Carbothermal synthesis of TiB2 powders of micron size

Abstract

The characteristic details of the carbothermal synthesis of TiB₂ powders from the stoichiometric mixture TiO₂–H₃BO₃–C at temperatures lower 1700 K are investigated using thermal analysis (ТG—thermogravimetry and DSC—differential scanning calorimetry), as well as X-ray diffraction and scanning electron microscopy. In the temperature interval 300 K → 1673 K → 1273 K and at a heating rate of 10 K/min, the reaction in the powder mixture begins at approximately 1300 K and ends at 1470 K during cooling. After 3 h of isothermal synthesis at 1473 K, the TiB₂ yield is more than 90%. The resulting products are hexagonal plate-like crystals 5–10 μm across with thickness of 3 to 4 μm. Kinetic analysis showed that in the temperature range of 1330 to 1673 K the TiB₂ synthesis reaction is of the first-order, and the calculated activation energy of the process is 315 ± 24 kJ/mol.