Structural changes of CAST soot during a thermal–optical measurement protocol

Author(s)
Theresa Haller, Christian Rentenberger, Jannik C. Meyer, Laura Felgitsch, Hinrich Grothe, Regina Hitzenberger
Abstract

Thermal–optical measurement techniques are widely used to classify carbonaceous material. The results of different methods for total carbon are comparable but can vary by >44 % for elemental carbon. One major cause of variation is the formation of pyrolyzed carbon during the heating process which occurs mainly in samples with a high amount of brown carbon (BrC). In this study the structural changes of two different CAST (combustion aerosol standard) aerosol samples caused by the heating procedure in a thermal–optical instrument were investigated with UV–VIS and Raman spectroscopy, the integrating-sphere technique (IS) and transmission electron microscopy. All analysis techniques showed significant structural changes for BrC-rich samples at the highest temperature level (870 ∘C) in helium. The structure of the heated BrC-rich sample resembles the structure of an unheated BrC-poor sample. Heating the BrC-rich sample to 870 ∘C increases the graphitic domain size within the material from 1.6 to 2 nm. Although the Raman spectra unambiguously show this increase in ordering only at the highest temperature step, UV–VIS and IS analyses show a continuous change in the optical properties also at lower temperatures. The sample with a negligible amount of BrC, however, did not show any significant structural changes during the whole heating procedure.

Organisation(s)
Aerosol Physics and Environmental Physics, Physics of Nanostructured Materials
External organisation(s)
Technische Universität Wien
Journal
Atmospheric Measurement Techniques
Volume
12
Pages
3503–3519
No. of pages
17
ISSN
1867-1381
DOI
https://doi.org/10.5194/amt-12-3503-2019
Publication date
07-2019
Peer reviewed
Yes
Austrian Fields of Science 2012
105208 Atmospheric chemistry, 103039 Aerosol physics, 103042 Electron microscopy
Portal url
https://ucris.univie.ac.at/portal/en/publications/structural-changes-of-cast-soot-during-a-thermaloptical-measurement-protocol(3e4fcf6c-fb06-4bf5-82d4-1793f4cdaa5a).html