engleski

The role of solvents on sol-gel derived calcium aluminate (CA)

High purity calcium aluminate (CA, CaAl2O4) samples were derived by sol-gel method using aluminium-sec-butoxide (ASB, Al(OSBu)3) and calcium nitrate tetrahydrate (CN, Ca(NO3)2·4H2O). In order to facilitate controllable synthesis process an ethyl acetoacetate (EAA, C6H10O3) was used as a chelating agent for ASB (Eaa : Asb = 3 : 2). Synthesis was performed using different solvents ; ethanol (EtOH, C2H6O), propanol (PrOH, C3H8O), buthanol (BuOH, C4H10O). The sol-to-gel reaction was monitored using Fourier Transform Infrared (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy methods. In CA system, Al was found to be highly prone to change of coordination states as a consequence of different synthesis parameters and thus various processes occurring ; hydrolysis, condensation, chelation, oligomerization. The introduction of different solvents was examined as the most beneficial way to influence the early stage of CA sol-gel synthesis. The derived gels were dried and thermally treated to form CA. The thermal evolution and crystallization behaviour of dried gels were monitored by means of Differential Thermal and Thermogravimetric analysis (DTA/TG) and X-Ray Diffraction (XRD). The role of different solvents observed in the properties of sols and gels also reflected in the properties of calcined CA powders like phase composition and crystallization parameters. The goal of this work was to enable better utilization of the CA sol-gel synthesis process only by slight modification of synthesis parameters.

Calcium aluminate; Sol-gel; Chelation; Solvents

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