Construction Of Phase Diagram Research Articles

Magnetic phase diagram of (Mo2/3RE1/3)2AlC, RE = Tb and Dy, studied by magnetization, specific heat, and neutron diffraction analysis

We report the results of magnetization, heat capacity, and neutron diffraction measurements on (Mo2/3RE1/3)2AlC with RE = Dy and Tb. Temperature and field-dependent magnetization as well as heat capacity were measured on a powder sample and on a single crystal allowing the construction of the magnetic field-temperature phase diagram. To study the magnetic structure of each magnetic phase, we applied neutron diffraction in a magnetic field up to 6 T. For (Mo2/3Dy1/3)2AlC in zero field, a spin density wave is stabilized at 16 K, with antiferromagnetic ordering at 13 K. Furthermore, we identify the coexistence of ferromagnetic and antiferromagnetic phases induced by magnetic fields for both RE = Tb and Dy. The origin of the field induced phases is resulting from the competing ferromagnetic and antiferromagnetic interactions.

Pore Dynamics of Lipid Vesicles Under Light-Induced Osmotic Stress

Understanding the physical mechanisms governing the response of lipid vesicles under an osmotic imbalance is crucial not only for advancing our knowledge of osmoregulation in living cells but also for guiding the design of biomedical vesicular systems. When placed under osmotic stress, lipid vesicles exhibit a variety of responses, from simple engorgement, to swelling with eventual pore formation, to the only recently observed irreversible explosion triggered by photoreactions. Here, we present a unifying model that incorporates all of these dynamic responses by elucidating the associated energy landscape of vesicle outcomes. We demonstrate the essential, yet previously unrecognized, role of the spontaneous curvature in determining vesicle responses under extreme osmotic stress. We utilize numerical experiments to construct phase diagrams of pore dynamics, which are consistent with the experimental observations, and we further discuss the impacts of compositional lipid properties. Our work not only advances a fundamental understanding of vesicle response in nonequilibrium environments, but also extends the possibility for precise design of vesicle systems regarding controlled release of therapeutic substances in biomedical applications.

Room-temperature tuning of magnetic anisotropy in samarium-thulium orthoferrites

Rare-earth orthoferrites $(R{\mathrm{FeO}}_{3})$ provide a flexible playground for magnetic materials design, combining the magnetic properties arising from complex interactions between ${R}^{3+}$ and ${\mathrm{Fe}}^{3+}$ cations within the robust framework of the perovskite structure. The most important magnetic property common to most orthoferrites is a spin reorientation transition in which the magnetic moments of ${\mathrm{Fe}}^{3+}$ cations rotate with respect to a crystallographic axis. ${\mathrm{SmFeO}}_{3}$ is unique among orthoferrites due to its high-temperature spin reorientation. It is possible to tune the spin reorientation transition to occur at room temperature by replacing Sm with Tm in the ${\mathrm{Sm}}_{0.70}{\mathrm{Tm}}_{0.30}{\mathrm{FeO}}_{3}$ perovskite. In this study, we show how small changes in composition in the ${\mathrm{Sm}}_{1\ensuremath{-}x}{\mathrm{Tm}}_{x}\mathrm{Fe}{\mathrm{O}}_{3}$ $(x=0.30\text{--}0.50)$ series provide a high degree of control over the magnetic properties. This work also offers a rather unusual look into the magnetic structure of a samarium-based perovskite by means of neutron powder diffraction, which was made possible by using $^{152}\mathrm{Sm}$. The combination of these results and magnetization measurements allowed the construction of the magnetic phase diagram of the series.

Thermal storage performances of the quaternary ammonium tetrachlorocuprate [1-CnH2n+1N(CH3)3]2CuCl4 (n = 16, 18) multiphase state as high efficient phase change materials (PCMs)

Traditional solid-solid phase change materials (PCMs) have fixed transition temperature due to their composition and structure determination, which impede their practical application in the field of thermal storage. In this work, according to the second law of thermodynamics and the phase equilibrium theory, PCMs can be further improved through form mixtures (molecular alloy) to regulate phase transition temperature and enthalpy for thermal energy storage. Herein, the binary molecular alloy of quaternary ammonium tetrachlorocuprate [1-CnH2n+1N(CH3)3]2CuCl4 (n = 16, C16C3Cu; n=18, C18C3Cu) as solid-solid PCMs were characterized over the entire composition range by DSC and XRD, and were further constructed phase diagram. Thus, a series of multiphase state materials of C16C3Cu-C18C3Cu, such as solid solutions (α, β, γ), intermediate compound ([1-C16H33N(CH3)3][1-C18H37N(CH3)3]CuCl4), and eutectoid compounds (α + γ, β + γ), could be selected from phase diagram to apply as PCMs with solid-solid phase transition temperature in the interval of 49 to 75 °C and enthalpy in the interval of 2.11 to 106.3 J•g−1, so as to extend the thermal performance of [1-CnH2n+1N(CH3)3]2CuCl4 as PCMs to adapt to thermal storage applications under different conditions.

Modeling of Phase Coexistence via Thermodynamic Potentials

Thermodynamic potentials can be used to study various phase phenomena. In particular, they can be used to determine the phase coexistence of a liquid and vapor for a simple van der Waals fluid, which relates the interactions and size of particles (molecules/atoms) represented by spheres as simple constants a and b, respectively. Phase coexistence at a given temperature for a simple fluid is determined using Newton’s method, thermodynamic potentials, and the conditions of phase coexistence. From this information, we are able to construct a phase diagram of the vapor and liquid densities versus the temperature. The constructed phase diagram shows how the simple van der Waals fluid predicts the occurrence of a critical point (point at which the fluid is no longer simply characterized as a gas or liquid but rather a liquid and gaseous fluid or critical fluid) as opposed to the ideal gas law. This phase diagram can then be further used to study homogeneous (a pure solution or solution containing a single molecule/atoms) and inhomogeneous (mixture or solution containing multiple molecules/atoms or a substrate/wall) nucleation by classical density functional theory in statistical mechanics.

Efficient construction of phase diagram by machine learning

Efficient construction of phase diagram by machine learning

Phase stabilities and equilibria of the Ti-Al-Nb ternary system at intermediate temperatures I. The 900 °C isothermal section

Determination of intermediate temperature phase diagrams is a challenging task due to sluggish transformation kinetics, metastable phases and low diffusion coefficients encountered under these conditions. The development of Ti-Al-Nb alloys has been hampered by scarcity of intermediate temperature phase diagrams. Through guidance from diffusion simulation results, we designed the composition of the diffusion components in a diffusion multiple capable of efficiently and accurately testing the Ti-Al-Nb ternary phase diagrams at intermediate temperatures, which is the service temperature of Ti-Al-Nb alloys. We systematically characterized the diffusion multiples using scanning electron microscopy (SEM), electron probe microanalysis (EPMA), electron backscatter diffraction (EBSD), transmission kikuchi diffraction (TKD) and transmission electron microscope (TEM), and constructed the whole composition range of the 900 °C isothermal section. The constructed range includes ten stable phases, nineteen two-phase regions and ten three-phase regions. Two ternary phases (O-Ti2AlNb and ωo-Ti4Al3Nb phases) were determined and the ωo phase was defined on the experimental phase diagram for the first time. The previous thermodynamic database at 900 °C is unreliable, based on the present work. The present experimental results will bridge the existing research gap by providing the missing thermodynamic data. The present diffusion multiple is expected to construct more isothermal sections of Ti-Al-Nb ternary system at intermediate temperatures in the future. The constructed phase diagrams are also invaluable tools to researchers and industry for development of Ti-Al-Nb alloys.

Phase stability of SrZnxFe(2−x)Fe16O27 (0.0 ≤ x ≤ 1.0) in low oxygen pressures

The phase stability of Zn-substituted strontium W-type hexaferrites (SrZnxFe(2-x)Fe16O27; SrZnxFe(2-x)W) in the low oxygen pressure (PO2) of 10−3 atm, and strontium W-type hexaferrite (SrFe18O27; SrW) in the PO2 region of 10−3–10−2 atm were systemically investigated. For this study, polycrystalline samples were sintered at high temperatures in low PO2 and then furnace-cooled. Analyses of the phases and microstructures of sintered samples revealed that the SrZnxFe(2-x)W phases are thermodynamically stable at the temperature regions of 1245–1320 °C, 1210–1285 °C, and 1190–1255 °C, for x = 0.0, 0.5, and 1.0, respectively in the PO2 of 10−3 atm. In addition, the SrW phase was found to be stable at the temperature region between 1245 and 1320 °C, and 1275 and 1380 °C in the PO2 of 10−3 and 10−2 atm, respectively, which enabled the construction of stability phase diagram of SrW on the PO2 versus 10 000/T (K) plot in the PO2 region of 10−3 to 0.21 atm.

Levofloxacin loaded clove essential oil nanoscale emulsion as an efficient system against Pseudomonas aeruginosa biofilm

Biofilm formation by bacteria has become one of the major reasons for escalation of antimicrobial resistance. The present research focused on the development, optimization and evaluation of antibiofilm potential of clove oil nanoscale emulsion (o/w) loaded with levofloxacin (LFX-NE) against Pseudomonas aeruginosa biofilm. The optimized NE was selected through the construction of pseudo-ternary phase diagrams and was found to be stable. The particle size and drug content of LFX-NE was found to be 18.84 ± 0.5 nm and 99.2 ± 0.5%, respectively. It demonstrated high antibacterial activity with 16-fold and 8-fold reduction in MIC of LFX against P. aeruginosa and Escherichia coli and Klebsiella pneumoniae, respectively. LFX-NE was able to eradicate pre-formed biofilm of P. aeruginosa as evidenced by field emission scanning electron microscopy and confocal laser scanning microscopy. Antiquorum sensing study revealed inhibition of quorum sensing activity. LFX-NE was found to be non-irritant and cytocompatible as confirmed by HET-CAM test and safety study in normal human epidermal keratinocytes (NHEK) cell line. This study demonstrates the potential of LFX-NE in possible treatment of non-healing wounds inflicted with bacterial biofilm.

Experimental Determination of Phase Equilibria in the Na2O-SiO2-WO3 System

The present study investigated phase equilibria in the Na2O-SiO2-WO3 system experimentally using high-temperature equilibration, quenching, and electron probe X-ray microanalysis (EPMA). New thermodynamic information on the Na2O-SiO2-WO3 system was derived based on the newly obtained experimental results and data from the literature. The primary phase fields of sodium metasilicate, sodium disilicate, and tridymite were determined along with the isotherms at 1073, 1173, and 1273 K. The solubilities of WO3 in SiO2, Na2Si2O5, and Na2SiO3, and the solubility of SiO2 in Na2WO4 were accurately measured using EPMA. Comparisons between the existing and newly constructed phase diagram were carried out and the differences are discussed. The phase equilibrium data will be beneficial to the future development of sustainable tungsten industries and thermodynamic modelling in WO3 related systems.

Liquid-liquid equilibrium data for the ternary system based on ionic liquid + organic solvents + water at 298 K and atmospheric pressure applied in antidepressant partitioning

Antidepressants are drugs widely used in nervous disorders, such as anxiety, depression, and panic, and are eliminated through the urinary system. In bodies of water, they present high persistence and toxicity, even at low concentrations, conforming to the classification of emerging micropollutants. This work addresses the construction of phase diagrams for different biphasic systems, based on ionic liquids (ILs) and organic solvents, and their subsequent application in the partitioning of antidepressants such as fluoxetine hydrochloride, paroxetine hydrochloride and sertraline hydrochloride. The phase diagrams were measured gravimetrically at 298.15 ± 1.00 K and atmospheric pressure using the turbidity method. The ILs of the imidazolium family, with shorter chain length [C2mim]+, were the only ones able to form biphasic systems using 1,3-dioxolane. The driving force for phase separation is the comparison of hydrophobic/hydrophilic characteristics between the constituents. In this sense, the pair of constituents [C2min][OAc] and 1,3-dioxolane provided the phase diagram with the largest biphasic area. The partitioning of antidepressants was studied in systems formed by IL (25 wt%) + 1,3-dioxolane (50 wt%) + water (25 wt%) containing 1.05 µg·L−1 of fluoxetine hydrochloride, 1.42 µg·L−1 of paroxetine hydrochloride or 0.23 µg·L−1 sertraline hydrochloride at 298.15 ± 1.00 K and atmospheric pressure. The partitioning followed the characteristics of antidepressant σ-profiles generated through COSMO-RS. The recoveries were high, and the proposed systems were shown to promote the selective isolation of pairs of these antidepressants.

Hydrogel composite containing azelaic acid and tea tree essential oil as a therapeutic strategy for Propionibacterium and testosterone-induced acne

Azelaic acid (AzA) is a USFDA bioactive prescribed against acne vulgaris. It possesses delivery challenges like poor aqueous solubility, low skin-penetrability, and dose-dependent side effects, which could be overcome by its synergistic combination with tea tree oil (TTO) as a microemulsion (ME)-based hydrogel composite. AzA-TTO ME was prepared to employ pseudo-ternary phase diagram construction. The best AzA-TTO ME was of uniform size (polydispersity index < 0.7), nano-range (~357.4 ± 2% nm), transmittance (> 90%), and negative zeta potential (−1.42 ± 0.25% mV) values. ME hydrogel composite with optimum rheological and textural attributes showed better permeation, retention, and skin-compliant characteristics, vis-a-vis marketed formulation (Aziderm™) when evaluated in Wistar rat skin. In vitro antibacterial efficacy in bacterial strains, i.e., Staphylococcus aureus, Propionibacterium acne, and Staphylococcus epidermidis, was evaluated employing agar well plate diffusion and broth dilution assay. ME hydrogel has shown an increase in zone of inhibition by two folds and a decrease in minimum inhibitory concentration (MIC) by eightfold against P. acnes vis-a-vis AzA. Finally, ME hydrogel composite exhibited a better reduction in the papule density (93.75 ± 1.64%) in comparison to Aziderm™ 72.69 ± 4.67%) on acne as developed in rats by inducing testosterone. Thus, the developed AzA-TTO ME hydrogel composite promises an efficacious and comparatively safer drug delivery system for the topical therapy of acne vulgaris.Graphical abstract

Vesicle dynamics in large amplitude oscillatory extensional flow

Although the behaviour of fluid-filled vesicles in steady flows has been extensively studied, far less is understood regarding the shape dynamics of vesicles in time-dependent oscillatory flows. Here, we investigate the nonlinear dynamics of vesicles in large amplitude oscillatory extensional (LAOE) flows using both experiments and boundary integral (BI) simulations. Our results characterize the transient membrane deformations, dynamical regimes and stress response of vesicles in LAOE in terms of reduced volume (vesicle asphericity), capillary number ( ${Ca}$ , dimensionless flow strength) and Deborah number ( ${De}$ , dimensionless flow frequency). Results from single vesicle experiments are found to be in good agreement with BI simulations across a wide range of parameters. Our results reveal three distinct dynamical regimes based on vesicle deformation: pulsating, reorienting and symmetrical regimes. We construct phase diagrams characterizing the transition of vesicle shapes between pulsating, reorienting and symmetrical regimes within the two-dimensional Pipkin space defined by ${De}$ and ${Ca}$ . Contrary to observations on clean Newtonian droplets, vesicles do not reach a maximum length twice per strain rate cycle in the reorienting and pulsating regimes. The distinct dynamics observed in each regime result from a competition between the flow frequency, flow time scale and membrane deformation time scale. By calculating the particle stresslet, we quantify the nonlinear relationship between average vesicle stress and strain rate. Additionally, we present results on tubular vesicles that undergo shape transformation over several strain cycles. Broadly, our work provides new information regarding the transient dynamics of vesicles in time-dependent flows that directly informs bulk suspension rheology.

Acceleration of phase diagram construction by machine learning incorporating Gibbs' phase rule

To efficiently construct phase diagrams of alloy systems, a machine learning-based method advanced by thermodynamics on phase equilibria is proposed. With the use of uncertainty sampling in active learning, the next point to be synthesized or measured can be recommended to efficiently draw the phase diagram. For appropriate recommendations, two ingenuities are introduced in the machine learning method: training data preparation when the multiphase coexisting region is detected and search space reduction based on the Gibbs’ phase rule. We demonstrate the construction of ternary phase diagrams using our machine learning method by incorporating these ingenuities. The complicated phase diagram of alloy systems could be effectively plotted even when knowing only the information of single-component systems in the initial step. The recommendation made by our machine learning method can help reduce the number of experiments required to construct a phase diagram to approximately 1/8 compared with random sampling.

Surface anchoring as a control parameter for shaping skyrmion or toron properties in thin layers of chiral nematic liquid crystals and noncentrosymmetric magnets.

Existence of topological localized states (skyrmions and torons) and the mechanism of their condensation into modulated states are the ruling principles of condensed matter systems, such as chiral nematic liquid crystals (CLCs) and chiral magnets (ChM). In bulk helimagnets, skyrmions are rendered into thermodynamically stable hexagonal skyrmion lattice due to the combined effect of a magnetic field and, e.g., small anisotropic contributions. In thin glass cells of CLCs, skyrmions are formed in response to the geometrical frustration and field coupling effects. By numerical modeling, I undertake a systematic study of skyrmion or toron properties in thin layers of CLCs and ChMs with competing surface-induced and bulk anisotropies. The conical phase with a variable polar angle serves as a suitable background, which shapes skyrmion internal structure, guides the nucleation processes, and substantializes the skyrmion-skyrmion interaction. I show that the hexagonal lattice of torons can be stabilized in a vast region of the constructed phase diagram for both easy-axis bulk and surface anisotropies. A topologically trivial droplet is shown to form as a domain boundary between two cone states with different rotational fashion, which underpins its stability. The findings provide a recipe for controllably creating skyrmions and torons, possessing the features on demand for potential applications.

FORMULATION AND DEVELOPMENT OF CURCUMIN BASED EMULGEL IN TREATMENT AND RECURRENCE OF VAGINAL CANDIDIASIS

Objective: The main causative agent of vaginal candidiasis is Candida albicans and it develops resistance against several synthetic antifungal drugs and it has a high rate of infection in women. According to WHO report, around 75% of women are infected by Candida albicans and 50 % are infected a second time by Candida albicans. Therefore, we choose Curcumin an antifungal agent that had reported antifungal properties against the various fungal species. The Curcumin-containing emulgel based microemulsion system was prepared for greater retention time and penetration across the vaginal mucosa. Methods: The screening of oil phase, surfactant, and cosurfactant for microemulsion formulation was selected based on the solubility study and followed by the construction of the pseudoternary phase diagram. The oil phase, surfactant and co-surfactant are selected from the pseudoternary phase diagram for the formulation of a stable microemulsion. The prepared Curcumin-loaded microemulsion was characterized by globule size, polydispersity index, Zeta potential, accelerated stability study, drug content, percent transmittance and antifungal assay by broth microdilution technique. The formulated microemulsion was converted into a vaginal emulgel by using Pluronic@F127. The formulated curcumin-loaded emulgel was characterized by different evaluation parameters and antifungal study by agar well diffusion method. Results: The result showed that the average globule size of emulgel was 286.3 nm, polydispersity index was 0.241, Zeta potential was+19.20 mv, conductivity was 0.0390 mS/cm, and drug content was found to be 95.58%. The texture of formulated emulgel was found to be soft and smooth, with shear-thinning, pseudoplastic behavior, and easily spreadable. The in vitro permeability study of emulgel shows slow and complete release of curcumin in 10 h. The microemulsion and developed emulgel showed promising antifungal activity against Candida albicans. Conclusion: The developed curcumin-loaded emulgel showed promising antifungal activity against Candida albicans as compared to the Fluconazole as an standard antifungal antibiotic. Our formulated Curcumin-containing emulgel can be a potential alternative as compared to the conventional dosage form for the treatment of vaginal candidiasis.

A novel surfactant-free microemulsion system for the synthesis of poly(methyl methacrylate)/Ag nanocomposite

Surfactant-free microemulsions (SFMEs) formed in the absence of traditional surfactants. It has been revealed that the SFMEs similar to the surfactant-based microemulsions (SBMEs), are expected to have comprehensive potential applications but the present understanding of SFMEs is very limited and many topics about SFMEs needs to be studied. Herein, we report a new SFME system consisting of methyl methacrylate (MMA) as the oil phase and 1-butanol as the amphi-solvent, to synthesis a polymer-based nanocomposite without using surfactant. For this purpose, after construction of the ternary phase diagram of the proposed system, the microstructures and structural transition of the SFME were investigated by measuring electrical conductivity and surface tension. The microenvironment polarity and salt solubility of water domains in the microemulsion region were also investigated. In the phase diagram three different microregions of water-in-MMA, bicontinuous and MMA-in-water regions were identified and compared with SBME system based on the Tween 80 surfactant. The size of the microemulsion droplets were characterized by dynamic light scattering technique. Finally, Ag nanoparticles were synthesized in the polymerizable systems of SFME and SBME to obtain stable colloids and consequently Ag/PMMA nanocomposites, after polymerization process. Transmission electron microscope and energy-dispersive X-ray analysis were used to characterize the synthesized nanocomposites in SFME and SBME systems. The antibacterial activity of the nanocomposites showed the similar results for the samples prepared in SFME and SBME systems. The approach established in current work can potentially be used as a viable and practical method for making numerous other uniforms and morphologically well-defined nanocomposites free of surfactants.

Dielectric responses and stimulative optical shuttering action of self-assembly supramolecular hydrogen bond liquid crystalline formation via x- and y-types benzoic acids

Investigations of a single hydrogen bonded liquid crystals are made between alkyloxy benzoic acids (x-BOA) and alkyloxy benzoic acids (y-BOA) and are discussed in the present investigation. Type of mesogenic phases exhibited are visualized and recorded with the help of a Polarizing Optical Microscopy (POM). Conventional phases such as ‘Nematic’ (Nematic droplets, ‘Schlieren’ or threaded textures, four brush textures), ‘Smectic C’ (Schlieren and broken focal conical texture), ‘Smectic F’ (chequered board texture) and ‘Smectic G’ (multi colored smooth mosaic texture) are observed. Newly investigated textural phases viz., ‘Smectic X’ (‘worm’ like texture) is also characterized to elucidate their structure. Phase diagrams are constructed to study in detail the thermal stability, occurrence and thermal span of the phases as a function of the chemical constitution of hydrogen bonded (HB) complexes. Thermal analysis include analysis of Differential Scanning Calorimetry (DSC) thermograms, study of the order of the transition by Navard & Cox parameter and construction of the relevant phase diagrams. Electrical attempts include measurement of permittvity and dielectric loss with respect to the electrical stimulus applied and light intensity profile analysis.

Bayesian learning of thermodynamic integration and numerical convergence for accurate phase diagrams

Accurate phase diagram calculation from molecular dynamics requires systematic treatment and convergence of statistical averages. In this work we propose a Gaussian process regression based framework for reconstructing the free energy functions using data of various origin. Our framework allows for propagating statistical uncertainty from finite molecular dynamics trajectories to the phase diagram and automatically performing convergence with respect to simulation parameters. Furthermore, our approach provides a way for automatic optimal sampling in the simulation parameter space based on Bayesian optimization approach. We validate our methodology by constructing phase diagrams of two model systems, the Lennard-Jones and soft-core potential, and compare the results with existing works studies and our coexistence simulations. Finally, we construct the phase diagram of lithium at temperatures above 300 K and pressures below 30 GPa from a machine-learning potential trained on ab initio data. Our approach performs well when compared to coexistence simulations and experimental results.

Improved anti-inflammatory effect of curcumin by designing self-emulsifying drug delivery system

Purpose of present study was to prepare and evaluate self-emulsifying drug delivery system (SEDDS) of curcumin (Cur) to enhance its solubility and percentage release for the evaluation of anti-inflammatory effect. Curcumin loaded SEDDS formulation was prepared, and zones of self-emulsification were recognized by dilution method for the construction of phase diagram. Lauroglycol FCC, Tween 80 (surfactant), and Transcutol HP (co-surfactant) were selected based on their solubility and highest emulsion region in phase diagram. Thermodynamic stability of Cur-SEDDS was calculated through globule size, zeta potential, polydispersity index (PDI), viscosity and pH. Cur-SEDDS were also characterized by encapsulation efficiency (EE %), FT-IR, in vitro release, and in vivo anti-inflammatory effect. Results revealed that droplet size of Cur-SEDDS was 19.77 ± 0.03 nm with their PDI 0.22 ± 0.19, zeta potential -19.33 ± 0.94 and viscosity 25.68 ± 0.86 cp. EE % of Cur-SEDDS was found to be 94.99 ± 0.38%, percentage release 65.83% compared with pure curcumin powder. The designed formulation possesses significant anti-inflammatory activity in paw edema when compared with positive control in carrageenan induced rat paw edema assay. Newly developed Cur-SEDDS with enhanced curcumin solubility, percentage release and better anti-inflammatory action may be an alternative source of oral delivery of curcumin.