Advance Growth Methods for Aligned and Ultra-long Carbon Nanotubes for Naval Applications
Navy SBIR 2014.1 - Topic N141-063
ONR - Ms. Lore Anne Ponirakis - loreanne.ponirakis@navy.mil
Opens: Dec 20, 2013 - Closes: Jan 22, 2014

N141-063 TITLE: Advance Growth Methods for Aligned and Ultra-long Carbon Nanotubes for Naval Applications

TECHNOLOGY AREAS: Materials/Processes, Electronics

OBJECTIVE: To develop new manufacturing approaches that allow the growth of ultra-long or continuous carbon nanotubes (CNTs), with low but controlled defect density, with controlled number of CNT walls, and high CNT density and alignment. The primary target application is structural, in the form of yarns, mats, prepegs, or nanocomposites but other applications such as electrical wires, electrodes, and cables are envisioned.

DESCRIPTION: Despite incremental morphological advances in this class of materials over the last 10 years, there are but a few companies that are able to manufacture small amounts of continuous yarns and mats made of short CNTs (between 0.1 - 1 mm). Of these, their thermal, electrical and mechanical properties are still between 5 and 10 times lower than the ultimate properties that this material could achieve. For example, the measured strain to failure for current CNT Yarn is only 1.5%, compared to 1.8% for standard IM7 carbon fiber and a predicted value of close to 20% for a continuous CNT.

What is limiting the attainment of the predicted, ultimate properties (and broadest use) of Carbon Nanotubes (CNTs) for structural, electrical, and thermal applications is our inability to grow these materials with an ultra-long or continuous length scale, with high densities, good alignment, and controlled defect densities at affordable costs. Paramount to this endeavor is the control of all aspects (geometrical, chemical, physical) of the catalyst particle, substrate, and growth environment. Any innovative growth methodology must be able to control at a minimum: the temperature of the catalyst particles; the supply of carbon feedstock and other gases into the processing chamber to optimize the supply of carbon to the catalyst particles; minimization of amorphous, carbonaceous or other poisonous deposits on the catalysts; immobilization of the catalyst particle either via chemical alloying or substrate texturing; deleterious inter CNT friction effects during growth due to differences in growth rates; the size and shape of the catalyst particles during growth; the CNT growth rate, and many other parameters. Novel, integrated substrate, reactor, and process control designs are needed for effective management of the above conditions to allow the next technical leap in CNT properties.

The ultimate goal is to attain the growth of ultra-long or continuous carbon nanotubes (CNTs), with low but controlled defect density, controlled number of CNT walls (or with a narrow distribution of diameters), and high density and alignment. Any small business submitting a proposal under this topic must have demonstrated previous experience in growing CNTs and clearly articulate how their new and innovative approach to CNT growth will control all the parameters mentioned above (and possibly many others).

PHASE I: The contractor will perform a laboratory scale demonstration of a new or improved: substrate; or reactor configuration; or catalyst; or any other process parameter for growth of high quality, dense, aligned and ultra-long (> 1 inch) or continuous Carbon Nanotubes (CNT). Precise control of catalyst composition, temperature, geometry, surface distribution, and anchoring method shall be demonstrated during CNT growth. Precise control of substrate texturing (via chemical or mechanical means) for feed stock gas distribution optimization, for controlling the size of a CNT bundles, for anchoring the catalyst particles or for other purposes shall be demonstrated. Accurate process control of carrier gases, carbon and catalyst feed stock gas chemistries, and gas temperature and pressure also shall be demonstrated. The contractor will grow CNTs with said process and processing chamber improvements and will measure their growth rate, ultimate length, diameter, crystallinity, areal density, and degree of alignment and will provide the data in a statistical format with a minimum average and standard distribution values. The contractor with the best overall values and most promising process in terms of scalability will move to the Phase II effort.

PHASE II: During the Phase II program the contractor will further develop, optimize and scale up the new technique demonstrated during Phase I and demonstrate the capability to manufacture continuous yarns (either of discreet, ultra-long , aligned CNTs or of continuous CNTs). The contractor will manufacture CNT yarns of several diameters ranging in size from 1 micrometer to several microns. The awardees will characterize the yarns elastic constant, strength, and strain to failure for various gauge lengths. The small business will also start exploring steps to lower the material manufacturing costs by possibly recycling process gases, increasing growth rates, scaling up the process, or other approaches.

PHASE III: The commercialization of the technology will be dependent upon the success of Phase I and II of the SBIR topic. Current naval needs for the technology are in the main rotor Hub in the H-1 helicopter, delamination resistant tail rotor flex beams in the CH-53K helicopter and thermally active nano-composites for de-icing applications in the MQ-4C Triton UAV. Which program will benefit most will not become clear until the program is well underway and at least the Phase II base is completed. At that time and appropriate program will be targeted. The commercial and military applications of a continuous and dense CNT fiber manufacturing process are endless. In addition to naval applications, the contractor will also pursue independent commercial applications in the sporting goods, transport, electronic and energy sectors.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The commercial aviation and shipping industry would benefit significantly from this new, low cost material form. The need for lightweight structural composites for next generation DoD naval platforms (ships, subs, and aircraft) also occurs in commercial counterparts. The commercial applications for this technology are very broad because of the extraordinary mechanical, electrical, and thermal properties that this material affords. Potential uses can be found in the transportation sector (primarily for aviation); in the energy sector (directly in the form of low resistance wires or high surface area electrodes); and in the space sector (for light weight structures and components; i.e. telescope baffles).

REFERENCES:
1. Nikolaev, P.; Bronikowski, M. J.; Bradley, R. K.; Rohmund, F.; Colbert, D. T.; Smith, K. A.; Smalley., R. E., "Gas-phase catalytic growth of single-walled carbon nanotubes from carbon monoxide" Chem. Phys. Lett. 313, p91-97 (1999).

2. Bronikowski, M. "Longer nanotubes at lower temperatures: the influence of effective activation energies on carbon nanotube growth by thermal chemical vapor deposition". J. Phys. Chem. C, 111, p17705-17712, (2007).

3. Meng, G.; Jung, Y. J.; Cao, A.; Vajtai, R.; Ajayan, P. M., "Controlled fabrication of hierarchically branched nanopores, nanotubes, and nanowires". PNAS 2005, 102, p7074-7078.

4. Gommes, C., Pirard, J. P., & Blacher, S. "Influence of the operating conditions on the production rate of multi-walled carbon nanotubes in a CVD reactor". Carbon, 42, p1473-1482 (2004).

5. G P Sklar, K Paramguru, M Misra and J C LaCombe. "Pulsed electrodeposition into AAO templates for CVD growth of carbon nanotube arrays" Nanotechnology 16, p12651271 (2005)

6. M. De Volder, S. Tawfick, R.H. Baughman, A.J. Hart. "Carbon nanotubes: present and future commercial applications" Science 339: p535-589 (2013)

7. Q. Yuan, Z. Xu, B.I. Yakobson, and F. Ding. "Efficient defect healing in catalytic carbon nanotube growth" Phys. Rev. Lett., 108, 245505 (2012).

KEYWORDS: Carbon Nanotubes, CNT Growth, Composite Structures, Nanocomposites

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