M 0224 (OTTO) Magnesium boride, ≥99.9% Cas Cas 12007-25-9 - used as propellants, pyrotechnics and explosives. M 0224 (OTTO) Magnesium boride, ≥99.9% Cas Cas 12007-25-9 - used as high temperature boron-based thermoelectric materials. It is also used in superconducting transformers, rotors, transmission cables, superconducting radio frequency cavities to minimize energy loss.