DMREF: Engineering Strong, Highly Conductive Nanotube Fibers Via Fusion

Northeastern University, Boston MA

Investigators

Abstract

In this NSF-Designing Materials to Revolutionize and Engineer our Future (DMREF) project funded by the Division of Chemistry and the Civil, Mechanical, Manufacturing and Innovation Division, Professors Yung Joon Jung, Carol Livermore-Clifford, Moneesh Upmanyu, and David Kaeli of Northeastern University are studying how to create high-performance carbon fibers that could be used for applications in aerospace, high power density energy storage, and lightweight cabling/wiring. The main challenge of creating such fibers is that they need to be mechanically strong while also being exceptional conductors of heat and electricity. To accomplish this goal, the researchers are studying how to fuse networks that contain many nanometer-sized carbon tubes ("carbon nanotubes") into a larger, more seamless structure. The variables being studied include ways to organize the carbon nanotubes into the network and to use electric voltage to fuse the carbon nanotubes together. Experimental studies, computational simulations, and data mining techniques are being applied to understand the complex relationships between the structure of the fused networks and how they perform. The combination of superior electronic, thermal, and mechanical properties makes carbon nanotube networks an ideal building block for high-performance multifunctional materials, but these advantages are eroded in van der Waals connected networks. If van der Waals interactions were replaced with covalent bonds to create macroscopic seamless carbon nanostructures, performance should increase significantly. This research project is focusing on a novel carbon nanostructure engineering process called nanotube fusion. The method controls input voltages across the network to create covalently bonded molecular junctions (cross-links) between carbon nanotubes, transforming them into larger diameter single-walled carbon nanotubes, multi-walled carbon nanotubes, or multi-layered graphene nanoribbons with measurable property improvement. The research is engaging interdependent experimental, simulation, and data mining efforts to enable scalable multifunctional fibers. The experimental parameters include fusion polarity, frequency, voltage, source-on-time, and external temperature, as well as carbon nanotube structure, assembly process and initial fiber architecture. Characterization data and coarse-grained atomistic simulation of fused fibers relate physical properties to structure and structure to processing. These efforts are complemented by statistical data mining efforts to extract the complex relationship between fiber processing and their properties. The team is working to involve high school students directly in the research; to enable research opportunities for undergraduates from a diversity of backgrounds; and to create symposia on materials science and on multifunctional nanostructured networks.