Understanding rheology and sedimentation of ultra-high temperature ceramics for digital light processing based additive manufacturing
Article
Agarwal, V, Nisar, A. (2025). Understanding rheology and sedimentation of ultra-high temperature ceramics for digital light processing based additive manufacturing
. CERAMICS INTERNATIONAL, 10.1016/j.ceramint.2025.09.427
Agarwal, V, Nisar, A. (2025). Understanding rheology and sedimentation of ultra-high temperature ceramics for digital light processing based additive manufacturing
. CERAMICS INTERNATIONAL, 10.1016/j.ceramint.2025.09.427
The processability of ultra-high temperature ceramics (UHTCs) in digital light processing (DLP) depends critically on the rheology and stability of ceramic-resin slurries. This study investigates the flow behavior, dispersant effects, and sedimentation characteristics of tantalum carbide (TaC), a high-density UHTC and titanium carbide (TiC), a comparatively lower-density UHTC slurries with 30–50 wt% solid loading in a photocurable resin. Increasing UHTC loading resulted in a nonlinear rise in slurry viscosity, primarily due to intensified interparticle crowding and agglomeration, which hindered particle mobility and disrupted flow homogeneity. TiC slurries showed stronger shear-thinning (∼66 % viscosity drop) and higher storage modulus than TaC, indicating better flow under shear and structural resilience. Sedimentation, evaluated via Stokes’ law and 24 h tracking simulation, was significantly lower for TiC (10.4 ± 0.4 wt%) compared to TaC (28.9 ± 0.6 wt%), owing to differences in particle density and suspension microstructure. Further, polyacrylic acid (PAA) was added as a dispersant to TaC slurry to prevent ceramic particle agglomeration. PAA reduced TaC slurry viscosity at 0.2 wt% via electrostatic and steric stabilization, but higher concentrations increased viscosity due to polymer entanglement. TiC slurries showed minimal dispersant benefit, likely due to early surface saturation. A 50 wt% TiC slurry (no dispersant) and a 45 wt% TaC slurry (0.2 wt% PAA) were selected for DLP trials. The TiC slurry achieved a curing thickness of ∼240 μm and produced coherent prints, while TaC exhibited poor curing and delamination due to sedimentation and light attenuation. Debinding of TiC parts led to cracking from trapped volatiles and resin gradients. These results demonstrate how interparticle interactions, rheology, and dispersant dynamics collectively influence slurry stability and DLP compatibility, providing a framework for printing high-density UHTCs.
