Effect of boron incorporation into the carbon-site in Nb2SC MAX phase: Insights from DFT

Abstract

Inherent and modified characteristics of MAX phase materials are important for technological applications in different fields. From this point of view, the present article gives a brief overview of the physical properties of Nb2SC1-xBx (x = 0.0–1.0) MAX phase solid solutions via the calculations of elastic, electronic, thermal and optical properties using density functional theory (DFT). The substitutional effect of B at the C site on the physical properties of Nb2SC is also discussed. The increase of B-content (x) enhances the elastic constants (except C12 and C13) and moduli (except B), Debye temperature, melting point, and minimum and lattice thermal conductivity of Nb2SC1-xBx. Conversely, the machinability and dry lubricity decrease gradually with the increase of x. The ductility decreases with the increase of x, and when x > 0.2, Nb2SC1-xBx becomes completely brittle and the brittleness increase with further increase of x. All the compositions of Nb2SC1-xBx have potential to be used as thermal barrier coating (TBC) and high temperature structural materials. Moreover, the investigated optical parameters are discussed on the basis of electronic structures. Average reflectivity in the visible light region is more than 45%, which make Nb2SC1-xBx systems capable of reducing the solar heating. It is expected that this study will stimulate the MAX phase research community to further explore the characteristics of these materials via experiment and theory.

Keywords

• MAX phase Solid solutions
• Nb2SC1-xBx
• Physical properties
• Density functional theory