Solid or liquid? Solidification of a nanoconfined liquid under nonequilibrium conditions

There has been a long-standing debate about the physical state and possible phase transformations of confined liquids. In this report, we show that a model-confined liquid can behave both as a Newtonian liquid with very little change in its dynamics and as a pseudosolid, depending solely on the rate of approach of the confining surfaces. Thus, the confined liquid does not exhibit any confinement-induced solidification in thermodynamic equilibrium. Instead, solidification is induced kinetically when the two confining surfaces are approached with a minimum critical rate. This critical rate is surprisingly slow (on the order of 6 A/s), explaining the frequent observation of confinement-induced solidification.     

Solid–liquid phase diagrams of binary mixtures

This study investigates the sorption of toluene and naphthalene by a sodium bentonite (BFN), an organoclay (WS35) and by their respective iron oxide hydrate composites Mag_BFN and Mag_S35. The organic matter content of WS35 and Mag_S35, determined by thermogravimetry, was used to obtain their organic matter sorption coefficients, which show that they are effective sorbents to remove organic contaminants from water, with a higher selectivity for naphthalene than for toluene sorption. The main iron oxide phase present in Mag_BFN and Mag_S35 is maghemite (γ-Fe₂O₃), which allows these sorbents to be separated from the effluent by a magnetic separation process after use.     

Solid–liquid interface analysis with in-situ Rutherford backscattering and electrochemical impedance spectroscopy

A novel Rutherford backscattering spectrometry (RBS) method is presented to investigate the interface between a solid surface and a surrounding liquid. The introduced measurement system allows to observe and quantify adsorption at the solid–liquid interface and the formation of the electrochemical double layer (EDL). BaCl₂ as a bicomponent electrolyte and a Si₃N₄ membrane surface are chosen as a model system to prove the capabilities of the setup. The results of these RBS measurements are combined with electrochemical impedance spectroscopy (EIS) to validate the findings for the solid–liquid interface under study. Complementary results and discrepancies regarding the formation of the EDL are discussed.     

Viscosity of liquid Cu–Sn alloys

We investigated of the kinematic viscosity of liquid Cu–Sn alloys upon heating and subsequent cooling by the method of the oscillating cylinder. For the liquids alloys Cu75Sn25, Cu50Sn50, Cu48Sn52, Cu32Sn68, and Cu17Sn83, the temperature dependencies of the viscosity upon heating deviate from the Arrhenius relation. The temperature dependencies of viscosity show the Arrhenius-like behaviour upon cooling for all investigated alloys. A discrepancy between the temperature dependencies of viscosity obtained upon heating and cooling arised. We built the concentration dependences of the kinematic viscosity of liquid Cu–Sn alloys upon cooling. The increase of the values of viscosity and activation energy of viscous flow in the concentration range corresponding to the existence of intermetallic compounds Cu₃Sn in the solid state was observed. These results were qualitatively interpreted using the concept of microheterogeneities of liquid alloys.     

Electrosynthesis of polyphenylpyrrole coated silver particles at a liquid–liquid interface

This communication reports the production of polyphenylpyrrole coated silver nanoparticles at the liquid/liquid interface by an EC-type mechanism. In the electrochemical step of the reaction N-phenylpyrrole facilitates the transfer of the silver ion from an aqueous to an organic phase. This step is followed by a slow homogeneous electron transfer reaction from the N-phenylpyrrole to the silver ion followed by polymerization and metal cluster growth.     

Voltammetric determination of perchlorate ion at a liquid–liquid microscopic interface

A method is proposed for the electrochemical determination of perchlorate ion by voltammetry at the interface between two immiscible phases (water–o-nitrophenyl octyl ether). A demountable original-design amperometric ion-selective electrode based on a laser-microperforated polymeric membrane was fabricated for voltammetric measurements. The conditions of analytical signal recording in the determination of ClO₄ ^? were determined. The effect of interfering ions was assessed and amperometric selectivity coefficients were calculated. The accuracy of the procedure was verified by the added–found method. The developed electrode was applied to the determination of perchlorate in natural and drinking waters.     

Mixing enthalpy of liquid Cu–Hf–Ni alloys at 1873 K

Journal of Thermal Analysis and Calorimetry - The mixing enthalpies of liquid Cu–Hf–Ni alloys were determined at 1873 K by applying a high-temperature isoperibolic calorimeter....     

Adsorption of cationic multicharged surfactants at liquid–gas interface

We present the review of the existing methods for describing adsorption at fluid interfaces that may be applicable for multiple charge cationic surfactant structures of various architectures—multiheaded (e.g., dicephalic) structures and multimeric surfactants (e.g., dimeric (so-called gemini), trimeric, tetrameric, etc.). We discuss the role of the prefactor the in the Gibbs adsorption equation originating from the number of charges present in the adsorbed layer and the reasons for the deviation from its thermodynamic value. We present several models of adsorption that can be used to describe surface tension isotherms and appreciate the role of prof. Peter Kralchevski in their development. Application of molecular dynamics methods combined with the approach based on the thermodynamic models of multicharged surfactant adsorption may lead to an explanation of some experimentally observed phenomena and can provide the basis for the development of novel materials designated for a variety of applications.     

Lipophilicity of ions electrogenerated at a Pt coated micropipette supported liquid–liquid interface

A novel method to readily determine the lipophilicity of electrogenerated charged species is reported. This is achieved by local electrolysis at a Pt coated micropipette and, subsequently, driving the electrogenerated species to transfer across the liquid–liquid interface supported at the tip of the micropipette under potential control. The formal potential of ion transfer can then be used to give a measure of its relative lipophilicity. The method proposed is facile and enables the study of potentially unstable charged products of electron transfer reactions.     

Onsager heat of transport at the aniline liquid–vapour interface

The heat of transport for passage of matter through a gas–liquid interface has been determined for the aniline liquid–vapour system, by measuring stationary-state pressure differences produced by known temperature differences over a distance of 2 mm on the vapour side of the interface. For the range of pressures used, 2 mm is between 6 and 34 mean free paths. Coupling of the heat and matter fluxes is significant over the whole of this range. At the higher pressures the heat of transport is more than 20% of the heat of condensation; at the lower pressures it is more than 50%.     

Estimation of spinodals from the density profile of the vapor–liquid interface

An extension of a recently proposed method for the calculation of the spinodals in pure fluid systems from the interfacial properties is elaborated, which requires the density profile as only input. The foundation of this approach is the so-called Fuchs-transformation which gives an estimate for the tangential pressure profile from the density profile. Using molecular dynamics simulation data for argon and carbon dioxide as well as lattice Boltzmann simulation data for the argon-like Shan–Chen fluid, the accuracy of the approach is analyzed. The Fuchs-transformation is qualitative, however it is possible to estimate the temperature–density projection of the spinodal. Depending on the underlying correlation function for the interfacial density profile reasonable results are obtained for the liquid and the vapor spinodal. The advantage of this method is that equilibrium data can be used to estimate the spinodal which is experimentally impossible to access because it is a highly non-equilibrium property. In the final consequence of this approach only the coexistence vapor and liquid densities are required to estimate the temperature–density projection of the spinodals.     

Cyclic voltammetry of the transfer of anionic surfactant across the liquid–liquid interface manifests electrochemical instability

Experimental evidence for the presence of the instability window in the polarized potential range of the phase-boundary potential has been obtained in cyclic voltammograms in the presence of the transfer of anionic surfactants across the 1,2-dichloroethane–water interface. Irregular current spikes and fluctuations appeared in the vicinity of the half-wave potential for the transfer of decyl sulfonate and dodecyl sulfate ions. Chaotic current became more pronounced with increasing the concentration of the ionic surfactant. This trend was in excellent agreement with the theoretical prediction based on the recently proposed concept of the electrochemical instability.     

Solid–liquid equilibrium,thermal and physicochemical studies of organic eutectics

The solid–liquid phase equilibrium data of two binary organic systems, namely, urea (U)–3-aminophenol (AP) and 3-hydroxybenzaldehyde (HB)–β-napthaol (BN) show formation of a eutectic in each case. The enthalpies of fusion of the pure components and binary eutectics have been determined using differential scanning calorimeter (Mettler DSC-4000) system. The thermal properties of the materials such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions were computed using the enthalpy of fusion values. The microstructures of eutectics were developed using unidirectional thermal gradient and interested region were photographed.     

Voltammetry at a liquid–liquid interface supported on a metallic electrode

A liquid–liquid interface supported on a metallic electrode has been used to study ion transfer (IT) and electron transfer (ET) reactions by cyclic voltammetry. The system is composed of an aqueous droplet supported on a platinum disc electrode and immersed into an organic electrolyte solution. Depending on the nature of the dissolved species present in the aqueous solution, and in the organic electrolyte solution, different electrochemical coupled reactions can be observed. This method enables a fast and convenient method to measure standard transfer potentials for example of ionised drug molecules.     

Activity Measurements of Solid Ni–In Alloys by EMF Method with Zirconia Solid Electrolyte

Summary. The EMF of galvanic cells with stabilized zirconia solid electrolyte was measured to determine the activity of indium in solid Ni–In alloys in the temperature range of 970–1170 K and composition range of 5–55 mol% In. Activity of indium increases sharply in the ζ phase and Ni₁₃In₉ phase. The activity values are compared with literature data.     

Solid–liquid equilibrium and thermochemical studies of organic analogue of metal–nonmetal system: Succinonitrile–pentachloronitrobenzene

The phase diagram of an organic analogue of a metal–nonmetal system, involving succinonitrile–pentachloronitrobenzene, shows the formation of a eutectic and a monotectic. The two immiscible liquid phases are in equilibrium with a single liquid phase and the consolute temperature being 53.5 °C above the monotectic horizontal. The phase equilibrium study confirms the alloy composition of monotectic and eutectic at 0.150 and 0.985 mol fractions of succinonitrile, respectively. The solidification behaviour shows the validity of Hilling–Turnbull equation. The thermal properties such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy, grain boundary energy and excess thermodynamic functions for parent components, monotectic and eutectic have been studied using their enthalpy of fusion values. The effects of solid–liquid interfacial energy on morphological change of monotectic have also been discussed. The microstructure of monotectic shows the lamellar growth along with droplets, however, eutectic infers the vertical growth of lamella.     

Solid–liquid phase equilibria for binary mixtures of propellant’s stabilizers

Solid–liquid equilibria for three binary mixtures of N-(2-acetoxyethyl)-p-nitroaniline (1) + 2-nitrodiphenylamine (2), N-(2-acetoxyethyl)-p-nitroaniline (1) + ethyl centralite (2) and N-(2-acetoxyethyl)-p-nitroaniline (1) + methyl centralite (2) have been determined experimentally using differential scanning calorimeter (DSC). Simple eutectic behaviours for these systems have been observed. The experimental results have been correlated by means of NRTL and UNIQUAC equations. The root-mean-square deviations of the solubility temperatures for all measured data vary from 0.61 to 3.32 K and depend on the particular model used. The best solubility correlation has been obtained with the UNIQUAC model.