Entire Composition Range Research Articles

Viscosity measurement and correlation for dense fluid mixture of carbon dioxide and ethanol at 313–343 K and 15–30 MPa

The viscosity ηm of dense fluid mixtures of carbon dioxide and ethanol was determined from the pressure drop between the inlet and outlet of a packed bed using the Ergun equation at temperatures from 313.2 K to 343.2 K and pressures from 15 MPa to 30 MPa over the entire range of ethanol composition. The ηm values for the fluid mixtures decreased with increasing temperature and increased with increasing pressure under isocratic conditions. In addition, the values measured ηm with Ergun eq. were correlated with the equation combining the Eyring theory and the perturbed chain statistical associating fluid theory equation of state (PC-SAFT EoS) and with that based on the rough hard-sphere (RHS) model proposed by Dymond and Assael. The accuracies of the Eyring + PC-SAFT EoS and the RHS model were 8.7% and 12%, respectively, in terms of average relative deviation for 80 conditions over the entire range of ethanol composition.

Volumetric properties of three nonylphenol ethoxylated nonionic surfactant mixtures with methanol: Experimental study and modeling with Tammann-Tait and PC-SAFT equation of state

Although physicochemical properties are essential for production and equipment design in oil and gas industries, there is still a lack of data for some systems because of hazardous temperature and pressure conditions. This work provides a volumetric behavior study of three different mixtures composed of nonylphenol ethoxylated nonionic surfactant (IGEPAL CO-520, CO-630, and CO-720) + methanol in the entire mole fraction composition range for temperatures from 313.15 K to 413.15 K and pressures up to 100.0 MPa. These systems behave as a regular liquid, with a volume contraction predominance. It was observed that for high methanol molar content, there is an increase in the cohesive forces because of the ethoxylated chain increases in oxyethylene units. Nevertheless, it was observed that the hydrogen bonds between ether oxygens and hydroxyl hydrogens decrease by increasing temperature, as given by internal pressure data and PC-SAFT modeling. Besides, a new set of parameters for the PC-SAFT equation of state is provided to calculate volumetric and second-order derivative properties.

Complete miscibility of immiscible elements at the nanometre scale.

Understanding the mixing behaviour of elements in a multielement material is important to control its structure and property. When the size of a multielement material is decreased to the nanoscale, the miscibility of elements in the nanomaterial often changes from its bulk counterpart. However, there is a lack of comprehensive and quantitative experimental insight into this process. Here we explored how the miscibility of Au and Rh evolves in nanoparticles of sizes varying from 4 to 1 nm and composition changing from 15% Au to 85% Au. We found that the two immiscible elements exhibit a phase-separation-to-alloy transition in nanoparticles with decreased size and become completely miscible in sub-2 nm particles across the entire compositional range. Quantitative electron microscopy analysis and theoretical calculations were used to show that the observed immiscibility-to-miscibility transition is dictated by particle size, composition and possible surface adsorbates present under the synthesis conditions.

Elastic Properties of Alloyed Cementite M3X (M = Fe, Cr; X = C, B) Phases from First-Principle Calculations and CALPHAD Model.

Fe-Cr-C-B wear-resistant steels are widely used as wear-resistant alloys in harsh environments. The M3X (M = Fe, Cr; X = C, B) cementite-type material is a commonly used strengthening phase in these alloys. This study investigated the mechanical properties of cementite (Fe, Cr)3(C, B) using the first-principle density functional theory. We constructed crystal structures of (Fe, Cr)3(C, B) with different concentrations of Cr and B. The bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and hardness of the material were calculated, and a comprehensive mechanical property database based on CALPHAD modeling of the full composition was established. The optimal concentrations of the (Fe, Cr)3(C, B) phase were systematically evaluated across its entire composition range. The material exhibited the highest hardness, shear modulus, and Young's modulus at Cr and B concentrations in the range of 70-95 at% and 40 at%, respectively, rendering it difficult to compress and relatively poor in machinability. When the B content exceeded 90 at%, and the Cr content was zero, the shear modulus and hardness were low, resulting in poor resistance to deformation, reduced stiffness, and ease of plastic processing. This study provides an effective alloying strategy for balancing the brittleness and toughness of (Fe, Cr)3(C, B) phases.

Composition-dependent brittleness and ductility of the multicomponent phase (Fe, Cr)23(C, B)6 in Fe–Cr–B–C alloys: First-principles calculations and modeling

(Fe, Cr)23(C, B)6, as a strengthening phase in Fe–Cr–B–C alloys, has not been reported on the relationship between its properties and composition over the entire composition range. (Fe, Cr)23(C, B)6 tends to exhibit brittleness, which is difficult to regulate through traditional experiments. The mechanical properties of (Fe, Cr)23(C, B)6 phase in Fe–Cr–B–C alloy have been studied by first principles calculation. With the help of CALPHAD method, the distribution of elastic constant, modulus, hardness and fracture toughness in the whole component space was obtained, so that the suitable component with good wear resistance and strong toughness was obtained. The mechanical properties of (Fe, Cr)23(C, B)6 phase is better in the range of ∼0.4–0.6 at. % B and ∼0.5–0.7 at. % Cr. The mechanism of these differences is explained in terms of state density, bond length, population analysis and differential charge density, as the addition of boron and the increase in chromium content led to a significant increase in the formation of covalent bonds between metals and non-metals, in which these bonds play a decisive role. The combination of the first principles calculation and the CALPHAD model provides a feasible model for constructing the composition-property relationship of medium entropy compounds.

Quantifying free energies through local composition fluctuations in binary solid solutions: A proof-of-concept study using atomistic embedded-atom simulations

While thermodynamic fluctuation theory has been extensively utilized in liquids for decades to obtain direct thermodynamic information, such as Gibbs free energies, from local composition fluctuations, this study presents an extension of the theory for its application in solids. It is demonstrated that composition fluctuations in solids are influenced by an additional elastic work term, which is specific to solids and encompasses liquids as a special case. To verify the extended fluctuation model, atomistic simulations were conducted on an exemplary Cu–Ni embedded-atom system. Monte Carlo simulations were performed in the semi-grandcanonical ensemble at a fixed temperature, covering the entire composition range. Composition fluctuations within a subvolume were monitored over time and statistically analyzed in terms of the variance. The atomistic results exhibit perfect agreement with the predictions derived from the extended model. This methodology has primarily been developed for the analysis of experimental atom probe tomography data, which provides three-dimensional chemical information with sub-nanometer precision. This technique enables the direct measurement of local composition fluctuations, facilitating the extraction of thermodynamic information from any allowed temperature–composition pair in the phase diagram.

Polarity of Organic Solvent/Water Mixtures Measured with Reichardt’s B30 and Related Solvatochromic Probes—A Critical Review

The UV/Vis absorption energies (νmax) of different solvatochromic probes measured in co-solvent/water mixtures are re-analyzed as a function of the average molar concentration (Nav) of the solvent composition compared to the use of the mole fraction. The empirical ET(30) parameter of Reichardt’s dye B30 is the focus of the analysis. The Marcus classification of aqueous solvent mixtures is a useful guide for co-solvent selection. Methanol, ethanol, 1,2-ethanediol, 2-propanol, 2-methyl-2-propanol, 2-butoxyethanol, formamide, N-methylformamide (NMF), N,N-dimethylformamide (DMF), N-formylmorpholine (NFM), 1,4-dioxane and DMSO were considered as co-solvents. The ET(30) values of the binary solvent mixtures are discussed in relation to the physical properties of the co-solvent/water mixtures in terms of quantitative composition, refractive index, thermodynamics of the mixture and the non-uniformity of the mixture. Significant linear dependencies of ET(30) as a function of Nav can be demonstrated for formamide/water, 1,2-ethanediol/water, NMF/water and DMSO/water mixtures over the entire compositional range. These mixtures belong to the group of solvents that do not enhance the water structure according to the Marcus classification. The influence of the solvent microstructure on the non-linearity ET(30) as a function of Nav is particularly clear for alcohol/water mixtures with an enhanced water structure.

Confocal μ-XANES as a tool to analyze Fe oxidation state in heterogeneous samples: the case of melt inclusions in olivine from the Hekla volcano

Abstract. Here we present a confocal Fe K-edge μ-XANES method (where XANES stands for X-ray absorption near-edge spectroscopy) for the analysis of Fe oxidation state in heterogeneous and one-side-polished samples. The new technique allows for an analysis of small volumes with high spatial 3D resolution of <100 µm3. The probed volume is restricted to that just beneath the surface of the exposed object. This protocol avoids contamination of the signal by the host material and minimizes self-absorption effects. This technique has been tested on a set of experimental glasses with a wide range of Fe3+ / ΣFe ratios. The method was applied to the analysis of natural melt inclusions trapped in forsteritic to fayalitic olivine crystals of the Hekla volcano, Iceland. Our measurements reveal changes in Fe3+ / ΣFe from 0.17 in basaltic up to 0.45 in dacitic melts, whereas the magnetite–ilmenite equilibrium shows redox conditions with Fe3+ / ΣFe ≤0.20 (close to FMQ, fayalite–magnetite–quartz redox equilibrium) along the entire range of Hekla melt compositions. This discrepancy indicates that the oxidized nature of glasses in the melt inclusions could be related to the post-entrapment process of diffusive hydrogen loss from inclusions and associated oxidation of Fe in the melt. The Fe3+ / ΣFe ratio in silicic melts is particularly susceptible to this process due to their low FeO content, and it should be critically evaluated before petrological interpretation.

Contribution to the Ti–Co–Sn system

The ternary phase diagram Ti–Co–Sn was studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Isothermal sections at 1000 and 1200 °C have been determined experimentally for the first time in the entire range of compositions. Thirteen and ten three-phase regions were found at 1000 °C and 1200 °C, respectively. Vertical sections at 10, 20 and 30 at.% Sn were plotted. The most striking feature of the ternary Ti–Co–Sn phase diagram is formation of a ternary compound TiCo2Sn (Heusler phase, τ), which was found at both investigated temperatures. The TiCoSn compound (half-Heusler phase) was not found. Among binary compounds, Ti5Sn3 and TiCo have the widest homogeneity regions. The Ti5Sn3 phase dissolves 10.0 and 9.8 at.% Co at 1200 and 1000 °C, respectively, forming an interstitial solid solution. The solubility of Sn in TiCo is more than 10 at.% at both 1200 and 1000 °C. The remaining binary intermetallic phases hardly dissolved the third component. The liquid phase at 1000 °C mainly exists in the Sn-rich corner, while at 1200 °C it stretches along Co–Sn side spreading from the Sn corner and is also present on the Ti-rich side. In addition, two four-phase invariant transition type reactions TiCo2 (h) + (αCo) ⇄ τ + TiCo3 and TiCo + TiCo2 (h) ⇄ τ + TiCo2 (c) were deduced.

New insight into defect energy levels in HgCdTe

The paper reports on a summary of the experimental data on the defect energy levels in HgCdTe, that have been collected in our experiments and from articles available over several decades. We have determined the location of the defect levels in HgCdTe for material composition from 0.17 to 0.6. It has been shown that that all specified trap levels are tied to the valence band and do not change (or change slightly) with temperature, and have the slopes with respect to the Cd molar content somewhat smaller than the HgCdTe energy gap.Two levels are formed by mercury vacancies – the first defect level is a shallow acceptor formed by neutral vacancy, the second deep level can be formed by singly negatively charged Hg vacancy. Contrary to earlier assumptions, it does not lie in the middle of the energy gap for the entire range of molar composition, but it is an acceptor-like for the wide-gap HgCdTe and a donor-like for the narrow gap, and may even be located in the conduction band forming a resonant state. Above this main defect level, two additional trap states can be found, most likely formed by oxygen atoms replacing Hg vacancies – positively charged and the neutral oxygen states.

Flash point and safety evaluation of binary mixture of diphenyl ether + biphenyl: A commonly utilized heat transfer fluid

The binary mixture of diphenyl ether and biphenyl finds wide applications in various industries. Notably, it is widely utilized in renewable energy systems such as concentrated solar power (CSP) facilities. This study addresses the lack of research on the flash point (FP) behavior of this blend, crucial due to high operating temperatures in related processes, especially when used as a heat transfer fluid. This study fills the research gap by analyzing the entire composition range, using experimental measurements, and a unique mathematical method based on SLE data; unlike the conventional method that relies on VLE data. The FP prediction results demonstrated satisfactory outcomes when compared to the experimental data. The findings of this study can be employed to mitigate the fire and explosion risks associated with processes using the binary mixture of diphenyl ether + biphenyl.

Investigations on the thermo physical properties of the binary mixtures of 2-methyl-pentanediol-2,4 with n-alkanols at various temperatures (hexylene glycol with 1-octanol, 1-nonanol, 1-decanol)

ABSTRACT Densities (ρ), speeds of sound (u) and viscosities (η) for three binary mixtures of hexylene glycol (2-methyl-2,4-pentanediol or MPD) with 1-octanol (D1), 1-nonanol (D2) and 1-decanol (D3) are calculated at temperatures ranging from 303.15 to 313.15 K and atmospheric pressure over the entire composition range. Experimental measurements are used to calculate the excess molar volume, excess isentropic compressibility, deviation in viscosity and excess Gibbs-free energy of activation of viscous flow. Partial molar properties and infinite dilution molar partial properties are also calculated for each binary system. The results obtained can be discussed in terms of weaker interactions and dispersion forces with the absence of specific intermolecular interactions in binary mixtures. Finally, the Prigogine-Flory-Patterson (PFP) theory is applied to identify the most predominant molecular interaction. Jouyban-Acree model results are discussed in terms of mean relative deviation (MRDs) and individual relative deviation (IRD) between calculated and experimental densities, speeds of sound and viscosities as an accuracy criterion.

Al-rich AlGaN Alloys: Unique Materials for Deep UV LEDs

Energy bandgap of AlxGa1−xN alloys can be tuned systematically from ∼ 3.4 to 6.1 eV by changing the alloy composition (x) from 0 to 1 and the direct bandgap nature is maintained in the entire range of alloy compositions which make the AlGaN alloys suitable materials for the development of light emitting diodes (LEDs) covering the ultraviolet (UV) spectral region from 210 to 400 nm. For LEDs in the deep UV regions (λ < 300 nm), Al-rich AlGaN alloys of Al content higher than 50% are required. Deep UV LEDs have applications in a wide range of fields including display, disinfection, medical, sensing, and communication. With recent progress in the material growth and electrical conductivity, Al-rich AlGaN alloys have emerged as unique wideband gap materials for the development of deep UV LEDs. In this review article, how the progress of Al-rich AlGaN alloys has made in terms of the material growth and electrical conductivity leading its emergence as deep UV materials have been reviewed. Challenges and prospects of the deep UV LEDs to improve the performance of the devices will also be discussed.

Densities, viscosities, and refractive indices of binary mixtures of tri-n-butyl phosphate with propan-2-ol and butan-2-ol at 303.15, 308.15, 313.15, 318.15, and 323.15 K

Densities, viscosities, and refractive indices of binary liquid mixtures of tri-n-butyl phosphate (TBP) with propan-2-ol and butan-2-ol at different temperatures between 303.15 and 323.15 K at an interval of 5 K and across the entire range of composition were measured. The data were used to calculate derived properties, such as excess molar volumes, excess thermal expansivities, deviations in viscosities, excess free energies of activation for viscous flow, and deviations in refractive index. The variation patterns of these properties concerning composition and temperature for the propan-2-ol + and butan-2-ol + TBP systems were discussed and attributed to probable intermolecular hydrogen bonding and geometric effects. Notably, the influence of hydrogen bonding was substantial, as evidenced by trends in excess molar volumes and deviations in viscosities. Concentration-dependent polynomial equations were used to fit the measured data of density, viscosity, and refractive index, while Redlich-Kister-type equations were applied for the excess properties. The densities and viscosities were correlated using the Jouyban-Acree model. The correlating abilities of various models, such as Grunberg-Nissan, Tamura-Kurata, Heric, Ausländer, McAllister-3, and McAllister-4 body models, were also evaluated using the viscosity data. Additionally, six new pairs of UNIFAC-VISCO group interaction parameters were computed to predict viscosities of TBP in systems involving alkanes, aromatics, and alcohols, extending the application range of the group contribution model.

Controlling the Charge Density Wave Transition in Single-Layer TiTe2xSe2(1-x) Alloys by Band Gap Engineering.

Closing the band gap of a semiconductor into a semimetallic state gives a powerful potential route to tune the electronic energy gains that drive collective phases like charge density waves (CDWs) and excitonic insulator states. We explore this approach for the controversial CDW material monolayer (ML) TiSe2 by engineering its narrow band gap to the semimetallic limit of ML-TiTe2. Using molecular beam epitaxy, we demonstrate the growth of ML-TiTe2xSe2(1-x) alloys across the entire compositional range and unveil how the (2 × 2) CDW instability evolves through the normal state semiconductor-semimetal transition via in situ angle-resolved photoemission spectroscopy. Through model electronic structure calculations, we identify how this tunes the relative strength of excitonic and Peierls-like coupling, demonstrating band gap engineering as a powerful method for controlling the microscopic mechanisms underpinning the formation of collective states in two-dimensional materials.

Accuracy, Performance, and Transferability of Interparticle Potentials for Al–Cu Alloys: Comparison of Embedded Atom and Deep Machine Learning Models

In several recent years, a significant progress has been made in atomistic simulation of materials, involving the application of machine learning methods to constructing classical interatomic interaction potentials. These potentials are many-body functions with a large number of variable parameters whose values are optimized with the use of energies and forces calculated for various atomic configurations by ab initio methods. In the present paper a machine learning potential is developed on the basis of deep neural networks (DP) for Al–Cu alloys, and the accuracy and performance of this potential is compared with the embedded atom potential. The analysis of the results obtained implies that the DP provides a sufficiently high accuracy of calculation of the structural, thermodynamic, and transport properties of Al–Cu alloys in both solid and liquid states over the entire range of compositions and a wide temperature interval. The accuracy of the embedded atom model (EAM) in calculating the same properties is noticeably lower on the whole. It is demonstrated that the application of the potentials based on neural networks to the simulation on modern graphic processors allows one to reach a computational efficiency on the same order of magnitude as those of the embedded atom calculations, which at least four orders of magnitude higher than the computational efficiency of ab initio calculations. The most important result is that about the possibility of application of DP parameterized with the use of configurations corresponding to melts and perfect crystals to the simulation of structural defects in crystals and interphase surfaces.

Molecular interactions between 2-methyltetrahydrofuran and alcohols: A combination of thermodynamic, spectroscopic and quantum chemistry studies

New data of density (ρ), viscosity (η), and speed of sound (u) have been determined at T = (288.15–303.15 K) and p = 93.2 kPa for the binary mixture of {2-methyltetrahydrofuran + ethanol, or + 1-propanol, or + 1-butanol, or + 1-pentanol} over the entire composition range. These results were used to calculate the excess molar volume (VmE), isentropic compressibility deviation (Δκs), viscosity deviation (Δη), and Gibbs excess activation energy (ΔG*E), which were correlated by a Redlich-Kister polynomial. For all systems studied, the values ​​of the deviation properties were negative, which probably indicates a predominance of structural and chemical effects over physical effects. Five viscosity models were employed to fit the viscosity data. The VmE data were also correlated by the Prigogine-Flory-Patterson Theory (PFP Theory) and the Peng-Robinson-Stryjek-Vera Equation of State (PRSV EOS). Furthermore, a Fourier Transform Infrared (FT-IR) spectroscopy study was performed to explain the hydrogen bonding interactions. Lastly, theoretical calculations using Density Functional Theory (DFT) at B3LYP-GD3(BJ)/6–311++G(3df,2p) level of theory were performed to understand the inter-interactions between the compounds present in the mixtures. The FT-IR and computational results were in good agreement with the experimental data.

Miscibility and crystallization behavior of Poly(butylene terephthalate)/Poly(ethylene terephthalate-co-1,4-cyclohexylene dimethylene terephthalate) blends

The miscibility and crystallization behavior of a series of polymer blends containing different content of poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate-co-1,4-cyclohexylene dimethylene terephthalate) (P(ET/CT)) have been studied. It is confirmed through DSC, SAXS and SEM that PBT is miscible with P(ET/CT) with different CT content. When the mole content of CT is 37 %, P(ET/CT) (abbreviated as P(ET/CT37 %)) is fully amorphous. But, as the mole ratio of CT is 66 %, P(ET/CT) (abbreviated as P(ET/CT66 %)) possesses crystallizability. Compared to the extremely fast crystallization of PBT, the crystallizability of P(ET/CT66 %) is so weak that non-isothermal crystallization (at a cooling rate of 10 °C/min) can hardly occur. Upon blending, however, it is interesting to find that the P(ET/CT66 %) could be involved in the crystallization of the blends within the entire composition range. In the DSC cooling curves, a double-peak crystallization could be observed, in which the Tc1 is attributed to the crystallization of PBT and the Tc2 to that of P(ET/CT66 %). Further, the two glass transition temperatures of the blends after crystallization confirm the occurrence of crystallization-induced phase separation at higher P(ET/CT) content. Therefore, the excluded P(ET/CT66 %) local domain or aggregation is regarded as the prerequisite of the P(ET/CT66 %) crystallization, and the previously formed PBT crystals act as its nucleating agent.

Volumetric and acoustic studies of binary mixtures of DEC with isomeric chlorobenzene at various temperatures

ABSTRACT Densities, ρ, and speeds of sound, u, of binary liquid mixtures of diethyl carbonate with 1,2-dichlorobenzene, 1,3-dichlorobenzene and 1,2,4-trichlorobenzene have been measured over the entire range of composition at 303.15 K, 308.15 K, 313.15 K and 318.15 K and at atmospheric pressure. From the experimental data of the density and speed of sound, the excess properties such as excess molar volume, V m E , excess isentropic compressibility, κ s E , excess molar isentropic compressibility, K s , m E , excess speed of sound, u E , and excess isobaric thermal expansion, α p E , have been calculated. For better knowledge of the solute and solvent interaction, excess partial molar volumes, V ˉ m , 1 E and V ˉ m , 2 E , and excess partial molar volumes, V ˉ m , 1 ∘ E and V ˉ m , 2 ∘ E of the components at infinite dilution have been measured. All the excess parameter values have been fitted using the Redlich–Kister polynomial smoothing equation. The calculated excess values have been analysed in terms of molecular interactions and structural effects.

Experimental and ab initio studies of the structural and optoelectronic properties of hexagonal wurtzite ZnO1-xSx alloys

The structural and optoelectronic properties of ZnO1-xSx alloys were investigated experimentally as well as theoretically. The ZnO1-xSx alloy thin films at different S concentrations (0.0 < x < 1.0) were deposited on quartz substrates by radiofrequency magnetron sputtering. The alloy composition was monitored with the help of optical emission spectroscopy. The ab initio density functional theory (DFT) based calculations were performed for the hexagonal wurtzite ZnO1-xSx system with the S compositions of x = 0.0, 0.0625, 0.125, 0.25, 0.5, 0.75, 0.875, 0.9375 and 1.0. The X-ray diffraction (XRD) and Raman spectroscopy measurements suggest the hexagonal wurtzite phase for the entire composition range. The films exhibit good crystalline quality with preferential growth along the c-axis. The linear change in the lattice parameter (c) was observed both from XRD analysis and DFT based calculations. The X-ray photoelectron spectroscopy confirms the anionic substitution of oxygen (O2−) and sulphur (S2−) in the hexagonal wurtzite lattice. Field emission scanning electron microscopy and atomic force microscopy were used to study the surface morphology. The optical properties were evaluated through transmittance spectroscopy and spectroscopic ellipsometry. The density of state calculations shows the forbidden region which confirms the semiconducting nature for all the alloy compositions. The energy band gap obtained from the respective Tauc's plots was found to vary from 2.9 to 3.6 eV with a bowing parameter of 3.2 eV. The same trend was observed in the calculated electronic band structures through DFT. The optical constants were evaluated from spectroscopic ellipsometry and the corresponding band gap values were compared with the values obtained from optical transmittance.