Bimaterial composites via colloidal rolling techniques: I, microstructure evolution during rolling

Laminate composites of Al2O3 and ZrO2 fabricated by repeated rolling and fo lding are demonstrated using aqueous slurries of ceramic powders without an y plasticizers or binders. Crack-free composites with a layer thickness of 4-60 mu m have been obtained. A novel interface instability during the roll ing of bimaterial slurries, which leads to the entrapment of the theologica lly harder phase in the softer phase, also has been discovered. This discov ery has been exploited to obtain layered materials, by matching the yield s tress of the slurries, or cellular materials with the desired included phas e, by mismatching the yield stress of the slurries. Adjustment of the yield stress can be realized by varying only the NH4NO3 salt concentration while keeping the pH and the solids loading (64 vol%) constant.