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In the present study, we review current progress in sol-gel techniques for synthesis of ferroelectric powders, thin films and rods in lead zirconate-titanate system, as well as methods for obtaining controlled particle morphology, primarily rod-like. Synthetic approaches in sol-gel process and heat treatment conditions for obtaining lead zirconate-titanate ceramics of pre-defined morphology are of primary focus in the present review.
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Direct femtosecond laser writing of phase optical elements in glasses opens up new possibilities for controlling light beams and developing new functional devices that operate on the birefringence effect. In this work, phase plates were written in the volume of silica and nanoporous glasses using a laser beam, and for the first time, chromatic dispersion curves of birefringence were measured for them using several methods. This makes it possible to estimate the retardance of birefringent elements fabricated by the direct laser writing even using commercial birefringence analysis systems operating at a specific wavelength.
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The optical properties and microstructure of composites based on yttrium aluminum garnet were studied. The composites were produced by vacuum sintering pre-formed compacts of nanocrystalline powder with the composition Y3Al4.995Cr0.005O12 in conjunction with a YAG single crystal. The light transmission spectra of composite samples showed absorption bands of Cr3+ after vacuum sintering and bands of Cr4+ after annealing in air. The effect of heating rate during vacuum sintering on the light transmission of composite samples was investigated. It was determined that the optimal heating rate during vacuum sintering of composites should not exceed 120 °C/h. The influence of vacuum sintering temperature on the optical properties and microstructure of YAG:Cr (ceramics)/YAG:Nd (single crystal) composite samples was also examined. The most transparent samples were obtained at a temperature of 1850 °C. Microstructure studies of the composites revealed the presence of regular residual porosity near the interface, primarily located in the YAG single crystal. It is hypothesized that the formation of these pores occurs during the fusion of ceramic grains with the single crystal during sintering.
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In the paper presents the process of producing glass ceramics based on corundum modified with borosilicate glass with various additives. The described Al2O3/SiO2–B2O3–CaO–MgO–Na2O–K2O system has developed for LTCC technology and got a sintering temperature less than 950 ?. The influence of additive content on the sintering temperature, microstructure, ceramic and electrophysical properties of ceramics has been investigated. Developed composition has a dielectric constant of ?r = 6.73…6.82 and tangent of the dielectric loss angle tg ? = 8.0…8.6?10–3 at a frequency f = 1 MHz.
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High-temperature thermal insulation materials are widely used in civil engineering as flame retardant materials, as well as in many industries. Rocks and industrial waste are used as raw materials for their production. The article confirms the possibility of using ceramovermiculite and keramoperlite materials on a wollastonite bond as high-temperature thermal insulation. The materials were obtained by firing a charge of chalk, diatomite and heat-resistant filler (expanded perlite, expanded vermiculite). The material of the fired samples with expanded vermiculite consists mainly of the crystalline phase of wollastonite and biotite with a small amount of quartz and ackermanite-helenite. When using expanded perlite as a heat-resistant filler, in addition to the crystalline phase of wollastonite, a small amount of plagioclases is present in the material of the burnt samples, and an amorphous phase also appears. The physicomechanical properties of the charge and the fired samples were determined, and the effect of the apparent density and phase composition of the developed materials on the change in their thermal insulation properties at high temperature was studied. The thermal insulation properties of materials at high temperature were determined by unilateral exposure of the sample to heat flow from the heating chamber of the muffle furnace. Samples from the developed materials have an apparent density from 375 kg/m3 to 630 kg/m3 and compressive strength from 0.95 MPa to 3.25 MPa. The developed keramoperlite materials on a wollastonite bond can be used as high-temperature thermal insulation up to +900 °C, and ceramovermiculite – up to +1050 °C. According to many physico-mechanical and thermophysical properties, the materials obtained are not inferior to known analogues.
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Describes a method for determining the physico-mechanical properties of a synthesized batch of propants. Industrial waste is one of the sources of anthropogenic impact on the environment on a global scale, being formed in the process of coal and oil extraction as a by-product. With the decrease in stocks of high-quality natural raw materials and the accumulation of man-made products, the problem of use becomes urgent.
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Preliminary results of experimental modeling of impact process on coal substance by short-pulse laser radiation are presented. During the experiments extremely high temperatures and pressures have been reached. Based on the analysis of transformation products of a target substance, coal melting has been established followed by its cooling with subsequent solidification and glass-like carbon formation. The experimental synthesis products can be a subject of interest as novel carbon materials formed at ultrahigh pressures and temperatures, such as high-pressure carbon polymers and hollow fullerene-like structures. The results of experimental modeling can be used for comparison with products of natural origin in order to explain the mechanisms of formation of natural high-pressure carbon substances from a non-graphite precursor.
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This review presents various interpenetrating phase composite (IPC) materials currently used in computer-aided design/computer-aided manufacturing (CAD/CAM) systems and to evaluates how the optical properties of those materials are affected by various factors. In the field of dentistry, selecting materials compatible with dental tissues is key to clinical success of restorative materials. Understanding the optical properties of a restorative material aids in material selection and provides insights into the material’s clinical performance and esthetic longevity. Such knowledge can in turn help clinicians select the best treatment option for their patients. Interpenetrating phase composite materials combine the optical and mechanical properties of ceramics and composite resins; they are often used in direct/indirect restorative options such as inlays, onlays, veneers, single crowns, implant-supported crowns, and short-span fixed partial dentures with esthetically favorable outcomes. The color of a material, which plays an essential role in the esthetic outcome, can change over time depending on different intrinsic and extrinsic factors. Those intrinsic factorss include chemical composition, resin-matrix structure, and filler particle sizes; extrinsic factors include surface treatment protocols, the patient’s smoking status, and the consumption of beverages such as coffee, tea, red wine, fruit juice, cola, etc. To fabricate restorations that complement a person’s natural teeth, it is essential to determine the color properties of these materials (e.g., translucence, hue, chroma, and opalescence).
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Glass and glass ceramics containing oxides of heavy metals (Bi, Ta, W) in amount of 40 wt. % were obtained for use in medicine as radiosensitizers. The properties of the composites were studied in vitro: generation of secondary radiation, chemical solubility, change in pH of the medium during resorption. Indicators of secondary radiation and the pH value of the environment decrease in the order: W>Ta>Bi. Solubility indices decrease in the order: W > Bi > Ta.
Despite the maximum generation of secondary ionizing radiation, W-containing ceramics based on Bioglass 45S5 are undesirable for use in vivo due to rapid dissolution and high alkalization of the environment.
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The purpose of the study was to develop compositions of colored glasses based on basalt from the Osmonsay deposit.
To synthesize glasses, compositions in the basalt–quartz–soda system were studied. Quartz sand from the Samarkand deposit was used as a source of quartz. Transparent, translucent and dimmed colored glasses were obtained. As a result of the research carried out, it was established that it is possible to obtain glass of a wide range of colors without the use of coloring components.
