Glass and Ceramics最新文献

The results of experimental modeling of glassy carbon production from high-pressure supercritical fluid (SCF) in the C–O–H system at a temperature of 800°C and pressures of 500 – 1000 atm are presented. Acomprehensive characterization of the carbon material is presented, using the data from CHNS-O analysis, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), x-ray and electron diffraction, infrared and multiwavelength Raman spectroscopy (Raman). In light of the characteristics and outcomes of the comparison with industrial glassy carbon, the synthesized carbon material was classified as a glassy substance. The findings of the experimental studies provide evidence for potentially different mechanisms of formation and, consequently, polygenicity of the glassy state of carbon. The material obtained through a radically distinct production method (polycondensation) may possess distinctive surface and bulk properties.

The preparation of copper green glaze was conducted using a combination of raw materials, including kaolin, feldspar, calcite, talc, limestone, quartz, and copper oxide. The influence of formulation composition and preparation process on the surface of green glaze was examined through the application of single-factor and orthogonal experimental design methodologies. The single factor experimental method entailed a systematic alteration of a single factor, such as the proportion of raw materials, firing temperature, or firing time, to examine its individual impact on the surface of the green glaze. In contrast, an orthogonal experimental design simultaneously considers multiple factors and assesses their relative importance for the glaze effect. The objective of this study is to optimize the formulation composition and preparation process of copper green glaze in order to achieve the desired surface effect and to improve the efficiency and quality of glazes in industrial manufacturing applications.

A methodology for the analytical calculation of the glass thermal conductivity coefficient is proposed. This methodology allows for the reliable calculation of thermal conductivity coefficients for glass products of varying thicknesses, taking into account the physical essence of the radiation-conductive heat transfer process in semitransparent media. Furthermore, this methodology facilitates the analysis of temperature conditions during glass melting and the operation of glass products.

Bi₂Zn_xMn_1–xTa₂O_9.5–∆ ceramics were synthesized for the first time using the solid phase synthesis method. The samples were found to contain cubic pyrochlore (sp. gr. Fd–3m) as the main phase and a triclinic modification (sp. gr. P-1) of BiTaO₄ as admixture. The amount of the triclinic modification is proportional to the manganese content in the samples. The formation of impurities is associated with the distribution of a fraction of the transition element ions into the cationic sublattice of bismuth (III). The unit cell parameter of the pyrochlore phase increases with increasing content of zinc ions in the samples from 10.4895(5) Å (x = 0.3) to 10.5325(5) Å (x = 0.7) in accordance with the Vegard rule. The formation of impurities in samples can be prevented by creating a bismuth ion deficiency in the bismuth sublattice by an amount proportional to the β-BiTaO₄ content. The unit cell parameter of single-phase pyrochlores Bi_2–yZn_xMn_1–xTa₂O_9.5–∆ synthesized in this way increases with increasing zinc ion content in the samples from 10.4764(5) Å (x = 0.3) to 10.5122(5) Å (x = 0.7). As observed through electron scanning microscopy, the ceramic samples exhibit a low-porosity microstructure with indistinct grain boundary outlines. The porosity of the samples decreases as the zinc content of the samples increases. The formation of a deficient bismuth sublattice during preparation is associated with a more porous microstructure, which can be attributed to a reduced concentration of the readily fusible component present in the reaction mixture, namely bismuth (III) oxide.

α–Al₂O₃–3YSZ porous ceramics were fabricated using the slip casting method with the incorporation of 15 wt% of submicron Al₂O₃ powders as sintering additives. The materials were prepared by solution combustion synthesis using glycine or urea as fuels. Following firing of the ceramics at 1550°C, the percentage of closed porosity was found to be in the range from 14.1 to 24.0%. The experimental results revealed a linear correlation between density and closed porosity of Al₂O₃–3YSZ corundum ceramics. Ceramic samples that underwent firing at 1550°C exhibited relative density values ranging from 75 to 85%, accompanied by an open porosity of 0.90 to 1.71%. The findings indicate that the morphology of the used aluminum oxide additives synthesized through combustion exerts a predominant influence on the strength characteristics.

The influence of the content and ratio of MgO and CaO sintering additives on the optical properties of YAG:Cr³⁺ and YAG:Cr⁴⁺ ceramic materials was investigated. All samples showed high transparency at 1100 nm (more than 80%). However, in the approx. 340 nm region, the light transmittance values of the samples decreased with increasing amounts of Ca²⁺ or Mg²⁺ ions. The most intense absorption in the range of 750 – 1100 nm after annealing in air was observed in the samples containing the highest value of sintering additives. The absorption of Cr⁴⁺ cations increased with the increase of Ca/Mg content. The optimum CaO content among the investigated samples was 0.12 wt.%. Above this value, additional absorption was observed due to the formation of microdefects. The data obtained by scanning electron microscopy showed that the ceramic samples had a granular structure with grain size ranging from 1 to 10 μm. There were no significant differences in the microstructure depending on the content and type of sintering additives.

The PbO–Ga₂O₃ glass-forming system with a lead oxide content of more than 50 mol.% was studied. The glass structure was found to be significantly affected by the introduction of lead oxide. Vibrational spectroscopy results showed that PbO significantly reduces the number of Ga–O–Ga bridging bonds, leading to a weakening of the glass network and the dominance of PbO₄ pyramids in it. Structural changes lead to a significant change in the physicochemical properties of glasses. The spectral and optical properties of the PbO–Ga₂O₃ glass system are discussed in detail. The glasses have a wide transparency window (from 0.5 to 7.1 μm), a high refractive index (approximately 2.2), and a small Abbe number (approximately 12). The developed materials show promise for optics and photonics applications in devices operating in the infrared range of the spectrum.

The structure of ZrO₂–Sc₂O₃ powders in the composition range from 1 to 15 mol.% of Sc₂O₃ with the addition of 0.1 mol.% Eu₂O₃ as a spectroscopic probe was studied. The powders were obtained by the coprecipitation method and subsequent heat treatment at temperatures ranging from 500 to 1200°C. The crystal structure was identified through x-ray diffraction analysis (XRD) and Raman spectroscopy. The local structure was evaluated based on the spectral and luminescent properties of the Eu³⁺ ion in the powder samples.

The results of the synthesis of complex YErYbNbO₇ paraniobate using different methods are presented. The chemical composition of the final synthesis products was determined. The peculiarities of the thermal behavior of the precursors are revealed. Crystallographic parameters of single phase samples were calculated and crystallite sizes were determined.

Influence of the specific surface area and filler concentration on the coefficient of linear thermal expansion (CLTE) of sintered composites based on high lead fused glass and lead titanate was investigated in order to obtain solder materials offering unusually low CLTE values. The microstructure of compositions was investigated by optical microscopy methods in combination with birefringence testing with a localization of about 1 μm. In samples containing up to 55% PbTiO₃ powder having a specific surface area of less than 560 cm²/g, near-zero and even negative values have been achieved.