Effect of surrounding polydimethylsiloxane frame and substrate on drying behavior of aqueous alumina suspensions

Abstract

The drying behavior of aqueous alumina suspensions surrounded with and without polydimethylsiloxane (PDMS) frames was studied. The capillary stress generated in the bodies was measured in situ using a cantilever deflection method. The relationship between the capillary stress and the formation of cracks was discussed. Compared with the suspensions dried without surrounding PDMS frames, the drying rates of the suspensions were significantly decreased by the surrounding PDMS frames. By drying a suspension on a strong hydrophilic substrate, the PDMS frame hardly reduced the capillary stress. When drying the suspension on a hydrophobic or weak hydrophilic substrate, the elastic deformation of thick PDMS frames could effectively release the capillary stress and therefore crack‐free ceramic green bodies could be obtained.

Using an added liquid to suppress drying defects in hard particle coatings

“…The sketches in Figure 5a summarize the drying behavior of the regular suspension. These sketches are consistent with the experimental results and confirm the findings of other researchers for film drying of particulate coatings [14,15,19,22,23,31,33]. Initially, the film is supersaturated (Figure 5a 1b.II) and darker region in the center of the cantilever for the dyed sample in Figure 2b.II.…”

“…In summary, capillary suspensions yield uniform coatings devoid of defects such as pinholes and trenches without the need for additives. The absence of polymeric additives reduces subsequent processing steps, such as binder burn out [13,16], and adds value to capillary suspensions with previously unrealized specifications on flat, narrow substrates [14,15,19,22,23,31,33]. The corner flow allows capillary suspensions to be efficiently dried under convective flow in industrial applications [56].…”