Synthesis, Characterization, Physical Properties and Applications of Metal Borides

Low temperature controllable synthesis of transition metal and rare earth borides mediated by molten salt

“…The negative Gibbs energy values calculated by using the Factsage package (Figure 4), 60 along with the relevant thermodynamic data and phase diagrams reported in the literature 1,6,11,23,[60][61][62][63][64][65][66][67][68][69][70] suggest that the reaction between a transition metal or rare earth metal, and elemental boron is thermodynamically favourable, at all the temperatures, which is the thermodynamic basis behind various synthesis routes, including the conventional high-temperature and high pressure arc-melting, 71,72 high temperature solid-state reaction, 73,74 as well as long time mechanical alloying. [74][75][76] Given the extremely exothermic nature of Reaction (1), 1,6,[60][61][62][63][64][65][66][67][68][69][70] the so-called self-propagating high-temperature synthesis (SHS) was also used. 77,78 These synthesis approaches suffer from various disadvantages, for example requirement of high temperature/pressure and/or long processing time and/or high agglomeration of product boride.…”