On the complex synthesis reaction mechanisms of the MAB phases: High-speed in-situ neutron diffraction and ex-situ X-ray diffraction studies of MoAlB

Phase Formation during the Synthesis of the MAB Phase from Mo-Al-B Mixtures in the Thermal Explosion Mode

“…Our findings, with the stages of MoAlB formation identified, show good agreement with the data reported in ref. [ 37 ], which reports an in situ study on the mechanism of MoAlB synthesis from element powders using neutron diffraction. The key differences are that stages corresponding to the formation of the intermediate MoAl 12 phase and the high-temperature orthorhombic modification of β-MoB instead of α-MoB are reported in ref.…”

“…The key differences are that stages corresponding to the formation of the intermediate MoAl 12 phase and the high-temperature orthorhombic modification of β-MoB instead of α-MoB are reported in ref. [37]. These differences are probably related both to the fact that neutrons are characterized by a deeper penetration ability and the crystal structure can be studied over a broad 2θ range = 15 • -120 • and to the different heating rates used in the experiments-~5 • C/min and ~500 • C/min-when heating the sample in a tube furnace and an induction furnace, respectively.…”

“…The key differences are that stages corresponding to the formation of the intermediate MoAl12 phase and the high-temperature orthorhombic modification of β-MoB instead of α-MoB are reported in ref. [37]. These differences are probably related both to the fact that neutrons are characterized by a deeper penetration ability and the crystal structure can be studied over a…”

“…The stages of the MoAlB phase formation were studied for the layer-by-layer combustion and thermal explosion modes as reported in refs. [ 13 , 37 ]. Time-resolved X-ray diffraction data [ 13 ] indicate that the crystallization of the MoAlB phase is not accompanied by the formation of intermediate compounds.…”

“…Time-resolved X-ray diffraction data [ 13 ] indicate that the crystallization of the MoAlB phase is not accompanied by the formation of intermediate compounds. In the meantime, Merz et al [ 37 ] discovered through neutron diffraction that in the case of rapid induction heating (~500 °C/min), the SHS process commences with the melting of aluminum. Subsequently, the MoAlB phase emerges following the transformation of β-MoB boride into α-MoB and the subsequent interaction with Al.…”