Reverse microemulsion region and composition optimization of the AEO9/alcohol/alkane/water system

A reverse microemulsion method was applied to prepare ceramic inks for formation by jet-printing. Different reverse microemulsion systems were studied and optimized in order to obtain high concentration ceramic inks, and an AEO₉/alcohol/alkane/water system was chosen for preparing these ceramic inks as a result of its excellent water-dissolving characteristics. In this paper, different kinds and amounts of alcohol as a co-emulsifier and n-octane as oil, respectively were used to systematically investigate their effects on the microemulsion region in the quasi-ternary phase diagram of the system studied. These were mixed with water to form reverse microemulsion after vigorous stirring. The microemulsion region was determined and the conditions for maximum water-dissolving were given. Additionally, the effect of temperature on the reverse microemulsion region was studied. It was shown that the AEO₉/n-butanol/n-octane/water reverse microemulsion system exhibited excellent behavior in enhancing the amount of water-dissolving and the best composition for maximum water content was AEO₉:n-butanol:n-octane=25.7%:16.8%:57.7% in mass.     

Thermal properties and phase diagrams of water–hydrocarbon systems

The phase equilibria of immiscible binary systems (water–n-hexane, water–n-pentane) are investigated using a constant-volume piezometer. The measurements were performed under normal conditions, based on P,V,T,x-data obtained in the temperature range of 300–680 K, pressures up to 60 MPa, and in a wide range of densities. Based on the experimental data, we constructed phase diagrams in the P–T and T–x coordinates and determined the Krichevskii parameters for the system of water–n-hexane near the critical point of the pure solvent.     

Predicting the High-Pressure Phase Equilibria of Binary Mixtures of n-Alkanes Using the SAFT-VR Approach

The phase behavior of selected alkane binary mixtures is studied using SAFT-VR, a version of the statistical associating fluid theory for potentials of variable attractive range (SAFT). We treat the n-alkane molecules as chains formed from united-atom hard-sphere segments with square-well potentials of variable range to describe the attractive interactions. We use a simple relationship between the number of carbon atoms in the n-alkane molecule and the number of segments in the united atom chains in order to predict the phase behavior of n-butane with other n-alkanes. The calculated vapor pressures and saturated liquid densities of the pure components are fitted to experimental data from the triple point to the critical point. These optimized parameters are rescaled by the respective experimental critical points and used to determine the critical lines and phase behavior of the mixtures. We use the Lorentz-Berthelot combining rule for the unlike interactions. We predict the phase behavior of n-butane + n-alkane binary mixtures, concentrating mainly on the critical region. The gas-liquid critical lines predicted by SAFT-VR for the n-alkane mixtures are in excellent agreement with the experimental data, and improve significantly on the results obtained with the simpler SAFT-HS approach where the attractive interactions are treated at the mean-field level.     

Hyperbaric reservoir fluids: High-pressure phase behavior of asymmetric methane +n-alkane systems

In this paper, experimental three-phase equilibrium (solidn-alkane + liquid + vapor) data for binary methane +n-alkane systems are presented. For the binary system methane + tetracosane, the three-phase curve was determined based on two phase equilibrium measurements in a composition range fromx _c24 = 0.0027 tox _c24 = 1.0. The second critical endpoint of this system was found atp = (1114.7 ± 0.5) M Pa.T = (322.6 ± 0.25) K, and a mole fraction of tetracosane in the critical fluidphase ofx _c24 = 0.0415 ± 0.0015. The second critical endpoint occurs where solid tetracosane is in equilibrium with a critical fluid phase (S _c24 +L =V). For the binary systems of methane with then-alkanes tetradecane, triacontane, tetracontane, and pentacontane, only the coordinates of the second critical endpoints were measured. The second critical endpoint temperature is found close to the atmospheric melting point temperature of then-alkane. The pressures at the second critical endpoints do not exceed 200 MPa. Based on these experimental data and data from the literature, correlations for the pressure. temperature, and fluid phase composition at the second critical endpoint of binary methane +n-alkane systems withn-alkanes between octane and pentacontane were developed.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Dipole moment of water clusters and the greenhouse effect

The dipole moments of neutral water clusters (H₂O) _n (n ≤ 100) have been simulated using the molecular dynamics method within the framework of the Stillinger-David polarization model. The spectral characteristics of emission from clusters have been calculated. It is shown that water clusters generated by flying vehicles in the Earth’s troposphere can initiate a trigger mechanism that enhances the greenhouse effect via the reactions CO ₂ ^* + (H₂O) _n → CO₂ + (H₂O) _n ^(*) → CO₂ + (H₂O) _n + hv.     

Vapor-liquid equilibria for the ternary system N2 + CO2 +n-C4H10 at 250 and 270 K1

The system studied was nitrogen + carbon dioxide +n-butane at 250 and 270 K and at pressures from 1.5 to 14 MPa. The Peng-Robinson equation was used to model the results, since it is the most widely accepted equation of state in the gas processing industry. In general, the predictions are most accurate at low and moderate pressures and poorest at high pressures, especially near the critical region.     

Magnetoresistance Study of Y3Ba5Cu8O18 Superconducting Phase Substituted by Nd3+ and Ca2+ Ions

Superconducting samples of type Y_3?x Nd _x Ba_5?x Ca _x Cu₈O₁₈ with 0.0 ≤ x ≤ 0.4 have been prepared via the solid-state reaction technique. The prepared samples were characterized using X-ray powder diffraction (XRD) technique for phase analysis. The elemental content of the prepared samples was determined using particle-induced X-ray emission (PIXE). In addition, the oxygen content of these samples was obtained using non-Rutherford backscattering spectroscopy (RBS) at 3 MeV proton beam. The results indicate that these substitutions do not affect the orthorhombic structure, while they decrease the oxygen content of Y-358 phase. The electrical resistivity of the prepared samples was measured by the conventional four-probe technique from room temperature down to the zero superconducting transition temperature (T ₀). A slight change in the superconducting transition temperature (T _c) is observed for 0 ≤ x ≤ 0.1, and then it decreases linearly with further increase in x. The linear decrease in T _c is attributed mainly to the partial substitution of Ba²⁺ ions by Ca²⁺ ions rather than the partial substitution of Y³⁺ ions by Nd³⁺ ions. The effect of magnetic fields up to 4.44 kG on the electrical resistivity has been studied to investigate the vortex dynamics for the prepared samples. The experimental data, in the second stage of superconducting transition, fit well with the thermally activated flux creep (TAFC) model, and the activation energy U(B) shows a power law dependence on magnetic field as B ^?β . Also, the transition width is related to the magnetic field according to the relation ΔT α B ⁿ . The values of β and n are strongly dependent on the Nd³⁺ and Ca²⁺ ion substitution. The magnetic field and temperature dependence of the activation energy U(B, T) is found to be U(B, T)? ΔT B ^?η , where η = β + n. Furthermore, the critical current density at zero temperature, J _c(0), as a function of the applied field was calculated for all the prepared samples. The result shows an enhancement in J _c(0) of Y-358 phase at x equals 0.4 at different applied fields.     

Epitaxial growth of anatase by reactive sputter deposition using water vapor as the oxidant

The growth of TiO₂ films in the anatase crystal structure was investigated using reactive sputter deposition with H₂O serving as the oxidizing species. With water vapor, the formation of phase-pure anatase TiO₂ thin films via epitaxial stabilization on (001) LaAlO₃ was achieved, although crystallinity was slightly inferior to that obtained when O₂ was employed. Films grown using water vapor exhibited a rougher surface morphology indicating a difference in growth mechanisms. At low H₂O pressure, the formation of a Ti_nO_2n−1 Magnéli phase was observed. When hydrogen was employed during growth, mixed phase films of rutile and anatase resulted. The development of crystallinity and phase as a function of deposition temperature and oxidant pressure are discussed.     

The Local Jahn-Teller Effect in (La/Sr)n+1MnnO3n+1

Lattice polarons play an important role in the mechanism of colossal magnetoresistance in the (La/Sr) _n+1Mn _n O_3n+1 manganites. Local lattice distortions were characterized by the pulsed neutron pair density function (PDF) analysis. The result shows that the doped holes form polarons related to the Jahn–Teller (JT) effect, both in the two-dimensional layered crystals (n=2) and in the perovskites (n=∞). The temperature effects are also similar in both systems suggesting that lattice polarons are largely independent of the crystal symmetry.     

Synthesis of zinc oxide nanostructures during zinc oxidation by sub-and supercritical water

Solid zinc (Zn)_S and liquid zinc (Zn)_L are oxidized by water with the formation of zinc oxide (ZnO) nanostructures and the evolution of hydrogen. The maximum rate of this process, called chemical supercondensation by water (CSW), is realized on approaching the melting temperature of zinc from the left and right with increasing density of supercritical water. The CSW process begins with the formation of (ZnO) _n clusters via the reaction (Zn)_S,L + nH₂O = [(Zn)_S,L · (ZnO) _n ] + nH₂, followed by their subsequent growth at n > 7 in the exothermal process of epitaxy on (Zn)_S and coagulation of (ZnO) _n in (Zn)_L. The CSW of (Zn)_S leads predominantly to the formation of nanowires and nanorods, while the CSW of (Zn)_L practically always proceeds with the formation of nanoparticles. The rate of (Zn)_S oxidation increases with the thickness of a layer converted into ZnO. This is related to the self-heating and local melting of (Zn)_S in the course of CSW. The complete CSR of (Zn)_S plates and cylinders results in the formation of highly porous nanostructural ceramics.     

Solubilities and vapor pressures of the lithium bromide+calcium nitrate+water system

Solubilities and vapor pressures of the lithium bromide+calcium nitrate+water system [LiBr/Ca(NO₃)₂ mass ratio=1.0] were measured in various absorbent (lithium bromide+calcium nitrate) concentration and temperature ranges. Solubilities were measured by a visual polythermal method in the temperature range from 282.55 to 343.45 K and the experimental values were correlated with two least-squares regression equations as a function of temperature. The average absolute deviation between the experimental and the calculated solubilities was 0.23%. Vapor pressures were measured by the boiling point method in the temperature range from 334.65 to 385.85 K and in the absorbent concentration range from 44.9 to 70.3 mass%. The experimental values were correlated with an Antoine-type equation and the overall average absolute deviation was found to be 1.06%.     

Freezing transition of Langmuir-Gibbs alkane films on water

We show that adding CTAB (CTAB, hexadecyltrimethylammonium bromide) in sub-millimolar bulk concentrations to water reduces its surface tension (ST) to a level where spontaneous surface spreading of a monolayer of medium-sized alkane (C_nH_2n+2, 12 ≤ n ≤ 17) occurs. ST and X-ray reflectivity (XR) measurements are used to show that the quasi two-dimensional (2D) liquid monolayer can be driven through a reversible surface freezing phase transition upon cooling. Grazing incidence diffraction (GID) shows that the frozen monolayer is crystalline, hexagonally packed, with surface-normal molecules, and a crystalline coherence length of at least a few hundred Å, very similar to the structure of surface-frozen (SF) monolayers at the surface of similar-length alkane melts.     

Growth of untwinned Bi2Sr2Ca n−1Cu n O2n+4+δ thin films on Nd : YAlO3 substrates

Thin film growth of Bi₂Sr₂Ca _n?1Cu _n O_2n+4+δ by molecular beam epitaxy is performed on Nd : YAlO₃ (001) substrates. It was revealed that the orthorhombicity of the Nd:YAlO₃ substrate is quite effective to the growth of untwinned Bi₂Sr₂Ca _n?1Cu _n O_2n+4+δ thin films. In all phases withn=1～3, the incommensurate structural modulation lies parallel to the Nd : YAlO₃ [100] direction, and this relation holds even in the case of superlattices. The origin of the epitaxial relation is discussed from the viewpoint of the lattice misfit. The orthorhombicity of the substrate competes with the step edges on a vicinally polished substrate for determining the in-plane growth direction. The rotation of the modulation direction was observed when the off angles are varied.     

Influence of temperature on phase separation in the ternary systems [Th(NO3)4(TBP)2]-decane-third organic component

The phase diagrams of ternary systems [Th(NO₃)₄(TBP)₂]-decane-third organic component (n-butanol, n-octanol, isobutanol, dimethylhexanol, chloroform, carbon tetrachloride, o-dichlorobenzene, tri-n-butyl phosphate, o-xylene, toluene, and linear carboxylic acids) were studied in the temperature range 288.15–333.15 K. These diagrams contain the fields of homogeneous solutions and the field of separation into two liquid phases (I, II). Phase I is enriched in Th(NO₃)₄(TBP)₂ and third component and phase II is enriched in decane. The phase separation is not appreciably influenced by temperature. In phase separation, the third component is predominantly concentrated in phase I, in spite of the fact that the third component and decane have infinite mutual solubility at all the temperatures. The composition of the ternary systems in the critical point is dependent on the kind of the third component.     

Diaphragm cell determination of the interdiffusion coefficient for succinonitrile + water

Using diaphragm cells, we have measured the interdiffusion coefficient for succinonitrile+water in the one-phase liquid region at a series of temperatures ranging form 25 to 60°C and compositions ranging from 34.5 to 96 mol% water. The diffusion coefficient was found to be a function of both temperature and concentration, varying from 1.66×10^–6 to 16.6×10^–6 cm²·s^–1. Critical slowing down of diffusion was readily detected at 60°C (critical temperature, 56.17°C) over a broad range of composition on either side of the critical composition (82.7 mol% water).Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A.     

Phase equilibrium and PVT-properties of 0.7223H2O + 0.1242 n-C6 H14 + 0.1535 n-C3H7OH ternary system

The results are given of experimental investigation of the PVT-properties and liquid-liquid and liquid-vapor phase equilibria of 0.7223H₂O + 0.1242 n-C₆ H₁₄ + 0.1535 n-C₃H₇OH ternary system along six different isochores. The measurements are performed by the constant-volume piezometer technique in the range of temperature from 309.26 to 678.82 K, density from 81.0 to 485.0 kg/m³, and pressure up to 60 MPa. The behavior of the system in the vicinity of the liquid-liquid and liquid-vapor critical points is treated using the scaling equations. The PVT-properties are described by the Peng-Robinson equation.Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 1, 2005, pp. 045–050. Original Russian Text Copyright © 2005 by S. M. Rasulov and A. R. Rasulov.     

Water driven enhanced photoluminescence of Ln (=Dy3+, Sm3+) doped LaVO4 nanoparticles and effect of Ba2+ co-doping

Well-dispersed Dy³⁺ and Sm³⁺ doped LaVO₄ nanoparticles have been synthesized at a relatively low temperature of 140 °C in ethylene glycol (EG), water, N,N′-dimethyl formamide (DMF) and mixed solvents. The samples prepared in water show mixed tetragonal and monoclinic phase where tetragonal planes are found to be dominated over the monoclinic planes. However, the samples prepared in EG and DMF show monoclinic phase. Due to the phase transformation of the samples prepared in water the luminescence intensity of these samples is highly enhanced than that of the samples prepared in EG and DMF. The mixed phase of the samples prepared in water transformed to pure monoclinic phase when heated at 900 °C. The luminescence intensity of Dy³⁺ and Sm³⁺ doped LaVO₄ prepared in EG are also enhanced when large divalent Ba²⁺ ions is used as co-activator. The optimum concentration for Ba²⁺ ions was found to be 1 at.% in both Dy³⁺ and Sm³⁺ doped systems. The prepared nanoparticles are subsequently dispersed in methanol and incorporated in polymer films of PVA which showed the characteristic emissions of Dy³⁺ and Sm³⁺ when irradiated under UV light.     

Superconductivity in the tetragonal phase of La1.9Bi0.1CuO4+δ annealed under high oxygen pressure

We have investigated the relation between the crystal structure and superconductivity in La_1.9Bi_0.1CuO_4+δ , in which the phase separation observed in La₂CuO_4+δ is suppressed. A phase diagram in theT?δ plane is given for La_1.9Bi_0.1CuO_4+δ with excess oxygen. For very smallδ values, the crystal structure is orthorhombic, and an orthorhombic-tetragonal phase transition occurs markedly atδ ～ 0.03 in the measured temperature range between 13 and 293 K. Superconductivity is observed in the range of 0.04<δ<0.11. This is clear evidence thathigh-T _c superconductivity also appears in the tetragonal phase.     

The sound velocity in liquid binary mixtures of <Emphasis Type="Italic">n</Emphasis>-alkanes

The method of direct measurement of the time of pulse transmission is used for investigating the sound velocity in liquid binary mixtures of n-alkanes, namely, n-hexane + n-hexadecane, n-octane + n-hexadecane, and n-decane + n-hexadecane in the range of temperatures from 298 to 433 K and pressures from 0.1 to 100.1 MPa. The maximal error of measurements is 0.1%. It is for the first time that experimental data for mixtures of n-octane + n-hexadecane and n-decane + n-hexadecane are obtained.