The effect of alkaline treatment on the destruction process and some surface characteristics of mechanically processed glass discs of lead-silicate glasses C87-2 and C78-4 has been studied. It is shown that the interaction of these glasses with barium hydroxide leads to the removal of silicic acid from the gel surface, which in turn improves the water wettability and optical transparency of the glasses. It is proposed in the production technology of electric vacuum devices, where lead-silicate glasses are used, to use washing with barite water for rapid coagulation of silica gel, which eliminates the appearance of foreign particles on the surface of the glasses.
The goal of the present contribution is to study the possible use of local clay of hydromica type for facing tile production. Pegmatite dust removal waste from the Chupa Milling and Dressing Factory was added as flux to the clay. Mineralogical, chemical and grain-size analyses of the clay and waste were performed. The mineral composition of the waste and clay were analyzed using the laboratory equipment of the Analytical Centre at the Institute of Geology, Karelian Research Centre, RAS. Experimental samples of ceramic tile were produced and the physico-mechanical properties of the products were assessed. The ceramics produced can be used for facing walls and furnaces. Local clay of hydromica type and pegmatite dust removal waste can be used to increase the mechanical bending strength and heat resistance of facing tiles, to decrease their thermal conductivity in comparison with samples containing clay, kaolin, feldspar and lime and to contribute to pegmatite waste utilization.
A dense-sintered protoenstatite ceramics based on fluorinated talc was obtained. Influence of BaO and Al2O3 additives on the sinterability, structure and strength of ceramics was investigated. It makes possible to reduce the sintering temperature to 1225 – 1250 °C due to formation of glassy phase. Additive of ZnO intensifies solid phase sintering at 1320 °C. It significantly improves compressive strength of ceramics up to 660 MPa that exceeds the strength of traditional steatite materials by 3 times.
This paper presents the results of experimental studies on the passage of an electron beam with an energy of 12 and 15 keV through glass tapered macrocapillaries. As a result of the measurement, the absence of an explicit dependence of the output current on the electron energy was shown. Time-dependent measurements of the beam current at the exit from the capillaries were carried out.
Specific mechanisms of grain structure effect on the thermoelectric properties (specific electrical resistivity and total thermal conductivity) of the Bi1.9Gd0.1Te3 compound have been analyzed. These mechanisms are as follows: 1) forming the surface Te vacancies at grain boundaries acting as donor centres; 2) changing the elemental composition of the grains at high-temperature Te evaporation under thermal treatment of material to prepare the samples with desired average grain size.
By means of the method of the spark plasma sintering (SPS) on the basis of nanodimensional powder of nickel oxide (with an average particle size of about 100 nm), the fine-grained (of 250 – 500 nanometers approximately), dense (5.93 g/cm3), strong ceramics with the high microhardness Hv = 8.2 GPa, ultimate compressive strength ?B = 0.4 GPa and Young?s modulus of elasticity E = 140 GPa is created. The obtained ceramic sample was nickel oxide NiO (73-1519) with cubic structure, space group Fm3m (No. 225) and lattice size a = 4.168 ?.
The paper presents the results of a study on the durability of cutting ceramics: a replaceable polyhedral plate developed at NSTU and cutting ceramics WOK-60 when processing hardened steel blanks made of 40X (45HRC) steel. As a result of the tests carried out, it was found that with the use of cutting modes developed at KNAU, the durability of SMP from cutting ceramics created at NSTU is more than 1.7 times higher than the performance of plates based on the WOK-60 material. At the same time, the roughness of the treated surface of the work piece was Ra = 0.35 ? 0.05 microns when using SMP from the developed ceramics Ra = 0.55 ? 0.05 microns when using WOK-60 plates. The stages of destruction of cutting ceramic plates are revealed, taking into account the hierarchy of structural scales.
In this work we studied the effect of mechanochemical activation on the formation of the cobalt ferrite phase from iron and cobalt oxalates. X-ray phase, X-ray diffraction and synchronous thermal analysis, scanning electron microscopy, low-temperature nitrogen adsorption-desorption method were used to study the composition and properties of the resulting product. It has been established that cobalt ferrite is formed at a temperature of 1100 °C during solid-phase interaction of the initial components, and the use of mechanochemical activation of the initial components in a roller-ring vibration mill makes it possible to reduce the synthesis temperature to 400 °C. It is shown that CoFe2O4 obtained using the method of mechanochemical synthesis has a more developed specific surface area and porous structure in comparison with cobalt ferrite obtained by the ceramic method.
In this work, the effect of the annealing temperature and the chemical history of the precipitate on the morphology and phase composition of the Nb2O5 powder was studied. Nb2O5?nH2O precipitate and gel-like niobium citrate were obtained by solution methods. The synthesis of niobium oxide was carried out at temperatures of 600, 1000, and 1200 °C, the synthesis products were analyzed using X-ray diffraction, scanning electron microscopy, X-ray microscopy, and differential thermal and thermogravimetric analysis. Annealing of niobium citrate at a temperature of 600 °C makes it possible to obtain niobium oxide particles with an average size of about 70 nm, which is 4 – 6 times smaller than Nb2O5 obtained from the Nb2O5?nH2O precipitate.
The article provides an overview of mineral oxide fibers of various chemical composition: aluminosilicate, alumina, silica, bio-soluble, zirconium oxide fibers and others. Methods for producing discrete and continuous fibers, such as spinning fibers from melts, sol-gel technology, spinning from solutions of metal salts, etc., are described. filtration for alumino-silicate and bio-soluble fibers; thermal insulation up to 1600 or 2000 C and reinforcement of composites used in the aerospace and defense industries for alumina fibers and fibers based on zirconium dioxide, etc. Producers of mineral oxide-containing fibers and products based on them abroad and in Russia are represented.
