Synthesis And Characterization Of Several One-dimensional Nanomaterials Prepared By Ultrasonic Hydration Method

One-dimensional nanomaterials are new nanomaterials which refer to the two dimensional direction for a nanometer criterion and the length for the macroscopic criterion. Since the discovery of carbon nanotubes by Iijima in 1991's, one-dimensional nanomaterials have raised much attention of scientists in material, physics, chemistry and many domain disciplines. During the past decade, many researchers have synthesized one-dimensional nanostructures such as nanowires, nanorods, nanobelts and nanotubes by various means. Because of their low dimensionality and high aspect of ratio, one-dimensional nanomaterials have become the focus of intensive research in their unique applications in chemistry, electromagnetics, nano-electronics, biological, medical analysis and so on.Great efforts have been placed on the synthesis of one-dimensional nanomaterials, and various preparation means towards diverse one-dimensional nanomaterials (elemental and compound semiconductors, metal oxides, metals, inorganic salts and so on), including templating direction, catalytic growth, electrochemistry, chemical vapor deposition, acoustic degradation method and solution-based solvothermal or hydrothermal treatment have been extensively exploited. However, the preparation of one-dimensional nanomaterials remains poorly studied, and only a few successful examples have been reported.Ultrasonic has become an important tool in chemistry in recent years. When solutions are exposed to strong ultrasonic irradiation, bubbles are implosively collapsed by acoustic fields in the solution. High-temperature and high-pressure fields are produced at the centers of the bubbles. This effect is known as acoustic cavitation. The temperature is estimated to be 5000K, the pressure reaches 20MPa, and the cooling rate is over 1010K/s when the bubbles implode, which enable many chemical reactions to occur. Ultrasonic offers a very attractive method for the preparation of nanosized materials. It has shown very rapid growth in its application to materials science due to its unique reaction effects. The advantages of ultrasonic irradiation include a rapid reaction rate, the controllable reaction conditions, and the ability to form nano-particles with uniform shapes, narrow size distributions, and high purities. Ultrasonic hydration method based on the phenomenon of ultrasonic irradiation provides a novel way and method for the synthesis of one-dimensional nanomaterials. The method can improve the reaction condition, avoid high temperature and high pressure, reduce the reaction time, enhance high purities and the selectivity. The method is relatively new, simple, and operational at ambient conditions.1. As AlO(OH) nano-fibers with uniform morphologies and big specific surface area was successfully synthesized in the initial work, we further studied hydrolytic process and the reaction mechanism of nano Al powder through the synthesis of hydrolyzed ingredient at different time and the different temperature by X-ray diffraction (XRD). The result shows that hydrolyzed ingredient is AlO(OH) at the suitable water bath temperature and hydrolysis time. On the basis of datum, the first production-bayerite was decompounded to form supersaturating aqua, and then to more stable crystallized AlO(OH). The surface area of hydrolysis products increased long with the temperature. When the temperature achieved 70℃, the surface area tended to crease slowly. In addition, we also studied the Influence of inorganic salt to the hydrolytic process and discovered that the suitable inorganic salt sodium would be helpful to enlarge the surface area of hydrolysis products.2. Taking nano Fe powders as raw material, pine needle-shaped, Dandelion-like and wiresα-FeOOH nanostructures have been successfully synthesized via a simple acid base–assisted hydration method. The SEM images present large-scale pine needle-shapedα-FeOOH with uniform growth in group. The as-prepared needle has about 2.16-5.51μm length. In virtue of analyzing XRD patterns from the structure and an ingredient analysis, we proposed a possible mechanism for the formation ofα-FeOOH, which shows that Fe forms the intermediate of Fe (Ⅱ) and Fe (Ⅲ) first, and then formsα-FeOOH material after the air oxidation. The influence of the concentration of NaOH, the deposition time and the reaction temperature on the morphology of the resulted products and material components were discussed in detail. Hysteretic loops were measured on vibrating sample magnetometer at room temperature. The result shows that pine needle-shapedα-FeOOH belongs to typical soft magnetic material. Judged by the low value of Hc, the as-prepared material has important significance to soft magnetism component's manufacture. 3. TiO2 nano-fibers were prepared at 85℃depending on optimizing experiment conditions on ultrasonic hydration method. The structure and morphology of as-prepared products were characterized with XRD, TEM and FT-IR, respectively. We have discussed the influence of the reaction parameters on the morphologies and specific surface area of the production. The results show that the diameter of TiO2 fiber is 3-12nm and the ratio of length to diameter is 30-50. The concentration of NaOH, the reaction temperature and the clean condition have impacts on the morphologies and specific surface area of TiO2. In summary, this method is feasible and easy to operate, which makes industrial production possible.