Mechanical And Optical Properties Of The Ti-doped NbAl Intermetallic Compounds

There are three Nb-Al intermetallic compounds in the binary niobium-aluminum phase diagram:DO22 type NbAl3,D8b type Nb2Al and A15 type Nb3Al.The thesis takes these three systems as the research objects,and uses the first-principles calculation method based on density functional theory to calculate the energy band diagrams of the system before and after doping with different concentrations of the third element Ti,Electronic structure,state density,dielectric function,absorption spectrum and reflection spectrum.The mechanical and optical properties of the system before and after doping are analyzed.The analysis results show that in the NbA13 and Nb3Al systems,with the increase of the Ti atom doping concentration,the crystal system and space group of the system have changed,and the formation energy analysis shows that the total Ti it is preferentially occupying the position of Nb atoms and doping to form a more stable structure.Further analysis of the density of electronic states reveals that as the doping concentration increases,the values of the electronic states of the three systems at the Fermi level all increase,This phenomenon is an important basis for improving the brittleness of the system at room temperature.And this mainly comes from the contribution of 3d orbital electrons of Ti atoms.The results of comprehensive mechanical performance analysis show that in the system of NbA13 and Nb3Al,with the increase of doping concentration,the values of bulk modulus,shear modulus and Young's modulus have decreased,while in the system of Nb2Al,When Ti atoms are used instead of Al atoms for doping,as the doping concentration of Ti atoms increases,the shear modulus and Young's modulus increase.These changes are mainly due to the substitution of Ti atoms.Site doping weakens the covalent bond between Nb and Al atoms.The above phenomena all indicate that the inherent brittleness of the three Nb-Al intermetallic compounds has been improved by Ti atom doping,and the greater ductility of the system has been improved.In addition,the optical properties of the three Nb-Al intermetallic compound systems have also been significantly improved after Ti atom doping,especially in the NbAl3 doping system and Nb2Al doping system.