(481f) Effect of Drying Uniformity on Stress Measurement and Cracking of Particulate Coatings

Many industrial products, such as battery electrodes and fuel cell catalyst layers, rely on coatings prepared from particulate suspensions. As a particle-based coating dries, the particle concentration increases until a solid particle network forms. At this critical point, constrained shrinkage results in tensile stress, which can cause cracking. Previous research from Price et al. (J. Am. Ceram. Soc., 2015) employed stress measurement and cryogenic scanning electron microscopy to establish that stress in a drying coating is negligible until this network forms. Then, the stress rises rapidly, reaching a peak of ~1 MPa (for ~1 µm silica particles) when liquid menisci appear within the solid network at the coating surface. The stress drops as drying continues and the pore space empties. They also found that a wall or barrier around the perimeter of the cantilever lessened lateral drying cantilever beam-based stress. The connection between stress development and cracking was not explored in this prior work.

The present study builds on this prior work to characterize stress development in particulate coatings that crack and those that do not. Cantilever beam deflection and in situ video imaging were used to measure stress and follow structural changes in several metal oxide particle coating systems during drying. Silicon cantilevers were equipped with polydimethylsiloxane walls to mitigate the propagation of non-uniform lateral drying fronts. Drying uniformity was also improved using higher-density particles that did not accumulate on the coating surface. Results showed distinct fracture characteristics in the stress profiles of uniformly dried coatings. Our findings highlight how cantilever beam deflection can be used as a diagnostic or screening tool for detecting and studying fracture in drying particulate coatings.