The article presents the results of research on the development of prototypes for obtaining mineral fibers based on the andesibazalt–slag–dolomit composition and the results of testing their physicochemical properties. Tests of chemical resistance of optimal compositions in aggressive conditions showed that the chemical resistance of the fibers depends on the content of metal oxides in the glass and their ratios that take into account the mutual influence of SiO2, Al2O3, Fe2O3, CaO, MgO, Na2O, K2O. It has been established that the studied andesibasalt of the Karahtay field is a promising raw material component for obtaining mineral fibers.
The formation of birefringent nanogratings by a femtosecond laser beam in the volume of sodium aluminoborate glasses is demonstrated. The dependences of the optical retardance of the nanogratings on the parameters of laser exposure and the chemical composition of the glass are determined. It was shown that an increase in the Al2O3 concentration at a constant [Na2O]/([B2O3 + Al2O3]) molar ratio does not affect the ranges of laser exposure parameter for nanogratings formation but leads to an increase in the retardance of the nanogratings.
Ceramics with phase composition after firing in the range of 600 – 900 °C represented by anhydrous calcium sulfate CaSO4, and calcium sodium sulfates (Na0,8Ca0,1)2SO4 and Na6Ca(SO4)4 were obtained from a powder mixture of sodium sulfate Na2SO4 and calcium sulfate dihydrate CaSO4?2H2O, taken at a molar ratio CaSO4?2H2O/Na2SO4 = 1. The phase composition of the powder mixture after homogenization in a planetary mill in an acetone medium, in addition to the starting salts, also included hydrated sodium calcium sulfate Na4Ca(SO4)3?2H2O. When kept in water for 5 and 60 min the mass loss of ceramic sample fired at 700 °C was 15 and 75 % respectively. Ceramics in the Na2O–CaO–SO3 system in the form of granules or complex shapes obtained using 3D printing can be used as a removable (soluble or leachable) porogen and/or a prototype of a porous space with a given architecture when creating porous polymer or inorganic materials.
Studies have been carried out on the topic of obtaining ceramic materials for construction purposes with an anorthite phase. Clay and blast-furnace gas cleaning sludge were used as raw materials. The chemical compositions of raw materials for their use in the production of ceramic products have been studied. The calcium- and iron-containing compounds included in the composition of the gas cleaning sludge contribute to a decrease in the temperature of the formation of solid solutions and the anorthite phase. It has been established that with the addition of sludge up to 80 wt.% into the composition of the ceramic mixture increases the likelihood of an anorthite phase formation. The physico-mechanical parameters of the obtained ceramic samples have been studied. It has been established that the amount of gas cleaning sludge in the composition of the charge is 10 – 40 wt.% allows to obtain products with compressive strength 18 % higher than the control sample. The improvement in physical and mechanical properties is associated with an increase in the amount of the formed anorthite phase, which is confirmed by the data of X-ray phase analysis.
Syntactic foams based on hollow ceramic microspheres and the ceramic-forming binder polycarbosilane, capable of transition to silicon carbide at elevated temperatures, are considered. The processes of heat treatment of compositions and the transition of polycarbosilane to silicon carbide are considered. The physicomechanical and thermophysical characteristics of syntactic foams are studied.
Lost-wax casting is one of the most advanced ways to obtain geometrically complex castings of high quality. One of the main factors influenced on the casting properties is the quality of the ceramic mold face layer. A uniform deposition of the ceramic slurry can be achieved by condition of the wax surface is well wetted by the suspension dispersion medium. Since the surface of the wax model is hydrophobic and the dispersion medium of ceramic suspension is water, an increase of wettability may be achieved not only by SAS-wetting agent adding in suspension composition but also by activating of the model surface by chemical or physical methods. The paper presents the results of the different ways of chemical activation influence on the wettability of the wax model surface.
The article describes a study of the physical and mechanical properties and microstructure of geopolymer materials for construction based on low-calcium fly ash from CHP-22, depending on the type of activator, temperature and humidity conditions of curing and the introduction of an additional source of calcium (CaO) in the amount of 10, 15 and 20 wt. %. It was found that for the fly ash under study, the most promising type of activator is a sodium silicate solution with a silicate modulus SiO2 / Na2O = 1; the preferred curing mode is steam treatment at 90 °C. With the introduction of 15 % CaO into the geopolymer mixture, it was possible to increase the compressive strength by more than 2.5 times (to 38 МПа), the open porosity decreased from 24 to 7 %, and the water absorption from 15 to 3 %. However, a further increase in the CaO content leads to degradation of properties due to a significant reduction in the setting time of the raw mixture.
Nickel pyrochlore of the composition Bi2NiTa2O9 was synthesized by the solid-phase reaction method (sp. gr. Fd-3m, a = 10.5238 ?). The process of phase formation of nickel-containing bismuth tantalate Bi2NiTa2O9 with a pyrochlore structure is investigated. The pyrochlore phase synthesis reaction is described by the interaction of orthorhombic bismuth orthotantalate and nickel oxide. Synthesis proceeds mainly at temperatures above 900 °С. The duration of calcination of the preparations leads to the coalescence of grains with the formation of larger particles. The calcination temperature did not significantly affect the microstructure of the samples. The samples are characterized by a porous dendritic microstructure with a grain size of 0.5 – 1.0 µm. The optimal conditions for obtaining pure pyrochlore can be considered a temperature of 1050 °С and calcination time of 15 hours.
The crystallisation kinetics and effects of doping on Bi2Sr2CaCu2Oδ (BSCCO) glass ceramic system with 0.0, 0.1, 0.3 and 0.5 % PbSe were investigated in this study. Using differential thermal analysis (DTA), the effects of PbSe doping on glass transition, nucleation and crystallisation temperature of glass were investigated. The DTA results were analysed using the Ozawa, Augis–Bennett, Takhor and Kissinger equations for nucleation kinetics to uncover the activation energies and Avrami parameters. Thermogravimetric analysis revealed that the amount of oxidation in the structure increased with increasing PbSe-doping concentration.
The rise of polarization-controlled birefringence under a series of femtosecond laser pulses in the bulk of lithium silicate and lithium aluminosilicate glasstentatively attributed to the formation of nanogratings is demonstrated. The dependences of the retardance of the light passing through the modified regions on the parameter of laser radiation and the chemical composition of the glass are determined. It is shown that an increase of Al2O3 content at the expense of alkali content in glass composition leads to an increase in the minimum number of pulses for the formation of a birefrin-gent region, as well as an increase in the retardance.
