▎ 摘　　要

Hexagonal boron nitride nanosheets (h-BNNS) and graphene (G) are considered to be the representative materials in the two-dimensional (2D) materials community. h-BNNS and G are considered to exhibit high potential in thermal management materials for their prominent thermal conductivity. However, the conventional methods to synthesize h-BNNS and G are restricted by several problems (e.g., high energy consumption, environmental pollution and complex preparation methods). In the present study, a xylitol (C5H12O5)-assisted ball milling method was developed for scalable synthesis of a 2D material mixture of h-BNNS and graphene (BNNS@G). With this method, about 52% yield could be achieved. Moreover, the produced mixture was re-dispersed; it also exhibited high stability in water. The method proposed in this study is capable of effectively transferring green chemistry solutions to the preparation. Besides, a green solution was also proposed to apply the synthesized BNNS@G. The as-obtained BNNS@G was mixed with the cellulose nanofiber solution to form a series of G@ BNNS/CNF membranes that exhibited high flexibility and ultrahigh thermal conductivity. Furthermore, 70 wt% BNNS@G membrane (3.4 W/mK) exhibited the in-plane thermal conductivity 300% higher than the membrane without BNNS@G. Thus, it is suggested that the synthesized membranes exhibit high potentials in the thermal management of portable mobile devices.