Phase equilibria in the stable KCl–KBr–K3FSO4 cutting triangle of the quaternary KF–KCl–KBr–K2SO4 system were studied by differential thermal analysis (DTA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). For the K3FSO4 compound, the enthalpy of fusion was determined to be 68.59 ± 2.06 kJ mol−1 at a melting temperature of 871 ± 1.5 °C, and the enthalpy of the polymorphic transition was found to be 2.65 ± 0.08 kJ mol−1 at 560 ± 1.5 °C. The polymorphic transition temperature was 560 °C, which is somewhat lower than the values reported in previous studies. The T−x phase diagram of the polythermal section [40 mol

The double oxalates MI3[MIII(C2O4)3] possess rich crystallochemistry and can be used as precursors for various ceramic materials. The article discusses a case of Li3[Al(C2O4)3]. A series of previously unknown hydrates (Li3[Al(C2O4)3] & sdot; 5.5H2O, Li3[Al(C2O4)3] & sdot; 4H2O, Li3[Al(C2O4)3] & sdot; H2O) was found for this composition, their crystal structure and temperatures of mutual transformations determined. Transformation from Li3[Al(C2O4)3] & sdot; 4H2O to Li3[Al(C2O4)3] & sdot; H2O was found to be accompanied by a change in the topology of the bonding network. Uniaxial negative thermal expansion was found for anhydrous Li3[Al(C2O4)3]. Thermal decomposition of Li3[Al(C2O4)3] was demonstrated to be a promising way to obtain precursors for aluminate ceramics. image

In this study, geopolymers based on mechanically activated mixtures of fly ash (FA) with SrCO3 (strontianite) and BaCO3 (witherite) were synthesized. NaOH solution was used as an alkaline agent and curing was carried out under ambient conditions. XRD, FTIR spectroscopy, thermogravimetry, and SEM were used to study the geopolymerization process and microstructure. The product of geopolymerization of the milled (FA + SrCO3) and (FA + BaCO3) blends was X-ray amorphous N-A-S-H gel. The beneficial impact of mechanical activation on the compressive strength of geopolymers was most evident during the initial stages of the curing process. The strength of geopolymers based on the (FA + carbonate) blends after 7 d was either less than the corresponding strength of geopolymers based on the 100% FA or, within the measurement accuracy, equal to it. With increasing curing time, the strength development of geopolymers synthesized from (70% FA + 30% carbonate) blends exceeded the strength growth of geopolymers containing less carbonates; after curing for 180 d, these geopolymers showed the highest compressive strength (20–27 MPa). This trend was more pronounced for the geopolymers based on the (FA + SrCO3) blends. The influence of SrCO3 and BaCO3 addition to the FA on the strength of composite geopolymers was explained by dilution and microfiller effects. The geopolymers based on the FA blended with SrCO3 and BaCO3 exhibit potential applications in immobilizing radioactive strontium and producing radiation shielding materials.

Moolooite, Cu(C2O4)·nH2O, is a typical biomineral which forms due to Cu-bearing minerals coming into contact with oxalic acid sources such as bird guano deposits or lichens, and no single crystals of moolooite of either natural or synthetic origin have been found yet. This paper reports, for the first time, on the preparation of single crystals of a synthetic analog of the copper-oxalate biomineral moolooite, and on the refinement of its crystal structure from the single-crystal X-ray diffraction (SCXRD) data. Along with the structural model, the SCXRD experiment showed the significant contribution of diffuse scattering to the overall diffraction data, which comes from the nanostructural disorder caused by stacking faults of Cu oxalate chains as they lengthen. This type of disorder should result in the chains breaking, at which point the H2O molecules may be arranged. The amount of water in the studied samples did not exceed 0.15 H2O molecules per formula unit. Apparently, the mechanism of incorporation of H2O molecules governs the absence of good-quality single crystals in nature and a lack of them in synthetic experiments: the more H2O content in the structure, the stronger the disorder will be. A description of the crystal structure indicates that the ideal structure of the Cu oxalate biomineral moolooite should not contain H2O molecules and should be described by the Cu(C2O4) formula. However, it was shown that natural and synthetic moolooite crystals contain a significant portion of “structural” water, which cannot be ignored. Considering the substantially variable amount of water, which can be incorporated into the crystal structure, the formula Cu(C2O4)·nH2O for moolooite is justified.

This study reports the effect of natural dolomite addition to fly ash and the mechanical activation of this blend on the geopolymerization process. Dolomite was replaced with fly ash at 1, 3, 5, and 10 wt.%. Geopolymers were synthesized at ambient temperature using NaOH solution as an alkaline agent. The geopolymerization process, reactivity of the raw material, compressive strength, and microstructure were studied using X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetry, and scanning electron microscopy. It was shown that blending fly ash with dolomite and mechanical activation improved the geopolymer strength, especially during the early age of curing. For geopolymers prepared using a 90% fly ash + 10% dolomite blend cured for 7 d, the strengths were 8.2-, 2.3-, and 1.4-fold higher than those for geopolymers prepared using 100% FA for 30 s, 180 s, and 400 s milling times, respectively. A simple method for evaluating the increments of mechanical activation, carbonate additives, and the synergistic effect in the increase in the compressive strength of the composite geopolymer is proposed.

The breaking of inversion symmetry can enhance the multifunctional properties of layered hybrid organic-inorganic perovskites. However, the mechanisms by which inversion symmetry can be broken are not well-understood. Here, we study a series of MnCl4-based 2D perovskites with arylamine cations, namely, (C6H5CxH2xNH3)2MnCl4 (x = 0, 1, 2, 3), for which the x = 0, 1, and 3 members are reported for the first time. The compounds with x = 1, 2, and 3 adopt polar crystal structures to well above room temperature. We argue that the inversion symmetry breaking in these compounds is related to the rotational degree of freedom of the organic cations, which determine the hydrogen bonding pattern that links the organic and inorganic layers. We show that the tilting of MnCl6 octahedra is not the primary mechanism involved in inversion symmetry breaking in these materials. All four compounds show 2D Heisenberg antiferromagnetic behavior. A ferromagnetic component develops in each case below the long-range magnetic ordering temperature of ∼42-46 K due to spin canting.

Cuban and Mexican zeolites are of particular interest from economic outlook because of their exceptional properties and abundance. Here, we present the results of the comparative study of the elemental, structural, morphological, thermal and textural properties of natural zeolites: clinoptilolite, mordenite and erionite from various deposits. Despite a complex phase and element compositions of the studied materials, some general features were detected. The observed dehydration steps are related to water desorption from porosity of different size ranges: mesopores, main and small zeolite voids. This dehydration pattern interferes with the exchangeable cation composition that also affects the general trends. Thermochemical properties of samples are influenced by the geographical location of the deposits. Depending on the origin of the sample, the dehydration enthalpy varies in quite a wide range, which is a function of both zeolite framework structure and exchangeable cation composition. The study of meso- and macropore systems reveals that all the samples exhibit multimodal pore size distribution and possess significant amounts of mesoporosity and even macroporosity. Among the studied samples, the mordenite from Palmarito de Cauto, the clinoptilolite from Etla and the erionite from Agua Prieta (Sonora) have a significant number of pores with average size of about 3 nm. All the samples, except erionite from Agua Prieta, show macroporosity with rather well-defined pore size between 0.3 and 2 μm. The porosity over mass does not change noticeably from one sample to other and varies from 0.32 to 0.65 cm 3 g −1 .

Mesostructured pillared zeolite materials in the form of lamellar phases with a crystal structure of mordenite (MOR) and ZSM-5 (MFI) were grown using CTAB as an agent that creates mesopores, in a one-pot synthesis; then into the CTAB layers separating the 2D zeolite plates were introduced by diffusion the TEOS molecules which were further hydrolyzed, and finally the material was annealed to remove the organic phase, leaving the 2D zeolite plates separated by pillars of silicon dioxide. To monitor the successive structural changes and the state of the atoms of the zeolite framework and organic compounds at all the steps of the synthesis of pillared MOR and MFI zeolites, the nuclear magnetic resonance method (NMR) with magic angle spinning (MAS) was applied. The 27Al and 29Si MAS NMR spectra confirm the regularity of the zeolite frameworks of the as synthetized materials. Analysis of the 1H and 13C MAS NMR spectra and an experiment with variable contact time evidence a strong interaction between the charged “heads” –[N(CH3)3]+ of CTAB and the zeolite framework at the place of [AlO4]− location. According to 27Al and 29Si MAS NMR the evacuation of organic cations leads to a partial but not critical collapse of the local zeolite structure.

Аннотация.Изучена трансформация вермикулитового субстрата в процессе длительной эксплуатации в гидропонной теплице.Изменение свойств вермикулита исследовано методами рентгенофазового и синхронного термического анализа с привлечением данных о гидрофизических свойствах и химическом составе

The effect of 1,1,9-trihydroperfluorononanol-1 immobilized on montmorillonite nanoclay on the nature of structural transformations and the properties of polycaproamide composites was studied. Using the methods of electron, atomic force microscopy and differential scanning calorimetry, we established the features of changing the diameter and height of spherulites in non-oriented films of this heterochain polymer, as well as the reorganization of its polymorphic composition due to the introduction of a fluorine-containing modifier. The stabilizing effect of the additive used on the mechanical properties and thermo-oxidative stability is shown.

Physicochemical properties of expanded vermiculite-phlogopite products from Kovdor (Murmansk region, Russia) used for 15 years as a hydroponics substratum were studied. The four investigated samples were as follows: natural vermiculite, initial expanded (roasted at 700 degrees C) vermiculite, spent expanded vermiculite and spent vermiculite roasted again at the same temperature. Data on the bulk density, field capacity, hygroscopicity, and expansion coefficients showed that the degradation of the substratum was accompanied by mechanical destruction, reduction of water absorption by half, and transformation of mineral phases. The structural transformation of expanded vermiculite was studied using X-ray diffraction (XRD), thermogravimetric analysis (TG), and differential scanning calorimetry (DSC), coupled with a mass spectrometric analysis of the released gases. Under conditions with a sufficient supply of plants with potassium of nutrient solution, a change in the mineral composition occurred: a decrease in the content of vermiculite and an increase in phlogopite. The formation of organomineral complexes on the surface of the vermiculite was detected. There was no noticeable change in the chemical composition of the expanded vermiculite during its use in hydroponics. In essence, the levels of potentially toxic elements (Mn, V, Ni, Cr, Co, Cu, Zn) met environmental regulations, and the levels of major elements (Mg, Ca, K, Fe, Mn) corresponded to those found in natural vermiculite. The chemical composition and structure of spent vermiculite allows its use as an ameliorant to improve soil, water, and air regimens.

Blends of fly ash and natural calcite, mechanically activated for 0–400 s in a planetary mill, were used to synthesize geopolymers at ambient temperature. The calcite content in the blends was 0–10 wt.%. Sodium hydroxide solution was used as an alkaline agent. Mechanical activation of the raw material considerably enhanced its reactivity with respect to the alkaline agent, as was observed using Fourier-transform infrared spectroscopy, isothermal conduction calorimetry, thermogravimetry coupled with mass spectrometry analysis of the evolved gas, and SEM/EDS. The addition of calcite to the fly ash improved the compressive strength of the geopolymers, especially during the early age of curing. For 7 d aged geopolymers based on the 90% fly ash + 10% calcite blend, the strength was 8.0-, 3.5- and 2.9-fold higher than that for the geopolymers based on the unblended fly ash for 30 s, 180 s and 400 s mechanical activation time, respectively. Using Mössbauer spectroscopy, it was revealed that iron present in the fly ash did not play a significant part in the geopolymerization process. The dominant reaction product was sodium containing aluminosilicate hydrogel (N-A-S-H gel). Calcite was found to transform, to a small extent, to vaterite and Ca(OH)2 in the course of the geopolymerization.

The derivative of 1,2,4-thiadiazole (TDZ) can be considered as a perspective agent for the Alzheimer’s disease prevention. Due to a highly lipophilic character, the compound reveals good membrane permeability properties and poor solubility in aqueous media. In order to solve this problem, water-soluble biodegradable polymers: PEG 6000 (PEG), PVP K29-30 (PVP) and linear (A–B–A type) ethylene oxide-propylene oxide block copolymer Pluronic F127 (F127) were used in the present investigation to obtain binary and ternary TDZ composites (solid dispersions) with improved solubility and dissolution rate. Composites were prepared by a mechanical grinding procedure. Differential scanning calorimetry and FTIR spectroscopy were used to characterize the obtained samples. The interaction of TDZ with PVP after the grinding procedure was revealed. Shake-flask method was applied to measure the solubility of the composites. A dramatical increase in the solubility was shown for the solid dispersion with F127 above the critical micelle concentration. The dissolution behavior was studied with the help of the basket method at pH 1.2 and pH 6.8. The dissolution of TDZ/polymer solid dispersions was substantially accelerated as compared to pure TDZ and physical mixtures. The dissolution mechanism was estimated through the Korsmeyer–Peppas model equation. Franz diffusion cell and new Permeapad™ barrier were applied for the permeability assay. The permeability of TDZ in solid dispersions through the Permeapad™ barrier was shown to decrease in comparison with the pure TDZ. It was concluded that composites with PEG, PVP and F127 are an effective tool for increasing the solubility and dissolution of 1,2,4-thiadiazole derivative.

Using the data obtained by Knudsen effusion mass spectrometry, the standard formation thermodynamic properties of La_2Hf_2O_7, Nd_2Hf_2O_7, and Gd_2Hf_2O_7 were calculated in the present study at high temperatures. Based on the results obtained, it was shown that the standard formation Gibbs energies of La_2Hf_2O_7, Nd_2Hf_2O_7, and Gd_2Hf_2O_7 from the elements at the temperature 2445 K were consistent with the empirical rule concerning decrease of stability of pyrochlore hafnate phase with decrease in lanthanoid ionic radius. The La_2Hf_2O_7 and Gd_2Hf_2O_7 heat capacities were obtained in the present study by differential scanning calorimetry. These data were used along with those found earlier to evaluate the standard formation Gibbs energies of La_2Hf_2O_7 and Gd_2Hf_2O_7 from the elements at the temperature 298 K, which equal (−3937 ± 10) kJ/mol and (−3895 ± 10) kJ/mol, respectively. The thermodynamic properties of La_2Hf_2O_7, Nd_2Hf_2O_7, and Gd_2Hf_2O_7 estimated in a wide temperature range allowed consideration of reliability of data available in the literature.

We studied the thermodynamic properties of calcium molybdate (CaMoO4) single crystal sample. Heat capacity was measured by DSC in the 255-766 K range. Isobaric thermodynamic functions (entropy, enthalpy, and Gibbs free energy) were calculated in the 298.15-766 K range. Melting point and enthalpy of melting were determined experimentally. We calculated isochoric heat capacity and thermodynamic functions up to the melting temperature of 1750 K by using low-temperature adiabatic calorimetry data within the framework of the effective sum method. We obtained the characteristic temperatures associated with the moments of the phonon density of states and its effective cutoff frequency. We estimated accuracy of the obtained results and compared the results with the known data.

This article is devoted to the investigation of water sorption by the layered perovskite-type titanate K2Nd2Ti3O10 and its intercalated protonated derivatives HxK2−xNd2Ti3O10·yH2O in a humid atmosphere. K2Nd2Ti3O10 was synthesized by the solid-state reaction. Metastable HxK2−xNd2Ti3O10·yH2O compounds were obtained by water flushing. The determination of the samples composition was carried out by XRD and TG analysis. The stability in a humid atmosphere was investigated by a water vapor sorption analyzer. It was found that humid atmosphere has influence only on K2Nd2Ti3O10 while HxK2−xNd2Ti3O10·yH2O phases are stable under experimental conditions. The study of K2Nd2Ti3O10 in humid atmosphere has shown that the intercalation process proceeds with a rate constant kint = 3.2 × 10−6 min−1 at 0–95% RH, and the protonation process takes place at RH more than 80%.

The production of apatite concentrate in the Arctic region of the Russian Federation is carried out using technology developed during the middle of the twentieth century. One of the most energy-consuming and environmentally dangerous stages of this technology is the drying of raw concentrate. Energy for drying is obtained from combustion of fuel oil, which leads to greenhouse gas emissions and environmental pollution. This study analyses the drying step in the apatite production process to optimize the environmental and economic aspects of this process. The characteristics of apatite concentrate during heating was studied through synchronous thermal analysis. Mass loss was determined during each stage. It was observed that drying of apatite concentrate does not require high temperatures, which are achieved in drum chambersthrough fuel oil combustion. Therefore, drying with flue gases is inexpedient. A method that involves dewatering the concentrate, which can be considered a form of clean technology and does not involve fuel oil combustion, is proposed. The results of this study can be used to modernize the current technology for the production of apatite concentrate.

To find promising analogues of naturally occurring enediyne antibiotics with a sufficient reactivity in the Bergman cyclization and moderately stable under isolation and storage, a scale of relative enediynes reactivity was created on the basis of calculated free activation energies for the Bergman cyclization within 12 known and new benozothiophene, benzene, and cinnoline annulated 9- and 10-membered enediynes. To verify the predicted reactivity/stability balance, three new carbocyclic enediynes fused to a benzothiophene core bearing 3,4,5-trimethoxybenzene, fluoroisopropyl, and isopropenyl substituents were synthesized using the Nicholas-type macrocyclization. It was confirmed that annulation of a 3,4,5-trimethoxybenzene moiety to a 10-membered enediyne macrocycle imparts high reactivity to an enediyne while also conferring instability under ambient temperature. Fluoroisopropyl-substituted 10-membered enediyne from the opposite end of the scale was found to be stable while moderately reactive in the Bergman cyclization. Along with the experimentally confirmed moderate reactivity (DSC kinetic studies), (fluoroisopropyl)enediyne showed a significant DNA damaging activity in plasmid cleavage assays comparable with the known anticancer drug Zeocin.

A lanthanum zirconate La2Zr2O7 was synthesized by soft mechanochemical method using zirconium oxynitrate ZrO(NO3)2·6H2O and lanthanum carbonate La2(CO3)3·8H2O as reagents. Mechanical activation of the reagents was carried out in a centrifugal planetary ball mill. The processes occurring during calcination of the jointly and the separately mechanically activated salt mixture were studied using DSC, TG coupled with mass spectrometry, XRD analysis, and FTIR spectroscopy. It was shown that in the course of joint mechanical activation in the mill alongside with intimate mixing of the reagents and their amorphization exchange reaction occurred, producing lanthanum nitrate, basic lanthanum nitrate, basic zirconium carbonate, and hydrated zirconium oxide. The DSC curve of the jointly mechanically activated salt mixture showed a strong exothermic peak at 878 °C which was not associated with mass loss. This peak was attributed to La2Zr2O7 crystallization in agreement with XRD data. Nanocrystalline lanthanum zirconate synthesized by annealing of the jointly mechanically activated salt mixture was characterized using XRD analysis, scanning, and transmission electron microscopy.

Comprehensive research of water behavior in Na- and Cu-mordenites with different Na/Cu ratio was done. Several steps of dehydration process were detected and analyzed, taking into account difference in chemical composition of the samples, reaction models and corresponding kinetic equations. Activation energies for these steps were calculated. It was shown that the majority of dehydration steps for all zeolite samples studied might be associated with chemical reaction mechanism corresponding to the second order kinetic model, except for the most high-temperature step for Cu-mordenite, for which the third-order model has the higher correlation coefficient. A detailed analysis of rehydration processes was studied by proton NMR spectroscopy. The obtained results allow one to distinguish different types of water and to associate them with a certain localization of water molecules in zeolite voids: the main channel for both Na and Cu-mordenites; a side pocket of Na-mordenite; molecules coordinated with Cu2+ cations in Cu-mordenite. The diffusion measurements carried out using static field gradient NMR technique proved that the water diffusion character below 300 K is essentially intracrystalline, whereas above 300 K it becomes intercrystalline. The activation energy of intercrystalline diffusion is about 28 kJ/mol and does not depend on the Na/Cu ratio. That allows us to suppose that in the studied zeolites the intercrystalline diffusion is governed by the morphology of the sample mainly.