Shear-Assisted Production of Few-Layer Boron Nitride Nanosheets by Supercritical CO2 Exfoliation and Its Use for Thermally Conductive Epoxy Composites

Xiaojuan Tian,Yushu Tang,Qi Li,Yun Li,Zhuo Chen,Liqiang Hou,Yongfeng Li,Jiaye Wu

doi:10.1038/s41598-017-18149-5

Xiaojuan Tian, Yushu Tang + Show 6 more

Open Access

https://doi.org/10.1038/s41598-017-18149-5

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Journal: Scientific Reports	Publication Date: Dec 1, 2017
Citations: 46	License type: open-access

Affiliation: China University of Petroleum, Beijing

Abstract

Boron nitride nanosheets (BNNS) hold the similar two-dimensional structure as graphene and unique properties complementary to graphene, which makes it attractive in application ranging from electronics to energy storage. The exfoliation of boron nitride (BN) still remains challenge and hinders the applications of BNNS. In this work, the preparation of BNNS has been realized by a shear-assisted supercritical CO2 exfoliation process, during which supercritical CO2 intercalates and diffuses between boron nitride layers, and then the exfoliation of BN layers is obtained in the rapid depressurization process by overcoming the van der Waals forces. Our results indicate that the bulk boron nitride has been successfully exfoliated into thin nanosheets with an average 6 layers. It is found that the produced BNNS is well-dispersed in isopropyl alcohol (IPA) with a higher extinction coefficient compared with the bulk BN. Moreover, the BNNS/epoxy composite used as thermal interface materials has been prepared. The introduction of BNNS results in a 313% enhancement in thermal conductivity. Our results demonstrate that BNNS produced by supercritical CO2 exfoliation show great potential applications for heat dissipation of high efficiency electronics.

Highlights

It is necessary to find a moderate, eco-friendly and large scale chemical engineering process to fabricate excellent Boron nitride nanosheets (BNNS)
The electron diffraction pattern suggests that the BNNS has the typical six-fold symmetry, which indicates that the supercritical CO2 exfoliation reserves the hexagonal structure of boron nitride (BN) well
It is demonstrated that bulk boron nitride is exfoliated efficiently by the supercritical CO2, which is confirmed Transmission electron microscopy (TEM) and atomic force microscope (AFM) measurements

Summary

Epoxy Composites

Our results demonstrate that BNNS produced by supercritical CO2 exfoliation show great potential applications for heat dissipation of high efficiency electronics. In terms of liquid-phase exfoliation method, the dispersion of pristine BN in isopropanol is subjected to sonication, consuming high energy/time and producing a large number of organic waste[18,19,20,21,22] When it comes to the ball milling method, it damages the structure of h-BN, resulting in a great deal of defects and degrading the properties of BNNS23. The morphology and thickness of the produced BNNS have been characterized by electron microscope and atomic force microscope, which indicates that the supercritical CO2 exfoliated bulk h-BN successfully, resulting in few-layer nanosheets. Experimental studies have shown that the 20 wt% BNNS results in a thermal conductivity enhancement (TCE) as high as 313%, which makes it a promising candidate as thermal interface materials[34,35]

Results and Discussion

Conclusion

Author Contributions

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