AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Comparison of the Mass-Specific Absorption Spectra of Graphenes to Soots
JAMES RADNEY, Christopher Zangmeister, Rian You, Courtney Grimes, Jessica Young, Michael Zachariah, Russell Dickerson, National Institute of Standards and Technology
Abstract Number: 541 Working Group: Combustion
Abstract Many measurements and studies treat black carbon aerosol as having a very narrow range of spectral properties; i.e. mass specific absorption cross section at λ = 550 nm (MAC$_550) of 7.5 ± 1.2 m$^2 g$^(-1) and an assumed power-law wavelength dependence (i.e. Absorption Angstrom Exponent, AAE) of 1. We will compare the MAC spectra of graphene and graphene oxide reduced (rGO) at 320 °C in N$_2 and soot aerosols across λ = 500 nm to 840 nm; soot aerosols were generated from ethylene, kerosene and diesel diffusion flames and spark discharge (i.e. fullerene soot). Measurements were made in situ by step scanning a photoacoustic spectrometer utilizing a supercontinuum laser with a tunable wavelength and bandwidth filter. While all of these samples have absorption spectra that would label them as spectrally black (AAE ≤ 1) the magnitude of the MAC values varied wildly. The graphene and rGO had MAC$_550 7.2 ± 0.4 m$^2 g$^(-1) and 7.7 ± 0.3 m$^2 g$^(-1) while ethylene, fullerene, diesel and kerosene soot had MAC$_550 of 3.7 ± 0.2 m$^2 g$^(-1), 6.1 ± 0.2 m$^2 g$^(-1), 12.1 ± 0.1 m$^2 g$^(-1) and 13.0 ± 0.1 m$^2 g$^(-1), respectively. Interestingly, only the graphenic samples would be considered black carbon under the accepted definition. Further, if we consider the radiative impact of these other “black carbon” materials, significant errors can arise from incorrectly parameterizing the absorption strengths. This would be especially true in areas where kerosene and diesel represent a large fraction of the particulate emissions since they are commonly used as fuels for heating and lighting.