Significance Statement
Defects in structures stimulate oxidation attacks toward defective carbon lattice and cause failure for carbon-based devices operating at a high input power. Hence, in order to improve the technological applications of carbon nanotubes, developing techniques for reducing unfavorable effects of structural defects on the carbon lattice needs to be implemented.
A metal such as aluminum which forms a thin layer of aluminum oxide thereby protecting it from further oxidation also shows huge relevance in heat transfer applications due to its high thermal conductivity and high melting point.
Researchers from University of Maryland and U.S. Army Research Laboratory led by Professor YuHuang Wang and Dr. Bryan Glaz presented a simple technique to significantly reduce the structural effects of defects in carbon nanotubes oxidation by selectively growing aluminum oxide on defect sites and experimentally show that the selective protection effectively blocks attacks by oxygen and other oxidative species in the air. A new paper describing this research was published in the peer-reviewed journal Advanced Materials.
The authors made use of atomic layer deposition technique which substitutes for both aluminum and oxygen chemistries when developing protective coating aluminum oxide on specific areas of carbon nanotubes where surface defect sites exist.
In order to provide more understanding on this deflection protection mechanism, the authors made use of high resolution scanning electron microscopy, transmission electron microscopy and Raman scattering to show characteristics of aluminum oxide-protected carbon nanotubes thin films at failure regions. Scanning electron microscopy images showed that aluminum oxide shells in failure regions evolved into nanobeads attaching on carbon nanotubes. High resolution transmission electron microscopy and electron diffraction patterns revealed amorphous aluminum oxide coating in the contact region which transformed into crystalline nanobeads in the breakdown regions.
A thermoacoustic device was fabricated by the authors from carbon nanotubes thin films protected with aluminum oxide in order to investigate the potential applications of the defect protection method. A higher power density of 6.8 Wcm-2 in air was achieved compared with unprotected control devices which also led to a higher sound pressure of 0.64 Pa with an improved audible sound pressure level of 90.1 dB compared with unprotected films.
Solving the problem of oxidation failure by the researchers can unlock further technological applications of carbon nanotubes. Moreover, the approach used in this study may be applied to other nanomaterials such as silver nanowires and graphene which can also suffer from oxidation failures.
Journal Reference
Chuan-Fu Sun1, Bryan J. Glaz2, Morihiro Okada1, Edward Baker III 1, Xi-Yuan Cheng1, Shashi P. Karna2, YuHuang Wang1. Blocking Oxidation Failures of Carbon Nanotubes through Selective Protection of Defects, Advanced Materials, Vol 28 Issue 31, 2016.
[expand title=”Show Affiliations”]- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, USA
- U.S. Army Research Laboratory, Aberdeen Proving Ground, Aberdeen, MD, USA
Go To Advanced Materials