Research on Humidity Resistance of Sodium Silicate Sand Hardened by Twice Microwave Heating Process

Abstract

To study the high moisture absorbability of the sodium silicate boned sand hardened by microwave heating, a new special water-based coat sprayed on the surface of the sand samples hardened by the first microwave heating and then sintered by the second microwave heating to form a compact coating layer was studied. The results showed that humidity resistance of the sand samples with the coating layer had great improvement compared to the sand samples without the coating layer, the compression strength (σ _4h ) of the sand samples with the coating layer increased 2.62 times than that without the coating layer. Scanning electron microscope (SEM) and X-ray diffraction (XRD) have been used to investigate phase and composition of the compact coating layer. The SEM analysis showed that the coated sand samples formed the compact layer which could greatly improve humidity resistance of the sand samples. The line scanning analysis confirmed that the coat composition appeared on the surface of the coated sand samples, and the surface XRD analysis demonstrated that the surface of the coated sand samples consisted of four new phases, including PbTiO₃, NaAlO₂, Pb₆Al₂Si₆O₂₁ and Al₂SiO₅, which are the main materials for increasing humidity resistance.

Keywords:

• Casting
• Coating
• Heating
• Humidity
• Microwave
• Resistance
• Sand
• Silicate
• Sodium
• Strength

Notes

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