engleski

Formation mechanisms of sol-gel derived cordierite

Gels with cordierite stoichiometry, Mg_2Al_4Si_5O_18, were prepared by sol-gel technique using three different starting aluminium sources: nano-sized gamma-Al_2O_3, aluminium nitrate nonahydrate and Al-sec-butoxide, using tetraetoxysilane (TEOS) and magnesium nitrate hexahydrate in all three gels as sources for silicon and magnesium. The influence of Al-precursors on formation mechanism and sintering behavior of gels was studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and dilatometry. Gels calcined at 700 °C were characterised by different specific surface area, pore sizes and different crystallization sequences. For gel with nano-sized gamma-Al_2O_3 alpha-cordierite was formed at 1220 °C through intermediate MgAl_2O_4 phase. If aluminium was introduced as Al-sec-butoxyde mu-codierite cyrstallized in tow steps (760 and 1070 °C) and the transformation mu-cordierite -> alpha-cordierite occured at 1250 °C. When Al(NO_3)_3˙9 H_2O was introduced as intermediate phase crystallized MgAl_2O_4 at ~870 °C and mu-coriderite at ~950 °C. Both phases reacted with amorphous silica forming alpha-cordierite at ~1210 °C. Compacts prepared from gels with aluminium -nitrates and Al-sec-butoxide, respectively, sintered between 700 and 1000 °C, whereas the gel derived from gamma-Al_2O_3 sintered in two steps ; between 700 and 1000 and 1010 and 1250 °C.

coriderite; sol-gel; formation mechanisms

Rad je kao poster prezentiran na skupu 11th International Ceramics Congress (CIMTEC 2006), održanom od 04.-09.06.2006., Acireale, Italija ; objavljen u Abstracts of CIMTEC 2006 / Vincenzini, Pietro (ur.). - Acireale : World Academy of Ceramics & International Ceramic Federation, 2006. ; 31-31.