Abstract
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 TiB2 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 TiB2 with alumina-magnesia spinel additives obtained by self-propagating high-temperature synthesis (SHS). TiB2 structure with uniform fine-grained distribution was obtained in an MgAl2O4 matrix. The material composition was confirmed by X-ray diffraction analysis (DRON-3M, filtered Со 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 TiB2 with a size of 5 µm are uniformly distributed in the alloy of alumina-magnesia spinel.
Highlights
Self-propagating high-temperature synthesis (SHS) is used to develop new technologies for the production of refractory nonmetallic composite materials with defined properties
Magnesium and aluminothermic synthesis is widely used for the production of refractory ceramic materials, e.g., with the use of metallothermic reduction in a TiO2 –MgO–Al2 O3 –Al system, the refractory materials based on MgAl2 O4 and titanium carbonitrides are obtained [2]
The formed surface layer of MgAl2 O4 on the grains boundary of TiB2 serves as a blocking protection from titanium diboride oxidation and prevents the growth of TiB2 crystals
Summary
Self-propagating high-temperature synthesis (SHS) is used to develop new technologies for the production of refractory nonmetallic composite materials with defined properties. To increase the refractory properties of metal carbides and borides, alumina-magnesia spinel MgAl2 O4 with the melting temperature of 2105 ◦ C, which corresponds to the high level of refractoriness [1], is used as an additive. High-strength porous ceramic material, containing in its composition MgAl2 O4 , TiB2 , TiO2 , Al4 B2 O6 , and Mg2 B2 O5 was obtained in a TiO2 –B2 O3 –Al system with MgO additives. This material can be used as a catalyst at temperatures of 600 ◦ C–700 ◦ C in an open atmosphere [3].
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