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Abstract
The present study focuses on the etching conditions and mechanism of MgO-Al2O3-SiO2 glass-ceramic (MAS) in hydrofluoric acid (HF). The results show that the amorphous phase has 218 times higher etching rate than pure cordierite crystal at room temperature. In addition, the activation energies of cordierite and amorphous phases in the HF solution are 52.5 and 30.6 kJ/mol, respectively. The time (tad) taken for complete dissolution of the amorphous phase depends on the HF concentration (CHF). Based on the etching experiments, a new model is established and refined to assess the tad evolution. In addition, a highly crystalline cordierite phase, with the high specific surface area (59.4 m2·g−1) and mesoporous structure, has been obtained by HF etching. This paper presents novel insights into the etching chemistry and opens up avenues for further research in the area of cordierite-based catalytic ceramics.
Highlights
Cordierite ceramic is an excellent choice as a catalytic converter substrate for automobile exhaust purification due to its outstanding properties such as low thermal expansion coefficient, high chemical durability, and desirable refractories [1,2,3]
The ratio of the Figure amorphous versus crystalized phase can be approximated to 7:13.theAdditionally, low1 presents the XRD
MgO-Al2O3-SiO2 glass-ceramic (MAS), which exhibits hexagonal (PDF#48-1600), which is the with the space group
Summary
Cordierite ceramic is an excellent choice as a catalytic converter substrate for automobile exhaust purification due to its outstanding properties such as low thermal expansion coefficient, high chemical durability, and desirable refractories [1,2,3]. A pine-like dendritic structure cordierite, as the main crystal phase, has been prepared based on MgO-Al2 O3 -SiO2 glass-ceramic (MAS), and the size of crystal gap in the dendritic cordierite is nanoscale [7]. He et al enlarges the surface area of porous cordierite ceramic prepared by the compression molding method to 19.47 m2 ·g−1 by acid treatment [8]. Few studies have been reported on Materials 2018, 11, 1631; doi:10.3390/ma11091631 www.mdpi.com/journal/materials
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