Multiwalled carbon nanotube films: fabrication techniques and applications
Rigueur, John Lucien
The first part of the dissertation focuses on randomly oriented freestanding films of multi-walled carbon nanotubes (MWCNTs), also known as buckypapers, which have been fabricated by a two-step process using electrophoretic deposition (EPD). These multi-walled carbon nanotubes films were cast onto stainless steel electrodes from aqueous suspensions by EPD. Using a facile mechanical cleavage technique, the films were liberated from their underlying electrodes to yield the buckypapers. We investigated the films’ thickness, morphology, and surface topology using, respectively, profilometry, scanning electron microscopy, and atomic force microscopy. Mechanical characterization of the buckypapers revealed the average tensile strength and Young’s modulus to be 14.5 MPa and 3.3 GPa, respectively. The second part of this dissertation focuses on vertically aligned multi-walled carbon nanotubes. The purpose of our investigation was to optimize the growth of catalyst assisted chemical vapor deposition (CVD) grown carbon nanotubes for use as a photon absorbers in mid- to far-infrared applications. Improvement of the height and density of the carbon nanotubes will effectively increase the films absorptivity, bringing this material closer to an ideal absorber. NASA is currently exploring the use of this technology towards improving the stray light suppression of space flight instruments for future earth and space science missions. Detrimental to these scientific instruments is the stray light that scatters on interior telescope and instrument surfaces, thereby reducing the performance of observational instruments. In order to control this undesired effect, low-reflectance surface treatments are implemented in structural instrument designs. Z306 black paint is traditionally used to absorb stray photons, but advanced absorbers that employ films of multi-walled carbon nanotubes have been shown to provide an order of magnitude improvement over current surface treatments in the UV-visible-near infrared wavelengths. To this end, we varied the thickness of the iron catalyst layer and deposition conditions; varied hydrogen exposure times of substrates to optimize the MWCNT length and film density for efficient absorption of longer wavelength photons. Scanning electron microscopy is used to characterize film density and MWCNT height, and hemispherical reflectance measurements are used to quantify performance of the absorptive films.