Improvements in sintering by optimizing the colloidal processing

GUSTAVO SUÁREZ

Tsukuba, Japon.

Simposio; MANA symposium 2009. WPI-MANA World Premier International Research Center (WPI)- Center for Materials Nanoarchitechtonics; 2009

Colloidal processing of nano powders is the most important and the initial step in ceramics conformation and it is proved to be to the way to control and improve some properties [1]. Ultrasonication treatment is a very useful deagglomeration process but heavy agglomerated particles can not be re-dispersed. In order to re-disperse these blocks of particles we apply the “bead-milling” treatment using 50 µm beads and high rotation speed. The use of small attrition media it is proved very effective to break the agglomeration [2]. In this work we are presenting the advances in deagglomeration by using the bead-milling treatment. Tetragonal zirconia presents better sinterability if the slip-cast samples are prepared with treated suspensions [3]. Bead-milling of a mixture 3mol% yttria with 97mol% monoclinic zirconia can produce by reaction sintering an homogeneous nanostructure sintered by two step sintering and presents a finer structure than 3YTZ prepared under the same conditions (figure). It is known that carbon nanotubes (CNT) can improve mechanical properties and electrical conductivity of some ceramics when they are forming composites but one of the biggest problems is the dispersion of the CNT in water. Bead-milling can disperse and well mix the zirconia with CNT homogeneously. Bead-milling treatment it was also tested in heavy agglomerated powder synthesized in our laboratory five years ago. This powder presents heavy agglomeration difficult to re-disperse with ultrasonication but suitable to prepare good dispersion by bead-milling. The re-dispersion of agglomerates can be followed by the measurement of particle size. In the table 1 are presented some results.