Steklo i Keramika (Glass and Ceramics). Monthly scientific, technical and industrial journal

 

ISSN 0131-9582 (Online)

VOL 94, No. 8 (2021)

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  • Study Y2O3–Al2O3–SiO2 System Coating Interaction with Water Vapors and Na2SO4 at Temperatures up to 1450 °C

    • Pages: 03-11
    • Views: 133
    For silicon carbide, when exposed to high temperatures in an oxygen atmosphere, passive and active oxidation processes are characteristic, therefore, materials based on SiC must be protected at temperatures above 1300 ° C. Sodium sulfate, the presence of which is possible as an impurity in the fuel, leads to the destruction of the protective layer of SiO2 formed during the oxidation of SiC. Coatings based on the Y2O3 – Al2O3 – SiO2 system are promising for protecting materials based on silicon carbide from the effects of an oxidizing atmosphere and water and salt vapors. Studies have been carried out on the interaction of coatings of the Y2O3–Al2O3–SiO2 system obtained by the sol-gel method with water vapor and Na2SO4 salt. As a result of the studies carried out, it was found that coatings based on the Y2O3 – Al2O3 – SiO2 system have good oxidative and chemical resistance to water vapor and Na2SO4 salt vapor in the temperature range of 1300 – 1450 °C. The weight gain for coated samples when tested in Na2SO4 salt vapor did not exceed 1 %. The initial SiC substrates are characterized by active oxidation processes with a weight decrease from 8 to 11 %. DSC analysis in combination with mass-spectrometry of the crystallized sample of the Y2O3–Al2O3–SiO2 system coating after heating in Na2SO4 salt vapor to a temperature of 1550 °С showed that at temperatures above 900 °С Na2SO4 decomposes with the release of SO2 and SO3–
  • Producing Titanium Nitride Whiskers from the Gas Phase

    • Pages: 12-21
    • Views: 118
    The article presents the results of the work on obtaining titanium nitride whiskers from the gas phase. Previously, a theoretical assessment was made of the possibility of homogeneous formation of micro-substrates of various types and composition in the gas phase, the conditions for condensation of the titanium nitride phase and the growth of filamentous crystals. Based on the results of thermodynamic analysis of the analyzed system, calculations of the existing critical supersaturation were carried out and the rates of homogeneous condensation in the gas phase of titanium and titanium nitride were estimated. Thermodynamic calculations of the compositions of the Ti–Cl–H, Ti–Cl–N, Ti–Cl–Ar subsystems determined the design elements of the laboratory installation and the technological features of the titanium nitride crystal growing process. Samples of titanium nitride whiskers were obtained and examined
  • Estimation of Bioactive Properties of the Mineral-Polymer Composite "Calcium Phosphates – Polylactide"

    • Pages: 22-28
    • Views: 126
    The paper studies the bioactivity of hybrid composite materials containing calcium phosphates up to 60 % by weight and polylactide (PLA) with additives of glycerol and sorbitol, in situ and in vitro. Studies were carried out in PBS and SBF media, cytotoxicity was determined on the cell culture of Neuro-2a mouse neuroblastoma. The use of a mixture of highly dispersed calcium phosphates as the mineral phase of composites with polylactide provides resorption in the PBS solution of the material with water absorption close to zero. It was found that at a calcium phosphate content of 40 % or more, apatite-type calcium phosphates are produced on the surface of composites during incubation in SBF. Composites in the studied range of compositions have a weak cytotoxic effect on the cell culture of Neuro-2a mouse neuroblastoma. The data obtained would suggest dynamic resorption and bioactivity of composites in vivo
  • Research of the Possibility of Using Light Aluminosilicate Components of Fly Ash for Production of Refractory Insulating Materials

    • Pages: 29-34
    • Views: 117
    A number of refractory heat-insulating ceramic materials were obtained using hollow aluminosilicate fly ash microspheres as a lightweight filler. Thermal insulation products obtained by various methods had density values from 0.5 g/cm3, thermal conductivity of 0.23 – 0.48 W/(mK) and compressive strength of at least 1.5 MPa. Low values of shrinkage of the developed materials in the process of high-temperature processing make it possible to obtain large-sized items of complex shape. The obtained materials can successfully compete with commercially available refractory heat-insulating materials
  • Influence of Mineral Additives on the Structure and Properties of Thermal Insulating Materials Based on Silica-Containing Raw Materials

    • Pages: 35-40
    • Views: 162
    The article presents a justification for the production of plate heat-insulating foam silicate materials based on by-products of apatite-nepheline ore processing by low-temperature technology. Methods for improving the performance characteristics of foamed materials by introducing mineral additives are proposed. According to the set of properties, the most effective additives are the tailings of the enrichment of vermiculite ores and diopside. Technical characteristics of the developed foam silicates: density 0.38 – 0.51 g/cm3, strength up to 6 MPa, thermal conductivity 0.09 – 0.107 W/(mK) and relatively low water absorption
  • New Method for Calculating Structural Parameters of Glass Membranes

    • Pages: 41-44
    • Views: 109
    A new method for calculating the structural parameters of glass membranes is proposed, which allows calculating the average coordination number, specific surface area, average radii of the necks of spherical pores (interporous bridges) of membranes and the tortuosity coefficient of membrane capillaries from ex-perimental values of porosity, the average radius of capillaries and spherical pores of membranes. The proposed method is used to analyze the structural parameters of membranes in comparison with known methods and experimental data
  • Anortite Ceramics Based on Loess Loam

    • Pages: 45-50
    • Views: 124
    The article presents data on the possibility of obtaining anorthite ceramics based on loess-like loam, which has the functional property of technical ceramics. In the CaO–Al2O3–SiO2 system, calcium-containing wastes from sugar production – defecate and lime fines – were used as a mineralize to obtain anorthite ceramics. With their participation, the possibilities of the formation of anorthite and its synthesis by the method of high-temperature synthesis have been opened. On the basis of experimental studies, it was possible to obtain a material with high mechanical strength, wear resistance and a low water absorption rate. The studies carried out show the possibility of the formation of the mineral anorthite in isothermal mixtures “loess-like loam–lime fines” and “loess-like loams–defect” at relatively low temperatures (950 – 1100 °С) than in conventional traditional mixtures, the formation of which is observed at temperatures not lower than 1200 °С