SYNTHESIS OF MAGNESIUM DIBORIDE POWDER BY SELF-PROPAGATING HIGH-TEMPERATURE

摘要

Self-propagating high-temperature synthesis (SHS) method was used to fabricate MgB_2 powder from Mg-B system. In this paper, the reaction process of Mg with B was studied by thermodynamic calculation, X-ray diffract-meter and micro-image analyzer. These results show that the single-phase MgB_2 can be synthesized by self-propagating high-temperature synthesis method. When Mg reacts with B, Mg firstly melts and then reacts with B to form MgB_2; but if the synthesis temperature is too high, MgB_2 can decompose into MgB_4 and Mg. These synthesized MgB_2 particles appear random geometry and fine crystal grain. At normal pressure, the decomposition temperature of MgB_2 is less than 1320K; but higher gas pressure is beneficial to lifting the decomposition temperature of MgB_2. And at high temperature, there are these phenomena that MgB_2 can also exist or MgB_2 directly decomposes into Mg and amorphous B.