Glass and Ceramics最新文献

This study examines the dielectric properties and total harmonic distortion of lead zirconate ceramics sintered at varying temperatures using PbO and ZrO₂ nanopowders with particle sizes of 500 nm and 20 nm, respectively. The use of nanoscale powders resulted in a decrease in sintering temperature in comparison to conventional ceramics fabricated from 1 μm particles. The highest dielectric permittivity was observed in samples sintered at 1100°C. A decrease in permittivity was recorded at sintering temperatures exceeding 1200°C. However, cooling within the 226 – 208°C range induced the formation of a ferroelectric phase.

Silica-based adsorbents incorporating organylsilsesquioxane fragments bearing organic radicals were synthesized for application in the adsorptive separation of oxygen-argon mixtures via pressure swing adsorption (PSA). Synthesis followed a base sol-gel protocol involving directed co-condensation of a reagent mixture. The materials were characterized using thermogravimetric analysis and low-temperature nitrogen adsorption. The presented results detail the oxygen and argon adsorption properties of the synthesized adsorbents. The sample functionalized with (diethylaminomethyl)silsesquioxane groups exhibited the greatest selectivity for argon. This material exhibited the greatest total volume of micropores and mesopores alongside a broad pore size distribution within the mesoporous range.

This study examines the feasibility of utilizing tailings from the beneficiation of banded iron formations (BIF) within the Kursk Magnetic Anomaly (KMA), along with waste from vanadium production, for the plasma synthesis of pigmented structural glass (PSG). Key design features of a specialized plasma glass-melting furnace are also outlined. The operational properties of the synthesized glass were evaluated, including its water resistance, frost resistance, microhardness, and phase composition. The color characteristics of the material were determined in the CIE L^*a^*b^* color space.

This study examines the physical and mechanical properties of corundum ceramics fabricated from domestically sourced G-00 grade alumina. The optimal mechanical strength was achieved in ceramics sintered at 1450°C with the addition of 5 wt.% yttrium oxide and 5 wt.% of a eutectic MnO–TiO₂ additive. The findings indicate the feasibility of import substitution of alumina.

This study presents the chemical and mineralogical characterization of hematite from the Kyzyltash deposit, both prior to and following calcination. Methods for its beneficiation were selected. Red and brown pigments were synthesized, and their phase composition and microstructure were subsequently analyzed using x-ray diffraction and electron microscopy. An investigation was conducted into the coloring properties of the obtained red and brown pigments. The results indicate that hematite from the Kyzyltash deposit can be used as a raw material component in the production of ceramic glazes and color pigments at construction material enterprises in Uzbekistan.

This paper investigates borophosphate glasses containing FLiNaK salt additive, a eutectic mixture of alkali metal fluorides (46.5 mol.% LiF, 11.5 mol.% NaF, and 42 mol.% KF) that is a byproduct of developing molten salt nuclear reactors and a form of radioactive waste. The synthesized glasses exhibit a high degree of FLiNaK incorporation, reaching 20 – 25 wt.%, while maintaining a homogeneous, amorphous structure and uniform elemental distribution. However, at FLiNaK concentrations exceeding 25 wt.%, the glasses crystallize, forming an elpasolite (K₂NaAlF₆) phase. X-ray diffraction analysis reveals specific trends in the fluoride content of the glass. These trends suggest a correlation between the transformation of the glass local structure and the formation of a crystalline phase. This relationship will be examined more closely in future studies. Studies of the chemical and mechanical stability of synthesized glasses containing up to 20 wt.% FLiNaK demonstrate that these materials meet regulatory requirements for glass matrices used to immobilize radioactive waste. Additionally, the dependence of these properties on FLiNaK content shows an extremum at a concentration of 7 wt.%. However, no direct correlations with structural changes have been identified.

The properties of composite ceramic materials sintered from SiO₂–Al₂O₃–ZrO₂ nanopowders were studied. Prior to sintering, the powders were subjected to mechanical activation in a planetary ball mill using zirconia balls as grinding bodies. The activated powders were pressed under compacting pressures of 50, 100, 200, and 300 MPa. Consolidation was carried out in an atmospheric high-temperature furnace at 1700°C. The surface of the sintered bulk samples was examined using a scanning electron microscope. Elemental analysis made it possible to establish patterns in the distribution of chemical elements. All the studied samples revealed the presence of two phases — Al₆Si₂O₁₃ and ZrSiO₄. The sample porosity and its dependence on the applied pressure were established. The mechanical properties of the samples were studied using nanoindentation, including indentation hardness and elastic modulus. The bending strength limits of the studied samples were determined by scratch testing. The crack resistance of the samples was determined by the indentation method using the Marshall–Evans relationship. The effect of the ratio of the initial components and the applied compacting pressure on the physical and mechanical properties of the resulting composite ceramics was determined.

This study examines the phase formation process of a novel antimony-containing pyrochlore (space group Fd-3m) Bi_2.7Zn_0.46Ni_0.70Sb₂O_10+∆. The solid-state synthesis of this pyrochlore using oxide precursors is a complex, multi-stage process. The active interaction of the oxide precursors commences at temperatures exceeding 600°C, leading to the formation of an initial intermediate phase, Bi₃SbO₇. Individual oxide precursors, including bismuth trioxide and antimony tri- and pentoxides, are present in the sample up to 750°C. At temperatures above this threshold, a stable cubic phase, Bi₃M_2/3Sb_7/3O₁₁ (space group Pn-3), is formed, which remains stable up to 900°C. The pyrochlore phase first emerges in the sample at 650°C, with a substantial increase in its proportion observed at temperatures above 850°C. The formation of a pure pyrochlore phase occurs within the temperature range of 950 – 1050°C. The sintering of fine-grained ceramic is carried out at 1050°C. The obtained microstructure is characterized by low porosity, which is attributed to the coalescence of small grains into larger crystallites with a longitudinal size of 2 – 4 μm. The unit cell parameter of the pyrochlore varies unsteadily within the temperature range of 650 – 1050°C, reaching a minimum value of 10.464 Å at 800°C. The lattice parameter of the pure pyrochlore phase Bi_2.7Zn_0.46Ni_0.70Sb₂O_10+∆ is 10.474 Å.

This study developed technical ceramics for grinding media and examined how a dispersed oxide affects its key properties. The alumina-containing component used was waste catalyst from the gas processing industry. Nanodispersed aluminum oxide was synthesized from chemical reagents via the citrate sol-gel method. The results show that adding 3 wt.% of nanodispersed alumina (over 100 wt.% of the total mass leads) improves abrasion, acid resistance, and mechanical strength of technical ceramics.

This study investigates the processing characteristics of clay from the Stolinskie Khutory deposit (Vidibar sector, Brest Region, Belarus). The results indicate that the natural fine-grained material can be classified in accordance with GOST 9169–2021. The clay was identified as a refractory material, characterized by high plasticity. Depending on the depth of the occurrence, the material exhibits either semi-acidity or acidity, with a high to medium content of coloring oxides. The material displays a coarse-grained structure and does not sinter within the firing temperature range of 900 – 1200°C. We analyzed the phase composition of the clay and the processes occurring during its heat treatment. The findings indicate that this clay is suitable for the production of common bricks, coarse stone, and clinker material, as well as ceramic floor tiles. Samples of ceramic material produced under laboratory conditions using the Stolinskie Khutory clay demonstrate the requisite set of physical, chemical, and performance characteristics.