Formation of zirconium diboride (ZrB2) by room temperature mechanochemical reaction between ZrO2, B2O3 and Mg

A mixture of magnesium, boric oxide and zirconium dioxide were mechanically milled under argon for up to 15 h in a laboratory scale ball mill. X-ray diffraction showed that there was an increasing conversion of ZrO2 to ZrB2 with milling time with >98% reaction after 15 h. Differential thermal analysis revealed there were multiple, overlapping reactions all of which seemed to be formation of ZrB2. The energy evolved decreased with milling time and the sample after 15 h milling showed no thermal reaction. After milling, separation of the ZrB2 from the coproduct MgO was easily achieved by a mild acid leaching leaving essentially pure ZrB2 with a crystallite size of ∼75 nm.