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Using mechanical activation of an oxide mixture containing 0.2 wt% hexagonal boron nitride, followed by high-temperature firing (1400–1500 °C), we prepared single-phase (La 0.2 Nd 0.2 Ho 0.2 Lu 0.2 Y 0.2) 2 ZrO 5 ceramic, a high-entropy oxide (HEO) analog of Gd 2 ZrO 5 , whereas we failed to obtain single-phase Gd 2 ZrO 5 under similar conditions: the material consisted of two phases, with the fluorite and bixbyite structures, like in the case of conventional synthesis or coprecipitation in previous work. Thus, the use of the HEOs allowed us to obtain a phase-pure compound with the fluorite structure at a markedly lower synthesis temperature. An important role was played by 0.2 wt% hyperstoichiometric hexagonal BN additions, which ensured considerable amorphization of the starting oxides. The start powders and resulting ceramics were studied by X-ray diffraction, SEM analyses and conductivity was measured by impedance spectroscopy method in dry and wet air. The highest proton conductivity, ∼2.5 × 10−5 S/cm at 630 °C, was offered by the (La 0.2 Nd 0.2 Ho 0.2 Lu 0.2 Y 0.2) 2 ZrO 5 HEO ceramic. The use of HEO analogs of various compounds can be helpful for not only assessing thermodynamic properties of ceramics (reduction in synthesis and polymorphic transformation temperatures), but also preparing proton conductors when it is necessary to enhance hydrating properties of the cation sublattice. [ABSTRACT FROM AUTHOR]

The microstructural characterization of duplex Fe-Cr-Ni-based alloy processed through sub-rapid solidification and subsequent solid solution heat treatment was investigated, and the mechanism underlying the phase transformation and the improvement in the tensile properties of the alloy was discussed. A metastable thermodynamic balance emerged immediately during sub-rapid solidification which promoted the multiple phase transformation deviate from equilibrium transformation, e.g., suppressed dendrite δ phase, coupled structure features and constrained constituent diffusion behavior. The phase transformation in subsequent solid solution heat treatment proceeded very quickly, which resulted in decomposition of the primary δ phase and the polymorphic transformation (γ → δ). The solid solution heat treatment also led the change of grain size and shape, crystallographic orientation and constituents' distribution characterization. The application of solid solution heat treatment significantly improves the yield strength from 643.65 to 1014.09 MPa, and the ultimate tensile strength from 729.54 to 1029.31 MPa, corresponding to an increase of 57.55% and 41.09%, respectively. The results showed that the lamellar structures in sub-rapid solidified could give rise to strain concentration during loading and result in performance deterioration, which is different with the adverse effect derived from coarse dendrites in previous research. The underlying mechanism for the enhanced mechanical performance after solid solution heat treatment is discussed. It is demonstrated that the crack propagation and their interaction with individual microstructure features (dislocation, dimple or inclusions) play a vital role in final enhance performance. And the crack propagation is essentially orientation dependent. [ABSTRACT FROM AUTHOR]

Polymorphic transformation is important in chemical industries, in particular, in those involving explosive molecular crystals. However, due to simulating challenges in the rare event method and collective variables, understanding the transformation mechanism of molecular crystals with a complex structure at the molecular level is poor. In this work, with the constructed order parameters (OPs) and K-means clustering algorithm, the potential of mean force (PMF) along the minimum free-energy path connecting β-HMX and δ-HMX was calculated by the finite temperature string method in the collective variables (SMCV), the free-energy profile and nucleation kinetics were obtained by Markovian milestoning with Voronoi tessellations, and the temperature effect on nucleation was also clarified. The barriers of transformation were affected by the finite-size effects. The configuration with the lower potential barrier in the PMF corresponded to the critical nucleus. The time and free-energy barrier of the polymorphic transformation were reduced as the temperature increased, which was explained by the pre-exponential factor and nucleation rate. Thus, the polymorphic transformation of HMX could be controlled by the temperatures, as is consistent with previous experimental results. Finally, the HMX polymorph dependency of the impact sensitivity was discussed. This work provides an effective way to reveal the polymorphic transformation of the molecular crystal with a cyclic molecular structure, and further to prepare the desired explosive by controlling the transformation temperature. [ABSTRACT FROM AUTHOR]

Nucleation control and isolation of polymorphic forms of the essential pharmaceutical medicine aspirin (ASP) was examined by a supersaturation-dependent swift cooling crystallization process using acetonitrile as solvent. In the present investigation, a saturated solution was prepared at 323 K and swiftly cooled down to various temperatures below the equilibrium temperature in steps of 1 K by conducting a series of 49 systematic cooling experiments which gave a very clear nucleation matrix, indicating the preferred nucleation region of all the three polymorphic forms of aspirin under different supersaturation conditions in the range 0.20 < σ < 1.65. Moreover, an observed solution-mediated polymorphic phase transformation (SMPT) under specific supersaturation conditions (σ = 0.97) indicates that the dissolution of characteristic faces {1¯ 0 2} and {1¯ 1 1} occurs in the grown metastable form-II, and the characteristic face {0 0 2¯} of form-I simultaneously nucleates and grows over form-II in the −c and +c crystallographic directions on the surface of form-II. This discovery may provide a better understanding of the intergrowth phenomenon of aspirin polymorphs. The occurrence of this peculiar phenomenon was further ensured by attachment energy calculations, morphology assessment, and relative area analyses. Also, the nucleation kinetics of the grown ASP polymorphs were evaluated using the experimentally obtained induction time and calculated supersaturation values, by the classical nucleation theory (CNT) approach, and these results are well matched with the obtained experimental results. The structural and phase stability of the grown polymorphs were ascertained by powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC) analyses. [ABSTRACT FROM AUTHOR]

Characterization of crystallization processes in situ is of great importance to furthering knowledge of how nucleation and growth processes direct the assembly of organic and inorganic materials in solution and, critically, understanding the influence that these processes have on the final physico‐chemical properties of the resulting solid form. With careful specification and design, as demonstrated here, it is now possible to bring combined X‐ray diffraction and Raman spectroscopy, coupled to a range of fully integrated segmented and continuous flow platforms, to the laboratory environment for in situ data acquisition for timescales of the order of seconds. The facility used here (Flow‐Xl) houses a diffractometer with a micro‐focus Cu Kα rotating anode X‐ray source and a 2D hybrid photon‐counting detector, together with a Raman spectrometer with 532 and 785 nm lasers. An overview of the diffractometer and spectrometer setup is given, and current sample environments for flow crystallization are described. Commissioning experiments highlight the sensitivity of the two instruments for time‐resolved in situ data collection of samples in flow. Finally, an example case study to monitor the batch crystallization of sodium sulfate from aqueous solution, by tracking both the solute and solution phase species as a function of time, highlights the applicability of such measurements in determining the kinetics associated with crystallization processes. This work illustrates that the Flow‐Xl facility provides high‐resolution time‐resolved in situ structural phase information through diffraction data together with molecular‐scale solution data through spectroscopy, which allows crystallization mechanisms and their associated kinetics to be analysed in a laboratory setting. [ABSTRACT FROM AUTHOR]

The microstructure, phase composition and elemental composition in the α- and β-phases of the two-phase wrought Ti-5.7Al-1.6V-3Mo titanium alloy at room temperature were studied by transmission electron microscopy and X-ray energy-dispersive spectroscopy. The temperature ranges of phase transformations in the alloy during heating from 298 to 1523 K were studied by differential scanning calorimetry (DSC). Two endothermic peaks were observed on the DSC curve at the temperatures of 1078 K and 1207 K, and one exothermic peak was observed at a temperature of 1123 K. The endothermic peak on the DSC curve at a temperature of 1078 K is due to the formation of α″-martensite, at a temperature of 1207 K is caused by α → β phase transformation. The exothermic peak at a temperature of 1123 K, presumably, corresponds to the polymorphic transformation of brookite → rutile in TiO2 oxide. High-temperature synchrotron studies were carried out from room temperature to 1373 K. It was found that the increase in lattice parameters during heating is nonlinear. Possible mechanisms of the nonlinear change in the lattice parameters at temperatures above 1200 K are discussed. At T > 1000 K α″-martensite was formed by β → α″ phase transformation. An increase in the volume fraction of α″-phase with increase in temperature was accompanied by a decrease in the volume fraction of β-phase. An increase in microstrain of the α-phase lattice and a decrease in microstrain of the β-phase lattice were observed upon heating. [ABSTRACT FROM AUTHOR]

This study investigates the solubility behavior of Naproxen (NAP) in binary solvent mixtures of 1-propanol (1-PrOH) and 2-propanol (2-PrOH) with ethylene glycol (EG) across a range of temperatures. The solubility of NAP was experimentally determined at five different temperatures (293.15 to 313.15 K), and the data were correlated using various thermodynamic models, including the van't Hoff, Jouyban-Acree, modified Wilson, mixture response surface, Jouyban-Acree-van't Hoff. The results demonstrated that NAP's solubility increases with temperature in both solvent systems. Notably, NAP exhibited higher solubility in mixtures with 1-PrOH compared to 2-PrOH, despite the lower polarity of 2-PrOH. This unexpected trend is attributed to the distinct molecular interactions, including hydrogen bonding, influenced by the structural differences between 1-PrOH and 2-PrOH. The X-ray diffraction analysis confirmed that no polymorphic transformation occurred in NAP during dissolution, maintaining its crystalline structure. The solubility data were well-correlated by the applied models, with overall MRDs% (mean relative deviation percentage) below 6.1. [ABSTRACT FROM AUTHOR]

Yttria-doped tetragonal zirconia polycrystalline (Y-TZP) is one of the most widely used materials in thermal applications and as a structural component due to its mechanical properties. Its drawbacks are the high cost of the starting raw materials and its polymorphic transformation to monoclinic phase associated with the occurrence of mechanical failures. In the present work, tetragonal zirconia materials were obtained by slip casting and also ZrO 2 /ZrSiO 4 composites by partially replacing the zirconia with low cost and high corrosion resistance zircon. The different parts showed a high microstructural homogeneity, as well as high hardness and Young's modulus (up to 16.7 and 354 GPa, respectively), even with the incorporation of 20 vol% zircon. The zircon-containing composites subjected to hydrothermal low-temperature degradation (LTD) at 205 °C for 240 h exhibited similar mechanical properties, unaffected microstructural integrity, and a crystallographic phase composition equal to the as-sintered samples, without phase transformation from t-ZrO 2 to m-ZrO 2. [ABSTRACT FROM AUTHOR]

BaAl 2 Si 2 O 8 (barium feldspar-based) materials are widely used in glass and ceramic industry due to high melting temperature, chemical resistance, low thermal expansion, low dielectric constants and attractive luminescence properties. The durability of barium feldspar ceramics strongly depends on reversible phase transitions between the low-temperature modification (celsian), and series of high-temperature (HT) polymorphs known as 'hexacelsian'. Numerous works have been devoted to the study of the thermal transitions of 'hexacelsian' by X-ray powder diffraction methods and transmission electron microscopy, the use of which provides limited information about structural changes. Here, the crystal structures, thermal properties and phase transitions of HT BaAl 2 Si 2 O 8 polymorphs are characterized for the first time using in-situ HT X-ray single-crystal structural study (SCXRD), and micro-Raman spectroscopy up to 1000 °C. The crystal structure of α-hexacelsian under ambient conditions is monoclinic (I 2/ a). The alpha-form undergoes two polymorphic transformations upon heating: into an orthorhombic (Fmmm) β-modification above 300 °C and into a hexagonal (P –62 m) γ-modification above 700 °C. These transitions lead to significant changes in the unit-cell volume: an obstacle in the production of BaAl 2 Si 2 O 8 -based ceramics. [ABSTRACT FROM AUTHOR]

Computational predictions of the polymorphic outcomes of a crystallization process, referred to as polymorph selection, can accelerate the process development for manufacturing solid products with targeted properties. Polymorph selection requires understanding the interplay between the thermodynamic and kinetic factors that drive nucleation. Moreover, post-nucleation events, such as crystal growth and polymorphic transformation, can affect the resulting crystal structures. Here, the nucleation kinetics of the Lennard-Jones (LJ) fluid from the melt is investigated with a focus on the competition between FCC and HCP crystal structures. Both molecular dynamics (MD) simulations and 2D free energy calculations reveal that polymorph selection occurs not during nucleation but when the cluster sizes exceed the critical cluster size. This result contrasts with the classical nucleation mechanism, where each polymorph is assumed to nucleate independently as an ideal bulk-like cluster, comprised only of its given structure. Using the 2D free energy surface and the MD simulation-derived diffusion coefficients, a structure-dependent nucleation rate is estimated, which agrees with the rate obtained from brute force MD simulations. Furthermore, a comprehensive population balance modeling (PBM) approach for polymorph selection is proposed. The PBM combines the calculated nucleation rate with post-nucleation kinetics while accounting for the structural changes of the clusters after nucleation. When applied to the LJ system, the PBM predicts with high accuracy the polymorphic distribution found in a population of crystals generated from MD simulations. Due to the non-classical nucleation mechanism of the LJ system, post-nucleation kinetic events are crucial in determining the structures of the grown crystals. [ABSTRACT FROM AUTHOR]

In this study, cocrystallization of n-propylparaben and a ditopic bipyridine-based azine derivative in a 2 : 1 stoichiometric ratio was carried out. The resulting single crystals of the cocrystal displayed crystal-to-crystal polymorphic phase transformation on heating. The phase transformation is associated with naked-eye visible expansion and cracking of the single crystals. The two polymorphs are distinct in their surface wettability. [ABSTRACT FROM AUTHOR]

In this work, the phase equilibria of the binary Ag-In system were determined using electron probe microanalysis and differential scanning calorimetry on equilibrated alloys and diffusion couples. The compositions of the phase boundaries of solid phases that are highly scattered in the literature have been precisely determined. The temperatures of the invariant reaction ζ ⇄ γ + L and the polymorphic transformation ζ ⇄ γ are substantially lower than previously reported values. In addition, it was found that the In-rich ζ phase phase-separates after months of room-temperature aging. [ABSTRACT FROM AUTHOR]

Purpose: Employing polymer additives is an effective strategy to realize the manipulation of polymorphic transformation. However, the manipulation mechanism is still not clear, which limit the precise selection of polymeric excipients and the development of pharmaceutical formulations. Methods: The solubility of cimetidine (CIM) in acetonitrile/water mixtures were measured. And the polymorphic transformation from CIM form A to form B with the addition of different polymers was monitored by Raman spectroscopy. Furthermore, the manipulation effect of polymers was determined based on the results of experiments and molecular simulations. Results: The solubility of form A is consistently higher than that of form B, which indicate that form B is the thermodynamically stable form within the examined temperature range. The presence of polyvinylpyrrolidone (PVP) of a shorter chain length could have a stronger inhibitory effect on the phase transformation process of metastable form, whereas polyethylene glycol (PEG) had almost no impact. The nucleation kinetics experiments and molecular dynamic simulation results showed that only PVP molecules could significantly decrease the nucleation rate of CIM, due to the ability of reducing solute molecular diffusion and solute–solute molecular interaction. A combination of crystal growth rate measurements and calculations of the interaction energies between PVP and the crystal faces of CIM indicate that smaller molecular weight PVP can suppress crystal growth more effectively. Conclusion: PVP K16-18 has more impact on the stabilization of CIM form A and inhibition of the phase transformation process. The manipulation mechanism of polymer additives in the polymorphic transformation of CIM was proposed. [ABSTRACT FROM AUTHOR]

Using the methods of advanced material physics, the structural-phase state of a layer of high-entropy high-speed non-equiatomic molybdenum tool steel formed by electric arc surfacing in a nitrogen atmosphere is studied. The thermodynamical and mechanical (elastic moduli) properties of the surfaced layer are examined in a temperature interval of 300–1400°C, and a phase-composition diagram is presented. It is observed that a temperature increase is accompanied by an α→γ polymorphic transformation, followed by a decrease in the content of carbide phases and elastic moduli. [ABSTRACT FROM AUTHOR]

In this paper, the melting memory effect generated by a novel cyclic thermal treatment protocol with form II as "seeds" on the polymorphic transformation in isotactic polybutylene-1(iPB-1) was investigated. Polar Optical Microscope (POM), wide angle X-ray diffraction (WAXD) and Fourier transform infrared spectroscopy (FTIR) were used to study the changes of morphology and crystal form II → I transition during aging. Selected crystallization temperature (Tsc) and melting temperature (Tsm) were applied to generate residual nuclei of form II. Both cycled and uncycled samples were analyzed to demonstrate the formation of crystal I and polymorphic transformation. The results indicate that the melting memory has a significant effect on tetragonal modification, leading to an increased nucleation density and an accelerated nucleation speed. The ordered chain sequences in crystal II initiated the formation of crystal nuclei of form I, resulting in a rapid conversion and increased transition degree during the hexagonal crystal growth. Form I was found to have two formation pathways, including the transformation of the unstable crystal form II and the direct formation from residual crystal and melt, which have been rarely discussed before and may shed light on understanding of crystal formation mechanism in polymorphism polybutene-1. [ABSTRACT FROM AUTHOR]

The article discusses the role of polymorphic transformations of titanium oxides in contributing to economic uranium mineralization in sandstone. The authors conducted a study on sandstone samples from the Yaojia Formations in China and found that titanium oxides, specifically anatase and rutile, play a significant role in concentrating uranium. The study utilized various analytical techniques such as scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and electron microprobe analysis to characterize the titanium oxides and determine their trace element concentrations. The findings provide valuable insights into the mineralization processes of uranium in sandstone formations. [Extracted from the article]

An external electric field is an effective tool to induce the polymorphic transformation of molecular crystals, which is important practically in the chemical, material, and energy storage industries. However, the understanding of this mechanism is poor at the molecular level. In this work, two types of order parameters (OPs) were constructed for the molecular crystal based on the intermolecular distance, bond orientation, and molecular orientation. Using the K-means clustering algorithm for the sampling of OPs based on the Euclidean distance and density weight, the polymorphic transformation of TNT was investigated using a finite temperature string (FTS) under external electric fields. The potential of mean force (PMF) was obtained, and the essence of the polymorphic transformation between o-TNT and m-TNT was revealed, which verified the effectiveness of the FTS method based on K-means clustering to OPs. The differences in PMFs between the o-TNT and transition state were decreased under external electric fields in comparison with those in no field. The fields parallel to the c-axis obviously affected the difference in PMF, and the relationship between the changes in PMFs and field strengths was found. Although the external electric field did not promote the convergence, the time of the polymorphic transformation was reduced under the external electric field in comparison to its absence. Moreover, under the external electric field, the polymorphic transformation from o-TNT to m-TNT occurred while that from m-TNT to o-TNT was prevented, which was explained by the dipole moment of molecule, relative permittivity, chemical potential difference, nucleation work and nucleation rate. This confirmed that the polymorphic transformation orientation of the molecular crystal could be controlled by the external electric field. This work provides an effective way to explore the polymorphic transformation of the molecular crystals at a molecular level, and it is useful to control the production process and improve the performance of energetic materials by using the external electric fields. [ABSTRACT FROM AUTHOR]

The crystallization behavior of 1,2,3-tripalmitoyl glycerol or PPP using differential scanning calorimetry (DSC), thermo-optical polarized light microscopy and in situ synchrotron radiation X-ray diffraction (SR-XRD) techniques was precisely examined under static isothermal and dynamic thermal treatments, and the results were compared with preceding studies. PPP was rapidly (15 °C min−1) cooled to target temperatures (from 40 to 59 °C) to determine the precise moment at which crystallization was initiated. Once crystallization ceased, polymorphic transformation and melting were analyzed during subsequent heating. α form was crystallized during isotherms from 40 to 46 °C, temperature at which it coexisted with β′ phase. The latter was solely formed from 47 to 53 °C, and polymorphic crystallization was directed to obtain exclusively most stable β at 54 °C and higher temperatures. Nucleation time values for the α, β′ and β polymorphs exhibited exponential growth type, and a good correlation was found between data obtained by DSC and SR-XRD. Dynamic experiments were based on the use of high (15 °C min−1), intermediate (2 °C min−1) and low (0.5 and 0.1 °C min−1) cooling and heating rates. Thermo-optical polarized light microscopy experiments also provided valuable information on microstructural changes occurring during polymorphic modifications. Less stable forms predominated at high cooling rates, whereas lower velocities leaded the polymorphic crystallization to obtain more stable forms. [ABSTRACT FROM AUTHOR]

Phase equilibria studies were performed in the Li2O-SiO2 system for heat-treated samples using Scanning Electron Microscope (SEM) and X-Ray Diffraction (XRD). The temperature of the eutectic reaction (Liq. ⇌ Li4SiO4 + Li2SiO3) was experimentally determined at 1289 K using Differential Thermal Analysis (DTA). No evidences of the Li6Si2O7 formation was found by the experimental investigation and therefore, it was not considered. Heat capacity of the Li8SiO6 phase was measured using Differential Scanning Calorimetry (DSC). Solid phases of the Li2O-SiO2 system were described as stoichiometric compounds and liquid phases by two-sublattice partially ionic liquid model. Four stoichiometric intermediate compounds were considered to be stable (Li8SiO6, Li4SiO4, Li2SiO3 and Li2Si2O5). The polymorphic transformation in Li2Si2O5 phase was accounted and the metastable liquid miscibility gap on SiO2-rich side was reproduced. The calculated phase diagram satisfactorily agrees with the experimental phase equilibria as well as calculated thermodynamic properties reproduces experimental values within uncertainty limits. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) has a wide range of uses such as food additives and raw materials for synthetic chemicals, while its application in the solid-state transformation of pharmaceutical crystals is rare. In this work, we report a case of using 1 atm CO2 as an accelerator to promote the polymorphic transformation of clarithromycin (CLA). Initially, crystal structures of Form 0′ and three solvates were successfully determined by single crystal X-ray diffraction (SCXRD) analysis for the first time and found to be isomorphous. Powder X-ray diffraction (PXRD) and thermal analysis indicated that the solvate desolvates and transforms into the structurally similar non-solvated Form 0′ at room temperature to ~50 °C. Form 0′ and Form II are monotropically related polymorphs with Form II being the most stable. Subsequently, the effect of CO2 on the transformation of CLA solvates to Form II was studied. The results show that CO2 can significantly facilitate the transformation of Form 0′ to Form II, despite no significant effect on the desolvation process. Finally, the molecular mechanism of CO2 promoting the polymorphic transformation was revealed by the combination of the measurement of adsorption capacity, theoretical calculations as well as crystal structure analysis. Based on the above results, a new pathway of preparing CLA Form II was designed: transform CLA solvates into Form 0′ in 1 atm air at 50 °C followed by the transformation of Form 0′ to Form II in 1 atm CO2 at 50 °C. This work provides a new idea for promoting the phase transformation of pharmaceutical crystals as well as a new scenario for the utilization of CO2. [ABSTRACT FROM AUTHOR]

A model is presented whereby metamorphic parageneses are governed by local, nano-scale reactions among adjacent phases along grain boundaries that are driven by local disequilibrium between the solid phases and the grain boundary composition. These reactions modify the grain boundary composition setting up compositional gradients that drive diffusion and change the grain boundary composition elsewhere in the rock, which drive local reactions in these locations. The process may be triggered by the nucleation of a new phase that is out of equilibrium with the existing assemblage and an example is presented based on the transformation of kyanite (Ky) to sillimanite (Sil). Model results reveal that a simple polymorphic transformation (Ky→Sil) can result in local reactions among all phases in the rock and some phases may grow in one locale and be consumed in another. An implication of these results is that interpretation of metamorphic parageneses based on growth or resorption and compositional changes of phases requires careful evaluation of nano-scale processes. [ABSTRACT FROM AUTHOR]

Elastoplastic and polymorphic α – ε transformations in iron films induced by ultra-short laser-driven shock waves are studied. Interpretation of time-resolved interferometric measurements is performed using an inverse analysis technique of experimental rear-side velocity profiles. The lasts are obtained by numerical differentiation of free surface displacements detected by probe laser pulses. The inverse analysis techniques are validated in consistent two-temperature hydrodynamics and molecular dynamics simulations of laser energy deposition and diffusion, generation, and propagation of shock waves in a polycrystalline iron sample. The stress–strain diagrams containing information about elastoplastic deformation and phase transformation are reconstructed by the inverse analysis. We found that the polymorphic transformation in iron under picosecond duration of loading requires much higher stress in contrast to that in microsecond-scale plate-impact experiments. Moreover, such transition may be accomplished partially even at very high stresses if an unloading tail after the shock front is too short. [ABSTRACT FROM AUTHOR]

For the polymorphic transformation of porous graphite in the shock, the previously proposed model linking the process of graphite phase transition with a change in the elastic energy of a substance has been tested. It is shown that the model plausibly describes the experimental results outside the transition zone in a fairly wide range of changes in the porosity of samples with their different initial structure. It is discussed how the model under consideration changes the currently existing ideas about the thermodynamics of the polymorphic transition of matter in a shock wave. [ABSTRACT FROM AUTHOR]

The equilibrium molar solubility of 2-hydroxybenzoic acid (salicylic acid, SA) in pseudo-binary mixed solvents of choline chloride/propylene glycol deep eutectic solvent (ChCl/PG DES, 1:3 molar ratio) and water was determined by a shake flask method at 293.15-313.15 K and ambient pressure (85 kPa). Based on the results, the maximum solubility of SA was observed in neat DES at 313.15 K (0.7604 mol·L−1) whereas it was minimum in neat water at 293.15 K (0.0112 mol·L−1). X-Ray power diffraction analysis of solid phase presented no polymorphic transformation or solvate formation in the experiments. Moreover, the molar solubility of SA was modeled mathematically with various cosolvency models attaining the average percentage deviations smaller than 6.1%, except for the modified Wilson-van't Hoff (12.6%). Further, more favorable and entropy-driven of SA dissolution in ChCl/PG DES-rich mixtures was achieved from the apparent thermodynamic analysis. [ABSTRACT FROM AUTHOR]

In situ monitoring and closed‐loop control of the solution crystallization process are the modern trends for pharmaceutical development, in which the critical process parameters (CPPs) as well as the product critical quality attributes (CQAs) can be regulated and guaranteed during the manufacturing process. In this study, an in situ image monitoring methodology based on a state‐of‐the‐art deep‐learning model was developed to track the CQAs such as polymorph ratio, two‐dimensional crystal size, and crystal shape in a solvent‐mediated polymorphic transformation (SMPT) process. Coupled with the multidimensional process information, a 2D population balance model (PBM) was developed and validated using the results of the in situ image‐based CQAs analysis. The 2D‐PBM was solved using a high‐resolution finite volume method (HR‐FVM) which could provide a high dimensional particle‐size distribution. Through the validation between the process image analysis and the 2D‐PBM, the accuracy of image analysis was discussed, and the potential and challenges of in situ image analysis were proposed. This work aims to integrate the crystal polymorphism and two‐dimensional crystal size distribution (2D‐CSD) information in the SMPT process using intelligent microscopic image analysis and then to validate the results of neural network processing by solving the numerical solution of the multidimensional PBM. [ABSTRACT FROM AUTHOR]

The polymorphism of Minodronic acid (MDA) monohydrates (form D and form E) was investigated in this work. The results revealed that the main difference lies in the discrepancy of hydrogen bonds in two polymorphisms. In addition, the atoms-in-molecules (AIM) analysis was conducted to assess the strength of hydrogen bonds. The hydrogen bonds in form D were estimated as electrostatic, while the corresponding hydrogen bonds in form E were partially covalent type. Then the polymorphic transformation mechanism was investigated by experiments coupled with molecular dynamic simulations. As the conformation of the water molecule transforms from Form D to Form E, the hydrogen bond interaction between water and MDA molecules gradually becomes stronger. The observations were consistent with the results obtained from molecular dynamic simulations. The energy barriers of the path I were in line with the simulation results. This indicates the reliability of the polymorphic transformation mechanism of the MDA monohydrates. [ABSTRACT FROM AUTHOR]

We studied the thermal stability and many-sided properties of Y0.5Sr0.5Cr0.5Mn0.5O3 chromite-manganite that was made using the sol-gel method. We focused on the syngony type, unit cell parameters, and x-ray analysis. To confirm the results of the chromite-manganite indexing, the inverse values of the squares of interplane distances (104/d2) and the consistency of the x-ray and pycnometric densities were found to be very close to each other. It was found that the synthesised chromite-manganite crystallises in orthorhombic syngony and has a perovskite-like structure. Scanning Electron Microscopy (SEM) shows that chromite-manganite is uniformly distributed, and the crystallites are sized between 6 and 20 microns. The analysis of the relationship between heat capacity and temperature using the Thermo Gravimetry Analysis (TGA) technique demonstrates the stability of the internal structure and the presence of polymorphic transformations in the sample under study. [ABSTRACT FROM AUTHOR]

The possibility of using microsilica in the production of mullite–silica refractories was assessed. The chemical and mineralogical compositions of the raw materials, refractory Arkalyk clay and microsilica, were studied. It has been found that primary mullite and quartz formation occurs due to dehydration of kaolinite with the formation of intermediate metakaolinite. The introduction of alumina and microsilica into the charge composition promotes the formation of secondary mullite due to the interaction of aluminum oxide and highly dispersed chemically active microsilica. Free silica in compositions undergoes polymorphic transformations with the formation of cristobalite and tridymite. Mullite–silica refractories with an open porosity of 21%, a compressive strength of 42 MPa, and a thermal deformation temperature under the load of 0.2 MPa–1350 °C were obtained. [ABSTRACT FROM AUTHOR]

Mango (Mangifera indica L.) seeds is an interesting source of fat, rich in stearic (St) and oleic (O) acid with three major triacylglycerols (TAG): StOSt, StOO, and StLSt. The kernel fat content and quality depend however on the varieties and their origin. The objective of this study was to investigate the crystallization and polymorphic behavior of mango kernel fat extracted from three selected Ivorian varieties which differ in terms of TAG composition: Kent (KT), Djakoumankoun (DN) and Brooks (BR). The isothermal crystallization behavior was examined at 15 and 20°C by pulsed nuclear magnetic resonance, differential scanning calorimetry, x‐ray diffraction (XRD) and polarized light microscope. Under static conditions, DN crystallized faster, followed by BR, then KT. At 15°C, an unusual evolution was observed for both DN and BR, which can be explained by a melt‐mediated polymorphic transition from α into more stable forms. Using a differential scanning calorimetry (DSC) stop‐and‐return technique, different crystallization behaviors were also observed. Isothermal XRD experiments confirmed that the kinetics of the polymorphic transformation was different within the three samples, even if the three fats were β‐3L‐tending. At 15°C, KT transformed from liquid state to stable form without passing through α‐form, while DN and BR crystallized first into α‐from which transformed further to β′, then into stable β‐form. At 20°C, DN and BR crystallized directly from liquid to β′, which later transformed into β‐form while KT did not crystallize under the same conditions. The huge differences observed result from the differences in the TAG profiles, mainly in the StOO and StOSt content. [ABSTRACT FROM AUTHOR]

We show that mechanochemically driven polymorphic transformations can require extremely long induction periods, which can be tuned from hours to days by changing ball milling energy. The robust design and interpretation of ball milling experiments must account for this unexpected kinetics that arises from energetic phenomena unique to the solid state. Detailed thermal analysis, combined with DFT simulations, indicates that these marked induction periods are associated with processes of mechanical activation. Correspondingly, we show that the pre‐activation of reagents can also lead to marked changes in the length of induction periods. Our findings demonstrate a new dimension for exerting control over polymorphic transformations in organic crystals. We expect mechanical activation to have a much broader implication across organic solid‐state mechanochemistry. [ABSTRACT FROM AUTHOR]

differential scanning calorimetry was used to study the regularities of polymorphic α ↔ β-transformation in polycrystalline cobalt. The value of the activation energy of the α ↔ β-transformation during heating of cobalt (290–50 kJ/mol), enthalpy and entropy, depending on the thermal history of the metal, is determined. It is shown that the mechanisms of recrystallization under heating are closer to the first-order I phase transformations. When cooling under conditions of limited diffusion mobility of cobalt atoms, recrystallization is apparently carried out due to the passage of several diffusion-free mechanisms of phase transformation, implemented in close temperature ranges. [ABSTRACT FROM AUTHOR]

A set of experimental data on the thermodynamic parameters of polymorphic transitions in the silica system is considered. Analysis of these parameters in dimensionless form is performed. A fundamental result of the analysis is that the thermodynamic parameters of all silica polymorphs after transitions are described by a single universal Hugoniot of polymorphic transition. It is shown that the two-shock model of polymorphic transformations proposed earlier by the author describes all the results obtained in the analysis. A joint consideration of the experimental data and model calculations leads to the conclusion that during a polymorphic transformation, the density of the new phase is determined from the condition that the elastic pressure components after the first shock and after the polymorphic transition are equal. [ABSTRACT FROM AUTHOR]

Interest in the modification of zirconium-containing ceramics is rooted in their great prospects for application as materials for creating inert matrices of dispersed nuclear fuel, which can replace traditional fuel containing uranium dioxide, as well as increase the degree of its burnup. Moreover, among the variety of different types of ceramics offered, zirconium dioxide is the most promising, since it has higher thermal conductivity values compared to other types of ceramics, as well as low volumetric thermal expansion. Moreover, the key limitations in the application of these types of ceramics as materials for creating inert matrices are polymorphic transformations, which have a negative impact on changes in the properties of ceramics under external influences. The evaluation results of the impact of change in the ZrO2 ceramics' phase composition on the radiation damage resistance when subjected to irradiation with heavy ions, comparable in energy to fission fragments, are presented. The objects of study were samples of ZrO2 ceramics doped with MgO, the variation in the concentration of which leads to an acceleration of the processes of polymorphic transformations during thermal sintering, as well as the formation of a ZrO2/MgO-type structure with inclusions in the form of MgO grains. The results of the irradiation effect on the stability of the crystal structure of ceramics to deformation swelling due to the accumulation of deformation inclusions showed that ceramics with a monoclinic structure type are the least stable, for which, in the case of high irradiation fluences, the accumulation of deformation distortions leads to polymorphic transformations of the m—ZrO2 → t—ZrO2 type. During the evaluation of the irradiation effect on the change in mechanical properties and the softening degree, it was found that phase transformations of the m—ZrO2 → t—ZrO2 and t—ZrO2 → c—ZrO2 types lead to an increase in crack resistance by 1.5–2.0 times. Meanwhile, the formation of a structure of the ZrO2/MgO type with inclusions in the form of MgO grains in the interboundary space results in a softening resistance growth by over 7-fold. During tests for determining thermophysical parameters, as well as maintaining stability to crystal structure thermal expansion during prolonged thermal exposure, it was found that phase transformations associated with polymorphic transformations of the t—ZrO2 → c—ZrO2 type led to the preservation of the stability of thermophysical properties, even in the case of high irradiation fluences. [ABSTRACT FROM AUTHOR]

The global extraction of several billions of clean clay resources, which destroy millions square meters of land, is triggering environmental problems. Incorporating different dosages of incinerated waste or dredged sediment in bricks production has been studied by many researchers. Research articulating the combined effect of incinerated waste material (IWM) and river dredged sediments (RDS) addition on the performance of bricks is scarce. This paper aims to present findings on the engineering performance of fired bricks developed with the addition of IWM and RDS. In this regard, bricks were made with 5 wt% IWM and different dosages of RDS (i.e., 0 – 15 wt%). Physical, durability, mechanical, thermal and microstructure of the developed bricks is examined. Bricks' shrinkages were found meeting quality performance criterion in the 1.42 – 4.11% range. The highest bulk density of 1.85 g/cm3 permit to classify bricks obtained as lightweight. Water absorptions were mostly within the acceptable 20% tolerance level postulating the developed bricks high durability standard. Compressive strength reductions, which were confined within 5.28 and 21.57 MPa, showed the developed bricks applicability to structural weight-supporting construction as well as specialized engineering construction works. The 40.5% thermal conductivity reduction in WB15 bricks (at 800 °C) theorized its suitability for thermal insulation construction. Mineralogical and morphological analyses of fired bricks clearly showed kaolinite polymorphic phase transformation, which contributed to the different morphologies in the brick matrices. Consequently, reuse of IWM and RDS offered a chance to advance sustainable use of scarce clay resources in lightweight and thermal insulation brick production. • Performance of bricks made with incinerated waste and dredged sediment is studied. • Developed bricks showed linear shrinkages within the 1.42–4.11% quality limits. • The highest 17.87% absorptions of bricks fired at 1000 °C indicate good quality. • 21.57–5.28 MPa reductions in produced bricks' compressive strengths acceptable. • The up to 40.5% reduction in the bricks' conductivities good for insulation. [ABSTRACT FROM AUTHOR]

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A multi-kinase inhibitor, pazopanib (PAZ) is cocrystallized with cyclooxygenase (COX) inhibitor fenamic acids to investigate the dissolution rate and inhibition of cell migration in VEGF-triggered HUVEC cells to test the efficacy of stoichiometric drug–drug combinations. Crystallization experiments at the sub-milligram level in an acetonitrile–methanol mixture yielded two drug–drug salt forms of PAZ with flufenamic acid (FFA) and niflumic acid (NFA) as PAZ+·FFA−·ACN (an acetonitrile solvate named as form I) and PAZ+·NFA−. Structures of the crystal forms were characterized by single crystal X-ray diffraction (SC-XRD) method. Crystal structures revealed that the presence of a 2-aminopyrimidine group in PAZ is a strong partner for the carboxyl group in all solid forms, forming an acid⋯pyrimidine heterosynthon with COX inhibitor fenamic acids. To perform dissolution experiments and cell line analysis, the scale-up of both salt forms were done in the acetonitrile–methanol mixture through crystallization, which showed a polymorphic transformation in the case of PAZ+·FFA−·ACN (an acetonitrile solvate named form II). The thermodynamic stability of PAZ+·FFA−·ACN (form II) and PAZ+·NFA− were analysed using slurry experiment under ambient conditions in pH 1.2 (0.1 N HCl) buffer medium and the residual solid phase was characterized by powder XRD, which showed that PAZ+·FFA−·ACN (form II) was a metastable solid form while PAZ+·NFA− was a stable solid form. The dissolution experiments at gastric pH 1.2 showed that the rate of dissolution of PAZ+·FFA−·ACN was 10 times higher than PAZ+·NFA−. The cell migration assay suggested that PAZ+·FFA−·ACN inhibited ∼25% and PAZ+·NFA− inhibited ∼20% migration of HUVEC cells compared to PAZ alone. These investigations suggested that the drug–drug salts PAZ+·FFA− and PAZ+·NFA− would be potential combo drug candidates for clinical trials. [ABSTRACT FROM AUTHOR]

A novel type of 4,40,5,50-tetranitro-1H,10H-(2,20-biimidazole)-1,10-diamine (DATNBI)/TNT energetic cocrystal (cocrystal-1) was prepared by the solvent evaporation method. The molar ratio of the cocrystal is 1:2 and the crystal density is 1.784 g cm-3 at 23℃. It belongs to the triclinic system with space group P1. The thermal stability, mechanical sensitivity and detonation performance of cocrystal-1 were studied. Compared with DATNBI, the mechanical sensitivity (H50 and FS, friction sensitivity) and thermal stability (Td, detonation temperature) of cocrystal-1 were significantly improved (H50, FS and Td of DATNBI and cocrystal-1 are, respectively, 27.8 cm, 160 N, 240℃ and 65.6 cm, >360 N, 253℃). Combining these results with other characterizations, it was found that cocrystal-1 exhibited a polymorphic transformation, phase separation and melting of the two single components in succession. The ability to control the properties and understand the structural stability of this explosive cocrystal is of great value. [ABSTRACT FROM AUTHOR]

S- and Se-based chalcogenide glasses are intrinsically metastable and exhibit a number of photo-induced effects unique to this class of materials, reversible photostructural changes and photo-induced anisotropy being major examples. These effects are usually interpreted in terms of the formation of valence alternation pairs and 'wrong' bonds. In this work, using density functional theory simulations, we demonstrate for the case example of As 2 S 3 that a strong decrease in the optical band gap can be achieved if a polymorphic transformation of the local structure from orpiment to that of tetradymite takes place. For the formation of the latter, the presence of lone-pair electrons in near-linear atomic configurations is crucial. Our results represent a novel approach to understanding the photo-induced structural changes in chalcogenide glasses as being due to the presence of polymorphism, and will lead to their wider use in various photonic devices. [ABSTRACT FROM AUTHOR]

The LiCl-KCl-GdCl3 quasi-ternary phase diagram has been investigated by differential thermal analysis (DTA) and x-ray diffraction (XRD) techniques. These experiments showed that the LiCl-KCl-GdCl3 system consists of several pseudo-ternary and quasi-ternary composition triangles. Coexisting phases in the solid state at 260 °C were characterised by XRD analysis of the equilibrated samples. Quasi-ternary compounds were not found. The ternary eutectic temperature was observed at 315 ± 2 °C and its composition was delineated at 57 mol.% LiCl-42 mol.% KCl-1 mol.% GdCl3 in the LiCl-KCl-K3GdCl6 composition triangle. The other ternary eutectic temperature was observed at 308 ± 2 °C in the LiCl-K3GdCl6-K2GdCl5 composition triangle. Its composition was deduced at 40.2 mol.% LiCl-41.7 mol.% KCl18.1 mol.% GdCl3. Another ternary eutectic temperature was observed at 360 ± 9 °C in the LiCl-K2GdCl5-KGd2Cl7 composition triangle. Its composition was deduced at 33.8 mol.% LiCl-29.5 mol.% KCl-36.7 mol.% GdCl3. The fourth ternary eutectic temperature was observed at 362 ± 4 °C in the LiCl-KGd2Cl7-LiGdCl4 composition triangle. Its composition was delineated at 48 mol.% LiCl-11 mol.% KCl-41 mol.% GdCl3. The ternary pseudo-peritectic reaction "L+GdCl3 ↔ LiGdCl4+KGd2Cl7" was observed at 370 ± 3 °C. Its composition was delineated at 46.7 mol.% LiCl-10.5 mol.% KCl-42.8 mol.% GdCl3. The primary and secondary crystallisation temperatures, as well as polymorphic phase transformation temperatures of the samples were deduced from the heating runs of DTA experiments. Further, phases responsible for the various thermal events were ascertained. Isothermal composition triangles at selected temperatures, Scheil diagram and the polythermal liquidus projection with isothermal contours of the ternary phase field were drawn. [ABSTRACT FROM AUTHOR]

In this work, the structural, electrical, and mechanical properties and phase composition of high-content cubic zirconium oxide ceramics stabilized with Ca were investigated. The novelty of this work lies in evaluating the potential use of porous ceramics obtained using calcium carbonate as a matrix for dispersed nuclear fuel. Experimental samples were prepared using solid-phase synthesis through sintering in air at 1500 °C. The X-ray diffraction method and Raman spectroscopy showed that the fraction of the cubic zirconium oxide ZrO2-c phase gradually increased as the mass concentration changed from Cw = 0.00 to Cw = 0.15, and the CaZrO3 phase was present at concentrations of Cw = 0.20 and Cw = 0.25. When the phase composition was altered, significant changes occurred in the internal microstructure of the ceramics due to the processes of grain sintering and pore formation. Quantitative XRD analysis demonstrated the incorporation of Ca into the cubic structure of the ZrO2-c polymorph. Dielectric spectroscopy at low frequencies revealed that the synthesized ceramics had a dielectric constant of 16.8–22 with a low dielectric loss of ~ 0.005. The microhardness value at a load of 200 kgf (HV0.2) of the obtained samples varied between 5 and 12 GPa and depended on the internal microstructure and phase composition. The obtained results clearly indicate that the mechanical and electrical properties and phase composition of synthesized ceramics make them suitable as a matrix for dispersed nuclear fuels. [ABSTRACT FROM AUTHOR]

Compounds of the argyrodite family are valuable environmentally friendly functional materials with mixed ion-electronic conductivity, thermoelectric, photovoltaic, optical, and other properties. This paper presents the results of a thermodynamic study of the Cu8GeS6 and Cu8GeSe6 compounds - representatives of this family using the EMF method with Cu4RbCl3I2 solid electrolyte in the 295-430 K temperature range. From the EMF measurement data, the partial molar functions of copper were calculated in both crystal modifications of the Cu8GeS6 and Cu8GeSe6 compounds, undergoing polymorphic transformations at 330 and 335 K, respectively. Based on solid-phase equilibria diagrams of the Cu-Ge-S(Se) systems, the potential-forming reactions responsible for the partial molar functions of copper in the alloys were determined and the thermodynamic functions of formation and standard entropies of both modifications of these compounds, as well as the thermodynamic functions of their polymorphic transitions, were calculated. The work also presents and analyzes the thermodynamic data for compounds of the argyrodite family available in the literature. [ABSTRACT FROM AUTHOR]

In this article, for the first time, TG-DSC and TG-FTIR investigations of potential pharmaceutics, i.e., analgesic and anticancer active annelated triazinones (1–9) have been presented. The thermal behaviour of these molecules was established in oxidative and inert conditions. The solid–liquid phase transition for each compound (1–9) was documented by one sharp DSC peak confirming the high purity of each sample studied. All the molecules were characterised in terms of calorimetric changes and mass changes during their heating. They revealed high thermal stability in oxidative and inert conditions. The observed tendency in thermal stability changes in relation to a substituent present at the phenyl moiety was found to be similar in air and nitrogen. It was confirmed that annelated triazinones 1–9 were stable up to a temperature range of 241–296 °C in air, and their decomposition process proceeded in two stages under oxidative conditions. In addition, it was established that their thermal stability in air decreased in the following order of R at the phenyl moiety: 4-Cl > 3,4-Cl2 > H > 3-Cl > 4-CH3 > 2-CH3 > 3-CH3 > 2-Cl > 2-OCH3. The volatile decomposition products of the investigated molecules were proposed by comparing the FTIR spectra collected during their thermogravimetric analysis in nitrogen with the spectra from the database of reference compounds. None of annelated triazinones 1–9 underwent any polymorphic transformation during thermal studies. All the compounds proved to be safe for erythrocytes. In turn, molecules 3, 6, and 9 protected red blood cells from oxidative damage, and therefore may be helpful in the prevention of free radical-mediated diseases. [ABSTRACT FROM AUTHOR]

The formation of materials with negative thermal expansion (NTE) based on a phase transition-type mechanism (NTE-II) in 50 T–x (temperature–composition) RF3-R'F3 (R = La-Lu) systems out of 105 possible is predicted. The components of these systems are "mother" RF3 compounds (R = Pm, Sm, Eu, and Gd) with polymorphic transformations (PolTrs), which occur during heating between the main structural types of RF3: β-(β-YF3) → t-(mineral tysonite LaF3). The PolTr is characterized by a density anomaly: the formula volume (Vform) of the low-temperature modification (Vβ-) is higher than that of the high-temperature modification (Vt-) by a giant value (up to 4.7%). In RF3-R'F3 systems, isomorphic substitutions chemically modify RF3 by forming R1−xR'xF3 solid solutions (ss) based on both modifications. A two-phase composite (β-ss + t-ss) is a two-component NTE-II material with adjustable parameters. The prospects of using the material are estimated using the parameter of the average volume change (ΔV/Vav). The Vav at a fixed gross composition of a system is determined by the β-ss and t-ss decay (synthesis) curves and the temperature T. The regulation of ΔV/Vav is achieved by changing T within a "window ΔT". The available ΔT values are determined using phase diagrams. A chemical classification (ChCl) translates the search for NTE-II materials from 15 RF3 into an array of 105 RF3-R'F3 systems. Phase diagrams are divided into 10 types of systems (TypeSs), in four of which NTE-II materials are formed. The tables of the systems that comprise these TypeSs are presented. The position of Ttrans of the PolTr on the T scale for a short quasi-system (QS) "from PmF3 to TbF3" determines the interval of the ΔTtrans offset achievable in the RF3-R'F3 systems: from −148 to 1186 ± 10 °C. NTE-II fluoride materials exceed known NTE-II materials by almost three times in this parameter. Equilibrium in RF3-R'F3 systems is established quickly. The number of qualitatively different two-component fluoride materials with the giant NTE-II can be increased by more than ten times compared to RF3 with NTE-II. [ABSTRACT FROM AUTHOR]

Ceramics based on magnesium-sodium double phosphate MgNaPO 4 and magnesium-sodium double orthophosphate Mg 4 Na(PO 4) 3 were synthesized. The most suitable calcination temperatures were found as 800 °C for MgNaPO 4 and 900 °C for Mg 4 Na(PO 4) 3. At higher sintering temperatures, crack formation was observed, which can be explained by the presence of polymorphic transformations and thermal decomposition of MgNaPO 4. The crystal structures and lattice parameters for magnesium-sodium double phosphates were refined by using powder X-ray diffraction method. Obtained ceramic samples based on MgNaPO 4 and Mg 4 Na(PO 4) 3 are characterized by pH values in aqueous solutions of 7.1 and 8.2, respectively, which are close values to physiological pH values. They also undergo resorption in a model environment, and may be promising in regenerative surgery. [ABSTRACT FROM AUTHOR]

Mechanically induced polymorphic transformation of polymorph III of carbamazepine into form IV was accelerated and brought to completion by contaminating deliberately a milling jar and ball by touching them with fingers. In model experiments with additives of water and fatty acids (important components of fingerprints), carbamazepine dihydrate and carbamazepine form II, respectively, were obtained, without any evidence of form IV, as a result of mechanical treatment under otherwise the same milling conditions. A possible interpretation was suggested. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the mechanisms of polymorphic transformations in ZrO2 ceramics doped with MgO with different concentrations during thermal isochronous annealing, as well as the effect of the phase composition of ceramics on the change in strength properties and resistance to mechanical stress. Solving the problem of polymorphic transformations in zirconium dioxide by doping them with MgO will increase the resistance of ceramics to external influences, as well as increase the mechanical strength of ceramics. According to the data of X-ray phase analysis, it was found that the addition of the MgO dopant to the composition of ceramics at the chosen thermal annealing temperature leads to the initialization of polymorphic transformation processes, while changing the dopant concentration leads to significant differences in the types of polymorphic transformations. In the case of an undoped ZrO2 ceramic sample, thermal annealing at a temperature of 1500 °C leads to structural ordering due to the partial removal of deformation distortions of the crystal lattice caused by mechanochemical grinding. During the study of the effect of MgO doping and polymorphic transformations in ZrO2 ceramics on the strength properties, it was found that the main hardening effect is due to a change in the dislocation density during the formation of a ZrO2/MgO type structure. At the same time, polymorphic transformations of the m—ZrO2 → t—ZrO2 type have a greater effect on hardening at low dopant concentrations than t—ZrO2 → c—ZrO2 type transformations.

The aim of this work was to study the mechanisms of polymorphic transformations in ZrO2 ceramics under irradiation with heavy ions, as well as to determine the nature of structural distortions in the case of t-ZrO2 → c-ZrO2 type transformations and associated anisotropic deformations. The samples of ZrO2 ceramics were irradiated with Kr15+ heavy ions with an energy of 150 MeV and fluences of 1011–1016 ion/cm2. During evaluation of the structural changes depending on the irradiation fluence, it was found that at low irradiation fluences (1011–1012 ion/cm2), the main role is played by deformation distortions of the crystal lattice, which have a pronounced anisotropic character. Meanwhile, at fluences above 1013 ion/cm2, the main role is played by polymorphic transformations of the t-ZrO2 → c-ZrO2 type, followed by amorphization of the damaged layer at fluences above 1015 ion/cm2. It was established that the anisotropic distortion of the crystal lattice is more pronounced along the crystallographic a axis, as well as the (011) texture orientation, which is characteristic of t-ZrO2. The polymorphic transformation processes of the t-ZrO2 → c-ZrO2 type occur at irradiation fluences of 1013–1014 ions/cm2, which are characterized by the formation of an overlap of local areas of defects that appear along the trajectory of ions in the material. The dependences of changes in the strength and thermophysical properties of ZrO2 ceramics on the irradiation fluence were obtained. The mechanisms of influence of the structural disorder and polymorphic transformations on the decrease in strength and crack resistance were established.

One of the complex problems relating to the thermodynamics of a substance is creating an adequate description of its thermal properties. For example, the Einstein and Debye models (as well as in various modifications of these models) the heat capacity is calculated only when mechanical vibrations of the lattice are taken into account. This leads to the impossibility of describing the increase in heat capacity with increasing temperature for most substances, including iron triad metals. In addition, there is not a single theoretical construction capable of calculating the temperature dependences of the heat capacity and thermal expansion coefficient during polymorphic transformations and structural, magnetic and other phase transitions in the system. They appear on the charts in the form of final jumps, peaks and holes. As a result, there is a need to develop a new approach to the calculation of thermal characteristics. It should take into account the occurrence of local equilibrium in small areas in initially non-equilibrium metal samples for research. The nonequilibrium of a sample can be caused by the presence of impurity atoms, defects, volatile components in it, residual stresses, the occurrence of irreversible processes, etc. For the analytical description of arrays of measured values, experimenters use different exponential expressions in different temperature intervals, sometimes with negative powers. Such theoretical and experimental approaches cannot be considered satisfactory. Therefore, for the creation of the new model, it is necessary to choose such values that would be sensitive to changes in the state of the system. Within the framework of the proposed model of a two-phase locally equilibrium region, such quantities are the absolute temperature of the system, the order parameter in the form of the difference in volume fractions of coexisting ideal phases, the phase composition of the ordering phase, and its derivative with respect to temperature. The developed model allows to calculate the temperature dependences of the heat capacities and coefficients of thermal linear expansion of the iron triad metals (Fe, Co, Ni) with a change in the aggregation state (crystal - liquid), the presence of structural, magnetic and other phase transitions. It has been shown that the used expressions adequately describe the experimental data in a wide temperature range, and also allow to extend the plotted curves to experimentally unexplored regions. A possible structural transition in cobalt at a temperature of about 1600 K, the existence of which requires additional experiments, was established. The obtained expressions are distinguished by their simplicity and universality of applicability; they can be used to create an automatic calculation of the thermophysical properties of not only iron triad metals, but also other solid substances

Crystal structures of high-temperature t- (LaF3-type) and low-temperature β- (β-YF3-type) modifications of 61(58Ce0.564Gd0.5)F3 – "pseudo61PmF3" near the temperature of a polymorphic transformation (PolTr) (−148 ± 5 °C) were studied by in situ X-ray diffraction (XRD). During the t- → β- "pseudo61PmF3" PolTr (at cooling) anions are ordered in the direction perpendicular to the hexagonal close packing (HCP) layers. This is accompanied by 13% stretching of the t-type crystal lattice in the <010> direction and compression in the <100> (0.8%) and <001> (0.9%) directions. The structural changes in t- and β- "pseudo61PmF3" at heating from −148 to +20 °C represent changes (decrease and increase) in cation–anion bond lengths (BL) without changing the shape of the coordination polyhedron (CP). "Pseudo61PmF3" is a material with giant negative thermal expansion at PolTr (NTE-II). The decrease in volume during the β- → t- "pseudo61PmF3" PolTr (at heating) is 3.8%. [ABSTRACT FROM AUTHOR]

[Display omitted] Low oral absorption and extensive first pass metabolism of progesterone is reported for many oral formulations which warrants investigation into other routes of administration. It is the aim of this study to investigate the generation of inhaled formulations of progesterone though a spray drying approach with a focus on how spray drying impacts the physicochemical properties of progesterone. Formulations of progesterone with L-leucine and hydroxypropyl methylcellulose acetate succinate (HPMCAS) are reported to this aim. X-ray diffraction, spectroscopy and thermal analysis were used to characterise these formulations and confirmed that progesterone crystallises as the Form II polymorph during spray drying regardless of the solvent used. The resultant formulations showed higher aqueous solubility than progesterone Form I starting material and the addition of HPMCAS was shown to temporarily enable a supersaturated state. Thermal analysis was used to show that the Form II polymorph was sensitive to transformation to Form I during heating. The addition of L-leucine to the formulations reduced the temperature for the polymorphic transformation by ∼ 10 °C. However, when HPMCAS was added to the formulation, the Form II polymorph was prevented from transforming to the Form I polymorph. Cascade impaction was used to determine the aerosol performance of the spray dried powders and showed promising lung deposition profiles (mass median aerodynamic diameter 5 µm) with significant variation depending on the organic solvent used and the ratio of organic to aqueous phase in the feedstock. However, further optimisation of formulations was required to direct more progesterone into the alveolar regions. The addition of HPMCAS was seen to increase the alveolar deposition and therefore formed a formulation with a lower fine particle fraction and mass median aerodynamic diameter. The most suitable formulation for inhalation was formed from a 50:50 acetone:water mixture and showed an ED, FPF and FPD of 81.7%, 44.5% and 7.3 mg respectively. Therefore, HPMCAS is suggested as a suitable excipient to increase solubility, prevent polymorphic transformation and improve inhalation properties of spray dried progesterone formulations. This study highlights the use of spray drying to form inhalable progesterone powders with higher solubility which may broaden the application of this medicine. [ABSTRACT FROM AUTHOR]