Intrinsic defect processes and elastic properties of Ti3AC2 (A = Al, Si, Ga, Ge, In, Sn) MAX phases

Abstract

M nþ1 AX n phases (M ¼ early transition metal; A ¼ group 13-16 element and X ¼ C or N) have a combination of advantageous metallic and ceramic properties, and are being considered for structural applications particularly where high thermal conductivity and operating temperature are the primary drivers: for example in nuclear fuel cladding. Here, we employ density functional theory calculations to investigate the intrinsic defect processes and mechanical behaviour of a range of Ti 3 AC 2 phases (A ¼ Al, Si, Ga, Ge, In, Sn). Based on the intrinsic defect reaction, it is calculated that Ti 3 SnC 2 is the more radiation-tolerant 312 MAX phase considered herein. In this material, the C Frenkel reaction is the lowest energy intrinsic defect mechanism with 5.50 eV. When considering the elastic properties of the aforementioned MAX phases, Ti 3 SiC 2 is the hardest and Ti 3 SnC 2 is the softest. All the MAX phases considered here are non-central force solids and brittle in nature. Ti 3 SiC 2 is elastically more anisotropic and Ti 3 AlC 2 is nearly isotropic.

Chemically stable new MAX phase V2SnC: a damage and radiation tolerant TBC material

“…Elastic calculations with CASEP code have been successful for all kind of crystal systems. [20][21][22][23][24][25][26][27][28][29][30][31] The lattice dynamic properties such as phonon dispersion and phonon density of states are calculated by means of the nite displacement supercell method executed with a 3 Â 3 Â 1 supercell within the code.…”

312 MAX Phases: Elastic Properties and Lithiation

“…The calculated results for the selected 312 MAX phases have been investigated in previous studies [44,45]. In Τable 1, we present the elastic properties of the 312 MAX phases.…”

“…Only the first five of them are independent, taking into account that c 66 = (c 11 − c 12 )/2. In order for the MAX compounds to be dynamically stable, the following conditions must be met [43]: The calculated results for the selected 312 MAX phases have been investigated in previous studies [44,45]. In Table 1, we present the elastic properties of the 312 MAX phases.…”

“…The shear modulus G has the lowest value in Zr 3 SnC 2, and so this MAX phase is more prone to shape change than the others. The Young's modulus Y, which is a measure of the stress required for deformation, has the lowest value in the Zr 3 SnC 2 MAX phase, compared to the other MAX phases in Table 1 (also refer to [44][45][46][47][48][49][50][51][52]). Table 1.…”

“…Calculated elastic constants Cij (GPa), bulk modulus B (GPa), shear modulus G (GPa), Young's modulus Y (GPa), Poisson's ratio v, Pugh's ratio B/G, elastic anisotropy factor A, and shear anisotropy factor (kc/ka) for the 312 MAX phases *. Comparison with previous studies [44][45][46][47][48][49][50][51][52]. In order to gain information about the brittle or ductile failure of the MAX phases, the Pugh's modulus (B/G) is used [53].…”