Thermal and electrical properties of Nb2AlC, (Ti, Nb)2AlC and Ti2AlC

Abstract

The heat capacities, thermal-expansion coefficients, thermal and electrical conductivities of Nb 2 AlC (actual Nb:Al:C mole fractions: 0.525 Ϯ 0.005, 0.240 Ϯ 0.002, and 0.235 Ϯ 0.005, respectively), Ti 2 AlC and (Ti, Nb) 2 AlC (actual Ti:Nb:Al:C mole fractions: 0.244 Ϯ 0.005, 0.273 Ϯ 0.005, 0.240 Ϯ 0.003, and 0.244 Ϯ 0.005, respectively) were measured as a function of temperature. These ternaries are good electrical conductors, with a resistivity that increases linearly with increasing temperatures. The resistivity of (Ti, Nb) 2 AlC is higher than the other members, indicating a solid-solution scattering effect. The thermal-expansion coefficients, in the 25 ЊC to 1000 ЊC temperature range, are comparable and fall in the narrow range of 8.7 to 8.9 ϫ 10 Ϫ6 K Ϫ1 , with that of the solid solution being the highest. They are all good conductors of heat, with thermal conductivities in the range between 15 to 45 W/m K at room temperature. The electronic component of the thermal conductivity is the dominant mechanism at all temperatures for Nb 2 AlC and (Ti, Nb) 2 AlC. The conductivity of Ti 2 AlC, on the other hand, is high because the phonon contribution to the conductivity is nonnegligible.M.W. BARSOUM, Professor, I. SALAMA, and T. EL-RAGHY are with

First-Principles Study on Thermodynamic Properties of Ti<SUB>2</SUB>AlC and Ti<SUB>2</SUB>SC

“…As reported previously, the volume thermal expansion coefficient of Ti 2 SC and Ti 2 AlC is experimentally measured to be 2:52 Â 10 À5 K À1 and 2:61 Â 10 À5 K À1 respectively, larger than the present calculation. 19,20) It is known that additional expansion can be caused by lattice vacancies. 21) It has been found that carbon vacancies in VC significantly increase the thermal expansion coefficient.…”

Oxygen incorporation in Ti2AlC thin films studied by electron energy loss spectroscopy and ab initio calculations

“…Alloying on M and A sites has been extensively studied, and a large number of MAX phases synthesized, with resultant change in, e.g., elastic properties and hardness of Ti 3 (Si,Al)C 2 [4] and (Ti.V) 2 AlC [5], respectively, or conductivity in (Ti,Nb) 2 AlC [6]. Partial replacement of one element by another can also increase the stability, observed for (Cr,V) 3 AlC 2 [7].…”

Solid Solubility and Magnetism upon Mn Incorporation in the Bulk Ternary Carbides Cr2AlC and Cr2GaC

“…[2] Partial substitution of the M, A, or X elements is a process by which the MAX phase properties can be tailored. For example, the elastic modulus of Ti 3 (Si,Al)C 2 , [3] hardness of (Ti,V) 2 AlC, [4] and conductivity of (Ti,Nb) 2 AlC [5] can be tuned in between the values of the end members. To date, most of the substitutions have been with elements chosen from those used in previously synthesized MAX phases.…”