Abstract

A first principle study was performed to investigate the electronic and thermostructural properties of the Ti₂AlC MAX-phase using quasi-harmonic Debye approximation. The thermodynamical properties of Ti₂AlC MAX-phase at various temperatures and pressure were calculated via the quasi-harmonic Debye approximation and explored the role of temperature and pressure on heat capacity, bulk modulus, thermal expansion coefficient, Debye temperature, enthalpy, entropy, and Gibbs free energy. Surprisingly, both the bulk modulus and Debye temperature was observed to drop with increase in temperature. However, a rise in both occurred as the pressure gradually builds up. This suggests that the heat capacity is influenced by pressure and temperature in opposing ways. The observation of increase in both heat capacities (C_p and C_v) due to increase in temperature infers an increase in the thermal velocity of the atoms. Consequently, the thermal velocity of the atoms decreases with a decrease in pressure which affects C_p and C_v, respectively. In addition, the Gibbs free energy slope increased at a little rate at constant pressure. These novel results possessing improved thermostructural properties could be useful for high-temperature fatigue-resistant applications specially in a gas turbine engine.

中文翻译：

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使用准谐波德拜近似计算 Ti2AlC MAX 相的温度和压力相关热结构特性

摘要

使用准谐波德拜近似进行第一原理研究，以研究 Ti ₂ AlC MAX相的电子和热结构特性。通过准谐波德拜近似计算了Ti 2 AlC MAX相在不同温度和压力下的热力学性质，探讨了温度和压力对热容、体积模量、热膨胀系数、德拜温度、焓、_熵、和吉布斯自由能。令人惊讶的是，观察到体积模量和德拜温度都随着温度的升高而下降。然而，随着压力逐渐增大，两者均出现上升。这表明热容以相反的方式受到压力和温度的影响。由于温度升高而导致热容量（ C _p和C _v ）增加的观察结果表明原子热速度增加。因此，原子的热速度随着压力的降低而降低，这分别影响C _p和C _v。此外，在恒压下吉布斯自由能斜率略有增加。这些具有改进的热结构性能的新颖结果可用于高温抗疲劳应用，特别是燃气涡轮发动机中。