Synthesis of refractory powders of the borides of titanium and chromium in burn mode

One of the most important directions of nanotechnology is the acquisition of nanosized powders. Changes in the fundamental properties of traditional materials in the nanodispersed state opens up a wide range of applications of nanopowders in the field of creating new materials and technologies. New materials creation with different properties and level of quality based on widely used raw materials, including man-made, is currently determined by the tasks of scientific and technological progress. One of the main sources of boron ores in Kazakhstan are borates from the Inder deposit. These wide available raw materials can be used to obtain boron-containing refractory powder materials. Popular methods of producing such materials are characterized by high energy consumption and high labor intensity. The use of self-propagating high-temperature synthesis (SHS) is currently one of the most effective approaches for creating new materials. An important role in obtaining materials in SHS mode is played by preliminary mechanochemical activation (MA), which allows achieving a high degree of particle dispersion and changing the structure, energy intensity, and high reactivity of the material. To obtain samples of boride powders of refractory transition metals, mixtures containing powdered titanium dioxide, chromium oxide, enriched borate ore (boron oxide content up to 40 %) and magnesium powder were prepared. Preliminary mechanical activation of the samples was performed in the ''Pulverizette-5'' of a high-energy planetary centrifuge mill. The TiO₂-B₂O₃(ore)-Mg and Cr₂O₃-B₂O₃(ore)-Mg systems were selected for synthesis to produce refractory titanium and chromium boride powders. The experiments were conducted in a high-pressure reactor. After SH-synthesis the resulting powders were leached with hydrochloric acid and washed with distilled water. The products SHS were characterized using X-ray diffraction analysis and scanning electron microscopy. SHS of diborides of titanium and chromium occurred in the following reactions in the combustion wave: TiO₂ + B₂O₃ + 5 Mg = TiB₂ + 5 MgO, Cr₂O₃ + 2 B₂O₃ + 9 Mg = 2 CrB₂ + 9 MgO. The possibility of using borate ore for production nanosized refractory of titanium and chromium borides powders by method of SHS is shown. (author)