Synthesis of copper monolayer and particles at aqueous–organic interface

Using aqueous–organic interface (water–oleic acid) reduction of Cu²⁺ by ascorbic acid, hydrophobic copper monolayer and copper particles have been prepared and characterized. The resultant monolayer could be transferred from the interface onto solid substrate or be dissolved to yield an organosol and copper nanoparticles.     

Excess molar heat capacity of isobutyric acid–water binary liquid mixtures near and far away from the critical temperature

The heat capacity of the liquid–liquid mixture isobutyric acid–water has been measured for the first time near and far away from its critical point using an adiabatic calorimeter. The measurements were performed at atmospheric pressure, in the one phase region as a function of three temperatures: (1) T − T_C = 0.055 °C, (2) T − T_C = 3.055 °C, (3) T − T_C = 8.055 °C and of the composition X in acid (IA). The heat capacity C_p decreases rapidly when X increases at the used temperatures. Near the critical composition, C_p is not affected by the correlation of the concentration fluctuations.

The molar excess heat capacity of the system under investigation was analysed along the phase diagram and considered as a structural transformation effect.     

Structure correlations of water molecules in a concentrated aqueous solution of ethanol

Monte Carlo calculation results for water–ethanol mixtures calculated in the isothermal and isobaric ensemble at T=300 K are presented. The analysis of the radial distribution functions for hydrogen bonding between ethanol molecule and water molecules was done. The concentrations of ethanol 0.75 show characteristics features of hydrogen-bonded liquids. The influence of the polar solvent molecule on water local structure and the hydrogen bond nets ware analyzed. Radial distribution functions for water–water interactions calculated in pure water and water–ethanol system are compared.     

Surface preparation of Ti–3Al–2.5V alloy tubes for welding using a fiber laser

Ti–3Al–2.5V tubes are widely used in aircraft hydraulic systems. Meticulous surface preparation before welding is necessary to obtain a sound weld involving these alloy tubes. Conventionally this is done by cleaning with environmentally malign toxic chemicals, such as, hydrofluoric acid and nitric acid. This paper describes the laser-cleaning process of the surface of these tubes with a fiber laser as a preparation for pulsed gas tungsten arc welding and results obtained. A simple one-dimensional heat equation has been solved to evaluate the temperature profile of the irradiated surface. It is shown that surface preparation by laser cleaning can be an environmentally friendly alternative process by producing acceptable welds with laser-processed tubes.     

Mott–Hubbard transition in a 2D He fluid monolayer

We discuss recent observations of the heat capacity and magnetization of a fluid ³He monolayer adsorbed on graphite plated with a bilayer of HD. Approaching the density at which the monolayer solidifies into a commensurate solid, we observe an apparent divergence of the effective mass. However, the inferred values of F₀^a tend to a constant. We interpret this in terms of a Mott–Hubbard transition between a 2D Fermi liquid and a magnetically disordered solid occurring via the Brinkman–Rice–Anderson–Vollhardt scenario.     

The water‐promoted Diels–Alder reaction in quaternary ammonium salts

Prevailing classification of salts based on their effect in solubility and stability of proteins in aqueous solution predicts that tetraalkylammonium salts, guanidinium chloride (GnCl), LiClO₄ act as salting‐in (S/I) and LiCl, NaCl act as salting‐out (S/O) in aqueous conditions. In the same context the behaviour of GnCl, LiClO₄ and LiCl are contradictory in polar solvents like ethylene glycol and formamide. In these solvents, expected salt effect shows just opposite nature from their usual expectation. However, in the aqueous solution salts like tetraalkylammonium halide (R₄NX, R = alkyl group, X = Br group) behave like salting‐in salts. The physicochemical origin of the salting in effect of R₄NX type of salts has been discussed elaborately in the present work. The role of cations in terms of substitution of various alkyl groups on R₄NX has been systematically presented here on the basis of experimental kinetic and thermodynamic studies. The abnormal behaviour of R₄NX salts in aqueous solution has also been explained by the Setschenov equation (k_s) and Δμ_solvation values, which highlights their individual nature out of common properties of R₄NX. Copyright © 2015 John Wiley & Sons, Ltd.     

Composite doped emeraldine–polyethylene oxide-bonded lithium-ion nano-tin anodes with electronic–ionic mixed conduction

Mixed-conducting lithium-ion doped emeraldine polyaniline (PAni)–polyethylene oxide (PEO) blends have been developed to achieve an optimal electronic–ionic conductivity balance in nano-tin composite anodes. Electrochemical evaluation was performed on the anodes with differing electrode preparation procedures, doping methods and PEO contents. Results indicate that both good electronic and ionic conductivity in the binder are required for rapid lithium insertion/extraction and low polarization. This doped PAni–PEO polymer blend is an attractive binder for high capacity composite anodes with low polarization.     

Significance of hydrophobic interactions in water–organic binary solvents

A LFE (Linear Free Energy) analysis of kinetic data for different organic reactions in various organic aqueous solutions was carried out. The rate constants of these reactions were compared with those for the solvolysis of tert-butyl chloride in the same solvents in terms of the LFE Relationships, and linear plots were observed in a wide range of the co-solvent content. This similarity points to a common nature of the solvent effect in these reactions in variety of water–organic mixtures, regardless of largely different reaction mechanisms. We explain these results by the prevalence of hydrophobic stabilization of the initial state of these reactions in water-rich solvent mixtures. Recently the same conclusion was also made on the basis of investigations into sonication effects in kinetics of organic reactions. A considerable contribution of hydrophobic effects to the Y scale by Grunwald and Winstein was deduced.     

Detection of water–ice phase transition based on Raman spectrum

A simplified dimensionless method was constructed to characterize the phase transition between water and ice based on Raman spectrum (RS) without contact testing samples. This method reduces the requirement of the spectrum intensity, simplifies the complex mathematical analysis and improves the resolution of detection which only depends on the relative intensity of RS. The current work establishes an important tool for accurate characterization of RS so that it could better interpret various phase transition mechanisms of water and aqueous solutions. Copyright © 2013 John Wiley & Sons, Ltd.     

Calorimetric investigation on the paramagnetic–antiferromagnetic phase transition in CoO

The paramagnetic–antiferromagnetic phase transition of a single crystal of CoO, whose first- or second-order character is controversial, has been studied using a high sensitive calorimetric technique. Although both specific heat and differential thermal analysis (DTA) trace obtained at very low temperature rate (0.1 K h⁻¹) show strong anomalies at the Néel temperature T_N, the DTA trace and that calculated from the specific heat anomaly coincides indicating a continuous phase transition. In agreement with the theoretical predictions, the specific heat follows the 3D Ising model in a temperature range of 3 K below T_N. Fisher relation for antiferromagnets is also obeyed in the same temperature range.     

Low-temperature specific heat of Ni–Mn–Ga ferromagnetic shape memory alloys

Results of the low-temperature specific heat measurements (2–80 K) for one austenitic and three martensitic Ni–Mn–Ga ferromagnetic alloys are presented. The alloy compositions are chosen to comprise a wide span of valence electron concentrations e/a=7.3–7.78. Debye temperature (261–345 K) is found to be an increasing function of e/a while the experimental values of the Sommerfeld coefficient (2.9–3.4 mJ/mol K²) appear to be increasing in the martensitic region only. Observation of those trends rekindles the discussion about the role of vibrational and electronic contributions to the lattice instability and transformation mechanism of studied alloys.     

Statistical approach of the effects of roughness on the polarization of light scattered by dust grains

In order to study the effect of shape on the optical properties of dust grains, we statistically analyze the linear polarized scattered light. We start by examining a homogeneous spherical grain using the discrete dipole approximation (DDA) Draine (Astrophys J 1988;333:848). Using a uniform law we remove elements of matter on the surface of the grain to describe a random roughness. Then, for various scattering angles, the linear polarization P_l is calculated. We successively repeat the simulation in order to obtain a sample of random variables constituting the values P_l of the linear polarization. The analysis of the results is then achieved through a Gaussian kernel method which provides the probability density function of P_l for each scattering angle. We present the results for a typical interstellar grain of water–ice with radius a comparable to the incident wavelength λ so that the parameter size x≡2πa/λ1. We apply this method for two wavelengths in the near IR, when water–ice is transparent at 1.9 μm, and, when water–ice is absorbing at 3.1 μm. We find that the shape of the density function of the linear polarization is asymmetric to the mean value of the density function and non-unimodal for several scattering angles. This allows us to separate the effects of roughness from those of volume. When water–ice is absorbing, we also observe a significant shift of the polarization peak toward greater scattering angles.     

Calorimetric and resistometric studies of La2CuO4+δ single crystals: Displasive character of phase transitions in 190–310 K

Measurements of heat capacity, resistivity, and magnetic susceptibility for the La₂CuO_4+δ single crystals in the range 0.001≤δ≤0.035 revealed that following four kinds of phase transitions appear between 10 and 320 K: superconducting transition around 33 K, a transition around 200 K with small heat anomaly, martensitic transition around at 250–270 K, and a second order transition at 295 K. These transition temperatures strongly depended on the amount of excess oxygen content. The heat capacity anomalies for the sample with δ=0.035 in the range of 190 to 310 K were interpreted as connected with cooperative displacements of ions involving no diffusion process of oxygen ion.     

Polyoxaethylene polypodands – powerful reduction catalysts in solid–liquid and liquid–liquid phase transfer systems

The excellent catalytic properties of polypodands, esters of inorganic acids, as phase‐transfer catalysts have been reported previously. Unfortunately, these compounds are unstable under hydrolytic conditions. A group of new, hydrolytically stable podands has been synthesized. Their complex forming abilities towards alkali metal ions have been studied. The podands studied have been used as catalysts in phase transfer catalysis conditions. The kinetics of this process has been determined. All compounds prepared have been found to complex metal ions and are a powerful catalysts in reduction of ketones by borohydrides in solid–liquid and liquid–liquid systems. Copyright © 2013 John Wiley & Sons, Ltd.     

Adatom lifetime in film growth at solid surfaces in the framework of the Johnson–Mehl–Avrami–Kolmogorov model

On the basis of the quasi-static approximation and for simultaneous nucleation the adatom lifetime, τ, during film growth at solid surfaces has been computed by Monte Carlo (MC) simulation. The quantity DN₀τ, N₀ and D being respectively the cluster density and the adatom diffusion coefficient, is found to depend upon the portion of surface covered by clusters and, very weakly, on N₀. Moreover, a stochastic approach based on the Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory has been developed to obtain the analytical expression of the MC curve. The collision factor of the mean island has been calculated and compared with those previously obtained from the uniform depletion approximation and the lattice approximation.     

Heat capacity of isotopically enriched Si, Si and Si in the temperature range 4 K<T<100 K

The heat capacity of isotopically enriched ²⁸Si, ²⁹Si, ³⁰Si samples has been measured in the temperature range between 4 and 100 K. The heat capacity of Si increases with isotopic mass. The values of the initial Debye temperature Θ_D(0) for the three isotopic varieties of silicon have been determined. Good agreement with the theoretical dependence of the heat capacity on isotopic mass has been found.     

Electrical transport, magnetic and thermal properties of icosahedral Al–Pd–Mn quasicrystals

We report measurements of electrical resistivity (ρ), Hall coefficient (R_H), magnetization (M) and specific heat (C_p(T)) of high-quality icosahedral Al_70.4Pd_20.8Mn_8.8 phases with different thermal treatment. An improvement in the quasi-crystallinity upon the annealing treatment caused a drastic increase in ρ up to 7000 μΩ cm accompanied by a very small electronic specific heat coefficient γ. The low temperature ρ(T) data has been analyzed in terms of weak localization and electron–electron interaction effects. The Hall resistivity (ρ_H) is found to be strongly temperature-dependent and varies linearly with the magnetization (M) for the same field and temperature. Magnetization measurement reveals that more conductive samples are more magnetic and vice versa. Magnetic susceptibility (χ) data of all the annealed samples agrees with the Curie–Weiss-like behavior implying the existence of localized moments. The negative Curie–Weiss temperature (θ) indicates strong antiferromagnetic coupling between individual Mn atoms. The magnetic Mn concentration is found to be small, ranging from 1.73×10^-4 for the less magnetic sample studied up to 3×10^-3 for the more magnetic one. The small electronic specific heat coefficient obtained for all the samples suggests a significant reduction in the electronic density of states (DOS) at the Fermi level (E_F) upon thermal annealing treatment.     

A TEM study of precipitation in Al–Mg–Si alloys

A set of extrusion samples of Al–Si–Mg alloys (0.5 wt%Mg and 0.3–0.8 wt%Si) were, respectively, T1- and T4-heat-treated. Differential scanning calorimetry (DSC) was used to heat the samples to particular temperatures to promote the formation of precipitates for study by transmission electron microscopy (TEM). It was found that, apart from β″, β′, and B′, there were many precipitates showing rectangular lattices when viewed along the long axes of the precipitates. It is considered that the residual stresses (or dislocations) in the extrusion after the T1-treatment facilitated the nucleation and growth of the precipitates during the heating in the DSC.     

Synthesis and high-frequency magnetic properties of sol–gel derived Ni–Zn ferrite–forsterite composites

Ni_0.5Zn_0.5Fe₂O₄–forsterite composites were synthesized by a sol–gel method. X-ray diffraction and SEM were used to characterize the crystallization behavior of the composite samples which were heat treated at temperatures varying from 800 to 1100°C. The results showed that Ni_0.5Zn_0.5Fe₂O₄ and forsterite (Mg₂SiO₄) can co-crystallize and the crystallites grow even more larger with increasing heat-treatment temperature. High-frequency (10 MHz–1 GHz) magnetic and dielectric properties of the composite samples were presented. Permeability increased with heat-treatment temperature. Quality factor was found to be two orders higher than that of equivalent pure, bulk ferrite.