Naslov
Crystallization studies of cordierite originated from sol-gel precursors

Autori
Tkalčec, Emilija ; Gržeta, Biserka ; Ivanković, Hrvoje ; Popović, Jasminka

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
10th International Conference and Exhibition of the European Ceramic Society. Abstracts. / Heinrich, Jurgen - Berlin : Deutche Keramische Gesellschaft e.V., 2007, B-1118

Skup
10th International Conference and Exhibition of the European Ceramic Society

Mjesto i datum
Berlin, Njemačka, 17.06.2007. - 21.06.2007

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
Cordierite; Sol-gel technique; Crystallization; X-ray powder diffraction

Sažetak
Cordierite ceramics has numerous important applications that especially utilize its low coefficient of thermal expansion and low dielectric constant. Gels with cordierite stoichiometry, Mg_2Al_4Si_5O_18, were prepared by sol-gel technique using Al-sec-butoxide or aluminium nitrate nonahydrate as aluminum source, and tetraetoxysilane (TEOS) and magnesium nitrate hexahydrate as sources for silicon and magnesium. Gels calcined at 700^oC showed different specific surface area, pore sizes and different crystallization sequences. The influence of Al-precursors on the crystallization behavior of gels was studied by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). DSC and RT X-ray diffraction showed that if aluminum was introduced as Al-sec-butoxide, mi-cordierite crystallized in two steps and the transformation mi→ alpha-cordierite occurred at about 1250^oC. When Al(NO_3)_3• 9H_2O was introduced, MgAl_2O_4 at ~870^oC and mi-cordierite at ~950^oC crystallized as intermediate phases. Both phases reacted with amorphous silica forming alpha-cordierite at ~1210^oC. High temperature in situ X-ray diffraction in the range from 820^oC-1170^oC revealed displacement of diffraction lines for mi- and alpha-cordierite toward higher Bragg angle. Such behavior indicated on smaller unit cells of those phases as crystallization proceeded in the examined temperature range. That probably was caused by higher silicon content in the mi- and alpha-cordierite, than reported in the literature.

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemijsko inženjerstvo

POVEZANOST RADA