Direct Casting Techniques - Temperature Induced Forming
Direct Casting Techniques are based on constant volume, i.e. the gelation of a liquified slurry is achieved without removal of the dispersing agent (e.g. water). Ceramic particle suspensions with high solids loading (>60 vol.%) are poured into dense molds and solidified by changing the colloidal stability. In this way complex-shaped ceramic green bodies can be achieved. My group in collaboration with Prof. Aldinger from the Max-Planck-Institute for Metals Research in Germany introduced one of the simplest direct casting techniques that is based on commercially available inexpensive compounds. This technique is referred to as Temperature Induced Forming (TIF) since the coagulation of a dispersed slurry is induced via a mild increase in temperature. The technique is based on a combination of fundamental science from solution chemistry and colloid stability.
This novel direct casting technique has been successfully applied to alumina, zirconia, and mullite powder systems, zirconia-toughened-alumina, zirconia-toughened-mullite, yttria-stabilized-zirconia binary ceramic powder systems, and yttiria-magnesia-stabilized-zirconia ternary ceramic system. We study the rheological behavior of the casting slips and developed a novel concept to quantitatively predict the gelation and wet green strength of a gelled body via a combination of percolation and crystallization theories.