Manipulation of Sintering Behavior by Initial Freeze Pressing an Aqueous Alumina Suspension

Forces created by the expansion of water during freezing (ice formation) are in nature responsible for many significant changes of materials. The coagulation of particles was observed after freezing and thawing of a particles suspension. Here we show how freezing of a suspension can create internal forces comparable with hundreds MPa of conventional pressure. The way of freezing and particle characteristics determine the quantity and character of formed aggregates. The morphology/particle packing of the green body after thawing and drying significantly influences the sintering behavior of the ceramic compact. Our results demonstrate a possibility to substitute an effect of high mechanical pressure by freeze pressing without shape limitations. We anticipate our work to be a novel way to combine various materials with different shrinkage behavior.