Complete Composition Range Research Articles

Dielectric relaxation study of sulfolane-water mixtures

Abstract In the present work broadband dielectric spectra are reported for sulfolane-water mixtures in the complete composition range. The complex dielectric permittivity was measured at frequencies between 100 MHz and 50 GHz and at three temperatures 298.15 K, 308.15 K and 318.15 K. The permittivity spectra in these mixtures reveal a single relaxation process, which can be described by the Cole-Davidson relaxation function. The dielectric parameters, static dielectric constant (e S ), relaxation time (τ) and relaxation strength (Δe) have been determined by the least squares fit method. The concentration and temperature dependent excess dielectric constant and excess inverse relaxation time of the binary mixtures have been calculated. The obtained results confirm that strong interactions take place between sulfolane and water molecules.

Activity coefficients and excess Gibbs energy functions of acetophenone with 1,2-dichloroethane and 1,1,2,2-tetrachloroethane binary mixtures by using NRTL, UNIQUAC, UNIFAC and VAN LAAR models at a local atmospheric pressure of 95.3 kPa

Bubble point temperatures of pure liquids (Acetophenone, 1,2-dichloroethane and 1,1,2,2-tetrachloroethane) and their liquid mixtures were measured over complete composition range at a local atmospheric pressure of 95.3 kPa using a Swietoslawski-type ebulliometer. The data were then correlated with Antoine's equation. From the data activity coefficients and Gibbs energies were calculated. The systems showed a positive deviation from Raoult's law which suggests the presence of the dispersal forces acting between component molecules in the liquid mixture. NRTL, UNIQUAC, UNIFAC and VAN LAAR models have also been applied and good results were obtained. Molecular interactions between the unlike molecules in the binary liquid mixtures are discussed.

On the use of non-MPB lead zirconium titanate (PZT) granules for piezoelectric ceramic–polymer sensorial composites

Modern flexible and sensitive sensors based on polymer–ceramic composites employ lead zirconate titanate (PZT) granulates having the morphotropic phase boundary (MPB) composition as the piezo active ingredient, as this composition gives the best properties in fully ceramic piezoelectric sensors. In this study, the possibility of using PZT granulates with compositions, which are not in the MPB region of the PZT phase diagram was investigated. Random 0–3 PZT–epoxy composites were prepared for the complete composition range of PZT ceramics [Pb(ZrxTi(1-x))0.99Nb0.01O3] with x ranging from x = 0 to x = 0.80. Piezoelectric and dielectric properties of such composites were systematically studied. It is shown that the highest voltage sensitivity (i.e. g33) of the piezoelectric composites is obtained for composition with much lower Zr levels (x < 0.1) than the MPB composition. The shift in optimal composition is related to shift in dielectric constant of PZT as a function of the Zr concentration.

Vibrational properties ofLiNb1−xTaxO3mixed crystals

Congruent lithium niobate and lithium tantalate mixed crystals have been grown over the complete compositional range with the Czochralski method. The structural and vibrational properties of the mixed crystals are studied extensively by x-ray diffraction measurements, Raman spectroscopy, and density functional theory. The measured lattice parameters and vibrational frequencies are in good agreement with our theoretical predictions. The observed dependence of the Raman frequencies on the crystal composition is discussed on the basis of the calculated phonon displacement patterns. The phononic contribution to the static dielectric tensor is calculated by means of the generalized Lyddane-Sachs-Teller relation. Due to the pronounced dependence of the optical response on the Ta concentration, lithium niobate tantalate mixed crystals represent a perfect model system to study the properties of uniaxial mixed ferroelectric materials for application in integrated optics.

Isothermal vapor–liquid equilibria measurements for binary systems of 2,3,3,3-tetrafluoropropene (HFO-1234yf) + 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) and 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) + 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb)

This paper presents the measurements of isothermal vapor-Liquid equilibria (VLE) data for two binary systems of 2,3,3,3-tetrafluoropropene (HFO-1234yf) + 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) and 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) + 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb). The measurements were performed with an apparatus based on the static-analysis method. The HFO-1234yf + HCFO-1233xf system was measured at three temperatures from (293.15 to 313.15) K, and the HCFO-1233xf + HCFC-244bb system was measured at three temperatures from (303.15 to 323.15) K. The system of HFO-1234yf + HCFO-1233xf shows a small deviation from Raoult's law and dose not exhibit azeotropic behavior, while the system of HCFO-1233xf + HCFC-244bb exhibits near azeotropic behavior within the complete range of composition. All of the experimental data were correlated with the Peng–Robinson equations of state with the van der Waals mixing rules. Good consistency was obtained between the experimental data and correlated values for the both systems in the experimental temperature range. Thermodynamic consistency testing was also performed by the data-reduction method for the observed experimental data.

Thermodynamic assessment of the Al–Cu–Zn system, Part III: Al–Cu–Zn ternary system

A comprehensive thermodynamic reassessment of the Al–Cu–Zn system is elaborated covering the complete ternary composition range and compared with all presently available experimental phase equilibrium and thermodynamic data. One key distinction compared to previous CALPHAD work is the thermodynamic modeling of the γ phases, which is based on a detailed discussion of the crystal structure and simplified only to an extent necessary for a viable application in the ternary system. That entails significant changes in the ternary solid solution range of these phases. Revised aspects of the Al–Cu and Cu–Zn binary systems, elaborated in the reassessment in Parts I and II of this series, are incorporated as basis of the ternary system in this final Part III.

Exploring the energy landscape of PtxAu115−x nanoalloys

A detailed structural analysis as a function of chemical composition is performed for the putative global minima of PtxAu115−x clusters. Minimum energy structures were obtained thoroughly exploring the energy landscape through the basin-hopping method, modeling interatomic interaction with the many-body Gupta potential. The structural analysis shows that, over the complete range of compositions, several morphological changes occur as a consequence of Pt doping. Our results show that clusters’ symmetry prevails until a critical composition is reached, where a geometry change arises. The relative stability of Pt–Au clusters as a function of composition is examined through excess energy plot finding that, for a range of compositions, core–shell rhombicosidodecahedral structures are particularly stable under this model potential. For this segregated structure, atomistic centrosymmetry parameter shows the existence of three well-defined shells from which the outermost layer can be interpreted as a surface reconstruction on the 55-atom Pt core that decrease energy and provide higher stability. Mixing energy is minimized at composition Pt55Au60 whose global minimum structure consists of an icosahedral 55-atom platinum core encapsulated by a 60-atom gold shell exhibiting Archimedean polyhedron geometry. The influence of Pt loading is observed trough the menagerie of structural motifs found, the most abundant showing Marks decahedral symmetry. Ab initio DFT calculations show that the truncated octahedron cluster is energetically favored.

Intramolecular Excimer Formation Dynamics of 1,3-Bis-(1-pyrenyl)propane within 1-Butyl-3-methylimidazolium Hexafluorophosphate and Its Polyethylene Glycol Mixtures.

Mixtures of ionic liquid with polyethylene glycol (PEG) have shown interesting features as solubilizing media. Intramolecular excimer formation dynamics of 1,3-bis-(1-pyrenyl)propane [1Py(3)1Py] is investigated within mixtures of a common and popular ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) with PEGs of average molecular weight (MW) 200 (PEG200), average MW 400 (PEG400), number-average MW Mn 570-630 (PEG600), and number-average MW Mn 950-1050 (PEG1000) over the complete composition range at a 10° interval in the temperature range 10-90 °C. Irrespective of the composition of the medium and the temperature, excited-state intensity decay of the excimer fluorescence best fits to a three-exponential decay function, suggesting the presence of one excited-state monomer and two kinetically distinguishable excimers where both excimers are populated simultaneously by the excited monomer with no interconversion between the two excimers. In neat PEGs for temperatures ≤ 50 °C, intensity decay data of monomer fluorescence best fits to a single-exponential decay function, which implies the dissociation of both excimers back to the monomer to be insignificant. As the temperature is increased, the fits become closer to a double-exponential decay function, implying dissociation of one of the excimers to become significant. In neat [bmim][PF6], while a double-exponential decay function is required to fit the monomer excited-state intensity decay data at lower temperatures, three exponentials are required to satisfactorily fit the data at higher temperatures, suggesting both excimers significantly dissociate back to the monomer at higher temperatures within the ionic liquid. Within long-chain PEG-containing ([bmim][PF6] + PEG) mixtures, PEG as opposed to [bmim][PF6] controls the excimer formation dynamics by supposedly wrapping around the excimer, thus hindering dissociation back to the monomer. The overall rate constant of the excimer formation within ([bmim][PF6] + PEG) mixtures is found to scale better with the microviscosity rather than the bulk viscosity of the mixtures.

Density and Viscosity of Binary Liquid Mixtures of Ethanol + 1-Hexanol and Ethanol + 1-Heptanol from (293.15 to 328.15) K at 0.1 MPa

This paper presents experimental viscosity and density measurements for two binary mixtures of ethanol with 1-hexanol and 1-heptanol that cover the complete composition range from (293.15 to 328.15) K at 0.1 MPa. A vibrating tube densimeter provides density measurements, whereas viscosities come from a pellet microviscometer. The excess molar volumes calculated from the experimental data have positive deviations from ideality over the temperature range. Calculated viscosity deviations from the experimental data show negative deviations from a mole fraction weighted average of the pure component viscosities over the temperature range. A Redlich–Kister type equation correlates the data satisfactorily. We have correlated the three-body McAllister to the experimental kinematic viscosity. Comparison of the experimental viscosity data to predictions from a generalized, three-body McAllister and a generalized corresponding states principle (GCSP) equation shows that the generalized McAllister equation is superio...

Effect of flue gas conditioning on the cohesive forces in fly ash layers in electrostatic precipitation

Flue gas conditioning (FGC) systems are an effective option for improving the performance of electrostatic precipitators (ESP). The effect of FGC on the cohesive forces in ash layers during electrostatic precipitation has been studied for a complete range of ash compositions. Cohesive forces have been determined by means of a laboratory apparatus specifically developed within this research work. SO3 and NH3 have been tested as conditioning agents.It is concluded that the effect of injecting NH3 on the cohesive properties is variable, and depends on the type of ash. The mechanism of NH3 adsorption, influenced by the carbon content in ash, appears to play an important role. On the other hand, SO3 addition involves the reduction of the cohesive forces in all the cases tested. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1379–1383, 2015

Self-assembly of imidazolium-based surfactants in magnetic room-temperature ionic liquids: binary mixtures.

The phase behaviour of binary mixtures of ionic surfactants (1-alkyl-3-imidazolium chloride, C(n)mimCl with n=14, 16 and 18) and imidazolium-based ionic liquids (1-alkyl-3-methylimidazolium tetrachloroferrate, C(n)mimFeCl4, with n=2 and 4) over a broad temperature range and the complete range of compositions is described. By using many complementary methods including differential scanning calorimetry (DSC), polarised microscopy, small-angle neutron and X-ray scattering (SANS/SAXS), and surface tension, the ability of this model system to support self-assembly is described quantitatively and this behaviour is compared with common water systems. The existence of micelles swollen by the solvent can be deduced from SANS experiments and represent a possible model for aggregates, which has barely been considered for ionic-liquid systems until now, and can be ascribed to the rather low solvophobicity of the surfactants. Our investigation shows that, in general, C(n)mimCl is a rather weak amphiphile in these ionic liquids. The amphiphilic strength increases systematically with the length of the alkyl chain, as seen from the phase behaviour, the critical micelle concentration, and also the level of definition of the aggregates formed.

Band-selective infrared photodetectors with complete-composition-range InAs(x)P(1-x) alloy nanowires.

Band-selective infrared photodetectors (PDs) are constructed with InAs(x)P(1-x) alloy nanowires from the complete composition range (0 ≤ x ≤ 1) achieved by a new growth route combining the vapor-liquid-solid mechanism with an additional ion-exchange process. Increasing the composition x value from 0 to 1 in the PDs allows the peak response wavelength to be gradually tuned from ca. 900 to ca. 2900 nm.

Composition dependent valence band order in c-oriented wurtzite AlGaN layers

The valence band order of polar wurtzite aluminum gallium nitride (AlGaN) layers is analyzed for a dense series of samples, grown heteroepitaxially on sapphire substrates, covering the complete composition range. The excitonic transition energies, found by temperature dependent photoluminescence (PL) spectroscopy, were corrected to the unstrained state using input from X-ray diffraction. k⋅p theory yields a critical relative aluminum concentration xc=(0.09±0.05) for the crossing of the uppermost two valence bands for strain free material, shifting to higher values for compressively strained samples, as supported by polarization dependent PL. The analysis of the strain dependent valence band crossing reconciles the findings of other research groups, where sample strain was neglected. We found a bowing for the energy band gap to the valence band with Γ9 symmetry of bΓ9=0.85eV, and propose a possible bowing for the crystal field energy of bcf=−0.12eV. A comparison of the light extraction efficiency perpendicular and parallel to the c axis of AlxGa1-xN/AlyGa1-yN quantum well structures is discussed for different compositions.

Post-consumer polyethylene terephthalate and polyamide 66 blends and corresponding short glass fiber reinforced composites

Blends of bottle-grade post-consumer polyethylene terephthalate (PET) and virgin polyamide 66 (PA66), over the complete composition range, and corresponding short glass fiber (SGF) reinforced composites were investigated. These materials were compounded in a twin-screw extruder and injection molded as standard specimens. Morphological investigation of the composites revealed that the short glass fibers have a good size distribution and are homogenously dispersed within a polymeric matrix. The PET/PA66/SGF composites showed good mechanical performance in flexural, tensile and impact tests demonstrating that the addition of SGFs to PET/PA66 blends is an interesting approach to obtaining new thermoplastic composites. In addition, this represents a potential application for post-consumer PET, an abundant and cheap material, in the well-established market of PA66/SGF composites, which are widely used in technical parts requiring high mechanical and thermal properties.

Distinctive Features of Water–Dimethyl Sulfoxide Mixtures: Dielectric Spectra Revisited

Broadband dielectric spectra (1 MHz to 80 GHz) are reported for dimethyl sulfoxide–water mixtures in the complete composition range. The spectra are evaluated in order to yield information about the underlying relaxation time distribution, the principal relaxation time, and the static permittivity of the liquids. With a view of gaining insights into the structure and microdynamics of water in its different states of interaction, these parameters are compared to such for mixtures of water with other protic and aprotic dipolar liquids as well as with non-polar substances. Also used for information about structure fluctuations are ultrasonic spectra of the dimethyl sulfoxide–water system (0.2 MHz to 2.75 GHz). A notable result is the composition dependence of the principal dielectric relaxation time. In conformity with the wait-and-switch model, it increases at low DMSO content and thus reflects the decrement in the concentration of hydrogen-bonding sites. The decreasing relaxation time at high DMSO content is clearly a result of the reduced association due to the reduced concentration of hydrogen-donating sites.

Enthalpies of formation of Cd–Pr intermetallic compounds and thermodynamic assessment of the Cd–Pr system

In the present study standard enthalpies of formation were measured by reaction and solution calorimetry at stoichiometric compositions of Cd2Pr, Cd3Pr, Cd58Pr13 and Cd6Pr. The corresponding values were determined to be −46.0, −38.8, −35.2 and −24.7kJ/mol(at), respectively. These data together with thermodynamic data and phase diagram information from literature served as input data for a CALPHAD-type optimization of the Cd–Pr phase diagram. The complete composition range could be described precisely with the present models, both with respect to phase equilibria as well as to thermodynamic input data. The thermodynamic parameters of all intermetallic compounds were modelled following Neumann–Kopp rule. Temperature dependent contributions to the individual Gibbs energies were used for all compounds. Extended solid solubilities are well described for the low- and high-temperature modifications of Pr and also for the intermetallic compound CdPr. A quite good agreement with all viable data available from literature was found and is presented.

Isothermal VLE measurements for the binary mixture of 2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf) + 1,1-difluoroethane (HFC-152a)

Isothermal vapor–liquid equilibrium (VLE) data for the binary mixture of 2,3,3,3-tetrafluoroprop-1-ene (HFO-1234yf)+1,1-difluoroethane (HFC-152a) were measured at temperatures from 283.15K to 323.15K using a recirculation apparatus. The experimental data were correlated by using PR EoS with vdW mixing rule, the comparison between the correlation results and experimental data showed a good agreement. HFO-1234yf (1)+HFC-152a (2) system shows not only azeotropic behavior but also near azeotropic behavior with a very small temperature glide of less than 0.4K within the complete range of composition and of temperature.

Thermodynamic modelling of Li–Sn liquid alloy based on Knudsen effusion mass spectrometric measurements

The mixing thermodynamic properties of liquid Li–Sn system, determined previously by Knudsen effusion mass spectrometry (KEMS), were successfully fitted to both Redlich–Kister (RK) sub-regular mixture and ideally associated mixture (IAMT) models. The RK binary interaction L parameters, as a function of temperature in the CALPHAD-type functional form, were obtained as follows: L(0)=-(108580±0.00171)+(16.4±1.6·10-5)·T+(1.96496·10-9±2.03133·10-6)·T·ln(T)L(1)=-(96600±4700)+(3.3±43.0)·T+(4.4±5.6)·T·ln(T)L(2)=-(64670±190)-(44.4±1.7)·T+(8.44±0.22)·T·ln(T)L(3)=-(20900±1500)-(29±14)·T+(4.3±1.8)·T·ln(T) The former literature data provided only qualitative information on possible liquid associates but no quantitative associate composition was given as a function of the sample composition and temperature. The experimental KEMS data in the composition range XLi=0 to ∼0.7 fit well with the Li(l)+Sn(l)+LiSn(l)+LiSn2(l)+Li2Sn(l) associate model. At XLi>0.7 no associate variations – including further associate variants such as Li4Sn(l) etc. – could be fitted to the KEMS data. Nevertheless, in this work the Li(l)+Sn(l)+LiSn(l)+LiSn2(l)+Li2Sn(l)+Li4Sn(l)+Li9Sn(l) associate model was successfully fitted to the thermodynamic data of a selected literature study over the complete composition range. The thermodynamic data of the associate-forming reactions were also given in this paper.

Experimental Investigation of the Ce-Mg-Mn Isothermal Section at 723 K (450 °C) via Diffusion Couples Technique

The isothermal section of the Ce-Mg-Mn phase diagram at 723 K (450 °C) was established experimentally by means of diffusion couples and key alloys. The phase relationships in the complete composition range were determined based on six solid–solid diffusion couples and twelve annealed key alloys. No ternary compounds were found in the Ce-Mg-Mn system at 723 K (450 °C). X-ray diffraction and energy-dispersive X-ray spectroscopy spot analyses were used for phase identification. EDS line-scans, across the diffusion layers, were performed to determine the binary and ternary homogeneity ranges. Mn was observed in the diffusion couples and key alloys microstructures as either a solute element in the Ce-Mg compounds or as a pure element, because it has no tendency to form intermetallic compounds with either Ce or Mg. The fast at. interdiffusion of Ce and Mg produces several binary compounds (CexMgy) during the diffusion process. Thus, the diffusion layers formed in the ternary diffusion couples were similar to those in the Ce-Mg binary diffusion couples, except that the ternary diffusion couples contain layers of Ce-Mg compounds that dissolve certain amount of Mn. Also, the ternary diffusion couples showed layers containing islands of pure Mn distributed in most diffusion zones. As a result, the phase boundary lines were pointing toward Mn-rich corner, which supports the tendency of Mn to be in equilibrium with all the phases in the system.

Experimental Data and Description of the Phase Equilibrium in the Binary System of Ethyl Fluoride and Polyol Ester Oil (Planetelf ACD 32)

Experimental measurement for the vapor–liquid equilibrium (VLE) of a binary mixture of ethyl fluoride (HFC-161) and polyol ester (POE) lubricant oil is an important task in the practical refrigeration system. In this work, the reliable p–T–x data of HFC-161 + POE (Planetelf ACD 32) are obtained from T = (283.15 to 343.15) K and over a complete range of compositions. Throughout the experiment, there was no stratification and no sediment generation, and the color of mixture liquid remained unchanged. Additionally, the vapor pressure of lubricant oil is negligibly small compared with the one of HFC-161 at the same temperature. Therefore, the mixture vapor is approximated as being pure HFC-161 in this work. The experimental data are correlated by the nonrandom two-liquid (NRTL) model. From the correlated results, the average relative deviation (ARD) of the pressure is 1.94 %, and the maximum relative deviation of the pressure is 5.71 %. The results showed a good agreement with the experimental data.