked. The data conceming the leaching procedure indicate that the analysed peats are rather stable materials under laboratory conditions. Although the concentration of some toxic elements (As, Se, Cd and Hg) in bulk peats are of the same order of magnitude as in muds used in pelotherapy, the release after similar leaching is lesser. The higher release from muds could be explained by the high exchange capacity of smectite minerals. These minerals are characterised by low cation selectivity because the chemical interactions between smectite and sorbed species is mainly ionic. On the other hand, the cation--organic matter interactions can establish a higher degree of covalent bonds, that are more stable during the interactions developed with leaching. An additional possibility can be considered taking into account the genetic conditions of peat formation. In the upper part, the acidic and oxidising conditions cause the depletion of mobile elements. This process can be seen as a natural cleaning, which occurs under relatively strong conditions compared to the use during medical treatments.
  • 机译 人体修复用粘土中有毒元素的表征
    摘要:The clay samples available in herbalist's shops, in pharmacies and a natural metal-rich cay have been studied from a mineralogical and a chemical point of view and the toxic elements present in the urine of rats fed with selected clays have been determined. The mineralogical data suggest that the pharmaceutical clay is mostly composed of smectite and organic matter, whereas the natural and the commercial herbalist clay show a more heterogenous composition containing various clay minerals, quartz, feldspars and accessories. The commercial herbalist clay contain also calcite and the natural clay sulphides. The concentration of the trace elements of the commercial herbalist clay is generally similar to crustal abundance; differences are present for Sr, Mo and Ga. The pharmaceutical clay shows an appreciable depletion of elements as Zn, V, Ga, Cr, Cd, Fe, Mo, Ni, Cu, Sb, S and Rb. Instead, the natural clay is characterised by high quantities of U, V, Cd, Mo, Tl, Ag, Ni, Cu, Sb, As, S, Se and Br, likely because of sulphide occurrence. The amount of these elements is several times higher then that of average shale. Considerable quantities of Se and As are present in the rats' urine. As and Se are always detectable, Ni, Cd, Sb and Tl show lower values, whereas Te, Pb and Hg are below the detection limits. The presence of toxic elements in the urine indicates that the absorptive processes occurs after clay ingestion, which causes a progressive increase of metals in the urine and in the blood. Despite the deep
  • 机译 铝柱状贝得石的红外发射光谱
    摘要:The structural changes of synthetic beidellite and Al_l3--pillared analogues during dehydroxylation were studied using infrared emission spectroscopy (IES). The OH-stretching region is characterised by 2 OH--stretching modes around 3605 cm~-I and 3650 cm~-l. These bands strongly decrease in intensity upon dehydroxylation of the beidellite up to 700--750deg.C. The Al_l3--pillared beidellite shows stronger OH-stretching bands, while the silanol band, originally visible in the beidellite spectra, is absent. The OH--stretching mode of the Al_l3 is visible around 3450 cm~-l and a very broad band is present around 3200 cm~-l assigned to water molecules in the Al~13 pillar. This band quickly disappears upon heating to 300deg.C while the OH-stretching band at 3450 cm~-l diminishes in intensity. The presence of two different OH-groups in beidellite is also reflected in the OH--bending modes around 880 cm~-l and 9l6 cm~-1 and in the OH--libration modes around 770 cm~-l and 804 cm~-l in the infrared (IR) absorption spectra. These bands show an intensity decrease upon dehydroxylation of the clay. Similar, slightly shifted, bands are observed in the IR emission spectra. Significant differences between the beidellite and its pillared analogue are the splitting of the single band at 8l4 cm~-l into two bands at 812 cm~-1 and 830 cm~-l and the bands associated with Al--OH modes show increased intensities for the pillared beidellite. These results show that upon calcination the pillars dehydroxylate, thereby releasing protons which are able to diffuse through the tetrahedral sheet into the octahedral sheet where they interact with the structural OH-groups and form water. In addition, the formation of Si--OH-- groups is observed in the IR emission spectra of the A~l3-pillared beidellite indicating that these protons can also interact with Si--O--Al bonds upon calcination and form new Si--OH--Al bonds. A reaction between the
  • 机译 孔隙水化学性质对压实黏土膨胀特性的影响
    摘要:The intluences of the exchange complex and pH of the solution used tbr cation saturation on Atterberg limits, compaction, and swelling potential of a compacted clay were investigated. The study involved transforming the exchange complex from a heterogeneous to a homogeneous one so that a frame of reference can be set for the clay behavior under such an ideal condition. The employed method for altering the exchange complex successfully yielded homo--ionic clay. The introduction of different species of cations gave rise to different particles associations. When introduced to the tested clay, potassium cations bond its particles with a rather strong bond (K-linkage), causing a drastic decrease in the specific area of the clay (about one-fourth of its untreated specific area), a decrease in the CEC, as well as a drastic decrease in the swell potential. For example, the swell pressure decreased from l.87 kg/cm~2 for the untreated samples to 0.4 kg/cm~2 for the K-treated samples (under the same conditions). Also, the swell potential vs. time relationships can be modeled accurately using a rectangular hyperbola.
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