Solubility and microstructural development of TiO2-containing 3Al2O3·2SiO2 and 2Al2O3·SiO2 mullites obtained from single-phase gels |
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| Affiliation: | 1. Department of Inorganic Chemistry, University of Valencia, 46100 Burjasot, Spain;2. Department of Geology, University of Valencia, 46100 Burjasot, Spain;3. Instytut Matematyki i Kryptologii, Wojskowa Akademia Techniczna, 00-908 Warszawa, Poland;1. Science School, Guangdong Ocean University, Zhanjiang 524088, China;2. School of Materials Science and Engineering, Shanghai Institute of Technology, Shanghai 201418, China;3. School of Physics and Engineering, Sun Yat-sen University, Guangzhou 510275, China;1. Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia;2. Ural Federal University, Mira St. 19, 620002 Yekaterinburg, Russia;3. Institute of Geology and Mineralogy SB RAS, Russkaya St. 43, 630058 Novosibirsk, Russia;1. Ural Federal University, 19, Mira Street, 620002 Ekaterinburg, Russia;2. Institute of Physics, University of Tartu, Riia 142, 51014 Tartu, Estonia;3. Institute of Geology and Mineralogy of SB RAS, 43, Russkaya St., 630058 Novosibirsk, Russia |
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| Abstract: | The interdependence of the titanium oxide amount and the anisotropic growth of mullites prepared from single-phase gels were investigated. Gels with stoichiometries 3(Al2?xTixO3)·2(SiO2) and 2(Al2?xTixO3)·(SiO2), with 0 ≤ x ≤ 0.15 were prepared by the semialkoxide method. Gels and specimens heated at temperatures between 1200 and 1600 °C were characterized by using infrared spectroscopy (IR), X-ray diffraction (XRD) and transmission and field emission scanning electron microscopies (TEM and FESEM). Al2TiO5 as minor impurity was detected in both series of mullites for gel precursor compositions x = 0.10 and x = 0.15, obtained at temperatures between 1200 and 1600 °C. Variations of lattice parameters of mullite, processed at temperatures from the range between 1400 and 1600 °C, with the starting nominal amount of titanium oxide indicated that the solubility limit of titanium oxide was in ranges 3.8–4.1 and 4.1–4.4 wt% TiO2 for 3:2 and 2:1 mullites series, respectively. The anisotropic growth of titanium-doped mullite crystalline grains was significant only when the nominal amount of titanium oxide exceeded the limit of solubility into the mullite structure (for both mullite series). Stronger anisotropy occurred for the 3:2 series specimens, i.e. for the SiO2-richer mullites. In both series of mullites, the anisotropic grain growth was observed for the process temperatures higher than 1400 °C; the crystalline grains of mullites processed at lower temperatures were equiaxials and of almost the same size. |
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