Role of -O functional groups at the Ti3C2O2(MXene)/Al interface in enhancing the mechanical properties of aluminum matrix composites: A first-principles study

MXenes gradually become an ideal reinforcement for aluminum matrix composites (AlMCs) due to their excellent mechanical properties and the characteristics of surface groups. In this work, the structural, adhesive, me-chanical and electronic properties of Ti3C2(O2)/Al composites are systematically investigated by first-principles calculations based on density functional theory (DFT), revealing the role of -O functional groups at the interface. The first-principles tensile simulation showed that the tensile strength of the composites increased from 6.93 GPa (Ti3C2/Al) to 8.49 GPa (Ti3C2O2/Al), indicating that the -O functional group was beneficial to enhance the tensile properties of the composites. The results of plane-averaged charge density difference and Bader charge quantitatively suggest that the Ti3C2O2/Al(1 1 1) system has greater charge transfer than Ti3C2/Al(1 1 1) system. In particular, the Ti3C2O2/Al interface has atomic orbital hybridization, forming highly localized Al-O and O-Ti bonds, which constitute an "Al-O-Ti" interlocking structure at the interface. Crystal orbital Hamilton population (COHP) indicate that the bonding strength at the Ti3C2O2/Al interface is higher than that at the Ti3C2/Al interface. Therefore, the "Al-O-Ti" interlocking structure enhances the load transfer capability of AlMCs and thus improves their mechanical properties. This work provides theoretical support for further understanding the strengthening mechanism of Mxene/Al composites.