How pencils gave us the great discovery of graphene
Created By RISC | 1 month ago
Pencils might seem an everyday item we’ve known since childhood but they also led to an amazing future material.
Pencil lead is formed of graphite, a type of carbon where atoms are joined by covalent bonds in a hexagonal structure in a two-dimensional plane. Each plane is attracted by Van der Waals forces. Graphene, on the other hand, is a graphite layer.
Andre Geim and Konstantin Novoselov of the University of Manchester were the first to discover graphene by using transparent tape to separate a single atom-thickness sheet of carbon from graphite.
Wrapping the tape around the pencil lead and peeling it off revealed a black powder of graphene in multiple layers. Using more pieces of tape, they eventually achieved the thinnest sheet possible with only one atom. An electron microscope was then used to look for a single layer of graphene.
Although physically identical, graphite has multiple overlapping planes while graphene only has one. Using a Van der Waals force to attract each plane makes graphite frailer and more brittle. That's why a pencil lead tends to shatter when we apply pressure to it. In the last post (https://bit.ly/3xCoEy3), we discussed how graphene has exceptional qualities, making it far more valuable than graphite.
Graphene was produced via mechanical exfoliation of graphite. But the lengthy manufacturing process made it hard to control the size and number of layers. Chemical reduction of graphite oxide is now generally used, which involves oxidizing graphite to create a functional group that divides the graphite layers and then performing a reduction process to lower the amount of functional groups. Reduced graphene oxide is produced using this process (rGO).
This approach produces lower-quality graphene than mechanical exfoliation but it can be made in large quantities at a minimal cost. A chemical vapor deposition (CVD) process releases methane into a furnace until only carbon atoms (graphene) remain on a metal sheet. This approach can create high-quality graphene with variable layer counts and electrical conductivity.
Graphene shows how small things can lead to big things, which is also true for graphite.
Story by: Supunnapang Raksawong, Materials Researcher, RISC
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การพิสูจน์เอกลักษณ์ และการประยุกต์ใช้. วารสารวิทยาศาสตร์และเทคโนโลยี มหาวิทยาลัยอุบลราชธานี. 22(2): 39-49.