To date,MoS_(2) can only be achieved at microscale.Edge pinning effect caused by structure defects is the most obvious barrier to expand the size of structural superlubricity to macroscale.Herein,we plan to pin edge p...To date,MoS_(2) can only be achieved at microscale.Edge pinning effect caused by structure defects is the most obvious barrier to expand the size of structural superlubricity to macroscale.Herein,we plan to pin edge planes of MoS_(2) with nanospheres,and then the incommensurate structure can be formed between adjacent rolling nanoparticles to reduce friction.The sputtered MoS_(2) film was prepared by the physical vapor deposition(PVD)in advance.Then enough Cu_(2)O nanospheres(~40 nm)were generated in situ at the edge plane of MoS_(2) layers by liquid phase synthesis.An incommensurate structure(mismatch angle(θ)=8°)caused by MoS_(2) layers was formed before friction.The friction coefficient of the films(5 N,1,000 r/min)was~6.0×10^(−3) at the most.During friction,MoS_(2) layers pinned on numerous of Cu_(2)O nanoparticles reduced its edge pinning effect and decreased friction.Moreover,much more incommensurate was formed,developing macro-superlubricity.展开更多
The space environment, particularly highly reactive atomic oxygen(AO), often causes performance degradation and accelerated wear of solid-lubricating materials used in aerospace applications. In this study, an in situ...The space environment, particularly highly reactive atomic oxygen(AO), often causes performance degradation and accelerated wear of solid-lubricating materials used in aerospace applications. In this study, an in situ oxygen-passivated WS_(2) lubricating film(W–S–Ti–O composite film) was deposited to withstand AO irradiation. The structural and tribological evolution of the film was examined after a six-month space exposure experiment conducted outside the Chinese Space Station. The results show that in situ oxygen passivation of sulfur vacancies in the WS_(2) film promoted the formation of a dominant WS_(x)O_(y) phase within the W–S–Ti–O composite film. This phase effectively suppressed excessive WO_(3) formation during prolonged AO exposure while maintaining a low friction coefficient. After space exposure, the film exhibited a low friction coefficient and a wear life exceeding 4.5 × 10^(5) cycles. This performance is attributed to two main factors:(1) the presence of friction-induced spherical WO_(3) nanoparticles(approximately 11 nm) embedded in the transfer film, which promoted a transition from pure sliding to a mixed rolling–sliding regime;and(2) the retention of oriented WS_(2)(002) crystalline layers in the tribofilm, which mitigated the plowing effect of nanoparticles and prevented a significant increase in the wear rate.展开更多
基金support provided by the National Natural Science Foundation of China(Grant Nos.51875551 and 51835012).
文摘To date,MoS_(2) can only be achieved at microscale.Edge pinning effect caused by structure defects is the most obvious barrier to expand the size of structural superlubricity to macroscale.Herein,we plan to pin edge planes of MoS_(2) with nanospheres,and then the incommensurate structure can be formed between adjacent rolling nanoparticles to reduce friction.The sputtered MoS_(2) film was prepared by the physical vapor deposition(PVD)in advance.Then enough Cu_(2)O nanospheres(~40 nm)were generated in situ at the edge plane of MoS_(2) layers by liquid phase synthesis.An incommensurate structure(mismatch angle(θ)=8°)caused by MoS_(2) layers was formed before friction.The friction coefficient of the films(5 N,1,000 r/min)was~6.0×10^(−3) at the most.During friction,MoS_(2) layers pinned on numerous of Cu_(2)O nanoparticles reduced its edge pinning effect and decreased friction.Moreover,much more incommensurate was formed,developing macro-superlubricity.
基金financially supported by the Space Utilization System of China Manned Space Engineering (Grant No.KJZ-YY-WCL05)。
文摘The space environment, particularly highly reactive atomic oxygen(AO), often causes performance degradation and accelerated wear of solid-lubricating materials used in aerospace applications. In this study, an in situ oxygen-passivated WS_(2) lubricating film(W–S–Ti–O composite film) was deposited to withstand AO irradiation. The structural and tribological evolution of the film was examined after a six-month space exposure experiment conducted outside the Chinese Space Station. The results show that in situ oxygen passivation of sulfur vacancies in the WS_(2) film promoted the formation of a dominant WS_(x)O_(y) phase within the W–S–Ti–O composite film. This phase effectively suppressed excessive WO_(3) formation during prolonged AO exposure while maintaining a low friction coefficient. After space exposure, the film exhibited a low friction coefficient and a wear life exceeding 4.5 × 10^(5) cycles. This performance is attributed to two main factors:(1) the presence of friction-induced spherical WO_(3) nanoparticles(approximately 11 nm) embedded in the transfer film, which promoted a transition from pure sliding to a mixed rolling–sliding regime;and(2) the retention of oriented WS_(2)(002) crystalline layers in the tribofilm, which mitigated the plowing effect of nanoparticles and prevented a significant increase in the wear rate.
