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Thermal conductivity of random polycrystalline BC3 nanosheets: A step towards realistic simulation of 2D structures
Journal of Molecular Graphics and Modelling ( IF 2.9 ) Pub Date : 2021-06-25 , DOI: 10.1016/j.jmgm.2021.107977
Sasan Fooladpanjeh 1 , Farrokh Yousefi 2 , Fatemeh Molaei 3 , Maryam Zarghami Dehaghani 4 , S Mohammad Sajadi 5 , Otman Abida 6 , Sajjad Habibzadeh 7 , Amin Hamed Mashhadzadeh 8 , Mohammad Reza Saeb 4
Affiliation  

Boron carbide nanosheets (BC3NSs) are semiconductors possessing non-zero bandgap. Nevertheless, there is no estimation of their thermal conductivity for practical circumstances, mainly because of difficulties in simulation of random polycrystalline structures. In the real physics world, BC3NS with perfect monocrystalline is rare, for the nature produces structures with disordered grain regions. Therefore, it is of crucial importance to capture a more realistic picture of thermal conductivity of these nanosheets. Polycrystalline BC3NS (PCBC3NSs are herein simulated by Molecular Dynamics simulation to take their thermal conductivity fingerprint applying ΔT of 40 K. A series of PCBC3NSs were evaluated for thermal conductivity varying the number of grains (3, 5, and 10). The effect of grain rotation was also modeled in terms of Kapitza thermal resistance per grain, varying the rotation angle (θ/2 = 14.5, 16, 19, and 25°). Overall, a non-linear temperature variation was observed for PCBC3NS, particularly by increasing grain number, possibly because of more phonon scattering (shorter phonon relaxation time) arising from more structural defects. By contrast, the heat current passing across the slab decreased. The thermal conductivity of nanosheet dwindled from 149 W m−1 K−1 for monocrystalline BC3NS to the values of 129.67, 121.32, 115.04, and 102.78 W m−1 K−1 for PCBC3NSs having 2, 3, 5, and 10 grains, respectively. The increase of the grain̛s rotation angle (randomness) from 14.5° to 16°, 19° and 25° led to a rise in Kapitza thermal resistance from 2⨯10−10 m2 K·W−1 to the values of 2.3⨯ 10−10, 2.9⨯10−10, and 4.7⨯ 10−10 m2 K·W−1, respectively. Thus, natural 2D structure would facilitate phonon scattering rate at the grain boundaries, which limits heat transfer across polycrystalline nanosheets.



中文翻译:

随机多晶 BC3 纳米片的热导率:迈向二维结构真实模拟的一步

碳化硼纳米片 (BC 3 NSs) 是具有非零带隙的半导体。然而,在实际情况下没有估计它们的热导率,主要是因为模拟随机多晶结构的困难。在真实的物理世界中,具有完美单晶的BC 3 NS 是罕见的,因为自然界会产生具有无序晶粒区域的结构。因此,捕捉这些纳米片的热导率的更真实图片至关重要。多晶 BC 3 NS(PCBC 3 NSs 在此通过分子动力学模拟得到它们的热导率指纹,应用 40 K 的 ΔT。一系列 PCBC 3NSs 的热导率被评估为不同的晶粒数量(3、5 和 10)。颗粒旋转的影响也根据每颗粒的 Kapitza 热阻建模,改变旋转角度(θ/2 = 14.5、16、19 和 25°)。总体而言,对于 PCBC 3 NS观察到非线性温度变化,特别是通过增加晶粒数,可能是因为更多的结构缺陷导致更多的声子散射(更短的声子弛豫时间)。相比之下,穿过板坯的热流减少了。纳米片的热导率从单晶 BC 3 NS 的149 W m -1  K -1 降低到PCBC 3 的129.67、121.32、115.04 和 102.78 W m -1  K -1 的NSs 分别具有 2、3、5 和 10 个晶粒。晶粒的旋转角(随机性)从 14.5° 增加到 16°、19° 和 25° 导致 Kapitza 热阻从 2⨯10 -10  m 2  K·W -1增加到 2.3⨯ 10 -10、2.9⨯10 -10和4.7⨯ 10 -10  m 2  K·W -1。因此,自然的 2D 结构将促进晶界处的声子散射率,这限制了多晶纳米片之间的热传递。

更新日期:2021-07-05
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