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The solubility of two n-alkanes in commercial organic liquids, such as diesel fuel and jet fuel represent a problem to industry, because they precipitate in an unpredictable fashion. First we calculated the metastable enthalpy and entropy of fusion of the low temperature forms of the n-alkanes. We analyzed the solubility of alkanes n-C22H46, n-C23H48, n-C24H50 and n-C28H58 in ethylbenzene, m-xylene, n-heptane and gas oil. All systems seem to be close ideal, possibly with a slight positive deviation. We analyzed the solubility at constant temperature of the ternary system solvent C22H46-C24H50, C23H48-C24H50, C13H28-C16H34, C20H42-C22H46, C20H42-C24H50 and C20H42-C28H58, and looked at cloud points in various ternary systems. When the difference in the number of carbon atoms in the two alkanes is small, four or less, a metastable solid solution precipitates from the solvent. If the difference in the number of carbon atoms is six or more, the ‘equilibrium’ phases, or at least phases with low solubility precipitate. [ABSTRACT FROM AUTHOR]

[Display omitted] • Metastable state of the liquid on wrinkled electrospun mats has been investigated. • Analytical model of apparent contact angle has been proposed and validated. • 3D input parameters obtained via X-ray microCT analysis served as key inputs. • Theory and experiments are in good agreement. • A 'doubly re-entrant' structure has been successfully created on electrospun fibers. Electrospun mats with targeted wettability are a way forward to diversify their mainstream applications and can facilitate in creating a platform for a remarkable set of properties. Limited control over the fiber morphology and surface chemistry, along with the complex architecture of electrospun mats, pose some of the key challenges for maneuvering the wettability. Herein, we present the design principles that underpin the key determinants responsible for a metastable state of a water droplet on electrospun mats possessing wrinkled surface topography. A 'first-of-its-kind' analytical model of apparent contact angle based on the modified Cassie-Baxter state has been proposed that accounts for the dual-scale roughness originating from fiber wrinkles and protuberances created by fiber–fiber contacts. Three-dimensional (3D) fiber and structural parameters obtained via X-ray microcomputed tomography (microCT) analysis served as key inputs for predictive modeling. The analytical model of the apparent advancing and receding contact angles has been validated with electrospun mats having well-defined orientation characteristics. In general, the theory and experiments are in reasonable agreement. Although similar magnitudes of static and advancing contact angles of water on surfaces of randomly and aligned electrospun mats have been experimentally observed, the receding contact angles differed significantly. [ABSTRACT FROM AUTHOR]

Disopyramide (DPA) is as a class IA antiarrhythmic drug and its crystallization from cyclohexane at ambient condition yields lower melting form crystals which belong to the monoclinic centrosymmetric space group P21/n, having two molecules in an asymmetric unit. Crystal structure analysis of pure DPA revealed closely associated DPA molecules aggregates via amide–amide dimer synthon through the N–H∙∙∙O hydrogen bond whereas the second amide hydrogen N–H engaged in an intramolecular N–H∙∙∙N hydrogen bond with N-nitrogen of 2-pyridine moieties. Crystallization of DPA and phthalic acid (PA) in 1: 1 stoichiometric molar ratio from acetone at ambient condition yielded block shape crystals of 1:1 DPA_PA salt. Its X-ray single crystal structure revealed the formation of salt by transfer of acidic proton from one of the carboxylic acidic groups of PA to the tertiary amino group of chain moiety (N3-nitrogen atom) of DPA molecules. DPA_PA salt crystals belong to the monoclinic centrosymmetric space group P21/n, comprising one protonated DPA and one PA¯ anion (hydrogen phthalate counterion) in an asymmetric unit and linked by N–H∙∙∙O and C–H∙∙∙O hydrogen bonds. Pure DPA and DPA_PA salt were further characterized by differential calorimetric analysis, thermal gravimetric analysis, powder x-ray diffraction and infrared spectroscopy. [ABSTRACT FROM AUTHOR]

Titanium (Ti) alloys are ubiquitous in the aerospace, defense, and biomedical industries for their high strength to density ratios and good corrosion resistance. Ti alloys are typically optimized for strength, but improved work hardening characteristics and ductility would broaden their use in engineering applications. Here we show desirable combinations of strength and ductility in Ti-10V-2Fe-3Al (wt.%), including a fourfold increase in yield strength without commensurate losses in ductility, overcoming the classic strength/ductility tradeoff. This is achieved by nanoscale ω phase precipitates produced by natural and artificial aging, in concert with TRansformation Induced Plasticity (TRIP). Opportunity exists to tailor these strengthening mechanisms to design microstructural and mechanical response, opening up the performance landscape for lightweight Ti alloys for structural applications, analogous to the design of advanced high strength steels that result in lightweighting and improved crashworthiness for transportation applications. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Bed states obtained under four typical operation modes were compared for the MFB. • MFB state depended also on operation mode within certain operating zones. • In these zones MFB could have different states at the same operating condition. • Internal friction inside the bed caused MFB to be polymorphic in these zones. • Many of these bed states were demonstrated to be amorphous and metastable. There exist four typical modes to operate the magnetized fluidized bed (MFB) reactor: magnetization-FIRST, de-fluidization, magnetization-LAST, and de-magnetization. This work aimed to compare the bed states obtained under these operation modes for both the MFB with purely magnetizable particles and the MFB with the binary admixture of magnetizable and nonmagnetizable particles. It was found that the covered operating range could be divided into four zones. Particularly in zones I to III, the bed state depended not only on the magnetic field intensity (H) and superficial gas velocity (U g) but also on the operation mode, i.e., the bed state was a path function. Such a path-dependence feature resulted from that the MFB therein could have different equilibrium states at the same H and U g. From our perspective, such a polymorphic characteristic was caused by the internal friction inside the bed. Furthermore, many of these bed states were demonstrated to be metastable. The metastable states in zones II and III behaved like the metastates of water. They evolved directly and quickly into the corresponding stable states after relatively large perturbations. The metastable states in zone I behaved like the amorphous/glass state. They resided at another metastable state during the evolution towards the stable state after relatively large perturbations. In zone I, the metastable states formed from the sharp increase of internal friction with decreasing U g. The particles lost the ability to move before reaching the stable positions and were entrapped at the intermediate and metastable positions. [ABSTRACT FROM AUTHOR]

I 2 -II-IV-VI 4 and I-III-VI 2 semiconductor nanocrystals have found applications in photovoltaics and other optoelectronic technologies because of their low toxicity and efficient light absorption into the near-infrared. Herein, we report the discovery of a metastable wurtzite-like polymorph of Cu 2 FeSnSe 4 , a member of the I 2 -II-IV-VI 4 family of semiconductors containing only earth-abundant metals. Density functional theory calculations on this metastable polymorph of Cu 2 FeSnSe 4 indicate that it may be a superior semiconductor for solar energy and optoelectronics applications compared to the thermodynamically preferred stannite polymorph, since the former displays a sharper dispersion of energy levels near the conduction band minimum that can enhance electron mobility and suppress hot electron cooling. The experimental optical band gap was measured by the inverse logarithmic derivative method to be direct, in agreement with theory, and in the range of 1.48-1.59 eV. Mechanistic studies reveal that this metastable phase derives from intermediate Cu 3 Se 2 nanocrystals that serve as a structural template for the final hexagonal wurtzite-like product. We compare the chemistry of wurtzite-like Cu 2 FeSnSe 4 to the related CuFeSe 2 material system. Our experimental and computational comparisons between Cu 2 FeSnSe 4 and CuFeSe 2 help explain both the crystal chemistry of CuFeSe 2 that prevents it from forming wurtzite-like polymorphs and the essential role of Sn in stabilizing the metastable structure of Cu 2 FeSnSe 4 . This work provides insight into the importance of elemental composition when designing syntheses for metastable materials.

X-ray photoelectron spectroscopy (XPS) was employed to investigate Mg80Ti20 thin film samples prepared by magnetron sputtering and density functional theory (DFT) calculations were performed on atomistic models with similar stoichiometry. As Ti is known to be immiscible in Mg, the microstructure and atomic distribution of Mg-Ti thin films are not fully understood. In this work, it was shown by DFT calculations that the density of states (DOS) depends strongly on whether Ti is arranged in nano-clusters or if it is distributed quasi-randomly. The calculated DOS was compared to valence band spectra measured by XPS, as a new way of indirectly probing short-range order of such thin films. The XPS results of Mg80Ti20 were found to correspond best with the DOS calculated for the nano-cluster model, supporting the view that Ti forms small clusters in such sputtered thin films. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystalline, supersaturated and metastable Al–Mg dendrites with stacks of smooth and rough globules were produced through electrodeposition. Rough globules always formed over the smooth ones. The smooth globules possessed face centered cubic (fcc)-Al(Mg) phase with ~20at.% Mg. The rough globules contained ~80at.% Mg and corresponded to hexagonal close packed (hcp)-Mg(Al) phase. Across the smooth-rough boundary a drastic jump in the composition from ~20 to ~80at.% Mg was observed in nanometer scale. The metastable equilibrium between the supersaturated fcc and hcp phases was explained using the estimated free energy change-composition (ΔG–x) curves. [Copyright &y& Elsevier]

We report an abnormal current–voltage (I–V) characteristic observed on an Au–Si interface fabricated by a unique focused ion beam sputtering microdeposition method. The Au–Si interface shows neither Schottky nor ohmic behavior, but the I–V curve has a dI/dV peak at zero voltage. High-resolution transmission electron microscopy studies reveal the existence and unstable nature of an ∼10nm thick interfacial layer at the Au–Si contact. The unusual electrical behavior is likely correlated with this metastable interfacial layer. [Copyright &y& Elsevier]

Alcohol Oxidation: Air-Assisted Transient Synthesis of Metastable Nickel Oxide Boosting Alkaline Fuel Oxidation Reaction (Adv. Keywords: alcohols oxidation reactions; metastable; nickel oxide; oxygen vacancies; transient thermal shock EN alcohols oxidation reactions metastable nickel oxide oxygen vacancies transient thermal shock 1 1 1 12/10/20 20201208 NES 201208 In article number 2001397, Yanan Chen, Yida Deng, and co-workers report the fabrication of metastable NiO nanoparticles on carbon cloth (NiO@C/CC) via an air-assisted thermal shock technique (ATS-tech) as an efficient alcohol oxidation reaction catalyst. Alcohols oxidation reactions, metastable, nickel oxide, oxygen vacancies, transient thermal shock. [Extracted from the article]

It is well known that long term stability in zirconia has been a problem because of the structural alteration from stabilized tetragonal zirconia to monoclinic that leads to fracture in implants. Microwave (MW) assisted sol-gel synthesis is employed in the present work to prepare stabilize zirconia nanoparticles. ZrOCl 2.8H 2 O is used as a precursor whereas de-ionized water is used as a solvent. Power of microwave radiations is varied in the range of 100–1000W. Zirconia nanoparticles have been characterized under as-synthesized, 6- and 12-months' room temperature (RT) aged conditions. Metastable phase (MP) of zirconia, appearing under as-synthesized conditions, transforms to phase pure tetragonal zirconia (t-ZrO 2) after RT aging that was prepared with MW powers of 100, 200 and 700–1000W. Whereas, MP transforms to mixed tetragonal-monoclinic phases at microwave powers of 300–600W after RT aging. XPS results show presence of oxygen-deficient state of ZrO 2 lattice along with surface defects contributing towards the tetragonal zirconia phase under all conditions. Value of dielectric constant (i.e. ~11–12 at log f = 4.0), hardness (~13 GPa) and fracture toughness observed under all conditions are well in agreement to be used for biological implants. Disks of aged t-ZrO 2 nanoparticles are checked for their biodegradation test by dipping in simulated body fluid for several weeks. ZrO 2 , with 26 weeks of immersion, shows small loss in hardness and weight. Stabilized tetragonal zirconia shows strong anti-oxidant activity. Stabilized ZrO 2 nanoparticles presented strong antibacterial activity against both gram positive (S. aureus, Bacillus) and gram negative (E. coli) bacteria. Thus, structural and mechanical stability of zirconia (checked after 6 and 12 months) make this material highly beneficial for long term use in biomedical applications. Image 1 • ZrO 2 nanoparticles were synthesized using microwave assisted sol-gel technique. • Metastable ZrO 2 phase transformed to t-ZrO 2 after 6 months' RT aging; structure remained stable after 12 months' aging. • Dielectric constant and hardness compatible for bone grafting / reconstruction were observed at 100, 200 and 700–1000W. • Comparable values of mechanical properties were observed for as-synthesized, 6 and 12 months' aged samples. • Small biodegradation, strong anti-oxidant & antibacterial activity were observed for tetragonal zirconia. [ABSTRACT FROM AUTHOR]

A novel facile solvothermal fluorination method was developed for metastable oxyfluorides preparation by filling anion vacancies in parent structures. High solubility of XeF 2 in acetonitrile and polarity of the solvent allowed for lower reaction temperature. The validity of the method was demonstrated by the preparation of a known oxyfluoride, SrCoO 2. 5 F 0.5 , at unprecedented low temperature (100 ​°C). Additionally, two new oxyfluorides with idealized stoichiometry of La 4 Ni 3 O 8 F 1 and La 4 Ni 3 O 8 F 2 , were prepared by the solvothermal fluorination via the La 4 Ni 3 O 8 infinite-layer intermediate. The proposed method allows preparation of metastable oxyfluorides, utilizes only inexpensive commercial autoclaves and can potentially find widespread utilization in materials synthesis. A facile solvothermal fluorination method was developed for metastable oxyfluorides preparation, which allowed the synthesis of new La 4 Ni 3 O 8 F 2 oxyfluoride. Image 1 [ABSTRACT FROM AUTHOR]

• Reflux improves the activity, stability and coke resistance of Ni/ZrO 2 catalyst. • Si and K are inevitably residual during the reflux process within basic solution. • Reflux can promote Ni dispersion, enrich the porosity and strengthen the basicity. • Residual Si and K ions stabilize metastable phase and affect acid-base properties. • Metastable structure is somewhat destroyed under long-life or high temperature run. Ni/ZrO 2 catalyst has been widely investigated for dry reforming of methane (DRM), but it suffers from rapid deactivation due to nickel aggregation and carbon deposition under the harsh conditions. Herein, we introduce the post-treatment of reflux in Ni/ZrO 2 catalyst prepared by the conventional co-precipitation method. The detailed characterization results demonstrate that the catalysts after reflux exhibit the metastable structure with enlarged specific surface area and abundant porosity, thereby highly dispersing the active Ni species. The residue of Si and K is inevitable during the reflux process under the basic solution and the residual amount increases with the extended reflux time and the raised solution pH value. The residual Si is undesirable to improve the acidity while the residual K is expected to enhance the desirable basicity. Therefore, the stabilized metastable structure and mediated properties should be considered comprehensively in practically designing the highly active and stable DRM catalyst. The evaluation at 700 °C with gas hourly space velocity of 50000 mL·g−1·h−1 (volume ratio: CH 4 /CO 2 = 1/1) and time on stream of 600 min demonstrates that the treatment of reflux remarkably improves the activity and stability of Ni/ZrO 2 catalyst. Especially, the catalyst with 5-day reflux displays the robust activity (CH 4 conversion: ~72%, CO 2 conversion: ~80%) and carbon-resistant ability (0.01 mg/mg cat.). However, although the metastable structure is somewhat stabilized by the treatment of reflux and the residual ions, eventually it is easily destroyed when suffering from long-life (6000 min) or high-temperature (beyond 800 °C) run, behaving as the sintering of Ni particles and carbon deposition. [ABSTRACT FROM AUTHOR]

Metastable CaTi 2 O 5 nano-structure has been selectively prepared by a template-free and surfactant-free solvothermal process in aqueous solution. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) are carried out to characterize the samples. The growth process for CaTi 2 O 5 shuttle-like structure was dominated by a crystallization – oriented attachment – Ostwald ripening growth mechanism. BET analysis shows that CaTi 2 O 5 shuttle-like structure owns a large surface area of 118.8 m2 g−1. Compared with the other samples synthesized at various time and P25, CaTi 2 O 5 shuttle-like structure synthesized at 36 h exhibits the highest photocatalytic activity. The photocatalytic rate (K) of CaTi 2 O 5 shuttle-like structure reaches 0.2001 min−1 for in 25 min methyl orange (MO) degradation under the ultraviolet (UV) light irradiation. And after combination with graphite, CaTi 2 O 5 showed an interesting photocatalytic behavior and the photocatalytic activity of 99.8% under visible light at 100 min. • A novel metastable CaTi 2 O 5 nanostructure were synthesized. • The formation mechanism was proposed for the evolution of CaTi 2 O 5 nanostructure. • CaTi 2 O 5 showed good photocatalytic activity, stability and repeatability. • The present study enlarges the family of similar oxides structures available. [ABSTRACT FROM AUTHOR]

We report the synthesis of room temperature (RT) stabilized γ–Bi2O3 nanoparticles (NPs) at the expense of metallic Bi NPs through annealing in an ambient atmosphere. RT stability of the metastable γ–Bi2O3 NPs is confirmed using synchrotron radiation powder X-ray diffraction and Raman spectroscopy. γ–Bi2O3 NPs exhibited a strong red-band emission peaking at ~701 nm, covering 81% integrated intensity of photoluminescence spectra. Our findings suggest that the RT stabilization and enhanced red-band emission of γ‒Bi2O3 is mediated by excess oxygen ion vacancies generated at the octahedral O(2) sites during the annealing process. [ABSTRACT FROM AUTHOR]

• 9 crucial features are identified to train the machine learning model. • 10-fold cross-validation is used to evaluate the performance of all models. • Grid search method is employed to optimize hyper-parameters of all models. • Gradient Boosting Decision Tree is the best classification model in this work. • 37 stable and 13 metastable ABO 3 perovskite candidates are screened out. Machine learning and Materials Project are used to investigate stable and metastable perovskite materials based on a dataset of 397 ABO 3 compounds. The best performance classification model Gradient Boosting Decision Tree (GBDT) can classify 397 compounds into 143 non-perovskites and 254 perovskites with a 94.6% accuracy over 10-fold cross-validation, which indicates that 9 descriptors are outstanding features for formability of perovskite: tolerance factor, octahedral factor, radius ratio of A to O, A-O and B-O bond length, electronegativity difference for A-O (B-O) multiplied by the radius ratio of A (B) to O, the Mendeleev numbers for A and B. Among 891 ABO 3 , the GBDT model predicts that 331 have perovskite structure and the top-174 within a probability ≥ 85%. Furthermore, based on the energy above the convex hull (E hull), 37 thermodynamically stable ABO 3 perovskites with 0 ≤ E hull < 36 m e V / a t o m and 13 metastable perovskites with 36 ≤ E hull < 70 m e V / a t o m are predicted for further synthesis and applications. [ABSTRACT FROM AUTHOR]

• Structural, magnetic, thermodynamic and thermoelectric properties have been studied. • Transition from AFM to FM is accompanied by increase in the volume and the Fe mm. • Stability of AFM orthorhombic configurations was corroborated with MD simulations. • The changes of entropy (ΔS) involved in the AFM-FM transition have been evaluated. • AFM-B configuration is the most favorable for the metamagnetic phase transition. In this work the structural, energetic, thermodynamic, magnetic and thermoelectric properties of FeRh alloy have been studied using first-principles calculations. The structural and magnetic results obtained for the FM phase are in agreement with experimental and other theoretical calculated values (local magnetization of about 3 μ B and 1 μ B for Fe and Rh atoms respectively). The transition AFM to the FM state is accompanied by a 2.4% increase in the volume of the cell and by 9.6% in the Fe spin magnetic moment. The characterization of the AFM phase shows a distortion of the cubic and tetragonal cell to the orthorhombic solving the instabilities observed in the phonon band structures curves of the corresponding to cubic structure. The stability of the AFM configurations was corroborated with molecular dynamics (MD) simulations. The magnitude of the Seebeck coefficient increases with the temperature at a certain chemical potential. While the magnitude of the electrical conductivity does not present meaningful changes with the temperature in the selected values, the thermal conductivity increases with the temperature. Another consequence of the AFM to FM transition is the drop of the resistivity ρ in the FM phase as compared to the AFM state. Based on the results obtained using MD simulations from stable AFM configurations and the results of entropy changes, the configuration AFM-B (type I) could be identified as the most favorable in achieving the metamagnetic phase transition. [ABSTRACT FROM AUTHOR]

Structural polymorphism is known for many bulk materials; however, on the nanoscale metastable polymorphs tend to form more readily than in the bulk, and with more structural variety. One such metastable polymorph observed for colloidal Ag 2 Se nanocrystals has traditionally been referred to as the "tetragonal" phase. While there are reports on the chemistry and properties of this metastable polymorph, its crystal structure, and therefore electronic structure, has yet to be determined. We report that an anti-PbCl 2 -like structure type (space group P 2 1 / n ) more accurately describes the powder X-ray diffraction and X-ray total scattering patterns of colloidal Ag 2 Se nanocrystals prepared by several different methods. Density functional theory (DFT) calculations indicate that this anti-PbCl 2 -like Ag 2 Se polymorph is a dynamically stable, narrow-band-gap semiconductor. The anti-PbCl 2 -like structure of Ag 2 Se is a low-lying metastable polymorph at 5-25 meV/atom above the ground state, depending on the exchange-correlation functional used.

Generation of induced oligodendrocyte progenitor cells (iOPCs) from somatic fibroblasts is a strategy for cell-based therapy of myelin diseases. However, iOPC generation is inefficient, and the resulting iOPCs exhibit limited expansion and differentiation competence. Here we overcome these limitations by transducing an optimized transcription factor combination into a permissive donor phenotype, the pericyte. Pericyte-derived iOPCs (PC-iOPCs) are stably expandable and functionally myelinogenic with high differentiation competence. Unexpectedly, however, we found that PC-iOPCs are metastable so that they can produce myelination-competent oligodendrocytes or revert to their original identity in a context-dependent fashion. Phenotypic reversion of PC-iOPCs is tightly linked to memory of their original transcriptome and epigenome. Phenotypic reversion can be disconnected from this donor cell memory effect, and in vivo myelination can eventually be achieved by transplantation of O4 + pre-oligodendrocytes. Our data show that donor cell source and memory can contribute to the fate and stability of directly converted cells., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 Elsevier Inc. All rights reserved.)

A15 Nb 3 Si is, until now, the only 'high' temperature superconductor produced at high pressure (∼110 GPa) that has been successfully brought back to room pressure conditions in a metastable condition. Based on the current great interest in trying to create metastable-at-room-pressure high temperature superconductors produced at high pressure, we have restudied explosively compressed A15 Nb 3 Si and its production from tetragonal Nb 3 Si. First, diamond anvil cell pressure measurements up to 88 GPa were performed on explosively compressed A15 Nb 3 Si material to trace T c as a function of pressure. T c is suppressed to ∼5.2 K at 88 GPa. Then, using these T c ( P ) data for A15 Nb 3 Si, pressures up to 92 GPa were applied at room temperature (which increased to 120 GPa at 5 K) on tetragonal Nb 3 Si. Measurements of the resistivity gave no indication of any A15 structure production, i.e. no indications of the superconductivity characteristic of A15 Nb 3 Si. This is in contrast to the explosive compression (up to P ∼ 110 GPa) of tetragonal Nb 3 Si, which produced 50%-70% A15 material, T c . The fact that 'annealing' the A15 explosively compressed material at room temperature for 39 years has no effect shows that slow kinetics can stabilize high pressure metastable phases at ambient conditions over long times even for large driving forces of 90 meV atom 3 Si structural transformation. Our theoretical calculations show that A15 Nb 3 Si has an enthalpy vs the tetragonal structure that is 70 meV atom -1 smaller at 100 GPa, while at ambient pressure the tetragonal phase enthalpy is lower than that of the A15 phase by 90 meV atom -1 . The fact that 'annealing' the A15 explosively compressed material at room temperature for 39 years has no effect shows that slow kinetics can stabilize high pressure metastable phases at ambient conditions over long times even for large driving forces of 90 meV atom -1 ., (© 2021 IOP Publishing Ltd.)