Wet forming of concentrated nano-BaTiO_3 suspensions

摘要

Nanostructured materials are currently being studied extensively due to their unusual physical and mechanical properties. One of the most important dielectric materials is barium titanate (BaTiO_3). Capacitors made of this material offer excellent frequency characteristics, high reliability, high breakdown voltage and excellent volumetric efficiency. It is believed that these properties may be significantly improved by achieving a structure at the nano-scale. In this work, nano-BaTiO_3 powders have been formed into complex-shaped green bodies using gelcasting as colloidal forming route. This procedure has been demonstrated to be very effective for shaping submicron-sized powders and in this manuscript the achievement of this technique for the shaping of nanosized powders is evaluated. The first step was the preparation of stable concentrated suspensions of the nanopowders through the optimization of the quantity of dispersant and time of homogenization. This was found to depend on the method of manufacture of the different commercial nanopowders investigated. Bulk components were then manufactured using aqueous gelcasting involving polysaccharides that gel on cooling. The performance of this consolidation technique for obtaining dense green bodies from the BaTiO_3 nanopowders will be discussed.