Vapor-liquid equilibrium,coexistence curve,and critical locus for binary HFC-32/HFC-134a mixture

Two kinds of equilibrium measurements of binary R-32/134a mixtures were carried out. The vapor-liquid equilibria were measured by the static method in the temperature range between 283 and 313 K. On the basis of the present experimental data, the temperature dependence of the binary interaction parameterk ₁₂ for two equations of state, namely, the Soave-Redlich-Kwong equation and Carnahan-Starling-De Santis equation, was discussed. The vapor-liquid coexistence curve near the critical point was also measured by the observation of meniscus disappearance. The critical temperatures and critical densities of 30 and 70 wt% R-32 mixtures were determined on the basis of the saturation densities along the coexistence curve in the critical region. In addition, a correlation of the critical locus for this mixture is proposed as a function of composition.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Changes in electronic structure of Li2−xCuO2

A single phase of Li₂CuO₂ was successfully prepared by solid state reaction. The crystal structure was refined by Rietveld method using a synchrotron radiation source. Electronic structures of x = 0 and 1 in Li_2−xCuO₂ were determined using the first principle calculation. We will discuss electrochemical properties of Li₂CuO₂ and changes in electronic structure of Li_2−xCuO₂, using both the information obtained from the calculation and that obtained experimentally. These results confirmed that Li-extraction of Li₂CuO₂ resulted in the oxidation of Cu²⁺ or O²⁻. The cuprate-based cathode materials have the potential showing high energy density. The calculation of electronic state will play a major role in designing the materials for Li-batteries.     

Vapor–Liquid Equilibria For The Binary Difluoromethane (R-32) + Propane (R-290) Mixture

The vapor–liquid equilibrium of the mixture composed of difluoromethane (R-32) and propane (R-290) was studied in the temperature range between 273.15 and 313.15 K. The experimental uncertainties of temperature, pressure, and composition measurements were estimated to be within ±10 mK, ±3 kPa, and ±0.4mol%, respectively. Comparisons between the present data and available experimental data were made using the Helmholtz free energy mixture model (HMM) adopted in the thermophysical properties program package, REFPROP 6.0, as a baseline. In addition, the existence of an azeotrope and the determination of new adjustable parameters for HMM for the R-32 + R-290 mixture are discussed.     

Thermal decomposition of vitamin C: An evolved gas analysis−ion attachment mass spectrometry study

Evolved gas analysis−ion attachment mass spectrometry (EGA−IAMS) was utilised to study the real-time non-isothermal decomposition of vitamin C. Dehydro-l-ascorbic acid, which has until this study been undetectable from the solid phase degradation of vitamin C, was observed as a decomposition product. While it is an important compound because it possesses some biological activity, dehydro-l-ascorbic acid is difficult to measure due to its chemical instability. In the present study using EGA−IAMS, we were able to detect dehydro-l-ascorbic acid from the thermal degradation of vitamin C. Our EGA−IAMS results obtained from the thermal decomposition of vitamin C were compared with a previous study employing pyrolysis-gas chromatography−mass spectrometry (Pyr-GC−MS). The observed quantitative and qualitative differences of the pyrolysis products obtained by the two techniques (EGA−IAMS vs. Pyr-GC–MS) are in part due to the difference in transportation time of the products out of the pyrolysis chamber.     

Water-soluble polyaniline/graphene prepared by in situ polymerization in graphene dispersions and use as counter-electrode materials for dye-sensitized solar cells

Water-soluble polyaniline/graphene nanocomposites have been prepared via a simple in situ polymerization of aniline in graphene dispersion. TEM measurement confirmed that polyaniline was homogeneously coated on the graphene sheets. The nanocomposites solution can be used for film fabrication by common technology, such as drop coating. When these different polyaniline/graphene nanocomposites were applied as the counter electrode materials for dye-sensitized solar cells, the short-circuit current density and power-conversion efficiency of the devices were measured to be 12.19 mA cm⁻² and 4.46%, respectively, which was comparable to 5.71% for the cell with a Pt counter electrode under the same experimental conditions.     

Development of temperature‐change sensor by thermoelectric elements and its response evaluation on dropping into water

A temperature‐change sensor by thermoelectric elements that is directly connected to a p‐type element and an n‐type element was developed. A β‐FeSi₂ thermoelectric semiconductor made by a spark plasma sintering method was used as a prototype sensor. Evaluation of this thermoelectric temperature‐change sensor was carried out by measuring its electromotive force when it was dropped into a thermostated water bath. It was confirmed that there existed a correlation between the temperature difference and the electromotive force of the sensor, i.e., approximately 5 mV of electromotive force was generated at a temperature difference of 30 K. In addition, the dependence of electromotive force on the size and properties of the thermoelectric elements was evaluated by carrying out FEM analysis. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20268     

Optical activity and electrogyration of KH2PO4

Accurate measurements of gyration tensors g₁₁ (=-g₂₂) and electrogyration effect of KH₂PO₄ were made by applying the improved HAUP method. g₁₁ diverges conspicuously when the temperature approaches Tc from above and below it, the behaviour being analyzed as obeying the Curie-Weiss law with a Curie-Weiss constant of 7.35×10^-4 K. An electrogyration coefficient π₁₃ referring to the polarization manifests a characteristic nature of improper ferroelectrics.     

New amphoteric surfactants containing a 2-hydroxyalkyl group: I preparation and properties of N-(2-hydroxyethyl)-N-(2-hydroxyalkyl)-β-alanines

A series of new amphoteric surfactants, sodium salts of N-(2-hydroxyethyl)-N-(2-hydroxyalkyl)-β-alanines (Na-HAA) was prepared by adding methyl acrylate to N-(2-hydroxyalkyl)-ethanolamine and subsequent saponification. Neutralization with HCl gave N-(2-hydroxyethyl)-N-(2-hydroxyalkyl)-β-alanines, and the addition of ethylene oxide to Na-HAA gave oxyethylated drivatives. The structures of these compounds prepared were confirmed by infrared spectra, proton magnetic resonance spectra, elementary analyses, etc. Solubility in water, surface tension, foaming power, and critical micelle concentration were determined.