Effect of Sn doping concentration on the oxidation of Al-containing MAX phase(Ti_(3)AlC_(2))combining simulation with experiment

Sn doping is usually adopted to prepare Ti_(3)AlC_(2)in mass production because it can reduce the synthesis temperature while increasing the phase purity.However,excessive Sn doping usually deteriorates the oxidation resistance of Ti_(3)AlC_(2).Therefore,an appropriate Sn doping concentration is a vital issue.In this work,the effect of Sn doping concentration on the oxidation behavior of Ti_(3)AlC_(2)was systematically investigated by combining theoretical calculations and experimental methods.Density function theory calculations suggest that the oxygen adsorption mechanisms for the(001)surface of Ti_(3)AlC_(2)with and without Sn doping are similar,and Ti-O bonds are always preferentially formed.The molecular dynamics simulation further indicates that Al atoms have a faster diffusion rate during the oxidation process.Therefore,a continuous Al_(2)O_(3)layer can form rapidly at high temperature.Nevertheless,when the Sn doping concentration exceeds 10 mol%,the continuity of the Al_(2)O_(3)layer is destroyed,thereby impairing the oxidation resistance of Ti_(3)AlC_(2).Furthermore,oxidation experiments verify the above results.The oxidation mechanisms of Ti3AlC2 with different Sn doping concentrations are also proposed.