Method and apparatus for forming variable density sintered ceramic using application of alternating voltage to aqueous ceramic suspension with ice-templating

A method of forming variable density ceramic structures, the method comprising:

• obtaining a ceramic powder having an ultrafine particle size;
• mixing the ceramic powder into a suspension fluid thus forming a ceramic suspension, the ceramic powder concentration in the suspension fluid being 20-35 vol. % solid loadings;
• providing a mold configured to retain the ceramic suspension, the mold being provided as PTFE Fluoropolymer;
• providing a plurality of electrodes about the mold;
• applying an alternating voltage to the plurality electrodes thus forming alternating electric currents through the suspension thus causing accumulation of ceramic particles on at least one of the electrodes, the voltages being applied between 100-190 volts at 0.1-2000 kHz for 3-10 minutes;
• reducing the temperature of the suspension thus inducing the formation of ice crystals therein;
• removing the plurality of electrodes without having ceramic particles formed thereon;
• freezing the ceramics suspension until the suspension fluid is completely frozen;
• drying the frozen ceramic suspension into a porous accumulated state by exposing the ceramic particles to freeze drying conditions of the suspension fluid;
• sintering the ceramic particles into a solid architecture retaining a common final structure with the ceramic particles in the porous accumulated state;
• wherein:
• the particle size of the ceramic powder being approximately 1 μm;
• the suspension fluid is deionized water;
• and one of the electrodes is configured to act as a Cold-finger;
• reducing the temperature of the Cold-finger below the freezing point of the suspension by exposing the Cold-finger to liquid nitrogen fluid;
• and varying the size of the ice crystals and a freezing rate of the suspension fluid by varying a distance between the Cold-finger and the liquid nitrogen.