Processing of Alumina Ceramics with Ultrahigh Porosity by Composite Poring Mechanisms

摘要

Alumina ceramics with ultrahigh porosity were fabricated by composite poring mechanisms of template and foaming.Light-weight polymer balls as solid template were added into the alumina slurry foamed with surfactants,which was solidified by gelcasting.The porosity was accurately tailored between 84.9 ％ to 90.4 ％ by changing the quantities of the added balls and foaming agent.The pores have two sizes:big pores of 1～2 mm due to balls and small pores of 100～200 μm due to bubbles.The compressive strengths of porous ceramics were 2～6 MPa.The thermal conductivity was 0.28 W·m-1·K-1 at 1000 °C for ceramics with the 90.4 ％ porosity.The material can be used as high-temperature heat insulators to save energy.