## 4 Results and Discussion
### Stabilization of CB  
The test procedure that was carried out for graphite dispersions was intended to also have been performed for CB. However, strong sedimentation occurred during the preparation of the dispersions for rheological and zeta potential measurement with both PVP and TX-100, and it was not possible to prepare a dispersion that would have been stable for the duration of the measurements. The measurements showed non-reproducible results with very high standard deviations. Therefore, an optical evaluation was chosen for CB to obtain an initial assessment regarding the suitability of PVP and TX-100.  
The sedimentation behavior was studied for aqueous CB dispersions containing varying contents of PVP and TX-100. Particle settling and sedimentation was observed with all investigated dispersions. In order to characterize the intensity of the sedimentation, the average gray value was plotted for the dispersion as-prepared, after 1 h, and 12 h, with both PVP (see Figure 10) and TX-100 (see Figure 11).  
A clear difference in the average gray values can be observed between the dispersions with and without dispersant for both PVP and TX-100. The average gray value of the dispersions without dispersant are significantly higher than those for the dispersions with PVP or TX-100. The minimum average gray value for the as-prepared dispersion is at 30 m% PVP and TX-100, respectively.  
The average gray values that were obtained for the dispersions with TX-100 are considerably lower than for the dispersions with PVP. However, it is evident that the change in the gray value over time is more significant for TX-100 than for PVP, although the values are still lower for TX-100 than for PVP after 12 h.  
These observations make it clear that TX-100 decelerates sedimentation more effectively than PVP, but it is still not enough to obtain a stable dispersion. It is assumed that the addition of TX-100 breaks up the largest particle aggregates, the agglomerates, while the smaller aggregates remain. Agglomerates and aggregates differ in their forces of  
Figure 11: Average gray value of CB dispersions as a function of TX-100 content at different times (**a**) as-prepared (**b**) after 1 h and (**c**) after 12 h (see Table 16).  
Figure 10: Average gray value of carbon black (CB) dispersions as a function of PVP content at different times (**a**) as-prepared (**b**) after 1 h and (**c**) after 12 h (see Table 15).  
attraction. Agglomerates are formed by the weak attractive forces between aggregates [51]. Aggregates are formed by strong attractive forces between the individual particles [51]. According to [PERSON] et al. [52], aggregates should be preserved, even if this results in larger particles. These aggregates have a strong impact on cluster formation in an electrode. The resulting clusters consist of binding agents with enclosed or attached CB particles. The embedded CB particles are needed in order to build up a conductive matrix that covers the entire cluster volume. Aggregated CB particles are more suitable than primary CB, since the former are stacked in a denser configuration [52]. A binder material, such as carboxymethyl cellulose (CMC), is added in the course of preparing an electrode dispersion. It is assumed that the resulting thickening additionally inhibits the sedimentation of smaller aggregates [25].  
Particle size was subsequently investigated while using syringe filters (Micropur GF 1 \(\upmu\)m, Altmann Analytik, Germany). Virtually any residues remained in the mesh. This corroborates the vast majority of CB aggregates being of smaller size than the threshold \(x_{t}\) for inkjet printing.