High-temperature hydroxylation of alumina crystalline surfaces

Atomic force microscopy, attenuated-total-reflection Fourier-transform infrared (FTIR) spectroscopy, and sum-frequency vibrational spectroscopy (SFVS) were employed to study effects of heat treatment in different gas atmospheres on three different alumina crystalline surfaces (a, c and r) and subsequent hydroxylation. Samples heat-treated at a higher temperature (1550 °C) exhibited more surface roughening and faceting than those heated at 1000 °C. Also, the roughening and faceting depended on the gaseous atmosphere used during heat treatment. The SFVS and FTIR spectra showed clearer spectral features of hydroxylation and higher degree of hydroxylation for heat treatment at higher temperatures. Different crystalline surfaces displayed different spectral features upon hydration. Hydration of sample surfaces in water appears to be more effective than in humid air.