Combustive mechanochemical reactions with titanium, zirconium and hafnium

The ignition of self propagating high temperature reactions by ball milling has been investigated for reactions of Ti, Zr, and Hf with Cu2O, Fe3O4, S, B, and C. The ignition times are much shorter when Zr is reacted with oxides or sulfur than for similar reactions with either Ti or Hf. However, the ignition time varies little among the three metals when carbides and borides are prepared from the elements. It is suggested that this behavior is related to the fast diffusion of oxygen in Zr oxides and sulfur in Zr sulfides, and the lack of similar behavior in borides and carbides. The above results are the first attempt to correlate ignition time with a property other than reaction heat or adiabatic temperature.