SH-synthesis of TiB<sub>2</sub>-MgAl<sub>2</sub>O<sub>4</sub> composites for heatresistant coatings
Metal borides are known to be widely used as heat-insulating materials, but their efficiency significantly reduces under high-temperature oxidizing conditions. To increase the heat resistance of structural materials based on titanium diboride and prevent the growth of TiB<sub>2</sub> crystals, chemically-resistant refractory magnesium-aluminate spinel was used. The purpose of this work was to study the structure of the TiB<sub>2</sub>-MgAl<sub>2</sub>O<sub>4</sub> composite obtained by the method of self-propagating high-temperature synthesis using two approaches. The first approach is the self-propagating high-temperature synthesis of titanium diboride from its elements with the addition of magnesium-aluminate spinel. Another approach to the obtaining of a heatresistant composite material is the self-propagating high-temperature synthesis of magnesium-aluminate spinel with the addition of titanium diboride. The best results were obtained using the first approach. A structure with a uniform distribution of fine TiB<sub>2</sub> grains was synthesized by adding 25 % wt. MgAl<sub>2</sub>O<sub>4</sub>. The compositions were investigated using X-ray diffraction (DRON-3M, filtered Cu-k<sub>α</sub>-radiation), IR spectroscopy (Nicolet 5700) and scanning electron microscopy (Philips SEM 515). The obtained material was a composite in which TiB<sub>2</sub> particles with a size not exceeding 5 microns were uniformly distributed in the matrix of magnesium-aluminate spinel.