State of the Dispersant and Particle Surface During Wet‐Jet Milling for Preparation of a Stable Slurry

Abstract

Wet‐jet‐milled alumina slurries exhibited distinctly different stability behavior compared with ball‐milled ones in terms of reflocculent efficiency and rheological properties. The distinction was attributed to the different behavior of the same dispersant (NH4+ salt of poly(acrylic acid); PAA–NH4+) in ball milling and wet‐jet milling. Alumina particles after the wet‐jet milling retained the initial surface conditions, although ball‐milled alumina particles yielded more hydroxyl groups on the surface. Furthermore, degradation of dispersant on milling was investigated qualitatively. Infra‐red analysis and isoelectric point measurements suggested that degradation of the dispersant occurred during ball milling, indicating neutralization of the dispersant due to formation of monodentate COOX groups. On the other hand, in the case of wet‐jet milling, COO− groups of PAA–NH4+ were not degraded at all, indicating maintenance of the structures of dispersant with electrostatic repulsion. Change in the polymer size of the dispersant by different milling methods was confirmed using high performance liquid chromatography (HPLC) measurements. The HPLC results of the wet‐jet milled samples showed that a dispersant with a larger molecular size was generated. Force measurement on approach via the colloid probe method in the centrifuged supernatant of the milled slurries confirmed that the interaction distance between an α‐alumina colloid probe and c‐sapphire surface was about two times larger in the wet‐jet‐milled slurry supernatant compared with the ball milled one. Thus, it was found that wet‐jet milling process led to a stable slurry because of the maintenance of not only steric repulsion but also electrostatic repulsion.

Effects of Milling pH and Hydrothermal Treatment on Formation of Nanostructured Boehmite Binder for Alumina Extrusion

“…Some isolated polycrystalline nanometric agglomerates were also observed in these powders (Figure 3(f)) but were absent in the powder milled under acidic pH condition. Similar coatings of low density aluminum trihydroxides were also observed in ball milled -alumina powders in other studies [33][34][35]. These results confirm that hydration occurs on the surface of alumina particles, in a process that is intensified under milling.…”

Fabrication of transparent MgAl2O4 spinel through homogenous green compaction by microfluidization and slip casting

“…reported that microfluidization enhances the electrostatic repulsion between the particles without degrading the dispersant or the particle surface and enhances the steric repulsion by increasing the average polymer molecular weight and length, which increases the interparticle distance and slurry stability [20]. Fig.…”

“…However, most studies in the field of ceramic processing have not specifically investigated the microfluidization process. Limited studies of Al 2 O 3 and ZnO using wet-jet milling were conducted by only one research group of AIST in Japan [20][21][22][23].…”

Fluidity of methyl cellulose-contained suspensions and pastes prepared from differently milled Al2O3 powder

“…In addition, cavitation, turbulent and shear flow are induced at high speeds. In our previous works, it has been demonstrated that the wet-jet milled suspensions exhibited distinctly different stability behavior as compared to ball-milled ones in terms of reflocculation efficiency and rheological properties [18,19]. Furthermore, the authors also showed that the surface of wet-jet milled particles was not damaged because the given collision energy during wet-jet milling was significantly smaller than that of during ball milling [18].…”