Structural and morphological evolution of powders nanostructured ceramics: transitional aluminas | Evolution structurale et morphologique des poudres de céramiques: alumines de transition
2013
Fillali, Laila | López-Andrés, Sol | López-Delgado, Aurora | Padilla, Isabel | Jiménez, José Antonio
Comunicación oral, presentada al International Congress on Materials & Structural Stability (Congrès International Matériaux & Stabilité Structurelle) CMSS 2013. 27-30 Nov. Rabat, Marruecos
Show more [+] Less [-]This work aims with the study of the transformation of boehmite into transitional aluminas. Boehmite was obtained by a sol-gel method from an aluminium hazardous waste. The thermal behaviour of boehmite was followed by thermogravimetry and differential thermal analysis to determine the transformation temperatures. By calcinations of boehmite at temperatures ranging between 250-1000ºC, transitional aluminas (γ, δ , θ-Al2O3) were synthesized and characterized by XRD, TEM and FTIR. All the transitional aluminas exhibit nanometric crystallite size, ranging from 2.5-15nm. γ-Al2O3 was obtained as a nanostructured material at 500ºC with a cell parameter a=7.923Å. δ-phase stars to appear at 850ºC with a crystallite size of 6nm and cell parameters a=5.672Å and c=24.600Å. For θ-Al2O3 the cell parameters, in Å, were a=11.817, b=2.912, c=5.621and β=103.8º. The progressive conversion of the transitional phase γ-Al2O3 into the stable polymorph α-alumina, takes place gradually and a four-phases region is achieved at 1000ºC, where coexist with other transitional phase such as δ- and θ-Al2O3.
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