Effect of desert-sand replacing pure SiO2 on crystallization, densification and properties of cordierite glass-ceramic

Abstract

Idle desert sand was utilized to replacing pure SiO2 in raw materials to synthesize cordierite glass-ceramics. The effects of desert sand addition on sinterability, phase transformation, microstructure, and mechanical and thermal properties of the glass-ceramics were studied. Results show that glass transition temperature and the crystallization temperatures of glass to μ-cordierite and further to α-cordierite were all monotonously decreased with an increase of the replacement from 10 wt% to 90 wt%. Densification of the glass powder compacts started from 900 °C and was improved with increasing the replacement of desert sand and sintering temperature. The highest bending strength of 133.6 MPa and hardness of 936.7 HV were occurred at 90 wt% replacement when sintered at 1000 °C and 1100 °C for 2 h respectively; the lowest thermal expansion coefficient of 1.92 × 10−6/°C was achieved by a 50 wt% replacement and sintering at 1100 °C for 2 h. Desert sand addition not only introduces main compositions of SiO2, Al2O3, and MgO but also introduces nucleation agents of Fe2O3 and TiO2 and fluxes of Na2O, K2O, and CaO. These impurities had significant effect on improvement of the crystallization, densification, and properties of products. This eliminates the need for nucleation agents and fluxes that are necessary in the case of using pure oxides and minerals as raw materials.

Keywords

• Desert sand
• Cordierite
• Glass-ceramic
• Sintering
• Crystallization
• Densification