Zhejiang University has developed a high thermal conductivity ultra-flexible graphene assembly film

　　Recently, the team of the Department of Polymer Science and Technology of Zhejiang University has developed a high thermal conductivity super-flexible graphene assembly film with a thermal conductivity of up to 2053 W/mK (Watt/mK), which is close to 40% of the thermal conductivity of an ideal single-layer graphene. A new record of thermal conductivity of the material;  at the same time, the material is assembled from micro-pleated large graphene, which is ultra-flexible and can be folded 6,000 times and subjected to bending for 100,000 times.

　　This latest achievement solves the worldwide problem of high thermal conductivity and high flexibility of macro materials, and is expected to gain important applications in high-efficiency thermal management, next-generation flexible electronic devices and aerospace. The article was published in Advanced Materials.

　　Electronic appliances generate heat when they work, and require efficient thermal management to ensure their normal operation. New generation devices also require bendability. However, the high thermal conductivity and high flexibility of existing macro materials are often difficult to achieve. The appearance of graphene provides a theoretical possibility to solve this contradiction.

　　It is reported that the superb team creatively proposed the idea of ​​“large pleats”: large graphene defects are few, and high thermal conductivity can be achieved; micro pleats allow the material to have sufficient strain space during stretching and bending to ensure high flexibility.

　　Gao Chao told the reporter of the Chinese Journal of Science and Technology that this new idea is very simple to implement. The three-step process can be completed:  a large piece of graphene oxide aqueous dispersion is formed into a film by knife coating;  at a high temperature heat treatment, the oxygen-containing functional group in the film decomposes at a high temperature to release a gas, and the graphene defect structure gradually increases with an increase in temperature. Repair, the gas is blocked inside the graphene film,  and the micro-balloon is formed by expansion;  the mechanical roller is pressed into a film, and the gas of the micro-balloon is discharged under the applied pressure to form micro-wrinkles.

　　The researchers also used ultra-large pieces of graphene oxide as a raw material to reduce edge phonon dissipation.  At the same time, the high temperature heat treatment is used to remove the functional groups on the surface of the graphene and repair the internal pores of the graphene to obtain a graphene structure with less defects. These structural changes were confirmed by Raman, XRD and transmission electron microscopy.  The average conductivity of the obtained graphene film was 1900 W/mK, and the highest value was 2053 W/mK.