Two-dimensional materials, such as graphene, boron nitride, and molybdenum disulfide, have excellent in-plane electrical and heat transfer characteristics, making them very suitable for energy and electrical applications. Assembling two-dimensional materials into a vertically arranged structure is very important for thermal interface materials (TIM) such as thermal grease and phase change materials that require efficient heat transfer. This is conducive to improving the working stability of the device and prolonging its service life. Therefore, it is of great significance to develop a general method for arranging two-dimensional materials in a preferred direction.
Professor Bai Shulin of Peking University and others proposed a simple and economical 3D printing method to prepare graphene vertically filled thermoplastic polyurethane (TPU) composites. When the graphene content is 45%, the printed vertical arrangement structure exhibits a through-surface thermal conductivity (TC) as high as 12 W m-1 K-1, which is 8 times that of the horizontal structure and exceeds many traditional particle enhancements. Polymer composites. The excellent TC is mainly attributed to the anisotropic structure design, which benefits from the good orientation of graphene and the multi-scale dense structure achieved by finely controlling the printing parameters. The finite element method confirmed the important influence of anisotropic TC design on high thermal conductivity composite materials. The research was published on "ACS nano" as a paper entitled "Highly Thermally Conductive 3D Printed Graphene Filled Polymer Composites for Scalable Thermal Management Applications".

Article highlights:
(1) The author reported the formation of asymmetrical arrangement of graphene-filled thermoplastic polyurethane (TPU) composites during 3D printing. In the 3D printing process, due to the shearing force generated by the extrusion and the compression effect with the substrate (or the lower layer), the graphene sheet tends to form an asymmetrical arrangement structure in the thickness direction. SEM, XRD and WAXS results verified the arrangement of graphene sheets, and each extruded microfilament showed a distribution of planar arrangement and vortex arrangement.
(2) The high TC is mainly attributed to the anisotropic structural design, which benefits from the preferred orientation degree of graphene at all contents. In addition, the multi-scale compact structure design effectively guarantees a compact structure, reduces pores and enhances interfacial adhesion.
(3) When the printed graphene/TPU composite material is used as a battery pack of three 18650 cells, the battery temperature of the graphene/TPU battery pack is 5.7°C lower than that of the pure TPU battery pack, which indicates 3D The printed graphene/TPU composite material has significant heat dissipation performance. And the design strategy can be extended to other two-dimensional materials to manufacture layered alignment structures for various thermal, electrical and mechanical applications.
In short, this work provides an effective method for the development of 3D printed graphene-based polymer composites, which can be used for scalable thermal-related applications, such as battery thermal management, electronic packaging, etc.

Original link:
https://pubs.acs.org/doi/10.1021/acsnano.0c10768