Preparation And Properties Of Vanadate Nanomaterials

In the dissertation the vanadate nano materials such as (NH4)2V4O9) nanosheets thin films, ultra-thin (NH4)2V3O8 nanosheets, (NH4)2V3O8 nanometer crystallite were chosen as the objects of study. Modem testing methods were used to study the preparation, strueture and properties of vanadate nanomaterials.The obtained main results are as follows:a) we report a facile one-step hydrothermal method to directly synthesize (NH4)2V4O9 thin films on substrate. It was found that the filmswere about dozens of microns in thickness, and the thickness of thesingle nanosheet was (50-800)nm.On the basis of the experimental results, we proposed that the oriented-attachment-exfoliation-recrystallization-crystal growth mechanism is responsible for the formation of the resulting products. Used as a cathode material, the nanosheets thin films show superior first charge and discharge capacity which was as high as 977 mA-h·g-1. What is more important, excellent cycling stability without considerable capacity loss for 500 cycles is observed. It is believed that the unique nanosheets thin films morphology and its intrinsic structural features is responsible for their excellent structure stability, and thus resulting in superior electrochemical performance.b) Ultra-thin (NH4)2V3O8 nanosheets have been directly fabricated by a facil one-step hydrothermal treatment of an aqueous solution of V2O5, tartaric acid and ammonium hydroxide. The morphology and microstructure of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Infrared analysis (IR). The energy gap (Eg) and thermal performance were further examined by UV-Vis spectroscopy and thermogravimetry/differential scanning calorimetry (TG/DSC). It was found that the obtained single-crystal (NH4)2V3O8 are quadrangulars, had good thermal stability, and the band gap was 1.04 eV.. Used as a photocatalyst material for the degradation of rhodamine B (RhB) dyes, the ultra-thin (NH4)2V3O8 nanosheets show superior photo catalytic performance, with they could almost completely degrade RhB dye in 1 h under UV-Vis irradiation.c) (NH4)2V3O8 single-crystal have been directly fabricated by a facil one-step hydrothermal treatment. The structure, morphology, microstructure of the samples were characterized by Single-Crystal X-ray Diffraction, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Infrared analysis (IR). Especially, ammonium hydroxide (NH33H20) was used as template and then three different morphologies of the (NH4)2V3O8:nanoflakes, tetragonals, and octagonals were obtained through the change of the experimental conditions. Furthermore,the magnetic properties of the (NH4)2V3O8 were investigated. The results indicated that all these (NH4)2V3O8 single-nanocrystal show good super paramagnetic phenomenon.