Technical Study On The Preparation Of Alumina Ultraflne Powder Via Non-hydrolytic Sol-Gel Method

Ultrafine α-Al2O3 powder with good dispersity was prepared via non-hydrolytic sol-gel process by using aluminium isopropoxide as aluminum source.The effects of single solvent type,composite solvents type,ratio of composite solvents,precursor concentration,calcination temperature and dispersant on the preparation and dispersion of α-Al2O3 was investigated by DTA-TG,XRD,FE-SEM,TEM and FT-IR.Meanwhile,α-Al2O3 powder was also prepared by using Al powder as aluminum source.The effects of the catalyst amount,the reflux temperature and time,the precursor concentration,and the dispersant amount on the phase composition and the sample dispersion effect have been investigated.The preparation mechanism of α-Al2O3 powder via non-hydrolytic sol-gel was studied,drawing the following conclusions:When α-Al2O3 powder was prepared by using aluminum isopropoxide as aluminum source,single solvent glycerol has obvious effect on the improvement of powder aggregation.Composite solvents have good solubility to raw materials.Especially,when using glycerol as one of solvents,the composite solvent has good dispersion.Too much or too little glycerol in the composite solvents can not reach this effect.Ultrafine α-Al2O3 powder with good dispersity can be prepared by using isopropyl alcohol and glycerol as composite solvent.The optimal precursor concentration is 0.1 mol/L with the volume ratio of 1:1 and the amount of dispersant PEG 600 is 3 wt.%,while the calcination temperature is 1100℃.When ultrafine α-Al2O3 powder was prepared by employing aluminum isopropoxide as aluminum source,the transition from γ-Al2O3 to α-Al2O3 was took place at 1050 ℃.The α-Al2O3 crystalline is more perfect with increasing the temperature.Ultrafine α-Al2O3 powder with good dispersity was achieved when the I2/Al molar ratio was 0.010 and the precursor concentration was 0.2 mol/L,followed by refluxing at 110℃ for 24 h and calcining at 1100℃.Too less dispersant PEG has no obvious effect on the dispersion improvement of α-Al2O3 powder,while too much leads to the long chain molecule of PEG intertwined with each others,resulting in the agglomeration again.The selection of cheap metal aluminum as precursor and iodine as catalyst via NHSG method overcomes the shortages of conventional metal alkoxides or anhydrous metal chlorides as precursors.The precursor is transformed from expensive metal alkoxide to inorganic salt,and finally to the cheap metal,expanding the select range of aluminum source and reducing the cost of raw materials.Thus,it laids the foundation for industrial production of ultrafine α-Al2O3 powder via NHSG method.