Brian J. Landi

Material and energy intensity of fullerene production.

Fullerenes are increasingly being used in medical, environmental, and electronic applications due to their unique structural and electronic properties. However, the energy and environmental impacts associated with their commercial-scale production have not yet been fully investigated. In this work, the life cycle embodied energy of C(60) and C(70) fullerenes has been quantified from cradle-to-gate, including the relative contributions from synthesis, separation, purification, and functionalization processes, representing a more comprehensive scope than used in previous fullerene life cycle studies. Comparison of two prevalent production methods (plasma and pyrolysis) has shown that pyrolysis of 1,4-tetrahydronaphthalene emerges as the method with the lowest embodied energy (12.7 GJ/kg of C(60)). In comparison, plasma methods require a large amount of electricity, resulting in a factor of 7-10× higher embodied energy in the fullerene product. In many practical applications, fullerenes are required at a purity >98% by weight, which necessitates multiple purification steps and increases embodied energy by at least a factor of 5, depending on the desired purity. For applications such as organic solar cells, the purified fullerenes need to be chemically modified to [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM), thus increasing the embodied energy to 64.7 GJ/kg C(60)-PCBM for the specified pyrolysis, purification, and functionalization conditions. Such synthesis and processing effects are even more significant for the embodied energy of larger fullerenes, such as C(70), which are produced in smaller quantities and are more difficult to purify. Overall, the inventory analysis shows that the embodied energy of all fullerenes are an order of magnitude higher than most bulk chemicals, and, therefore, traditional cutoff rules by weight during life cycle assessment of fullerene-based products should be avoided.

Recycling single-wall carbon nanotube anodes from lithium ion batteries

Large scale incorporation of nanomaterials into industrial systems and commercial products is relatively new, and therefore little attention has been given for options when these products reach their end-of-life. During the course of this study, the ability to recycle end-of-life (EOL) single-wall carbon nanotubes (SWCNTs), recovered from lithium ion battery electrodes, was investigated. Specifically, SWCNT–Li+ coin cells were forced to their EOL though extended cycling at high charge rates and recycled using a series of acid and thermal treatments originally developed for the purification of as-produced SWCNT material. The recycling treatments were successful in removing the EOL byproducts (e.g. solid electrolyte interphase, lithium) and upgrading the SWCNT material to its pre-cycling functionality. The material was characterized at each step in the recycling process through a combination of scanning electron microscopy, thermogravimetric analysis, Raman spectroscopy, and optical absorption spectroscopy. The energy required for each of the recycling procedures was measured and compared to the energy of SWCNT synthesis. The recycled-SWCNT material was successfully incorporated into Li+ battery coin cells with insertion and extraction capacities of 650 mA h g−1, comparable to the virgin pure-SWCNT electrodes. Therefore, the ability to refunctionalize “used” SWCNTs from a device, through chemical processing, to their initial purity and functionality has been demonstrated. The direct energy required to refunctionalize the SWCNTs was measured and is less than half of the direct energy required to synthesize new material. Thus, the ability to preserve the nanoscale properties of SWCNTs with reduced impact offers new opportunities for end-of-life management.

Ion irradiation of electronic-type-separated single wall carbon nanotubes: A model for radiation effects in nanostructured carbon

The structural and electrical properties of electronic-type-separated (metallic and semiconducting) single wall carbon nanotube (SWCNT) thin-films have been investigated after irradiation with 150 keV 11B+ and 150 keV 31P+ with fluences ranging from 1012 to 1015 ions/cm2. Raman spectroscopy results indicate that the ratio of the Raman D to G′ band peak intensities (D/G′) is a more sensitive indicator of SWCNT structural modification induced by ion irradiation by one order of magnitude compared to the ratio of the Raman D to G band peak intensities (D/G). The increase in sheet resistance (Rs) of the thin-films follows a similar trend as the D/G′ ratio, suggesting that the radiation induced variation in bulk electrical transport for both electronic-types is equal and related to localized defect generation. The characterization results for the various samples are compared based on the displacement damage dose (DDD) imparted to the sample, which is material and damage source independent. Therefore, it is poss...

Surface oxidation of single-walled carbon nanotube paper with oxygen atoms

Single-walled carbon nanotube paper was surface oxidized with gaseous oxygen atoms produced by low-pressure: (1) vacuum UV (λ = 104.8 and 106.7 nm) photo-oxidation and (2) downstream microwave plasma discharge of an Ar–O2 mixture. X-ray photoelectron spectroscopy was used to detect the carbon- and oxygen-containing functional groups in the top 2–5 nm of the sample’s surface. Both methods produced a saturation level of ca. 12 at.% oxygen with the predominant formation of the epoxide/ether groups.