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Innovative Green Bio-Filler and Bio-Flux Calcium Carbonate from Eggshells to Hard-Soft Porcelain Preparation

Tangboriboon N, Selarak P, Shamunee P, and Sirivat A

Calcium carbonate (CaCO3) powder was prepared from raw coturnix bird eggshells acted as a bio-ceramic material. Embedding raw bird eggshell powder in porcelain products can increase physical, thermal, and mechanical properties. The main composition of raw bird eggshell is calcium carbonate or calcite more than 97.44% wt and other oxide compounds. CaCO3 can react with silica (SiO2) and alumina (Al2O3) in porcelain clay via slip casting process at room temperature. When porcelain products were fired, the phase can transform to calcium feldspar or anorthite (CaAl2Si2O8). Anorthite is one kind of feldspars and can reduce firing temperature called sintered aid. However, the excess amount of eggshell added into porcelain and fired at very high firing temperature and long firing time affects to crack and brittle samples. In this study, the amount of 0, 5, 10, 15, and 20% vol raw bird eggshell powder was added, mixed with porcelain slip containing sodium silicate as a dispersing agent to prevent particles agglomeration, and fired at 600°, 700°, 800°, and 900°C for 1, 3, and 5 h at each firing temperature. The best porcelain product is the sample encoded 10-5-900. It means 10% vol raw bird eggshell adding, soaking time for 5 h, and firing temperature at 900°C. The XRD phase transformation, true density, thermal expansion coefficient, and mechanical properties are reported here.