Glass and Ceramics最新文献

The results of investigations of the preparation of electrical porcelain based on available customary raw materials of Uzbekistan are presented. It is shown that in conditions of a shortage of high-grade mineral raw materials for the preparation of electrical porcelain it is advisable to introduce about half of the kaolin in a pre-calcined state into the mixture. In addition the products of firing primary and secondary Angrenskoe kaolins at 1350°C allow us to consider them as a mullite-containing component that subsequently imparts high physicomechanical and dielectric properties to the porcelain material. The phase composition of the resulting porcelain is represented mainly by new crystalline components — mullite and cristobalite, which allows it to be classified as an electric porcelain of the mullite-type.

The influence of humidity and oxygen on the formation of the structure and strength properties of manufactured products based on magnesium oxide and the organic binder SFPR-054 was studied. It was ascertained that conduction of the polymerization process at 25°C without access to air effects approximately five-fold higher sample strength compared to the samples polymerized in dry form at 300°C. The data obtained suggest that an increase in the structural and mechanical properties of manufactured products on the basis of magnesium oxide contributes to moistening of the batch, retention of the pressed product and the polymerization process in an oxygen-free environment or in an atmosphere of water vapors.

Bismuthate-borate glasswas synthesized with the compositions (wt.%) 70 Bi₂O₃, 2 GeO₂, 25 B₂O₃, 3 MoO₃; 70 Bi₂O₃, 17 GeO₂, 10 B₂O₃, 3 MoO₃ and 80 Bi₂O₃, 4 GeO₂, 5 MoO₃, 11 SiO₂; 80 Bi₂O₃, 8 GeO₂, 8.5 SiO₂, 3.5 MoO₃. Methods were developed for forming a receptor layer on the resulting glass by means of ultrasonic spraying of the interacting components and applying a water-insoluble polymer film obtained via a chemical reaction between the polymer poly-N,N-dimethyl-3,4-dimethylenepyrrolidinium chloride and the modifier potassium hexacyanoferrate (II). The sensors prepared based on these glasses make it possible to determine to within2– 4% the content of hydrogen sulfide and water vapor in air.

The crystallization properties of glass with a Li₂O–Al₂O₃–SiO₂ based multicomponent composition were studied. Using the Marotta, et al. method, it was found that at 670°C with 2-h soaking affords the maximum rate of nucleation of the crystalline phase of β-eucryptite-like solid solutions. The activation energy of nucleation and the Avrami parameter were measured by means of DSC. Using the gradient crystallization method, the temperature ranges of heat treatments where transparent sitalls obtain were determined. More accurate determination of the temperature-time parameters of the nucleation stage made it possible to shorten the time of the second stage of sitallization that is necessary for the complete formation of the structure of transparent sitalls. By varying the soaking time at 710°C it was possible to vary the LTEC evenly in the temperature interval –120... +500°C in the range (–3... +41) × 10 ^–7 K^–1.

The Gibbs energy is calculated for the chemical reactions of ZrO₂, Al₂O₃, SiO₂, TiO₂, CaO, and MnO with carbon and carbon (II) monoxide in the temperature range 1273 – 2273 K (1000 – 2000°C) for selecting a eutectic additive for structural ceramics in the system Al₂O₃–ZrO₂ – eutectic additive – carbon nanotubes. Taking into account the multicomponent structure of the ceramic matrix composite in the Al₂O₃–ZrO₂ – eutectic additive – CNT system, it is necessary to consider the process of possible carbidization, which worsens the strength characteristics of the synthesized material. As a result of the analysis, it was found that eutectic additives containing Al₂O₃, SiO₂, TiO₂, and CaO can be recommended for use.

The preparation and identification of microstructure features as well as the texturing of the thermoelectric material Bi₂ Te_2.7 Se_0.3 doped with dysprosium are considered. The textured compounds Bi_2–x Dy_x Te_2.7 Se_0.3 with x = 0.0000; 0.0010; 0.0025; 0.0050; 0.0100, and 0.0200 were obtained by means of solvothermal synthesis of the original powders and their subsequent spark plasma sintering. Dysprosium doping effects several interrelated phenomena. The first one is particle size reduction of the original powder with increasing x. This effect is explained by an increase in the ionicity of the covalently polar bonds Bi(Dy)–Te with increasing Dy content on account of the difference in the electro-negativity of Bi and Dy. The second effect is associated with average grain size reduction with increasing x in bulk samples, which is determined by a corresponding change in the particle size in the original powder with different amounts of alloying. This phenomenon also effects greater texturing in the samples.

The possibility of producing geometrically complex mechanical-engineering products based on reaction-sintered silicon carbide using two methods was investigated — mechanical processing of polymerized workpieces before sintering and molding by hot slip casting under pressure. The resulting silicon carbide ceramic materials are characterized by low density of the order of 3.04 – 3.07 g/cm³, porosity ≤ 1%, and bending strength 320 – 360 MPa. Materials based on silicon carbide modified with boron carbide have density 2.72 g/cm³, porosity about 1%, and bending strength of 280 MPa.

The characteristics of glass-ceramic materials prepared by means of thermal plasma were investigated. The influence of the ash content of a thermal power plant (TPP) on the properties of glass-ceramic materials is considered. Samples of glass-ceramic materials with an ash mass content of 70% and the following characteristics were obtained: compressive strength 530 MPa, bending strength 115 MPa, and density 2700 kg/m³.