Synthesis and phase transformations of mullites obtained from SiO2Al2O3 gels

Infrared and Mössbauer studies of iron in aluminosilicate glasses

“…1). The band around 800 cm À1 is characteristic of symmetric stretching vibrations of SiO 4 units [15]. This band exhibits a shift toward lower wave number at 1200 and 1300°C.…”

“…In the spectra of the samples heat-treated at 1000, 1200 and 1300°C a band near 600 cm À1 (Fig. 1) can be attributed to the vibrations of FeO 4 [13], AlO 4 or AlO 6 [15] units. In all the samples a band near 470 cm À1 is present.…”

Effect of boron oxide on the microstructure of mullite-based glass-ceramic glazes for floor-tiles in the CaO–MgO–Al2O3–SiO2 system

“…the splitting of (1 2 0) and (2 1 0) reflections is larger for SiO 2 -richer mullites. 17 The observed splitting in the mullite peaks of glass-ceramics at 1160 • C indicates, therefore, that these mullites are rich in silica. From the relative intensity of the crystalline phases in Figs.…”

Low-temperature Ti-containing 3:2 and 2:1 mullite nanocrystals from single-phase gels

“…Recent studies of mullite synthesis have emphasized the utilization of chemically synthesized precursors which convert into mullite in a low temperature range from ∼850 to ∼1250 • C. [6][7][8][9][10] According to the homogeneity of prepared gels two categories of preparation routes can be considered. First, single-phase or molecularly mixed gels, in which aluminium and silicon species exhibit homogeneity on the molecular level, crystallize directly a metastable alumina-rich mullite with x > 0.40 at ∼980 • C. 11 In the other type of gels, colloidal or diphasic gels, in which the scale of homogeneity is in the range from 10 to 100 nm, mullite crystallizes at ∼1250 • C via spinel formation at ∼980 • C. 12 The influence of several additives, such as Ti, Zr, Mg, etc., on the temperature and formation rate of mullite during the process of mullitization of kaolinite has been studied [13][14][15] . Also, there are some available reports regarding with the effect of various impurities on mullite formation in diphasic gels.…”