Naslov
Thermal evolution of calcium aluminate gel

Autori
Mandić, Vilko ; Šipušić, Juraj ; Kurajica, Stanislav

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

Izvornik
XXI. Hrvatski skup kemičara i kemijskih inženjera / Novak, predrag ; Pičuljan, Katarina ; Smolec, Sonja - Zagreb : Hrvatsko društvo kemijskih inženjera i tehnologa (HDKI) ; Hrvatsko kemijsko drustvo, 2009

ISBN
987-953-6894-38-3

Skup
XXI. Hrvatski skup kemičara i kemijskih inženjera

Mjesto i datum
Trogir, Hrvatska, 2009

Vrsta sudjelovanja
Poster

Vrsta recenzije
Domaća recenzija

Ključne riječi
Calcium aluminate; sol-gel

Sažetak
Calcium aluminate (CaAl2O4) powder was prepared by sol– gel technique using calcium nitrate tetrahydrate and aluminium sec-butoxide as precursors and ethyl acetoacetate as chelating agent. The dried gel and thermally treated samples were characterized by means of simultaneous Differential Thermal and Thermo-Gravimetric Analysis (DTA/TGA), Fourier Transform Infrared spectroscopy (FTIR), and X-Ray Diffraction (XRD). From the results obtained, the thermal evolution of prepared gel, crystallization behavior and crystallization kinetics are discussed. In the presence of Asb the reactive enol form of Eaa substitutes the alkoxy groups of Asb, forming a stable chelate. It has been established that the decomposition of chelate and the evaporation of ethyl-acetoacetate followed by an auto-combustion process occur in lower temperature range. The crystallization process starts at temperatures higher than 900°C. Calcium aluminate, CaAl2O4, appears as a major crystalline phase, and calcium dialuminate, CaAl4O7, and dodecacalcium heptaaluminate, Ca12Al14O33, as minor phases. The crystallization processes of all three phases proceed simultaneously and independently. The occurrence of aluminium and calcium rich phases in stoichiometric CA gel is assigned to local segregation due to a formation of [Al(OH)3-x(Eaa)x]n oligomers and crystallization of Ca(NO3)2´4H2O. Higher temperatures of thermal treatment increase the amount of CA and decrease the amount of minor components, while by prolonged anneling at the same temperature the system remains unchanged. Kinetic analysis revealed that the amorphous to crystalline transformation in studied sample cannot be described by a simple mechanism. Complex reactions involving several processes with different activation energies and mechanisms are involved in overall crystallization process.

Izvorni jezik
Engleski

Znanstvena područja
Kemijsko inženjerstvo

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