Detecting Carbon in Carbon: Application of Differential Charging to Obtain Information on the Chemical Identity and Spatial Location of Carbon Nanotube Aggregates in Composites by Imaging X-ray Photoelectron Spectroscopy
Justin M. Gorham, William A. Osborn, Jeremiah W. Woodcock, Keana C. Scott, John M. Heddleston, Angela R. Hight Walker, Jeffrey W. Gilman
The surface contributions and dispersion properties of multiwalled carbon nanotubes (MWCNT) within a composite are important measurements to perform on nano-enabled products in order to help answer environmental health and safety questions associated with nanomaterial risk assessment. In the current study, a novel X-ray photoelectron spectroscopy (XPS) method was developed which enables chemical imaging of MWCNT aggregates near the composites surface by exploiting differential charging. Local regions of high graphitic carbon concentrations did not charge, as is consistent with conductive surfaces, and were spectrally well separated from their more insulating counterparts. XPS imaging revealed these highly localized regions of conductivity, presumably due to MWCNT aggregation, within the well dispersed composite. Multiple sample concentrations were studied including (1, 4 and 5) % by mass MWCNTs within an epoxy matrix. Images acquired at one spot in periodic energy intervals were processed using custom algorithms designed to efficiently extract spectra from regions of interest. Raman imaging and scanning electron microscopy were employed as orthogonal techniques for validating this XPS-based methodology. Application of XPS imaging on composite samples of varying conductance has been demonstrated to be an effective means of chemically detecting MWCNT aggregates in polymer composites while simultaneously assessing dispersion quality.
, Osborn, W.
, Woodcock, J.
, Scott, K.
, Heddleston, J.
, Hight, A.
and Gilman, J.
Detecting Carbon in Carbon: Application of Differential Charging to Obtain Information on the Chemical Identity and Spatial Location of Carbon Nanotube Aggregates in Composites by Imaging X-ray Photoelectron Spectroscopy, Carbon, [online], https://doi.org/10.1016/j.carbon.2015.10.073
(Accessed December 10, 2023)