Synthesis Of Magnetic Metal Nanocrystallines By High Temperature Liquid Phase Method

The nanocrystallines of transitional metals have the unique electronic and magnetic properties. They also exhibit the behavior of strong self-assembly into ordered structures. Therefore, they are promising for applications in future electronic devices. The synthesis of uniform nanocrystallines of different shapes is critcal to the realization of their properties and their applications. In this paper, we address this key issue, and studied the synthesis of metal nanocrystallines by the high temperature liquid phase method. Specifically, we studied the control of the size and shapes of the metal nanocrystallines including Co,Fe,Ni. Based on the synthesized nanocrystallines, we loaded the metal nanocrystallines onto carbon nanotubes (CNTs) and SiO2 nanofibers. Using the supported metal nanocrystallines as the active catalysts, we grew carbon nanotubes from the chemical vapor deposition reactions.First, we synthesized Co,Fe,Ni nanocrystallines by the high temperature liquid phase method using oleic acid and TOP as surfactant. By this, we achieved monodispersed spherical metal nanocrystallines. These nanocrystallines displayed the behavior of self-assembly in 2D and 3Dordered structures.Second, based on the knowledge of the growth of the hcp phase Co nanocrystallines, we changed the drwelling time of reactions and the injection temperatures reductants by which we altered the size of the Co nanocrystallines. By turning the amount of the surfactant the cobalt precursors and the addition of the alkali metal sal, we turned the shapes of the nanocrystallines from spherical to cubic. Third, as a step closer to functional devices of the nanocrystallines, we studied the assembly of the metal nanocrystallines on carbon nanotubes and silica nanofibers. By this, we achieved ordered assemblies of the Fe nanocrystallines on carbon nanotubes. We also loaded Co nanocrystallines onto the carbon and silica nanofibers. Comparing to the Co nanocrystallines, the Fe nanocrystallines generated better assemblies on the SiO2 nanofibers.Fourth, the synthesized metal nanocrystallines were employed as the catalysts to generate carbon nanotubes by the chemical vapor deposition methods. By this we grew carbon nanotubes successfully from the metal carstals on the silica nanofibers. In the growth of CNTs, we found that the Co nanocrystallines exhibited better catalytic effects than the Fe nanocrystallines and the catalytic effect of Co was further enhanced when the metal nanocrystallines was doped withby sulfur. Finally, we loaded the Fe nanocrystallines into a ceramic precursor and pyrolyzed the mixture to form the SiCO ceramics dispersed with the magnetic Fe nanocrystallines. The composites exhibited magnetism at room temperature.