Preparation Of Ultrafine Nanopowder By Ultrasonic Atomization Method

Ultrasonic atomization technology was widely used for preparing nanomaterials. But a method of atomizing reaction liquid simultaneously to preparing nanomaterials wasn't publicly reported. Nano-α-Al₂O₃, CeO₂ and CuO/CeO₂ powders were synthesized by ultrasonic atomization and were characterized by SEM, TEM, DLS, DSC, BET and XRD. The process parameters which influenced the size and dispersion of nano-powder were investigated. The catalytic property of CeO₂ and CuO/CeO₂ for CO oxidation was studied.Droplets produced by ultrasonic atomization and ordinary atomization were tested. The results showed that ultrasonic atomization had small size in the droplets, uniform distribution, with easily controllable results. The diameter size of droplets produced by ultrasonic atomization was distributed at 3～5μm and Ordinary atomization at 50～100pm.Nano-Al₂O₃ powders were prepared by using aluminum sulfate and ammonium carbonate as raw materials. Ultrasonic atomization, single atomization and dropwise technology were carried on comparison. The experimental results showed that the size and morphology of precursor were obviously influenced by mixed method. The reaction by ultrasonic atomization was considered in micro-area. Ultra-fine Al₂O₃ powders could be easy obtained by ultrasonic atomization. Precursor prepared by ultrasonic atomization could be changed into a phase at 1100℃with 10nm average individual diameter.Precursor could change from sphere to rod and became platelets at last. But this change took longer time in ultrasonic atomization technology than ordinary technology. Precursor was collected by two methods. One was quick solid/liquid separation, and the other was using ethanol. It was found that the dispersion of the precursor collected in ethanol was improved with small size after calcining.Nano-CeO₂ powders were synthesized by ultrasonic atomization technology besides nano-Al₂O₃ using cerium nitrate as raw materials, ammonium bicarbonate or ammonia as precipitator after calcining at 300℃for 20min. The results indicted that CeO₂ particles obtained using ammonium bicarbonate as precipitator had the advantages of uniformed distribution, well-dispersing capability. It was believed that gas decomposed had an effect on agglomeration. Carbon monoxide oxidation was carried over CeO₂ and Cu/CeO₂ catalysts. It was found that the catalysis property of CeO₂ prepared by ultrasonic atomization was better than by ordinary technology. Catalysis activity became higher with increasing of ratio of Cu:Ce. When the ratio was Cu:Ce=0.1, the catalyst had high activity and CO conversion was as well as 98% at 400℃.