Grantee Research Project Results
Final Report: Low-Cost Catalytic Production of High-Quality Carbon Nanotube for Advanced Conductive Composites
EPA Contract Number: EPD04056Title: Low-Cost Catalytic Production of High-Quality Carbon Nanotube for Advanced Conductive Composites
Investigators: Omstead, Thomas R.
Small Business: Intematix Corporation
EPA Contact: Richards, April
Phase: II
Project Period: April 1, 2004 through June 30, 2005
Project Amount: $224,953
RFA: Small Business Innovation Research (SBIR) - Phase II (2004) Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , Nanotechnology , SBIR - Nanotechnology
Description:
The purpose of this research is to develop a low-cost method for the production of nanotubes using modern methods such as physical vapor deposition (PVD) and chemical vapor deposition (CVD). The nanotubes will be used to modify plastic formulations so as to make them electrically conductive. This will enable automobile parts manufactured using these conductive polymers to be coated using an electrostatic painting process. Electrostatic painting is much better environmentally than tradition spray coating methods and it requires four times less paint and, hence, produces much less volatile organic components (VOCs).
Intematix Corp. has successfully developed a production-oriented combination PVD/CVD process for the production of nanotubes. Intematix has also achieved very high yield of nanotubes for a given amount of nickel catalyst. The nanotubes have been characterized as having very high conductivity and meeting the requirements for application to the polymer resistivity reduction application. Intematix has performed a full optimization of nanotube deposition conditions and their relationship to structure and yield. The firm has also worked on the solubilization of the nanotubes in solvent for mixing with polymers. In addition, Intematix has designed and fabricated a very large (12-inch) PVD/CVD system for nanotube production.
Intematix chose to work with a conveyor-based PVD system with an integrated RF etch station. A CVD station for integration onto the system was then developed. This method has been chosen because of the high cost and complexity of performing CVD of expensive metals, such as nickel, cobalt and molybdenum. For example, the cost of 5 g of a typical nickel precursor, bis(methylcyclopentadienyl)nickel(II), was found to exceed $100 per gram, or approximately $500 per gram of nickel. Intematix also did extensive nanotube development in a tube furnace-based CVD system.
The system chosen for continued development on this program was a used CPA 9900 conveyor- based sputtering system (Figure 1).
Figure 1. System at Intematix’s Facility. This system was configured for PVD on large area substrates up to 15-by-12 inches in size. The initial configuration of the system utilized linear sputtering (PVD) capability together with an existing CVD furnace, in which nanotubes were already growing.
Summary/Accomplishments (Outputs/Outcomes):
Nanotubes can be fabricated at very high yields using a combination nickel/cobalt (Ni/Co) catalyst. Intematix has found that a temperature ramping process creates the highest possible yield and the best process reproducibility. Increasing nickel thickness and the addition of cobalt was found to increase nanotube diameter and yield. Intematix was able to produce 400 mm thick matt carbon nanotubes using only 400 Å of catalyst. Surface modification of the nanotubes together with ultrasound treatment was found to facilitate their dissolution into the solvent so that they can be suitably mixed with polymer.
To grow nanotubes, it is first necessary to deposit a nickel catalyst layer using sputtering (PVD). This is a high-vacuum process in which an argon plasma is used to deposit metal. The linear CPA nanotube system, as previously discussed, was purchased for and used in the project for PVD and is being used to deposit nickel catalyst for large-scale nanotube growth. Transport systems, vacuum systems and plasma power-delivery systems were repaired and upgraded as necessary. Process was developed using glass wafers on the 12-by-12 inch pallet. In Figure 2, one pallet is shown with glass substrates deposited on (back) and undeposited (front). Up to 10 of these pallets can be loaded at once and transported to the other load-lock chamber for the high throughput growth of nanotubes.
Figure 2. CPA Load-Lock Chamber With Deposited Glass Substrates
To be able to be make nanotubes in sufficient quantities for use in conductive plastics, it was necessary to scale the CVD process to a larger size. Intematix has thus recently scaled up of the tube furnace reactor to 2.25 inches. Intematix has performed process development with the new larger tube and has been able to deposit on 2-by-8 inch substrates with success. This allows for at least a fivefold increase in the amount of nanotubes produced during each run. Intematix has combined the larger substrate area with its high-deposition rate, high-efficiency process that the firm has also further enhanced.
As shown in Figure 3, Intematix is capable of routinely producing high yields of very high aspect ratio nanotubes using the firm’s tube furnace reactor. Intematix can produce as much as a 200 mm thick matt of nanotubes using 500 to 1,200 Å of catalyst in approximately 40 minutes of total growth time.
Figure 3. Nanotubes Produced Using the Split-tube Horizontal CVD System
Nanotubes have been deposited using a variety of methods at a variety of pressures. Intematix has also experimented with different catalyst compositions. One of Intematix’s unique compositions was found to yield the desired high-diameter nanotubes. Intematix is experimenting with additional process optimization to further enhance the nanotube characteristics.
Conclusions:
The work for this contract was focused on the development of carbon nanotubes for application to polymeric resistivity reduction. Numerous other applications exist for nanotube deposition, however, and could be well served by the cost-reduced, high-quality nanotubes developed in Intematix’s work. Potential applications include microelectronics, hydrogen storage, hydrogen fuel cells, micromachinery, field emission displays, and batteries. Intematix feels that its ability to coat large, flat substrates is particularly applicable to the microelectronic and fuel cell applications. Intematix plans to explore these opportunities, in parallel, to the commercialization of its polymeric resistivity-reduction opportunity.
Journal Articles:
No journal articles submitted with this report: View all 1 publications for this projectSupplemental Keywords:
physical vapor deposition, chemical vapor deposition, nanotubes, conductive composites, electrostatic painting, nickel catalyst, cobalt, molybdenum, linear sputtering, furnace reactor, microelectronics, hydrogen storage, hydrogen fuel cells, micromachinery, field emission displays, batteries, EPA, small business, SBIR,, Scientific Discipline, TREATMENT/CONTROL, Sustainable Industry/Business, Environmental Chemistry, Technology, New/Innovative technologies, Environmental Engineering, clean technologies, plastic composits, green engineering, nanotechnology, carbon nanotubes, catalytic studies, chemical vapor deposition, electric conductivity, innovative technologies, pollution preventionSBIR Phase I:
Combinatorial Screening of High-Efficiency Catalysts for Large-Scale Production of Pyrolytic Carbon Nanotubes | Final ReportThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.