High quality graphite has excellent mechanical strength, thermal stability, high flexibility and very high in-plane thermal and electrical conductivity, making it one of the most important advanced materials for many applications such as photothermal conductors used as batteries in telephones. For example, a special type of graphite, highly ordered pyrolytic graphite (HOPG), is one of the most commonly used in laboratories. Material. These excellent properties are due to the layered structure of graphite, where strong covalent bonds between the carbon atoms in the graphene layers contribute to excellent mechanical properties, thermal and electrical conductivity, while very little interaction between the graphene layers. The action results in a high degree of flexibility. graphite. Although graphite has been discovered in nature for more than 1000 years and its artificial synthesis has been studied for more than 100 years, the quality of graphite samples, both natural and synthetic, is far from ideal. For example, the size of the largest single crystal graphite domains in graphite materials is typically less than 1 mm, which is in stark contrast to the size of many crystals such as quartz single crystals and silicon single crystals. The size can reach the scale of a meter. The very small size of single-crystal graphite is due to the weak interaction between the graphite layers, and the flatness of the graphene layer is difficult to maintain during growth, so graphite is easily broken into several single-crystal grain boundaries in disorder. . To solve this key problem, Professor Emeritus of the Ulsan National Institute of Science and Technology (UNIST) and his collaborators Prof. Liu Kaihui, Prof. Wang Enge of Peking University, and others have proposed a strategy for synthesizing thin order-of-magnitude graphite single crystals. film, down to the inch scale. Their method uses a single-crystal nickel foil as a substrate, and carbon atoms are fed from the back of the nickel foil through an “isothermal dissolution-diffusion-deposition process”. Instead of using a gaseous cardboard source, they opted for a solid carbon material to facilitate graphite growth. This new strategy makes it possible to produce single-crystal graphite films with a thickness of about 1 inch and 35 microns, or more than 100,000 graphene layers in a few days. Compared to all available graphite samples, single-crystal graphite has a thermal conductivity of ~2880 W m-1K-1, an insignificant content of impurities, and a minimum distance between layers. (1) Successful synthesis of single-crystal nickel films of large size as ultra-flat substrates avoids disordering of synthetic graphite; (2) 100,000 layers of graphene are grown isothermally in about 100 hours, so that each layer of graphene is synthesized in the same chemical environment and temperature, which ensures the uniform quality of graphite; (3) The continuous supply of carbon through the reverse side of the nickel foil allows the layers of graphene to continuously grow at a very high rate, approximately one layer every five seconds,”
Post time: Nov-09-2022