Mullite porous ceramics with high strength for high-temperature thermal insulation

Abstract

To address the low thermal efficiency and serious energy consumption of industrial kilns, the gel casting method is used herein for the successful preparation of porous mullite thermal insulation materials with good thermal and mechanical properties. The effects of poly-γ-glutamic acid (γ-PGA) content (0.6–2.2 wt%) on the performances of the slurries, green bodies, and sintered bodies are comprehensively investigated based on the gelation mechanism. The mullite slurries show good flowability and stability, and the powders are evenly dispersed. Furthermore, the green bodies have sufficiently high mechanical strengths to meet the conditions of processing into complex shapes. The sample open porosity is shown to increase, and the pore size gradually becomes more uniform, as the γ-PGA content is increased. At a γ-PGA content of 1.8 wt%, the open porosity reaches 75.85 %, the compressive strength is 14.02 MP. The thermal conductivity increases from 0.263 W/(m⋅K) to 0.544 W/(m⋅K) as the temperature increases from 25 °C to 1000 °C. At the same time, the Gong model accurately describes the relationship between the thermal conductivity and porosity. In addition, infrared thermographic analysis and alcohol lamp ablation experiments macroscopically demonstrate the excellent thermal insulation performance of the porous mullite at high temperatures.