Interlayer Complex Research Articles

Analysis of shear-torque fatigue test for bituminous pavement interlayers

The laboratory characterisation of bituminous interlayers is a challenging issue because of the difficulty of establishing loading conditions that can simulate field behaviour. This paper describes a shear-torque fatigue test procedure aimed at investigating the fatigue behaviour of bituminous pavement interlayers. A preliminary experimental investigation, able to evaluate the damage process occurring in both single- and double-layered specimens, showed that the presence of the interface constitutes a weakness zone, noticeably influencing the shear fatigue performance of the pavement structure. Thus, a model for the description of the evolution of the interlayer damage by using the variation of the interlayer complex shear modulus was proposed and preliminarily validated. Moreover, a new fatigue failure criterion has been proposed to be used in the result analysis of the shear-torque fatigue tests.

Organo-modified Fe-montmorillonite as a solid acid catalyst for reduction of nitroarenes and Biginelli reactions

In order to develop a new class of solid acid catalysts, interlayer ferric ions of Fe(III)-montmorillonite (Mt) was reduced to Fe2+ and coordinated with o-phenanthroline (L) during the solid-state reaction at >150 °C. Such a reduction is ascribed to the partial aggregation of Fe3+–O-Fe3+ followed by self-reduction to Fe2+ with the elimination of oxide ion. In-situ complexation to form ferroin, [FeL3]2+ at the interlayer is evident from TG/DTA, DR UV–Vis spectra, XRD, FT-IR, photoluminescence spectra and SQUID magnetometer. Basal spacing (d001) of Fe(III)-Mt-L was 18 Å for the products heated from 200 to 350 °C. The decomposition of this interlayer complex occurred around 450 °C. Fe(III)-Mt-L@200 °C showed characteristic absorption for [FeL3]2+ around 510 nm. Lewis and Brønsted acid sites are confirmed from the FTIR spectra of pyridine adsorbed samples. The catalytic behavior of Fe(III)-Mt-L@300 °C was observed during the reduction of 4-nitrophenol to 4-aminophenol and also in the Biginelli reactions.

Crystal structure of uranyl-oxide mineral wölsendorfite revisited

The crystal structure of the rare supergene Pb2+-containing uranyl-oxide mineral wölsendorfite has been revisited employing the single-crystal X-ray diffraction. The new structure refinement provided deeper insight into the complex structure of this mineral, revealing additional H2O sites in the interlayer complex and confirming the entrance of the Ca2+ into the structure. Studied wölsendorfite is orthorhombic, space group Cmcm, with unit cell dimensions a = 14.1233(8) Å, b = 13.8196(9) Å, c = 55.7953(12) Å, V = 10890.0(10) Å3, and Z = 8. The structure has been refined to an agreement index (R) of 10.74% for 3815 reflections with I > 3σ(I) collected using a microfocus X-ray source from the microcrystal. In line with the previous structure determination, the refined structure contains U–O–OH sheets of the wölsendorfite topology and an interstitial complex comprising nine symmetrically unique Pb sites, occupied dominantly by Pb2+. Nevertheless, one of the sites seems to be plausible for hosting Ca2+. Its presence has been successfully modeled by the refinement and further supported by the crystal-chemical considerations. The structural formula of wölsendorfite crystal studied is Pb6.07Ca0.68[(UO2)14O18(OH)5]O0.5(H2O)12.6, with Z = 8, Dcalc. = 6.919 g·cm–3 (including theoretical 30.2 H atoms). The rather complex structure of wölsendorfite makes it the third most complex known uranyl-oxide hydroxy-hydrate mineral.

In−situ complexation of o−phenanthroline in the interlayer of Fe(II)−montmorillonite

Abstract The solid state reaction between Fe(II)−montmorillonite (Mt) and o−phenanthroline (L) resulted in the in-situ complexation of interlayer Fe(II) ions with L. The formation of the [FeL3]2+ complex in the interlayer was confirmed from X−ray diffraction (XRD), thermal analysis (TG/DTA), infrared (FT−IR) and diffused reflectance (DR) UV−Vis spectra. The basal spacing (d001) of this inorganic-organic hybrid material, Fe(II)−Mt−L, was found to be 18 A at room temperature. The XRD pattern shows the self-oriented (stacked) layer structure, which is independent of relative humidity. The TG−DTA curve shows the decomposition of interlayer complex at about 450 °C. The FTIR spectra show the prominent C−H bending for L around 720 cm−1 and 845 cm−1 in addition to other structural features of clay mineral. The DR UV−Vis spectra shows the absorption at about 510 nm, which is a characteristic value for [FeL3]2+ complex. The FE−SEM image and magnetic behaviour of the Fe(II)−Mt−L are compared with Fe(II)−Mt. The Fe(II)−Mt−L was heated upto 500 °C, and it was found that the structural integrity remained same until 350 °C as indicated by XRD, FTIR and TG-DTA. The d001 was reduced to 11.7 A at about 400 °C and then the clay interlayer collapsed irreversibly to d001 of 9.6 A. These hybrid materials are expected to show selective adsorption and catalytic property in organic (ca. Bigineli-type) reactions. As a first step, we have focused here only on preparation and characterization of these modified clay minerals by innovative approach.

Intercalation of Ethylene Glycol in Smectites: Several Molecular Simulation Models Verified by X-Ray Diffraction Data

AbstractOrgano-clays represent a special challenge for molecular simulations because they require accurate representation of the clay and the organic/aqueous sections of the model system and accurate representation of the interactions between them. Due to the broad range of force-field models available, an important question to ask is which sets of parameters will best suit the molecular modeling of the organo-intercalated smectites? To answer this question, the structure of the ethylene glycol (EG)-smectite complex is used here as a testing model because the intercalation of EG in smectites provides a stable interlayer complex with relatively constant basal spacing.Three smectite samples with substantially different layer charge and charge localization were selected for X-ray diffraction (XRD) measurements. Their molecular models were built and molecular-dynamics simulations performed using various combinations of the organic force fields (CGenFF, GAFF, CVFF, and OPLS-aa) with ClayFF and INTERFACE force fields used to describe smectites. The simulations covered a range of different EG and water contents. For every structure, the density distribution of interlayer species along the direction perpendicular to the layer plane was calculated and then used to optimize the XRD patterns for these simulated models.A comparison of these results with experimental XRD patterns shows very large discrepancies in the structures and basal spacings obtained for different layer charges as well as for different force fields and their combinations. The most significant factor affecting the accuracy of the calculated XRD patterns was the selection of the clay-mineral force-field parameters. The second important conclusion is that a slight modification of the basal oxygen parameters for non-electrostatic interactions (increase of their effective atomic diameters) may be a simple and straightforward way to improve significantly the agreement between the modeled XRD patterns with experiments, especially for high-charge smectites. Generally, among organic force fields, the least accurate results were obtained with CGenFF. For unmodified ClayFF, its combination with GAFF gave the best results, while the two other sets (OPLS-aa and CVFF) gave the best results in combination with ClayFFmod. The INTERFACE and INTERFACEmod produced much better results for low-charge montmorillonite than for high-charge smectites.

Study on PIDNN-Based Flow Control in Layered Water Injection Technology in Oilfield

This paper takes the layered water injection technology in oil production engineering as research object. This technology is characterized by strong nonlinearity, strong interlayer interference, time variation and complex model. Focusing on these characteristics, this paper proposes a novel control strategy based on PID-NN algorithm to satisfy the requirements of layered water injection technology. Many performance indexes of the controller are optimized, including model establishment of nonlinear controlled object, multi-parameter decoupling, controller acceleration and precision improvement. The simulation and experiment show that compared with traditional controller based on PID and controller based on BP neural network, the optimized controller has stronger robustness, faster response and better flow control, so it has an advantage over traditional controllers of dealing with discrete events and multi-variable decoupling problems.

Insertion of chromium(III) ascorbate complex into layered double hydroxide through reduction of intercalated chromate by ascorbic acid

The reaction of ascorbic acid with intercalated chromate of MgAl layered double hydroxides (LDH) at neutral pH leads to in-situ formation of the chromium(III) ascorbate complex, [Cr(Hasc) 2(OH) 2] −(Hasc = ascorbate dianion), in the interlayer space. The isolated solid was characterised by elemental analyses, powder X-ray diffraction (PXRD), thermal studies, FT-IR and UV–Visible diffuse reflectance spectroscopy (UV–Vis/DR). PXRD showed an increase of the basal spacing to 10.5 Å indicating the intercalation of the Cr(III) complexes. FT-IR and UV–Vis/DR spectra also confirmed the in-situ formation of the ascorbate complex in the interlayer space. The interlayer complex was stable up to ~ 200 °C and was decomposed above 400 °C with the formation of small amounts of Cr 6+ as indicated by the UV–Vis/DR spectra. This described method may be useful for intercalation of other biologically important anionic metal complexes in LDHs.

Sorption of Isoxaflutole and DKN on Organoclays

AbstractSorption of the herbicide isoxaflutole and its main degradate, diketonitrile (DKN), to natural clays, SAz-1, SWy-2 and SHCa-1, and the organoclay derivatives (octadecylammonium (ODA) and hexadecyltrimethylammonium (HDTMA)) of these clays was investigated. Isoxaflutole hydrolysis to DKN was too rapid in aqueous solutions with organoclays to characterize sorption. No measurable DKN sorption was observed for the natural clays. Sorption of DKN was greater on organoclays with an interlayer paraffin-like complex that were prepared from the high-charge SAz-1 clay than on organoclays with a bilayer or monolayer interlayer complex prepared using lower-charge SWy-2 or SHCa-1 clays. Desorption isotherms indicated that sorption was irreversible. For SAz-1 with HDTMA at ∼100% of the clay CEC, the d001 values suggest that DKN enters the interlamellar space of the organoclay and dissociates into the anion. The DKN anion forms a very stable chelate complex with the residual cations and/or partially-coordinated structural cations. This strong interaction supports the irreversibility of the sorptive process.

EXAFS studies on adsorption–desorption reversibility at manganese oxide–water interfaces: II. Reversible adsorption of zinc on δ-MnO 2

Microscopic structures of Zn(II) adsorbed at δ-MnO 2–water interfaces were studied using extended X-ray absorption fine structure (EXAFS) spectroscopy. In a 0.1 M NaNO 3 solution of pH 5.50, hydrous Zn(II) was adsorbed onto the solid surface in the form of octahedral coordination. Adsorbed octahedral Zn(II) was located above and below the vacancy sites of δ-MnO 2. Each Zn was coordinated on one side to H 2O molecules forming an H 2O sheet and on the other side to oxygen atoms shared with layer MnO 6 octahedra forming a corner-sharing octahedral interlayer complex. The average ZnO and ZnMn distances were 2.07±0.01 and 3.52±0.01 Å, respectively. Macroscopic adsorption–desorption isotherms showed that, in contrast to that of the Zn γ-MnOOH system, adsorption of Zn(II) on δ-MnO 2 was highly reversible. EXAFS results indicated that the highly reversible adsorption was due to the weak adsorption mode of the corner-sharing linkage between the adsorbate and adsorbent polyhedra.

Intercalation of [Cr(C2O4)3]3 - complex in mg,al layered double hydroxides.

A Mg,Al layered double hydroxide (LDH) with [Cr(C(2)O(4))(3)](3)(-) anions in the interlayer has been synthesized following two different routes: reconstruction from a mildly calcined Mg,Al-carbonate LDH, and anion exchange from a Mg,Al-nitrate LDH. The solids prepared have been characterized by elemental chemical analysis, powder X-ray diffraction, FT-IR and UV-vis/DR (diffuse reflectance) spectroscopies, thermal methods, nitrogen adsorption at -196 degrees C, and FT-IR monitoring of pyridine adsorption. The results obtained indicate that the most appropriate method is anion exchange, leading to a well crystallized LDH with an interlayer spacing of 10 A. Due to the high pH value (>8) of the solution in the reconstruction method, however, a polyphasic system is obtained, where, in addition to a phase with the LDH structure, amorphous magnesium oxalate and chromium oxohydroxides are also formed due to hydrolysis of the complex. The interlayer complex is stable up to 200 degrees C, but the layered structure is stable up to 330 degrees C, probably because of the presence of interlayer oxalate anions formed during decomposition of the complex. Calcination leads to oxidation of Cr(3+) ions to the six-valent state, which reverts to Cr(3+) when the calcination temperature is further increased.

BASAL SPACING OF MONTMORILLONITE/AMINO ACID COMPLEXES AT DIFFERENT RELATIVE HUMIDITY

Complexes of Na-montmorillonite with three amino acids: lysine, arginine and histidine were prepared at different pH values. The basal spacings of the complexes were assessed by X-ray diffractometry at controlled condition of relative humidity. For those complexes, the basal spacing unchanged with relative humidity with the exception of those at high pH (10 and 13). For these samples the change in the basal spacing with relative humidity was the same as that seen for montmorillonite alone. At high pH (>10) lysine, arginine and histidine were apparently not intercalated into montmorillonite. These observations may be explained in terms of the pH-dependent charge characteristics (dissociation) of the amino acids used. Lysine, arginine and histidine have an amino group in both the main and side chain of the molecules. At low pH, both amino groups will be positively charged. At high pH, amino groups will hardly have no charge, though a carboxyl group will almost charged negatively. Since interlayer complex formation is dependent on molecular charge, the basal spacing of montmorillonite-amino acid complexes is sensitive to variations in relative humidity.

Structure of heavy metal sorbed birnessite. Part III: Results from powder and polarized extended X-ray absorption fine structure spectroscopy

The local structures of divalent Zn, Cu, and Pb sorbed on the phyllomanganate birnessite (Bi) have been studied by powder and polarized extended X-ray absorption fine structure (EXAFS) spectroscopy. Metal-sorbed birnessites (MeBi) were prepared at different surface coverages by equilibrating at pH 4 a Na-exchanged buserite (NaBu) suspension with the desired aqueous metal. Me/Mn atomic ratios were varied from 0.2% to 12.8% in ZnBi and 0.1 to 5.8% in PbBi. The ratio was equal to 15.6% in CuBi. All cations sorbed in interlayers on well-defined crystallographic sites, without evidence for sorption on layer edges or surface precipitation. Zn sorbed on the face of vacant layer octahedral sites (□), and shared three layer oxygens (O layer) with three-layer Mn atoms (Mn layer), thereby forming a tridentate corner-sharing (TC) interlayer complex (Zn-3O layer-□-3Mn layer). TCZn complexes replace interlayer Mn 2+ (Mn inter 2+) and protons. TCZn and TCMn inter 3+ together balance the layer charge deficit originating from Mn layer 4+ vacancies, which amounts to 0.67 charge per total Mn according to the structural formula of hexagonal birnessite (HBi) at pH 4. At low surface coverage, zinc is tetrahedrally coordinated to three O layer and one water molecule ( [IV]TC complex: (H 2O)- [IV]Zn-3O layer). At high loading, zinc is predominantly octahedrally coordinated to three O layer and to three interlayer water molecules ( [VI]TC complex: 3(H 2O)- [VI]Zn-3O layer), as in chalcophanite ( [VI]ZnMn 3 4+O 7·3H 2O). Sorbed Zn induces the translation of octahedral layers from − a/3 to + a/3, and this new stacking mode allows strong H bonds to form between the [IV]Zn complex on one side of the interlayer and oxygen atoms of the next Mn layer (O next): O next…(H 2O)- [IV]Zn-3O layer. Empirical bond valence calculations show that O layer and O next are strongly undersaturated, and that [IV]Zn provides better local charge compensation than [VI]Zn. The strong undersaturation of O layer and O next results not only from Mn layer 4+ vacancies, but also from Mn 3+ for Mn 4+ layer substitutions amounting to 0.11 charge per total Mn in HBi. As a consequence, [IV]Zn,Mn layer 3+, and Mn next 3+ form three-dimensional (3D) domains, which coexist with chalcophanite-like particles detected by electron diffraction. Cu 2+ forms a Jahn-Teller distorted [VI]TC interlayer complex formed of two oxygen atoms and two water molecules in the equatorial plane, and one oxygen and one water molecule in the axial direction. Sorbed Pb 2+ is not oxidized to Pb 4+ and forms predominantly [VI]TC interlayer complexes. EXAFS spectroscopy is also consistent with the formation of tridentate edge-sharing ( [VI]TE) interlayer complexes (Pb-3O layer-3Mn), as in quenselite (Pb 2+Mn 3+O 2OH). Although metal cations mainly sorb to vacant sites in birnessite, similar to Zn in chalcophanite, EXAFS spectra of MeBi systematically have a noticeably reduced amplitude. This higher short-range structural disorder of interlayer Me species primarily originates from the presence of Mn layer 3+, which is responsible for the formation of less abundant interlayer complexes, such as [IV]Zn TC in ZnBi and [VI]Pb TE in PbBi.

Preparation of drug-montmorillonite UV-radiation protection compounds by gas-solid adsorption

AbstractEthyl cinnamate/montmorillonite intercalation complexes were obtained by gaseous adsorption of the drug on the clay surface. They were characterized by powder X-ray diffraction, differential thermal and thermogravimetric analyses and by visible-UV and IR spectroscopies. It was found that after 1 day of adsorption, most of the drug enters the interlayer space of the clay by substitution of water molecules, and is removed only after heating at high temperature. In addition, a portion is physisorbed on the external surface of the crystallites, being removed easily below 100°C. The interlayer complex improves the protecting ability of the pure clay or the pure drug against ultraviolet radiation, specially in the so-called ‘C’ range (290–190 nm).

Study of the wear behavior and adhesion of diamond films deposited on steel substrates by use of a Cr–N interlayer

In the present work, we report on the wear behavior and adhesion of diamond films deposited on steel coated by a Cr–N interlayer. The wear behavior of the diamond films was studied under fretting conditions. Fretting was used as a typical wear process occurring during vibration and friction. Wear grooves obtained after the fretting test under different loads and for different numbers of cycles were studied by profilometry, high-resolution scanning electron microscopy and electron probe microbeam analysis. The adhesion of the deposited diamond films was measured by using scratch and indentation tests. The fracture behavior of the diamond film/nitrided chromium interlayer complex under different conditions was studied and correlated to the interlayer nitridation conditions.

Intercalation and co-ordination of ammonia and 1,2-diaminoethane into cobalt(II)-, nickel(II)-, copper(II)-, and vanadium(IV)-exchanged α-tin phosphate

The reactions of gaseous ammonia and 1,2-diaminoethane (en) with α-SnM(PO4)2·H2O (M = Co2+, Ni2+, Cu2+, or VO2+) have been investigated. Reactions occur with retention of the layered phosphate structure, the NH3-containing materials giving rise to an interlayer separation of 10.0 ± 0.05 A. Co-ordination of NH3 occurs in all cases except for VO2+(as deduced from electronic absorption spectra); Co2+ is present in a tetrahedral, probably CoN3O, environment not found in classical co-ordination chemistry, presumably as a consequence of the restricted space available in the interlayer. Ammonia co-ordinates to Ni2+ to give a cis-octahedral NiN3O3 environment and for Cu2+ a tetragonal octahedral environment, probably CuN2O2O′2. An extensive surface and interlayer complex chemistry is displayed by low (2%) loaded Cu2+-exchanged materials, for which e.s.r. studies have been made. The layer structure is retained on heating to 110 °C, stability to loss of ammonia being in the order: Cu2+ > Co2+ > Ni2+, with the greatest change in geometry for the partially dehydrated products occurring in the case of Ni2+ which adopts a five-co-ordinate environment. 1,2-Diaminoethane co-ordinates to both Cu2+ and Co2+, although only as a monodentate ligand; it does not appear to co-ordinate to either Ni2+ or VO2+, instead showing a tendency to hydrogen-bond to phosphate groups in the interlayer.

X-ray photoelectron spectroscopic evidence of interlayer complex formation between Co(II) and N-heterocycles in α-Zr(hpo 4) 2 · H 2O

Evidence from XPS Spectroscopy for coordination of the Co(II) in zirconium phosphate-phen composite is described. Analysis of the shape of the Co2 p photoelectron peak indicates that high-spin N-coordinated Co(II) is present mixed with O-coordinated Co(II). Comparison of the N1 s peak with those in parent α-Zr(HPO 4) 2(phen) 0.5 · 2H 2O confirms that Co(II) is indeed N-coordinated, but that some phenanthroline molecules anchored to the host are also present.

Interaction of some organophosphorus pesticides with vermiculite

The adsorption and mechanism of interaction of vermiculite with the organophosphorus pesticides dichlorvos, phosdrin, sumithion and dimethoate were studied. Dichlorvos and phosdrin are adsorbed at a solution of 0.3 M in 1,2-dichloroethane forming a defined interlayer complex of 16.05 Å d 001 basal spacing. The nature of the interlayer cation of the vermiculite and the polarity and molecular size of the pesticide are factors which influence the formation of this complex. Sumithion and dimethoate do not form a defined complex. The I.R. results show that the PO and CO groups (phosdrin) and the PO group (dichlorvos) are involved in the mechanism of interaction. A study was also performed on the adsorption of dichlorvos and phosdrin by Na-, Mg- and Ca-vermiculites in aqueous media at 30° and 45°C. The isosteric heats of adsorption determined from the isotherms show the endothermic nature of the process.

THE OCCURRENCE OF INTERLAYER CLAY-ORGANIC COMPLEXES IN TWO NEW ZEALAND SOILS

By using x-ray diffractometry and /sup 13/C-NMR spectroscopy, in combination with chemical and heat pretreatments, the authors have found good evidence for the occurrence of interlayer clay-organic complexes in two New Zealand soils. Here, the clay mineral is a regularly interstratified mica-smectite, and the organic species is a humic substance with a polymethylene chain structure. The organic material in the complex is resistant to peroxidation and pyrophosphate extraction. It is also thermally stable, being extensively decomposed only after the complex is heated at 400/sup 0/C. A combination of soil factors seems necessary for interlayer complex formation. This includes a smectitic clay mineralogy, an accumulation of organic matter associated with a low microbial activity, and a highly acid soil reaction.

Reactions Between Fulvic Acid, A Soil Humic Compound, and Montmorillonite

AbstractThe magnitudes of d001 spacings of fulvic acid‐Na‐montmorillonite complexes were not affected by temperatures between 25 and 60°C. Slightly more than one half of the total amount of fulvic acid adsorbed by Na‐montmorillonite was in the interlamellar spaces, with the remainder on external surfaces. The d001 spacings and amounts of fulvic acid adsorbed in the interlamellar spaces of Pb++−, Mg++−, Co++− and Ni++− saturated montmorillonite decreased with increase in pH. The capacities of cation saturated clays to adsorb fulvic acid in interlamellar spaces decreased in the following order: Pb++ > Mg++ > Co++ > Ni++. The exotherm near 670°C in the DTA curve of the fulvic acid‐Na‐montmorillonite complex signalized the formation of an interlayer complex.

Organo-Metallic Clay Complexes Part II*

Complex formation enhances the sorption of various diamines from aqueous solutions by montmorillonite in the presence of copper and vice versa. A distinct difference was observed betv, een chelating and nonchelating diamines. The effects were measured quantitatively, and the resulting structures were investigated by X-ray diffraction tethniques. No direct correlation was observed between cell height and the configuration of the interlayer complex ions; 'keying o f organic and organometallic cations into the oxygen surfaces is inferred.