Fabrication And Characterization Of Nanomaterials By Hydrothermal Method

Since the discovery of the C nanotubes, low-dimensional nanostructures of materials have received great research attention because of their unique photochemistry, photophysical and electron-transport properties different from those of bulky materials. On the basis of well-defined low-dimension nanostructures, many new and promising fields have been established, including nanofabrication, nanodevices, nanobiology and nanocatalysis, etc. Among of the challenges in this field, the main one is how to precisely control the sizes, dimensionalities, compositions, and crystal structures of materials in nanoscale.This paper mainly introduces the way of fabrication and characterization of the low-dimension of nanomaterials. The structure, morphology and character of the nanomaterials were characterized. And the nanomaterials as the lithium-ion battery anode were studied. The important results are as follows:1. Fabrication of Pb(Zr_0.52Ti_0.48)O₃ (PZT) nanorollsWell-crystalline Pb(Zr_0.52Ti_0.43)O₃ nanorolls were synthesized by hydrothermal and PVA-assistant hydrothermal methods. The "rolling mechanism" for the formation of PZT nanorolls was discussed.2. Fabrication of rod- and flower-like NiSWell-crystalline flower- and rod-like NiS nanostructures were synthesized by an organic-free hydrothermal process at a low temperature of 200℃. The effects of temperature and reaction time on the morphology were investigated. The two-step flake-cracking mechanism for the formation of flower- and rod-like NiS nanostructures was discussed.3. Fabrication of CdS dendritesLarge-scale hierarchical CdS dendrites were synthesized by a simple hydrothermal method using 3CdSO₄·8H₂O and SC(NH₂)₂ as the original reactant. The room-temperature PL reveals that the as-prepared CdS products have visible emission of about 485, 561 and 617 nm, and an infrared red (IR) emission centered at 750 nm. The possible photoluminescence mechanisms are proposed.4. Spindle-like ZnOSpindle-like ZnO doped with 2-5 at.% cobalt powders were prepared by a low temperature aqueous solution method. The structural and magnetic properties of the products were investigated. The obtained products were identified to be of hexagonal wurtzite structure without any impurity phase. Also, the Co was incorporated in the ZnO lattice as Co²⁺ and substituted for the Zn site with no evidence of metallic Co. Ferromagnetic behavior was clearly observed at room temperature for the Co-doped samples. Photoluminescence intensity due to the vacancies varies with the Co concentration, and the ferromagnetism moment increases with the increment of oxygen vacancies.5. Fabrication ofα-Fe₂O₃ dendritesHematiteα-Fe₂O₃ dendrites with lengths of 1-4.5μm along the trunk were synthesized by a low-temperature hydrothermal method. The morphology and the crystal structure of the final products were characterized. The magnetic evaluations showed that the as-preparedα-Fe₂O₃ dendrites have excellent ferromagnetic characteristics. The electrochemical performance as anode material for lithium-ion batteries was further evaluated by charge-discharge measurement. It was demonstrated that the material could provide an initial capacity of 1560, 1095 and 670 mA h/g at a current density of 0.1, 0.2, and 1 mA/cm², respectively. However, the cycle life is very poor, how to improve it is very important.6. Fabrication of sheaf-like CuOSheaf-like CuO nanostructures have been synthesized by a simple hydrothermal process conducted at 120℃for 24 h. The growth process of the sheaf-like nanostructures was clarified. The electrochemical performance as anode material for lithium-ion batteries was further evaluated by charge-discharge measurements. It was found that the sheaf-like CuO electrode can exhibit a high initial discharge capacity of 965 mAh/g. After 41 cycles, the electrode can deliver a capacity of 580 mAh/g. And a high rate capability was also obtained.