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.
The article discusses the mechanochemical synthesis of a catalyst for the synthesis of methanol. Comparative mechanical activation of both individual components of the catalyst (copper oxide, zinc oxide, and aluminum oxide) and their various mixtures under different conditions has been carried out. The article discusses the structural characteristics of the catalyst for the synthesis of methanol, obtained using X-ray phase analysis, scanning microscopy and low-temperature adsorption of nitrogen.
The results of synthesis of lanthanum borate glasses modified with highly polarizable cations (Nb, Ti, Zr, Ta) are described. Their crystallization properties and structural features are studied by IR spectroscopy. It was found, that in the range of compositions 25La2O3–xMnOm–(75 – x)B2O3 (M = Nb, Ta, Ti, Zr, x = 0 – 25 mol %) glass specimens with a refractive index higher than 1,8 can be obtained. It is assumed that in the studied glasses in addition to the borate network a network of M cations corner-sharing of large polyhedra is formed. That preserves ability of the melt to glass formation
The process of crystallization of mullite during the synthesis of a ceramic composite material “mullite – zirconium oxide” obtained from a two-phase gel by a method combining co-deposition and sol-gel synthesis was investigated. Powders of the ceramic composite material “mullite – ZrO2” were obtained, their heat treatment was carried out at 1150 and 1350 °C. Samples of the ceramic composite material “mullite-zirconium oxide” were made from the obtained powders by semi-dry pressing. The microstructure and phase composition of ceramics were studied
The insertion into the impregnating suspension based on hydroxyapatite powder heat-treated at 800 °C, 24 wt. % of monocalcium phosphate monohydrate powder after firing at 1200 °C leads to the formation of calcium phosphate foam ceramic based on ?-tricalcium phosphate and ?-calcium pyrophosphate. Successive application of hydroxyapatite and biomimetic apatite to calcium phosphate foam ceramic leads to an increase in strength and enrichment in a-tricalcium phosphate and hydroxyapatite. Multiphase calcium phosphate foam ceramic has a porosity of 35 - 60 %, a static strength up to 0.08 MPa, and increased bioactivity due to the biomimetic apatite layer
The effect of the anionic composition of zinc salts on the preparation of powders in the ZnO–SnO2 system by the sol-gel method has been investigated. It was determined that the synthesis and microstructure of the obtained powders depend on the activity of the acid forming the zinc salt. According to the data of X-ray phase analysis and scanning electron microscopy, the optimal raw material for obtaining zinc orthostannate is zinc sulfate
