溶胶-凝胶燃烧法制备La_2O_3和La(OH)_3纳米晶的研究

采用燃烧法合成纳米La(OH)3材料,分别以硝酸镧和柠檬酸为镧源和络合剂,以氨水调节pH值为2～4、柠檬酸与硝酸镧的物质的量比为1～1.2∶1之间,加热凝胶至自蔓延燃烧后并在700～750℃煅烧1～2 h,得到膨松粉末状产物,即La2O3纳米晶。利用X射线衍射和透射电镜等测试方法对凝胶热分解过程及最终形成的La2O3纳米晶颗粒进行分析和表征。结果表明:用该方法得到的纳米La2O3产物的平均粒径在30～100 nm之间可控;纳米La2O3在空气中是不稳定的,在自然吸潮情况下和空气中的H2O发生反应生成La(OH)3,控制湿度即可得到纯La(OH)3纳米晶。

Preparation of La2O3 and La(OH)3 Nano-cryatalline by Sol-Gel Combustion Synthesis

La(OH)3 nano-particles were synthesized by sol-gel combustion synthesis that citric acid monohydrate was used as the complexing agent and La(NO3)3·6H2O was used as the lanthanum source,the mixture that mole ratio of citric acid and La(NO3)3 was 1~1.2∶1 were dissolved in the water,and ammonia solution was added to adjust pH value between 2~4.Then the wet gel was obtained and subsequently heated to cause the self-propagating combustion at 700~750 ℃ for 1~2 h.The fluffy La2O3 nano-crystalline was synthesized.The structure and pattern of the as-prepared powders were characterized by XRD and TEM.The results showed that La2O3 nano-crystalline particles with grain diameter in range from 30 nm to 100 nm were prepared and the size was controlled.La2O3 nano-crystalline was unstable to deliquesce with the moisture in the air and finally form La(OH)3.So pure La(OH)3 nano-crystalline was prepared by way of controlling moisture.