Preparation And Characterization Of Three-dimensionally Ordered Macroporous Polyanion-type Oxide Materials

Three-dimensionally ordered macroporous material is a type of a solid with orderedspherical pores (>50nm). Because its large specific surface area and periodic micro-nanostructure, it has potential applications on optical as well as energy conversion and storagedevices. In this work, we have synthesized KTiOPO4photonic crystals，macroporousLi2V3(PO4)3/C and Li2FeSiO4/C nanocomposite materials by nanocasting process usingcolloidal crystals as moulds. The structures and properties of the synthesized materials arecarefully studied. The obtained reulsts are as follows:KTiOPO4-SiO2nanophase glass-ceramics were prepared by the sol-gel method. Theeffects of the nanostructures on the transparency of the glass-ceramics are analysed accordingto Rayleigh model. The results show that the large ratio of the refractive indices decreases theoptical transmittance of the materials in the visible region. By infiltrating KTiOPO4precursorsol into the SiO2template, bluk KTiOPO4opal photonic crystals materials composed of theordered SiO2colloid crystals and KTiOPO4nanocrystals residing thevoids between SiO2colloid spheres and were obtained through calcining the gels at750℃. Also, bluk KTiOPO4inverse opal photonic crystals materials were prepared by using polystyrene (PS) colloidcrystal as a mould. These materials exhibit second harmonic generation under laser irradiationat1064nm wavelength.A three-dimensionally ordered macroporous (3DOM) Li2V3(PO4)3/C cathode materialwith small-sized macropores is successfully synthesized by using polymethyl methacrylate(PMMA) colloid crystal template. The3DOM architecture is built up from fully denselysintered Li2V3(PO4)3/C nanocomposite ceramics particles and coated with a layer ofamorphous carbon，the pore size is about50-140nm. The resultant3DOM Li2V3(PO4)3/Cnanocomposite exhibits a stable and highly reversible discharge capacity up to151mAh·g-1at0.1C, and an excellent high-ratecapability of70mAh·g-1at20C. Compared to thecorresponding bulk nanocomposite, the3DOM Li2V3(PO4)3/C cathode exhibits a signifcantlyimproved high-rate performance.Using triblock copolymer P123as a carbon source, by infiltrating Li2FeSiO4precursor sol into a PS colloid crystal template, macroporous Li2FeSiO4/C nanocomposite wereobtained through calciningthe gels at650℃. But the pore yield is not high. When the currentrate is10C, specific capacitiy of macroporous Li2FeSiO4/C is slightly higher than thenon-templated Li2FeSiO4/C nano-powder at the current density of10C. In the Further, inorder to improve the rate performances, the material with high yield pore have to be preparedby optimizating proccessing conditions.