Transparent acryl–clay nanohybrid films with low thermal expansion coefficient

The aim of this study was to prepare transparent nanohybrid films with low coefficient of thermal expansion (low CTE), which consist of acryl resin and nanosized clay. The hybrid films with different clay contents were prepared by UV curing of tricyclodecane dimethanol diacrylate (TCDDMDA) including nanosized clay. All obtained films were transparent similar to pure poly(TCDDMDA). In addition, the film containing 40 wt.% of clay showed a low CTE of 10 ppm/K in 150–200 °C, which is similar to that of inorganic materials such as glass. The significant property improvement is related to shape effect and orientation of clay in polymer matrix. Wide-angle X-ray diffraction measurement was carried out to investigate orientation of nanosized clay in polymer matrix. From this measurement, it was confirmed that the clay platelets were oriented parallel with film surface with increasing clay content, and orientation coefficient of the clay in polymer matrix reached to f?=?0.65 for the hybrid film containing 40 wt.% of clay. Though, in comparison with the matrix, the flexibility of the hybrid film evaluated by the wind roll test with steel bar was lowered by increase of clay content, the hybrid film containing 40 wt.% of clay could be rewound with steel bar 10 mm across, and its flexibility was retained.     

Zone fluidics for measurement of octanol–water partition coefficient of drugs

A novel zone fluidics (ZF) system for the determination of the octanol–water partition coefficient (P_ow) of drugs was developed. The ZF system consisted of a syringe pump with a selection valve, a holding column, a silica capillary flow-cell and an in-line spectrophotometer. Exact microliter volumes of solvents (octanol and phosphate buffer saline) and a solution of the drug, sandwiched between air segments, were sequentially loaded into the vertically aligned holding column. Distribution of the drug between the aqueous and octanol phases occurred by the oscillation movement of the syringe pump piston. Phase separation occurred due to the difference in densities. The liquid zones were then pushed into the detection flow cell. In this method, absorbance measurements in only one of the phase (octanol or aqueous) were employed, which together with the volumes of the solvents and pure drug sample, allowed the calculation of the P_ow. The developed system was applied to the determination of the P_ow of some common drugs. The log (P_ow) values agreed well with a batch method (R² = 0.999) and literature (R² = 0.997). Standard deviations for intra- and inter-day analyses were both less than 0.1log unit. This ZF system provides a robust and automated method for screening of P_ow values in the drug discovery process.     

Frost-resistant polyurethane compositions with a low temperature coefficient of Young’s modulus

Single-phase and microheterogeneous unplasticized and plasticized polyurethane compositions based on oligo(diisocyanates) and their blends were synthesized. The frost resistance and temperature dependence of Young’s modulus were examined for these materials in relation to their structural organization.     

A review of Barker’s activity coefficient method and VLE data reduction

The method of Barker is a popular scheme for determination of activity coefficients from total pressure measurements. A comprehensive review of this method is presented in this study. While discussing this technique various aspects of (vapor + liquid) equilibrium (VLE) data reduction process including types of algorithms applied, roles of saturated vapor pressures and equilibrium vapor compositions data, and types of objective functions used are analyzed. Activity coefficient or liquid state models frequently used in VLE data reduction are shown and their comparisons are investigated. More so, advantages and limitations of Barker’s method are demonstrated.     

The osmotic second virial coefficient and the Gibbs–McMillan–Mayer framework

The osmotic second virial coefficient is a key parameter in light scattering, protein crystallisation, self-interaction chromatography, and osmometry. The interpretation of the osmotic second virial coefficient depends on the set of independent variables. This commonly includes the independent variables associated with the Kirkwood–Buff, the McMillan–Mayer, and the Lewis–Randall solution theories. In this paper we analyse the osmotic second virial coefficient using a Gibbs–McMillan–Mayer framework which is similar to the McMillan–Mayer framework with the exception that pressure rather than volume is an independent variable. A Taylor expansion is applied to the osmotic pressure of a solution where one of the solutes is a small molecule, a salt for instance, that equilibrates between the two phases. Other solutes are retained. Solvents are small molecules that equilibrate between the two phases. The independent variables of the solvents are temperature, pressure, and chemical potentials. The derivatives in the Gibbs–McMillan–Mayer framework are transformed into derivatives in the Gibbs framework. This offers the possibility for an interpretation and correlation of the osmotic second virial coefficient using activity coefficient models.     

Vapor–liquid equilibria of asymmetrical systems using UNIFAC-NRF group contribution activity coefficient model

The UNIFAC-NRF group contribution activity coefficient model is used for the calculation of vapor–liquid equilibria of binary systems of the heavy alkanes and light gases such as CH₄, C₂H₆, CO₂ and N₂. The linear combination mixing rule, LCVM, of the Huron–Vidal and Michelsen, Chen et al. modification of PSRK and Universal Group Contribution Equation of State of Ahlers and Gmehling are combined with the UNIFAC-NRF group activity coefficient model to correlation of the vapor–liquid equilibrium of both light and heavy hydrocarbons. The results show that the LCVM mixing rule combing with UNIFAC-NRF group contribution model correlate the asymmetric systems better than the LCVM-UNIFAC and the other EOS/G^E models. Also the group contribution model is used for the prediction of the phase envelope of the synthetic fluid with accurate results.     

Comment on “Towards the development of theoretically correct liquid activity coefficient models”

The “New activity coefficient model” recently proposed by Lin et al. is shown to be identical to the special, homogeneous case of the COSMOSPACE model [A. Klamt, G.J.P. Krooshof, R. Taylor, AlChE J. 48 (2002) 2332–2349]. Also the proof of theoretical shortcomings of the UNIQUAC method as well as the demonstration of the striking agreement of this model with corresponding lattice Monte Carlo simulations presented by Lin et al. have already been presented in the same paper in a very similar way.     

Determination of the emanation coefficient and the Henry’s law constant for the groundwater radon

The radon emanation coefficient (ε) from aquifer rock and the Henry’s law constant (H) of radon were determined by measuring activity concentrations using liquid scintillation counter (LSC). For the evaluation of the method, the coefficients were measured at 0, 10 and 20 °C and the temperature dependency of the coefficients was compared with others. The radon emanation coefficients from the rock particles used in this work are 0.0845, 0.1007 and 0.1308 at 0, 10 and 20 °C, respectively. The dimensionless Henry’s law constants for the groundwater used in this work are 0.994, 1.153 and 2.641 at 0, 10 and 20 °C, respectively. The results show a good agreement with those in literatures.     

Using ab initio “data” to accurately determine the fourth density virial coefficient of helium

We combine accurate ab initio calculations of the second and third density virial coefficients, B(T) and C(T), of ⁴He with measurements of its (p–ρ–T) behavior to determine the fourth density virial coefficient D(T). The measurements were made with a two-sinker, magnetic-suspension densimeter at pressures up to 38 MPa. The measurements on isotherms from T = 223 K to T = 323 K were previously published; new measurements from T = 323 K to T = 500 K are presented here. On each isotherm, a regression of the virial expansion was constrained to the ab initio values of B(T) and C(T); the regression determined D(T) as well as two apparatus-dependent parameters that compensated for systematic errors in the measurements. The percentage uncertainties of D(T) ranged from 2.6% at T = 223 K to 9.5% at T = 400 K to 24.7% at T = 500 K, where these uncertainties are expanded uncertainties with coverage factor of k = 2 corresponding to a 95% confidence interval. These uncertainties are 1/6th of the uncertainty obtained without the ab initio values of B(T) and C(T). The apparatus-dependent parameters can be used to calibrate the densimeter, and this will reduce the uncertainty of other measurements made with this two-sinker densimeter. The new values of D(T) will find applications in accurate gas metrology, such as a primary pressure standard based on the refractive index of helium.     

A study for structure and inter-diffusion coefficient of liquid K1− x Cs x metal alloys

Inter-diffusion coefficients of liquid K_{1? x} Cs _x metal alloys are calculated using scaling law proposed by Samanta et al. [A. Samanta, Sk.M. Ali, and S.K. Ghosh, Phys. Rev. Lett. 87, 245901 (2001)] following Dzugutov [M. Dzugutov, Nature 381, 137 (1996)], which express the possible relationship between the excess entropy and diffusion coefficient. The interatomic interactions are described from the individual version of the electron–ion potential proposed by Fiolhais et al. [C. Fiolhais, J.P. Perdew, S.Q. Armster, J.M. McLaren, and M. Brajczewska, Phys. Rev. B 51, 14001 (1995)]. The partial pair distribution functions and structure factors are calculated from the solution of Ornstein–Zernike integral equation with Rogers–Young closure. The evaluations with the composition of static structure and the inter-diffusion properties are discussed.     

Comparison between different ways to determine diffusion coefficient and by solving Fick’s equation for spherical coordinates

The following document covers the determination of the diffusion coefficient of two powder materials: LiFePO₄ and LiMn₂O₄ by using potentiostatic intermittent titration technique (PITT) and impedance spectroscopy methodology and compares relevant results with the following relation: , which is obtained by solving Fick’s spherical coordinate equation (where I ₀ is the initial step current in the PITT experiment, R is the particle radius, Q is the charge that intercalated during the step, and α is the percentage of the theoretical intercalated charge). This procedure allowed the verification of the validity of the spherical model for the powder materials, the accuracy of the expression proposed for the diffusion coefficient determination, and the correctness of the measures that had been taken.     

Atmospheric chemistry of (Z)-CF3CH═CHCF3: OH radical reaction rate coefficient and global warming potential

Rate coefficients, k, for the gas-phase reaction of the OH radical with (Z)-CF(3)CH═CHCF(3) (cis-1,1,1,4,4,4-hexafluoro-2-butene) were measured under pseudo-first-order conditions in OH using pulsed laser photolysis (PLP) to produce OH and laser-induced fluorescence (LIF) to detect it. Rate coefficients were measured over a range of temperatures (212-374 K) and bath gas pressures (20-200 Torr; He, N(2)) and found to be independent of pressure over this range of conditions. The rate coefficient has a non-Arrhenius behavior that is well-described by the expression k(1)(T) = (5.73 ± 0.60) × 10(-19) × T(2) × exp[(678 ± 10)/T] cm(3) molecule(-1) s(-1) where k(1)(296 K) was measured to be (4.91 ± 0.50) × 10(-13) cm(3) molecule(-1) s(-1) and the uncertainties are at the 2σ level and include estimated systematic errors. Rate coefficients for the analogous OD radical reaction were determined over a range of temperatures (262-374 K) at 100 Torr (He) to be k(2)(T) = (4.81 ± 0.20) × 10(-19) × T(2) × exp[(776 ± 15)/T], with k(2)(296 K) = (5.73 ± 0.50) × 10(-13) cm(3) molecule(-1) s(-1). OH radical rate coefficients were also measured at 296, 345, and 375 K using a relative rate technique and found to be in good agreement with the PLP-LIF results. A room-temperature rate coefficient for the O(3) + (Z)-CF(3)CH═CHCF(3) reaction was measured using an absolute method with O(3) in excess to be <6 × 10(-21) cm(3) molecule(-1) s(-1). The atmospheric lifetime of (Z)-CF(3)CH═CHCF(3) due to loss by OH reaction was estimated to be ~20 days. Infrared absorption spectra of (Z)-CF(3)CH═CHCF(3) measured in this work were used to determine a (Z)-CF(3)CH═CHCF(3) global warming potential (GWP) of ~9 for the 100 year time horizon. A comparison of the OH reactivity of (Z)-CF(3)CH═CHCF(3) with other unsaturated fluorinated compounds is presented.     

Osmotic coefficient data for Na2SiO3 and Na2SiO3–NaOH by an isopiestic method and modeling using Pitzer's model

Osmotic coefficient and water activity data for Na₂SiO₃ and mixed Na₂SiO₃–NaOH aqueous solutions were obtained at 25°C by employing the isopiestic method. The binary Pitzer's parameters, β⁽⁰⁾, β⁽¹⁾, and C^φ, for Na₂SiO₃ and the mixing parameters, θ_{OH⁻SiO²⁻3 and} Ψ_{Na⁺OH⁻SiO²⁻3} were estimated using the osmotic coefficient data. The experimental osmotic coefficient data were correlated well with Pitzer's model. Mean activity coefficients of Na₂SiO₃ and NaOH for the solutions were predicted by Pitzer's model with the parameters obtained. Finally, the presence of metasilicic species, when sodium metasilicate (Na₂SiO₃·9H₂O) is dissolved in aqueous alkaline solution, was established by titration with hydrochloric acid.     

Dépendance du coefficient homogénéisé par rapport à la forme des inclusions dans un matériau composite

In case of a two components material with a matrix reinforced by a large number of inclusions, we describe explicitely the dependence of the homogenized coefficients in function of the inclusions shape.