Simulation study of effects of grain boundary and helium bubble on lattice thermal resistance of tungsten

• Published in: Fusion engineering and design 2021-07, Vol.168, p.112682, Article 112682
• Main Authors: Ding, Yingmei, Wu, Xuebang, Zhan, Jie, Chen, Ze, Mao, Shifeng, Ye, Minyou
• Format: Article
• Language: English
• Subjects: Atomic properties; Conduction heating; Conductive heat transfer; Coupling (molecular); Diffusion barriers; Distortion; Grain boundaries; Grain boundary; Grain boundary energy; Helium; Helium bubble; Ion irradiation; Kapitza resistance; Molecular dynamics; The Kapitza resistance; Thermal resistance; Thermal simulation; Thermodynamic properties; Transport properties; Tungsten
• ISSN: 0920-3796; 1873-7196
• DOI: 10.1016/j.fusengdes.2021.112682

•The phonons thermal resistances of tungsten grain boundaries (GBs) and the ones containing nano helium (He) bubble are systematically calculated by non-equilibrium molecular dynamics (NEMD) methods.•It is proven that the thermal resistances are positively correlated with the lattice distortion energies.•When considered the He atoms inserted in the middle of GBs with a spherical bubble, the influence of number of He atoms has increasing trend after the number reaches a certain number.•The internal pressure in He bubble is finally saturated due to the coupling of the bubble and GBs when the He atoms numbers increasing. Tungsten (W) as plasma facing material (PFM) has been used in ITER divertor. Many experiments indicate that due to helium (He) ion irradiation the thermal conductivities (TCs) of W can be significantly reduced. In this work, the lattice thermal transport property is studied based on the non-equilibrium molecular dynamics (NEMD) method. Firstly, the Kapitza resistance of grain boundaries (GBs) in W is obtained. It can be confirmed that the Kapitza resistance is positively correlated with GB energies, which reflect the lattice distortion degree in a sense. The result indicates that the distortion energy may play a key role in the thermal properties. Further simulation is performed to study the thermal resistance of GBs with nano He bubble. When the number of He atoms in bubble is less than a value, the thermal resistances are stable and change little. It implies that the effect of GBs is more significant than He bubble to block phonons diffusion. With the number of He atoms increasing, the property of heat conduction deteriorates further because the coupling of He bubble and GBs change the lattice distortion degree.