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.