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Characterization and Thermal Decomposition Behavior of Carbon Nanotubes and Nanocomposites

Zhao, Qi
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378113311

Abstract Details

2013, MS, University of Cincinnati, Engineering and Applied Science: Environmental Engineering.
Carbon nanotubes (CNTs) have become attractive for various applications due to their many distinctive properties. However, because of their fibrous structure and nanoscale diameters, the potential impact of these materials on human health and the environment is drawing much attention. To date, research on CNTs and composite materials is not comprehensive enough to understand their adverse impacts, or to establish regulations. An objective of this research is to better understand the physical and chemical properties of commercial CNTs and their polymer composites. The aerodynamic size distributions of five CNT products were studied. The prevalent size based on mass was from about 3.5 - 6 micrometers (µm), and the modes of geometric mean diameter ranged from about 4 - 9 µm. The morphology of these CNTs was observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For all bulk materials, large agglomerates were found with fibrous surface structures. After being aerosolized by an AG-5025 aerosol generator, individual fibers were found for CNT#1 (Mitsui) and CNT#5 (NTL) on lower stages of a Marple cascade impactor, and small agglomerates were found for the other materials. About 80-95% of the particles were less than 10 µm and considered inhalable, while 15-30% were less than 2.5 µm, a size that can penetrate deeply into the lung, reaching the alveolar (gas exchange) region. Morphology studies also indicated that the visual diameter, as determined by SEM, was not the same as the aerodynamic diameter, based on particle separation in a cascade impactor. This discrepancy is attributed to differences in the densities and dynamic properties of the varying particle structures. In addition to structure, residual metals in different CNT products may influence their toxicity and environmental impact. Thus, the metal contents of CNTs, their composites, and also the residue from the composites after thermal decomposition were analyzed. Prior to analysis (by inductively coupled plasma atomic emission spectroscopy [ICP-AES]), samples must be fully digested into solutions. Two digestion methods were examined: acid digestion on a hot plate and microwave (with acid) digestion. Results for a standard reference material (NIST SRM 2483) indicated the two methods were comparable and reliable, with the developed microwave procedure being advantageous in that it is simpler and much quicker. Iron (Fe) was the main metal detected in CNT#1 Mitsui (4.6 µg/mg), CNT#3T Arkema Treated (16.7 µg/mg), CNT#3UT Arkema Untreated (15.6 µg/mg), and CNT#4 CNano (9.74 µg/mg). Relatively high amounts of aluminum (Al) also were found in CNT#3T (18.12 µg/mg), CNT#3UT (30.39 µg/mg) and CNT#4 (5.32 µg/mg). Cobalt was detected in CNT#2 (Baytubes) with a concentration of 2.75 µg/mg. The metals detected in the nanocomposites were from the CNT fillers, and after thermal decomposition, most metals remained in the residual ash, as was expected. Thermal behavior of CNTs and nanocomposites was studied by thermogravimetric analysis (TGA). The peak decomposition temperature in air for CNTs ranged from 500? to 850?. CNT#1 (Mitsui) had the highest decomposition temperature. The TGA results for the nanocomposites revealed that CNTs in polycarbonate (PC) lowered the PC decomposition temperature relative to the pure polymer both in air and in nitrogen, but this was not found for other composites.
Mingming Lu, Ph.D. (Committee Chair)
Eileen Birch, Ph.D. (Committee Member)
Ming Chai, Ph.D. (Committee Member)
Vesselin Shanov, Ph.D. (Committee Member)
203 p.
Environmental Engineering
Nanocomposite; Carbon Nanotube; Metal Concentration; Thermal Decomposition; Size Distribution

Recommended Citations

Citations

  • Zhao, Q. (2013). Characterization and Thermal Decomposition Behavior of Carbon Nanotubes and Nanocomposites [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378113311

    APA Style (7th edition)

  • Zhao, Qi. Characterization and Thermal Decomposition Behavior of Carbon Nanotubes and Nanocomposites. 2013. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378113311.

    MLA Style (8th edition)

  • Zhao, Qi. "Characterization and Thermal Decomposition Behavior of Carbon Nanotubes and Nanocomposites." Master's thesis, University of Cincinnati, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378113311

    Chicago Manual of Style (17th edition)

ucin1378113311
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© 2013, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.