Synthesis of continuous length single crystalline carbon nanotubes on metal wire templates by a roll-to-roll process
Abstract
Carbon nanotubes (CNTs) are the strongest and lightest materials to mankind knowledge up to date. They are made of wrapped graphene sheets having sp2 hybridized carbon bonds, strongest known chemical bond. Yet, engineers are still incapable of taking advantage of these superior properties by constructing load-bearing composites from CNTs. This problem can be traced back to the nature of available raw CNT materials. CNTs are typically synthesized by a catalytic chemical vapor deposition (CVD) process. The current state-of-the art CVD takes place at high temperature usually >700C, yet leads to CNTs having short length (typically < mm), uncontrolled number of walls and a large number of defects and grain boundaries. Varying the synthesis conditions does not lead to satisfactory high quality CNTS due to fundamental tradeoffs among these required characteristics.This proposal presents a new concept to make CNTs approaching the theoretical limit of crystalline quality and strength, in addition to having long length (> 0.1 m). The work is driven by the hypothesis that when the growing carbon lattice of the CNTs stays in contact with the catalyst throughout synthesis process, the density of defects can be significantly reduced leading to almost ideal CNTs having a single domain. This hypothesis is supported by new results in the PI lab and elsewhere. For example, the PI lab demonstrated single domain monolayer graphene having mean Raman ID/IG ratio of 0.07, among the highest quality reported in the literature. To test this hypothesis, the PI will create catalyst nanowire templates extending more than 0.1 m length and synthesize a monolayer of high quality graphene wrapping around them by CVD, then dissolve the nanowire to obtain a ???collapsed??? single walled CNT having a width of 100 nm.The proposal is organized into five tasks. Task 1 and 2 will be accomplished in parallel during the first year. Task 1 will focus on patterning catalyst materials (namely Pd, Cu, Ni and Pt) which are commercially available in square sheets into nanowires. The patterning will use interference lithography and top-down etching. Task 2 will design and build a CVD system using localized heating, gas nozzles and motorized catalyst feed stages to synthesize the CNTs on 0.1 m long nanowires. Task 3 is the synthesis understanding and optimization effort. This task will use the new CVD setup to adapt the current recipes developed in the PI???s lab to moving nanowire and localized heating. This task will result not only in recipes to synthesize high quality monolayer CNT growth, but also mechanistic understanding of the synthesis mechanism. The nanowire metal cores will be etched from the CNTs to obtain collapsed CNTs. The CNT quality will be measured by Raman spectroscopy and atomic force and electron microscopy. Task 4 will study stability of the nanowires of smaller diameter at high temperature towards making long length CNTs having sub- 50 nm diameter and Task 5 will explore novel sustainable processes for removing the metal wire from the CNT shells.If successful, this new concept will demonstrate for the first time CNT with continuous length, near ideal CNTs crystal structure, and exhibiting one order of magnitude larger strength to weight ratio than state-of-the art carbon fibers used in reinforced polymers.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 10, 2018
- Source ID
- N000141812457
Entities
People
- Sameh Tawfick
Organizations
- Office of Naval Research
- United States Navy
- University of Illinois Urbana–Champaign