Acid-Catalysed Al2o3 Sol And Its Gel Material: Influence Of Hno3 Content And Stability

A series of Al2O3 sols were prepared by HNO3 catalysis of aluminum isopropoxide (AIP), using different molar ratios of HNO3/AIP (n(H)). The changes in sol densities, viscosities, refractive indices, stability and particle sizes were reported. Derived properties such as Gibbs energies (Delta G*) and the reaction rate constant (k) have been calculated from the experimental density and viscosity data. The phase-chemical structures of Al2O3 materials were characterized using Fourier transform infrared (FTIR) and X-ray diffraction (XRD) measurement. The results show that, when the molar ratio of HNO3/AIP is 0.25, the prepared Al2O3 sol was transparent, uniform and stable, and the sol average particle size gets the minimum. The chemical structure of the non-calcined Al2O3 gel material is dominated by Al-O-H and Al-O bonds. After calcination at 350 degrees C, the Al-O-H bond will break and is transformed into Al-O bonds, and the phase structure is changed from gamma-AlOOH to gamma-Al2O3.