Stress Development During Drying of Aqueous Zirconia Based Tape Casting Slurries Measured by Transparent Substrate Deflection Method

During drying of water-based tape casting slurries, high stresses can occur, which lead to crack formation. Under the variety of different techniques to measure the drying stresses, the deflect measurement technique is very common. Due to the nontransparent substrate, this technique has the disadvantage, that a direct observation of the changes in the drying regions during the drying process is not possible. Thus, it cannot be ensured that homogeneous drying occurs, which is the prerequisite for the validity of the Corcoran's equation. Nonuniform drying causes cracks and might lead to errors in data interpretation, if nonuniformity of drying is not visible. To make drying uniformity visible, the deflect measurement technique was improved by the usage of a transparent substrate. The benefit of the new technique is the direct observation of saturation uniformity during drying. The differentiation of nonuniform drying and uniform drying, which is characterized by an optimum permeation of the solvent to the surface, is ensured. The advantage of the method is demonstrated by the characterization of the drying behavior of water-based stabilized zirconia slurries in the presence of dispersants and latex binders. Particularly with regard to slurries containing latex particles as a binder, progress was achieved in understanding drying. Measures to decrease drying stresses are summarized.