Glass and Ceramics最新文献

Calcium monoaluminate was synthesized by the sol–gel method and the effect of europium and neodymium oxides on the synthesis and structuring kinetics was studied in the temperature range 500 – 1000°C. It was determined that the formation of the structure of calcium monoaluminate occurs at 1000°C and with exposure for 4 h of a xerogel obtained based on a mixture of Al(NO₃)₃ + Ca(NO₃)₂ at a compound ratio of 2 : 1, respectively. In the sample obtained, the intermediate mineral is mayenite Ca₁₂Al₁₄O₃₃. With the introduction of the mineralizing europium oxide Eu₂O₃ in an amount of 1.5 wt.% greater than 100 wt.% in Al(NO₃)₃ + Ca(NO₃)₂ composition, at a synthesis temperature of 1000°C, the exposure time for maximum formation of calcium monoaluminate is reduced to 1 h. In samples containing Nd₂O₃, for the maximum formation of calcium monoaluminate at the same exposure time, it is necessary to introduce it in an amount of 5 wt.%.

LuAG:Ce ceramic powders of the compositions Lu_2.98Ce_0.02Al₅O₁₂ and Lu_2.93Ce_0.07Al₅O₁₂ were synthesized by means of chemical deposition. Luminescent ceramic samples were made from ceramic powders in the vacuum sintering temperature range 1600 – 1800°C. The influence of the cerium concentration in LuAG:Ce as well as the vacuum sintering temperature on the optical properties of the ceramic was studied. The spectral and luminescent properties of LuAG:Ce ceramic samples were studied. It was demonstrated that the luminescence intensity depends on the activator concentration and the vacuum sintering temperature. A shift of the maxima of the luminescence spectral bands of LuAG:Ce ceramics was found on variation of the vacuum sintering temperature in the range 1600 – 1800°C.

A comparative investigation was performed on the possibility of controlling the average sizes of nano-sized powders of silicon dioxide and aluminum oxide, obtained by electron-beam evaporation and by pyrogenic, liquid chemical, and plasma chemical methods, by keeping them in the temperature range 800 – 1300°C in an air atmosphere. The average sizes of the resulting particles were estimated from measurements of the specific surface area using the Brunauer–Emmett–Taylor (BET) adsorption method at liquid nitrogen temperature. The crystallographic parameters in the treated powders were assessed by means of x-ray diffraction analysis. It is shown that by making a suitable choice of temperatures and initial powder it is possible to achieve in the resulting powder the phase composition and an average particle size close to a specified value.

The possibility of using quartz sands from the Oinakum deposit as a promising source of high-quality quartz-containing raw materials for the glass industry in order to obtain higher grades of glass is considered. The chemical, granulometric, and mineralogical compositions of quartz sands of the Oinakum deposit were investigated; different enrichment schemes were used to obtain high concentrations of quartz sand.

Anew polyfunctional heat-resistant coating for protection from high-temperature gas corrosion (up to 900°C) swas synthesized based on glass in the system BaO–B₂O₃–SiO₂. The synthesized heat-resistant polyfunctional coating has enhanced resistance to high-temperatures and high dielectric properties, thereby making it polyfunctional. The high level of the properties is afforded by a composition that is based on refractory glass and by the introduction of a coupling activator.

This study presents a performance evaluation of MgAl-binary oxide-coated multi-walled carbon nanotubes (MWCNTs) as a reinforcement phase in a magnesium aluminate spinel (MgAl₂O₄) ceramic composite system fabricated using a pressureless sintering technique. The physical properties, including porosity, bulk density, and flexural strength of spinel composites were evaluated in the temperature range of 1500 – 1600°C. The results reveal the coated MWCNTs architecture’s promising influence on the composite system’s property enhancement. The developed thin-film coating on the MWCNTs favors enhanced dispersibility with better matrix-reinforcement interfacial connectivity, thereby improving the mechanical and thermo-mechanical performance of the composites.

The experimental investigations performed in this work and practice have shown that the main defects significantly reducing the service life of enamel-coated pipes are the roughness of the inner surface of a pipe and the presence of small bubbles and layers of macro- and microcracks. The problem of the occurrence of defects in the enamel coating that destroy the integrity of the enamel is considered in this article. The causes of these defects are associated with an incorrect choice of the technological regime when applying an enamel coating to the inner surface of the pipes. The choice of the technological regime on application of a coating depends on the geometric dimensions and technological parameters of the pipes.

It is known that imprecise implementation of the technology for applying enamel coatings to the inner surface of pipes effects the formation of microcracks. Taking this into account, the main objectives of this work are to automatically adjust the parameters of the technological regime of the device and to adjust the control system so as to prevent the formation of microcracks during coating application and to improve the automatic regulation of the process.

Self-propagating high-temperature synthesis (SHS) was used to prepare SHS compositions based on the system Si₃N₄–Yb₂O₃ system. Synthesis was conducted in a nitrogen atmosphere at 4 MPa in a 30 L reactor. The weight of the loaded charge was 3 kg. It was ascertained that the amount of ytterbium oxide in the charge affects the combustion temperature and the phase composition of the synthesis products. As the proportion of ytterbium oxide in the charge increases, the α-Si₃N₄ content decreases, and the secondary phases are represented by quaternary silicon ytterbium oxynitride and ytterbium disilicate.