MoS₂ Nanocomposite Films with High Irradiation Tolerance and Self-Adaptive Lubrication

Although nanostructures and oxide dispersion can reduce radiation-induced damage in materials and enhance radiation tolerance, previous studies prove that MoS₂ nanocomposite films subjected to several dpa heavy ion irradiation show significant degradation of tribological properties. Even in YSZ-doped MoS₂ nanocomposite films, irradiation leads to obvious disordering and damage such as vacancy accumulation to form lamellar voids in the amorphous matrix, which accelerates the failure of lubrication. However, after thermal annealing in vacuum, YSZ-doped MoS₂ nanocomposite films exhibit high irradiation tolerance, and their wear duration remains unchanged and the wear rate was nearly three orders of magnitude lower than that of the as-deposited films after 7 dpa irradiation. This successful combination of anti-irradiation and self-adaptive lubrication mainly results from the manipulation of the nanosize and the change of composition by annealing. Compared with the smaller nanograins in as-deposited MoS₂/YSZ nanocomposite films, the thermally annealed MoS₂ nanocrystals (7-15 nm) with fewer intrinsic defects exhibited remarkable stabilization upon irradiation. Abundant amorphous nanocrystal phases in ion-irradiated thermally annealed films, where each has advantages of their own, greatly inhibit accumulation of voids and crack growth in irradiation; meanwhile, they can be easily self-assembled under induction of friction and achieve self-adaptive lubrication.