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1

The roles of BrØnsted and Lewis surface acid sites in acid-treated montmorillonite supported ZnCl 2 alkylation catalysts  

Microsoft Academic Search

The catalyst known as “clayzic” (ZnCl2 supported on acid-treated montmorillonite) exhibits both BrØnsted and Lewis surface acidities. The relative catalytic activities of these two types of acid site have been determined in a range of reactions, by comparing the activities of clayzic with those of related catalysts which exhibit only one type of surface acidity. Acid-treated montmorillonite has been used

J. Massam; D. R. Brown

1995-01-01

2

Probing the role of surface treated montmorillonite on the properties of semi-aromatic polyamide/clay nanocomposites  

NASA Astrophysics Data System (ADS)

Semi-aromatic polyamide/organoclay nanocomposites were generated through solution blending technique. Surface modification of the montmorillonite clay was performed with p-amino benzoic acid for ample compatibilization with the polyamide matrix. The polymer chains were produced from the condensation of 4-aminophenyl sulfone with sebacoyl chloride. Interaction between the two phases was established by modifying the polymer chains with amine end groups using 1% surplus diamine near the completion of the reaction. The effect of clay dispersion and the interaction between clay and polyamide chains on the properties of nanocomposites were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile testing of thin films, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and water uptake measurements. The structural investigations confirmed the formation of delaminated nanostructures at low clay contents and disordered intercalated morphology at higher clay loadings. This morphology of the nanocomposites resulted in their enhanced mechanical and thermal properties. The tensile behavior and thermal stability significantly amplified while permeability decreased with increasing dispersibility of organoclay in the polyamide matrix.

Zulfiqar, Sonia; Kausar, Ayesha; Rizwan, Muhammad; Sarwar, Muhammad Ilyas

2008-12-01

3

Characterization of montmorillonite surfaces after modification by organosilane  

Microsoft Academic Search

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 (CHSiCl) and octadecyltrimethoxysilane [CHSi(OMe)] are highly

Kang Song; G. Sandi

2001-01-01

4

Modification of Wyoming montmorillonite surfaces using a cationic surfactant.  

PubMed

Surfaces of Wyoming SWy-2-Na-montmorillonite were modified using ultrasonic and hydrothermal methods through the intercalation and adsorption of the cationic surfactant octadecyltrimethylammonium bromide (ODTMA). Changes in the surfaces and structure were characterized using X-ray diffraction (XRD), thermal analysis (TG), and electron microscopy. The ultrasonic preparation method results in a higher surfactant concentration within the montmorillonite interlayer when compared with that from the hydrothermal method. Three different molecular environments for surfactants within the surface-modified montmorillonite are proposed upon the basis of their different decomposition temperatures. Both XRD patterns and TEM images demonstrate that SWy-2-Na-montmorillonite contains superlayers. TEM images of organoclays prepared at high surfactant concentrations show alternate basal spacings between neighboring layers. SEM images show that modification with surfactant reduces the clay particle size and aggregation. Organoclays prepared at low surfactant concentration display curved flakes, whereas they become flat with increasing intercalated surfactant. Novel surfactant-modified montmorillonite results in the formation of new nanophases with the potential for the removal of organic impurities from aqueous media. PMID:16142947

Xi, Yunfei; Frost, Ray L; He, Hongping; Kloprogge, Theo; Bostrom, Thor

2005-09-13

5

Heterogeneous reaction of NO2 on the surface of montmorillonite particles.  

PubMed

The studies on heterogeneous reactions over montmorillonite, which is a typical 2:1 layered aluminosilicate, will benefit to the understanding of heterogeneous reactions on clay minerals. Montmorillonite can be classified as sodium montmorillonite or calcium montmorillonite depending on the cation presented between the different layers. Using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the heterogeneous reaction mechanism of NO2 on the surface of montmorillonite was firstly investigated. Results showed that the reaction of NO2 on the surface of sodium and calcium montmorillonite fit a first-order kinetics, and the reaction duration of calcium montmorillonite was longer than that of sodium montmorillonite under the dry condition. For either sodium or calcium montmorillonite, the uptake coefficient decreased as humidify increased. PMID:23520844

Zhang, Zefeng; Shang, Jing; Zhu, Tong; Li, Hongjun; Zhao, Defeng; Liu, Yingju; Ye, Chunxiang

2012-01-01

6

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

7

Acidity of edge surface sites of montmorillonite and kaolinite  

NASA Astrophysics Data System (ADS)

Acid-base chemistry of clay minerals is central to their interfacial properties, but up to now a quantitative understanding on the surface acidity is still lacking. In this study, with first principles molecular dynamics (FPMD) based vertical energy gap technique, we calculate the acidity constants of surface groups on (0 1 0)-type edges of montmorillonite and kaolinite, which are representatives of 2:1 and 1:1-type clay minerals, respectively. It shows that tbnd Si-OH and tbnd Al-OH2OH groups of kaolinite have pKas of 6.9 and 5.7 and those of montmorillonite have pKas of 7.0 and 8.3, respectively. For each mineral, the calculated pKas are consistent with the experimental ranges derived from fittings of titration curves, indicating that tbnd Si-OH and tbnd Al-OH2OH groups are the major acidic sites responsible to pH-dependent experimental observations. The effect of Mg substitution in montmorillonite is investigated and it is found that Mg substitution increases the pKas of the neighboring tbnd Si-OH and tbnd Si-OH2 groups by 2-3 pKa units. Furthermore, our calculation shows that the pKa of edge tbnd Mg-(OH2)2 is as high as 13.2, indicating the protonated state dominates under common pH. Together with previous adsorption experiments, our derived acidity constants suggest that tbnd Si-O- and tbnd Al-(OH)2 groups are the most probable edge sites for complexing heavy metal cations.

Liu, Xiandong; Lu, Xiancai; Sprik, Michiel; Cheng, Jun; Meijer, Evert Jan; Wang, Rucheng

2013-09-01

8

Theoretical characterization of formamide on the inner surface of montmorillonite  

NASA Astrophysics Data System (ADS)

Density functional theory calculations were performed to characterize the low-lying structures of formamide (FA) and protonated formamide (FAH) in the interlayer space of montmorillonite (MMT). The interactions among FA/FAH, H2O, Na+, and the inner surface of MMT were systematically analyzed. The carbonyl-O of FA/FAH has strong coulomb interaction with Na+, while its amide-H forms hydrogen bonds (HBs) with water and MMT surface. The adsorption of FA is promoted by H2O, which exhibits a cooperative adsorption effect by enhancing the FA–Na+ coulomb interaction and by forming HBs with FA. Our study reveals the structural basis of FA/FAH as an intercalator for MMT splitting.

Shi, Jing; Lou, Zhaoyang; Yang, Mingli; Zhang, Yao; Liu, Houbin; Meng, Yingfeng

2014-06-01

9

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

10

Control of Montmorillonite Surface Coatings on Quartz Grains in Bentonite by Precursor Volcanic Glass  

NASA Astrophysics Data System (ADS)

The pathogenic tendencies of respirable-sized quartz grains may be dependent on inherent characteristics of the quartz as well as external factors. Surface coatings on quartz are of particular interest as they modify both physical and chemical properties of quartz grain surfaces and sequester the grain from contact with reactive lung fluids. Wendlandt et al. (Appl. Geochem. 22, 2007) investigated the surface properties of respirable-sized quartz grains in bentonites and recognized pervasive montmorillonite surface coatings on the quartz that resisted removal by repeated vigorous washings and reaction with HCl. To understand the persistence of montmorillonite coatings on quartz grains of igneous origin, volcanic ash deposits of varying age and degree of alteration to montmorillonite were sampled in Utah, including the distal Lava Creek (c. 0.64 Ma) and Bishop Tuffs (c. 0.74 Ma), and SW Colorado (Conejos Fm, San Juan Volcanic Field) for comparison with commercial grade Cretaceous-age "western" and "southern" bentonites. Quartz grains, hand-picked from these samples, were analyzed using FE-SEM and HRTEM. Continuous coatings of volcanic glass occur on quartz grains from the distal volcanic ash samples. As glass alteration to montmorillonite becomes more extensive, quartz grain surfaces start to display patches of montmorillonite. These patches become continuous in extent on quartz grains from the bentonites. Late precipitation of opal- CT lepispheres is consistent with the alteration reaction for volcanic glass: Volcanic glass + H2O = montmorillonite + SiO2(am) + ions(aq). HRTEM of quartz grains reveals an amorphous surface layer, consistent with a volcanic glass coating. Our results indicate that persistent montmorillonite coatings on quartz grains in bentonites are related to precursor volcanic glass coatings on these grains. The absence of glass coatings on other mineral grains in bentonite (feldspar, biotite) may be a consequence of the presence of strong cleavage in these minerals and resultant grain disaggregation during eruption. The reaction of glass and montmorillonite coatings in simulated lysosomal lung fluid (pH=4.55) at 37°C is under investigation and the persistence of these coatings directly impacts human health risk from respirable quartz in bentonite.

Wendlandt, R. F.; Harrison, W. J.

2008-12-01

11

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

2013-10-15

12

Influence of heavy metals adsorption on the surface-energy properties of fluorinated montmorillonite clays “Rassoul”  

Microsoft Academic Search

We investigate the adsorption strength of some very toxic substances like lead, cadmium and mercury and sodium triphosphate, a highly environmental contaminant, on purified and homogenized fluorinated sodium montmorillonite NaFMt or “Rassoul”, and the influence on its electronic and surface-energy properties. The changes in the wettability of this clay due to the adsorbed elements are discussed in terms of the

A. Khaldoun; G. H. Wegdam; E. Eiser; M. L. Kerkeb; J. D. Garcia Duran; F. González-Caballero; D. Bonn

2006-01-01

13

Influence of Clay Surface Modification on Morphology and Rheology of Polyethylene Glycol\\/Montmorillonite Nanocomposites  

Microsoft Academic Search

The effects of surface modification of Na-montmorillonite (Na-MMT) on morphology and the rheological properties of polyethylene glycol\\/ organoclay nanocomposites are investigated. Dodecyltrimethylammonium bromide (DTABr) is used to modify the clay surface. Adsorption of DTABr on Na-MMT is monitored by zeta potential measurements. From zeta potential measurements, three DTABr concentrations, 1 × 10—3, 7.5 × 10— 3, and 5 × 10—2

Sevim I?çi; Nurfer Güngör; Ayse Alemdar; Ö. Isik Ece

2007-01-01

14

FT-IR spectroscopic investigations of surface and intercalated 2-aminopyrimidine adsorbed on sepiolite and montmorillonite from Anatolia  

NASA Astrophysics Data System (ADS)

The adsorption of 2-amino pyrimidine (2APM) on sepiolite and montmorillonite has been investigated using FT-IR spectrometry. The intercalation of 2-amino pyrimidine within montmorillonite has been shown by X-ray diffraction to increase the interlayer spacings. 2APM interacted with montmorillonite by direct or indirect coordination (through water molecules) to the exchangeable cations. Adsorption on sepiolite was due to hydrogen bonding with surface Si-OH groups. It is concluded that endocyclic nitrogen is mainly involved in coordination. Moreover, amino group hydrogens may be involved in hydrogen bonding interaction with water molecules (NH…OH 2).

Akyüz, S.; Akyüz, T.

2003-06-01

15

Sorption of Eu on Na and Ca-montmorillonites: experimental investigations and modelling with cation exchange and surface complexation  

Microsoft Academic Search

The 2-site protolysis no electrostatics surface complexation and cation exchange (2SPNE\\/CE) model used in previous work to model the sorption of Ni and Zn on Na- and Ca-montmorillonites was applied to sorption edges and isotherms measured for Eu on these two montmorillonite forms. The aim was to further test the applicability of the sorption model on a trivalent element with

M. H Bradbury; B. Baeyens

2002-01-01

16

Reflectance Spectroscopy of Palagonite and Iron-Rich Montmorillonite Clay Mixtures: Implications for the Surface Composition of Mars  

NASA Technical Reports Server (NTRS)

Mixtures of a Hawaiian palagonite and an iron-rich, montmorillonite clay (15.8 +/- 0.4 wt% Fe as Fe2O3) were evaluated as Mars surface spectral analogs from their diffuse reflectance spectra. The presence of the 2.2 microns absorption band in the reflectance spectrum of clays and its absence in the Mars spectrum have been interpreted as indicating that highly crystalline aluminous hydroxylated clays cannot be a major mineral component of the soil on Mars. The palagonite sample used in this study does not show this absorption feature in its spectrum. In mixtures of palagonite and iron-rich montmorillonite, the 2.2 microns Al-OH clay lattice band is not seen below 15 wt% montmorillonite. This suggests the possibility that iron-rich montmorillonite clay may be present in the soil of Mars at up to 15 wt% in combination with palagonite, and remain undetected in remotely sensed spectra of Mars.

Orenberg, James; Handy, Jonathan

1992-01-01

17

Modification of the surfaces of Wyoming montmorillonite by the cationic surfactants alkyl trimethyl, dialkyl dimethyl, and trialkyl methyl ammonium bromides.  

PubMed

Surfaces of a Wyoming SWy-2 sodium montmorillonite were modified using microwave radiation through intercalation with the cationic surfactants octadecyl-trimethyl ammonium bromide, dimethyldioctadecylammonium bromide, and methyl-tri-octadecyl ammonium bromide by an ion exchange mechanism. Changes in the surfaces and structure were characterized using X-ray diffraction (XRD), thermal analysis (TG) and infrared (IR) spectroscopy. Different configurations of surfactants within montmorillonite interlayer are proposed based on d(001) basal spacings. A range of surfactant molecular environments within the surface-modified montmorillonite are proposed based upon their thermal decomposition. IR spectroscopy using a smart endurance single bounce diamond attenuated total reflection (ATR) cell has been used to study the changes in the spectra of CH asymmetric and symmetric stretching modes of the surfactants to provide more information of the surfactant molecular configurations. PMID:17045287

Xi, Yunfei; Frost, Ray L; He, Hongping

2007-01-01

18

Sol-gel network silica/modified montmorillonite clay hybrid nanocomposites for hydrophobic surface coatings.  

PubMed

Sol-gel silica/nanoclay composites were prepared through sol-gel polymerization technique using tetraethylorthosilicate precursor and montmorillonite (MMT) clay in aqueous media. In this study, both montmorillonite-K(+) and organically modified MMT (OMMT) clays were used. The prepared composites were coated on glass substrate by making 1 wt% solution in ethyltrichlorosilane. The incorporation of nanoclay does not alter the intensity of characteristic Si-O-Si peak of silica network. Thermogravimetric studies show that increasing clay content increased the degradation temperature of the composites. Differential scanning calorimetry (DSC) results of organically modified MMT nanoclay incorporated composite show a shift in the melting behavior up to 38°C. From DSC thermograms, we observed that the ?H value decreased with increasing clay loading. X-ray diffraction patterns prove the presence of nanoclay in the composite and increase in the concentration of organically modified nanoclay from 3 to 5 wt% increases the intensity of the peak at 2?=8° corresponds to OMMT. Morphology of the control silica gel composite was greatly influenced by the incorporation of OMMT. The presence of nanoclay changed the surface of control silica gel composite into cleaved surface with brittle in nature. Contact angle measurements were done for the coatings to study their surface behavior. These hybrid coatings on glass substrate may have applications for hydrophobic coatings on leather substrate. PMID:22056084

Meera, Kamal Mohamed Seeni; Sankar, Rajavelu Murali; Murali, Adhigan; Jaisankar, Sellamuthu N; Mandal, Asit Baran

2012-02-01

19

Correlation of catalytic activity with infra-red, 29Si MAS NMR and acidity data for HCl-treated fine fractions of montmorillonites  

Microsoft Academic Search

The <2 ?m fractions of SAz-1 (Cheto, Arizona, USA) and JP (Jelšový Potok, Slovakia) montmorillonites were treated with 6 M HCl for 30, 300 and 900 minutes at 95°C. The materials obtained were investigated by X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetry (TG), infrared (IR) spectroscopy, and 29Si MAS NMR spectroscopy. The number of acid sites was determined from the

Christopher Breen; Jana Madejová; Peter Komadel

1995-01-01

20

Structure modification of montmorillonite nanoclay by surface coating with soy protein.  

PubMed

To achieve exfoliated and/or intercalated structures, montmorillonite (MMT) was surface-coated by soy protein at 60 °C, at MMT/soy protein powder mass ratios of 49:1, 9:1, 4:1, and 2:1 and pH 2.0-10.0. The protein-coated MMT was triple-washed and lyophilized for characterization. Protein coating was observed at all pH conditions, based on data from X-ray diffraction, Fourier transform infrared spectroscopy, zeta potential, and quantification of protein remaining in the continuous phase and present in the triple-washed MMT. At a mass ratio of 4:1, >90% protein bound with MMT, with the largest d-spacing at pH 9.0. When the mass ratio was increased to 2:1, protein-coated MMT at pH 9.0 demonstrated the highest degree of intercalation/exfoliation, corresponding to disappearance of the diffraction peak characteristic of pristine MMT. This study thus demonstrated that intercalation/exfoliation of MMT can be easily achieved by coating with low-cost soy protein for manufacturing nanocomposite materials. PMID:23163488

Jin, Minfeng; Zhong, Qixin

2012-12-01

21

Selective removal and inactivation of bacteria by nanoparticle composites prepared by surface modification of montmorillonite with quaternary ammonium compounds.  

PubMed

The purpose of the present study was to prepare new nanocomposites with antibacterial activities by surface modification of montmorillonite using quaternary ammonium compounds that are widely applied as disinfectants and antiseptics in food-processing environments. The intercalation of four quaternary ammonium compounds namely benzalkonium chloride, cetylpyridinium chloride monohydrate, hexadecyltrimethylammonium bromide, tetraethylammonium chloride hydrate into montmorillonite layers was confirmed by X-ray diffraction. The antibacterial influences of the modified clay variants against important foodborne pathogens differed based on modifiers quantities, microbial cell densities, and length of contact. Elution experiments through 0.1 g of the studied montmorillonite variants indicated that Staphylococcus aureus, Pseudomonas aeroginosa, and Listeria monocytogenes were the most sensitive strains. 1 g of hexadecyltrimethylammonium bromide intercalated montmorillonites demonstrated maximum inactivation of L. monocytogenes populations, with 4.5 log c.f.u./ml units of reduction. In adsorption experiments, 0.1 g of tetraethylammonium chloride hydrate montmorillonite variants significantly reduced the growth of Escherichia coli O157:H7, L. monocytogenes, and S. aureus populations by 5.77, 6.33, and 7.38 log units respectively. Growth of wide variety of microorganisms was strongly inhibited to undetectable levels (montmorillonite variants. This investigation highlights that reduction in counts of microbial populations adsorbed to the new nanocomposites was substantially different from that in elution experiments, where interactions of nanocomposites with bacteria were specific and more complex than simple ability to inactivate. Treatment columns packed with modified variants maintained their inactivation capacity to the growth of Salmonella Tennessee and S. aureus populations after 48 h of incubation at room temperature with maximum reductions of 6.3 and 5.0 log units respectively. New nanocomposites presented in this research may have potential applications in industrial scale for the control of foodborne pathogens by their incorporation into high-performance filters in food processing plant environments where selectivity in removal and/or inactivation of species in fluid flow streams is desirable. Nevertheless, extensive in vitro and in vivo studies of these new nanocomposites is essential to outpace the understanding of their potential impacts and consequences on human health and the environment if they will make an appearance in commercialized food packaging and containment food materials in the future. PMID:23709187

Khalil, Rowaida K S

2013-10-01

22

Surface characteristics of thermally treated titanium surfaces  

PubMed Central

Purpose The characteristics of oxidized titanium (Ti) surfaces varied according to treatment conditions such as duration time and temperature. Thermal oxidation can change Ti surface characteristics, which affect many cellular responses such as cell adhesion, proliferation, and differentiation. Thus, this study was conducted to evaluate the surface characteristics and cell response of thermally treated Ti surfaces. Methods The samples were divided into 4 groups. Control: machined smooth titanium (Ti-S) was untreated. Group I: Ti-S was treated in a furnace at 300? for 30 minutes. Group II: Ti-S was treated at 500? for 30 minutes. Group III: Ti-S was treated at 750? for 30 minutes. A scanning electron microscope, atomic force microscope, and X-ray diffraction were used to assess surface characteristics and chemical composition. The water contact angle and surface energy were measured to assess physical properties. Results The titanium dioxide (TiO2) thickness increased as the treatment temperature increased. Additional peaks belonging to rutile TiO2 were only found in group III. The contact angle in group III was significantly lower than any of the other groups. The surface energy significantly increased as the treatment temperature increased, especially in group III. In the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, after 24 hours of incubation, the assessment of cell viability showed that the optical density of the control had a higher tendency than any other group, but there was no significant difference. However, the alkaline phosphatase activity increased as the temperature increased, especially in group III. Conclusions Consequently, the surface characteristics and biocompatibility increased as the temperature increased. This indicates that surface modification by thermal treatment could be another useful method for medical and dental implants.

Lee, Yang-Jin; Cui, De-Zhe; Jeon, Ha-Ra; Chung, Hyun-Ju; Park, Yeong-Joon; Kim, Ok-Su

2012-01-01

23

[Stability of HDTMA modified montmorillonite].  

PubMed

In order to probe the stability of organic montmorillonite, the nature montmorillonite was modified with hexadeeyltrimethylammonium (HDTMA) in different cation exchange capacity (CEC). The results of experiments showed that the stability of modified montmorillonite declined as its CEC was big and HDTMA was desorbed from 1.0 CEC modified montmorillonite. HDTMA bound to the montmorillonite surface was resistant to temperature(70 degrees C) and instable to strong ultrasonic and to vibrational intensity(180 r/min). The result also indicated that the stability of modified montmorillonite increased to NaCl(1.8 mol/L) but decreased to CaCl2 (1.8 mol/L) and modified montmorillonite was more stable in high-pH environment(12.00) than in low-pH environment(2.06). On the basis of the results of these studies, low CEC modified montmorillonite appeared suitable as a sorbent for wastewater chemical treatment and as carrier for wastewater biotreatment in low stir environment. PMID:12048827

Yang, Liuyan; Fu, Qiuqin; Jiang, Lijuan; Wang, Xiaorong

2002-03-01

24

Effect of interlayer cations of montmorillonite on the biodegradation and adsorption of crude oil polycyclic aromatic compounds.  

PubMed

Cation exchange capacity, surface acidity and specific surface area are surface properties of clay minerals that make them act as catalysts or supports in most biogeochemical processes hence making them play important roles in environmental control. However, the role of homoionic clay minerals during the biodegradation of polycyclic aromatic compounds is not well reported. In this study, the effect of interlayer cations of montmorillonites in the removal of some crude oil polycyclic aromatic compounds during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The homoionic montmorillonites were prepared via cation exchange reactions by treating the unmodified montmorillonite with the relevant metallic chloride. The study indicated that potassium-montmorillonite and zinc-montmorillonite did not enhance the biodegradation of the polycyclic aromatic hydrocarbons whereas calcium-montmorillonite, and ferric-montmorillonite enhanced their biodegradation significantly. Adsorption of polycyclic aromatic hydrocarbons was significant during biodegradation with potassium- and zinc-montmorillonite where there was about 45% removal of the polycyclic aromatic compounds by adsorption in the experimental microcosm containing 5:1 ratio (w/w) of clay to oil. PMID:24813351

Ugochukwu, Uzochukwu C; Manning, David A C; Fialips, Claire I

2014-09-01

25

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

26

Degradation of polystyrene using montmorillonite clay catalysts  

Microsoft Academic Search

Summary The performance of acid-treated montmorillonite catalysts in the degradation of polystyrene (PS) was investigated in this study. The degradation was carried out in a semi-batch reactor with a mixture of PS and catalyst at 400-450oC. The commercial Süd Chemie acid-treated montmorillonite clays (K-series) showed good catalytic activity for the degradation of PS. The styrene monomer and ethylbenzene were major

Byung-Sik Jang; Kyo-Hyun Cho; Kyung-Hoon Kim; Dae-Won Park

2005-01-01

27

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

28

The role of anionic microparticles in a poly(acrylamide)-montmorillonite flocculation aid system  

Microsoft Academic Search

The hetero-flocculation of wood fibres and fines was investigated for different bridging configurations of poly(acrylamide) and montmorillonite. Montmorillonite platelets are effective bridging agents between adsorbed polymer layers. This was attributed to the high surface charge density, which causes a higher attraction of the cationic polymer segments protruding from the cellulosic surfaces. The polymer therefore strongly attaches to the montmorillonite surface

Tom Asselman; Gil Garnier

2000-01-01

29

NANOFILTRATION FOULANTS FROM A TREATED SURFACE WATER  

EPA Science Inventory

The foulant from pilot nanofiltration membrane elements fed conventionally-treated surface water for 15 months was analyzed for organic, inorganic, and biological parameters. The foulant responsible for flux loss was shown to be a film layer 20 to 80 um thick with the greatest de...

30

Thermal decomposition of alkyl ammonium ions and its effects on surface polarity of organically treated nanoclay  

Microsoft Academic Search

The surface free energy and surface polarity of organically modified montmorillonite clay change when exposed to elevated temperatures. This was verified in this study using contact angle measurements and Wu's harmonic-mean equation. It was observed that the surface polarity of organically modified clay measured from the values of contact angle of water and diiodomethane reduced significantly owing to thermal degradation

Dhawal Dharaiya; Sadhan C. Jana

2005-01-01

31

Development of Surface Complexation Models of Cr(VI) Adsorption on Soils, Sediments and Model Mixtures of Kaolinite, Montmorillonite, ?-Alumina, Hydrous Manganese and Ferric Oxides and Goethite  

SciTech Connect

Hexavalent chromium is a highly toxic contaminant that has been introduced into aquifers and shallow sediments and soils via many anthropogenic activities. Hexavalent chromium contamination is a problem or potential problem in the shallow subsurface at several DOE sites, including Hanford, Idaho National Laboratory, Los Alamos National Laboratory and the Oak Ridge Reservation (DOE, 2008). To accurately quantify the fate and transport of hexavalent chromium at DOE and other contaminated sites, robust geochemical models, capable of correctly predicting changes in chromium chemical form resulting from chemical reactions occurring in subsurface environments are needed. One important chemical reaction that may greatly impact the bioavailability and mobility of hexavalent chromium in the subsurface is chemical binding to the surfaces of particulates, termed adsorption or surface complexation. Quantitative thermodynamic surface complexation models have been derived that can correctly calculate hexavalent chromium adsorption on well-characterized materials over ranges in subsurface conditions, such pH and salinity. However, models have not yet been developed for hexavalent chromium adsorption on many important constituents of natural soils and sediments, such as clay minerals. Furthermore, most of the existing thermodynamic models have been developed for relatively simple, single solid systems and have rarely been tested for the complex mixtures of solids present in real sediments and soils. In this study, the adsorption of hexavalent chromium was measured as a function of pH (3-10), salinity (0.001 to 0.1 M NaNO3), and partial pressure of carbon dioxide(0-5%) on a suite of naturally-occurring solids including goethite (FeOOH), hydrous manganese oxide (MnOOH), hydrous ferric oxide (Fe(OH)3), ?-alumina (Al2O3), kaolinite (Al2Si2O5(OH)4), and montmorillonite (Na3(Al, Mg)2Si4O10(OH)2?nH2O). The results show that all of these materials can bind substantial quantities of hexavalent chromium, especially at low pH. Unexpectedly, experiments with the clay minerals kaolinite and montmorillonite suggest that hexavalent chromium may interact with these solids over much longer periods of time than expected. Furthermore, hexavalent chromium may irreversibly bind to these solids, perhaps because of oxidation-reduction reactions occurring on the surfaces of the clay minerals. More work should be done to investigate and quantify these chemical reactions. Experiments conducted with mixtures of goethite, hydrous manganese oxide, hydrous ferric oxide, ?-alumina, montmorillonite and kaolinite demonstrate that it is possible to correctly predict hexavalent chromium binding in the presence of multiple minerals using thermodynamic models derived for the simpler systems. Further, these models suggest that of the six solid considered in this study, goethite is typically the solid to which most of the hexavalent chromium will bind. Experiments completed with organic-rich and organic-poor natural sediments demonstrate that in organic-rich substrates, organic matter is likely to control uptake of the hexavalent chromium. The models derived and tested in this study for hexavalent chromium binding to ?-alumina, hydrous manganese oxide, goethite, hydrous ferric oxide and clay minerals can be used to better predict changes in hexavalent chromium bioavailability and mobility in contaminated sediments and soils.

Koretsky, Carla [Western Michigan University] [Western Michigan University

2013-11-29

32

Mössbauer study of iron oxide modified montmorillonite  

NASA Astrophysics Data System (ADS)

Montmorillonite particles were modified by iron oxides using the precipitation process with the aim to monitor the differences in the structural and magnetic properties of intercalated and adsorbed Fe3+. The Mössbauer spectra recorded at 5 K in zero and 6 T external fields, IR spectra and TG curves measured in zero and 32 mT fields identified the ferrihydrite pillars in an interlayer space of the montmorillonite structure and ?-Fe2O3 nanoparticles adsorbed on the mineral surface. The temperature dependent Mössbauer spectra (25 300 K) reflect the superparamagnetic behaviour of maghemite nanoparticles and ferrihydrite pillars with the blocking temperatures of about 80 and 25 K, respectively.

Bartonkova, H.; Mashlan, M.; Zboril, R.; Pechousek, J.; Schneeweiss, O.; Martinec, P.

2005-09-01

33

Dispersibility of Amphibious Montmorillonite  

NASA Astrophysics Data System (ADS)

The objective of this study is to develop a suitable method to convert hydrophilic montmorillonite into amphibious montmorillonite by replacing the sodium ions normally found in clay with poly(oxyethylene) (POE)-amide chlorite cations. Amphibious montmorillonite has a high d-spacing and good dispersion characteristics in many different types of solutions, including those having an intermediate hydrophilic lipophilic balance (HLB) value. Four different modifying cations are tested and X-ray diffraction analysis is performed to measure the resulting changes in the d-spacing of the MMT. Scanning electron microscopy is employed to investigate the morphology of the modified clays. A laser-doppler particle analyzer is used to measure the particle size of the clays in various solutions. Dobrat’s method is applied to calculate the dispersibility of each clay and Stoke’s law is used to evaluate the settling rate. The results indicate that the d-spacing of the POE-amide chlorite cation modified montmorillonite increases from 1.28 to 3.51 nm. The amphibious montmorillonite demonstrates good dispersion characteristics in eight commonly employed coating solutions with intermediate HLB values.

Yeh, Meng-Heng; Hwang, Weng-Sing; Kuo, Wuei-Jueng

2005-09-01

34

NUCLEAR MAGNETIC RESONANCE (NMR) STUDY OF Cd 2+ SORPTION ON MONTMORILLONITE  

Microsoft Academic Search

Abstrac~z13Cd solid-state nuclear magnetic resonance (NMR) was used to identify possible Cd 2+ ad- sorption sites in montmorillonite. The montmorillonite was treated with 0.1 and 1 M CdC12 aqueous solutions and samples with 13 and 8-txm particle size were used. The data are consistent with a two-site model for sorption of Cd 2+ on montmorillonite. Cd 2+ is localized in

PAOLA D

35

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

36

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

2013-12-01

37

Montmorillonite Dissolution in Simulated Lung Fluids  

NASA Astrophysics Data System (ADS)

Because lung fluids" first interaction is with the surface of inhaled grains, the surface properties of inhaled mineral dusts may have a generally mitigating effect on cytotoxicity and carcinogenicity. Wendlandt et al. (Appl. Geochem. 22, 2007) investigated the surface properties of respirable-sized quartz grains in bentonites and recognized pervasive montmorillonite surface coatings on silica grains. The purpose of this study was to determine the dissolution rate and biodurability of montmorillonite in simulated lung fluids and to assess its potential to mitigate silica cytotoxicity. Modified batch reaction experiments were conducted on purified and size fractionated calcic (SAz-2; 0.4-5 ?m) and sodic (DC-2; 0.4-2 ?m) montmorillonites for 120 to 160 days of reaction time at 37°C in both simulated extracellular lung fluid (Lu) and simulated lysosomal fluid (Ly). Modified batch experiments simulated a flow-through setup and minimized sample handling difficulties. Reacted Lu and Ly fluid was analyzed for Mg, Al, and Si on an ICP-OE spectrometer. Steady state dissolution was reached 90-100 days after the start of the experiment and maintained for 40-60 days. Measured montmorillonite dissolution rates based on BET surface areas and Si steady state release range from 4.1x10-15 mol/m2/s at the slowest to 1.0x10-14 mol/m2/s at the fastest with relative uncertainties of less than 10%. Samples reacting in Ly (pH = 4.55) dissolved faster than those in Lu (pH = 7.40), and DC-2 dissolved faster than SAz-2. The measured range of biodurabilities was 1,300 to 3,400 years for a 1 ?m grain assuming a spherical volume and a molar volume equal to that of illite. The difference in salinities of the two fluids was too slight to draw conclusions about the relationship of ionic strength to dissolution rate. Results indicate that montmorillonite dissolution is incongruent and edge controlled. Dissolution rates for DC- 2 and SAz-2 clays were comparable to those reported in the literature. Biodurability results fall well beyond the lifespan of humans confirming montmorillonite's potential to mitigate silica cytotoxicity.

Schmidt, M.; Wendlandt, R. F.

2008-12-01

38

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] [ETH Zurich (Switzerland). Inst. of Terrestrial Ecology

1999-09-01

39

Surface characterization of plasma-treated polypropylene fibers  

Microsoft Academic Search

Plasma treatment is increasingly being used for surface modification of different materials in many industries. In this study, different techniques were employed to characterize the surface properties of plasma treated polypropylene fibers. The chemical nature of the fiber sufaces has been investigated by X-ray photoelectron spectroscopy (XPS). The XPS examination indicated the presence of oxygen-containing functional groups on fiber surfaces

Q. F Wei

2004-01-01

40

Study of elastomeric polyurethane nanocomposites prepared from grafted organic–montmorillonite  

Microsoft Academic Search

4,4?-Diphenylmethane diisocyanate (MDI) was grafted on to organic–montmorillonite (OMMT) by reaction between hydroxyl groups (?OH) on surface of the montmorillonite and the isocyanate groups (?NCO) of MDI, thus forming grafted organic–montmorillonite (MOMMT). Intercalated nanocomposites based on polyurethane (PU) and MOMMT were prepared by solution intercalation technology. The interface interaction of PU\\/MOMMT nanocomposites was better than that of PU\\/MMT composites. The

Aimin Cheng; Shishan Wu; Dingjun Jiang; Fen Wu; Jian Shen

2006-01-01

41

Preparation and Characterization of Titania-Pillared Montmorillonite  

NASA Astrophysics Data System (ADS)

In this work, a Ti-pillared montmorillonite with high thermal stability has been prepared by using a Na-montmorillonite as the host clay and polyhydroxy-titania ions as the pillaring precursor. The formation of Ti-pillared montmorillonite has been confirmed from the characterizations through X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric-differential scanning calorimeter, and specific surface area analyses. In the preparation of Ti-pillared montmorillonite several parameters, such as the type of solvent in which the synthesis is realized, the ratio of polyhydroxy-titania ions and montmorillonite, the intercalation time, the calcining temperature, and calcining time, were tested to understand their effects on the basal spacing. It was shown that this method could produce a Ti-pillared montmorillonite with the basal spacing of 3.74 nm, specific surface area of 409 m2/g, and mean pore size of 2.94 nm, as well as a high thermal stability up to 900°C.

Zhang, Yimin; Song, Shaoxian; Zhang, Min; Tuo, Biyang

42

Sol-gel hybrid films based on organosilane and montmorillonite for corrosion inhibition of AA2024.  

PubMed

The present work reports the production of films on AA2024-T3 composed of vinyltrimethoxysilane (VTMS)/tetraethylorthosilicate (TEOS) with incorporation of montmorillonite (sodium montmorillonite and montmorillonite modified with quaternary ammonium salt, abbreviated Na and 30B, respectively), generated by the sol-gel process. According to FT-IR analyses the incorporation of montmorillonite does not affect silica network. Electrochemical characterization was performed by electrochemical impedance spectroscopy measurement in 0.05molL(-1) NaCl solution. Results indicate that montmorillonite incorporation improves the corrosion protection compared to the non-modified system. Scanning electron microscopy micrographs reveal that high concentrations of montmorillonite provide agglomerations on the metallic surface, which is in detriment of the anticorrosive performance. The VTMS/TEOS/30B films with the lowest concentration (22mgL(-1)) of embedded clay provide the highest corrosion protection. PMID:24863798

Dalmoro, V; Dos Santos, J H Z; Armelin, E; Alemán, C; Azambuja, D S

2014-07-15

43

Material, Mechanical, and Tribological Characterization of Laser-Treated Surfaces  

NASA Astrophysics Data System (ADS)

Laser treatment under nitrogen assisting gas environment of cobalt-nickel-chromium-tungsten-based superalloy and high-velocity oxygen-fuel thermal spray coating of nickel-chromium-based superalloy on carbon steel was carried out to improve mechanical and tribological properties. Superalloy surface was preprepared to include B4C particles at the surface prior to the laser treatment process. Material and morphological changes in the laser-treated samples were examined using scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction (XRD) analysis. Residual stresses present at the surface region of the laser-treated layer were determined from the XRD data. The microhardness of the laser-treated surface was measured by indentation tests. Fracture toughness of the coating surfaces before and after laser treatment were also measured using overload indentation tests. Macrowear and macrofriction characterization were carried out using pin-on-disk tests.

Yilbas, Bekir Sami; Kumar, Aditya; Bhushan, Bharat; Aleem, B. J. Abdul

2014-04-01

44

Peptide Formation Mechanism on Montmorillonite Under Thermal Conditions  

NASA Astrophysics Data System (ADS)

The oligomerization of amino acids is an essential process in the chemical evolution of proteins, which are precursors to life on Earth. Although some researchers have observed peptide formation on clay mineral surfaces, the mechanism of peptide bond formation on the clay mineral surface has not been clarified. In this study, the thermal behavior of glycine (Gly) adsorbed on montmorillonite was observed during heating experiments conducted at 150 °C for 336 h under dry, wet, and dry-wet conditions to clarify the mechanism. Approximately 13.9 % of the Gly monomers became peptides on montmorillonite under dry conditions, with diketopiperazine (cyclic dimer) being the main product. On the other hand, peptides were not synthesized in the absence of montmorillonite. Results of IR analysis showed that the Gly monomer was mainly adsorbed via hydrogen bonding between the positively charged amino groups and negatively charged surface sites (i.e., Lewis base sites) on the montmorillonite surface, indicating that the Lewis base site acts as a catalyst for peptide formation. In contrast, peptides were not detected on montmorillonite heated under wet conditions, since excess water shifted the equilibrium towards hydrolysis of the peptides. The presence of water is likely to control thermodynamic peptide production, and clay minerals, especially those with electrophilic defect sites, seem to act as a kinetic catalyst for the peptide formation reaction.

Fuchida, Shigeshi; Masuda, Harue; Shinoda, Keiji

2014-06-01

45

Preparation and characterization of mixed hydroxy-Fe-Al pillared montmorillonite with large basal spacing.  

PubMed

Mixed hydroxy-Al-Fe pillared montmorillonites with large basal spacing were successfully prepared through cation-exchanging of Na+ - montmorillonite with mixed hydroxy-Al and hydroxy-Fe pillaring solutions made from hydrolysis of corresponding metal salts, followed by calcination to convert hydroxy-Al and hydroxy-Fe into intercalated polycations. According to XRD analysis, the basal spacing d(001) of pillared products dramatically enlarged from 12.7 A in the Na-montmorillonite to 81 A in the hydroxy-Fe -montmorillonite and 77.5 A in mixed hydroxy-Al-Fe-montmorillonite. The N2 BET surface areas of the pillared montmorillonites also greatly increased to more than 200 m2/g as compared to about 27 m2/g for the Na-montmorillonite. IR analysis of hydroxy-Fe, and mixed hydroxy-Al-Fe pillared montmorillonites revealed a new absorption vibration at 1384 cm(-1) wavelength. XRF elemental analysis data also showed a high content of Fe2O3 in the hydroxy-Fe pillared montmorillonite. PMID:14971465

Zeng, Xiu-qiong; Liu, Wei-ping

2004-01-01

46

Aflatoxin toxicity reduction in feed by enhanced binding to surface-modified clay additives.  

PubMed

Animal feeding studies have demonstrated that clay additives, such as bentonites, can bind aflatoxins in ingested feed and reduce or eliminate the toxicity. Bentonite deposits are found throughout the world and mostly consist of expandable smectite minerals, such as montmorillonite. The surfaces of smectite minerals can be treated with organic compounds to create surface-modified clays that more readily bind some contaminants than the untreated clay. Montmorillonites treated with organic cations, such as hexadecyltrimethylammonium (HDTMA) and phenyltrimethylammonium (PTMA), more effectively remove organic contaminants, such as benzene and toluene, from water than untreated clay. Similarly, montmorillonite treated with PTMA (K(d) = 24,100) retained more aflatoxin B1 (AfB1) from aqueous corn flour than untreated montmorillonite (K(d) = 944). Feed additives that reduced aflatoxin toxicity in animal feeding studies adsorbed more AfB1 from aqueous corn flour than feed additives that were less effective. The organic cations HDTMA and PTMA are considered toxic and would not be suitable for clay additives used in feed or food, but other non-toxic or nutrient compounds can be used to prepare surface-modified clays. Montmorillonite (SWy) treated with choline (K(d) = 13,800) and carnitine (K(d) = 3960) adsorbed much more AfB1 from aqueous corn flour than the untreated clay (K(d) = 944). A choline-treated clay prepared from a reduced-charge, high-charge montmorillonite (K(d) = 20,100) adsorbed more AfB1 than the choline-treated high-charge montmorillonite (K(d) = 1340) or the untreated montmorillonite (K(d) = 293). Surface-modified clay additives prepared using low-charge smectites and nutrient or non-toxic organic compounds might be used to more effectively bind aflatoxins in contaminated feed or food and prevent toxicity. PMID:22069725

Jaynes, William F; Zartman, Richard E

2011-06-01

47

SYNTHESIS OF IRON OXIDE-MONTMORILLONITE COMPOSITE AND STUDY OF ITS STRUCTURAL STABILITY AGAINTS SULFURIC ACID Sintesis Komposit Oksida-Besi Montmorillonit dan Uji Stabilitas Strukturnya Terhadap Asam Sulfat  

Microsoft Academic Search

The synthesis and characterization of iron oxide-montmorillonite and its structural stability test with various concentration of sulfuric acid were conducted. Synthesis was performed by treating Na- montmorillonite clay with oligocations of iron, followed by calcinating the intercalation compound of oligocations-montmorillonite at 200oC for 24 hours. Calcined product was then characterized to determine the iron content, basal spacing and its porosities

Karna Wijaya; Eko Sugiharto; Ika Liawati; Jurusan Kimia

48

Study of cetyltrimethylammonium and cetylpyridinium adsorption on montmorillonite.  

PubMed

Adsorption of cetyltrimethylammonium (CTA) and cetylpyridinium (CP) onto Na-rich montmorillonite (MMT) was studied. For this purpose, the adsorption isotherms of CTA and CP, along with desorption curves of metal cations (Na+, K+, Ca2+, Mg2+), were obtained by means of capillary isotachophoresis and atomic absorption spectrometry. Infrared, X-ray diffraction pattern, specific surface area, porosity, and moisture adsorption measurements of montmorillonite revealed that CTA and CP were adsorbed in monolayer arrangements. CTA is assumed to be attached to the negatively charged MMT surface mainly by electrostatic forces. On the other hand, CP, adsorbed in higher amounts, can be additionally bound via other interactions of pyridinium rings, such as induced and pi-pi interactions. By the surfactant adsorption, the montmorillonite surface became hydrophobic and its micro- and mesopores were significantly diminished. Using scanning electron microscopy, aggregation of such organically modified MMT particles was observed. PMID:17007866

Praus, Petr; Turicová, Martina; Studentová, Sona; Ritz, Michal

2006-12-01

49

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

50

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

51

40 CFR 721.10573 - Magnesium hydroxide surface treated with substituted alkoxysilanes (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Magnesium hydroxide surface treated with substituted...Chemical Substances § 721.10573 Magnesium hydroxide surface treated with substituted...chemical substance identified generically as magnesium hydroxide surface treated with...

2013-07-01

52

Induced hydrophobic recovery of oxygen plasma-treated surfaces  

PubMed Central

Plasma treatment is a widely used method in microfabrication laboratories and the plasticware industry to functionalize surfaces for device bonding and preparation for mammalian cell culture. However, spatial control of plasma treatment is challenging because it typically requires a tedious masking step that is prone to alignment errors. Currently, there are no available methods to actively revert a surface from a treated hydrophilic state to its original hydrophobic state. Here, we describe a method that relies on physical contact treatment (PCT) to actively induce hydrophobic recovery of plasma-treated surfaces. PCT involves applying brushing and peeling processes with common wipers and tapes to reverse the wettability of hydrophilized surfaces while simultaneously preserving hydrophilicity of non-contacted surfaces. We demonstrate that PCT is a user-friendly method that allows 2D and 3D surface patterning of hydrophobic regions, and the protection of hydrophilic surfaces from unwanted PCT-induced recovery. This method will be useful in academic and industrial settings where plasma treatment is frequently used.

Guckenberger, David J.; Berthier, Erwin; Young, Edmond W. K.; Beebe, David J.

2014-01-01

53

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.

2014-05-01

54

Photopolymerization nanocomposite initiated by montmorillonite intercalated initiator  

Microsoft Academic Search

A quaternized ammonium photoinitiator was synthesized via Michael-addition reaction and quaternization reaction, then ion-exchanged\\u000a with montmorillonite (MMT). An ordered swollen structure of the intercalated montmorillonite was confirmed by X-ray powder\\u000a diffraction (XRD) and thermogravimetric analysis (TGA). UV–vis absorption spectroscopy was employed to investigate the maximal\\u000a absorption of photoinitiator and the intercalated montmorillonite. The modified montmorillonite was then mixed with urethane

Ziping Zhang; Xiaohua Qin; Jun Nie

55

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

56

Treating ocular surface disease: new agents in development  

PubMed Central

This paper reviews recent advances and investigation in the treatment of ocular surface pathology. There is significant investment in this area, paralleling the growing demand for more effective alternatives to current treatments. Clinicians are becoming more aware of surface pathology, yet the ability to treat the most common forms of ocular pathology are still limited to the few medications approved by the US Food and Drug Administration. Medicines and devices currently under investigation are very promising. It is absolutely critical to understand the emerging options and think of their role in the treatment paradigm.

Fahmy, Ahmad M; Hardten, David R

2011-01-01

57

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

58

Molecular dynamics simulation of the intercalation behaviors of methane hydrate in montmorillonite.  

PubMed

The formation and mechanism of CH4 hydrate intercalated in montmorillonite are investigated by molecular dynamics (MD) simulation. The formation process of CH4 hydrate in montmorillonite with 1?~?8 H2O layers is observed. In the montmorillonite, the "surface H2O" constructs the network by hydrogen bonds with the surface Si-O ring of clay, forming the surface cage. The "interlayer H2O" constructs the network by hydrogen bonds, forming the interlayer cage. CH4 molecules and their surrounding H2O molecules form clathrate hydrates. The cation of montmorillonite has a steric effect on constructing the network and destroying the balance of hydrogen bonds between the H2O molecules, distorting the cage of hydrate in clay. Therefore, the cages are irregular, which is unlike the ideal CH4 clathrate hydrates cage. The pore size of montmorillonite is another impact factor to the hydrate formation. It is quite easier to form CH4 hydrate nucleation in montmorillonite with large pore size than in montmorillonite with small pore. The MD work provides the constructive information to the investigation of the reservoir formation for natural gas hydrate (NGH) in sediments. PMID:24906646

Yan, KeFeng; Li, XiaoSen; Xu, ChunGang; Lv, QiuNan; Ruan, XuKe

2014-06-01

59

Quantitative mechanistic description of Ni, Zn and Ca sorption on Na-Montmorillonite. Part III: Modelling.  

National Technical Information Service (NTIS)

Titration and sorption measurements, carried out under a wide variety of conditions on Na-montmorillonite, were examined in terms of cation exchange and surface complexation mechanisms. A computer code called MINSORB was developed and used throughout this...

B. Baeyens M. H. Bradbury

1995-01-01

60

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

61

A Study on Structure and Mechanical Properties of Polyurethane\\/Organic-Montmorillonite Nanocomposites  

Microsoft Academic Search

The intercalated nanocomposites of polyurethane (PU) with organic-montmorillonite (OMMT) treated by cetryltrimethyl ammonium bromide was prepared. The interlayer spacing of PU\\/OMMT nanocomposites was 3–4 nm. The interface interaction of PU\\/OMMT nanocomposites was improved compared to that of PU\\/montmorillonite (MMT) composites. The orderly arrangement of the PU chains was hindered because of strong interface interaction between the silicate layers dispersed in the

Shishan Wu; Aimin Cheng; Hongyan Hua; Jian Shen

2006-01-01

62

Osteoblasts behavior on chemically treated commercially pure titanium surfaces.  

PubMed

Surface modifications of commercially pure titanium (Cp-Ti), a material widely used to produce dental implants, can induce specific responses on osteoblastic cells after implantation. This work aims to investigate the influence of chemically modified surfaces of Cp-Ti by acid etching or acid etching plus alkaline treatment on the gene expression of human osteoblastic (Hob) cells. Roughness and contact angle measurements were carried out to evaluate the surface properties of the samples. The surface morphology was investigated with scanning electron microscopy. Chemical composition was analyzed by energy dispersive X-ray spectroscopy (EDS). The expression levels of some bone-related genes (ALPL, COL1A1, COL3A1, SPP1, RUNX2, and SPARC) were analyzed using real time Reverse Transcription-Polymerase Chain Reaction (real time RT-PCR). The results showed that all the chemical modifications studied in this work influenced the surface morphology, wettability, roughness and induced an osteoconductive behavior. The samples that were acid etched and alkaline treated showed a more pronounced effect. PMID:23784958

Oliveira, D P; Palmieri, A; Carinci, F; Bolfarini, C

2014-06-01

63

Nickel and lead sequestration in manganese oxide-coated montmorillonite.  

PubMed

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 6x10(-4) to 1.2x10(-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(-12) to 10(-13) cm2/s for Ni and 10(-17) to 10(-20) cm2/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. PMID:16920131

Boonfueng, Thipnakarin; Axe, Lisa; Xu, Ying; Tyson, Trevor A

2006-11-01

64

Surface characteristics and antistatic mechanism of plasma-treated acrylic fibers  

Microsoft Academic Search

Acrylic fibers are treated by nitrogen glow-discharge plasma to promote surface antistatic properties. The treated surfaces are characterized by scanning electron microscopy (SEM), specific surface area analysis (BET) and X-ray photoelectron spectroscopy (XPS). Plasma treatment is found to increase the surface roughness, to modify the nature and density of surface functionalities, and to drastically improve the wettability and antistatic ability

Yan-Chun Liu; Yan Xiong; Da-Nian Lu

2006-01-01

65

The mechanical and NIR studies on ultrafine calcium carbonate treated by four surface modifiers  

NASA Astrophysics Data System (ADS)

Calcium carbonate was surface treated by acrylic acid monomer, its polymerization with varied mean molecular weight and PS/PAA copolymer. Coating efficiencies for these four series of surface-treated calcium carbonate were investigated. They differ from each other in many aspects. We hypothesize that the treating molecules bond to and align on the particle surface in different ways before and after monolayer coverage was reached. NIR spectra of surface-treated samples studied not only reflected the amount of bonded treating agents by means of the value of absorbance, but also gave rich structural information of surface layer. This gave us a powerful means to investigate the interface of particle surface.

Shui, Miao; Yue, Linhai; Xu, Zhude

2004-01-01

66

Heavy Metal Adsorption by Montmorillonites Modified with Natural Organic Cations  

Microsoft Academic Search

Agricultural and industrial pollution release large amounts of heavy metals into the atmosphere, surface water, soil, and plants. The protection and restoration of soils and water contaminated with heavy metals generate a great need to develop efficient adsorbents for these pollutants. This study reports the adsorption of Pb(II) and Hg(II) by two reference montmorillonites, Wyoming (SWy-2) and Arizona (SAz-1), that

M. Cruz-Guzmán; R. Celis; M. C. Hermosín; W. C. Koskinen; E. A. Nater; J. Cornejo

2006-01-01

67

Method and system for treating an interior surface of a workpiece using a charged particle beam  

DOEpatents

A method and system of treating an interior surface on an internal cavity of a workpiece using a charged particle beam. A beam deflector surface of a beam deflector is placed within the internal cavity of the workpiece and is used to redirect the charged particle beam toward the interior surface to treat the interior surface.

Swenson, David Richard (Georgetown, MA) [Georgetown, MA

2007-05-23

68

Diffusion mechanism of sodium ions in compacted montmorillonite under different NaCl concentration  

NASA Astrophysics Data System (ADS)

Compacted bentonite, the major mineral being montmorillonite, is a candidate buffer material for geological disposal of high-level radioactive waste. The diffusion behavior of radionuclides in the compacted montmorillonite is an important issue to be clarified for the safety assessment of geological disposal. In this study, one-dimensional, non-steady diffusion experiments using 22Na at different diffusion temperatures and the measurement of the basal spacings by XRD were conducted for Na-montmorillonite saturated with NaCl solutions of different concentrations. Some basal spacings of the montmorillonite were found to decrease from 1.88 to 1.56 nm as the NaCl concentration increased from 0 to 0.1 M. The apparent self-diffusion coefficients at 298 K obtained in this study slightly increased as the NaCl concentration increased from 0 to 0.5 M, while the activation energies, calculated from the temperature dependences of the diffusion coefficients, were found to be 14, 22, and 17 kJ mol -1 at NaCl concentrations of 0, 0.1, and 0.5 M, respectively. These NaCl concentration dependences of the diffusion coefficients and their activation energies can be explained by assuming three independent diffusion processes (diffusion in pore water, on external surface of montmorillonite, and in interlayer of montmorillonite).

Kozaki, Tamotsu; Liu, Jinhong; Sato, Seichi

69

Controllable surface morphology and properties via mist polymerization on a plasma-treated polymethyl methacrylate surface.  

PubMed

Surface modification by grafting polymers on solid materials is an important strategy used to improve surface properties. This article reports that under appropriate conditions, very thin layers with desired morphologies may be constructed on a plasma-treated substrate by feeding a small quantity of a monomer with a mist stream carrying droplets produced from monomer solutions. We investigate the effects of process parameters that affect layer morphology, including exposure time to the mist stream, concentration of the monomer solution, and solvent selectivity. For a methyl methacrylate solution in ethanol, nanoparticles are uniformly grown with increasing monomer concentration or exposure time and finally form a porous layer at 3.65 mol L(-1) for 30 min. Decreasing solvent polarity not only affects surface morphology, but also increases hydrophobicity of the resulting surface. With 2,2,3,4,4,4-hexafluorobutyl methacrylate as the monomer, SEM and AFM micrographs indicated that mist polymerization results in numerous microspheres on the activated surface. These experimental results were interpreted by a mechanism in terms of an in situ polymerization accompanied by a phase transformation of the resulting polymer. Specifically, plasma treatment provides highly active cations and radicals to initiate very rapid polymerization, and the resulting polymers are consequently deposited from the liquid onto the surface under phase transition mechanisms. PMID:24835436

Wan, S J; Wang, L; Xu, X J; Zhao, C H; Liu, X D

2014-01-14

70

Controlled Release of Agrochemicals Intercalated into Montmorillonite Interlayer Space  

PubMed Central

Periodic application of agrochemicals has led to high cost of production and serious environmental pollution. In this study, the ability of montmorillonite (MMT) clay to act as a controlled release carrier for model agrochemical molecules has been investigated. Urea was loaded into MMT by a simple immersion technique while loading of metalaxyl was achieved by a rotary evaporation method. The successful incorporation of the agrochemicals into the interlayer space of MMT was confirmed by several techniques, such as, significant expansion of the interlayer space, reduction of Barrett-Joyner-Halenda (BJH) pore volumes and Brunauer-Emmett-Teller (BET) surface areas, and appearance of urea and metalaxyl characteristic bands on the Fourier-transform infrared spectra of the urea loaded montmorillonite (UMMT) and metalaxyl loaded montmorillonite (RMMT) complexes. Controlled release of the trapped molecules from the matrix was done in water and in the soil. The results reveal slow and sustained release behaviour for UMMT for a period of 10 days in soil. For a period of 30 days, MMT delayed the release of metalaxyl in soil by more than 6 times. It is evident that MMT could be used to improve the efficiency of urea and metalaxyl delivery in the soil.

2014-01-01

71

Controlled release of agrochemicals intercalated into montmorillonite interlayer space.  

PubMed

Periodic application of agrochemicals has led to high cost of production and serious environmental pollution. In this study, the ability of montmorillonite (MMT) clay to act as a controlled release carrier for model agrochemical molecules has been investigated. Urea was loaded into MMT by a simple immersion technique while loading of metalaxyl was achieved by a rotary evaporation method. The successful incorporation of the agrochemicals into the interlayer space of MMT was confirmed by several techniques, such as, significant expansion of the interlayer space, reduction of Barrett-Joyner-Halenda (BJH) pore volumes and Brunauer-Emmett-Teller (BET) surface areas, and appearance of urea and metalaxyl characteristic bands on the Fourier-transform infrared spectra of the urea loaded montmorillonite (UMMT) and metalaxyl loaded montmorillonite (RMMT) complexes. Controlled release of the trapped molecules from the matrix was done in water and in the soil. The results reveal slow and sustained release behaviour for UMMT for a period of 10 days in soil. For a period of 30 days, MMT delayed the release of metalaxyl in soil by more than 6 times. It is evident that MMT could be used to improve the efficiency of urea and metalaxyl delivery in the soil. PMID:24696655

Wanyika, Harrison

2014-01-01

72

Electrical and optical characteristics of surface treated ZnO nanotubes  

SciTech Connect

Highlights: ? ZnO nanotubes were formed onto an ITO glass and were surface treated. ? Photoluminescence and fluorescence imaging for ZnO nanotubes showed blue emission. ? Surface treated samples that showed green emissions. ? Lifetime measurements showed higher excitonic times in surface treated samples. ? Conductance measurements showed significant improvement for the treated samples. -- Abstract: Vertical ZnO nanotubes were electrochemically deposited onto an indium doped tin oxide glass substrate. These nanotubes were surface treated with zinc acetate and annealed at 450 °C, resulting in a nanotubes/nanoparticles composite layer. Scanning electron microscopy of the surface treated samples showed nanoparticles been dispersed uniformly along the ZnO tubular matrix, which was confirmed by X-ray diffractrometry. Photoluminescence and fluorescence microscopy showed untreated ZnO nanotubes exhibiting blue emission, while the treated samples exhibited green emissions. Ultra-violet spectroscopy of treated samples revealed lower band gap values compare to their untreated counterparts. Lifetime measurements showed higher excitonic lifetimes in treated samples. Conductance studies using atomic force microscopy showed significant improvement in the conductance values for the treated samples. A significant increase in photocurrent was observed in treated samples when used as photo-anodes in dye sensitized solar cells.

Ranjusha, R.; Sreeja, R.; Mini, P.A.; Subramanian, K.R.V. [Nano Solar Division, Amrita Center for Nanosciences, Kochi 682 041 (India)] [Nano Solar Division, Amrita Center for Nanosciences, Kochi 682 041 (India); Nair, Shantikumar V., E-mail: nairshanti@gmail.com [Nano Solar Division, Amrita Center for Nanosciences, Kochi 682 041 (India); Balakrishnan, Avinash, E-mail: avinash.balakrishnan@gmail.com [Nano Solar Division, Amrita Center for Nanosciences, Kochi 682 041 (India)] [Nano Solar Division, Amrita Center for Nanosciences, Kochi 682 041 (India)

2012-08-15

73

Biodegradable Bovine Gelatin\\/Na-Montmorillonite Nanocomposite Films. Structure, Barrier and Dynamic Mechanical Properties  

Microsoft Academic Search

Biodegradable films based on gelatin and Na-Montmorillonite were prepared by mixing of gelatin solutions with ultrasonically pre-treated clay suspensions under controlled conditions. The DRX patterns and AFM images suggested that ultrasonication process resulted in homogeneously distributed layered silicates inside the matrix but not fully exfoliated. Transparency was retained, suggesting that filler is mostly distributed at the nanoscale. The results of

J. F. Martucci; R. A. Ruseckaite

2010-01-01

74

Spectroscopic ellipsometry studies of HF treated Si (100) surfaces  

NASA Technical Reports Server (NTRS)

Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effect of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that, after a 20-sec 9:1 HF dip without rinse, the Si (100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si (100) surface was observed, in an ultrahigh vacuum chamber (UHV), and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface layer, after being heated to about 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces.

Yao, Huade; Woollam, John A.; Alterovitz, Samuel A.

1993-01-01

75

Spectroscopic ellipsometry studies of HF treated Si (100) surfaces  

NASA Technical Reports Server (NTRS)

Both ex situ and in situ spectroscopic ellipsometry (SE) measurements were employed to investigate the effects of HF cleaning on Si surfaces. The hydrogen-terminated (H-terminated) Si surface was modeled as an equivalent dielectric layer, and monitored in real time by SE measurements. The SE analyses indicate that after a 20-s 9:1 HF dip without rinse, the Si(100) surface was passivated by the hydrogen termination and remained chemically stable. Roughness of the HF-etched bare Si(100) surface was observed, in an ultrahigh vacuum (UHV) chamber, and analyzed by the in situ SE. Evidence for desorption of the H-terminated Si surface-layer, after being heated to approximately 550 C in the UHV chamber, is presented and discussed. This is the first use of an ex situ and in situ real-time, nondestructive technique capable of showing state of passivation, the rate of reoxidation, and the surface roughness of the H-terminated Si surfaces.

Yao, Huade; Woollam, John A.; Alterovitz, Samuel A.

1993-01-01

76

FT-IR spectroscopic investigation of adsorption of 3-aminopyridine on sepiolite and montmorillonite from Anatolia  

NASA Astrophysics Data System (ADS)

The adsorption of 3-aminopyridine by natural sepiolite and montmorillonite from Eskisehir (Anatolia) was investigated in the temperature range from 20 to 125°C by infrared spectrometry using a variable temperature unit. The spectroscopic results indicate that the 3-aminopyridine molecules adsorbed on sepiolite are coordinated to Lewis acidic sites and/or surface hydroxyls by H-bonding interaction through pyridine ring nitrogen lone pairs. Surface Bronsted acid strength of sepiolite is weak and 3-aminopyridinium is not detected under the conditions applied in this study. It must be noted that the adsorption of aminopyridine affected the hydroxyl group vibrations of sepiolite. The intercalation of 3-aminopyridine within montmorillonite has been shown by X-ray diffraction to increase the interlayer spacing. IR spectroscopy indicates that sorbed 3-aminopyridine molecules by montmorillonite are mostly coordinated to exchangeable cations directly or indirectly through water bridges. The formation of 3-aminopyridinium cation is also detected at elevated temperatures.

Akyüz, S.; Akyüz, T.; Yakar, A. E.

2001-05-01

77

Synthesis and properties of melamine-formaldehyde/ montmorillonite nanocomposites.  

PubMed

In this paper, intercalated and partially exfoliated melamine-formaldehyde (MF)/montmorillonite (MMT) nanocomposites have been synthesized successfully via in-situ polymerization based on pristine montmorillonite, acidified montmorillonite and organic modified montmorillonite respectively. The obtained nanocomposites were characterized by XRD, TEM, TGA, and Raman spectroscopy. Free formaldehyde content of those composites was also determined by acetyl acetone technique. It was found that acidified montmorillonite and organic modified montmorillonite could catalyze the polycondensation reaction of methylolmelamines. The thermal stability and chemical resistance of those two nanocomposites were also improved dramatically compared to pure melamine-formaldehyde resin. PMID:18572577

Wang, Haitao; Meng, Xiangfu; Qian, Zhongzhong; Zhoul, Hu; Ding, Yanfen; Zhang, Shimin; Yang, Mingshu

2008-04-01

78

Surface metal ion enhancement of thermally treated zeolites  

SciTech Connect

During the past several years the area of zeolite science has received increasingly intense attention owing to the preparation of new molecular sieves and the availability of modern spectroscopic methods for the study of these materials. The majority of spectroscopic studies of zeolites have focused on measurements of bulk magnetic, electronic, and structural properties, but few surface studies have been reported. Surface-inhomogeneous aluminum and silicon species have recently been reported by Barr and co-workers. In this study the authors have heated metal ion containing zeolites under controlled conditions in order to probe interactions between the zeolite and the metal ion. Here they present preliminary results for Ag/sup +//NaY and Cs/sup +//NaY zeolites studied by X-ray photoelectron spectroscopy (XPS), static secondary ion mass spectrometry (SSIMS), and ion scattering spectroscopy (ISS).

Willis, W.S.; Suib, S.L.

1986-09-03

79

Bone regeneration performance of surface-treated porous titanium.  

PubMed

The large surface area of highly porous titanium structures produced by additive manufacturing can be modified using biofunctionalizing surface treatments to improve the bone regeneration performance of these otherwise bioinert biomaterials. In this longitudinal study, we applied and compared three types of biofunctionalizing surface treatments, namely acid-alkali (AcAl), alkali-acid-heat treatment (AlAcH), and anodizing-heat treatment (AnH). The effects of treatments on apatite forming ability, cell attachment, cell proliferation, osteogenic gene expression, bone regeneration, biomechanical stability, and bone-biomaterial contact were evaluated using apatite forming ability test, cell culture assays, and animal experiments. It was found that AcAl and AnH work through completely different routes. While AcAl improved the apatite forming ability of as-manufactured (AsM) specimens, it did not have any positive effect on cell attachment, cell proliferation, and osteogenic gene expression. In contrast, AnH did not improve the apatite forming ability of AsM specimens but showed significantly better cell attachment, cell proliferation, and expression of osteogenic markers. The performance of AlAcH in terms of apatite forming ability and cell response was in between both extremes of AnH and AsM. AcAl resulted in significantly larger volumes of newly formed bone within the pores of the scaffold as compared to AnH. Interestingly, larger volumes of regenerated bone did not translate into improved biomechanical stability as AnH exhibited significantly better biomechanical stability as compared to AcAl suggesting that the beneficial effects of cell-nanotopography modulations somehow surpassed the benefits of improved apatite forming ability. In conclusion, the applied surface treatments have considerable effects on apatite forming ability, cell attachment, cell proliferation, and bone ingrowth of the studied biomaterials. The relationship between these properties and the bone-implant biomechanics is, however, not trivial. PMID:24811260

Amin Yavari, Saber; van der Stok, Johan; Chai, Yoke Chin; Wauthle, Ruben; Tahmasebi Birgani, Zeinab; Habibovic, Pamela; Mulier, Michiel; Schrooten, Jan; Weinans, Harrie; Zadpoor, Amir Abbas

2014-08-01

80

Core-shell structured iron nanoparticles well dispersed on montmorillonite  

NASA Astrophysics Data System (ADS)

Iron nanoparticles have been successfully synthesized using sodium borohydride solution reduction of ferric trichloride hexahydrate in the presence of montmorillonite as an effective protective reagent and support as well. A combination of characterizations reveals the well disperse of these obtained iron nanoparticles supported on the external surface of clay with roughly spherical morphology and mean diameter of 55 nm. The particles are oxidation resistant well with iron core-iron oxide shell structure. The shell thickness of 3 nm remains almost invariable under ambient conditions. Discernable hysteresis loop reveals ferromagnetic behavior of the iron nanoparticles, which make them easy for magnetic separation and potential in some practical applications.

Fan, Mingde; Yuan, Peng; Zhu, Jianxi; Chen, Tianhu; Yuan, Aihua; He, Hongping; Chen, Kangmin; Liu, Dong

2009-10-01

81

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

82

Surface characterization of plasma-treated and PEG-grafted PDMS for micro fluidic applications  

Microsoft Academic Search

The contact angle measurements have shown that polydimethyl siloxane (PDMS) surfaces treated by air plasma can recover up to about 40% of its hydrophobic nature in less than 20min of air exposure. Therefore, poly(ethylene glycol) (PEG) silane was grafted after plasma treatment to permanently change the PDMS surface as hydrophilic in nature for micro fluidic application. The surface chemistry of

Vikash Sharma; Marshal Dhayal; Govind; S. M. Shivaprasad; S. C. Jain

2007-01-01

83

Surface treated polyethylene fibres as reinforcement for acrylic resins.  

PubMed

The use of poly(methyl methacrylate) as a bone and dental cement material over several decades has provided us with experience related to processing and performance. A recognized disadvantage of such cements is their mechanical behaviour, expressed by low crack propagation resistance, impact strength, fatigue resistance and reduced fracture toughness. Many attempts have been made to resolve these problems either by modifying the poly(methyl methacrylate) chemical structure via copolymerization or incorporating reinforcing additives. The latter is of great importance, because it can lead to the preparation of composite materials with considerably improved performance. Besides reinforcement, the incorporation of additives, such as fibres, results in better processing characteristics, e.g. lowers polymerization exotherm. In this work, poly(methyl methacrylate) reinforced with Tekmilon ultra high modulus polyethylene fibres was studied, focussing on the interfacial bonding between matrix and reinforcement. Some finishing agents were used to treat the fibres and their efficiency was mainly evaluated through the effect on the mechanical properties of the composite material prepared. PMID:2009351

Andreopoulos, A G; Papaspyrides, C D; Tsilibounidis, S

1991-01-01

84

Preparation and characterization of microporous SiO 2-ZrO 2 pillared montmorillonite  

NASA Astrophysics Data System (ADS)

SiO 2-ZrO 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 Å and the calcined SZM samples showed large specific surface areas up to 320 m 2/g at 400 °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 °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; Yamanaka, Shoji

2006-04-01

85

Microstructure and mechanical properties of neoprene montmorillonite nanocomposites  

NASA Astrophysics Data System (ADS)

To investigate the microstructure and mechanical properties of neoprene-montmorillonite nanocomposite, three modified montmorillonite are used. An X-ray diffractometer is used to measure the corresponding change in d-spacing. Scanning electron microscopy is employed to investigate the morphology of the various composites. Transmission electron microscopy is employed to investigate the composite of montmorillonite and neoprene. The results indicate that the addition of montmorillonite enhances the mechanical properties of neoprene significantly.

Yeh, Meng-Heng; Hwang, Weng-Sing; Cheng, Lin-Ri

2007-03-01

86

Modelling the sorption of Mn(II), Co(II), Ni(II), Zn(II), Cd(II), Eu(III), Am(III), Sn(IV), Th(IV), Np(V) and U(VI) on montmorillonite: Linear free energy relationships and estimates of surface binding constants for some selected heavy metals and actinides  

NASA Astrophysics Data System (ADS)

In solution thermodynamics, and more recently in surface chemistry, it is well established that relationships can be found between the free energies of formation of aqueous or surface metal complexes and thermodynamic properties of the metal ions or ligands. Such systematic dependencies are commonly termed linear free energy relationships (LFER). A 2 site protolysis non-electrostatic surface complexation and cation exchange (2SPNE SC/CE) model has been used to model "in house" and literature sorption edge data for eleven elements: Mn(II), Co(II), Ni(II), Zn(II), Cd(II), Eu(III), Am(III), Sn(IV), Th(IV), Np(V) and U(VI) to provide surface complexation constants for the strong sites on montmorillonite. Modelling a further 4 sets of sorption isotherms for Ni(II), Zn(II), Eu(III) and U(VI) provided complexation constants for the weak sites. The protolysis constants and site capacities derived for the 2SPNE SC/CE model in previous work were fixed in all of the calculations. Cation exchange was modelled simultaneously to provide selectivity coefficients. Good correlations between the logarithms of strong SKx-1 and weak W1Kx-1 site binding constants on montmorillonite and the logarithm of the aqueous hydrolysis constants OHK x were found which could be described by the following equations: Strong (?S SOH) sites: logK=8.1±0.3+(0.90±0.02)logK Weak (?S W1OH) sites: logK=6.2±0.8+(0.98±0.09)logK where x is an integer. Sorption data for heavy metals and actinides such as Pd(II), Pb(II), Pu(III), Zr(IV), U(IV), Np(IV), Pu(IV) and Pa(V), are important in safety studies for radioactive waste repositories and are either very poorly known or not available at all. The LFER approach was used to estimate surface complexation constants for these radionuclides on both site types. The surface protolysis constants, site capacity values, selectivity coefficients and surface complexation constants given in this work, coupled with the LFERs established for the strong and weak sites on montmorillonite, are considered to form a sound basis for a thermodynamic sorption database.

Bradbury, Michael H.; Baeyens, Bart

2005-02-01

87

Fractionation of humic acids upon adsorption on montmorillonite and palygorskite  

NASA Astrophysics Data System (ADS)

The adsorption of three humic acid (HA) preparations by clays—montmorillonite (Wyoming, USA) and palygorskite (Kolomenskoe district, Moscow oblast)—has been studied. The HA preparations were isolated from samples of the humus-accumulative horizons of a leached chernozem (Voronezh) and a chestnut soil (Volgograd), and a commercial preparation of sodium humate (Aldrich) was also used. The solid-state 13C NMR spectroscopy and IR spectroscopy revealed the selective adsorption of structural HA fragments (alkyls, O-alkyls (carbohydrates), and acetal groups) on these minerals. As a result, the aromaticity of the organic matter (OM) in the organic-mineral complexes (OMCs) and the degree of its humification have been found to be lower compared to the original HA preparations. The fractionation of HAs is controlled by the properties of the mineral surfaces. The predominant enrichment of OMCs with alkyls has been observed for montmorillonite, as well as an enrichment with O-alkyls (carbohydrates) for palygorskite. A decrease in the C : N ratio has been noted in the elemental composition of the OM in complexes, which reflected its more aromatic nature and (or) predominant sorption of N-containing structural components of HA molecules. The adsorption of HA preparations by montmorillonite predominantly occurs on the external surface of mineral particles, and the interaction of nonpolar alkyl groups of HAs with this mineral belongs to weak (van der Waals, hydrophobic) interactions. The adsorption of HA preparations by palygorskite is at least partly of chemical nature: Si-OH groups of minerals are involved in the adsorption process. The formation of strong bonds between the OM and palygorskite explains the long-term (over 300 million years) retention of fossil fulvate-type OM in its complex with palygorskite, which we revealed previously.

Alekseeva, T. V.; Zolotareva, B. N.

2013-06-01

88

Driving force for the hydration of the swelling clays: case of montmorillonites saturated with alkaline-earth cations.  

PubMed

Important structural modifications occur in swelling clays upon water adsorption. The multi-scale evolution of the swelling clay structure is usually evidenced by various experimental techniques. However, the driving force behind such phenomena is still not thoroughly understood. It appears strongly dependent on the nature of the interlayer cation. In the case of montmorillonites saturated with alkaline cations, it was inferred that the compensating cation or the layer surface could control the hydration process and thus the opening of the interlayer space, depending on the nature of the interlayer cation. In the present study, emphasis is put on the impact of divalent alkaline-earth cations compensating the layer charge in montmorillonites. Since no experimental technique offers the possibility of directly determining the hydration contributions related to interlayer cations and layer surfaces, an approach based on the combination of electrostatic calculations and immersion data is developed here, as already validated in the case of montmorillonites saturated by alkaline cations. This methodology allows to estimate the hydration energy for divalent interlayer cations and therefore to shed a new light on the driving force for hydration process occurring in montmorillonites saturated with alkaline-earth cations. Firstly, the surface energy values obtained from the electrostatic calculations based on the Electronegativity Equalization Method vary from 450 mJ m(-2) for Mg-montmorillonite to 1100 mJ m(-2) for Ba-montmorillonite. Secondly, considering both the hydration energy for cations and layer surfaces, the driving force for the hydration of alkaline-earth saturated montmorillonites can be attributed to the interlayer cation in the case of Mg-, Ca-, Sr-montmorillonites and to the interlayer surface in the case of Ba-montmorillonites. These results explain the differences in behaviour upon water adsorption as a function of the nature of the interlayer cation, thereby allowing the macroscopic swelling trends to be better understood. The knowledge of hydration processes occurring in homoionic montmorillonites saturated with both the alkaline and the alkaline-earth cations may be of great importance to explain the behaviour of natural clay samples where mixtures of the two types of interlayer cation are present and also provides valuable information on the cation exchange occurring in the swelling clays. PMID:23352873

Salles, Fabrice; Douillard, Jean-Marc; Bildstein, Olivier; Gaudin, Cedric; Prelot, Benedicte; Zajac, Jerzy; Van Damme, Henri

2013-04-01

89

Adsorption of Co(II) from Aqueous Medium on Natural and Acid Activated Kaolinite and Montmorillonite  

Microsoft Academic Search

Hazardous metal cations enter water through the natural geochemical route or from the industrial wastes. Their separation and removal can be achieved by adsorptive accumulation of the cations on a suitable adsorbent. In the present work, toxic Co(II) ions are removed from water by accumulating them on the surface of clay minerals. Clay adsorbents are obtained from kaolinite, montmorillonite, and

Krishna G. Bhattacharyya; Susmita Sen Gupta

2007-01-01

90

Preparation and Characterization of Nano Gold Supported over Montmorillonite Clays  

NASA Astrophysics Data System (ADS)

The use of montmorillonite clays as a matrix, or as a host, for obtaining intercalated/supported metal particles has potential applications in catalysis and other areas. The gold nanoparticles were obtained from the most common anionic gold precursor HAuCl4·3H2O by deposition-precipitation (DP) methods. However, it is difficult to prepare nanoscale gold catalysts supported on silica surfaces with lower isoelectric point (IEP). Homogeneous precipitation method using urea also fails on silica surfaces. Reasons for the inefficiency of these methods are the negative charge of the metal precursor as well as the support surface and the high pH required for depositing gold nanoparticles. In the present work, we use glucose as the reductant in the presence of stabilizer for preparation of nano gold supported on montmorillonite clay. There is no need of increasing the pH of the solution to reduce the Au3+ ions. The prepared systems are characterized using various techniques such as using X-ray fluorescence (XRF), UV-VIS Diffuse reflectance spectra (DRS) and Fourier Transform infra red spectra (FTIR) to prove the efficiency of the present method.

Suraja, P. V.; Binitha, N. N.; Yaakob, Z.; Silija, P. P.

2011-02-01

91

Helmholtz Fermi surface harmonics: an efficient approach for treating anisotropic problems involving Fermi surface integrals  

NASA Astrophysics Data System (ADS)

We present a new efficient numerical approach for representing anisotropic physical quantities and/or matrix elements defined on the Fermi surface (FS) of metallic materials. The method introduces a set of numerically calculated generalized orthonormal functions which are the solutions of the Helmholtz equation defined on the FS. Noteworthy, many properties of our proposed basis set are also shared by the FS harmonics introduced by Philip B Allen (1976 Phys. Rev. B 13 1416), proposed to be constructed as polynomials of the cartesian components of the electronic velocity. The main motivation of both approaches is identical, to handle anisotropic problems efficiently. However, in our approach the basis set is defined as the eigenfunctions of a differential operator and several desirable properties are introduced by construction. The method is demonstrated to be very robust in handling problems with any crystal structure or topology of the FS, and the periodicity of the reciprocal space is treated as a boundary condition for our Helmholtz equation. We illustrate the method by analysing the free-electron-like lithium (Li), sodium (Na), copper (Cu), lead (Pb), tungsten (W) and magnesium diboride (MgB_{2}).

Eiguren, Asier; Gurtubay, Idoia G.

2014-06-01

92

Laser surface hardening of AISI 420 stainless steel treated by pulsed Nd:YAG laser  

Microsoft Academic Search

The AISI 420 martensitic stainless steel was surface-hardened by a pulsed Nd:YAG laser. The influences of process parameters (laser pulse energy, duration time and travel speed) on the depth and hardness of laser treated area and its corrosion behavior were Investigated. In the optimum process parameters, maximum hardness (490VHN) in the laser surface treated area was achieved. The pitting corrosion

B. Mahmoudi; M. J. Torkamany; A. R. Sabour Rouh Aghdam; J. Sabbaghzade

2010-01-01

93

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

94

Composition, structure, and luminescence of montmorillonites saturated with different aggregates of methylene blue.  

PubMed

The distribution of various aggregates (dimers, trimers, and tetramers) of methylene blue (MB) formed in aqueous solution at various concentrations of dye has been calculated using the equilibrium aggregation constants betaq. Two montmorillonite samples with different cation exchange capacities, surface areas, and interlayer distances d001, Na-SWy, and Ca-Cheto, were saturated with methylene blue (MB) solutions with various ratios between monomers and higher aggregates of dye. The total amount of MB in the intercalated montmorillonite samples (MB-SWy and MB-Cheto) increases with increasing concentration of dye in water solutions, i.e., with increasing aggregates/monomers ratio of MB in water solution. In all intercalated montmorillonite samples with methylene blue except guest qth aggregate cations [MBqq+] low contents of Na+ (in MB-SWy) and Ca2+ (in MB-Cheto) cations were also determined. A very good positive correlation between the basal spacing d001 and the MB/montmorillonite molar ratio was revealed for saturated MB-montmorillonite samples. Structural analysis using a combination of diffraction data with molecular modeling revealed the differences in the interlayer arrangement of MB guests in MB-SWy and MB-Cheto intercalates. Also, fluorescence measurements showed the strong effect of the silicate layer charge on the spectroscopic behavior of MB guests intercalated in montmorillonite. Methylene blue exhibits a certain luminescence in MB-SWy samples with cation exchange capacity 0.80 meq g-1 and almost no luminescence in MB-Cheto samples with higher cation exchange capacity 1.50 meq g-1. PMID:17395193

Klika, Z; Capková, P; Horáková, P; Valásková, M; Malý, P; Machán, R; Pospísil, M

2007-07-01

95

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

96

Swelling properties of copolymer hydrogels in the presence of montmorillonite and alkylammonium montmorillonite  

Microsoft Academic Search

Copolymers of different compositions were produced by polymerization of various acrylic compounds [N-isopropyl-acrylamide (NIPAAm), acrylamide (AAm) and acrylic acid (AAc)]. The swelling stability of the gels was enhanced by the addition of fillers [Na-montmorillonite (Na-m.) and montmorillonites hydrophobized with alkylammonium ions (Cn-m.), n=4, 12, 18]. Verified by X-ray diffraction (XRD) measurements that exfoliated and\\/or intercalated nanocomposites were formed.In the course

László Janovák; János Varga; Lajos Kemény; Imre Dékány

2009-01-01

97

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

98

Rheology of Ion-Exchanged Montmorillonite Clays.  

National Technical Information Service (NTIS)

The Bureau of Mines is investigating a method to dewater fine-particle clay waste. In order to more fully understand the effect of ion exchange on clay dewatering, an investigation of the rheological properties of ion-exchanged montmorillonite was underta...

D. A. Stanley S. W. Webb B. J. Scheiner

1984-01-01

99

The bond of two adhesive resins to alumina blasted and heat-treated gold alloy surfaces.  

PubMed

The purpose of this study was to test in shear mode the bond strengths of two BIS-GMA resin cements bonded to alumina blasted and heat-treated gold alloy surfaces. This was carried out in order to investigate the manufacturer's claim of the superiority of Panavia 21 over Panavia Ex. Alumina blasted gold alloy surfaces were cemented in pairs with either Panavia Ex or Panavia 21 resin cements. Heat-treated gold alloy surfaces were similarly paired. The luted pairs were stored in water at 37 degrees C for 48 h before bond was tested with shearing forces. Although the differences were not statistically significant, it was found that Panavia 21 formed stronger bonds on the alumina blasted surfaces than Panavia Ex. However, Panavia Ex exhibited higher mean strength values than Panavia 21 on the heat-treated surfaces. Not only was this difference statistically significant, but the bond strength values obtained for Panavia Ex on this surface were the highest in the data set. On the basis of bond testing in shear, it would appear that Panavia 21 is inferior to Panavia Ex on heat-treated gold alloy surfaces. PMID:10887913

Ogunyinka, A

2000-05-01

100

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

PubMed

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. PMID:22330878

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

2012-01-01

101

Characterization of the surface and the interphase of PVC-copper amine-treated wood composites  

NASA Astrophysics Data System (ADS)

Contact angles and surface energy of wood, as well as interfacial shear strength between wood and polyvinyl chloride (PVC) were investigated and used to monitor the modifications generated on the surfaces of wood treated with a copper ethanolamine solution. An increase in surface energy of wood after treatments promotes wetting of PVC on wood surfaces. Improved interfacial shear strength between treated wood and PVC matrix can be attributed to the formation of a stronger wood-PVC interphase. This suggests that treatment may be used to improve the adhesion between wood surface and PVC in the formulation of wood fiber composites to yield products with enhanced mechanical properties and better biological and physical performance against decay and insect destroying wood.

Jiang, Haihong; Kamdem, D. Pascal

2010-05-01

102

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

103

Surface properties of fluoride treated hydroxyapatite as judged by interactions with albumin and lysozyme.  

PubMed

Hydroxyapatite treated with fluoride containing both alkali soluble fluoride (CaF2) and alkali stable fluoride (FAp) was shown to take up less albumin than hydroxyapatite but more lysozyme. The affinity of the adsorption of albumin to fluoride treated apatite was increased, whereas no difference was demonstrated in the affinity of lysozyme. Tooth surfaces in vivo contain both calcium fluoride and fluoroapatite. Protein adsorption to mixed phases may thus have clinical significance. PMID:6314484

Eggen, K H; Rölla, G

1983-10-01

104

Antibacterial Property and Tribological Behavior of Duplex-Surface-Treated AISI 304 Stainless Steel  

Microsoft Academic Search

The duplex treatment of plasma alloying with Cu on plasma alloyed AISI 304 stainless steel with Ni is carried out using a double-glow plasma surface alloying technique. The antibacterial and unlubricated tribological properties of the un- treated, Ni-modified, and duplex-treated stainless steel have been investigated by using a spread plate method and a ball-on-disk wear testing method, respectively. The element

Xiangyu Zhang; Ailan Fan; Ruihua Zhu; Yong Ma; Bin Tang

2011-01-01

105

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

2011-12-15

106

Evaluation of Stability of Surface-Treated Mini-Implants in Diabetic Rabbits  

PubMed Central

Introduction. The purpose of this study was to investigate effects of surface treatment of mini-implants in diabetes-induced rabbits by comparing osseointegration around mini-implants. Methods. Twelve New Zealand white rabbits were divided into two groups (alloxan-induced diabetic group and control group). A total of 48 mini-implants were placed after four weeks of diabetic induction. 24 mini-implants were surface-treated with SLA (sandblasted with large grit, and acid etched) and the remaining 24 mini-implants had smooth surfaces. Four weeks after placement, 32 mini-implants were removed from 4 control and 4 diabetic rabbits. Insertion and removal torques were measured. The remaining 16 mini-implants from the two groups were histomorphometrically analyzed. Results. Maximum insertion torque showed no difference between diabetic and control groups, but total insertion energy was higher in control group. In surface-treated mini-implants, maximum removal torque was higher in both diabetic and control groups. Bone-implant contact (BIC) was increased in the control group when compared to the diabetic group. Surface-treated group had higher BIC than smooth surface group in both control and diabetic groups. However, there was no significantly statistical difference. Conclusions. Type 1 diabetes mellitus and surface treatment method of mini-implant affected primary stability of mini-implants. In addition, the use of orthodontic mini-implants in a diabetic patient is likely to show results similar to the healthy patient.

Oh, Nam-Hee; Kim, Eun-Young; Paek, Janghyun; Kook, Yoon-Ah; Jeong, Do-Min; Cho, Il-Sik; Nelson, Gerald

2014-01-01

107

Thermal and mechanical properties of polyurethane\\/montmorillonite nanocomposites based on a novel reactive modifier  

Microsoft Academic Search

Polyurethane\\/montmorillonite (PU\\/MMT) nanocomposites based on thermally stable, aromatic amine modifier containing active groups (methylene-bis-ortho-chloroanilline, MOCA) were synthesized by intercalative polymerisation. The cured hybrid exhibited higher thermal stability and better mechanical strength than pure polyurethane or polyurethane\\/cetyltrimethyl-ammonium-bromide (CTAB)-modified MMT (PU\\/C16-MMT). The moduli and the onset degradation temperature for the PU were obviously increased by addition of MMT treated with the MOCA

Jiawen Xiong; Yunhang Liu; Xiaohui Yang; Xinling Wang

2004-01-01

108

Synthesis and properties of modified rapeseed oil\\/montmorillonite nanocomposite fatliquoring agent  

Microsoft Academic Search

Modified rapeseed oil\\/montmorillonite (MRO\\/MMT) nanocomposite was prepared by using rapeseed oil, ethylene diamine, acrylic acid, and MMT. In order to compare MRO\\/MMT with MRO and a market product XQ-F3, they were applied in leather fatliquoring process, respectively. Sensory evaluation, physical and mechanical properties, and flame-retardant property of leather treated with different fatliquoring agents were measured. X-ray diffraction (XRD) results showed

Bin Lü; Jian-zhong Ma; Dang-ge Gao; Lei Hong; Jing Zhang; Qun-na Xu

2011-01-01

109

Propriétés catalytiques de la montmorillonite intercalée au titane dans l'oxydation de l'alcool allylique (E)-hex-2-én-1-ol  

Microsoft Academic Search

Catalytic properties of Ti-pillared montmorillonite for the epoxidation of (E)-hex-2-en-1-ol allylic alcohol. The present work is relative to the epoxidation of allylic alcohols by a well-characterised Ti-pillared montmorillonite (Ti-PILC) prepared by intercalating polymeric Ti cations formed by partial hydrolysis of TiCl4 with HCl. The interlayer distance, the specific surface area and thermal stabilities of the resulting pillared clays depend mainly

Lilia Khalfallah Boudali; Abdelhamid Ghorbel; Hassen Amri; François Figueras

2001-01-01

110

Material properties of portland cement paste with nano-montmorillonite  

Microsoft Academic Search

The nano-montmorillonite, which has characteristics of high aspect ratio and interaction between polymer chains and dispersed\\u000a nanolayers, has been widely used in the development of new reinforced nanocomposite polymers to improve their mechanical properties.\\u000a Since a potential pozzolanic reaction may occur between Portland cement paste and high amount of silicon dioxide (SiO2) in nano-montmorillonite, the effects of introduction of montmorillonite

Ta-Peng Chang; Jeng-Ywan Shih; Kuo-Ming Yang; Tien-Chin Hsiao

2007-01-01

111

Microstructure and mechanical properties of neoprene–montmorillonite nanocomposites  

Microsoft Academic Search

To investigate the microstructure and mechanical properties of neoprene–montmorillonite nanocomposite, three modified montmorillonite are used. An X-ray diffractometer is used to measure the corresponding change in d-spacing. Scanning electron microscopy is employed to investigate the morphology of the various composites. Transmission electron microscopy is employed to investigate the composite of montmorillonite and neoprene. The results indicate that the addition of

Meng-Heng Yeh; Weng-Sing Hwang; Lin-Ri Cheng

2007-01-01

112

Catalytic degradation of polystyrene using albite and montmorillonite  

Microsoft Academic Search

The performance of albite and montmorillonite clay in the catalytic degradation of polystyrene (PS) was investigated in this\\u000a study. The degradation was carried out in a semi-batch reactor with a mixture of PS and catalyst at 400-450C. Untreated montmorillonite\\u000a (Mont), aluminium pillared montmorillonite (Al-PILMont), and albite (HA) showed good catalytic activity for the degradation\\u000a of PS with very high selectivity

Kyo-Hyun Cho; Dal-Rae Cho; Kyung-Hoon Kim; Dae-Won Park

2007-01-01

113

Preparation and Characterization of Novel Montmorillonite Nanocomposites  

NASA Astrophysics Data System (ADS)

Clay minerals have historically played a consequential role in human health. While the beginnings were rooted in geophagy, a primitive act of consuming earth, the health-related uses of clay minerals have evolved and diversified over time.. As excipients in pharmaceutical formulations, clay minerals can attribute novel properties onto intercalated compounds. Intercalating oxybenzone, a UV filter, within the interlamellar space of montmorillonite is desirable in order to minimize direct contact with skin. Intercalating resveratrol, a compound known for attributing beneficial effects onto human health, may be advantageous since this compound is susceptible to cis-trans isomerisation. The strategy of using alkylammonium--modified clay was undertaken and proved successful for the intercalation of oxybenzone. The field of biopolymer/layered silicate nanocomposites is heavily researched for use in a multitude of applications. Novel montmorillonite nanocomposites were prepared with neutral guar gum and cationic guar gum, using an environmentally friendly process and are fully characterized.

Mansa, Rola

114

Permethrin transfer from treated cloth to the skin surface: Potential for exposure in humans  

Microsoft Academic Search

Permethrin is an agricultural insecticide of great interest to the military because of its repellency toward disease?bearing insects when impregnated into uniforms. However, migration of the substance from clothing to the skin surface is of toxicological importance. To quantitate leaching from treated clothing, studies were performed in which swatches of fabric impregnated with C?labeled permethrin were applied to the backs

Hubert L. Snodgrass

1992-01-01

115

Time-related wettability characteristic of acrylic resin surfaces treated by glow discharge  

Microsoft Academic Search

Statement Of Problem. Adhesion and cohesion have important roles in denture retention, and attempts have been made to improve the wettability of the acrylic resin material by surface treatments. Purpose. This study examined the initial and subsequent wettability of an acrylic resin denture base material treated under air or argon plasma atmosphere before and after exposure to air or distilled

Nehir Özden; Funda Akaltan; Sefik Suzer; Guneri Akovali

1999-01-01

116

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

NASA Astrophysics Data System (ADS)

The leaching of nickel from the surface of porous Nitinol (PNT) is mainly dependent on its surface characteristics, which can be controlled by appropriate surface treatments. In this investigation, PNT was subjected to two surface treatments, namely, water-boiling and dry-heating passivations. Phosphate buffer saline (PBS) solutions obtained from cyclic potentiodynamic polarization tests on PNT were employed to assess the cytotoxicity of Ni contained therein on osteoblast cells by Sulforhodamine B (SRB) assay. In addition, similar concentrations of Ni were added exogenously to cell culture media to determine cytotoxic effects on osteoblast cells. The morphologies of the untreated and the surface-treated PNTs were examined using SEM and AFM. Furthermore, growth of human osteoblast cells was observed on the PNT surfaces.

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

2011-07-01

117

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

PubMed Central

The leaching of nickel from the surface of porous Nitinol (PNT) is mainly dependent on its surface characteristics, which can be controlled by appropriate surface treatments. In this investigation, PNT was subjected to two surface treatments, namely, water-boiling and dry-heating passivations. Phosphate buffer saline (PBS) solutions obtained from cyclic potentiodynamic polarization tests on PNT were employed to assess the cytotoxicity of Ni contained therein on osteoblast cells by Sulforhodamine B (SRB) assay. In addition, similar concentrations of Ni were added exogenously to cell culture media to determine cytotoxic effects on osteoblast cells. The morphologies of the untreated and the surface-treated PNTs were examined using SEM and AFM. Furthermore, growth of human osteoblast cells was observed on the PNT surfaces.

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

2011-01-01

118

An investigative study of polymer adsorption onto montmorillonite clay  

NASA Astrophysics Data System (ADS)

For colloidal systems with adsorbed polymer, the mechanisms governing stabilization and flocculation are defined by the critical overlap concentration, c*. Below c*, steric stabilization or bridging flocculation are viable mechanisms of adsorption, while above c* associative thickening stabilization, depletion stabilization or depletion flocculation may occur. While these types of systems have been described by their mechanism of interaction, few studies have been geared towards evaluating and actually defining these interactions. This research focuses on elucidating the mechanisms of interaction for a series of polyacrylamide copolymers adsorbed onto montmorillonite clay. The well-defined copolymers synthesized and characterized for these studies include: nonionic polyacrylamide, (PAm); cationic poly(acrylamide-co-[3-(methacryloylamino) propyl] trimethylammonium chloride), (PAmMaap Quat); nonionic/anionic poly(acrylamide-co-acrylic acid), (PAmAA); and anionic poly(acrylamide-co-[2-acrylamido-2-methylpropane sulfonic acid]), (PAmAmps). By combining the results from the following experiments it was possible to determine the mechanisms of interaction for each of the clay/polymer systems at pH 3, 7 and 10. The adsorption capacity of each of the copolymers was determined from constructing adsorption isotherms while the polymer conformation was determined from 13C NMR line-broadening experiments. FTIR spectroscopy verified which surface of the clay was involved in adsorption along with the polymer moiety bound to the surface. Finally, the stabilization behavior was evaluated from statistically designed phase diagrams as a function of polymer and clay concentrations. By evaluating the phase behavior as well as c* for the polymer/solvent systems, it was determined that there was no direct correlation between c* for a polymer/solvent system and the mechanism of interaction for colloid/polymer/solvent systems previously defined by Vincent, Sato and Napper. In general, the nonionic polymers act as H-bond acceptors (amide and acid moieties) and donators (acid groups) which result in associatively stabilized homogeneous montmorillonite clay dispersions. The cationic copolymers exhibit strong, irreversible interactions with the clay resulting in heterogeneous bridging flocculation, which was shown to be dependent on the charge density of the copolymer. Furthermore, the anionic copolymers show no signs of adsorption, but create a network of repulsive forces with the montmorillonite clay, which ultimately results in depletion stabilization with some degree of depletion flocculation.

McConnell Boykin, Cheri Lynn

119

Fibroblastic response and surface characterization of O(2)-plasma-treated thermoplastic polyetherurethane.  

PubMed

Injection-molded samples of thermoplastic polyetherurethane (TPU) were treated with low-temperature oxygen plasma for different processing times in order to enhance cellular attachment for a gastric implant. Its effects were investigated by contact angle measurement, surface topography, cytotoxicity and cell colonization tests. No significant changes were found in the surface roughness of plasma treatment with plasma treatment time of less than 5 min. Longer treatment showed significantly higher surface roughness. It seems that there was a link between the changes in contact angle and enhanced cell growth on the treated surface, although only for the range up to plasma treatment times of 3 min. Prolonged treatment times did not cause any major changes in the water contact angle, but strongly improved the number of growing cells on the surface. Plasma treatment for 3-7 min led to a twofold increase in the number of cells compared to untreated samples and did not significantly alter the WST-1 nor worsened the lactate dehydrogenase activity compared to the control. Thus, it appears that O(2) plasma treatment is a suitable surface modification method for a gastric implant made of TPU in order to improve surface cell attachment where 3-7 min is the recommended treatment time. PMID:20208128

Schlicht, Henning; Haugen, Håvard J; Sabetrasekh, Roya; Wintermantel, Erich

2010-04-01

120

Boronizing Transition-Metal Surfaces: Treated surfaces are hardened and protected against corrosion.  

National Technical Information Service (NTIS)

This citation summarizes a one-page announcement of technology available for utilization. A new process chemically bonds a surface layer of boron to a transition-metal substrate. The method might be used to provide corrosion resistance for the positive-el...

1983-01-01

121

Study of reticulated vitreous carbon surface treated by plasma immersion ion implantation for electrodes production  

NASA Astrophysics Data System (ADS)

RVC samples were treated by nitrogen plasma immersion ion implantation (N-PIII) for electrodes production. High-voltage pulses with amplitudes of -3.0 kV or -10.0 kV were applied to the RVC samples while the treatment time was 10, 20 and 30 min. The samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The SEM images present an apparent enhancement of the surface roughness after the treatment probably due to the surface sputtering during the PIII process. This observation is in agreement with the specific electrochemical surface area (SESA) of RVC electrodes. An increase was observed of the SESA values for the PIII-treated samples compared to the untreated specimen. Some oxygen and nitrogen containing groups were introduced on the RVC surface after the PIII treatment. Both plasma-induced process: the surface roughening and the introduction of the polar species on the RVC surface are beneficial for the RVC electrodes application.

Silva, L. L. G.; Conceição, D. A. S.; Oishi, S. S.; Toth, A.; Ueda, M.

2012-03-01

122

Stability of the hydrophilic and superhydrophobic properties of oxygen plasma-treated poly(tetrafluoroethylene) surfaces.  

PubMed

Poly(tetrafluoroethylene) (PTFE) materials were exposed to low and high-energy oxygen plasma, and the stability of the materials' surface was evaluated using contact angle, surface roughness, and surface chemistry characterizations. Lower-energy oxygen plasma treatments exhibited hydrophilic behavior with contact angles as low as 87°, and the higher-energy oxygen plasma treatments exhibited superhydrophobic behavior with contact angles as high as 151°. The wettability of all the treated samples as stored in air and in water was found to be stable in time as evidenced by the statistically insignificant differences in the advancing, receding, and hysteresis contact angles. Low contact angle hysteresis (?H<5°) and low sliding angle (??4°) were exhibited by the superhydrophobic surface. The surface morphology was found to be responsible for the changes in the wettability of the PTFE samples since (1) there was an increase in the surface rms roughness as the plasma discharge energy was increased, and (2) there were no significant changes in the observed group frequencies of the FT-IR spectra of the treated PTFE from the untreated PTFE. PMID:23403114

Salapare, Hernando S; Guittard, Frédéric; Noblin, Xavier; Taffin de Givenchy, Elisabeth; Celestini, Franck; Ramos, Henry J

2013-04-15

123

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

124

Study of Np(V) Sorption by Ionic Exchange on Na, K, Ca and Mg-Montmorillonite  

NASA Astrophysics Data System (ADS)

The transport behavior of actinides in soil and ground water are highly influenced by clay minerals due to their ubiquity in the environment, reactivity and colloidal properties. Neptunium(V) has been introduced in the environment as a result of nuclear weapons testing [e.g. 1, 2] and is a radionuclide of potential interest for safety assessment of high level radioactive waste disposal because its long half-life and high toxicity [3]. Surface complexation and ionic exchange have been identified as Np(V) sorption mechanisms onto montmorillonite. At pH below 5, Np(V) sorption is mainly attributed to ionic exchange. This study examines Np(V) ion exchange on Na, K, Ca and Mg forms of montmorillonite. Experiments were carried out using 237Np concentrations between 2 x 10-8 M and 5 x 10-6 M at three different ionic strengths 0.1, 0.01 and 0.001M. The pH was maintained at 4.5. Np(V) sorption to montmorillonite homoionized with monovalent cations (Na and K) demonstrated a markedly different behavior to that observed for montmorillonite homoionized with divalent cations (Ca and Mg). Np sorption to Na and K-montmorillonite was greater than Np sorption to Ca and Mg-montmorillonite. Isotherms with Na and K-montmorillonite showed a strong dependence on ionic strength: the percentage of Np adsorbed was near zero at 0.1M ionic strength, but increased to 30% at 0.001 M ionic strength. This suggests ionic exchange is the main Np adsorption mechanism under the experimental conditions investigated. Dependence on ionic strength was not observed in the Np sorption isotherms for Ca and Mg-montmorillonite indicating a low exchange capacity between Np and divalent cations. Modeling of the sorption experimental data will allow determination of the Na+?NpO2+ and K+?NpO2+ ionic exchange constants on montmorillonite. References: [1] A. R. Felmy; K. J. Cantrell; S. D. Conradson, Phys. Chem. Earth 2010, 35, 292-297 [2] D. K. Smith; D. L. Finnegan; S. M. Bowen, J. Environ. Radioact. 2003, 67, (1), 35-51 [3] N. Kozai; T. Ohnuki; S. Muraoka, J. Nucl. Sci. Technol. 1993, 30, (11), 1153-1159 This work was funded by U. S. DOE Office of Biological & Environmental Sciences, Subsurface Biogeochemistry Research Program, and performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344. A. Benedicto was supported by a Spanish Ministry of Science and Innovation 'FPI' pre-doctoral contract in CIEMAT (Spain). LLNL-ABS-570160

Benedicto, A.; Begg, J.; Zhao, P.; Kersting, A. B.; Zavarin, M.

2012-12-01

125

ADSORPTION OF NONIONIC AND ANIONIC POLYMERS ON ?-ALUMINA AND NA-MONTMORILLONITE AND THEIR MIXTURES  

Microsoft Academic Search

Adsorption isotherms of nonionic polyvinylpyrrolidone (PVP) and anionic ionized polyacrylic acid (PAA) polymers on single Na-montmorillonite clay and ?-alumina adsorbents in 0.01M NaCl and pH 5.6 are reported and compared to results obtained with aqueous adsorbent mixtures. Microeiectrophoretic behaviours of adsorbents are also observed.It can be shown that antagonistic effects due to interactions between oppositely charged adsorbent surfaces largely limit

F. Baßmann; J.-M. Sèquaris; H.-D. Narres; M. J. Schwuger

1999-01-01

126

Stearyl Amine Ethoxylate (SAM) Grafted Montmorillonite Clay - Styrene Butadiene Rubber (SBR) Nanocomposites  

Microsoft Academic Search

Present study describes the modification montmorillonite clay (kunipia F) surface by grafting Stearyl Amine Ethoxylate (SAM). Wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) provided the evidences of formation of nanocomposite. The inter layer spacing of the kunipia clay was increased from 1.22 nm (unmodified) to 1.53 nm (modified). TEM study revealed the intercalated and partially exfoliated nature of the

Sugata Chakraborty; Partha Protim Mallick; Saikat Dasgupta; Rabindra Mukhopadhyay

2012-01-01

127

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

128

Diffusion mechanism of chloride ions in sodium montmorillonite  

Microsoft Academic Search

For safety assessment of geological disposal of HLW, it is necessary to understand the diffusion mechanism of radionuclides in compacted bentonite. In this study, the diffusion behavior of chloride ions in compacted montmorillonite was studied from the viewpoints of the activation energy for apparent diffusion and the basal spacing of the compacted montmorillonite. A unique change in the activation energy

Tamotsu Kozaki; Koichi Inada; Seichi Sato; Hiroshi Ohashi

2001-01-01

129

Flame treatment on plastic: A new surface free energy statistical prediction model and characterization of treated surfaces  

NASA Astrophysics Data System (ADS)

Flame treatments on polymeric materials improve surface free energy (SFE) and consequently the wettability and adhesion of coatings, metallizations, varnish and glues. In this paper, using a statistical methodological approach based on DoE technique and multivariate analysis of flame treatment process parameters, a mathematical model of SFE and wettability is obtained. Contact angle experimental technique was applied to measure the improvement of wettability and SFE. In order to study the oxygen diffusion within the polymer, morphological variation and change of its structure, analyses of treated surface sample were carried out on micro and nano scales. X-ray photoelectron spectroscopy analysis, performed before and after flame treatment, showed the O-radical group improvement on a polymeric surface. Focused ion beam and transmission electron microscopy technology were used to determine the exact thickness of the polymeric material influenced by flame treatment, identifying a composite change on nano scale and a porosity change on microscale.

Mazzola, L.; Bemporad, E.; Carassiti, F.

2011-01-01

130

Residual Stress Assessment in Surface-Treated Metals by Laser-Ultrasonic Spectroscopy  

SciTech Connect

This paper presents experimental data obtained on shot-peened aluminum 2024-T351 samples, which indicate that the dispersion of the surface wave is affected by surface roughness, compressive residual stress, and cold work. Although the surface roughness induced component is often the dominant part in the overall dispersion of the SAW, the experimental data indicate that it is feasible to observe a substantial and highly characteristic change in the velocity of the SAW when the specimen is heat treated at different annealing temperatures. The part of the dispersion, which changes during annealing via thermal relaxation, is due to near-surface residual stresses and the decay of texture, although at high frequencies non-uniform grain coarsening could also play a significant role.

Ruiz, A.; Nagy, P.B. [Department of Aerospace Engineering and Engineering Mechanics, University of Cincinnati, Cincinnati, Ohio 45221-0070 (United States)

2004-02-26

131

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

132

High temperature erosion characteristics of surface treated SUS410 stainless steel  

Microsoft Academic Search

This study investigated the high temperature erosion characteristics of two types of surface-treated SUS410 steels; overlay welding and forging of the base metal. Two-layer overlay welding of 6mm and forging with a 10% reduction, were used on a base metal of SUS410, to prepare specimens. High temperature solid particle erosion tests using a test temperature of 1173K were performed using

K. Shimizu; Y. Xinba; M. Ishida; T. Kato

2011-01-01

133

Chemical and structural modifications of laser treated iron surfaces: investigation of laser processing parameters  

Microsoft Academic Search

This study focuses on the chemical, morphological and structural characterization of iron surfaces treated by laser in ambient air. Incorporation of nitrogen over a 1–2?m thickness (10–30at.% at the profile maximum) and superficial oxidation on 200–400nm depth have been evidenced by nuclear reaction analyses. X-ray diffraction at grazing incidence has shown the formation of FeO and Fe3O4 oxide phases as

A. L Thomann; A. Basillais; M. Wegscheider; C. Boulmer-Leborgne; A. Pereira; P. Delaporte; M. Sentis; T. Sauvage

2004-01-01

134

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

135

[Streptococcus mutans colonization on titanium surfaces treated with various fluoride-containing preventive solutions].  

PubMed

Fluoride is a reductive agent and may modify the oxide layer of titanium (Ti) in the transgingival region of dental implants. The low pH and the high fluoride concentration of prophylactic mouthwashes and gels (used in caries prevention) may play a role in this phenomenon. Our main goal was to examine whether changes on the surface structure of Ti caused by high fluoride concentration and acidic pH alter the adherence and the colonization of bacteria. Polished commercially pure Ti discs (CP grade 4, Camlog, Biotechnologies AG, Switzerland) were used in the study. Each sample was treated for 1 hour with one of the solutions: mouthwash containing 0.025% (250 ppm) fluoride, a gel containing 1.25% (12500 ppm) fluoride, and a solution of 1% NaF (3800 ppm fluoride), pH 4.5. The surface structure of the discs was analyzed by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The colonization of Streptococcus mutans was studied by scanning electron microscope (SEM) after a 5-day incubation period. The roughness of the treated sample surfaces (Ra), as revealed by AFM measurements, increased 1.3 times for the gel and the mouthwash, and approximately seven folds for the 1% NaF solution, as compared to the control surface. The high fluoride concentration and acidic pH of the gel and the 1% NaF solution resulted in a strong corrosion and a modification of the composition of the Ti surface. The XPS spectra showed the formation of a fluoride containing complex (Na2TiF6) bound strongly to the surface. A correlation was revealed between the roughness of the surface and thickness and maturity of the S. mutans bacterial colonies developed on the modified Ti surface. High fluoride concentration and acidic pH increased the roughness of the Ti surface. Bacterial biofilm colonization on this rough surface proved to be more mature. The amount of bacteria was increased due to the changes in the surface caused by fluoride treatment. The present study indicates that high fluoride concentration in an acidic pH environment may affect the development of a healthy transgingival epithelial junction on the Ti surface. This work was supported by the SIMI-NAS Project of the 5th FWP of the European Commission (Growth Program, GRD3-2001-61801), the Hungarian Ministry of Economy and the EC (GVOP-3.2.1.-2004-04-0408/3.0), the Hungarian Ministry of Health (ETT, 434/2006), and the Hungarian Scientific Research Fund (OTKA F-68440). PMID:19618781

Stájer, Anette; Urban, Edit; Mihalik, Erzsébet; Rakonczay, Zoltán; Nagy, Erzsébet; Fazekas, András; Turzó, Kinga; Radnai, Márta; Nagy, Katalin

2009-06-01

136

Thermal transitions of montmorillonite\\/polyurethane nanocomposites  

Microsoft Academic Search

The hard-segment phase thermal transitions and heat-resistance of benzidine-modified-montmorillonite (BZD-Mont)\\/polyurethane\\u000a nanocomposites of different hard segment contents were found to be affected by a small amount of BZD-Mont. In particular,\\u000a the presence of less than 5 wt% layered silicates from BZD-Mont can result in hard segments not only having a more thermally\\u000a stable long-range order and a higher melting temperature, but

Y. I. Tien; K. H. Wei

2000-01-01

137

Corrosion behavior of Al-surface-treated steels in liquid Pb?Bi in a pot  

NASA Astrophysics Data System (ADS)

Corrosion tests were performed in oxygen-saturated liquid Pb-Bi at 450 °C and 550 °C in a pot for 3000 h for Al-surface-treated steels containing various levels of Cr contents. The Al surface treatments were achieved using a gas diffusion method and a melt dipping method. Al 2O 3, FeAl 2 and AlCr 2 produced by the gas diffusion method exhibited corrosion resistance to liquid Pb-Bi, while the surface layer produced by the melt dipping method suffered a severe corrosion attack. Fe 4Al 13 and Fe 2Al 5 produced by the melt dipping method disappeared during the corrosion test at 550 °C and only FeAl remained.

Kurata, Y.; Futakawa, M.; Saito, S.

2004-12-01

138

Effects of pH on Dielectric Relaxation of Montmorillonite, Allophane, and Imogolite Suspensions.  

PubMed

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. Copyright 1999 Academic Press. PMID:10072285

Ishida; Makino

1999-04-01

139

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] [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.] [National Inst. of Agro-Environmental Sciences of Japan, Tsukuba, Ibaraki (Japan). Soil Chemistry Lab.

1999-04-01

140

Sorption/Desorption Interactions of Plutonium with Montmorillonite  

NASA Astrophysics Data System (ADS)

Plutonium (Pu) release to the environment through nuclear weapon development and the nuclear fuel cycle is an unfortunate legacy of the nuclear age. In part due to public health concerns over the risk of Pu contamination of drinking water, predicting the behavior of Pu in both surface and sub-surface water is a topic of continued interest. Typically it was assumed that Pu mobility in groundwater would be severely restricted, as laboratory adsorption studies commonly show that naturally occurring minerals can effectively remove plutonium from solution. However, evidence for the transport of Pu over significant distances at field sites highlights a relative lack of understanding of the fundamental processes controlling plutonium behavior in natural systems. At several field locations, enhanced mobility is due to Pu association with colloidal particles that serve to increase the transport of sorbed contaminants (Kersting et al., 1999; Santschi et al., 2002, Novikov et al., 2006). The ability for mineral colloids to transport Pu is in part controlled by its oxidation state and the rate of plutonium adsorption to, and desorption from, the mineral surface. Previously we have investigated the adsorption affinity of Pu for montmorillonite colloids, finding affinities to be similar over a wide range of Pu concentrations. In the present study we examine the stability of adsorbed Pu on the mineral surface. Pu(IV) at an initial concentration of 10-10 M was pre-equilibrated with montmorillonite in a background electrolyte at pH values of 4, 6 and 8. Following equilibration, aliquots of the suspensions were placed in a flow cell and Pu-free background electrolyte at the relevant pH was passed through the system. Flow rates were varied in order to investigate the kinetics of desorption and hence gain a mechanistic understanding of the desorption process. The flow cell experiments demonstrate that desorption of Pu from the montmorillonite surface cannot be modeled as a simple first order process. Furthermore, a pH dependence was observed, with less desorbed at pH 4 compared to pH 8. We suggest the pH dependence is likely controlled by reoxidation of Pu(IV) to Pu(V) and aqueous speciation. We will present models used to describe desorption behavior and discuss the implications for Pu transport. References: Kersting, A.B.; Efurd, D.W.; Finnegan, D.L.; Rokop, D.J.; Smith, D.K.; Thompson J.L. (1999) Migration of plutonium in groundwater at the Nevada Test Site, Nature, 397, 56-59. Novikov A.P.; Kalmykov, S.N.; Utsunomiya, S.; Ewing, R.C.; Horreard, F.; Merkulov, A.; Clark, S.B.; Tkachev, V.V.; Myasoedov, B.F. (2006) Colloid transport of plutonium in the far-field of the Mayak Production Association, Russia, Science, 314, 638-641. Santschi, P.H.; Roberts, K.; Guo, L. (2002) The organic nature of colloidal actinides transported in surface water environments. Environ. Sci. Technol., 36, 3711-3719. This work was funded by U. S. DOE Office of Biological & Environmental Sciences, Subsurface Biogeochemistry Research Program, and performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344. LLNL-ABS-570161

Begg, J.; Zavarin, M.; Zhao, P.; Kersting, A. B.

2012-12-01

141

The stability of radio-frequency plasma-treated polydimethylsiloxane surfaces.  

PubMed

Polydimethylsiloxane (PDMS) is a widely used material for manufacturing lab-on-chip devices. However, the hydrophobic nature of PDMS is a disadvantage in microfluidic systems. To transform the hydrophobic PDMS surface to hydrophilic, it was treated with radio-frequency (RF) air plasma at 150, 300, and 500 mTorr pressures for up to 30 min. Following the surface treatment, the PDMS specimens were stored in air, deionized water, or 0.14 M NaCl solution at 4 degrees C, 20 degrees C, and 70 degrees C. The change in the hydrophilicity (wettability) of the PDMS surfaces was 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 was 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 tended toward a more hydrophilic/less hydrophobic environment during the relaxation processes. The correlation between the FTIR-ATR spectral information and the contact angle data supports this interpretation. PMID:17279784

Chen, I-Jane; Lindner, Ernö

2007-03-13

142

Sorption of tetracycline on organo-montmorillonites.  

PubMed

Tetracycline (TC) is a veterinary antibiotic that is frequently detected as pollutant in the environment. Powerful adsorbents are required for removing TC. The present paper compares the TC adsorption capacity of Na-montmorillonite (Na-mont) with six organo-montmorillonites (organo-monts). Three quaternary ammonium cations (QACs) with different alkyl-chain lengths were used as modifiers. Powder X-ray diffraction indicated that the d(001) values of organo-monts increased with increasing the QACs loading and alkyl-chain length. The CECs of the organo-monts were substantially lower than that of Na-mont and decreased with QACs chain length and increased loading. The modeling of the adsorption kinetics revealed that the processes of TC adsorption on the tested samples could be well fitted by the pseudo-second-order equation. The maximum adsorption capacities of TC on the organo-monts (1000-2000mmol/kg) were considerably higher than that on Na-mont (769mmol/kg). Both the Langmuir and Freundlich model could fit the adsorption isotherms. The TC adsorption to the organo-monts increase significantly with decreasing the pH below 5.5 because of the electrostatic interaction, and a high QACs loading performed better than a low loading at around pH 3. PMID:22609390

Liu, Niu; Wang, Ming-xia; Liu, Ming-ming; Liu, Fan; Weng, Liping; Koopal, Luuk K; Tan, Wen-feng

2012-07-30

143

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

144

Aggregation of montmorillonite and organic matter in aqueous media containing artificial seawater  

PubMed Central

Background The dispersion-aggregation behaviors of suspended colloids in rivers and estuaries are affected by the compositions of suspended materials (i.e., clay minerals vs. organic macromolecules) and salinity. Laboratory experiments were conducted to investigate the dispersion and aggregation mechanisms of suspended particles under simulated river and estuarine conditions. The average hydrodynamic diameters of suspended particles (representing degree of aggregation) and zeta potential (representing the electrokinetic properties of suspended colloids and aggregates) were determined for systems containing suspended montmorillonite, humic acid, and/or chitin at the circumneutral pH over a range of salinity (0 – 7.2 psu). Results The montmorillonite-only system increased the degree of aggregation with salinity increase, as would be expected for suspended colloids whose dispersion-aggregation behavior is largely controlled by the surface electrostatic properties and van der Waals forces. When montmorillonite is combined with humic acid or chitin, the aggregation of montmorillonite was effectively inhibited. The surface interaction energy model calculations reveal that the steric repulsion, rather than the increase in electronegativity, is the primary cause for the inhibition of aggregation by the addition of humic acid or chitin. Conclusion These results help explain the range of dispersion-aggregation behaviors observed in natural river and estuarine systems. It is postulated that the composition of suspended particles, specifically the availability of steric polymers such as those contained in humic acid, determine whether the river suspension is rapidly aggregated and settled or remains dispersed in suspension when it encounters increasingly saline environments of estuaries and oceans.

2009-01-01

145

Electrochemical analysis of the UV treated bactericidal Ti6Al4V surfaces.  

PubMed

This research investigates in detail the bactericidal effect exhibited by the surface of the biomaterial Ti6Al4V after being subjected to UV-C light. It has been recently hypothesized that small surface currents, occurring as a consequence of the electron-hole pair recombination taking place after the excitation process, are behind the bactericidal properties displayed by this UV-treated material. To corroborate this hypothesis we have used different electrochemical techniques, such as electrochemical impedance spectroscopy (EIS), potentiodynamic polarization plots and Mott-Schottky plots. EIS and Mott-Schottky plots have shown that UV-C treatment causes an initial increase on the surface electrical conduction of this material. In addition, EIS and polarization plots demonstrated that higher corrosion currents occur at the UV treated than at the non-irradiated samples. Despite this increase in the corrosion currents, EIS has also shown that such currents are not likely to affect the good stability of this material oxide film since the irradiated samples completely recovered the control values after being stored in dark conditions for a period not longer than 24h. These results agree with the already-published in vitro transitory behavior of the bactericidal effect, which was shown to be present at initial times after the biomaterial implantation, a crucial moment to avoid a large number of biomaterial associated infections. PMID:23827637

Pacha-Olivenza, Miguel A; Gallardo-Moreno, Amparo M; Vadillo-Rodríguez, Virginia; González-Martín, M Luisa; Pérez-Giraldo, Ciro; Galván, Juan C

2013-04-01

146

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

147

Attachment of polymer chains on plasma-treated surfaces: experiments and modeling  

NASA Astrophysics Data System (ADS)

Deposition of linear polymers, such as polyethylene glycol (PEG), on a plasma-treated surface has been studied experimentally and theoretically by means of Monte Carlo (MC) simulations. Acrylic acid is deposited on a silicon wafer in the presence of argon at a pressure of 10 Pa by applying 30 W external power. Active carboxyl sites are obtained having a surface number density of ~2 sites nm-2. A homogeneous PEG solution is brought into contact with the treated surface (over 24 h) and a thin film of attached PEG chains is formed. Two different PEGs having molecular weights of 3000 and 5000 g mol-1, respectively, are considered. The corresponding thin film widths, W, are measured, yielding W(3000)=4.3±3.1 nm and W(5000)=8.8±1.8 nm. For the MC simulations, the linear polymers are modeled as an ensemble of self-avoiding walks of length N (number of monomers) on a simple cubic lattice, executing worm-like or reptation dynamics, which can become attached at an active carboxyl site on the surface. The numerical results for the film widths are in good agreement with the experimental findings. We find that less than 20% of active sites are effectively occupied by attached chains, corresponding to less than 5% of the total available surface sites. Scaling arguments predict universal power-law dependences of the film density, ?(N), as a function of polymer length, i.e. ?(N)~c/N?, with csime5 g cm-3 and ?sime0.6. The model also predicts a dependence of the prefactor c on the density of carboxyl active sites.

Riccardi, C.; Roman, H. E.; Ziano, R.

2010-07-01

148

X-ray photoelectron spectroscopy of surface-treated indium-tin oxide thin films  

NASA Astrophysics Data System (ADS)

Angle-resolved X-ray photoelectron spectroscopy and photothermal deflection spectroscopy are used to study the oxygen-plasma or aquaregia treated indium-tin oxide (ITO) anodes for organic light-emitting diodes. Detailed analysis of the O1s core-level spectra and their dependence on photoemission angle was performed. The results indicate the presence of different chemical forms of oxygen atoms (two types of O 2-, OH -, organic oxygens and H 2O) which evolve with surface treatment. We find that the treatments lead to a modification of the surface chemical states and therefore of the physico-chemical properties of ITO, which in turn control the performance of organic light-emitting diodes.

Kim, J. S.; Ho, P. K. H.; Thomas, D. S.; Friend, R. H.; Cacialli, F.; Bao, G.-W.; Li, S. F. Y.

1999-12-01

149

A nanomedicine to treat ocular surface inflammation: performance on an experimental dry eye murine model.  

PubMed

MUC5AC is a glycoprotein with gel-forming properties, whose altered expression has been implicated in the pathogenesis of dry eye disease. The aim of our study was to achieve an efficient in vivo transfection of MUC5AC, restore its normal levels in an inflamed ocular surface and determine whether restored MUC5AC levels improve ocular surface inflammation. Cationized gelatin-based nanoparticles (NPs) loaded with a plasmid coding a modified MUC5AC protein (pMUC5AC) were instilled in healthy and experimental dry eye (EDE) mice. MUC5AC expression, clinical signs, corneal fluorescein staining and tear production were evaluated. Ocular specimens were processed for histopathologic evaluation, including goblet cell count and CD4 immunostaining. Neither ocular discomfort nor irritation was observed in vivo after NP treatment. Expression of modified MUC5AC was significantly higher in ocular surface tissue of pMUC5AC-NP-treated animals than that of controls. In healthy mice, pMUC5AC-NPs had no effect on fluorescein staining or tear production. In EDE mice, both parameters significantly improved after pMUC5AC-NP treatment. Anterior eye segment of treated mice showed normal architecture and morphology with lack of remarkable inflammatory changes, and a decrease in CD4+ T-cell infiltration. Thus, pMUC5AC-NPs were well tolerated and able to induce the expression of modified MUC5A in ocular surface tissue, leading to reduction of the inflammation and, consequently improving the associated clinical parameters, such as tear production and fluorescein staining. These results identify a potential application of pMUC5AC-NPs as a new therapeutic modality for the treatment of dry eye disease. PMID:22809996

Contreras-Ruiz, L; Zorzi, G K; Hileeto, D; López-García, A; Calonge, M; Seijo, B; Sánchez, A; Diebold, Y

2013-05-01

150

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

151

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

152

Montmorillonite-induced Bacteriophage ?6 Disassembly  

NASA Astrophysics Data System (ADS)

It is estimated that there are 1031 virus particles on Earth making viruses an order of magnitude more prevalent in number than prokaryotes with the vast majority of viruses being bacteriophages. Clays are a major component of soils and aquatic sediments and can react with RNA, proteins and bacterial biofilms. The clays in soils serve as an important moderator between phage and their host bacteria, helping to preserve the evolutionary balance. Studies on the effects of clays on viral infectivity have given somewhat contradictory results; possibly a consequence of clay-virus interactions being dependent on the unique structure of particular viruses. In this work, the interaction between montmorillonite and the bacteriophage ?6 is investigated. ?6 is a member of the cystovirus family that infects Pseudomonas syringe, a common plant pathogen. As a member of the cystovirus family with an enveloped structure, ?6 serves as a model for reoviruses, a human pathogen. Experiments were conducted with ?6 suspended in dilute, purified homoionic commercial-grade montmorillonite over a range of virus:clay ratios. At a 1:100000 virus:clay ratio, the clay reduced viral infectivity by 99%. The minimum clay to virus ratio which results in a measurable reduction of P. syringae infection is 1:1. Electron microscopy demonstrates that mixed suspensions of smectite and virus co-aggregate to form flocs encompassing virions within the smectite. Both free viral particles as well as those imbedded in the flocs are seen in the micrographs to be missing the envelope- leaving only the nucleocapsid (NC) intact; indicating that smectite inactivates the virus by envelope disassembly. These results have strong implications in the evolution of both the ?6 virus and its P. syringae host cells. TEM of aggregate showing several disassembled NCs.

Trusiak, A.; Gottlieb, P.; Katz, A.; Alimova, A.; Steiner, J. C.; Block, K. A.

2012-12-01

153

Disassembly of the cystovirus ?6 envelope by montmorillonite clay.  

PubMed

Prior studies of clay-virus interactions have focused on the stability and infectivity of nonenveloped viruses, yielding contradictory results. We hypothesize that the surface charge distribution of the clay and virus envelope dictates how the components react and affect aggregation, viral stability, and infectivity. The bacteriophage Cystoviridae species ?6 used in this study is a good model for enveloped pathogens. The interaction between ?6 and montmorillonite (MMT) clay (the primary component of bentonite) is explored by transmission electron microscopy. The analyses show that MMT-?6 mixtures undergo heteroaggregation, forming structures in which virtually all the virions are either sequestered between MMT platelet layers or attached to platelet edges. The virions swell and undergo disassembly resulting in partial or total envelope loss. Edge-attached viral envelopes distort to increase contact area with the positively charged platelet edges indicating that the virion surface is negatively charged. The nucleocapsid (NCs) remaining after envelope removal also exhibit distortion, in contrast to detergent-produced NCs which exhibit no distortion. This visually discernible disassembly is a mechanism for loss of infectivity previously unreported by studies of nonenveloped viruses. The MMT-mediated sequestration and disassembly result in reduced infectivity, suggesting that clays may reduce infectivity of enveloped pathogenic viruses in soils and sediments. PMID:24357622

Block, Karin A; Trusiak, Adrianna; Katz, Al; Gottlieb, Paul; Alimova, Alexandra; Wei, Hui; Morales, Jorge; Rice, William J; Steiner, Jeffrey C

2014-02-01

154

Disassembly of the cystovirus ?6 envelope by montmorillonite clay  

PubMed Central

Prior studies of clay–virus interactions have focused on the stability and infectivity of nonenveloped viruses, yielding contradictory results. We hypothesize that the surface charge distribution of the clay and virus envelope dictates how the components react and affect aggregation, viral stability, and infectivity. The bacteriophage Cystoviridae species ?6 used in this study is a good model for enveloped pathogens. The interaction between ?6 and montmorillonite (MMT) clay (the primary component of bentonite) is explored by transmission electron microscopy. The analyses show that MMT–?6 mixtures undergo heteroaggregation, forming structures in which virtually all the virions are either sequestered between MMT platelet layers or attached to platelet edges. The virions swell and undergo disassembly resulting in partial or total envelope loss. Edge-attached viral envelopes distort to increase contact area with the positively charged platelet edges indicating that the virion surface is negatively charged. The nucleocapsid (NCs) remaining after envelope removal also exhibit distortion, in contrast to detergent-produced NCs which exhibit no distortion. This visually discernible disassembly is a mechanism for loss of infectivity previously unreported by studies of nonenveloped viruses. The MMT-mediated sequestration and disassembly result in reduced infectivity, suggesting that clays may reduce infectivity of enveloped pathogenic viruses in soils and sediments.

Block, Karin A; Trusiak, Adrianna; Katz, Al; Gottlieb, Paul; Alimova, Alexandra; Wei, Hui; Morales, Jorge; Rice, William J; Steiner, Jeffrey C

2014-01-01

155

Transport Properties of Water Vapor in Polylactide\\/Montmorillonite Nanocomposites  

Microsoft Academic Search

Both intercalated and exfoliated poly(L?lactide) (PLA) layered aluminosilicate nanocomposites were synthesized and characterized in terms of barrier properties. Intercalated polylactide\\/montmorillonite nanocomposites were obtained by melt blending PLA and a montmorillonite modified with bis?(2?hydroxyethyl)methyl (tallowalkyl) ammonium cations (MMT) (1, 3, 5, and 10 wt\\/wt%). A sample containing 3 wt% of MMT was prepared with 20 wt% of PEG1000 as plasticizer. Exfoliated nanocomposite containing 3 wt%

Giuliana Gorrasi; Loredana Tammaro; Vittoria Vittoria; Michael Alexandre; Philippe Dubois

2005-01-01

156

Thermal behaviour of montmorillonite pillared with different metal oxides  

Microsoft Academic Search

Natural montmorillonite was pillared by various polyhydroxy cations. The resulting pillared layer clays (PILCs) were characterized by X-ray fluorescence, X-ray diffraction (XRD) and infrared (IR) spectroscopies. The thermal behaviour of Al-PILC was investigated in detail by a combonation of XRD, derivatography IR spectroscopy and a comparison to natural montmorillonite is given. It was found that thermal stability of Al-PILC is

I. Pálinkó; I. Kiricsi; Gy. Tasi; K. Varga

1993-01-01

157

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

158

Copper nucleation by chemical vapour deposition on organosilane treated SiO 2 surfaces  

NASA Astrophysics Data System (ADS)

Self-assembled monolayers of organosilanes deposited onto SiO 2/Si substrate surfaces by either vapour-phase or wet chemical methods can act as ultrathin interfacial barriers which effectively prevent the diffusion of copper into the SiO 2 dielectric, enhance its adhesion onto it and also offer the possibility of achieving selective copper chemical vapour deposition. The initial stages of copper nucleation by chemical vapour deposition on organosilane treated SiO 2 surfaces at different substrate temperatures are investigated in detail by scanning electron and atomic force microscopy. The growth behaviour of copper clusters before coalescence is elucidated and analysed in detail. At temperatures below 190 °C nucleation occurs mostly on already formed copper clusters and coalescence is obtained due to an increase of the size of clusters in three dimensions. Above that temperature, secondary nucleation of smaller size clusters on the gaps among the larger clusters is observed, leading to coalescence almost in two dimensions. The stable clusters density initially increases with precursor injection time, passes through a maximum and then decreases, due to an increase at low temperatures of the size of clusters. An almost substrate temperature independent maximum clusters density which is obtained in the low temperatures region, indicates that nucleation of copper atoms occurs on surface defect sites which are assumed to be Cu (I) atoms. A low value of the apparent activation energy for nucleation, indicates higher affinity for copper chemical vapour deposition of the organosilane treated SiO 2 as compared to TiN substrates used previously. At 200 °C, coalescence following the initial nucleation period, results in continuous films with low roughness and low average height, thus leading to the practical realization of a thin yet continuous film.

Semaltianos, N. G.; Pastol, J.-L.; Doppelt, P.

2004-08-01

159

Uptake of Ni(II) Ions from Aqueous Solution by Kaolinite and Montmorillonite: Influence of Acid Activation of the Clays  

Microsoft Academic Search

Kaolinite and montmorillonite were treated with 0.25 M H2SO4 and the acid activated clays along with the parent clays were tested for their uptake capacity for Ni(II) ions from aqueous solution. The batch adsorption experiments were conducted under a set of variables (concentration of Ni(II) ion, amount of clay, pH, time and temperature of interaction). Increasing pH favored Ni(II) uptake till

Krishna G. Bhattacharyya; Susmita Sen Gupta

2008-01-01

160

Removal of o-nitrobenzoic acid by adsorption on to a new organoclay: montmorillonite modified with HDTMA microemulsion.  

PubMed

A new organoclay, consisting of montmorillonite modified by a hexadecyl trimethyl ammonium (HDTMA) microemulsion, was synthesized, characterized and used as an adsorbent for the removal of o-nitrobenzoic acid from aqueous solution. Adsorption kinetics, isotherms and effects of operating variables, such as adsorbent dosage, ionic strength and initial solution pH, were also investigated. The results of Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analysis and BET surface area determination indicated that HDTMA molecules had entered into the interlayer of the montmorillonite. The optimized experimental conditions for the adsorption of o-nitrobenzoic acid by montmorillonite modified by HDTMA microemulsion were 0.5 g adsorbent dosage, 0.4 mL of 0.1 mol lbL(-1) CaCl2 solution, initial solution pH of 6.0 and contact time of 6 h. The adsorption isotherms of o-nitrobenzoic acid fitted the Langmuir model well (R2 = 0.9880). The adsorption kinetics data fitted the pseudo-second-order equation (R2 = 0.9999). These above results indicate that montmorillonite modified by an HDTMA microemulsion can be used as adsorbent for o-nitrobenzoic acid because of its high adsorption capacity and low cost. PMID:21780712

Xin, Xiao-Dong; Wang, Jin; Yu, Hai-Qin; Du, Bin; Wei, Qin; Yan, Liang-Guo

2011-01-01

161

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

162

Synthesis and Non-isothermal Crystallization Behavior of PET\\/Surface-treated TiO2Nanocomposites  

Microsoft Academic Search

Poly(ethylene terephthalate) (PET)\\/TiO2 nanocomposites were prepared by melt-blending PET and surface-treated TiO2. The crystallization behavior and the non-isothermal crystallization kinetics of these composites were investigated by differential scanning calorimetry (DSC). Jeziorny and Mo's methods were applied to describe the kinetics of the non-isothermal crystallization process. It was found that the PET matrix with incorporated surface-treated TiO2 particles has lower crystallization

Xiuling Zhu; Biao Wang; Shiyan Chen; Chaosheng Wang; Yumei Zhang; Huaping Wang

2008-01-01

163

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

Code of Federal Regulations, 2013 CFR

...treated manganese ferrite with acrylic ester polymer (generic). 721.10223 Section...treated manganese ferrite with acrylic ester polymer (generic). (a) Chemical substance...treated manganese ferrite with acrylic ester polymer (PMN P-09-582) is subject to...

2013-07-01

164

Optimization of electrocoagulation process to treat grey wastewater in batch mode using response surface methodology  

PubMed Central

Background Discharge of grey wastewater into the ecological system causes the negative impact effect on receiving water bodies. Methods In this present study, electrocoagulation process (EC) was investigated to treat grey wastewater under different operating conditions such as initial pH (4–8), current density (10–30 mA/cm2), electrode distance (4–6 cm) and electrolysis time (5–25 min) by using stainless steel (SS) anode in batch mode. Four factors with five levels Box-Behnken response surface design (BBD) was employed to optimize and investigate the effect of process variables on the responses such as total solids (TS), chemical oxygen demand (COD) and fecal coliform (FC) removal. Results The process variables showed significant effect on the electrocoagulation treatment process. The results were analyzed by Pareto analysis of variance (ANOVA) and second order polynomial models were developed in order to study the electrocoagulation process statistically. The optimal operating conditions were found to be: initial pH of 7, current density of 20 mA/cm2, electrode distance of 5 cm and electrolysis time of 20 min. Conclusion These results indicated that EC process can be scale up in large scale level to treat grey wastewater with high removal efficiency of TS, COD and FC.

2014-01-01

165

Ocular surface changes in glaucomatous patients treated with and without preservatives Beta-blockers.  

PubMed

Abstract Purpose: To determine whether there were ocular surface changes in glaucomatous patients treated with preservatives beta-blockers who switched to preservative-free beta-blockers. Methods: This was a prospective, longitudinal, open-labeled study. One hundred thirty-two patients with primary open angle glaucoma treated with a preserved beta-blocker were enrolled. All the patients underwent perimetric and gonioscopic examination, complete ophthalmologic examination, intraocular pressure (IOP) measurements, evaluation of ocular surface, Schirmer's test, blood pressure and heart rate at baseline and 1-3 months after changing the medical treatment to a preservative-free timolol 0.1% (Timogel 0.1; Thea). At baseline, after 1 month and at the end of the study (3 months), all patients underwent a questionnaire on the visual quality and symptoms and on the quality of life (QoL). Data were analyzed by t-test when the distribution of the data was normal, by Mann-Whitney when the distribution was not normal. Results: No significant difference was found for IOP before switching from preserved beta-blockers to preservative-free ones. No significant difference was found in blood pressure and heart rate. However, a statistically significant difference was found for abnormal fluorescein staining of the cornea and conjunctiva, eyelid erythema, conjunctival hyperemia, and follicular hyperplasia. A significant difference was found for break-up time (from 9.38±4.7?s at baseline to 10.64±4.7?s after 3 months) and Schirmer's test (from 12.9±5.96?mm at baseline to 14.2±5.87?mm after 3 months). The questionnaire showed that the patient improved the dryness and foreign body sensation. Conclusion: In glaucomatous patients, preservative-free 0.1 timolol treatment improved their QoL. Similar dry eye signs or symptoms improved after 3 months of treatment reducing dryness, hyperemia, follicular hyperplasia, and foreign body sensation. PMID:24787056

Iester, Michele; Telani, Serena; Frezzotti, Paolo; Motolese, Ilaria; Figus, Michele; Fogagnolo, Paolo; Perdicchi, Andrea

2014-08-01

166

Adsorption of organic diacids and sodium polyacrylate onto montmorillonite  

SciTech Connect

Organic diacid (oxalic and succinic) adsorption onto montmorillonite is feasible, but weak. The comparison of chemical and radiochemical determinations reveals that 80% of the acid in contact with the smectite is used to attach the clay lattice. The pH is the main parameter involved in adsorption, and fixation passes through a minimum for pH 6 to 7. Polyacrylate adsorption also is weak. It changes with the nature of the exchangeable cation of smectite. Its pH dependence displays a pronounced maximum for a value corresponding to the pKa of the acidic functions (pH = approx. = 6.8), and a minimum at approximately pH 8. On the assumption that a polyacrylate macromolecule is 100% hydrolyzed, it follows that the -COOH groups carried by 20% hydrolyzed polyacrylamide molecules (such as those used in the tertiary recovery of petroleum) contribute at the very most to 10% of the total adsorption onto clay. Therefore, fixation involves predominantly protonation of the amide functions at the edge surfaces of the clay. The acidic functions play a minor role in the adsorption phenomenon in that they affect the length of the macromolecule. However, the extent of this contribution is virtually impossible to estimate. 17 references.

Siffert, B.; Espinasse, P.

1980-01-01

167

Effect of the intercalation conditions of a montmorillonite with octadecylamine.  

PubMed

Intercalation of montmorillonite with octadecylamine under several conditions is reported. Octadecylamine was protonated in situ with HCl to obtain octadecylammonium cations. Water and water/ethanol mixtures were used as reaction medium, and the ratios amine/clay and HCl/amine were also varied. Intercalation was successful when the amine/clay ratio was in the range 1-3 mmol/g; optimal results were obtained for an amine/clay ratio of 2.0 mmol/g. For a given amine/clay ratio, the HCl/amine ratio also influences the intercalation. Basal spacings of the intercalated solids were between 13.4-36.7 angstroms. The amount of organic matter incorporated into the solids also varied widely; up to 40 wt% is fixed. Specific surface area is very low in all the intercalated solids because of the blockage of the clay porosity by the organic molecules. Co-intercalation of octadecylammonium and of the inorganic polycation [Al13O4(OH)24(H2O)12]7+ was also considered, giving rise to intercalated solids with basal spacings between 17 and 22 A, also with a high fixation of organic matter. PMID:15752808

Pérez-Santano, A; Trujillano, R; Belver, C; Gil, A; Vicente, M A

2005-04-01

168

The Performance of Ce Surface Treated Ferritic Stainless Steels for Solid Oxide Fuel Cell Interconnects  

SciTech Connect

This research deals with the effect of a Ce surface treatment on the behavior of Fe-Cr-Mn ferritic stainless steels which may have application in SOFC technology. This treatment consisted of applying a slurry of CeO2 and a halide activator to the surface of coupons. After the slurry dried the coupons were heated to 900C in a controlled atmosphere furnace for 12 hours. The effectiveness of the treatment on commercial (Type 409 (12Cr), Type 430 (18Cr), Crofer 22APU (22Cr), Type 446(26Cr)) and experimental (NETL F9 (12Cr) and NETL F5 (22Cr)) alloys as a function of Cr content will be presented. The oxidation behavior of the alloys was assessed by exposing coupons (untreated and treated) to moist air at 800C. Area specific resistance (ASR) was measured at 800C. In general, the rare earth treatment effectively reduced the oxidation rate, resulting in thinner oxide scales and less internal oxidation.

Alman, D.E.; Jablonski, P.D.

2007-09-01

169

FTIR investigation of CTAB-Al-montmorillonite complexes.  

PubMed

In this study, CTAB-Al-montmorillonite complexes were synthesized by pre-modifying montmorillonite using different concentrations of surfactant (resulting in different surfactant loadings and basal spacings), then pillaring the organoclays with hydroxy-Al cations. The resultant inorganic-organic montmorillonite complexes were characterized using FTIR, with a combination of XRD, TG and chemical analysis. This study indicates that the basal spacings of the CTAB-Al-montmorillonite complexes and the amounts of Al-contained pillars strongly depend on the surfactant loadings in the clay interlayer space, resulted from the mobility variation of the intercalated surfactants. During pillaring hydroxy-Al cations into clay interlayer space, part of the intercalated surfactants were removed, resulting in a decrease of the ordering of alkyl chains and the frequency shifts of Si(Al)-O, Si-O-Al and (M-O)(Td) stretching vibrations. The hydrophobicity of the CTAB-Al-montmorillonite complex also strongly depends on the surfactant loading whereas that of the CTAB-Al-montmorillonite complex is relative lower than that of the corresponding organoclay, indicated by the frequency shift of the vibrations corresponding to the sorbed water and their contents estimated by TG curves. With the decrease of the sorbed water content, the frequency of the band of H-O-H bending (nu(2)) shifts to higher frequency while the O-H stretching vibration (nu(1) and nu(3)) shifts to lower frequency, indicating that H(2)O is less hydrogen bonded. Meanwhile, the ordered conformations of the alkyl chains in CTAB-Al-montmorillonite complex decrease when compared with that of the corresponding organoclay. PMID:17289428

Xue, Weihong; He, Hongping; Zhu, Jianxi; Yuan, Peng

2007-07-01

170

FTIR investigation of CTAB-Al-montmorillonite complexes  

NASA Astrophysics Data System (ADS)

In this study, CTAB-Al-montmorillonite complexes were synthesized by pre-modifying montmorillonite using different concentrations of surfactant (resulting in different surfactant loadings and basal spacings), then pillaring the organoclays with hydroxy-Al cations. The resultant inorganic-organic montmorillonite complexes were characterized using FTIR, with a combination of XRD, TG and chemical analysis. This study indicates that the basal spacings of the CTAB-Al-montmorillonite complexes and the amounts of Al-contained pillars strongly depend on the surfactant loadings in the clay interlayer space, resulted from the mobility variation of the intercalated surfactants. During pillaring hydroxy-Al cations into clay interlayer space, part of the intercalated surfactants were removed, resulting in a decrease of the ordering of alkyl chains and the frequency shifts of Si(Al)-O, Si-O-Al and (M-O) Td stretching vibrations. The hydrophobicity of the CTAB-Al-montmorillonite complex also strongly depends on the surfactant loading whereas that of the CTAB-Al-montmorillonite complex is relative lower than that of the corresponding organoclay, indicated by the frequency shift of the vibrations corresponding to the sorbed water and their contents estimated by TG curves. With the decrease of the sorbed water content, the frequency of the band of H-O-H bending ( ?2) shifts to higher frequency while the O-H stretching vibration ( ?1 and ?3) shifts to lower frequency, indicating that H 2O is less hydrogen bonded. Meanwhile, the ordered conformations of the alkyl chains in CTAB-Al-montmorillonite complex decrease when compared with that of the corresponding organoclay.

Xue, Weihong; He, Hongping; Zhu, Jianxi; Yuan, Peng

2007-07-01

171

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

172

Structure of tetraalkylammonium ionic liquids in the interlayer of modified montmorillonite.  

PubMed

We perform molecular dynamics simulations of tetraalkylammonium ionic liquids confined in the interlayer of montmorillonite (MMT). We study the structure and energetics of the systems, which consist of cations with two different alkyl chain lengths and several ionic liquid concentrations. The results we obtained for the structure, namely the presence of a strong layering in all systems and the formation of nonpolar domains with interdigitated alkyl chains in some cases, are largely consistent with previous surface force balance experiments performed on similar systems. Finally, we show that swelling of the organo-modified MMT by a large amount of ionic liquid seems energetically favorable in all cases. PMID:24920411

Duarte, Daniel; Salanne, Mathieu; Rotenberg, Benjamin; Bizeto, Marcos A; Siqueira, Leonardo J A

2014-07-16

173

Structure of tetraalkylammonium ionic liquids in the interlayer of modified montmorillonite  

NASA Astrophysics Data System (ADS)

We perform molecular dynamics simulations of tetraalkylammonium ionic liquids confined in the interlayer of montmorillonite (MMT). We study the structure and energetics of the systems, which consist of cations with two different alkyl chain lengths and several ionic liquid concentrations. The results we obtained for the structure, namely the presence of a strong layering in all systems and the formation of nonpolar domains with interdigitated alkyl chains in some cases, are largely consistent with previous surface force balance experiments performed on similar systems. Finally, we show that swelling of the organo-modified MMT by a large amount of ionic liquid seems energetically favorable in all cases.

Duarte, Daniel; Salanne, Mathieu; Rotenberg, Benjamin; Bizeto, Marcos A.; Siqueira, Leonardo J. A.

2014-07-01

174

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

PubMed

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 H(2)O/Li-MMT. PMID:23110845

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

2012-11-28

175

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

176

Interaction of sodium dodecylsulfate (SDS) with homoionic montmorillonites: adsorption isotherms and metal-ion release  

Microsoft Academic Search

The interaction of dodecylsulfate anions (DS-) with homoionic Ca-, Mg-, Ni-, Cu-, Cd-, Pb- and Fe-montmorillonites were investigated. Mg- and Cd-montmorillonite do not adsorb DS-, and an anion exchange at the edges of the clay mineral does not take place. Three different adsorption processes are identified on the other montmorillonites: i) Fe-montmorillonite is covered with amorphous iron hydroxide, and DS--anions

M. Ilic; J. González; A. Pohlmeier; H. D. Narres; M. J. Schwuger

1996-01-01

177

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

178

Hydrogen bonding and mechanical properties in segmented montmorillonite\\/polyurethane nanocomposites of different hard segment ratios  

Microsoft Academic Search

Hydrogen bonding in the hard segments of the synthesized montmorillonite\\/polyurethane nanocomposites of various hard segment ratios was found to decrease with the increasing amount of montmorillonite regardless of the hard segment ratios, but reached plateau values at 5wt% montmorillonite concentration. The maximal reductions of the hydrogen bonding in the polyurethane nanocomposites ranged from 20 to 37%, depending on the hard

Y. I Tien; K. H Wei

2001-01-01

179

Properties of thermo-chemically surface treated carbon fibers and of their epoxy and vinyl ester composites  

SciTech Connect

High strength carbon fibers were surface treated by a continuous gas phase thermo-chemical surface treatment. The surface and the mechanical properties of the fibers were investigated before and after treatment and compared to the properties obtained with a conventional industrial electro-chemical surface treatment. An increase of the oxygen atomic content from 3 % to 20 % with a preferential generation of carboxylic acid functionalities and hydroxyl groups was highlighted after the thermo-chemical surface treatment, compared to an oxygen atomic content of 7 % and a wide variety of oxygen moieties with the electro-chemical surface treatment. The tensile strength of the fibers increased slightly after the thermo-chemical surface treatment and remained the same after the electro-chemical surface treatment. Short beam shear and 90 flexural tests of composites revealed that the improvement of interfacial adhesion with a vinyl ester matrix was limited, revealing that oxidation of the carbon fiber surface alone cannot tremendously improve the mechanical properties of carbon fiber-vinyl ester composites. Atomic force microscopy showed that the creation of roughness with both surface treatments at a nanometric scale. Although the surface is slightly rougher after the electro-chemical surface treatment and is expected to lead to higher adhesion due to mechanical interlocking between the fiber surface and the matrix, the effect of covalent bonding coming from the high concentration of chemical groups on the surface results in higher adhesion strength, as obtained with the thermo-chemical surface treatment.

Vautard, Frederic [ORNL; Ozcan, Soydan [ORNL; Meyer III, Harry M [ORNL

2012-01-01

180

The Effect of Surface Treated Nanoparticles on Single and Multi-Phase Flow in Porous Media  

NASA Astrophysics Data System (ADS)

Surface treated nanoparticles have been suggested to be an additive to CO2 storage scenarios. This is because 1) the nanoparticles have been shown to freely transport through permeable media, and 2) the nanoparticles can stabilize a CO2 in water foam by adhering to the surface of CO2 bubbles/droplets preventing their coalescence. In terms of storage, The formation of CO2 foam will limit the CO2 mobility which can potentially help limit the CO2 leakage. Here, we will show how nanoparticles in porous media can have many interesting properties in single and multi-phase flow. For multi-phase CO2, we have performed experiments where high pressure liquid CO2 displaces brine and vice versa with and without nanoparticles in the brine. We measure the displacement pattern and in-situ CO2 saturation using CT scanning and measure the pressure drop using pressure transducers. We find that the flow is less preferential and the pressure drop is greater than when nanoparticles are present. This suggest the formation of in-situ foam/emulsion. We also show that on a brine chase, the residual saturation of CO2 is greater in the presence of nanoparticles. In terms of nanoparticle transport, it is observed that nanoparticles accumulate at the front of a brine/octane displacement. We hypothesize that this occurs due to the nanoparticles being size excluded from portions of the pore-space. To determine if this occurs in single phase flow, we have also performed experiments single-phase flow with the nanoparticles and tracer. We find that the nanoparticles arrive roughly 5% faster than the tracer. This also has implications for the positioning of nanoparticles in the pore space and how this can change the effective viscosity of the nanoparticle suspension.

DiCarlo, D. A.; Aminzadeh, B.; Chung, D.; Zhang, X.; Wung, R.; Huh, C.; Bryant, S. L.

2013-12-01

181

Cosorption of Zn(II) and 2-, 3-, or 4-aminopyridine by montmorillonite.  

PubMed

Data from acid-base titrations at 25 degrees C of Zn(NO(3))(2) and 2-, 3-, or 4-aminopyridine in 10 mM KNO(3) as background electrolyte suggested that soluble complexes ZnL(2+) and Zn(OH)L(+) form, where L represents aminopyridine. Zinc-hydroxyaminopyridine complexes have not been reported previously. The cosorption of Zn(II) with each of the aminopyridines to K-saturated Wyoming (SWy-K) and Texas (STx-K), and Ca-enriched Texas (STx-Ca) montmorillonites was measured at 25 degrees C, with 10 mM KNO(3) or 3.3 mM Ca(NO(3))(2) as background electrolyte. Comparison with previous data for sorption of Zn(II) and the aminopyridines separately and surface complexation modeling of the cosorption data showed that under acid conditions competition between Zn(2+) and aminopyridinium ions for the permanent negatively charged sites of montmorillonite results in suppression of the uptake of each sorbate by the other, but only when a large excess of the competing sorbate is present. Under alkaline conditions the sorption of Zn(II) was not affected by the presence of even a large excess of aminopyridine, but the sorption of 4-aminopyridine in particular was slightly enhanced when a large excess of Zn(II) was present. The enhancement was attributed to the formation of metal-bridged ternary surface complexes at the variable-charge sites on the edges of the montmorillonite crystals. PMID:15780275

Ikhsan, Jaslin; Angove, Michael J; Johnson, Bruce B; Wells, John D

2005-04-15

182

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

PubMed

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. PMID:23395956

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

2013-03-01

183

Nanoscale Protein Arrays of Rich Morphologies via Self-assembly on Chemically Treated Diblock Copolymer Surfaces  

PubMed Central

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. 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 to 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 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

2013-01-01

184

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

185

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

186

The effects of some laser parameters on the surface and near surface region of laser treated cast iron cylinder bore  

Microsoft Academic Search

The environmental and pollution materials emission standards in Europe are going to be more and more strict. In order to keep the standards, a large European automotive manufacturer makes a laser treatment on the cast iron cylinder bores of the V-engine blocks. Samples of laser treated cast iron cylinder bore with lamellar graphite were investigated. Four samples were treated with

K. Májlinger; P. J. Szabó

2010-01-01

187

Interfacial interaction of in situ Cu growth on tetrasulfide self-assembled monolayer on plasma treated parylene surface  

SciTech Connect

The interfacial reactions of in situ grown Cu and functionalized parylene surfaces were examined using the x-ray photoelectron spectroscopy (XPS). It is observed that bis[3(triethoxysilane)propyl]tetrasulfide (tetrasulfide) forms a self-assembled monolayer (SAM) only on a parylene surface treated with either He plasma or N{sub 2} plasma, but not on the as-deposited parylene surface due to its lack of functional groups. The functional groups on the plasma treated parylene surface facilitate the formation of tetrasulfide SAM that subsequently improves the reactivity of parylene to Cu. The XPS spectra show a strong shift ({approx}1.1 eV) of the S 2p peaks from a higher binding energy to a lower binding energy, which suggests the existence of an interaction between sulfide and Cu. In addition, the result of a higher XPS intensity ratio of Cu 2p{sub 3/2}/C 1s for Cu growth on tetrasulfide SAM/plasma treated parylene surface than that of an as-deposited parylene surface indicates that the formation of tetrasulfide moiety (-SSSS-) on functionalized parylene surface leads to the increase of Cu growth rate.

Pimanpang, S.; Wang, Pei-I; Juneja, Jasbir S.; Wang, G.-C.; Lu, T.-M. [Center for Integrated Electronics, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590 and Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180-3590 (United States)

2006-09-15

188

Intercalated polyaniline\\/Na-montmorillonite nanocomposites via oxidative polymerization  

Microsoft Academic Search

This work focuses on the preparation, characterization and electrical conductive properties of intercalated polyaniline\\/Na-montmorillonite\\u000a nanocomposites. These materials consisting of polyaniline and Na-montmorillonite were prepared by oxidative polymerization\\u000a with benzoyl peroxide as oxidizing agent. The synthesized nanocomposites were investigated by a series of characterization\\u000a techniques; including Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and thermal\\u000a analysis. X-ray diffraction and

Meltem Çelik; Mü?erref Önal

2007-01-01

189

The effect of iron on montmorillonite stability. (II) Experimental investigation  

NASA Astrophysics Data System (ADS)

Several designs proposed for high-level nuclear waste (HLW) repositories include steel waste canisters surrounded by montmorillonite clay. This work investigates montmorillonite stability in the presence of native Fe, magnetite and aqueous solutions under hydrothermal conditions. Two series of experiments were conducted. In the first, mixtures of Na-montmorillonite, magnetite, native Fe, calcite, and NaCl solutions were reacted at 250 °C, Psat for between 93 and 114 days. In the second series, the starting mixtures included Na-montmorillonite, native Fe and solutions of FeCl 2 which were reacted at temperatures of 80, 150, and 250 °C, Psat, for 90-92 days. Experiments were analysed using XRD, FT-IR, TEM, ICP-AES, and ICP-MS. In the first series of experiments, native Fe oxidised to produce magnetite and the starting montmorillonite material was transformed to Fe-rich smectite only when the Fe was added predominantly as Fe metal rather than Fe oxide (magnetite). The Fe-rich smectite was initially Fe(II)-rich, which oxidised to produce an Fe(III)-rich form on exposure to air. The expansion of this material on ethylene glycol solvation was much reduced compared to the montmorillonite starting material. TEM imaging shows that partial loss of tetrahedral sheets occurred during transformation of the montmorillonite, resulting in adjacent layers becoming H-bonded with a 7 Å repeat. The reduced swelling property of the Fe-smectite product may be due predominantly to the structural disruption of smectite layers and the formation of H-bonds. Solute activities corresponded to the approximate stability field calculated for hypothetical Fe(II)-saponite. In the second series of experiments, significant smectite alteration was only observed at 250 °C and the product contained a small proportion of a 7 Å repeat structure, observable by XRD. In these experiments, solute activities coincide with berthierine. The experiments indicate that although bentonite is still a desirable choice of backfill material for HLW repositories, some loss of expandability may result if montmorillonite is altered to Fe-rich smectite at the interface between steel canisters and bentonite.

Wilson, James; Cressey, Gordon; Cressey, Barbara; Cuadros, Javier; Ragnarsdottir, K. Vala; Savage, David; Shibata, Masahiro

2006-01-01

190

First Low-Iron Materials on Mars and Possibility of a Major Montmorillonite Component  

NASA Astrophysics Data System (ADS)

During exploration of Columbia Hills at Gusev crater, the Spirit rover of the MER mission has discovered several separate occurrences of material with a unique elemental signature. As measured by x-ray fluorescence emission using the APXS instrument, these samples stand out for their low Fe content, accompanied by corresponding increases in Al and Si but without high concentrations of mineralogically important cations such as Ca, Mg, Na, or K. No previous martian samples, from five landed missions and numerous martian meteorites, have such low iron content. Chemical trends implicate Mg sulfates and Ca phosphates are important but minor accessory minerals. Moessbauer analysis indicates some or all Ti to be present as ilmenite. The remaining component has high Al and Si abundances in proportions within the range of classical montmorillonite compositions found at various locations on Earth, including their correspondingly low concentrations of major cations. Typically the result of weathering of basaltic ash and often associated with more arid environments, the formation of montmorillonite or its alteration-product precursor implies that significant aqueous activity to facilitate geochemical separations occurred. In addition, various of these samples contain trace element anomalies that are unique for martian materials, including enrichments in Cu, Ni, Y, Ga, Cr, and possibly Pb, Co, Sr, and Zn. Adsorption by high cation exchange minerals such as montmorillonite clays or other alteration materials (allophane, silica, imogolite) often bear similar fingerprints due to their high-area charged surfaces which confer affinities for multivalent metal ions in solution. Samples of this "Independence Class" of materials have been found at three separated sites in the upper portion of Husband Hill. The samples are disparate in form, including clods (or peds), an outcrop, and a "rock". Their lighter color and rugged morphology are a common feature. The latter may indicate susceptibility to fragmentation, with possible derivation from a deeper-lying layer of source material.

Clark, B. C.; Richter, L.; Gellert, R.; Farrand, W.; Ming, D. W.; Morris, R. V.; Yen, A.

2005-12-01

191

Feasibility of using nanofiltration as a polishing process for removal of cyanobacterial exudates from treated surface water  

Microsoft Academic Search

Nanofiltration (NF) membrane technology is effective for removal of natural organic matter (NOM) and Disinfection By-Product (DBP) precursors from treated surface water (Allgeier et al., 1995, Chellam et al., 2000, Smith et al., 2002). However, there is a need to control other micropollutants, such as compounds released from algal blooms. In this research, the feasibility of using NF for removal

Anand J Mody

2004-01-01

192

Surface characteristics and osteoblastic cell response of alkali-and heat-treated titanium-8tantalum-3niobium alloy  

PubMed Central

Purpose The aim of the present study was to evaluate the biological response of alkali- and heat-treated titanium-8tantalum-3niobium surfaces by cell proliferation and alkaline phosphatase (ALP) activity analysis. Methods Commercial pure titanium (group cp-Ti) and alkali- and heat-treated titanium-8tantalum-3niobium (group AHT) disks were prepared. The surface properties were evaluated using scanning electron microscopy, energy dispersed spectroscopy and X-ray photoelectron spectroscopy (XPS). The surface roughness was evaluated by atomic force microscopy and a profilometer. The contact angle and surface energy were also analyzed. The biological response of fetal rat calvarial cells on group AHT was assessed by cell proliferation and ALP activity. Results Group AHT showed a flake-like morphology microprofile and dense structure. XPS analysis of group AHT showed an increased amount of oxygen in the basic hydroxyl residue of titanium hydroxide groups compared with group cp-Ti. The surface roughness (Ra) measured by a profilometer showed no significant difference (P>0.05). Group AHT showed a lower contact angle and higher surface energy than group cp-Ti. Cell proliferation on group AHT surfaces was significantly higher than on group cp-Ti surfaces (P<0.05). In comparison to group cp-Ti, group AHT enhanced ALP activity (P<0.05). Conclusions These results suggest that group AHT stimulates osteoblast differentiation.

Lee, Bo-Ah; Kang, Choong-Hee; Vang, Mong-Sook; Jung, Young-Suk; Piao, Xing Hui; Kim, Ok-Su; Chung, Hyun-Ju

2012-01-01

193

Properties of aged montmorillonite-wheat gluten composite films.  

PubMed

The properties of new and aged glycerol-plasticized vital wheat gluten films containing < or =4.5 wt % natural or quaternary ammonium salt modified montmorillonite clay were investigated. The films were cast from pH 4 or pH 11 ethanol/water solutions. The films, aged for < or =120 days, were characterized by tensile testing, X-ray diffraction, and transmission electron microscopy. In addition, water vapor permeability (11% relative humidity) and the content of volatile components were measured. The large reduction in the water vapor permeability with respect to the pristine polymer suggests that the clay platelets were evenly distributed within the films and oriented preferably with the platelet long axis parallel to the film surface. The film prepared from pH 11 solution containing natural clay was, as revealed by transmission electron microscopy and X-ray diffraction, almost completely exfoliated. This film was consequently also the strongest, the stiffest, and the most brittle and, together with the pH 11 film containing modified clay, it also showed the greatest decrease in water vapor permeability. The large blocking effect of the clay had no effect on the aging kinetics of the films. During aging, the pH 4 and pH 11 film strength and the pH 4 film stiffness increased and the pH 4 film ductility decreased at the same rate with or without clay. This suggests that the aging was not diffusion rate limited, that is, that the loss of volatile components or the migration of glycerol or glycerol/wheat gluten phase separation was not limited by diffusion kinetics. The aging rate seemed to be determined by slow structural changes, possibly involving protein denaturation and aggregation processes. PMID:16478249

Olabarrieta, Idoia; Gällstedt, Mikael; Ispizua, Iban; Sarasua, Jose-Ramon; Hedenqvist, Mikael S

2006-02-22

194

Synthesis of silver/montmorillonite nanocomposites using ?-irradiation  

PubMed Central

Silver nanoparticles (Ag-NPs) were synthesized into the interlamellar space of montmorillonite (MMT) by using the ?-irradiation technique in the absence of any reducing agent or heat treatment. Silver nitrate and ?-irradiation were used as the silver precursor and physical reducing agent in MMT as a solid support. The MMT was suspended in the aqueous AgNO3 solution, and after the absorption of silver ions, Ag+ was reduced using the ?-irradiation technique. The properties of Ag/MMT nanocomposites and the diameters of Ag-NPs were studied as a function of ?-irradiation doses. The interlamellar space limited particle growth (d-spacing [ds] = 1.24–1.42 nm); powder X-ray diffraction and transmission electron microscopy (TEM) measurements showed the production of face-centered cubic Ag-NPs with a mean diameter of about 21.57–30.63 nm. Scanning electron microscopy images indicated that there were structure changes between the initial MMT and Ag/MMT nanocomposites under the increased doses of ?-irradiation. Furthermore, energy dispersive X-ray fluorescence spectra for the MMT and Ag/ MMT nanocomposites confirmed the presence of elemental compounds in MMT and Ag-NPs. The results from ultraviolet-visible spectroscopy and TEM demonstrated that increasing the ?-irradiation dose enhanced the concentration of Ag-NPs. In addition, the particle size of the Ag-NPs gradually increased from 1 to 20 kGy. When the ?-irradiation dose increased from 20 to 40 kGy, the particle diameters decreased suddenly as a result of the induced fragmentation of Ag-NPs. Thus, Fourier transform infrared spectroscopy suggested that the interactions between Ag-NPs with the surface of MMT were weak due to the presence of van der Waals interactions. The synthesized Ag/MMT suspension was found to be stable over a long period of time (ie, more than 3 months) without any sign of precipitation.

Shameli, Kamyar; Ahmad, Mansor Bin; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Gharayebi, Yadollah; Sedaghat, Sajjad

2010-01-01

195

Effect of reactive species on surface crosslinking of plasma-treated polymers investigated by surface force microscopy  

SciTech Connect

Polymer surface modification by ions, uncharged particles, and photons of inductively coupled Ar plasma was investigated with a surface force microscope. Optical windows consisting of crystals with different cutoff wavelengths and a metal shield were used to deconvolute the effects of the various plasma species on the modification of the surface nanomechanical properties of polyethylene. The extent of surface crosslinking was related to the frictional energy dissipated during nanoscratching. It is shown that surface crosslinking is primarily due to the simultaneous effects of uncharged particles and vacuum ultraviolet photons, while the ion bombardment effect is secondary.

Tajima, S.; Komvopoulos, K. [Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States)

2006-09-18

196

Nanocomposite materials based on polyurethane intercalated into montmorillonite clay  

Microsoft Academic Search

Polyurethane organoclay nanocomposites have been synthesized via in situ polymerization method. The organoclay has been prepared by intercalation of diethanolamine or triethanolamine into montmorillonite clay (MMT) through ion exchange process. The syntheses of polyurethane–organoclay hybrids were carried out by swelling the organoclay into different kinds of diols followed by addition of diisocyanate. The nanocomposites with dispersed structure of MMT was

Ahmed Rehab; Nehal Salahuddin

2005-01-01

197

Adsorption of organic diacids and sodium polyacrylate onto montmorillonite  

Microsoft Academic Search

Organic diacid (oxalic and succinic) adsorption onto montmorillonite is feasible, but weak. The comparison of chemical and radiochemical determinations reveals that 80% of the acid in contact with the smectite is used to attach the clay lattice. The pH is the main parameter involved in adsorption, and fixation passes through a minimum for pH 6 to 7. Polyacrylate adsorption also

B. Siffert; P. Espinasse

1980-01-01

198

Study on the Polyvinylalcohol\\/Montmorillonite Composite Hydrogel  

Microsoft Academic Search

A series of alkyl ammonium\\/montmorillonite (MMT) were compounded with polyvinyl alcohol (PVA) to prepare the composite hydrogel with improved water absorbency and mechanical property. The effect of the nature of the surfactants on the intercalation of PVA chains within the silicate galleries, the interfacial compatibility and the properties of the composites was studied. A proper type and content of MMT

Yuanyuan Gu; Lin Ye

2009-01-01

199

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] [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] [Univ. Pierre et Marie Curie, Paris (France). Lab. de Reactivite de Surface

1999-04-15

200

Evaluation of surface roughness of a plasma treated polymeric membrane by wavelet analysis and quantification of its enhanced performance  

NASA Astrophysics Data System (ADS)

The change in roughness of polyethersulfone (PES) ultrafiltration membranes by plasma treatment is quantified by atomic force microscopy (AFM). A wavelet-based analysis of surface morphology images from AFM is used to evaluate the surface roughness changes of polymeric membranes. Discrete wavelet transform with 3D image analysis is used to capture patterns at all relevant frequency scales — which are not possible with other traditional techniques of image analysis. The hydrophilic nature and roughness of the membrane surfaces are related to fouling over the membrane surfaces with associated change in solvent flux. The changes in flux of the plasma treated membranes are quantified by measuring the enhancement in flux of a model solution of bovine serum albumin (BSA). The results clearly demonstrate that a PES membrane being more hydrophilic and having smoother surface by optimal treatment of cold CO 2 plasma is easier to clean and the augmented permeability can be retained in successive use.

Pal, S.; Ghatak, S. K.; De, S.; DasGupta, S.

2008-12-01

201

PARAMETERS OF TREATED STAINLESS STEEL SURFACES IMPORTANT FOR RESISTANCE TO BACTERIAL CONTAMINATION  

EPA Science Inventory

Use of materials that are resistant to bacterial contamination could enhance food safety during processing. Common finishing treatments of stainless steel surfaces used for components of poultry processing equipment were tested for resistance to bacterial attachment. Surface char...

202

Hydrothermal interactions of cement or mortar with zeolites or montmorillonites  

SciTech Connect

Concretes, grouts, clays and/or zeolites are candidate borehole, shaft or tunnel plugging materials for any nuclear waste repository. Interactions between these plugging materials may take place under mild hydrothermal conditions during the life of a repository. Class H cement or motar (PSU/WES mixture) was reacted with one of two montmorillonites, clinoptilolite or mordenite at 100/sup 0/ and 200/sup 0/C for different periods under a confining pressure of 30 MPa. The solid reaction products were characterized by x-ray powder diffraction and scanning electron microscopy after the hydrothermal treatments. When zeolites were in contact (not intimate mixture) with class H cement, they did not seem to alter but clinoptilolite altered to analcime, and mordenite became poorly crystalline in the presence of mortar (containing NaCl) at both 100/sup 0/ and 200/sup 0/C. When cement or mortar was intimately mixed with zeolites or montmorillonites and reacted hydrothermally, the reaction resulted in the formation of Al substituted tobermorite (11A type) in all cases (this type of reaction is expected at the interface) at both 100/sup 0/ and 200/sup 0/C. The mechanism of tobermorite formation includes the decomposition of zeolites or montmorillonites in the presence of alkaline (pH approx. = 12) cement or mortar and recrystallization to form Al substituted tobermorite. Cesium sorption measurements in 0.01N CaCl/sub 2/ on the reaction products revealed that selective Cs sorption increased in most cases, even though little or none of the original zeolites and montmorillonites remained in the products. For example, Cs sorption K/sub d/ (mL/g) increased from 80 in the untreated mortar + Ca montmorillonite mixture to 1700 in the interaction product which is Al substituted tobermorite. Thus, we discover here that Al substituted tobermorite has good selectivity for Cs.

Komarneni, S.; Roy, D.M.

1983-01-01

203

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

204

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

Microsoft Academic Search

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

H. Angermann

2002-01-01

205

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

206

Preparation and surface characterization of plasma-treated and biomolecular-micropatterned polymer substrates  

Microsoft Academic Search

A micropatterning process creates distinct microscale domains on substrate surfaces that differ from the surfaces' original chemical\\/physical properties. Numerous micropatterning methods exist, each having relative advantages and disadvantages in terms of cost, ease, reproducibility, and versatility. Polymeric surfaces micropatterned with biomolecules have many applications, but are specifically utilized in tissue engineering as cell scaffolds that attempt to controlled tissue generation

Bryan Alfred Langowski

2007-01-01

207

Structure Analysis of Montmorillonite Intercalated with Cetylpyridinium and Cetyltrimethylammonium: Molecular Simulations and XRD Analysis.  

PubMed

Molecular mechanics and molecular dynamics simulations combined with X-ray powder diffraction were used in structure investigation of montmorillonite intercalated with cetylpyridinium (CP) and cethyltrimethylammonium (CTA) cations. Molecular modeling revealed the interlayer structure and differences in intercalation behavior of CP and CTA cations in montmorillonite. The experimental and calculated values of basal spacing were in good agreement for both intercalates: in the case of CP-montmorillonite d(exp)=20.59 Å, d(calc)=20.60 Å; for CTA-montmorillonite d(exp)=18.00 Å and d(calc)=18.10 Å. CTA-montmorillonite exhibits significantly higher total sublimation energy and higher host-guest interaction energy than the CP-montmorillonite. The main difference between both intercalates is in charge distribution on the host layers and guest species. The charge transfer from the guest species to the host layer is higher in CTA-montmorillonite than in CP-montmorillonite, and consequently the charge polarization between the host and guest layers is much higher in CTA-montmorillonite. This leads to much stronger host-guest electrostatic interaction in the case of CTA-montmorillonite. Copyright 2001 Academic Press. PMID:11254337

Pospísil, Miroslav; Capková, Pavla; Merínská, Dagmar; Malác, Zdenek; Simoník, Josef

2001-04-01

208

Influence of annealing on the metal/semiconductor contacts deposited on sulfur-treated n-GaAs surface  

SciTech Connect

Comparative analysis of the influence of thermal annealing on Ge/Au/Ni-, Ge/Au/Ti/Au-, and Ge/Au/Ni/Ti/Au-based ohmic contacts and Ti/Au-based Schottky contacts deposited on an n-GaAs (100) surface treated and nontreated in (NH{sub 4}){sub 2}S aqueous solution have been performed. Annealing conditions for ohmic contacts are found that lead to a decrease in the specific contact resistance of sulfur-treated samples by a factor of 2.5-15 in comparison with the nontreated samples. Optimal annealing conditions are also determined for sulfur-treated GaAs samples with Schottky contacts, which make it possible to reduce the ideality factor and increase the barrier height and the breakdown voltage with respect to the nontreated samples.

Erofeev, E. V. [Micran Research and Production Company (Russian Federation); Kagadei, V. A., E-mail: vak@micran.ru [OOO Submicron Technologies (Russian Federation)

2011-09-15

209

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

2013-09-01

210

Characterization of microstructure and surface properties of heat-treated PAN-and rayon-based activated carbon fibers  

Microsoft Academic Search

Polyacrylonitrile- and rayon-based activated carbon fibers (ACFs), subject to heat treatment over 600–1,100°C under N2 flow, were investigated using a number of surface analytical methods, including N2 adsorption isotherm, elemental analysis, and X-ray photoelectron spectroscopy. The adsorption capacities of benzene, carbon\\u000a tetrachloride, and water vapor on as-received and heat-treated ACFs were determined. Results show that the ACFs under study\\u000a were

Yu-Chun Chiang; Chien-Cheng Lee; Hung-Chih Lee

2007-01-01

211

Molecular Dynamics Simulations of Carbon Dioxide Intercalation in Hydrated Na-Montmorillonite  

SciTech Connect

Molecular dynamics simulations using classical force fields were carried out to study the structural and transport properties of clay mineral?water?CO{sub 2} systems at pressure and temperature relevant to geological carbon storage. The simulations show that the degree of swelling caused by intercalation of CO{sub 2} strongly depends on the initial water content in the interlayer space and that CO{sub 2} intercalation stimulates inner-sphere adsorption of the positively charged interlayer ions on the internal clay surfaces, which modifies the wetting properties of the surfaces. DFT-based molecular dynamics simulations were used to interpret the origin of the observed shift in the asymmetric stretch vibration of CO{sub 2} trapped in montmorillonite. The origin of the shift is attributed to the electric field effects on the CO{sub 2} molecules induced by the water molecules.

Myshakin, Evgeniy M.; Saidi, Wissam A.; Romanov, Vyacheslav N.; Cygan, Randall T.; Jordan, Kenneth D.

2013-02-01

212

Reaction Characteristics on the Green Surface of Moso Bamboo (Phyllostachys pubescens Mazel) Treated with Chromated Phosphate  

Microsoft Academic Search

Summary Phyllostachys pubescens Mazel Chromated phosphate (CP) Green color protection FTIR spectrometry ESR spectrometry ESCA spectrometry Standing moso bamboo (Phyllostachys pubescens Mazel) culm is attractive to many people for its green color, but it fades readily if it is not chemically treated. Chromated phosphate (CP) has been successfully used to protect the green color of bamboo. In order to understand

Shang-Tzen Chang; Ting-Feng Yeh; Jyh-Horng Wu; David N.-S. Hon

2002-01-01

213

Surface studies of corona-treated silicone rubber high-voltage insulation  

Microsoft Academic Search

XPS (X-ray photoelectron spectroscopy) and microscopy studies of the brittle layer that is produced have established that corona exposure forms a wettable silica-like layer on the surface of most polydimethylsiloxane (PDMS) elastomers. This is consistent with similar effects from oxygen and inert gas plasma treatment. Such a layer cannot readily reorient between hydrophilic and hydrophobic states at the surface, suggesting

Patrick J. Smith; Michael J. Owen; Peter H. Holm; George A. Toskey

1992-01-01

214

Montmorillonite Clay-Catalyzed Synthesis of RNA Oligomers  

NASA Astrophysics Data System (ADS)

It is proposed that catalysis had a central role in the origins of life. This will be illustrated using the montmorillonite clay-catalyzed synthesis of oligomers of RNA from activated monomers, (Ferris and Ertem, 1993) a possible step in the origin of the RNA world (Ferris, 2005). Structural analysis of oligomers formed in the reaction of the activated monomer of 5'-AMP with that of 5'-CMP demonstrated that the oligomers formed were not produced by random synthesis but rather the sequences observed were directed by the montmorillonite catalyst (Miyakawa and Ferris, 2003). RNA oligomers containing up to 40 mers have been synthesized in reactions performed in water at 25 oC in the presence of montmorillonite (Huang and Ferris, 2003). Analysis of the structure elements in these oligomers from the 7 to 39 mers showed that they did not vary. Reaction of D, L-mixtures of the activated monomers of A and U resulted in the formation of greater amounts of the homochiral amounts of dimers and trimers of A than would be expected if there was no selectivity in the reaction. A limited number of the dimers and trimers of U were also formed but here the selectivity was for the formation of an excess of heterochiral products (Joshi et al., 2000). A postulate that explains why homochiral trimers of U are not formed and the significance of catalysis in prebiotic synthesis will be discussed. Ferris, J.P. (2005) Origins of life, molecular basis of. In R.A. Meyers, Ed. Encyclopedia of Molecular Cell Biology and Molecular Medicine, 10. Wiley-VCH Verlag, Weinheim, Germany. Ferris, J.P., and Ertem, G. (1993) Montmorillonite catalysis of RNA oligomer formation in aqueous solution. A model for the prebiotic formation of RNA. J. Am. Chem. Soc., 115, 12270-12275. Huang, W., and Ferris, J.P. (2003) Synthesis of 35-40 mers of RNA oligomers from unblocked monomers. A simple approach to the RNA world. Chem. Commun., 1458-1459. Joshi, P.C., Pitsch, S., and Ferris, J.P. (2000) Homochiral selection in the montmorillonite-catalyzed and uncatalyzed prebiotic synthesis of RNA. Chem. Commun., 2497-2498. Miyakawa, S., and Ferris, J.P. (2003) Sequence- and Regioselectivity in the montmorillonite-catalyzed synthesis of RNA. J. Am. Chem. Soc., 125, 8202-8208.

Ferris, J. P.; Miyakawa, S.; Huang, W.; Joshi, P.

2005-12-01

215

Analysis of the Release Characteristics of Cu-Treated Antimicrobial Implant Surfaces Using Atomic Absorption Spectrometry  

PubMed Central

New developments of antimicrobial implant surfaces doped with copper (Cu) ions may minimize the risk of implant-associated infections. However, experimental evaluation of the Cu release is influenced by various test parameters. The aim of our study was to evaluate the Cu release characteristics in vitro according to the storage fluid and surface roughness. Plasma immersion ion implantation of Cu (Cu-PIII) and pulsed magnetron sputtering process of a titanium copper film (Ti-Cu) were applied to titanium alloy (Ti6Al4V) samples with different surface finishing of the implant material (polished, hydroxyapatite and corundum blasted). The samples were submersed into either double-distilled water, human serum, or cell culture medium. Subsequently, the Cu concentration in the supernatant was measured using atomic absorption spectrometry. The test fluid as well as the surface roughness can alter the Cu release significantly, whereby the highest Cu release was determined for samples with corundum-blasted surfaces stored in cell medium.

Zietz, Carmen; Fritsche, Andreas; Finke, Birgit; Stranak, Vitezslav; Haenle, Maximilian; Hippler, Rainer; Mittelmeier, Wolfram; Bader, Rainer

2012-01-01

216

Natural montmorillonite induced photooxidation of As(III) in aqueous suspensions: roles and sources of hydroxyl and hydroperoxyl/superoxide radicals.  

PubMed

Photooxidation of arsenite(As(III)) in a suspension of natural montmorillonite under the irradiation of metal halide lamp (? ? 313 nm)has been investigated. The results showed that the natural montmorillonite induced the photooxidation of As(III) by generating hydroxyl radicals (HO·) and hydroperoxyl/superoxide radicals (HO?·/O??·). HO· which was responsible for the As(III) photooxidation. Approximately 38% of HO· was generated by the photolysis of ferric ions, and the formation of the remaining 62% was strongly dependent on the HO?·/O??·. The presence of free ironions (Fe(2+) and Fe(3+)), made significant contributions to the photogeneration of these reactive oxygen species (ROS). The photooxidation of As(III) in natural montmorillonite suspensions was greatly influenced by the pH values. The photooxidation of As(III) by natural montmorillonite followed the Langmuir-Hinshelwood equation. In addition, the photooxidation of As(III) could be enhanced by the addition of humic acid. This work demonstrates that photooxidation may be an important environmental process for the oxidation of As(III) and may be a way to remove As(III) from acidic surface water containing iron-bearing clay minerals. PMID:23770489

Wang, Yajie; Xu, Jing; Li, Jinjun; Wu, Feng

2013-09-15

217

Effects of blending of desalinated and conventionally treated surface water on iron corrosion and its release from corroding surfaces and pre-existing scales.  

PubMed

This study examined effects of blending desalinated water with conventionally treated surface water on iron corrosion and release from corroding metal surfaces and pre-existing scales exposed to waters having varying fractions of desalinated water, alkalinities, pH values and orthophosphate levels. The presence of desalinated water resulted in markedly decreased 0.45 ?m-filtered soluble iron concentrations. However, higher fractions of desalinated water in the blends were also associated with more fragile corroding surfaces, lower retention of iron oxidation products and release of larger iron particles in the bulk water. SEM, XRD and XANES data showed that in surface water, a dense layer of amorphous ferrihydrite phase predominated in the corrosion products. More crystalline surface phases developed in the presence of desalinated water. These solid phases transformed from goethite to lepidocrocite with increased fraction of desalinated water. These effects are likely to result from a combination of chemical parameters, notably variations of the concentrations of natural organic matter, calcium, chloride and sulfate when desalinated and conventionally treated waters are blended. PMID:23651514

Liu, Haizhou; Schonberger, Kenneth D; Peng, Ching-Yu; Ferguson, John F; Desormeaux, Erik; Meyerhofer, Paul; Luckenbach, Heidi; Korshin, Gregory V

2013-07-01

218

Chemical and structural modifications of laser treated WTi surfaces at different ambient conditions  

NASA Astrophysics Data System (ADS)

In this work we have studied the influence of laser modification on the composition and structure of tungsten titanium (WTi) thin films, deposited on n-type (100) silicon wafers. After deposition, the samples were multi-pulse laser irradiated in a nitrogen, oxygen, and helium ambient. The composition of the WTi/Si sample was determined by Elastic Recoil Detection Analysis (ERDA). Surface morphology was monitored by Atomic Force Microscopy (AFM). In the experiment, typical laser output parameters were: wavelength 1064 nm, pulse duration 150 ps, and laser pulse energy 30 mJ. Surface concentrations of W and Ti, as well as the concentration of gas components nitrogen and oxygen were determinated before and after the action of laser radiation in different ambient conditions. The contents of W and Ti decreased after irradiation due to adsorbed gases from the surrounding atmosphere. After surface irradiation in the inert ambient (He), the concentrations of the components were not significantly changed. In other cases, oxygen was the dominant component at the surface, probably due to the high affinity of thin film components. Also, the morphological changes occurred at the surface of WTi, as an increase in the surface roughness and formation of the granular structures are a result of laser-induced surface oxidation and recrystallization.

Petrovi?, S.; Peruško, D.; Milovanovi?, D.; Siketi?, Z.; Jakši?, M.; Kova?, J.; Gakovi?, B.; Milosavljevi?, M.; Trtica, M.

2011-11-01

219

Changes in wetting properties of silica surface treated with DPPC in the presence of phospholipase A 2 enzyme  

NASA Astrophysics Data System (ADS)

Wetting properties of silica plates contacted with dipalmitoylphosphatidylcholine (DPPC) or DPPC/enzyme (phospholipase PLA 2) in NaCl solution were determined by thin layer wicking and with a help of Washburn equation. The wicking experiments were performed both for bare plates and the silica plates precontacted overnight with the probe liquid saturated vapors the silica plates, as well as untreated and DPPC (or DPPC/enzyme) treated. Adsorption of DPPC on original silica plates increases a bit hydrophobic character of silica surface in such a way that hydrocarbon chains are directed outwards and the polar part towards the silica surface. However, after the enzyme action the products of DPPC hydrolysis by PLA 2 (palmitic acid and lysophosphatidylcholine) increase again hydrophilic character of silica surface (an increase in acid-base interactions, ?sAB). The changes of silica surface wettability are evidently dependent on the time of enzyme contacting with DPPC in NaCl solution. Although, the changes of total surface free energy of silica after treatment with DPPC/enzyme solution are minor about 2-6 mJ/m 2, the changes of the electron-donor ( ?s-) and Lifshitz-van der Waals ( ?sLW) component of the surface free energy are noticeable. Despite, these results are somehow preliminary, it seems that thin layer wicking method is an interesting tool for investigation of the effect of adsorbed DPPC on hydrophobicity/hydrophilicity of silica surface and influence of enzyme PLA 2 action.

Wi?cek, Agnieszka Ewa

220

In vitro potential genotoxic effects of surface drinking water treated with chlorine and alternative disinfectants  

Microsoft Academic Search

A battery of in vitro short-term tests revealing different genetic end-points was set up in order to study surface-water genotoxicity after disinfection with different biocides: sodium hypochlorite (NaClO), chlorine dioxide (ClO2) and peracetic acid (PAA). The surface water both before and after disinfection was concentrated by adsorption on C18 silica cartridges and the concentrates containing non-volatile organics were divided into

Licia Guzzella; Silvano Monarca; Claudia Zani; Donatella Feretti; Ilaria Zerbini; Annamaria Buschini; Paola Poli; Carlo Rossi; Susan D. Richardson

2004-01-01

221

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

222

Mixed-Layer Kaolinite—Montmorillonite from the Yucatan Peninsula, Mexico  

Microsoft Academic Search

Abstract-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, elec- tron 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 ran- domly,interlayered kaolinite and montmorillonite layers. The montmorillonite structural

L. G. Schultz; A. O. Shepard; P. D. Blackmon; H. C. Starkey

1971-01-01

223

Synthesis and antimicrobial activities of polymer\\/montmorillonite–chlorhexidine acetate nanocomposite films  

Microsoft Academic Search

The PDMS\\/montmorillonite–chlorhexidine acetate (PDMS\\/OMMT) nanocomposite films were successfully obtained by intercalation from solution. Organo-montmorillonite (OMMT) with antibacterial activity was prepared from Na+-montmorillonite (Na+-MMT) and chlorhexidine acetate (CA) by ion exchange. The microstructure of these nanocomposite films were characterized by TEM and XRD. The effect of OMMT on mechanical properties and thermal stability of the nanocomposites was investigated. When the OMMT

Na Meng; Ning-Lin Zhou; Shuang-Quan Zhang; Jian Shen

2009-01-01

224

Adsorption of heavy metals on kaolinite and montmorillonite: a review.  

PubMed

The process of adsorption is considered to be one of the best water treatment technologies around the world. Different heavy metals, due to their toxic and hazardous nature, are possibly the most widespread groundwater contaminants imposing a serious threat to human health. In this review, an attempt has been made to discuss the use of two common clay materials, namely kaolinite and montmorillonite, along with their modified forms for heavy metal removal on the basis of published reports (2008 onwards). The modifications of clays have been attempted by the process of pillaring, intercalation, acid/base activation, functionalization, etc. The adsorption of toxic metals, viz., As, Cd, Cr, Co, Cu, Fe, Pb, Mn, Ni, Zn, etc., has been studied predominantly. Montmorillonite and its modified forms have much higher metal adsorption capacity compared to that of kaolinite as well as modified-kaolinite. The modification often boosted the adsorption capacities of the clays, however, reverse trends are also reported in some cases. PMID:22499238

Sen Gupta, Susmita; Bhattacharyya, Krishna G

2012-04-12

225

Spectroscopic Studies of Poly(?-Caprolactone)/Sodium Montmorillonite Nanocomposites  

NASA Astrophysics Data System (ADS)

Polymer-layered silicate nanocomposites belong to a new class of hybrid materials consisting of organic-synthetic polymer matrix and inorganic filler-layered structure clay minerals. The paper presents the results of FTIR, NMR, and SAXS studies of poly(?-caprolactone)/sodium montmorillonite nanocomposites. We observed a correlation between the concentration of poly(?-caprolactone) in nanocomposite samples and structural changes both of the clay mineral and the intercalated polymer. Stiffening of the clay structure appears as a result of poly(?-caprolactone) intercalation into a clay structure. 27Al NMR studies indicated in nanocomposites two non-equivalent sites of aluminium ions, i.e. in octahedral and tetrahedral coordination, whereas in the montmorillonite clay structure the aluminium ions are located in the interlayer space too. We found also that the temperatures of structural changes and softening process of poly(?-caprolactone) chains in the nanocomposites depend on the concentration of poly(?-caprolactone).

Krzaczkowska, J.; Fojud, Z.; Kozak, M.; Jurga, S.

2006-07-01

226

The microstructural study of thermal treatment montmorillonite from Heping, China  

NASA Astrophysics Data System (ADS)

The montmorillonite samples from Heping, China had been studied by chemical analysis, DAT, TG, XRD and MAS NMR. The results showed that the hydroxyl in octahedra sheets begins dehydrating, when the thermal treatment temperature reaches 650 °C, but the layer structure remains, the corresponding Al(VI) was turned into Al(IV) in octahedra sheets. When the temperature reaches 900 °C, the layer structure of montmorillonite is destroyed, and the new mineral phase ?-cordierite is found. When the temperature reaches 1200 °C, the ?-cordierite phase loses stability, and decomposes into cristobalite phase and mullite phase, meanwhile, the recrystallization phenomena in thermal treatment products is obvious. There is a small quantity of Al(VI) signal in MAS NMR spectrum, this Al(VI) corresponds to the Al of mullite. When the temperature reaches 1350 °C, the cristobalite and mullite phases reduce slightly, and more Fe-cordierite phase appear. There is corresponding Fe-cordierite spectrum in XRD and MAS NMR.

Wu, Pingxiao; Wu, Honghai; Li, Rong

2005-10-01

227

SiOC glass modified by montmorillonite clay  

Microsoft Academic Search

The addition of inexpensive montmorillonite clay to a silicone resin employed as preceramic polymer was found to be advantageous for the production of SiOC glass matrix composites. Dense SiOC based monoliths were achieved with the addition of a substantial amount of calcined clay (30wt.%) to the preceramic polymer; these composites exhibited remarkable hardness and fracture toughness, higher than those of

Enrico Bernardo; Paolo Colombo; Evangelos Manias

2006-01-01

228

Interlayer water structure in Na- and Li-montmorillonite clays  

NASA Astrophysics Data System (ADS)

We measured the neutron diffraction patterns of dry Li-montmorillonite and its D2O hydrate at an incident wavelength of 1.057 Å. We used a difference method to obtain the diffraction pattern due to the interlayer water. Comparison with data for liquid D2O shows that the interlayer water has a liquid-type structure, although water molecules may be associated with specific crystallographic sites.

Powell, D. H.; Tongkhao, Kowut; Kennedy, Shane J.; Slade, Phillip G.

1998-04-01

229

FTIR spectra of hydroxyls and dehydroxylation kinetics mechanism in montmorillonite  

Microsoft Academic Search

The application of Fourier transform infrared (FTIR) spectroscopy to the analysis of the hydroxyl groups bands' intensities of montmorillonite from Texas shows four regions of intensity loss rate for thermally shocked samples at 290T2O molecules below the hexagonal hole or cavity. The vibrational analysis of the stretching and bending modes of water and hydroxyl groups at 290T3+-OH groups are dehydroxylated.

V. M. Malhotra; A. A. Ogloza

1989-01-01

230

Adsorption and Interactions of Methyl Green with Montmorillonite and Sepiolite  

Microsoft Academic Search

The divalent organic cation, methyl green (MG), undergoes a slow transformation (6 h) to a monovalent cation, carbinol (MGOH+) 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

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

2000-01-01

231

Reinforcement of polyurethane composites with an organically modified montmorillonite  

Microsoft Academic Search

A clay with reactive activity prepared by treatment of natural montmorillonite with Methylene-bis-ortho-chloroaniline (MOCA) was incorporated into polyurethane matrix and a series of PU\\/clay nanocomposites were obtained by in situ polymerization. The microstructure of the nanocomposites with different content of the clay was examined by atomic force microscopy (AFM). The thermal and mechanical properties of the nanocomposites with different organic

Jiawen Xiong; Zhen Zheng; Hongmei Jiang; Sufang Ye; Xinling Wang

2007-01-01

232

Fracture Toughness Enhancement of Epoxy by Organo-Montmorillonite  

Microsoft Academic Search

Epoxy nanocomposites were prepared by addition of organo-montmorillonite (OMMT). The intercalation-ability of the OMMT was characterized using X-ray diffraction (XRD). The fracture toughness of the epoxy\\/OMMT nanocomposites was examined using single edge notched bending (SENB) tests. The OMMT (1–4 wt%) was successfully exfoliated in the epoxy matrix, however, the epoxy\\/OMMT (5 wt%) exhibited intercalated structure. Surprisingly, the fracture toughness of epoxy nanocomposites

S. R. Lim; W. S. Chow

2011-01-01

233

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

234

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] [Purdue Univ., West Lafayette, IN (United States). Dept. of Agronomy

1996-09-25

235

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

236

Molecular modeling of polymer-clay nanocomposite precursors: Lysine in montmorillonite interlayers.  

PubMed

The layered structure of clays with interlayer cations leads to unique chemical and mechanical properties, which have been capitalized on in the field of polymer/layered silicate nanocomposites. Hydrophilic silica surfaces can become organophilic with the inclusion of alkylammonium cations, which improve the wetting characteristics of the polymer matrix. In fact, the molecular level interactions of amino acids, either natural or non-natural, with clay surfaces are at the heart of fields of study as diverse as nanocomposites fabrication, drug delivery, bio-remediation of soils and catalysis of biological polymers, to name a few. The ubiquity of these systems and the potential uses to which they could be put suggests the necessity of a deeper understanding of the interplay of bonds, conformations, and configurations between the molecules and the hosts. The interactions of the amino acid lysine with sodium montmorillonite were studied using theoretical molecular modeling methods. The interlayer spacing of montmorillonite was increased by incorporating water molecules and allowing the system to evolve with molecular mechanics. Care was taken to retain the sodium cations in the interlayer. The initial amino acid conformation was obtained surrounding the molecule with numerous discrete water molecules and minimizing the system at the semi empirical level. The optimized amino acid was then placed in the interlayer space in a series of initial positions. Molecular mechanics calculations were performed and the final positions were analyzed. The results tended to indicate the preponderance of configurations which included surface-sodium-amino acid complexes with a variety of spatial arrangements. These results were compared with molecular dynamics calculations of similar systems from the literature. PMID:17987601

Davis, Alicia M; Joanis, Gary; Tribe, Lorena

2008-04-30

237

Vis-NIR Spectroscopy of Mineral Mixtures with Montmorillonite and Silica: Implications for Detecting Alteration Products on Mars  

NASA Astrophysics Data System (ADS)

Introduction. A variety of secondary silicates have been identified on Mars using Vis-NIR spectroscopic data from the Observatoire pour la Mineralogie, l’Eau, les Glaces et l’Activite (OMEGA) on Mars Express and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on Mars Reconnaissance Orbiter, including smectite, chlorite, kaolinite, and illite clay minerals and hydrous amorphous silica [1-4]. The detection of these materials is significant because they provide important information about past aqueous environments on Mars. Vis-NIR spectra of specific secondary silicates can be distinguished by the positions and shapes of hydration features. Here, we investigate the detection of secondary silicates by vis-NIR spectroscopy of mixtures with basaltic igneous minerals and either hydrous amorphous silica or montmorillonite. Experimental Procedure. Minor amounts of <2 ?m amorphous silica or montmorillonite clay (2.5, 5, 10, and 20 wt%) were physically mixed with augite, andesine, or olivine (75-106 ?m). A portion of each mixture was compressed into a pellet. Vis-NIR spectra (0.32-2.55 ?m) of particulate and pellet mixtures were measured at RELAB at Brown University, and each spectrum was visually inspected to determine detection limits of secondary silicates based on hydration features. Preliminary Results. Absorptions at 1.4 and 1.9 ?m (OH stretch overtone and H2O bend and stretch, respectively) occur in almost all mixture spectra; however, the strength, shape, and position are dependent on the igneous mineral and secondary silicate abundance in the mixture. The morphology of absorptions at ~2.2 ?m (from metal-OH bonds) differs between amorphous silica and montmorillonite [3,4], so we use these absorptions to determine the detection limits of amorphous silica and montmorillonite. The 2.2 ?m absorption is present in all montmorillonite-mixture spectra, indicating the montmorillonite detection limit is <2.5 wt%; however, the 2.2 ?m absorption is generally present in silica-mixture spectra that contain >10 wt% silica. Conclusions. Vis-NIR spectra of our mineral mixtures show that montmorillonite has a lower detection limit than amorphous silica, based on the presence of the ~2.2 ?m absorption. This indicates that chemically weathered surfaces on Mars that contain silica must have much more alteration material to be detected than surfaces with clay. Furthermore, the shape and position of the 1.4 and 1.9 ?m features changes with igneous mineral type and silica abundance, which adds to the difficulty in using vis-NIR to detect amorphous silica on Mars. Our study is consistent with a previous study that demonstrates the inability to detect thin silica coatings on basaltic particulates by vis-NIR spectroscopy [5], and suggests acidic chemical weathering and the precipitation of amorphous silica on Mars may be more pervasive and intense than vis-NIR spectroscopic data indicate. References. [1] J.-P. Bibring et al. (2006) Science, 312, 400-404. [2] F. Poulet et al. (2005) Nature, 438, 623-627. [3] J.F. Mustard et al. (2008) Nature, 454, 305-309. [4] R.E. Milliken et al. (2008) Geology, 36, 847-850. [5] M.D. Kraft et al. (2007) 7th Int. Conf. Mars, 3396.

Rampe, E. B.; Kraft, M. D.; Sharp, T. G.

2009-12-01

238

In situ X-ray Photoemission Spectroscopy Analysis of Aromatic Polyester Surface Treated with Argon Plasma  

NASA Astrophysics Data System (ADS)

Effects of surface modification treatment by argon plasma processing of two types of aromatic polyester, poly(ethylene terephthalate) (PET) and poly(oxybenzonate-co-oxynaphthoate) (POCO), were investigated. This paper presents a description of our experiment and a discussion of the surface modification mechanism, which uses a simple and inexpensive procedure to conduct analysis without breaking vacuum after plasma processing. In situ analysis of the chemical composition of a polymer surface was attempted without exposing the sample to air after argon plasma processing. In particular, the respective actions of each active species were investigated for electrons and ions in argon plasma. Electrons and ions in argon plasma break some polymer bonds. Specifically, ester groups are broken and oxygen atoms are kicked out in PET and POCO. No oxygen functional group is formed after argon plasma processing, but such groups are formed if the sample is exposed to air.

Narushima, Kazuo; Okamoto, Nanami

2013-10-01

239

Investigation of the surface free energy components of thermally treated controlled porosity glasses by inverse gas chromatography  

NASA Astrophysics Data System (ADS)

Adsorption isotherms of n-octane and toluene were measured on thermally treated controlled porosity glasses (CPG) and on boron-coated silica gel (SG). From the isotherms the film pressure (?) for both adsorbates was determined. Based on extrapolated ? max values the dispersion (? dS) and the non-dispersion (? nS) components of the surface free energy for all the investigated materials were calculated. It was found that the changes in ? dS caused by the surface modification were relatively small (˜ 4mJ/m 2), while those of ? nS were significant. The boron compounds decrease the ? nS value from 145-160 to 37-55 mJ/m 2. The dependences between ??/? a and the adsorbed amount can give some suggestion about the adsorption mechanism and surface homogeneity. The presence of Na on the surface of both CPG and SG seems to be a more important factor for adsorption than that of boron. The significant changes in non-dispersion interactions were attributed to surface dehydroxylation, which may result from both the thermal treatment and the presence of boron on the surface.

Bili?ski, Bogdan; Wójcik, Wies?aw; Dawidowicz, Andrzej L.

1991-01-01

240

Surface modifications of some nanocomposites containing starch  

NASA Astrophysics Data System (ADS)

Polymer-layered silicate nanocomposites have attracted strong interest in today's materials research, due to the possible impressive enhancements of material properties, comparatively with those of pure polymers. Several starch/poly(vinylalcohol)/montmorillonite nanocomposites have been subjected to surface modification by physical treatments such as dielectric barrier discharge (DBD) exposure and coating with proteins (albumin) or polysaccharides (chitosan), for improving their biocompatibility. Untreated and treated surfaces have been comparatively studied by contact angle measurements, FT-IR and 2D-FT-IR spectroscopy and optical microscopy. It has been established that enhancement of the surface characteristics depends on the type and number of incorporated nanoparticles as well as on the treatment applied. Coupling of DBD exposure and coating techniques appears to be highly efficient.

Pascu, M.-C.; Popescu, M.-C.; Vasile, C.

2008-09-01

241

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

242

Study on surface properties of PDMS microfluidic chips treated with albumin  

Microsoft Academic Search

Electrokinetic properties and morphology of PDMS microfluidic chips intended for bioassays are studied. The chips are fabricated by a casting method followed by polymerization bonding. Microchannels are coated with 1% solution of bovine serum albumin (BSA) in Tris buffer. Albumin passively adsorbs on the PDMS surface. Electrokinetic characteristics (electro-osmotic velocity, electro-osmotic mobility, and zeta potential) of the coated PDMS channels

Walter Schrott; Marek Nebyla

2009-01-01

243

Effectiveness of electrolyzed water as a sanitizer for treating different surfaces.  

PubMed

The effectiveness of electrolyzed (EO) water at killing Enterobacter aerogenes and Staphylococcus aureus in pure culture was evaluated. One milliliter (approximately 10(9) CFU/ml) of each bacterium was subjected to 9 ml of EO water or control water (EO water containing 10% neutralizing buffer) at room temperature for 30 s. Inactivation (reduction of > 9 log10 CFU/ ml) of both pathogens occurred within 30 s after exposure to EO water containing approximately 25 or 50 mg of residual chlorine per liter. The effectiveness of EO water in reducing E. aerogenes and S. aureus on different surfaces (glass, stainless steel, glazed ceramic tile, unglazed ceramic tile, and vitreous china) was also evaluated. After immersion of the tested surfaces in EO water for 5 min without agitation, populations of E. aerogenes and S. aureus were reduced by 2.2 to 2.4 log10 CFU/ cm2 and by 1.7 to 1.9 log10 CFU/cm2, respectively, whereas washing with control water resulted in a reduction of only 0.1 to 0.3 log10 CFU/cm2. The washing of tested surfaces in EO water with agitation (50 rpm) reduced populations of viable cells on the tested surfaces to < 1 CFU/cm2. For the control water treatment with agitation, the surviving numbers of both strains on the tested surfaces were approximately 3 log10 CFU/cm2. No viable cells of either strain were observed in the EO water after treatment, regardless of agitation. However, large populations of both pathogens were recovered from control wash solution after treatment. PMID:12182480

Park, Hoon; Hung, Yen-Con; Kim, Chyer

2002-08-01

244

Effects of Fe Addition on the Snoek-Type Damping Behavior of Surface-Oxidation-Treated Ti-Mo Alloys  

NASA Astrophysics Data System (ADS)

Effects of Fe addition on the oxygen diffusion and the Snoek-type relaxation damping behavior of the Ti-15 wt pct Mo alloy were investigated in this study. After surface oxidation treatment, the Ti-15 wt pct Mo-1 wt pct Fe alloy exhibits a higher damping capacity compared to the Ti-15 wt pct Mo alloy. The dual-phase zone and the oxygen-enriched ?-phase zone in the surface-oxidation-treated Ti-Mo alloys were determined by electron backscattered diffraction (EBSD) and hardness measurements. Based on the oxygen distributions in both alloys obtained through a diffusion model, the relative damping capacity of different zones contributing to the beam sample damping was estimated to be proportional to the thickness of the oxygen dissolved zones. On the other hand, the substitutional solute of Fe in the Ti-Mo-Fe alloy is considered to affect the oxygen distribution by lengthening the oxygen diffusion zone and increasing the oxygen concentration in this zone. As a result, the addition of Fe in Ti-Mo alloy improves the damping capacity of the surface-oxidation-treated alloys.

Lu, Hui; Li, Chunxia; Yin, Fuxing; Fang, Qianfeng; Umezawa, Osamu

2011-08-01

245

Thermal Characteristics of ThermoBrachytherapy Surface Applicators (TBSA) for Treating Chestwall Recurrence  

PubMed Central

Purpose To study temperature and thermal dose distributions of ThermoBrachytherapy Surface Applicators (TBSA) developed for concurrent or sequential high dose rate (HDR) brachytherapy and microwave hyperthermia treatment of chest wall recurrence and other superficial disease. Methods A steady state thermodynamics model coupled with the fluid dynamics of water bolus and electromagnetic radiation of hyperthermia applicator is used to characterize the temperature distributions achievable with TBSA applicators 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) TBSA. 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 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) and tumor blood perfusion (?b=2–5 kg/m3/s) to characterize their influence on thermal dosimetry. Results Steady state SAR patterns of R- and L-TBSA demonstrate the ability to produce conformal and localized power deposition inside 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 2 L/min 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 thermal enhancement ratio (TER) in the most sensitive skin where maximum radiation dose is delivered and to extend thermal enhancement of radiation dose deeper. Conclusion This computational study indicates that well-localized elevation of tumor target temperature to 40–44 °C can be accomplished by large surface-conforming TBSA applicators using appropriate selection of coupling bolus temperature.

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

2010-01-01

246

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

247

Kinetic Analysis of Spontaneous Whisker Growth on Pre-treated Surfaces with Weak Oxide  

NASA Astrophysics Data System (ADS)

This study sought to clarify the relationship between cracks in surface oxide layers and the growth behavior of tin whiskers. The number, length, and total volume of extrusions were precisely calculated and residual stress was measured using synchrotron radiation x-ray diffractometry. The aim was to elucidate the influence of stress on the driving force and flux involved in atomic diffusion. The distance between weak spots was shown to be the most significant factor involved in the growth of whiskers. The results could explain why increasing the density of the surface weak spots could reduce the number of long whiskers. Measuring the dimensions of whiskers yielded a precise kinetic model capable of describing the migration of atoms to the root of whiskers, resulting in their spontaneous growth.

Su, Chien-Hao; Chen, Hao; Lee, Hsin-Yi; Liu, Cheng Yi; Ku, Ching-Shun; Wu, Albert T.

2014-05-01

248

Chemical and structural modifications of laser treated WTi surfaces at different ambient conditions  

Microsoft Academic Search

In this work we have studied the influence of laser modification on the composition and structure of tungsten titanium (WTi)\\u000a thin films, deposited on n-type (100) silicon wafers. After deposition, the samples were multi-pulse laser irradiated in a nitrogen, oxygen, and helium\\u000a ambient. The composition of the WTi\\/Si sample was determined by Elastic Recoil Detection Analysis (ERDA). Surface morphology\\u000a was

S. Petrovic; D. Perusko; D. Milovanovic; Z. Siketic; M. Jaksic; J. Kovac; B. Gakovic; M. Milosavljevic; M. Trtica

2011-01-01

249

Antiplane shear Lamb's problem treated by gradient elasticity with surface energy  

Microsoft Academic Search

The consideration of higher-order gradient effects in a classical elastodynamic problem is explored in this paper. The problem is the anti-plane shear analogue of the well-known Lamb's problem. It involves the time-harmonic loading of a half-space by a single concentrated anti-plane shear line force applied on the half-space surface. The classical solution of this problem based on standard linear elasticity

H. G. Georgiadis; I. Vardoulakis

1998-01-01

250

SURFACE MODIFICATIONS AND ADHESION OF VULCANIZED SBR RUBBER TREATED WITH RF PLASMAS OF DIFFERENT GASES  

Microsoft Academic Search

The surface modifications produced by treatment of a synthetic vulcanized styrene-butadiene rubber (R1) with oxidizing (oxygen, air, carbon dioxide) and nonoxidizing (nitrogen, argon) RF plasmas have been assessed by ATR-IR and XPS spectroscopy, SEM, and contact angle measurements. The effectiveness of the treatment depended on the gas atmosphere used to generate the RF plasma. In general, acceptable adhesion values of

Ana B. Ortíz-Magán; M. Mercedes Pastor-Blas; José Miguel Martín-Martínez

2004-01-01

251

Surface and pore structure of deoiled acid-and heat-treated spent bleaching clays  

Microsoft Academic Search

Samples of spent bleaching clay were deoiled by hexane, methanol, hexane-methanol, and supercritical CO2 extractions. The deoiled clays were regenerated by acid and heat treatments. Nitrogen adsorption isotherms for these samples\\u000a are type IV with hysteresis loops corresponding to type H3, indicating slit-shaped pores. Used deoiled and dried samples have\\u000a smaller surface areas and pore volumes than unused clay. The

K. F. Ng; N. K. Nair; K. Y. Liew; Ahmad M. Noor

1997-01-01

252

Copper chemical vapour deposition on organosilane-treated SiO 2 surfaces  

NASA Astrophysics Data System (ADS)

Copper thin films were grown on SiO 2 substrates by chemical vapour deposition using the precursor (2-methyl-1-hexene-3-yne)Cu(1,1,1,5,5,5-hexafluoroacetylacetonate) ((MHY)Cu(hfac)) and were examined by scanning electron and atomic force microscopy. The affinity for copper chemical vapour deposition of the substrate surface is higher after the formation of self-assembled monolayers of organosilanes onto the substrate surface. Furthermore, the affinity is greatly enhanced by a subsequent UV light irradiation of the organosilane monolayer, in air, prior to deposition. The dependence of film morphology and statistical surface parameters on substrate temperature and amount of vapour precursor introduced during deposition, provide information for the optimisation of external parameters towards obtaining a thin yet continuous film. Self-assembled monolayers of organosilanes can be used for a selective metallization of SiO 2 substrates by copper chemical vapour deposition, in addition to acting as ultrathin barriers which prevent copper diffusion into the SiO 2, thus opening a route for a technology useful in microelectronic industrial applications.

Semaltianos, N. G.; Pastol, J.-L.; Doppelt, P.

2004-01-01

253

Surface analytical study of CuInSe{sub 2} treated in Cd-containing partial electrolyte solution  

SciTech Connect

Junction formation in CuInSe{sub 2} (CIS) has been studied by exposing thin films and single-crystal samples to solutions containing NH{sub 4}OH and CdSO{sub 4}. The treated samples were analyzed by secondary ion mass spectrometry to determine the amount and distribution of Cd deposited on the surface of the films. Cadmium is found to react with the surface for all the solution exposure times and temperatures studied. The reaction rapidly approaches the endpoint and remains relatively unchanged for subsequent solution exposure. Cadmium in-diffusion, as measured by secondary ion mass spectrometry, is obscured by topography effects in the thin-film samples and by ion-beam mixing and topography in the single-crystal sample. {copyright} {ital 1999 American Institute of Physics.}

Asher, S.E.; Ramanathan, K.; Wiesner, H.; Moutinho, H. [National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401 (United States)] Niles, D.W. [Hewlett-Packard Corporation, 3404 Harmony Road, MS6, Fort Collins, Colorado 80528 (United States)

1999-03-01

254

Surface analytical study of CuInSe[sub 2] treated in Cd-containing partial electrolyte solution  

SciTech Connect

Junction formation in CuInSe[sub 2] (CIS) has been studied by exposing thin films and single-crystal samples to solutions containing NH[sub 4]OH and CdSO[sub 4]. The treated samples were analyzed by secondary ion mass spectrometry to determine the amount and distribution of Cd deposited on the surface of the films. Cadmium is found to react with the surface for all the solution exposure times and temperatures studied. The reaction rapidly approaches the endpoint and remains relatively unchanged for subsequent solution exposure. Cadmium in-diffusion, as measured by secondary ion mass spectrometry, is obscured by topography effects in the thin-film samples and by ion-beam mixing and topography in the single-crystal sample. [copyright] [ital 1999 American Institute of Physics.

Asher, S.E.; Ramanathan, K.; Wiesner, H.; Moutinho, H. (National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, Colorado 80401 (United States)) Niles, D.W. (Hewlett-Packard Corporation, 3404 Harmony Road, MS6, Fort Collins, Colorado 80528 (United States))

1999-03-01

255

Resonator structures on AlN ceramics surface treated by laser radiation  

NASA Astrophysics Data System (ADS)

In this paper a method for producing resonant structures using laser micromachining is presented. In the spot of laser beam impact on AlN ceramics surface a conductive aluminum layer is formed. Compilation of process parameters allows for the fabrication of structures with resistance at Rs ~ 0.01?/Rs. It has been also found out that the maximum value of resistance for which spiral resonator structures manifest their unique properties is at the level of Rs = 1.43 ?. Furthermore, the occurrence of mutual capacity which value is dependent on the arrangement of individual SR structures with respect to each other was observed and examined. Based on satisfactory results for SR structures, it has been attempted to produce a resonant structures dedicated to the THz range based on the process of direct metallization of AlN ceramics surface. As a result, the Split Ring Resonator structure whose properties were verified by using the THz -TDS method was manufactured. In case of the field E perpendicular to SRR structure and one resonance area for 0.50 THz with field E parallel to the structure, two characteristic resonant dips for 0.22 THz and 0.46 THz were obtained. The studies confirmed that the method of direct metallization of AlN ceramics allows to produce resonant structures in the THz range.

Koziol, Pawel E.; Antonczak, Arkadiusz J.; Stepak, Bogusz; Gorski, Przemyslaw A.; Walczakowski, Michal; Palka, Norbert; Abramski, Krzysztof M.

2014-03-01

256

Studies on the removal of some toxic metal ions. Part II (removal of lead and cadmium by montmorillonite and kaolinite)  

Microsoft Academic Search

Clay samples (montmorillonite and kaolinite) have been characterised and used for the removal of lead and cadmium metals. The adsorption of Pb and Cdis greater on montmorillonite, and the sorption capacity increases with increasing pH. Adsorption on montmorillonite follows the Langmuir model. The uptake is found to decrease in the presence of cationic surfactants while the anionic surfactants enhance the

S. K. Srivastava; Renu Tyagi; Nalini Pant; Naresh Pal

1989-01-01

257

Electrical treeing in EVA-Boehmite and EVA-Montmorillonite nanocomposites  

Microsoft Academic Search

The present experimental work focuses on the growth of electrical treeing inside different Ethylene-vinyl acetate (EVA) nanocomposites containing Bohemite (an aluminum oxide hydroxide) and Montmorillonite (a phyllosilicate clay mineral) nanoparticles. Bohemite and Montmorillonite particles have different aspect ratios: the first one has a nanometric cube-like symmetry, while the latter has a typical layered structure. The results evidence that the growth

F. Guastavino; A. Dardano; G. C. Montanari; L. Testa; F. Bellucci

2009-01-01

258

The Effect of Montmorillonite Partial Density on the Role of Colloid Filtration by a Bentonite Buffer  

Microsoft Academic Search

Japan's concept for high-level radioactive waste disposal includes a barrier of compacted bentonite (montmorillonite) that, based on its microstructure, buffers the waster package and prevents migration of colloids with sizes between 1 and 1,000 nm. However, results of experimental studies indicate that colloid migration through the barrier (breakthrough) depends upon the partial density of the montmorillonite buffer. To assess the

Susumu KUROSAWA; Satoru TANAKA; Scott C. JAMES; Mikazu YUI

2006-01-01

259

Organo-montmorillonites as catalysts for selective synthesis of glycerol monolaurate  

Microsoft Academic Search

Montmorillonite was modified with cetyl trimethylammonium bromide (CTAB) and tetra-n-butylammonium bromide (TBAB) to catalyze the production of glycerol monolaurate. The reaction was conducted at 130°C for up to 8h. With TBAB montmorillonite, a higher glycerol monolaurate selectivity of about 73% was obtained at a lauric acid conversion of about 80%.

Tri Yogo Wibowo; Ahmad Zuhairi Abdullah; Ridzuan Zakaria

2010-01-01

260

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

261

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

262

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

263

Synthesis and rheological properties of oligoimide\\/montmorillonite nanocomposites  

Microsoft Academic Search

We report a facile strategy for preparing polyimides (PI)\\/montmorillonite (MMT) nanocomposites at moderate temperatures that avoids thermal degradation of organically-modified MMT (organo-MMT) that is commonly observed during conventional melt-blending of organo-MMT with commercial high molecular weight PI at elevated temperatures. Novel polyimides of low molecular weight (oligoimides) based on 1,3-bis(3?,4,-dicarboxyphenoxy)benzene and 4,4? bis(4?-aminophenoxy)diphenylsulfone were synthesized and subsequently melt-blended at temperatures

V. E. Yudin; G. M. Divoux; J. U. Otaigbe; V. M. Svetlichnyi

2005-01-01

264

Synthesis and properties of polystyrene-organoammonium montmorillonite hybrid  

Microsoft Academic Search

Summary  \\u000a Styrene monomer was mixed with quaternary ammonium montmorillonites(org-MMTs) and polymerized in the presence of radical initiator.\\u000a The resulting materials showed an expansion of interlayer distance. These hybrid materials exhibited higher thermal stability\\u000a compared with the virgin polystyrene(PS) or PS\\/pristine-MMT microcomposite. PS\\/Bz-MMT, containing benzyl-unit similar to styrene\\u000a in org-MMT, exhibited higher decomposition temperature even for MMT loading as low as

Jae Goo Doh; Iwhan Cho

1998-01-01

265

Assessment of dry season surface, ground, and treated water quality in the Cape Coast municipality of Ghana.  

PubMed

This aim of this monitoring was to assess water quality in a dry season for the Cape Coast municipality in Ghana, which has been experiencing chronic water shortages. Fifteen different sampling stations--four surface, five ground, and six tap water samples--were analyzed for physicochemical and microbiological parameters during January to April 2005. Levels or trends in water quality that may be deleterious to sensitive water uses, including drinking, irrigation, and livestock watering have been noted with reference to well-established guidelines. Exceedances to some health-based drinking water guidelines included positive coliform for various water samples; pH for all groundwater samples (pH 5.9+/-0.3); conductivity for 50% groundwater; color for about a third of groundwater and tap water; Mn for 44% tap water, 67% groundwater, and 50% surface water samples. The World Health Organization laundry staining Fe guideline of 0.3 mg/l was exceeded by 75% of surface water, 44% tap water, and 53% groundwater samples. The corresponding Mn guideline of 0.1 mg/l was exceeded by all the water samples. Respectively, all surface water samples and also 75% of the surface water exceeded some known Cu and Zn guideline for the protection of aquatic life. Compared to some historic data for Fosu Lagoon, the current study shows a lowering of approximately 1 pH unit, increase of approximately 65% NH3, one to two orders of magnitude increase in PO4(3-), and more than two orders of magnitude increase in NO3-. In several instances, tap water samples collected at the consumers' end of the distribution system did not reflect on the true quality of the treated water. Mn, SO4(2-), PO4(3-), Cu, and Zn were among the chemical contaminations observed to occur in the distribution system. PMID:19234753

Quagraine, E K; Adokoh, C K

2010-01-01

266

Montmorillonite-chitosan bionanocomposites as adsorbents of the herbicide clopyralid in aqueous solution and soil/water suspensions.  

PubMed

Montmorillonite (SWy-2)-chitosan bionanocomposites (SW-CH) were prepared following different methodologies, characterized, and assayed as adsorbents of the herbicide clopyralid (3,6-dichloropyridine-2-carboxylic acid) in aqueous solution and soil/water suspensions, to assess the potential of the materials to prevent and remediate soil and water contamination by anionic pesticides. The SW-CH bionanocomposites were good adsorbents for the herbicide at pH levels where both the anionic form of the herbicide (pK(a)=2.3) and the cationic form of CH (pK(a)=6.3) predominated. The performance of the SW-CH bionanocomposites as adsorbents of clopyralid depended on the amount and arrangement of chitosan in the samples. Clopyralid adsorption was rapid and mostly linear up to herbicide concentrations as high as 0.5mM. High salt concentrations (0.1M NaCl) promoted desorption of the adsorbed pesticide from SW-CH, strongly suggesting that adsorption of clopyralid occurred primarily through an ion exchange mechanism on positively charged CH sites at the montmorillonite surface. Amendment of an acidic soil (pH=4.5) with SW-CH at rates of 5% and 10% led to a significant increase in clopyralid adsorption, whereas this effect was negligible when SW-CH was added to an alkaline soil (pH=8.0), reflecting the absence of positively charged sites in SW-CH at high pH values. Montmorillonite-CH bionanocomposites can be useful as adsorbents for the removal and/or immobilization of anionic pesticides in soil and water under mild acidic conditions. PMID:22284171

Celis, R; Adelino, M A; Hermosín, M C; Cornejo, J

2012-03-30

267

Enterococcal surface protein Esp does not facilitate intestinal colonization or translocation of Enterococcus faecalis in clindamycin-treated mice.  

PubMed

Enterococcal surface protein (Esp) is a cell wall-associated protein of Enterococcus faecalis that has been identified as a potential virulence factor. We used a mouse model to examine whether Esp facilitates intestinal colonization or translocation of E. faecalis to mesenteric lymph nodes. After clindamycin treatment, similar levels of high-density colonization were established after orogastric inoculation of an E. faecalis isolate containing the esp gene within a large pathogenicity island and an isogenic mutant created by allelic replacement of the esp gene with a chloramphenicol resistance cassette (P=0.7); translocation to mesenteric lymph nodes was detected in 3 of 12 (25%) mice in both groups. Isogenic mutants of FA2-2 (a plasmid-free derivative of E. faecalis strain JH2) with or without the esp gene failed to establish colonization of clindamycin-treated mice. These results suggest that Esp does not facilitate intestinal colonization or translocation of E. faecalis. PMID:15621440

Pultz, Nicole J; Shankar, Nathan; Baghdayan, Arto S; Donskey, Curtis J

2005-01-15

268

Nitric Acid Trihydrate Formation on Na-montmorillonite Clay  

NASA Astrophysics Data System (ADS)

Polar stratospheric clouds (PSCs) composed of large nitric acid trihydrate (NAT) particles have recently been observed in the Arctic polar stratosphere. In addition to heterogeneous chlorine activation, large NAT particles can influence ozone (O3) destruction by promoting denitrification due to particle sedimentation. However, potential effects on future O3 loss are hard to determine because the formation mechanisms of these large NAT particles are still unknown. Recently, stratospheric micrometeorites have been suggested as potentially important selective nuclei for formation of PSCs. In the current study, FT-IR spectroscopy was used in a high vacuum chamber to study the heterogeneous formation of NAT on a smectite clay, Na-montmorillonite. We find that NAT forms on Na-montmorillonite at relative humidities with respect to liquid water greater than 40% and saturation ratios with respect to crystalline NAT of SNAT > 8. This value of SNAT is lower than all previous laboratory studies of NAT nucleation and neatly coincides with reported conditions of NAT particles observed in the field. Smectites are not only components on clay minerals, but also of micrometeorites. Thus, formation of NAT on micrometeorites is a possible mechanism for formation of large NAT particles in the Arctic polar stratosphere.

Mashburn, C. D.; Gough, R. V.; Tolbert, M. A.; Toon, O. B.

2005-12-01

269

Sorption and Fractionation of a Peat Derived Humic Acid by Kaolinite, Montmorillonite, and Goethite *1 *1 Project supported by the Federal Hatch Program, USA (No. MAS 8532); the Cheung Kong Scholar Program, Ministry of Education of China; and the CSREES, USDA National Research Initiative Competitive Grants Program, USA (No. 2005-35107-15278)  

Microsoft Academic Search

Sorption of humic acid (HA) on mineral surfaces has a profound interest regarding the fate of hydrophobic organic contaminants (HOCs) and carbon sequestration in soils. The objective of our study is to determine the fractionation behavior of HA upon sorption on mineral surfaces with varying surface properties. HA was coated sequentially on kaolinite (1:1 clay), montmorillonite (2:1 clay), and goethite

S. GHOSH; Zhen-Yu WANG; S. KANG; P. C. BHOWMIK; B. S. XING

2009-01-01

270

U(VI) sorption on montmorillonite in the absence and presence of carbonate: A macroscopic and microscopic study  

NASA Astrophysics Data System (ADS)

The mechanism of U(VI) sorption on montmorillonite (Na-SWy-1) in the absence and presence of carbonate was investigated through a combination of different approaches: macroscopic sorption experiments, surface complexation modelling using the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange sorption model and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. U(VI) sorption measurements were performed in the absence of carbonate at fixed ionic strength (0.1 M NaClO4) as a function of pH at U(VI) trace concentration (˜9 × 10-8 M) and as a function of U(VI) concentration (˜10-7-10-4 M) at a fixed pH (5, 6.8 and 8). In the presence of carbonate, experiments were carried out in equilibrium with atmospheric pCO2 and in 1, 3 and 5 mM NaHCO3. The pH dependent sorption measurements at trace concentration in the absence of carbonate were modelled by considering the formation of the following surface species, tbnd SOUO2+, tbnd SOUOOH, tbnd SOUO(OH)2- and tbnd SOUO(OH)32- on the strong sites. From the isotherms the formation of tbnd SOUO2+ and tbnd SOUOOH on the weak sites was inferred. Two additional surface complexes on the strong sites, tbnd SOUOCO3- and tbnd SOUO(CO)23- and one surface complex on the weak sites, SOUOCO3-, were necessary to reproduce the sorption data obtained in the presence of carbonate. The EXAFS measurements did not allow to verify the formation of ternary uranyl-carbonate complexes on the montmorillonite surface. However, the obtained fit results, i.e. splitting of the equatorial oxygen shell, one Si/Al shell at ˜3.09 Å and one Si/Al at ˜3.29 Å or one Fe shell at ˜3.42 Å, clearly indicate that under the given experimental conditions (pH, U(VI) loading) U(VI) forms inner-sphere surface complexes on montmorillonite edge sites via binding to aluminum octahedra and/or silicon tetrahedra.

Marques Fernandes, M.; Baeyens, B.; Dähn, R.; Scheinost, A. C.; Bradbury, M. H.

2012-09-01

271

pH profile of the adsorption of nucleotides onto montmorillonite. II - Adsorption and desorption of 5-prime-AMP in iron-calcium montmorillonite systems  

NASA Technical Reports Server (NTRS)

The interaction of 5-prime-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-prime-AMP per gram of clay. Two desorption stages were employed - H2O wash and NaOH extraction (pH = 12.0). 5-prime-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-prime-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 attaction and repulsion of 5-prime-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.

1985-01-01

272

Staphylococcus epidermidis adhesion to He, He\\/O 2 plasma treated PET films and aged materials: Contributions of surface free energy and shear rate  

Microsoft Academic Search

Adhesion studies of bacteria (Staphylococcus epidermidis) to plasma modified PET films were conducted in order to determine the role of the surface free energy under static and dynamic conditions. In particular, we investigated the effect of the ageing time on the physicochemical surface properties of helium (He) and 20% of oxygen in helium (He\\/O2) plasma treated polyethylene terephthalate (PET) as

M. Katsikogianni; E. Amanatides; D. Mataras; Y. F. Missirlis

2008-01-01

273

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

274

Enhancement of Surface Potential Buildup and Decay of Tris(8-quinolinato)aluminum Film Deposited on Ultraviolet/Ozone-Treated Gold Electrodes  

NASA Astrophysics Data System (ADS)

The enhancement of the surface potential of tris(8-quinolinato)aluminum (Alq3) film deposited on ultraviolet (UV)/ozone-treated gold electrodes was confirmed by surface potential measurement, and the ordering of molecular dipoles was suggested. The enhanced surface potential of the order of 10 V decayed rapidly by photoirradiation, due to molecular dipole disordering, but a surface potential of 100-400 mV remained. Interestingly, this remaining surface potential of Alq3 on the UV/ozone-treated gold electrode was always smaller than that of Alq3 film on an untreated gold electrode. It was concluded that the UV/ozone treatment is effective in decreasing the density of surface states at the Alq3-metal interface as well as for the enhancement of molecular dipole ordering.

Kajimoto, Norifumi; Muhamad, Muhamad Rasat; Rahman, Saadah Abdul; Manaka, Takaaki; Iwamoto, Mitsumasa

2005-02-01

275

Fe(II) sorption on a synthetic montmorillonite. A combined macroscopic and spectroscopic study.  

PubMed

Extended X-ray absorption fine structure (EXAFS) and Mössbauer spectroscopy combined with macroscopic sorption experiments were employed to investigate the sorption mechanism of Fe(II) on an iron-free synthetic montmorillonite (Na-IFM). Batch sorption experiments were performed to measure the Fe(II) uptake on Na-IFM at trace concentrations as a function of pH and as a function of sorbate concentration at pH 6.2 and 6.7 under anoxic conditions (O2 < 0.1 ppm). A two-site protolysis nonelectrostatic surface complexation and cation exchange sorption model was used to quantitatively describe the uptake of Fe(II) on Na-IFM. Two types of clay surface binding sites were required to model the Fe(II) sorption, the so-called strong (?S(S)OH) and weak (?S(W)OH) sites. EXAFS data show spectroscopic differences between Fe sorbed at low and medium absorber concentrations that were chosen to be characteristic for sorption on strong and weak sites, respectively. Data analysis indicates that Fe is located in the continuity of the octahedral sheet at trans-symmetric sites. Mössbauer spectroscopy measurements confirmed that iron sorbed on the weak edge sites is predominantly present as Fe(II), whereas a significant part of surface-bound Fe(III) was produced on the strong sites (?12% vs ?37% Fe(III) species to total sorbed Fe). PMID:23249208

Soltermann, Daniela; Fernandes, Maria Marques; Baeyens, Bart; Dähn, Rainer; Miehé-Brendlé, Jocelyne; Wehrli, Bernhard; Bradbury, Michael H

2013-07-01

276

Adsorption and Interactions of Methyl Green with Montmorillonite and Sepiolite.  

PubMed

The divalent organic cation, methyl green (MG), undergoes a slow transformation (6 h) to a monovalent cation, carbinol (MGOH(+)) 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(c)/kg clay), no measurable amount of MG remained in solution. The maximal amounts of MGOH(+) adsorbed were larger than those of MG(2+), being 1.15 and 0.75 mol MG/kg clay, respectively, corresponding to 140% of the CEC in the first case. On a charge basis the adsorption of added MG(2+) amounts to 185% of the CEC, which raises the possibility that a certain fraction of MG(2+) transformed into the monovalent form during the incubation period, since other divalent organic cations previously studied only adsorbed up to the CEC (paraquat), or slightly above it (diquat). Adsorption of MG on sepiolite (CEC=0.15 mol(c)/kg) further emphasizes the two patterns of its adsorption. The maximal adsorbed amounts of MG(2+) and MGOH(+) were 0.09 and 0.30 mol/kg clay, respectively. X-ray diffraction measurements gave lower values for the basal spacings for montmorillonite-MG(+) than for MGOH(+), suggesting that MG(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(+), 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. Copyright 2000 Academic Press. PMID:10655119

Rytwo; Nir; Crespin; Margulies

2000-02-01

277

Physicochemical study of amino-functionalized organosilicon cubes intercalated in montmorillonite clay: H-binding and metal uptake.  

PubMed

Two organic-modified montmorillonite clays were prepared by embedding organosilanes bearing different chelating amino-functional groups [Apteos] (3-amino-propyltriethoxysilane), and [Edaptmos] (3-(2-aminoethylamino)propyltrimethoxysilane), in the interlayer space of a Zenith montmorillonite. XRD and FTIR spectroscopic data show that the amino organosilanes are intercalated into the interlamelar space forming cube-like structures bearing one polymanino tail at each cube apex. The intercalated cubes cause an increase of the interlayer spacing of the clay sheets by 6.6 A in [Zenith-Apteos] and by 7.1 A in [Zenith-Edaptmos]. The H-binding properties of the intercalated polyamino organosilanes were studied by potentiometric titration. The Cu-, Cd-, and Pb-binding capacity of [Zenith-Apteos] and [Zenith-Edaptmos] were evaluated in aqueous solution as a function of the pH. Both [Zenith-Apteos] and [Zenith-Edaptmos] showed improvement vs Zenith for metal binding in the order Cu > Pb > Cd. [Zenith-Edaptmos] showed the most important results vs Zenith. Theoretical analysis of the pH edge, achieved by a surface complexation model, shows that (a) the amino-functionalized cube-like structures constitute high affinity metal-binding sites; and (b) the metal ions are bound in a monodendate mode with the amino group of the cube, thus resulting in a maximization of metal-binding efficiency. PMID:18571193

Balomenou, Georgia; Stathi, Panagiota; Enotiadis, Apostolos; Gournis, Dimitrios; Deligiannakis, Yiannis

2008-09-01

278

Effects of Surface Morphology on the Wear and Corrosion Resistance of Post-Treated Nitrided and Nitrocarburized 42CrMo4 Steel  

NASA Astrophysics Data System (ADS)

The surface of alloyed carbon steel was subjected to thermochemical modification by nitrocarburizing and nitriding with or without postoxidation in order to improve its mechanical properties, corrosion, and wear resistance. Treated samples were characterized by testing their basic properties (compound layer thickness, nitriding, nitrocarburizing depth, and surface hardness) according to standards. Detailed estimation of the modified metal surface was performed by additional testing: X-ray diffraction, microstructure, surface roughness and topography, and wear and corrosion resistance. The surface layer obtained after nitrocarburizing treatment consists mainly of ?-Fe2-3(N,C) and ?'-Fe4(N,C); similarly, the nitrided surface is formed by ?-Fe2-3N and ?'-Fe4N iron nitrides. The surface layer after postoxidation contains additionally Fe3O4. The results obtained show that nitrocarburization, nitridation, and postoxidation result in better mechanical, wear, and corrosion resistance of 42CrMo4 steel, and postoxidized sample properties are influenced by surface morphology.

Sola, Ramona; Poli, Giorgia; Veronesi, Paolo; Giovanardi, Roberto

2014-06-01

279

Development of chitosan/montmorillonite nanocomposites with encapsulated ?-tocopherol.  

PubMed

Nanocomposites of chitosan (CS) were developed and characterized in a full factorial design with varying levels of montmorillonite (MMTNa) and encapsulated tocopherol (toc-encap). The structural properties (XRD, FTIR), morphology (TEM), hygroscopic properties (water vapour permeability, hydrophobicity, sorption isotherms) and optical properties (haze, CIELab parameters) of the resulting materials were evaluated. Toc-encap contents up to 10% influenced the intercalation of MMTNa in the CS matrix, resulting in films with reduced water vapour permeability (3.48×10(-11)(g/msPa)), increased hydrophobicity (?GHydroph |7.93-59.54|mJm(-2)) and lower equilibrium moisture content (EMC), thus showing potential for active food packaging materials. At levels above 10%, toc-encap agglomerates occurred, which deteriorated the properties of the resulting films, as shown with the TEM. As the toc-encap content increased, the films became slightly more yellow, more irregular and less transparent, with a higher haze index. PMID:25038682

Dias, Marali Vilela; Machado Azevedo, Viviane; Borges, Soraia Vilela; Soares, Nilda de Fátima Ferreira; de Barros Fernandes, Regiane Victória; Marques, João José; Medeiros, Eber Antonio Alves

2014-12-15

280

Eco-Friendly Magnetic Iron Oxide Pillared Montmorillonite for Advanced Catalytic Degradation of Dichlorophenol  

EPA Science Inventory

Eco-friendly pillared montmorillonites, in which the pillars consist of iron oxide are expected to have interesting and unusual magnetic properties that are applicable for environmental decontamination. Completely “green” and effective composite was synthesized using ...

281

Comparison of nutrient cycling in a surface-flow constructed wetland and in a facultative pond treating secondary effluent.  

PubMed

There is a growing interest in the possibilities offered by combinations of waste stabilisation ponds (WSP) and constructed wetlands (CW). The purpose of our study was to compare treatment performances and nutrient cycling in a surface-flow wetland (SFW) and in a WSP treating secondary effluent. In the period between 2000 and 2003, a pilot SFW and a pilot WSP were constructed at the outlet of the wastewater treatment plant and their performance monitored while both were active under the same conditions. The SFW was planted with Phragmites australis and Eichhornia crassipes, while in the WSP development of algae was spontaneous. Performance efficiency was monitored by means of evaluation of physical and chemical parameters in water, by measurement of plant productivity and by analysis of N and P contents in biomass. The SFW with macrophytes proved more efficient in decreasing the suspended solids (64.6%), settleable solids (91.8%), organic N (59.3%), total N (38%), COD (67.2%) and BOD5 (72.1%) than the WSP. The WSP with algae was more efficient in treatment of ammonia nitrogen (48.9%) and ortho-phosphate (43.9%). The results of this study provide data that are of help in optimising combinations of SFW and WSP. PMID:16114697

Sajn Slak, A; Bulc, T G; Vrhovsek, D

2005-01-01

282

Interaction and properties of highly exfoliated soy protein/montmorillonite nanocomposites.  

PubMed

The soy protein isolate (SPI)/ Na+ -montmorillonite (MMT) plastics were successfully prepared, and their structures and properties were characterized with X-ray diffraction, transmission electron microscopy, differential scanning calorimetry, thermogravimetric analysis, and tensile testing. The interactions between the soy protein macromolecules and MMT in aqueous media were analyzed with zeta-potential measurements, Fourier transform infrared spectroscopy, and electrostatic surface potential calculations. The results revealed that the heterogeneous distribution of the surface positive charges provided the positive-charge-rich domains for the soy globulins bearing net negative charges to anchor into the negatively charged MMT galleries. There were electrostatic attraction and hydrogen bonding interactions on the interfaces of the soy protein and MMT, which led to the good dispersion of the phyllosilicate layers in the protein matrix. The highly exfoliated MMT layers with a dimension of 1-2 nm in thickness were randomly dispersed in the protein matrix containing MMT lower than 12 wt %, whereas the intercalated structure was predominant when the MMT content was higher than 12 wt %. Consequently, the fine dispersion of the MMT layers and the strong interactions between SPI and MMT created the significant improvement of the mechanical strength and thermo-stability of the SPI/MMT plastics. In addition, a schematic illustration was proposed to describe the electrostatic interaction between SPI and MMT as well as the correlation between the interaction and structure in protein/clay systems. PMID:16768387

Chen, Pu; Zhang, Lina

2006-06-01

283

Preparation and characterization of silver loaded montmorillonite modified with sulfur amino acid  

NASA Astrophysics Data System (ADS)

The Na+ montmorillonite (MMT) was modified with sulfur containing amino acid (L-cystine, L-cysteine or L-methionine) and characterized by energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectrum (FT-IR). The results showed the modification was smooth and the surface condition of MMT was changed with sulfur containing groups. Then silver was loaded on the modified MMTs via ion-exchange reaction under microwave irradiation, the spectra of X-ray photoelectron spectroscopy (XPS), EDS and FT-IR confirmed the successful loading of massive silver and the strong interaction between sulfur and silver, the silver loaded L-cystine modified MMT (Ag@AA-MMT-3) with a silver content of 10.93 wt% was the highest of all. Further more, the Ag@AA-MMT-3 was under the irradiation of a UV lamp to turn silver ions to silver nano particles (Ag NPs). The XPS, specific surface area (SSA), transmission electron microscopy (TEM), XRD patterns and UV-vis spectra proved the existence of uniform nano scaled metallic Ag NPs. By contrast, the UV irradiated Ag@AA-MMT-3 (Ag@AA-MMT-UV) showed a much better slow release property than Ag@AA-MMT-3 or Ag@MMT. The Ag@AA-MMT-UV showing a large inhibition zone and high inhibition ratio presented very good antibacterial property.

Li, Tian; Lin, Oulian; Lu, Zhiyuan; He, Liuimei; Wang, Xiaosheng

2014-06-01

284

Morphology, structure and properties of a poly(1-butene)\\/montmorillonite nanocomposite  

Microsoft Academic Search

A specifically formulated nanocomposite based on isotactic poly(1-butene) (PB) and montmorillonite was studied, by wide angle X-ray diffraction (WAXD), small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and polarized light optical microscopy, investigating the polymorphism of the polymer, and examining the interaction between PB and the silicate. Montmorillonite was found to disrupt the ordered morphology of the polymer, determining

Valerio Causin; Carla Marega; Antonio Marigo; Giuseppe Ferrara; Gulnaz Idiyatullina; Fabiana Fantinel

2006-01-01

285

Immobilization of Ni by Al-modified montmorillonite: A novel uptake mechanism  

Microsoft Academic Search

The sorption capacity of montmorillonite clay minerals for small cations, such as Ni2+, can be greatly enhanced by modifying the clay mineral with Al(III). In this study, the mechanisms of Ni uptake by Al-modified montmorillonite were studied using extended x-ray absorption fine structure (EXAFS) spectroscopy of powders and polarized EXAFS spectroscopy of self-supporting clay films to delineate the binding structure

Maarten Nachtegaal; André M. Scheidegger; Rainer Dähn; Daniel Chateigner; Gerhard Furrer

2005-01-01

286

Microsphere pressure sensitive adhesives—acrylic polymer\\/montmorillonite clay nanocomposite materials  

Microsoft Academic Search

In this study, the synthesis and characterization of acrylic polymer\\/montmorillonite (MMT) clay nanocomposite pressure sensitive adhesives (PSA) are presented. Different types and amounts of modified and unmodified montmorillonite clays were dispersed in ethyl acrylate (EA)\\/2-ethylhexyl acrylate (2-EHA) monomer mixture, which was then polymerized using a suspension polymerization technique. Polymerization was monitored in-line using attenuated total reflectance-fourier transform infrared (ATR-FTIR) spectroscopy.

J. Kajtna; U. Šebenik

2009-01-01

287

Thermal properties from membrane of polyamide 6\\/montmorillonite clay nanocomposites obtained by immersion precipitation method  

Microsoft Academic Search

The aim of this work was to obtain membranes from polyamide 6\\/montmorillonite clay nanocomposites through the phase inversion\\u000a technique. The nanocomposites and membranes from polyamide 6\\/montmorillonite clay were characterized by X-ray diffraction\\u000a (XRD), Scanning Electron Microscopy (SEM), Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC). Microporous\\u000a and asymmetric membranes were successfully obtained from nanocomposites and the results showed that the salts

A. M. D. Leite; L. F. Maia; R. A. Paz; E. M. Araújo; H. L. Lira

2009-01-01

288

Effects of montmorillonite nano-clay fillers on PEI mixed matrix membrane for CO 2 removal  

Microsoft Academic Search

This paper focuses on the effect of montmorillonite nano-clay fillers on polyetherimide (PEI) mixed matrix membrane, specifically upon the removal of carbon dioxide. Five different types of montmorillonite (MMT) nano-clays, including unmodified and industrially modified clays, were used as filler to fabricate asymmetric flat sheet mixed matrix membrane (MMM) via a dry\\/wet phase inversion technique. The five types of clay

S. A. Hashemifard; A. F. Ismail; T. Matsuura

2011-01-01

289

Nanoporous Nanocomposite Hydrogels Composed of Polyvinyl Alcohol and Na-montmorillonite  

Microsoft Academic Search

Polyvinyl alcohol nanoporous nanocomposite hydrogels containing various levels of Na-montmorillonite were prepared by a cyclic freezing-thawing technique. An exfoliated morphology of silicate layers was observed for the nanocomposite hydrogels. The uniaxial tensile test indicated that the tensile modulus and tensile strength of the nanocomposite hydrogels increased with increasing Na-montmorillonite content, while their elongation-at-break values decreased. The results showed that by

M. SIROUSAZAR; M. KOKABI; Z. M. HASSAN; A. R. BAHRAMIAN

2012-01-01

290

The carbothermal reduction process of a montmorillonite-polyacrylonitrile intercalation compound  

Microsoft Academic Search

To develop a carbothermal reduction process for the conversion of oxides to nitrides, a montmorillonite-polyacrylonitrile (PAN) intercalation compound was applied as a precursor. Montmorillonite-carbon mixtures were heated as well as the intercalation compound in N2 at 1100 to 1500° C for comparison. From the intercalation compound, ß-sialon, AIN and SiC were mainly formed. Oxides were reduced without their crystallization. On

Yoshiyuki Sugahara; Kazuyuki Kuroda; Chuzo Kato

1988-01-01

291

Characterization of montmorillonite doped PVA/SA blends using X-ray diffraction  

NASA Astrophysics Data System (ADS)

PVA films doped with Montmorillonite was prepared by slow evaporation technique. These films have been used to record X-ray patterns at room temperature. Correlation lengths and microstructural parameters were computed using in-house program employing X-ray data. Results show that correlation lengths as well as crystallite size increases with increase in the concentration of Montmorillonite which is inconformity with the conductivity studies.

Hemalatha, K.; Mahadevaiah, Somashekarappa, H.; Somashekar, R.

2014-04-01

292

Preparation, structure, properties and thermal behavior of rigid-rod polyimide\\/montmorillonite nanocomposites  

Microsoft Academic Search

Polyimide\\/montmorillonite nanocomposites were prepared from solution of poly(amic acid) precursors and the dodecyl-montmorillonite (DMONT) using N-methyl-2-pyrrolidone as a solvent. The cured films of the rigid-rod polyimide\\/DMONT hybrids as characterized by FTIR, TEM and WAXD were exfoliated nanocomposites at low DMONT content (<1 wt.%) and partially exfoliated nanocomposites at high DMONT content (containing aggregates of DMONT). The nanocomposite showed optimum properties

Rathanawan Magaraphan; Wittaya Lilayuthalert; Anuvat Sirivat; Johannes W. Schwank

2001-01-01

293

Diffusion mechanism of sodium ions in compacted montmorillonite under different NaCl concentration  

Microsoft Academic Search

Compacted bentonite, the major mineral being montmorillonite, is a candidate buffer material for geological disposal of high-level radioactive waste. The diffusion behavior of radionuclides in the compacted montmorillonite is an important issue to be clarified for the safety assessment of geological disposal. In this study, one-dimensional, non-steady diffusion experiments using 22Na at different diffusion temperatures and the measurement of the

Tamotsu Kozaki; Jinhong Liu; Seichi Sato

2008-01-01

294

Synergistic Effect of Phosphorus-Containing Montmorillonite with Intumescent Flame Retardant in Polypropylene  

Microsoft Academic Search

Phosphorus-containing montmorillonite (P-MMT) was successfully prepared via intercalating resorcinol bis(diphenyl phosphate) (RDP) into montmorillonite (MMT) layers, and was utilized as a synergistic agent in the polypropylene\\/melamine pyrophosphate\\/pentaerythritol (PP\\/MPP\\/PER) intumescent flame retardant (IFR) system. The synergistic effect of P-MMT and IFR was investigated by dynamic mechanical analysis (DMA), thermogravimetry (TG), limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CCT), and

Xuejun Lai; Xingrong Zeng; Hongqiang Li; Feng Liao; Changyu Yin; Haili Zhang

2012-01-01

295

Synergistic Effect of Phosphorus-containing Montmorillonite with Intumescent Flame Retardant in Polypropylene  

Microsoft Academic Search

Phosphorus-containing montmorillonite (P-MMT) was successfully prepared via intercalating resorcinol bis(diphenyl phosphate) (RDP) into montmorillonite (MMT) layers, and was utilized as a synergistic agent in the polypropylene\\/melamine pyrophosphate\\/pentaerythritol (PP\\/MPP\\/PER) intumescent flame retardant (IFR) system. The synergistic effect of P-MMT and IFR was investigated by dynamic mechanical analysis (DMA), thermogravimetry (TG), limiting oxygen index (LOI), UL-94 test, cone calorimeter test (CCT) and

Xuejun Lai; Xingrong Zeng; Hongqiang Li; Feng Liao; Changyu Yin; Haili Zhang

2011-01-01

296

Effect of hydration state on the frictional properties of montmorillonite-based fault gouge  

Microsoft Academic Search

We report on laboratory experiments examining the effect of hydration state on the frictional properties of simulated clay and quartz fault gouge. We tested four mixtures of Ca-montmorillonite and quartz (100, 70, 50, and 30% montmorillonite) at four hydration states: dry (16.0 wt% water). We controlled the hydration state using either oven drying (for 13 wt% H2O under conditions of

Matt J. Ikari; Demian M. Saffer; Chris Marone

2007-01-01

297

Influence of montmorillonite layered silicate on plasticized poly( l-lactide) blown films  

Microsoft Academic Search

Plasticized poly(l-lactide) (PLA) montmorillonite layered silicate (MLS) nanocomposites were compounded and blown-film processed using a co-rotating twin screw extruder. PLA was mixed with 10wt% acetyltriethyl citrate ester plasticizer and 5wt% of an organically modified montmorillonite at various screw speeds. Wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) determined that the compounded pellets and the blown film PLA\\/MLS nanocomposites were

Christopher Thellen; Caitlin Orroth; Danielle Froio; David Ziegler; Jeanne Lucciarini; Richard Farrell; Nandika Ann D'Souza; Jo Ann Ratto

2005-01-01

298

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

299

Efficacy of two different types of montmorillonite to reduce the toxicity of aflatoxin in pigs  

Microsoft Academic Search

Experiments were conducted to compare the efficacy of montmorillonite (M) and montmorillonite nanocomposite (MN) to reduce the toxicity of aflatoxin (AF) in growing\\/finishing pigs. A total of 144 weaned pigs were assigned to six dietary treatment groups (0 g of adsorbents and 0 mg of AF\\/kg feed; 3 g of M\\/kg feed; 3 g of MN\\/kg feed; 0.11 mg of

Ying Hua Shi; Zi Rong Xu; Cheng Zhang Wang; Yu Sun

2007-01-01

300

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

301

Influence of heating on the solid acidity of montmorillonite: A combined study by DRIFT and Hammett indicators  

Microsoft Academic Search

The solid acidity of montmorillonite and its heated products was determined by combining Hammett indicators and diffuse reflectance Fourier transform infrared spectroscopy. The total amount of solid acid sites was 0.10mmol\\/g montmorillonite and increased after heating. The amount of Lewis acid sites, unsaturated Al3+ ions, increased due to the dehydration and dehydroxylation of montmorillonite. The Brønsted acid sites resulted from

Dong Liu; Peng Yuan; Hongmei Liu; Jingong Cai; Zonghua Qin; Daoyong Tan; Qing Zhou; Hongping He; Jianxi Zhu

2011-01-01

302

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

303

Correlation between primary stability and bone healing of surface treated titanium implants in the femoral epiphyses of rabbits.  

PubMed

The aim of this study was to analyse the stability and osseointegration of surface treated titanium implants in rabbit femurs. The implants were either grit-blasted and acid-etched (BE Group), calcium phosphate (CaP) coated by using the electrodeposition technique, or had bioactive molecules incorporated into the CaP coatings: either cyclic adenosine monophosphate (cAMP) or dexamethasone (Dex). Twenty four cylindrical titanium implants (n = 6/group) were inserted bilaterally into the femoral epiphyses of New Zealand White, female, adult rabbits for 4 weeks. Implant stability was measured by resonance frequency analysis (RFA) the day of implantation and 4 weeks later, and correlated to histomorphometric parameters, bone implant contact (BIC) and bone growth around the implants (BS/TS 0.5 mm). The BIC values for the four groups were not significantly different. That said, histology indicated that the CaP coatings improved bone growth around the implants. The incorporation of bioactive molecules (cAMP and Dex) into the CaP coatings did not improve bone growth compared to the BE group. Implant stability quotients (ISQ) increased in each group after 4 weeks of healing but were not significantly different between the groups. A good correlation was observed between ISQ and BS/TS 0.5 mm indicating that RFA is a non-invasive method that can be used to assess the osseointegration of implants. In conclusion, the CaP coating enhanced bone formation around the implants, which was correlated to stability measured by resonance frequency analysis. Furthers studies need to be conducted in order to explore the benefits of incorporating bioactive molecules into the coatings for peri-implant bone healing. PMID:24818874

Rozé, Julie; Hoornaert, Alain; Layrolle, Pierre

2014-08-01

304

Poly(lactide)-vitamin E derivative/montmorillonite nanoparticle formulations for the oral delivery of Docetaxel.  

PubMed

Four systems of nanoparticles of biodegradable polymers were developed in this research for oral delivery of anticancer drugs with Docetaxel used as a model drug, which include the poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs), the poly(lactide)-vitamin E TPGS nanoparticles (PLA-TPGS NPs), the poly(lactic-co-glycolic acid)-montmorillonite nanoparticles (PLGA/MMT NPs) and the poly(lactide)-vitamin E TPGS/montmorillonite nanoparticles (PLA-TPGS/MMT NPs). Vitamin E TPGS stands for d-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS), which is a water-soluble derivative of natural vitamin E formed by esterification of vitamin E succinate with polyethylene glycol (PEG) 1000. The design was made to take advantages of TPGS in nanoparticle technology such as high emulsification effects and high drug encapsulation efficiency, and those in drug formulation such as high cellular adhesion and adsorption. MMT of similar effects is also a detoxifier, which may cure some side effects caused by the formulated drug. The drug-loaded NPs were prepared by a modified solvent extraction/evaporation method and then characterized for their MMT content, size and size distribution, surface charge and morphology, physical status and encapsulation efficiency of the drug in the NPs, and in vitro drug release profile. Cellular uptake of the coumarin 6-loaded NPs was investigated. In vitro cancer cell viability experiment showed that judged by IC(50), the PLA-TPGS/MMT NP formulation was found 2.89, 3.98, 2.12-fold more effective and the PLA-TPGS NP formulation could be 1.774, 2.58, 1.58-fold more effective than the Taxotere((R)) after 24, 48, 72h treatment, respectively. In vivo PK experiment with SD rats showed that oral administration of the PLA-TPGS/MMT NP formulation and the PLA-TPGS NP formulation could achieve 26.4 and 20.6 times longer half-life respectively than i.v. administration of Taxotere((R)) at the same 10mg/kg dose. One dose oral administration of the NP formulations could realize almost 3 week sustained chemotherapy in comparison of 22h of i.v. administration of Taxotere((R)). The oral bioavailability can be enhanced from 3.59% for Taxotere((R)) to 78% for the PLA-TPGS/MMT NP formulation and 91% for the PLA-TPGS NP formulation respectively. Oral chemotherapy by nanoparticles of biodegradable polymers is feasible. PMID:19299012

Feng, Si-Shen; Mei, Lin; Anitha, Panneerselvan; Gan, Chee Wee; Zhou, Wenyou

2009-07-01

305

Effects of exchanged cation and layer charge on the sorption of water and EGME vapors on montmorillonite clays  

USGS Publications Warehouse

The effects of exchanged cation and layer charge on the sorption of water and ethylene glycol monoethyl ether (EGME) vapors on montmorillonite have been studied on SAz-1 and SWy-1 source clays, each exchanged respectively with Ca, Na, K, Cs and tetramethylammonium (TMA) cations. The corresponding lattice expansions were also determined, and the corresponding N2 adsorption data were provided for comparison. For clays exchanged with cations of low hydrating powers (such as K, Cs and TMA), water shows a notably lower uptake than does N2 at low relative pressures (P/P0). By contrast, EGME shows higher uptakes than N2 on all exchanged clays at all P/P0. The anomaly for water is attributed to its relatively low attraction for siloxane surfaces of montmorillonite because of its high cohesive energy density. In addition to solvating cations and expanding interlayers, water and EGME vapors condense into small clay pores and interlayer voids created by interlayer expansion. The initial (dry) interlayer separation varies more significantly with cation type than with layer charge; the water-saturated interlayer separation varies more with cation type than the EGME-saturated interlayer separation. Because of the differences in surface adsorption and interlayer expansion for water and EGME, no general correspondence is found between the isotherms of water and EGME on exchanged clays, nor is a simple relation observed between the overall uptake of either vapor and the cation solvating power. The excess interlayer capacities of water and of EGME that result from lattice expansion of the exchanged clays are estimated by correcting for amounts of vapor adsorption on planar clay surfaces and of vapor condensation into intrinsic clay pores. The resulting data follow more closely the relative solvating powers of the exchanged cations.

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

1997-01-01

306

Changes in surface levels of mercury, silver, tin, and copper of dental amalgam treated with carbamide peroxide and hydrogen peroxide in vitro  

Microsoft Academic Search

Objectives. The effect of 10% carbamide peroxide or 10% hydrogen peroxide on the surface levels of mercury, silver, tin, and copper of amalgam fillings was tested in vitro with scanning electron microscopy and energy dispersive spectrometric microanalysis.Study design. Samples of amalgam were treated for 14 and 28 days with either 10% carbamide peroxide or 10% hydrogen peroxide solutions and compared

Ilan Rotstein; Chaim Mor; Joel R Arwaz

1997-01-01

307

Transparent films based on PLA and montmorillonite with tunable oxygen barrier properties.  

PubMed

Polylactide (PLA) is viewed as a potential material to replace synthetic plastics (e.g., poly(ethylene terephthalate) (PET)) in food packaging, and there have been a number of developments in this direction. However, for PLA to be competitive in more demanding uses such as the packaging of oxygen-sensitive foods, the oxygen permeability coefficient (OP) needs to be reduced by a factor of ~10. To achieve this, a layer-by-layer (Lbl) approach was used to assemble alternating layers of montmorillonite clay and chitosan on extruded PLA film surfaces. When 70 bilayers were applied, the OP was reduced by 99 and 96%, respectively, at 20 and 50% RH. These are, to our knowledge, the best improvements in oxygen barrier properties ever reported for a PLA/clay-based film. The process of assembling such multilayer structures was characterized using a quartz crystal microbalance with dissipation monitoring. Transmission electron microscopy revealed a well-ordered laminar structure in the deposited multilayer coatings, and light transmittance results demonstrated the high optical clarity of the coated PLA films. PMID:22229499

Svagan, Anna J; Åkesson, Anna; Cárdenas, Marité; Bulut, Sanja; Knudsen, Jes C; Risbo, Jens; Plackett, David

2012-02-13

308

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, Iñigo; López-Gónzalez, Mar; Corrales, Teresa; Marcelo, Gema

2012-11-01

309

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

2012-01-01

310

Modified Montmorillonite Clay Microparticles for Stable Oil-in-Seawater Emulsions.  

PubMed

Environmentally benign clay particles are of great interest for the stabilization of Pickering emulsions. Dodecane-in-synthetic seawater (SSW) emulsions formed with montmorillonite (MMT) clay microparticles modified with bis(2-hydroxyethyl)oleylamine were stable against coalescence, even at clay concentrations down to 0.1% w/v. Remarkably, as little as 0.001% w/v surfactant lowered the hydrophilicity of the clay to a sufficient level for stabilization of oil-in-SSW emulsions. The favorable effect of SSW on droplet size reduction and emulsion stability enhancement is hypothesized to be due to reduced electrostatic repulsion between adsorbed clay particles and a consequent increase in the continuous phase (an aqueous clay suspension) viscosity. Water/oil (W/O) emulsions were inverted to O/W either by decreasing the mass ratio of surfactant-to-clay (transitional inversion) or by increasing the water volume fraction (catastrophic inversion). For both types of emulsions, coalescence was minimal and the sedimentation or creaming was highly correlated with the droplet size. For catastrophic inversions, the droplet size of the emulsions was smaller in the case of the preferred curvature. Suspensions of concentrated clay in oil dispersions in the presence of surfactant were stable against settling. The mass transfer pathways during emulsification of oil containing the clay particles were analyzed on the droplet size/stability phase diagrams to provide insight for the design of dispersant systems for remediating surface and subsurface oceanic oil spills. PMID:24932773

Dong, Jiannan; Worthen, Andrew J; Foster, Lynn M; Chen, Yunshen; Cornell, Kevin A; Bryant, Steven L; Truskett, Thomas M; Bielawski, Christopher W; Johnston, Keith P

2014-07-23

311

Bisphenol A sorption by organo-montmorillonite: Implications for the removal of organic contaminants from water.  

PubMed

Remediation of bisphenol A (BPA) from aqueous solutions by adsorption using organoclays synthesized from montmorillonite (MMT) with different types of organic surfactant molecules was demonstrated. High adsorption capacities of the organoclays for the uptake of BPA were observed and these demonstrated their potential application as strong adsorbents for noxious organic water contaminants. The adsorption of BPA was significantly influenced by pH, with increased adsorption of BPA in acidic pH range. However, the organoclays intercalated with highly loaded surfactants and/or large surfactant molecules were less influenced by the pH of the environment and this was thought to be due to the shielding the negative charge from surfactant molecules and the development of more positive charge on the clay surface, which leads to the attraction of anionic BPA even at alkaline pH. The hydrophobic phase created by loaded surfactant molecules contributed to a partitioning phase, interacting with BPA molecules strongly through hydrophobic interaction. Pseudo-second order kinetic model and Langmuir isotherm provided the best fit for the adsorption of BPA onto the organoclays. In addition, the adsorption process was spontaneous and exothermic with lower temperature facilitating the adsorption of BPA onto the organoclays. The described process provides a potential pathway for the removal of BPA from contaminated waters. PMID:24412097

Park, Yuri; Sun, Zhiming; Ayoko, Godwin A; Frost, Ray L

2014-07-01

312

Structure-property relationships in isotactic poly(propylene)/ethylene propylene rubber/montmorillonite nanocomposites.  

PubMed

Nanocomposites based on isotactic polypropylene/ethylene propylene rubber (iPP/EPR) were prepared adding different amounts of montmorillonite and maleated polypropylene. The structure and morphology of the samples were characterized by small angle X-ray scattering, wide angle X-ray diffraction, electronic and optical microscopy and differential scanning calorimetry, iPP showed a polymorphic behavior. Clay disrupted the ordered crystallization of iPP and had a key role in shaping the distribution of iPP and EPR phases: larger filler contents brought about smaller, less coalesced and more homogeneous rubber domains. Clay distributed itself only in the continuous phase and not in the rubber domains. Tactoids persisted on the surface of the sample, while delamination proceeded to a greater degree in the bulk of the materials. Melt flow rate, impact strength, flexural and tensile properties, were also measured and a structure-property correlation was sought. Clay produced its most significant effect on physical-mechanical properties by controlling the size of rubber domains in the heterophasic matrix. This allowed to obtain nanocomposites with increased stiffness and impact strength, a remarkable achievement for polymer layered-silica nanocomposites that usually suffer the drawback of being stiffer than the unfilled matrix, but at the same time with a lower resistance to impact. A beneficial effect of clay on thermal stability was also observed. PMID:18572583

Causin, Valerio; Marega, Carla; Marigo, Antonio; Ferraro, Giuseppe; Ferrara, Angelo; Selleri, Roberta

2008-04-01

313

Removal of herbicides from aqueous solutions by modified forms of montmorillonite.  

PubMed

This investigation for the removal of agricultural pollutants, imazaquin and atrazine was conducted using montmorillonite (MMT) exchanged with organic cations through ion exchange. The study found that the adsorption of the herbicides was affected by the degree of organic cation saturations, the size of organic cations and the different natures of the herbicides. The modified clays intercalated with the larger surfactant molecules at the higher concentrations tended to enhance the adsorption of imazaquin and atrazine. In particular, the organoclays were highly efficient for the removal of imazaquin while the adsorption of atrazine was minimal due to the different hydrophobicities. Both imazaquin and atrazine were influenced by the changes of pH. The amphoteric imazaquin exists as an anion at the pH 5-7 and the anionic imazaquin was protonated to a neutral and further a cationic form when the pH is lower. The weak base, atrazine was also protonated at lower pH values. The anionic imazaquin had a strong affinity to the organoclays on the external surface as well as in the interlayer space of the MMT through electrostatic and hydrophobic interactions. In this study, the electrostatic interaction can be the primary mechanism involved during the adsorption process. This study also investigated a comparative adsorption for the imazaquin and atrazine and the lower adsorption of atrazine was enhanced and this phenomenon was due to the synergetic effect. This work highlights a potential mechanism for the removal of specific persistence herbicides from the environment. PMID:24267339

Park, Yuri; Sun, Zhiming; Ayoko, Godwin A; Frost, Ray L

2014-02-01

314

Photocatalytic reactions of nanocomposite of ZnS nanoparticles and montmorillonite  

NASA Astrophysics Data System (ADS)

ZnS nanoparticles stabilized by cetyltrimethylammonium bromide (CTAB) were deposited on montmorillonite (MMT) forming a ZnS-CTA-MMT nanocomposite. The nanocomposite was characterized by scanning electron microscopy (SEM), Fourier transformed infrared (FTIR) and UV diffuse reflectance spectra (DRS) spectrometry, X-ray powder diffraction (XRD) and specific surface area measurements. Thereafter, it was used for photocatalytic reactions under UV irradiation (Hg lamp) in three different reaction media with different pH: NaOH solution, HCl solution and water. Prior to the photocatalytic reactions the dispersions were saturated by carbon dioxide to buffer the systems. The main reaction products in gas phase determined by gas chromatography were hydrogen and methane. The reactions were monitored by measuring oxidation-reduction potentials. The highest yields of hydrogen were obtained in the dispersion acidified by HCl but the concentrations of methane were similar in all tested media. Hydrogen was supposed to be formed by the reaction of two hydrogen radicals. Methane was formed by the reduction of carbon dioxide and by the partial decomposition of CTAB.

Praus, P.; Reli, M.; Ko?í, K.; Obalová, L.

2013-06-01

315

Low-temperature atomic layer deposition of Al{sub 2}O{sub 3} on blown polyethylene films with plasma-treated surfaces  

SciTech Connect

In this study, a layer of Al{sub 2}O{sub 3} was deposited on blown polyethylene films by atomic layer deposition (ALD) at low temperatures, and the surface characteristics of these Al{sub 2}O{sub 3}-coated blown polyethylene films were analyzed. In order to examine the effects of the plasma treatment of the surfaces of the blown polyethylene films on the properties of the films, both untreated and plasma-treated film samples were prepared under various processing conditions. The surface characteristics of the samples were determined by x-ray photoelectron spectroscopy, as well as by measuring their surface contact angles. It was confirmed that the surfaces of the plasma-treated samples contained a hydroxyl group, which helped the precursor and the polyethylene substrate to bind. ALD of Al{sub 2}O{sub 3} was performed through sequential exposures to trimethylaluminum and H{sub 2}O at 60 Degree-Sign C. The surface morphologies of the Al{sub 2}O{sub 3}-coated blown polyethylene films were observed using atomic force microscopy and scanning electron microscopy/energy-dispersive x-ray spectroscopy. Further, it was confirmed that after ALD, the surface of the plasma-treated film was covered with alumina grains more uniformly than was the case for the surface of the untreated polymer film. It was also confirmed via the focused ion beam technique that the layer Al{sub 2}O{sub 3} conformed to the surface of the blown polyethylene film.

Beom Lee, Gyeong; Sik Son, Kyung; Won Park, Suk; Hyung Shim, Joon; Choi, Byoung-Ho [School of Mechanical Engineering, Korea University, Seoul 136-707 (Korea, Republic of)

2013-01-15

316

Imazaquin adsorbed on pillared clay and crystal violet-montmorillonite complexes for reduced leaching in soil.  

PubMed

Ground water pollution due to herbicide leaching has become a serious environmental problem. Imazaquin [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)quinoline-3-carboxylic acid] is an herbicide used to control broadleaf weeds in legume crops. Imazaquin is negatively charged at the basic pH of calcareous soils and exhibits high leaching potential in soils. Our aim was to design formulation of imazaquin to reduce herbicide leaching. Imazaquin sorption on pillared clay (PC) and crystal violet (CV)-montmorillonite complexes was studied. The CV-montmorillonite complexes become positively charged with adsorption of CV above the cation exchange capacity (CEC) of montmorillonite, and thus can sorb imazaquin. The Langmuir equation provides a good fit to isotherms of imazaquin sorption on PC and CV-montmorillonite complexes, but for charged complexes an equation that combines electrostatics with specific binding was preferred. Maximal imazaquin sorption was 17.3 mmol kg-1 for PC and 22.2 mmol kg-1 for CV-montmorillonite complexes. The extents of imazaquin desorption into water were 21% for PC and 5% for CV-clay complexes. The presence of anions decreased imazaquin sorption on both sorbents in the sequence phosphate > acetate > sulfate. Reduction of imazaquin sorption by the anions and the extent of its desorption in electrolyte solutions were higher for PC than for CV-clay complexes. Leaching of imazaquin from CV-montmorillonite formulations through soil (Rhodoxeralf) columns was two times less than from PC formulations and four times less than that of technical imazaquin. The CV-montmorillonite complexes at a loading above the CEC appear to be suitable for preparation of organo-clay-imazaquin formulations that may reduce herbicide leaching significantly. PMID:12371183

Polubesova, Tamara; Nir, Shlomo; Gerstl, Zev; Borisover, Mikhail; Rubin, Baruch

2002-01-01

317

Effects of Graded Levels of Montmorillonite on Performance, Hematological Parameters and Bone Mineralization in Weaned Pigs  

PubMed Central

The aim of this study was to investigate the effects of graded levels of montmorillonite, a constituent of clay, on performance, hematological parameters and bone mineralization in weaned pigs. One hundred and twenty, 35-d-old crossbred pigs (Duroc×Large White×Landrace, 10.50±1.20 kg) were used in a 28-d experiment and fed either an unsupplemented corn-soybean meal basal diet or similar diets supplemented with 0.5, 1.0, 2.5 or 5.0% montmorillonite added at the expense of wheat bran. Each treatment was replicated six times with four pigs (two barrows and two gilts) per replicate. Feed intake declined (linear and quadratic effect, p< 0.01) with increasing level of montmorillonite while feed conversion was improved (linear and quadratic effect, p<0.01). Daily gain was unaffected by dietary treatment. Plasma myeloperoxidase declined linearly (p = 0.03) with increasing dietary level of montmorillonite. Plasma malondialdehyde and nitric oxide levels were quadratically affected (p<0.01) by montmorillonite with increases observed for pigs fed the 0.5 and 1.0% levels which then declined for pigs fed the 2.5 and 5.0% treatments. In bone, the content of potassium, sodium, copper, iron, manganese and magnesium were decreased (linear and quadratic effect, p<0.01) in response to an increase of dietary montmorillonite. These results suggest that dietary inclusion of montmorillonite at levels as high as 5.0% does not result in overt toxicity but could induce potential oxidative damage and reduce bone mineralization in pigs.

Duan, Q. W.; Li, J. T.; Gong, L. M.; Wu, H.; Zhang, L. Y.

2013-01-01

318

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

319

Effect of Organic Modifier and Preparation Method on the Morphology and Crystalline Structure of Poly(vinylideneflouride)-Montmorillonite Nanocomposites  

NASA Astrophysics Data System (ADS)

Polymer-layered silicate nanocomposites have proven to be an effective method of improving the physical properties of many different polymers, but PVDF-clay composites have received relatively little attention. In this study, two commercially available montmorillonite-based nanoclays with different organic modifiers were each used to prepare both solution cast and precipitated PVDF-clay composites from dimethylformamide (DMF) solutions. Structure and morphology of the PVDF-clay nanocomposites have been investigated. Depending on which organically modified nanoclay was used, solution cast composites showed either a phase-separated or a partially intercalated morphology, while precipitating the PVDF with water always yielded a completely exfoliated morphology. For solution cast samples, it has also been observed that the nanoclay layers are parallel to the film surface. The presence of the nanoclay in any morphology promoted the crystallization of PVDF's ? polymorph.

Dillon, Douglas

2005-03-01

320

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 Brønsted acid sites.

Chmielarz, Lucjan; Gil, Barbara; Ku?trowski, Piotr; Piwowarska, Zofia; Dudek, Barbara; Michalik, Marek

2009-05-01

321

The microbiological and clinical outcome of guide wire exchanged versus newly inserted antimicrobial surface treated central venous catheters  

PubMed Central

Introduction The management of suspected central venous catheter (CVC)-related sepsis by guide wire exchange (GWX) is not recommended. However, GWX for new antimicrobial surface treated (AST) triple lumen CVCs has never been studied. We aimed to compare the microbiological outcome of triple lumen AST CVCs inserted by GWX (GWX-CVCs) with newly inserted triple lumen AST CVCs (NI-CVCs). Methods We studied a cohort of 145 consecutive patients with GWX-CVCs and contemporaneous site-matched control cohort of 163 patients with NI-CVCs in a tertiary intensive care unit (ICU). Results GWX-CVC and NI-CVC patients were similar for mean age (58.7 vs. 62.2 years), gender (88 (60.7%) vs. 98 (60.5%) male) and illness severity on admission (mean Acute Physiology and Chronic Health Evaluation (APACHE) III: 71.3 vs. 72.2). However, GWX patients had longer median ICU lengths of stay (12.2 vs. 4.4 days; P < 0.001) and median hospital lengths of stay (30.7 vs. 18.0 days; P < 0.001). There was no significant difference with regard to the number of CVC tips with bacterial or fungal pathogen colonization among GWX-CVCs vs. NI-CVCs (5 (2.5%) vs. 6 (7.4%); P = 0.90). Catheter-associated blood stream infection (CA-BSI) occurred in 2 (1.4%) GWX patients compared with 3 (1.8%) NI-CVC patients (P = 0.75). There was no significant difference in hospital mortality (35 (24.1%) vs. 48 (29.4%); P = 0.29). Conclusions GWX-CVCs and NI-CVCs had similar rates of tip colonization at removal, CA-BSI and mortality. If the CVC removed by GWX is colonized, a new CVC must then be inserted at another site. In selected ICU patients at higher central vein puncture risk receiving AST CVCs GWX may be an acceptable initial approach to line insertion.

2013-01-01

322

Electrochemical determination of phenol using CTAB-functionalized montmorillonite electrode.  

PubMed

Montmorillonite calcium (MMT) was modified with cetyltrimethylammonium bromide (CTAB) via replacement of its inorganic exchangeable cations. The resulting CTAB-modified MMT (CTAB/MMT) was used to modify the carbon paste electrode (CPE). The electrochemical behaviours of phenol at the unmodified CPE, MMT-modified CPE and CTAB/MMT-modified CPE were examined. It was found that the oxidation signal of phenol was remarkably improved at the CTAB/MMT-modified CPE, which was attributed to the higher accumulation efficiency of CTAB/MMT. Based on this, a sensitive and convenient electrochemical method was proposed for the determination of phenol. The effect of supporting electrolyte on the oxidation of phenol was examined, and 0.1 mol l(-1) NaOH was finally employed. In addition, the influences of mass content of CTAB/MMT and accumulation time were also investigated. The optimal mass content of CTAB/MMT is 25%, and the accumulation time is 3 min. Under the optimized conditions, the oxidation peak current of phenol is proportional to its concentration over the range from 1.0 x 10(-7) to 3.0 x 10(-5) mol l(-1), and the limit of detection is estimated to be 6.0 x 10(-8) mol l(-1). Finally, the CTAB/MMT-modified CPE was successfully applied to determine phenol in water samples. PMID:19705607

Huang, Wensheng; Zhou, Dazhai; Liu, Xiaopeng; Zheng, Xiaojiang

2009-06-01

323

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

324

The effect of dispersion technique of montmorillonite on polyisocyanurate nanocomposites  

NASA Astrophysics Data System (ADS)

The biomass represents an abundant, renewable, competitive and low cost resource that can play an alternative role to petrochemical resources. The central topic of the research activity reported is the use of rape seed oil (RO) as a raw material for the production of rigid polyisocyanurate foams (PIR). The content of the renewable resource-derived polymers achieved in ready foams is up to 20%. By using biopolymers as a matrix, a prospective way is to reinforce them with nanoparticles, organically modified clays, for improvement of mechanical properties while, at the same time, replacing petrochemical raw materials. Organoclay Cloisite® 15A was tested as a filler of PIR foams. Three different techniques - ultrasonification, mixing by three-roll mills, and high-pressure homogenization were used for dispergation of nanoclays in polyols. Composite polyisocyanurate foams and solid polymer samples were produced and tested for stiffness and strength. This paper discusses the studies into the use of RO as a renewable source in rigid PIR foams filled with organomodified montmorillonite clay with loadings from 1 to 5% by weight.

Cabulis, U.; Fridrihsone, A.; Andersons, J.; Vlcek, T.

2014-05-01

325

Mechanism of amitriptyline adsorption on Ca-montmorillonite (SAz-2).  

PubMed

The uptake of amitriptyline (AMI) from aqueous environment by Ca-montmorillonite (SAz-2) was studied in a batch system under different physicochemical conditions. The adsorbent was characterized by X-ray diffraction and Fourier transform infrared (FTIR) analyses. The AMI adsorption on SAz-2 obeyed the Langmuir isotherm with a capacity of 330mg/g (1.05mmol/g) at pH 6-7. The adsorption kinetics was fast, almost reaching equilibrium in 2h, and followed a pseudo-second-order kinetic model. Desorption of exchangeable cations correlated with the AMI adsorption well, indicating that cation exchange was the major mechanism. X-ray diffraction patterns showing significant expansions of the d001 spacing and characteristic FTIR band shifts toward higher frequencies after AMI adsorption onto SAz-2 indicated that the adsorbed AMI molecules were intercalated into the interlayers of the mineral. Thermodynamic parameters based on partitioning coefficients suggested that the AMI adsorption was an endothermic physisorption at high adsorption levels. At low and higher AMI adsorption levels, the intercalated AMI molecules take a horizontal monolayer and bilayer conformation, respectively. The higher adsorption capacity suggested that SAz-2 could be a good candidate to remove AMI from wastewater and would be an important environmental sink for the fate and transport of AMI in soils and groundwater. PMID:24373983

Chang, Po-Hsiang; Jiang, Wei-Teh; Li, Zhaohui; Kuo, Chung-Yih; Jean, Jiin-Shuh; Chen, Wan-Ru; Lv, Guocheng

2014-07-30

326

Synthesis of silver nanoparticles in montmorillonite and their antibacterial behavior  

PubMed Central

Silver nanoparticles (Ag NPs) were synthesized by the chemical reducing method in the external and interlamellar space of montmorillonite (MMT) as a solid support at room temperature. AgNO3 and NaBH4 were used as a silver precursor and reducing agent, respectively. The most favorable experimental conditions for synthesizing Ag NPs in the MMT are described in terms of the initial concentration of AgNO3. The interlamellar space limits changed little (d-spacing = 1.24–1.47 nm); therefore, Ag NPs formed on the MMT suspension with d-average = 4.19–8.53 nm diameter. The Ag/MMT nanocomposites (NCs), formed from AgNO3/MMT suspension, were characterizations with different instruments, for example UV-visible, PXRD, TEM, SEM, EDXRF, FT-IR, and ICP-OES analyzer. The antibacterial activity of different sizes of Ag NPs in MMT were investigated against Gram-positive, ie, Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) and Gram-negative bacteria, ie, Escherichia coli, Escherichia coli O157:H7, and Klebsiella pneumoniae, by the disk diffusion method using Mueller-Hinton agar (MHA). The smaller Ag NPs were found to have significantly higher antibacterial activity. These results showed that Ag NPs can be used as effective growth inhibitors in different biological systems, making them applicable to medical applications.

Shameli, Kamyar; Ahmad, Mansor Bin; Zargar, Mohsen; Yunus, Wan Md Zin Wan; Rustaiyan, Abdolhossein; Ibrahim, Nor Azowa

2011-01-01

327

Adhesive properties of polypropylene (PP) and polyethylene terephthalate (PET) film surfaces treated by DC glow discharge plasma  

Microsoft Academic Search

In this study, the adhesive properties of the plasma modified polypropylene (PP) and polyethylene terephthalate (PET) film surfaces have been investigated. Hydrophilicity of these polymer film surfaces was studied by contact angle measurements. The surface energy of the polymer films was calculated from contact angle data using Fowkes method. The chemical composition of the polymer films was analyzed by X-ray

K. Navaneetha Pandiyaraj; V. Selvarajan; R. R. Deshmukh; Changyou Gao

2008-01-01

328

A comparison of the corrosion behaviour and surface characteristics of vacuum-brazed and heat-treated Ti6Al4V alloy.  

PubMed

The corrosion characteristics of the brazed Ti6Al4V specimens were analysed and compared with respect to the conventionally heat-treated specimens by an electrochemical corrosion test. The object of this research was to explore the potentiality of the brazed titanium for biomaterials. The characteristics of the 1300 degrees C heat-treated and the 970 degrees C brazed specimens, with passivation and sterilization treatment, were evaluated by measurement of corrosion potential, Ecorr, corrosion current densities, Icorr, polarization resistance of the reacted surface films, Rp, in a potentiodynamic test. The experimental results show that the corrosion rates of the heat-treated and the brazed samples are similar at Ecorr, and the value of Ecorr for the brazed sample is noble to the heat-treated samples. The passive current density of the brazed specimen is either lower or higher than the heat-treated specimen, depending on the polarization potential. By Auger electron spectroscopic and high-resolution X-ray photoelectron spectroscopic analysis on specimens from the potentiostatic test, the elements of copper and nickel in the brazing filler were not detected while less alumina was found in the reacted film of the brazed specimens when compared with the heat-treated specimens. The implication of the results is discussed. PMID:15348855

Lee, T M; Chang, E; Yang, C Y

1998-08-01

329

Photoinduced catalytic adsorption of model contaminants on Bi/Cu pillared montmorillonite in the visible light range  

EPA Science Inventory

Montmorillonite K10 clay was pillared with BiCl3 and Cu(NO3)2 to extend its applicability as catalytic adsorbent to degrade aqueous solution of anionic azo-dye Methyl Orange (MO) in the presence of visible light irradiation. The preparation of Bi/Cu-montmorillonite utilized benig...

330

Preparation and study of the adsorption properties of microporous sorbents based on montmorillonite and basic aluminum salts  

Microsoft Academic Search

Sorbents based on montmorillonite and basic aluminum chlorides with platelike micropores 0.77 nm thick were synthesized. The parameters of the primary and secondary pore structure of these materials were estimated from adsorption and x-ray data. A method was proposed for estimating the amount of initial montmorillonite stacks and stacks modified by the basic aluminum cations.

Yu. I. Tarasevich; V. E. Doroshenko; V. M. Rudenko; Z. G. Ivanova

1986-01-01

331

Effects of dextrose and lipopolysaccharide on the corrosion behavior of a Ti-6Al-4V alloy with a smooth surface or treated with double-acid-etching.  

PubMed

Diabetes and infections are associated with a high risk of implant failure. However, the effects of such conditions on the electrochemical stability of titanium materials remain unclear. This study evaluated the corrosion behavior of a Ti-6Al-4V alloy, with a smooth surface or conditioned by double-acid-etching, in simulated body fluid with different concentrations of dextrose and lipopolysaccharide. For the electrochemical assay, the open-circuit-potential, electrochemical impedance spectroscopy, and potentiodynamic test were used. The disc surfaces were characterized by scanning electron microscopy and atomic force microscopy. Their surface roughness and Vickers microhardness were also tested. The quantitative data were analyzed by Pearson's correlation and independent t-tests (??=?0.05). In the corrosion parameters, there was a strong lipopolysaccharide correlation with the Ipass (passivation current density), Cdl (double-layer capacitance), and Rp (polarization resistance) values (p<0.05) for the Ti-6Al-4V alloy with surface treatment by double-acid-etching. The combination of dextrose and lipopolysaccharide was correlated with the Icorr (corrosion current density) and Ipass (p<0.05). The acid-treated groups showed a significant increase in Cdl values and reduced Rp values (p<0.05, t-test). According to the topography, there was an increase in surface roughness (R2?=?0.726, p<0.0001 for the smooth surface; R2?=?0.405, p?=?0.036 for the double-acid-etching-treated surface). The microhardness of the smooth Ti-6Al-4V alloy decreased (p<0.05) and that of the treated Ti-6Al-4V alloy increased (p<0.0001). Atomic force microscopy showed changes in the microstructure of the Ti-6Al-4V alloy by increasing the surface thickness mainly in the group associated with dextrose and lipopolysaccharide. The combination of dextrose and lipopolysaccharide affected the corrosion behavior of the Ti-6Al-4V alloy surface treated with double-acid-etching. However, no dose-response corrosion behavior could be observed. These results suggest a greater susceptibility to corrosion of titanium implants in diabetic patients with associated infections. PMID:24671257

Faverani, Leonardo P; Assunção, Wirley G; de Carvalho, Paulo Sérgio P; Yuan, Judy Chia-Chun; Sukotjo, Cortino; Mathew, Mathew T; Barao, Valentim A

2014-01-01

332

Effects of Dextrose and Lipopolysaccharide on the Corrosion Behavior of a Ti-6Al-4V Alloy with a Smooth Surface or Treated with Double-Acid-Etching  

PubMed Central

Diabetes and infections are associated with a high risk of implant failure. However, the effects of such conditions on the electrochemical stability of titanium materials remain unclear. This study evaluated the corrosion behavior of a Ti-6Al-4V alloy, with a smooth surface or conditioned by double-acid-etching, in simulated body fluid with different concentrations of dextrose and lipopolysaccharide. For the electrochemical assay, the open-circuit-potential, electrochemical impedance spectroscopy, and potentiodynamic test were used. The disc surfaces were characterized by scanning electron microscopy and atomic force microscopy. Their surface roughness and Vickers microhardness were also tested. The quantitative data were analyzed by Pearson's correlation and independent t-tests (??=?0.05). In the corrosion parameters, there was a strong lipopolysaccharide correlation with the Ipass (passivation current density), Cdl (double-layer capacitance), and Rp (polarization resistance) values (p<0.05) for the Ti-6Al-4V alloy with surface treatment by double-acid-etching. The combination of dextrose and lipopolysaccharide was correlated with the Icorr (corrosion current density) and Ipass (p<0.05). The acid-treated groups showed a significant increase in Cdl values and reduced Rp values (p<0.05, t-test). According to the topography, there was an increase in surface roughness (R2?=?0.726, p<0.0001 for the smooth surface; R2?=?0.405, p?=?0.036 for the double-acid-etching-treated surface). The microhardness of the smooth Ti-6Al-4V alloy decreased (p<0.05) and that of the treated Ti-6Al-4V alloy increased (p<0.0001). Atomic force microscopy showed changes in the microstructure of the Ti-6Al-4V alloy by increasing the surface thickness mainly in the group associated with dextrose and lipopolysaccharide. The combination of dextrose and lipopolysaccharide affected the corrosion behavior of the Ti-6Al-4V alloy surface treated with double-acid-etching. However, no dose-response corrosion behavior could be observed. These results suggest a greater susceptibility to corrosion of titanium implants in diabetic patients with associated infections.

Faverani, Leonardo P.; Assuncao, Wirley G.; de Carvalho, Paulo Sergio P.; Yuan, Judy Chia-Chun; Sukotjo, Cortino; Mathew, Mathew T.; Barao, Valentim A.

2014-01-01

333

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

334

Method for treating underground formations  

SciTech Connect

Disclosed is a method for treating subterranean formations such as underground petroleum-containing formations penetrated by a well, and particularly a formation penetrated by a producing well which formation contain a plurality of zones, one or more of which are producing petroleum and one or more of which are producing water. The treatment selectively reduces the permeability of the water-producing intervals without adversely affecting the permeability of the oil producing intervals, thereby reducing the production of water and reducing the water-oil ratio of the fluid being produced from the well. The treatment method involves introducing an effective amount of a liquid comprising a hydrocarbon having dispersed therein an unhydrated water swellable clay such as bentonite, a sodium montmorillonite. The clay swells on contacting water in the water-producing intervals and plugs or reduces the permeability of the flow channels in the water-producing intervals.

Noles, J.R.; Walker, C.O.; White, N.F.

1981-04-14

335

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, Håkan

2013-01-01

336

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

337

Influence of operating parameters on surface properties of RF glow discharge oxygen plasma treated TiO?/PET film for biomedical application.  

PubMed

In this paper, a thin transparent titania (TiO2) film was coated on the surface of flexible poly(ethylene terephthalate) (PET) film using the sol-gel method. The surface properties of the obtained TiO2/PET film were further improved by RF glow discharge oxygen plasma as a function of exposure time and discharge power. The changes in hydrophilicity of TiO2/PET films were analyzed by contact angle measurements and surface energy. The influence of plasma on the surface of the TiO2/PET films was analyzed by atomic force microscopy (AFM) as well as the change in chemical state and composition that were investigated by X-ray photo electron spectroscopy (XPS). The cytotoxicity of the TiO2/PET films was analyzed using human osteoblast cells and the bacterial eradication behaviors of TiO2/PET films were also evaluated against Staphylococcus bacteria. It was found that the surface roughness and incorporation of oxygen containing polar functional groups of the plasma treated TiO2/PET films increased substantially as compared to the untreated one. Moreover the increased concentration of Ti(3+) on the surface of plasma treated TiO2/PET films was due to the transformation of chemical states (Ti(4+)?Ti(3+)). These morphological and chemical changes are responsible for enhanced hydrophilicity of the TiO2/PET films. Furthermore, the plasma treated TiO2/PET film exhibited no citotoxicity against osteoblast cells and antibacterial activity against Staphylococcus bacteria which can find application in manufacturing of biomedical devices. PMID:24433917

Pandiyaraj, K Navaneetha; Deshmukh, R R; Mahendiran, R; Su, Pi-G; Yassitepe, Emre; Shah, Ismat; Perni, Stefano; Prokopovich, Polina; Nadagouda, Mallikarjuna N

2014-03-01

338

Effects of Oxygen Addition and Treating Distance on Surface Cleaning of ITO Glass by a Non-Equilibrium Nitrogen Atmospheric-Pressure Plasma Jet  

Microsoft Academic Search

Effects of oxygen addition and treating distance on cleaning organic contaminants on stationary and non-stationary (1–9 cm\\/s)\\u000a ITO glass surfaces by a parallel-plate nitrogen-based dielectric barrier discharge (DBD) are investigated experimentally;\\u000a the DBD is driven by a 60 kHz bipolar quasi-pulsed power source. The results show that two regimes of favorable operating\\u000a condition for improving the hydrophilic property of the surface (reducing

M.-H. Chiang; K.-C. Liao; I.-M. Lin; C.-C. Lu; H.-Y. Huang; C.-L. Kuo; J.-S. Wu; C.-C. Hsu; S.-H. Chen

2010-01-01

339

Effect of sintering temperatures on corrosion and wear properties of sol–gel alumina coatings on surface pre-treated mild steel  

Microsoft Academic Search

Sol–gel alumina coatings were developed on the surface pre-treated (zinc-phosphated) mild steel substrate and subsequently sintered at 300°C, 400°C and 500°C. The alumina sol was synthesised using aluminium iso-propoxide as a precursor material. FTIR of the boehmite (AlOOH) gel sintered at above-mentioned temperatures was employed to identify the presence of various functional groups. The microstructural features and the phase analysis

G. Ruhi; O. P. Modi; A. S. K. Sinha; I. B. Singh

2008-01-01

340

Synthesis and characterization of silver/montmorillonite/chitosan bionanocomposites by chemical reduction method and their antibacterial activity  

PubMed Central

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.

Shameli, Kamyar; Ahmad, Mansor Bin; Zargar, Mohsen; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Shabanzadeh, Parvaneh; Moghaddam, Mansour Ghaffari

2011-01-01

341

The effect of iron on montmorillonite stability. (I) Background and thermodynamic considerations  

NASA Astrophysics Data System (ADS)

It is envisaged that high-level nuclear waste (HLW) will be disposed of in underground repositories. Many proposed repository designs include steel waste canisters and bentonite backfill. Natural analogues and experimental data indicate that the montmorillonite component of the backfill could react with steel corrosion products to produce non-swelling Fe-rich phyllosilicates such as chamosite, berthierine, or Fe-rich smectite. In K-bearing systems, the alteration of montmorillonite to illite/glauconite could also be envisaged. If montmorillonite were altered to non-swelling minerals, the swelling capacity and self-healing properties of the bentonite backfill could be reduced, thereby diminishing backfill performance. The main aim of this paper was to investigate Fe-rich phyllosilicate mineral stability at the canister-backfill interface using thermodynamic modelling. Estimates of thermodynamic properties were made for Fe-rich clay minerals in order to construct approximate phase-relations for end-member/simplified mineral compositions in logarithmic activity space. Logarithmic activity diagrams (for the system Al 2O 3-FeO-Fe 2O 3-MgO-Na 2O-SiO 2-H 2O) suggest that if pore waters are supersaturated with respect to magnetite in HLW repositories, Fe(II)-rich saponite is the most likely montmorillonite alteration product (if f values are significantly lower than magnetite-hematite equilibrium). Therefore, the alteration of montmorillonite may not be detrimental to nuclear waste repositories that include Fe, as long as the swelling behaviour of the Fe-rich smectite produced is maintained. If f exceeds magnetite-hematite equilibrium, and solutions are saturated with respect to magnetite in HLW repositories, berthierine is likely to be more stable than smectite minerals. The alteration of montmorillonite to berthierine could be detrimental to the performance of HLW repositories.

Wilson, James; Savage, David; Cuadros, Javier; Shibata, Masahiro; Ragnarsdottir, K. Vala

2006-01-01

342

PLASMA ETCHING RATES AND SURFACE COMPOSITION OF BULK NIOBIUM TREATED IN Ar/Cl2 MICROWAVE DISCHARGE  

SciTech Connect

To achieve theoretically predicted values of the accelerating fields in superconducting radiofrequency (SRF) cavities, their inside surface should be fairly smooth and free of impurities. Thus, surface preparation is the critical step in production of SRF cavities. Plasma etching process is a dry chemistry technique that can be used to achieve these requirements. It is based on interaction between reactive halogen species produced in the glow discharge and the surface. During this process, volatile Nb halides are evaporated from the surface of Nb, removing the mechanically damaged and contaminated layer. We present a treatment of bulk Nb samples in the Ar/Cl2 microwave discharge. We have shown that etching rates of bulk Nb as high as 1.5 mm/min can be achieved without introducing impurities in Nb. The rate dependence on various discharge parameters and reactive gas composition is presented. Surface composition and topology measurements were carried out before and after plasma treatment

Raskovic, Marija; Upadhyay, Janardan; Valente, Anne-Marie; Phillips, H.

2008-07-01

343

Rheological and Electrokinetic Properties of Sodium Montmorillonite Suspensions.  

PubMed

In this article, we describe the rheology of Na montmorillonite suspensions as a function of pH, at constant ionic strength. The observed behavior is discussed quantitatively in terms of the potential energy of interaction between particles, keeping in mind the anisotropic nature of clay particles. The extended DLVO model that includes electrostatic, van der Waals, and polar acid-base contributions to the total energy is used. It is found that face-to-face interactions are virtually independent of pH, whereas edge-to-edge interactions are most attractive at the isoelectric point of edges (pH approximately 7). The most significant variations occur in face-to-edge potential energy, with strong attractions at pH<7. Steady-state viscometry showed that the yield stress decreases up to an order of magnitude between pH 3 and pH 7, with a much slower rate of decrease in the 7-11 pH interval. Concerning oscillatory measurements, it is found that both the elastic (G') and viscous (G") moduli are practically independent of frequency. It is also demonstrated that G'>G", the difference being larger at acid pH values. These results, in addition to potential energy calculations, suggest the existence of an elastic, coagulated structure up to pH 7, whereas as the pH is increased such structure is more relaxed because of electrostatic repulsions. Similar conclusions are reached when creep-recovery data are analyzed. Copyright 2000 Academic Press. PMID:10942547

Durán; Ramos-Tejada; Arroyo; González-Caballero

2000-09-01

344

Fabrication of functional waterborne polyurethane/montmorillonite composites by click chemistry method.  

PubMed

"Click" chemistry method was used to fabricate novel waterborne polyurethane (WPU)/montmorillonite (MMT) composites based on alkyne-containing WPU and azide-modified montmorillonite. The morphology of these composites was characterized by x-ray diffractometer, scanning electron microscope. The mechanical properties, thermal stability, and flame resistance of the composites were investigated by tensile, thermogravimetry and cone calorimetric experiments, etc. The experimental results show that the tensile strength, water resistance and flame retardancy of the WPU/MMT composites have been reinforced efficiently owing to the linking of MMT by click reaction. PMID:22480239

Sun, Daoxing; Li, Rong; Li, Xingjian; Wang, Wenjuan; Hu, Jing

2012-08-01

345

Adsorption behaviors of Congo red on the N, O-carboxymethyl-chitosan\\/montmorillonite nanocomposite  

Microsoft Academic Search

A series of N,O-carboxymethyl-chitosan\\/montmorillonite (N,O-CMC–MMT) nanocomposites were prepared by controlling the molar ratios of N,O-carboxymethyl-chitosan (N,O-CMC) and montmorillonite (MMT). The nanocomposites were characterized by FTIR, XRD and SEM. Adsorption of Congo red (CR) anionic dye from aqueous solution onto N,O-CMC–MMT was studied. The results showed that the nanocomposite with the molar ratio of N,O-CMC to MMT of 5:1 exhibited the

Li Wang; Aiqin Wang

2008-01-01

346

Preparation and characterization of high-specific-surface-area activated carbons from K 2CO 3-treated waste polyurethane  

Microsoft Academic Search

An activated carbon with high specific surface area was prepared from polyurethane foam by chemical activation with K2CO3 and the influences of carbonization temperature and impregnation ratio on the pore structure of the prepared activated carbon were investigated. It was found that the specific surface area of the activated carbon was at a maximum value (about 2800 m2\\/g) at a

J. Hayashi; N. Yamamoto; T. Horikawa; K. Muroyama; V. G. Gomes

2005-01-01

347

Thermal fatigue resistance of H13 steel treated by selective laser surface melting and CrNi alloying  

NASA Astrophysics Data System (ADS)

In this study, the selective laser surface melting and laser surface alloying technologies were adopted to improve the thermal fatigue resistance of medium carbon hot-work die steel (H13) by a CO2 laser. Two kinds of mixed chromium (Cr) and nickel (Ni) powders were used as the laser alloying materials, and the effects of the mixing ratio on the thermal fatigue resistance were investigated thoroughly. Some important results such as cross-sectional morphology, phases, hardness and thermal fatigue behavior were analyzed and evaluated. It indicates that the laser surface alloying technique using mixed powder with ratio of 75%Cr-25%Ni can considerably enhance the thermal fatigue resistance of the H13 steel. The laser alloyed zone has excellent properties such as preventing crack initiation and oxidation corrosion compared with original H13. Thermal cracking and oxidation corrosion that occurred at substrate surface can be surrounded and intercepted by a gridded laser strengthened structure. Therefore, the naturally developed cracks could be effectively prevented. Theses results and analysis show that laser surface technique can be positively used to improve surface mechanical properties of H13 dies.

Tong, Xin; Dai, Ming-jiang; Zhang, Zhi-hui

2013-04-01

348

Influence of gas and treatment time on the surface modification of EPDM rubber treated at afterglow microwave plasmas  

NASA Astrophysics Data System (ADS)

The ethylene propylene diene monomer (EPDM) rubber possesses excellent physical/chemical bulk properties, is cost-effective, and has been used in the mechanical and aerospace industry. However, it has an inert surface and needs a surface treatment in order to improve its adhesion properties. Plasma modification is the most accepted technique for surface modification of polymers without affecting the properties of the bulk. In this study, an afterglow microwave plasma reactor was used to generate the plasma species responsible for the EPDM surface modification. The plasma modified surfaces were analyzed by means of contact angle measurement, adhesion tests, attenuated total reflection-infrared spectroscopy, X-ray photoelectron spectroscopy and scanning electron microscopy. Two experimental variables were analyzed: type of the plasma gases and exposure time were considered. The predominant failure mode was adhesive, for long treatment times a mixture of adhesive and cohesive failure can be observed and the best conditions tested there was an increase of the rupture strength of about 27%, that can be associated mainly with the creation of oxygen containing functional groups on the rubber surface (CO, COC and CO) identified by spectroscopic methods. The predominant failure mode was adhesive, for long treatment times a mixture of adhesive and cohesive failure can be observed. In various conditions tested the contact angles easily decreased more than 500%. What can be concluded that high wettability is a necessary condition to obtain good adhesion, but this is not a sufficient condition.

da Maia, J. V.; Pereira, F. P.; Dutra, J. C. N.; Mello, S. A. C.; Becerra, E. A. O.; Massi, M.; Sobrinho, A. S. da Silva

2013-11-01

349

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 2³. Residual activities of 145.1 and 148.5% were observed for LPG (30 bar, 6 h, and depressurization rate of 20 bar?min?¹) and propane (270 bar, 1 h, and depressurization rate of 100 bar?min?¹), 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

2013-02-01

350

Correlation between the plasma characteristics and the surface chemistry of plasma-treated polymers through partial least-squares analysis.  

PubMed

We investigated the effect of various plasma parameters (relative density of atomic N and H, plasma temperature, and vibrational temperature) and process conditions (pressure and H2/(N2 + H2) ratio) on the chemical composition of modified poly(tetrafluoroethylene) (PTFE). The plasma parameters were measured by means of near-infrared (NIR) and UV-visible emission spectroscopy with and without actinometry. The process conditions of the N2-H2 microwave discharges were set at various pressures ranging from 100 to 2000 mTorr and H2/(N2+H2) gas mixture ratios between 0 and 0.4. The surface chemical composition of the modified polymers was determined by X-ray photoelectron spectroscopy (XPS). A mathematical model was constructed using the partial least-squares regression algorithm to correlate the plasma information (process condition and plasma parameters as determined by emission spectroscopy) with the modified surface characteristics. To construct the model, a set of data input variables containing process conditions and plasma parameters were generated, as well as a response matrix containing the surface composition of the polymer. This model was used to predict the composition of PTFE surfaces subjected to N2-H2 plasma treatment. Contrary to what is generally accepted in the literature, the present data demonstrate that hydrogen is not directly involved in the defluorination of the surface but rather produces atomic nitrogen and/or NH radicals that are shown to be at the origin of fluorine atom removal from the polymer surface. The results show that process conditions alone do not suffice in predicting the surface chemical composition and that the plasma characteristics, which cannot be easily correlated with these conditions, should be considered. Process optimization and control would benefit from plasma diagnostics, particularly infrared emission spectroscopy. PMID:24313888

Mavadat, Maryam; Ghasemzadeh-Barvarz, Massoud; Turgeon, Stéphane; Duchesne, Carl; Laroche, Gaétan

2013-12-23

351

Effect of organic matters on CO2 hydrate phase equilibrium conditions in Na-montmorillonite clay  

NASA Astrophysics Data System (ADS)

Formation of gas hydrates provides an attractive idea for storing greenhouse gases in a long-term stable geological formation. Since the phase equilibrium conditions of gas hydrates indicate the stability of hydrates, estimation of the phase equilibrium conditions of gas hydrates in marine geological conditions is necessary. In this study, we have identified the effects of organic matters (glycine, glucose, and urea) and solid surface (montmorillonite (MMT)) on the three-phase (liquid-hydrate-vapor) equilibrium conditions of CO2 hydrate. CO2 phase equilibrium experiments were conducted using 0.5mol% organic matter solutions with and without 10g soil mineral were experimentally conducted. Addition of organic matters shifted the phase equilibrium conditions of CO2 hydrate to the higher pressure or lower pressure region because of higher competition of water molecules due to the dissolved organic matters. Presence of MMT also leaded to the higher equilibrium pressure due to the interaction of cations with water molecules. By addition of organic matters to the clay suspension, the hydrate phase equilibrium conditions were less inhibited compared to those of MMT and organic matters independently. The diminished magnitudes by addition of organic matters to the clay suspension (MMT > MMT+urea > MMT+glycine > MMT+glucose > DIW) were different to the order of inhibition degree without MMT (Glucose > glycine > urea > DIW). X-ray diffraction (XRD), scanning electron microscope (SEM), and ion chromatography (IC) analysis were conducted to support the hypothesis that the organic matters interact with cations in MMT interlayer space, and leads to the less inhibition of phase equilibrium conditions. The present study provides basic information for the formation and dissociation of CO2 hydrates in the geological formation when sequestering CO2 as a form of CO2 hydrate.

Park, T.; Kyung, D.; Lee, W.

2013-12-01

352

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

2007-05-01

353

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

354

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

355

Improved performance of dye-sensitized solar cells with surface-treated TiO{sub 2} as a photoelectrode  

SciTech Connect

We report on the effects of surface-modified TiO{sub 2} on the performance of dye-sensitized solar cells (DSSCs). TiO{sub 2} surface was modified with Na{sub 2}CO{sub 3} via a simple dip coating process and the modified TiO{sub 2} was applied to photoelectrodes of DSSCs. By dipping of TiO{sub 2} layer into aqueous Na{sub 2}CO{sub 3} solution, the DSSC showed a power conversion efficiency of 9.98%, compared to that (7.75%) of the reference device without surface treatment. The UV–vis absorption spectra, the impedance spectra and the dark current studies revealed that the increase of all parameters was attributed to the enhanced dye adsorption, the prolonged electron lifetime and the reduced interfacial resistance.

Park, Su Kyung; Chung, Chinkap [Department of Chemistry, Keimyung University, Daegu 704-701 (Korea, Republic of)] [Department of Chemistry, Keimyung University, Daegu 704-701 (Korea, Republic of); Kim, Dae-Hwan; Kim, Cham; Lee, Sang-Ju [Green Energy Research Division, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873 (Korea, Republic of)] [Green Energy Research Division, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 711-873 (Korea, Republic of); Han, Yoon Soo, E-mail: yshancu@cu.ac.kr [Department of Advanced Energy Material Science and Engineering, Catholic University of Daegu, Gyeongbuk 712-702 (Korea, Republic of)

2012-10-15

356

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

357

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

358

Thermal analysis of montmorillonites modified with quaternary phosphonium and ammonium surfactants  

Microsoft Academic Search

The thermal stability of seven organically modified montmorillonites (‘organoclays’) has been investigated using differential thermal analysis, differential scanning calorimetry, and thermogravimetry in conjunction with X-ray diffractometry. Six organoclays were synthesised by replacing the interlayer inorganic cations, initially present, with quaternary phosphonium and ammonium surfactant cations. The samples modified with tetrabutylphosphonium (TBP), and butyltriphenylphosphonium (BTPP) ions have an appreciably higher thermal

C. B. Hedley; G. Yuan; B. K. G. Theng

2007-01-01

359

Hydrodynamic and chemical factors in clogging by montmorillonite in porous media.  

PubMed

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 1 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. PMID:17874771

Mays, David C; Hunt, James R

2007-08-15

360

Intestine-Specific, Oral Delivery of Captopril/Montmorillonite: Formulation and Release Kinetics  

PubMed Central

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.

2011-01-01

361

Rheology of Na-Rich Montmorillonite Suspension as Affected by Electrolyte Concentration and Shear Rate  

Microsoft Academic Search

Rheolo gical measurements were used to evaluate the particle-particle associations of Na-rich montmorillonite in suspensions, under various electrolyte concentrations. A 2% free electrolyte clay sus- pension showed pseudoplastic flow behavior and had a high apparent viscosity, attributed at low shear rates to the high volume fraction of the suspended clay platelets, the flexibility of the platelets, and the presence of

Hadar Heller; RAMI KEREN

2001-01-01

362

Phase Composition of Frozen Montmorillonite-Water Mixtures from Heat Capacity Measurements.  

National Technical Information Service (NTIS)

Equations are presented which form the basis of a method for determining the unfrozen water content of frozen clay-water mixtures from heat capacity measurements. The heat capacity of frozen sodium-montmorillonite water mixtures was determined at -4.7 and...

D. M. Anderson

1967-01-01

363

Microstructure of montmorillonite\\/silica sand mixture and its effects on the diffusion of strontium ions  

Microsoft Academic Search

A mixture of bentonite and silica sand is expected to be an important engineered barrier in a high-level radioactive waste repository. Therefore, the diffusion behavior of radionuclides in this mixture is a key issue for the safety assessment of geological disposal.This study determined the apparent diffusion coefficients of strontium ions in montmorillonite and silica sand mixtures under different temperatures at

J. Liu; T. Kozaki; Y. Horiuchi; S. Sato

2003-01-01

364

Transport number of sodium ions in water-saturated, compacted Na-montmorillonite  

NASA Astrophysics Data System (ADS)

Diffusion of radionuclides in bentonite buffer material has been studied by many researchers. The nuclides in a form of ion diffuse in the bentonite satisfying electro-neutrality. It is important to examine major charge carriers as a possible counter ion for understanding the diffusion behavior in the bentonite. In this study, transport numbers of Na + ions, which are the major exchangeable cations in the sodium montmorillonite, which is the major mineral of bentonite, were experimentally determined as a function of dry density by a moving boundary method, using electromigration and electro-osmosis in the montmorillonite. The transport numbers were determined based on the electromigration of the Na + ions, because the contribution of the electro-osmosis to the migration of the cations is considered to be negligible. The effect of pore water ionic strength in the montmorillonite on the transport number was also examined. It was found that the transport numbers did not depend on the dry density and were nearly equal to 1. Therefore, the Na + ions behave as the predominant charge carrier in the montmorillonite. When salinity was increased up to 0.5 M, the transport numbers decreased down to 0.8. This suggests that the major part of the charge was carried by the Na + ions but the contribution of other ions to the charge carrier increased gradually with increase of the ionic strength.

Higashihara, Tomohiro; Kinoshita, Kumiko; Akagi, Yorimasa; Sato, Seichi; Kozaki, Tamotsu

365

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

366

Indicators of Production Sustainability in Intercropped Vegetable Farming on Montmorillonitic Soils in India  

Microsoft Academic Search

The studies were carried out to ascertain the sustainability of intercropped versus sole crop vegetable cultivation in black montmorillonitic clay soil (Typic Haplustert), on the basis of response on indices of sustainability such as growth attributes, yield, quality, net return analysis, crop nutrient uptake, soil fertility changes, land equivalent ratio (LER) and sustainability value index (SVI). The combination of cabbage

Lily Varghese

2000-01-01

367

Ion equilibrium between montmorillonite interlayer space and an external solution—Consequences for diffusional transport  

Microsoft Academic Search

Bentonite clay is proposed as buffer material in several concepts of High Level Radioactive Waste repositories, and a correct description of ion diffusion in this material is of vital importance for any quantification of the chemical evolution of the repository near field.This study investigates the importance of ion equilibrium between montmorillonite interlayer space and an external solution for the diffusional

Martin Birgersson; Ola Karnland

2009-01-01

368

Surface-Treated versus Untreated Large-Bore Catheters as Vascular Access in Hemodialysis and Apheresis Treatments  

PubMed Central

Background. Catheter-related infections, thrombosis, and stenosis are among the most frequent complications associated with catheters, which are inserted in vessels. Surface treatment processes of the outer surface, such as ion-beam-assisted deposition, can be used to mitigate such complications. Methods. This retrospective study (1992–2007) evaluated silver-coated (54 patients) and noncoated (105 patients) implanted large-bore catheters used for extracorporeal detoxification. The catheters were inserted into the internal jugular or subclavian veins. After removal, the catheters were cultured for bacterial colonization using standard microbiologic assays. They also were examined using scanning electron microscope. Results. The silver coated catheters showed a tendency towards longer in situ time. The microbiologic examinations of the catheter tips were in both catheter types high positive, but not significant. Conclusion. The silver-coated catheters showed no significantly reduction in infection rate by evaluation of all collected data in this retrospective study. There was no association between both catheters in significantly reducing savings in treatment costs and in reducing patient discomfort. Other new developed catheter materials such as the microdomain-structured inner and outer surface are considered more biocompatible because they mimic the structure of natural biological surface.

Bambauer, Rolf; Schiel, Ralf; Bambauer, Carolin; Latza, Reinhard

2012-01-01

369

Atomic force microscopy study of polypropylene surfaces treated by UV and ozone exposure: modification of morphology and adhesion force  

Microsoft Academic Search

Exposing polypropylene (PP) to ozone in the presence of UV light is a simple and effective way of modifying its surface to improve its wettability and adhesion. Atomic force microscopy (AFM) showed a dramatic change in the morphology and a clear increase in the adhesion force resulting from the modification of a PP film by UV\\/ozone exposure. A relationship has

H.-Y Nie; M. J Walzak; B Berno; N. S McIntyre

1999-01-01

370

Healing of periodontal defects treated with enamel matrix proteins and root surface conditioning—an experimental study in dogs  

Microsoft Academic Search

Application of enamel matrix proteins has been introduced as an alternative method for periodontal regenerative therapy. It is claimed that this approach provides periodontal regeneration by a biological approach, i.e. creating a matrix on the root surfaces that promotes cementum, periodontal ligament (PDL) and alveolar bone regeneration, thus mimicking the events occurring during tooth development. Although there have been numerous

Umur Sakall?o?lu; Gökhan Aç?kgöz; Bülent Ayas; Tu?rul K?rt?lo?lu; Eser Sakall?o?lu

2004-01-01

371

Surface and interfacial reaction study of half cycle atomic layer deposited HfO{sub 2} on chemically treated GaSb surfaces  

SciTech Connect

An in situ half-cycle atomic layer deposition/X-ray photoelectron spectroscopy (XPS) study was conducted in order to investigate the evolution of the HfO{sub 2} dielectric interface with GaSb(100) surfaces after sulfur passivation and HCl etching, designed to remove the native oxides. With the first pulses of tetrakis(dimethylamido)hafnium(IV) and water, a decrease in the concentration of antimony oxide states present on the HCl-etched surface is observed, while antimony sulfur states diminished below the XPS detection limit on sulfur passivated surface. An increase in the amount of gallium oxide/sulfide is seen, suggesting oxygen or sulfur transfers from antimony to gallium during antimony oxides/sulfides decomposition.

Zhernokletov, D. M. [Department of Physics, University of Texas at Dallas, Richardson, Texas 75080 (United States)] [Department of Physics, University of Texas at Dallas, Richardson, Texas 75080 (United States); Dong, H.; Brennan, B.; Kim, J. [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States)] [Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States); Yakimov, M.; Tokranov, V.; Oktyabrsky, S. [College of Nanoscale Science and Engineering, University at Albany - SUNY, Albany, New York 12203 (United States)] [College of Nanoscale Science and Engineering, University at Albany - SUNY, Albany, New York 12203 (United States); Wallace, R. M. [Department of Physics, University of Texas at Dallas, Richardson, Texas 75080 (United States) [Department of Physics, University of Texas at Dallas, Richardson, Texas 75080 (United States); Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080 (United States)

2013-04-01

372

Surface and interfacial reaction study of half cycle atomic layer deposited HfO2 on chemically treated GaSb surfaces  

NASA Astrophysics Data System (ADS)

An in situ half-cycle atomic layer deposition/X-ray photoelectron spectroscopy (XPS) study was conducted in order to investigate the evolution of the HfO2 dielectric interface with GaSb(100) surfaces after sulfur passivation and HCl etching, designed to remove the native oxides. With the first pulses of tetrakis(dimethylamido)hafnium(IV) and water, a decrease in the concentration of antimony oxide states present on the HCl-etched surface is observed, while antimony sulfur states diminished below the XPS detection limit on sulfur passivated surface. An increase in the amount of gallium oxide/sulfide is seen, suggesting oxygen or sulfur transfers from antimony to gallium during antimony oxides/sulfides decomposition.

Zhernokletov, D. M.; Dong, H.; Brennan, B.; Yakimov, M.; Tokranov, V.; Oktyabrsky, S.; Kim, J.; Wallace, R. M.

2013-04-01

373

Surface Electrical Stimulation for Treating Swallowing Disorders after Stroke: A Review of the Stimulation Intensity Levels and the Electrode Placements  

PubMed Central

Neuromuscular electrical stimulation (NMES) for treating dysphagia is a relatively new therapeutic method. There is a paucity of evidence about the use of NMES in patients with dysphagia caused by stroke. The present review aimed to introduce and discuss studies that have evaluated the efficacy of this method amongst dysphagic patients following stroke with emphasis on the intensity of stimulation (sensory or motor level) and the method of electrode placement on the neck. The majority of the reviewed studies describe some positive effects of the NMES on the neck musculature in the swallowing performance of poststroke dysphagic patients, especially when the intensity of the stimulus is adjusted at the sensory level or when the motor electrical stimulation is applied on the infrahyoid muscles during swallowing.

Poorjavad, Marziyeh; Talebian Moghadam, Saeed; Daemi, Mostafa

2014-01-01

374

Assessment of dry season surface, ground, and treated water quality in the Cape Coast municipality of Ghana  

Microsoft Academic Search

This aim of this monitoring was to assess water quality in a dry season for the Cape Coast municipality in Ghana, which has\\u000a been experiencing chronic water shortages. Fifteen different sampling stations—four surface, five ground, and six tap water\\u000a samples—were analyzed for physicochemical and microbiological parameters during January to April 2005. Levels or trends in\\u000a water quality that may be

E. K. Quagraine; C. K. Adokoh

2010-01-01

375

[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

376

Effect of micro-scale Young’s modulus and surface roughness on adhesion property to plasma-treated rubber surface  

Microsoft Academic Search

Adhesion between rubbers and metals is often the main cause of machine trouble. Therefore, efficient utilization of rubber\\u000a in dynamic and static applications requires the modification of the adhesion property of the rubber surface without affecting\\u000a the bulk characteristics. In this work, we have studied the mechanism of the reduction in adhesion force between medical rubber,\\u000a chloride-isobutene-isoprene rubber (CIIR), and

Jong-Hyoung Kim; Noritsugu Umehara; Hiroyuki Kousaka; Mamoru Shimada; Mitsuru Hasegawa

2010-01-01

377

Macrostructure des systemes smectites-eau. Influence de polyelectrolytes anioniques sur l'organisation de suspensions de montmorillonite. (Macrostructure of smectite - water systems: influence of anionic polyelectrolytes upon organization of montmorillonite suspensions).  

National Technical Information Service (NTIS)

In this report, we have investigated aqueous smectite clay suspensions (montmorillonite or laponite), containing a low molecular weight sodium polyacrylate. Actually, this polyelectrolyte serves as a dispersing agent in drilling fluids based on smectite a...

M. Morvan

1993-01-01

378

In vitro biomimetic deposition of apatite on alkaline and heat treated Ti6A14V alloy surface  

Microsoft Academic Search

Titanium alloy (Ti6A14V) substrates, having the ability of biomimetic calcium phosphate-based materials, especially hydroxyapatite\\u000a deposition in a simulated body fluid (SBF) means of chemical treatment (alkaline treatment) and subsequent heat treatment,\\u000a was studied. The effects of alkaline treatment time, concentration and heat treatment temperature on the formation of calcium\\u000a phosphate (carbonate-hydroxyapatite) on Ti6A14V surface were examined. For this purpose, the

K. Fatehi; F. Moztarzadeh; M. Solati-Hashjin; M. Tahriri; M. Rezvannia; R. Ravarian

2008-01-01

379

An atmospheric-pressure plasma-treated titanium surface potentially supports initial cell adhesion, growth, and differentiation of cultured human prenatal-derived osteoblastic cells.  

PubMed

An atmospheric-pressure plasma (APP) treatment was recently reported to render titanium (Ti) surfaces more suitable for osteoblastic cell proliferation and osteogenesis. However, the mechanism of action remains to be clearly demonstrated. In this study, we focused on cell adhesion and examined the effects of the APP treatment on the initial responses of human prenatal-derived osteoblastic cells incubated on chemically polished commercially pure Ti (CP-cpTi) plates. In the medium containing 1% fetal bovine serum, the initial cell adhesion and the actin polymerization were evaluated by scanning electron microscopy and fluorescence microscopy. The expression of cell adhesion-related molecules and osteoblast markers at the messenger RNA level was assessed by real-time quantitative polymerase chain reaction. Although the cells on the APP-treated CP-cpTi surface developed fewer cytoskeletal actin fibers, they attached with higher affinity and consequently proliferated more actively (1.46-fold over control at 72 h). However, most of the cell adhesion molecule genes were significantly downregulated (from 40 to 85% of control) in the cells incubated on the APP-treated CP-cpTi surface at 24 h. Similarly, the osteoblast marker genes were significantly downregulated (from 49 to 63% of control) at 72 h. However, the osteoblast marker genes were drastically upregulated (from 197 to 296% of control) in these cells by dexamethasone and ?-glycerophosphate treatment. These findings suggest that the APP treatment improves the ability of the CP-cpTi surface to support osteoblastic proliferation by enhancing the initial cell adhesion and supports osteoblastic differentiation when immature osteoblasts begin the differentiation process. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 102B: 1289-1296, 2014. PMID:24449377

Kawase, Tomoyuki; Tanaka, Takaaki; Minbu, Hiromi; Kamiya, Mana; Oda, Masafumi; Hara, Toshiaki

2014-08-01

380

Exposure to methoxyfenozide-treated surfaces reduces the responsiveness of adult male codling moth (Lepidoptera: Tortricidae) to codlemone and pear ester lures in a wind tunnel.  

PubMed

The responsiveness of male codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), exposed to surfaces treated with the ecdysteroid agonist methoxyfenozide, toward lures loaded with the synthetic sex pheromone codlemone and/or the pear ester kairomone were investigated in wind tunnel experiments. Five different kinds of commercially available codling moth monitoring lures (obtained from Tr6c6 Inc., Adair, OK) were used in the bioassay: Pherocon CM Standard lure (loaded with 1 mg of codlemone), Pherocon CM Long-Life L2 (loaded with 3.5 mg of codlemone), Pherocon CM 10X (loaded with 10 mg of codlemone), Pherocon CM-DA Combo (loaded with 3.0 mg of codlemone and 3.0 mg of pear ester), and Pherocon DA (loaded with 3.0 mg of pear ester). Results from the study revealed that male codling moth exposed to surfaces treated with methoxyfenozide and the surfactant exhibited a significant decline in responsiveness toward lures loaded with either codlemone or pear ester. The full impact of how this negative effect might alter current moth monitoring procedures in orchards receiving ecdysone agonist sprays requires further investigation. PMID:21061970

Barrett, Bruce A

2010-10-01

381

Nonlysosomal processing of cell-surface heparan sulfate proteoglycans. Studies of I-cells and NH/sub 4/Cl-treated normal cells  

SciTech Connect

The metabolism of cell-associated proteoglycans, labeled in the glycosaminoglycan portion with /sup 35/SO/sub 2-4/, was studied in normal skin fibroblasts (SL66 cells), NH/sub 4/Cl-treated SL66 fibroblasts, and in I-cells derived from patients with mucolipidosis II. Kinetic data from label-chase experiments and gel filtration analysis of the molecular weight distribution of the radiolabeled glycosaminoglycans indicated that I-cells and NH/sub 4/Cl-treated normal fibroblasts (a) internalize cell surface proteoglycans, (b) remove glycosaminoglycan chains from proteoglycan core proteins, and (c) degrade heparan sulfate glycosaminoglycan chains via an endoglycosidic activity. These processes occur with rates comparable to those in normal fibroblasts. The data are consistent with the hypothesis that the glycosaminoglycan chains of cell-surface proteoglycans are separated from the protein cores in a nonlysosomal compartment prior to the transport of these chains to lysosomes for degradation. These observations also raise the possibility that this early step in separation of glycosaminoglycan chains from protein cores may serve to regulate the levels of glycosaminoglycan-free core protein observed in various cells.

Brauker, J.H.; Wang, J.L.

1987-09-25

382

Immunohistochemical evaluation of cell proliferation and apoptosis markers in ovarian surface epithelial cells of cladribine-treated rats.  

PubMed

Cladribine has been used in the treatment of hairy cell leukemia for about 30 years. In addition, the number of indications for the application of 2-CdA is constantly increasing. The treatment with cladribine, of younger persons and even children, appears to be a major factor stimulating the more exact recognition of its activities. However, till now, little has been known about the impact of cladribine on the reproductive system. The aim of the study was to evaluate the immunohistochemical expression of cell proliferation and apoptosis markers in ovarian surface epithelial (OSE) cells. In our study, ten rats were placed into two equal groups. The study group received daily subcutaneous injections of cladribine in a dose of 0.10 mg/kg of weight/day for one cycle lasting 7 days. The control group received only saline injections. The rats were sacrificed 24 h after the last injection, and their ovaries were extracted. The sections were immunohistochemically stained with cell proliferation marker Ki-67 and the apoptosis marker caspase 3. The expressions of the markers were evaluated using a light microscope. An analysis was made using an image analysis system and the CellAD software. The results were then statistically explored by way of the Mann-Whitney U test. The proliferative index (Ki-67) of ovarian surface epithelial cells was significantly lower in the study group than in the control group (p?

J?drych, Marian; Wawryk-Gawda, Ewelina; Jod?owska-J?drych, Barbara; Chyli?ska-Wrzos, Patrycja; Jasi?ski, Ludwik

2013-10-01

383

Efficacy of a Brazilian calcium montmorillonite against toxic effects of dietary aflatoxins on broilers reared to market weight.  

PubMed

Abstract 1. The protective effect of a natural Brazilian calcium montmorillonite (CaMont) against aflatoxins was studied in broiler chickens. 2. A total of 1056-d-old Cobb male broilers were housed in experimental pens (22 chickens per pen) for 42 d. Three levels of CaMont (0, 2.5 and 5 g/kg) and two levels of aflatoxins (0 and 3 mg/kg) were assayed. Each treatment had 8 replicate pens of 22 broiler chickens each. 3. Of all the chickens tested in the experiment, the ones treated with aflatoxins were the most adversely affected. CaMont treatment at concentrations of 2.5 and 5 g/kg improved body weight of chickens at 42 d of age by 13.3% and 22.7%, increased daily feed intake by 9.7% and 24.7%, and improved the productive efficiency index of chickens by 53% and 66.5%, respectively. 4. Dietary CaMont positively affected parameters such as weight of liver, heart and gizzard; however, serum potassium concentration decreased by 15.3% compared with that of chickens given only the aflatoxin-contaminated diet. 5. CaMont did not cause adverse effects in chickens that did not receive aflatoxins. 6. CaMont at pH 8.5 partially reduced the toxic effects of aflatoxins in broilers when included at levels of 2.5 and 5 g/kg in the diet. PMID:24423730

Eckhardt, J C; Santurio, J M; Zanette, R A; Rosa, A P; Scher, A; Dal Pozzo, M; Alves, S H; Ferreiro, L

2014-04-01

384

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

385

Thermal treatment of organoclays: Effect on the aqueous sorption of nitrobenzene on n-hexadecyltrimethyl ammonium montmorillonite  

Microsoft Academic Search

The aim of this work was to examine the effect of thermal treatment on organoclay sorptive properties. Aqueous sorption of nitrobenzene used as a probe compound was studied on Na-montmorillonite and two types of HDTMA-montmorillonite (where HDTMA is n-hexadecyltrimethyl ammonium exchanged by 41 and 90% of the clay cation exchange capacity) heated in air at 150, 250, 360 and 420°C.

Mikhail Borisover; Nadezhda Bukhanovsky; Isaak Lapides; Shmuel Yariv

2010-01-01

386

Residual monomer content and its release into water from the denture base nanocomposite using organic montmorillonite as reinforcement  

Microsoft Academic Search

A novel kind of denture base nanocomposite was prepared by polymethyl methyacrylate(PMMA) and cethyltrimethylammonium bromide\\u000a modified organic montmorillonite (OMMT). The dispersion of montmorillonite in the polymer matrix was characterized by x-ray\\u000a diffraction (XRD) and transimission electron microscope (TEM).The content of residual MMA in nanocomposites and the amount\\u000a of MMA released to water from nanocomposites were determined by gas chromatography (GC).

Hongbo Li; Chao Zhang; Zhi’an Li; Yining Wang; Qun Xiao

2008-01-01

387

Use of various Fe-modified montmorillonite samples for 4-nitrophenol degradation by H 2O 2  

Microsoft Academic Search

4-nitrophenol is degraded by H2O2 with iron (III)-exchanged and pillared montmorillonite as catalysts. The influence of different types of catalysts, their amounts and the H2O2 concentration were investigated.At optimal conditions, a solution containing 10?3 M of 4-nitrophenol and 10?2 M of H2O2 was degraded in less than 6 h in the presence of (1 g\\/l) of mixed (Al–Fe) pillared montmorillonite

L Chirchi; A Ghorbel

2002-01-01

388

Viability of Listeria monocytogenes on commercially-prepared hams surface treated with acidic calcium sulfate and lauric arginate and stored at 4°C.  

PubMed

We demonstrated the effectiveness of delivering an antimicrobial purge/fluid into shrink-wrap bags immediately prior to introducing the product and vacuum sealing, namely the "Sprayed Lethality In Container" (SLIC™) intervention delivery method. The pathogen was Listeria monocytogenes, the antimicrobials were acidic calcium sulfate (ACS; calcium sulfate plus lactic acid; 1:1 or 1:2 in dH(2)O) and lauric arginate (LAE; Ethyl-N-dodecanoyl-l-arginate hydrochloride; 5% or 10% in dH(2)O), and the product was commercially prepared "table brown" ham (ca. 3 pounds each). Hams were surface inoculated with a five-strain cocktail of L. monocytogenes (ca. 7.0 log(10) CFU per ham), added to shrink-wrap bags that already contained ACS or LAE, vacuum-sealed, and stored at 4°C for 24h. Pathogen levels decreased by 1.2, 1.6, 2.4, and 3.1 log(10) CFU/ham and 0.7, 1.6, 2.2, and 2.6 log(10) CFU/ham in samples treated with 2, 4, 6, and 8mL of a 1:1 and 1:2 solution of ACS, respectively. In samples treated with 2, 4, 6, and 8mL of a 5% solution of LAE, pathogen levels decreased by 3.3, 6.5, 5.6, and 6.5 log(10) CFU/ham, whereas when treated with a 10% solution of LAE pathogen levels decreased ca. 6.5 log(10) CFU/ham for all application volumes tested. The efficacy of ACS and LAE were further evaluated in shelf-life studies wherein hams were surface inoculated with either ca. 3.0 or 7.0 log(10) CFU of L. monocytogenes, added to shrink-wrap bags that contained 0, 4, 6, or 8mL of either a 1:2 solution of ACS or a 5% solution of LAE, vacuum-sealed, and stored at 4°C for 60 days. For hams inoculated with 7.0 log(10) CFU, L. monocytogenes levels decreased by ca.1.2, 1.5, and 2.0 log(10) CFU/ham and 5.1, 5.4, and 5.5 log(10) CFU/ham within 24h at 4°C in samples treated with 4, 6, and 8mL of a 1:2 solution of ACS and a 5% solution of LAE, respectively, compared to control hams that were not treated with either antimicrobial. Thereafter, pathogen levels remained relatively unchanged (±1.0 log(10) CFU/ham ) after 60 days at 4°C in hams treated with 4, 6, and 8mL of a 1:2 solution of ACS and increased by ca. 2.0-5.0 log(10) CFU/ham in samples treated with 4, 6, and 8mL of a 5% solution of LAE. For hams inoculated with 3.0 log(10) CFU, L. monocytogenes levels decreased by 1.3, 1.9, and 1.8 log(10) CFU/ham within 24h at 4°C in samples treated with 4, 6, and 8mL of a 1:2 solution of ACS, respectively, compared to control hams that were not treated. Likewise, levels of the pathogen were reduced to below the limit of detection (i.e., 1.48 log(10) CFU/ham) in the presence of 4, 6, and 8mL of a 5% solution of LAE within 24h at 4°C. After 60 days at 4°C, pathogen levels remained relatively unchanged (±0.3 log(10) CFU/ham) in hams treated with 4, 6, and 8mL of a 1:2 solution of ACS. However, levels of L. monocytogenes increased by ca. 2.0 log(10) CFU/ham in samples treated with 4 and 6mL of a 5% LAE solution within 60 days but remained below the detection limit on samples treated with 8mL of this antimicrobial. These data confirmed that application via SLIC™ of both ACS and LAE, at the concentrations and volumes used in this study, appreciably reduced levels of L. monocytogenes on the surface of hams within 24h at 4°C and showed potential for controlling outgrowth of the pathogen over 60 days of refrigerated storage. PMID:22064055

Luchansky, J B; Call, J E; Hristova, B; Rumery, L; Yoder, L; Oser, A

2005-09-01

389

Effect of PAC dosage in a pilot-scale PAC-MBR treating micro-polluted surface water.  

PubMed

To address the water scarcity issue and advance the traditional drinking water treatment technique, a powdered activated carbon-amended membrane bioreactor (PAC-MBR) is proposed for micro-polluted surface water treatment. A pilot-scale study was carried out by initially dosing different amounts of PAC into the MBR. Comparative results showed that 2g/L performed the best among 0, 1, 2 and 3g/L PAC-MBR regarding organic matter and ammonia removal as well as membrane flux sustainability. 1g/L PAC-MBR exhibited a marginal improvement in pollutant removal compared to the non-PAC system. The accumulation of organic matter in the bulk mixture of 3g/L PAC-MBR led to poorer organic removal and severer membrane fouling. Molecular weight distribution of the bulk liquid in 2g/L PAC-MBR revealed the synergistic effects of PAC adsorption/biodegradation and membrane rejection on organic matter removal. Additionally, a lower amount of soluble extracellular polymer substances in the bulk can be secured in 21 days operation. PMID:24412856

Hu, Jingyi; Shang, Ran; Deng, Huiping; Heijman, Sebastiaan G J; Rietveld, Luuk C

2014-02-01

390

Influence of a Cerium Surface Treatment on the Oxidation Behavior of Cr2O3-Forming Alloys (title on slides varies: Oxidation Behavior of Cerium Surface Treated Chromia Forming Alloys)  

SciTech Connect

Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This temperature will require the construction of boiler and turbine components from austenitic stainless steels and nickel alloys. Many of the alloys being considered for use are primarily Cr2O3 forming alloys [1-4]. It is well known that the addition of a small amount of reactive elements, such as the rare earths elements Ce, La, and Y, can significantly improve the high temperature oxidation resistance of both iron- and nickel- base alloys. A list of the benefits of the reactive element effect include: (i) slowing scale growth, (ii) enhancing scale adhesion; and (iii) stabilizing Cr2O3 formation at lower Cr levels. The incorporation of the reactive element can be made in the melt or through a surface infusion or surface coating. Surface modifications allow for the concentration of the reactive element at the surface where it can provide the most benefit. This paper will detail a Ce surface treatment developed at NETL that improves the high temperature oxidation resistance of Cr2O3 forming alloys. The treatment consists of painting, dip coating, or spraying the alloy surface with a slurry containing CeO2 and a halide activator followed by a thermal treatment in a mild (x10-3 Torr) vacuum. During treatment the CeO2 reacts with the alloy to for a thin CrCeO3-type scale on the alloy surface. Upon subsequent oxidation, scale growth occurs at a reduced rate on alloys in the surface treated condition compared to those in the untreated condition.

Alman, D.E.; Holcomb, G.R.; Adler, T.A.; Jablonski, P.D.

2007-04-01

391

Multifunctional chitosan nanocomposites: The effect of silver supported on montmorillonite platelets on barrier and mechanical properties  

NASA Astrophysics Data System (ADS)

Multifunctional bionanocomposites have been prepared by loading chitosan matrix with silver-montmorillonite antimicrobial nanoparticles obtained by replacing Na+ ions of natural montmorillonite with silver ions followed by thermal reduction to metallic nanoparticles. This filler has been chosen for its twofold advantage to serve as silver supporting material and to confer new and better performance to the obtained material. It has been proved that the ultrasound-assisted procedure resulted in an efficient tool for the chitosan macromolecules to intercalate into the silicate galleries. The achievement of the intercalation as well as the interaction between chitosan and silver nanoparticles lead to an enhancement of barrier properties of the bionanocomposites and to an improvement of their mechanical strengths mainly due to a better load transfer between matrix and fillers.

Lavorgna, M.; Buonocore, G. G.; Tescione, F.; Capezzuto, F.; Yan, N.; Amendola, E.

2014-05-01

392

Modification of montmorillonite with cationic surfactant and application in electrochemical determination of 4-chlorophenol.  

PubMed

Herein, montmorillonite calcium was exchanged with a cationic surfactant: cetyltrimethylammonium bromide (CTAB). The resulting CTAB-modified montmorillonite calcium (CTAB-MMT) shows higher accumulation efficiency to 4-chlorophenol compared with the unmodified MMT. At the CTAB-MMT-modified carbon paste electrode, the oxidation peak current of 4-chlorophenol remarkably increases. Based on this, a novel, sensitive and convenient electrochemical method was developed for the determination of 4-chlorophenol. The oxidation peak current of 4-chlorophenol is proportional to its concentration over the range from 5.0 x 10(-8) to 1.0 x 10(-5) mol L(-1). The limit of detection is evaluated to be 2.0 x 10(-8) mol L(-1) for 2 min accumulation. Finally this newly proposed method was successfully applied to determine 4-chlorophenol in water samples. PMID:18539012

Yang, Hongyu; Zheng, Xiaojiang; Huang, Wensheng; Wu, Kangbing

2008-09-01

393

Preparation and properties of poly HTBN-based urethane-urea/organo reactive montmorillonite nanocomposites  

NASA Astrophysics Data System (ADS)

With ultrasonic assistant mixing way, an intercalated mixture of polyol/organo reactive montmorillonite (ORMMT) was pretreated. The prepolymer composed MMT clay was prepared by reaction of polyol/ORMMT mixture with toluene diisocyanate (TDI). The resultant prepolymer reacted with extender (DMTDA) and then the polyurethane-urea/organo reactive montmorillonite (PUU/ORMMT) nanocomposites were obtained. The structure, morphology and properties of PUU/ORMMT nanocomposites were characterized by FT-IR, TEM, AFM, strain-stress machine, TGA, and dynamic mechanical analysis (DMA). The results showed that when the OMMT content is 3%, the PUU/ORMMT nanocomposities performed super mechanical properties. Because of the presence of ORMMT, both T g of the soft segment and tan ? of the PUU increased, and the decomposition temperature for the first step and the second step increased respectively. TEM images showed that the organophilic MMT particles in the PUU composite exhibit a high degree of intercalation and exfoliation.

Li, Zai-Feng; Wu, Yuan; Zhang, Fu-Tao; Cao, Yu-Yang; Wu, Shou-Peng; Wang, Ting

2012-12-01

394

Adsorption of a few heavy metals on natural and modified kaolinite and montmorillonite: a review.  

PubMed

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 cations of Zr4+, Al3+, Si4+, Ti4+, Fe3+, Cr3+or Ga3+, etc. Preparation of pillared clays with quaternary ammonium cations, namely, tetramethylammonium-, tetramethylphosphonium- and trimethyl-phenylammonium-, N'-didodecyl-N, N'-tetramethylethanediammonium, etc, are also common. Moreover, the acid treatment of clays often boosted their adsorption capacities. The adsorption of toxic metals, viz., As, Cd, Cr, Co, Cu, Fe, Pb, Mn, Ni, Zn, etc., have been studied predominantly. Montmorillonite and its modified forms have much higher metal adsorption capacity compared to that of kaolinite as well as modified-kaolinite. PMID:18319190

Bhattacharyya, Krishna Gopal; Gupta, Susmita Sen

2008-08-01

395

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

396

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

Microsoft Academic Search

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), (Si3.02Al0.98)IV (Mg2.27Al0.12Fe0.283+Fe0.052+Ti0.07)VI O10(OH)2 Ca0.09Na0.21K0.50 from West China and montmorillonite (M), (Si3.96Al0.04)IV (Al1.20Fe0.343+Mg0.42Ti0.02)VI O10 (OH)2Ca0.15Na0.14K0.08 from

Marta Valásková; Marianna Hundáková; Kate?ina Mamulová Kutláková; Jana Seidlerová; Pavla ?apková; Erich Pazdziora; Kate?ina Mat?jová; Martin Hermánek; Volker Klemm; David Rafaja

2010-01-01

397

Engineering New Layered Solids from Exfoliated Inorganics: a Periodically Alternating Hydrotalcite - Montmorillonite Layered Hybrid  

PubMed Central

Two-dimensional (2D) nanosheets obtained by exfoliating inorganic layered crystals have emerged as a new class of materials with unique attributes. One of the critical challenges is to develop robust and versatile methods for creating new nanostructures from these 2D-nanosheets. Here we report the delamination of layered materials that belonging to two different classes - the cationic clay, montmorillonite, and the anionic clay, hydrotalcite - by intercalation of appropriate ionic surfactants followed by dispersion in a non-polar solvent. The solids are delaminated to single layers of atomic thickness with the ionic surfactants remaining tethered to the inorganic and consequently the nanosheets are electrically neutral. We then show that when dispersions of the two solids are mixed the exfoliated sheets self-assemble as a new layered solid with periodically alternating hydrotalcite and montmorillonite layers. The procedure outlined here is easily extended to other layered solids for creating new superstructures from 2D-nanosheets by self-assembly.

Chalasani, Rajesh; Gupta, Amit; Vasudevan, Sukumaran

2013-01-01

398

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

399

ZnCl 2Zn 2+Montmorillonite composite: efficient solid acid catalyst for benzylation of benzene  

Microsoft Academic Search

A newer type of metal salt–metal ion exchanged Montmorillonite (Mont), MCl2-Mn+-Mont (M=Ni, Cu, Zn; n=2) have been prepared and evaluated as solid acid catalysts for Friedel–Crafts reactions particularly for benzylation of benzene. The activity of such composites depends upon the amount of loading of metal salts on the metal ion exchanged-Mont support and 1.5mmol loading per mole of the support

Anjali Phukan; Jatindra Nath Ganguli; Dipak Kumar Dutta

2003-01-01

400

The hydrometallurgical extraction of lithium from egyptian montmorillonite-type clay  

NASA Astrophysics Data System (ADS)

The processing of El-Fayoum montmorillonite-type clay deposits is attained through leaching with commercial sulfuric acid using a ball-mill-type autoclave. This process yields lithium sulfate, which can be used either for the production of lithium carbonate or to produce lithium metal. The effects of temperature, grain size, and sulfuric acid concentration and leaching on lithium recovery as well as the kinetics of the leaching process have been studied.

Amer, A. M.

2008-10-01

401

Structural characterization and transport properties of organically modified montmorillonite\\/polyurethane nanocomposites  

Microsoft Academic Search

Samples of polyurethane and organically modified montmorillonite (OMont) were prepared, covering a wide range of inorganic composition, up to 40wt%. They were obtained by a three step process using diphenylmethane diisocyanate, poly(?-caprolactone), di(ethylene glycol) and poly(?-caprolactone)–OMont (NPCL) nanocomposites. The NPCL nanocomposites were used as soft segments for a partial replacement of the di(ethylene glycol) in the hard-segment of the polymeric

Mariarosaria Tortora; Giuliana Gorrasi; Vittoria Vittoria; Giancarlo Galli; Stefano Ritrovati; Emo Chiellini

2002-01-01

402

SlowRelease Formulations of Sulfometuron Incorporated in Micelles Adsorbed on Montmorillonite  

Microsoft Academic Search

The design and tests of slow-release formulations of sulfometuron (SFM), an anionic sulfonylurea herbicide, are described. The formulations are based on incorporation of the herbicide in octadecyl- trimethylammonium (ODTMA) micelles, which adsorb on a clay mineral, montmorillonite. An optimization of herbicide\\/micelle clay ratios yielded high adsorption of SFM (95%), and at a 1% (w\\/ w) water suspension only 0.5% of

Yael Golda Mishael; Tomas Undabeytia; Onn Rabinovitz; Baruch Rubin; Shlomo Nir

2002-01-01

403

The hydrometallurgical extraction of lithium from egyptian montmorillonite-type clay  

Microsoft Academic Search

The processing of El-Fayoum montmorillonite-type clay deposits is attained through leaching with commercial sulfuric acid\\u000a using a ball-mill-type autoclave. This process yields lithium sulfate, which can be used either for the production of lithium\\u000a carbonate or to produce lithium metal. The effects of temperature, grain size, and sulfuric acid concentration and leaching\\u000a on lithium recovery as well as the kinetics

A. M. Amer

2008-01-01

404

The hydrometallurgical extraction of lithium from egyptian montmorillonite-type clay  

Microsoft Academic Search

The processing of El-Fayoum montmorillonite-type clay deposits is attained through leaching with commercial sulfuric acid using a ball-mill-type autoclave. This process yields lithium sulfate, which can be used either for the production of lithium carbonate or to produce lithium metal. The effects of temperature, grain size, and sulfuric acid concentration and leaching on lithium recovery as well as the kinetics

A. M. Amer

2008-01-01

405

Immobilization of Zinc and Cadmium in Polluted Soils by Polynuclear Al13 and Al-Montmorillonite  

Microsoft Academic Search

We investigated the suitability of two aluminum-based binding agents, polynuclear Al13 and Al-coated montmorillonite (Al-mont-morillonite), for the immobilization of heavy metals in two contaminated agricultural soils: a loamy luvisol from an arable site in Rafz, Canton Zürich, Switzerland, and a sandy podsol from Szopienice, Upper Silesia, Poland. Both soils were polluted by lead, zinc, and cadmium: the soil from Szopienice

Aleksandra Badora; Gerhard Furrer; Anna Grünwald; Rainer Schulin

1998-01-01

406

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

407

Adsorption and binding of AmpliTaq® DNA polymerase on the clay minerals, montmorillonite and kaolinite  

Microsoft Academic Search

Adsorption at equilibrium and binding of AmpliTaq® DNA polymerase (TDP) on clay minerals, two montmorillonites (W–M and Ap–M) and a kaolinite (K), were studied. Equilibrium adsorption isotherms were of the L type, and a plateau was reached with Ap–M and K, whereas no plateau was obtained with W–M. Adsorption of TDP was most rapid on W–M, maximal at pH 6

C Vettori; L Calamai; M Yoder; G Stotzky; E Gallori

1999-01-01

408

Mechanical, Morphological and Thermal Properties of Polycarbonate\\/SEBS-G-MA\\/Montmorillonite Nanocomposites  

Microsoft Academic Search

Nanocomposites based on polycarbonate (PC) containing sodium montmorillonite (NaMMT) and maleic anhydride grafted styrene-ethylene\\/butylene-styrene (SEBS-g-MA) were prepared by melt compounding method followed by injection molding. X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed the formation of intercalated nanocomposites. Incorporation of SEBS-g-MA into the PC\\/MMT nanocomposites enhanced ductility and impact strength but slightly reduced tensile strength and stiffness. The

W. S. Chow; S. S. Neoh

2009-01-01

409

Study on nonisothermal crystallization of maleic anhydride grafted polypropylene\\/montmorillonite nanocomposite  

Microsoft Academic Search

This paper studies the nonisothermal crystallization behavior of maleic anhydride grafted polypropylene\\/montmorillonite nanocomposite by differential scanning calorimetry (DSC) in comparison with the maleic anhydride grafted polypropylene matrix (PP-g-MAH). The nanocomposite was prepared by melt-intercalation, and its microstructure was characterized by wide angle X-ray diffraction and transmission electron microscopy. The DSC results show that the presence of MMT resulted in the

Jian Li; Chixing Zhou; Wang Gang

2003-01-01

410

How organo-montmorillonite truly affects the structure and properties of polypropylene  

Microsoft Academic Search

Polypropylene (PP)\\/organo-montmorillonite (OMMT) nanocomposites were prepared by using a highly effective PP solid-phase graft as compatibilizer. As a very low amount of PP graft was used, the properties of the PP matrix were maintained. The effects of the OMMT on the structure and properties of PP were studied fully. The intercalated structure of the nanocomposites was characterized by X-ray diffraction

Chao Ding; Demin Jia; Hui He; Baochun Guo; Haoqun Hong

2005-01-01

411

Preparation, characterization and properties of poly (vinyl chloride)\\/compatibilizer\\/organophilic-montmorillonite nanocomposites by melt intercalation  

Microsoft Academic Search

Poly (vinyl chloride)\\/compatibilizer\\/organophilic-montmorillonite (OMMT) nanocomposites have been prepared by melt intercalation by the masterbatch process. PVC\\/OMMT nanocomposites have also been prepared by directly blending PVC with OMMT for comparison. All the composites were characterized by Wide-angle X-ray Diffraction (WAXD) and Transmission Electron Microscopy (TEM). The results of WAXD and TEM indicate that PVC\\/VAc\\/OMMT nanocomposites with exfoliated structure have been successfully

Jie Ren; Yanxia Huang; Yan Liu; Xiaozhen Tang

2005-01-01

412

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

413

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?

414

Removal of Basic Dye Crystal Violet from Aqueous Solution by Cu(II)Loaded Montmorillonite  

Microsoft Academic Search

The effects of contact time, reaction temperature, and ionic strength on crystal violet adsorption onto Cu(II)-loaded montmorillonite were studied. The kinetic experimental data were analyzed using pseudo-first-order, pseudo-second-order, and Elovich equations to examine the adsorption mechanism. The result suggested that the adsorption was best represented by the pseudo-second-order equation. The suitability of the Langmuir, Freundich, and Temkin isotherms to equilibrium

Xue Song Wang; Wei Zhang

2011-01-01

415

Investigation of polymer and nanoclay orientation distribution in nylon 6\\/montmorillonite nanocomposite  

Microsoft Academic Search

A method to determine the orientation distribution function of montmorillonite clay in nylon 6 nanocomposite films by a combination of infrared (FTIR) trichroic analysis and transmission electron microscopy (TEM) image analysis is described. The structural absorbance of the nanoclay Si–O vibrations was obtained by the sample tilting method described by Schmidt [Schmidt PG. J Polym Sci: Part A 1963;1:1271–1292]. A

Leslie S. Loo; Karen K. Gleason

2004-01-01

416

An electron paramagnetic resonance (EPR) study of the adsorption of copper complexes on montmorillonite and imogolite  

NASA Astrophysics Data System (ADS)

The adsorption of three copper species, the hydrated cupric ion, bisglycine Cu(II) and a Cu(II)-humic acid complex, on montmorillonite and imogolite at pH 7 was investigated by electron paramagnetic resonance (EPR) spectroscopy. The spectra of the supernatant solutions indicated that adsorption of the glycine complexes was very much less than that of the uncomplexed ion for both minerals and that montmorillonite adsorbed significantly more Cu from the humic acid solution than did imogolite. In every case the adsorbed Cu was characterized by more than one type of chemical environment and the spectral parameters show differences between the adsorbed species depending on their freedom of movement and their mode and site of adsorption. Qualitatively similar spectra were obtained when the uncomplexed ion was adsorbed on either of the mineral species and it is suggested that simple Cu(II) ions were involved and that their coordination environments comprised water molecules and hydroxyl groups. With the bisglycine Cu(II) complexes, the spectra were characterized by two components which may be accounted for by adsorption at two different types of site in the structures. In each case one component had parameters that are similar to those of the bisglycine Cu(II) in the solid state, but the second component in the spectra of the montmorillonite sample was quite different to that obtained with imogolite. The Cu(II)-humic acid complex with montmorillonite gave spectra that were similar to that from copper humate, but with imogolite the spectra from the Cu(II)-humic acid system were similar to those obtained with the uncomplexed Cu(II) ion, indicating that imogolite is able to extract copper from humic acid.

Goodman, B. A.; Green, H. L.; Mcphail, D. B.

1984-10-01

417

Selectivity of montmorillonite catalyzed prebiotic reactions of D, L-nucleotides  

NASA Astrophysics Data System (ADS)

The montmorillonite-catalyzed reactions of the 5?-phosphorimidazolides of D, L-adenosine (D, L-ImpA) (Figure 1a. N = A, R = H) and D, L-uridine