Structural Study Of Alumina Carrier Coating Fabricated Via Sol-Gel Method

Firstly, in this dissertation the precursor-ethoxyl aluminate was fabricated via direct reaction between aluminum and ethanol with present of a proper catalyst; then porous alumina was gained through sol-gel processing, eg. hydrolysis, condensation, drying and heat treatment. The experimental result shows that alumina with high specific area has a fractal structure under low or medium temperature(500). However, the specific area of porous alumina decreases sharply and the fractal character vanishes as temperature increases. It decreases by 39.9% at 800 and by 56.5% at 1000. The causes of this decrease have been analyzed.The stack of crystal particles and the pores in alumina were changed through adding PEG to the pseudo-boehmite sol. The specific area of alumina was enhanced by 18.3% at 800. However, this effect was not distinct at 1000 These phenomena resulted from the transformation of the crystal type and the sintering of the pore structure, as a result the PEG effect was weakened.Sr (NO3) 2 2H2O was selected as the thermostable reagent to enhance the specific area of alumina under high temperature. It was found that Sr (NO3) 2 2H2O could counteract the transformation of phase, defer the alteration of the stack of crystal particles, and weaken the sintering ofpores in alumina. Through adding Sr (NO3) 2 2H2O, the specific area of alumina decreased by 5.4% at 1000 and alumina remains a still good fractal structure at 1200.In conclusion, after adding PEG and Sr (NOs) 2 2H2O ,alumina carrier coating that is fabricated by Sol-Gel has high thermostaility and large specific area. It's property surpasses evidently the carrier coating used ordinarily in the automobile exhaust gas catalytic converters.