Solvent-dependent poly(vinyl pyrrolidone) adsorption and stability in highly loaded tantalum carbide suspensions

EtOH/BA composition regulated PVP retention and suspension behavior. • Apparent retention and near-surface PVP signal followed different trends. • 80 wt% EtOH gave the lowest viscosity and slowest 48 h clarification. • Maximum apparent PVP retention did not give the best suspension performance. Solvent composition can alter polymer adsorption and polymer–solvent interactions, but how these coupled effects govern highly loaded non-aqueous suspensions remains unclear. Here, 75 wt% tantalum carbide (TaC) suspensions containing 4–10 mg g −1 poly(vinyl pyrrolidone) (PVP) were prepared in ethanol/benzyl alcohol (EtOH/BA) mixed solvents. Rheology, sedimentation, particle-size analysis, thermogravimetry (TG), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and solvent-quality calculations were combined to relate suspension behavior to apparent PVP retention, the relative near-surface PVP signal, and PVP–solvent compatibility. The suspension containing 80 wt% EtOH and 8 mg g −1 PVP exhibited the lowest viscosity, the smallest 48 h sedimentation ratio (33.3%, compared with 45.2% and 49.0% at 70 and 90 wt% EtOH, respectively), and the most uniform particle-size distribution. The TG-derived apparent PVP retention indicator followed the order 70 wt% EtOH > 80 wt% EtOH > 90 wt% EtOH, whereas the XPS-derived N 1 s/Ta 4p 3/2 fitted peak-area ratio, R N / T a , followed 80 wt% EtOH > 70 wt% EtOH > 90 wt% EtOH. FTIR showed a shift of the PVP carbonyl band after contact with TaC, while solvent-quality calculations indicated increasingly favorable PVP–solvent compatibility with increasing EtOH content. These results show that the TG-derived apparent retention indicator did not directly correspond to the relative near-surface PVP signal or suspension behavior. The optimum performance at 80 wt% EtOH was therefore consistent with a favorable balance among apparent PVP retention, the relative near-surface PVP signal, and PVP–solvent compatibility. Download: Download high-res image (199KB) Download: Download full-size image