Controlled Synthesis and Characterization of Tungsten and Nickel Nanoparticles, and Studies on Preparation of Co-Ni Alloy Nanoparticles under Wet Chemical Process
|Course||Physical and chemical|
|Keywords||Nanomaterials Wolfram Nickel Cobalt and nickel|
The preparation of nanomaterials is a great challenge in the fields ofsynthetic chemistry and materials science, because materials at nano-scale and micro-scale structure have unique properities.Nanostructures with controlled size and shape are important from bothfundamental applied and technological viewpoints. In fact, it iswell-known that the size and shape are two primary variablesdetermining physical(such as magnetic, optical, etc.) as well aschemical(reactivity, catalysis, etc.) properties of nanoparticles. Here,we report some new methods to synthesize nanoparticles of tungsten,nickel, nanoalloy of cobalt-nickel under relative mild condition bydeveloping effective synthetic technique.The wet chemical synthesis process of tungsten nanoparticles hasbeen systematically studied by examining the processing parametersto control the crystalline sizes and phases of samples. The aqueouschemical reduction method has been proposed to prepareunaggregated nanocrystals of tungsten in hydrochloric acid medium.The effect of additive sequence of stock materials, reactiontemperatures, cyclohexane on the formation of tungsten nanopowdershave been described in detail using X-ray diffraction(XRD),transmission electron microscopy microscope(TEM), scanningelectron microscope(SEM), energy-dispersive spectroscope(EDS). Itwas found that rod-like nanocrystalline tungsten particles werederived by aqueous reduction process at 80℃ for 90 min.Another part of my research work is the production of nickelnanoparticles and Co-Ni alloy powders. The synthesis of nickel andCo-Ni alloy nanoparticles by wet chemical reduction with hydrazineat relative low temperature, without soluble polymer as a protectiveagent, has been studied. We also found that it is not necessary toperform the reactions under a nitrogen atmosphere and can obtain pureNi nanocrystallines without oxides. The resultant particles werecharacterized to be pure nickel and pure Co-Ni crystallines.Furthermore, by high-resolution scanning electron microscopy, it wasfound that nickel nanoparticles were protected by a flower-like surfacelayer which was formed under magnetic field, and Co-Ni alloypowders were self-assembled bigger spheres of about 200nm withsmaller particles of 10-20nm.In short, the procedures described in this essay offer the possibilityof a generalized approach to production of other metal nanoparticlesunder wet chemical redox process.