Characterization of Dimensions of Carbon Nanotubes using Online Techniques

Burkhard Stahlmecke (1), Lavanya Ravi (1), Nkwenti Azong-Wara (1), CHRISTOF ASBACH (1), Heinz Fissan (1,2), Thomas A. J. Kuhlbusch (1,2)

(1) Institute of Energy and Environmental Technology (IUTA), Division Air Quality & Sustainable Nanotechnology, Duisburg, Germany (2) Center for Nanointegration Duisburg Essen, CeNIDE, Duisburg, Germany

     Abstract Number: 265
     Last modified: May 3, 2010

Abstract
Carbon nanotubes (CNT) are one of the major nanomaterials to be incorporated in a broad range of commercial products. Industrial production of CNT has significantly increased over the last few years, making CNT a mass product now. With respect to exposure to CNT in the environment toxicological issues and the question of how to measure exposure to CNT in environmental media are of high importance for risk assessment. This is especially true for the airborne state.
Standard equipment for online measurements of number size distributions of airborne particles is usually based on their electrical mobility for sizing (DMA) followed by a counting device (CPC). The number size distribution measured is based on a calibration with spherical particles of known size. For particles with high aspect ratios, like CNT, the assumption of a spherical particle is no longer valid. In this case the electrical mobility depends on two geometric properties besides the charge: length and diameter. To fully describe the number size distribution of a CNT aerosol both properties have to be measured simultaneously.
The current work presents the development of a data evaluation procedure for deriving number concentrations as a function of fiber length and diameter. This is an improvement to earlier works that require the assumption of a known CNT diameter.
Model calculations and simulation results will be presented that improve the understanding of charging and airborne transport processes of CNT. The results are compared to analytical solutions and earlier transport-only models. First results of a new transport model that was extended by Monte Carlo simulations of fiber charging are presented together with the results from the new data evaluation procedure for straight fibers.

This work is funded by the German Federal Ministry of Education and Research (BMBF) as part of the Inno.CNT initiative through Grant No. 03X0043D.