▎ 摘　　要

A new preparation scheme of few-layer graphene water nanofluids was developed by exfoliating graphite in water with the help of polymer. The approach used centrifugation to classify the graphene nanosheets that made the graphene nanoflake length controllable. Population balance model was used to study the mechanism of exfoliation of graphite and the results revealed that the abrasion, cleavage and fracture all happened in these different stages of the exfoliation process. Mechanisms behind the size selection were also discussed and the terminal velocity was the critical factor to control the flake length. A simple model was developed to guide future similar experiments to obtain desired length graphene nanofluids. The stability of graphene nanofluid was also investigated and the result revealed that the obtained nanofluid showed enhanced stability suggesting great potential in heat transfer applications.