Increasing Wet Green Strength of Alumina Body During Microfabrication by Colloidal Isopressing

摘要

Colloidal Isopressing involves formulating a slurry with a weakly attractive particle network that can be pre-consolidated to a high relative density by pressure filtration and still retain fluid-like characteristics. The pre-consolidated slurry is injected into an elastomeric mold and isopressed. Isopressing rapidly convert the slurry into an elastic body that can be removed from the mold without shape distortion. Not only is this process rapid, but since the water saturated compact produced by this method does not shrink during drying, it can also be converted into a dense body without a long drying period. It is demonstrated that micron-size surface features, such as 5 micrometers wide channels with a depth/width ratio of 2, can be rapidly produced on the surface of alumina powder compacts. It was shown that surface features of this size were enabled when the saturated, isopressed body was strengthened. Namely, the fracturing of thin vertical portions of a micro patterned surface during pressure release and demolding is an obstacle to obtaining micron size features with high aspect ratios. It was shown that concentration controlled gelation of a PVA-Tyzor(Registered) TE additive effectively increased the strength of the elastic, isopressed body, saturated with water, while maintaining the low viscosity of the pre-consolidated body, which is required for transfering the pre-consolidated slurry into a rubber mold prior to isopressing.