Preparation of porous Al2O3 ceramic microspheres by a novel micro-droplet jetting rapid forming method

Porous Al2O3 ceramic microspheres were prepared by a novel micro-droplet jetting rapid forming method using a polyvinyl alcohol (PVA) solution as a binder and a boric acid as a curing agent. The droplet jetting and slurry curing procedures are mainly responsible for the uniformity and production rate of the Al2O3 ceramic micro spheres during this novel method. A slurry with a PVA content of 3 wt % and a solid loading of 45 vol % exhibited a high solid loading and a low viscosity, and it was suitable for the droplet jetting process. The curing process was determined by the cross-linking reaction between the boric acid and PVA, and the Al2O3 ceramic microsphere green bodies had a good and stable formability with a boric acid content of 10 wt %. The size of sintered Al2O3 ceramic microspheres with a good sphericity was precisely controlled in a small range. Furthermore, the sintering temperature had a significant effect on the performance of the Al2O3 ceramic microspheres. With a sintering temperature of 1400 degrees C for 3 h, the Al2O3 ceramic microspheres with a uniform microstructure were obtained, exhibiting superior performances that include a grain size below 5 mu m, a sintered shrinkage of 6.67%, a relative density of 82.1%, an open porosity of 10.6% as well as a crush load of 76 N.