Microwave-assisted synthesis of hydroxyl modified fluorinated graphene with high fluorine content and its high load-bearing capacity as water lubricant additive for ceramic/steel contact

The fluorinated graphene (FG) has been reported in diverse applications for its unique chemical and physical properties, resulting from the 2D carbon-skeleton and decorated C - F bonds. How to substitute the FG's fluorine atom with other active functional groups and retain its fluorine content is still a challenge. In this work, a microwave-assisted liquid-phase synthetic route was introduced to obtain hydroxyl modified fluorinated graphene (HOFG) with high fluorine content. The as-prepared product exhibits excellent water dispersibility with far less fluorine loss than previously reported methods. It is found that the HOFG's fluorine/oxygen (F/O) ratio plays a crucial role in the water dispersibility and lubricating property. The as-prepared HOFG exhibits excellent dispersibility at a high F/O ratio (35). Used as the water lubrication additive for ceramic-steel pair, the as-prepared HOFG significantly improves water's load-bearing capacity from 250N to 600N. The friction-reduction and anti-wear ability of water are also improved with the addition of the HOFG samples. Compared with pure water, the aquous dispersion of HOFG-40M at a concentration of 1.5 mg/mL shows the best lubricating property with a nearly 20 % reduction of friction coefficient and a 30 % decrease of wear.

Automated summary

Fluorinated graphene with high fluorine content was successfully obtained through a microwave-assisted liquid-phase synthetic route, showing excellent water dispersibility and potential lubricating properties. The fluorine/oxygen ratio of hydroxyl modified fluorinated graphene (HOFG) plays a crucial role in determining water dispersibility and lubricating performance.