Complete Composition Range Research Articles

Integrated experimental and thermodynamic modelling study of phase equilibria in the “CuO0.5”-PbO-CaO system in equilibrium with Cu/Pb metal

Phase equilibria studies were undertaken on the “CuO0.5”-PbO-CaO system in equilibrium with Cu/Pb metal as part of the integrated experimental and thermodynamic modelling study of phase equilibria in the Cu-Pb-Zn-Fe-Ca-Si-Al-Mg-O-S-(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co and Na) gas/oxide liquid/matte/speiss/metal/solids system in support of the development and optimisation of pyrometallurgical processes. The equilibration and quenching technique followed by the electron probe X-ray microanalysis (EPMA) was used in the present study. The primary phase fields of massicot (PbO), copper plumbite (Cu2PbO2), cuprite (Cu2O) and lime (CaO) were experimentally characterised. The experimental data obtained in the present study, as well as available literature data on the phase equilibria and thermodynamics of the “CuO0.5”-PbO-CaO system in equilibrium with Cu/Pb were used for the optimisation of the model parameters of the discussed system in agreement with the Cu-Pb-Zn-Fe-Ca-Si-Al-Mg-O-S-(As, Sn, Sb, Bi, Ag, Au, Ni, Cr, Co and Na) gas/oxide liquid/matte/speiss/metal/solids system to obtain a self-consistent set of parameters of the thermodynamic model for all phases. The predicted liquidus surface of the “CuO0.5”-PbO-CaO system was presented for the first time in the complete range of temperatures and compositions.

Excess Thermodynamic Parameters of Binary Liquid Mixtures of Dimethyl Malonate with Isomeric Xylenes at Different Temperatures

Over the complete composition range of mole fractions, densities and ultrasonic velocities of binary liquid mixtures of dimethyl malonate with o-xylene, p-xylene and m-xylene were investigated at 303.15-318.15 K. These parameters were chosen to investigate the impact of substituents and specific locations on several thermodynamic characteristics of binary mixtures. The deviation in adiabatic compressibility (∆βad), excess molar volume (VE) and excess intermolecular free length (LfE) were estimated using the experimental measurements. These extraneous parameters are fitted to a polynomial equation of the Redlich-Kister type. Along with the obtained parameter values, the standard deviation (σ) was also determined.

Thermodynamic properties of P-methyl acetophenone with cyclohexylamine, cyclohexanol, and cyclohexane at various temperatures (strong and weak interactions)

ABSTRACT The density, viscosity and sound velocity of the binary liquid mixtures of P-methyl acetophenone with cyclohexylamine, cyclohexanol, and cyclohexane are measured over the complete composition range at temperatures of 303.15–313.15 K and at atmospheric pressure of 0.1 M. Excess molar volume, excess isentropic compressibility and viscosity deviation are calculated from the experimental measurements. The sign and magnitude of the derived parameters reveal the nature and type of interactions between the constituent molecules in the binary mixtures. Thermodynamic properties for this work reveal association interactions between dissimilar molecules in the binary systems P-methyl acetophenone + cyclohexylamine and P-methyl acetophenone + cyclohexanol systems, whereas dispersion forces cause the opposite trend in the other binary system P-methyl acetophenone + cyclohexane.

Overcoming the Miscibility Gap of GaN/InN in MBE Growth of Cubic InxGa1-xN.

The lack of internal polarization fields in cubic group-III nitrides makes them promising arsenic-free contenders for next-generation high-performance electronic and optoelectronic applications. In particular, cubic InxGa1-xN semiconductor alloys promise band gap tuning across and beyond the visible spectrum, from the near-ultraviolet to the near-infrared. However, realization across the complete composition range has been deemed impossible due to a miscibility gap corresponding to the amber spectral range. In this study, we use plasma-assisted molecular beam epitaxy (PAMBE) to fabricate cubic InxGa1-xN films on c-GaN/AlN/3C-SiC/Si template substrates that overcome this challenge by careful adjustment of the growth conditions, conclusively closing the miscibility gap. X-ray diffraction reveals the composition, phase purity, and strain properties of the InxGa1-xN films. Scanning transmission electron microscopy reveals a CuPt-type ordering on the atomistic scale in highly alloyed films with x(In) ≈ 0.5. Layers with much lower and much higher indium content exhibit statistical distributions of the cations Ga and In. Notably, this CuPt-type ordering results in a spectrally narrower emission compared to that of statistically disordered zincblende materials. The emission energies of the films range from 3.24 to 0.69 eV and feature a quadratic bowing parameter of b = 2.4 eV. In contrast, the LO-like phonon modes that are observed by Raman spectroscopy exhibit a one-mode behavior and shift linearly from c-GaN to c-InN.

Thermodynamic properties of binary mixtures of 2-chlorotoluene + alkanol at T = 298.15 K to 318.15 K

Density (ρ), viscosity (η), and ultrasonic speed (u) of 2-chlorotoluene with methanol and ethanol binary mixtures were measured at 298.15 to 318.15 K in the composition range 0⩽x1⩽1. Based on the experimental data, the excess molar volume (VmE), deviation in viscosity (Δη), and deviation in ultrasonic speed (Δu) values were calculated. The VmE values exhibited negative for binary mixtures but at higher concentrations of 2-chlorotoluene, these were changes sign and positive at all temperatures. The excess isentropic compressibility (κsE) values increase with the number of C-atoms of the alkanol. The order of κsE for 2-chlorotoluene + alkanol is similar to that observed in the case of VmE. Additionally, Δη and Δu values were positive throughout the complete range of composition. At 298.15 K, the η and u values were analyzed using various correlations. Among the correlation Nomoto’s correlation for ultrasonic exhibits a high predictive power compared to others. A binary mixture has been discussed in terms of its excess functions which provide insights into molecular interactions. The Δη and κsE were also interpreted in terms of the ab initio approach that yielded interaction parameters that not give the extent of unlike interactions and depolymerization of self-associated alkanol but also predict the Δη and κsE for these systems. Singh’s model for viscosity further authenticates the findings of the ab initio approach.

Lithium‐ion Mobility in Li6B18(Li3N) and Li Vacancy Tuning in the Solid Solution Li6B18(Li3N)1−x(Li2O)x

AbstractAll‐solid‐state batteries are promising candidates for safe energy‐storage systems due to non‐flammable solid electrolytes and the possibility to use metallic lithium as an anode. Thus, there is a challenge to design new solid electrolytes and to understand the principles of ion conduction on an atomic scale. We report on a new concept for compounds with high lithium ion mobility based on a rigid open‐framework boron structure. The host–guest structure Li6B18(Li3N) comprises large hexagonal pores filled with Li7N] strands that represent a perfect cutout from the structure of α‐Li3N. Variable‐temperature 7Li NMR spectroscopy reveals a very high Li mobility in the template phase with a remarkably low activation energy below 19 kJ mol−1 and thus much lower than pristine Li3N. The formation of the solid solution of Li6B18(Li3N) and Li6B18(Li2O) over the complete compositional range allows the tuning of lithium defects in the template structure that is not possible for pristine Li3N and Li2O.

Lithium-ion Mobility in Li6 B18 (Li3 N) and Li Vacancy Tuning in the Solid Solution Li6 B18 (Li3 N)1-x (Li2 O)x.

All-solid-state batteries are promising candidates for safe energy-storage systems due to non-flammable solid electrolytes and the possibility to use metallic lithium as an anode. Thus, there is a challenge to design new solid electrolytes and to understand the principles of ion conduction on an atomic scale. We report on a new concept for compounds with high lithium ion mobility based on a rigid open-framework boron structure. The host-guest structure Li6 B18 (Li3 N) comprises large hexagonal pores filled with Li7 N] strands that represent a perfect cutout from the structure of α-Li3 N. Variable-temperature 7 Li NMR spectroscopy reveals a very high Li mobility in the template phase with a remarkably low activation energy below 19 kJ mol-1 and thus much lower than pristine Li3 N. The formation of the solid solution of Li6 B18 (Li3 N) and Li6 B18 (Li2 O) over the complete compositional range allows the tuning of lithium defects in the template structure that is not possible for pristine Li3 N and Li2 O.

Phase transitions study of the liquid crystal DIO with a ferroelectric nematic, a nematic, and an intermediate phase and of mixtures with the ferroelectric nematic compound RM734 by adiabatic scanning calorimetry.

High-resolution calorimetry has played a significant role in providing detailed information on phase transitions in liquid crystals. In particular, adiabatic scanning calorimetry (ASC), capable of providing simultaneous information on the temperature dependence of the specific enthalpy h(T) and on the specific heat capacity c_{p}(T), has proven to be an important tool to determine the order of transitions and render high-resolution information on pretransitional thermal behavior. Here we report on ASC results on the compound 2,3',4',5'-tetrafluoro[1,1'-biphenyl]-4-yl 2,6-difluoro-4-(5-propyl-1,3-dioxan-2-yl) benzoate (DIO) and on mixtures with 4-[(4-nitrophenoxy)carbonyl]phenyl 2,4-dimethoxybenzoate (RM734). Both compounds exhibit a low-temperature ferroelectric nematic phase (N_{F}) and a high-temperature paraelectric nematic phase (N). However, in DIO these two phases are separated by an intermediate phase (N_{x}). From the detailed data of h(T) and c_{p}(T), we found that the intermediate phase was present in all the mixtures over the complete composition range, albeit with strongly decreasing temperature width for that phase with decreasing mole fraction of DIO (x_{DIO}). The x_{DIO} dependence on the transition temperatures for both transitions could be well described by a quadratic function. Both these transitions were weakly first order. The true latent heat of the N_{x}-N transition of DIO was as low as L=0.0075±0.0005J/g and L=0.23±0.03J/g for the N_{F}-N_{x} transition, which is about twice the previously reported value of 0.115 J/g for the N_{F}-N transition in RM734. In the mixtures both transition latent heats decrease gradually with decreasing x_{DIO}. At all the N_{x}-N transitions pretransition fluctuation effects are absent and these transitions are purely but very weakly first order. As in RM734 the transition from the N_{F} to the higher-temperature phase exhibits substantial pretransitional behavior, in particular, in the high-temperature phase. Power-law analysis of c_{p}(T) resulted in an effective critical exponent α=0.88±0.1 for DIO and this value decreased in the mixtures with decreasing x_{DIO} toward α=0.50±0.05 reported for RM734. Ideal mixture analysis of the phase diagram was consistent with ideal mixture behavior provided the total transition enthalpy change was used in the analysis.

Mixed micelle formation by sodium dodecylsulfate and dodecyltrimethylammonium bromide in aqueous ionic liquid media

Surfactant self-aggregation within ionic liquid (IL) - based media has been investigated to compare and contrast the role of such media with that of water. Behavior of a surfactant mixture constituting of two surfactants with oppositely charged head groups, namely anionic sodium dodecylsulfate (SDS) and cationic n-dodecyltrimethylammonium bromide (DTAB), is assessed in aqueous IL media. Contrary to what is observed in water, it is shown earlier that effective charge screening of the surfactant headgroups by IL ions in a typical IL 1-ethyl-3-methylimidazolium ethylsulfate ([C2C1im][EtSO4]) results in formation of (SDS + DTAB) mixed micelles with critical micelle concentrations (CMCs) ranging between those of SDS and DTAB, respectively. The miscibility of (SDS + DTAB) mixture in aqueous [C2C1im][EtSO4] reveals that as the content of IL [C2C1im][EtSO4] is increased, the miscibility of the surfactant mixture improves indicating increased charge screening involving ions of the IL and the surfactant headgroups. For water mole fraction (XW) ≤ 0.90, (SDS + DTAB) surfactant mixture is miscible in aqueous [C2C1im][EtSO4] system in all proportions. For 1.00 ≥ XW≥ 0.90, while synergism persists due to the presence of attractive electrostatic attraction between SDS and DTAB headgroups leading to mixture CMCs below the CMCs of SDS and DTAB, respectively, the extent of synergism diminishes with increase in IL [C2C1im][EtSO4] in the solution. For XW = 0.80, the (SDS + DTAB) mixture exhibits CMC values that are closest to the values estimated assuming ideal behavior. For 0.70 ≥ XW ≥ 0.30, the (SDS + DTAB) exhibits antagonistic trend with CMC values higher than those estimated for ideal solution; the antagonistic trend gradually decreases with increase in [C2C1im][EtSO4] and again attains close to ideal behavior in neat IL [C2C1im][EtSO4]. This trend is subsequently manifested in the composition of the mixed micelles as well as in the net interaction parameter, β. Addition of small proportion of IL to water helps in solubilization of surfactant mixture of oppositely charged surfactants due to effective charge screening of the surfactant headgroups and results in formation of mixed micelles in aqueous IL media over complete composition range.

Using Raman spectroscopy and x-ray diffraction for phase determination in ferroelectric mixed Hf1−xZrxO2-based layers

The discovery of ferroelectric properties in the doped HfO2 and mixed Hf1−xZrxO2 systems made precise phase determination very important. However, due to the similarities of the diffraction peaks between the tetragonal and the orthorhombic phases, the discrimination of these two critical phases by x-ray diffraction remains challenging. This work introduces Raman spectroscopy as a structural characterization method to unambiguously identify phases by comparing experimental data with density functional simulation results for the mixed hafnia–zirconia system in the complete composition range. Raman modes for the non-polar monoclinic and tetragonal phases are presented in comparison to those of the polar orthorhombic phase. Changes in phonon mode frequencies in the hafnia–zirconia system with Hf/Zr composition are related to the appearance of ferroelectric properties.

Kinetic and Product Composition Studies of 9,10-Anthraquinone-2,7-Disulfonic Acid: Correlating Transient/Steady-State Modeling with Experimental Analysis

Organic-based quinones have been studied for use as an electrolyte for redox-based flow batteries due to their good chemical stability, high solubility, and low cost. In biological applications, quinones can be more advantageous than other charge carriers, such as viologens, due to all of the aforementioned reasons as well as their lower toxicity. One such quinone, 9,10-anthraquinone-2,7-disulfonic acid (AQDS), is reported to have lower redox potentials [1], but the reaction pathways to form desired AQDS products are more highly pH-dependent [2], which can be problematic in biological applications with restrictive pH ranges to maintain biocatalyst reactivity. Competition with dimerization has also been reported to be an issue, inhibiting the production of desired charged species for use in catalysts [3]. Consequently, there is a need to reliably predict the state of the charge carrier, requiring more robust theoretical models.The kinetics of AQDS are first studied here experimentally in a single-cell configuration with a buffer selected to maintain a neutral pH condition (pH = 7). Cyclic voltammetry (CV) studies revealed highly reversible kinetics for AQDS, indicating an advantage in its choice as a charge carrier over viologens, which tend to have certain additional irreversible redox reactions. Furthermore, a Randles-Sevcik analysis of the peak current vs. scan rate revealed strong equivalence in the reduction and oxidation reactions. Diffusion coefficients of 1-2 x 10-9 m2/s are consistent with previously reported values [4]. Additionally, kinetic constants were determined using the Kochi equation [5] and were found to be on the order of 10-3 to 10-5 cm/s, indicating more sluggish kinetics than would otherwise be anticipated.Chronoamperometry studies were conducted in an H-cell reactor with 10 mM AQDS in the cathode chamber with a pH buffer. One set of experiments was run using CO2 as the purge gas (used in biological applications to convert to usable organic products, decreasing pH to 6.3), and the other set was run using N2 (to serve as an inert gas and help maintain near neutral pH). Charging with -0.75 V vs. Ag/AgCl over a duration of 1.5 hours, the AQDS displayed high initial currents relative to a blank sample; however, longer steady-state times suggested slower reaction kinetics consistent with the CV study. Under the more pH neutral conditions, initial AQDS reduction was further delayed, indicating greater product favorability in more acidic environments. This knowledge is useful for battery applications where inert gases are typically used to purge but poses a challenge when catalysts such as enzymes are highly sensitive to pH.Finally, a transient-based equilibrium model is developed for AQDS in a batch reactor. The model is simulated using Butler-Volmer kinetics until steady-state is reached, using the same conditions studied for the experimental chronoamperometry. AQDS displays a lower charge input than other charge carriers, such as viologens, at -0.5 V vs. Ag/AgCl but is limited by slower kinetics. An extended transient study revealed AQDS kinetics taking nearly 10 hours to reach final equilibrium concentrations. The product composition of AQDS depends heavily on pH as well as voltage, with four unique product composition ranges. The use of a steady-state equilibrium model to connect with the transient model for the complete range of product compositions is reported here at various pH and voltage values. Designing charge carrier reduction experiments around such conditions predicted theoretically, rather than only -0.75 V, may enable more rapid and reliable charge carrier production to assist in applications such as fuel cells, batteries, and catalytic CO2 conversion to value-added products. Forster RJ, O'Kelly JP. Protonation reactions of anthraquinone-2, 7-disulphonic acid in solution and within monolayers. Journal of Electroanalytical Chemistry. 2001 Feb 16;498(1-2):127-35.Batchelor-McAuley C, Li Q, Dapin SM, Compton RG. Voltammetric characterization of DNA intercalators across the full pH range: Anthraquinone-2, 6-disulfonate and anthraquinone-2-sulfonate. The Journal of Physical Chemistry B. 2010 Mar 25;114(11):4094-100.Wiberg C, Carney TJ, Brushett F, Ahlberg E, Wang E. Dimerization of 9, 10-anthraquinone-2, 7-Disulfonic acid (AQDS). Electrochimica Acta. 2019 Sep 10;317:478-85.Huskinson B, Marshak MP, Suh C, Er S, Gerhardt MR, Galvin CJ, Chen X, Aspuru-Guzik A, Gordon RG, Aziz MJ. A metal-free organic–inorganic aqueous flow battery. Nature. 2014 Jan;505(7482):195-8.Klingler RJ, Kochi JK. Electron-transfer kinetics from cyclic voltammetry. Quantitative description of electrochemical reversibility. The Journal of Physical Chemistry. 1981 Jun;85(12):1731-41. Figure 1

Controlling transition metal atomic ordering in two-dimensional Mo1−x W x S2 alloys

The unique optical and electronic properties of two-dimensional transition metal dichalcogenides (2D TMDs) make them promising materials for applications in (opto-)electronics, catalysis and more. Specifically, alloys of 2D TMDs have broad potential applications owing to their composition-controlled properties. Several important challenges remain regarding controllable and scalable fabrication of these alloys, such as achieving control over their atomic ordering (i.e. clustering or random mixing of the transition metal atoms within the 2D layers). In this work, atomic layer deposition is used to synthesize the TMD alloy Mo1−x W x S2 with excellent composition control along the complete composition range 0 ⩽ x ⩽ 1. Importantly, this composition control allows us to control the atomic ordering of the alloy from well-mixed to clustered while keeping the alloy composition fixed, as is confirmed directly through atomic-resolution high-angle annular dark-field scanning transmission electron micrography imaging. The control over atomic ordering leads to tuning of the bandgap, as is demonstrated using optical transmission spectroscopy. The relation between this tuning of the electronic structure and the atomic ordering of the alloy was further confirmed through ab-initio calculations. Furthermore, as the atomic ordering modulates from clustered to well-mixed, the typical MoS2 and WS2 A1g vibrational modes converge. Our results demonstrate that atomic ordering is an important parameter that can be tuned experimentally to finely tune the fundamental properties of 2D TMD alloys for specific applications.

Insight into the solute-solvent interactions by physicochemical and excess properties in binary systems of the ether- and allyl-based functionalized ionic liquids with acetonitrile

• The ether- and allyl-based functionalized ionic liquids [C 1 OC 2 pyrr][DCA], [C 1 OC 2 pyrr][NTf 2 ] and [Amim][NTf 2 ] were synthesized and characterized. • The excess properties α p E and V E values are all negative, which could be interpreted in terms of H-bonding interaction and structural effect, and Δ n D findings are also well supported by the results. • The molar refraction, R m and the molar polarizability α, which suggest that the existent interactions between ILs and acetonitrile are ion-dipole interactions. Ionic liquid is a significant new media and one of the most compelling solvents mentioned in many fields. It is clear that the introduction of ether or allyl group has the advantages of low viscosity and wide application. In this work, [C 1 OC 2 pyrr][DCA], [C 1 OC 2 pyrr][NTf 2 ] and [Amim][NTf 2 ] were synthesized and characterized. The density, surface tension, and refractive index of the three ionic liquids and their binary systems with acetonitrile were investigated across a complete composition range. The thermal expansion coefficient ( α p E ), excess molar volumes ( V E ), and refractive index deviations (Δ n D ) are also calculated. The α p E and V E are all negative while the Δ n D are found positive in the entire concentration range, indicating the presence of strong interactions between ionic liquids and acetonitrile. The properties are fitted to a Redlich-Kister equation and the results have been interpreted in terms of H-bonding interaction and structural effect, at the same time, the corresponding IR spectra are also carried out. The molar refraction and the molar polarizability calculated which suggest that the existent interactions between ionic liquids and acetonitrile are ion-dipole interactions. The molar Gibbs free energy can be measured and explained properly by the improved Eӧtvӧs equation. And the molar surface enthalpy also can be gained and is a temperature-independent constant.

Composition-Dependent Cytotoxic and Antibacterial Activity of Biopolymer-Capped Ag/Au Bimetallic Nanoparticles against Melanoma and Multidrug-Resistant Pathogens.

Nanostructured silver (Ag) and gold (Au) are widely known to be potent biocidal and cytotoxic agents as well as biocompatible nanomaterials. It has been recently reported that combining both metals in a specific chemical composition causes a significant enhancement in their antibacterial activity against antibiotic-resistant bacterial strains, as well as in their anticancer effects, while preserving cytocompatibility properties. In this work, Ag/Au bimetallic nanoparticles over a complete atomic chemical composition range were prepared at 10 at% through a green, highly reproducible, and simple approach using starch as a unique reducing and capping agent. The noble metal nanosystems were thoroughly characterized by different analytical techniques, including UV-visible and FT-IR spectroscopies, XRD, TEM/EDS, XPS and ICP-MS. Moreover, absorption spectra simulations for representative colloidal Ag/Au-NP samples were conducted using FDTD modelling. The antibacterial properties of the bimetallic nanoparticles were determined against multidrug-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus, showing a clear dose-dependent inhibition even at the lowest concentration tested (5 µg/mL). Cytocompatibility assays showed a medium range of toxicity at low and intermediate concentrations (5 and 10 µg/mL), while triggering an anticancer behavior, even at the lowest concentration tested, in a process involving reactive oxygen species production per the nanoparticle Au:Ag ratio. In this manner, this study provides promising evidence that the presently fabricated Ag/Au-NPs should be further studied for a wide range of antibacterial and anticancer applications.

Experimental investigation and thermodynamic calculation of ternary Al–Ca–Mg phase equilibria

Abstract The ternary Al –Ca –Mg phase equlibria were investigated using X-ray diffraction methods, metallography, scanning electron microscopy with energy- and wave-length-dispersive X-ray microanalysis, and differential thermal analysis. The phase diagram was determined in the complete composition range. Large ternary solubilities were found for the binary phases CaMg2, Al2Ca and Al3Ca8. Microstructures of samples with compositions near the ternary monovariant eutectic L → CaMg2 + Al2Ca show remarkable rod-like crystals that are identified as intergrowth between CaMg2 and Al2Ca. A consistent thermodynamic model was developed using the Calphad method incorporating all experimental data. It was used to calculate all pertinent phase equilibria of the Al –Ca –Mg system.

Sulfosalts record evolution of Cu-Bi-Co-Ni-As mineralization at Baycheh-Bagh deposit, NW Iran

Minerals of the tetrahedrite group and Bi-bearing sulfosalts and sulfides have been identified in different mineral associations in the polymetallic (Cu-Bi-Co-Ni-As) vein deposit at Baycheh-Bagh, Zanjan Province, NW Iran. The tetrahedrite group members span the complete compositional range from tetrahedrite to tennantite with Fe and less common Zn being the dominant divalent cation. Two generations of tetrahedrite group minerals can be distinguished recording changes in chemical as well as redox conditions of the mineralizing fluid. The first generation (Ia, Ib) includes tennantite-(Fe) succeeded by tetrahedrite-(Zn) to tennantite-(Fe) of variable intermediate composition. Bismuthian tennantite-(Fe) containing up to 1.17 apfu Bi represents the second generation (II) formed during the final hydrothermal stage. Bismuthian tennantite is characterized by primary growth zoning and slight Cu excess; the latter indicating an increase in the oxidation state of the fluid. The compositional variation and zoning of tetrahedrite group minerals reflect multiple pulses of hydrothermal solutions with varying As/Sb content. The significant substitution of Bi for (As + Sb) in the X site in generation II tennantite indicates higher activity of Bi in the late ore fluids. The late-stage Bi-rich assemblages also comprise emplectite, wittichenite, bismuthinite, aikinite and native bismuth. Luzonite is also found with these assemblages. These minerals mainly belong to the final stage of mineralization and formed between ∼200 and 300 °C.

The surface tension and interfacial composition of water/ethanol mixture

This study develops a model to fit the surface tension of the water/ethanol mixture for the complete composition range from 0 to 1. The theoretical framework complements Van Der Waals theory on the density gradient. The modelling results overcome the limitation of Gibbs adsorption isotherm, which completely ignores the composition of the interfacial layer. Furthermore, the model presents a new method to correctly calculate the composition of the interfacial layer for binary liquid mixture and surfactant solutions.

The effect of hydrogen bonding on the copolymerization kinetics of 2‐methoxyethyl acrylate with 2‐hydroxyethyl methacrylate in alcohol and aqueous solutions

AbstractThe influence of alcohol and alcohol/water solutions on the radical copolymerization kinetics of 2‐hydroxyethyl methacrylate (HEMA) with 2‐methoxyethyl acrylate (MEA) is studied using pulsed‐laser‐polymerization coupled with size exclusion chromatography. It is found that MEA incorporation into the copolymer is increased in butanol, methanol (MeOH), and MeOH/H2O solutions relative to the bulk system. Copolymer composition can be represented for solvent levels ≥50 vol.% by a single pair of reactivity ratios ( = 2.39 ± 0.16, = 0.28 ± 0.02) that differ from those in bulk ( = 3.14 ± 0.44, = 0.27 ± 0.04). MeOH as solvent slightly reduces the propagation rate coefficient of HEMA compared to the bulk system, in contrast to the increase in the MEA value. Thus, the value of is higher in MeOH for MEA‐rich systems compared to bulk, with the effect of the solvent reduced as the HEMA content in the comonomer mixture is increased. Adding water as cosolvent significantly increases values for both monomers, with in MeOH/H2O higher than bulk values over the complete composition range. Furthermore, for 50% monomer in the solvent systems studied can be represented by the implicit penultimate unit model using a single pair of radical reactivity ratios. It is concluded that the strongest influence of hydrogen‐bonding solvents compared to bulk is on the homopropagation values, rather than on copolymerization parameters, and that the difference in relative reactivity of non‐functional and functional monomers in bulk and aqueous solution should be accounted for when studying emulsion copolymerization.

New insights on photocatalytic hydrogen evolution of ZnFe2−xGaxO4 (0 ≤ x ≤ 2) solid solutions: Role of oxygen vacancy and ZnO segregated phase

The exponential increase in global energy and clean energy demands lead to the necessity for development of efficient photocatalyst for hydrogen evolution. Herein, photocatalytic hydrogen evolution activity with nano-structured ZnFe2-xGaxO4 (0 ≤x ≤ 2) solid solution samples synthesized by citrate-gel method at 550 °C is reported. The prepared materials have been characterized for their structure and optical properties. The formation of solid solution with spinel type structure in the complete range of composition and a systematically decreasing trend of unit cell parameters with increasing Ga3+ concentration is observed from powder XRD studies. The band gap of these solid solutions could be tuned from 1.9 to 3.1 eV by increasing the Ga3+ concentration. Without any co-catalyst, ZnFe2O4 shows poor catalytic activity (378μmolh−1g−1) for photocatalytic hydrogen evolution from water. Whereas its activity enhances with loading of co-catalyst and touches a maximum activity of 3089μmolh−1g−1 with loading 1 wt% of Pt. The catalytic activity increases systematically with increasing Ga concentration in the solid solutions and reaches to 3989μmolh−1g−1 for ZnGa2O4 nanomaterials. Electrochemical impedance spectroscopic and transient photocurrent measurements also support the observed increasing trend. The lower catalytic activity of ZnFe2O4 has been attributed to the faster e-h recombination due to lower band gap and inherent oxygen vacancies. A smaller amount of oxygen vacancies and segregated ZnO phase observed in Ga substituted ZnFe2O4 samples favor the e-h pair separation and that facilitate the hydrogen generation from water.

Asymmetric Co-unit Inclusion in Statistical Copolyesters

The biodegradation of isodimorphic random butanediol-succinate/adipate copolymers (PBSAs) can be affected by a change in the semicrystalline morphology. A crucial point for the final semicrystalline structure is the incorporation of monomers of the minority component into the crystals of the majority component. We use proton time-domain NMR and wide-angle X-ray scattering to characterize the copolymers across their complete composition range and analyze the possible inclusion of minority comonomers in the PBA-rich 20/80 and the PBS-rich 60/40 composition by applying different solid-state 13C NMR experiments. For the PBA-rich copolymers, we find a nearly constant volumetric crystallinity of 50% up to the 50/50 composition combined with an increase of the crystalline lamella thickness. NMR has detected the BS units incorporated into the BA crystalline structure, where on average every tenth monomer is a BS comonomer. In PBS-rich crystals, the crystallinity and crystallite thickness decrease from neat PBS to PBSA 60/40 by 37% and ∼20%, respectively. We also find evidence that the BA units are excluded from the bulk crystal but accumulate at the crystallite surface. The amount of BA units in these pocket-like structures can be estimated to be 7–9% of the BA comonomer content.