Surface hydration states of commercial high purity α-Al2O3 powders evaluated by temperature programmed desorption mass spectrometry and diffuse reflectance infrared Fourier transform spectroscopy

Abstract

The surface of three different grades of commercial high-purity α-Al2O3 powders produced by hydrolysis of aluminum alkoxide, which differ each other in SSA are evaluated by temperature programmed desorption mass spectrometry (TPDMS) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. For the DRIFT evaluation the powders were heated in situ under vacuum from 25 to 700 8C. The TPDMS spectra of desorbed H2O were obtained by heating the samples under ultra high vacuum at a rate of 20 K minK1 up to 1200 8C.The presence of hydrogen bonded water molecules, amorphous Al(OH)3 and AlOOH structures, as well as associated and isolated hydroxyl groups on the surface of all the a-Al2O3 powders investigated is demonstrated. On the surface of one of the powders the presence of crystalline Al(OH)3 structures, as evidenced by an additional sharp peak in the H2O TPDMS spectrum, is confirmed.