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1

Surface area evaluation of montmorillonite  

SciTech Connect

Adsorption of molecules of different sizes on montmorillonite and on hydroxy-Al montmorillonite was studied to examine the effect of sorbate size on the experimental value of the surface area of the clays. For each clay the number of adsorbate units at the adsorption maximum per gram of clay produces a single hyperbolic curve, when plotted as a function of the area occupied by adsorbate, in the range of areas of 22--180 {angstrom}{sup 2} per sorbate. The equations of the curves are: N A = 657.7 m{sup 2}/g for the clay and N A = 202.8 {angstrom}{sup 27} for the hydroxy-Al montmorillonite. A dependence of the surface area of the hydroxy-Al montmorillonite on adsorbate size was observed and was attributed to surface irregularities produced by hydroxy-Al interlayering.

Helmy, A.K.; Ferreiro, E.A.; Bussetti, S.G. de [Univ. Nacional del Sur, Bahia Blanca (Argentina)

1999-02-01

2

Adsorption of organic phenols onto hexadecyltrimethylammonium-treated montmorillonite  

SciTech Connect

Montmorillonite used as an adsorbent was organically modified by using a cationic surfactant, hexadecyltrimethylammonium (HDTMA), to enhance the removal capacity of organic phenol contaminants dissolved in an aqueous solution. This modification produces a change of the surface property of montmorillonite from hydrophilic to organophilic. The single- and multicomponent competitive adsorptions were performed in a batch reactor to investigate the removal of three toxic organic phenols, 2-chlorophenol, 3-cyanophenol, and 4-nitrophenol, on the modified HDTMA-montmorillonite. It was observed from the experimental results that the adsorption affinity for HDTMA-montmorillonite was 2-chlorophenol, 4-nitrophenol, 3-cyanophenol in decreasing order. Langmuir and the Redlich-Peterson models were used to analyze the single-component adsorption results, while the IAST and the LCM models predicted the multicomponent adsorption equilibria. These models yielded favorable representations of both individual and competitive adsorption behaviors.

Kim, Young S.; Song, Dong I.; Jeon, Young W.; Choi, Sang J. [Kyungpook National Univ., Taegu (Korea, Republic of)

1996-12-01

3

Modeling the acid–base surface chemistry of montmorillonite  

Microsoft Academic Search

Proton uptake on montmorillonite edge surfaces can control pore water pH, solute adsorption, dissolution kinetics and clay colloid behavior in engineered clay barriers and natural weathering environments. Knowledge of proton uptake reactions, however, is currently limited by strong discrepancies between reported montmorillonite titration data sets and by conflicting estimates of edge structure, reactivity and electrostatics. In the present study, we

Ian C. Bourg; Garrison Sposito; Alain C. M. Bourg

2007-01-01

4

Monomers of cutin biopolymer: sorption and esterification on montmorillonite surfaces  

NASA Astrophysics Data System (ADS)

One of the important precursors for soil organic matter is plant cuticle, a thin layer of predominantly lipids that cover all primary aerial surfaces of vascular plants. In most plant species cutin biopolymer is the major component of the cuticle (30-85% weight). Therefore cutin is the third most abundant plant biopolymer (after lignin and cellulose). Cutin is an insoluble, high molecular weight bio-polyester, which is constructed of inter-esterified cross linked hydroxy-fatty acids and hydroxyepoxy-fatty acids. The most common building blocks of the cutin are derivatives of palmitic acid, among them 9(10),16 dihydroxy palmitic acid (diHPA) is the main component. These fatty acids and their esters are commonly found in major organo-mineral soil fraction-humin. Hence, the complexes of cutin monomers with minerals may serve as model of humin. Both cutin and humin act as adsorption efficient domains for organic contaminants. However, only scarce information is available about the interactions of cutin with soil mineral surfaces, in particular with common soil mineral montmorillonite. The main hypothesize of the study is that adsorbed cutin monomers will be reconstituted on montmorillonite surface due to esterification and oligomerization, and that interactions of cutin monomers with montmorillonite will be affected by the type of exchangeable cation. Cutin monomers were obtained from the fruits of tomato (Lycopersicon esculentum). Adsorption of monomers was measured for crude Wyoming montmorillonites and montmorillonites saturated with Fe3+ and Ca2+. To understand the mechanism of monomer-clay interactions and to evaluate esterification on the clay surface, XRD and FTIR analyses of the montmorillonite-monomers complexes were performed. Our results demonstrated that the interactions of cutin monomers with montmorillonite are affected by the type of exchangeable cation. Isotherms of adsorption of cutin monomers on montmorillonites were fitted by a dual mode model of sorption, which combines site specific adsorption mechanism (Langmuir) and partitioning mechanism. Adsorption of monomers by Fe3+-montmorillonite was higher than for Ca2+ and crude -montmorillonites. XRD measurements showed expansion of d-spacing of montmorillonite samples with the increase in diHPA loading from 12.32, 12.66 and 12.17 Ĺ for Fe3+- Ca2+- and crude-montmorillonite up to 16.84, 16.62 and 16.79 Ĺ for organo-clay complexes of Fe3+-, Ca2+- and crude-montmorillonites respectively. This significant expansion of d-spacing suggests interlayer, and probably, multilayer diHPA adsorption by montmorillonite. Based on FTIR data we suggest that diHPA forms inner-sphere complexes with Fe3+-montmorillonite surface but not with Ca2+ and crude-montmorillonites. However all montmorillonite samples induce esterification and oligomerization of the monomers, which was demonstrated by FTIR spectra of the organo-montmorillonite complexes and by LC-MS analysis of the organic material extracted from organo-clay complexes. These results confirmed our hypothesis about oligomerization of cuticular monomers on mineral surfaces. We assume that esterification and oligomerization of monomers on montmorillonite surfaces simulate similar soil processes, which result in the formation of soil organo-mineral complexes and humin.

Olshansky, Yaniv; Polubesova, Tamara; Chefetz, Benny

2013-04-01

5

Ion exchange and surface charge on montmorillonite clay  

SciTech Connect

An ion-exchange model originally developed for pure oxides prepared in the laboratory is extended to study of ion exchange and surface charge on a naturally occurring montmorillonite clay. The range of surface charges measured for montmorillonite with various electrolyte solutions and clay pretreatments is within the range of those measured for a wide variety of oxides prepared in the laboratory, including MnO{sub 2}-IC1, MnO{sub 2}-IC12, MnO{sub 2}-IC22, titanium dioxide, ferric oxide, and aluminum oxide. In addition, fitted parameter values for lateral interaction constants and equilibrium constants for the acid sites that characterize ion exchange on montmorillonite are on the same order of magnitude as those obtained for pure oxides. Surface charge of montmorillonite in sodium nitrate solution is measured to be approximately 15 to 25% greater than that measured between a pH of 4 and 9 in calcium chloride solution. This difference is attributed to the greater charge on the calcium (2{sup +}) ion; thus, its stronger electrostatic attraction to the acid hydroxyl site. An order of magnitude change in solids concentration (C{sub p}) can lead to a difference in measured net surface charge density of the same oxide sample of several orders of magnitude. This difference increases at higher pH, indicating the importance of reporting the corresponding C{sub p} at which experiments are conducted.

Sperry, J.M.; Peirce, J.J.

1999-05-01

6

RTV silicone rubber filled with surface modified montmorillonite  

Microsoft Academic Search

The surface modification of pristine montmorillonite (MMT) with four kinds of coupling agents for reinforcement of the room temperature vulcanized vinyl-terminated polydimethylsiloxane (RTV PDMS) networks was investigated. The four coupling agents containing ?-glycidoxypropyltrimethoxysilane (KH-560), ?-methacryloxypropyltrimethoxysilane (KH-570), isopropyl trioleic titanate (NDZ-105) and stearic acid (SA) without N, P, or S compounds were used because they were harmless to the platinum catalyst

Zhenmei Jia; Shuangjun Chen; Jun Zhang

2012-01-01

7

Thermo-XRD-analysis of montmorillonite treated with protonated Congo-red. Curve fitting  

Microsoft Academic Search

The adsorption of protonated Congo red (CR) by montmorillonite was investigated by thermo-XRD-analysis. Montmorillonite was loaded at pH 1 with increasing amounts of CR up to 75 mmol per 100 g clay. Diffractograms of samples treated at 420 °C showed broad peaks and were curve-fitted to determine the different basal spacings, which composed the XRD peaks. The broad peak of

Z. Yermiyahu; I. Lapides; S. Yariv

2005-01-01

8

Characterization of montmorillonite surfaces after modification by organosilane.  

SciTech Connect

X-ray powder diffraction (XRD), thermal gravimetric analysis (TGA), surface area measurements, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy were used to examine the surface properties of organosilane-modified smectite-type aluminosilicate clays. Organic modified clays derived from the reactions of montmorillonite (containing 93-95% montmorillonite from a bentonite, <1% quartz, and 4-6% opal CT) with octadecyltrichlorosilane (C{sub 18}H{sub 37}SiCl{sub 3}) and octadecyltrimethoxysilane [C{sub 18}H{sub 37}Si(OMe){sub 3}] are highly hydrophobic. Surface loadings of the modified clays depend on the organosilane and the solvent, and they range from 10 to 25 wt. %. The organic species are probably adsorbed to the outer surfaces and bound to the edges of the clay via condensation with edge-OH groups. Encapsulation of montmorillonite with C{sub 18}H{sub 37}SiCl{sub 3} and C{sub 18}H{sub 37}Si(OMe){sub 3} resulted in hydrophobic coating that acts like a 'cage' around the clay particles to limit diffusion. Basal spacings of the organic modified clays remain at {approx}15 {angstrom} upon heating to 400{sup o}C in N{sub 2}, whereas those of unmodified clays collapse to {approx}10 {angstrom}. A considerable reduction in surface area (by 75-90%) for organic modified clays is observed, which is consistent with the existence of a surface coating. The solvent used can affect the amount of organic silane coated on the clay particles, whereas the difference between the products prepared using C{sub 18}H{sub 37}SiCl{sub 3} and C{sub 18}H{sub 37}Si(OMe){sub 3} in the same solvent is relatively small. The carbon and oxygen K-edge NEXAFS spectroscopy of the modified montmorillonite surfaces showed that surface coatings on the outside of the clay particles exist. The encapsulating system may allow for economical remediation and storage of hazardous materials.

Song, K.; Sandi, G.; Chemistry

2001-04-01

9

Adhesion of silver nanoparticles on the montmorillonite surface  

Microsoft Academic Search

Adhesion of silver nanoparticles on the montmorillonite substrate was investigated using molecular modeling (force field calculations) and experiment (infrared spectroscopy, high-resolution transmission electron microscopy). Modeling revealed the preferred orientation of silver nanoparticles on the silicate substrate and showed the strong dependence of total energy and stability of nanocomposite structure on two factors: (1) the mutual crystallographic orientation of nanoparticle and

Jonás Tokarský; Pavla ?apková; Volker Klemm; David Rafaja; Jana Kukutschová

2010-01-01

10

Effect of calcium ion and montmorillonite clay on bitumen displacement by water on a glass surface  

Microsoft Academic Search

Experiments were conducted to study the effect of calcium ion and montmorillonite clay on bitumen displacement by an aqueous phase on a glass surface. Upon exposure to an aqueous environment containing calcium ion and clays, a thin coating of bitumen on a glass surface displaced spontaneously in the inward radial direction. The initially circular bitumen disk took the shape of

Suddhasatwa Basu; K. Nandakumar; Steven Lawrence; Jacob Masliyah

2004-01-01

11

Surface area of montmorillonite from the dynamic sorption of nitrogen and carbon dioxide  

USGS Publications Warehouse

Surface area determinations were made on a montmorillonite with various cations emplaced on the exchangeable sites, utilizing nitrogen and carbon dioxide as adsorbates at 77 ??K and 195 ??K, respectively, in a dynamic system. From the fraction of a Mississippi montmorillonite less than about 1 ?? in size, samples were prepared by replacing the original exchangeable cations with Li+, Na+, K+, Rb+, Cs+, Mg++, Ca++, Ba++, and NH4+, forming a series of homoionic montmorillonite species. Surface areas from 3-point B.E.T. plots (half-hour adsorption points), with nitrogen as the adsorbate, ranged from 61 m2/g for Li-montmorillonite to 138 m2/g for Cs-montmorillonite, thus reflecting a certain degree of nitrogen penetration between layers. Complete penetration should theoretically result in a surface area of over 300 m2/g for this clay with a nitrogen monolayer between each pair of platelets. The experimental data indicate that the extent of penetration is time-dependent and is also a function of the interlayer forces as governed by the size and charge of the replaceable cation. This finding negates the generally accepted concept that nitrogen at 77 ??K does not penetrate the layers and provides a measure only of the external surface of expandable clay minerals. A further measure of the variation of interlayer forces is provided by the adsorption of carbon dioxide at 195 ??K. Surface area values ranged from 99 m2/g for Li-montmorillonite to 315 m2/g for Csmontmorillonite. Although the carbon dioxide molecule is larger than the nitrogen molecule, its greater penetration apparently is a result of its being kinetically more energetic (with a larger diffusion coefficient) at its higher adsorption temperature. Similar differences have been found with both adsorbates in the study of microporous substances, such as coal, where activated diffusion is of considerable significance. ?? 1968.

Thomas, Jr. , J.; Bohor, B. F.

1968-01-01

12

Behind adhesion of uranyl onto montmorillonite surface: A molecular dynamics study.  

PubMed

We have performed molecular dynamics simulations to investigate the adsorption of radionuclide elements species onto substituted Montmorillonite (001) surface in the presence of different counterions. The structure and the dynamics of uranyl ion as well as its aquo, chloride ion, and carbonate complexes are analyzed. In addition, we have studied the surface energy between layered Montmorillonite sheets and the work of adhesion between radionuclide and charged Montmorillonite. The clay model used here is a Wyoming-type Montmorillonite with 0.75e negative charge per unit cell resulting from substitutions in Octahedral and Tetrahedral sheets. The system model was constructed based on CLAYFF force field potential model. To evaluate the thermodynamic work of adhesion, each surface and clay layer regions are converted to a thin film model. One and two species of radionuclide elements (UO2(H2O)5,UO2CO3(H2O)5, and UO2Cl2(H2O)5) were deposited near the clay surface in a pseudo-two-dimensional periodic cell. Analysis shows that the uranyl ion structure is preserved with two axial oxygen atoms detected at 1.8?. Radial distribution functions results indicate that average UOw distances are 2.45-2.61?, and 2.29-2.40? for UOc distance. Average UCl distances are 2.78-3.08?, which is relatively larger than that of Uranium atom-Oxygen atom because of electrostatic factors. PMID:23933290

Yang, W; Zaoui, A

2013-07-24

13

Size effects of exchange cation on the pore structure and surface fractality of montmorillonite  

SciTech Connect

Ca-montmorillonites were exchanged with both metal cations (manganese and copper) and organic cations (tetramethylammonium (TMA) and hexadecyltrimmethylammonium (HDTMA)) to study the cation size effects on the pore structure and surface roughness of montmorillonite based on the classical and fractal analysis of their nitrogen adsorption isotherms. The surface fractal dimension D was calculated from their nitrogen isotherms with the aid of the recently proposed Neimark equation. The decrease of BET surface area of montmorillonite induced by the larger size of exchange cation was interpreted with both the coverture of some surface roughness (surface screening effect) and the inhibition of nitrogen molecule into some pores (pore blocking effect). The pore blocking effect was examined with the changes of mean pore size. Meanwhile, the D value was used to examine whether or not the surface screening effect existed. It was concluded that the combination of classical and fractal analyses of nitrogen isotherms may facilitate understanding of the evolution of pore and surface structures of clay exchanged with different cations.

Lee, J.F.; Lee, C.K.; Juang, L.C.

1999-09-01

14

Surface and Fouling-Release Properties of Silicone\\/Organomodified Montmorillonite Coatings  

Microsoft Academic Search

Poly(dimethylsiloxane) (PDMS)\\/organomodified montmorillonite (OMMT) nanocomposites have been prepared, characterised and the fouling-release properties of these materials have been studied through laboratory assays involving a representative soft-fouling species, the green alga, Ulva. The bulk mechanical properties of the polymer matrix have been slightly changed by the addition of OMMT, i.e., to a higher Young's modulus value. The surface properties of the

Alexandre Beigbeder; Céline Labruyčre; Pascal Viville; Michala E. Pettitt; Maureen E. Callow; James A. Callow; Leila Bonnaud; Roberto Lazzaroni; Philippe Dubois

2011-01-01

15

Photochemical behaviour of phenylbenzoquinone at the surface of the clays: Kaolinite, bentonite and montmorillonite  

Microsoft Academic Search

The kinetics of direct photochemical transformation of phenylbenzoquinone (PhQ) was studied at the surface of clays, light absorbing and scattering supports. When compared to the spectrum in solution, the UV absorption of PhQ on clays shows a hyperchromic as well as a solvatochromic effects. In kaolinite, bentonite and montmorillonite, the shift was about ??=30nm and the molar absorption coefficient was

Mattieu Menager; Marie Siampiringue; Mohamed Sarakha

2009-01-01

16

Molecular modeling of surface modification of Wyoming and Cheto montmorillonite by methylene blue.  

PubMed

The surface area of various types of montmorillonites (MMT) with different values of layer charge plays a very important role in surface arrangement of methylene blue cations (MB). Photoluminescence measurements can be strongly or partially influenced by this surface arrangement of cations. For these reasons and on the basis of our previous results, molecular simulations were performed for various types of montmorillonites covered with methylene blue cations. Adsorption of methylene blue cations on Na-Wyoming MMT surface is different from Ca-Cheto MMT. In the case of Wyoming with a lower layer charge, MB cations lie parallel to the silicate layer for all investigated samples. On the other hand, Cheto surface is covered with a higher amount of MB cations. The results obtained from molecular modeling indicate that MB lies parallel to low loading case and become tilted with respect to layer for a higher loading. Moreover, a higher amount of MB cations covering the silicate layer are much less energy-stable. A higher loading of MB cations leads to aggregates but at low loading MB cations degrade to monomers. PMID:19418076

Kovár, Petr; Pospísil, Miroslav; Malý, Petr; Klika, Zdenek; Capková, Pavla; Horáková, Petra; Valásková, Marta

2009-05-06

17

Theoretical study of the adsorption of DNA bases on the acidic external surface of montmorillonite.  

PubMed

In the present study, DFT periodic plane wave calculations, at the PBE-D level of theory, were carried out to investigate the interaction of DNA nucleobases with acidic montmorillonite. The surface model was considered in its octahedral (Osub) and tetrahedral (Tsub) substituted forms, known to have different acidic properties. The adsorption of adenine, guanine and cytosine was considered in both orthogonal and coplanar orientations with the surface, interacting with the proton via a given heteroatom. In almost all considered cases, adsorption involved the spontaneous proton transfer to the nucleobase, with a more pronounced character in the Osub structures. The binding energy is about 10 kcal mol(-1) larger for Osub than for Tsub complexes mainly due to the larger acidity in Osub surfaces and due to the better stabilization by H-bond contacts between the negatively charged surface and the protonated base. The binding energy of coplanar orientations of the base is observed to be as large as the orthogonal ones due to a balance between electrostatic and dispersion contributions. Finally the binding of guanine and adenine on the acidic surface amounts to 50 kcal mol(-1) while that of cytosine rises to 44 kcal mol(-1). PMID:22124483

Mignon, Pierre; Sodupe, Mariona

2011-11-28

18

Montmorillonite surface properties and sorption characteristics for heavy metal removal from aqueous solutions.  

PubMed

Surface properties of montmorillonite (MMT) and its adsorption characteristics for heavy metals have been investigated with nickel and copper as sorbate from aqueous solutions. Employing the potentiometric and mass titration techniques in batch experimental methods, the point of zero charge (PZC) and point of zero net proton charge (PZNPC) of MMT edges at different ionic strengths present pH(PZC) and pH(PZNPC) to be 3.4+/-0.2. A crossing point was observed for the proton adsorption vs. pH curves at different ionic strengths of KCl electrolyte and in investigating MMT remediation potentialities as sorbent for heavy metals polluted waters, the effects of heavy metal concentration, pH, MMT dosage, reaction time and temperature for Cu(2+) and Ni(2+) uptake were studied. The sorption of metal ions by MMT was pH dependent and the adsorption kinetics revealed sorption rate could be well fitted by the pseudo-second-order rate model. The data according to mass transfer and intraparticle diffusion models confirmed diffusion of solutes inside the clay particles as the rate-controlling step and more important for the adsorption rate than the external mass transfer. Adsorption isotherms showed that the uptake of Cu(2+) and Ni(2+) could be described by the Langmuir model and from calculations on thermodynamic parameters, the positive Delta G degrees values at different temperatures suggest that the sorption of both metal ions were non-spontaneous. Change in enthalpy (Delta H degrees) for Ni(2+) and Cu(2+) were 28.9 and 13.27 kJ/mol K respectively, hence an endothermic diffusion process, as ion uptake increased with increase in temperature. Values of DeltaS degrees indicate low randomness at the solid/solution interface during the uptake of both Cu(2+) and Ni(2+) by MMT. Montmorillonite has a considerable potential for the removal of heavy metal cationic species from aqueous solution and wastewater. PMID:19131158

Ijagbemi, Christianah Olakitan; Baek, Mi-Hwa; Kim, Dong-Su

2008-12-03

19

Molecular dynamics simulation of uranyl(VI) adsorption equilibria onto an external montmorillonite surface.  

PubMed

We used molecular dynamics simulations to study the adsorption of aqueous uranyl species (UO(2)(2+)) onto clay mineral surfaces in the presence of sodium counterions and carbonato ligands. The large system size (10,000 atoms) and long simulation times (10 ns) allowed us to investigate the thermodynamics of ion adsorption, and the atomistic detail provided clues for the observed adsorption behavior. The model system consisted of the basal surface of a low-charge Na-montmorillonite clay in contact with aqueous uranyl carbonate solutions with concentrations of 0.027 M, 0.081 M, and 0.162 M. Periodic boundary conditions were used in the simulations to better represent an aqueous solution interacting with an external clay surface. Uranyl adsorption tendency was found to decrease as the aqueous uranyl carbonate concentration was increased, while sodium adsorption remained constant. The observed behavior is explained by physical and chemical effects. As the ionic strength of the aqueous solution was increased, electrostatic factors prevented further uranyl adsorption once the surface charge had been neutralized. Additionally, the formation of aqueous uranyl carbonate complexes, including uranyl carbonato oligomers, contributed to the decreased uranyl adsorption tendency. PMID:16294234

Greathouse, Jeffery A; Cygan, Randall T

2005-09-08

20

Mobility of Na and Cs on montmorillonite surface under partially saturated conditions.  

PubMed

Cs migration in soils at contaminated sites or in clay-rich backfill of waste disposal sites can take place under partially saturated conditions. To understand the molecular mechanism of Cs migration in partially saturated clays, Grand Canonical Monte Carlo simulations were applied to model adsorption of water films onto external surfaces of Cs and Na montmorillonites as function of partial water pressure. The surface complexation and diffusivity of Cs and Na at different partial water pressure was obtained by molecular dynamics simulations. The results suggest that ion mobility in adsorbed water films on external basal surfaces of clay is similar to that in the near-surface water of a saturated pore as far as the thickness of the adsorbed water film is more than two water layers. At lower partial water pressure (i.e., in thinner water films) the ion mobility dramatically decreases. In contrast, the average water mobility in thin water film is higher than in the water-saturated system due to enhanced mobility of water molecules close to vapor-film interface. The results of the simulations were applied to interpret recent laboratory measurements of tritiated water and Cs diffusivity in Callovo-Oxfordian Claystones under partially saturated conditions. PMID:23909661

Churakov, Sergey V

2013-08-19

21

Molecular dynamics simulation of uranyl(VI) sorption equilibria onto an external montmorillonite surface.  

SciTech Connect

We used molecular dynamics simulations to study the adsorption of aqueous uranyl species (UO22+) onto clay mineral surfaces in the presence of sodium counterions and carbonato ligands. The large system size (10 000 atoms) and long simulation times (10 ns) allowed us to investigate the thermodynamics of ion adsorption, and the atomistic detail provided clues for the observed adsorption behavior. The model system consisted of the basal surface of a low-charge Na-montmorillonite clay in contact with aqueous uranyl carbonate solutions with concentrations of 0.027 M, 0.081 M, and 0.162 M. Periodic boundary conditions were used in the simulations to better represent an aqueous solution interacting with an external clay surface. Uranyl adsorption tendency was found to decrease as the aqueous uranyl carbonate concentration was increased, while sodium adsorption remained constant. The observed behavior is explained by physical and chemical effects. As the ionic strength of the aqueous solution was increased, electrostatic factors prevented further uranyl adsorption once the surface charge had been neutralized. Additionally, the formation of aqueous uranyl carbonate complexes, including uranyl carbonato oligomers, contributed to the decreased uranyl adsorption tendency.

Cygan, Randall Timothy; Greathouse, Jeffery A.

2005-06-01

22

Cetylpyridinium aggregates at the montmorillonite- and muscovite-water interfaces: a Monte Carlo study of surface charge effect.  

PubMed

Monte Carlo simulations of the interface between the external surface of montmorillonite and aqueous cetylpyridinium chloride (CPCl) solution at ambient conditions are reported and compared with the preceding simulation study of muscovite. Simulation results reveal that a segregation of inorganic ions into the regions near the montmorillonite-water and bilayer-water interfaces leads to a nearly complete displacement of water molecules from the intermediate region of the bilayer aggregate. Such segregation does not occur for muscovite because of a considerably higher surface concentration of inorganic cations compensating its mineral charge. The presence of hydrated inorganic ions in the interfacial region containing the aliphatic part of the bilayer aggregate on muscovite leads to a more compact aggregate structure in agreement with a previously experimentally observed effect of added electrolyte. It also results in a lateral segregation of hydrophilic and hydrophobic clusters in this region in agreement with earlier experimental observations of striped surfactant structures on the muscovite surface. A configuration of the surfactant adsorption complex is found to strongly depend on the water content at the mineral-aggregate interface and suggested to be controlled by the types of inorganic counter- and co-ions present there. A transformation between characteristic configurations of the surfactant adsorption complexes is proposed as an explanation for previous experimental observations of the slow secondary surfactant adsorption. PMID:19351106

Meleshyn, Artur

2009-06-01

23

Effect of pH in an Aqueous Medium on the Surface Area, Pore Size Distribution, Density, and Porosity of Montmorillonite  

Microsoft Academic Search

Surface area, pore volume distribution, and porosity of montmorillonite are determined after being exposed to aqueous solutions with various pH values. For measurement, after each pH treatment the clay samples were freeze–dried in order to keep the structure of the clay same as that in the aqueous solution. Surface area and pore size distribution measurements were performed on an unmodified

Orhan Altin; H. Önder Özbelge; Timur Dogu

1999-01-01

24

Cadmium ion adsorption controls the growth of CdS nanoparticles on layered montmorillonite and calumit surfaces  

SciTech Connect

Adsorption isotherms have been determined for the intercalation of cadmium ions (Cd{sup 2+}) into layered hydrophobized montmorillonite (HDP-M) and calumit (DBS-C) sheets dispersed in ethanol (1)-cyclohexane (2) mixtures. The amount of Cd{sup 2+} adsorbed depended strongly on the composition of the binary liquid; at an ethanol mole fraction of 0.05 (x{sub 1} = 0.05), 95% of the added Cd{sup 2+} is located in the ethanolic nanoreactor at the HDP-M (or DBS-C) surface. CdS nanoparticles have been generated in situ in ethanolic nanoreactors at the HDP-M and DBS-C surfaces. Absorption spectrophotometric measurements provided information on the number of CdS nanoparticles formed and on their absorption edges, bandgaps, and mean diameters. Good correlations have been obtained between the adsorption isotherms and the size (and the amount) of the CdS formed. X-ray diffractometry established that CdS nanoparticles stretched the HDP-M and DBS-C lamellas unevenly upon intercalation.

Dekany, I.; Turi, L. [Hungarian Academy of Sciences (Hungary); Galbacs, G. [Attila Jozsef Univ., Szeged (Hungary). Dept. of Inorganic and Analytical Chemistry; Fendler, J.H. [Clarkson Univ., Potsdam, NY (United States). Center for Advanced Materials Processing

1999-05-15

25

Water structure and aqueous uranyl(VI) adsorption equilibria onto external surfaces of beidellite, montmorillonite, and pyrophyllite: results from molecular simulations.  

PubMed

Molecular dynamics simulations were performed to provide a systematic study of aqueous uranyl adsorption onto the external surface of 2:1 dioctahedral clays. Our understanding of this key process is critical in predicting the fate of radioactive contaminants in natural groundwaters. These simulations provide atomistic detail to help explain experimental trends in uranyl adsorption onto natural media containing smectite clays. Aqueous uranyl concentrations ranged from 0.027 to 0.162 M. Sodium ions and carbonate ions (0.027-0.243 M) were also present in the aqueous regions to more faithfully model a stream of uranyl-containing groundwater contacting a mineral system comprised of Na-smectite. No adsorption occurred near the pyrophyllite surface, and there was little difference in uranyl adsorption onto the beidellite and montmorillonite, despite the difference in location of clay layer charge between the two. At low uranyl concentration, the pentaaquouranyl complex dominates in solution and readily adsorbs to the clay basal plane. At higher uranyl (and carbonate) concentrations, the mono(carbonato) complex forms in solution, and uranyl adsorption decreases. Sodium adsorption onto beidellite occurred both as inner- and outer-sphere surface complexes, again with little effect on uranyl adsorption. Uranyl surface complexes consisted primarily of the pentaaquo cation (85%) and to a lesser extent the mono(carbonato) species (15%). Speciation diagrams of the aqueous region indicate that the mono(carbonato)uranyl complex is abundant at high ionic strength. Oligomeric uranyl complexes are observed at high ionic strength, particularly near the pyrophyllite and montmorillonite surfaces. Atomic density profiles of water oxygen and hydrogen atoms are nearly identical near the beidellite and montmorillonite surfaces. Water structure therefore appears to be governed by the presence of adsorbed ions and not by the location of layer charge associated with the substrate. The water oxygen density near the pyrophyllite surface is similar to the other cases, but the hydrogen density profile indicates reduced hydrogen bonding between adsorbed water molecules and the surface. PMID:16830554

Greathouse, Jeffery A; Cygan, Randall T

2006-06-15

26

Effect of pH in an aqueous medium on the surface area, pore size distribution, density, and porosity of montmorillonite  

SciTech Connect

Surface area, pore volume distribution, and porosity of montmorillonite are determined after being exposed to aqueous solutions with various pH values. For measurement, after each pH treatment the clay samples were freeze-dried in order to keep the structure of the clay same as that in the aqueous solution. Surface area and pore size distribution measurements were performed on an unmodified and four pH (2.5, 4.0, 5.5, 9.0)-adjusted clay samples using N{sub 2} and CO{sub 2} as adsorbates. The surface area measurements at lower pH are lower than those measured at higher pH due to the replacement of Na{sup +} ions from interlayers at lower pH which may be followed by the reduction of repulsive forces. As the pH of the montmorillonite increases to 9.0, the surface area increases almost seven times compared to that at pH 2.5. Pore size distribution was determined by CO{sub 2} adsorption at 273 K for micropores (<20 {angstrom}), by N{sub 2} adsorption at 77 K for mesopores (between 20 and 500 {angstrom}), and by using both Hg intrusion and N{sub 2} adsorption for macropores (>500 {angstrom}). Since N{sub 2} molecules undergo a molecular sieving at 77 K, CO{sub 2} gas at 273 K was used to measure the micropore surface area and gave higher surface area measurements than those measured by N{sub 2}. Surface area values measured by CO{sub 2} adsorption ranged between 30 and 200 m{sup 2}/g for montmorillonite while those measured by N{sub 2} adsorption were 13.7--70 m{sup 2}/g in the pH range studied.

Altin, O.; Ozbelge, H.O.; Dogu, T.

1999-09-01

27

Adsorption of phenol and nitrophenol isomers onto montmorillonite modified with hexadecyltrimethylammonium cation  

SciTech Connect

Single- and two-component competitive adsorptions were carried out in a batch adsorber to investigate the adsorption behavior of phenol and 2-, 3-, and 4-nitrophenols in aqueous solution at 25 C onto hexadecyltrimethylammonium (HDTMA)-treated montmorillonite. HDTMA cation was exchanged for metal cations on the montmorillonite to prepare HDTMA-montmorillonite, changing its surface property from hydrophilic to organophilic. Effective solid diffusivity of HDTMA cation in the montmorillonite particle was estimated to be about 3 {times} 10{sup {minus}12} cm{sup 2}/s by fitting the film-solid diffusion model to a set of HDTMA adsorption kinetic data onto montmorillonite. Adsorption affinity on HDTMA-montmorillonite was found to be in the order 3-nitrophenol {approx} 4-nitrophenol > 2-nitrophenol > phenol. The Langmuir and the Redlich-Peterson (RP) adsorption models were used to analyze the single component adsorption equilibria. The ideal adsorbed solution theory (IAST) and the Langmuir competitive model (LCM) were used to predict the multicomponent competitive adsorption equilibria. These models yielded favorable representations of both individual and competitive adsorption behaviors.

Kwon, S.C.; Song, D.I.; Jeon, Y.W. [Kyungpook National Univ., Taegu (Korea, Republic of)

1998-09-01

28

Elaboration et caracterisation de nanocomposites polyethylene/montmorillonite  

NASA Astrophysics Data System (ADS)

This research project consists in preparing polyethylene/montmorillonite nanocomposites for film packaging applications. Montmorillonite is a natural clay with an exceptional aspect ratio. In recent years, its incorporation in polymer matrices has attracted great interest. The pioneer work from Toyota on polyamide-6/montmorillonite composites has shown that it was possible to disperse the clay at a nanometric scale. Such a structure, so-called exfoliated, leads to a significant increase in mechanical, barrier and fire retardant properties, even at low volumetric fractions of clay. This allows a valorization of the polymeric material at moderate cost. Due to its high polarity, montmorilloite exfoliation in polymeric matrices is problematic. In the particular case of polyolefin matrices, the platelets dispersion remains limited: most frequently, the composites obtained exhibit conventional structures (microcomposites) or intercalated structures. To solve this problem, two techniques are commonly employed: the surface treatment of the clay, which allows the expansion of the interfoliar gallery while increasing the affinity between the clay and the polymer, and the use of a polar compatibilizing agent (grafted polyolefin). The first part of this thesis deals with the preparation and the characterization of highly thermally stable organophilic montmorillonites. Commercial organophilic montmorillonites are treated with quaternary ammonium intercalating agents. However, those intercalating agents present a poor thermal stability and are susceptible to decompose upon processing, thus affecting the clay dispersion and the final properties of the nanocomposites. In this work, it was proposed to modify the clay with alkyl pyridinium, alkyl imidazolium and alkyl phosphonium intercalating agents, which are more stable than ammonium based cations. Organophilic montmorillonites with enhanced thermal stabilites compared to commercial organoclays (+20°C to +70°C) were prepared. The effect of the chemical structure of the intercalating agent on the capacity of the organoclay to be dispersed in polyethylene matrices was analyzed. In addition, the influence of the dispersion on the thermal stability of the nanocomposites prepared is discussed. In a second part, the effect of the compatibilizing agent characteristics on the quality of the clay dispersion in polyethylene/montmorillonite nanocomposites was analyzed. The mechanical properties and the oxygen permeability of the nanocomposites were evaluated and related to the level of clay delamination and to the strength of the polymer/clay interface, which was evaluated through surface tension measurements.

Stoeffler, Karen

29

Preparation and properties of hybrids of organo-soluble polyimide and montmorillonite with various chemical surface modification methods  

Microsoft Academic Search

Montmorillonite (MMT)\\/Organo-soluble polyimide (PI) hybrids were prepared using a monomer solution intercalation polymerization method. The organo-soluble polyimide was based on pyromellitic dianhydride and 4,4?-diamino-3,3?-dimethyldiphenylmethane. The MMT was organo-modified with three types of intercalation agents: amino acids, primary aliphatic amines and quaternary ammonium salt. The dispersion behavior of MMT in organic solvents and polyimide depends on the type of the functional

Yong Yang; Zi-kang Zhu; Jie Yin; Xin-yu Wang; Zong-eng Qi

1999-01-01

30

Isomerisation of ?-pinene using modified montmorillonite clays  

Microsoft Academic Search

Liquid phase catalytic isomerisation of ?-pinene with natural Indian Montmorillonite modified by sulphuric acid treatment and cation exchange was studied. More than 96% ?-pinene conversion is observed for acid treated clays with camphene selectivity ranging from 39 to 49%. For acid treated clays prepared by treating with low normality acid (1–4N), limonene is the main product whereas clay samples prepared

Mukesh Kr Yadav; Chintansinh D Chudasama; Raksh V Jasra

2004-01-01

31

Synthesis and Properties of Titanium Oxide Cross-Linked Montmorillonite  

Microsoft Academic Search

Abstract-- Titanium was introduced into the montmorillonite structure by cation exchange with polymeric Ti cations, formed by partial hydrolysis of TIC1, in HC1. On further hydrolysis and heating, TiO2 pillars in the form of anastase were formed between the montmorillonite layers. The resulting TiOE-Cross-linked montmorillonites possessed surface areas in the range 200-350 m2\\/g and pore volumes of about 0.2 cm3\\/g

Johan Sterte

1986-01-01

32

Impact modified epoxy\\/montmorillonite nanocomposites: synthesis and characterization  

Microsoft Academic Search

Diglycidyl ether of bisphenol A type epoxy resin-polyether polyol-organically treated montmorillonite ternary nanocomposites were synthesized in this study. The effects of addition of polyether polyol as an impact modifier on morphological, thermal and mechanical properties of nanocomposites were investigated by X-ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry, impact and tensile testing. The results showed that organically treated montmorillonite

Isil Isik; Ulku Yilmazer; Goknur Bayram

2003-01-01

33

Nickel sorption mechanisms in a pyrophyllite-montmorillonite mixture  

SciTech Connect

Nickel sorption on pyrophyllite, montmorillonite and a 1:1 pyrophyllite-montmorillonite mixture was studied at pH 7.5 and a reaction time of 40 min. The main modes of Ni uptake under these reaction conditions are adsorption on montmorillonite and surface precipitation on pyrophyllite. For the clay mixture, where adsorption on the montmorillonite component and surface precipitation on the pyrophyllite component compete for Ni uptake, X-ray absorption fine structure spectroscopy (XAFS) was used to estimate the distribution of Ni over the mixture components. This was done by comparison to pyrophyllite-montmorillonite mixtures with known Ni distributions over the mixture components. Nickel uptake on singly reacted pyrophyllite was slightly higher than on singly reacted montmorillonite. This was consistent with the XAFS results for the clay mixture, which suggested that the pyrophyllite component sorbed slightly more Ni than the Montmorillonite component. The findings suggested that both adsorption and surface precipitation were important mechanisms in the overall Ni uptake in the clay mixture, and that neither sorption mechanism truly out-competed the other in the reaction time of 40 min employed. Therefore, both mechanisms should be considered when modeling Ni sorption in similar systems.

Elzinga, E.J.; Sparks, D.L. [Univ. of Delaware, Newark, DE (United States). Dept. of Plant and Soil Sciences

1999-05-15

34

The adsorption of nucleotides and polynucleotides on montmorillonite clay  

NASA Astrophysics Data System (ADS)

The binding of adenine derivatives to Na+-montmorillonite increases in the order 5'-AMP, 3'-AMP, 5'-ADPmontmorillonite surface and binding is a consequence of the electrostatic interaction between the protonated base and the negative charges on the surface of the montmorillonite. Different binding trends were observed with Cu2+-montmorillonite with AMP binding more strongly than adenosine and UMP binding more strongly than uridine. It is concluded that ligation to the Cu2+ is a major force in the binding of nucleotides to Cu2+-montmorillonite. RNA homopolymers exhibit strong adsorption to Na+- and Cu2+-montmorillonite and are not readily washed from the clay. Factors contributing to the binding are discussed. Watson-Crick hydrogen bonding of 5'-AMP to poly(U) and 5'-GMP to poly(C) was observed when the homopolymers are bound to the surface of the clay. No association of 5'-UMP to poly(U) bound to clay was detected. The possible role of montmorillonite clays in the prebiotic formation of RNA is discussed.

Ferris, James P.; Ertem, Gözen; Agarwal, Vipin K.

1989-03-01

35

The limited swelling of montmorillonite  

SciTech Connect

The attraction forces responsible for the occurrence of limited swelling of montmorillonite having divalent counterions were evaluated from (a) the electrostatic attraction between the negative charges of one surface and the effective charges of the counterions of the other interlayer surface and (b) van der Waals attraction between the two interlayer surfaces. Both methods of calculation almost account for the force required to maintain limited swelling of the clay. It is found that a Hamaker constant of 2.25 {times} 10{sup {minus}13} erg in place of 2.72 {times} 10{sup {minus}13} erg and a counterion charge screening factor of 0.82[1 {minus} exp({minus}{kappa}{chi})] in place of [1 {minus} exp({minus}{kappa}{chi})] reproduce the true value of the attraction force.

Helmy, A.K. [Univ. Nacional del Sur, Bahia Blanca (Argentina)

1998-11-01

36

Characterization of TDMAC-Heparin Treated Surfaces.  

National Technical Information Service (NTIS)

TDMAC-heparin treated polymer samples were provided for nine programs within the Biomaterials Program. Materials treated included Silastic, RTV Silastic, SRI polyurethane, Lexan, polyvinylchloride, polyurethane, polypropylene, polycarbonate, glass, and Lu...

J. P. Crowly R. I. Leininger

1977-01-01

37

On exfoliation of montmorillonite in epoxy  

Microsoft Academic Search

Nanocomposite formation of octadecyl amine treated montmorillonite clays in epoxy was investigated by small-angle X-ray scattering and atomic force microscopy. When diglycidyl ether of bisphenol A (DGEBA) was cured with equimolar or higher amounts of meta-phenylene diamine (MPDA), only intercalated nanostructures were obtained. Exfoliated nanocomposites were formed with DGEBA cured with less than stoichiometric amounts of MPDA or with auto-polymerization

In-Joo Chin; Thomas Thurn-Albrecht; Ho-Cheol Kim; Thomas P. Russell; Jing Wang

2001-01-01

38

Effect of modified montmorillonites on the biodegradation and adsorption of biomarkers such as hopanes, steranes and diasteranes.  

PubMed

The effect of modified montmorillonites on the biodegradation and adsorption of selected steranes, diasteranes and hopanes was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The unmodified montmorillonite was treated with didecyldimethylammonium bromide, hydrochloric acid and the relevant metallic chloride to produce organomontmorillonite, acid activated montmorillonite and homoionic montmorillonite respectively which were used in this study. The study indicated that organomontmorillonite, acid activated montmorillonite and potassium montmorillonite did not support the biodegradation of the selected steranes, diasteranes and hopanes as alteration of the biomarkers via biodegradation varied from a paltry 2-6 %. The adsorption of the selected biomarkers on acid activated montmorillonite and organomontmorillonite was also poor. However, adsorption of the biomarkers on potassium montmorillonite was relatively high. Sodium montmorillonite and unmodified montmorillonite appear to stimulate the biodegradation of the selected biomarkers moderately (30-35 %) with adsorption occurring at low level. Calcium montmorillonite and ferric montmorillonite effected significant biodegradation (51-60 %) of the selected biomarkers. PMID:23749373

Ugochukwu, Uzochukwu C; Head, Ian M; Manning, David A C

2013-06-01

39

Immobilization of zinc and cadmium by montmorillonite compounds: Effects of aging and subsequent acidification  

SciTech Connect

The addition of aluminum treated montmorillonites as binding agents that immobilize heavy metals is an innovative approach for the remediation of arable soils polluted with heavy metals. The authors investigated the influence of aging and subsequent sudden acidification on the binding of zinc and cadmium by montmorillonite, Al-montmorillonite and Al{sub 13}-montmorillonite increased, probably due to a partial incorporation in the aluminum hydroxide lattice. Sorption and desorption were hysteretic with respect to pH, i.e., desorption required lower pH values that adsorption to reach the same state of metal partitioning between solid phase and solution. In addition, these minerals enhance the pH buffer capacity of the soil. The results suggest that Al-montmorillonite and Al{sub 13}-montmorillonite are suitable minerals to be used as binding agents for the gentle immobilization of heavy metals in polluted soils.

Lothenbach, B.; Furrer, G.; Schaerli, H.; Schulin, R. [ETH Zurich (Switzerland). Inst. of Terrestrial Ecology

1999-09-01

40

Effects of SEBS-G-MA on the Tribological Behaviour of PA66\\/Montmorillonite Nanocomposites  

Microsoft Academic Search

The tribological behaviour of PA66, PA66\\/Montmorillonite nanocomposites and PA66\\/(SEBS-g-MA+Montmorillonite) nanocomposites was studied by means of a ring-on-block tribometer. The morphologies of the worn surfaces of specimens were observed with a scanning electron microscopy (SEM). Wear of all of the specimens increases with increasing load; meanwhile the friction coefficient decreases. Wear of PA66\\/Montmorillonite is larger than that of PA66. Adding SEBS-g-MA

X. H. Liang

2012-01-01

41

Solar Absorber Surfaces Treated by Femtosecond Laser  

Microsoft Academic Search

Using a femtosecond laser surface structuring technique, we produce technologically important solar absorbers (black aluminum, titanium, tungsten, copper, and stainless steel) with absorptance of about 85-95% over a broad wavelength range from ultraviolet to infrared. Scanning electron microscopy shows that the enhanced absorption of the black metals is caused by a rich variety of nano- and microscale surface structures. The

Anatoliy Y. Vorobyev; Chunlei Guo

2010-01-01

42

Analysis of peptides synthesized in the presence of SAz-1 montmorillonite and Cu(2+) exchanged hectorite.  

PubMed

We have investigated the synthesis of oligopeptides containing glycine and tyrosine in the presence of the clay minerals montmorillonite (non-exchanged, SAz-1) and Cu(2+) exchanged hectorite. In both cases, homopolymers of the two amino acids are formed, as are mixed peptides. In the case of Cu(2+) hectorite, mixed oligopeptides up to trimers are detected in small amounts. For montmorillonite, heterogeneous oligopeptides up to hexamers are detected. Our experiments indicate montmorillonite is more effective in promoting oligopeptide formation than Cu(2+) hectorite. Analysis of the oligopeptide sequences formed on the montmorillonite surfaces indicates preferential synthesis of certain Gly-Tyr sequences over others. PMID:11429201

Porter, T L; Eastman, M P; Bain, E; Begay, S

2001-07-01

43

Immobilization of Pb(II), Cd(II) and Ni(II) ions on kaolinite and montmorillonite surfaces from aqueous medium.  

PubMed

The present study investigates the immobilization of Pb(II), Cd(II) and Ni(II) on clays (kaolinite and montmorillonite) in aqueous medium through the process of adsorption under a set of variables (concentration of metal ion, amount of clay, pH, time and temperature of interaction). Increasing pH favours the removal of metal ions till they are precipitated as the insoluble hydroxides. The uptake is rapid with maximum adsorption being observed within 180 min for Pb(II) and Ni(II) and 240 min for Cd(II). A number of available models like the Lagergren pseudo first-order kinetics, second-order kinetics, Elovich equation, liquid film diffusion and intra-particle diffusion are utilized to evaluate the kinetics and the mechanism of the immobilization interactions. Two isotherm equations due to Langmuir and Freundlich showed good fits with the experimental data. Kaolinite and montmorillonite have considerable Langmuir monolayer capacity with respect to Pb(II), Cd(II) and Ni(II), the values being in the range of 6.8-11.5mg/g (kaolinite) and 21.1-31.1mg/g (montmorillonite). The Freundlich adsorption capacity follows a similar order. The thermodynamics of the immobilization process indicates the same to be exothermic with Pb(II) and Ni(II), but endothermic with Cd(II). The interactions with Pb(II) and Ni(II) are accompanied by decrease in entropy and Gibbs energy while the endothermic immobilization of Cd(II) is supported by an increase in entropy and an appreciable decrease in Gibbs energy. The results have established good potentiality for kaolinite and montmorillonite to remove heavy metals like Pb(II), Cd(II) and Ni(II) from aqueous medium through adsorption-mediated immobilization. PMID:17499423

Sen Gupta, Susmita; Bhattacharyya, Krishna G

2007-05-11

44

Laser beam surface treating and coating  

SciTech Connect

This book presents information on selected laser beam treatments of materials. The authors discuss how the promising aspects of existing and future applications of the new heat source laser will have a stimulating effect on the laser surfacing community, with increased consideration from industry regarding the unique possibilities in metallurgy, automation, and increase of process-economy.

Sepoid, G. (Bremer Inst. fuer Angewandte Strahltechnik, Bremen (Germany, F.R.))

1988-01-01

45

EFFECT OF ACIDITY IN MONTMORILLONITE INTERLAYERS ON THE SORPTION OF ANILINE DERIVATIVES  

Microsoft Academic Search

Sorption of aniline and its derivatives by montmorillonite substituted by cations of widely different acidity depends upon the polarizing power of the interlayer cations. Infra-red spectra indicate that the anilines are mostly bound to the interlayer cations through water molecules, except in Cs montmorillonite, where bonding to the oxygen surfaces of the alumino-silicate sheets seems to predominate. Anilines are weak

N. KAUFHERR

46

Direct measurement of the relation between interlayer force and interlayer distance in the swelling of montmorillonite  

Microsoft Academic Search

The relationship between interlayer repulsive force and interlayer separation for a series of montmorillonites with a wide range of measured surface charge densities was studied. Successively higher pressures were applied by a nitrogen gas piston to montmorillonite in a closed chamber between the piston and a porous ceramic plate in contact with a solution of sodium chloride maintained at atmospheric

B. E. Viani; P. F. Low; C. B. Roth

1983-01-01

47

Effect of in-situ bonding system and surface modification of montmorillonite on the properties of butyl rubber/MMT composites  

NASA Astrophysics Data System (ADS)

Isobutylene-isoprene rubber (IIR)/nanoclay composites were prepared by solution intercalation method. Cloisite Na+ nanoclays and organo-modified montmorillonite (OMT) Cloisite 10 A,.15 A and 20 A were used in this study. The effect of In-situ bonding system HRH (hexametylene tetramine: resorcinol: hydrated silica) on the dispersion of used nanoclays in the rubber matrix were examined by X-ray diffraction and atomic force microscopy (AFM). Characterization of the prepared composites was performed by studying the rheometeric and mechanical properties. The burning out behavior of the nanocomposites with and without the bonding system was also measured.

Halim, S. F.; Lawandy, S. N.; Nour, M. A.

2012-07-01

48

The relationship between acidic activation and microstructural changes in montmorillonite from Heping, China.  

PubMed

The montmorillonite sample from Heping, China had been studied by chemical analysis, XRD, IR, AFM and MAS NMR. The results showed that acid concentration had much influence on surface structure of montmorillonite. When the acid concentration reached 2M, the Q3Si structure in silica-oxygen tetrahedron recombined, some Q3Si structure in montmorillonite transformed to distortion Q3Si structure and Q4Si structure. However, the structure of Al had no changes, according with the observation results of atomic force microscope. The Brřnsted acid site of montmorillonite increases with the accretion of the concentration of acid activation, while oversize concentration of acid activation will decrease the surface site of montmorillonite. PMID:15979936

Wu, Pingxiao; Ming, Caibing

2005-06-24

49

A model for metal adsorption on montmorillonite  

SciTech Connect

A consistent thermodynamic model is developed for metal sorption on expanding 2:1 layer clays such as montmorillonite. The particle of clay, including lamellae and interlayers, is represented as a porous solid bearing a permanent negative charge (resulting from isomorphic substitution) with an infinite plane interface (i.e., edges) with the solution. Cation exchange occurs inside the clay particle as the result of the negative potential of the clay. Surface complexation reactions take place at the interface whose surface charge and potential are pH dependent. The potential in the bulk of the clay and near the interface, as well as the surface potential-surface charge density relation, are calculated taking into account the effect of the permanent negative charge. The results are discussed and compared with the classic Gouy-Chapman theory. A subroutine (Clayeql) with the new potential-charge relationships is implemented in the thermodynamic equilibrium program Mineql + 3.0 and is used to fit an extensive published experimental data set on adsorption of transition metals on montmorillonite. The model is shown not only to fit satisfactorily all the data, but also to explain specific features of adsorption on clays compared to oxides. In particular, the increase in the surface concentration of protons with decreasing ionic strength is successfully reproduced and the weaker dependence of metal sorption on pH compared to oxides is correctly fitted.

Kraepiel, A.M.L.; Keller, K.; Morel, F.M.M. [Princeton Univ., NJ (United States)

1999-02-01

50

Alkylammonium montmorillonites as adsorbents for organic vapors from air  

SciTech Connect

Montmorillonite clays may be modified by the exchange of the inorganic interlayer cations with alkylammonium ions, resulting in a fixed internal porosity. The pore size and shape depend on the nature of the alkylammonium ion. A number of different ions were used to prepare adsorbents with varying properties, and these were examined for their potential application to sampling organic vapors in air. Characterization involved determination of nitrogen and water contents, surface area, interlayer spacing, thermal stability, and breakthrough volumes of organic vapors. The adsorbent that showed the most promise (tetramethylammonium montmorillonite (TMA)) was further evaluated for use as an adsorbent in both thermal- and solvent-desorable sampling systems.

Harper, M.; Purnell, C.J. (London School of Hygiene and Tropical Medicine (England))

1990-01-01

51

X-ray Photoelectron Spectroscopic Study of the Effect of Heating on Montmorillonite Containing Sodium and Potassium Cations  

Microsoft Academic Search

The effect of heating on montmorillonites containing exchangeable Na and K has been studied by X-ray photoelectron spectroscopy (XPS). The surface composition of the unheated montmorillonite was consistent with the bulk composition, but after the sample recrystallized at 1 100~ the surface abundance of Na increased, whereas that of K decreased. Because Na and K were not present in the

Haruhiko Seyama; MITSUYUKI SOMA

1986-01-01

52

Adsorption of polyacrylic acid and polyacrylamide on montmorillonite  

NASA Astrophysics Data System (ADS)

The effect of process duration, temperature, and concentration on the adsorption of polyacrylic acid and polyacrylamide by montmorillonite is studied. It is shown that the pattern of interaction of the studied polyelectrolytes with the sorbent surface is determined by the nature of the polymers, the prevalence of acid-base sites, and the pore structure of the mineral.

Akimkhan, A. M.

2013-11-01

53

Clays, Nanoclays, and Montmorillonite Minerals  

NASA Astrophysics Data System (ADS)

The recent introduction of nanoclays as fillers or additives in polymers for various desired effects is a subject of an increased interest for research and development to establish various applications. An increased consumption is indicated by the wider applications of clay nanocomposites approaching to almost one-quarter (24 pct) in 2005 of the total nanocomposites used. However, an interesting concern, along with the studies addressing how nanoclays change the behavior of polymeric materials, is to discover what are clays, nanoclays and montmorillonite minerals. The various structures of montmorillonite available in nature and their modification for application are discussed. An attempt is made to review the origin of using clays when nanotechnology did not exist, coupled with the effects of montmorillonite-based nanoclays on commercially known polymers.

Uddin, Faheem

2008-12-01

54

Montmorillonite-Alginate Composites as a Drug delivery System: Intercalation and In vitro Release of Diclofenac sodium  

PubMed Central

Diclofenac sodium and alginate was intercalated into montmorillonite to form uniform sized beads by gelation method. The structure and surface morphology of the synthesized composite beads were characterized by powdered X-ray diffraction, Fourier transform infrared spectroscopy, thermo gravimetric analysis and scanning electron microscopy. Diclofenac release kinetics of the composite in simulated intestinal fluid medium (pH 7.4) and effect of montmorillonite content on the in vitro release of diclofenac from diclofenac-montmorillonite-alginate composites bead was investigated by UV/Vis spectrophotometer. Diclofenac encapsulation efficiency in the montmorillonite-alginate composites bead increases with an increase in the montmorillonite content. The control release of diclofenac from diclofenac-montmorillonite-alginate composites beads was observed to be better as compared to diclofenac-alginate beads.

Kevadiya, B. D.; Patel, H. A.; Joshi, G. V.; Abdi, S. H. R.; Bajaj, H. C.

2010-01-01

55

Biodegradable polylactide/montmorillonite nanocomposites.  

PubMed

Our continuing research on the preparation, characterization, materials properties, and biodegradability of polylactide (PLA)/organically modified layered silicate (OMLS) nanocomposites has yielded results on PLA/montmorillonite nanocomposites. Montmorillonite (mmt) modified with dimethyldioctadecylammonium cation was used as an OMLS for nanocomposite preparation. The internal structure of nanocomposites on the nanometer scale was established with the use of wide-angle X-ray diffraction patterns and transmission electron micrographic observation. All nanocomposites exhibited significant improvement in crystallization behavior, mechanical properties, flexural properties, heat distortion temperature, and O2 gas permeability when compared with pure PLA. PMID:15002130

Ray, Suprakas Sinha; Yamada, Kazunobu; Okamoto, Masami; Ueda, Kazue

2003-12-01

56

Biocompatibility Evaluation of Nanosecond Laser Treated Titanium Surfaces  

NASA Astrophysics Data System (ADS)

We developed surface modification technologies for dental implants in this study. The study contributes to shortening the time required for adhesion between alveolar bone and fixtures which consist of dental implants. A Nd:YVO4 nanosecond laser was used to modify the surfaces of commercially pure titanium (CP Ti) disks, and their biocompatibility was evaluated cytocompatibility and bioactivity. First, rows of 200 µm spaced rectilinear laser treatments were performed on surfaces of CP Ti disks. Osteoblasts derived from rat mesenchymal stem cells were then cultured on the treated surfaces. Cytocompatibility on the laser treated area was evaluated by observing adhesion behavior of cells on these surfaces. The results indicated that the micro-order structure formed by the laser treatment promoted adhesion of osteoblasts and that traces of laser treatment without microstucture didn't affect the adhesion. Second, surfaces of CP Ti disks were completely covered by traces of laser treatment, which created complex microstructures of titania whose crystal structure is rutile and anatase. This phenomenon allowed the creation of hydroxyapatite on the surface of the disks in 1.5-times simulated body fluid (1.5SBF) while no hydroxyapatite was observed on conventional polished surfaces in the same conditions. This result indicates that bioactivity was enabled on CP Ti by the laser treatment. From these two results, laser treatment for CP Ti surfaces is an effective method for enhancing adhesion of osteoblasts and promoting bioactivity, which are highly appreciated properties for dental implants.

Honda, Ryo; Mizutani, Masayoshi; Ohmori, Hitoshi; Komotori, Jun

57

Transformation of montmorillonite to kaolinite during weathering  

USGS Publications Warehouse

Extensive deposits of kaolinite in Florida are formed by transformation of montmorillonite during low-temperature supergene weathering. The transformation occurs by intracrystalline leaching of interlayer cations and tetrahedral silica layers. Interposition of stripped layers within montmorillonite creates a regular 1:1 mixed-layered montmorillonite-kaolinite, a new clay structure. Kaolin-like layers are nourished by lateral epitaxy, as the iron-rich montmorillonite decomposes. Hexagonal outgrowths of new kaolinite develop at the edges of montmorillonite flakes and nucleate new vertical growth. Kaolinitic sands impregnated with goethite are ultimately formed, and the released silica enriches groundwater and forms secondary chert.

Altschuler, Z. S.; Dwornik, E. J.; Kramer, H.

1963-01-01

58

The effect of pillaring montmorillonite and beidellite on the conversion of trimethylbenzenes  

SciTech Connect

Natural montmorillonite, synthetic mica-montmorillonite (SMM), and Ni-substituted SMM were treated with hydroxy-Al solutions and the activities of the respective unpillared and pillared clays were tested using 1,2 4-trimethylbenzene as a reactant. Pillaring montmorillonite and, to a lesser extent, synthetic beidellite gave the largest % increase in the conversion level. The selectivity to 1,2,4,5-tetramethylbenzene, the smallest of the tetramethylbenzene isomers, was found to be a function not of the extent of pillaring, but rather of the extent of isomerization of the alkylbenzenes.

Kojima, M.; Hartford, R.; O'Connor, C.T. (Univ. of Cape Town, Rondebosch (South Africa))

1991-04-01

59

The adsorption and reaction of adenine nucleotides on montmorillonite  

NASA Astrophysics Data System (ADS)

The binding of AMP to Zn2+-montmorillonite was investigated in the presence of buffers and salts. Good's buffers, piperazine-N,N'-bis(2-ethanesulfonate) [PIPES] and morpholine-N-2-ethanesulfonate [MES], perturbed the exchangeable cations to a lesser extent (only 9% of Zn2+ displaced by 0.2 M buffer) than was observed with imidazole and lutidine buffers or NaCl and KCl salts (up to 80% of Zn2+ displaced). AMP adsorption isotherms measured in the presence of 0.2 M PIPES, MES or Na2SO4 exhibited normal Langmuir-type behavior. The adsorption coefficient, KL, is 3-fold greater in the presence of HEPES or PIPES than it is in the absence of buffers. Basal spacings measured by X-ray diffraction for Zn2+-montmorillonite are 13 and 15 Ĺ in the presence of PIPES, while a value of 12.8 Ĺ was determined in the absence of PIPES. These data are interpreted in a model in which the adsorption of AMP is mediated by a Zn2+ complex of PIPES in different orientations in the interlamellar region of the montmorillonite. The type of exchangeable cation does not affect the ability of the lattice-bound Fe3+ in the montmorillonite to oxidize diaminomaleonitrile (DAMN). Exchangeable Cu2+ oxidizes DAMN, but exchangeable Fe3+ is nearly ineffective as an oxidant. The addition if DISN to 3'-AMP bound to Zn2+-montmorillonite in the presence of 0.2 M PIPES resulted in a higher yield of 2', 3'-cAMP than is observed with a comparable concentration of Zn2+, a result which implicates surface catalystis by the montmorillonite.

Ferris, James P.; Hagan, William J.

1986-03-01

60

Sorption of sodium dodecylbenzene sulfonate by montmorillonite.  

PubMed

Sorption of linear alkylbenzene sulfonates by soils and sediments is an important process that may affect their fate, transport, toxicity and their application in remediation of contaminated soil and groundwater. In this study, batch experiments were conducted to elucidate the sorption of a widely used anionic surfactant, sodium dodecylbenzene sulfonate (SDBS), by montmorillonite. It was observed that: (i) SDBS was sorbed significantly by montmorillonite saturated with Ca(2+), but little by Na-saturated montmorillonite; (ii) the amount of SDBS sorbed by Ca(2+)-montmorillonite was enhanced by NaCl; and (iii) no significant intercalation of SDBS into Ca(2+)-montmorillonite was observed by X-ray diffraction (XRD) analysis. These results indicate that the removal of SDBS by Ca(2+)-montmorillonite was primarily attributed to the precipitation between DBS(-) and Ca(2+) in solution which was released from montmorillonite via cation exchange. These results will help us to understand the sorption behavior and environmental effects of anionic surfactants. PMID:16759775

Yang, Kun; Zhu, Lizhong; Xing, Baoshan

2006-06-08

61

40 CFR 721.10223 - Styrenyl surface treated manganese ferrite with acrylic ester polymer (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Styrenyl surface treated manganese ferrite with acrylic ester polymer...721.10223 Styrenyl surface treated manganese ferrite with acrylic ester polymer...generically as styrenyl surface treated manganese ferrite with acrylic ester...

2013-07-01

62

40 CFR 721.10222 - Styrenyl surface treated manganese ferrite (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Styrenyl surface treated manganese ferrite (generic). 721.10222...721.10222 Styrenyl surface treated manganese ferrite (generic). (a) Chemical...generically as styrenyl surface treated manganese ferrite (PMN P-09-581) is...

2013-07-01

63

Surface-treated mica based on muscovite for anticorrosive coatings  

Microsoft Academic Search

The paper deals with using lamellar pigments for anticorrosive barrier coatings. By depositing a ferric oxide layer on a muscovite particle a pigment is obtained, which being applied to coatings improves the mechanical properties thereof, resistance to UV radiation and acts as an anticorrosion barrier. The optimum concentration of lamellar surface-treated muscovite in the coatings amounts to 20 vol. %.

Andréa Kalendová

2002-01-01

64

Simulations of the Viking Gas Exchange Experiment using palagonite and Fe-rich montmorillonite as terrestrial analogs: implications for the surface composition of Mars.  

PubMed

Simulations of the Gas Exchange Experiment (GEX), one of the Viking Lander Biology Experiments, were run using palagonite and Fe-rich montmorillonite as terrestrial analogs of the Martian soil. These terrestrial analogs were exposed to a nutrient solution of the same composition as that of the Viking Landers under humid (no contact with nutrient) and wet (intimate contact) conditions. The headspace gases in the GEX sample cell were sampled and then analyzed by gas chromatography under both humid and wet conditions. Five gases were monitored: CO2, N2, O2, Ar, and Kr. It was determined that in order to simulate the CO2 gas changes of the Viking GEX experiment, the mixture of soil analog mineral plus nutrient medium must be slightly (pH = 7.4) to moderately basic (pH = 8.7). This conclusion suggests constraints upon the composition of terrestrial analogs to the Mars soil; acidic components may be present, but the overall mixture must be basic in order to simulate the Viking GEX results. PMID:11539578

Quinn, R; Orenberg, J

1993-10-01

65

Nickel and Lead Sequestration in Manganese Oxide-coated Montmorillonite  

SciTech Connect

Amorphous hydrous manganese oxide (HMO) is an important mineral in soils and sediments influencing the mobility and bioavailability of metal contaminants. In this study, nickel and lead sorption to discrete HMO and HMO-coated montmorillonite was investigated mechanistically. The effect of pH and concentration revealed that when normalized to the mass of oxide present, the HMO-coated montmorillonite behaved similarly to the discrete Mn oxide, where both ions sorbed onto HMO-coated montmorillonite as inner-sphere complexes. Ni coordinated to the vacancy sites in the Mn oxide structure, while Pb formed bidentate corner-sharing complexes. These coordination environments were observed not only as a function of loading, pH, and ionic strength, but also in long-term studies where sorption increased by as much as 100% (from 6 x 10{sup -4} to 1.2 x 10{sup -3} mol Ni/g HMO-coated montmorillonite). In this slower sorption process, intraparticle diffusion, the internal surface sites along microporous walls appear to be no different than external ones. Best fit diffusivities ranged from 10{sup -12} to 10{sup -13} cm{sup 2}/s for Ni and 10{sup -17} to 10{sup -20} cm{sup 2}/s for Pb. The significant difference in the diffusivities for the two ions is consistent with site activation theory, where theoretical surface diffusivities were predicted and given their error were in agreement with experimental results. Mn oxides sequester heavy metals in the environment.

Boonfueng,T.; Axe, L.; Xu, Y.; Tyson, T.

2006-01-01

66

Electrolyte diffusion in compacted montmorillonite engineered barriers  

SciTech Connect

The bentonite-based engineered barrier or packing is a proposed component of several designs conceived to dispose of high-level nuclear waste in geologic repositories. Once radionuclides escape the waste package, they must first diffuse through the highly impermeable clay-rich barrier before they reach the host repository. To determine the effectiveness of the packing as a sorption barrier in the transient release period and as a mass-transfer barrier in the steady release period over the geologic time scales involved in nuclear waste disposal, a fundamental understanding of the diffusion of electrolytes in compacted clays is required. We present, and compare with laboratory data, a model quantifying the diffusion rates of cationic cesium and uncharged tritium in compacted montmorillonite clay. Neutral tritium characterizes the geometry (i.e., tortuosity) of the particulate gel. After accounting for cation exchange, we find that surface diffusion is the dominant mechanism of cation transport, with an approximate surface diffusion coefficient of 2 x 10 W cmS/s for cesium. This value increases slightly with increasing background ionic strength. The implications of this work for the packing as a migration barrier are twofold. During the transient release period, K/sub d/ values are of little importance in retarding ion migration. This is because sorption also gives rise to a surface diffusion path, and it is surface diffusion which controls the diffusion rate of highly sorbing cations in compacted montmorillonite. During the steady release period, the presence of surface diffusion leads to a flux through the packing which is greatly enhanced. In either case, if surface diffusion is neglected, the appropriate diffusion coefficient of ions in compacted packing will be in considerable error relative to current design recommendations. 11 refs., 4 figs., 1 tab.

Jahnke, F.M.; Radke, C.J.

1985-09-01

67

Biodegradable poly(lactic acid)\\/chitosan-modified montmorillonite nanocomposites: Preparation and characterization  

Microsoft Academic Search

In this study, the biodegradable poly(lactic acid) (PLA)\\/montmorillonite (MMT) nanocomposites were successfully prepared by the solution mixing process of PLA polymer with organically-modified montmorillonite (m-MMT), which was first treated by n-hexadecyl trimethyl-ammonium bromide (CTAB) cations and then modified by biocompatible\\/biodegradable chitosan to improve the chemical similarity between the PLA and m-MMT. Both X-ray diffraction data and transmission electron microscopy images

Tzong-Ming Wu; Cheng-Yang Wu

2006-01-01

68

Diffusion of ion-exchanging electrolytes in montmorillonite gels  

SciTech Connect

The primary contributions of this work are: (1) Development of a unique radially perfused diffusion cell suitable for measuring transient diffusion rates in compacted, highly adsorbing and swelling porous media such as montmorillonite clay gels; (2) examination of the effective diffusion coefficient (D{sub 6}) of electrolytes in montmorillonite clay gels; and (3) Measurement of the transient diffusion rates of cesium, chloride and tritium in 15 w/o montmorillonite clay gels at pH 9 and sodium chloride backgrounds of 10{sup {minus}1} to 10{sup {minus}3} kmol/m{sup 3}. Results are interpreted by using the dilute limit of the multicomponent transport equations derived for species migration in a single clay pore after macroscopic averaging. The tortuosity of the clay gel is found by tritium diffusion. Transient chloride diffusion rates are found to be at molecular rates. Negative adsorption of anions from the clay gel, required for an a priori prediction of chloride profiles, are calculated from site-binding theory. Surface diffusion is the primary mode of cesium transport in montmorillonite clay gels. Migration of cesium is primarily along the inner Helmholtz plane of clay particles. The primary implication for the montmorillonite clay-based packing as a nuclear waste migration barrier is that surface diffusion must be included to describe properly diffusion rates of either anions or cations. Currently surface diffusion is neglected and cesium penetration into the packing is drastically underestimated. Penetration depths of anions is grossly overestimated. In either case, the appropriate diffusion coefficient of ions in compacted packing will be in considerable error relative to current design recommendations.

Jahnke, F.M.

1987-01-01

69

Adsorption of ammonia on treated stainless steel and polymer surfaces  

NASA Astrophysics Data System (ADS)

Adsorption of dynamically diluted ammonia at part-per-billion to low part-per-million concentrations in dry nitrogen was studied with treated and non-treated stainless steel and polymer test tubes. The treatments included electropolishing and two types of coatings based on amorphous silicon. Cavity ring-down spectroscopy with an external cavity diode laser operating in the near-infrared wavelength range was used to monitor the adsorption process in real time in continuous-flow conditions to obtain quantitative assessment of the adsorptive properties of the studied surfaces. The investigated polymers were all less adsorptive than any of the treated or non-treated stainless steel surfaces. Some of the commercial coatings reduced the adsorption loss of stainless steel by a factor of ten or more. Polyvinylidene fluoride was found to be superior (less adsorption) to the four other studied polymer coatings. The number of adsorbed ammonia molecules per surface area obtained at different ammonia gas phase concentrations was modeled with Langmuir and Freundlich isotherms. The time behavior of the adsorption-desorption process occurring in the time scale of seconds and minutes was simulated with a simple kinetic model.

Vaittinen, O.; Metsälä, M.; Persijn, S.; Vainio, M.; Halonen, L.

2013-08-01

70

Wear behavior of different surface treated cam spindles  

Microsoft Academic Search

In this study wear behavior of cam spindles made of five different surface treated nodular cast iron (GGG50) and induction hardened CK45 steels was investigated. In the experiments; PVD–TiN-coated, both borided and PVD–TiN-coated, only hardened, both hardened and PVD–TiN-coated and only borided spherical graphite cast iron and induction hardened CK45 were used. The wear behavior of two type of steel

H. Sert; A. Can; H. Ar?kan; B. Selcuk; H. Toprak

2006-01-01

71

Nylon 6\\/Na–montmorillonite nanocomposites prepared by compounding Nylon 6 with Na–montmorillonite slurry  

Microsoft Academic Search

We report a novel compounding process using Na–montmorillonite water slurry for preparing novel nylon 6\\/Na–montmorillonite nanocomposites. In this compounding process, the Na–montmorillonite slurry was blended with melting nylon 6 using an extruder, followed by removing the water. The Na–montmorillonite silicate layers were found to be exfoliated and dispersed homogeneously at nanometer level in the nanocomposites with an electron transmission microscope.

Naoki Hasegawa; Hirotaka Okamoto; Makoto Kato; Arimistu Usuki; Norio Sato

2003-01-01

72

Mechanism of palm oil bleaching by montmorillonite clay activated at various acid concentrations  

Microsoft Academic Search

The mechanism of bleaching by a nonswelling montmorillonite clay activated at various acid concentrations was studied in the\\u000a bleaching of palm oil. Montmorillonite clay was activated by 2 parts of H2SO4 at concentrations of 10-40%. Chemical composition, bleaching ability, specific surface area and phosphorus content were studied.\\u000a The study showed that an initial increase in bleaching ability by clay activated

S. C. Kheok; E. E. Lim

1982-01-01

73

XAS of uranium(VI) sorbed onto silica, alumina, and montmorillonite  

NASA Astrophysics Data System (ADS)

The purpose of this work is to determine the speciation (oxidation state and molecular structure) of uranium sorbed onto surfaces of silica, alumina, and montmorillonite, in order to investigate the modes of uranium sorption on these minerals. Characterization of actinide sorption onto silicates, aluminates, and aluminosilicates such as montmorillonite is vital for the prediction of the environmental impact and risk assessment of actinide migration from nuclear waste storage sites, underground test sites, and mining sites. .

Sylwester, E. R.; Allen, P. G.; Hudson, E. A.

2000-07-01

74

Adsorption of basic dyes onto montmorillonite  

Microsoft Academic Search

Ca-montmorillonite (Ca-Mont) was exchanged with titanium cations and the adsorption equilibrium and kinetics of Basic Green 5 (BG5) and Basic Violet 10 (BV10) on these montmorillonites were measured to examine the ion-exchange effects on the basic dyes adsorption. The relationship between the dye adsorption and the alteration of pore structures of montmorillonite induced by ion-exchange processes was discussed. Moreover, the

Cheng-Cai Wang; Lain-Chuen Juang; Ting-Chu Hsu; Chung-Kung Lee; Jiunn-Fwu Lee; Fu-Chuang Huang

2004-01-01

75

The Stabiliy of Radio-Frequency Plasma Treated Polydimethylsiloxane Surface  

PubMed Central

Polydimethylsiloxane (PDMS) is a widely used material for manufacturing lab-on-chip devices. However, the hydrophobic nature of PDMS is a disadvantage in micro-fluidic systems. To transform the hydrophobic PDMS surface to hydrophilic it has been treated with radio frequency (RF) air plasma at 150, 300 and 500 mtorr pressure for up to 30 minutes. Following the surface treatment, the PDMS specimens were stored in air, deionized water or 0.14 M NaCl solution at 4 °C, 20 °C, and 70 °C. The change in the hydrophilicity (wettability) of the PDMS surfaces has been followed by contact angle measurements and Fourier Transform Infrared Attenuated Total Reflectance (FTIR-ATR) Spectroscopy as a function of time. As an effect of the RF plasma treatment the contact angles measured on PDMS surfaces dropped from 113±4 degrees to 9±3 degrees. The chamber pressure and the treatment time had no or negligible effect on the results. However, the PDMS surface gradually lost its hydrophilic properties in time. The rate of this process is influenced by the difference in the dielectric constants of the PDMS and its ambient environment. It has been the smallest at low temperatures in deionized water and largest at high temperatures in air. Apparently, the OH groups generated on the PDMS surface during the plasma treatment tend towards a more hydrophilic/less hydrophobic environment during the relaxation processes. The correlation between FTIR–ATR spectral information and contact angle data supports this interpretation.

Chen, I-Jane

2008-01-01

76

Surface energy increase of oxygen-plasma-treated PET  

SciTech Connect

Prosthetic composite is a widely used biomaterial that satisfies the criteria for application as an organic implant without adverse reactions. Polyethylene therephthalate (PET) fiber-reinforced composites have been used because of the excellent cell adhesion, biodegradability and biocompatibility. The chemical inertness and low surface energy of PET in general are associated with inadequate bonds for polymer reinforcements. It is recognized that the high strength of composites, which results from the interaction between the constituents, is directly related to the interfacial condition or to the interphase. A radio frequency plasma reactor using oxygen was used to treat PET fibers for 5, 20, 30 and 100 s. The treatment conditions were 13.56 MHz, 50 W, 40 Pa and 3.33x10{sup -7} m{sup 3}/s. A Rame-Hart goniometer was used to measure the contact angle and surface energy variation of fibers treated for different times. The experimental results showed contact angle values from 47 deg. to 13 deg. and surface energies from 6.4x10{sup -6} to 8.3x10{sup -6} J for the range of 5 to 100 s, respectively. These results were confirmed by the average ultimate tensile strength of the PET fiber/ polymethylmethacrylate (PMMA) matrix composite tested in tensile mode and by scanning electron microscopy.

Cioffi, M.O.H.; Voorwald, H.J.C.; Mota, R.P

2003-03-15

77

Structural evidence for the sorption of Ni(II) atoms on the edges of montmorillonite clay minerals: A polarized X-ray absorption fine structure study  

Microsoft Academic Search

The nature of surface complexes formed on Ni uptake onto montmorillonite (a dioctahedral smectite) has been investigated over an extended time period by polarized extended X-ray absorption fine structure (P-EXAFS) spectroscopy. Self-supporting films of Ni-sorbed montmorillonite were prepared by contacting Ni and montmorillonite at pH 7.2, high ionic strength (0.3 M NaClO4), and low Ni concentration ((Ni)initial 19.9 M) for

E M. SCHEIDEGGER; ALAIN MANCEAU; MICHEL L. SCHLEGEL; BART BAEYENS; MICHAEL H. BRADBURY; DANIEL CHATEIGNER

2003-01-01

78

The Chemical Modelling of Clay\\/Electrolyte Interactions for Montmorillonite  

Microsoft Academic Search

A B S T R A C T : A study of the ion-exchange properties of montmorillonite has been performed in order to facilitate computer predictions of the chemical properties of natural fluids and mineral assemblies. Clay\\/electrolyte interactions can be described using a technique based on the concept of hypothetical surface complex formation. This technique, which is compatible with ion-association

P. Fletcher; G. SPOSITO

1989-01-01

79

Cation exchange interaction between antibiotic ciprofloxacin and montmorillonite.  

PubMed

Exploring the interactions between antibiotics and soils/minerals is of great importance in resolving their fate, transport, and elimination in the environment due to their frequent detection in wastewater, river water, sewage sludge and soils. This study focused on determining the adsorption properties and mechanisms of interaction between antibiotic ciprofloxacin and montmorillonite (SAz-1), a swelling dioctahedral mineral with Ca(2+) as the main interlayer cation. In acidic and neutral aqueous solutions, a stoichiometric exchange between ciprofloxacin and interlayer cations yielded an adsorption capacity as high as 330 mg/g, corresponding to 1.0 mmol/g. When solution pH was above its pK(a2) (8.7), adsorption of ciprofloxacin was greatly reduced due to the net repulsion between the negatively charged clay surfaces and the ciprofloxacin anion. The uptake of ciprofloxacin expanded the basal spacing (d(001)) of montmorillonite from 15.04 to 17.23 A near its adsorption capacity, confirming cation exchange within the interlayers in addition to surface adsorption. Fourier transform infrared results further suggested that the protonated amine group of ciprofloxacin in its cationic form was electrostatically attracted to negatively charged sites of clay surfaces, and that the carboxylic acid group was hydrogen bonded to the basal oxygen atoms of the silicate layers. The results indicate that montmorillonite is an effective sorbent to remove ciprofloxacin from water. PMID:20675045

Wang, Chih-Jen; Li, Zhaohui; Jiang, Wei-Teh; Jean, Jiin-Shuh; Liu, Chia-Chuan

2010-07-15

80

Surface oxidation of selenium treated GaAs(100)  

SciTech Connect

The surface oxidation of Se treated GaAs(100) has been investigated in order to understand in greater detail the degradation of the Se passivated GaAs surface upon exposure to atmosphere. An increase in band bending is initially observed at relatively low exposure times, which corresponds to an increase in the O 2p intensity in the valence band. At this stage, oxygen is thought to weakly physisorb at the Ga vacancy sites. At intermediate exposure levels, the other unadsorbed oxygen atom of O{sub 2} attacks the nearest Ga atom. The bond between the nearest Ga atom and Se is then severed, resulting in the formation of Se, which closely resembles amorphous Se. Ultimately, both Se states are converted to the amorphouslike state and at longer exposure times are oxidized. At longer exposure times, the oxidation of Se is also accompanied by As oxidation. In contrast to S treated GaAs, Se/GaAs is relatively resistant to oxidation where only about 10% of the As is oxidized (As{sub 2}O{sub 3}) after 180 min of exposure versus oxidation of 34% of the As atoms for S/GaAs after only 20 min of atmosphere exposure. This relative oxidation resistance is attributed to greater penetration of Se into GaAs relative to S into GaAs. 11 refs., 7 figs., 1 tab.

Scimeca, T.; Watanabe, Y.; Maeda, F.; Berrigan, R.; Oshima, M. [NTT Interdisciplinary Research Laboratories, Tokyo (Japan)

1994-11-01

81

A density functional theory study on the origin of lithium-montmorillonite's conductivity at low water content: A first investigation  

NASA Astrophysics Data System (ADS)

The nature of electric charge carriers of Lithium-montmorillonite at low water content has been investigated using density functional theory (DFT) calculation. Results show that in the presence of H2O molecule, the Li easily migrates from the MMT surface to a distance above the surface with the barrier for Li migration of 0.09 eV. We found the possibility of Li as charge carrier in the H2O/Li-montmorillonite.

Wungu, Triati Dewi Kencana; Rusydi, Febdian; Kresno Dipojono, Hermawan; Kasai, Hideaki

2012-10-01

82

Comparison of the inhibitory action of KCl and guanidine hydrochloride solutions on montmorillonite swelling  

SciTech Connect

This study compares the effectiveness of potassium chloride with guanidine chlorhydrate in the prevention of clay swelling. The results given on various swelling tests on calcic montmorillonite led to the conclusions that (1) guanidine chlorhydrate is more effective than potassium chloride, especially in low concentrations, and (2) water immersion of samples treated by both solutions shows the permanent feature of the inhibitive action of guanidine chlorhydrate in swelling on one hand and the important increase in swelling of immersed samples treated by potassium chloride on the other. The viscosity measure of montmorillonite suspensions, before and after solution ion elimination by dialysis, confirms these observations.

Iltis, M.; Didier, G.; Lareal, P.

1982-08-01

83

Comparative studies on montmorillonite-supported zero-valent iron nanoparticles produced by different methods: reactivity and stability.  

PubMed

To mitigate the aggregation and enhance the reactivity of nanosized zero-valent iron (nZVI), montmorillonite is employed as a template-supporting matrix to prepare nZVI through two different pathways: heterogeneous nucleation and homogeneous nucleation processes. Dispersed sub-nanosized ZVI clusters with an average size around 0.5 nm (perpendicular to the clay layers) are intercalated in clay interlayers when using montmorillonite as a template in preparation via heterogeneous nucleation process. However, the particle sizes spanned from 0.62 nm (perpendicular to the clay layers) for the ZV1 intercalated in montmorillonite interlayers to 1-50 nm for the ZVI residing on an external surface when using montmorillonite as a dispersion agent in the preparation via homogeneous nucleation. Furthermore, parallel batch experiments have been conducted with nZVIs synthesized by the two different methods in solutions of nitrobenzene and their reactivity is evaluated via response of nZVI to nitrobenzene remediation. As a result, the reactivity of ZVI synthesized by heterogeneous nucleation is greater than that by homogeneous nucleation, which is inversely correlated to the size of ZVI supported by montmorillonite clay. Evaluation of the stability of montmorillonite-supported ZVI showed that ZVI intercalated in the interlayers of montmorillonite is more stable than that located on the external surface, which can be attributed to the protective effect of montmorillonite layers on ZVI from oxidation. These results suggest that the great reactivity and high stability of montmorillonite-intercalated ZVI synthesized through heterogeneous nucleation process warrants its significant potential in developing in situ remediation and treatment technologies for organic contaminants. PMID:23530312

Jia, Hanzhong; Wang, Chuanyi

84

Antibacterial activity of montmorillonites modified with silver  

Microsoft Academic Search

The antibacterial properties of silver modified montmorillonites from Pellegrini Lake, Argentina were tested in growth inhibition of Escherichia coli bacteria. Montmorillonite was first submitted to different treatments: (a) calcination at 550°C for 3h and (b) grinding during 300s. After that, the samples were loaded with silver by ion exchange. Structural characterization was performed by X-ray diffraction (XRD), Fourier transformed infrared

S. M. Magańa; P. Quintana; D. H. Aguilar; J. A. Toledo; C. Ángeles-Chávez; M. A. Cortés; L. León; Y. Freile-Pelegrín; T. López; R. M. Torres Sánchez

2008-01-01

85

The effect of complex-forming agent (EDTA) on the exchange of manganese ions on calcium-montmorillonite II. Calcium-montmorillonite?Mn(ClO 4) 2?Na 2EDTA system  

Microsoft Academic Search

The ion exchange of manganese(II) ions is studied on the surface of calcium-montmorillonite in the presence of EDTA as a complex-forming agent at different pH values. The composition of the solution was found to affect the interlayer composition of montmorillonite in a high, and at low pH, unexpected degree. The conditions needed for the desorption of hydrogen and other cations

József Kónya; Noémi M. Nagy; Róbert Király; Judit Gelencsér

1998-01-01

86

The sedimentation capabilities of hexadecyltrimethylammonium-modified montmorillonites.  

PubMed

Natural montmorillonite was modified with a quaternary ammonium compound, hexadecyltrimethylammonium (HDTMA). The sedimentation capabilities of unmodified and modified montmorillonites were then investigated. The sedimentation velocity of modified montmorillonites increased if the amounts of adsorbed HDTMA were from 0.3 to 1.0 times the cation exchange capacitity (CEC). It also emerged that the sedimentation capability of modified montmorillonites was improved and that the variously CEC-modified montmorillonites had similar sedimentation capabilities after they had sorbed organic matter from oily wastewater. Thus, modified montmorillonites (especially 0.5 CEC treatment) had good sedimentation capabilities for sorbing organic substance and can act as carriers in wastewater biotreatment. PMID:12152749

Yang, Liuyan; Jiang, Lijuan; Zhou, Zhi; Chen, Yuangao; Wang, Xiaorong

2002-07-01

87

REVEGETATION AUGMENTATION OF SURFACE MINES WITH TREATED ACID MINE DRAINAGE  

EPA Science Inventory

This study provided a field demonstration of an earlier feasibility study. Treated acid mine drainage was utilized to augment revegetation on graded spoil areas. Acid mine drainage was treated utilizing limestone (rock dust) and the resulatant water was spray irrigated under high...

88

Thermal Stability and Flammability of Polypropylene/Montmorillonite Composites  

NASA Astrophysics Data System (ADS)

Smectite clays, such as montmorillonite, are a valuable class of mineral for industrial applications because of their high aspect ratio, plate morphology, and intercalative capacity. After preparation, smectite clays may be used as a nano-scalled inorganic fillers to prepare polymer/layered silicate nanocomposites, which has unique properties such as improved strength, modulus, heat resistance, surface scratch resistance and good barrier properties, at very low filler. In the present work, polypropylene/montmorillonite (PP/MMT) composites were prepared and their thermal stability and flammability were investigated. Regardless of the micro-dispersed or submicro-dispersed structure, the composites exhibit higher thermal stability and considerably reduced peak heat release rate (PHRR). It is likely caused by the physical-chemical adsorption of the volatile degradation products on the silicates. On the other hand, the addition of MMT can catalyze the initial decomposition of PP matrix and accelerate the ignition of PP matrix in combustion. It has been observed that a ceramic-like char formed on the surface of the composites during burning test. The characterization of the char surface before ignition indicates that it is an inorganic-rich surface, which provided a better barrier property, leading to the improvement of the thermal stability and reduction of flammability of the composites.

Yang, Ming-Shu; Qin, Huai-Li; Zhang, Shi-Min; Han, Charles C.

2004-03-01

89

Modification and characterization of montmorillonite fillers used in composites with vulcanized natural rubber  

Microsoft Academic Search

Parent Ca-montmorillonite (Jelšový Potok, Slovakia, Ca-JP) and Na-montmorillonite Kunipia-F (Japan, Na-KU) were ion-exchanged\\u000a with octadecyltrimethylammonium (ODTMA) cations. Characteristics of the samples were studied by X-ray diffraction (XRD), Fourier\\u000a transform infrared spectroscopy (IR) and thermogravimetry (TG). Surface areas were measured by sorption of N2 and ethyleneglycol monoethyl ether. Scanning electron microscopy photographs (SEM) were used to characterize the texture\\u000a of samples.

Jana Hrachová; Ivan Chodák; Peter Komadel

2009-01-01

90

Analysis of Oligonucleotide DNA Binding and Sedimentation Properties of Montmorillonite Clay Using Ultraviolet Light Spectroscopy  

PubMed Central

Smectite clays such as montmorillonite form complexes with a variety of biomolecules, including the nucleic acids DNA and RNA. Most previous studies of DNA adsorption onto clay have relied upon spectrophotometric analysis after separation of free nucleic acids from bound complexes by centrifugation. In the current work we demonstrate that such studies produce a consistent error due to (a) incomplete sedimentation of montmorillonite and (b) strong absorbance of the remaining clay at 260 nm. Clay sedimentation efficiency was strongly dependent upon cation concentration (Na+ or Mg2+) and on the level of dispersion of the original suspension. An improved clay:DNA adsorption assay was developed and utilized to assess the impact of metal counterions on binding of single-stranded DNA to montmorillonite. X-ray diffraction demonstrated, for the first time, formation of intercalated structures consistent with orientation of the DNA strands parallel to the clay surface. Observed gallery spacings were found to closely match values calculated utilizing atomistic modeling techniques.

Beall, Gary W.; Sowersby, Drew S.; Roberts, Rachel D.; Robson, Michael H.; Lewis, L. Kevin

2009-01-01

91

On the surface topography of ultrashort laser pulse treated steel surfaces  

NASA Astrophysics Data System (ADS)

This paper concentrates on observations of the surface topography by scanning electron microscopy (SEM) on alloyed and stainless steels samples treated by ultrashort laser pulses with duration of 210 fs and 6.7 ps. Globular-like and jet-like objects were found depending on the various levels of the fluence applied. It is shown that these features appear due to solid-liquid and liquid-gas transitions within surface layer irradiated by intense laser light. The observations are confronted to the theory of short-pulsed laser light-matter interactions, including interference, excitation of electrons, electron-phonon coupling as well as subsequent ablation. It is shown that the orientation of small ripples does not always depend on the direction of the polarization of laser light.

Vincenc Obona, J.; Ocelík, V.; Skolski, J. Z. P.; Mitko, V. S.; Römer, G. R. B. E.; Huis in't Veld, A. J.; De Hosson, J. Th. M.

2011-12-01

92

Biopolymer chitosan\\/montmorillonite nanocomposites: Preparation and characterization  

Microsoft Academic Search

Biopolymer chitosan\\/montmorillonite nanocomposites have been prepared in which montmorillonite (MMT) is used as nanofiller and diluted acetic acid is used as solvent for dissolving and dispersing chitosan and montmorillonite. Morphology and properties of chitosan nanocomposites with and without acetic acid residue have been studied compared with those of pure chitosan. The effect of acetic acid residue and MMT loading in

S. F. Wang; L. Shen; Y. J. Tong; L. Chen; I. Y. Phang; P. Q. Lim; T. X. Liu

2005-01-01

93

Intumescent flame retardant-montmorillonite synergism in ABS nanocomposites  

Microsoft Academic Search

A synergistic effect was observed between montmorillonite and a novel intumescent flame retardant, poly (4, 4-diaminodiphenyl methane spirocyclic pentaerythritol bisphosphonate) (PDSPB) in ABS nanocomposites. Montmorillonite dispersion was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal stability and flammability properties were investigated by thermogravimetric analysis (TGA) and cone calorimeter tests. Incorporating PDSPB together with montmorillonite enhanced thermal stability

Haiyun Ma; Lifang Tong; Zhongbin Xu; Zhengping Fang

2008-01-01

94

Reduction of residual stress in montmorillonite\\/epoxy compounds  

Microsoft Academic Search

An epoxy resin was cured while in intimate contact with small amounts of epoxyphilic montmorillonites. It was determined that cured epoxy exists within the montmorillonite interlayer by the observation of very high interlayer spacings, even greater than 8 nm, Generally, epoxy compounds containing montmorillonites that had been swollen in the curing agent prior to curing exhibited larger interlayer spacings, especially

P. Kelly; A. Akelah; S. Qutubuddin; A. Moet

1994-01-01

95

Surface characterization of silane-treated industrial glass fibers  

Microsoft Academic Search

The adsorption of silane coupling agents onto glass fiber surfaces has been investigated. The type of adsorption was elucidated using electron spectroscopy for chemical analysis (ESCA or XPS). The surface charging was recorded using streaming potential analysis. The silane bond strength was tested by boiling the silanized fibers in water for 2 h. Thereafter the conductivity of the water was

A. E. E. Norström; H. M. Fagerholm; J. B. Rosenholm

2001-01-01

96

Surface modification of polymers treated by various fluorinating media.  

PubMed

Fluorination processes of polymer surfaces are able to lead to drastic modifications of the surface properties without changing the bulk characteristics of the virgin material. In this paper, two types of polymers, i.e. ultrahigh molecular weight polyethylene (UHMWPE) and high density polyethylene (HDPE), are considered. The surface of these materials have been modified using two different fluorination routes, both carried out at room temperature: the direct fluorination with 10% F2 + 90% He gaseous mixtures and the radio-frequency plasma-enhanced fluorination (PEF) using either O2/CF4 mixtures or c-C4F8. The effect of these processes on the surface of the polymer samples are compared using mostly XPS results. The different components of the C1s spectra are assigned in term of CFx bonding, giving valuable information on the surface fluorination rate. PMID:24169703

Tressaud, Alain; Durand, Etienne; Labrugčre, Christine; Kharitonov, Alexander P; Simbirtseva, Galina V; Kharitonova, Larisa N; Dubois, Marc

2013-01-01

97

Sorption of phenol and alkylphenols from aqueous solution onto organically modified montmorillonite and applications of dual-mode sorption model  

SciTech Connect

Single- and multisolute competitive sorptions were carried out in a batch reactor to investigate the uptake of phenol, 4-methylphenol (MeP), 2,4-dimethylphenol (DMeP), and 4-ethylphenol (EtP) dissolved in water at 25 C onto organically modified montmorillonite. Hexadecyltrimethylammonium (HDTMA) cation was exchanged for metal cations on the montmorillonite to the extent of the cation-exchange capacity (CEC) of the montmorillonite to prepare HDTMA-montmorillonite, changing its surface property from hydrophilic to organophilic. It was observed from the experimental results that the adsorption affinity on HDTMA-montmorillonite was in the order 4-EtP {approx} 2,4-DMeP > 4-MeP > phenol. The Langmuir, dual-mode sorption (DS), and Redlich-Peterson (RP) models were used to analyze the single-solute sorption equilibria. The competitive Langmuir model (CLM), competitive dual-mode sorption model (CDSM), and ideal adsorbed solution theory (IAST), coupled with the single-solute models (i.e., Langmuir, DS, and RP models), were used to predict the multisolute competitive sorption equilibria. All the models considered in this work yielded favorable representations of both single- and multisolute sorption behaviors. DSM, CDSM, and IAST coupled with the DSM were found to be other satisfactory models to describe the single- and multisolute sorption of the phenolic compounds onto HDTMA-montmorillonite.

Huh, J.K.; Song, D.I.; Jeon, Y.W.

2000-01-01

98

Synthesis and Characterization of the Hybrid Clay- Based Material Montmorillonite-Melanoidin: A Potential Soil Model  

SciTech Connect

The study of the interactions among metals, minerals, and humic substances is essential in understanding the migration of inorganic pollutants in the geosphere. A considerable amount of organic matter in the environment is associated with clay minerals. To understand the role of organic matter in the environment and its association with clay minerals, a hybrid clay-based material (HCM), montmorillonite (STx-1)-melanoidin, was prepared from L-tyrosine and L-glutamic acid by the Maillard reaction. The HCM was characterized by elemental analysis, nuclear magnetic resonance, x-ray photoelectron spectroscopy (XPS), scanning transmission x-ray microscopy (STXM), and thermal analysis. The presence of organic materials on the surface was confirmed by XPS and STXM. The STXM results showed the presence of organic spots on the surface of the STx-1 and the characterization of the functional groups present in those spots. Thermal analysis confirmed the existence of organic materials in the montmorillonite interlayer, indicating the formation of a composite of melanoidin and montmorillonite. The melanoidin appeared to be located partially between the layers of montmorillonite and partially at the surface, forming a structure that resembles the way a cork sits on the top of a champagne bottle.

V Vilas; B Matthiasch; J Huth; J Kratz; S Rubert de la Rosa; P Michel; T Schäfer

2011-12-31

99

Pu(V) and Pu(IV) sorption to montmorillonite.  

PubMed

Plutonium (Pu) adsorption to and desorption from mineral phases plays a key role in controlling the environmental mobility of Pu. Here we assess whether the adsorption behavior of Pu at concentrations used in typical laboratory studies (?10(-10) [Pu] ? 10(-6) M) are representative of adsorption behavior at concentrations measured in natural subsurface waters (generally <10(-12) M). Pu(V) sorption to Na-montmorillonite was examined over a wide range of initial Pu concentrations (10(-6)-10(-16) M). Pu(V) adsorption after 30 days was linear over the wide range of concentrations studied, indicating that Pu sorption behavior from laboratory studies at higher concentrations can be extrapolated to sorption behavior at low, environmentally relevant concentrations. Pu(IV) sorption to montmorillonite was studied at initial concentrations of 10(-6)-10(-11) M and was much faster than Pu(V) sorption over the 30 day equilibration period. However, after one year of equilibration, the extent of Pu(V) adsorption was similar to that observed for Pu(IV) after 30 days. The continued uptake of Pu(V) is attributed to a slow, surface-mediated reduction of Pu(V) to Pu(IV). Comparison between rates of adsorption of Pu(V) to montmorillonite and a range of other minerals (hematite, goethite, magnetite, groutite, corundum, diaspore, and quartz) found that minerals containing significant Fe and Mn (hematite, goethite, magnetite, and groutite) adsorbed Pu(V) faster than those which did not, highlighting the potential importance of minerals with redox couples in increasing the rate of Pu(V) removal from solution. PMID:23614502

Begg, James D; Zavarin, Mavrik; Zhao, Pihong; Tumey, Scott J; Powell, Brian; Kersting, Annie B

2013-05-13

100

High-Resolution of Electron Microscopy of Montmorillonite and Montmorillonite/Epoxy Nanocomposites.  

National Technical Information Service (NTIS)

Using high resolution transmission electron microscopy the structure and morphology of montmorillonite (MMT), a material of current interest for use in polymer nanocomposites, was characterized. Using both imaging theory and experiment, the procedures nee...

L. F. Drummy K. Farmer A. Tan B. L. Farmer R. A. Vaia

2005-01-01

101

Selected herbicides in treated and untreated surface water  

Microsoft Academic Search

Atrazine, simazine, propazine, alachlor, and molinate were determined in raw (Po river) and treated waters of an advanced water supply treatment plant (WSTP) equipped with a granular activated carbon (GAC) column. Continous liquid?liquid (LLE) and C18 solid?phase (SPE) extractions were used to isolate the herbicides before the gas Chromatographic analysis using nitrogen?phosphorus (HRGC?NPD) and mass spectrometry (HRGC?MS) detection. The concentrations

A. Marcomini; G. Perin; S. Stelluto; M. Da Ponte; P. Traverso

1991-01-01

102

Discrete surface state related to nitrogen-vacancy defect on plasma-treated GaN surfaces  

NASA Astrophysics Data System (ADS)

Detailed studies on the defect-related surface states of plasma-exposed n-GaN surfaces were carried out. An anomalous flat portion appeared in the metal-insulator-semiconductor capacitance-voltage characteristics for the sample exposed to H2 plasma, corresponding to a localized peak at EC-0.5 eV in the surface state density distribution. Atomic-force microscope and x-ray photoemission studies revealed the formation of Ga droplets on H2-plasma-treated GaN surfaces, caused by the desorption of nitrogen atoms in the form of NHx. These results suggested that a nitrogen-vacancy-related state near the conduction-band edge was introduced on the H2-plasma-treated GaN surface. No such effects took place on the N2-plasma-treated GaN surfaces.

Hashizume, Tamotsu; Nakasaki, Ryusuke

2002-06-01

103

Tribocorrosion behaviour of duplex surface treated AISI 304 stainless steel  

Microsoft Academic Search

This paper reports on the corrosion and tribocorrosion behaviour of AISI 304 stainless steel surfaces after processed by a duplex treatment consisting of plasma nitriding and a CrN coating by physical vapour deposition (PVD). An industrial evaporation PVD reactor chamber has been adapted to produce a nitriding layer using arc-enhanced glow discharge (AEGD) in the presence of nitrogen gas. Subsequently,

A. de Frutos; M. A. Arenas; G. G. Fuentes; R. J. Rodríguez; R. Martínez; J. C. Avelar-Batista; J. J. de Damborenea

2010-01-01

104

Plasma-treated switchable wettability of parylene-C surface  

Microsoft Academic Search

The wetting behavior of biomaterials is of great importance for the issues such as biofouling control and biocompatibility improvement. Therefore, tailoring of their wettability is particularly useful and has been attracting a lot of interests. This paper focuses on the modification of surface wettability on the parylene-C film, which is exclusively used as a coating material for insulating implantable biomedical

Xiao-Peng Bi; Nathan L. Ward; Brian P. Crum; Wen Li

2012-01-01

105

Surface energy increase of oxygen-plasma-treated PET  

Microsoft Academic Search

Prosthetic composite is a widely used biomaterial that satisfies the criteria for application as an organic implant without adverse reactions. Polyethylene therephthalate (PET) fiber-reinforced composites have been used because of the excellent cell adhesion, biodegradability and biocompatibility. The chemical inertness and low surface energy of PET in general are associated with inadequate bonds for polymer reinforcements. It is recognized that

M. O. H. Cioffi; H. J. C. Voorwald; R. P. Mota

2003-01-01

106

Identification of the Dispersion Behavior of Surface Treated Nanoscale Powders  

Microsoft Academic Search

The stability of highly acidic metal oxide surface treatments on rutile titanium dioxide nanopowders (40 nm nominal particle size) is examined. Dispersions are characterized in terms of their sedimentation behavior and light scattering pattern. Using elliptically polarized light scattering (EPLS), agglomerates are identified as fractal structures and size analysis is performed according to the measured fractal dimension. The effect of

C. Saltiel; Q. Chen; S. Manickavasagam; L. S. Schadler; R. W. Siegel; M. P. Menguc

2004-01-01

107

Force Field for Mica-Type Silicates and Dynamics of Octadecylammonium Chains Grafted to Montmorillonite  

SciTech Connect

Layered silicates are widely used in nanotechnology and composite materials. We describe a force field for phyllosilicates (mica, montmorillonite, and pyrophyllite) on the basis of physically justified atomic charges, van der Waals parameters, vibrational constants, and distributions of charge defects in agreement with solid state {sup 29}Si NMR data. Unit cell parameters deviate only {approx}0.5% relative to experimental X-ray measurements and surface (respectively cleavage) energies deviate less than 10% from experimental data, including the partition between Coulomb and van der Waals contributions. Reproduction of surface energies facilitates quantitative simulations of hybrid interfaces with water, organics, and biomolecules for which accurate force fields are available. Parameters are consistent with the force fields PCFF (polymer consistent force field), CVFF (consistent valence force field), CHARMM (chemistry at Harvard macromolecular mechanics), and GROMACS (Groningen machine for chemical simulations). As an example of interest, we investigate the structure and dynamics of octadecylammonium montmorillonite ('C{sub 18}'-montmorillonite, cation exchange capacity = 91 mmol/100 g) by molecular dynamics simulation. The surfactant chains assemble essentially as a bilayer with minimal interpenetration within the gallery while the ammonium headgroups are hydrogen-bonded to cavities in the montmorillonite surface. In contrast to quaternary ammonium ions, no rearrangements on the surface have been observed (cavity crossing barrier >5 kcal/mol). The alkyl chains are in a liquidlike state with approximately 30% gauche conformations, in agreement with previous Fourier-transform infrared and solid-state NMR measurements. Computed X-ray diffraction patterns of sodium and C18-montmorillonite agree very well with X-ray patterns from experiment, and the computational model can assist in the assignment of complex reflections.

Heinz,H.; Koerner, H.; Anderson, K.; Vaia, R.; Farmer, B.

2005-01-01

108

Surface modification for hydrophilic property of stainless steel treated by atmospheric-pressure plasma jet  

Microsoft Academic Search

Surface of a stainless steel has been modified by atmospheric-pressure plasma jet method at room temperature. The impulse voltage is applied to ignite a plasma discharge using high purity (99.999%) reactive gases: N2 and O2. The treated stainless steel is characterized by the activation property of the surface using a contact angle analyzer. Surface energy for the treated stainless steel

M. C. Kim; D. K. Song; H. S. Shin; S.-H. Baeg; G. S. Kim; J.-H. Boo; J. G. Han; S. H. Yang

2002-01-01

109

In vitro Remineralization of Caries Lesions Treated with Surface-Active Phosphates  

Microsoft Academic Search

Intact human enamel was demineralized in vitro to obtain artificial caries lesions. Part of the lesions was then treated with different surface-active compounds and remineralized with a remineralizing solution. The other part of the lesions was de- and remineralized in the same way, but was not treated with a surface-active compound. The results indicate that none of the surface-active compounds

J. M. P. M. Borggreven; P. C. Lammers; T. Hoeks; B. Zwanenburg; F. C. M. Driessens

1991-01-01

110

Sorption of sodium dodecylbenzene sulfonate by montmorillonite  

Microsoft Academic Search

Sorption of linear alkylbenzene sulfonates by soils and sediments is an important process that may affect their fate, transport, toxicity and their application in remediation of contaminated soil and groundwater. In this study, batch experiments were conducted to elucidate the sorption of a widely used anionic surfactant, sodium dodecylbenzene sulfonate (SDBS), by montmorillonite. It was observed that: (i) SDBS was

Kun Yang; Lizhong Zhu; Baoshan Xing

2007-01-01

111

Selenium sorption by kaolinite and montmorillonite  

Microsoft Academic Search

Toxic selenium (Se) concentrations were found recently in shallow ground water on the west side of the San Joaquin Valley in California. The origin of the Se and the mechanism by which it accumulated in the ground water are not known. The objective of this work was to study Se sorption by kaolinite and montmorillonite at different pH levels, as

B. Bar-Yosef; D. Meek

1987-01-01

112

A Model for Metal Adsorption on Montmorillonite  

Microsoft Academic Search

A consistent thermodynamic model is developed for metal sorption on expanding 2:1 layer clays such as montmorillonite. The particle of clay, including lamellae and interlayers, is represented as a porous solid bearing a permanent negative charge (resulting from isomorphic substitution) with an infinite plane interface (i.e., edges) with the solution. Cation exchange occurs inside the clay particle as the result

Anne M. L. Kraepiel; Klaus Keller; François M. M. Morel

1999-01-01

113

Heterogeneous uptake of nitric acid on Na-montmorillonite clay as a function of relative humidity  

NASA Astrophysics Data System (ADS)

Atmospheric mineral aerosol is a potentially important reactive surface that may provide a heterogeneous sink for gas phase species such as nitric acid (HNO3). We have studied the uptake of HNO3 on Na-montmorillonite, a swelling clay mineral, at low temperatures as a function of relative humidity (RH), HNO3 pressure and clay mass. Condensed phase products were probed with transmission Fourier transform infrared spectroscopy while the loss of HNO3 from the gas phase was simultaneously monitored with mass spectrometry. We find that below 16% RH, uptake of HNO3 on Na-montmorillonite is below our detection limit. However, at 29% RH the lower limit to the uptake coefficient for loss of HNO3 on Na-montmorillonite is ? = 8 × 10-5 as calculated using the BET surface area. This value increases to ? = 4 × 10-4 at 44% RH. The HNO3 content, water content and ? all increase with increasing RH, but are independent of temperature from 210 to 232 K and independent of pressure from 1 × 10-5 to 3 × 10-4 torr HNO3. Surprisingly, at 44% RH, Na-montmorillonite can contain approximately 20% water and 30% HNO3 by weight. The results of this study suggest that swelling clays can impact the partitioning of gas phase HNO3 when sufficient water vapor is available and may serve as a potentially important cloud condensation nucleus in the troposphere.

Mashburn, C. D.; Frinak, E. K.; Tolbert, M. A.

2006-08-01

114

Permeability and frictional strength of cation-exchanged montmorillonite  

NASA Astrophysics Data System (ADS)

Smectites, such as montmorillonite, are abundant throughout the upper crust and are commonly found in fault gouge. They are known for their weak frictional strength and low permeability. Smectites are swellable clays in which the interlayer cation can easily be exchanged. In this study, we measure permeability and frictional strength of montmorillonite exchanged with Na+, K+, Ca2+, and Mg2+ using a triaxial shear apparatus. We find that the interlayer cation influences both permeability and the friction coefficient. K-montmorillonite is significantly stronger (?=0.26) than Na-montmorillonite (?=0.15) and Ca- or Mg-montmorillonite (?=0.11). Permeability for all four clays is between 10-21 and 10-23 m2 in the pressure range between 10 MPa and 100 MPa, with K-montmorillonite the most permeable clay gouge. Mg-, Ca-, and Na-montmorillonite show relative similar permeabilities of which Na-montmorillonite is least permeable. We relate the higher frictional strength and permeability of K-montmorillonite to reduce interlayer water content caused by differences in cation hydration and adsorption. The results show that the rapid cation exchange process in montmorillonite can influence macroscale parameters, such as permeability and strength, which can contribute to changes in local pressure conditions and frictional strength of shallow fault zones.

Behnsen, J.; Faulkner, D. R.

2013-06-01

115

Influence of montmorillonite tactoid size on Na-Ca cation exchange reactions.  

PubMed

The spatial organisation of swelling clay platelets in a suspension depends on the chemical composition of the equilibration solution. Individual clay platelets can be well dispersed, with surfaces entirely in contact with the external solution, or be stacked in tactoids, where part of the surfaces forms parallel alignments embedding interlayer water and cations. External and interlayer surfaces do not exhibit similar affinities for cations having different hydration and charge properties and the clay platelet stacking arrangement influences the clay affinity for these cations. This paper aims to establish the link between exchange properties and clay tactoid size and organisation for Na-Ca exchange on montmorillonite. Different montmorillonite samples behave differently with regards to Na-Ca exchange, from ideal to non-ideal exchange behaviour. A simple model coupling the tactoid stacking size to different Na/Ca relative affinities of the external and interlayer clay surfaces enables these differences to be reproduced. PMID:21920529

Tournassat, Christophe; Bizi, Mohamed; Braibant, Gilles; Crouzet, Catherine

2011-08-16

116

Montmorillonite, Oligonucleotides, RNA and Origin of Life  

NASA Astrophysics Data System (ADS)

Na-montmorillonite prepared from Volclay by the titration method facilitates the self-condensation of ImpA, the 5'-phosphorimidazolide derivative of adenosine. As was shown by AE-HPLC analysis and selective enzymatic hydrolysis of products, oligo(A)s formed in this reaction are 10 monomer units long and contain 67% 3',5'-phosphodiester bonds (Ferris and Ertem, 1992a). Under the same reaction conditions, 5'-phosphorimidazolide derivatives of cytidine, uridine and guanosine also undergo self-condensation producing oligomers containing up to 12-14 monomer units for oligo(C)s to 6 monomer units for oligo(G)s. In oligo(C)s and oligo(U)s, 75-80% of the monomers are linked by 2',5'-phosphodiester bonds. Hexamer and higher oligomers isolated from synthetic oligo(C)s formed by montmorillonite catalysis, which contain both 3',5'- and 2',5'-linkages, serve as catalysts for the non-enzymatic template directed synthesis of oligo(G)s from activated monomer 2-MeImpG, guanosine 5'-phospho-2-methylimidazolide (Ertem and Ferris, 1996). Pentamer and higher oligomers containing exclusively 2',5'-linkages, which were isolated from the synthetic oligo(C)s, also serve as templates and produce oligo(G)s with both 2',5'- and 3',5'-phosphodiester bonds. Kinetic studies on montmorillonite catalyzed elongation rates of oligomers using the computer program SIMFIT demonstrated that the rate constants for the formation of oligo(A)s increased in the order of 2-mer <3-mer <4-mer ... <7-mer (Kawamura and Ferris, 1994). A decameric primer, dA(pdA)8pA bound to montmorillonite was elongated to contain up to 50 monomer units by daily addition of activated monomer ImpA to the reaction mixture (Ferris, Hill and Orgel, 1996). Analysis of dimer fractions formed in the montmorillonite catalyzed reaction of binary and quaternary mixtures of ImpA, ImpC, 2-MeImpG and ImpU suggested that only a limited number of oligomers could have formed on the primitive Earth rather than equal amounts of all possible isomers (Ertem and Ferris, 2000). Formation of phosphodiester bonds between mononucleotides by montmorillonite catalysis is a fascinating discovery, and a significant step forward in efforts to find out how the first RNA-like oligomers might have formed in the course of chemical evolution. However, as has been pointed out in several publications, these systems should be regarded as models rather than a literal representation of prebiotic chemistry (Orgel, 1998; Joyce and Orgel, 1999; Schwartz, 1999).

Ertem, Gözen

2004-12-01

117

Studies on interaction of dodecyltrimethylammonium bromide with Na- and Al-montmorillonite  

SciTech Connect

Adsorption of surfactants on clay minerals can change such surface properties, as wetting, flocculation, aggregation, and reduction of swelling. Thus, they have been used widely in environmental control and enhancement of oil recovery. The adsorption isotherms and adsorption enthalpies of dodecyltrimethylammonium bromide (DDTMAB) on Na- and Al-montmorillonite were determined in the pH range 2--12. The basal spacings of the clays were also studied by X-ray diffraction. Interactions of DDTMAB with the two montmorillonites predominate mostly through cation exchange in the pH range studied. In the case of Na-montmorillonite, the amount of adsorption increases with pH, but adsorption enthalpy decreases with pH. For Al-montmorillonite, adsorption enthalpy exhibits nonmonotonic variation with pH, although the amount of adsorption increases with pH monotonously. The adsorption enthalpies of DDTMAB on the clays are negative. The adsorbed DDTMAB molecules in clay interlayers present a bilayer arrangement at saturation.

Pan, J.; Yang, G.; Han, B.; Yan, H. [Academia Sinica, Beijing (China). Inst. of Chemistry

1997-10-15

118

Evaluation of Residual Stress Relaxation in Surface-Treated Engine Alloys.  

National Technical Information Service (NTIS)

Recent research results indicate that eddy current conductivity measurements can be exploited for nondestructive evaluation of subsurface residual stresses in surface-treated nickel-base superalloy components. According to this approach, first the depth-d...

P. B. Nagy

2008-01-01

119

RESIDUAL STRESS ASSESSMENT IN SURFACE-TREATED NICKEL-BASE SUPERALLOYS  

Microsoft Academic Search

Experimental results are presented to illustrate that there exists a unique window of opportunity for eddy current NDE of residual stress in surface-treated nickel-base superalloys. In light of its frequency-dependent penetration depth, the measurement of eddy current conductivity has been suggested as a possible means to allow the nondestructive evaluation of subsurface residual stresses in surface-treated components. This technique is

M. P. Blodgett; P. B. Nagy

120

Interaction of cationic surfactants with iron and sodium montmorillonite suspensions  

SciTech Connect

Calorimetry, static technique, and X-ray diffraction (XRD) analysis were employed to study the adsorption of cetyltrimethylammonium bromide (CTAB) and dodecyltrimethylammonium bromide (DTAB) on Fe-montmorillonite and Na-montmorillonite suspensions. The results show that the process of adsorption is exothermic and that the type of clay and the alkyl chain length of surfactant affect the amount of adsorption and the enthalpy of adsorption significantly but that the effect of temperature is very limited in the temperature range studied. The magnitudes of adsorption amount and adsorption enthalpy follow the order Na-montmorillonite > Fe-montmorillonite, CTAB > DTAB. The basal spacings determined by X-ray powder diffraction indicate that the CTAB adsorbed between the clay interlayers in a bilayer arrangement, while the DTAB formed bilayers or monolayers at saturation adsorption between the Na-montmorillonite and Fe-montmorillonite interlayers, respectively. The adsorption mechanism is also discussed on the basis of the experimental data.

Chen, G.; Han, B.; Yan, H. [Chinese Academy of Sciences, Beijing (China). Inst. of Chemistry

1998-05-15

121

Heat shock structure of luciferase on wet-treated Si surface  

NASA Astrophysics Data System (ADS)

Heat shock structure of luciferase on a wet-treated Si surface was estimated by molecular dynamics simulations. The structural changes in the active site of luciferase were smaller on the hydrophobic Si surface than on the hydrophilic Si surface at high temperature, although the structural changes in the active site of luciferase were smaller on the hydrophilic Si surface than on the hydrophobic Si surface at room temperature. The fine wet-treatment could improve the heat shock resistance of luciferase on the Si surface.

Nishiyama, Katsuhiko; Hoshino, Tadatsugu

2009-09-01

122

Preparation and characterization of antibacterial silver/vermiculites and silver/montmorillonites  

NASA Astrophysics Data System (ADS)

The reason for the preparation and characterization of the novel antibacterial silver/vermiculites (Ag/V) together with the silver/montmorillonites (Ag/M) was that the information on the vermiculite structure change and stability of Ag/V in water as well as its effect on bacteria are sporadic. The vermiculite (V), (Si 3.02Al 0.98) IV (Mg 2.27Al 0.12Fe0.283+Fe0.052+Ti 0.07) VI O 10(OH) 2 Ca 0.09Na 0.21K 0.50 from West China and montmorillonite (M), (Si 3.96Al 0.04) IV (Al 1.20Fe0.343+Mg 0.42Ti 0.02) VI O 10 (OH) 2Ca 0.15Na 0.14K 0.08 from Ivan?ice (Czech Republic), fraction <0.4 ?m were the starting clay materials for sample preparation. The samples V1 and M1 were prepared via reaction of the V and M with the 0.01 mol L -1 AgNO 3 aqueous solution. The samples V2 and M2 were treated with the aqueous solution of AgNO 3 for two times. The cation exchange and reduced metallic silver on M1 and V1 evoked the specific surface area (SSA) diminution, the mean particle-size diameter extension and appearance of micropores with radius (<0.4 nm). Repeated silver cation exchange in M2 and V2 reduced particle size, increased slightly SSA and micropores with radius of 0.4-0.5 nm. Samples Ag/V and Ag/M showed higher content of pores with radius 0.5-1.0 nm than original V and M. The Ag concentration was found higher in Ag/V than in Ag/M and higher in repeatedly treated samples: 0.9 wt.% Ag in V1, 1.4 wt.% Ag in V2, 0.6 wt.% Ag in M1 and 1.0 wt.% Ag in M2. Vermiculite structure consisting of the hydrated interstratified phases and the mica-like phase changed to the cation-one-zero layer hydrate interstratification structure in V1 and to the random of two-one layer hydrate interstratifications in V2. Infrared and Mössbauer spectroscopy revealed no changes in the structure of the clay minerals that could be related directly to the sorption and crystallization of silver. Transmission electron microscopy showed that the silver nanoparticles size distribution was much narrower for the samples Ag/M than for Ag/V. The mean size of the Ag particles was between 40 and 50 nm. Although the Ag nanoparticles did not adhere sufficiently at the clay minerals surface and migrated moderately into water, all samples under study were approved to be effective inhibitors of the bacterial growth persisting for the whole testing period of 6 days. Silver/vermiculite was antimicrobial more efficient against Klebsiella pneumoniae and Pseudomonas aeruginosa than silver/montmorillonite.

Valášková, Marta; Hundáková, Marianna; Kutláková, Kate?ina Mamulová; Seidlerová, Jana; ?apková, Pavla; Pazdziora, Erich; Mat?jová, Kate?ina; He?mánek, Martin; Klemm, Volker; Rafaja, David

2010-11-01

123

Biosensoring of hydrogen peroxide using new methylene blue N incorporated in a montmorillonite-modified horseradish peroxidase immobilization matrix as an electron shuttle  

Microsoft Academic Search

A novel H2O2 sensor is described. New methylene blue N, a cation dye mediator, was incorporated in the montmorillonite-horseradish peroxidase (HRP) hydrogel cross-linked on a glassy carbon electrode surface via bovine serum albumin (BSA)-glutaraldehyde to construct the sensor. The interaction of the dye with sodium montmorillonite colloidal particles was investigated by employing visible spectrometry, X-ray photoelectron spectroscopy (XPS), and electrochemical

Chenghong Lei; Zhanen Zhang; Haiying Liu; Jilie Kong; Jiaqi Deng

1996-01-01

124

Eddy current spectroscopy for near-surface residual stress profiling in surface treated nonmagnetic engine alloys  

NASA Astrophysics Data System (ADS)

Recent research results indicated that eddy current conductivity measurements can be exploited for nondestructive evaluation of near-surface residual stresses in surface-treated nickel-base superalloy components. Most of the previous experimental studies were conducted on highly peened (Almen 10-16A) specimens that exhibit harmful cold work in excess of 30% plastic strain. Such high level of cold work causes thermo-mechanical relaxation at relatively modest operational temperatures; therefore the obtained results were not directly relevant to engine manufacturers and end users. The main reason for choosing peening intensities in excess of recommended normal levels was that in low-conductivity engine alloys the eddy current penetration depth could not be forced below 0.2 mm without expanding the measurements above 10 MHz which is beyond the operational range of most commercial eddy current instruments. As for shot-peened components, it was initially felt that the residual stress effect was more difficult to separate from cold work, texture, and inhomogeneity effects in titanium alloys than in nickel-base superalloys. In addition, titanium alloys have almost 50% lower electric conductivity than nickel-base superalloys; therefore require proportionally higher inspection frequencies, which was not feasible until our recent breakthrough in instrument development. Our work has been focused on six main aspects of this continuing research, namely, (i) the development of an iterative inversion technique to better retrieve the depth-dependent conductivity profile from the measured frequency-dependent apparent eddy current conductivity (AECC), (ii) the extension of the frequency range up to 80 MHz to better capture the peak compressive residual stress in nickel-base superalloys using a new eddy current conductivity measuring system, which offers better reproducibility, accuracy and measurement speed than the previously used conventional systems, (iii) the lift-off effect on high frequency eddy current spectroscopy, (iv) the development of custom-made spiral coils to allow eddy current conductivity characterization over the whole frequency range of interest with reduced coil sensitivity to lift off, (v) the benefits of implementing a semi-quadratic system calibration in reducing the coil sensitivity to lift-off, and (vi) the feasibility of adapting high-frequency eddy current residual stress characterization for shot-peened titanium alloys.

Abu-Nabah, Bassam A.

125

An investigation on surface properties of treated low carbon and alloyed steels (boriding and carburizing)  

Microsoft Academic Search

In this study, the wear behaviour of the borided and carburized AISI 1020 and 5115 steels are investigated. Some of the samples prepared from test materials are carburized and some borided. The microstructure, worn surface and hardness distribution of the samples are examined. After and before wear testing, the surface phases of the treated samples are determined by X-ray diffraction

B Selçuk; R Ipek; M. B Karami?; V Kuzucu

2000-01-01

126

Limited receptive area neural classifier for texture recognition of mechanically treated metal surfaces  

Microsoft Academic Search

The Limited Receptive Area (LIRA) neural classifier is proposed for texture recognition of mechanically treated metal surfaces. It may be applied in systems that have to recognize position and orientation of complex work pieces during micromechanical device assembly as well as in surface quality inspection systems. The performance of the proposed classifier was tested on a specially created image database

Oleksandr Makeyev; Edward Sazonov; Tatiana Baidyk; Anabel Martín

2008-01-01

127

Cardiopulmonary Bypass Circuit Treated With Surface-Modifying Additives: A Clinical Evaluation of Blood Compatibility  

Microsoft Academic Search

Background. The cardiopulmonary bypass (CPB) circuit induces blood activation and a systemic inflammatory response in cardiac surgical patients. The CPB circuit treated with surface-modifying additive (SMA) has been found to reduce blood activation by in vitro and ex vivo experiments. This study evaluates the surface thrombogenicity and complement activation of SMA circuits during clinical CPB.Methods. Twenty patients undergoing coronary artery

Y. John Gu; Piet W. Boonstra; Anthony A. Rijnsburger; Johan Haan; Willem van Oeveren

1998-01-01

128

Samarium Ion Exchanged Montmorillonite for High Temperature Cumene Cracking Reaction  

NASA Astrophysics Data System (ADS)

Montmorillonite clay is cation exchanged with samarium and its catalytic influence in cumene cracking reaction is investigated. Effect of exchange with sodium ions on further exchange with samarium ions is also noted. Acidity measurements are done using Temperature Programmed Desorption (TPD) of ammonia. The retention of basic structure is proved from FTIR spectra and XRD patterns. Elemental analysis result shows that samarium exchange has occurred, which is responsible for the higher catalytic activity. Surface area and pore volume remains more or less unaffected upon exchange. Thermogravimetric analysis indicates the enhanced thermal stability on exchanging. Cumene cracking reaction is carried out at atmospheric pressure in a fixed bed glass reactor at 673 K. The predominance of Brřnsted acidity is confirmed from high selectivity to benzene.

Binitha, N. N.; Silija, P. P.; Suraj, V.; Yaakob, Z.; Sugunan, S.

2011-02-01

129

Preparation and characterization of microporous SiO{sub 2}-ZrO{sub 2} pillared montmorillonite  

SciTech Connect

SiO{sub 2}-ZrO{sub 2} pillared montmorillonite (SZM) was prepared by the reaction of Na-montmorillonite with colloidal silica-zirconia particles which were prepared by depositing zirconium hydroxy cations on silica particles. By pillaring with the colloidal particles, the basal spacing of montmorillonite was expanded to ca. 45 A and the calcined SZM samples showed large specific surface areas up to 320 m{sup 2}/g at 400 deg. C. In spite of large interlayer separation, adsorption results indicated the presence of micropores generated between the colloidal particles. The microporous structure was maintained at least up to 600 deg. C and exhibited specific shape selectivity for the adsorption of large organic molecules, especially between toluene and mesitylene. According to the temperature-programmed-desorption (TPD) spectra of ammonia, the calcined SZM showed weakly acidic sites.

Han, Yang-Su [Nanospace Co. Ltd., Business Incubator, Korea Institute of Ceramic Engineering and Technology, 233-5 Gasan-dong Guemcheon-Gu, Seoul 153-801 (Korea, Republic of)]. E-mail: yshan@inanospace.com; Yamanaka, Shoji [Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Higashi-Hiroshima 739 (Japan)

2006-04-15

130

Transition metal oxide pillared clay. 1: A comparative study of textural and acidic properties of Fe(III) pillared montmorillonite and pillared acid activated montmorillonite  

SciTech Connect

Fe(III) pillared montmorillonite samples have been prepared by intercalating trinuclear acetato hydroxy-iron (III) nitrate [Fe(COOCH{sub 3}){sub 7}OH 2H{sub 2}O]{sup +} NO{sub 3}{sup {minus}} between the layers of both Na-exchanged and acid-activated montmorillonite, followed by calcination and characterized by various techniques. The multistep ion exchange process gave better complex loading than the single step process. FTIR and Moessbauer spectral analysis showed the presence of the complex inside the silicate layers. Materials prepared from the two starting materials are thermally stable up to 500 C, having basal spacings of 18.0 and 17.6 {angstrom} and high surface areas of 284 and 276 m{sup 2}/g, respectively. The acid-activated pillared montmorillonite shows somewhat low complex intake, but has high acidity in comparison to the Na-exchanged material. Iron oxide pillared clay has gained considerable importance as it can be used in demetalization, reduction of NO by NH{sub 3}, and Fischer-Tropsch reactions.

Mishra, T.; Parida, K.M.; Rao, S.B. [Council of Scientific and Industrial Research, Bhubaneswar (India). Regional Research Lab.

1996-10-15

131

Indium tin oxide exhibiting high poly-crystallinity on oxygen plasma-treated polyethylene terephthalate surface  

NASA Astrophysics Data System (ADS)

Low-resistivity indium tin oxide [ITO] film was successfully deposited on oxygen plasma-treated polyethylene terephthalate [PET] surfaces at room temperature. X-ray diffraction [XRD] measurements demonstrated that the film deposited on the PET surface that had not been treated with oxygen plasma had an amorphous structure. In contrast, after the low-power oxygen plasma treatment of the PET surface, the ITO film deposited on the PET surface had a poly-crystalline structure due to interactions between electric dipoles on the PET surface and electric dipoles in the ITO film. The minimum resistivity of the poly-crystalline ITO was about 3.6 times lower than that of the amorphous ITO film. In addition, we found that the resistivity of ITO film is proportional to the intensity of the (400) line in the film's XRD spectra.

Son, Phil Kook; Choi, Suk-Won; Kim, Sung Soo

2012-02-01

132

Biocidal action of ozone-treated polystyrene surfaces on vegetative and sporulated bacteria  

NASA Astrophysics Data System (ADS)

Surfaces of materials can be modified to ensure specific interaction features with microorganisms. The current work discloses biocidal properties of polystyrene (PS) Petri-dish surfaces that have been exposed to a dry gaseous-ozone flow. Such treated PS surfaces are able to inactivate various species of vegetative and sporulated bacteria on a relatively short contact time. Denaturation of proteins seems likely based on a significant loss of enzymatic activity of the lysozyme protein. Characterization of these surfaces by atomic-force microscopy (AFM), Fourier-transform infra-red (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) reveals specific structural and chemical modifications as compared to untreated PS. Persistence of the biocidal properties of these treated surfaces is observed. This ozone-induced process is technically simple to achieve and does not require active precursors as in grafting.

Mahfoudh, Ahlem; Barbeau, Jean; Moisan, Michel; Leduc, Annie; Séguin, Jacynthe

2010-03-01

133

The structure of uranium (VI) sorption complexes on silica, alumina, and montmorillonite  

Microsoft Academic Search

We have investigated the adsorption of the uranyl ion (UO22+) in contact with amorphous silica (SiO2), ?-alumina (Al2O3), and montmorillonite surfaces in the pH range of 3.1–6.5, using X-ray absorption fine structure (XAFS) spectroscopy to observe the local structure around the uranium atom. Analysis shows that in all samples the uranyl ion structure is preserved, with two axial oxygen atoms

E. R Sylwester; E. A Hudson; P. G Allen

2000-01-01

134

Heterogeneous uptake of nitric acid on Na-montmorillonite clay as a function of relative humidity  

Microsoft Academic Search

Atmospheric mineral aerosol is a potentially important reactive surface that may provide a heterogeneous sink for gas phase species such as nitric acid (HNO3). We have studied the uptake of HNO3 on Na-montmorillonite, a swelling clay mineral, at low temperatures as a function of relative humidity (RH), HNO3 pressure and clay mass. Condensed phase products were probed with transmission Fourier

C. D. Mashburn; E. K. Frinak; M. A. Tolbert

2006-01-01

135

Hydroconversion of Heptane over Pt\\/Al-Pillared Montmorillonites and Saponites. A Comparative Study  

Microsoft Academic Search

Montmorillonites and saponites have been pillared with oxo-hydroxy-aluminium solutions (OH\\/Al molar ratio of 1.6). The solids have been examined by X-ray diffraction. The textural properties, residual cation exchange capacities, and acid contents have been established. The pillared clays exhibit thermally stable spacings, specific surface areas, and micropore volumes typical of such materials. Higher acid contents were found for pillared saponites

S. Moreno; R. Sun Kou; G. Poncelet

1996-01-01

136

Modeling of H+ and Cu2+ Adsorption on Calcium-Montmorillonite  

Microsoft Academic Search

The interaction of H § and Cu2+-ions with Ca-montmorillonite was investigated in 0.1 tool\\/ dm 3 solutions of Ca(CIO4)z at 298.2 K by potentiometric titrations using both glass electrodes (for H + ) and ion specific electrodes (for Cu z + ). The experimental data were interpreted on the basis of the surface complexation model. The calculations were performed with

Markus Stadler; PAUL W. SCHINDLER

1993-01-01

137

Abiotic transformation of TNT in montmorillonite and soil suspensions under reducing conditions  

Microsoft Academic Search

Abiotic reduction of nitrobenzenes by Fe+2 adsorbed to various surfaces has been demonstrated by others. The objective of this study was to describe abiotic TNT transformation as a function of pH and confirm the possibility of an abiotic Fe+2 reduction pathway in reduced soils.Effects of pH on abiotic transformations of TNT were examined in buffered batch tests with montmorillonite and

James M. Brannon; Cynthia B. Price; Charolett Hayes

1998-01-01

138

Surface characterization of alkali- and heat-treated Ti with or without prior acid etching  

NASA Astrophysics Data System (ADS)

Titanium and its alloys are used as implant materials in dental and orthopaedic applications. The material affinities to host bone tissue greatly concern with the recovery period and good prognosis. To obtain a material surface having excellent affinity to bone, acid etching prior to alkali- and heat-treatment of Ti was conducted. The surface characteristics of the prepared sample indicated that the roughness as well as the wettability increased by pre-etching. Bone-like apatite was formed on pre-etched, alkali- and heat-treated Ti surface in simulated body fluid (SBF) within 3 days, while it takes 5 days on the solely alkali- and heat-treated surface. Osteoblastic cells showed better compatibility on the per-etched surface compared to the pure Ti surface or alkali- and heat-treated surface. Moreover, the pre-etched surface showed better pull-off tensile adhesion strength against the deposited apatite. Thus, acid etching prior to alkali- and heat-treatment would be a promising method for enhancing the affinity of Ti to host bone tissue.

An, Sang-Hyun; Matsumoto, Takuya; Miyajima, Hiroyuki; Sasaki, Jun-Ichi; Narayanan, Ramaswamy; Kim, Kyo-Han

2012-03-01

139

PREPARATION AND CHARACTERIZATION OF POLYPROPYLENE\\/MONTMORILLONITE NANOCOMPOSITES  

Microsoft Academic Search

The aim of the present work is to prepare and study nanocomposites based on polypropylene and montmorillonite to contribute in the understanding of the relationship between the structural characteristics of these composites and their properties. Two montmorillonites are considered in the study, one obtained from an Argentinean bentonite and modified with octadecylammonium chloride, and an organophilic commercial one. Small amounts

Cora O. Rohlmann; Lidia M. Quinzani; Marcelo D. Failla

140

Structural characterization of the montmorillonite clay nanometric particles  

Microsoft Academic Search

In this work we characterize the clays of a place named “Las Pulgas”, in the Charo Canyon, State of Michoacan, Mexico. It is found that these mineral species are mainly montmorillonite, cristobalite, tridimite and albite, including quartz. Montmorillonite is the most abundant clay in this region, and has a nanometric twinned small particle habit. All this opens a potential technical

G. Carbajal De la Torre; I. Israde Alcántara; M. A. Espinosa Medina; J. Serrato; A. Negron-Mendoza; S. Ramos; G. Albarrán; J. Reyes-Gasga

1997-01-01

141

Comparison of surface-treated and untreated orthodontic bands: Evaluation of shear force and surface roughness  

Microsoft Academic Search

In an attempt to increase retention of orthodontic bands, orthodontic companies market bands with surfaces prepared to increase roughness. A comparison of six groups of bands, including two with untreated surfaces, revealed a wide range of variation in shear forces. Three classes of retention may be differentiated on the basis of non–statistically significantly different mean shear forces in each category:

Robert A Penna; Francis Mante; Bryan D Huey; Joseph Ghafari

1998-01-01

142

Tribological behaviors of steel surfaces treated with ion sulphurization duplex processes  

Microsoft Academic Search

Low temperature ion sulphurization process and its duplex treatments combining with ion-nitriding and shot-peening were used to treat 1045 steel. The anti-scuffing, friction-reducing and wear-resistant behaviors of these treated surfaces were investigated using a ball-on-disc tester under engine oil lubrication conditions. SEM, EDX, XRD, and AES were used to examine the morphologies and compositions of layers, and wear scars. The

Ning Zhang; Da-Ming Zhuang; Jia-Jun Liu

2009-01-01

143

Pedogenic formation of montmorillonite from a 2:1-2:2 intergrade clay mineral  

USGS Publications Warehouse

Montmorillonite was found to be the dominant clay mineral in surface horizons of certain soils of the North Carolina Coastal Plain whereas a 2:1-2:2 intergrade clay mineral was dominant in subjacent horizons. In all soils where this clay mineral sequence was found, the surface horizon was low in pH (below 4??5) and high in organic matter content. In contrast, data from studies of other soils of this region (Weed and Nelson, 1962) show that: (1) montmorillonite occurs infrequently; (2) maximum accumulation of the 2:1-2:2 intergrade normally occurs in the surface horizon and decreases with depth in the profile; (3) organic matter contents are low; and (4) pH values are only moderately acid (pH 5-6). It is theorized that the montmorillonite in the surface horizon of the soils studied originated by pedogenic weathering of the 2:1-2:2 intergrade clay mineral. The combined effects of low pH (below 4??5) and high organic matter content in surface horizons are believed to be the agents responsible for this mineral transformation. The protonation and solubilization (reverse of hydrolysis) of Al-polymers in the interlayer of expansible clay minerals will occur at or below pH 4??5 depending on the charge and steric effects of the interlayer. A low pH alone may cause this solubilization and thus mineral transformation, but in the soils studied the organic matter is believed to facilitate and accelerage the transformation. The intermediates of organic matter decomposition provide an acid environment, a source of protons, and a source of watersoluble mobile organic substances (principally fulvic acids) which have the ability to complex the solubilized aluminum and move it down the profile. This continuous removal of solubilized aluminum would provide for a favorable gradient for aluminum solubilization. The drainage class or position in a catena is believed to be less important than the chemical factors in formation of montmorillonite from 2:1-2:2 intergrade, because montmorillonite is present in all drainage classes if the surface horizon is low in pH and high in organic matter. ?? 1969.

Malcolm, R. L.; Nettleton, W. D.; McCracken, R. J.

1969-01-01

144

Surface energy of preservative-treated southern yellow pine ( Pinus spp.) by contact angle measurement  

Microsoft Academic Search

In this study, the contact angles of four different reference liquids (including distilled water, diiodomethane, formadide\\u000a and glycerol) formed on the surfaces of wood, treated with chromated copper arsenate (CCA) and two other emerging copper-based\\u000a water-borne systems (commercial names: NW and NS) were measured with sessile drop method. Based on the contact angle data,\\u000a the surface energy was obtained from

Jinzhen Cao; Pascal D. Kamdem

2007-01-01

145

Modification of montmorillonite with cationic surfactants. Thermal and chemical analysis including CEC determination  

Microsoft Academic Search

The thermal stability of synthesized and commercial organically modified montmorillonites has been investigated using thermogravimetric analysis (TGA). Four organo-montmorillonites have been prepared by replacing the inorganic cations of a commercial montmorillonite with aliphatic and aromatic ammonium bromide or chloride salts. The modification has been carried out by cation exchange to obtain a high level of intercalation in the montmorillonite. Conformations

A. Vazquez; M. López; G. Kortaberria; L. Martín; I. Mondragon

2008-01-01

146

Surface work function of indium tin oxide treated using plasma immersion ion implantation  

NASA Astrophysics Data System (ADS)

Oxygen plasma immersion ion implantation (O-PIII) was introduced to modify the surface of indium tin oxide (ITO) thin films. X-ray photoelectron spectroscopy and Kelvin probe were employed to study the surface work function of the treated ITO films. The results showed that the surface work function of ITO can be further enhanced by O-PIII treatment based on an oxygen inductively coupled plasma (O-ICP). The change in surface work function correlated largely with the surface stoichiometry and the high work function should be attributed to the elimination of oxygen vacancies. The surface work function of the modified ITO films showed a rapid decreasing trend with a time-dependent curve immediately after O-ICP and O-PIII treatments. However, a stabler modification effect was achieved by O-PIII.

He, Long; Wu, Zhonghang; Li, Zebin; Ju, Jiaqi; Ou, Qiongrong; Liang, Rongqing

2013-05-01

147

Dehydration enthalpy of alkali-cations-exchanged montmorillonite from thermogravimetric analysis.  

PubMed

Dehydration of a series of homoionic alkali-exchanged montmorillonites is studied at different treatment temperatures by means of thermogravimetric analysis. More specifically, we investigate the last stages of dehydration when the number of adsorbed water molecules corresponds, at maximum, to a monolayer. Weight losses are measured at several constant temperatures as a function of time. Application of Van't Hoff's law yields the dehydration enthalpy. Trends and data similar to those reported from other experimental conditions are found. Comparison with X-ray data and with the dissociation enthalpy of alkali cation/water complexes shows that dehydration of weakly hydrated homoionic alkali montmorillonites results from the competition between opposite energy contributions due to (i) the cation solvation, (ii) the hydration of the silicate interlayer surface, and (iii) the structural swelling. So, depending on the balance between these various energy contributions, different behaviors are observed according to the nature of the alkali cations. PMID:18973904

Kharroubi, M; Balme, S; Henn, F; Giuntini, J C; Belarbi, H; Haouzi, A

2008-10-29

148

IR and X-ray diffraction study of chlorpheniramine maleate-montmorillonite interaction.  

PubMed

As a contribution to studies on the adsorption of drugs by clay minerals aimed at achieving sustained action in the oral administration of antihistamines, the adsorption of chlorpheniramine maleate by sodium montmorillonite was studied by X-ray diffraction and IR spectroscopy. The results indicated that the chlorphenirammonium ion penetrated into the interlayer space of montmorillonite, producing an increase in the basal spacing, d001, of the silicate. This increase was influenced, as was the amount adsorbed, by the pH and the concentration of the chlorpheniramine maleate solution. At pH 7.0, the amount adsorbed was close to the exchange capacity, and the complex formed had a basal spacing of 17.14 A (delta = 7.54 A). The only mechanism responsible for the interaction was cation exchange. The complex at 17.14 A must be a monolayer with the benzene rings positioned perpendicular to the surface of the oxygen atoms. PMID:7420278

Sánchez Camazano, M; Sánchez, M J; Vicente, M T; Domínguez-Gil, A

1980-10-01

149

Effects of pH on dielectric relaxation of montmorillonite, allophane, and imogolite suspensions  

SciTech Connect

Dielectric measurements were performed on montmorillonite, allophane, and imogolite suspensions under various pH conditions, using time domain reflectometry over the frequency range 10 kHz--20 GHz. A dielectric relaxation peak due to bound water could be observed for all the clays. Allophane has two peaks, indicating that its peaks are very similar to those of silica-alumina gels. Although imogolite has a similar chemical composition, only one peak was found. The relaxation strength of montmorillonite is greater than that of the other two clays. For all the clays, the relaxation strength depended on the pH. A change in the relaxation strength according to a change in pH is explained in terms of the different network structures of the clay particles. It is suggested that bound water influences the network structure formation. In montmorillonite, a great relaxation process detected at low frequency is caused by surface polarization of counterions. The change in measure of the structural unit with the pH, identified from Schwartz`s theory, has a tendency similar to that postulated by other experimental techniques, and surface charge densities identified are close to those estimated from CEC.

Ishida, Tomoyuki [Kagawa Univ., Miki, Kagawa (Japan). Dept. of Agricultural Engineering; Makino, Tomoyuki [National Inst. of Agro-Environmental Sciences of Japan, Tsukuba, Ibaraki (Japan). Soil Chemistry Lab.

1999-04-01

150

Dechlorinating chloroacetanilide herbicides by dithionite-treated aquifer sediment and surface soil.  

PubMed

The prevalent use of chloroacetanilide herbicides has resulted in nonpoint contamination of some groundwater and surface water. We determined the efficacy of dithionite-treated sediment and soils to transform chloroacetanilides. When used alone, dithionite rapidly dechlorinates chloroacetanilides in water, with the following order of reactivity: propachlor > alachlor > acetochlor > metolachlor. Stoichiometric release of chloride occurs during reaction with dithionite, and thiosulfate herbicide derivatives are produced. Treating aquifer sediment with dithionite reduces native Fe(lII), creating a redox barrier of Fe(ll)-bearing minerals and surface-bound Fe(ll). Washing the reduced sediment (buffered with citrate-bicarbonate) with oxygen-free water removed Fe(ll) and excess dithionite and no alachlor transformation was observed. In contrast, a dithionite-treated surface soil, rich in clay and iron, effectively dechlorinated alachlor after washing. Exposing alachlor to aquifer sediment treated with dithionite in potassium carbonate buffer (pH 8.5-9.0) produced dechlorinated alachlor as the major degradation product. Our results provide proof-of-concept that dechlorination of chloroacetanilide herbicides by dithionite and dithionite-treated aquifer sediment and soil is a remediation option in natural environments where iron-bearing minerals are abundant. PMID:16719109

Boparai, Hardiljeet K; Shea, Patrick J; Comfort, Steve D; Snow, Daniel D

2006-05-01

151

Surface transformation hardening on steels treated with solar energy in central tower and heliostats field  

Microsoft Academic Search

The possibility of surface hardening on AISI 4140 steel treated with concentrated solar energy in solar installations for electricity production has been studied. The samples were slides from a 35 mm diameter steel bar and their height was 35 mm. The quenching was made in water but also was considered the possibility of self-quenching by cooling in air. The amount

G. P. Rodríquez; V. López; J. J. de Damborenea; A. J. Vázquez

1995-01-01

152

Preparation of PTFE Film With Adhesive Surface Treated by Atmospheric-Pressure Nonthermal Plasma Graft Polymerization  

Microsoft Academic Search

A surface modification technique that improves the adhesion of fluorocarbon polymer films such as polytetrafluoroethylene (PTFE), perfluoroalkoxy fluoroplastics, and polychlorotrifluoroethylene is developed using argon at atmospheric pressure and acrylic acid vapor nonthermal plasma. The results of the T-type peeling test show that the peeling strength of the treated PTFE film is approximately 70 times greater than that of the untreated

Masaaki Okubo; Mitsuru Tahara; Yasushi Aburatani; Tomoyuki Kuroki; Toshitomo Hibino

2010-01-01

153

Adsorption of hexavalent chromium onto montmorillonite modified with hydroxyaluminum and cetyltrimethylammonium bromide  

NASA Astrophysics Data System (ADS)

Aluminum hydroxypolycation and cetyltrimethylammonium bromide (CTMAB) were chosen to synthesize inorganic-organic pillared montmorillonite. Three different methods were employed for the intercalation. The characteristics of natural and modified montmorillonite were determined with X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), X-ray photoelectron spectrum (XPS), and zeta potential. It was found that aluminum hydroxypolycation and CTMAB had either entered the interlayer or sorbed on the external surface of the clay. Different intercalation orders can result in different structures. Batch adsorption of hexavalent chromium (Cr 6+) onto modified montmorillonite was also investigated. The experimental data revealed that if aluminum hydroxypolycation was intercalated before CTMAB, the adsorption capacity was better than that of intercalated simultaneously or CTMAB pre-intercalated. The pH of the solution and environmental temperature had significant influences on the adsorption of Cr 6+. The optimal pH for the removal was about 4, and the temperature of 298 K was best suitable. All adsorption processes were rapid during the first 5 min and reached equilibrium in 20 min. The adsorption kinetics can be described quite well by pseudo-second-order model. The adsorption rates of ACM, CAM and ACCOM were 3.814, 0.915, and 3.143 mg/g/min, respectively. The adsorption capacities of Cr 6+ at 298 K on ACM, CAM, and ACCOM inferred from the Langmuir model were 11.970, 6.541, and 9.090 mg/g, respectively. The adsorption of Cr 6+ on modified montmorillonite was mainly induced by the surface charge and the complexation reaction between CTMA + and hexavalent chromium species at the edge of the clay particle.

Hu, Bingjie; Luo, Hanjin

2010-11-01

154

Adsorption of Uranium from Solutions by Montmorillonite; Compositions and Properties of Uranyl Montmorillonites  

Microsoft Academic Search

Wyoming montmorillonite, <2-\\/xm particle size, saturated with Na, K, Mg, Ca, and Ba ions, was reacted with uranyl nitrate solutions in the concentration range 1-300 ppm uranium. With constant amounts of clay and solution volume, the adsorption isotherms of uranyl ions on the clay followed Lang- muir-type curves with increasing concentration of uranium. The maximum adsorption derived from linear Langmuir

A. Tsunashima; G. W. BR; MARIJA BASTOVANOV

1981-01-01

155

Stratified assemblies of magnetite nanoparticles and montmorillonite prepared by the layer-by-layer assembly  

SciTech Connect

Hybrid thin films are prepared from 8 to 10 nm Fe{sub 3}O{sub 4} nanoparticles and exfoliated montmorillonite clay by using layer-by-layer assembly on poly(diallyldimethylammonium bromide), PDDA. Distinct stratification of the Fe{sub 3}O{sub 4}/PDDA/clay films is obtained due to the sheetlike structure of the clay particles. This feature distinguishes these assemblies from their polyelectrolyte-polyelectrolyte analogues, where the layers of individual polyelectrolytes are strongly interdigitated. Being adsorbed on PDDA strictly parallel to the substrate surface, montmorillonite produces a dense layer of overlapping alumosilicate sheets, which virtually flawlessly separates one magnetite layer from another. The difference in magnetic properties between assemblies of various architectures is attributed to the insulation effect of clay layers inserted between magnetic layers. The montmorillonite sheets disrupt the electron exchange interactions between the magnetite nanoparticles in adjacent layers, thereby limiting the magnetization reversal to two dimensions. Some optical properties of Fe{sub 3}O{sub 4}/PDDA films are investigated as well. When they are deposited on thin plastic substrate, oscillations of optical density were observed in the red part of the UV-vis spectrum. This effect, which has never been observed for conventional, thick substrates such as glass slides, stems from the interference of the light beams passed through and reflected off of the assembled film.

Mamedov, A.; Ostrander, J.; Aliev, F.; Kotov, N.A.

2000-04-18

156

Comparative evaluation of roughness of titanium surfaces treated by different hygiene instruments  

PubMed Central

Purpose The use of appropriate instruments to clean surfaces with minimal change, is critical for the successful maintenance of a dental implant. However, there is no consensus about the type and methodology for such instruments. The aim of this study was to characterize changes in the roughness of titanium surfaces treated by various scaling instruments. Methods Thirty-seven identical disks (5 mm in diameter) were investigated in this study. The specimens were divided into eight groups according to the types of instrumentation and the angle of application. Ultrasonic scaling systems were applied on a titanium disk to simulate standard clinical conditions. The equipment included a piezoelectric ultrasonic scaler with a newly developed metallic tip (NS group), a piezoelectric ultrasonic scaler with a conventional tip (CS group), a piezoelectric root planer ultrasonic scaler with a conventional tip (PR group), and a plastic hand curette (PH group). In addition, the sites treated using piezoelectric ultrasonic scaler systems were divided two sub-groups: 15 and 45 degrees. The treated titanium surfaces were observed by scanning electron microscopy (SEM), and the average surface roughness (Ra) and mean roughness profile depth (Rz) were measured with a profilometer. Results SEM no significant changes in the titanium surfaces in the NS group, regardless of the angle of application. The PH group also showed no marked changes to the titanium surface, although some smoothening was observed. All CS and PR sites lost their original texture and showed irregular surfaces in SEM analysis. The profilometer analysis demonstrated that the roughness values (Ra and Rz) of the titanium surfaces increased in all, except the PH and NS groups, which showed roughness decreases relative to the untreated control group. The Ra value differed significantly between the NS and PR groups (P<0.05). Conclusions The results of this study indicated that changes in or damage to titanium surfaces might be more affected by the hardness of the scaler tip than by the application method. Within the limitations of this study, the newly developed metallic scaler tip might be especially suitable for peri-implant surface decontamination, due to its limited effects on the titanium surface.

Unursaikhan, Otgonbayar; Lee, Jung-Seok; Cha, Jae-Kook; Park, Jung-Chul; Jung, Ui-Won; Kim, Chang-Sung; Cho, Kyoo-Sung

2012-01-01

157

Surface state of TiO 2 treated with low ion energy plasma  

NASA Astrophysics Data System (ADS)

The effect of low pressure radio frequency (rf) plasma treatment on TiO 2 surface states has been studied using X-ray photoelectron spectroscopy. Three different oxidation states of oxygen in untreated TiO 2 powder were observed, which suggests the existence of adsorbed water and carbon on the surface. The ratio of oxygen to titanium (O/Ti) was decreased for the low ion dose plasma treated samples due to desorption of water from the surface. In the case of Ti 2p about 20% of surface states were converted to Ti 3+ 2p 3/2 state after plasma treatment with a very good stability, whereas untreated TiO 2 remained mostly as Ti 4+ state. A rapid decrease in the ratio of carbon to titanium (C/Ti) at TiO 2 surface was also observed after plasma treatment and more than 90% of carbon atoms were removed from the surface. Therefore, the plasma treatment of TiO 2 has advantages to surface carbon cleaning, increasing O - and Ti 3+ surface states, hence improving the activity of TiO 2 for different environmental, energy and biological applications.

Jun, Jin; Shin, Joong-Hyeok; Dhayal, Marshal

2006-03-01

158

Surface Characterization of Plasma Treated Carbon Fibers and Adhesion to Polyethersulfone.  

NASA Astrophysics Data System (ADS)

A series of RF plasmas was chosen to modify the surface chemical composition of Hercules IM7 carbon fibers. A two-liquid tensiometric method was used to determine the surface energy parameters gamma_sp {rm s}{rm d} and I_sp{rm sf}{rm p} of the fibers. An XPS analysis of air and argon plasma treated fibers indicated a significant surface oxidation of the fibers which translated into low gamma_sp{rm s}{ rm d} values and high I_sp {rm sf}{rm p} values. An ammonia plasma was shown to remove an outer layer from the surface of the fibers. It also increased gamma_sp{rm s}{rm d}, compared to as-received fibers, without affecting the non-dispersion term (I_sp {rm sf}{rm p}). XPS results indicated that methane and ethylene plasmas deposited a layer of low surface energy hydrocarbon on the fiber surface. A trifluoromethane plasma and a tetrafluoromethane plasma introduced a significant amount of fluorine containing groups in the fiber surface in the form of a fluorinated plasma polymer in the first case and through direct attack of the fiber surface by fluorine atoms in the second case. The surface chemical composition and the surface energy parameters of two series of commercially treated carbon fibers were also determined and compared to the results on IM7 carbon fibers. The adhesion of carbon fibers to polyethersulfone (PES) was measured by using the microbond pull-out test, and compared to the adhesion of the same fibers to an epoxy resin. The load required to debond the microdroplet was used as a measure of the bond strength. The data were also analyzed in terms of interfacial fracture energy according to the model developed by Jiang and Penn (1992). The microbond pull-out test results showed no significant relation between the fiber surface chemical composition or the fiber surface energy, and the adhesion to PES. However, plasmas which have a strong ablative character such as the ammonia and the tetrafluoromethane plasmas did improve the fiber-PES adhesion, when compared to as-received fibers. The study of the fiber-epoxy systems revealed that a chemical effect contributed to the adhesion improvement but to a lesser extent than the "cleaning" effect of the surface treatment. The results support the two part mechanism proposed by Drzal and extend its application to carbon fiber-thermoplastic systems, but in this case the chemical effect is minimal.

Commercon, Pascal

159

Genotoxicity and inflammatory investigation in mice treated with magnetite nanoparticles surface coated with polyaspartic acid  

NASA Astrophysics Data System (ADS)

In this study, some biological tests were carried out with a magnetic fluid (MF) sample based on magnetite nanoparticles (MNPs) surface coated with polyaspartic acid (PAMF). The tests were performed from 1 to 30 days after injection of 50 ?L of PAMF in Swiss mice. The PAMF biocompatibility/toxicity was evaluated through cytometry, micronuclei assay, and morphology of several organs. All observed results were time and dose dependent. The data indicate that MNPs surface-treated with polyaspartic acid may be considered as a potential precursor of anticancer drugs.

Sadeghiani, N.; Barbosa, L. S.; Silva, L. P.; Azevedo, R. B.; Morais, P. C.; Lacava, Z. G. M.

2005-03-01

160

Dissolution of alkaline earth sulfates in the presence of montmorillonite  

USGS Publications Warehouse

In a study of the effect of montmorillonite on the dissolution of BaSO4 (barite), SrSO4 (celestite), and 226Ra from U mill tailings, it was found that: (1) More of these substances dissolve in an aqueous system that contains montmorillonite than dissolve in a similar system without clay, due to the ion exchange properties of the clay; (2) Na-montmorillonite is more effective in aiding dissolution than is Ca-montmorillonite; (3) the amount of Ra that moves from mill tailings to an exchanger increases as solution sulfate activity decreases. Leaching experiments suggest that 226Ra from H2SO4-circuit U mill tailings from Edgemont, South Dakota, is not present as pure Ra sulfate or as an impurity in anhydrite or gypsum; it is less soluble, and probably occurs as a trace constituent in barite.

Eberl, D. D.; Landa, E. R.

1985-01-01

161

Poliovirus Interaction with Montmorillonite Clay: Electron Microscopy and Flocculation Studies.  

National Technical Information Service (NTIS)

The objective of this research was to gain an understanding of the interaction between montmorillonite clay particles and Type I poliovirus particles. This knowledge would be useful in the quantification of viral contamination of underground water reservo...

P. C. Butler

1980-01-01

162

TiO2-montmorillonite composites via supercritical intercalation.  

PubMed

The successful preparation of TiO2-montmorillonite mesoporous composites using intercalation of titanium isopropoxide dissolved in supercritical carbon dioxide involved ion exchange of interlayer cations by hydrophobic cations. PMID:12189876

Yoda, Satoshi; Sakurai, Yuichiro; Endo, Akira; Miyata, Tatsuhiko; Otake, Katsuto; Yanagishita, Hiroshi; Tsuchiya, Toshio

2002-07-21

163

Two types of adsorbed water in natural montmorillonites at low temperatures by dielectric spectroscopy  

NASA Astrophysics Data System (ADS)

Dielectric spectroscopy was applied to natural clay mineral - montmorillonite with the exchangeable K+ and Ni2+ cations where the effect of water adsorption in the samples on the dielectric response was examined in the temperature from -115°C to -75°C and frequency from 1 Hz to 1 MHz ranges. Two relaxation processes (1 and 2) were revealed. The process 1 was related to the adsorbed ordered water structures formed on the interior surface of interlayer channels while the relaxation process 2 was attributed to the disordered water structures built between two surface water monolayers.

Vasilyeva, M. A.; Gusev, Yu A.; Shtyrlin, V. G.

2012-11-01

164

Mineral catalysis of the formation of the phosphodiester bond in aqueous solution: The possible role of montmorillonite clays  

Microsoft Academic Search

The binding of adenosine to Na+-montmorillonite 22A is greater than 5'-AMP, at neutral pH. Adenine derivatives bind more strongly to the clay than the corresponding uracil derivatives. These data are consistent with the protonation of the adenine by the acidic clay surface and a cationic binding of the protonated ring to the anionic clay surface. Other forces must be operative

James P. Ferris; Gözen Ertem; Kamaluddin; Vipin Agarwal; Lu Lin Hua

1989-01-01

165

Influence of Additives in Adhesion of UV Radiation Surface-Treated SBS Rubber  

Microsoft Academic Search

In this study, the effect of additives (oils, lubricants) included in the formulations of different block styrene–butadiene–styrene (SBS) rubbers on the effectiveness of the ultraviolet (UV) radiation treatment to improve adhesion to polyurethane adhesive was analyzed. The modifications on the UV-treated rubber surfaces for different lengths of treatment have been characterized by contact-angle measurements (ethylene glycol, 25°C), Attenuated Total Reflectance-Infrared

María D. Romero-Sánchez; José Miguel Martín-Martínez

2006-01-01

166

Cavitation erosion of cobalt based STELLITE alloys, cemented carbides and surface treated low alloy steels  

Microsoft Academic Search

Results are given for erosion-resistance tests involving several STELLITE alloys, cemented carbides and surface-treated alloy steels. It is shown that the cobalt-rich, solid-solution phase of the STELLITE alloys is the basis of their erosion resistance, while the erosion of cemented carbides is predominantly controlled by the binder phase. It is also found that nickel-based tungsten carbides are more erosion-resistant than

C. J. Heathcock; A. Ball; B PROTHEROE

1981-01-01

167

Surface roughness and color characteristics of wood treated with preservatives after accelerated weathering test  

Microsoft Academic Search

Wood samples treated with ammonium copper quat (ACQ 1900 and ACQ 2200), chromated copper arsenate (CCA), Tanalith E 3491 and Wolmanit CX-8 have been studied in accelerated weathering experiments. The weathering experiment was performed by cycles of 2h UV-light irradiation followed by water spray for 18min. The changes on the surface of the weathered samples were characterized by roughness and

Ali Temiz; Umit C. Yildiz; Ismail Aydin; Morten Eikenes; Gry Alfredsen; Gürsel Çolakoglu

2005-01-01

168

Dislodgeable copper, chromium and arsenic from CCA-treated wood surfaces.  

PubMed

Chromated copper arsenate (CCA) is commonly used to preserve wood, but its use poses risk of arsenic exposure. In order to evaluate the extent of exposure to As from physical contact with CCA-treated wood, dislodgeable As from treated wood surfaces (as well as Cu and Cr) was determined as a function of weathering time using dampened polyester wipe materials. Six sets of 2.5-m-long CCA-treated boards, three-four boards per set, were purchased from lumber yards and cut into 30- or 60-cm coupons. A total of 44 such coupons were placed outdoors and the dislodgeable CCA components from the surfaces of the wooden coupons were periodically determined over a 1- or 2-year period by a systematic wipe method followed by nitric acid extraction of the CCA components from the cloth. In all 316 samples, appreciable amounts of the three elements, Cu, Cr and As, were detected. The amounts of surface-dislodgeable As, the most potentially hazardous element and the one of major concern in this study, varied from 5 to 122 microg/100 cm(2) with an average value of 37+/-22 microg/100 cm(2). There was considerable variation in As dislodged among coupons, boards, sets and time. Test coupons that tended to release relatively higher (or lower amounts) over time initially, continued to do so over time. However, the amounts of arsenic dislodged over time did not follow a simple pattern. While the As dislodged tended to decrease with time during the first year, it approached the initial value or increased somewhat during the second year, presumably due to surface rejuvenation effects caused by erosion and weathering. When all the data were normalized to the initial values, no trend emerged, as indicated by the average normalized value of 1.0+/-0.4 for As dislodged over time. Apparently, on installations constructed with CCA-treated wood, arsenic may remain available for a number of years. PMID:12873405

Stilwell, David; Toner, Michael; Sawhney, Brij

2003-08-01

169

Interactions of pendimethalin with organo-montmorillonite complexes  

Microsoft Academic Search

Pendimethalin (PM) is a dinitroaniline herbicide, highly hydrophobic and with a very low solubility in water. It is used for pre-emergence weed control, is usually applied before sowing, and mechanically incorporated into the soil. We tested sorption of PM on montmorillonite and on two different organo-montmorillonites in a mixed water–chloroform environment, to determine the feasibility of developing an environmentally oriented

Giora Rytwo; Yotam Gonen; Shmuel Afuta; Stefan Dultz

2005-01-01

170

Calcium Alginate Barrier Films Modified by Montmorillonite Clay  

Microsoft Academic Search

The goal of decreasing the permeation of small molecules through calcium alginate films is addressed by incorporating small amounts of montmorillonite clay into the polymer. Incorporation is achieved by (i) blending up to 3 wt% pre?exfoliated montmorillonite into sodium alginate polymer solutions, (ii) casting thin films, (iii) cross?linking the chains with calcium chloride solution into insoluble calcium alginate, and (iv) drying

James M. Vale; Ryan S. Justice; Dale W. Schaefer; James E. Mark

2005-01-01

171

Preparation and Solvation Properties of Some Variable Charge Montmorillonites  

Microsoft Academic Search

Ahstraet-Li-, Na-, K- and Ca-saturated Wyoming montmorillonites have been prepared and used to obtain Li,Na-, Li,K-, and Li,Ca-montmorillonites with a range of Li contents. These were heated at 220~ for 24 hr, causing the Li § ions to migrate mainly into the layer structure and leaving varying amounts of Li +, Na +, K § and Ca '2§ ions in

G. W. Brindley; ZEN ERTEM

1971-01-01

172

Swelling of Formamide-Montmorillonite Complexes in Polar Liquids  

Microsoft Academic Search

A new osmotic-swelling system for montmorillonite with formamide (FA) is described. Water and a variety of polar organic liquids were used to swell FA-montmorillonite complexes. The post- swelling behavior of the complex is interpreted in terms of the bi-functionality of FA as an electron donor\\/ acceptor and the magnitude of the donor number (DN) of the polar liquid relative to

Masanobu Onikata; MITSUJI KONDO; SHOJI YAMANAKA

1999-01-01

173

Survival of enteric microorganisms on grass surfaces irrigated with treated effluent.  

PubMed

Treated effluent can be reused for the irrigation of parks and sports grounds but there is an associated potential public health risks from microbial pathogens present on the grass surface, particularly when used for contact sports. The main aim of this study was to investigate the survival of pathogenic and indicator microorganisms on the grass surface of a sports ground irrigated with treated effluent under differing climatic conditions. Results showed that Salmonella enterica serotype typhimurium, Escherichia coli, Enterococcus faecalis and Staphylococcus aureus decayed faster under direct sunlight than MS2 with one log(10) reduction (T(90)) varying from 3 to 11 hours. Rapid decay (T(90) 3 to 4 hours) of bacterial pathogens occurred in both sunlight and shade during the summer. In contrast, T(90) times for the bacteria during the winter varied from 6 to 11 hours in direct sunlight and from 23 to 38 hours in shade. No significant seasonal variation was observed in the inactivation of the bacteriophage MS2. Enteric viruses are expected to show inactivation rates similar to MS2. The results show that rapid inactivation of enteric bacteria can be expected on grass surface irrigated with treated effluent at higher ambient temperatures, in direct sunlight and low moisture content. PMID:18209287

Sidhu, J P S; Hanna, J; Toze, S G

2008-06-01

174

The lower cation exchange capacity limit of montmorillonite  

SciTech Connect

Wyoming montmorillonite (Volclay) with different charges were produced by Li-incorporation and the interlayer cations were replaced by tetramethyl ammonium. Their XRD pattern showed a regular sequence of expanded and collapsed interlayers. The regularly interstratified structure corresponds to a regularity of Reichweite R = 1. The expanded part of the interlayers was calculated by comparing XRD pattern with simulations using NEWMOD software. The calculations of the cation exchange capacity CEC for the expanded interlayer part gives a constant value of 65 {+-} 2 mmol/100 g fully swellable montmorillonite. This value is denoted as the lower CEC limit of montmorillonite. The authors propose a model which considers montmorillonite to be a stacked two-dimensional polyelectrolyte. The model proposes that interlayers of the stack collapse spontaneously by cation shifting into the neighboring interlayers, if the charge density of a montmorillonite has a value below the lower CEC value. The shifted cations of the collapsed interlayer increase the charge density in the neighboring interlayers and prevent their collapse. A regularly interstratified structure arises with the sequence expanded/collapsed/expanded interlayer, which can be observed by XRD. The behavior of low charged montmorillonite is explained with the properties of a two-dimensional polyelectrolyte. Below the critical layer charge, the Van der Waals forces dominate over electrostatic repulsive forces and the interlayers collapse.

Meier, L.P.; Nuesch, R.

1999-09-01

175

Influence of montmorillonite on antimicrobial activity of tetracycline and ciprofloxacin  

NASA Astrophysics Data System (ADS)

Antibiotics are used not only to fight infections and inhibit bacterial growth, but also as growth promotants in farm livestock. Farm runoff and other farm-linked waste have led to increased antibiotic levels present in the environment, the impact of which is not completely understood. Soil, more specifically clays, that the antibiotic contacts may alter its effectiveness against bacteria. In this study a swelling clay mineral montmorillonite was preloaded with antibiotics tetracycline and ciprofloxacin at varying concentrations and bioassays were conducted to examine whether the antibiotics still inhibited bacterial growth in the presence of montmorillonite. Escherichia coli was incubated with montmorillonite or antibiotic-adsorbed montmorillonite, and then the number of viable bacteria per mL was determined. The antimicrobial activity of tetracycline was affected in the presence of montmorillonite, as the growth of non-resistant bacteria was still found even when extremely high TC doses were used. Conversely, in the presence of montmorillonite, ciprofloxacin did inhibit E. coli bacterial growth at high concentrations. These results suggest that the effectiveness of antimicrobial agents in clayey soils depends on the amount of antibiotic substance present, and on the interactions between the antibiotic and the clays in the soil, as well.

Lv, Guocheng; Pearce, Cody W.; Gleason, Andrea; Liao, Libing; MacWilliams, Maria P.; Li, Zhaohui

2013-11-01

176

Nanocomposite of silk fibroin nanofiber and montmorillonite: fabrication and morphology.  

PubMed

The purpose of our research is creating a new nanocomposite material. Generally silk fibroin (SF) is regarded as a promising base material for biomedical uses. The incorporation of montmorillonite (MMT) into SF fibers would improve physical properties of the SF fibers. We investigated a new method of combining electospun SF with MMT. Specifically, electrospun silk nanofibers were treated with methanol and dipped in a MMT suspension. We could obtain a nanosheet composite of silk nanofibers and MMT. Their ultrastructures were successfully visualized by high resolution transmission electron microscopy. This compound was comprised of individual silk nanofibers surrounded by thin layers of MMT, each with a thickness of about 1.2 nm. This structure was confirmed by elemental analysis. We also performed IR, NMR and X-ray diffraction analyses in conjunction with morphological data. Conclusively we obtained a new composite of silk nanofiber and MMT, which has never been reported. Using this unique nanocomposite biological tests of its application for a scaffold for tissue engineering are under way. PMID:23500446

Kishimoto, Yuki; Ito, Fuyu; Usami, Hisanao; Togawa, Eiji; Tsukada, Masuhiro; Morikawa, Hideaki; Yamanaka, Shigeru

2013-03-13

177

Occurrence of phthalates in surface runoff, untreated and treated wastewater and fate during wastewater treatment.  

PubMed

Dimethyl phthalate, diethyl phthalate, dibuthyl phthalate, butylbenzyl phthalate, bis(2-ethylbenzyl) phthalate (DEHP) and dioctyl phthalate were analysed in raw and treated wastewater as well as in surface runoff samples from traffic roads. All six investigated phthalates have been detected in all raw sewage samples, in nearly all wastewater treatment plant (WWTP) effluent samples and in all road runoff samples, with DEHP being the most abundant compound. DEHP inflow concentrations ranged 3.4-34 microg L(-1) and effluent concentrations 0.083-6.6 microg L(-1). In two WWTPs the fate of the phthalates was assessed by performing mass balances. Overall removal efficiencies of approx 95% were calculated. Removal is attributed to biotransformation and adsorption and the relevance of the removal via adsorption to sludge increased with increasing molecular weight and increasing lipophilic character of the compound. Except DEHP phthalate concentrations were higher in treated effluent samples than in road runoff. The environmental quality standard (EQS) for DEHP in surface waters is exceeded only in a few effluent samples, whereas nearly all road runoff samples were higher than the EQS. An assessment based on pure concentrations is not feasible and a mass balance based approach is required. Nevertheless the observations highlight the relevance of stormwater emissions and direct emissions from separated sewer systems to surface waters in relation to emissions from WWTPs and the necessity to consider all potential influences in the assessment of the status of surface water bodies with reference to xenobiotics. PMID:20096917

Clara, M; Windhofer, G; Hartl, W; Braun, K; Simon, M; Gans, O; Scheffknecht, C; Chovanec, A

2010-01-22

178

Synthesis and properties of polystyrene\\/Fe-montmorillonite nanocomposites using synthetic Fe-montmorillonite by bulk polymerization  

Microsoft Academic Search

Fe-montmorillonite (Fe-MMT) was hydrothermally synthesized. It was modified by cetyl trimethylammonium bromide (CTAB) and successfully synthesized polystyrene\\/Fe-montmorillonite (PS\\/Fe-MMT) nanocomposites via bulk polymerization for the first time. The resulting nanocomposites were characterized by X-ray diffraction (XRD) spectra, transmission electron microscopy (TEM), high resolution electronic microscopy (HREM), thermal gravimetric analysis (TGA) and cone calorimeter. XRD, TEM and HREM indicated that both intercalated

Qinghong Kong; Yuan Hu; Hongdian Lu; Zuyao Chen; Weicheng Fan

2005-01-01

179

Effect of ball milling on the structure of Na +-montmorillonite and organo-montmorillonite (Cloisite 30B)  

Microsoft Academic Search

The effect of high energy ball milling under different conditions on the structure of Na+-montmorillonite (Na-MMT), and the organo-montmorillonite (Cloisite 30B) was investigated. Ball milling increased the structural disorder: peeling off of layers from the particles was observed, followed by the exfoliation of the particles, indicated by the disappearance of the (001) reflection. X-ray diffraction and infrared spectra revealed that

Adham R. Ramadan; Amal M. K. Esawi; Ahmed Abdel Gawad

2010-01-01

180

Microwave absorbing properties of structural nanocomposites with surface treated Co ferrite nanoparticles as filler  

NASA Astrophysics Data System (ADS)

An analysis of the microwave absorbing properties of several polymer-(epoxy) based nanocomposites is presented. The nanoparticles of interest for this study were cobalt ferrite nanoparticles. For better dispersion of the nanoparticles in the polymer matrix surface treatment of the nanoparticles with silane compounds was performed. The nanoparticles were surface-treated with 3-glycidoxypropyl- (GPTMS), aminopropyl- (APTMS) or methyl-silsesquioxane (MTMS). The nanoparticles with GPTMS-coating dispersed well in epoxy without sedimentation while the other nanoparticles formed agglomerates in epoxy. The GPTMS-based composites showed higher fracture toughness than the MTMS-based composites. The microwave properties, permittivity and permeability, of GPTMS-based composites were measured in the frequency range between 3.95 GHz and 18 GHz and showed no influence of surface treatment on permeability.

Jänis, A.; Olsson, R. T.; Savage, S. J.; Klement, U.

2010-03-01

181

Characterization of Surface Treated Aero Engine Alloys by Rayleigh Wave Velocity Dispersion  

NASA Astrophysics Data System (ADS)

In aero engines mechanically high stressed components made of high-strength alloys like IN718 and Ti6Al4V are usually surface treated by shot-peening. Other methods, e.g. laser-peening, deep rolling and low plasticity burnishing are also available. All methods introduce compres-sive residual stress desired for minimize sensitivity to fatigue or stress corrosion failure mechanisms, resulting in improved performance and increased lifetime of components. Beside that, also cold work is introduced in an amount varying from method to method. To determine the remaining life time of critical aero engine components like compressor and turbine discs, a quantitative non-destructive determination of compressive stresses is required. The opportunity to estimate residual stress in surface treated aero engine alloys by SAW phase velocity measurements has been re-examined. For that original engine relevant material IN718 has been used. Contrary to other publications a significant effect of the surface treatment to the sound velocity was observed which disappeared after thermal treatment. Also preliminary measurements of the acousto-elastic coefficient fit into this picture.

Köhler, B.; Barth, M.; Schubert, F.; Bamberg, J.; Baron, H.-U.

2010-02-01

182

Adhesion strength measurements of excimer-laser-treated PTFE surfaces using liquid photoreagents  

NASA Astrophysics Data System (ADS)

The most known feature of polytetrafluoroethylene (PTFE) is its adhesion behavior: it is hydrophobic and oleophobic at the same time. This can cause serious problems and obstacles during the surface treatment and fixing of PTFE objects. During our experiments Teflon films were irradiated by an ArF excimer laser beam in presence of liquid photoreagents containing amine groups (aminoethanol, 1,2-diaminoethane, triethylene-tetramine). In consequence of the treatment the adhesion of the modified surfaces significantly increased, the samples could be glued and moistened. The adhesion strength of the glued surfaces was measured in the function of the applied laser fluence. The adhesion strength increased drastically between 0 - 1 mJ/cm2 and showed saturation above 1 mJ/cm2 at approximately 5 - 9 MPa values depending on the applied photoreagents. On the basis of our experiments it was found that the treatment with triethylene-tetramine was the most effective. The surface chemical modifications of the treated Teflon samples can be due to the incorporation of amine groups into the surface layer.

Hopp, Bela; Smausz, Tomi; Kresz, Norbert; Ignacz, Ferenc

2003-04-01

183

Osteoclasts but not osteoblasts are affected by a calcified surface treated with zoledronic acid in vitro  

SciTech Connect

Bisphosphonates are potent inhibitors of osteoclast-mediated bone resorption. Recent interest has centered on the effects of bisphosphonates on osteoblasts. Chronic dosing of osteoblasts with solubilized bisphosphonates has been reported to enhance osteogenesis and mineralization in vitro. However, this methodology poorly reflects the in vivo situation, where free bisphosphonate becomes rapidly bound to mineralized bone surfaces. To establish a more clinically relevant cell culture model, we cultured bone cells on calcium phosphate coated quartz discs pre-treated with the potent nitrogen-containing bisphosphonate, zoledronic acid (ZA). Binding studies utilizing [{sup 14}C]-labeled ZA confirmed that the bisphosphonate bound in a concentration-dependent manner over the 1-50 {mu}M dose range. When grown on ZA-treated discs, the viability of bone-marrow derived osteoclasts was greatly reduced, while the viability and mineralization of the osteoblastic MC3T3-E1 cell line were largely unaffected. This suggests that only bone resorbing cells are affected by bound bisphosphonate. However, this system does not account for transient exposure to unbound bisphosphonate in the hours following a clinical dosing. To model this event, we transiently treated osteoblasts with ZA in the absence of a calcified surface. Osteoblasts proved highly resistant to all transitory treatment regimes, even when utilizing ZA concentrations that prevented mineralization and/or induced cell death when dosed chronically. This study represents a pharmacologically more relevant approach to modeling bisphosphonate treatment on cultured bone cells and implies that bisphosphonate therapies may not directly affect osteoblasts at bone surfaces.

Schindeler, Aaron [Department of Orthopaedic Research and Biotechnology, Children's Hospital at Westmead, Sydney (Australia) and Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, Sydney (Australia)]. E-mail: AaronS@chw.edu.au; Little, David G. [Department of Orthopaedic Research and Biotechnology, Children's Hospital at Westmead, Sydney (Australia); Discipline of Paediatrics and Child Health, Faculty of Medicine, University of Sydney, Sydney (Australia)

2005-12-16

184

Effects of exchanged cation on the microporosity of montmorillonite  

USGS Publications Warehouse

The micropore volumes of 2 montmorillonites (SAz- 1 and SWy-1), each exchanged with Ca, Na, K, Cs and tetramethylammonium (TMA) ions, were calculated from the measured vapor adsorption data of N2 and neo-hexane by use of t- and ??s-plots. The corresponding surface areas of the exchanged clays were determined from Brunauer-Emmett-Teller (BET) plots of N2 adsorption data. Micropore volumes and surface areas of the samples increased with the size of exchanged cation: TMA > Cs > K> Ca > Na. The SAz-1 exchanged clays showed generally greater micropore volumes and surface areas than the corresponding SWy-1 clays. The vapor adsorption data and d(001) measurements for dry clay samples were used together to evaluate the likely locations and accessibility of clay micropores, especially the relative accessibility of their interlayer spacing. For both source clays exchanged with Na, Ca and K ions, the interlayer spacing appeared to be too small to admit nonpolar gases and the accessible micropores appeared to have dimensions greater than 5.0 A??, the limiting molecular dimension of neo -hexane. In these systems, there was a good consistency of micropore volumes detected by N2 and neo-hexane. When the clays were intercalated with relatively large cations (TMA and possibly Cs), the large layer expansion created additional microporosity, which was more readily accessible to small N2 than to relatively large neo-hexane. Hence, the micropore volume as detected by N2 was greater than that detected by neo-hexane. The micropore volumes with pore dimensions greater than 5 A?? determined for clays exchanged with Na, Ca and K likely resulted from the pores on particle edges and void created by overlap regions of layers. The increase in micropore volumes with pore dimensions less than 5 A?? determined for clays exchanged with TMA and possibly Cs could be caused by opening of the interlayer region by the intercalation of these large cations.

Rutherford, D. W.; Chiou, C. T.; Eberl, D. D.

1997-01-01

185

Study of the influence of surface carbon on the tribological properties of ion-treated steels  

NASA Astrophysics Data System (ADS)

Samples of 100Cr6 steel were treated by different ion beams in order to study the evolution of their tribological properties. A strong correlation was found between the amount of surface carbon, whatever its origin (contamination, direct C implantation or ion-beam mixing of a deposited carbon layer), and the reduction of the friction coefficient as well as the improvement of the wear resistance. These results are discussed in the framework of a recent statistical model founded on the asperity concept and describing the tribological behaviour of bilayer systems.

Benyagoub, Abdenacer; Faussemagne, Arielle

1999-01-01

186

Regulation of cell-surface galactosyltransferase in isoproterenol-treated mouse parotid glands.  

PubMed

Chronic injection of isoproterenol into mice resulted in hypertrophy and hyperplasia of the parotid gland. As previously described for the rat, cell proliferation was accompanied by an increase in total membrane-associated galactosyltransferase. A plasma membrane localization was determined by fluorescence-activated sorting of intact cells. Co-administration of the galactosyltransferase modifier protein, alpha-lactalbumin, or the calmodulin inhibitor, trifluoperazine, blocked acinar cell proliferation by 96 h post-treatment but not at 24 h. While alpha-lactalbumin appeared to interfere with galactosyltransferase-substrate interactions, trifluoperazine prevented the appearance of cell-surface enzyme in isoproterenol-treated animals. PMID:1776922

Maeda, N; Purushotham, K R; Koller, M M; Humphreys-Beher, M G

1991-01-01

187

Surface Modification of Plasma-Treated Polyamide6 with Fluorinated Alcohols and Azobenzene Compounds using Chlorinated Phosphazenes as Coupling Agents  

Microsoft Academic Search

A three-step procedure for surface functionalization of polyamide-6 plates is presented. The substrate was first treated with cold, low pressure Ar plasma to generate surface OH groups, which were successively reacted with chlorophosphazenes to ensure grafting of these molecules. Substitution of the residual chlorines of the phosphazenes with fluorinated alcohols and 4-hydroxyazobenzene yielded the final surface modification. Characterization was performed

Roberto Milani; Mario Gleria; A. Sassi; R. De Jaeger; A. Mazzah; C. Jama; L. Gengembre

2008-01-01

188

X-ray photoemission analysis of chemically treated GaTe semiconductor surfaces for radiation detector applications  

SciTech Connect

The surface of the layered III-VI chalcogenide semiconductor GaTe was subjected to various chemical treatments commonly used in device fabrication to determine the effect of the resulting microscopic surface composition on transport properties. Various mixtures of H{sub 3}PO{sub 4}:H{sub 2}O{sub 2}:H{sub 2}O were accessed and the treated surfaces were allowed to oxidize in air at ambient temperature. High-resolution core-level photoemission measurements were used to evaluate the subsequent chemistry of the chemically treated surfaces. Metal electrodes were created on laminar (cleaved) and nonlaminar (cut and polished) GaTe surfaces followed by chemical surface treatment and the current versus voltage characteristics were measured. The measurements were correlated to understand the effect of surface chemistry on the electronic structure at these surfaces with the goal of minimizing the surface leakage currents for radiation detector devices.

Nelson, A. J.; Conway, A. M.; Sturm, B. W.; Behymer, E. M.; Reinhardt, C. E.; Nikolic, R. J.; Payne, S. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Pabst, G.; Mandal, K. C. [EIC Laboratories, Inc., 111 Downey Street, Norwood, Massachusetts 02062 (United States)

2009-07-15

189

First principles calculation on the adsorption of water on lithium-montmorillonite (Li-MMT)  

NASA Astrophysics Data System (ADS)

The interaction of water molecules and lithium-montmorillonite (Li-MMT) is theoretically investigated using density functional theory (DFT) based first principles calculation. The mechanism of water adsorption at two different water concentrations on Li-MMT as well as their structural and electronic properties are investigated. It is found that the adsorption stability in Li-MMT is higher in higher water concentration. It is also found that an adsorbed water molecule on Li-MMT causes the Li to protrude from the MMT surface, so it is expected that Li may be mobile on H2O/Li-MMT.

Dewi Kencana Wungu, Triati; Kemal Agusta, Mohammad; Gandaryus Saputro, Adhitya; Kresno Dipojono, Hermawan; Kasai, Hideaki

2012-11-01

190

Cavitation erosion of cobalt based STELLITE alloys, cemented carbides and surface treated low alloy steels  

SciTech Connect

Results are given for erosion-resistance tests involving several STELLITE alloys, cemented carbides and surface-treated alloy steels. It is shown that the cobalt-rich, solid-solution phase of the STELLITE alloys is the basis of their erosion resistance, while the erosion of cemented carbides is predominantly controlled by the binder phase. It is also found that nickel-based tungsten carbides are more erosion-resistant than those based on cobalt. It is demonstrated for the case of the low-alloy steels that surface treatment can improve their erosion rates, and that application of a proprietary nitrocarburizing method to the same steels results in a similar performance improvement only after the initial loss of the compound layer.

Heathcock, C.J. (Cape Town, Univ., Rondebosch, Republic of South Africa); Ball, A.

1981-03-30

191

Passivation of (NH4)2S-treated GaAs surface with an As2S3 film  

Microsoft Academic Search

This letter describes the suppression of (NH4)2S-treated GaAs surface degradation by coating the treated surface with an evaporated As2S3 film. The photoluminescence intensity of the treated GaAs surface shows no decrease even after 100 days. The properties of the As2S3\\/GaAs interface were also evaluated by metal-insulator-semiconductor techniques. A small hysteresis capacitance-voltage curve with reduced frequency dispersion was obtained, which indicates

Yoichi Mada; Kazumi Wada; Yoshinori Wada

1992-01-01

192

The use of trehalose-treated freeze-dried amniotic membrane for ocular surface reconstruction.  

PubMed

The aim of this study was to evaluate the efficacy and safety of trehalose-treated freeze-dried amniotic membrane (TT-FDAM) for ocular surface reconstruction. Human AM deprived of amniotic epithelial cells was first incubated with 10% trehalose solution, and then freeze-dried, vacuum-packed, and sterilized with gamma-irradiation. The resultant newly developed TT-FDAM was characterized for its physical, biological, and morphological properties by comprehensive physical assays, immunohistochemistry, electron microscopy, cell adhesion assay, 3D cell culture, and an in vivo biocompatibility test. The adaptability of TT-FDAM was markedly improved as compared to FDAM. Immunohistochemistry for several extracellular matrix molecules revealed that the process of freeze-drying and irradiation apparently did not affect its biological properties, however, electron microscopy revealed that the detailed morphological appearance of TT-FDAM is more similar to that of native AM than to FDAM. Intracorneal and scleral-surface transplantation of TT-FDAM showed excellent biocompatibility with ocular surface tissues. Thus, TT-FDAM retained most of the physical, biological, and morphological characteristics of native AM, consequently it is a useful biomaterial for ocular surface reconstruction. PMID:18547637

Nakamura, Takahiro; Sekiyama, Eiichi; Takaoka, Maho; Bentley, Adam J; Yokoi, Norihiko; Fullwood, Nigel J; Kinoshita, Shigeru

2008-06-10

193

Influence of ionic strength and inorganic complex formation on the sorption of trace amounts of Cd by montmorillonite  

Microsoft Academic Search

Cadmium sorption by montmorillonite from solutions in the 15 to 120 ppb range was studied in the presence of increasing concentrations of NaClCOâ, NaCl, and NaâSOâ solutions. The ionic strengths ranged from 0.01 to 1.00. Increasing ionic strengths decreased the amount of Cd sorbed on the clay surfaces. The percentage sorbed decreased from around 90 percent for l = 0.01

J. Garcia-Miragaya; A. L. Page

1976-01-01

194

Preparation, characterization and properties of amino-functionalized montmorillonite and composite layer-by-layer assembly with inorganic nanosheets  

Microsoft Academic Search

An amino-functionalized montmorillonite (APTMS-MMT) was prepared by the grafting of 3-aminopropyltrimethoxysilane (APTMS) on the surface of MMT via the ultrasonic synthesis process and characterized by a variety of techniques: FT-IR, thermogravimetic analysis (TGA), particles size analysis and ?-potential measurement. The results showed the size and size distribution of APTMS-MMT particles were decreased, and the ?-potential of particles was increased obviously

Guo-bo Huang; Chang-hua Ge; Bing-jing He

2011-01-01

195

Studies on employing tetrathiafulvalene as an electron shuttle incorporated in a montmorillonite-modified immobilization matrix for an enzyme electrode  

Microsoft Academic Search

A new strategy to immobilize an electron transfer mediator for construction of a second generation amperometric biosensor is described. The strategy was implemented with the mediator-oxidase reactor system. Non-soluble tetrathiafulvalene (TTF) as a mediator and glucose oxidase (GOD) were co-immobilized in the montmorillonite-modified bovine serum albumin (BSA) + glutaraldehyde matrix on a glassy carbon electrode surface. The mediating redox couple,

Chenghong Lei; Zhanen Zhang; Haiying Liu; Jiaqi Deng

1996-01-01

196

Sorption of triclosan onto activated carbon, kaolinite and montmorillonite: Effects of pH, ionic strength, and humic acid  

Microsoft Academic Search

Sorption of triclosan on three sorbents, viz., activated carbon, kaolinite and montmorillonite was studied as a function of pH, ionic strength and humic acid (HA) concentration through controlled batch experiments. Triclosan sorption was found to be higher in the acidic pH range, as varying pH showed significant influence on the surface charge of the sorbents and degree of ionization of

Shishir Kumar Behera; Seok-Young Oh; Hung-Suck Park

2010-01-01

197

High capacity mercury adsorption on freshly ozone-treated carbon surfaces  

PubMed Central

A set of carbon materials was treated by a choice of common oxidizers to investigate the mercury capture capacities at varying temperature conditions. It was found that ozone treatment dramatically increases the mercury capture capacity of carbon surfaces by factors up to 134, but the activity is easily destroyed by exposure to the atmosphere, to water vapor, or by mild heating. Freshly ozone-treated carbon surfaces are shown to oxidize iodide to iodine in solution and this ability fades with aging. FTIR analysis shows broad C–O stretch features from 950 to 1300 cm?1, which decay upon atmospheric exposure and are similar to the C-O-C asymmetric stretch features of ethylene secondary ozonide. The combined results suggest that the ultra-high mercury capture efficiency is due to a subset of labile C-O functional groups with residual oxidizing power that are likely epoxides or (epoxide-containing) secondary ozonides. The results open the possibility for in situ ozonolysis to create high-performance carbon-based Hg sorbents.

Manchester, Shawn; Wang, Xuelei; Kulaots, Indrek; Gao, Yuming; Hurt, Robert H.

2008-01-01

198

The extraction of {sup 137}Cs and {sup 89}Sr from waste simulants using pillared montmorillonite  

SciTech Connect

Two samples of a silica-pillared montmorillonite produced using 3-aminopropyltrimethoxy silane and an alumina-pillared montmorillonite were evaluated for the removal of {sup 137}Cs and {sup 89}Sr from a simulated nuclear waste solution and a simulated groundwater, and the results were compared to the parent montmorillonite and two zeolites, AW500 (chabazite) and clinoptilolite. The parent and pillared clays were characterized using x-ray powder diffraction and surface area analysis by nitrogen adsorption/desorption studies. The pillared clays exhibited d-spacings of between 17.43 and 18.32 {angstrom} after calcination, and surface areas ranging from 71.3 to 264.4 m{sup 2}/g. Both of the silica-pillared clays and the alumina-pillared clay exhibited excellent K{sub d}s for {sup 137}Cs from simulated groundwater with values of 23,650, 23,260 and 144,570 mL/g, respectively. These were far better than the K{sub d}s obtained by clinoptilolite and AW500 which had K{sub d}s of only 14,560 and 9,650 mL/g, respectively. None of the pillared clays showed a high selectivity for {sup 89}Sr from groundwater or {sup 137}Cs from simulated alkaline tank waste. They did, however, show a slight selectivity for {sup 89}Sr in the simulated Hanford tank wastes, but this is thought to be due to a precipitation mechanism rather than to ion exchange.

Sylvester, P.; Clearfield, A. [Texas A and M Univ., College Station, TX (United States). Dept. of Chemistry

1998-08-01

199

The origin of the pozzolanic activity of calcined clay minerals: A comparison between kaolinite, illite and montmorillonite  

SciTech Connect

This paper investigates the decomposition of three clayey structures (kaolinite, illite and montmorillonite) when thermally treated at 600 {sup o}C and 800 {sup o}C and the effect of this treatment on their pozzolanic activity in cementitious materials. Raw and calcined clay minerals were characterized by the XRF, XRD, {sup 27}Al NMR, DTG and BET techniques. Cement pastes and mortars were produced with a 30% substitution by calcined clay minerals. The pozzolanic activity and the degree of hydration of the clinker component were monitored on pastes using DTG and BSE-IA, respectively. Compressive strength and sorptivity properties were assessed on standard mortars. It was shown that kaolinite, due to the amount and location of OH groups in its structure, has a different decomposition process than illite or montmorillonite, which results in an important loss of crystallinity. This explains its enhanced pozzolanic activity compared to other calcined clay-cement blends.

Fernandez, Rodrigo, E-mail: fernandezrod@gmail.co [Laboratory of Construction Materials, IMX, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland); Martirena, Fernando [Centro de Investigacion y Desarrollo de Estructuras y Materiales (CIDEM), Universidad Central 'Marta Abreu' de Las Villas, 54830 Santa Clara (Cuba); Scrivener, Karen L. [Laboratory of Construction Materials, IMX, Ecole Polytechnique Federale de Lausanne, 1015 Lausanne (Switzerland)

2011-01-15

200

High-Power Diode Laser Surface Treated HVOF Coating to Combat High Energy Particle Impact Wear  

NASA Astrophysics Data System (ADS)

High-velocity oxy-fuel (HVOF)-sprayed coatings have performed exceptionally well in low-energy particle impact wear and are accepted worldwide. However, their application for high-energy particle impact wear (HEPIW) requires a different approach and more efforts. HVOF-coating systems typically use WC-Co, WC-Co-Cr, WC-Ni-Cr, and FeCrAlY-Cr3C2 powders. WC-Co-Cr powders are preferred when there is a high demand for corrosion resistance. WC-10Co-4Cr coating powder has been selected in the current study. To improve coating properties such as microhardness, fracture toughness, and HEPIW resistance, a new approach of surface treatment with robotically controlled high-power diode laser (HPDL) is attempted. The robotically controlled HVOF-coating deposition and laser surface treatment were monitored using real-time diagnostic control. The HPDL-treated coating has been compared with "as-sprayed" HVOF coating for HEPIW resistance, fracture toughness, microhardness and microstructure. The coating characteristics and properties after laser surface treatment have improved many times compared with "as-sprayed" HVOF coating. This is due to the elimination of pores in the coating and formation of a metallurgical bond between coating and substrate. This new development opens up a possibility of using such laser treatments in specialized areas where HEPIW damages are acute. The fracture toughness and HEPIW resistance along with optical micrographs of HPDL-treated and untreated HVOF coatings are discussed and reported in this article. HEPIW resistance is observed to be proportional to the product of fracture toughness and microhardness of the HVOF coating.

Mann, B. S.; Arya, Vivek; Pant, B. K.

2013-07-01

201

Speciation of uranium(VI) sorption complexes on montmorillonite  

SciTech Connect

Environmental contaminant releases that contain uranium are among the most serious problems that must be confronted by restoration programs. To facilitate restoration, information concerning the speciation of uranium is needed. Under oxidizing conditions, dissolved uranium is predominantly in the U(VI) (uranyl) form and is quite mobile in the environment, however sorption onto soils may retard its movement. In this study, we have investigated the effects of changes in solution speciation on the nature of uranyl sorption complexes on montmorillonite, a common soil constituent. Aqueous U(VI) solutions between pH 3 to 7 were batch-equilibrated with montmorillonite for several days; specific pH values were selected such that the solutions consisted of dominantly monomeric, oligomeric, or a mix of monomeric and oligomeric aqueous uranyl species. Emission spectroscopy was used to investigate the nature of U(VI) sorbed to montmorillonite.

Chisholm-Brause, C.J.; Morris, D.E. [Los Alamos National Lab., NM (United States); Richard, R.E. [Fort Lewis Coll., Durango, CO (United States). Dept. of Chemistry

1992-05-01

202

Kinetics of bacterial degradation of benzylamine in a montmorillonite suspension  

SciTech Connect

A model was developed for the biodegradation by nongrowing microbial populations of sorbed organic chemicals that are readily desorbed. The model requires inputs in the form of parameters provided by separate measurements of the adsorption isotherm under aseptic conditions and the rate of biodegradation in the absence of sorbent. The only parameter that must be provided by the data to be simulated is the fraction of carbon from the test compound that is incorporated into microbial cells or retained by the sorbent. The model was tested with benzylamine as test compound, a bacterial isolate able to mineralize the chemical, and montmorillonite as sorbent. Benzylamine mineralization by high cell densities of the bacterium was slower in the presence of montmorillonite than in the absence of the clay. Experimental curves for bacterial mineralization of benzylamine in well-dispersed suspensions of montmorillonite were reproduced by the model with standard deviations of usually less than 4%.

Miller, M.E.; Alexander, M. (Cornell Univ., Ithaca, NY (USA))

1991-02-01

203

Speciation of uranium(VI) sorption complexes on montmorillonite  

SciTech Connect

Environmental contaminant releases that contain uranium are among the most serious problems that must be confronted by restoration programs. To facilitate restoration, information concerning the speciation of uranium is needed. Under oxidizing conditions, dissolved uranium is predominantly in the U(VI) (uranyl) form and is quite mobile in the environment, however sorption onto soils may retard its movement. In this study, we have investigated the effects of changes in solution speciation on the nature of uranyl sorption complexes on montmorillonite, a common soil constituent. Aqueous U(VI) solutions between pH 3 to 7 were batch-equilibrated with montmorillonite for several days; specific pH values were selected such that the solutions consisted of dominantly monomeric, oligomeric, or a mix of monomeric and oligomeric aqueous uranyl species. Emission spectroscopy was used to investigate the nature of U(VI) sorbed to montmorillonite.

Chisholm-Brause, C.J.; Morris, D.E. (Los Alamos National Lab., NM (United States)); Richard, R.E. (Fort Lewis Coll., Durango, CO (United States). Dept. of Chemistry)

1992-01-01

204

Formation of RNA Oligomers on Montmorillonite: Site of Catalysis  

NASA Astrophysics Data System (ADS)

Certain montmorillonites catalyze the self condensation of the 5'-phosphorimidazolide of nucleosides in pH 8 aqueous electrolyte solutions at ambient temperatures leading to formation of RNA oligomers. In order to establish the nature of the sites on montmorillonite responsible for this catalytic activity, oligomerization reactions were run with montmorillonites which had been selectively modified (I) at the edges by (a) fluoride treatment, (b) silylation, (c) metaphosphate treatment of the anion exchange sites (II) in the interlayer by (a) saturation with quaternary alkylammonium ions of increasing size, (b) aluminum polyoxo cations. High pressure liquid chromatography, HPLC, analysis of condensation products for their chain lengths and yields indicated that modification at the edges did not affect the catalytic activity to a significant extent, while blocking the interlayer strongly inhibited product formation.

Ertem, Gözen; Ferris, James P.

1998-10-01

205

Nitrate removal in surface-flow constructed wetlands treating dilute agricultural runoff in the lower Yakima Basin, Washington  

Microsoft Academic Search

Constructed treatment wetlands (CTWs) have been used effectively to treat a range of wastewaters and non-point sources contaminated with nitrogen (N). But documented long-term case studies of CTWs treating dilute nitrate-dominated agricultural runoff are limited. This study presents an analysis of four years of water quality data for a 1.6-ha surface-flow CTW treating irrigation return flows in Yakima Basin in

Marc W. Beutel; Crystal D. Newton; Elaine S. Brouillard; Richard J. Watts

2009-01-01

206

Synthesis of an intercalated compound of montmorillonite and 6-polyamide  

Microsoft Academic Search

Natural montmorillonite, fractionated from bentonite produced in Yamagata, Japan, was ion-exchanged for NH3+-(CH2)11-COOH, NH3+-(CH2)5-COOH, Al3+, Cu2+, Mg2+, Co2+, Li+, K+ and H+. The mixtures of the ion-exchanged montmorillonite and e-caprolactam were heated at 263°C in glass ampoules for various periods. The intercalated compounds before and after the heating were examined by X-ray powder diffraction, DSC and GPC. Although e-caprolactam was

Yoshiaki Fukushima; Shinji Inagaki

1987-01-01

207

Uranium uptake by hectorite and montmorillonite: a solution chemistry and polarized EXAFS study.  

PubMed

The mechanism of U(VI) retention on montmorillonite and hectorite at high ionic strength (0.5 M NaCl) was investigated by solution chemistry and, at near-neutral pH, polarized EXAFS spectroscopy. Uranium(VI) sorption increases from pH 3 to 7 on the two clays, but with a steeper edge for hectorite. Uranium(VI) is no longer retained at pH > 9, presumably owing to the formation of soluble anionic complexes. Polarized EXAFS showed that U(VI) retains its uranyl conformation on montmorillonite (U_mont) and hectorite (U_hect), with uranyl O at 1.79(2) A for U_mont and 1.82(2) A for U_hect, and split equatorial O shells at 2.29(2) and 2.47(2) A (U_mont), or 2.35(2) and 2.53(2) A (U_hect). An additional atomic shell of approximately 0.5 Al/Si at 3.3 A is detected for U_mont, but neither the oxygen nor the cationic shell exhibit clear angular dependence. These results indicate the formation of mononuclear complexes at the edges of montmorillonite platelets, with the orientation of the uranyl axis equal to the magic angle, as constrained by the edges' structural properties. In contrast to U_mont, the U-O signal varies with the polarization angle in U_hect, and the cationic Mg/Si contribution at 3.2 A is weak. The structure of this surface complex is not completely elucidated; it may correspond either to sorption on silanol sites, or to coprecipitation. These results lay out the fundamental molecular-scale basis to understand U retention by neoformed clay layers of nuclear glasses. PMID:20028057

Schlegel, Michel L; Descostes, Michael

2009-11-15

208

Hydrophobic recovery of UV\\/ozone treated poly(dimethylsiloxane): adhesion studies by contact mechanics and mechanism of surface modification  

Microsoft Academic Search

Silicone elastomers (Sylgard 184 and 170), based on poly(dimethylsiloxane) (PDMS), were surface treated by a combined exposure to UV and ozone. The effects of the treatments were analyzed as a function of time elapsed after stopping the treatments using different standard surface characterization techniques, such as water contact angle measurements, XPS and atomic force microscopy (AFM). However, the primary focus

Attila Oláh; Henrik Hillborg; G. Julius Vancso

2005-01-01

209

Aging of surface properties of ultra high modulus polyethylene fibers treated with He\\/O 2 atmospheric pressure plasma jet  

Microsoft Academic Search

To investigate the relationship between aging of the treatment effect and the gas composition of atmospheric pressure plasma treatment, ultra high modulus polyethylene (UHMPE) fibers were selected as a model fiber to study the aging behavior of fiber surface treated by atmospheric pressure plasma jet (APPJ) with pure helium, helium+1% oxygen, and helium+2% oxygen. Atomic force microscopy showed increased surface

Yu Ren; Chunxia Wang; Yiping Qiu

2008-01-01

210

[Joint prostheses components of warm-forged and surface treated Ti-6Al-7Nb alloy].  

PubMed

In 1978 development of a TiAl alloy with the inert alloying element niobium was initiated. In 1984, the optimal composition was found to be Ti-6Al-7Nb (Protasul-100). This custom-made alloy for implants has the same alpha/beta micro-structure and equally good mechanical properties as Ti-6Al-4V. The corrosion resistance of Ti-6Al-7Nb is better than that of pure titanium and Ti-6Al-4V, due to the very dense and stable passive layer. Since 1985, highly stressed anchoring stems of various hip prosthesis designs have been manufactured from hot-forged Ti-6Al-7Nb/Protasul-100. Polished surfaces of hip, knee or wrist joints made of Ti-6Al-7Nb intended to articulate with polyethylene are surface-treated by the application of a very hard, 3-5 microns thick titanium nitride coating (Tribosul-TiN), or by oxygen diffusion hardening (Tribosul-ODH) to a depth of 30 microns. PMID:1859861

Semlitsch, M; Weber, H; Streicher, R M; Schön, R

1991-05-01

211

Observation of HCl- and HF-Treated GaAs Surfaces by Measuring Contact Angles of Water Droplets  

NASA Astrophysics Data System (ADS)

A GaAs surface chemically treated with hydrochloric acid (HCl) or hydrofluoric acid (HF) has been characterized by measurements of the contact angle between the surface and a water droplet on it in air. The contact angle measured from the GaAs samples dipped into water shows the formation of a thin surface layer on the GaAs surface and the subsequent removal of the layer upon chemical treatment with HCl or HF solution. Annealing in nitrogen atmosphere is shown to be effective in stabilizing the surface against water.

Matsushita, Koichi; Miyazaki, Shuji; Okuyama, Sumio; Kumagai, Yasuji

1994-08-01

212

Self-diffusion of sodium ions in compacted sodium montmorillonite  

SciTech Connect

Diffusion of sodium ions through compacted sodium montmorillonite in a water-saturated state was studied to obtain fundamental information for performance assessments of geological disposal of high-level radioactive waste. Basal spacings obtained from X-ray diffraction measurements indicated a decrease in the interlamellar spacing with increasing dry density of the montmorillonite; the three-water-layer hydrate was observed at low dry density, and the two-water-layer hydrate was observed at high dry density, whereas both were observed at dry densities between 1.4 and 1.5 Mg/m{sup 3}. Activation energies from 14.1 to 24.7 kJ/mol were obtained from the temperature dependence of the self-diffusion coefficients of sodium ions. Activation energies lower than that for the diffusion of sodium ions in free water were found for montmorillonite specimens with dry densities of {le} 1.2 Mg/m{sup 3}, while higher activation energies were observed at dry densities {ge} 1.4 Mg/m{sup 3}. The pore water diffusion model, the general model used for migration of nuclides, is based on geometric parameters; however, findings cannot be explained by only the changes in the geometric parameters. Possible explanations for the dry density dependence of the activation energy are changes in the temperature dependence of the distribution coefficients of sodium ions on the montmorillonite, changes in the diffusion process with an increase in dry density, or both.

Kozaki, Tamotsu; Fujishima, Atsushi; Sato, Seichi; Ohashi, Hiroshi [Hokkaido Univ., Sapporo (Japan)

1998-01-01

213

Emulsion Polymerized Polystyrene\\/Montmorillonite Nanocomposite and its Viscoelastic Characteristics  

Microsoft Academic Search

A novel polystyrene (PS)\\/clay nanocomposite was synthesized using a simple emulsion polymerization method in the presence of sodium ion exchanged montmorillonite (Na?MMT). Prior to the radical polymerization procedure with potassium persulfate (KPS) as an initiator, the hydrophobic styrene monomer was intercalated into hydrophilic clay layers using sodium dodecyl sulfate (SDS) as a surfactant. The FTIR spectra of the products showed

Bong Jun Park; Tae Heon Kim; Hyoung Jin Choi; Jae Heung Lee

2007-01-01

214

A comparative study of the acidity toward the aqueous phase and adsorptive properties of Al{sub 13}-pillared montmorillonite and Al{sub 13}-pillared saponite  

SciTech Connect

The selectivity of an Al{sub 13}-pillared saponite and an Al{sub 13}-pillared montmorillonite for Cd{sup 2+} and Cu{sup 2+} adsorption was studied. The quantity of metal adsorbed on both pillared clays depends on the pH of the solution and the pillars density. Adsorption equilibria are regulated by the protonation equilibria of the amphoteric sites on the pillars. Pillared clays adsorb more cadmium and copper than classic aluminum hydroxides which is simply attributable to a higher density of surface aluminum groups. Significant differences in behavior are observed between pillared montmorillonite and pillared saponite. Pillared montmorillonite appears to be more acidic, which is correlated with a more advanced degree of structural modification of the pillars on calcination. The authors propose a tentative, partial structural model of pillar transformation compatible with these differences. At the same time, both pillared clays have similar affinities for cadmium II at low pH (5--6), but pillared montmorillonite seems to be a more efficient cadmium trap at pH = 8 when its surface groups are negatively ionized. Thus, the nature of the clay layers conditions the structural modifications of the intercalated [Al{sub 13}] polycations, which in turn determine adsorptive behavior.

Bergaoui, L.; Mrad, I.; Ghorbel, A. [Faculte des Sciences de Tunis (Tunisia). Lab. de Chimie des Materiaux et Catalyse; Lambert, J.F. [Univ. Pierre et Marie Curie, Paris (France). Lab. de Reactivite de Surface

1999-04-15

215

The effects of oil on As(V) adsorption on illite, kaolinite, montmorillonite and chlorite  

NASA Astrophysics Data System (ADS)

The effect of oil on As(V) adsorption on clay minerals has been investigated using batch experiments at low and high pH, NaCl concentration and oil contents. Four clay minerals were chosen because of their abundance in sediments and their different crystal chemistry: illite, kaolinite, montmorillonite, and chlorite. The values for pH were 4 and 8 and salt concentrations were 0.001 and 0.7 M NaCl to appreciate the effects of changing salinity, e.g. from fresh water to seawater conditions. For the coating experiments, a well-characterised oil was used to survey the main effects of complex organic mixtures on adsorption and oil to clay mineral (w/w) ratios were 0.0325 and 0.3250. As(V) adsorption increased with increasing NaCl concentration, suggesting that the mechanisms of As(V) adsorption are related to the formation of surface complexes in which Na+ ions act as bridges between the clay surface and the As(V) anions. Cation bridging is also indicated by zeta potential measurements which show that higher NaCl concentrations along with the presence of As(V) can cause the clay particles and adsorbed ions to have a more negative overall charge. Adsorption is lower at higher pH due to the reduced number of positively charged sites on the edge of clay mineral layers. Oil coating reduces As(V) adsorption by decreasing the available surface area of clay minerals, except in the case of oil-coated montmorillonite, where surface area following dispersion in water is increased. The main variables controlling As(V) adsorption are surface area and surface charge density, as confirmed by a simplified quantitative model. These findings advance our ability to predict the effects of complex pollution events in various freshwater and marine settings.

Wainipee, Wimolporn; Cuadros, Javier; Sephton, Mark A.; Unsworth, Catherine; Gill, Martin G.; Strekopytov, Stanislav; Weiss, Dominik J.

2013-11-01

216

Monte Carlo study of the adsorption and aggregation of alkyltrimethylammonium chloride on the montmorillonite-water interface.  

PubMed

Organically modified clays exhibit adsorption capacities for cations, anions, and nonpolar organic compounds, which make them valuable for various environmental technical applications. To improve the understanding of the adsorption processes, the molecular-scale characterization of the structures of organic aggregates assembled on the external basal surfaces of clay particles is essential. The focus of this Monte Carlo simulation study was on the effects of the surface coverage and the alkyl chain length n on the structures of alkyltrimethylammonium chloride ((C(n)TMA)Cl) aggregates assembled on the montmorillonite-water interface. We found that the amount of adsorbed C(n)TMA(+) ions is independent of the alkyl chain length and increases with the C(n)TMA(+) surface coverage. The C(n)TMA(+) ions predominantly adsorb as inner-sphere complexes; the fraction of outer-sphere adsorbed ions equals only about 10%. The conformational order of the C(n)TMA(+) alkyl chains substantially decreases with decreasing alkyl chain length. In agreement with previous experiments, the amount of C(n)TMA(+) ions that are aggregated at the mineral surface increases with increasing chain length. The maximum value of 0.66 C(n)TMA(+) adsorption complex per unit cell area of the clay surface considerably exceeds the amount of cations required to compensate the negative charge of the montmorillonite surface. Furthermore, in most of the studied systems, fractions of Na(+) surface cations remain adsorbed on montmorillonite. The resulting interfacial positive charge excess is counterbalanced by coadsorbed chloride ions forming ion pairs with both C(n)TMA(+) and Na(+). PMID:22894657

Klebow, Birthe; Meleshyn, Artur

2012-08-31

217

Characterization and Catalytic Performance of Montmorillonites with Mixed Aluminium/Lanthanide Pillars  

NASA Astrophysics Data System (ADS)

Pillared montmorillonites with mixed Al/lanthanide pillars were prepared. The materials present characteristics that are very different from montmorillonite pillared with only aluminium. Nuclear magnetic resonance studies indicated total absence of tetrahedral aluminium in the pillars when lanthanide cations are incorporated between the clay layers. They have a high thermal stability, high specific surface area and porosity, with pores at the limit between the microporosity and mesoporosity. The textural parameters maintained high values up to 700 °C. The number and the strength of the acid sites in these materials were also high. The increase of the conversion in dehydration of 1-butanol as in hydroisomerization of n-heptane shows their better behaviour as acid catalysts. The Al/lanthanide-pillared samples showed increased conversion and improved the selectivity towards the products of cracking. The study of 1-butanol dehydration showed that there is an increase in the acidity, thermal stability and smaller deactivation by carbonaceous deposits in the Al/lanthanide-pillared sample.

González, F.; Pesquera, C.; Blanco, C.

218

Adsorption and degradation of model volatile organic compounds by a combined titania-montmorillonite-silica photocatalyst.  

PubMed

A series of adsorptive photocatalysts, combined titania-montmorillonite-silica were synthesized. The resultant photocatalysts consisted of more and more spherically agglomerated TiO(2) particles with increasing of TiO(2) content, and anatase was the only crystalline phase with nano-scale TiO(2) particles. With increasing of the cation exchange capacity to TiO(2) molar ratio, specific surface area and pore volume increased very slightly. In a fluidized bed photocatalytic reactor by choosing toluene, ethyl acetate and ethanethiol as model pollutants, all catalysts had relatively high adsorption capacities and preferred to adsorb higher polarity pollutants. Langmuir isotherm model better described equilibrium data compared to Freundlich model. Competitive adsorptions were observed for the mixed pollutants on the catalysts, leading to decrease adsorption capacity for each pollutant. The combined titania-montmorillonite-silica photocatalyst exhibited excellent photocatalytic removal ability to model pollutants of various components. Almost 100% of degradation efficiency was achieved within 120 min for each pollutant with about 500 ppb initial concentration, though the efficiencies of multi-component compounds slightly decreased. All photocatalytic reactions followed the Langmuir-Hinshelwood model. Degradation rate constants of multi-component systems were lower than those for single systems, following the order of toluene

Chen, Jiangyao; Li, Guiying; He, Zhigui; An, Taicheng

2011-03-27

219

Surface chemistry and optical property of TiO{sub 2} thin films treated by low-pressure plasma  

SciTech Connect

The low temperature RF plasma treatment was used to control the surface chemistry and optical property of TiO{sub 2} thin films deposited by RF magnetron sputtering with a very good uniformity at 300 deg. C substrate heating temperature. The XRD pattern indicates the crystalline structure of the film could be associated to amorphous structure of TiO{sub 2} in thin film. The plasma treatment of TiO{sub 2} film can increase the proportion of Ti{sup 3+} in Ti2p and decrease in carbon atoms as alcohol/ether group in C1s at the surface. The optical transmittance of the film was enhanced by 50% after the plasma treatment. The surface structure and morphology remain the same for untreated and low-pressure plasma-treated films. Therefore, increase in the optical transmission could be due to change in surface chemistry and surface cleaning by plasma treatment. - Graphical abstract: The surface chemistry and surface states of TiO{sub 2} films was modified using low-pressure RF plasma treatment. The surface roughness and crystalline structure remain unchanged for low-pressure plasma-treated films. There was an increase in the Ti{sup 3+} surface states of Ti2p at the surface and this can be useful to increase the photocatalytic activities of TiO{sub 2} films. The proportion of carbon atoms as carboxyl group in C1s was also increased after plasma treatment. All the plasma-treated films show a higher optical transmittance when untreated and it was increased when the power was increased. The increase in the optical transmission could be due to surface cleaning of films by plasma treatment and possibly due to change in the surface chemistry.

Dhayal, Marshal [Liquid Crystal and Self Assembled Monolayer Section, Engineering Material Division, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India)], E-mail: marshaldhayal@yahoo.com; Jun, Jin [Department of Environmental Engineering, Dongshin University, 252 Deaho-dong, Naju, Chonnam (Korea, Republic of); Gu, Hal Bon; Hee Park, Kyung [Department of Electrical Engineering, Chonnam National University, 300 Yongbong-dong, Buk-gu, Gwangju (Korea, Republic of)

2007-10-15

220

Reflection High-Energy Electron Diffraction Intensity Oscillations during Si MBE Growth on HF-Treated Si(111) Surface  

NASA Astrophysics Data System (ADS)

Reflection high-energy electron diffraction (RHEED) intensity oscillations were observed when Si was directly grown at 450°C on the Si(111) surfaces treated with pH-modified (pH=9-10) buffered HF (BHF) solution without a conventional high-temperature cleaning step in ultrahigh vacuum (UHV). On the other hand, a 5% HF-treated Si(111) surface showed weak RHEED intensity oscillations even if a 800°C, 20 min heat treatment was performed before growth in UHV. These results indicate that the Si(111) surface treated with pH-modified BHF is flat and clean enough for direct Si molecular beam epitaxy (MBE) growth on it.

Kumagai, Yoshinao; Fujii, Kunihiro; Matsumoto, Hisashi; Hasegawa, Fumio

1992-08-01

221

Vacuum ultraviolet photoelectron spectroscopy of (NH sub 4 ) sub 2 S-treated GaAs (100) surfaces  

SciTech Connect

The surface chemistry and band bending of the ammonium sulfide-treated GaAs (100) surface has been studied using surface-sensitive synchrotron radiation photoemission spectroscopy. We find that the treatment leaves the GaAs surface terminated with roughly a monolayer of sulfur bonded to both As and Ga atoms. An {ital n}-type barrier height of 0.8 eV is measured. The thermal stability of the various chemical components is studied and various issues of the passivating mechanism are discussed.

Spindt, C.J. (Stanford Electronics Laboratories, Stanford University, Stanford, California 94035 (US)); Liu, D. (Varian Central Research, Varian Associates, 611 Hansen Way, Palo Alto, California 94303); Miyano, K. (Varian Central Research, Varian Associates, 611 Hansen Way, Palo Alto, California 94303); Meissner, P.L. (Varian Central Research, Varian Associates, 611 Hansen Way, Palo Alto, California 94303); Chiang, T.T. (Varian Central Research, Varian Associates, 611 Hansen Way, Palo Alto, California 94303); Kendelewicz, T. (Varian Central Research, Varian Associates, 611 Hansen Way, Palo Alto, California 94303); Lindau, I. (Varian Central Research, Varian Associates, 611 Hansen Way, Palo Alto, California 94303); Spicer, W.E. (Stanford Electronics Laboratories, Stanford University, Stanford, California 94035)

1989-08-28

222

Fungistatic activity of heat-treated flaxseed determined by response surface methodology.  

PubMed

The objective of this study was to evaluate the effect of heat treatment on the fungistatic activity of flaxseed (Linum usitatissimum) in potato dextrose agar (PDA) medium and a fresh noodle system. The radial growth of Penicilliumn chrysogenum, Aspergillus flavus, and a Penicillium sp. isolated from moldy noodles, as well as the mold count of fresh noodle enriched with heat treated flaxseed, were used to assess antifungal activity. A central composite design in the response surface methodology was used to predict the effect of heating temperature and time on antifungal activity of flaxseed flour (FF). Statistical analysis determined that the linear terms of both variables (that is, heating temperature and time) and the quadratic terms of the heating temperature had significant (P<0.05) effects on the radial growth of all 3 test fungi and the mold count log-cycle reduction of fresh noodle. The interactions between the temperature and time were significant for all dependent variables (P<0.05). Significant reductions in antifungal activities were found when FF was subjected to high temperatures, regardless of heating time. In contrast, prolonging the heating time did not substantially affect the antifungal activities of FF at low temperature. However, 60% of the antifungal activity was retained after FF was heated at 100 degrees C for 15 min, which suggests a potential use of FF as an antifungal additive in food products subjected to low to mild heat treatments. PMID:19241553

Xu, Y; Hall, C; Wolf-Hall, C

2008-08-01

223

Nanoscale protein arrays of rich morphologies via self-assembly on chemically treated diblock copolymer surfaces  

NASA Astrophysics Data System (ADS)

Well-controlled assembly of proteins on supramolecular templates of block copolymers can be extremely useful for high-throughput biodetection. We report the adsorption and assembly characteristics of a model antibody protein to various polystyrene-block-poly(4-vinylpyridine) templates whose distinctive nanoscale structures are obtained through time-regulated exposure to chloroform vapor. The strong adsorption preference of the protein to the polystyrene segment in the diblock copolymer templates leads to an easily predictable, controllable, rich set of nanoscale protein morphologies through self-assembly. We also demonstrate that the chemical identities of various subareas within individual nanostructures can be readily elucidated by investigating the corresponding protein adsorption behavior on each chemically distinct area of the template. In our approach, a rich set of intricate nanoscale morphologies of protein arrays that cannot be easily attained through other means can be generated straightforwardly via self-assembly of proteins on chemically treated diblock copolymer surfaces, without the use of clean-room-based fabrication tools. Our approach provides much-needed flexibility and versatility for the use of block copolymer-based protein arrays in biodetection. The ease of fabrication in producing well-defined and self-assembled templates can contribute to a high degree of versatility and simplicity in acquiring an intricate nanoscale geometry and spatial distribution of proteins in arrays. These advantages can be extremely beneficial both for fundamental research and biomedical detection, especially in the areas of solid-state-based, high-throughput protein sensing.

Song, Sheng; Milchak, Marissa; Zhou, Hebing; Lee, Thomas; Hanscom, Mark; Hahm, Jong-in

2013-03-01

224

Cell attachment and viability on micro-arc-oxidation (MAO) microwave/hydrothermal treated titanium surface.  

PubMed

The purpose of this study is to investigate the cell attachment and viability on the micro-arc oxidization (MAO) microwave/hydrothermal treated titanium surfaces. The MAO samples were microwave irradiated in vessels containing 50mL of double-distilled water for 30 minutes (MWDD). The immersion solution consisted of 0.05mM calcium hydroxide and 0.03mM ammonium dihydrogen phosphate (MWCP), and same solution with the pH value adjusted to 9.6 (MWCP9.6) were compared. The hydrothermal (HT) samples were conducted under DD water at 250°C for 3hr. The cell viability (WST assay) results show that there was no significant different on the cell viability at 4hrs. After cultured for 1 day, the cell viability of MG63 cells on the samples from high to low is HT = MWDD = MWCP > MWCP9.6 > MAO. No significant different was found on the cell number between groups. However, the percentages of spreading cells to total adherent cells are higher on the MWDD, MWCP, and MWCP9.6 groups (75.7%, 69.9%, 69.4%, respectively), when compare to MAO and HT groups (48.4% and 41.5%). These results demonstrate that increased cell spreading on a MW groups with submicro-to- nano scale calcium phosphates on titania produced by microwave/hydrothermal process. PMID:24111349

Lin, Dan-Jae; Fuh, Lih-Jyh; Chen, Chiing-Chang

2013-07-01

225

Correlation Between the Extent of Catalytic Activity and Charge Density of Montmorillonites  

PubMed Central

Abstract The clay mineral montmorillonite is a member of the phyllosilicate group of minerals, which has been detected on martian soil. Montmorillonite catalyzes the condensation of activated monomers to form RNA-like oligomers. Extent of catalysis, that is, the yield of oligomers, and the length of the longest oligomer formed in these reactions widely varies with the source of montmorillonite (i.e., the locality where the mineral is mined). This study was undertaken to establish whether there exists a correlation between the extent of catalytic property and the charge density of montmorillonites. Charge density was determined by saturating the montmorillonites with alkyl ammonium cations that contained increasing lengths of alkyl chains, [CH3-(CH2)n-NH3]+, where n?=?3–16 and 18, and then measuring d(001), interlayer spacing of the resulting montmorillonite-alkyl ammonium-montmorillonite complex by X-ray diffractometry (XRD). Results demonstrate that catalytic activity of montmorillonites with lower charge density is superior to that of higher charge density montmorillonite. They produce longer oligomers that contain 9 to 10 monomer units, while montmorillonite with high charge density catalyzes the formation of oligomers that contain only 4 monomer units. The charge density of montmorillonites can also be calculated from the chemical composition if elemental analysis data of the pure mineral are available. In the next mission to Mars, CheMin (Chemistry and Mineralogy), a combined X-ray diffraction/X-ray fluorescence instrument, will provide information on the mineralogical and elemental analysis of the samples. Possible significance of these results for planning the future missions to Mars for the search of organic compounds and extinct or extant life is discussed. Key Words: Mars—Origin of life—Montmorillonite—Mineral catalysis—Layer charge density—X–ray diffractometry. Astrobiology 10, 743–749.

Steudel, Annett; Emmerich, Katja; Lagaly, Gerhard; Schuhmann, Rainer

2010-01-01

226

Adsorption Properties of Montmorillonite and Synthetic Saponite as Packing Materials in Liquid-Column Chromatography  

Microsoft Academic Search

The adsorption of tris(1,10-phenanthroline)-ruthenium(II) (Ru(phen)32+ ) by two kinds of col- loidaIly dispersed clays, sodium montmorillonite and synthetic saponite, was studied by spectrophoto- metric and electron-optical methods. Montmorillonite adsorbed this complex stronger than saponite. The electronic spectrum measurements suggested that the electronic states of the complex were more perturbed on adsorption by montmorillonite than by saponite. High-performance liquid chromatography was

Yuji Nakamura; AKIHIKO YAMAGISHI; TOSCHITAKE IWAMOTO; MAKOTO KOGA

1988-01-01

227

Polymer-clay nanocomposites: Free-radical grafting of polystyrene on to organophilic montmorillonite interlayers  

Microsoft Academic Search

Vinyl monomer-montmorillonite intercalates, which are able to swell and disperse in organic solvents, have been prepared by a cation exchange process by the interaction between the Na+ or Ca2+ cations of montmorillonite and vinylbenzyltrimethylammonium chloride. The resulting vinyl monomer-montmorillonite materials have been identified by X-ray diffraction (XRD), elemental analysis and infrared absorption spectra. Free-radical solution polymerizations of the penetrated styrene

A. Akelah; A. Moet

1996-01-01

228

Adsorption of lead and cadmium ions from aqueous solution to the montmorillonite\\/water interface  

Microsoft Academic Search

In order to prevent contamination of subsoil and groundwater by leachates containing heavy metals, montmorillonite linings are used on landfill bottoms. It is therefore important to understand ion uptake by this clay. The sorption of Pb(II) and Cd(II) from aqueous solution to the montmorillonite\\/water interface has been studied as a function of pH, for three concentrations. Two montmorillonites have been

F. Barbier; G. Duc; M. Petit-Ramel

2000-01-01

229

Vapor barrier properties of polycaprolactone montmorillonite nanocomposites: effect of clay dispersion  

Microsoft Academic Search

Different compositions of poly(?-caprolactone) (PCL) and (organo-modified) montmorillonite were prepared by melt blending or catalyzed ring opening polymerization of ?-caprolactone. Microphase composites were obtained by direct melt blending of PCL and sodium montmorillonite (MMT-Na+). Exfoliated nanocomposites were obtained by in situ ring opening polymerization of ?-caprolactone with an organo-modified montmorillonite (MMT-(OH)2) by using dibutyltin dimethoxide as an initiator\\/catalyst. Intercalated nanocomposites

Giuliana Gorrasi; Mariarosaria Tortora; Vittoria Vittoria; Eric Pollet; Bénédicte Lepoittevin; Michael Alexandre; Philippe Dubois

2003-01-01

230

Freezing and thawing of montmorillonite — A time-resolved synchrotron X-ray diffraction study  

Microsoft Academic Search

The evolution of phases over time during freezing and thawing of unconfined Na- and Ca-montmorillonites (Wyoming, MX-80) was studied with time-resolved synchrotron X-ray diffraction. The clay samples were: (i) powder equilibrated to ambient atmosphere and (ii) pastes of 30mass% montmorillonite in pure water. The phases were characterised in-situ using a stream of nitrogen gas for temperature control.The behaviour of montmorillonite

Per Daniel Svensson; Staffan Hansen

2010-01-01

231

Phenotypic and molecular biological characterization of cyanobacteria from marble surfaces of treated and untreated sites of Propylaea (Acropolis, Athens)  

Microsoft Academic Search

Cyanobacteria cause aesthetic damage to marble surfaces and in particular their endolithic mode of life contributes to the breakdown of rock crystalline structures. The aim of this work was to estimate, with both phenotypical and molecular approach, the composition of cyanobacterial communities on the Propylaea marbles of the Acropolis Monuments. The two selected sampling sites were treated and untreated with

Vasiliki Lamprinou; Maria Mammali; Efstathios A. Katsifas; Adriani I. Pantazidou; Amalia D. Karagouni

2012-01-01

232

Influence of pore size on penetration of surface modification into woven fabric treated with atmospheric pressure plasma jet  

Microsoft Academic Search

One of the biggest difference between atmospheric pressure plasma jet (APPJ) and other plasma surface treatment is that only one side (top) of substrate is contacted with plasma jet at atmospheric pressure while in other plasmas two sides (top and bottom) of substrate are both contacted with plasma. The modification of the bottom side of woven fabric treated by APPJ

C. X. Wang; M. Du; Y. P. Qiu

2010-01-01

233

Sublethal exposure to methoxyfenozide-treated surfaces reduces the attractiveness and responsiveness in adult oriental fruit moth (Lepidoptera: Tortricidae).  

PubMed

The chemical communication (female attractiveness and male responsiveness) of adult oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide for 48 h were investigated in two laboratory wind tunnel assays. The recapture assay examined the ability of treated males to orient to a single cage of treated females, and the data gathered were mean percentage of males recaptured per treatment. The male sexual behavior assay examined some specific orientation behaviors (associated with sexual excitability) of treated males when they were given a choice of two competing pheromone sources (cages of treated females), and the data gathered were mean time males spent in upwind plume orientations and at source contact (female cage) per treatment. Data from the recapture assay suggests that exposure to methoxyfenozide impacts male responsiveness more than female attractiveness. In contrast, data from the sexual behavior assay strongly revealed that exposure to methoxyfenozide-treated surfaces does negatively impact both the ability of calling females to attract males and of aroused males to display sustained upwind flight behavior and time spent at the female cages. PMID:17370812

Reinke, Michael D; Barrett, Bruce A

2007-02-01

234

Studies of structures of poly-?-caprolactam\\/montmorillonite nanocomposite  

Microsoft Academic Search

Using the novel version of thermomechanical analysis (TMA) method, a poly-?-caprolactam (PA6) and its nanocomposite (PNC) containing 1.6wt.% of montmorillonite (MMT) were examined. Several disc specimens of those as investigated in the first part of this article were then melted, annealed, and sheared at a rate of 0.5s?1 engendering ca. 140% strain at 240°C in a rotational rheometer, and next

B. Jurkowski; Y. A. Olkhov

2004-01-01

235

Adsorption of 1-n-Alkyl Pyridinium Bromides by Montmorillonite  

Microsoft Academic Search

Adsorption isotherms of 1-n-alkyl pyridinium bromides on Na-montmoriltoni~e, and in addition of cetyl pyridinium bromide on Ca-montmorillonite, have been determined. For up to eight carbon atoms in the alkyl chain adsorption has a limit close to the exchange capacity of the clay. With larger ions adsorption occurs beyond this and is accompanied by adsorption of the bromide ion. Adsorption of

D. J. Greenland; J. P. QUIRK

1960-01-01

236

Synthesis and Characterization of palladium crystallites intercalated in montmorillonite  

SciTech Connect

Reduction of electrophilic Pd(II) complexes intercalated in montmorillonite under mild conditions (0[degrees]C in MeOH) has been shown to afford highly despersed metallic palladium, located mainly in the interlamellar regions of the clay. Transmission electron microscopy reveals an unusual platelet morphology for the interlammellar metal particles, suggesting that the clay structure may impose a kinetic constraint on the attainment of a thermodynamically more favorable spherical morphology. 15 refs., 3 figs., 2 tabs.

Crocker, M.; Buglass, J.G.; Herold, R.H.M. (Koninklijke/Shell-Lab., Amsterdam (Netherlands))

1993-01-01

237

Modeling Arsenate Competitive Adsorption on Kaolinite, Montmorillonite and Illite  

Microsoft Academic Search

The adsorption of arsenate (As(V)) on kaolinite, montmorillonite and illite was investigated at varying pH and competing anion concentration while holding As(V) concentration (6.7 x 10 7 M), clay suspension density (2.5 g L 1) and ionic strength (0.1 M NaC1) constant. The effects of 2 concen- trations of phosphate (P) or molybdate (Mo) (6.7 X 10 -7 and 6.7

Bruce A. Manning; S. GOLDBERG

1996-01-01

238

Structure property relationships in polyethylene\\/montmorillonite nanodielectrics  

Microsoft Academic Search

The influence of a montmorillonite (MMT) nanoclay, functionalized with dimethyl-di(hydrogenated tallow) quaternary amine, on structural evolution and electrical characteristics of a designed polyethylene system has been studied. Samples were prepared by mixing a polyethylene\\/MMT masterbatch into a matrix system containing 10% high density polyethylene and 90% low density polyethylene using an extruder; X-ray diffraction results suggest good dispersion and exfoliation,

C. D. Green; A. S. Vaughan; G. R. Mitchell; T. Liu

2008-01-01

239

Thermal behaviour of intercalated 8-hydroxyquinoline (oxine) in montmorillonite clay  

Microsoft Academic Search

The composite montmorillonite-8-hydroxyquinoline (Swy-1-8-HQ) was prepared by two different processes and studied by using\\u000a thermogravimetric analysis (TG\\/DTG and DSC), as well as helpful techniques as fluorescence in the UV-visible region and X-ray\\u000a diffraction. The composites developed fluorescent appearance, however with quantum poor efficiency and they exhibited distinct\\u000a TG and DSC thermal behavior. The fluorescence data of spectra associated to the

I. A. Pastre; A. B. S. Moitinho; G. R. de Souza; E. Y. Ionashiro; F. L. Fertonani

2004-01-01

240

Preparation and characterization of flame retardant ABS\\/montmorillonite nanocomposite  

Microsoft Academic Search

Flame retardant acrylonitrile–butadiene–styrene (ABS)\\/montmorillonite (MMT) nanocomposites were prepared by direct melt intercalation of ABS, organophilic clay and conventional fire retardants (decabromodiphenyl oxide (DB) and antimony oxide (AO)). Morphology and flammability properties were characterized by X-ray power diffractionmeter (XRD), high resolution electron microscopy (HREM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), limiting oxygen index (LOI) test, UL-94 test and cone

Shaofeng Wang; Yuan Hu; Ruowen Zong; Yong Tang; Zuyao Chen; Weicheng Fan

2004-01-01

241

Enthalpy changes accompanying the collapse of montmorillonite layers and the penetration of electrolyte into interlayer space  

SciTech Connect

The enthalpy changes, {Delta}H, in suspensions of Li-, Na-, and K-montmorillonite were determined as functions of the molal concentrations of LiCl, NaCl, and KCl, respectively, by microcalorimetry. These changes were compared with the corresponding changes in interlayer distance, {lambda}, as determined by X-ray diffraction. It was found that {Delta}H values accompanying the collapse of the montmorillonite layers from {lambda} > 14 nm to {lambda} {approx_equal} 1.0 nm were essentially negligible; however, {Delta}H values accompanying the collapse of layers of Li- and Na-montmorillonite from {lambda} {approx_equal} 1.0 nm to {lambda} {approx_equal} 0.6 nm, and the collapse of layers of K-montmorillonite from {lambda} {approx_equal} 0.6 nm, were not negligible. No additional collapse of Li- and Na-montmorillonite layers occurred after {lambda} {approx_equal} 0.6 nm, and for K-montmorillonite layers after {lambda} {approx_equal} 0.3 nm, but {Delta}H continued to change with increasing salt addition. This change was attributed to the penetration of electrolyte into the interlayer space. A notable observation was that the value of {Delta}H was positive for Li-montmorillonite, but negative for Na- and K-montmorillonite. These observations were interpreted to mean that {Delta}H changes in the montmorillonite suspension were largely attributable to reorganization of the interlayer space by the added electrolytes.

Yan, L.; Low, P.F.; Roth, C.B. [Purdue Univ., West Lafayette, IN (United States). Dept. of Agronomy

1996-09-25

242

Influences of surface chemistry and swelling of salt-treated polyelectrolyte multilayers on migration of smooth muscle cells.  

PubMed

The cell migration plays a crucial role in a variety of physiological and pathological processes and can be regulated by the cell-substrate interactions. We found previously that the poly(sodium 4-styrenesulphonate) (PSS)/poly(diallyldimethylammonium) chloride (PDADMAC) multilayers post-treated in 1-5 M NaCl solutions result in continuous changes of their physico-chemical properties such as thickness, chemical composition, surface charge, swelling ratio and wettability. In this study, the responses of human smooth muscle cells (SMCs) on these salt-treated multilayers, particularly the governing factors of cellular migration that offer principles for designing therapeutics and implants, were disclosed. The cell migration rate was slowest on the 3 M NaCl-treated multilayers, which was comparable with that on tissue culture plates, but it was highest on 5 M NaCl-treated multilayers. To elucidate the intrinsic mechanisms, cell adhesion, proliferation, adhesion and related gene expressions were further investigated. The SMCs preferred to attach, spread and proliferate on the PSS-dominated surfaces with well-organized focal adhesion and actin fibres, especially on the 3 M NaCl-treated multilayers, while were kept round and showed low viability on the PDADMAC-dominated surfaces. The relative mRNA expression levels of adhesion-related genes such as fibronectin, laminin and focal adhesion kinase, and migration-related genes such as myosin IIA and Cdc42 were compared to explain the different cellular behaviours. These results reveal that the surface chemistry and the swelling of the salt-treated multilayers govern the cell migration behaviours. PMID:22896570

Han, Lulu; Mao, Zhengwei; Wu, Jindan; Zhang, Yuying; Gao, Changyou

2012-08-15

243

Cytotoxicity of Ni from Surface-Treated Porous Nitinol (PNT) on Osteoblast Cells  

Microsoft Academic Search

The leaching of nickel from the surface of porous Nitinol (PNT) is mainly dependent on its surface characteristics, which\\u000a can be controlled by appropriate surface treatments. In this investigation, PNT was subjected to two surface treatments, namely,\\u000a water-boiling and dry-heating passivations. Phosphate buffer saline (PBS) solutions obtained from cyclic potentiodynamic polarization\\u000a tests on PNT were employed to assess the cytotoxicity

C. Pulletikurthi; N. Munroe; P. Gill; S. Pandya; D. Persaud; W. Haider; K. Iyer; A. McGoron

2011-01-01

244

Correlation Between the Extent of Catalytic Activity and Charge Density of Montmorillonites  

NASA Astrophysics Data System (ADS)

The clay mineral montmorillonite is a member of the phyllosilicate group of minerals, which has been detected on martian soil. Montmorillonite catalyzes the condensation of activated monomers to form RNA-like oligomers. Extent of catalysis, that is, the yield of oligomers, and the length of the longest oligomer formed in these reactions widely varies with the source of montmorillonite (i.e., the locality where the mineral is mined). This study was undertaken to establish whether there exists a correlation between the extent of catalytic property and the charge density of montmorillonites. Charge density was determined by saturating the montmorillonites with alkyl ammonium cations that contained increasing lengths of alkyl chains, [CH3-(CH2)n-NH3]+, where n = 3-16 and 18, and then measuring d(001), interlayer spacing of the resulting montmorillonite-alkyl ammonium-montmorillonite complex by X-ray diffractometry (XRD). Results demonstrate that catalytic activity of montmorillonites with lower charge density is superior to that of higher charge density montmorillonite. They produce longer oligomers that contain 9 to 10 monomer units, while montmorillonite with high charge density catalyzes the formation of oligomers that contain only 4 monomer units. The charge density of montmorillonites can also be calculated from the chemical composition if elemental analysis data of the pure mineral are available. In the next mission to Mars, CheMin (Chemistry and Mineralogy), a combined X-ray diffraction/X-ray fluorescence instrument, will provide information on the mineralogical and elemental analysis of the samples. Possible significance of these results for planning the future missions to Mars for the search of organic compounds and extinct or extant life is discussed.

Ertem, Gözen; Steudel, Annett; Emmerich, Katja; Lagaly, Gerhard; Schuhmann, Rainer

2010-09-01

245

Correlation between the extent of catalytic activity and charge density of montmorillonites.  

PubMed

The clay mineral montmorillonite is a member of the phyllosilicate group of minerals, which has been detected on martian soil. Montmorillonite catalyzes the condensation of activated monomers to form RNA-like oligomers. Extent of catalysis, that is, the yield of oligomers, and the length of the longest oligomer formed in these reactions widely varies with the source of montmorillonite (i.e., the locality where the mineral is mined). This study was undertaken to establish whether there exists a correlation between the extent of catalytic property and the charge density of montmorillonites. Charge density was determined by saturating the montmorillonites with alkyl ammonium cations that contained increasing lengths of alkyl chains, [CH?-(CH?)(n)-NH?](+), where n?=?3-16 and 18, and then measuring d(???), interlayer spacing of the resulting montmorillonite-alkyl ammonium-montmorillonite complex by X-ray diffractometry (XRD). Results demonstrate that catalytic activity of montmorillonites with lower charge density is superior to that of higher charge density montmorillonite. They produce longer oligomers that contain 9 to 10 monomer units, while montmorillonite with high charge density catalyzes the formation of oligomers that contain only 4 monomer units. The charge density of montmorillonites can also be calculated from the chemical composition if elemental analysis data of the pure mineral are available. In the next mission to Mars, CheMin (Chemistry and Mineralogy), a combined X-ray diffraction/X-ray fluorescence instrument, will provide information on the mineralogical and elemental analysis of the samples. Possible significance of these results for planning the future missions to Mars for the search of organic compounds and extinct or extant life is discussed. PMID:20854214

Ertem, Gözen; Steudel, Annett; Emmerich, Katja; Lagaly, Gerhard; Schuhmann, Rainer

2010-09-21

246

Characterization of wet-chemically treated silicon interfaces by surface photovoltage measurements.  

PubMed

A non-destructive and surface-sensitive surface photovoltage (SPV) technique was employed to investigate the influence of important wet-chemical treatments on the electronic surface properties. The preparation-induced surface roughness as well as the hydrogen and oxide coverage were additionally determined by spectroscopic ellipsometry (SE). High values of interface charge and a high density of rechargeable interface states were observed on atomically rough surfaces and interfaces after HF-treatment and conventional wet-chemical oxidation. Both interface charge and density of rechargeable interface states could be reduced significantly by preparing an atomically flat Si surface and a well-ordered silicon/silicon oxide interface by applying special H-termination and hot-water oxidation procedures. PMID:12397491

Angermann, H

2002-08-28

247

Surface characterization of radio frequency water plasma treated and annealed polycrystalline tin oxide thin films  

Microsoft Academic Search

Angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and electron energy loss spectroscopy (EELS) have been used to examine the consequences of the interaction of radio frequency water plasmas with polycrystalline tin oxide surfaces. Results from AR-XPS and EELS indicate that an extensive surface hydroxylation or gel layer (> 10 â«) does not form on the tin oxide surface from exposure to atmosphere

M. J. Tarlov; J. F. Evans

2009-01-01

248

An approach for treating contact surfaces in Lagrangian cell-centered hydrodynamics  

NASA Astrophysics Data System (ADS)

A new method is presented for modeling contact surfaces in Lagrangian cell-centered hydrodynamics (CCH). The contact method solves a multi-directional Riemann-like problem at each penetrating or touching node along the contact surface. The velocity of a penetrating or touching node and the corresponding forces are explicitly calculated using the Riemann-like nodal solver. The contact method works with material strength and allows surfaces to impact, slide, and separate. Results are presented for several test problems involving both gases and materials with strength. The new contact surface approach extends the modeling capabilities of CCH.

Morgan, Nathaniel R.; Kenamond, Mark A.; Burton, Donald E.; Carney, Theodore C.; Ingraham, Daniel J.

2013-10-01

249

Interstratification patterns from the pH-dependent intercalation of a tetracycline antibiotic within montmorillonite layers.  

PubMed

Little is known about the distribution of the intercalated molecules within the interstratified layers resulting from the pH-dependent interlayer adsorption of ionizable organic molecules, including antibiotics, within smectite-type clay minerals. Here we employed experimental and simulated X-ray diffraction (XRD) to characterize interstratification (or mixed layering) from the intercalation of oxytetracycline (OTC), a commonly used tetracycline antibiotic, within Na-montmorillonite layers at pHs 4, 5, 6, and 8. Our XRD data reveal that OTC is distributed nonrandomly in the interlayers such that Na- and OTC-saturated interlayers coexist. The profile of the full width at half-maximum intensity (fwhm), monitored as a function of increasing layer-to-layer distance (d001), resulting from an increasing amount of intercalated OTC, reflects such mixed-layer crystals under the acidic pH conditions. A minimum in fwhm occurs at a d spacing of about 1.8 nm, which is to be the optimal d001 for OTC-saturated layers, in agreement with molecular modeling results. Using the coordinates of the thermodynamically favorable configuration of the adsorptives in a model montmorillonite interlayer, we simulated XRD profiles to unravel the different patterns of interstratification from the experimental data. At both pHs 4 and 5, Na- and OTC-interlayers are randomly interstratified, whereas at pH 6, these layers are clustered, as characterized by a segregated interstratification pattern. The theoretical layer stacking sequences of the simulated XRD illustrate, as pH increases, the clustering of similar layer types with the exclusion of OTC intercalation from clay populations enriched in Na. At pH 8, both fwhm and d001 indicate OTC adsorption primarily on external surface sites, not within interlayers. Our findings imply that, in addition to chemical speciation, a pH-dependent formation of montmorillonite crystallites with unexfoliated layers may be responsible both for the decreased OTC intercalation and for the increased binding on external sites, thus resulting in the different patterns of interstratification as a function of increasing pH. PMID:23527541

Aristilde, Ludmilla; Lanson, Bruno; Charlet, Laurent

2013-03-25

250

Surface energy approach and AFM verification of the (CF)n treated surface effect and its correlation with adhesion reduction in microvalves  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to outline an approach that will determine the optimal surface pairs to use in a MEMS device with demonstrated stiction problems. The approach uses the contact angle and atomic force microscopy (AFM) pull-off measurements to predict adhesion at the solid-solid interface. The results are compared to microvalves that have been fabricated with different surfaces at the seat/membrane interface. For microfabricated mechanical devices with surfaces that touch or have a small gap distance, stiction can occur during fabrication or during use. Fabricating multiple devices with different surfaces to determine the lowest stiction can be costly and time consuming. Identifying the surface pair with the least amount of surface adhesion before fabrication can lead to a reduction in device failure due to stiction, and/or time it takes to find the lowest energy surfaces via trial and error. Surface energies are obtained using the van Oss equation based on the contact angle measurements, and surface energy can be used to show the relative adhesions between two surface pairs. An AFM pull-off test is performed using nano- and micro-sized tips to quantify the effect of the different surfaces on adhesion between the solid-solid surface pairs, including SiO2/PI, CFn/PI, CFn/SiO2 and CFn/CFn. The work of adhesion of the surface pairs is obtained using the Derjaguin-Muller-Toporotov (DMT) and Johnson-Kendall-Roberts (JKR) theories. The surfaces treated with a C4F8/Ar plasma to form a CFn coating showed the least amount of surface adhesion. The CFn surface treatment effects on adhesion are quantified and correlated with the reduction in the opening pressure of the microvalve whose interfaces are coated with a CFn film. The AFM pull-off test was more closely related to adhesive forces between the surfaces of the valves as seen in the opening pressure data. The adhesion calculation based on the contact angle measurements predicts the adhesion force with a similar trend but does not take into account the meniscus forces.

Han, Jeahyeong; Yeom, Junghoon; Mensing, Glennys; Joe, Daniel; Masel, Richard I.; Shannon, Mark A.

2009-08-01

251

Characteristics of plasma surface treated composite adhesive joints at high environmental temperature  

Microsoft Academic Search

When an adhesive joint is exposed to high environmental temperature, the load transmission capability of the adhesive joint decreases because the stiffness and strength of structural adhesive decrease. The load transmission capability of adhesive joint at high environmental temperature can be improved by increasing the surface free energy of adherends with surface pretreatments.In this paper, a capacitively coupled radio frequency

Jin Kook Kim; Dai Gil Lee

2002-01-01

252

Comparative study of wear mechanism of surface treated AISI 316L stainless steel  

Microsoft Academic Search

Coating is a technique employed for the surface of materials to have thermal insulation, hot corrosion and oxidation resistance. Ion implantation forms modifications in surface composition or morphology of solids which yield to a change of physical and especially mechanical properties such as hardness and modulus of elasticity. The objective of this investigation is to concentrate on the friction and

Halit Dogan; Fehim Findik; Ahmet Oztarhan

2003-01-01

253

Chlorpyrifos-treated crops in the vicinity of surface water contamination in the san joaquin valley, california, USA.  

PubMed

Due to frequent contamination of streams in the San Joaquin Valley, California, USA, with the insecticide chlorpyrifos, researchers are working to identify crop-specific management practices that will reduce the offsite movement of this compound into surface waters. To guide this effort, crops treated with chlorpyrifos in the vicinity of contaminated streams were identified; walnut, alfalfa, and almond were the primary crops identified. Use was higher on walnut and almond, but due to irrigation practices offsite movement in surface runoff may be more likely from alfalfa. Based on these findings, development of management practices to reduce off-site movement of chlorpyrifos in irrigation runoff from treated alfalfa fields is recommended. PMID:23749038

Starner, Keith; Goh, Kean S

2013-06-09

254

Organo-montmorillonite as substitute of carbon black in natural rubber compounds  

Microsoft Academic Search

The use of octadecylamine modified montmorillonite as substitute of carbon black in natural rubber (NR) compounds is studied. Rubber with 10 parts per hundred resin (phr) of pristine (clay) and octadecylamine modified montmorillonite (organoclay) were compared with 10 and 40phr carbon black as filler. The modified silicate is analysed by X-ray, FTIR and thermogravimetric analysis. Vulcametric curves show that the

M Arroyo; M. A López-Manchado; B Herrero

2003-01-01

255

Adsorption of heavy metals on Na-montmorillonite. Effect of pH and organic substances  

Microsoft Academic Search

Clays (especially montmorillonite and bentonite) are widely used as barriers in landfills to prevent contamination of subsoil and groundwater by leachates containing heavy metals. For this reason it is important to study the adsorption of metals by these clays. The sorption of seven metals (Cd, Cr, Cu, Mn, Ni, Pb and Zn) on Na-montmorillonite was studied as a function of

O. Abollino; M. Aceto; M. Malandrino; C. Sarzanini; E. Mentasti

2003-01-01

256

Shear Induced Pore Pressure Generation in Montmorillonite-Based Fault Gouge  

Microsoft Academic Search

Understanding the frictional properties of fault gouge is crucial to understanding the generation and nature of earthquakes and the strength of crustal faults. Montmorillonite is of particular interest because it can exhibit exceptionally low friction and it has been suggested as a candidate source of fault weakness. Previous work shows that the weakness of montmorillonite is associated with its hydration

M. Ikari; D. Saffer; C. Marone; J. Samuelson

2006-01-01

257

Effects of organic acids on adsorption of lead onto montmorillonite, goethite and humic acid  

Microsoft Academic Search

Adsorption isotherms for Pb onto six soil components (quartz, feldspar, kaolinite, montmorillonite, goethite and humic acid) were studied. The influence of pH, EDTA and citric acid on the adsorption of Pb onto montmorillonite, goethite and humic acid were considered. Results indicate that the experimental data fit the Langmuir Adsorption Isotherm. The adsorption capacity for Pb at pH 6 was found

Zhenghua Wu; Zhimang Gu; Xiaorong Wang; Les Evans; Hongyan Guo

2003-01-01

258

Quantitative analysis of small angle neutron scattering data from montmorillonite dispersions  

Microsoft Academic Search

A new model is presented which can describe quantitatively the small angle neutron scattering from montmorillonite-type clay dispersions and polymer-clay nanocomposites. The model is shown to be able to describe well the data from a series of dilute montmorillonite in water dispersions in which the deuterium content of the water phase is varied. The fits combined with information from other

Helen E. Hermes; Henrich Frielinghaus; Wim Pyckhout-Hintzen; Dieter Richter

2006-01-01

259

Lattice Expansion and Rheological Behavior Relationships in Water-Montmorillonite Systems  

Microsoft Academic Search

Some divergent experimental data have been reported on the swelling behavior of sodium montmorillonite. At water contents above 50 percent (based on the weight of dry clay) the basal reflection of sodium montmorillonite at 19.2 A becomes weak and very diffuse ; some workers have stated that it disappears, altogether while others report a persistent weak line even at very

William R. Foster; J. G. SAu; J. M. WAITE

1954-01-01

260

The effect of cerium surface treated ferritic stainless steel current collectors on the performance of solid oxide fuel cells (SOFC)  

Microsoft Academic Search

Laboratory scale solid oxide fuel cells (“button” cells) were operated with untreated or cerium surface treated Fe–22Cr–0.5Mn (composition by weight percent, wt%) ferritic stainless steel current collectors attached to the cathode. After a brief stabilization (or “burn-in”) period, the power density of a cell with the untreated current collector rapidly decreased. By contrast, there was little degradation in power density

D. E. Alman; C. D. Johnson; W. K. Collins; P. D. Jablonski

2007-01-01

261

Treated enamel surface patterns associated with five orthodontic adhesive systems--surface morphology and shear bond strength.  

PubMed

The chief aim of this study was to evaluate the influence of three different types of pretreatment solutions (phosphoric acid, self-etching primers, and polyacrylic acid) on enamel surfaced when used in association with one of the five orthodontic adhesive systems. In the same vein, the shear bond strength of orthodontic metal brackets was also measured to evaluate the influence of bonding procedure. After the enamel surfaces of extracted human maxillary incisors were pretreated with the five adhesive systems, scanning electron microscopy (SEM) was used to observe the effects of pretreatment on enamel. Additionally, the shear bond strength of metal brackets bonded with the five adhesives was measured (n=6). SEM observation revealed different etching patterns on the enamel surface after pretreatment. As for shear bond strength, no statistically significant differences were observed among the five different adhesives (p>0.05). It was found that self-etching primers and polyacrylic acid produced a less aggressive etching pattern than phosphoric acid. Nonetheless, all the five adhesive systems provided acceptable bond strength and attachment of orthodontic brackets. PMID:18309605

Shinya, Makiha; Shinya, Akikazu; Lassila, Lippo V J; Gomi, Harunori; Varrela, Juha; Vallittu, Pekka K; Shinya, Akiyoshi

2008-01-01

262

Monte Carlo molecular simulation of the hydration of K-montmorillonite at 353 K and 625 bar.  

PubMed

Monte Carlo molecular simulations of the hydration of K-saturated Wyoming-type montmorillonite at constant stress in the NPzzT ensemble and at constant chemical potential in the grand canonical muVT ensemble, under basin-like conditions of 353 K and 625 bar, show a strong tendency of the K+ ions to adhere to the siloxane surface, forming predominant inner-sphere complexes with tetrahedral oxygen atoms and adsorbed water molecules. Simulations in the grand canonical ensemble predict that none of the K-montmorillonite hydrates, the one-, two-, and three-layer hydrates, are stable in this environment of high depth, temperature, and pressure. The most nearly stable configuration corresponds to the one-layer hydrate, characterized by a d001 spacing of 12.75 A, the adsorbed water being 60 molecules/layer or 180.83 mg of H2O/g of clay, an internal energy of -22.73 kcal/mol, an interlayer density of 0.365 g/mL, and a pressure tensor, Pzz, of 1999.9 bar. The interlayer structure consists of two close layers of water molecules 0.50 A from the midplane, with broad shoulders on the sides, the protons oriented toward the midplane and the siloxane surfaces, and the K+ ions close to the clay surfaces and on the interlayer midplane. PMID:15544414

Chávez, M de Lourdes; de Pablo, Liberto; de Pablo, Juan J

2004-11-23

263

Plasma-treated nanostructured TiO(2) surface supporting biomimetic growth of apatite.  

PubMed

Although some types of TiO(2) powders and gel-derived films can exhibit bioactivity, plasma-sprayed TiO(2) coatings are always bioinert, thereby hampering wider applications in bone implants. We have successfully produced a bioactive nanostructured TiO(2) surface with grain size smaller than 50 nm using nanoparticle plasma spraying followed by hydrogen plasma immersion ion implantation (PIII). The hydrogen PIII nano-TiO(2) coating can induce bone-like apatite formation on its surface after immersion in a simulated body fluid. In contrast, apatite cannot form on either the as-sprayed TiO(2) surfaces (both <50 nm grain size and >50 nm grain size) or hydrogen-implanted TiO(2) with grain size larger than 50 nm. Hence, both a hydrogenated surface that gives rise to negatively charged functional groups on the surface and small grain size (<50 nm) that enhances surface adsorption are crucial to the growth of apatite. Introduction of surface bioactivity to plasma-sprayed TiO(2) coatings, which are generally recognized to have excellent biocompatibility and corrosion resistance as well as high bonding to titanium alloys, makes them more superior than many current biomedical coatings. PMID:15927251

Liu, Xuanyong; Zhao, Xiaobing; Fu, Ricky K Y; Ho, Joan P Y; Ding, Chuanxian; Chu, Paul K

2005-11-01

264

Influence of laser surface treated on the characterization and corrosion behavior of Al-Fe aerospace alloys  

NASA Astrophysics Data System (ADS)

In this research laser surface remelting without protective coating with a 2 kW Yb-fiber laser (IPG YLR-2000S) was applied in the Al-1.5 wt.%Fe alloy in order to investigate the layer treated with different techniques of superficial characterization, thereby, the technique of optical microscopy, atomic force microscopy and low-angle X-ray diffraction were used. The present work mainly focuses on the corrosion study by diverse techniques in aggressive environment of the laser-treated area and the substrate material was carried out, thereby, at open circuit potential testing, the results have shown a displacement to more anodic values in the corrosion potential for the laser-treated specimen when compared to the untreated specimen; in potentiodynamic polarization tests have shown that as a result of the laser treatment, the corrosion current can be reduced by as much as ten times, and a passive region was obtained, which served as an effective barrier for reducing anodic dissolution and finally, the result in cyclic polarization curves of the untreated sample there was a greater area of the hysteresis loop, implying that it is more susceptible to corrosion. This study was complemented by other techniques mentioned above in order to elucidate this study. Laser surface remelting process has definitely modified the surface film, which results in higher corrosion resistance, a large range of passivation and a lower area of the hysteresis loop.

Pariona, Moisés Meza; Teleginski, Viviane; dos Santos, Kelly; de Lima, Angela A. O. C.; Zara, Alfredo J.; Micene, Katieli Tives; Riva, Rudimar

2013-07-01

265

Biofilm formation on surfaces of glass and Teflon exposed to treated water  

Microsoft Academic Search

Biofilm formation on glass and Teflon cylinders, situated on top of each other in vertical glass columns exposed to different types of treated water at a flow rate of 0.2 m\\/s, was determined using ATP analysis and heterotrophic plate counts. Biofilm formation rates (BFR) of these water types, as calculated from the linear relationship between exposure time and biomass accumulated

Dick van der Kooij; Harm R. Veenendaal; Cynthia Baars-Lorist; Daan W. van der Klift; Yvonne C. Drost

1995-01-01

266

Intercalation in montmorillonite of molybdenum cations containing the Mo6Cl8 cluster core  

NASA Astrophysics Data System (ADS)

Molybdenum cations containing the Mo6Cl8 cluster core have been intercalated in montmorillonite. Cluster ions of the type [Mo6Cl8(H2O)6-n(OH)n](4-n)+ were formed by argentometric titration of [Mo6Cl8]Cl4 . 2H2O to remove the four terminally bonded chlorines. At pH = 1.5 the clusters occupy the gallery region between the silicate layers of montmorillonite by displacement of Na+. The relationship between Na+ released and cluster bound indicates the cluster intercalates mainly as monopositive cations (n = 3), along with some dispositive cations (n = 2). As the cluster loading approaches the cation exchange capacity of the clay, the gallery acidity decreases and additional cluster binds as neutral molecules with n = 4. Thus the maximum cluster loading (80 mmoles/100 g) exceeds the value expected on the basis of ion exchange alone (60 mmoles/100 g). The gallery height of 7.3 Ĺ for the new intercalate is compatible with the C4 axis of the Mo6Cl8 core being oriented perpendicular to the silicate layers. Thermolysis of the intercalated clusters at 240°C results in the oxidation of the intercalated clusters to molybdenum oxide. Cluster decomposition is accompanied by the collapse of some galleries, while others remain propped open by 3.9 Ĺ. The latter value corresponds to two layers of oxygen in the galleries. Thus the oxide is nonuniformly distributed on both the internal and external surfaces of the clay. Complete gallery collapse is observed at 300°C.

Christiano, Steven P.; Pinnavaia, Thomas J.

1986-10-01

267

An Infrared Spectroscopy Study Of Pb(II) And Siderophore Sorption To Montmorillonite  

NASA Astrophysics Data System (ADS)

Aerobic microorganisms exude low molecular weight organic ligands known as siderophores in order to acquire nutrient Fe. Because siderophores can also bind other metals such as Pb, Zn, and Cd, they may affect metal sorption, fate, and transport. This study combined batch sorption experiments, thermodynamic modeling, X-ray diffraction (XRD), and spectroscopic analysis, to investigate Pb(II) and desferrioxamine B (DFOB) sorption to montmorillonite, alone and in combination, at pH 3-9, ~22 C, and in 0.1 M NaCl. Samples at pH 3, 5.5, and 7.5 were analyzed by XRD and Fourier-Transform Infrared Spectroscopy (FTIR) and samples at pH5.5 were analyzed by in-situ Attenuated Total Reflection Infrared Spectroscopy (ATR-FTIR). DFOB does not bind Pb substantially at pH 3, and sorption results showed that the ligand only minimally affects Pb sorption at this pH. However, combination of batch sorption experiments with XRD, FTIR, and ATR-FTIR analysis suggested that Pb(II)/DFOB (co)absorption in the interlayer is likely an important sorption mechanism at pH 5.5 and 7.5 under both air-dried and aqueous conditions. The precise structure of the sorption complex(es) could not be determined by these methods. Some adsorption of Pb(II)/DFOB to the external clay surface is also possible. In the absence of DFOB, a Pb-carbonate complex or precipitate (perhaps hydrocerrusite) was detected by FTIR. Overall, results showed that a microbial siderophore may affect Pb sorption to montmorillonite, that (co)absorption in the interlayer region can be important, and that sorption effects can vary substantially depending upon solution conditions.

Maurice, P. A.; Hunter, E. L.; Quicksall, A. N.; Haack, E.; Johnston, C. T.

2010-12-01

268

Montmorillonite as an adsorbent for extraction and concentration of atrazine, propazine, deethylatrazine, deisopropylatrazine and hydroxyatrazine.  

PubMed

Adsorption properties of the clay mineral montmorillonite in the potassium homoionic form (KMT) was investigated to achieve the extraction and concentration of the herbicides atrazine (AT) and propazine (PROP), as well as the main degradation products of atrazine, namely deethylatrazine (DEA), deisopropylatrazine (DIA) and hydroxyatrazine (ATOH). A batch approach was proposed, with recovery percentages for AT, PROP and DIA higher than 90% at concentrations of 0.50 and 2.50 microg L(-1). For DEA and ATOH, however, low recoveries were obtained. For DEA, this fact can be explained by its low K(d) with KMT, contrary to ATOH, which interacts strongly with the mineral surface, hindering the complete desorption and hence, generating low recovery percentages. The influence of pH, ionic strength and humic acid was studied, and a comparison with the C(18) phase as SPE cartridges was carried out. Montmorillonite showed a similar performance to commercial cartridge for concentrations of AT, DEA and PROP, but better recoveries for DIA was obtained using the clay mineral. For ATOH the recovery was also higher on the clay mineral, although for this compound the most suitable SPE cartridge is constituted by cation exchange resin. After the concentration and elution steps, the 0.50 and 2.50 microg L(-1) gave chromatographic peak areas that could be easily quantified with an analytical curve obtained in the concentration range between 7.5 and 100 microg L(-1). The obtained concentration factors are suitable to allow the application of the method to the monitoring of triazine residues in drinking water. PMID:17723731

Zarpon, Lílian; Abate, Gilberto; dos Santos, Luciana B O; Masini, Jorge C

2006-07-14

269

Characterization of treated indium-tin-oxide surfaces used in electroluminescent devices  

NASA Astrophysics Data System (ADS)

The influence of oxidative and reductive treatments of indium-tin-oxide (ITO) on the performance of electroluminescent devices is presented. The improvement in device performance is correlated with the surface chemical composition and work function. The work function is shown to be largely determined by the surface oxygen concentration. Oxygen-glow discharge or ultraviolet-ozone treatments increase the surface oxygen concentration and work function in a strongly correlated manner. High temperature, vacuum annealing reduces both the surface oxygen and work function. With oxidation the occupied, density of states (DOS) at the Fermi level is also greatly reduced. This process is reversible by vacuum annealing and it appears that the oxygen concentration, work function, and DOS can be cycled by repeated oxygen treatments and annealing. These observations are interpreted in terms of the well-known, bulk properties of ITO.

Mason, M. G.; Hung, L. S.; Tang, C. W.; Lee, S. T.; Wong, K. W.; Wang, M.

1999-08-01

270

Transition metal pillared clay 4. A comparative study of textural, acidic and catalytic properties of chromia pillared montmorillonite and acid activated montmorillonite  

Microsoft Academic Search

The preparation, characterisation and catalytic activities of chromia pillared montmorillonites were investigated. The Na-exchanged montmorillonite shows higher uptake of chromium(III) acetato complex than that of acid activated clay. However, in both the cases, stepwise ion-exchange process results in better intercalation compared to the single step process. Both the pillared materials are found thermally stable up to 773 K. Materials prepared

Trilochan Mishra; Kulamani Parida

1998-01-01

271

Surface state of TiO 2 treated with low ion energy plasma  

Microsoft Academic Search

The effect of low pressure radio frequency (rf) plasma treatment on TiO2 surface states has been studied using X-ray photoelectron spectroscopy. Three different oxidation states of oxygen in untreated TiO2 powder were observed, which suggests the existence of adsorbed water and carbon on the surface. The ratio of oxygen to titanium (O\\/Ti) was decreased for the low ion dose plasma

Jin Jun; Joong-Hyeok Shin; Marshal Dhayal

2006-01-01

272

Surface Characterization of Vulcanized Rubber Treated with Sulfuric Acid and its Adhesion to Polyurethane Adhesive  

Microsoft Academic Search

Modifications produced on a vulcanized styrene –butadiene rubber surface by treatment with sulfuric acid were studied and several experimental variables were considered.The treatment of R1 rubber with sulfuric acid produced a noticeable decrease in contact angle which was mainly ascribed to an increase in surface energy due to the formation of sulfonic acid moieties and C?O bonds, and the removal

Carmen M. Cepeda-Jiménez; M. Mercedes Pastor-blas; Teresa P. Ferrándiz-Gómez; José Miguel Martín-Martínez

2000-01-01

273

Adsorption and interactions of methyl green with montmorillonite and sepiolite  

SciTech Connect

The divalent organic cation, methyl green (MG), undergoes a slow transformation (6 h) to a monovalent cation, carbinol (MGOH{sup +}) upon dilution of its solution (10 mM), or in a buffer at neutral pH. Adsorption isotherms of MG on montmorillonite were determined by two procedures, both of which yield a final pH of suspensions between 7 to 7.4. When the amounts of MG in suspension were lower than the cation-exchange capacity (CEC) of the clay (0.8 mol{sub c}/kg clay), no measurable amount of MG remained in solution. The maximal amounts of MGOH{sup +} adsorbed were larger than those of MG{sup 2+}, being 1.15 and 0.75 mol MG/kg clay, respectively, corresponding to 140% of the CEC in the first case. Adsorption of MG on sepiolite (CEC = 0.15 mol{sub c}/kg) further emphasizes the two patterns of its adsorption. The maximal adsorbed amounts of MG{sup 2+} and MGOH{sup +} were 0.09 and 0.30 mol/kg clay, respectively. X-ray diffraction measurements gave lower values for the basal spacings for montmorillonite-MG{sup +} than for MGOH{sup +}, suggesting that MG{sup 2+} binds two clay platelets together, as in the case of other divalent cations. A competition for adsorption between MG and the monovalent organic cation, acriflavin (AF), gave lower adsorbed amounts of AF when competing with MG{sup +}, which is interpreted to be due to the smaller basal spacing in this case, which partially inhibits the entry of AF molecules into the interlammelar space. Spectra of montmorillonite-MG particles in the visible range exhibited significant differences between clay-MG and clay-carbinol.

Rytwo, G.; Nir, S.; Crespin, M.; Margulies, L.

2000-02-01

274

Oligomerization reactions of deoxyribonucleotides on montmorillonite clay: the effect of mononucleotide structure, phosphate activation and montmorillonite composition on phosphodiester bond formation.  

PubMed

2'-d-5'-GMP and 2'-d-5'-AMP bind 2 times more strongly to montmorillonite 22A than do 2'-d-5'-CMP and 5'-TMP. The dinucleotide d(pG)2 forms in 9.2% yield and the cyclic dinucleotide c(dpG)2 in 5.4% yield in the reaction of 2'-d-5'-GMP with EDAC in the presence of montmorillonite 22A. The yield of d(pC)2 (2.0%) is significantly lower but comparable to that obtained from 5'-TMP. The yield of dimers which contain the phosphodiester bond decreases as the reaction medium is changed from 0.2 M NaCl to a mixture of 0.2 M NaCl and 0.075 M MgCl2. A low yield of d(pA)2 was observed in the condensation reaction of 5'-ImdpA on montmorillonite 22A. The cyclic nucleotide (3',5'-cdAMP) was obtained in 14% yield from 3'-ImdpA. The yield of d(pA)2 obtained when EDAC is used as the condensing agent increases with increasing iron content of the Na(+)-montmorillonite used as a catalyst. Evidence is presented which shows that the acidity of the Na(+)-montmorillonite is a necessary but not sufficient factor for the montmorillonite catalysis of phosphodiester bond formation. PMID:11537409

Ferris, J P; Kamaluddin; Ertem, G

1990-01-01

275

Comparison between immediate and delayed laser-treated implants surface with switching platform: a clinical retrospective study.  

PubMed

The aim of the present study was to compare immediate (Im) versus delayed (De) placement of laser-treated implants surface with switching platform to confirm the predictability and performance of this type of implant. The implants were placed in pos exodontia and healed sites at the incisor, canine, premolar, and molar regions of the maxilla or the mandible. A protocol was prepared in which patient age, sex, implant length, diameter, and use of bone graft were recorded. The study included 44 GEASS Srl (Udine, Italy) implants with laser surface and morse taper connection, placed in 27 patients (mean age: 56 years; range: 25-80 years).The survival rates were 100% in the Im group and in the De group. The patients were followed for a minimum of 12 months. Implants with laser surface and morse connection presented when placed in fresh sockets showed similar results to implants placed in mature bone after 12 months of follow-up. PMID:22214180

de Moraes, Eduardo José; Rao Genovese, Francesco

2012-01-03

276

Chromium(III) and chromium(VI) surface treated galvanized steel for outdoor constructions: environmental aspects.  

PubMed

The long-term degradation of chromium(III) (Zn-Cr(III)) and chromium(VI)-based (Zn-Cr(VI)) surface treatments on galvanized steel and their capacities to hinder the release of zinc induced by atmospheric corrosion at nonsheltered urban and marine exposure conditions for 2 years are investigated. Compared to bare zinc sheet, both surface treatments revealed high corrosion protection abilities and capacities to hinder the release of zinc, still evident after 2 years of exposure. The zinc barrier properties of the thinner Zn-Cr(VI) (10 nm) treatment were during the first 100 days of urban exposure slightly improved compared with Zn-Cr(III) (35 nm). However, their long-term protection capacities were inverse. Released concentrations of total chromium correspond to annual release rates less than 0.000032 (Zn-Cr(III)) and 0.00014 g Cr m(-2) yr(-1) (Zn-Cr(VI)) after 1 year of urban exposure. Aging by indoor storage of the surface treatments prior to outdoor exposure reduced the released Cr concentrations from the surface treatments. No Cr(VI) was released from the aged surfaces but from the freshly exposed Zn-Cr(VI). Marine exposure conditions resulted in a faster reduction of chromate to chromium(III)oxide compared with urban conditions, and a significantly lower amount of both chromium(III) and chromium(VI) released from Zn-Cr(VI) at the marine site compared with the urban site. PMID:20462267

Lindström, David; Hedberg, Yolanda; Odnevall Wallinder, Inger

2010-06-01

277

Nanofabrication via direct transfer of BOE treated PDMS stamp patterns onto SiO2 surfaces  

Microsoft Academic Search

Various PDMS patterns with a few microns to sub-micron size and thickness of 20~30 nanometers were successfully transferred on the substrate via simple printing process of a buffered oxide etchant-treated PDMS stamp on the SiO2 substrate. The patterned PDMS layer acted as sacrificial layer for metal-film patterning and as chemical passivation layer for the selective adsorption of V2O5 nanowires. In

Yong-Kwan Kim; Jae-Hyun Park; Gun-Chul Shin; Jeong Sook Ha; So Jeong Park; Seong Min Yi; Gyu Tae Kim

2007-01-01

278

A study of the reciprocating-sliding wear performance of plasma surface treated titanium alloy  

Microsoft Academic Search

Triode plasma nitriding was used in conjunction with electron-beam plasma-assisted physical vapour deposition of TiN and CrAlN to enhance the wear resistance of Ti–6Al–4V titanium alloy. Linear reciprocating-sliding ball-on-plate wear tests were performed to assess the tribological performance of the treated alloy. Wear volumes were correlated to changes in coefficient of friction, which is often indicative of breakdown of the

G. Cassar; J. C. Avelar-Batista Wilson; S. Banfield; J. Housden; A. Matthews; A. Leyland

2010-01-01

279

Surface structure and corrosion resistance of short-time heat-treated NiTi shape memory alloy  

NASA Astrophysics Data System (ADS)

NiTi alloys are attractive materials that are used for medicine, however, Ni-release may cause allergic reactions in an organism. The Ni-release rate is strongly affected by the surface state of the NiTi alloy that is mainly determined by its processing route. In this study, a NiTi shape memory alloy (50.9 at.% Ni) was heat-treated by several regimes simulating the shape setting procedure, the last step in the manufacture of implants. Heating temperatures were between 500 and 550 °C and durations from 5 to 10 min. Heat treatments were performed in air at normal and low pressure and in a salt bath. The purpose of the treatments was to obtain and compare different surface states of the Ni-Ti alloy. The surface state and chemistry of heat-treated samples were investigated by electron microscopy, X-ray photoelectron spectroscopy and Raman spectrometry. The amount of nickel released into a model physiological solution of pH 2 and into concentrated HCl was taken as a measure of the corrosion rate. It was found that the heat treatments produced surface TiO 2 layers measuring 15-50 nm in thickness that were depleted in nickel. The sample covered by the 15-nm thick oxide that was treated at 500 °C/5 min in a low pressure air showed the best corrosion performance in terms of Ni-release. As the oxide thickness increased, due to either temperature or oxygen activity change, Ni-release into the physiological solution accelerated. This finding is discussed in relation to the internal structure of the oxide layers.

Vojt?ch, D.; Vod?rová, M.; Fojt, J.; Novák, P.; Kubásek, T.

2010-12-01

280

Montmorillonite-based porous clay heterostructures (PCHs) intercalated with silica-titania pillars-synthesis and characterization  

SciTech Connect

Porous clay heterostructures (PCHs) were synthesized using natural montmorillonite as a raw material. Apart from pure silica pillars also silica-titania pillars were intercalated into the interlayer space of the parent clay. The detailed studies of the calcination process of the as-prepared PCH samples as well as thermal stability of the pillared structure of these materials were performed. The pillared structure of PCHs intercalated with both silica and silica-titania clusters was found to be thermally stable up to temperatures exceeding 600 deg. C. It was found that titanium incorporated into the silica pillars was present mainly in the form of separated tetracoordinated cations. For the samples with the higher Ti loading also small contribution of titanium in the form of the polymeric oxide species was detected. Titanium incorporated into the PCH materials significantly increased their surface acidity forming mainly Bronsted acid sites. - Graphical abstract: Synthesis of the montmorillonite based porous clay heterostructures (PCHs) intercalated with silica-titania pillars has been performed. The mechanism of the thermal degradation of organic templates in the pore system of PCHs was studied. PCHs were characterized with respect to structure, texture, composition, surface acidity, thermal stability and form of introduced titanium.

Chmielarz, Lucjan, E-mail: chmielar@chemia.uj.edu.p [Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Krakow (Poland); Gil, Barbara; Kustrowski, Piotr; Piwowarska, Zofia; Dudek, Barbara [Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Krakow (Poland); Michalik, Marek [Jagiellonian University, Institute of Geological Sciences, Oleandry 2a, 30-063 Krakow (Poland)

2009-05-15

281

Preparation of polystyrene\\/montmorillonite nanocomposites using a new radical initiator-montmorillonite hybrid via in situ intercalative polymerization  

Microsoft Academic Search

Polystyrene\\/montmorillonite (PS\\/MMT) nanocomposites were prepared by in situ free radical intercalative polymerization, using 1, 3 and 5 wt% of a new cationic radical initiator-MMT hybrid. The corresponding nanocomposites were designated as PS\\/MMT-1, PS\\/MMT-3 and PS\\/MMT-5, respectively. The silicate layers were well exfoliated and randomly dispersed in the PS\\/MMT-1 and PS\\/MMT-3, but were less exfoliated in the PS\\/MMT-5, due to the

Periyayya Uthirakumar; Kee Suk Nahm; Yoon Bong Hahn; Youn-Sik Lee

2004-01-01

282

Developing improved models of oxidatively treated carbon fibre surfaces, using molecular simulation  

Microsoft Academic Search

In this work computer modelling investigations are reported into the chemical functional groups that are believed to contribute to composite fibre\\/matrix adhesion. The CERIUS [Compos A: Appl Sci Manuf 29 (1998) 1291] and MOPAC computational packages are employed to simulate the sorption interactions of small molecules at a range of functionalised surfaces. The results of these calculations are compared with

R. D Allington; D Attwood; I Hamerton; J. N Hay; B. J Howlin

2004-01-01

283

Surface Functionalization of Plasma Treated Ultrananocrystalline Diamond/Amorphous Carbon Composite Films  

NASA Astrophysics Data System (ADS)

Diamond possesses a number of outstanding properties which make it a perspective material as platform for preparation of biosensors. The diamond surface needs to be activated before the chemical attachment of crosslinkers with which biomolecules can interact. In the current work we have investigated the modification of ultrananocrystalline diamond/amorphous carbon (UNCD/a-C) films by oxygen and ammonia plasmas. Afterwards the layers were functionalized in a further step to obtain thiol-active maleimide groups on the surface. We studied the possibility for direct binding of maleimide to terminal OH-groups on the UNCD surface and for silanization with 3-aminopropyltriethoxysilane (APTES) to obtain NH2-groups for the following attachment of sulfosuccinimidyl 4-(N-maleimidomethyl)-cyclohexane-1-carboxylate (SSMCC). The thiol-bearing fluorescein-related dye 5-((2-(and-3)-S-(acetylmercapto) succinoyl) amino) fluorescein (SAMSA) was immobilized as an model biomolecule to evaluate the achieved thiol-activity by fluorescence microscopy. The results of the above mentioned surface modification and functionalization steps were investigated by Auger electron spectroscopy (AES) and contact angle measurements.

Koch, Hermann; Popov, Cyril; Kulisch, Wilhelm; Spassov, G.; Reithmaier, Johann Peter

284

Process for Surface-Treating Metals by the Application of Silicate Films.  

National Technical Information Service (NTIS)

A published disclosure is given of a supplementary patent application for a method of protecting metal surfaces, e.g. silverware, by applying a film containing an SiO2:Na2O ratio greater than 3.3:1, preferably between 3.9:1 and 5.5:1. The claims cover: ai...

A. Seidl F. Leonhard

1973-01-01

285

Fatigue and fracture behaviour of a laser surface heat treated martensitic high-nitrogen tool steel  

Microsoft Academic Search

High nitrogen tool steels offer a superior corrosion resistance compared to conventional nitrogen-free tool steels at similar mechanical and tribological properties. For this reason they are nowadays applied for ball bearings in the aircraft industry. A laser-surface treatment can lead to a further improvement of this combination of properties. The aim of this research project is to improve the tribological

M Heitkemper; C Bohne; A Pyzalla; A Fischer

2003-01-01

286

Genotoxicity and inflammatory investigation in mice treated with magnetite nanoparticles surface coated with polyaspartic acid  

Microsoft Academic Search

In this study, some biological tests were carried out with a magnetic fluid (MF) sample based on magnetite nanoparticles (MNPs) surface coated with polyaspartic acid (PAMF). The tests were performed from 1 to 30 days after injection of 50?L of PAMF in Swiss mice. The PAMF biocompatibility\\/toxicity was evaluated through cytometry, micronuclei assay, and morphology of several organs. All observed

N. Sadeghiani; L. S. Barbosa; L. P. Silva; R. B. Azevedo; P. C. Morais; Z. G. M. Lacava

2005-01-01

287

Properties of GaP(001) surfaces treated in aqueous HF solutions  

SciTech Connect

Chemically cleaned GaP(001) surfaces in aqueous HF solutions have been studied using spectroscopic ellipsometry (SE), ex situ atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), wettability, and photoluminescence (PL) measurements. The SE data clearly indicate that the solutions cause removal of the native oxide film immediately upon immersing the sample ({<=}1 min). The SE data, however, suggest that the native oxide film cannot be completely etch-removed. This is due to the fact that as soon as the etched sample is exposed to air, the oxide starts to regrow. The SE estimated roughness is {approx}1 nm, while the AFM roughness value is {approx}0.3 nm. The XPS spectra confirm the removal of the native oxide and also the presence of regrown oxide on the HF-etched GaP surface. The wettability measurements indicate that the HF-cleaned surface is hydrophobic, which is in direct contrast to those obtained from alkaline-cleaned surfaces (hydrophilic). A slight increase in the PL intensity is also observed after etching in aqueous HF solutions.

Morota, Hiroaki; Adachi, Sadao [Department of Electronic Engineering, Faculty of Engineering, Gunma University, Kiryu-shi, Gunma 376-8515 (Japan)

2007-06-01

288

Nanofabrication via direct transfer of BOE treated PDMS stamp patterns onto SiO2 surfaces  

NASA Astrophysics Data System (ADS)

Various PDMS patterns with a few microns to sub-micron size and thickness of 20~30 nanometers were successfully transferred on the substrate via simple printing process of a buffered oxide etchant-treated PDMS stamp on the SiO2 substrate. The patterned PDMS layer acted as sacrificial layer for metal-film patterning and as chemical passivation layer for the selective adsorption of V2O5 nanowires. In particular, the electrical measurement of the patterned V2O5 nanowire network showed the semiconducting non-ohmic behavior in the channel.

Kim, Yong-Kwan; Park, Jae-Hyun; Shin, Gun-Chul; Ha, Jeong Sook; Park, So Jeong; Yi, Seong Min; Kim, Gyu Tae

2007-03-01

289

Tantalum-pillared montmorillonite: I. Synthesis and physicochemical characterization  

SciTech Connect

The synthesis method of a stable, large-pore tantalum-pillared montmorillonite family (Ta-PILC) and its physicochemical characterization are reported. The clay used is a sodium montmorillonite. The tantalum pillaring solution is prepared by careful control of the hydrolysis of a tantalum alkoxide precursor, Ta(OC{sub 2}H{sub 5}){sub 5}, in an ethanolic acidic solution. From XRD analysis it has been concluded that the Ta-PILC possesses a high thermal stability, the pillared structure is preserved even after calcination at 600{degrees}C, and the basal spacing, 26 {Angstrom} at 500{degrees}C, is one of the greatest values described in the literature. On the basis of the bibliographic data concerning tantalum alkoxide hydrolysis and condensation, and taking into account the experimental results obtained for this series of Ta-PILCs, a structure of type [Ta{sub 8}O{sub 10}(OR){sub 20}], R = H, C{sub 2}H{sub 5}, has been proposed as the precursor molecule of the tantalum pillars. 28 refs., 9 figs., 3 tabs.

Guiu, G.; Gil, A.; Grange, P. [Universite Catholique de Louvain (Belgium)] [and others

1997-06-01

290

Thermal characteristics of thermobrachytherapy surface applicators for treating chest wall recurrence  

NASA Astrophysics Data System (ADS)

The aim of this study was to investigate temperature and thermal dose distributions of thermobrachytherapy surface applicators (TBSAs) developed for concurrent or sequential high dose rate (HDR) brachytherapy and microwave hyperthermia treatment of chest wall recurrence and other superficial diseases. A steady-state thermodynamics model coupled with the fluid dynamics of a water bolus and electromagnetic radiation of the hyperthermia applicator is used to characterize the temperature distributions achievable with TBSAs in an elliptical phantom model of the human torso. Power deposited by 915 MHz conformal microwave array (CMA) applicators is used to assess the specific absorption rate (SAR) distributions of rectangular (500 cm2) and L-shaped (875 cm2) TBSAs. The SAR distribution in tissue and fluid flow distribution inside the dual-input dual-output (DIDO) water bolus are coupled to solve the steady-state temperature and thermal dose distributions of the rectangular TBSA (R-TBSA) for superficial tumor targets extending 10-15 mm beneath the skin surface. Thermal simulations are carried out for a range of bolus inlet temperature (Tb = 38-43 °C), water flow rate (Qb = 2-4 L min-1) and tumor blood perfusion (?b = 2-5 kg m-3 s-1) to characterize their influence on thermal dosimetry. Steady-state SAR patterns of the R- and L-TBSA demonstrate the ability to produce conformal and localized power deposition inside the tumor target sparing surrounding normal tissues and nearby critical organs. Acceptably low variation in tissue surface cooling and surface temperature homogeneity was observed for the new DIDO bolus at a 2 L min-1 water flow rate. Temperature depth profiles and thermal dose volume histograms indicate bolus inlet temperature (Tb) to be the most influential factor on thermal dosimetry. A 42 °C water bolus was observed to be the optimal choice for superficial tumors extending 10-15 mm from the surface even under significant blood perfusion. Lower bolus temperature may be chosen to reduce the thermal enhancement ratio (TER) in the most sensitive skin where maximum radiation dose is delivered and to extend the thermal enhancement of radiation dose deeper. This computational study indicates that well-localized elevation of tumor target temperature to 40-44 °C can be accomplished by large surface-conforming TBSAs using appropriate selection of coupling bolus temperature.

Arunachalam, K.; Maccarini, P. F.; Craciunescu, O. I.; Schlorff, J. L.; Stauffer, P. R.

2010-04-01

291

Thermal characteristics of thermobrachytherapy surface applicators for treating chest wall recurrence.  

PubMed

The aim of this study was to investigate temperature and thermal dose distributions of thermobrachytherapy surface applicators (TBSAs) developed for concurrent or sequential high dose rate (HDR) brachytherapy and microwave hyperthermia treatment of chest wall recurrence and other superficial diseases. A steady-state thermodynamics model coupled with the fluid dynamics of a water bolus and electromagnetic radiation of the hyperthermia applicator is used to characterize the temperature distributions achievable with TBSAs in an elliptical phantom model of the human torso. Power deposited by 915 MHz conformal microwave array (CMA) applicators is used to assess the specific absorption rate (SAR) distributions of rectangular (500 cm(2)) and L-shaped (875 cm(2)) TBSAs. The SAR distribution in tissue and fluid flow distribution inside the dual-input dual-output (DIDO) water bolus are coupled to solve the steady-state temperature and thermal dose distributions of the rectangular TBSA (R-TBSA) for superficial tumor targets extending 10-15 mm beneath the skin surface. Thermal simulations are carried out for a range of bolus inlet temperature (T(b) = 38-43 degrees C), water flow rate (Q(b) = 2-4 L min(-1)) and tumor blood perfusion (omega(b) = 2-5 kg m(-3) s(-1)) to characterize their influence on thermal dosimetry. Steady-state SAR patterns of the R- and L-TBSA demonstrate the ability to produce conformal and localized power deposition inside the tumor target sparing surrounding normal tissues and nearby critical organs. Acceptably low variation in tissue surface cooling and surface temperature homogeneity was observed for the new DIDO bolus at a 2 L min(-1) water flow rate. Temperature depth profiles and thermal dose volume histograms indicate bolus inlet temperature (T(b)) to be the most influential factor on thermal dosimetry. A 42 degrees C water bolus was observed to be the optimal choice for superficial tumors extending 10-15 mm from the surface even under significant blood perfusion. Lower bolus temperature may be chosen to reduce the thermal enhancement ratio (TER) in the most sensitive skin where maximum radiation dose is delivered and to extend the thermal enhancement of radiation dose deeper. This computational study indicates that well-localized elevation of tumor target temperature to 40-44 degrees C can be accomplished by large surface-conforming TBSAs using appropriate selection of coupling bolus temperature. PMID:20224154

Arunachalam, K; Maccarini, P F; Craciunescu, O I; Schlorff, J L; Stauffer, P R

2010-03-12

292

Near surface analysis of duplex PIII treated CoCr alloys  

NASA Astrophysics Data System (ADS)

The formation of expanded austenite in CoCr alloys is a well established process for forming hard and wear resistant surfaces for biomedical applications. However, even nitrogen implantation at reduced temperatures of 350 °C, where no CrN formation is observed, leads to a significant increase in the corrosion current, together with selective release of Co ions. By using a duplex nitrogen/oxygen process, a strong reduction of the corrosion rate is possible when the processing temperatures are limited to 300-350 °C. Detailed investigations into the chemical environment imply that a strong influence of grain boundaries or defects on the corrosion rate exists, which is not visible when measuring XPS spectra across a sufficiently large surface area.

Mändl, S.; Díaz, C.; Gerlach, J. W.; García, J. A.

2013-07-01

293

Evaluation of electro-oxidation of biologically treated landfill leachate using response surface methodology.  

PubMed

Box-Behnken statistical experiment design and response surface methodology were used to investigate electrochemical oxidation of mature landfill leachate pretreated by sequencing batch reactor (SBR). Titanium coated with ruthenium dioxide (RuO(2)) and iridium dioxide (IrO(2)) was used as the anode in this study. The variables included current density, inter-electrode gap and reaction time. Response factors were ammonia nitrogen removal efficiency and COD removal efficiency. The response surface methodology models were derived based on the results. The predicted values calculated with the model equations were very close to the experimental values and the models were highly significant. The organic components before and after electrochemical oxidation were determined by GC-MS. PMID:21334807

Zhang, Hui; Ran, Xiaoni; Wu, Xiaogang; Zhang, Daobin

2011-02-01

294

Evaluation of electro-oxidation of biologically treated landfill leachate using response surface methodology  

Microsoft Academic Search

Box–Behnken statistical experiment design and response surface methodology were used to investigate electrochemical oxidation of mature landfill leachate pretreated by sequencing batch reactor (SBR). Titanium coated with ruthenium dioxide (RuO2) and iridium dioxide (IrO2) was used as the anode in this study. The variables included current density, inter-electrode gap and reaction time. Response factors were ammonia nitrogen removal efficiency and

Hui Zhang; Xiaoni Ran; Xiaogang Wu; Daobin Zhang

2011-01-01

295

Method of treating steel surfaces to prevent wear, and coating obtained thereby  

Microsoft Academic Search

An object of the present invention is a method for the anti-wear treatment of the surface of steel parts having a carbon content of at least 0.15% and the coating obtained thereby. The method is characterized by the fact that an addition of sulfur, by depositing of a metal sulfide for example, and a vapor-phase chromizing are carried out in

1984-01-01

296

Interpretation of small-angle x-ray scattering data from dilute montmorillonite suspensions using a modified Guinier approximation  

SciTech Connect

Smectites are a group of 2:1-layer phyllosilicate minerals that have been extensively studied by small-angle x-ray scattering (SAXS) because of their industrial and environmental significance. In previous studies, a Guinier plot has been used to obtain the radius of gyration of the clay particles, from which geometric information of the particle structure is derived. Using an indirect Fourier transform to treat SAXS data from a dilute montmorillonite suspension, a negative electron contrast at the clay-water interface is observed. This electron inhomogeneity has violated the assumption underlying the application of the Guinier plot, which requires particles to have a uniform electron density. The presence of this inhomogeneity explains the inability of previous studies to correctly determine particle dimensions using the Guinier plot. Using this model of the clay-water interface, a modified Guinier plot has been derived and was experimentally verified. The calculation shows the presence of negative electron contrast at montmorillonite-water interfaces, which is in accordance with the results from the indirect Fourier transform method. This approximation has the potential to predict the geometric information for similar colloids studied by small-angle scattering.

Shang, C.; Rice, J. A.

2001-08-01

297

Synthesis and photocatalytic performances of the TiO2 pillared montmorillonite.  

PubMed

TiO(2) pillared clay materials were prepared by montmorillonite (Mt) and acidic solutions of hydrolyzed Ti alkoxides in the presence of high-molecular-weight polyoxypropylene (POP)-backboned di-quaternary salts (POP). The as-prepared materials were characterized by means of XRD, FTIR, TG-DTA, XRF, specific surface area and porosity determinations, TEM and SEM, respectively. The experiments showed that the resulting material was a porous delaminated structure containing pillared fragments and nano-scaled TiO(2) particles well dispersed among each other. Introducing polymer surfactant POP as an expanding agent of Mt cannot only promote the formation of the delaminated structure, but significantly improve the porosity and surface area of the composites. The resulting TiO(2) pillared Mt exhibited a good thermal stability as indicated by its surface area after calcination at 800 °C. No phase transformation from anatase to rutile was observed even under calcination at 900 °C. The grain size of anatase in as-prepared sample decreased with the increase of the POP concentration, but increased with the increment of calcination temperature. The photocatalytic performances of these new porous materials were evaluated by using methylene blue degradation. The composite solid exhibited superior photocatalyic property and the maximum removal efficiency was up to 98% within 90 min. PMID:22884731

Chen, Daimei; Zhu, Qian; Zhou, Fengsan; Deng, Xutao; Li, Fatang

2012-07-24

298

Cu(II) sorption mechanism on montmorillonite: An electron paramagnetic resonance study  

SciTech Connect

The mechanism of Cu(II) sorption on montmorillonite was studied with electron paramagnetic resonance (EPR) spectroscopy. The major sorbed species were successfully identified by EPR spectroscopy as they showed distinct signals due to their strength of binding and local structure. The EPR results together with macroscopic sorption data show that the sorption involves at least three different mechanisms. The dominant sorption mechanism changed with pH and Na{sup +} content in solution. In the acidic pH range, the sorption is independent of pH but is dependent on Na{sup +} concentration. Like free copper ions, the sorbed Cu(II) shows an isotropic absorption line. It is thought that the Cu(II) is ion-exchanged in the interlayer site and is capable of free tumbling motion despite electrostatic binding force. In the near neutral pH range, the sorption is strongly pH dependent and the sorbed Cu(II) shows no EPR signal. It is interpreted that the CU(II) is sorbed by a surface complexation mechanism to form an inner-sphere surface complex. The EPR spectrum with a dipolar splitting pattern means that the dimeric CU(II) surface species is the dominant sorbed species in the basic pH region where the Cu-Cu internuclear distance of the dimer is estimated to be {approximately}3.3{angstrom}.

Hyun, S.P.; Cho, Y.H.; Kim, S.J.; Hahn, P.S.

2000-02-15

299

The termiticidal properties of superhydrophobic wood surfaces treated with ZnO nanorods  

Microsoft Academic Search

ZnO is a cost-effective and more environmentally friendly wood preservative than other metallic-based formulations. ZnO-stearate\\u000a treatment imparts superhydrophobicity to wood surfaces, thereby providing triple protection to wood products, i.e., superhydrophobicity,\\u000a inhibition to insects and microorganisms, and UV radiation protection. The objective of this study was to evaluate ZnO-stearate\\u000a hydrophobic treatments of southern pine sapwood for resistance to Formosan subterranean termites.

Todd Shupe; Cheng Piao; Cran Lucas

300

Corrosion resistance, surface mechanical properties, and cytocompatibility of plasma immersion ion implantation-treated nickel-titanium shape memory alloys.  

PubMed

Nickel-titanium shape memory alloys are promising materials in orthopedic applications because of their unique properties. However, for prolonged use in a human body, deterioration of the corrosion resistance of the materials becomes a critical issue because of the increasing possibility of deleterious ions released from the substrate to living tissues. We have investigated the use of nitrogen, acetylene, and oxygen plasma immersion ion implantation (PIII) to improve the corrosion resistance and mechanical properties of the materials. Our results reveal that the corrosion resistance and mechanical properties such as hardness and elastic modulus are significantly enhanced after surface treatment. The release of nickel is drastically reduced as compared with the untreated control. In addition, our in vitro tests show that the plasma-treated surfaces are well tolerated by osteoblasts. Among the three types of samples, the best biological effects are observed on the nitrogen PIII samples. PMID:16078209

Yeung, K W K; Poon, R W Y; Liu, X Y; Ho, J P Y; Chung, C Y; Chu, P K; Lu, W W; Chan, D; Cheung, K M C

2005-11-01

301

A hydrogen peroxide sensor based on colloidal MnO 2\\/Na-montmorillonite  

Microsoft Academic Search

A novel amperometric sensor for the determination of hydrogen peroxide was prepared based on the enhanced oxidation of H2O2 at a glassy carbon electrode modified with colloidal MnO2–Na-montmorillonite (nano-MnO2\\/Na-Mont\\/GCE). The montmorillonite has been devised to support and dispense the MnO2 nanoparticles. Scanning electron microscopy images (SEM) showed that the MnO2 nanoparticles were homogeneously dispersed in the colloidal Na-montmorillonite. This colloidal

Shaojun Yao; Shuai Yuan; Junhui Xu; Ying wang; Jianlin Luo; Shengshui Hu

2006-01-01

302

Tribocorrosion behaviour of anodic treated titanium surfaces intended for dental implants  

NASA Astrophysics Data System (ADS)

Tribocorrosion plays an important role in the lifetime of metallic implants. Once implanted, biomaterials are subjected to micro-movements in aggressive biological fluids. Titanium is widely used as an implant material because it spontaneously forms a compact and protective nanometric thick oxide layer, mainly TiO2, in ambient air. That layer provides good corrosion resistance, and very low toxicity, but its low wear resistance is a concern. In this work, an anodizing treatment was performed on commercial pure titanium to form a homogeneous thick oxide surface layer in order to provide bioactivity and improve the biological, chemical and mechanical properties. Anodizing was performed in an electrolyte containing ?-glycerophosphate and calcium acetate. The influence of the calcium acetate content on the tribocorrosion behaviour of the anodized material was studied. The concentration of calcium acetate in the electrolyte was found to largely affect the crystallographic structure of the resulting oxide layer. Better tribocorrosion behaviour was noticed on increasing the calcium acetate concentration.

Alves, A. C.; Oliveira, F.; Wenger, F.; Ponthiaux, P.; Celis, J.-P.; Rocha, L. A.

2013-10-01

303

Genotoxicity of unmodified and organo-modified montmorillonite.  

PubMed

The natural clay mineral montmorillonite (Cloisite) Na+) and an organo-modified montmorillonite (Cloisite 30B) were investigated for genotoxic potential as crude suspensions and as suspensions filtrated through a 0.2-microm pore-size filter to remove particles above the nanometre range. Filtered and unfiltered water suspensions of both clays did not induce mutations in the Salmonella/microsome assay at concentrations up to 141microg/ml of the crude clay, using the tester strains TA98 and TA100. Filtered and unfiltered Cloisite) Na+ suspensions in culture medium did not induce DNA strand-breaks in Caco-2 cells after 24h of exposure, as tested in the alkaline comet assay. However, both the filtered and the unfiltered samples of Cloisite 30B induced DNA strand-breaks in a concentration-dependent manner and the two highest test concentrations produced statistically significantly different results from those seen with control samples (p<0.01 and p<0.001) and (p<0.05 and p<0.01), respectively. The unfiltered samples were tested up to concentrations of 170microg/ml and the filtered samples up to 216microg/ml before filtration. When tested in the same concentration range as used in the comet assay, none of the clays produced ROS in a cell-free test system (the DCFH-DA assay). Inductively coupled plasma mass-spectrometry (ICP-MS) was used to detect clay particles in the filtered samples using aluminium as a tracer element characteristic to clay. The results indicated that clay particles were absent in the filtered samples, which was independently confirmed by dynamic light-scattering measurements. Detection and identification of free quaternary ammonium modifier in the filtered sample was carried out by HPLC-Q-TOF/MS and revealed a total concentration of a mixture of quaternary ammonium analogues of 1.57microg/ml. These findings suggest that the genotoxicity of organo-modified montmorillonite was caused by the organo-modifier. The detected organo-modifier mixture was synthesized and comet-assay results showed that the genotoxic potency of this synthesized organo-modifier was in the same order of magnitude at equimolar concentrations of organo-modifier in filtrated Cloisite) 30B suspensions, and could therefore at least partly explain the genotoxic effect of Cloisite) 30B. PMID:20433941

Sharma, Anoop Kumar; Schmidt, Bjřrn; Frandsen, Henrik; Jacobsen, Nicklas Raun; Larsen, Erik Husfeldt; Binderup, Mona-Lise

2010-04-28

304

Self-assembly of montmorillonite platelets during drying.  

PubMed

This work is prompted by the quest for nanocomposites in which ordered, layered reinforcement preforms similar in structure to the arrangements seen in nacre are achieved without complex automated layer-by-layer assembly. Lamellar structures were obtained in montmorillonite films simply by slow drying without the use of additives. Clay alignment was found in films derived from suspensions of less than 0.9 vol%, ranging over a pH range of 2-11, at low drying rates and with both the natural ionic strength of the clay suspension and adjusted ionic strength. The greatest degree of order was found at the unadjusted pH and ionic strength. This method offers a potentially simple way of preparing clay preforms for polymer-clay nanocomposites at a drying rate at or below 23 nm s(-1). PMID:22835910

Walley, P; Zhang, Y; Evans, J R G

2012-07-27

305

Reinforcement of natural rubber latex by nanosize montmorillonite clay  

NASA Astrophysics Data System (ADS)

Based on the unique character of montmorillonite namely its layer structure and the ability of silicate particles to separate into nanometer-size platelets, natural rubber (polyisoprene)/clay composites were obtained by mixing rubber latex with clay-water dispersion and coagulating the mixture. The resulting film had greatly improved mechanical properties compared with films using micron-sized fillers. Further, both modulus and toughness were improved; in many composite system an improvement in modulus leads to a loss of toughness. X-ray diffraction results indicated that clay platelets dispersed in the rubber matrix on the nanoscale level with some macromolecules intercalated into the clay gallery. The observed considerable improvement in mechanical properties, coupled with a theoretical model of composite modulus suggests a dispersed structure of clay in the composite. While not all clay particles are exfoliated, data suggest that a reasonable fraction of exfoliated materials is required to explain the experimental results.

Tantatherdtam, Rattana

306

Stability of Organically Modified Montmorillonites and Their Polystyrene Nanocomposites After Prolonged Thermal Treatment  

SciTech Connect

Melt intercalation of montmorillonite (MMT) into polymeric matrices to improve the mechanical properties of polymers has evolved into a subject of tremendous fundamental and technological interest. The thermal treatment experienced during processing or end use can substantially affect the clay and diminish the target properties of polymer/clay nanocomposites (NCs) because of deintercalation or degradation of surface modifiers. In this work, changes in morphology, chemistry, and thermal stability of organically modified (OM) MMT after annealing in O{sub 2}-rich and N{sub 2} environments are investigated. Degradation of the alkyl ammonium cation occurs at temperatures as low as 105 {sup o}C upon prolonged exposure in an O{sub 2}-rich environment. X-ray diffractometry (XRD) performed in situ establishes the response of two OM-MMTs to elevated temperatures at short times, whereas ex situ XRD provides insight into high-temperature exposure at long times. Active sites on the silicate surfaces are found to induce scission of, as well as chemical interaction with, the chains comprising a polystyrene (PS) matrix. Size-exclusion chromatography indicates that PS chain scission occurs primarily after relatively short annealing times, whereas branching and cross-linking are more prevalent after long exposure times in an O{sub 2}-rich environment.

Frankowski,D.; Capracotta, M.; Martin, J.; Khan, S.; Spontak, R.

2007-01-01

307

Sulfosulfuron incorporated in micelles adsorbed on montmorillonite for slow release formulations.  

PubMed

Slow release formulations of the anionic herbicide sulfosulfuron (SFS) were prepared by incorporating it in micelles of an organic cation octadecyltrimethylammonium, which adsorb on the clay-mineral montmorillonite. The fraction of SFS adsorbed on the micelle-clay complex reached 98%, whereas for monomer-clay complexes, its adsorption was insignificant. Fluorescence studies showed surface contact between the micelles and the clay surface. The rate of SFS release from the micelle-clay formulations in aqueous suspensions was slow (<1%, 72 h). Spraying SFS formulations on a thin soil layer in a funnel, followed by irrigations (50 mm), resulted in complete elution of SFS from the commercial formulation (dispersible granular) versus 4% from the micelle-clay formulation. A plant bioassay in Rehovot soil showed that these respective formulations yielded 23 and 65% of shoot growth inhibition of foxtail. Consequently, the slow release micelle-clay formulations of SFS yield significantly reduced leaching and enhanced biological activity, thus providing environmental and agricultural advantages. PMID:12670166

Mishael, Yael G; Undabeytia, Tomas; Rabinovitz, Onn; Rubin, Baruch; Nir, Shlomo

2003-04-01

308

Removal of 8-quinolinecarboxylic acid pesticide from aqueous solution by adsorption on activated montmorillonites.  

PubMed

Sodium montmorillonite (Na-M), acidic montmorillonite (H-M), and organo-acidic montmorillonite (Org-H-M) were applied to remove the herbicide 8-quinolinecarboxylic acid (8-QCA). The montmorillonites containing adsorbed 8-QCA were investigated by transmission electron microscopy, FT-IR spectroscopy, X-ray diffraction analysis, X-ray fluorescence thermogravimetric analysis, and physical adsorption of gases. Experiments showed that the amount of adsorbed 8-QCA increased at lower pH, reaching a maximum at pH 2. The adsorption kinetics was found to follow the pseudo-second-order kinetic model. The Langmuir model provided the best correlation of experimental data for adsorption equilibria. The adsorption of 8-QCA decreased in the order Org-H-M > H-M > Na-M. Isotherms were also used to obtain the thermodynamic parameters. The negative values of ?G indicated the spontaneous nature of the adsorption process. PMID:23925862

Mekhloufi, M; Zehhaf, A; Benyoucef, A; Quijada, C; Morallon, E

2013-08-08

309

Pillared montmorillonites: Cesium-selective ion-exchange materials  

SciTech Connect

A zirconia-pillared and an alumina-pillared montmorillonite clay were found to exhibit high K{sub d}S for trace levels of cesium (2.5 ppb) in the presence of high concentrations of Ca{sup 2+}, Mg{sup 2+}, and Na{sup +} ions with distribution coefficients (K{sub d}S) for {sup 137}Cs exceeding 1 {times} 10{sup 5} mL/g over a wide range of competing ion concentrations. An excess of K{sup +} ions, however, caused a dramatic reduction in the Cs K{sub d}S for both of the materials. These results were in contrast to the parent montmorillonite which exhibited far lower K{sub d}S for {sup 137}Cs, particularly in the presence of high concentrations of Mg{sup 2+} and Ca{sup 2+}. Batch tests in simulated groundwaters showed that both pillared clays efficiently removed {sup 137}Cs from solution, with the best K{sub d}S being approximately 8.5 {times} 10{sup 5} mL/g in a potassium-free groundwater. The materials performed less well in a groundwater with a high potassium concentration, but still gave K{sub d}S similar to commercially available zeolites. The rate of {sup 137}Cs uptake was found to be rapid with both the alumina- and zirconia-pillared clays extracting >90% of the {sup 137}Cs from a 0.1 M NaNO{sub 3} solution within 5 minutes.

Sylvester, P.; Clearfield, A.; Diaz, R.J. [Texas A and M Univ., College Station, TX (United States). Dept. of Chemistry

1999-09-01

310

Detailed surface analyses and improved mechanical and tribological properties of niobium treated by high temperature nitrogen plasma based ion implantation  

NASA Astrophysics Data System (ADS)

Transition metal nitrides, as is the case of NbN, exhibit an attractive mixture of physical, chemical and mechanical properties and can be used to overcome a severe constraint of pure niobium, that is the high oxidation rate for temperature above 400 °C. In this work nitrogen ions were implanted into niobium by means of plasma based ion implantation (PBII) and high temperature PBII (HTPBII) in order to produce NbN on the surface of the material. In the case of HTPBII the treatment was performed in the temperature of 1000 °C and 1250 °C. In the process, negative pulses of 10 kV/20 ?s/500 Hz were applied to Nb samples for 1 h. The depth of the modified layer reached up to 4.5 ?m due to the diffusion of nitrogen atoms implanted into the material. X-ray diffraction spectra showed the presence of ?-NbN, ?-Nb2N and ?-Nb4N3 phases. Wear rate was reduced from 1.5 × 10-2 mm3/Nm up to 2.6 × 10-6 mm3/Nm for treated samples at high temperature in comparison with pristine samples, while friction coefficient was reduced from 0.8 to 0.25. Hardness was significantly increased. Surface topography was measured by optical profilometry. Surface roughness increases with the sample temperature but it remains lower than the one obtained by conventional PBII, very probably due to the heating method, which was performed by electron bombardment.

Oliveira, R. M.; Oliveira, A. C.; Carreri, F. C.; Gomes, G. F.; Ueda, M.; Silva, M. M. N. F.; Pichon, L.; Tóth, A.

2013-10-01

311

Effect of alkyl quaternary ammonium on processing discoloration of melt-intercalated PVC-montmorillonite composites  

Microsoft Academic Search

The effects of alkyl quaternary ammonium on the processing thermal stability of poly (vinyl chloride)\\/alkyl quaternary ammonium modified montmorillonite (PVC\\/OMMT) composites were investigated. PVC\\/sodium montmorillonite (MMT) composites were prepared for comparison. The intercalated PVC\\/OMMT composites exhibited a non-terminal rheological behavior, and showed better mechanical properties and higher thermal degradation stability than the PVC\\/MMT composites. However, under identical melt processing conditions,

Chaoying Wan; Yong Zhang; Yinxi Zhang

2004-01-01

312

Adsorption enthalpy and adsorption isotherm of tetradecylpyridinium bromide on Na-montmorillonite  

SciTech Connect

The adsorption enthalpy and the adsorption isotherm of tetradecylpyridinium bromide (TPB) onto a Na-montmorillonite suspension and the dilution enthalpy of the TPB solution have been determined at 298.15 K. The dilution process is endothermic and the adsorption process is exothermic. For ion exchange adsorption, the interaction between TP{sup +} and the montmorillonite because the cumulative adsorption enthalpy increases dramatically with adsorption amount. For molecular adsorption, however, the interaction between TPB and the clay is much weaker.

Chen, G.; Song, X.; Zhao, Y.; Han, B.; Yan, H. [Academia Sinica, Beijing (China). Inst. of Chemistry

1997-02-01

313

Enthalpy Changes Accompanying the Collapse of Montmorillonite Layers and the Penetration of Electrolyte into Interlayer Space  

Microsoft Academic Search

The enthalpy changes, ?H, in suspensions of Li–, Na–, and K–montmorillonite were determined as functions of the molal concentrations of LiCl, NaCl, and KCl, respectively, by microcalorimetry. These changes were compared with the corresponding changes in interlayer distance, ?, as determined by X-ray diffraction. It was found that ?Hvalues accompanying the collapse of the montmorillonite layers from ? > 14

Laibin Yan; Philip F. Low; Charles B. Roth

1996-01-01

314

Synthesis of co-containing aluminosilicates with a microporous layered columnar structure from montmorillonite clays  

NASA Astrophysics Data System (ADS)

The conditions of synthesis of cobalt-containing aluminosilicates with a microporous layered columnar structure from montmorillonite clays were correlated with their texture characteristics. The main factors governing the texture properties of the material were shown to be the montmorillonite content in natural clay, the calcination temperature, and the type of hydrolyzing agent and OH-: Me n+ ratio during the preparation of the modifying solution.

Kon'kova, T. V.; Alekhina, M. B.; Rysev, A. P.

2013-10-01

315

ZnO\\/montmorillonite for photocatalytic and photochemical degradation of methylene blue  

Microsoft Academic Search

Synthesis of a ZnO\\/montmorillonite photocatalyst based on an Indonesian natural montmorillonite was conducted using a sol–gel intercalation method. The physicochemical properties of the material were determined by XRD, N2 adsorption–desorption, SEM, TEM and UV–Vis diffuse reflectance. The activity was evaluated in photocatalytic and photochemical degradation of methylene blue (MB) with and without H2O2. Characterization showed that the ZnO particles were

Shaobin Wang; Dessy Wulandari

2011-01-01

316

Structure and characteristics of film composites based on methyl cellulose, poviargol, and montmorillonite  

Microsoft Academic Search

The structure of film composites based on methyl cellulose and fillers, such as montmorillonite and silver nanoparticles stabilized\\u000a by poly(vinylpyrrolidone) (Poviargol), is studied by X-ray diffraction. In the composite, montmorillonite nanoparticles exist\\u000a in the exfoliated state; when the content of the nanoparticles is below 7 wt %, the crystallinity of methyl cellulose increases.\\u000a Owing to the presence of the filler

I. P. Dobrovol’skaya; V. E. Yudin; N. F. Drozdova; V. E. Smirnova; I. V. Gofman; E. N. Popova; A. M. Bochek; N. M. Zabivalova; I. V. Plugar’; E. F. Panarin

2011-01-01

317

Synthesis and catalytic activity in selective hydrogenation of palladium complexes anchored in montmorillonite  

SciTech Connect

Functional groups such as diphenylphosphine, triphenylphosphine, and 4-picoline have been intercalated in montmorillonite, a swelling smectite clay; subsequent complexation with palladium has led to syntheses of various interlamallar montmorillonite-anchored palladium(II) complexes. These montmorillonite ligands and their complexes are characterized by elemental analyses, IR, XRD, and ESCA. Diphenylphosphinomontmorillonite-palladium(II) complex 4B(ii), the best catalyst of the series for hydrogenation reactions, hydrogenated alkynes to alkenes and to alkanes selectively, yields are quantitative. Catalyst 4B(ii) has shown consistent activity for a number of recycles in the hydrogenation of styrene, and hex-1-ene. Data indicates that transient homogeneous complex species formed in the pretreatment remain unchanged during the recycles. Catalyst 4B(ii) hydrogenated mono and disubstituted alkynes and alkenes in ethanol. On the other hand, diphenylphosphinite-montmorillonite-palladium(II) complex (2B) selectively hydrogenated monosubstituted alkynes and alkenes only under identical conditions. Catalyst 2B, with its lower initial interlamellar spacings, has induced size selectivity as evidenced in the selective hydrogenation of monosubstituted reactants only, because the preferred perpendicular orientation of the transient reactant-palladium complex formed with monosubstituted olefins in the interlayer spacings of montmorillonite requires a space smaller than that expected for disubstituted ones. Easy adjustment of interlayer spacings by the incorporation of complex moieties of different sizes in the interlayers makes montmorillonite a practical alternative to zeolites for inducing size selectivity.

Choudary, B.M.; Kumar, K.R.; Kantam, M.L. (Indian Institute of Chemical Technology, Hyderabad (India))

1991-07-01

318

Polymer-layered silicate nanocomposites. 1. A study of poly(ethylene oxide)\\/Na +-montmorillonite nanocomposites as polyelectrolytes and polyethylene-block-poly(ethylene glycol) copolymer\\/Na +-montmorillonite nanocomposites as fillers for reinforcement of polyethylene  

Microsoft Academic Search

Poly(ethylene oxide) PEO\\/Na+-montmorillonite and polyethylene–poly(ethylene glycol) (PE–PEG) diblock copolymer\\/Na+-montmorillonite nanocomposites have been prepared by melt intercalation method. The effect of thermal treatment on the amount of PEO and PE–PEG diblock copolymer intercalated into layers of Na+-montmorillonite and on ionic conductivity of PEO\\/Na+-MMT nanocomposites have been evaluated. It was found that PEO can be intercalated into the layers of Na+-MMT by

Bing Liao; Mo Song; Haojun Liang; Yongxin Pang

2001-01-01

319

[Effects of morphology evolution on surface plasmon resonance of nano-Ag films treated by different thermal annealing temperatures].  

PubMed

The nano-Ag films were prepared by RF magnetron sputtering technique, and all of them were treated by rapid thermal annealing at different temperatures. The structure, the morphology and the optical properties of the annealed nano-Ag films were characterized by X-ray diffraction, scanning electron microscopy, and UV-Vis-NIR spectroscopy. The experimental results show that the open area fraction of the film and spacing between islands or nanoparticles increase with the increase of the annealing temperature, while the aspect ratio decreases. The anisotropic worm-like island films have been reshaped into isotropic nanospheres. The surface plasmon (SP) resonance band blue shifts and narrows continuously with increasing heating temperature. Analyses show that the SP resonance of the nano-Ag films can be modulated by morphology evolution induced by rapid thermal annealing. PMID:23841396

Yu, Wei; Liu, Yu-Mei; Dai, Wan-Lei; Wang, Xin-Zhan; Lu, Wan-Bing; Li, Xiao-Wei; Fu, Guang-Sheng

2013-04-01

320

Microstructure and its effect on toughness and wear resistance of laser surface melted and post heat treated high speed steel  

NASA Astrophysics Data System (ADS)

High speed steel hacksaw blade blanks were laser surface melted and rapidly solidified along one edge. The laser melting resulted in complete carbide dissolution. By subsequent machining and heat treatments saw teeth were manufactured with a refined internal structure of the edges and corners. The structure was fully martensitic with a uniform and dense dispersion of small primary carbides. Sawing tests in quenched and tempered steel showed that blade life was somewhat improved, as compared to conventionally heat treated blades. The increased wear resistance is believed to be due to improved toughness along with high hardness caused by the refined carbide structure. Sawing tests in austenitic stainless steel did not give any significant improvement in performance. The effect of the altered microstructure on performance is likely to be more or less pronounced depending on application, tool and work material.

Ĺhman, Leif

1984-10-01

321

Detect-to-treat: development of analysis of bacilli spores in nasal mucus by surfaced-enhanced Raman spectroscopy  

NASA Astrophysics Data System (ADS)

As the war on terrorism in Afghanistan and Iraq continue, future attacks both abroad and in the U.S.A. are expected. In an effort to aid civilian and military personnel, we have been investigating the potential of using a surface-enhanced Raman spectroscopy (SERS) sampling device to detect Bacillus anthracis spores in nasal swab samples. Such a device would be extremely beneficial to medical responders and management in assessing the extent of a bioterrorist attack and making detect-to-treat decisions. The disposable sample device consists of a glass capillary filled with a silver-doped sol-gel that is capable of extracting dipicolinic acid (DPA), a chemical signature of Bacilli, and generating SERS spectra. The sampling device and preliminary measurements of DPA extracted from spores and nasal mucus will be presented.

Inscore, Frank E.; Gift, Alan D.; Farquharson, Stuart

2004-12-01

322

Methyl t-Butyl Ether (MTBE) Production: A Comparison of Montmorillonite-Derived Catalysts with an Ion-Exchange Resin  

Microsoft Academic Search

Montmorillonite-based catalysts were compared with an acidic ion-exchange resin of the type used industrially for the production of methyl t-butyl ether (MTBE) from methanol and isobutene or t-butanol. When 1,4-dioxan was used as solvent, Al3+-exchanged montmorillonites had about half the efficiency of the resin Arnberlyst 15 at 60~ they were, however, about twice as efficient at this temperature at Ti3+-montmorillonite

J. M. Adams; K. MARTIN; R. W. MCCABE; S. MURRAY

1986-01-01

323

In vitro biocompatibility and antimicrobial activity of poly(?-caprolactone)/montmorillonite nanocomposites.  

PubMed

A triblock copolymer based on poly(?-caprolactone) (PCL) and 2-(N,N-diethylamino)ethyl methacrylate (DEAEMA)/2-(methyl-7-nitrobenzofurazan)amino ethyl acrylate (NBD-NAcri), was synthesized via atom transfer radical polymerization (ATRP). The corresponding chlorohydrated copolymer, named as PCL-b-DEAEMA, was prepared and anchored via cationic exchange on montmorillonite (MMT) surface. (PCL)/layered silicate nanocomposites were prepared through melt intercalation, and XRD and TEM analysis showed an exfoliated/intercalated morphology for organomodified clay. The surface characterization of the nanocomposites was undertaken by using contact angle and AFM. An increase in the contact angle was observed in the PCL/MMT(PCL-b-DEAEMA) nanocomposites with respect to PCL. The AFM analysis showed that the surface of the nanocomposites became rougher with respect to the PCL when MMTk10 or MMT(PCL-b-DEAEMA) was incorporated, and the value increased with the clay content. The antimicrobial activity of the nanocomposites against B. subtilis and P. putida was tested. It is remarkable that the biodegradation of PCL/MMT(PCL-b-DEAEMA) nanocomposites, monitored by the production of carbon dioxide and by chemiluminescence emission, was inhibited or retarded with respect to the PCL and PCL/1-MMTk10. It would indicate that nature of organomodifier in the clay play an important role in B. subtilis and P. putida adhesion processes. Biocompatibility studies demonstrate that both PCL and PCL/MMT materials allow the culture of murine L929 fibroblasts on its surface with high viability, very low apoptosis, and without plasma membrane damage, making these materials very adequate for tissue engineering. PMID:23153018

Corrales, T; Larraza, I; Catalina, F; Portolés, T; Ramírez-Santillán, C; Matesanz, M; Abrusci, C

2012-11-28

324

Characterization of cell surface polypeptides of unfertilized, fertilized, and protease-treated zona-free mouse eggs  

SciTech Connect

The polypeptide composition of unfertilized, fertilized, and protease-treated zona-free mouse eggs was evaluated in this study. Zona-free eggs were radioiodinated by an Iodogen-catalyzed reaction. Light microscopic autoradiography of egg sections revealed that labeling was restricted to the cell surface. Labeled eggs were solubilized, and cell surface polypeptides were identified by one-dimensional SDS polyacrylamide gel electrophoresis and autoradiography. The unfertilized egg demonstrated 8-10 peptides that incorporated {sup 125}I, with major bands observed at approximately 145-150, 94, and 23 kilodaltons (kD). Zona-free eggs fertilized in vitro and then radiolabeled demonstrated several new bands in comparison to unfertilized eggs, with a major band appearing at approximately 36 kD. Treatment of radiolabeled unfertilized eggs with either trypsin or chymotrypsin (1 mg/ml for 5-20 min) caused enzyme-specific modifications in labeled polypeptides. Trypsin (T) treatment resulted in time-dependant modification of the three major peptides at 145-150, 94, and 23 kD. Chymotrypsin (CT) treatment, in contrast, was associated with loss or modification of the 94 kD band, with no apparent effect on either the 145-150 or 23 kD band. Taken together with previous data indicating that T or CT egg treatment interferes with sperm-egg attachment and fusion, these results suggest a possible role for the 94 kD protein in sperm-egg interaction.

Boldt, J.; Gunter, L.E.; Howe, A.M. (Medical College of Georgia, Augusta (USA))

1989-05-01

325

Joint replacement components made of hot-forged and surface-treated Ti-6Al-7Nb alloy.  

PubMed

We have developed a titanium-aluminium alloy with the inert alloying element niobium. The optimal composition was found to be Ti-6Al-7Nb (Protasul-100). This custom-made alloy designed for implants shows the same alpha/beta structure as Ti-6Al-4V and exhibits equally good mechanical properties. The corrosion resistance of Ti-6Al-7Nb in sodium chloride solution is equivalent to that of pure titanium and Ti-6Al-4V. This is due to a very dense and stable passive layer. Highly stressed anchorage stems of different hip prosthesis designs have been made from hot-forged Ti-6Al-7Nb. The polished surfaces of hip, knee and wrist joints made of Ti-6Al-7Nb and articulating against polyethylene are surface-treated by means of a very hard and 3-5 microns thick titanium nitride coating (Tribosul-TiN) or by oxygen diffusion hardening (Tribosul-ODH) to a depth of 30 microns. PMID:1391401

Semlitsch, M F; Weber, H; Streicher, R M; Schön, R

1992-01-01

326

Poly(D,?L-lactide-co-glycolide)/montmorillonite nanoparticles for improved oral delivery of exemestane.  

PubMed

The aim of this study was to develop poly(D,L-lactide-co-glycolide)/montmorillonite (PLGA/MMT) nanoparticles formulations for improved oral delivery of exemestane. Exemestane-loaded PLGA nanoparticles and PLGA/MMT nanoparticles were prepared by a modified solvent extraction/evaporation technology with vitamin E succinated polyethylene glycol 1000 (TPGS) as emulsifier. The content of MMT was estimated by thermal gravimetric analysis. The drug encapsulation efficiency and in vitro drug release kinetics were measured by high-performance liquid chromatography. The size, size distribution, surface charge and morphology of the exemestane-loaded nanoparticles were characterized using a Zetasizer Nano ZS and field emission scanning electron microscopy. The physical status of exemestane in the nanoparticles was characterized by differential scanning calorimetry. In vitro cellular uptake of coumarin-6-loaded nanoparticles was investigated by confocal laser scanning microscope, demonstrating that the fluorescence nanoparticles were internalized by Caco-2 cells (as an in vitro gastrointestinal model). The results of in vitro cytotoxicity experiment on MCF-7 cells (as a model of breast cancer cells) showed the exemestane-loaded nanoparticles resulted in lower cell viability versus the pure exemestane solution. The cytotoxicity against MCF-7 cells for exemestane-loaded nanoparticles and pure exemestane solution was dependent on the drug concentration and incubation time. In conclusion, this study indicates the capability of PLGA nanoparticles and PLGA/MMT nanoparticles in enhancing the oral delivery of exemestane. PMID:23517067

Li, Zhen; Liu, Kexin; Sun, Pengyuan; Mei, Lin; Hao, Tangna; Tian, Yan; Tang, Zeyao; Li, Lei; Chen, Dawei

2013-03-21

327

Seeming steady-state uphill diffusion of (22)na(+) in compacted montmorillonite.  

PubMed

Whereas the transport of solutes in nonreactive porous media can mostly be described by diffusion driven by the concentration gradients in the external bulk water phase, the situation for dense clays and clay rocks has been less clear for a long time. The presence of fixed negative surface charges complicates the application of Fick's laws in the case of ionic species. Here we report the seeming uphill diffusion of a (22)Na(+) tracer in compacted sodium montmorillonite, that is, transport directed from a low to a high tracer concentration reservoir. In contrast to the classical through-diffusion technique the present experiments were carried out under the conditions of a gradient in the background electrolyte and using equal initial (22)Na(+) tracer concentrations on both sides of the clay sample. We conclude that the dominant driving force for diffusion is the concentration gradient of exchangeable cations in the nanopores. Commonly used diffusion models, based on concentration gradients in the external bulk water phase, may thus predict incorrect fluxes both in terms of magnitude and direction. PMID:24059910

Glaus, Martin A; Birgersson, Martin; Karnland, Ola; Van Loon, Luc R

2013-10-07

328

Hybrid materials: Magnetite-Polyethylenimine-Montmorillonite, as magnetic adsorbents for Cr(VI) water treatment.  

PubMed

Hybrid materials formed by the combination of a sodium rich Montmorillonite (MMT), with magnetite nanoparticles (40 nm, Fe(3)O(4) NPs) coated with Polyethylenimine polymer (PEI 800 g/mol or PEI 25000 g/mol) were prepared. The intercalation of the magnetite nanoparticles coated with PEI among MMT platelets was achieved by cationic exchange. The resulting materials presented a high degree of exfoliation of the MMT sheets and a good dispersion of Fe(3)O(4) NPs on both the surface and among the layers of MMT. The presence of amine groups in the PEI structure not only aids the exfoliation of the MMT layers, but also gives to the hybrid material the necessary functionality to interact with heavy metals. These hybrid materials were used as magnetic sorbent for the removal of hexavalent chromium from water. The effect that pH, Cr(VI) concentration, and adsorbent material composition have on the Cr(VI) removal efficiency was studied. A complete characterization of the materials was performed. The hybrid materials showed a slight dependence of the removal efficiency with the pH in a wide range (1-9). A maximum amount of adsorption capacity of 8.8 mg/g was determined by the Langmuir isotherm. Results show that these hybrid materials can be considered as potential magnetic adsorbent for the Cr(VI) removal from water in a wide range of pH. PMID:22841705

Larraza, Ińigo; López-Gónzalez, Mar; Corrales, Teresa; Marcelo, Gema

2012-06-29

329

pH profile of the adsorption of nucleotides onto montmorillonite  

NASA Astrophysics Data System (ADS)

The interaction of 5'-AMP with montmorillonite saturated with various ratios of two metals found ubiquitously on the surface of Earth, that is, iron and calcium, is investigated. Adsorption and desorption of the nucleotide were studied in the pH range of 2 12 at three levels of addition: 0.080, 0.268 and 0.803 mmole 5'-AMP per gram of clay. Two desorption stages were employed — H2O wash and NaOH extraction (pH=12.0). 5'-AMP was preferentially adsorbed on the Fe-containing clays relative to the Ca clay. The nucleotide was fully recovered by the two desorption stages, mostly by the NaOH extraction. The evidence at hand indicates that 5'-AMP reaction with clay is affected by electrostatic interactions involving both attraction and repulsion forces. Some specific adsorption, possibly the result of covalent bonding and complex formation with the adsorbed ion, cannot be ruled out for iron but does not appear to operate for calcium. Changes in pH cause varying degrees of attraction and repulsion of 5'-AMP and may have been operating on the primitive Earth, leading to sequences of adsorption and release of this biomolecule.

Banin, A.; Lawless, J. G.; Mazzurco, J.; Church, F. M.; Margulies, L.; Orenberg, J. B.

1985-06-01

330

Pulsed electric linear dichroism of triphenylmethane dyes adsorbed on montmorillonite K10 in aqueous media  

SciTech Connect

Electric linear dichroism (ELD) spectra of two cationic triphenylmethane dyes, crystal violet (CV) and malachite green (MG), bound to sodium montmorillonite K10 (MK-10) were studied at 20 C in aqueous media at two mixing ratios, D/S, of 0.10 and 0.24 in the 700- to 400 nm wavelength region and in the applied electric field strength range between 0 and 3 kV/cm. The specific parallel and perpendicular dichroism ({Delta}A{sub {parallel}}/A and {Delta}A{sub {perpendicular}}/A) spectra of dye-adsorbed MK-10 suspension were measured at a fixed field strength with an apparatus equipped with a 512-channel photodiode array detector. By changing the field strength over a wide range, a series of the reduced dichroism values of the bound dyes were measured at a fixed wavelength. By fitting these dichroism values to theoretical orientation functions, the intrinsic reduced dichroism ({Delta}A/A){sub int} spectra at the limiting high fields (ELD spectrum) were determined for CV and MG bound to MK-10. No appreciable difference was observed at the two D/S values. The ELD spectra of these bound dyes are undulatory but never constant, throughout their absorption region; thus, the dye plane does not lie flatly either on the surface or between layers of MK-10 particle.

Yamaoka, Kiwamu; Sasai, Ryo

2000-05-01

331

Hydration of a Na(+)-montmorillonite studied by thermally stimulated depolarization current.  

PubMed

Thermally stimulated depolarization current (TSDC) technique is a powerful tool for probing dipole re-orientational motions in condensed matter. In the case of cation-exchangeable aluminosilicates, it allows the assessment of the potential barrier related to the hopping mechanism of cations and, consequently, the measurement of its evolution when molecules, i.e. water, are adsorbed and interact with the cations embedded in the solid framework. Then, using suitable models based on thermodynamics, the analysis of TSDC signals obtained at various hydration states provides insights about the surface properties of the studied solid and the mechanism of adsorption at the cationic site. In this work, TSDC is used to study the first stage, i.e. when the number of adsorbed molecules is below the occurrence of the water monolayer, of water adsorption in a Na(+)-montmorillonite from Mostaganem (Algeria). It is shown that the hydration process follows two stages. Using the "chemical force" concept it can then be concluded that when the number of adsorbed water molecules per cation is lower than 2, cation-water interaction dominates the energetics of adsorption, whereas at higher water loading the water "chemical force" is also involved into water-water and/or water-clay framework interactions. The number of water molecules for the monohydrated state is found to be about 7. PMID:17229436

Belarbi, H; Haouzi, A; Douillard, J M; Giuntini, J C; Henn, F

2006-12-16

332

Adhesion of the clay minerals montmorillonite, kaolinite, and attapulgite reduces respiration of Histoplasma capsulatum.  

PubMed

The respiration of three phenotypes of Histoplasma capsulatum, the causal agent of histoplasmosis in humans, was markedly reduced by low concentrations of montmorillonite but was reduced less by even higher concentrations of kaolinite or attapulgite (palygorskite). The reduction in respiration followed a pattern that suggested saturation-type kinetics: an initial sharp reduction that occurred with low concentrations of clay (0.01 to 0.5% [wt/vol]), followed by a more gradual reduction with higher concentrations (1 to 8%). Increases in viscosity (which could impair the movement of O2) caused by the clays were not responsible for the reduction in respiration, and the clays did not interfere with the availability of nutrients. Scanning electron microscopy after extensive washing showed that the clay particles were tightly bound to the hyphae, suggesting that the clays reduced the rate of respiration of H. capsulatum by adhering to the mycelial surface and, thereby, interfered with the movement of nutrients, metabolites, and gases across the mycelial wall. PMID:3954340

Lavie, S; Stotzky, G

1986-01-01

333

Activity of Laccase Immobilized on TiO2-Montmorillonite Complexes  

PubMed Central

The TiO2-montmorillonite (TiO2-MMT) complex was prepared by blending TiO2 sol and MMT with certain ratio, and its properties as an enzyme immobilization support were investigated. The pristine MMT and TiO2-MMT calcined at 800 °C (TiO2-MMT800) were used for comparison to better understand the immobilization mechanism. The structures of the pristine MMT, TiO2-MMT, and TiO2-MMT800 were examined by HR-TEM, XRD and BET. SEM was employed to study different morphologies before and after laccase immobilization. Activity and kinetic parameters of the immobilized laccase were also determined. It was found that the TiO2 nanoparticles were successfully introduced into the MMT layer structure, and this intercalation enlarged the “d value” of two adjacent MMT layers and increased the surface area, while the calcination process led to a complete collapse of the MMT layers. SEM results showed that the clays were well coated with adsorbed enzymes. The study of laccase activity revealed that the optimum pH and temperature were pH = 3 and 60 °C, respectively. In addition, the storage stability for the immobilized laccase was satisfactory. The kinetic properties indicated that laccase immobilized on TiO2-MMT complexes had a good affinity to the substrate. It has been proved that TiO2-MMT complex is a good candidate for enzyme immobilization.

Wang, Qingqing; Peng, Lin; Li, Guohui; Zhang, Ping; Li, Dawei; Huang, Fenglin; Wei, Qufu

2013-01-01

334

Studies on the defluoridation of water using conducting polymer/montmorillonite composites.  

PubMed

Conducting polymer/inorganic hybrid composites have large surface areas, which makes the adsorbent properties of the polymer composites as good the constituents. Polyaniline/montmorilonite (PANi-MMT) and polypyrrole/montmorillonite (PPy-MMT) composites were prepared, characterized (Fourier transform infrared, scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction patterns) and were employed as adsorbents for the removal of fluoride ions from aqueous solution by the batch sorption method. The spectral studies of the adsorbents before and after the adsorption are recorded to get better insight into the mechanism of the adsorption process. The results indicated that the removal of fluoride ions from water by these composites occurs via the combined effect of both the constituents, that is, through a physico-chemical mechanism. The amount of fluoride ion adsorbed by PANi-MMT and PPy-MMT at 30 degrees C is observed to be 2.3 and 5.1 mg g(-1), respectively, when compared to 0.77 and 2.66 mg g(-1), respectively, for the polymers alone. The Langmuir, Freundlich and Dubinin-Radushkevich isotherms were used to describe the adsorption equilibrium. PMID:22720396

Karthikeyan, M; Kumar, K K Satheesh; Elango, K P

335

Do contaminants originating from state-of-the-art treated wastewater impact the ecological quality of surface waters?  

PubMed

Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0-100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive. PMID:23593263

Stalter, Daniel; Magdeburg, Axel; Quednow, Kristin; Botzat, Alexandra; Oehlmann, Jörg

2013-04-08

336

Do Contaminants Originating from State-of-the-Art Treated Wastewater Impact the Ecological Quality of Surface Waters?  

PubMed Central

Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0–100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive.

Stalter, Daniel; Magdeburg, Axel; Quednow, Kristin; Botzat, Alexandra; Oehlmann, Jorg

2013-01-01

337

Speciation of uranium in surface-modified, hydrothermally treated, (UO{sub 2}){sup 2+}-exchanged smectite clays  

SciTech Connect

A successful solution to the problem of disposal and permanent storage of water soluble radioactive species must address two issues: exclusion of the radionuclides from the environment and the prevention of leaching from the storage media into the environment. Immobilization of radionuclides in clay minerals has been studied. In addition to the use of clays as potential waste forms, information about the interactions of radionuclides with clays and how such interactions affect their speciations is crucial for successful modeling of actinide-migration. X-ray absorption spectroscopy (XAS) is used to determine the uranium speciation in exchanged and surface-modified clays. The XAS data from uranyl-loaded bentonite clay are compared with those obtained after the particle surfaces have been coated with alkylsilanes. These silane films, which render the surface of the clay hydrophobic, are added in order to minimize the ability of external water to exchange with the water in the clay interlayer, thereby decreasing the release rate of the exchanged-uranium species. Mild hydrothermal conditions are used in an effort to mimic potential geologic conditions that may occur during long-term radioactive waste storage. The XAS spectra indicate that the uranyl monomer species remain unchanged in most samples, except in those samples that were both coated with an alkylsilane and hydrothermally treated. When the clay was coated with an organic film, formed by the acidic deposition of octadecyltrimethoxysilane, hydrothermal treatment results in the formation of aggregated uranium species in which the uranium is reduced from U{sup VI} to U{sup IV}.

Giaquinta, D.M.; Soderholm, L.; Yuchs, S.E.; Wasserman, S.R. [Argonne National Lab., IL (United States). Chemistry Div.

1997-08-01

338

Conjunctivochalasis as a Contributing Factor for the Development of Ocular Surface Disease in Medically Treated Glaucoma Patients.  

PubMed

PURPOSE:: To evaluate the impact of conjunctivochalasis (CCh) and its severity on the ocular surface parameters of glaucoma subjects treated with topical antiglaucomatous medication. MATERIALS AND METHODS:: One hundred patients with the clinical diagnosis of glaucoma were recruited for this study. CCh was graded based on the extent of inferior lid margin involvement as follows: 1=single (temporal) location, 2=two locations (nasal and temporal), and 3=whole lid. For all the subjects, the break-up time (BUT), lissamine green (LG) staining, and Schirmer test (under topical anesthesia) was performed for both eyes. Ocular Surface Disease Index (OSDI) questionnaire scores were also noted for each subject. Student t test, Mann-Whitney U test, and Kruskal-Wallis test was used for statistical evaluations. RESULTS:: Sixty-three subjects had evidence of CCh; 32 had grade 1, 24 had grade 2, 7 had grade 3 CCh, and 37 glaucoma patients had no evidence of CCh. There were significant differences in the BUT scores (7.2±2.7 vs. 10.1±2.4 s, P<0.001), Schirmer values (7.7±3.9 vs. 13.3.±4.0 mm, P<0.001), LG staining score (1.6±1.0 vs. 0.3±0.5, P<0.001), and the OSDI scores (19.4±17.2 vs. 6.7±5.2, P<0.001) between patients who had CCh and those without CCh. The BUT scores and Schirmer test values of patients with grades 2 and 3 CCh were significantly lower than those of grade 1 CCh and those without CCh (P<0.001). The LG grading and OSDI scores were significantly higher in grade 2 and 3 patients as compared with those with grade 1 CCh and those without CCh (P<0.001). CONCLUSIONS:: The functional characteristics of the ocular surface appear to be adversely influenced by the presence and the extent of CCh in glaucoma patients. PMID:23377585

Kocabeyoglu, Sibel; Mocan, Mehmet C; Irkec, Murat; Orhan, Mehmet; Karakaya, Jale

2013-01-31

339

Montmorillonite-based porous clay heterostructures (PCHs) intercalated with silica-titania pillars—synthesis and characterization  

NASA Astrophysics Data System (ADS)

Porous clay heterostructures (PCHs) were synthesized using natural montmorillonite as a raw material. Apart from pure silica pillars also silica-titania pillars were intercalated into the interlayer space of the parent clay. The detailed studies of the calcination process of the as-prepared PCH samples as well as thermal stability of the pillared structure of these materials were performed. The pillared structure of PCHs intercalated with both silica and silica-titania clusters was found to be thermally stable up to temperatures exceeding 600 °C. It was found that titanium incorporated into the silica pillars was present mainly in the form of separated tetracoordinated cations. For the samples with the higher Ti loading also small contribution of titanium in the form of the polymeric oxide species was detected. Titanium incorporated into the PCH materials significantly increased their surface acidity forming mainly Brřnsted acid sites.

Chmielarz, Lucjan; Gil, Barbara; Ku?trowski, Piotr; Piwowarska, Zofia; Dudek, Barbara; Michalik, Marek

2009-05-01

340

In vitro evaluation of the biocompatibility of contaminated implant surfaces treated with an Er : YAG laser and an air powder system.  

PubMed

Titanium platelets with a sand-blasted and acid-etched surface were coated with bovine serum albumin and incubated with a suspension of Porphyromonas gingivalis (ATCC 33277). Four groups with a total of 48 specimens were formed. Laser irradiation of the specimens (n = 12) was performed on a computer-controlled XY translation stage at pulse energy 60 mJ and frequency 10 pps. Twelve specimens were treated with an air powder system. After the respective treatment, human gingival fibroblasts were incubated on the specimens. The proliferation rate was determined by means of fluorescence activity of a redox indicator (Alamar Blue Assay) which is reduced by metabolic activity related to cellular growth. Proliferation was determined up to 72 h. Contaminated and non-treated as well as sterile specimens served as positive and negative controls. Proliferation activity was significantly (Mann-Whitney U-test, P < 0.05) reduced on contaminated and non-treated platelets when compared to sterile specimens. Both on laser as well as air powder-treated specimens, cell growth was not significantly different from that on sterile specimens. Air powder treatment led to microscopically visible alterations of the implant surface whereas laser-treated surfaces remained unchanged. Both air powder and Er : YAG laser irradiation have a good potential to remove cytotoxic bacterial components from implant surfaces. At the irradiation parameters investigated, the Er : YAG laser ensures a reliable decontamination of implants in vitro without altering surface morphology. PMID:15642029

Kreisler, Matthias; Kohnen, Wolfgang; Christoffers, Ann-Babett; Götz, Hermann; Jansen, Bernd; Duschner, Heinz; d'Hoedt, Bernd

2005-02-01

341

Dielectric properties of polyaniline-montmorillonite clay hybrids.  

PubMed

Polyaniline (PANI)-montmorillonite clay (MMT) hybrid (PANI-MMT) was prepared by mechanical grinding of ANI and MMT in the presence of potassium perdisulphate (KPS) followed by soaking the mass in 0.1 (M) HCI for 24 h. The formation of PANI-MMT hybrid was confirmed by Fourier transform infrared spectroscopic analyses. XRD studies revealed the intercalation of PANI into two-dimensional silicate galleries of MMT HRTEM analyses indicated particle size distribution to be in the range of 40-55 nm. The real part of the dielectric constant reached values as high as 4500 at frequency - 10(2) Hz for a MMT:PANI = 1:1 weight ratio, the value decreasing with increasing frequency up to 25 kHz, and also with increasing MMT loading in the hybrids. This dispersion was indicative of the interfacial space charge polarization (Maxwell Wagner type). Grain boundary resistance and capacitance of the hybrid along with the conductivity-relaxation time for the hybrid at several PANI:MMT weight ratios were evaluated from the complex impedance plot considering the Maxwell-Wagner Two-Layered Model AC conductivity was independent of frequency in the range 0.1-1 kHz and thereafter found to rise in the range 1-25 kHz due to trapped charges. DC conductivity values of the hybrids were lower than the PANI homopolymer. PMID:23755599

Haldar, Ipsita; Biswas, Mukul; Nayak, Arabinda; Ray, Suprakas Sinha

2013-03-01

342

Morphological and thermal properties of cellulose-montmorillonite nanocomposites.  

PubMed

Cellulose-layered montmorillonite (MMT) nanocomposites were prepared by precipitation from N-methylmorpholine- N-oxide (NMMO)/water solutions. Two hybrid samples were obtained to investigate the influence of the reaction time on the extent of clay dispersion within the matrix. It was observed that longer contact times are needed to yield nanocomposites with a partially exfoliated morphology. The thermal and thermal oxidative properties of the hybrids, which might be of interest for fire-resistant final products, were investigated by thermogravimetry and chemiluminescence (CL). The nanocomposites exhibited increased degradation temperatures compared to plain cellulose, and the partially exfoliated sample showed the maximum stability. This result was explained in terms of hindered transfer of heat, oxygen, and degraded volatiles due to the homogeneously dispersed clay filler. Kinetic analysis of the decomposition process showed that the degradation of regenerated cellulose and cellulose-based hybrids occurred through a multistep mechanism. Moreover, the presence of nanoclay led to drastic changes in the dependence of the activation energy on the degree of degradation. CL analysis showed that longer permanence in NMMO/water solutions brought about the formation of carbonyl compounds on the polymer backbone. Moreover, MMT increased the rate of dehydration and oxidation of cellulose functional moieties. As a consequence, cellulose was found to be less stable at temperatures lower than 100 degrees C. Conversely, at higher temperatures, the hindering of oxygen transfer prevailed, determining an increase in thermo-oxidative stability. PMID:18842055

Cerruti, Pierfrancesco; Ambrogi, Veronica; Postiglione, Alessandro; Rychlý, Jozef; Matisová-Rychlá, Lyda; Carfagna, Cosimo

2008-10-09

343

XRD, TEM, and thermal analysis of Arizona Ca-montmorillonites modified with didodecyldimethylammonium bromide.  

PubMed

An Arizona SAz-2 calcium montmorillonite was modified by a typical dialkyl cationic surfactant (didodecyldimethylammonium bromide, abbreviated to DDDMA) through direct ion exchange. The obtained organoclays were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), high-resolution thermogravimetric analysis (HR-TG), and infrared emission spectroscopy (IES). The intercalation of surfactants greatly increased the basal spacing of the interlayers and the conformation arrangement of the loaded surfactant were assessed based on the XRD and TEM measurements. This work shows that the dialkyl surfactant can be directly intercalated into the montmorillonite without first undergoing Na(+) exchange. Moreover, the thermal stability of organoclays and the different arrangements of the surfactant molecules intercalated in the SAz-2 Ca-montmorillonite were determined by a combination of TG and IES techniques. The detailed conformational ordering of different intercalated surfactants under different conditions was also studied. The surfactant molecule DDDMA has proved to be thermally stable even at 400°C which indicates that the prepared organoclay is stable to significantly high temperatures. This study offers new insights into the structure and thermal stabilities of SAz-2 Ca-montmorillonite modified with DDDMA. The experimental results also confirm the potential applications of organic SAz-2 Ca-montmorillonites as adsorbents and polymer-clay nanocomposites. PMID:23932082

Sun, Zhiming; Park, Yuri; Zheng, Shuilin; Ayoko, Godwin A; Frost, Ray L

2013-07-25

344

High-Frequency Eddy Current Conductivity Spectroscopy for Near-Surface Residual Stress Profiling in Surface-Treated Nickel-Base Superalloys  

NASA Astrophysics Data System (ADS)

Recent research indicated that eddy current conductivity measurements can be exploited for nondestructive evaluation of subsurface residual stress in surface-treated components. This technique is based on the so-called piezoresistive effect, i.e., the stress-dependence of electric conductivity. Previous experimental studies were conducted on excessively peened (Almen 10-16A peening intensity levels) nickel-base superalloy specimens that exhibited harmful cold work in excess of 30% plastic strain. The main reason for choosing peening intensities above recommended normal levels was that the eddy current penetration depth could not be decreased below 0.2 mm without conducting accurate measurements above 10 MHz, which is beyond the operational range of most commercially available eddy current instruments. In this paper we report the development of a new high-frequency eddy current conductivity measuring system that offers an extended inspection frequency range up to 80 MHz with a single probe coil. In addition, the new system offers better reproducibility, accuracy, and measurement speed than the previously used conventional system.

Abu-Nabah, Bassam A.; Nagy, Peter B.

2007-03-01

345

Synthesis of exfoliated polystyrene\\/montmorillonite nanocomposite by emulsion polymerization using a zwitterion as the clay modifier  

Microsoft Academic Search

Montmorillonite (MMT) was modified with zwitterion aminoundecanoic acid (AUA). First AUA was protonized to facilitate molecules to get into the galleries of the montmorillonite to accomplish ion exchange, and the carboxyl groups were then ionized in the alkaline aqueous media to enable exfoliation of the clay. It was demonstrated by rheological measurements and atomic force microscopic studies that exfoliation of

Hao Li; Yunzhao Yu; Yukun Yang

2005-01-01

346

Water Vapor Isotherms and Heat of Immersion of Na and Ca-Montmorillonite Systems. III. Thermodynamics1  

Microsoft Academic Search

The integral thermodynamic quantities of adsorbed water on Na- and Ca-montmorillonite have been calculated from water adsorption isotherms on Na- and Ca-montmorillonite at 298 ~ and 313~ and from one adsorption isotherm and calorimetric measurements at 298~ The integral entropy values de- crease and then increase as the amount of adsorbed water approaches zero. In both systems, the curves approach

R. Keren; I. SHAINBERG

1980-01-01

347

Zearalenone removal in synthetic media and aqueous part of canned corn by montmorillonite K10 and pillared montmorillonite K10.  

PubMed

The capacities of montmorillonite K10 (K10), aluminum pillared K10 (Al-K10), and iron pillared K10 (Fe-K10) to eliminate zearalenone (ZEN) from synthetic media and the aqueous part of canned corn were studied. Original clay and pillared clays were characterized in terms of X-ray powder diffraction analysis and N(2) adsorption-desorption isotherms. The maximum amounts of adsorption of ZEN by K10, Al-K10, and Fe-K10 at 25°C and pH 7 were 0.202, 1.305, and 1.028 mg/g and 0.264, 0.096, and 0.255 mg/g, calculated from Langmuir and Freundlich isotherms, respectively. The adsorption of ZEN was also studied as a function of adsorbent amount (1 to 30 mg), ZEN concentration (2 to 20 mg/liter), pH of solution (pH 4 to 10), and contact time. Pillared clays could be an excellent alternative for removing ZEN in contaminated food samples and are potentially low-cost adsorbents with a promising future as an alternative to more costly materials. PMID:21669073

Bekci, Zehra Molu; Antep, Mine Kurtbay; Merdivan, Melek; Yurdakoç, Kadir

2011-06-01

348

Intercalation behavior of poly(ethylene glycol) in organically modified montmorillonite  

NASA Astrophysics Data System (ADS)

In this paper, two kinds of organically modified montmorillonite (OMMT) were prepared using alkylammonium surfactants with different alkyl chain numbers. XRD results showed the interlayer spacing of OMMT increased with low concentration surfactants. With further increasing the surfactants concentration, the interlayer spacing of OMMT was unchanged. Meanwhile, FTIR was used to characterize the local environments of surfactants in the interlayer space of OMMT. The results suggested that the double chain surfactant D-18 preferred to adopt highly ordered conformation compared with single chain surfactant S-18 in interlayer space of OMMT. It indicated that the surface property of the OMMT is affected by the concentration and configuration of the intercalated surfactants. Moreover, the effect of the OMMT type, or more particularly the chemical nature of the organic modifier in the interlayer spacing and the poly(ethylene glycol) (PEG) concentration onintercalation behavior of PEG chains in OMMT were investigated with XRD and DSC.The results indicated that PEG chains could not intercalate into Na-MMT when the surfactants were saturated in interlayer space of Na-MMT. PEG chains could intercalate into the interlayer space of SM when the S-18 concentration was lower than 2.00CEC, implying that the low surfactant concentration modified SM provided a better environment (presumably through the balanced hydrophobic and hydrophilic surfaces) for the PEG intercalation as well. However, PEG did not intercalate into the interlayer space of DM when the D-18 concentration was higher than 1.00CEC. It could be attributed to the hydrophobic double alkyl chains of DM increased with D-18. The increased hydrophobic properties in the interlayer space of 1.50DM hybrids can prevent the intercalation of hydrophilic PEG.

Zhu, Shipeng; Peng, Hongmei; Chen, Jinyao; Li, Huilin; Cao, Ya; Yang, Yunhua; Feng, Zhihai

2013-07-01

349

Synthesis and characterization of silver/montmorillonite/chitosan bionanocomposites by chemical reduction method and their antibacterial activity.  

PubMed

Silver nanoparticles (AgNPs) of a small size were successfully synthesized using the wet chemical reduction method into the lamellar space layer of montmorillonite/chitosan (MMT/Cts) as an organomodified mineral solid support in the absence of any heat treatment. AgNO3, MMT, Cts, and NaBH4 were used as the silver precursor, the solid support, the natural polymeric stabilizer, and the chemical reduction agent, respectively. MMT was suspended in aqueous AgNO3/Cts solution. The interlamellar space limits were changed (d-spacing = 1.24-1.54 nm); therefore, AgNPs formed on the interlayer and external surface of MMT/Cts with d-average = 6.28-9.84 nm diameter. Characterizations were done using different methods, ie, ultraviolet-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray fluorescence spectrometry, and Fourier transform infrared spectroscopy. Silver/montmorillonite/chitosan bionanocomposite (Ag/MMT/Cts BNC) systems were examined. The antibacterial activity of AgNPs in MMT/Cts was investigated against Gram-positive bacteria, ie, Staphylococcus aureus and methicillin-resistant S. aureus and Gram-negative bacteria, ie, Escherichia coli, E. coli O157:H7, and Pseudomonas aeruginosa by the disc diffusion method using Mueller Hinton agar at different sizes of AgNPs. All of the synthesized Ag/MMT/Cts BNCs were found to have high antibacterial activity. These results show that Ag/MMT/Cts BNCs can be useful in different biological research and biomedical applications, including surgical devices and drug delivery vehicles. PMID:21499424

Shameli, Kamyar; Bin Ahmad, Mansor; Zargar, Mohsen; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Shabanzadeh, Parvaneh; Moghaddam, Mansour Ghaffari

2011-01-27

350

Computational Materials Science and Surface Engineering Finite element modelling of the fracture behaviour of surface treated Ti6Al4V alloy  

Microsoft Academic Search

Purpose: Surface treatments of the titanium alloys are frequently applied in order to modify the surface layer microstructure and to improve tribological properties or resistance to high temperature oxidation of the alloy. Various surface engineering techniques can be used to increase the surface hardness, e.g. deposition of the coatings composed of metallic carbides, nitrides or more recently DLC. The stiffness

W. Ziaja

351

FT-IR study of montmorillonite-chitosan nanocomposite materials  

NASA Astrophysics Data System (ADS)

Bone defect is one of the most frequent problems in bone tissue reconstruction in which application of a biomaterial filling is necessary. It creates a still rising demand of biomaterials for bone surgery. Polymer-ceramic nanocomposites (e.g. based on chitosan matrix) is a group of novel materials whose properties such as strength, Young's modulus, bioactivity and controlled degradation time make them suitable materials for filling bone defects. Investigations of nanocomposite foils which consisted of biopolymer-chitosan (CS) matrix and montmorillonite (MMT) as a nano-filler was the subject of the work. The nanocomposite materials were produced by a two-step dispersion of the nanoparticles in the biopolymer matrix. The first stage involved mechanical stirring and the second one - ultrasonic agitation. Mechanical tests were performed on the nanocomposites and their Young's modulus was estimated. Significant improvement of mechanical properties of the nanocomposites in comparison with the pure polymer (CS) was observed. The nanocomposite foils (CS/MMT) were subjected to FT-IR spectroscopy investigations whose objective was to explain the reason of the change in mechanical characteristics of the nanocomposites. Transmission and ATR techniques operating in MIR range were used to study the nanocomposites. The FT-IR techniques were used to determine interactions at nanoparticle-biopolymer matrix interface. A pure unmodified CS foil was used as a reference material for FT-IR studies. It was proven that application of FT-IR techniques allows not only to identify phases, but also to explain structural changes in the systems studied.

Paluszkiewicz, C.; Stodolak, E.; Hasik, M.; Blazewicz, M.

2011-08-01

352

Evaluation of Subsurface Flow and Free-water Surface Wetlands Treating NPR-3 Produced Water - Year No. 1  

SciTech Connect

This paper is a summary of some of the activities conducted during the first year of a three-year cooperative research and development agreement (CRADA) between the Department of Energy (DOE) Rocky Mountain Oilfield Testing Center (RMOTC) and Texaco relating to the treatment of produced water by constructed wetlands. The first year of the CRADA is for design, construction and acclimation of the wetland pilot units. The second and third years of the CRADA are for tracking performance of pilot wetlands as the plant and microbial communities mature. A treatment wetland is a proven technology for the secondary and tertiary treatment of produced water, storm water and other wastewaters. Treatment wetlands are typically classified as either free-water surface (FWS) or subsurface flow (SSF). Both FWS and SSF wetlands work well when properly designed and operated. This paper presents a collection of kinetic data gathered from pilot units fed a slipstream of Wyoming (NPR-3) produced water. The pilot units are set up outdoors to test climatic influences on treatment. Monitoring parameters include evapotranspiration, plant growth, temperature, and NPDES discharge limits. The pilot wetlands (FWS and SSF) consist of a series of 100-gal plastic tubs filled with local soils, gravel, sharp sand and native wetland plants (cattail (Typha spp.), bulrush (Scirpus spp.), dwarf spikerush (Eleocharis)). Feed pumps control hydraulic retention time (HRT) and simple water control structures control the depth of water. The treated water is returned to the existing produced water treatment system. All NPDES discharge limits are met. Observations are included on training RMOTC summer students to do environmental work.

Myers, J. E.; Jackson, L. M.

2001-10-13

353

Nitrogen behavior in a free water surface constructed wetland used as posttreatment for anaerobically treated swine wastewater effluent.  

PubMed

The aim of this study was to evaluate the behavior of total nitrogen (TN) in its different forms in a Free Water Surface constructed wetland (FWS) used as posttreatment for anaerobically treated swine wastewater. The experiment was conducted in a glasshouse from July 2010 to November 2011. The system consists in a FWS mesocosm inoculated with Typha angustifolia L. using as pretreatment an UASB reactor (upflow anaerobic sludge blanket). The operation are based on the progressive increase of the nitrogen loading rate (NLR) (2.0-30.2 kg TN/ha·d) distributed in 12 loads, with an operational time of 20 d. The results indicate that the behavior of the TN in the FWS, mainly depends on the NLR applied, the amount of dissolved oxygen available and the seasonality. The FWS operated with an NLR between 2.0-30.2 kg TN/ha·d, presents average removal efficiency for TN of 54.8%, with a maximum removal (71.7%) between spring-summer seasons (17.3-21.7°C). The availability of dissolved oxygen hinders the nitrification/denitrification processes in the FWS representing a 0.3-5.6% of TN removed.The main route of TN removal is associated with ammonia volatilization processes (2.6-40.7%), mainly to NLR over 25.8 kg TN/ha· d and with temperatures higher than 18°C. In a smaller proportion, the incorporation of nitrogen via plant uptake was 10.8% whereas the TN accumulated in the sediments was a 5.0% of the TN applied during the entire operation (550 d). An appropriate control of the NLR applied, can reduce the ammonia volatilization processes and the phytotoxicity effects expressed as growth inhibition in 80.0% from 496.0 mg NH(+) 4-N/L (25.8 kg TN/ha·d). PMID:24171422

De Los Reyes, Catalina Plaza; Pozo, Guillermo; Vidal, Gladys

2014-01-01

354

Behavior of Listeria monocytogenes on frankfurters surface treated with lauric arginate and/or a liquid smoke extract delivered using the Sprayed Lethality in Container (SLIC®) technology  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this study was to determine the viability of Listeria monocytogenes (LM) on commercially-produced frankfurters prepared without lactates that were surface treated with 0 or 4 mL of a blend of LAE (CytoGuard; 1.0% LAE final concentration) diluted in a concentrated liquid smoke extrac...

355

Molecular stability, mechanical properties, surface characteristics and sterility of biodegradable polyurethanes treated with low-temperature plasma  

Microsoft Academic Search

Biodegradable medical polyurethanes with varying hydrophilic-to-hydrophobic segment ratios based on hydrophilic poly(ethylene oxide) and hydrophobic poly(?-caprolactone) diol, were treated with low-temperature, low-pressure plasmas of hydrogen peroxide, oxygen, carbon dioxide and ammonia. All samples treated with hydrogen peroxide plasma were sterile, while samples treated with oxygen, carbon dioxide and ammonia plasmas were nonsterile. The treatment caused a 7% drop in molecular

Katarzyna Gorna; Sylwester Gogolewski

2003-01-01

356

Study on the surface of fluorosilicone acrylate RGP contact lens treated by low-temperature nitrogen plasma  

NASA Astrophysics Data System (ADS)

In order to improve the surface hydrophilicity of fluorosilicone acrylate rigid gas permeable (RGP) contact lens, low temperature nitrogen plasma was used to modify the lens surface. Effects of plasma conditions on the surface structures and properties were investigated. Results indicated that the surface hydrophilicity of RGP contact lens was significantly improved after treatment. X-ray photoelectron spectroscopy (XPS) results showed that the nitrogen element was successfully incorporated into the surface. Furthermore, some new bonds such as N sbnd C dbnd O, F - and silicate were formed on the lens surface after nitrogen plasma treatment, which could result in the improvement of the surface hydrophilicity. Scanning electronic microscope (SEM) results indicated that nitrogen plasma with moderate power could make the surface smoother in some degree, while plasma with higher power could etch the surface.

Ren, Li; Yin, Shiheng; Zhao, Lianna; Wang, Yingjun; Chen, Hao; Qu, Jia

2008-11-01

357

Efficiency of aluminum-pillared montmorillonite on the removal of cesium and copper from aqueous solutions.  

PubMed

Aluminum-pillared-layered montmorillonites (PILMs) were tested for their potential application in the removal of copper or cesium from aqueous solutions. By varying the initial conditions, several PILMs were prepared and characterized by means of X-ray fluorescence (XRF), proton induced gamma-ray emission (PIGE), X-ray diffraction (XRD) and sorption isotherms. Uptake of metals was studied by means of XRF spectrometry for copper sorption or gamma-ray spectrometry for cesium, using 137Cs as radiotracer. The sorption kinetics and capacity of PILMs were determined in relation to the effects of factors such as the initial metal concentration, initial pH of the solution and the presence of competitive cations. Kinetic studies showed that an equilibrium time of few minutes was needed for the adsorption of metal ions on PILMs. A pseudo-first-order equation was used to describe the sorption process for either copper or cesium. The most effective pH range for the removal of copper and cesium was found to be 4.0-6.0 and 3.0-8.0, respectively. Cesium sorption isotherms were best represented by a two-site Langmuir model while copper isotherms followed the Freundlich or the two-site Langmuir model. Cesium sorption experiments with inorganic or organic competitive cations as blocking agents revealed that the high selective sites of PILMs for cesium sorption (1-2% of total) are surface and edge sites in addition to interlayer exchange sites. In copper sorption, the two sites were determined as interlayer sites of PILMs after restoring their cation exchange capacity and sites associated with the pillar oxides. PMID:17374545

Karamanis, D; Assimakopoulos, P A

2007-03-19

358

Nature of organic fluid-montmorillonite interactions: an FTIR spectroscopic study.  

PubMed

The changes in the H-O-H stretching vibration in the interlayer water and Si-O stretching vibration of a Na-montmorillonite (MMT) structure in the FTIR (Fourier transform infrared) spectra provide insight into the effect of fluids of different dielectric constants on the clay structure. Mechanisms by which the different fluids of varying polarities enter into the clay interlayer and the rates at which these molecules interact with the clay structure and the interlayer water are studied at the molecular level using six different fluids with dielectric constants ranging from 110 to 2.4. The shift in H-O-H bending vibrations of interlayer water and changes in the Si-O vibration bands of MMT occur almost immediately after mixing with the solvent regardless of the polarity of the solvent. However, the extent and the rate of changes in H-O-H bending and Si-O stretching are dependent on the polarity of the solvent. Results show a very good correlation between the polarity of the solvent and the shift in H-O-H bending of interlayer water, and also between the polarity of the fluids and the d(001) spacing of the MMT-solvent samples. Low polar fluids such as methanol tend to make weak electrostatic interactions with clay surface oxygen and interlayer-water molecules, which result in an increase in interlayer spacing. Although, the alteration of the Si-O structure due to high polar molecules such as formamide is a continuous process, the influence of nonpolar fluids such as TCE (trichloroethylene) on the Si-O structure is almost instantaneous, which may result in high hydraulic conductivity in the clay. PMID:19539947

Amarasinghe, Priyanthi M; Katti, Kalpana S; Katti, Dinesh R

2009-05-13

359

Improved HCF Performance and FOD Tolerance of Surface Treated Ti-6-2-4- 6 Compressor Blades.  

National Technical Information Service (NTIS)

High cycle fatigue (HCF) strength and the resistance to foreign object damage (FOD) can be improved by the use of mechanical surface treatments like shot peening and low plasticity burnishing (LPB) to introduce beneficial surface layers of compressive res...

P. S. Prevey N. Jayaraman M. J. Shepard

2004-01-01

360

Effect of silica sand on activation energy for diffusion of sodium ions in montmorillonite and silica sand mixture.  

PubMed

The effect of silica sand on the diffusion of sodium ions in mixtures of montmorillonite and silica sand was studied by measuring the apparent diffusion coefficients, activation energies for diffusion, and the basal spacing of the mixed samples. These diffusion experiments suggest that the apparent diffusion coefficients of sodium ions in the mixed samples were almost the same as those of pure montmorillonite samples having the same partial dry densities of montmorillonite. The activation energy dependence for diffusion of sodium ions on the partial dry density was different between the mixed samples and the pure montmorillonite samples. The activation energy increased by adding silica sand at the partial dry density of 1.0 Mg m(-3), and decreased by adding silica sand at the partial dry densities higher than 1.2 Mg m(-3). A change in the XRD profile was observed after adding silica sand at the partial dry density of 1.6 Mg m(-3). Here, a three-water-layer hydrate state of montmorillonite was found in the mixed sample whereas only a two-water-layer hydrate state was observed in the pure montmorillonite sample. These experimental results suggest that silica sand changed the montmorillonite microstructure in the mixed samples, which then altered the sodium-ion diffusion process. PMID:12598096

Liu, Jinhong; Yamada, Hiromichi; Kozaki, Tamotsu; Sato, Seichi; Ohashi, Hiroshi

2003-03-01

361

Laser induced surface structuring and ion conversion in the surface oxide of titanium: possible implications for the wetability of laser treated implants.  

PubMed

In the present study, commercially pure titanium was irradiated with UV-light with varying wavelengths using a Q-switched Nd:YAG-laser. This was performed in order to investigate if a laser treatment can be employed to rapidly introduce hydrophilic properties to titanium surfaces, which is believed to facilitate protein adsorption and cell attachment. It was demonstrated that irradiation with 355 nm light (10 Hz, 90 mJ/shot) for 1 min or more caused an ion conversion of Ti(4+) to Ti(3+) sites in the surface oxide which lead to an increase in hydrophilicity of the surface. Furthermore, shorter irradiation times at 355 nm caused a surface structuring that gave rise to an unexpected and unstable hydrophobic state at the surface. Irradiation with 266 nm light (10 Hz, 40 mJ/shot) did not introduce any ion conversion in the surface oxide, nor did it give rise to any hydrophobicity of the surface. PMID:23053809

Forsgren, Johan; Paz, María Dolores; León, Betty; Engqvist, Hĺkan

2012-10-05

362

Melt-intercalation studies of polystyrene ionomers in pristine montmorillonite  

NASA Astrophysics Data System (ADS)

The main objective of this study was to examine the use of ionomers, specifically alkylamine-neutralized sulfonated polystyrene (SPS) for promoting intercalation into unmodified sodium montmorillonite clay and its use as a compatabilizer for intercalating another polymer into unmodified silicate clay. The processing parameters and chemical structure of polymers which led to the formation of partially intercalated/exfoliated morphologies were investigated. Melt-intercalated polymer layered silicate nanocomposites (PLSNs) are made by mixing polymers and organically modified silicates by the application of shear forces. However, the thermal decomposition temperatures of the organic modifications are usually comparable to the processing temperatures of most of the polymers. Hence, in this work modification of the polymer, rather than the clay, for promoting melt intercalation, specifically the introduction of alkyl ammonium salt groups along the polymer chain was considered. In this study the effects of viscosity, shear rates and mixing times on the morphology of nanocomposites were investigated. The effect of ionic content in the polymer chain of SPS in the batch mixtures of SPS and PS was researched. We also compared the effect on the extent of intercalation in these silicate clay galleries as a function of size of the counter-ions by varying the alkyl chain length and as a function of basicity of these counter-ions by varying the number of alkyl substituents that are attached on the N of the amine. The melt mixing of pristine Na-Mmt with alkyl ammonium and quaternary ammonium salts of SPS ionomers, resulted in an increase in the silicate gallery spacing consistent with intercalation. Mixtures of the ionomer with PS exhibited similar gallery spacing increases, indicating that the ionomer is an effective compatibilizing agent for the melt-intercalation of hydrophobic polymers into the clay. The extent of intercalation was independent of the melt processing conditions employed in this study and also did not change as the molecular weight of ionomer was varied. Intercalation appeared to be dependent on the charge ratio between the ionomer and the clay. The increase in gallery spacing achieved was a function of size of the alkylamine counter-ions used. The nanocomposites containing ionomers exhibited higher storage moduli compared to nanocomposites without the compatibilizer.

Bhiwankar, Nikhil N.

363

Comparison of molecular dynamics simulations with triple layer and modified Gouy-Chapman models in a 0.1M NaCl-montmorillonite system.  

PubMed

Molecular dynamics (MD) simulations of a montmorillonite/water interface at the pore scale were carried out at 0.1molL(-1) NaCl concentration in order to constrain cation, anion, and water distribution and mobility influenced by the mineral surface. MD results enabled anion exclusion and cation condensation at the surface to be quantified. MD-derived values could then be compared with macroscopic model results obtained from the Modified Gouy-Chapman (MGC) theory. While the Na concentration profile is well reproduced in the diffuse layer, anion exclusion is overestimated by the MGC theory under our experimental conditions. We also showed that MD simulations can be used to constrain Basic Stern model parameters or, in combination with zeta potential measurements, can be used to constrain triple layer model (TLM) parameters by providing suitable values for the capacitance values. Na sorption intrinsic equilibrium constant values for clay basal surfaces are given accordingly. PMID:19683248

Tournassat, Christophe; Chapron, Yves; Leroy, Philippe; Bizi, Mohamed; Boulahya, Faďza

2009-06-27

364

Synthesis of fructooligosaccharides from Aspergillus niger commercial inulinase immobilized in montmorillonite pretreated in pressurized propane and LPG.  

PubMed

Commercial inulinase from Aspergillus niger was immobilized in montmorillonite and then treated in pressurized propane and liquefied petroleum gas (LPG). Firstly, the effects of system pressure, exposure time, and depressurization rate, using propane and LPG, on enzymatic activity were evaluated through central composite design 2ł. Residual activities of 145.1 and 148.5% were observed for LPG (30 bar, 6 h, and depressurization rate of 20 bar?min?ą) and propane (270 bar, 1 h, and depressurization rate of 100 bar?min?ą), respectively. The catalysts treated at these conditions in both fluids were then used for the production of fructooligosaccharides (FOS) using sucrose and inulin as substrates in aqueous and organic systems. The main objective of this step was to evaluate the yield and productivity in FOS, using alternatives for enhancing enzyme activity by means of pressurized fluids and also using low-cost supports for enzyme immobilization, aiming at obtaining a stable biocatalyst to be used for synthesis reactions. Yields of 18% were achieved using sucrose as substrate in aqueous medium, showing the potential of this procedure, hence suggesting a further optimization step to increase the process yield. PMID:23271628

de Oliveira Kuhn, Graciele; Rosa, Clarissa Dalla; Silva, Marceli Fernandes; Treichel, Helen; de Oliveira, Débora; Oliveira, J Vladimir

2012-12-29

365

Removal of methylene blue from colored effluents by adsorption on montmorillonite clay  

Microsoft Academic Search

In this study, montmorillonite clay (MC) has been utilized as the adsorbent for the removal of a cationic dye, methylene blue (MB), from aqueous solution by the batch adsorption technique under different conditions of initial dye concentration, adsorbent concentration, contact time, solution pH, and temperature. Attempts were made to fit the isothermal data using Langmuir and Freundlich equations. The experimental

C. A. P. Almeida; N. A. Debacher; A. J. Downs; L. Cottet; C. A. D. Mello

2009-01-01

366

Comparison of saponite and montmorillonite behaviour during static and stirring maturation with seawater for pelotherapy  

Microsoft Academic Search

Two different bentonites (saponite and montmorillonite) have been used for maturation with seawater. These bentonites are very rich in phyllosilicates (>90%), with calcite, silica minerals (quartz, cristobalite) and feldspars (plagioclase) as subordinated minerals. Maduration tests have been realized both in static and stirring conditions and sampling points at 0, 15, 30, 60, 90 and 120 days have been established. Several mineralogical

María Isabel Carretero; Manuel Pozo; Carlos Sánchez; Francisco J. García; José Antonio Medina; José Manuel Bernabé

2007-01-01

367

Polymer–clay nanocomposites: exfoliation of organophilic montmorillonite nanolayers in polystyrene  

Microsoft Academic Search

A polymerizable cationic surfactant, vinylbenzyldimethyldodecylammonium chloride (VDAC) was synthesized for functionalization of montmorillonite (MMT) and preparation of exfoliated polystyrene–clay nanocomposites. Organophilic MMT was prepared by cationic exchange between inorganic ions of MMT and ammonium cations of VDAC in an aqueous medium. Dispersions of intercalated clay (VDAC–MMT) in styrene monomer formed gels. Shear thinning behavior of the gels was observed via

X Fu; S Qutubuddin

2001-01-01

368

Hydrodynamic and Chemical Factors in Clogging by Montmorillonite in Porous Media  

PubMed Central

Clogging by colloid deposits is important in water treatment filters, groundwater aquifers, and petroleum reservoirs. The complexity of colloid deposition and deposit morphology preclude models based on first principles, so this study extends an empirical approach to quantify clogging using a simple, one-parameter model. Experiments were conducted with destabilized suspensions of sodium- and calcium-montmorillonite to quantify the hydrodynamic and chemical factors important in clogging. Greater clogging is observed at slower fluid velocity, consistent with previous investigations. However, calcium-montmorillonite causes one order of magnitude less clogging per mass of deposited particles compared to sodium-montmorillonite or a previously published summary of clogging in model granular media. Steady state conditions, in which the permeability and the quantity of deposited material are both constant, were not observed, even though the experimental conditions were optimized for that purpose. These results indicate that hydrodynamic aspects of clogging by these natural materials are consistent with those of simplified model systems, and they demonstrate significant chemical effects on clogging for fully destabilized montmorillonite clay.

Mays, David C.; Hunt, James R.

2008-01-01

369

Influence of ?-radiation on the reactivity of montmorillonite towards H2O2  

NASA Astrophysics Data System (ADS)

Compacted and water saturated bentonite will be used as an engineered barrier in deep geological repositories for radioactive waste in many countries. Due to the high dose rate of ionizing radiation outside the canisters holding the nuclear waste, radiolysis of the interlayer and pore water in the compacted bentonite is unavoidable. Upon reaction with the oxidizing and reducing species formed by water radiolysis (OH•, e-(aq), H•, H2O2, H2, HO2•, H3O+), the overall redox properties in the bentonite barrier may change. In this study the influence of ?-radiation on the structural Fe(II)/FeTot ratio in montmorillonite and its reactivity towards hydrogen peroxide (H2O2) was investigated in parallel experiments. The results show that under anoxic conditions the structural Fe(II)/FeTot ratio of dispersed Montmorillonite increased from ?3 to 25-30% after ?-doses comparable to repository conditions. Furthermore, a strong correlation between the structural Fe(II)/FeTot ratio and the H2O2 decomposition rate in montmorillonite dispersions was found. This correlation was further verified in experiments with consecutive H2O2 additions, since the structural Fe(II)/FeTot ratio was seen to decrease concordantly. This work shows that the structural iron in montmorillonite could be a sink for one of the major oxidants formed upon water radiolysis in the bentonite barrier, H2O2.

Holmboe, Michael; Jonsson, Mats; Wold, Susanna

2012-02-01

370

New Insights to Characterize Mineralogical and Physicochemical Properties of Nanoporous and Nanostructured Bentonites (Montmorillonites)  

Microsoft Academic Search

Bentonite is rich in montmorillonite, which is a nanostructured and nanoporous member of smectite group. Mineralogical and physicochemical properties of bentonites play a key role in choosing appropriate bentonites for different applications. Scanning electron microscopy (SEM) reveals the morphological form and size of mineral phase of the studied bentonite samples. X-ray diffraction (XRD) analysis showed that the studied bentonites predominantly

M. Hayati-Ashtiani

2012-01-01

371

Generation of electrospun fibers of nylon 6 and nylon 6-montmorillonite nanocomposite  

Microsoft Academic Search

Dissolution and reprocessing of exfoliated montmorillonite–nylon 6 (NLS) nanocomposite is demonstrated, illustrating the potential of using polymer nanocomposites as the foundation for fabricating nano- and mesoscopic structures, nanofibers in this case, and thus exerting hierarchical control of morphology and form through the combination of a nanostructured material and a nanoscale fabrication technique. Exfoliated morphology, present in the melt-fabricated NLS nanocomposite,

Hao Fong; Weidong Liu; Chyi-Shan Wang; Richard A. Vaia

2002-01-01

372

Hydroesterification of olefins catalyzed by Pd(OAc){sub 2} immobilized on montmorillonite  

SciTech Connect

Palladium acetate immobilized on montmorillonite is an efficient catalyst for the hydroesterification of olefins with carbon monoxide and methanol, in the presence of triphenylphosphine and an acid promoter, affording branched chain esters. The reaction is regiospecific for aryl olefins as well as vinyl benzoate and regioselective for aliphatic olefins. 4 tabs.

Lee, Chul Woo; Alper, H. [Univ. of Ottawa, Ontario (Canada)

1995-01-13

373

Frictional strength and the effective pressure law of montmorillonite and illite clays  

Microsoft Academic Search

Abstract Low-strength clay minerals are a common constituent of fault gouges, and are often cited as a possible explanation for the low ambient shear stresses along the San Andreas fault inferred from heat flow constraints and in situ stress measurements. Montmorillonite, the weakest of the clay minerals, undergoes a gradual phase transition to illite with depth. In order to compare

C. Morrow; B. Radney; J. D. Byerlee

1992-01-01

374

Adsorption of a few heavy metals on natural and modified kaolinite and montmorillonite: A review  

Microsoft Academic Search

The feasibility of using two important and common clay minerals, kaolinite and montmorillonite, as adsorbents for removal of toxic heavy metals has been reviewed. A good number of works have been reported where the modifications of these natural clays were done to carry the adsorption of metals from aqueous solutions. The modification was predominantly done by pillaring with various polyoxy

Krishna Gopal Bhattacharyya; Susmita Sen Gupta

2008-01-01

375

Calcium montmorillonite clay reduces urinary biomarkers of fumonisin B1 exposure in rats and humans  

Technology Transfer Automated Retrieval System (TEKTRAN)

Background: Fumonisin B1 (FB1) is often a co-contaminant with aflatoxin (AF) in grains and may enhance AF’s carcinogenicity by acting as a cancer promoter. An oral dose of calcium montmorillonite clay (i.e. NovaSil, NS) was able to reduce aflatoxin exposure in a Ghanaian population at risk. In vitro...

376

Mixed-layer kaolinite-montmorillonite from the Yucatan Peninsula, Mexico  

USGS Publications Warehouse

Clay beds 1-2 m thick and interbedded with marine limestones probably of early Eocene age are composed of nearly pure mixed-layer kaolinite-montmorillonite. Particle size studies, electron micrographs, X-ray diffraction studies, chemical analyses, cation exchange experiments, DTA, and TGA indicate that clays from three different localities contain roughly equal proportions of randomly interlayered kaolinite and montmorillonite layers. The montmorillonite structural formulas average K0??2Na0??2Ca0??2Mg0??2(Al2??5Fe1??03+Mg0??5)(Al0??75Si7??25)O20+(OH)4-, with a deficiency of structural (OH) in either the montmorillonite or kaolinite layers. Nonexchangeable K+ indicates that a few layers are mica-like. Crystals are mostly round plates 1 10 to 1 20 ?? across. The feature most diagnostic of the mixed-layer character is an X-ray reflection near 8 A?? after heating at 300 ??C. The clays are inferred to have developed by weathering of volcanic ash and subsequent erosion and deposition in protected nearshore basins. ?? 1971.

Schultz, L. G.; Shepard, A. O.; Blackmon, P. D.; Starkey, H. C.

1971-01-01

377

Intestine-Specific, Oral Delivery of Captopril/Montmorillonite: Formulation and Release Kinetics  

NASA Astrophysics Data System (ADS)

The intercalation of captopril (CP) into the interlayers of montmorillonite (MMT) affords an intestine-selective drug delivery system that has a captopril-loading capacity of up to ca. 14 %w/w and which exhibits near-zero-order release kinetics.

Madurai, Suguna Lakshmi; Joseph, Stella Winnarasi; Mandal, Asit Baran; Tsibouklis, John; Reddy, Boreddy, Sr.

2010-12-01

378

SEDIMENTOLOGICAL AND TECHNICAL STUDIES ON THE MONTMORILLONITIC CLAYS OF ABU TARTUR PLATEAU, WESTERN DESERT, EGYPT  

Microsoft Academic Search

One of the most known sedimentary formation among Egyptian Upper Cretacous rock units is named Duwi Formation (Lower Maastrichtian), an outcrop at the Abu Tartur plateau, Kharga Oasis, Western Desert, Egypt. This formation displays three montmorillonitic clayey layers. The investigations of these sediments provide information on the texture, constituents and type of clay minerals, which helps define and describe their

Kadry N. SEDIEK; Ashraf M. AMER

379

Adsorption of uranium and thorium from aqueous solutions by the clay minerals montmorillonite and vermiculite  

Microsoft Academic Search

The adsorption of uranium and thorium from aqueous solutions by montomorillonite and vermiculite has been studied. The uranium and thorium concentration of the solutions varied between 100 and 2000 ppm. The behaviour of vermiculite as adsorbent of uranyl ions was found to be identical to montmorillonite, whereas the quantity of the adsorbed hydroxy?Th ions was much lower than its theoretical

C. A. Sikalidis; C. Alexiades; P. Misaelides

1989-01-01

380

Surface chemical model of the bentonite-water interface and its implications for modelling the near field chemistry in a repository for spent fuel.  

National Technical Information Service (NTIS)

Understanding the surface chemical properties of montmorillonite in near-neutral and alkaline media is essential for establishing a chemical model of the bentonite/water interaction applicable for repository conditions. A pretreated and well-characterised...

E. Wieland H. Wanner Y. Albinsson P. Wersin O. Karnland

1994-01-01

381

Pharmaceuticals and personal care products (PPCPs) in surface and treated waters of Louisiana, USA and Ontario, Canada  

Microsoft Academic Search

A newly developed analytical method was used to measure concentrations of nine pharmaceuticals and personal care products (PPCPs) in samples from two surface water bodies, a sewage treatment plant effluent and various stages of a drinking water treatment plant in Louisiana, USA, and from one surface water body, a drinking water treatment plant and a pilot plant in Ontario, Canada.

Glen R. Boyd; Helge Reemtsma; Deborah A. Grimm; Siddhartha Mitra

2003-01-01

382

Comparison of the protection effectiveness of acrylic polyurethane coatings containing bark extracts on three heat-treated North American wood species: Surface degradation  

NASA Astrophysics Data System (ADS)

High temperature heat-treatment of wood is a very valuable technique which improves many properties (biological durability, dimensional stability, thermal insulating characteristics) of natural wood. Also, it changes the natural color of wood to a very attractive dark brown color. Unfortunately, this color is not stable if left unprotected in external environment and turns to gray or white depending on the wood species. To overcome this problem, acrylic polyurethane coatings are applied on heat-treated wood to delay surface degradations (color change, loss of gloss, and chemical modifications) during aging. The acrylic polyurethane coatings which have high resistance against aging are further modified by adding bark extracts and/or lignin stabilizer to enhance their effectiveness in preventing the wood aging behavior. The aging characteristic of this coating is compared with acrylic polyurethane combined with commercially available organic UV stabilizers. In this study, their performance on three heat-treated North American wood species (jack pine, quaking aspen and white birch) are compared under accelerated aging conditions. Both the color change data and visual assessment indicate improvement in protective characteristic of acrylic polyurethane when bark extracts and lignin stabilizer are used in place of commercially available UV stabilizer. The results showed that although acrylic polyurethane with bark extracts and lignin stabilizer was more efficient compared to acrylic polyurethane with organic UV stabilizers in protecting heat-treated jack pine, it failed to protect heat-treated aspen and birch effectively after 672 h of accelerated aging. This degradation was not due to the coating adhesion loss or coating degradation during accelerated aging; rather, it was due to the significant degradation of heat-treated aspen and birch surface beneath this coating. The XPS results revealed formation of carbonyl photoproducts after aging on the coated surfaces and chain scission of Csbnd N of urethane linkages.

Kocaefe, Duygu; Saha, Sudeshna

2012-04-01

383

RHEOLOGICAL STUDY OF SOME MELTS OF HIGH-DENSITY POLYETHYLENE INTENSIVELY CHARGED WITH SURFACE-TREATED CaCO3. II. THE ELASTIC COMPONENT  

Microsoft Academic Search

The present paper resumes the studies devoted to the obtention of charged polyolefins and discusses the influence of the CaCO3 surface treated with a compatibilization agent (polyethylene oligomer) on the elastic component of composites possessing a high-density polyethylene matrix. Based on a genuine algorithm, which starts from the output pressure off the rheological nozzle, the rheological parameters characterizing the elastic

Filip Petraru; Marcel Popa; Radu Tudose

2001-01-01

384

Characteristics of Ni–Ir and Pt–Ir hard coatings surface treated by pulsed Nd:YAG laser  

Microsoft Academic Search

The subjects of the presented paper are to develop a laser surface treatment technology for the protective coatings of glass-molding dies and to better understand the interaction between laser beam and materials coated on the die surface. A variety of alloy films, including Ir-25 at.% Pt, Ir-50 at.% Pt, Ir-75 at.% Pt, Ir-25 at.% Ni, Ir-50 at.% Ni, and Ir-75

Shih-Feng Tseng; Wen-Tse Hsiao; Kuo-Cheng Huang; Ming-Fei Chen; Chao-Te Lee; Chang-Pin Chou

2010-01-01

385

Differences in bonding to acid-etched or Er:YAG-laser–treated enamel and dentin surfaces  

Microsoft Academic Search

Statement of Problem. Er:YAG (erbium-doped yttrium aluminium garnet) lasers have been effective in the removal of dental tissues. It has been suggested that they are also useful for preparing dental surfaces for adhesion, but results to date have been controversial. Purpose. This study compared the tensile strength of bracket-tooth bonds obtained after preparation of the surface for adhesion (dentin or

Arturo Mart??nez-Insua; Luis da Silva Dominguez; Francisco Guitián Rivera; Urbano A. Santana-Pen??n

2000-01-01

386

Promotion of Pt–Ru\\/C catalysts driven by heat treated induced surface segregation for methanol oxidation reaction  

Microsoft Academic Search

Carbon supported Pt–Ru\\/C (1:1) alloy catalysts supplied by E-TEK are widely used for fuel cell research. Heat treatments in various atmospheres are conducted for the promotion of the methanol oxidation reaction (MOR) and the investigation of the structure–activity relationship (SAR) of the catalysts. The alloy structures, surface compositions, surface species, and electro-catalytic activities of the alloy catalysts are characterized by

Yu-Chen Wei; Chen-Wei Liu; Wei-Jung Chang; Kuan-Wen Wang

2011-01-01

387

Cell proliferation and controlled drug release studies of nanohybrids based on chitosan-g-lactic acid and montmorillonite  

Microsoft Academic Search

The present paper reveals the potential uses of novel hybrids of chitosan-g-lactic acid and sodium montmorillonite (MMT) in controlled drug delivery and tissue engineering applications. The drug-loaded novel nanohybrid films and porous scaffolds have been prepared by solvent casting and freeze-drying of the grafted polymer solution, respectively. Sodium Ibuprofen was loaded into nanohybrids of chitosan-g-lactic acid\\/sodium montmorillonite (CS-g-LA\\/MMT). Grafting of

Dilip Depan; Annamalai Pratheep Kumar; Raj Pal Singh

2009-01-01

388

Mechanism of p-nitrophenol adsorption from aqueous solution by HDTMA +-pillared montmorillonite—Implications for water purification  

Microsoft Academic Search

HDTMA+-pillared montmorillonites were obtained by pillaring different amounts of the surfactant hexadecyltrimethylammonium bromide (HDTMAB) into sodium montmorillonite (Na-Mt) in an aqueous solution. The optimum conditions and batch kinetics of sorption of p-nitrophenol from aqueous solutions are reported. The solution pH had a very important effect on the sorption of p-nitrophenol. The maximum p-nitrophenol absorption\\/adsorption occurs when solution pH (7.15–7.35) is

Qin Zhou; Hong Ping He; Jian Xi Zhu; Wei Shen; Ray L. Frost; Peng Yuan

2008-01-01

389

Composites of TiO 2-aluminum pillared montmorillonite: Synthesis, characterization and photocatalytic degradation of methylene blue  

Microsoft Academic Search

Aluminum pillared montmorillonite was prepared and used as a porous support for synthesis of TiO2-based photocatalysts with varying TiO2 loading. The physicochemical properties of the TiO2-pillared montmorillonite samples were characterized by X-ray diffraction, N2 adsorption isotherm, UV–visible diffuse reflectance spectroscopy, scanning electron microscopy and transmission electron microscopy. Photocatalytic activity of the materials was evaluated by methylene blue photodegradation in aqueous

Shaobin Wang; Narsito; Karna Wijaya

2010-01-01

390

Comparative studies on montmorillonite-supported zero-valent iron nanoparticles produced by different methods: reactivity and stability  

Microsoft Academic Search

To mitigate the aggregation and enhance the reactivity of nanosized zero-valent iron (nZVI), montmorillonite is employed as a template-supporting matrix to prepare nZVI through two different pathways: heterogeneous nucleation and homogeneous nucleation processes. Dispersed sub-nanosized ZVI clusters with an average size around 0.5 nm (perpendicular to the clay layers) are intercalated in clay interlayers when using montmorillonite as a template

Hanzhong Jia; Chuanyi Wang

2012-01-01

391

Desorption of ciprofloxacin from clay mineral surfaces.  

PubMed

Desorption from soil clay components may affect the transport and fate of antibiotics in the environment. In this study, ciprofloxacin (CIP) desorption from a kaolinite and a montmorillonite was investigated under different pHs, different concentrations of metal cations of various valencies (Na(+), Ca(2+) and Al(3+)) and a cationic surfactant hexadecyltrimethylammonium (HDTMA), and different desorption cycles. Desorption of CIP from kaolinite and montmorillonite was strongly pH-dependent and desorption isotherms were well fitted with the Langmuir equation. The percentage of CIP desorbed increased with increasing initial CIP loadings, desorbing cation concentrations, and desorption cycles. Comparatively, CIP was more readily desorbed from kaolinite than from montmorillonite. Moreover, the hysteresis index values were all negative, suggesting that the presence of metal cations and HDTMA in solution promoted CIP desorption from clay minerals, owing to cation exchange. The XRD analyses indicated that desorption of CIP occurred from both external and interlayer surfaces of montmorillonite. Formation of Al-CIP complex on solid surface and then detachment of Al-CIP from the solid surface may contribute to the higher CIP desorption by Al(3+) in comparison to Na(+) and Ca(2+). PMID:23123088

Wu, Qingfeng; Li, Zhaohui; Hong, Hanlie; Li, Rongbiao; Jiang, Wei-Teh

2012-10-13

392

Tribological characterization of surface-treated commercially pure titanium for femoral heads in total hip replacement: a feasibility study.  

PubMed

Most noncemented total hip replacements combine a titanium alloy stem, a CoCrMo femoral head and an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup. In spite of its nickel content of up to 1% and the resulting biocompatibility issues in some clinical situations, the higher cost and some difficulties in machining, CoCrMo alloy is preferred to titanium alloys thanks to its outstanding tribological properties, higher hardness and elastic modulus. Nowadays most of the heads of hip prostheses use CoCrMo as bearing material. The present study investigates the effect of various surface treatments and combinations of treatments, such as electrochemical oxidation (anodization), laser surface melting and barrel polishing, on the tribological properties of commercially pure grade 2 titanium. The aim of the study was to characterize surface treatments capable of improving the tribological properties of titanium surface to the same extent as CoCrMo. The tribological properties were characterized by multidirectional pin-on-flat screening wear tests, using UHMWPE pins as bearing surface. The experiments showed the possibility of improving the wear resistance of titanium to the degree of CoCrMo. Although further efforts will be required to optimize the treatments studied, the results are encouraging enough to warrant pursuing this direction of investigation. PMID:17219358

Cotogno, G; Holzwarth, U; Franchi, M; Rivetti, S; Chiesa, R

2006-12-01

393

Corrosion Behavior of Surface-Treated Implant Ti-6Al-4V by Electrochemical Polarization and Impedance Studies  

NASA Astrophysics Data System (ADS)

Implant materials for orthopedic and heart surgical services demand a better corrosion resistance material than the presently used titanium alloys, where protective oxide layer breaks down on a prolonged stay in aqueous physiological human body, giving rise to localized corrosion of pitting, crevice, and fretting corrosion. A few surface treatments on Ti alloy, in the form of anodization, passivation, and thermal oxidation, followed by soaking in Hank solution have been found to be very effective in bringing down the corrosion rate as well as producing high corrosion resistance surface film as reflected from electrochemical polarization, cyclic polarization, and Electrochemical Impedance Spectroscopy (EIS) studies. The XRD study revealed the presence of various types of oxides along with anatase and rutile on the surface, giving rise to high corrosion resistance film. While surface treatment of passivation and thermal oxidation could reduce the corrosion rate by 1/5th, anodization in 0.3 M phosphoric acid at 16 V versus stainless steel cathode drastically brought down the corrosion rate by less than ten times. The mechanism of corrosion behavior and formation of different surface films is better understood from the determination of EIS parameters derived from the best-fit equivalent circuit.

Paul, Subir; Yadav, Kasturi

2011-04-01

394

Comparative evaluation of effect of acidic beverage on enamel surface pre-treated with various remineralizing agents: An In vitro study  

PubMed Central

Aim: This study aimed at quantitatively evaluating the effect of colabased beverage on the calcium loss of enamel surface pre-treated with fluorideenriched casein phosphopeptideamorphous calcium phosphate (CPP-ACPF) and ?eta-ricalcium phosphate (?-TCP) using energy dispersive X-ray analysis (EDX). Materials and Methods: 24 enamel specimens were prepared from the buccal and palatal surfaces of extracted intact human premolars and were randomly assigned to study groups and control group. Specimens of Group II were pre-treated with CPP-ACPF and Group III treated with ?-TCP twice daily for 4 for 28 days, followed by storage in artificial saliva. All specimens were evaluated for mineral (calcium and phosphorus) content (wt%) after pre-treatment using SEM-EDAX. The specimens were then placed in the acidic beverages for 4 days for 10 Mineral content was again measured using SEM-EDAX. Results: Statistical analysis using one-way ANOVA followed by Tukey's HSD test was applied to compare the re-mineralization and de-mineralization of the samples. Conclusion: The present study concluded that both the remineralizing agents tested were found to be effective in inhibiting the de-mineralization caused by colabased beverage. Among the remineralizing agents tested, ?-TCP was found to be more effective than CPP-ACPF.

Hegde, Mithra N; Devadiga, Darshana; Jemsily, Prince A

2012-01-01

395

Thermoplastic polymer nanocomposites with montmorillonite-Lab vs industrial scale fabrication  

NASA Astrophysics Data System (ADS)

Fabrication of polypropylene or polyamide-6/montmorillonite nanocomposites in a laboratory- and industrial-scale by melt processing has been described. Depending on the fabrication scale, different technological problems were observed that need to be taken into account during production of PP and PA-6-based nanocomposites with MMT which constitute a promising class of modern materials for engineering and packaging applications. Fabrication of PP and PA-6 nanocomposites with montmorillonite both on laboratory and industrial scale needs to be optimized in terms of processing conditions that include pre-mixing parameters, feeding rate, temperature of the barrel zone and extrusion die, screw speed and head pressure. Proper cleaning procedures need to be applied and the selection of the 'main' fraction enables to get nanostructured materials with enhanced properties.

Giacomelli, M.; Pielichowski, K.; Leszczy?ska, A.

2012-09-01

396

Hexacyanoferrate(III) transport in coated montmorillonite clay films. Effects of water-soluble polymers  

SciTech Connect

Hexacyanoferrate(III) Fe(CN){sub 6}{sup 3{minus}}, transport through coated montmorillonite clay films at a platinum electrode is studied with the cyclic voltammetric method. Experimental conditions are first established guaranteeing voltammetric detection based on a linear diffusion in the clay film. The square of the ratio (R{sup 2}) of current intensities obtained at the clay modified electrode (CME) and the bare Pt electrode measures the relative variation of the Fe(CN){sub 6}{sup 3{minus}}, diffusion coefficient in the clay film. Thus, the effects of bathing electrolyte concentrations on R{sup 2} are investigated and related to the swelling properties of the montmorillonite clay characterized by X-ray diffraction and sedimentation volume results.

Sequaris, J.M.

2000-02-08

397

Cation exchange capacities of safranin, toluidine and alizarin complexes with montmorillonite  

SciTech Connect

To obtain information about the cation exchange capacity (CEC) of montmorillonite as affected by the sorption of charged organic molecules, montmorillonite samples were loaded with different amounts of positively charged molecules of safranin, toluidine blue, and negatively charged alizarin red S. Dye sorption by the clay was carried out by equilibrating samples with different concentrations of the dye. The adsorbed amounts were determined from initial and final dye concentrations using spectrophotometric methods. The CEC of the clay-organic complexes were determined by the BaCl{sub 2} base exchange capacity method. The CEC was found to decrease linearly with the increase in the amount of safranin and toluidine in the complex, giving rise to a 1:1 charge neutralization ratio. For alizarin the CEC increased linearly but was not in proportion to the amounts of alizarin in the complex. This noncumulative phenomenon was attributed to the hindering of free diffusion of exchanging cations by the adsorbed molecules.

Peinemann, N.; Helmy, A.K.

1999-09-01

398

In Situ Molecular Spectroscopic Evidence for CO2 Intercalation into Montmorillonite in Supercritical Carbon Dioxide  

SciTech Connect

The interaction of anhydrous supercritical CO2 (scCO2) with both kaolinite and ~1W (i.e. close to but less than one layer of hydration) calcium-saturated montmorillonite was investigated under conditions relevant to geologic carbon sequestration (50 °C and 90 bar). The CO2 molecular environment was probed in situ using a combination of three novel high-pressure techniques: X-ray diffraction, magic angle spinning nuclear magnetic resonance spectroscopy and attenuated total reflection infrared spectroscopy. We report the first direct evidence that the expansion of montmorillonite under scCO2 conditions is due to CO2 migration into the interlayer. Intercalated CO2 molecules are rotationally constrained and do not appear to react with waters to form bicarbonate or carbonic acid. In contrast, CO2 does not intercalate into kaolinite. The findings show that predicting the seal integrity of caprock will have complex dependence on clay mineralogy and hydration state.

Loring, John S.; Schaef, Herbert T.; Turcu, Romulus VF; Thompson, Christopher J.; Miller, Quin RS; Martin, Paul F.; Hu, Jian Z.; Hoyt, David W.; Qafoku, Odeta; Ilton, Eugene S.; Felmy, Andrew R.; Rosso, Kevin M.

2012-04-25

399

Adsorption and interaction of 5-fluorouracil with montmorillonite and saponite by FT-IR spectroscopy  

NASA Astrophysics Data System (ADS)

Adsorption of 5-fluorouracil (5-FU) on montmorillonite and saponite has been investigated using FT-IR spectrometry. The intercalation of 5-FU within montmorillonite or saponite has been shown by X-ray diffraction to increase the interlayer spacing. In order to investigate interaction of 5-FU with clays, the harmonic and anharmonic vibrational wavenumbers of free 5-FU and 5-FU interacting with Al(OH)3 have been calculated at the DFT/B3LYP level with 6-31++G(d,p) basis set by using Gaussian 03 program set. The solution effect on 5-FU was also calculated by using polarizable continuum model (PCM). Experimental and calculated results indicated that 5-FU interacted with clays by direct or indirect coordination (through water molecules) to the Lewis acidic centers.

Akalin, Elif; Akyuz, Sevim; Akyuz, Tanil

2007-05-01

400

Chitosan-montmorillonite biocomposite as an adsorbent for copper (II) cations from aqueous solutions.  

PubMed

Chitosan-montmorillonite (KSF-CTS) beads were prepared by crosslinking with pentasodium tripolyphosphate (TPP). Montmorillonite (KSF-Na), CTS and KSF-CTS biocomposite were used to remove Cu(II) from aqueous solutions. These materials were characterized before and after copper adsorption by XRD, FTIR and thermogravimetry (TG). The data indicated that the adsorption process proceeds kinetically according to a pseudo-second-order model. The adsorption processes were adjusted to the Langmuir model for KSF-Na and CTS and to the Temkin model for KSF-CTS. The maximum adsorption capacity followed the order CTS>KSF-CTS>KSF-Na. Percentages desorption of copper ions from the KSF-CTS composite after three desorption cycles were 86%, 85% and 84%, respectively, using EDTA as regeneration agents. PMID:23973496

Pereira, F A R; Sousa, K S; Cavalcanti, G R S; Fonseca, M G; de Souza, Antônio G; Alves, A P M

2013-08-22

401

Calcium montmorillonite clay reduces urinary biomarkers of fumonisin B1 exposure in rats and humans  

PubMed Central

Fumonisin B1 (FB1) is often a co-contaminant with aflatoxin (AF) in grains and may enhance AF’s carcinogenicity by acting as a cancer promoter. Calcium montmorillonite (i.e. NovaSil, NS) is a possible dietary intervention to help decrease chronic aflatoxin exposure where populations are at risk. Previous studies show that an oral dose of NS clay was able to reduce AF exposure in a Ghanaian population. In vitro analyses from our laboratory indicated that FB1 (like aflatoxin) could also be sorbed onto the surfaces of NS. Hence, our objectives were to evaluate the efficacy of NS clay to reduce urinary FB1 in a rodent model and then in a human population highly exposed to AF. In the rodent model, male Fisher rats were randomly assigned to either, FB1 control, FB1 + 2% NS or absolute control group. FB1 alone or with clay was given as a single dose by gavage. For the human trial, participants received NS (1.5 or 3 g day?1) or placebo (1.5 g day?1) for 3 months. Urines from weeks 8 and 10 were collected from the study participants for analysis. In rats, NS significantly reduced urinary FB1 biomarker by 20% in 24 h and 50% after 48 h compared to controls. In the humans, 56% of the urine samples analyzed (n = 186) had detectable levels of FB1. Median urinary FB1 levels were significantly (p < 0.05) decreased by > 90% in the high dose NS group (3 g day?1) compared to the placebo. This work indicates that our study participants in Ghana were exposed to FB1 (in addition to AFs) from the diet. Moreover, earlier studies have shown conclusively that NS reduces the bioavailability of AF and the findings from this study suggest that NS clay also reduces the bioavailability FB1. This is important since AF is a proven dietary risk factor for hepatocellular carcinoma (HCC) in humans and FB1 is suspected to be a dietary risk factor for HCC and esophageal cancer in humans.

Robinson, A.; Johnson, N.M.; Strey, A.; Taylor, J.F.; Marroquin-Cardona, A.; Mitchell, N.J.; Afriyie-Gyawu, E.; Ankrah, N.A.; Williams, J.H.; Wang, J.S.; Jolly, P.E.; Nachman, R.J.; Phillips, T.D.

2012-01-01

402

Calcium montmorillonite clay reduces urinary biomarkers of fumonisin B? exposure in rats and humans.  

PubMed

Fumonisin B? (FB?) is often a co-contaminant with aflatoxin (AF) in grains and may enhance AF's carcinogenicity by acting as a cancer promoter. Calcium montmorillonite (i.e. NovaSil, NS) is a possible dietary intervention to help decrease chronic aflatoxin exposure where populations are at risk. Previous studies show that an oral dose of NS clay was able to reduce AF exposure in a Ghanaian population. In vitro analyses from our laboratory indicated that FB? (like aflatoxin) could also be sorbed onto the surfaces of NS. Hence, our objectives were to evaluate the efficacy of NS clay to reduce urinary FB? in a rodent model and then in a human population highly exposed to AF. In the rodent model, male Fisher rats were randomly assigned to either FB? control, FB??+?2% NS or absolute control group. FB? alone or with clay was given as a single dose by gavage. For the human trial, participants received NS (1.5 or 3?g?day?ą) or placebo (1.5?g?day?ą) for 3 months. Urines from weeks 8 and 10 were collected from the study participants for analysis. In rats, NS significantly reduced urinary FB? biomarker by 20% in 24?h and 50% after 48?h compared to controls. In the humans, 56% of the urine samples analysed (n?=?186) had detectable levels of FB?. Median urinary FB? levels were significantly (p?90% in the high dose NS group (3?g?day?ą) compared to the placebo. This work indicates that our study participants in Ghana were exposed to FB? (in addition to AFs) from the diet. Moreover, earlier studies have shown conclusively that NS reduces the bioavailability of AF and the findings from this study suggest that NS clay also reduces the bioavailability FB?. This is important since AF is a proven dietary risk factor for hepatocellular carcinoma (HCC) in humans and FB? is suspected to be a dietary risk factor for HCC and oesophageal cancer in humans. PMID:22324939

Robinson, A; Johnson, N M; Strey, A; Taylor, J F; Marroquin-Cardona, A; Mitchell, N J; Afriyie-Gyawu, E; Ankrah, N A; Williams, J H; Wang, J S; Jolly, P E; Nachman, R J; Phillips, T D

2012-02-10

403

Bleaching with alternative layered minerals: A comparison with acid-activated montmorillonite for bleaching soybean oil  

Microsoft Academic Search

An extensive series of layered minerals including montmorillonite was studied to determine if the fundamental physicochemical\\u000a properties responsible for pigment adsorption could be identified. Samples were subjected to a uniform preparation regimen\\u000a to eliminate such secondary effects as particle size, moisture content, level of activation and degree of washing. By doing\\u000a so, it has been possible to show that both

Dennis R. Taylor; Dennis B. Jenkins; Charles B. Ungermann

1989-01-01

404

Positive Temperature Coefficient Effect of Polypropylene\\/Carbon Nanotube\\/Montmorillonite Hybrid Nanocomposites  

Microsoft Academic Search

Ternary polypropylene\\/multiwalled carbon nanotube\\/montmorillonite (PP\\/MWNT\\/MMT) nanocomposites were prepared by melt compounding of a ball-milled MWNT and MMT mixture in a Haake mixer at a screw rotation rate of 200 r\\/min. The electrical conducting behavior of such hybrid composites was examined. The results showed that the conducting behaviors of PP\\/MWNT\\/MMT nanocomposites were strongly dependent on the MWNT and MMT contents. The

Su P. Bao; Guo D. Liang; Sie C. Tjong

2009-01-01

405

Oligomerization of uridine phosphorimidazolides on montmorillonite: A model for the prebiotic synthesis of rna on minerals  

Microsoft Academic Search

The 5'-phosphorimidazolide of uridine reacts on Na+-montmorillonite 22A in aqueous solution to give oligomers as long as 7 mers. The maximum chain length increases to 9 mers and the overall oligomer yield increases when 9:1 ImpU, A5' ppA mixtures react under the same conditions. The oligomer yield and maximum chain length decreases with the structure of the added pyrophosphate in

Ping Z. Ding; Kunio Kawamura; James P. Ferris

1996-01-01

406

The Desorption of Toluene from a Montmorillonite Clay Adsorbent in a Rotary Kiln Environment  

Microsoft Academic Search

The vaporization of toluene from pre-drled, 3 mm montmorillonite clay particles was studied In a 130 kW pilot-scale rotary kiln with Inside dimensions of 0.61 by 0.61 meters. Vaporization rates were obtained with a toluene weight fraction of 0.25 percent as a function of kiln fill fractions from 3 to 8 percent, rotation rates from 0.1 to 0.9 rpm, and

Warren D. Owens; Geoffrey D. Silcox; JoAnn S. Lighty; Xiao Xue Deng; David W. Pershing; Vic A. Cundy; Christopher B. Leger; Allen L. Jakway

1992-01-01

407

Intercalated polypyrrole\\/Na +-montmorillonite nanocomposite via an inverted emulsion pathway method  

Microsoft Academic Search

An inverted emulsion pathway polymerization method was introduced to synthesize conducting polypyrrole (PPy) into the layer of inorganic clay within a nanolevel, using dodecylbenzenesulfonic acid (DBSA) as both an emulsifier and a dopant. The synthesized PPy\\/Na+-montmorillonite (MMT) nanocomposite was confirmed to have a layered structure with a folded or penetrated PPy from X-ray diffraction, and it was further characterized via

J. W Kim; F Liu; H. J Choi; S. H Hong; J Joo

2003-01-01

408

Melt intercalation\\/exfoliation of polystyrene–sodium-montmorillonite nanocomposites using sulfonated polystyrene ionomer compatibilizers  

Microsoft Academic Search

Quaternary ammonium salts of sulfonated polystyrene (SPS) were used as compatibilizers for melt intercalation of PS and pristine Na-montmorillonite. Tetra-octyl ammonium SPS and tetra-decyl ammonium SPS ionomeric compatibilizers produced significant exfoliation and a homogeneous dispersion of the polymer–clay nanocomposites. Wide angle X-ray diffraction and transmission electron microscopy were primarily used to characterize the morphology of the nanocomposites. Image analysis was

Nikhil N. Bhiwankar; R. A. Weiss

2006-01-01

409

Kinetic analysis of the thermal degradation of polystyrene–montmorillonite nanocomposite  

Microsoft Academic Search

Nanocomposites exhibit a combination of unique properties, such as increased heat distortion temperature, reduced permeability, reduced flammability and improved mechanical properties. In this work, a polystyrene (PS) clay nanocomposite was prepared via bulk polymerization using a novel organically modified montmorillonite (MMT). The organic-modifier is the N,N-dimethyl-n-hexadecyl-(4-vinylbenzyl) ammonium chloride (VB16). The thermal stability of PS–VB16 compared to pure PS is examined

Serge Bourbigot; Jeffrey W. Gilman; Charles A. Wilkie

2004-01-01

410

Influence of clay modification on the structure and mechanical properties of EPDM\\/montmorillonite nanocomposites  

Microsoft Academic Search

Conditions were established for dispersing organic montmorillonite (OMMT) nanolayers into ethylene–propylene–diene rubber (EPDM) matrix in a HAAKE mixer. The experimental results of X-ray diffraction and transmission electron microscopy showed that the MMT modified with trimethyloctadecylamine or dimethylbenzyloctadecylamine existed in the form of an intercalated layer structure and the MMT modified with methlybis(2-hydroxyethyl)cocoalkylamine was fully exfoliated in the EPDM matrix. The

Hua Zheng; Yong Zhang; Zonglin Peng; Yinxi Zhang

2004-01-01

411

Magnesium hydroxide sulfate hydrate whisker flame retardant polyethylene\\/montmorillonite nanocomposites  

Microsoft Academic Search

Flame retardant maleated polyethylene\\/magnesium hydroxide sulfate hydrate whisker (MAPE\\/MHSH) composites containing organo-modified\\u000a montmorillonite (OMT) were prepared by direct melt intercalation. Their morphology, combustion behaviour and thermal stability\\u000a were carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), cone calorimetry and thermogravimetric\\u000a analyses (TGA). The exfoliation of silicate layers within MAPE has been verified by XRD and TEM images. Cone

Hongdian Lu; Yuan Hu; Junfeng Xiao; Zhengzhou Wang; Zuyao Chen; Weicheng Fan

2006-01-01

412

Oligomerization of Ribonucleotides on Montmorillonite: Reaction of the 5'-Phosphorimidazolide of Adenosine  

Microsoft Academic Search

The regiospecific formation of oligomers from unblocked monomers in aqueous solution is one of the central tenets in research on the origins of life on earth. Direct experimental support for this hypothesis has been obtained in studies of the condensation of the 5'-phosphorimidazolide of adenosine (ImpA) with itself and with P^1,P^2-diadenosine-5',5'-pyrophosphate (AppA) in water in the presence of a montmorillonite

James P. Ferris; Gozen Ertem

1992-01-01

413

Thermodynamics of Chromium(VI) Anionic Species Sorption onto Surfactant-Modified Montmorillonite Clay  

Microsoft Academic Search

Batch sorption experiments performed on Cr(VI) species sorption showed a significantly enhanced removal of inorganic hexavalent chromium anionic species from aqueous solution by montmorillonite clays modified with quaternary amine, hexadecyltrimethylammonium (HDTMA) bromide. Unmodified clay had no affinity for chromium(VI) species. The sorption of Cr(VI) species has been carried out as a function of pH, contact time, adsorbate concentration (4.14×10?5 to

B. S. Krishna; D. S. R. Murty; B. S. Jai Prakash

2000-01-01

414

Temperature dependence of polymer crystalline morphology in nylon 6\\/montmorillonite nanocomposites  

Microsoft Academic Search

The influence of nanodispersed montmorillonite layers and process history on the crystal structure of nylon 6 between room temperature and melting is examined with simultaneous small- and wide-angle X-ray scattering and modulated differential scanning calorimetry. For the examined process history, nylon 6 exhibits predominantly ?-phase behavior from room temperature to melting, with a gradual shift in chain–chain and sheet–sheet spacings

Derek M Lincoln; Richard A Vaia; Zhi-Gang Wang; Benjamin S Hsiao; Ramanan Krishnamoorti

2001-01-01

415

Heavy metal removal from water by sorption using surfactant-modified montmorillonite  

Microsoft Academic Search

Removal of Cu2+ and Zn2+ from aqueous solutions by sorption on the montmorillonite modified with sodium dodecylsulfate (SDS) was investigated. Experiments were carried out as a function of solution pH, solute concentration, and temperature (25–55°C). The Dubinin–Kaganer–Radushkevick model was adopted to describe the single-solute sorption isotherms. Also, the binary-solute sorption equilibria could be reasonably predicted by the competitive Langmuir model,

Su-Hsia Lin; Ruey-Shin Juang

2002-01-01

416

PREPARASI DAN UJI KUALITATIF Cu-AI203-MONTMORILLONIT SEBAGAI BAHAN ANTIBAKTERI Staphylococcus aureus  

Microsoft Academic Search

The preparation and qualitative test of Cu-AlzOrmontmorillonite as an antibacterial material of Staphylococcus aureus has been done. The research was initiated by preparation of AlzOrmontmorillonite. AlzOrmontmorillonite was prepared by intercalating Keggin ions (AI lJ04(OHh4(HzO) d7+, into interlayer of montmorillonite followed by calcining the resulting material using furnace at 300 °C for 5 hours to convert the Keggin ions into the

Kama Wijaya; Iqmal Tahir; Laity Awalina M

417

Polyethersulfone?Modified Montmorillonite Hybrid Beads for the Removal of Bisphenol A  

Microsoft Academic Search

Na?Montmorillonite (Na?MMT) was modified by cetyltrimethylammonium bromide first, then polyethersulfone (PES)?MMT hybrid beads were prepared using a liquid?liquid phase separation technique for the removal of bisphenol (BPA). The interlayer spacing of the MMT increased after the modification. Adsorption data showed that the modified MMT had excellent adsorption ability to BPA due to the hydrophobic interaction and large porosity. An adsorption

Yin Chen; Tian Chen; Fuming Cao; Zehua Yin; Xiaojun He; Jian Gao; Anqi Zhang; Changsheng Zhao

2008-01-01

418

Effect of montmorillonite on gelation and swelling behavior of sulfonated polyacrylamide nanocomposite hydrogels in electrolyte solutions  

Microsoft Academic Search

Nanocomposite hydrogels were prepared by cross-linking of aqueous solutions of sulfonated polyacrylamide\\/sodium montmorillonite with chromium triacetate. The gelation process and effects of clay content and ionic strength on swelling behavior were investigated. X-ray diffraction patterns indicated that exfoliated type of microstructure was formed. Study of the gelation behavior using dynamic rheometery showed that the limiting storage modulus of the nanocomposite

Jamal Aalaie; Ebrahim Vasheghani-Farahani; Ali Rahmatpour; Mohammad Ali Semsarzadeh

2008-01-01

419

Montmorillonite alignment induced by magnetic field: Evidence based on the diffusion anisotropy of water molecules  

Microsoft Academic Search

Diffusion coefficients of water in Na-montmorillonite (Na-mon) suspensions have been determined by pulsed-field gradient spin–echo (PGSE) NMR spectroscopy for three directions (x, y, and z), where x and y mean the directions perpendicular to the static magnetic field, and z the direction parallel to it. Diffusion anisotropy was observed in the suspensions with Na-mon weight fractions of 0.63, 1.82, and

Takafumi Takahashi; Takahiro Ohkubo; Yasuhisa Ikeda

2006-01-01

420

Selectivity of montmorillonite catalyzed prebiotic reactions of D, L-nucleotides  

Microsoft Academic Search

The montmorillonite-catalyzed reactions of the 5?-phosphorimidazolides of D, L-adenosine (D, L-ImpA) (Figure 1a. N = A, R\\u000a = H) and D, L-uridine (Figure 1a., N = U, R = H) yields oligomers that were as long as 7 mers and 6 mers, respectively. The\\u000a reactions of dilute solutions of D-ImpA and D-ImpU under the same conditions gave oligomers as long

Prakash C. Joshi; Stefan Pitsch; James P. Ferris

2007-01-01

421

Synergistic Effect of Montmorillonite and Intumescent Flame Retardant on Flame Retardance Enhancement of ABS  

Microsoft Academic Search

The synergistic effects of organic montmorillonite (OMMT) and intumescent flame retardant (IFR) based on the ammonium polyphosphate (APP) and pentaerythritol (PER) on flame retardant enhancement of acrylonitrile-butadiene-styrene copolymer (ABS) were investigated by using the limiting oxygen index (LOI), the UL-94 (vertical flame) test, thermogravimetric analysis (TGA), x-ray diffractometry (XRD) and scanning electron microscopy (SEM). The LOI data and vertical flame

Ying Xia; Xi-gao Jian; Jian-feng Li; Xin-hong Wang; Yan-yan Xu

2007-01-01

422

Preparation and performance of a Nafion ®\\/montmorillonite nanocomposite membrane for direct methanol fuel cell  

Microsoft Academic Search

Direct methanol fuel cells (DMFC) have major technical problems, e.g. slow methanol oxidation kinetics and high methanol crossover, to use as power sources for several applications. To overcome these problems it has been proposed to increase the fuel cell operating temperature to over 100–150°C and to reduce the methanol permeability.In this work, we made Nafion®\\/montmorillonite (MMT) nanocomposite membranes and carried

D. H. Jung; S. Y. Cho; D. H. Peck; D. R. Shin; J. S. Kim

2003-01-01

423

Preparation, characterization and mechanical properties of the polylactide\\/perlite and the polylactide\\/montmorillonite composites  

Microsoft Academic Search

In this study polylactide (PLA)\\/perlite and PLA\\/montmorillonite (MMT) composites were prepared by melt extrusion and solvent\\u000a dissolution methods. The effects of organic\\/inorganic ratios and the kind of inorganic compounds on the characterization of\\u000a the composite materials were investigated. The thermal stability of the organic–inorganic composite materials was evaluated\\u000a by TGA and DSC, and the morphology of these composites was measured

Hongyan Tian; Hideyuki Tagaya

2007-01-01

424

Effect of kaolinite and Ca-montmorillonite on the alleviation of soil water repellency  

Microsoft Academic Search

The effects of adding 1-3% (weight) kaolinite or Ca-montmorillonite on the weability of silica sand, made highly water repellent with stearic acid, was studied during weing and prolonged drying phases at 50°C. The persistence of water repellency was estimated with the water drop penetration time (WDPT) test. Aer weing water repellency disappeared in all the samples. During the drying phase,

P. Dlapa; S. H. Doerr; M. Tesa?

425

Competitive sorption of anionic and cationic dyes onto cetylpyridinium-modified montmorillonite  

Microsoft Academic Search

Single-and multi-solute competitive sorptions of anionic dyes; Eriochrome Black T (EBT), Orange II (OR) and Methyl Orange (MO) and cationic dyes; Thioflavin T (TT), Methylene Blue (MB) and Crystal Violet (CV) onto montmorillonite modified with a cationic surfactant, cetylpyridinium chloride (CP), were investigated. In single-solute sorption, the sorption affinity, as represented by Freundlich sorption coefficient (KF) and Langmuir sorption capacity

Won Sik Shin

2008-01-01

426

The use of montmorillonite as a reinforcing and compatibilizing filler for NBR\\/SBR rubber blend  

Microsoft Academic Search

Montmorillonite clay was added at different ratios to some polymer blends of acrylonitrile–butadiene rubber (NBR) and styrene–butadiene rubber (SBR). Both the reinforcing and compatibilizing performance of the filler were investigated using rheometric measurements, physico-mechanical properties, scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). There was a remarkable decrease in the optimum cure time (tc90) and the scorch time (ts2),

Hisham Essawy; Doaa El-Nashar

2004-01-01

427

Effect of montmorillonite clay on flax fabric reinforced poly lactic acid composites with amphiphilic additives  

Microsoft Academic Search

Bio-composites (PF) were successfully prepared by reinforcing poly lactic acid (PLA) with woven flax fibers (F) in the presence of mandelic acid, benzilic acid, dicumyl peroxide (DCP) and zein as additives. To improve the mechanical properties of the bio-composites, montmorillonite clay (MMT) was also added. Characterizations of the bio-composites in presence and absence of MMT were performed by FTIR, DSC,

Rakesh Kumar; Mohammed K. Yakabu; Rajesh D. Anandjiwala

2010-01-01

428

Removal of Cd2+ from aqueous solution by adsorption using Fe-montmorillonite.  

PubMed

Fe-montmorillonite (Fe-Mont.) is obtained by exchanging the original interlayer cations of montmorillonite by poly-hydroxyl ferric. In this paper, Fe-Mont. was synthesized by using Ca-montmorillonite (Ca-Mont.) directly under ultrasonic treatment with the aim to enhance the ability of removal of heavy metal ions from wastewater. The modified materials were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR). Batch equilibrium experiments of Cd(II) ions (Cd(2+)) adsorption on the Fe-Mont. were performed. Effects of the initial pH of the solution and contact time on the adsorption of Cd(2+) were studied. Four types of adsorption isotherms were applied to describe the adsorption isotherms of Cd(2+) by Fe-Mont. The relationship between adsorbing capacity (q(e)) and equilibrium mass concentration (C(e)) is in accordance with the isothermal adsorption equation of Langmuir. Three kinetic models, including pseudo-first-order, pseudo-second-order and the Elovich equation model, were used to analyze the Cd(2+) adsorption process. The pseudo-second-order chemical reaction kinetics provide the best correlation of the experimental data, therefore the adsorption dynamics follows the laws of pseudo-second-order kinetics. PMID:19443105

Wu, Pingxiao; Wu, Weimin; Li, Shuzhen; Xing, Ning; Zhu, Nengwu; Li, Ping; Wu, Jinghua; Yang, Chen; Dang, Zhi

2009-04-14

429

Preparation and characterization of montmorillonite modified by phosphorus-nitrogen containing quaternary ammonium salts  

NASA Astrophysics Data System (ADS)

A novel class of phosphorous-nitrogen containing quaternary ammonium salts (PNQAS) were synthesized and used as modifiers for sodium montmorillonite (Na-MMT). Montmorillonites modified by PNQAS (PNQAS-MMT) were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), dispersibility measurement and thermogravimetric analysis (TGA). The results show that the PNQAS have been intercalated into the montmorillonite layers successfully and the basal spacing of PNQAS-MMT is 1.70-2.65 nm. The XRD results show that the basal spacing of PNQAS-MMT reaches a maximum when PNQAS/CEC molar ratio is above 1.2. The increase of chain length of PNQAS is beneficial to expand the interlayer space of the MMT. The TEM and dispersibility measurement results show that PNQAS-MMT have stronger hydrophobicity and better dispersion than Na-MMT. The TGA results reveal that the thermal stability for PNQAS-MMT is affected by the structure and composition of intercalated PNQAS cations. The Tinital of PNQAS-MMT is between 286 °C and 385 °C, which can be applied to the modification of the polymer as a halogen-free flame retardant.

Huang, Guobo; Gao, Jianrong; Wang, Xu

2012-02-01

430

[XPS characterization of TiN layer on bearing steel surface treated by plasma immersion ion implantation and deposition technique].  

PubMed

Titanium nitride (TIN) hard protective films were fabricated on AISI52100 bearing steel surface employing plasma immersion ion implantation and deposition (PIIID) technique. The TiN films were characterized using a variety of test methods. Atomic force microscope (AFM) revealed that the titanium nitride film has extremely smooth surface, very high uniformity and efficiency of space filling over large areas. X-ray diffraction (XRD) result indicated that (200) crystal face of titanium nitride phase is the preferred orientation and three kinds of titanium components exist in the surface modified layer. Tailor fitting analysis of X-ray photoelectron spectroscopy (XPS) combined with Ar ion etching proved that Ti2p(1/2) and Ti2p(3/2) have two peaks in the titanium nitride film layer, respectively. It is shown that different chemical state exists in titanium compound. N(1s) bond energy of XPS has also three fitting peaks at 396.51, 397. 22 and 399.01 eV, corresponding to the nitrogen atom in TiNxOy, TiN and N--N, respectively. Combined with the XPS Tailor fitting analysis results of O(1s) bond energy, it was shown that there is a large amount of titanium nitride phase in addition to a small amount of simple substance nitrogen and oxide of titanium in the surface layer. The whole film system is made up of TiN, TiO2, N--N and Ti--O--N compound. PMID:19950682

Liu, Hong-xi; Jiang, Ye-hua; Zhan, Zhao-lin; Tang, Bao-yin

2009-09-01

431

Microstructure and its effect on toughness and wear resistance of laser surface melted and post heat treated high speed steel  

Microsoft Academic Search

High speed steel hacksaw blade blanks were laser surface melted and rapidly solidified along one edge. The laser melting resulted\\u000a in complete carbide dissolution. By subsequent machining and heat treatments saw teeth were manufactured with a refined internal\\u000a structure of the edges and corners. The structure was fully martensitic with a uniform and dense dispersion of small primary\\u000a carbides. Sawing

Leif Ĺhman

1984-01-01

432

Performance of a sub-surface flow constructed wetland in polishing pre-treated wastewater—a tropical case study  

Microsoft Academic Search

This paper reports on the performance of three units of a sub-surface horizontal flow constructed wetland (CW) pilot plant in polishing effluent from the upflow anaerobic sludge blanket (UASB) reactor plant. Studies on the use of UASB for on-site wastewater pre-treatment were initiated in Tanzania for the first time in 1993, while initial research works on the application of CW

M. E Kaseva

2004-01-01

433

Effect of Surface-treated Nano-silica on Thermal Behavior and Flame Retardant Properties of EVA\\/ATH composites  

Microsoft Academic Search

The effects of nano-silica with different surface treatment on thermal stability, flame retardant properties and mechanical properties of ethylene-vinyl acetate copolymer (EVA) \\/alumina trihydrate (ATH) composites are discussed by thermal gravimetric analysis (TG), limited oxygen index (LOI) and tensile properties. The results of TG show better thermal stability of composites with nano-silica. The maximal weight loss rate is obviously decreased

Zhi-dong Han; Chanjun Diao; Limin Dong; Xianyou Zhang

2007-01-01

434

Preparation, characterization and properties of amino-functionalized montmorillonite and composite layer-by-layer assembly with inorganic nanosheets  

NASA Astrophysics Data System (ADS)

An amino-functionalized montmorillonite (APTMS-MMT) was prepared by the grafting of 3-aminopropyltrimethoxysilane (APTMS) on the surface of MMT via the ultrasonic synthesis process and characterized by a variety of techniques: FT-IR, thermogravimetic analysis (TGA), particles size analysis and ?-potential measurement. The results showed the size and size distribution of APTMS-MMT particles were decreased, and the ?-potential of particles was increased obviously via the ultrasonic synthesis process. The particles of 30% APTMS-MMT US (MMT modified with 30 wt% APTMS with ultrasonic synthesis process) had a z-average diameter of about 500 nm and a polydispersity index of 0.2. The resultant 30% APTMS-MMT US was dispersed uniformly and stably in water. The poly(acrylic acid) (PAA)/APTMS-MMT multilayer films were grown through layer-by-layer (LBL) deposition of PAA and APTMS-MMT. SEM results indicated that the ultrasonic synthesis of APTMS-MMT increased dispersability of clay sheets at high loadings. The thermal stability and mechanical properties of PAA/APTMS-MMT composites were investigated by TGA and tensile test respectively. The results showed the ultrasonic synthesis of APTMS-MMT enhanced the thermal stability and mechanical properties of PAA/APTMS-MMT composites significantly. PAA/30% APTMS-MMT US composite displayed 3 times higher strength and 6 times higher Young's modulus when compared with pure PAA polymer.

Huang, Guo-bo; Ge, Chang-hua; He, Bing-jing

2011-06-01

435

Characterization of pillared montmorillonites with the atomic force microscope (AFM)  

Microsoft Academic Search

An atomic force microscope (AFM) has been used to investigate the surface features of samples of Ca-bentonite from Texas and Na-bentonite from Wyoming that were pillared with alumina clusters. Atomic-scale-resolution images of the clay surface consist of hexagonal arrays of bright spots. The nearest-neighbor distance in the two parent clays was found to be consistently greater after pillaring in numerous

M. L. Occelli; B. Drake; S. A. C. Gould

1993-01-01

436

A combined X-ray photoelectron and Auger electron spectroscopic study of cesium in variable-charge montmorillonites  

SciTech Connect

A combined X-ray photoelectron and Auger electron spectroscopic investigation of sorption and characterization of bonding states of Cs in montmorillonite (M) and in four reduced-charge montmorillonites (RCMs) were carried out. The nondestructive analysis of sorption of Cs in variable-charge montmorillonites obtained by XPS is consistent within 4--8% to those obtained by solution analysis using AAS. The core-level Cs 3d{sub 5/2} photoelectron binding energy was observed to be enhanced with the reduction of electron population from higher to lower charge montmorillonite. The charge potential model has been used to interpret such core-level short-range chemical shifts. However, a larger shift in the Auger Cs-M{sub 4}N{sub 4,5}N{sub 4,5} line was observed and Cs-Auger kinetic energy was found to decrease from higher charge RCM to lower charge RCM, which may be attributed to the effect of extra-atomic relaxation from surrounding oxygen atoms; this effect implies that the flow of electronic charge to the Cs ion is larger for higher charge RCM than for lower charge RCM. However, this effect is enhanced by the extra contribution of Li that has migrated. A comparison of Cs 3d binding energies and Cs-Auger kinetic energies in a two-dimensional chemical state plot indicates multiple bonding states of Cs in variable-charge montmorillonites. The extra-atomic relaxation energy ({Delta}E{sub r}) value of each of the Cs-montmorillonites was unique, which indicates that this is dependent on the chemical environment and on the availability of electron density in montmorillonites. Also, the binding energy value of Cs 3d{sub 5/2} was found to be nearer to CsOH than to CsCl, which reflects that the bonding state of Cs is not as ionic as CsCl.

Dutta, N.C.; Iwasaki, Takashi; Ebina, Takeo; Hayashi, Hiromichi [Tohoku Nation