Synthesis And Properties Of Nanocrystalline Iron Electrodeposited Under Magnetic Field

One-dimensional magnetic nanomaterials have great magnetic anisotropy and superior magnetism than 2D magnetic nano-film when it is magnetized under a magnetic field parallel to its long axis. Among them, 1D nanocrystalline iron has good conductivity of electricity and heat, wear resistance, high strength and modulus for its excellent performance of internal structure, magnetism, heat-resistant and melting point. It is widely applied in electronic, electromagnetic and medical fields, such as electromagnetic wave absorbing materials, high density magnetic recording materials, high-quality-sensitivity components, medical and biologic engineering materials.In this thesis, 1D nanocrystalline iron is synthesized by a self-developed novel, simple and highly efficient method: immediate electrodeposition induced by magnetic field. The process does not employ any templates, precursors or inducing seeds. Deposits are characterized by SEM, FSEM, TEM, XRD and VSM, the results show that:Slice, dentrite and crosslinking slice nanocrystallineα-Fe are electrodeposited in aqueous solution of Fe²⁺ at current density of 0.05-0.3A/cm², electrolyte concentration of 0.25-2.0mol/L and solution temperature of 20-30℃, without magnetic field or organic additive. By adding SDS or glycerin into the solution, electrodeposits grow into triangle truncated cone for the mechanism of helix dislocation couple and into round slice for 2D grain-growth mechanism, respectively. Under magnetic field, deposits grow mainly into thin slice. When organic additives and magnetic field occur together, their effects on the morphology of deposits are mutually exclusive. Tropism of [110] of deposits becomes prominent with the appearance of magnetic field, but the prominence diminishes gradually with the increase of current density.1D nanocrystalline iron is electrodeposited in aqueous solution of Fe²⁺ at current density of 0.1-0.2A/cm², electrolyte concentration of 0.5-1.0mol/L, solution temperature of 25℃and electrode space of 10-20mm, under magnetic field and with SDBS. The deposit isα-Fe with tropism of [110], diameter of 40-60nm, aspect ratio of 50-60, smooth surface and no divarication. Magnetism of the deposit is anisotropy, axial saturation magnetization (140.3emu/g) is greater than radial saturation magnetization (121.1emu/g), axial residual magnetization (19.25emu/g) and axial coercivity (193.41Oe) are less than radial residual magnetization (23.27emu/g) and radial coercivity (207.15Oe), respectively. The easy magnetization direction is the radial direction.1D nanocrystalline iron grows at the direction of magnetic field on the thick crystal face, for mechanisms of continuous grain-growth and step-growth. The lateral growth of the deposit is restricted by magnetic field for its effects on discharge process of Fe²⁺ and diffusion of absorbing Fe atoms into crystal lattice.