Determination of optimum slurry evaluation method for the prediction of BaTiO₃ green sheet density

Abstract

In this study, the particle dispersion state in a dense BaTiO 3 slurry containing a dispersant and binder was assessed by various slurry evaluations such as particle size distribution measurement by laser diffraction, viscosity measurement, dynamic viscoelasticity measurement, and hydrostatic pressure measurement, which is a novel slurry evaluation technique developed by our group. Then, the relationship between the slurry evaluation results and the packing fraction of green sheets fabricated from these slurries was discussed. We found that the particle size distribution and the relative viscosity and yield stress by dynamic viscoelasticity measurement could not properly estimate the packing fraction of green sheets. In contrast, the hydrostatic pressure measurement was able to distinguish the particle dispersion state, and the results show an acceptable correlation with the packing fraction. The reason is that our developed method evaluates not only the initial particle dispersion state, but also its change as the particle concentration increases. ARTICLE HISTORY

Effect of medium condition change on green body density during casting and drying

“…These authors reported that this was caused by insufficient inter‐particle repulsion forces, the interaction between the dispersant and the binder, and the degradation of the dispersant by the dispersing process. In our past studies, which examined pH‐controlled alumina slurry 24,25 and slurry containing PCA and PVA, 32,39 the change of particle dispersion state in the slurry during sedimentation had already been confirmed; so it was expected that this phenomena would also occur in the current study. Consequently, a verification test to confirm it was conducted, and the changes of particle dispersion state were demonstrated, as shown in Figure .…”

“…Generally, a slurry whose particles are well dispersed has low apparent/relative viscosity and is assumed to form a dense sediment; however, our study demonstrates different results. Some findings reported in previous studies indicated that the apparent viscosity of the just‐prepared slurry did not completely correlate with the packing fraction of the sediment, or the particle dispersion state changed over time 24,25,32,37–39 . These authors reported that this was caused by insufficient inter‐particle repulsion forces, the interaction between the dispersant and the binder, and the degradation of the dispersant by the dispersing process.…”

“…We have proposed a slurry evaluation technique using a hydrostatic pressure method based on the particle sedimentation phenomena reported in several studies 24–32 . Additionally, in a previous study, this technique was applied to an aqueous dense barium titanate slurry, which demonstrated that the relationship between the measurement result and packing fraction of green sheet had a better correlation than other slurry evaluations 32 . In addition to highlighting the importance of direct measurement without dilution for tape casting slurry, this report 32 showed that the evaluation of particle settling and the sedimentation process simulating the drying and condensation of green sheet was necessary.…”

Evaluation of alumina slurry dispersion by nuclear magnetic resonance relaxation as a comparison to conventional dispersion evaluation methods

“…Ceramic slurries are of great importance in applications ranging from ceramic manufacturing processes to ceramic shaping processes such as slip-casting, tapecasting, and spray-drying. [1][2][3] In the ceramic manufacturing process, the dispersion characteristics of the powder affect the physical and sintering properties of the slurry. Here, dispersion refers to a state in which solid particles are homogeneous and form a stable suspension in a solvent.…”

Investigation of the effect of surface phosphate ester dispersant on viscosity by coarse‐grain modeling of BaTiO slurry

“…Enabling the creation of a computational connection between the rheological characteristic of the slurry and the dispersion and aggregation states of the particles would be useful, because slurry is often practically evaluated by measuring viscosity, which is fast and easy to perform. [16][17][18][19][20][21][22][23] The adsorption of dispersant for various particles was also studied by molecular dynamics (MD) simulations and density functional theory (DFT) calculations because the behavior of dispersant close to the solid surface plays a major role in predicting the rheological characteristic of a slurry. [24][25][26] Numerous experiments and theoretical simulations have been performed for the optimization of slurry preparation, but a molecular-level exploration of the microstructurerheology relationship is still lacking.…”