Formation of TaB2 powders from high energy ball milling and borothermal reduction process

Abstract

TaB2 powders were fabricated at reduced temperatures via borothermal reduction route by high energy ball milling of Ta2O5 and B powder blends. The effects of milling media (Steel, ZrO2 and WC), milling time (1,3,5 and 7 h) and heat treatment temperature (1650 °C and 1350 °C) on the formation and microstructural characteristics of TaB2 and related phases were extensively investigated. Increasing the milling time up to 7h was found to be decreased the common formation temperature of the TaB2. Ta-rich Ta3B4 and TaB phases were formed after heat treatment at 1650 °C for 5 h milled samples in ZrO2 and WC media which were associated with the generation of different impact energies. Depending on the C diffusion from graphite mold and the wearing of milling jar and balls, TaC formation was also observed. The predicted reactions and experimental results were compared, and the reaction mechanism of the Ta2O5–B system was explained by using FactSage thermochemical software, differential thermal analysis (DTA) and X-ray diffractometry (XRD). TaB2 based fine powders comprising TaC were obtained from powder blends milled for 3 h in ZrO2 and WC media and heat treated at 1350 °C for 1 h.