Flexible adjusting the combustion mode to synthesize transition metal borides in seconds by arc plasma

The combustion synthesis has been widely employed for the preparation of transition metal borides (TMBs). The preparation of TMBs via the thermal explosion mode in combustion synthesis typically requires long heating and holding times. Furthermore, the self-propagating high-temperature synthesis mode usually requires an ignition enhancer. In this paper, a simple, universal, and mass production method for preparing TMBs in seconds via arc plasma-induced combustion synthesis (APCS), which leverages the ultrahigh temperature and ultrafast heating rate characteristics of plasma. Depending on whether the adiabatic temperature ( T ad ) is greater than 1800 K, arc plasma-induced combustion synthesis to the self-propagating high-temperature synthesis mode (APCS-SHS) or arc plasma-induced combustion synthesis to the thermal explosion mode (APCS-TE) is adjusted to prepare TMBs. A variety of TMBs (FeB, CoB, NiB, VB 2 , TiB 2 , ZrB 2 , and TaB 2 ) were successfully synthesized by APCS within 2∼10 s. To clarify the mechanism of synthesizing TMBs, the T ad of the TMBs system was calculated, the influence of boron content on the phase composition of the product was studied, and an ultrafast heating-reaction-growth mechanism was proposed. The synthesis mode of APCS can be flexibly selected according to the adiabatic temperature of the system, thus enabling its extension to the synthesis of other transition metal carbides, phosphates, nitrides, and oxides, providing a powerful technology for the production of metal compounds.