Production of sintered three-dimensional ceramic bodies

A freeze-forging method for producing a net-shape transparent sintered three-dimensional magnesium aluminate spinel body of a desired complex geometry, comprising the steps of:

• (a) providing a ready-to-sinter spinel powder consisting of a nanomixture of magnesium aluminate spinel nanoparticles and a uniformly distributed controlled concentration of nanoparticles of an inorganic sintering aid;
• (b) providing a nonaqueous liquefied vehicle comprising a sublimable organic binding agent and having a solidification temperature of from about room temperature to below about 200° C.;
• (c) mixing the spinel powder with the liquefied vehicle to form a homogeneous pseudoplastic spinel mix comprising from about 30 to about 50 weight percent of said spinel powder dispersed in said liquefied vehicle;
• (d) reducing the temperature of said spinel mix to below the solidification temperature of said vehicle to thereby freeze the spinel mix;
• (e) crushing the frozen spinel mix into powdered form;
• (f) cold forging the powdered frozen spinel mix in a mold of said desired geometry to form a solidified green body of said desired geometry;
• (g) densifying said green body by hot pressing or pressureless sintering into a sintered spinel body of said desired geometry and substantially free of said vehicle and said sintering aid;
• and
• (h) subjecting said sintered spinel body to further densification via hot isostatic pressing to thereby substantially eliminate any residual porosity in said sintered body.