Fe-substituted ceramic materials of the NASICON family, corresponding to the generally accepted formula Na3+yМ(III)yZr2–ySi2PO12, with a dopant concentration from 5 to 20 mol. % were studied. Doping changes the morphology and phase composition of ceramics. Electron paramagnetic resonance spectra indicate the presence of Fe3+ atoms both in the crystalline phase (with g ~ 2.0) and in disordered phases with a strong rhombic component of the crystal field on impurity ions (with g ~4.3 and ~4.2). A quantitative analysis of the distribution of paramagnetic centres in ceramics was performed. It was noted that the dopant is predominantly found in the crystalline phase of the sample. It was shown that Fe-substituted NASICON complexes correspond to the composition Na3М(III)yZr2–ySi2–yP1+yO12. The Fe3+ content in the crystalline phase of these complexes is 36% higher than in samples obtained in accordance with Na3+yМ(III)yZr2–ySi2PO12.
To produce Al–Al2O3 cermet with a heterogeneous granular-layered structure, mixing of flake aluminum powder of the PAP-2 brand with the plasma-chemical alumina powder (PCAP) consisting of nano-thick lamellar agglomerates in a planetary ball mill in the mechanical alloying mode was carried out. The resulting charge, consisting of layered granules containing alternating alumina and aluminum layers, was compacted under a pressure of 700 MPa. Sintering of green samples was carried out in a vacuum (10–5 mm Hg) at a temperature of 650 ? for 1 hour. The content of the alumina component in the cermet composition in the amount of 15% by weight ensured a combination of low density – 2.54 g/cm3 with significant indicators of its mechanical properties (flexural strength – 280 MPa, axial compression strength – 350 MPa, crack resistance – 8.5 MPa?m1/2, microhardness – 1070 MPa) as a result of achieving a compromise between the plasticity of this composite and its hardness. Cermet can be used as lightweight armor protection elements, wear-resistant elements and special abrasive tools.
The adhesion properties of polyurethane- and polyurea-based polymer coatings designed to protect concrete were studied under the climatic conditions of Yakutia. Coated concrete samples were exposed to outdoor conditions for two years, where temperatures ranged from +20 °C in summer to –42.8 °C in winter. The results showed that climatic factors primarily affect the surface layers. During the first year, coating adhesion decreased approximately equally for all samples. However, as the testing period increased, the decrease in adhesion properties became more pronounced and uneven. This is presumably due to moisture absorption by the polymer and concrete, the intensity of which depends on the coating thickness. Freezing of moisture leads to the formation of internal stresses and microcracks, weakening the bond between the coating and concrete. Frequent temperature fluctuations accelerate this process. It was established that the physical and mechanical properties of the coatings are determined by the composition of the original components and the nature of the chemical bonds, while curing temperature has a significant impact on their mechanical characteristics.
In this paper the experience of using regular and specially developed resistive pastes for resistors compatible with LTCC substrates is reviewed. Characteristics of surface, buried, and 3D resistors manufactured using DuPont, Ferro, Shoei, and ESL pastes on ceramics from various manufacturers are examined. Results of a study of the resistors' microstructure, phase and elemental composition, sheet resistance, tolerance, hot (HTCR) and cold (CTCR) temperature coefficient of resistance, frequency behaviour, noise indices, gauge factors, as well as their performance after thermal aging, laser trimming, and high-voltage pulse loads are presented. The influence of process conditions, resistor dimensions and the physicochemical interactions of the materials on these characteristics is assessed.
Glasses in the TeO2–ZnO system doped with Er3+, Yb3+, Nd3+ were studied. The influence of the synthesis atmosphere on the properties was determined. The photoluminescence intensity, absorption, refractive index, and impurity purity of the glasses were experimentally determined. The stability of the spectral-luminescent properties to the tropical climate conditions of Southeast Asia was studied.
Some ceramic materials formed by sintering layered green bodies formed the compacted powders of the basic potassium polytitanate and this one modified with Mn compound are produced and investigated. Using impedance spectroscopy, the electrical properties of the resulting multilayer ceramic materials are studied in the range up to 1 MHz. It is recognized that the frequency dependence of the electrical properties of capacitor structures formed by multiple layers of varied highly polarizable dielectrics differs significantly from those obtained with monolayer dielectrics. Possible applications of multilayer ceramic structures with high permittivity as dielectrics and electrochemically active materials are analyzed.
The work is devoted to the production of iron oxide from industrial waste for its further use in the production of ceramics, catalysts and sorbents. It is proposed to use iron-containing waste from the Zavolzhsky Chemical Plant of the Ivanovo region as a starting material. The raw materials were subjected to heat treatment at temperatures of 300, 500 and 1000 ?. The possibility of removing some of the impurities by calcination of the feedstock is shown. The obtained samples were cleaned of residual impurities with various acids. Fe2O3 and Fe3O4 was obtained by precipitation from solution. The phase composition and textural characteristics of iron (III) oxide samples obtained by X-ray phase analysis, scanning electron microscopy, energy dispersion analysis, and low-temperature nitrogen adsorption/desorption are shown. The work experimentally confirmed the possibility of obtaining iron oxide from iron-containing waste in order to use it as an intermediate for the production of catalysts, sorbents and ceramics.
This study presents aspects of developing a technology for producing granulated mineral fertilizer based on phosphate foam glass. It has been established that phosphate foam glasses, with their slow solubility and ability to improve soil physical properties, are promising fertilizers for agricultural crops. A raw material mixture for melting phosphate glass was developed, comprising monopotassium phosphate, apatite concentrate from the Khibiny deposit, and orthophosphoric acid. The phosphate glass was melted at 900 °C, yielding an amorphous glassy product with a P2O5 content of 59.88 %. Based on the resulting product, phosphate foam glass samples with varying amounts of a gas-generating additive (dolomite flour) were synthesized. The optimal dolomite flour content was found to be 6 %. Phosphate foam glass granules with the optimal dolomite flour content were synthesized using a tubular rotary kiln. As a result of the synthesis, granules with a bulk density of 222 kg/m3 were obtained.
The article presents the results of studies of heat-resistant insulating ceramics, as well as a mechanism of cordierite phase formation during single firing of compositions containing polymineral clay raw materials, technical alumina and talc; phase transformations during heat treatment of experimental compositions; the effect of firing temperatures on phase formation of ceramics. The research results are of theoretical and practical interest for synthesizing heat-resistant materials, expand the understanding of the processes occurring in multicomponent systems, and allow to better understand the sequence for crystalline phases formation, creating prerequisites for structurally controlled synthesis of ceramics with a given set of technical and operational characteristics.
A series of glass-crystalline composites were produced by heating at 1350 °C of powdered mixtures of helleflinta (quartz-feldspar waste from the Kostomuksha GOK) and 5, 10, 20 and 40 mass. % of shungite rock. The phase composition and structural features of the obtained composites were studied using X-ray phase analysis, Raman spectroscopy, and scanning electron microscopy. The relative changes of the electrical conductivity and the collapsing force of the samples were determined.
