Effect of helium on thermal transport properties in single- and bi-crystals of Ni: a study based on molecular dynamics

Abstract

Nuclear structures are prone to irradiation induced defects that makes them susceptible to alternation in mechanical and thermal properties. Transmutation of Ni to insoluble He atoms are considered responsible for the embrittlement in Ni. Helium bubbles are considered responsible for the deterioration of mechanical and thermal properties of the Ni crystal, which needs to be studied in detail to predict the lifespan of the ageing nuclear structures. Aim of this article is to study the effect of helium on the thermal transport phenomenon in single and bi-crystals of Ni. Molecular dynamics-based simulations in conjunction with hybrid force field was performed to study the effect of helium bubble on the thermal transport phenomenon in Ni crystal. These simulations were further extended to study the effect of symmetrical tilt grain boundaries (STGB) in conjunction with doping of helium atoms on the thermal transport phenomenon in bicrystal Ni. The effect of helium concentration in the bubble significantly alters the thermal transport in single crystal Ni. The STGB configuration also introduces interfacial thermal resistance as a function of mis-orientation angle. The helium doped grain boundaries further increases the resistance to phonon movement and increases Kapitza resistance. The increase in Kapitza resistance was more dominant in higher mis-orientation angle grain boundaries.