Preparation of low-cost foam ceramics with mullite extracted from fly ash

Abstract

Foam ceramic materials with uniform pore structure were prepared by adopting organic foam impregnation method using mullite (0.0450.075mm) extracted from fly ash as raw materials, aluminum dihydrogen phosphate and kaolin (0.0450.088mm) as bonding reagent and plasticizer, respectively. The influence of phosphate content, solid (mullite and kaolin) content and ball-milling time on performance of mullite slurry has been investigated. Especially, the relationship between various properties of the slurry and obtained foam ceramics have been discussed. Furthermore, the physical properties and sintering behaviors of the as-prepared samples at different temperatures were systematically investigated. The result indicated that a high-quality slurry with low sedimentation degree, suitable viscosity and small particle D50 can be prepared under the condition of phosphate content of 12.5 mass%, solid phase content of 62 mass% and ball milling time of 8 h. Finally, the mullite foam ceramic products with a compressive strength of 1.62MPa, an apparent porosity of 87% and a thermal shock resistance of 13 times were prepared after sintering at 1450 °C for 4 h.