Iron, Lanthanum Oxide Preparation And Electrochemical Properties Of Porous Materials Characterization

Transition metal oxides have unique chemical properties, due to their variety of components and variable of valence. What is more, porous materials own serials of novel physical and chemical properties because of their unique structure and large surface area. However, the following problems for porous transition metal oxide have happened during the preparation, such as:the construction of the pore structure depends on the template too much, hole wall collapses easily and stability of structure is poor.We suppose that the porous could be constructed by nanoparticles, which can keep the hole wall and the stability of the firm structure and depend on no template. In this thesis, a novel two-step method has been employed to synthesis porous iron oxide and lanthanumoxide Microspheres. First regular brick-shaped and flower shaped precursors were synthesized by hydrotherma and solvotherma method. Then a following calcination process was carried out to obtain the final porous mental oxide materials under different temperature and different porous diameter structure, the same phase of alpha Fe2O3was obtained. Then using different solvent system, different morphology ferrous oxalate can be obtained. Especially, the uniform particles with slender shape was prepared in ethanol-water system. Lanthanum oxide Microspheres was also synthesized using the similar route. Monodispersed lanthanum tartrate micro aggregations with flower-like spherical shape were successfully prepared in ethanol/water mixed solvents. The Lanthanum oxide with reserved shape was fabricated by a following decomposition process. What is more, precursors with different morphology were fabricated in organic-water system respectively. The metal oxide can keep the shape of the precursors, consequently; it provides a facile method to modulate the particle size and morphology.XRD, SEM, TG-DTA and N2physical adsorption-desorption measurements were applied to characterize the phase, morphology and pore structure of the samples. The results showed that:the metal oxides materials retain morphologies of their precursors. The morphology of the precursors are strongly affected by the solvent system, Size of the precursors decrase with the vol.%of organic increasing. These alterations can be interpreted by the changing dielectric constant of mixed solvent and the selective solvation of ions. The pore characters depend strongly on the annealing temperature. The pore diameters of the material surface increase gradually with the increasing of decomposition temperature.Performance tests were carried out using porous iron oxides as the anode active materials in lithium battery. It shows that the iron oxides prepared in the ethanol/water mixed solvent. The first and the50th discharge and charge capacities were measured to be as high as932mAh·g-1and96.5mAh-g-1, respectively.