Glass and Ceramics最新文献

The paper presents the investigation on the influence of humidity, heat treatment temperature, the grain size distribution of periclase, aging time prior to heat treatment, and the amount of carbon in the charge on the strength properties of periclase-carbon samples. It is established that the moistening prior to heat treatment and aging duration have no influence on the mechanical strength of the materials. The mechanical strength of the samples increases with the increase in the concentration of finer particles of periclase in the charge. Given that the variation in carbon content (ranging from 3 to 11%) has no significant impact on the mechanical strength of the samples, it is recommended that the carbon content (in the form of graphite) in the charge mixture be determined on a case-by-case basis, in line with the intended use of the periclase-carbon products. In the investigated temperature range (125 – 250°C), the highest mechanical strength of the samples was observed at a heat treatment temperature of 200°C.

Polyoxotungstosilicates with the general formulas Cat₄[SiW₁₂O₄₀] · mH₂O and Cat₆[SiW₁₁O₃₉Ni(H₂O)] · nH₂O were synthesized, where Cat = Rb⁺, Cs⁺, (CH₃)₄N⁺. By means of IR spectroscopy and x-ray diffraction analysis, it was shown that the compounds have the Keggin anion structure. The thermolysis of the obtained compounds within the temperature range of 600 – 800°C resulted in the formation of previously unknown pyrochlore-structure phases Rb_12/13Si_2/13W_22/13Ni_2/13O₆ and Cs_12/13Si_2/13W_22/13Ni_2/13O₆ with the with the unit cell parameters a of 10.284 and 10.309 Å, as well as phases with tungsten bronze structure Rb_12/20Si_3/20W_36/20O₆ and Si_3/38W_36/38O₃. The synthesis of tungsten silicates with pyrochlore and tungsten bronze structure through thermolysis of polyoxotungstosilicates reduces the temperature of their preparation to 600 – 650°C and heating time to 1 h, thus extending the ranges of chemical compositions and their morphological diversity.

The article presents a method for one-sided etching of channel openings in unetched microchannel plate blanks using dilute hydrofluoric acid. In this work, we used the blanks of MCP 18-10 microchannel plates. The treatment was carried out in 0.2 N hydrofluoric acid solution at room temperature without oscillating or stirring the solution. Following etching, the diameter of channel openings increased by over 10% of the diameter of MCP 18-10 channels, which increased the electron transmission of the device.

The article proposes a method for obtaining a new composite material derived from igneous gabbro rock that is reinforced with basalt fiber. Laboratory samples were prepared and their properties (pycnometric density and Brinell hardness) were determined.

Cracks represent a significant challenge to the structural integrity of piping systems. Therefore, this study is devoted to the detection of macro-micro cracks in pipes with silicate-enamel coatings, which are commonly used to enhance corrosion resistance. While the process of detecting macro cracks on the surface of the coating is currently underway, the identification of macro-micro cracks remains a significant challenge. The article highlights the significance of their timely detection to prevent potential leakage and design failures, underscoring the implications for economic advancement and security. An algorithm for detecting microcracks on the surface of the pipes with silicate-enamel coatings was developed. The test voltage of the enhanced holiday detector was increased to 40 kV, which allowed the microcracks as small as 1.5 mm long to be detected. A methodology for the remote detection of oil leaks from oil trunk pipelines was presented. Following the testing process, the coordinates and geometric parameters of the cracks were determined.

The phase composition of the powder synthesized from aqueous solutions of sodium silicate Na₂SiO₃ and iron sulfate FeSO₄ at the molar ratio Fe/Si = 2, as determined by x-ray diffraction (XRD) data, included hydrated sodium iron sulfate Na₂Fe(SO₄)₂ · 4H₂O and an x-ray amorphous product based on hydrated iron and silicon oxides. The phase composition of the powder obtained by fourfold washing of the synthesized powder in distilled water was represented by an x-ray amorphous product.

Following firing in the air at temperatures ranging from 400 to 1200°C, hematite (Fe₂O₃) and cristobalite (SiO₂) were identified in powder samples and the corresponding ceramics. Following firing at 900°C in graphite powder bedding, the phase composition of ceramic samples included magnetite (Fe₃O₄), laihunite (Fe_4.74(SiO₄)₃), and fayalite (Fe₂SiO₄). The powder prepared from the product isolated from the mother liquor included hydrated sodium iron sulfate, Na₂Fe(SO₄)₂ · 4H₂O, and sodium iron sulfate hydroxide hydrate (metasideronatrite), Na₄Fe₂(SO₄)₄(OH)₂ · 3H₂O. Following heat treatment at 400°C, sodium iron sulfate (Na₃Fe(SO₄)₃) was identified as the predominant phase in the powder. Powders resulting from the interaction of aqueous solutions of sodium silicate and iron sulfate can be used in the manufacture of high-temperature dyes and materials with magnetic properties, the creation of analogs of lunar or Martian regolith, as well as the development of functional (cathode) materials for Na-ion batteries.

The study reviews the current progress in the sol-gel method for the synthesis of ferroelectric powders, thin films, and rods in the lead zirconate-titanate system. In addition, it examines methods for obtaining controlled particle morphology, primarily rod-like. The synthetic approaches in the sol-gel process and heat treatment conditions for obtaining lead zirconate-titanate ceramics of pre-defined morphology are the primary focus of the present review.

Glass and glass ceramics containing 40 wt.% of heavy metal oxides (Bi, Ta, and W) were obtained for use in medicine as radiosensitizers. The properties of the composites were studied in vitro, including the generation of secondary radiation, chemical solubility, and the variations in the pH of the medium during resorption. The results demonstrated that the secondary radiation indicators and pH value of the medium decreased in the order: W > Ta > Bi. Solubility indices decreased in the order: W > Bi > Ta. Despite the highest generation of secondary ionizing radiation, W-containing ceramics based on Bioglass 45S5 are unsuitable for in vivo use due to their rapid dissolution and high alkalization of the environment.

The optical properties and microstructure of composites based on yttrium aluminum garnet were studied. The composites were produced by vacuum sintering of pre-formed compacts of nanocrystalline powder (Y₃Al_4.995Cr_0.005O₁₂) with a YAG single crystal. The transmittance spectra of the composite samples exhibited the presence of Cr³⁺ absorption bands following vacuum sintering, as well as Cr⁴⁺ bands following annealing in air. The impact of varying heating rates during vacuum sintering on the transmittance of composite samples was examined. It was determined that the optimal heating rate during the vacuum sintering of composites should be less or equal to 120 K/h. In addition, the impact of the vacuum sintering temperature on the optical properties and microstructure of YAG:Cr (ceramics)/YAG:Nd (single crystal) composite samples was investigated. The samples exhibiting the highest transparency were obtained at a temperature of 1850°C. Microstructure studies of the composites revealed the presence of regular residual porosity in the vicinity of the interface, predominantly located in the YAG single crystal. It is postulated that the formation of these pores occurs during the fusion of ceramic grains with a single crystal during sintering.

This paper presents a process for obtaining glass ceramics based on corundum modified by borosilicate glass with various additives. The described Al₂O₃ /SiO₂–B₂O₃–CaO–MgO–Na₂O–K₂O system has been developed for use in LTCC technology and exhibits a sintering temperature of less than 950°C. The impact of varying the sintering additive content on the firing temperature, microstructure, ceramic, and electrophysical properties of the resulting ceramics was investigated. The developed material exhibited a dielectric constant of ε_r= 6.73 – 6.82 and tangent of the dielectric loss angle of tan δ = 8.0 – 8.6 × 10 ^–3 at a frequency of f = 1 MHz.