The results of producing cobalt-bearing spinels of a blue-sky to blue color range by self-propagating high-temperature synthesis (SHS) are described. The effect of the conditions of synthesis and the mixture composition on the structure of compounds obtained is demonstrated. The SHS method makes it possible to obtain spinels that can be used as ceramic pigments.One of the methods for producing pigments of the spinel type for ceramic paints and glazes is self-propagating hightemperature synthesis (SHS). It is based on using the heat from exothermic reactions and is faster and more cost-efficient than traditional methods.The purpose of the present paper is to obtain pigments of the spinel type by SHS and to study the effect of the initial composition and conditions of synthesis on the structure formation processes.Pigments were synthesized using Al 2 O 3 , Co 2 O 3 , ZnO, MgO, and aluminum powder ASD-4. Synthesis was performed in a constant-pressure plant in an argon atmosphere and in air. The obtained pigments were identified by x-ray phase analysis on a DRON-UM1 diffractometer (filtered CoK a radiation) and infrared spectroscopy in the range of 1400 -400 cm -1 on a Nicolet 5700 IR-Fourier diffractometer with a diffuse reflection device in KBr. The microstructure of samples was studied using light microscopy (Axiovert 200M).Blue pigments were obtained in the CoO -Al 2 O 3 system. According to the x-ray phase analysis data, the products of synthesis performed in the argon atmosphere contain, besides aluminocobalt spinel CoAl 2 O 4 , also a substantial amount of corundum (Al 2 O 3 ). Furthermore, the products contain metallic cobalt and Co(AlO 2 ) 2 . The IR spectroscopic analysis 2 indicates the formation of a mixed spinel (Fig. 1, curve 1 ) in the system, since in addition to the octahedral aluminum atom [AlO 6 ] whose vibrations are manifested at 560.0 cm -1 , which is typical of normal spinels, we observed also absorption bands of the tetrahedral atom [AlO 4 ] at 624.5 cm -1 , which is present in inverse spinels. Moreover, there is an intense absorption band at 1088.9 cm -1 related to the vibrations of the ion (AlO 2 ) -[1 -3].Synthesis performed in the air atmosphere produces pigments with better color characteristics, which is directly related to their composition and structure. The modification of the structure is clearly visible in the IR spectra of the pigments. Thus, the absorption bands at 886.1, 979.5, and
with aluminum powder ASD-4 and MgO and ZnO additives by the method of self-propagating high-temperature synthesis (SHS) is investigated. A blue and an ultramarine pigment are obtained. Their phase composition, IR spectra, and structural and color characteristics are studied. It is demonstrated that the SHS method is promising for producing heat-resistant spinel-type pigments of a blue-sky-blue color range.
In this study the influence of scandium on the structural and phase state of the Ti-Al alloy obtained by the method of “Hydride Technology” (HT). The Rietveld method has allowed for determining the content of basic phases of the 49at.%Ti-49at.%Al-2at.%Sc system. By means of the methods of transmission electron microscopy (TEM) and X-ray spectral microanalysis, it has been established that scandium additives into the Ti-Al system result in the change of the quantitative content of phases in local regions of the structure. The Ti2Al5 phase has been found, and Ti2Al has been absent. In the morphology of substructures Ti-Al and Ti-Al-Sc there are lamellar structures or lamellae; the peculiarities of the distribution, fraction and size of which are influenced by scandium additives. The average width of Al-rich lamellae has been 0.85 µm, which is four times greater than that for the Ti-Al system (0.21 µm). For Ti-rich lamellae of the sample of the Ti-Al-Sc alloy, the average width of the lamellae has been 0.54 µm, and for Ti-Al it has been 0.34 µm. Based on the obtained data, a scheme of the distribution of phases in the composition of the Ti-Al-Sc alloy in the lamellar structures has been proposed. It has been established that in the Ti-Al-Sc system there is growth of the near-surface strength relative to Ti-Al. In this way, the microhardness of the Ti-Al-Sc alloy has amounted to 1.7 GPa, that is of the Ti-Al alloy which is 1.2 GPa.
Metal borides are widely used as heat-insulating materials, however, the range of their application in high-temperature conditions with oxidative medium is significantly restricted. To improve the thermal stability of structural materials based on titanium boride, and to prevent the growth of TiB 2 crystals, additives based on alumina-magnesia spinel with chemical resistant and refractory properties have been used. The aim of this work is to study the structure of TiB 2 with alumina-magnesia spinel additives obtained by self-propagating high-temperature synthesis (SHS). TiB 2 structure with uniform fine-grained distribution was obtained in an MgAl 2 O 4 matrix. The material composition was confirmed by X-ray diffraction analysis (DRON-3M, filtered Co kα-emission), FTIR spectroscopy (Thermo Electron Nicolet 5700, within the range of 1300-400 cm −1 ), and scanning electron microscopy (Philips SEM 515). The obtained material represents a composite, where the particles of TiB 2 with a size of 5 µm are uniformly distributed in the alloy of alumina-magnesia spinel.
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