MoAlB as a typical member of MAB phases has attracted much-growing attention due to its unique properties. However, the low production of MoAlB powders limits its further development and potential applications. In the present work, the ultra-fast preparation of high-purity MoAlB powders in a few seconds is achieved by self-propagating high-temperature synthesis (SHS) using a raw powder mixture at an atomic ratio of Mo : Al : B = 1 : 1.3 : 1. SHS reaction mechanism is obtained by analyzing the corresponding composition changes of starting materials. Furthermore, the thermodynamic prediction for the SHS reaction is consistent with the present experiments, where the preparation of MoAlB also conforms to two common self-propagating conditions of the SHS. The enthalpy vs. temperature curve shows that the adiabatic temperature of the reaction decreases with the amount of excuse Al increasing but increases when pre-heating the reactants. Also, this thermodynamic calculation provides a new idea for the preparation of other MAB phases by the SHS.

Mo₂Ga₂C is a new MAX phase with a stacking Ga-bilayer as well as possible unusual properties. To understand this unique MAX phase structure and promote possible future applications, the structure, chemical bonding, and mechanical and thermodynamic properties of Mo₂Ga₂C were investigated by first-principles. Using the "bond stiffness" model, the strongest covalent bonding (1162 GPa) was formed between Mo and C atoms in Mo₂Ga₂C, while the weakest Ga-Ga (389 GPa) bonding was formed between two Ga-atomic layers, different from other typical MAX phases. The ratio of the bond stiffness of the weakest bond to the strongest bond (0.33) was lower than 1/2, indicating the high damage tolerance and fracture toughness of Mo₂Ga₂C, which was confirmed by indentation without any cracks. The high-temperature heat capacity and thermal expansion of Mo₂Ga₂C were calculated in the framework of quasi-harmonic approximation from 0 to 1300 K. Because of the metal-like electronic structure, the electronic excitation contribution became more significant with increasing temperature above 300 K.