Preparation Of Graphene By Exfoliation Of Graphite Intercalation Compounds And Its Properties

Graphene is the first two-dimensional atomic crystal that researchers found. The one-atom-thick fabric of carbon combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, and other excellent performance, all of which make graphene highly attractive for many application areas. Over the past decade, the preparation of graphene has been into a great breakthrough, but the large-scale, commercial preparation of graphene still has many problems. Kilograms of graphene oxide can be obtained using a redox method. But the oxidation of graphite introduces oxygen-containing groups and defects in the graphene sheets, resulting in reducing the electrical and thermal properties.In this paper, we describe a new method for the preparation of graphene. We use graphite intercalation compounds (GICs) as a precursor to produce graphene by high-temperature thermal expansion. With the co-intercalators of ferric chloride (FeCl3) and aluminum chloride (AlCl3), GICs has been successfully obtained from natural graphite. AlCl3 can be vaporized at relatively low temperatures and FeCl3 can provide chlorine (Cl2) for the intercalation reaction. GICs can be prepared in relatively mild conditions with the use of co-intercalators. We find that AlCl3 can not insert the graphite layers without Cl2. GICs is successfully obtained above 180 ℃ with the simultaneous use of FeCl3 and AlCl3, and as the temperature increases, the structure of obtained GICs is different. At 200 ℃, the main intercalator between the graphite layers is AlCl3, and the reaction of AlCl3 and water can destroy the regular structure of the graphite sheets in the cleaning process. Above 250 ℃, the main intercalator is FeCl3, and GICs can maintain a layered structure.Further, we prepare graphene from GICs with high-temperature thermal expansion. When the heat treatment temperature is 500 ℃, the intercalator will remove from GICs. When the temperature exceeds 800 ℃, the vapor pressure exceeds the force between the GICs sheets, the rapid gasification of intercalator will make GICs occur significant volume expansion and the lamellar spacing of the sample increases. The sample forms a worm-like structure. After a short, low-power ultrasonic cleaning process, graphene nanosheets can be obtained. The graphene sheet size is 10 μm or more, and the thickness is about 2-8 nm. A small amount of transition metal compounds still remain between the grapheme sheets, which will impact on the performance of graphene.The innovation of this project is to find a new route for preparing graphene. The method does not require the use of strong oxidants. We can obtain large-size graphene nanosheets from natural flake graphite through the process of intercalation, thermal expansion and sonication. The graphene nanosheets can size up to several tens of micrometers.