The article shows the effect of an ultra-high pressing load of 1,20 GPa at 1800°C during spark plasma sintering, compaction pressure of 2,30 GPa at 1260°C during the explosive sintering of the particles of solid solutions of ceramic and metallic phases with the additive of oxide powders mixture, NiCr on the phase composition, microstructure, grain size of the crystalline phases, relative density, linear shrinkage, microstructural features of the boundary layers, microcrack paths, physico-mechanical properties of mullite–c-ZrO2–c-BC2N–NiCr–V–Mo–Zr–W and mullite–c-ZrO2–c-BC2N–NiCr–Cr–Mo–Nb–Ta. Spark-plasma sintered c-ZrO2 at pressing load 35 MPa and temperature 1400°C, g-BC2N at pressing load 60 MPa and temperature 1600°C show evoluted crystallization of the c-ZrO2 and g-BC2N phases, respectively, crystalline, uniform, dense microstructures. Samples sintered by the spark-plasma method at an ultra-high pressing load of 1,20 GPa at 1800°C show evoluted mullitization, crystallization of c-ZrO2, c-BC2N, NiCr, β-V, Mo, W, Zr, β-Cr, Mo, Nb, Ta phases, more crystalline, more uniform and more densely sintered microstructures, variously dispersed grains of the crystalline phases. Samples sintered by both methods differ by the relative density, linear shrinkage, density, uniformity, width, path and moving microcracks across these boundary layers, crack resistance and values of physico-mechanical properties.
A study of a two-stage method for the formation of nanostructured Ni3Fe is presented. Nanostructured Ni3Fe hollow microspheres were synthesized by ultrasonic spray pyrolysis (URP) from a mixture of aqueous solutions (10 wt.
A method for producing a composite sorbent with a honeycomb structure (a system of parallel directed permeable pores) for capturing platinum aerosols in high-temperature catalytic processes is proposed. The composite sorbent is prepared from cordierite ceramics with the addition of active calcium oxide. The calcium oxide precursor is introduced into the molding mass as calcium carbonate powder or by impregnating the matrix material with a solution of calcium nitrate. The mechanism of synthesis of the composite sorbent is investigated. Its physicochemical properties are given. Pilot tests of composite sorbents in an industrial reactor have shown its resistance to technological conditions of ammonia conversion and the ability to capture platinum catalyst aerosols.
Polymorphic transformations of the first and second kind of the type C ordered cubic structure into the type C1 disordered structure were found during heating of samples of Y2O3 oxide grade (99.990
The efficiency of using a mechanoacoustic method for preparing a multicomponent charge for producing ceramics from highly dispersed aluminosilicate raw materials is evaluated. The influence of ultrasonic dispersion and mechanical activation on the dispersed phase structural state is evaluated using x-ray diffraction analysis based upon changes in the size of particles and crystallites that make up an aggregate. It is established that with the help of mechanoacoustic treatment in powder represented by a mixture of differently active particles it is possible to achieve maximum structural homogeneity by reducing the size of local inhomogeneities. It is shown that use of montmorillonite as an additive to a charge in combination with mechanical-acoustic treatment reduces the sintering temperature and makes it possible to prepare ceramic with a more uniform structure and high strength.
