<p>Carbon nanotubes (CNTs) have been a subject of development and investigation in the last two decades due to their superior physical and chemical properties, such as high electrical conductivity, high thermal conductivity, high mechanical and elastic properties, and relative inexpensiveness. These structures are cylindrically-shaped molecules made of carbon atoms. A sheet of graphene can be rolled-up to make a carbon nanotube. CNTs can be single-walled (SWCNT) if made from one layer of carbon atoms, or multi-walled (MWCNT) when consisting of several layers of graphene sheets. The electronics industry has a number of applications for the CNT in photovoltaics, sensors, semiconductor devices, displays conductors and energy conversion devices. For instance, carbon nanotubes are used for making transistors and are also used as conductive layer for the touch screen market. This paper aims to grow CNTs in the lab and then investigate its manufacturability and relevant properties changes using the laser ablation process. The CNTs were grown using Chemical Vapor Deposition (CVD) in the Nanotechnology and Nanostructures Laboratory. The catalyst used for the growth was Iron on a Silicon substrate. The average size of the substrate samples is 5 mm by 5 mm. Continuum Surelite Class III laser with 1064 nm wavelength of single pulse mode is used to ablate the CNTs to assess property changes in CNTs resulting from laser-matter interaction. Several parameters (laser beam energy, beam diameter) are varied to investigate their influences on properties changes in CNTs. The laser beam energy ranges from 0.063 J to 0.35 J and the beam diameter is adjusted using an optical lens, for which the focal length is 150 mm. Eight samples have been tested and Scanning Electron Microscopy (SEM) and Raman Spectroscopy have been used to characterize the samples before and after laser ablation. As for the SEM, several images are taken for each of the samples to have a better understanding on how the CNT density would look before ablation compared to after ablation. Several contrast and zoom configurations are used for all samples. As for the Raman Spectroscopy characterization, the device used was developed by Renishaw technologies and the corresponding wavelength for the laser has a wavelength of 532 nm. A Raman spectrum was taken 4 to 6 times for each of the samples before the ablation. The density of the population for both SWCNT and MWCNT is demonstrated on the spectrum. It is found that when 0.153 J is used with the distance between sample and lens being equal to the focal length of the lens, SEM imaging and Raman Spectrum show a bright burned circumference caused by the laser beam and the CNTs at a distance of 200 micrometers around are found to be broken down as well due to the heat propagation from the laser beam.</p>

Experimental Investigation of Nanosecond Laser Ablation of Carbon Nanotubes

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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