Novel DLC/ionic liquid/graphene nanocomposite coatings towards high-vacuum related space applications

Abstract

It is currently a challenge for space tribology to develop a long lifetime and high bearing capacity lubricant meeting the requirements of space applications. Herein, we dispersed graphene into ionic liquid, prepared novel composite coatings of diamond-like carbon (DLC)/ionic liquid (IL)/graphene with different graphene concentrations, and investigated its space performance under high vacuum and space radiation conditions. IL/graphene nanofluids with different concentrations were examined by Fourier transform infrared spectroscopy (FTIR). Furthermore, IL/graphene nanofluids after friction tests were investigated by X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The results showed that the graphene concentration would obviously affect the spatial tribology performance of the composite coatings. Because the excess graphene in the IL would tend to form irreversible agglomerates, leading to reduction of the effective graphene dose, an optimum graphene concentration (0.075 mg ml À1 ) in IL for the composite coatings was required to exhibit the lowest friction coefficient, the highest bearing capacity and the strongest anti-irradiation in a simulated space environment. In addition, XPS spectra further confirmed that the formation of a fluorinated oilcontaining carbon-rich tribofilm between the friction pairs further ensured the good antifriction and wear resistance performance of DLC/IL/graphene.

Ionanocarbon Lubricants. The Combination of Ionic Liquids and Carbon Nanophases in Tribology

“…Liu et al [57], prepared DLC/IL/graphene composite coatings with different graphene concentrations, and studied their performance under high vacuum and space radiation conditions. The results showed that the addition of excess graphene to the IL would form irreversible agglomerates, finding an optimum graphene concentration of 0.075 mg mL −1 in IL for the best tribological performance in a simulated space environment.…”

Ionic Liquids in Surface Protection

“…Some new nanocomposite coatings from DLC/ IL [68] or even DLC/ IL/graphene [67] combinations are being developed for space applications.…”

“…There still remains the field of space and vacuum tribology, where the nonvolatile nature of the ILs makes them the ideal candidates [67].…”

Highly thermally conductive and electrically insulating polymer nanocomposites with boron nitride nanosheet/ionic liquid complexes

“…687 eV, which was attributed to [PF 6 ] anion. [48][49][50] These XPS spectra indicate the attachment of [PF 6 ] anions on the BNNS surfaces. In addition, the XPS surface elemental analysis for 2a (Table S2 †) shows that the F/P ratio was approx.…”