Characterization of the acid-base properties of alumina surfaces
Three aluminas have been characterized by electrophoretic mobilities measurements in polar nonaqueous solvents, differential thermal analysis, and infrared spectroscopy, in order to study the acid-base properties of their surfaces. The solvents were chosen according to the Gutmann donor/acceptor concept to cover a wide range of electron acceptor and electron donor numbers. The electron donor properties of the three alumina surfaces are different and correlate with water desorption and OH abundance as seen by DTA and IR spectroscopy. Conversely, the electron acceptor properties are identical for the three surfaces. These facts are interpreted as results of the presence of electropositive (Al) or electronegative (O) atoms in different quantities at the surface of the oxides.