SrO Al2O3 Research Articles

Coupled reactions in the system SrO–BaO–Al2O3–SiO2

Progress in the field of aircraft construction is usually determined by the functional capabilities of those materials that are used for the creation of aircraft equipment. Compositions of celsian-slawsonite ceramics belonging to the BaO–SrO–Al2O3–SiO2 oxide system are promising for use in the aircraft industry due to their high operational properties. In this regard, a theoretical study of its subsolidus structure is of great interest. The paper presents the results of calculating the Gibbs free energy for coupled reactions in the selected multicomponent system. The temperature intervals of the coexistence of phase combinations are given and the formed elementary tetrahedra are constructed. According to the results of theoretical studies, it is established that the considered multicomponent system is divided into 28 elementary tetrahedra. The existence of a combination of Sr2Al2SiO7–2SrSiO3–BaSiO3 phases in the temperature range of 300–700 K is confirmed, a "filled triangle" being formed between them. Based on the results of thermodynamic calculations, it is established that the reaction between Ba2SiO4 and SrAl2Si2O8 phases does not occur at temperatures up to 1200 K, and it is thermodynamically possible in the range of 1200–1700 K with the formation of a combination of BaSiO3–BaAl2O4–Sr2Al2SiO7 phases, which form a "filled circuit".

Exploring luminescence in transparent Glass–Ceramic coating: Study on Pr3+/ Dy3+ Co-doped SrO–Al2O3–SiO2 Glass–Ceramic particles

This study aimed to fabricate transparent glass–ceramic coatings with luminescent characteristics. To this end, a SrO–Al2O3–SiO2 glass–ceramic system doped with Pr3+ and Dy3+ ions, referred to as luminescent glass–ceramic (LGC), was synthesized via melting at 1550 °C for 1 h. LGCs were added as mill additives to the transparent glass–ceramic coating recipe at increasing weight percentages of 5, 10, 20, and 40% (5Pr, 10Pr, 20Pr, and 40Pr, respectively). The coating specimens fabricated through the wet spraying technique were vitrified and recrystallized at 820 °C for 4 min, resulting in an LGC coating. Further, the chemical composition, phase structure, thermal behavior, and bonding characteristics of the LGC systems were analyzed, and spectrofluorometer and scanning electron microscope (SEM) analyses were performed after the coating procedure. The SEM indicated an increase in particle intensity per unit surface area. The spectrofluorometric analysis revealed that the standard sample did not display any discernible peaks; however, samples supplemented with particles exhibit emission bands at wavelengths of 485 (4F9/2 → 6H15/2, blue) and 575 nm (4F9/2 → 6H13/2, yellow) for Dy3+ ions and at 485 nm (3P0→3H4, blue) for Pr3+ ions. According to the CIE color graph, an increase in the quantity of added particles resulted in the region shifting toward the green–white area from the center of the blue–green region in the standard sample.

Technological Methods for Increasing the Fluorine Content in SrO–Al2O3–P2O3–SiO2–F Glass for Glass-Ionomer Cement

Technological Methods for Increasing the Fluorine Content in SrO–Al2O3–P2O3–SiO2–F Glass for Glass-Ionomer Cement

Effect of Eu3+ ions concentration on visible red luminescence and radiative shielding properties of SrO–Al2O3– BaCl2–B2O3– TeO2 glasses

Trivalent europium (Eu3+) ions doped 10SrO-(10-x)Al2O3–10BaCl2–60B2O3–10TeO2 glasses were fabricated by the melt-and-quenching technique and characterized for excitation, absorption, emission, decay methods to analyze the suitability of the glasses for photonic device applications. In addition, gamma attenuation data of the prepared glasses were Obtained for energies 15 keV ≤ E ≤ 10 MeV using FLUKA and XCOM methods to check their suitability for radiative shielding purposes. Direct allowed, indirect allowed band gaps and Urbach energies were estimated from absorption spectra. Emission spectra obtained for an excitation wavelength of 362 nm have been used to estimate J-O intensity parameters Ωλ (where λ = 2, 4). The intensity parameters Ω2 and Ω4 were again used to evaluate various radiative properties for the emission transition 5D0→7F2 of Eu3+ ions doped OCBT glasses. Decay curves were well fitted by single exponential and in turn used to estimate experimental lifetime (τexp) of metastable state (5D0) of Eu3+ions. The analysis on radiative properties showed that 2.5 mol % of Eu3+ ions activated OCBT glasses for the emission transition 5D0→7F2 is well suitable for visible red lasers and display applications. Analysis of evaluated interaction parameters for gamma radiation fast and thermal neutrons showed clear cut dependence on the Eu2O3 content of the glasses. In addition, the radiation absorption ability of the glasses was compared with different classes of concrete, commercial glass shields, and nonconventional shielding materials. The present glasses showed great potential for deployment in radiation absorption roles in nuclear technologies.

Thermodynamic analysis of the reactions of strontium anorthite formation during the firing of thermal shock resistance ceramics based on the eutectic glasses of the SrO–Al2O3–SiO2 systems

Thermal shock resistance ceramic materials must have a high degree of sintering to ensure the required mechanical strength, erosion resistance, and resistance to high-temperature oxidation. However, the search for effective ways to achieve a high degree of sintering of ceramic materials based on the SrO–Al2O3–SiO2 system at low temperatures requires a large amount of experimental research. The aim of this work is to analyze thermodynamically the reactions of strontium-anorthite phase formation at the points of triple eutectics of the SrO–Al2O3–SiO2 system under low-temperature firing conditions. The eutectic points were selected in the region of strontium anorthite crystallization and had a temperature not exceeding 14000C. It has been established that in the case of compliance with the stoichiometric ratio, the final product of the interaction of the components of eutectic glasses S-1 and S-2 with the charging components is the strontium anorthite phase. The most probable is the formation of strontium anorthite in the interaction of eutectic glass components with Al2O32SiO2, which is a product of kaolinite dehydration (Al2O32SiO22H2O). It has been found that the compounds SrOSiO2 and 2SrOAl2O3SiO2 are most active in the interaction with the charging components in the direction of formation of the strontium anorthite phase than SiO2 tridymite. As a result, the sintering of strontium-anorthite compositions at a temperature of 9000C causes a significant increase in the content of the crystalline phase of strontium anorthite. The determined patterns allow making a reasonable choice of glass in the SrO–Al2O3–SiO2 system for the further manufacture of low-temperature strontium-anorthite ceramics.

Thermally stable illuminating characteristics of Tb3+/Sm3+ ions activated BaO–SrO–Al2O3–B2O3–SiO2 glasses for photonic applications

A set of Tb3+ and Tb3+/Sm3+ co-doped barium strontium aluminium borosilicate (BaSrAlBSi) glasses were produced to examine optical properties carefully. The transparent BaSrAlBSi glass amorphous nature was established by the XRD pattern. The absorption profile demonstrates the various peaks from n-UV to NIR range caused by the Tb3+ as well Sm3+ ions in BaSrAlBSi glass. BSi:Tb1.0 glasses give intense green emission under λex = 368 nm, BSi:Sm1.0 glasses exhibit the emission spectrum caused by the transitions of the Sm3+ ions. The Tb3+/Sm3+ co-doped BaSrAlBS glasses exhibit a mixture of emission exhibited by individual ions when excited at 368 nm, whereas it exhibits only red-orange light emission when excited under 402 nm. The PL lifetimes demonstrated a reduction in decay time as Sm3+ ions concentration increased in Tb3+ doped BaSrAlBSi glasses. CIE coordinates show the green emission was tuned towards the warm white region via co-doping of Sm3+ in Tb3+ doped BaSrAlBSi glasses. The strong thermal stability of BSi:TbSm1.0 glass is confirmed via a temperature-dependent emission profile. The observed results indicate that the transparent BSi:TbSm1.0 glasses as made will be directly useful for photonic device applications as n-UV pumping results in green warm white and orange emissions.

Radio-photoluminescence phenomenon in Cs2O-SrO-Al2O3-P2O5 glasses doped with different concentrations of Ag2O

In this study, Ag2O–Cs2O–SrO–Al2O3–P2O5 glasses with different Ag concentrations (0, 0.1, 0.3, 1.0, and 3.0 mol.%) were made by the melt-quenching method. In addition, the photoluminescence (PL) properties, the radio-photoluminescence (RPL) phenomenon, and spatial resolution on the X-ray imaging by the RPL were studied. The RPL was observed by irradiating with X-rays as an appearance of a new PL emission at around 590 nm. According to the shape of the PL spectrum and lifetime, the luminescence was confirmed to be due to Ag2+ with a lifetime constant of 14.7–45.5 ns. From the X-ray imaging resolution test, the 3.0% Ag-doped sample showed a spatial resolution of at least 10.0 LP/mm.

Glassy Functional Fillers of Glass-Ionomer Cements in the System SrO–Al2O3–P2O5–SiO2–F

Glassy Functional Fillers of Glass-Ionomer Cements in the System SrO–Al2O3–P2O5–SiO2–F

STUDY OF TECHNOLOGICAL PARAMETERS OF OBTAINING CELSIANE AND SLAWSONITE CERAMICS USING SINGLE-STAGE TECHNOLOGY

On the basis of the RO–Al2O3–SiO2 system, radiotransparent ceramic materials of cordierite, celsian, and anorthite composition, which have low dielectric characteristics, are obtained. These requirements are met by one of the main phases of the BaO–Al2O3–SiO2 system – celsian (BaAl2Si2O8), the melting point of which is 1740 °C, and the beginning of active phase formation occurs at a processing temperature of 1300 °C, as well as one of the main phases of the SrO–Al2O3–SiO2 is slavsonite (SrAl2Si2O8), which undergoes congruent melting at a temperature of 1765 °C, and the beginning of active phase formation occurs at a processing temperature of 1400 °C. The purpose of the work is to study the technological parameters of obtaining celsian and slavsonite ceramics by one-stage technology. According to the subsolidus structure of the three-component system RO–Al2O3–SiO2 (RO = ВаО, SrO), it is advisable to synthesize the necessary phases from pure raw materials and, taking into account the presence of impurities that impair the dielectric characteristics, the synthesis of the necessary crystalline phases is carried out from technical raw materials. Figurative points of the compositions of the selected compounds correspond to their stoichiometric composition (for slavsonite, wt. %: SrO – 31,99; Al2O3 – 30,93; SiO2 – 37,08; for celsian, wt. %: BaO – 40,85; Al2O3 – 27,17; SiO2 – 31,98). It was established that the physical characteristics of the obtained samples improve with an increase in the firing temperature by 100 °C, but they are far from the desired level. The dielectric characteristics of the obtained materials are within the requirements for radio-transparent materials. Taking into account the investigated physical properties and the obtained radiographs of fired samples in order to obtain a densely sintered material, it was decided to investigate model compositions with the addition of intensifying additives and to study their influence on the properties of fired samples

Vaporization and the Thermodynamic Properties of the SrO–Al2O3–SiO2 System

Vaporization and the Thermodynamic Properties of the SrO–Al2O3–SiO2 System

Mass spectrometric study and modeling of the thermodynamic properties of SrO-Al2 O3 melts at high temperatures.

The SrO-Al2 O3 system holds promise as a base for a wide spectrum of advanced materials, which may be synthesized or applied at high temperatures. Therefore, studying vaporization and high-temperature thermodynamic properties of this system is of great practical importance. Samples of the SrO-Al2 O3 system were obtained by solid-state synthesis and identified by X-ray fluorescence analysis, X-ray phase analysis, scanning electron microscopy, electron probe microanalysis, simultaneous thermal analysis, and thermogravimetric analysis. The thermodynamic properties of the SrO-Al2 O3 system were studied by the Knudsen effusion mass spectrometric (KEMS) method and were fitted by the Redlich-Kister and Wilson polynomials. The thermodynamic values obtained were also optimized within the generalized lattice theory of associated solutions (GLTAS). The vapor composition, temperature, and concentration dependences of the partial vapor pressures over the samples under study as well as the SrO activities in melts of the SrO-Al2 O3 system were determined by the KEMS method. Usage of the Redlich-Kister and Wilson polynomials allowed calculation of the excess Gibbs energies, enthalpies of mixing, and excess entropies in the concentration range 0-33 mol% of SrO at temperatures of 2450 and 2550 K. Significant negative deviations from the ideality were observed in the melts of the SrO-Al2 O3 system at 2450, 2550, and 2650 K. The Wilson polynomial was found to be the optimal approach to describe the thermodynamic properties in the system studied. Optimization of the experimental data using the GLTAS approach allowed the characteristic features of the thermodynamic description of the SrO-Al2 O3 system to be elucidated and explained.

Vaporization and the Thermodynamic Properties of the SrO–Al2O3–SiO2 System

Vaporization and thermodynamic properties of the SrO–Al2O3–SiO2 system are studied by high-temperature differential mass spectrometry in the concentration range from 90 to 10 mol % of SrO and the molar ratio of x(Al2O3)/x(SiO2) = 1.5. The samples are evaporated from Knudsen effusion cell made of tungsten. The partial pressures of the molecular forms of the vapor, the activities of the condensed phase components, the Gibbs energies, and the excess Gibbs energies are determined. It is established that the studied system is characterized by a slight negative deviation from the ideal behavior. For mullite (Al6Si2O13) the value of the standard enthalpy of formation is determined. The melting points of the synthesized samples are established by high-temperature microscopy.

GLASSY FUNCTIONAL FILLERS OF GLASS IONOMER CEMENTS IN THE SrO–Al2O3–P2O5–SiO2–F SYSTEM

Based on glass in the SrO–Al2O3–P2O5–SiO2–F system, functional glass fillers for glass ionomer cements containing up to 13 wt. % fluorine were obtained. The high level of radiopacity of the filling material is due to the presence of the absorbing component of the glass filler - oxide and strontium fluoride, which are introduced into the glass together. The use of fusible fluorine-containing raw materials makes it possible to reduce the glass transition temperatures, which opens up prospects for the industrial development of the developed compositions at melting temperatures below 1500 °C. The value of the refractive index of glasses with a high fluorine content nD ~ 1.50 is more in line with the refractive index of the polymer matrix of glass ionomer cement, which ensures high aesthetic characteristics of the filling material. Samples of transparent filling glass ionomer cement with high compressive strength > 100 MPa and hardening time of 5 min were obtained.

GLASS FILLERS BASED ON THE SrO–Al2O3–B2O3–SiO2 SYSTEM FOR DENTAL COMPOSITES

Dental composite ?lling materials based on glass in the SrO–Al2O3–B2O3–SiO2 system was obtained. The glass filler meets the modern level of requirements for filling materials, and is characterized by high chemical resistance to water, acids and alkalis (class I), high transparency (more than 80 %), consistency with the polymer matrix according to CTE while maintaining of an acceptable melting temperature and no tendency to crystallization. It is shown that the developed glass filler provides a high level of biomedical, operational and functional properties of a dental composite based on it and competitiveness with respect to popular foreign analogue materials.

Vaporization and Thermodynamic Properties of SrO–Al2O3 Ceramics at High Temperatures

Vaporization and Thermodynamic Properties of SrO–Al2O3 Ceramics at High Temperatures

THE EFFECT OF BORON OXIDE ON THE TECHNOLOGICAL PROPERTIES OF STRONTIUM-ALUMINUM SILICATE GLASSES FOR DENTISTRY

The effect of boron oxide additives in the amount from 0 to 11 mol. % was studied on the melting characteristic of glasses in the SrO–Al2O3–TiO2–ZrO2–B2O3–SiO2 system for use as fillers in dental filling composites in order to reduce the melting temperature to technologically acceptable values (no more than 1500 ?C) and increase the transparency of the produced granulate. It was found that with an increase in the B2O3 content, the melting temperature can be reduced from 1600 ?C (in glasses without B2O3 additives) to 1480 ?C with a B2O3 content of 11.8 mol. %, while the glass transition temperature decreases from 820 to 743 ?C. Already with a B2O3 content of 6 mol. % at a melting temperature of 1500 ?C, transparent glasses with light transmission of 80 % are produced, promising for the creation of sealing composites.

STUDY OF THE INFLUENCE OF INTENSIFYING ADDITIVES ON LOW-TEMPERATURE SYNTHESIS OF SLAVSONITE AND CELZIAN IN THE CREATION OF RADIOTRANSPARENT CERAMIC MATERIALS

The studies carried out concern the development of structural radiotransparent ceramic materials based on the four-component system BaO–SrO–Al2O3–SiO2. Due to the widespread use of radar equipment at modern aviation facilities, the development of radiotransparent fairings for them is a rather important and urgent task.The purpose of the fairings is to protect the antenna devices of radar stations from environmental influences during flight. Based on this, the fairings must meet a complex set of requirements for aerodynamic, thermal, radio engineering and mechanical properties. These requirements at supersonic flight speeds of modern objects increase significantly, since the improvement of the aerodynamic shape, the increase in the mechanical strength and thermal stability of the fairings contradicts the interests of radio engineering, leading to a significant deterioration in their radiotransparency and to distortions of antenna directional patterns. The consequence is a decrease in the range of radar stations and serious deterioration in their accuracy characteristics.The aim of the research was to obtain, on the basis of the BaO–SrO–Al2O3–SiO2 system, crystalline phases of slavsonit and celsian at low temperatures and times of synthesis, by introducing sintering intensifiers with fluxing and modifying action.The influence of a number of additives on the intensification of the low-temperature synthesis of slavsonit and celsian is investigated. The positive effect of the eutectic additive of the SnO2–Li2O system on the preparation of a densely sintered ceramic material based on solid solutions of slavsonit and monoclinic celsian is shown. It has been established that, according to its dielectric properties, the obtained ceramic material can be classified as structural radio-transparent materials.

Synthesis and performance of aluminous cements containing zirconium and strontium as alternatives to the calcium aluminate cements designed for the production of high performance refractories

Composite cements belonging to the CaO–Al2O3–ZrO2 (C-A-Z) and CaO–SrO–Al2O3–ZrO2 (C–Sr-A-Z) systems were evaluated as alternatives to calcium aluminate cements (CACs) for use in the refractory castables technology. The mineralogical phases in the as-synthesized C-A-Z and C–Sr-A-Z clinkers confirmed by XRD and SEM-EDS were CaAl2O4, Ca7ZrAl6O18 and CaZrO3 or (Ca,Sr)Al2O4, (Ca,Sr)Al4O7 and (Ca,Sr)ZrO3, respectively. The present work aimed at developing novel Zr-containing cements with excellent mechanical performance, i.e. modulus of rupture and cold crushing strength. Both hydration behavior of the C-A-Z, C–Sr-A-Z, CAC and their hydration products, were studied with isothermal calorimetry, XRD, SEM-EDS and NMR. Impedance camera instrument was firstly successfully applied for time-resolved electrochemical impedance spectroscopy measurements under nonstationary conditions and record the time-dependent evolution of the Nyquist plots for hydrating cement pastes. A sharp increase in the real part of impedance Z’ versus hydration time were corresponded to the second exothermic peak detected on the calorimetry curves.

Vaporization and thermodynamic properties of the SrO-Al2 O3 system studied by Knudsen effusion mass spectrometry.

Strontium aluminates can be used as refractory construction materials at temperatures up to 2000°С or as the materials for immobilization of long-lived radioactive waste. The SrО-Al2 O3 system is one of the more complicated oxide systems used for the creation of new radio-transparent materials. The exploitation of such materials at high temperatures demands the knowledge of the thermal stability of the compounds and solid solutions formed in the SrО-Al2 O3 system. The synthesis of the samples in the SrO-Al2 O3 system was carried out by a ceramic method at 1250°C. The characterization of the samples was accomplished with the use of X-ray diffraction (XRD). The vaporization of the samples under study was performed from a twin tungsten effusion cell using the Knudsen effusion mass spectrometry method. The temperature dependences of partial pressures of vapor species over 4SrO·Al2 O3 , 3SrO·Al2 O3 , SrO·Al2 O3 , SrO·2Al2 O3 and SrO·6Al2 O3 in a wide range of temperatures were determined. The component activities, the Gibbs energies of mixing and the standard enthalpies of individual strontium aluminates were obtained. The thermodynamic properties of the SrO-Al2 O3 system at high temperatures are characterized by negative deviation from ideality. The vaporization processes and thermodynamic properties of the SrO-Al2 O3 system were obtained for the first time.

Radiation Response Characteristics of Pr3+-activated SrO–Al2O3–TeO2 Glasses

Radiation Response Characteristics of Pr3+-activated SrO–Al2O3–TeO2 Glasses