Effects of Al substitution by Si in Ti3AlC2 nanolaminate

M A Hadi,Md Roknuzzaman,A Chroneos,U Monira,A K M A Islam,Kostya Ostrikov,S H Naqib,Jose A Alarco,M T Nasir

doi:10.1038/s41598-021-81346-w

Abstract

Recently, a series of high-purity Ti3(Al1−xSix)C2 solid solutions with new compositions (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been reported with interesting mechanical properties. Here, we have employed density functional theory for Ti3(Al1−xSix)C2 solid solutions to calculate a wider range of physical properties including structural, electronic, mechanical, thermal and optical. With the increase of x, a decrease of cell parameters is observed. All elastic constants and moduli increase with x. The Fermi level gradually increases, moving towards and past the upper bound of the pseudogap, when the value of x goes from zero to unity, indicating that the structural stability reduces gradually when the amount of Si increases within the Ti3(Al1−xSix)C2 system. In view of Cauchy pressure, Pugh’s ratio and Poisson’s ratio all compositions of Ti3(Al1−xSix)C2 are brittle in nature. Comparatively, low Debye temperature, lattice thermal conductivity and minimum thermal conductivity of Ti3AlC2 favor it to be a thermal barrier coating material. High melting temperatures implies that the solid solutions Ti3(Al1−xSix)C2 may have potential applications in harsh environments. In the visible region (1.8–3.1 eV), the minimum reflectivity of all compositions for both polarizations is above 45%, which makes them potential coating materials for solar heating reduction.

Highlights

A series of high-purity Ti3(Al1−xSix)C2 solid solutions with new compositions (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been reported with interesting mechanical properties
M n+1AXn (MAX) phases possess a unique combination of properties, both metallic and ceramic in nature due to the layered structure
The inclusion of a new element on the M, A, and/or X sites leads to isostructural MAX phase solid solutions

Summary

Introduction

Ti3AlC2 belongs to the family of M n+1AXn (MAX) phases with more than 80 members These are layered, machinable, nanolaminated ternary carbides, nitrides and borides, where M is an early transition metal, A is an A-group element, mainly from groups 13–16 and X is C or N or B1–3. Ceramic properties include low density, elastic rigidity, oxidation and creep resistance, and the ability to maintain the strength up to very high temperatures[3,4,5] These properties constitute MAX phases technologically important materials. There are potential uses of MAX phases as high temperature heating elements, tough, machinable and thermal shock resistant refractories, neutron irradiation resistant parts for nuclear applications, coatings for electrical contacts, precursor for the synthesis of carbide-derived carbon and MXenes, a family of two-dimensional transition metal carbides, nitrides, borides, and c arbonitrides[3,4,5,6]. According to a theoretical study, the partial inclusion of Nb atoms in Ti2SC and Zr2SC improves the mechanical strength[17]

Methods

Results

Conclusion