Mullite Ceramics Derived from Fly Ash Powder by Using Albumin as an Organic Gelling Agent

Mullite is a combination compound of alumina (Al2O3) and silica (SiO2). During the last two decades, mullite ceramics have become the crucial oxide material for both traditional and advanced applications due to their favorable properties, such as good strength at very high temperatures, low density, good thermal shock resistance, and chemically stable. Mullite is also known for its stoichiometry 3Al2O3.2SiO2, or sometimes it is called 3/2 mullite. In this present investigation, the authors attempt to fabricate mullite-based ceramic through a gel casting process by using an organic binder (egg white) to consolidate powder particles, followed by low-temperature sintering. Fly ash powder, china clay powder, and alumina powder were used as raw materials to make mullite ceramic. Green bodies were fabricated by taking various proportions of fly ash, china clay, and alumina, followed by sintering at 1200C, 1250C, and 1300C for 2 hours. The stability of slurries was studied by measuring zeta potential, and green sample fracture surfaces were analyzed by Field Emission Scanning Electron Microscopy (FESEM). Physical properties of sintered samples, such as linear shrinkage, density, porosity, and water absorption, were also calculated. Evidence of mullite formation was characterized by Field Emission Scanning Electron Microscopy (FESEM scanning electron microscopy (SEM) techniques. The samples containing 45 wt.% fly ash, 15 wt.% china clay, and 40 wt.% aluminas showed the best physical properties compared to other batch compositions and were well supported by the results obtained from FESEM results.