Electrostatic stabilization of liquid crystalline ordering in binary melts of sodium and potassium alkanoates

Abstract

The mesophase electrostatic stabilization energy (E) has been examined by using the ionic continuous solid solution model for binary systems of sodium and potassium alkanoates with a common anion. It is found that E increases with a decrease in chain length of the alkanoate anion and that there is an inverse proportionality between E and the square of the mesophase bilayer spacing. The electrostatic stabilization factor is shown to be responsible for the formation of an ionic mesophase in binary acetate and propionate systems derived from two non-mesomorphic components.     

Electrostatic stabilization of liquid crystalline ordering in binary melts of sodium and potassium alkanoates

The mesophase electrostatic stabilization energy (E) has been examined by using the ionic continuous solid solution model for binary systems of sodium and potassium alkanoates with a common anion. It is found that E increases with a decrease in chain length of the alkanoate anion and that there is an inverse proportionality between E and the square of the mesophase bilayer spacing. The electrostatic stabilization factor is shown to be responsible for the formation of an ionic mesophase in binary acetate and propionate systems derived from two non-mesomorphic components.     

Surface properties of the binary mixed systems of alkylpyridinium halides and sodium alkylsulfonates

Surface properties of the binary mixed systems of decyl- and dodecylpyridinium chloride or bromide and sodium pentyl- and heptylsulfonate have been investigated. The surface tension of solutions of equimolar mixtures of surfactants and individual surfactants was measured, and the composition of mixed monolayers and surface interaction parameter β were calculated with the regular solution theory. Our results indicate that the properties of mixed films depend on both ionic strength and the kind of added inorganic electrolyte. With the increase of inorganic electrolyte concentration, the content of more surface active ions in the adsorption films enhances and is the highest in the presence of NaI and the smallest when solutions contain NaCl. Mutual interactions in mixed adsorbed films were found to be attractive. However, the strength of interaction weakens with the increase of ionic strength and depends on the kind of inorganic ions in the order: Cl⁻>Br⁻>I⁻.     

Thermal conductivities of solid and liquid phases for pure Al,pure Sn and their binary alloys

The variations of thermal conductivities of solid phases versus temperature for pure Sn, pure Al and Sn–0.5 wt.% Al, Sn–2.2 wt.% Al, Sn–25 wt.% Al, Sn–50 wt.% Al, Sn–75 wt.% Al binary alloys were measured with a radial heat flow apparatus. From thermal conductivity variations versus temperature, the thermal conductivities of the solid phases at their melting temperature and temperature coefficients for same materials were also found to be 60.60 ± 0.06, 208.80 ± 0.22, 69.70 ± 0.07, 80.30 ± 0.08, 112.30 ± 0.12, 142.00 ± 0.15, 188.50 ± 0.20 W/K m and 0.00098, 0.00062, 0.00127, 0.00114, 0.00112, 0.00150, 0.00116 K⁻¹, respectively. The thermal conductivity ratios of liquid phase to solid phase for the pure Sn, pure Al and eutectic Sn–0.5 wt.% Al alloy at their melting temperature are found to be 1.11, 1.13, 1.06 with a Bridgman type directional solidification apparatus, respectively. Thus the thermal conductivities of liquid phases for pure Sn, pure Al and eutectic Sn–0.5 wt.% Al binary alloy at their melting temperature were evaluated to be 67.26, 235.94 and 73.88 W/K m, respectively by using the values of solid phase thermal conductivities and the thermal conductivity ratios of liquid phase to solid phase.     

Phase states of binary systems of sodium,potassium and cesium propionates

Differential thermal analysis and hot-stage polarization microscopy were used to study the phase diagrams of binary systems of sodium, potassium, and cesium propionates. The induction of type-A smectic liquid crystals was observed in the sodium-containing systems. Liquid crystal formation in systems composed of components, which are individually nonmesomorphic, is attributed to latent mesomorphism of sodium propionate or potassium propionate.Translated from Teoreticheskaya and Éksperimental'naya Khimiya, Vol. 30, No. 2, pp. 89–94, March–April, 1994.     

Mechanical properties of vanadium-base binary alloys

The fabricability and tensile properties of solid-solution-strengthened vanadium-base binary alloys containing aluminium, titanium, niobium, tantalum, chromium, molybdenum or iron were studied. The alloys were prepared by non-consumable arc melting and contained 150–370 ppm O, 20–250 ppm N and 40–130 ppm C. The VTi, VNb and VTa alloys were superior to the other alloys in their fabricabilities into sheet. The tensile properties were examined between room temperature and 1000 °C. The tensile strength values of the VNb and the VTa alloys were higher than those of the VAl and the VCr alloys. The tensile strengths of the VAl, VCr and VMo alloys increased in proportion to the increase in atomic per cent of alloying element, while those of the VNb, VTa and VFe alloys increased with the square root of the atomic per cent of the alloying element.     

Surface tension of binary liquid mixtures

Experimental measurements of the liquid-air interfacial tension are reported for the systems benzene + n-hexane at 20°C and acetone + isooctane at 25°C. The excess surface tension for both systems is negative while the surface tension itself for the second system, when plotted against composition, exhibits a flat minimum. An attempt is made to interpret this behavior in terms of basic thermodynamic quantities of the mixtures such as the excess free enthalpy, the heat of mixing, the excess volume, and the isothermal compressibility.     

Theoretical calculation of electrical resistivity in liquid sodium and potassium

As a direct numerical test of Ziman formula for the static resistivity of monovalent liquid metals, constant pressure resistivities of liquid potassium at 338 K and 408 K and liquid sodium at 373 K and 473 K have been calculated using a recently proposed form factor and a liquid structure factor obtained from Monte Carlo calculations. The procedure is fundamental in that no parameters have been adjusted to fit experimental values at any stage. The resistivity results are in good agreement with experiment at the above mentioned temperatures, but it appears that the formula may become less accurate at higher temperatures.     

Enthalpies of mixing of liquid alloys in the In-Pd-Sn system and the limiting binary systems

The partial and integral enthalpies of mixing of molten binary In-Pd (up to about 29 at.% Pd), In-Sn (entire compositional range) and Pd-Sn (up to about 53 at.% Pd) alloys were determined at 900 °C. A Calvet-type microcalorimeter was used for the measurements employing a drop calorimetric technique. Additionally, five sections in the ternary In-Pd-Sn system (compositions up to about 40 at.% Pd) were investigated at 900 °C. The ternary interaction parameters were fitted using the Redlich-Kister-Muggiano model for substitutional solutions. The isoenthalpy curves for In-Pd-Sn at 900 °C were constructed for the integral molar enthalpy of mixing. Furthermore, the experimental results in the ternary system were compared with calculated values obtained by employing different binary extrapolation models.     

Thermodynamic properties of liquid Cu-Ni-Co-Fe alloys

Data on boundary binary systems in conjunction with geometric models and the Redlich-Kister method were used to calculate the integral thermodynamic characteristics and the activities of the components for liquid Cu-Ni-Co-Fe alloys at 1600°C.     

Thermodynamic properties of liquid magnesium-nickel alloys

Summary Magnesium vapor pressures were determined over liquid Mg-Ni alloys for compositionsx _Mg>0.65 using an isopiestic method. Data points between 760 and 890°C were evaluated to derive corresponding partial thermodynamic properties. The composition dependence of the magnesium activities in liquid alloys is shown for a temperature of 1073 K. Additionally, it is possible to obtain the shape of the liquidus curve between about 60 and 70 at% Mg from the results of the isopiestic measurements.

---

Thermodynamische Eigenschaften flüssiger Mg-Ni Legierungen

Zusammenfassung Magnesiumdampfdrücke wurden mit Hilfe einer isopiestischen Methode über flüssigen Mg-Ni-Legierungen mit einer Zusammensetzungx _Mg>0.65 bestimmt. Aus experimentellen Punkten zwischen 760 und 890°C wurden die entsprechenden partiellen thermodynamischen Eigenschaften abgeleitet. Es wird die Konzentrationsabhängigkeit der Magnesiumaktivitäten in flüssigen Legierungen bei 1073 K gezeigt. Zusätzlich kann aus dem Ergebnis der isopiestischen Messungen der Verlauf der Liquiduskurve zwischen etwa 60 und 70 At% Mg ermittelt werden.

     

Electrical transport properties of liquid alloys

Two complementary mechanisms have been proposed for relatively high temperature superconductor MgB₂. While the first is the electron–phonon mechanism of BCS theory, advocated strongly by Pickett and co-workers, the second, by Bianconi et al., invokes Feshbach shape resonances. While we cannot presently discount the second mechanism, and while both proposals exploit the multiband nature of the electronic structure of MgB₂, we show here that five body-centred cubic (bcc) transition metals, whose superconducting transition temperature correlate intimately with elastic constants and therefore are plainly BCS-like in character, lie on a curve which has MgB₂ at the high T _c end. Any alternative mechanism to electron–phonon interaction in MgB₂ will need to account quantitatively for this circumstance.     

Thermodynamic properties of liquid zinc-bismuth alloys

Thermodynamic properties of liquid Zn–Bi alloys were investigated between 5 and 95 at % Zn from the liquidus curve to 750°C using anemf method with a molten salt electrolyte. Partial and integral values were calculated and compared with results from the literature. From theemf data the liquidus curve was calculated. The thermodynamic data of the Zn–Bi system are well established and consistent with the phase diagram. The entropies of mixing of various group IIB-VA systems are compared and discussed with respect to compound formation in the liquid state.With 5 Figures     

Sorption properties of celluloses in binary liquid mixtures

The adsorption capacity for methanol-benzene andn-propanol-water mixtures was measured on two kinds of microcrystalline celluloses and cotton linters. Excess adsorption isotherms were obtained; the free energy of displacement was calculated from the isotherms. The enthalpy of displacement for one crystalline cellulose was measured by flow calorimetry. The entropic function of displacement was derived from the enthalpy and free energy of displacement. The preferential adsorption of methanol andn-propanol was characterized by the adsorption equilibrium constant.On leave from the Department of Physical and Colloid Chemistry, Wageningen Agricultural University, The Netherlands     

Raman spectroscopy of the acetates of sodium, potassium and magnesium at liquid nitrogen temperature

A comprehensive Raman spectroscopic study of the acetates of potassium, sodium and magnesium in the solid state have been made at both 298 and 77 K. Band separation of the C=O stretching region was not achieved in the 298 K spectra but was in the 77 K spectra. The CO stretching vibration is observed as a single band in both the 298 and 77 K spectra and its frequency is cation dependent. Single C–C stretching bands are observed for the acetates in the 77 K spectra. The OCO deformation vibrations were also cation dependent. Low frequency vibrations of magnesium acetate are observed at 338, 253 and 268 cm⁻¹ and are assigned to the MgO stretching vibration of the magnesium bisacetato complex. Low frequency bands were also observed for sodium acetate at 219, 277 and 288 cm⁻¹.     

Thermodynamic properties of liquid Al-Si and Al-Cu alloys

The partial and integral enthalpies of mixing in liquid Al-Si and Al-Cu alloys were determined by high-temperature isoperibolic calorimetry at 1750±5 and 1590±5, respectively. The thermodynamic properties of Al-Si melts were also studied by electromotive force method in temperature range 950-1270 K. The partial and integral excess Gibbs free energies of mixing in liquid Al-Si and Al-Cu alloys were also calculated from literature data on thermodynamic activity of aluminium. The comparison of our experimental results with literature data has been performed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Thermodynamic properties of liquid alloys Ni-Eu and Ni-Yb

Mixing enthalpies of melts of the binary Ni-Eu (0 < x _Ni < 0.89) and Ni-Yb (0 < x _Ni < 1) systems at 1300–1750 K were investigated using the isoperibolic calorimetry. They have alternating signs depending on the melt concentration. With the combined analysis of the data determined by us and in literature, the models of the liquid and solid alloys were obtained, and the phase diagrams were calculated.