J.M. Spry, S.P. Compton
MVA Scientific Consultants,
Keywords: carbon black, soot, elemental carbon, black carbon, aciniform, TEM, HRTEM, EDS, microstructure, turbostratic, atlas
Summary:Soot is a major source of airborne particulate and typically contains primary particles which are less than one micrometer in diameter. Soot particles form as an undesired combustion by-product originating from a variety of different sources like wildfires, candles, and diesel exhaust. Carbon black, on the other hand, is a controlled or engineered combustion product designed for specific properties in a variety of applications. Both soot and carbon black can be characterized by an "aciniform" structure. The ASTM Method, "Standard Practice for Sampling and Testing of Possible Carbon Black Fugitive Emissions or Other Environmental Particulate, or Both," provides a guideline for comparing carbon black to various soot sources as well as other darkening agents. Characterization of aciniform carbon particles from soot using high resolution transmission electron microscopy [HRTEM] have also been reported previously; however, no investigation into microstructural variations of primary particles from soots of different sources is publicly available. As such, the authors have investigated aciniform primary particles using HRTEM from a variety of sources. The ultimate goal is to develop an atlas of microstructural characteristics and elemental compositions that complements the ASTM standard practice and aids in the determination of sources for soot particles observed in the ambient air or collected from settled dust.