【摘要】 以分子量为600的聚乙二醇(PEG600)为分散剂,通过Ce(NO3)3.6H2O和无水Na2CO3的固相反应制备出混相碳酸铈盐[Ce2O(CO3)2.H2O和Ce2(CO3)3.8H2O]前驱体,热分解该前驱体获得CeO2纳米晶。XRD研究表明,产物归属于立方晶系的方铈石相,空间群为Fm3m。混相碳酸铈盐前驱体的反应活性较高,350℃热处理已使其分解完全,获得平均晶粒度仅为6.5 nm的纯CeO2纳米粉体,600℃焙烧产物的平均晶粒度达到27.1 nm,该温度下获得的CeO2微粒呈薄板状,板面平滑,大体呈规整的六边形,板径主要在30 nm~40 nm之间,径/厚比为5~7。在透射电镜下直接观察到的平均颗粒度与采用Scherrer公式计算的平均晶粒度相近,反映出由此固相合成法制备的纳米粉体颗粒较为均匀,从团聚体生长出来的大颗粒较少。更多还原

【Abstract】 Mixed phase precursor composed of Ce2O(CO3)2·H2O and Ce2(CO3)3·8H2O was synthesized by solid state reaction of Ce(NO3)3·6H2O and Na2CO3 in the presence of PEG600 at room temperature.Its XRD peaks were very weak and broad,depicting a poor crystallinity.The precursor was decomposed to nano-ceria products at temperatures ≥350 ℃.XRD patterns showed that the calcined products were crystallized and all peaks could be indexed to standard CeO2 with Fm3m space group(JCPDS Files No.34-0394).Calcining the precursor at 350 ℃ for 2 h yielded weakly crystallized CeO2 powders with average crystalline size of 6.5 nm,indicating higher reactivity of the precursor.Calcination at higher temperature led to sharper XRD peaks,grain coarsening and formation of tabular morphology.The CeO2 powders calcined at 600 ℃ had well-defined XRD peaks and an average crystallite size of 27.1 nm.According to TEM images,the grains were polygon tabular in shape and mainly exhibited hexagon morphology.The width of the tabular crystals was around 30 nm～40 nm and the aspect ratio was 5~7.The observed average particle size was close to the crystallite size determined via XRD peak broadening analysis.Nearly no abnormal grain growth,which generally derived from severe agglomerated particulates,was observed.The results showed that the size-distribution of the nano-ceria was rather narrow.更多还原