Carbon black surface characterization by TOF-SIMS and XPS

The functional groups present at the carbon black (CB) surface contribute, along with the surface microstructure, to the CB surface activity which is known to be an important parameter for the rubber reinforcing properties. A direct detection of the foreign elements (H, N, O, S, Cl,...) present at the CB surface can be achieved with surface analytical techniques such as rime-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and X-ray Photoelectron Spectoscopy (XPS). The combination of these two techniques is found to be very fruitful. Indeed. although the TOF-SIMS sensitivity is much higher than for XPS, allowing trace detection, this technique suffers from a lack of quantification which can be fulfilled by XPS. The chemical information on the functional groups obtained by both methods is complementary In XPS, this information is deduced from the electron core level chemical shifts which are mainly influenced by the first neighboring atoms; whereas, in TOF-SIMS, the full molecular environment can be detected. Not only information on the surface groups, but also some structural information can be obtained. Indeed, the TOF-SIMS spectra of carbon black exhibit molecular ions which are characteristic of the surface aromaticity (graphene structure) and also specific clusters at high masses which seem to be related to the basic building block of carbon black particles.