Design and characterization of porous mullite based semi-vitrified ceramics

Three porous ceramic composites were prepared from readily available raw materials (kaolin, bauxite, feldspar and kyanite). The porous ceramic formulations were sintered at different temperatures ranging from 1200 to 1400°C. The fired specimens were characterized by determining their porosity, bulk density, flexural strength, thermochemical stability, microstructure, water and mercury permeability. Apparent porosity and bulk density in the range 15.57 ± 1.56-42.73 ± 2.28 vol% and 2.23 ± 0.31-2.68 ± 0.41 g cm−3 respectively were obtained after firing. The flexural strength was in the range of 32.31 ± 2.1-74.88 ± 2.57 MPa and the thermal expansion coefficient of 5-9 × 10−6 C−1. The values of water permeability were 745.4, 641.45 and 525.91 L/m2 h kPa respectively for PK3, PK4 and PK5. It was found that at high temperature (1400 °C), kyanite particles enhanced the porosity and thermal stability by reducing glass formation and improving crystallization. The presence of the interconnected pores with size between 0.03 and 4.50 µm, the high total volume of pores together with the high flexural strength and thermal stability make the synthesized porous ceramics suitable for high-pressure filtering applications.