LAUSR

Abstract A new ternary-phase binder system incorporating alumina (Al2O3) precursors was successfully developed through process control to improve the sand mold's strength for casting of large objects. Three types of Al2O3 precursors with different molecular structures, such as Al(OH)3, Al(OEt)3, and Al(NO3)3 were employed in the ternary-phase binder system. A dual-dipping process was developed. The first dipping includes the ternary-phase binder composition and heat treatment at 1000 or 1200 °C. The second dipping uses a binary-phase binder composed of TEOS and NaOMe and heat treatment at 1000 °C. The results show that sodium aluminosilicate was synthesized in the ternary-phase binder at both temperatures, and amorphous silica was formed only in the ternary composition of TEOS/NaOMe/Al(OEt)3. In contrast, sodium silicate was formed in the binary-phase binder. The strength of the mold prepared with precursor Al(OEt)3 was higher than those with Al(OH)3 and Al(NO3)3, due to its improved glassification efficiency of Al(OEt)3. Additionally, the mold strength was increased with increasing content of TEOS in the ternary-phase binder composition. Finally, the optimal highest strength was obtained with the ternary-phase binder composition of TEOS/NaOMe/Al(OEt)3 in the mole ratio of 5:1:1.