Mutsuaki Murakami announces the Fabrication of high-quality and large area graphite thin films by pyrolysis and graphitization of polyimides

Today, the graphite films have a large market as a thermal diffusion film in a mobile phone. However, the range of the industrially manufactured film’s thickness was limited from 10 μm to 75 μm. The production of the graphite film less than 10 μm was difficult due to the delicate nature of the graphite film that caused wrinkles and breakage during the production process.

A new research paper “Fabrication of high-quality and large area graphite thin films by pyrolysis and graphitization of polyimides” (Carbon 145 (2019) 23-30) led by Mutsuaki Murakami through forming a collaboration with Atsushi Tatami (Japan) and Masamitsu Tachibana (Japan) reported on new thin graphite films. The new industrially produced graphite overcomes the problem in the manufacturing process and releases a film of 0.5 to 3μm thick by using high temperature (2800 ~ 3200 ° C) processing of polyimide thin film. The new graphite films have large areas with good physical properties that are close to those of natural graphite crystals and can be effectively handled.  The films of 1.0-3.0 μm thick can be effectively dealt with a self-supporting film by hand and the films of 0.5-1.0 μm thick can be taken care with tweezers and it could be used for some industrial applications. The high electrical, thermal conductivity and portability the film gets from the homogeneous graphite layers which are useful for various applications in mechanical, thermal and electrical research areas. In fact, these films are already expanding its application as a charge conversion film and a sensor for particle accelerators.

The graphitization reaction of a film with thickness less than 3 μm proceeds uniformly in the film and the subsequent structure of the graphite film arranges well-oriented uniform layers in the plane direction of the film, which helps electrons and heat move at high speed along the film direction. Typical physical values of the film surface direction of the obtained graphite film are attractive from a useful viewpoint, and are as follows. Electrical conductivity: 24,800 S / cm, carrier mobility: 11,700 V / cm 2, thermal conductivity: 1900-2000 W / mK, elastic constant:600-1000 GPa. Murakami and the team have demonstrated that the magnitude of graphite domain size is clearly impacted by the film thickness. The size effectively develops at low temperature into a thinner film and into a thicker film at a higher temperature.

Graphene (single-layer graphite) has extremely attractive physical properties, and many kinds of research and developments are being conducted worldwide. However, single-layer graphene is difficult to handle, and it is difficult to develop applications for it in fields such as energy transport and mechanical. Also, handling of multi-layer graphene is easy compared to single-layer graphene, but its quality is lower compared to single-layer graphene or high-quality graphite film.

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