Preparation And Magnetic Performance Research Of Fe Based Magnetic Nanoparticles

FePt alloy nanoparticles with different components, Fe3O4magnetic nanoparticles, and FePt-Fe3O4nanocomposite particles were synthesized by thermal decomposition method under highboiling temperature solvents. We chose platinum acetylacetonate (Pt(acac)2) as the precursor ofPt, and iron pentacarbonyl (Fe(CO)5) as the precursor of Fe, and used two different kinds ofsurfactants, oleic acid (C17H33COOH) and oil amine(C18H35NH2,), simultaneously. Severaltechniques, for example, Laser particle size analyzer, X-ray diffraction (XRD), Inductively coupledplasma emission spectrometer (ICP), High-resolution transmission electron microscopy (HRTEM),Vibrating sample magnetometer (VSM) and Superconducting quantum interface (SQUID) havebeen employed to study the composition, morphologies, size distributions, phase constitution,microstructure and magnetic properties. The mechanism of nanoparticle growth is also discussedfor the Fe3O4magnetic nanoparticles in different preparing processes. The main achievements areas follows:(1). The monodisperse FePt nanoparticles have been synthesized successfully by thermaldecomposition, and all the particle size are less than10nm (6nm~8nm). After annealing at700oC for1hour on the silicon slice, the FCC structure for as-prepared FePt nanoparticle has changedto FCT structure, and the coercivity is large as1T for the Fe-Pt composition ration with1:1.0.(2). The monodisperse, morphology/size-controllable Fe3O4nanoparticles have beensynthesized successfully by thermal decomposition. The study shows that the growth of Fe3O4nanoparticles underwent two processes: one is the so-called nucleation stage near thedecomposition temperature of precursor, the other is the subsequent growing up of the crystalunder the refluxing of the solution near the boiling point of the solvent. The two surfactants, oleicacid and oleylamine, play different roles during the process of the particle growth. Oleic acidmainly combined with the precursors, and thus controlled the nucleation process. While oleylaminemainly stabilized the formed nanoparticles, so as to control the grow up step of the particles.Oleylamine has different stabilization adsorption with different crystal surfaces of the iron oxidenanocrystal. As for Fe3O4cystal, the binding force with {111} surface is stronger than that with{100}. (3). FePt-Fe3O4composite nanoparticles have been synthesized successfully by thermaldecomposition. The structure of the composite nanoparticles is heterogeneous and, the particles ofFePt and Fe3O4coupled perfectly, in which there is no lattice defects or matching dislocation onthe coupling interface between the two phases.(4). A signification of this article is that we successfully synthesized the Fe-baesd magneticnanoparticles without using reductants. The as-prepared FePt, Fe3O4, and FePt/Fe3O4nanoparticlesare of monodisperse, and the nanocomposite particles obtain the perfect coupling interface betweenthe two phases.