This article presents the results of a study of new solid solutions formed in the system of diphosphates of alkaline elements and zinc: K2Zn3(P2O7)2–Cs2Zn3(P2O7)2. The obtained materials are promising as matrices for creating phosphors. The formation of phases containing two alkali cations is established on samples obtained by solid-phase synthesis by X-ray phase analysis, and the results of studying their thermal stability are presented.
A single-stage centrifugation method is used for the precipitation and crystallization of a solution of a hybrid halide perovskite compound of the CH3NH3PbI3 composition. The perovskite films are annealed in the temperature range of 80–140°C, during which the excess of the N-methylpyrrolidone solvent was removed by evaporation. The X-ray phase analysis of the synthesized perovskite layer is carried out. The morphology of the surface of the layers after crystallization and the transmission spectra in the optical range are studied. The experiments and research results showed that the optimal temperature regime for the formation and crystallization of lead triiodide methylammonium perovskite films is 100–110°C. The perovskite layers obtained in these processing regimes have a surface morphology with a uniform granular crystal structure and are highly uniform. Moreover, in solar cells based on perovskite-like CH3NH3PbI3 structures with an annealing temperature of 100–110°C, the short-circuit currents reached 16.0 mA/cm2. At the same time, at annealing temperatures of perovskite layers above 120°С, the maximum value of the short-circuit currents did not exceed 14.0 mA/cm2.
The use of glass powder instead of cement as an auxiliary cementitious material can better alleviate environmental problems and energy problems. This experiment studies the influence of the fineness of glass powder and the substitution rate on the performance of mortar, to guide the actual project. The study found that with the increase of the substitution rate, the initial setting time becomes longer, the finer the fineness, the longer the initial setting time, but the difference between P-60 and P-90 decreases with the increase of the substitution rate. With the increase of substitution rate, the compressive strength of 7, 28 and 90 d increased first and then decreased. When the substitution rate was 5%, the compressive strength reached the maximum, but the 7 d compressive strength of P-30 with 5% substitution rate decreased slightly. With the increase of substitution rate, the cumulative hydration heat decreased gradually. The difference between P-60 and P-90 was not significant. Similar to the cumulative hydration heat, the hydration heat flow per gram of cement decreased gradually with the increase of substitution rate. It can be seen from nanoindentation that fineness and substitution rate have little effect on the properties of hydration products. With the increase of substitution rate, the total porosity decreases first and then increases. The porosity of glass powder mixed with P-30 is the largest, followed by P-60 and P-90, but the difference between the total porosity of P-60 and P-90 is not significant. In practical engineering, these two factors need to be considered in combination.
The data of X-ray diffraction and IR spectroscopy of synthetic aluminosilicates of the kaolinite subgroup with different degrees of crystallinity are analyzed. The samples are obtained under hydrothermal conditions in alkaline and neutral media with different durations of synthesis. It is shown that as the synthesis time increases a gradual transition of the amorphous phase to the crystalline phase is observed, which is reflected in the IR spectra by the shift of the bands related to the oscillations of the groups in the octahedral and tetrahedral grids. The first band of stretching vibrations of hydroxyl groups at 3628 cm–1 appears after three days of hydrothermal treatment in a neutral medium, and under alkaline conditions with the same duration of treatment, two more bands are observed at 3687 and 3668 cm–1. The detected changes in the IR spectra correspond to the appearance of the characteristic X-ray reflections of halloysite according to the XRD data. Thus, IR spectroscopy can be considered as a method for a qualitative assessment of the degree of crystallinity.
MgO–Al2O3–SiO2 (MAS) glass has widespread applications due to the excellent chemical stability and mechanical strength. Accommodation of macroscopic properties requires a systematic investigation of the microstructure of glass caused by compositional adjustment. In this work, effects of progressive replacement of MgO by Al2O3 or SiO2 on glass structure and Vickers hardness were investigated. With the replacement of MgO by Al2O3 or SiO2, the glass network was strengthened, as a result, the glass transition temperature was increased and the crystallization tendency was weakened. The degree of structural changes caused by substitution of SiO2 for MgO is more significant than that of Al2O3 substitute for MgO. The strengthened glass network promotes the increase of Vickers hardness, and the coefficient of thermal expansion can be tailored in a large range. The results show that MAS glass maybe useful in the field of glass substrates for TFT–LCDs.
Herein, we systematically studied the thermodynamic and kinetic aspects of glass forming compositions in Ca–Mg–Cu alloy obtained by drawing the isocontour. Parameter ({{P}_{{{text{HS}}}}}) derived from the enthalpy of chemical mixing (ΔHchem) and normalized mismatch entropy ( (Delta {{S}_{sigma }}/{{k}_{{text{B}}}}) ) is used as a glass-forming ability (GFA) parameter. Variation of ({{P}_{{{text{HS}}}}}) with reported and calculated compositions is evaluated. Linear relation of Cu with ({{P}_{{{text{HS}}}}}) is observed, whereas inverse relation of Ca and Mg is obtained. The linear variation of ({{P}_{{{text{HS}}}}}) with a supercooled liquid region (SCLR) ( (Delta {{T}_{{text{x}}}}) ) is studied. Inverse correlation of critical cooling rate ( ({{R}_{{text{C}}}}) ) with ({{P}_{{{text{HS}}}}}) is obtained. ({{R}_{{text{C}}}}) for predicted compositions is found close to that of reported compositions. Therefore, Cu should be added carefully with other elements to improve the GFA and reduce the cooling rate of Ca‒Mg‒Cu glassy. In this paper, an empirical correlation of (Delta {{T}_{{text{x}}}}) with ({{P}_{{{text{HS}}}}}) is proposed, and the modeled values are found to agree with the experimental values.
A new method for molecular dynamics (MD) modeling of the glass structure using a crystal structural template is proposed. The template is based on the unit cell of the crystalline phase, whose composition is qualitatively similar to the modeled glass. Using this approach and multistage MD simulation, the model of the spatial structure of grade E borosilicate glass, reproducing its physicochemical characteristics, is obtained. The proposed method enables to model the glass structure using classical MD methods with greater productivity and stability.
In this work an attempt is made to study the impact of the quenching rate upon structure, hyperfine interactions, magnetic and mechanical properties of Fe78Si9B13 metallic glasses. Other involved parameters in melt spinning method were kept invariant. Analytical techniques comprising X-ray diffraction, transmission Mössbauer spectrometry, vibration sample magnetometer, Vickers microhardness and differential scanning calorimetry were employed. Minor effect of quenching rate upon the macroscopic magnetic properties was detected. It was shown that notable changes in the local atomic arrangement, structure, and mechanical properties were unveiled, dominantly by represent the crystallization at the lowest quenching rate.
Two compositions of heat-resistant electrical insulating organosilicate coatings are developed using fine glassy additives in the compositions: aluminoborosilicate and vanadium antimony phosphate glass. The coatings have a heat resistance of 700 and 800°С and resistance to sudden temperature changes from the maximum permissible temperature to 20°С three times. The electrical insulating and physical-mechanical properties of the coatings are determined.
The stability of synthetic and natural zeolites in model biological media simulating the environment of the stomach (pH 1.8), blood plasma (pH 6.9), and intestines (pH 8) is studied. The effect of long-term exposure (up to 7 days) to biological media on the crystal structure of Beta, Rho, Y, and clinoptilolite zeolites is studied. The degree of degradation of the crystal structure of zeolites is controlled by X-ray phase analysis. Based on the results obtained, conclusions are drawn on the prospects for the use of synthetic and natural zeolites as drug carriers.
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