Leveling and thixotropic characteristics of concentrated zirconia inks for screen-printing

• Published in: Rheologica acta 2009-03, Vol.48 (2), p.121-133
• Main Authors: Phair, John W., Lundberg, Mats, Kaiser, Andreas
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Characterization and Evaluation of Materials; Chemical industry and chemicals; Chemistry and Materials Science; Complex Fluids and Microfluidics; Cross-disciplinary physics: materials science; rheology; Deformation; material flow; Ethyl cellulose; Exact sciences and technology; Food Science; Green strength; Inks; Leveling; Materials Science; Mechanical Engineering; Microscopy; Miscellaneous; Optical microscopy; Original Contribution; Physics; Polymer Sciences; Printing; Recovery; Rheological properties; Rheology; Rheometry; Scanning electron microscopy; Shear rate; Soft and Granular Matter; Solid oxide fuel cells; Surface roughness; Technical ceramics; Thick films; Thickness; Thixotropy; Thixotropy; thickening flows; Viscosity; Yield strength; Yield stress; Zirconium dioxide
• ISSN: 0035-4511; 1435-1528
• DOI: 10.1007/s00397-008-0301-4

Screen-printing is a cost-effective method for the mass manufacture of zirconia-based solid oxide fuel cells (SOFCs) and oxygen separation membranes. The present work outlines an investigation into the leveling, thixotropic, and screen-printing characteristics of concentrated zirconia inks by a variety of rheological and imaging methods. A combination of viscosity, shear rate jump experiments, creep and recovery analysis, and yield stress measurements were used to assess ink thixotropy. Oscillatory rheometry and scanning electron microscopy/optical microscopy revealed a consistent effect of ethyl cellulose (binder) content upon the thixotropic and leveling characteristics of zirconia inks. While the yield stress ( τ 0 ), extent of recovery R(%), and rate of recovery (K) increase with increasing binder content, so did the surface roughness and thickness of the screen-printed films. Increasing the binder content not only increases the network strength of the thick films but also leads to increased leveling time. As a result, rheological modifiers are proposed to be necessary to improve the leveling characteristics of zirconia inks without losing the green strength of the thick films.