Role of vermiculite and zirconium-vermiculite on the formation of zircon-cordierite nanocomposites

The Zr4+-vermiculites were studied in their new role of the zircon precursor in the clay minerals mixtures which were prepared for firing of the zircon-cordierite nanocomposites. Currently there is a lack of data available about the structure of Zr4+-vermiculites, on which this study was performed. The modeling of the arrangement of interlayer material in the Zr4+-vermiculite led to new findings that water molecules are attracted more strongly by Mg2+ cations than by Zr-tetrameric cations, and that both the tetrameric cations [Zr-4(OH)(14)(H2O)(10)](2+) and [Zr-4(OH)(8)(H2O)(16)](8+) may be present in the interlayer space of the Zr4+-vermiculites. Vermiculites from two different localities Czech Republic (Verm1) and from Brazil (Verm2) were intercalated using the zirconyl chloride (ZrOCl2-30% solution in HCl) and the prepared Zr4+-vermiculites were designated as Zr4+-Verm1 and Zr4+-Verm2, respectively. Influence of the Zr4+-Verm1 and Zr4+-Verm2 in the mixtures of clay minerals on the properties of zircon-cordierite nanocomposites were investigated by their comparison with the properties of the zircon-cordierite nanocomposites, which were prepared using saturation of the clay minerals mixtures containing Verm1 and Verm2 with the zirconyl chloride (ZrOCl2-30% solution in HCl). The zircon-cordierite nanocomposites fired from the clay mineral mixtures containing Zr4+-Verm1 and Zr4+-Verm2 showed a maximum porosity of P = 58 and 60%, skeletal density SD = 3.2 and 3.6, and the smallest pores with a median pores diameter MDP = 18 and 15 mu m, respectively, in comparison with the zircon-cordierite nanocomposites fired from the clay mineral mixtures containing Verm1 and Verm2 and saturated with zirconyl chloride solution. The type of vermiculite Verm1 or Verm2 in the clay mineral mixtures did not affect the contents of the crystalline mineral phases in cordierite and zircon-cordierite nanocomposites. (C) 2013 Elsevier B.V. All rights reserved.