Studies On Controlled Synthesis Of Iron Group Metallic/alloy Nanoparticles Under Wet Chemical Process

The preparation of nanomaterials is a great challenge in the fields of synthetic chemistry and materials science, because materials at nanoscale and micro-scale structure have unique properities. Nanostructures with controlled size and shape are important from both fundamental applied and technological viewpoints. In fact, it is well-known that the size and shape are two primary variables determining physical(such as magnetic, optical, etc.) as well as chemical(reactivity, catalysis, etc.) properties of nanoparticles. Here, we report some new methods to synthesize nanoparticles and nanoalloy of iron group metal under relative mild condition by developing effective synthetic technique.A simple method for the synthesis of iron nanoparticles is reported. In this method, iron nanoparticles with particle sizes about 17-30 nm were prepared by the reduction of ferrous chloride with hydration hydrazine in aqueous solution at room temperature, with citric acid's appearance. The resulting metallic powders were characterized by XRD, EDX and FESEM. The magnetic performance of the obtained Fe nanoparticles are also discussed.One-dimensional rods of metallic iron with width fluctuation were prepared in the presence of magnetic fields.One-dimensional rods of metallic iron with lengths up to 400 nanometers and an average diameter of about 30 nm were prepared in the presence of magnetic fields, while without an applied magnetic field metallic iron nanospheres were obtained as usual.Based on our experimental results, it is concluded that a magnetic field applied during the chemical reaction can synchronously influence the parallel growth of iron. Furthermore, the possible growth model that the chemical reduction of Fe(II) may easily occur along the magnetic lines of force instead of in the whole reaction system was proposed. It is suggested that weak magnetic fields could be developed as promising approaches to control the growth of materials in chemical reactions, leading to the enhancement of magnetic properties.Another part of my research work is the production of metallic nickel cobalt nanoparticles and Co-Ni alloy powders. The synthesis of metallic nickel cobalt nanoparticles and Co-Ni alloy powders by wet chemical reduction with hydrazine at relative low temperature, without soluble polymer as a protective agent, has been studied. We also found that it is not necessary to perform the reactions under a nitrogen atmosphere and can obtain pure Ni and Co nanocrystallines without oxides. Furthermore, by high-resolution scanning electron microscopy, it wasfound that cobalt and nickel metallic nanoparticles were protected by a flower-like surface layer which was formed under magnetic field, and Co-Ni alloy powders were self-assembled bigger spheres of about 200nm with smaller particles of 10-20nm.In short, the procedures described in this essay offer the possibility of a generalized approach to production of other metal nanoparticles under wet chemical redox process.