First-principles study on the stability and properties of β-SiC/Mn+1AlCn (M=Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta; n=1,2) interfaces

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In this work, first principles calculations are performed to investigate the structural, electronic, and mechanical properties of the interface between β-SiC ceramics and Mn+1AlCn (M = Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta; n = 1,2) phases, with particular focus on Ti3AlC2 and Ti2AlC. The interface between the β-SiC(111) and Tin+1AlCn (0001) (n = 1,2) surfaces is most likely a stable interface because of the small misfit in lattice constants. Six different interface models between β-SiC(111) and Tin+1AlCn(0001) are examined. The optimized interfacial distances are determined using the universal binding energy relation method, and then each model is fully relaxed to calculate work of adhesion. By comparison, it is determined that the junctions connecting the C-terminated SiC(111) and Ti-terminated Tin+1AlCn(0001) surfaces are the most stable structures. Then the electronic structures for this interface model of Ti3AlC2/SiC are analyzed from the density of states, atomic charges, total electron densities and electron density difference. The elastic moduli are also computed in this study, and the data show that the mechanical properties for the composite Tin+1AlCn/SiC slab are between those of bulk Tin+1AlCn and β-SiC, with enhanced plasticity. Finally, the results for β-SiC/Tin+1AlCn are extended to study the interfacial stabilization of β-SiC ceramics and the wider class of Mn+1AlCn phase coatings (M = Sc, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta; n = 1,2). It is found that SiC ceramics may be effectively joined by Mn+1AlCn with stable interfacial chemical bonding, which provides a theoretical basis for the effective junction in SiC composites.