胶晶模板法制备3DOM尖晶石型LiMn_2O_4及表征

Preparation of Three-dimensionally Ordered Macroporous Spinel LiMn_2O_4 by Colloidal Crystal Template and Its Characterization

通过乳液聚合获得粒径为280nm左右的聚甲基丙烯酸甲酯（PMMA）微球，从其母液中离心沉降制得胶晶模板．将LiNO3，Mn（Ac）2·4H2O和柠檬酸按摩尔比1：2：2配成前驱物的醇水混合溶液，填充于PMMA胶晶模板间隙中，经干燥和焙烧氧化成孔制得了三维有序大孔（3DOM）锂锰氧化物．实验结果表明，当n（Li）／rKMn）=0．6，前驱液浓度在0．6～1．0mol／L之间和升温速率为2℃／min时，分别在300与600℃下两段恒温焙烧2～3h有利于目标产物的形成．SEM测试结果表明，PMMA胶晶模板和3DOM锂锰氧化物均为面心立方紧密堆积，排列规则有序，大孔直径在200～240砌之间，孔壁厚度在30～45砌之间．产物经XRD晶相测定和EDTA，KMnO4滴定分析确证为正尖晶石型LiMn2O4．

The colloidal crystal template was prepared by the centrifugal settling of microspheres, whose particle diameters were about 280 nm, from the mother liquor of polymethyl methacrylate （PMMA） obtained by emulsion polymerization. The ethanol-water solution of precursor was formulated with LiNO3, Mn （Ac）2 4H2O, and citric acid in the molar ratio of 1：2：2 and was filled into the interstices of PMMA colloidal crystal template. The lithium manganese oxide of three-dimensional ordered macropore （3DOM） was prepared with their composite being dried and roasted in air to form holes. The experiments indicate that the formation of objective product is facilitated when n（ IA）/n（Mn） =0. 6, the concentration of the precursor was in the range of 0. 6-1.0 mol/L, and the roasting temperatures in the two isothermal sections were 300 ℃ and 600 ℃ for 2-3 h separately, and the heating rate was 2 ℃/min. SEM images show that the PMMA colloidal crystal template as well as the 3DOM lithium manganese oxide was arrayed periodically in face-centered cubic closed packing. The macropore diameters were between 200-240 nm, and the pore wall thicknesses between 30-45 nm. Through XRD determination of the crystal phase and the titration analyses of EDTA and KMnO4, the final product was proved conclusively to be normal spinel LiMn2O4.