Mechano-Chemical Changes of Nano Sized alpha-Al_2O_3 During Wet Dispersion in Stirred Ball Mills

摘要

The mechano-chemical changes in synthetic alpha-Al_2O_3 during wet dispersion in a stirred ball mill,are studied.It is shown that a second phase is generated which can be identified as an aluminum hydroxide (Bayerite) by use of dynamic scanning calorimetry (DSC),X-ray diffraction (XRD),thermogravimetry (TG),Fourier transformed infrared (FTIR) spectroscopy and transmission electron microscopy (TEM).The amount of the Bayerite phase produced increases with milling time.A comparison of the evaluated amounts from TG- and DSC-measurements are in reasonable agreement.Furthermore,the measured BET surface area shows a strong dependence on the temperature of sample preparation.Depending on the temperature,the bayerite phase is seen to convert to the alpha-phase again and also forms meso- and possibly micro-pores,leading to a high BET surface area.In this paper,we highlight the necessity for using different methods to characterize the dispersion process,and for a correct interpretation of the measurement results.