The stability of phenol-urea-formaldehyde (PUF) binder and 3-aminopropylsilane (APS) on composite silicate materials (fibers and wafers) was studied with surface sensitive techniques (X-ray photoelectron spectroscopy (XPS) and streaming potential) through a wide range of humidity and temperature and ab initio modelling complemented the results. Behavior was compared for wettability properties, determined by vapor adsorption and contact angle analysis. APS and PUF, deposited on the silicate surfaces, decrease surface energy and wettability but water adsorption remains high, facilitating hydrolytic decomposition of the composite material. Deposited APS is unstable at T>50°C and 75% RH, while PUF is less sensitive to high humidity and temperature. Molecular dynamics confirmed APS sensitivity to humidity. Water adsorption and surface energy decrease, and material stability increases when a hydrophobization agent is applied to APS/PUF treated surfaces. The direct correlation between wettability and stability of PUF/APS/fiber composites can contribute in designing new materials with controlled hydrophobic properties.

The heterocyclic donor molecule 2,4,7,9-tetramethyl-1,6-dithiapyrene (TMDTP) has been synthesized in five steps. Oxidation of TMDTP is facile (E 1 1/2 = 0.27 V and E 2 1/2 = 0.79 V vs. SCE). The charge-transfer complex, TMDTP-TCNQ, has been prepared and the salt, (TMDTP)3(PF6)2·2THF, obtained by electrocrystallization. The structure of TMDTP, TMDTP-TCNQ and (TMDTP)3(PF6)2·2THF has been characterized by X-ray crystallography and computationally.

Interactions between organic molecules in aqueous environments, whether in the fluid phase or adsorbed on solids, are often affected by the cations present in the solution. We investigated, at nanometer scale, how surface carboxylate interactions are influenced by dissolved divalent cations: Mg2+, Ca2+, Sr2+, and Ba2+. Self-assembled monolayer (SAM) surfaces with exposed terminations of alkyl, -CH3, carboxylate, -COO-, or dicarboxylate, -DiCOO(-), were deposited on gold-coated tips and substrates. We used atomic force microscopy (AFM), in chemical force mapping (CFM) mode, to measure adhesion forces between various combinations of SAMs on the tip and substrate, in solutions of 0.5 M NaCl, that contained 0.012 M of one of the divalent cations. The type of cation, the number of carboxyl groups that interact, and their structure on the SAM influenced adhesion between the surfaces. The effect of the reference solution, which only contains Na+ cations, on adhesion force was mainly attributed to van der Waals and hydrophobic forces, explaining the lower force in systems that are more hydrophilic, i.e., -COO- -COO-, and higher force for more hydrophobic systems. For charged surfaces, i.e., -COO- and -DiCOO(-), in divalent cation solutions results were consistent with ion bridging. The inclusion of a hydrophobic surface, i.e., the -CH3-COO- or -CH3-DiCOO(-) system, decreased the possibility for strong cation bridging with the charged surface, resulting in lower adhesion. For systems including -COO-, the adhesion force series followed the inverse cation hydrated radius trend (Na+ approximate to Mg2+ < Sr2+ < Ca2+ < Ba2+) whereas -DiCOO(-) was responsible for lower adhesion force and modified trends, depending on the corresponding surface in the system. Differences in force magnitude between the monolayers were correlated with lower charge availability on the -DiCOO(-) surface as a result of fewer active sites, probably because of the tendency of exposed malonate surface groups to interact between them, as well as high rigidity, resulting from the molecule structure. The characteristic response of the -DiCOO(-) surface in solutions of Sr2+ and Ca2+ was correlated with possible malonate complexation modes. Comparison with previous studies suggested that the strong response of a -DiCOO(-) surface to Sr2+ resulted from bidentate chelation, whereas Ca2+ response was attributed to alpha-mode association to malonate.

Phenol-urea-formaldehyde (PUF) resin is one of the most important thermosetting polymers. It is widely used in many industrial and construction applications as an organic coating and adhesive. For example, in production of mineral wool for insulation, PUF is used together with the coupling agent (3-aminopropylsilane, APS) and serves as a binder for attaching mineral fibers to each other and to create the necessary mechanical integrity and shape of the final product. However, during ageing under high humidity (95%) and temperature (70 degrees C), hydrolysis can degrade PUF, decreasing product quality. A better understanding of the chemical processes caused by hydrolysis would promote development of more stable PUF binders. We investigated the composition and stability changes during ageing of cured PUF powder binder and mineral wool fibers where PUF binds the fibers together. We aged the samples in hot water (80 degrees C) or in a controlled climate chamber (70 C; 91% RH) and analyzed them using X-ray photoelectron spectroscopy (XPS), element analysis and thermogravimetric (TG) analysis. We investigated the composition of species released from PUF during hydrolysis by electrospray ionization (ESI) of the aqueous solutions. The results show that the extent of PUF curing and the presence of APS as the coupling agent have an important impact on its stability. XPS revealed that poorly cured PUF contains a high fraction of NH-CH2-O-CH2-NH bonds which are easily hydrolyzed, while longer curing results mostly in more stable methylene bridges, NH-CH2-NH. We also observed evidence for urea NH CO bond decomposition by ESI analysis. Mineral wool fiber ageing studies showed that PUF rearranges on the fiber surface and detaches from it, together with the APS coupling agent. This improved understanding of the effects of ageing provides clues for designing a more robust binder, leading to increased quality and stability of mineral wool insulation. (C) 2018 Elsevier Ltd. All rights reserved.

Removal of organic compounds is a common first step in surface characterization of inorganic materials. To explore the surface reactivity of environmental samples such as rocks, soil, and sediments, it is essential to know if they are pure or covered with organic material. Our purpose was to evaluate the influence of some common cleaning procedures on the surface composition of inorganic solids and to investigate if such treatments result in completely clean mineral surfaces. We used Soxhlet solvent extraction and chemical oxidation to remove crude oil from samples that we synthesized to represent oil bearing sandstone. After each cleaning step, we tracked surface composition using X-ray photoelectron spectroscopy. We demonstrated that (i) it was impossible to completely remove the organic material with any of the methods, (ii) the oxidation treatment dissolved soluble minerals, and (iii) surface composition was dominated by clay particles adhering to the larger grains and thus was responsible for a significant fraction of the residual adsorbed organic compounds. The most important conclusion is that the pore surface composition, i.e. the clay fraction not the bulk matrix composition, ought to be used for thermodynamic and kinetic calculations to predict pore fluid composition and evolution during transport through pore networks.

Using a proper cooling procedure, a controllable amount of nonmagnetic structural disorder can be introduced at low temperature in (TMTSF) 2 ClO 4. Here we performed simultaneous measurements of transport and magnetic properties of (TMTSF) 2 ClO 4 in its normal and superconducting states, while finely covering three orders of magnitude of the cooling rate around the anion ordering temperature. Our result reveals, with increasing density of disorder, the existence of a crossover between homogeneous defect-controlled d-wave superconductivity and granular superconductivity. At slow cooling rates, with small amount of disorder, the evolution of superconducting properties is well described with the Abrikosov-Gorkov theory, providing further confirmation of non-s-wave pairing in this compound. In contrast, at fast cooling rates, zero resistance and diamagnetic shielding are achieved through a randomly distributed network of superconducting puddles embedded in a normal conducting background and interconnected by proximity effect coupling. The temperature dependence of the ac complex susceptibility reveals features typical for a network of granular superconductors. This makes (TMTSF) 2 ClO 4 a model system for granular superconductivity where the grain size and their concentration are tunable within the same sample.

2014 X-ray diffuse scattering studies of one dimensional conductors (TMTSF)2ReO4 and (TMTSF)2NO3 reveal the formation of low temperature superstructures which might involve an ordering of the counter ions ReO-4 and NO-3. The superstructure reflections are characterized by wave vectors q = (1/2, 1/2, 1/2) for the perrhenate and q = (1/2, 0, 0) for the nitrate, which double the unit cell volume in both cases. In (TMTSF)2ReO4 this phase transition coincides with the metal insulator transition observed at 180 K, whereas in (TMTSF)2NO3 it corresponds to a better conducting state observed below 41 K. J. Physique LETTRES 42 (1981) L-543 L-546 15 DÉCEMBRE 1981

Grain size increases when crystals respond to dynamic equilibrium in a saturated solution. The pathway to coarsening is generally thought to be driven by Ostwald ripening, that is, simultaneous dissolution and reprecipitation, but models to describe Ostwald ripening neglect solid solid interactions and crystal shapes. Grain coarsening of calcite, CaCO3, is relevant for biomineralization and commercial products and is an important process in diagenesis of sediments to rock during geological time. We investigated coarsening of pure, synthetic calcite powder of sub-micrometer diameter crystals and aged it in saturated solutions at 23, 100, and 200 degrees C for up to 261 days. Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area analysis showed rapid coarsening at 100 and 200 degrees C. Evidence of particle growth at 23 degrees C was not visible by SEM, but high resolution X-ray diffraction (XRD) data demonstrated steady growth of nanometer crystallites. The results can be described by theory where grains coarsen preferentially by aggregation at early times and high temperatures and by Ostwald ripening at later stages. Crystal form and dimension are influenced by the transition from one growth mechanism to the other. This has been poorly described by mean field coarsening models and offers predictive power to grain coarsening models.

The interaction of water and organic molecules with mineral surfaces controls many processes in nature and industry. The thermodynamic property, surface tension, is usually determined from the contact angle between phases, but how does one understand the concept of surface tension at the nanoscale, where particles are smaller than the smallest droplet? We investigated the energy required to exchange M2+ and SO42- from aqueous solution into calcite {10.4} surfaces using density functional theory. Mg2+ substitution for Ca2+ is favored but only when SO42- is also present and MgSO4 incorporates preferentially, substituted calcite surface as ion pairs at solution calcite interfaces. Mg2+ incorporation weakens organic molecule adhesion while strengthening water adsorption so Mg2+ substitution renders calcite more water wet. When Mg2+ replaces 10% of surface Ca2+, the contact angle changes dramatically, by 40 to 70 degrees, converting a hydrophobic surface to a mixed wet surface or rendering a mixed wet surface hydrophilic. This increase in water wettability decreases affinity for organic compounds. An important outcome is that we can now explain why oil recovery from carbonate reservoirs is enhanced when both Mg2+ and SO42- are present in the pore water. Incorporation of MgSO4 into calcite, which is energetically favored, decreases surface tension and releases polar oil compounds.

In time-resolved laser pump, X-ray probe wide-angle X-ray scattering experiments on systems in solution the structural response of the system is accompanied by a solvent response. The solvent response is caused by reorganization of the bulk solvent following the laser pump event, and in order to extract the structural information of the solute, the solvent response has to be treated. Methodologies capable of doing so include both theoretical modelling and experimental determination of the solvent response. In the work presented here, we have investigated how to obtain a reproducible solvent response—the solvent term—experimentally when applying laser pump, X-ray probe time-resolved wide-angle X-ray scattering. The solvent term describes difference scattering arising from the structural response of the solvent to changes in the hydrodynamic parameters: pressure, temperature and density. We present results based on NIR and dye mediated solvent heating, and demonstrate that the solvent response is independent of the heating method. The NIR heating is shown to be rendered unusable by higher order effects under certain experimental conditions, while the dye mediated solvent heating is demonstrated to exhibit first order behaviour with respect to the amount of energy deposited in the solution. We introduce a standardized method for recording solvent responses in laser pump, X-ray probe time-resolved X-ray wide-angle scattering experiments by using dye mediated solvent heating. Furthermore, we have generated a library of solvent terms, which can be used to describe the solvent term in any TRWAXS experiment, and made it available online.

The organic materials (TMTSF)(2)X are unique unconventional superconductors with archetypal quasi-one-dimensional (Q1D) electronic structures. Here, based on our comprehensive field-angle-resolved calorimetry of (TMTSF)(2)ClO4, we succeeded in mapping the nodal gap structure by discriminating between the Fermi wave vectors and Fermi velocities. In addition, the thermodynamic phase diagrams of (TMTSF)(2)ClO4 for all principal field directions are obtained. These findings, providing strong evidence of nodal spin-singlet superconductivity, serves as solid bases for the further elucidation of anomalous superconducting phenomena in (TMTSF)(2)X.

The silicate mineral olivine, (Mg,Fe)(2)SiO4, reacts exothermally with CO2 and forms secondary minerals, including carbonates. Therefore olivine reaction is a promising process for carbon sequestration, to convert carbon dioxide from the atmosphere to mineral form. The purpose of this study was (1) to explore the composition, structure and reactivity of olivine surfaces during exposure to air and to water at ambient conditions, (2) to investigate the effect of elevated CO2 pressure and temperature, and (3) to identify the secondary minerals.Olivine surfaces have been examined with atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), before and after reaction with CO2. Experiments were carried out in pure water equilibrated with CO2 at total pressures up to 80 bars, at temperatures 25 degrees C and 120 degrees C and both in the absence and presence of oxygen. New formation products appeared on the olivine surface as a homogeneous layer of bumps, less than 100 nm in diameter, within hours of exposure to air. Olivine crystals, exposed to water, dissolved and secondary minerals formed within days. Colonies of bacteria populated olivine surfaces on samples stored in water for more than 4 days at room temperature. Loosely attached material formed on olivine surfaces and could easily be scraped away with the AFM tip. A red precipitate formed when crystals where reacted at increased temperatures and CO2 partial pressures for less than 4 days. The new phases were identified as goethite, hematite, silica and carbonate minerals. Olivine surfaces oxidize and iron oxides form even when oxygen is absent, suggesting hydrolysis, where water is converted to hydrogen and oxygen. (C) 2011 Elsevier Ltd. All rights reserved.

Coccoliths are micrometer scale shields made from 20 to 60 individual calcite (CaCO(3)) crystals that are produced by some species of algae. Currently, coccoliths serve as an important sink in the global carbon cycle, but decreasing ocean pH challenges their stability. Chalk deposits, the fossil remains of ancient algae, have remained remarkably unchanged by diagenesis, the process that converts sediment to rock. Even after 60 million years, the fossil coccolith crystals are still tiny (< 1 μm), compared with inorganically produced calcite, where one day old crystals can be 10 times larger, which raises the question if the biogenic nature of coccolith calcite gives it different properties than inorganic calcite? And if so, can these properties protect coccoliths in CO(2) challenged oceans? Here we describe a new method for tracking dissolution of individual specimens, at picogram (10(-12) g) resolution. The results show that the behavior of modern and fossil coccoliths is similar and both are more stable than inorganic calcite. Organic material associated with the biogenic calcite provides the explanation. However, ancient and modern coccoliths, that resist dissolution in Ca-free artificial seawater at pH > 8, all dissolve when pH is 7.8 or lower. Ocean pH is predicted to fall below 7.8 by the year 2100, in response to rising CO(2) levels. Our results imply that at these conditions the advantages offered by the biogenic nature of calcite will disappear putting coccoliths on algae and in the calcareous bottom sediments at risk.

Comparing resistivity data of the quasi-one-dimensional superconductors (TMTSF)2PF6 and (TMTSF)2ClO4 along the least conducting c(⋆)-axis and along the high conductivity a-axis as a function of temperature and pressure, a low temperature regime is observed in which a unique scattering time governs the transport along both directions of these anisotropic conductors. However, the pressure dependence of the anisotropy implies a large pressure dependence of the interlayer coupling. This is in agreement with the results of first-principles density functional theory calculations implying methyl group hyperconjugation in the TMTSF molecule. In this low temperature regime, both materials exhibit for ρ(c) a temperature dependence aT + bT(2). Taking into account the strong pressure dependence of the anisotropy, the T-linear ρ(c) is found to correlate with the suppression of the superconducting Tc, in close analogy with ρ(a) data. This work reveals the domain of existence of the three-dimensional coherent regime in the generic (TMTSF)2X phase diagram and provides further support for the correlation between T-linear resistivity and superconductivity in non-conventional superconductors.

Transport measurements along the least conducting direction of the organic superconductors (TMTSF)2PF6 and (TMTSF)2ClO4 reveal a pronounced sublinear temperature dependence visible up to about four times the superconducting Tc either when pressure is close to the critical pressure for superconductivity in (TMTSF)2PF6 or under ambient pressure in (TMTSF)2ClO4 and ClO4-ReO4 solid solutions. Given the linear temperature dependence of the single-particle scattering in the metallic state derived from a previous investigation, the excess conduction insensitive to magnetic field but suppressed by lattice defects in the solid solution has been ascribed to sliding of fluctuating spin density waves in the vicinity of the antiferromagnetic order. This is the first observation of fluctuating spin density waves contributing to conduction.

Organic single-crystalline nanowire arrays, with a length of several hundreds of micrometers and controllable width, are grown on a substrate surface by vertically pulling the substrate out of an organic solution of the molecule of interest. Optical microscopy and atomic force microscopy show that the large-scale arrays are oriented parallel to the pulling direction and are well adhered to the substrate surface. Cross-polarized microscopy, polarized UV-vis absorption, and grazing incidence X-ray diffraction confirm that the arrays have high crystal quality. On the basis of this method, the fabrication of organic devices is realized in one step. The results presented here for three different small molecules show the promising potential of this facile solution-based process for the growth of high-quality organic semiconductors, the fabrication of high-density and high-performance devices, and the fabrication of controlled assemblies of nanoscale circuits for fundamental studies and future applications.

A general synthetic route to a novel type of triamino-substituted planar carbenium ions (5) is reported. The synthetic method is based on a facile and selective nucleophilic aromatic substitution on the tris(2,4,6-trimethoxyphenyl)carbenium ion (1) with amines and gives access to a wide variety of more complex amino-substituted carbenium ions. X-ray crystallography shows that the 2,6,10-tris(N-pyrrolidinyl)-4,8,12-trioxatriangulenium ion (5b) is planar and forms segregated stacks of cations and PF6 anions in the solid phase. The stability of the 2,6, 10-tris(diethylamino)-4,8,12-trioxatriangulenium ion 5a is expressed as the pK(R+) value, which is determined in strongly basic nonaqueous solution on-the basis of a new acidity function C-. The pK(R+) value of 5a is measured to be 19.7, which is 10 orders of magnitude higher than the values found for the most stable carbenium ions previously reported. Electrochemical reduction of compound 5a leads to rapid dimerization. Two consecutive one-electron oxidations are identified by cyclic voltammetry.