Effect of Silica Nanoparticle Dispersion on Flexural Strength of Sand Mold with Sodium Silicate Binder

Abstract

Sodium silicate solutions are used as an eco-friendly binder in the casting process. However, the strength of sand molds using the sodium silicate solutions is reduced because of their low humidity resistance. In this study, silica nanoparticles were added to a sodium silicate solution with a constant SiO2/Na2O ratio to improve the humidity resistance of the inorganic binder. The effects of the dissolution times and particle size of the silica on the flexural strength of the molds was also investigated. The physiochemical properties of the inorganic binders were characterized by viscometer, Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). Sand molds for the flexural strength test were prepared by mixing artificial sand and inorganic binders. The addition of silica nanoparticles reduced the viscosity and water evaporation rate of the inorganic binders and improved the humidity resistance of the molds due to an increase in the SiO2/Na2O ratio. The flexural strength of the molds increased as the size of the silica nanoparticles increased, due to formation of discrete silica aggregates with high surface area. However, as the dissolution times of the silica nanoparticles increased, the strength of the molds decreased due to an enhanced Q2/Q3 ratio. Therefore, we suggest that the addition of silica nanoparticles will improve the humidity resistance of molds, and that varying the particle size and dissolution time of the silica nanoparticles affects the strength of the molds.

Enhancement of Flexural Strength by Slip Casting Cordierite Ceramics with h-BN Nanoparticles

“…At the same time, the controlled microstructure and reduced grain size induced by the addition of h-BN contribute to the improved mechanical properties of the material. It is noted that the flexural strength reached its highest value in the sample with 2 wt% added h-BN nanoparticles, while the sample with 3 wt% addition showed rather lower flexural strength due to the agglomeration of h-BN nanoparticles [16], as depicted in Figure 3(e). This result suggests that the change in the rheological characteristics of the slurry, which originates with the addition of nanoparticles, is a crucial factor in the manufacturing of the nanocomposite through slip casting.…”