Glass and Ceramics最新文献

The modified sol-gel method (Pechini method) is shown to synthesize multielement oxides on the basis of bismuth niobate that crystallize in the pyrochlore structure (space group Fd-3m). The temperature for the synthesis of a single-phase sample amounts to 950°C, which is 100°C lower than the calcination temperature used in the conventional ceramic method of synthesis. The average crystallite size determined radiographically varies from 39 nm (850°C) to 48 nm (1050°C) depending on the sintering temperature. According to x-ray diffraction analysis, the unit cell parameter is equal to 10.4872(6) Å. The conducted elemental mapping indicates a uniform distribution of metal atoms on the sample surface, while energy dispersive x-ray analysis shows that the chemical composition of the synthesized sample corresponds to the specified theoretical composition.

Bismuth germanate glasses were modified with sodium oxide, and the resulting glasses were studied in order to determine the influence of the modifier on their spectral-luminescent properties. The ratios of Bi₂O₃ and Na₂O concentrations at which the infrared luminescence of these glasses is possible were identified.

The article examines temperature conditions for the thermal synthesis of silica from rice husk and different conditions for subsequent milling. In the study, the following methods were used: elemental analysis, x-ray diffraction analysis, petrographic analysis, electron and atomic force microscopy, differential scanning calorimetry, and laser granulometry. The occurrence of silica was detected at about 650°C; its structure remained stable during pyrolysis and subsequent thermal treatment in the presence of air. Following thermal treatment at 1000 – 1100°C, cristobalite remained the predominant phase. The milling of thermal treatment products involved a significant loss of process efficiency due to the cellular structure of aggregates and their plastic failure.

Bismuth-containing chromates, Bi_xCrO_1.5x+3 , were synthesized using a ceramic method from bismuth (III) and chromium (III) oxides, with a variable molar ratio of 1 ≤ n (Bi)/n (Cr) ≤ 38. The calcined samples exhibit a color variation from green to dark red, depending on the n (Bi)/n (Cr) ratio. The ceramic materials undergo a color change from green to red when a mixture of oxides with a significant predominance of bismuth oxide n (Bi₂O₃)/n (Cr₂O₃) ≥ 3 is subjected to a high-temperature treatment in air (at 650°C). It is noteworthy that the calcination of chromium (III) oxide under similar conditions occurs without the oxidation of chromium ions. X-ray diffraction analysis confirmed the formation of chromates, including Bi₆Cr₂O₁₅, Bi₁₀Cr₂O₂₁, Bi₃₁Cr₅O_61.5, and Bi₁₄CrO₂₄ . X-ray spectroscopy studies of the samples revealed that the NEXAFS Cr2p spectra of the red bismuth-chromium ceramics exhibited similarities in the main details of the K₂CrO₄ spectrum, indicating the presence of chromium in the oxide ceramics in the form of tetrahedral ({text{CrO}}_{4}^{2-}) ions. In addition, scanning electron microscopy data demonstrated that the samples exhibited a dense, low-porosity microstructure.

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.