Penn State scientists have shown how adding graphene to carbon fiber could help boost the material’s strength and stiffness.
This could someday lead to the production of lightweight, high-strength materials that can help improve the safety and reduce costs associated with manufacturing cars.
Carbon fiber currently sells for about $15 per pound and the Penn State team – together with scientists from University of Virginia, Oak Ridge National Laboratory, Solvay and Oshkosh – wants to reduce that to $5 per pound by making changes to the complex production process.
“Currently most carbon fibers are produced from a polymer known as polyacrylonitrile, or PAN, and it is pretty costly,” says Penn State researcher Małgorzata Kowalik. “The price of PAN makes up about 50% of the production cost of carbon fibers.”
PAN is used to create 90% of carbon fibers found in the market today, but its production requires an enormous amount of energy.
First of all, PAN fibers have to be heated to 200-300 degrees Celsius to oxidize them. Next, they must be heated to 1,200-1,600 degrees Celsius to transform the atoms into carbon. Finally, they have to be heated to 2,100 degrees Celsius so that the molecules are aligned properly.
Without this series of steps, the resulting material would lack its needed strength and stiffness.
The Penn State team has now reported that by adding trace amounts of graphene – only 0.075% concentration by weight – to the first stages of this process, they can create a carbon fiber that has 225% greater strength and 184% greater stiffness than the conventionally made PAN-based carbon fibers.
“We connected experiments of different scales to not only show that this process works, but it gave us an atomistic-scale reason why these types of additives work,” says Penn professor Adri van Duin, who is also the director of the MRI’s Materials Computation Center and an ICDS associate. “That knowledge allows us to optimize the process further.”
The team is now exploring ways to further use graphene in this production process by utilizing cheaper precursors, with a goal of cutting out one or more of the production steps altogether, thereby reducing costs even more.
Image and content: Margaret Kowalik and Adri van Duin/Penn State