Plasma-enhanced chemical vapor deposition (PECVD) is a well-known method for the synthesis of carbon nanotube (CNT) forests with the electric field in the plasma sheath being responsible for the vertical orientation of CNTs. Here, we investigate the deformation mechanism and mechanical properties of pristine and conformally coated PECVD CNT forests under compressive loading. Our in situ indentation experiments reveal that local buckles form along the height of pristine CNTs progressing downward from the starting point at the tips. For CNT forests coated from their roots to top with alumina using atomic layer deposition (ALD), the deformation mechanism depends strongly on the coating thickness. The buckling behavior does not change significantly when the coating is 5-nm thick. However, with a 10-nm-thick coating, the nanotubes fracture—that is, at both the CNT core and alumina coating. Ex situ indentation experiments with a flat punch reveal 8- and 22-fold increase in stiffness with the 5- and 10-nm coating, respectively. Comparing the behavior of the PECVD forests with CNTs grown with thermal chemical vapor deposition (CVD) shows that the mechanical behavior of PECVD CNTs depends on their characteristic morphology caused by the growth parameters including plasma. Our findings could serve as guidelines for tailoring the properties of CNT structures for various applications in which CNT compliance or deformation plays a critical role.
Mechanical Behavior of Carbon Nanotube Forests Grown With Plasma Enhanced Chemical Vapor Deposition: Pristine and Conformally Coated
Brigham and Women's Hospital,
Harvard Medical School,
65 Landsdowne Street,
Cambridge, MA 02139
e-mails: ppourshahidsaeedabadi@bwh.harvard.edu; pourshahid@gmail.com
Materials and Manufacturing Directorate,
Composites Branch,
Wright-Patterson Air Force Base, OH 45433;
Beavercreek, OH 45432;
Department of Mechanical and Aerospace Engineering,
University of Missouri,
Columbia, MO 65211
Purdue University,
West Lafayette, IN 47907
Purdue University,
West Lafayette, IN 47907
Materials and Manufacturing Directorate,
Composites Branch,
Wright-Patterson Air Force Base, OH 45433
Georgia Institute of Technology,
771 Ferst Drive,
Atlanta, GA 30332
Georgia Institute of Technology,
771 Ferst Drive,
Atlanta, GA 30332
Brigham and Women's Hospital,
Harvard Medical School,
65 Landsdowne Street,
Cambridge, MA 02139
e-mails: ppourshahidsaeedabadi@bwh.harvard.edu; pourshahid@gmail.com
Materials and Manufacturing Directorate,
Composites Branch,
Wright-Patterson Air Force Base, OH 45433;
Beavercreek, OH 45432;
Department of Mechanical and Aerospace Engineering,
University of Missouri,
Columbia, MO 65211
Purdue University,
West Lafayette, IN 47907
Purdue University,
West Lafayette, IN 47907
Materials and Manufacturing Directorate,
Composites Branch,
Wright-Patterson Air Force Base, OH 45433
Georgia Institute of Technology,
771 Ferst Drive,
Atlanta, GA 30332
Georgia Institute of Technology,
771 Ferst Drive,
Atlanta, GA 30332
Contributed by the Materials Division of ASME for publication in the JOURNAL OF ENGINEERING MATERIALS AND TECHNOLOGY. Manuscript received June 28, 2015; final manuscript received November 24, 2016; published online March 23, 2017. Assoc. Editor: Ashraf Bastawros.
This work is in part a work of the U.S. Government. ASME disclaims all interest in the U.S. Government's contributions.
Pour Shahid Saeed Abadi, P., Maschmann, M. R., Hodson, S. L., Fisher, T. S., Baur, J. W., Graham, S., and Cola, B. A. (March 23, 2017). "Mechanical Behavior of Carbon Nanotube Forests Grown With Plasma Enhanced Chemical Vapor Deposition: Pristine and Conformally Coated." ASME. J. Eng. Mater. Technol. July 2017; 139(3): 034502. https://doi.org/10.1115/1.4035622
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