Preparation And Properties Of Nanomaterials With Special Strutures

Synthesis of nanomaterials with special constructions is extensively studied in recent years in materials science. The properties of materials not lie on constitute but related to its microstructure. The nanomaterials with special constructions have unique performance of optical,electrical,magnetic and catalytic superior their bulk counterparts. In this dissertation, synthesis routes and performance with CeO₂ with spindle-like structure, Fe₃O₄/C/TiO₂ with core/shell structure and hollow C/TiO₂ were investigated. The principal results of the dissertation are discussed as follows:(1)Single-crystalline Ce(OH)CO₃ with spindle-like structures were fabricated using one step procedure without surfactant or template at 120℃for 8h. Furthermore, single-crystalline CeO₂ with spindle-like structure was obtained after calcination of Ce(OH)CO₃ precursor. The reaction time and the concentration of Ce(NO₃)₃·6H₂O played the important role during the growth process of Ce(OH)CO₃ with spindle-like structures. The spindle-like structure CeO₂ with the width which increased from the ends to the center was obtained with duration of reaction time. And during increased the concentration of Ce(NO₃)₃·6H₂O, the Ce(OH)CO₃ sample with spherical and spindle-like structure with rough surface coexist in the reaction mixture. The growth mechanism of Ce(OH)CO₃ with spindle-like structures were also discussed. At last, the catalytic properties of CeO₂ were measured in CO oxidation. The result showed that The CO conversion rates could reach 66.06% at 190℃, and when the temperature was 220℃, the CO conversion rates could reach 95%, the single-crystalline spindle-like CeO₂ showed a high catalytic activity on CO conversion.(2)Magnetic photocatalyst Fe₃O₄/C/TiO₂ with core-shell structure was successfully fabricated by hydrothermal. From SEM and TEM, Fe₃O₄/C had clear core-shell structure and the thickness of C was about 50nm, the diameter of Fe₃O₄/C/TiO₂ was about 325nm which was 65nm bigger than Fe₃O₄ microsphere. The UV-Vis and VSM showed that the Fe₃O₄/C/TiO₂ absorbed the entire spectra across the complete UV and visible range. The paramagnetic behaviour of the synthesize microspheres at room temperature ccould be inferred from their low values of remanence magnetization (6.5emu/g) and coercivity (73Oe), which could decrease the final cost of the treatment process for reuse. Moreover, the formation mechanism of Fe₃O₄/C and Fe₃O₄/C/TiO₂ were researched.(3)SiO₂/C/TiO₂ was obtained used the same preparation method for and hollow C/TiO₂ was obtained by removal of silica. The size of the as-prepared hollow spheres measured from the SEM and TEM was 500nm in outer diameter, and the wall thickness was about 70nm. The XRD confirmed that the product with anatase TiO₂ and SiO₂ had been removed. The amount of glucoses played the important role during the growth process of Fe₃O₄/C. The results showed that the thickness of shell became large with the increase of glucoses, but the dispersity turned badly. Compared to the result of experiment, the best amount of glucoses was 5g.