High Rate Synthesis of Infinitely Long Core-Shell Nickel Carbon Nanotube Fibers
Abstract
HIGH RATE SYNTHESIS OF INFINITELY LONG CORE-SHELL NICKEL-CARBON NANOTUBE FIBERS PI: Sam Tawfick, Mechanical Science and Engineering, University of Illinois at Urbana- Champaign The proposed research aims at investigating a novel route to manufacture infinitely long multiwalled carbon nanotubes (CNT) having a continuous nickel (Ni) nanowire metal core. The pursuit of long high quality carbon nanotube is driven by a myriad of application lined-up for the strongest synthetic fiber ever produced. With > 10 GPa experimentally measured strength and high electrical and thermal conductivity exceeding copper (density normalized), CNT promise higher performance than the best pristine or metal coated carbon fiber, Dyneema or Kevlar. However, despite tremendous efforts, manufacturing of infinitely long CNTs has been so far elusive; while staple yarns made of short CNTs have low strength not exceeding 1 N/tex. This is due to the uncontrolled morphology of the yarns especially the presence of voids, and the difficulty in aligning short CNTs along the yarn axis. The proposed synthesis approach is based on 2 steps: (1) ultra-fast (~m/s) Ni nanowire drawing developed in the PI lab down to <100 nm using CO2 laser heating of a commercially available Ni wire embedded in silica; followed by (2) synthesized of pre-determined number of graphene layers (100-200) by low pressure chemical vapor deposition thus forming a cylindrical CNT shell around the Ni core. The composition ratio of the Ni-CNT core-shell fiber will be tuned to obtain pre-designed mechanical, thermal and electrical properties exceeding carbon fibers (CF) or Ni coated CF. In addition to synthesis, the study will also shed light on the load transfer mechanisms between a metal Ni core and outer CNT shells. Using in situ TEM techniques, the fracture and dislocation dynamics of the fiber in quasi-static mode will be analyzed to establish processing-structureproperty relationship. This study will leverage the enhanced mechanical properties of Ni at submicron scale, as demonstrated by its elemental ultimate strength reaching 2 GPa owing its unique dislocation dynamics. We expect to achieve continuous CNT-Ni composite fibers having specific mechanical and electrical properties, possibly exceeding 4 N/tex and 1.5 kS.m2/kg respectively. This new concept is orthogonal to all previous attempts because it doesn’t attempt to grow from a small nm diameter seed for extended length of time. Instead, it is focused on (1) manufacturing a continuous Ni nanowire core; followed by (2) growth of graphene shells around the core to continuously form one long CNT. In this process, the quality of the CNT being synthesized will not be reduced with synthesis time (unlike all previous methods) and the CNT are perfectly straight. This process is directly amenable to scalable manufacturing. Yarns made out of these nano fibers will be manufactured in the last phase of the project with diameter of 7 ?m consisting of ~ 1000 CNT-Ni fibers. Integration of the yarns into polymer matrix composites will shed a light on the ultimate strength and multi-functionality including electrical and thermal transport that can be obtained from such compound fibers. The composite mechanical modulus and strength will be measured.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512469
Entities
People
- Sam Tawfick
Organizations
- Office of Naval Research
- United States Navy
- University of Illinois Urbana–Champaign