Preparation, characterization, and properties of ceramic foams from waste foundry sand by particle-stabilized foam method

Waste foundry sand (WFS) is a solid waste by-product generated during the sand casting process in foundries. Promoting resourceful recycling of WFS is of significance for environmental and efficient resource utilization. In this study, WFS was used as the raw material to fabricate ceramic foams using the particle-stabilized foam method. The results showed that the ball-milled fine WFS particles in the slurry were able to adhere to air bubbles, leading to the formation of ceramic foams with closed pores after drying and sintering. The liquid phase generated during the sintering process from melted WFS contributed to the development of dense pore walls. The porosity of the ceramic foams first decreased from 30.93% to 22.83%, and then increased to 40.22% with the rise in slurry pH from 2 to 5. Moreover, the porosity gradually decreased from 49% to 3% as the sintering temperature increased from 1000°C to 1300°C. The variations in the pore structure significantly influenced their properties. The WFS-based ceramic foams were produced with 0.68‒1.32 g/cm 3 volume density, 32.4‒210.3 MPa compressive strength, and 0.18‒0.87 W/(m K) thermal conductivity. This study facilitated the reuse of WFS, enhancing cost-effective, efficient production of high-performance ceramic materials for building insulation.