Synthesis and Characterization of BaTiO_3-Based Foams with a Controlled Microstructure

摘要

BaTiO_3 foams were synthesized via the direct foaming method using commercial powders. In order to control the microstructure and by extension the properties, synthesis parameters such as foaming agent, composition, sintering time, and sintering temperature were varied to determine their influence. The effect of each parameter on the microstructure was measured and characterized using scanning electron microscopy, image analysis, helium pycnometry, and mercury porosimetry. Microstructure was classified in terms of strut characteristics, average grain size, average cell window size, porosity, and grain boundary integrity. For example, foams with 30% ceramic volume were synthesized using a laboratory-developed and a commercial polyurethane (PU) system, both silicon (Si) free. When sintered at 1400℃ for 8 h, they produced thick, dense struts and uniform pore-size distributions, although with different characteristics. The foam prepared with the laboratory-synthesized PU had a porosiry of 90%, an average grain size of 44.4 μm, and an average cell window size of 66.7 μm, while the foam prepared with the commercial PU had a porosity of 87%, an average grain size of 20 μm, and an average cell window size of 99 μm.