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Structure, Morphology Controlling and Surface Functionalization of Spinel Ferrite

Author: BuHeBaTeEr
Tutor: FuHongGang
School: Heilongjiang University
Course: Inorganic Chemistry
Keywords: Spinel ferrites Nanocrystals Morphology controlling Reduction Surface modification
CLC: O614.811
Type: PhD thesis
Year: 2013
Downloads: 121
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Abstract


As typical spinel ferrites, AB2O4nanoparticles（NPs） are receiving increasing interestin recent years for many of their magnetic properties, such as special saturationmagnetization and coercivity, can be greatly effected by their particle size and theirgood biocompatibility. And they have been widely used in many importanttechnological applications, such as high-density magnetic data storage, biological sensor,bioseparation, antiradar coatings, magnetic fluid and magnetic resonance image （MRI）etc. In this thesis, ferric oleate are proposed to systhesize spinel ferrite magneticnanoparticles, and the main efforts are devoted to the research on effects of structureand morphology control on the magnetic performance, distribute stability of the spinelferrites after surface functionalization and their application in magnetic fluids. Magneticperformance changing of their reduction alloy nanomaterial is also carried out. And byloading graphene with magnetic spinel ferrites, the changes of electromagnetic waveabsorbing properties corresponding to the effect of the graphene are discussed.1. The Fe3O4NPs with average particle size of11nm are prepared by chemicalco-precipitation method, and they are coated with oleic acid as the primary layersurfactant in aqueous phase. Then the oleic acid coated Fe3O4NPs are transferred toheptane to be re-coated with succinimide to synthesize bilayer coated Fe3O4magneticNPs, and the reason for the stability of the bilayer coated Fe3O4magnetic NPs isdiscussed. Stable magnetic fluids of bilayer coated Fe3O4magnetic NPs are obtained bydispersing them in PAO-2carrier. The viscosity, specific saturation magnetization anddensity dependence of the magnetic fluids on the content of the bilayer coated Fe3O4NPs is analyzed. Result shows that these properties can be obviously improved as thecontent of the bilayer coated Fe3O4NPs increasing. The magnetic fluids have goodmagnetic stability for no phase separation happens after360days, which may havepotential application in machinery. 2.The low-cost homemade Feoleate3, oil soluble polymer surfactant polyisobutenesuccimide （PIBA） and paraffin oil, are separately used as iron precursor, surfactantandand solvent. Via thermal decomposition method, the micro-sized（less than15nm） Fe3O4NCs with cubic, cuboctahedral and octahedral morphology are successfully prepared.And the effects of surfactant, reaction temperature, heating rate on the morphology andparticle size of the Fe3O4NCs are respectively discussed. Result shows that morphologycontrolling of the Fe3O4NCs can be realized through changing heating rate of thereaction. In the thermal decomposition reaction, the surfactant PIBA realizes thepurpose of being as stabilizer and surface modifier at the same time, which can improvethe dispersibility of Fe3O4NCs. The PIBA coated Fe3O4NCs can be easily dispersed ineither low or high boiling point solution to obtain magnetic fluid. And the obtainedmagnetic fluid shows good stability even in strong magnetic field. All the raw materialsin the reaction are cheap and nontoxic which make it easy to industrialize.3. The homemade oleic acid metal （Co, Mn, Zn, Ni） salts are used in replacing theidentity of the divalent M2+cation（A place） of the AB2O4structure Fe3O4NCs to obtainspinel CoFe2O4, MnFe2O4, ZnFe2O4, NiFe2O4magnetic NCs with average particle sizeof nearly5nm. And through changing reaction conditions, magnetic NCs with differentparticle sizes can be successfully prepared. Result presents the magnetic properties ofthe magnetic NCs can be controlled by their structure adjusting. And by reducing thesemagnetic NCs with H2, CoFe, MnFe, ZnFe, NiFe alloy nanomaterials are separatelysysthesized, their structure and magnetic properties are compared with the magneticNCs. It can be drown through the comparation that both the particle size and magneticproperties changed greatly after reduction. Spinel MFe2-xLaxO4（x=0.05,0.1,0.15）magnetic NCs are prepared by replacing part of the trivalent Fe3+cations （B place） ofthe AB2O4structure Fe3O4NCs with La3+., We can draw through experiments that bothLa2O3content and remanence and coercivity of the magnetic NCs increase with thegrowth of La addition amount in the spinel MFe2-xLaxO4systems. Afterwards the oleic acid coated MnFe2O4NCs are re-functionalized with secondary ligands such ascetyltrimethylammonium bromide （CTAB）, sodium dodecyl benzene sulfonate （SDBS）and sodium dodecylsulfate （SDS） to obtain well-dispersed water-soluble NCs. Theaqueous solutions of bilayer functionalized NCs are used in adsorbing Pb2+out ofwastewater. Test result shows CTAB coated NCs have the highest efficiency of Pb（II）associativity （nearly90%）.4. The graphene/NiFe2O4nanocomposite with graphene loading amount of10%,20%and30%are respectively prepared via hydrothermal reaction of Feoleate3, Ni（oleate）2and graphene at160℃for12h. And graphene loading amount are controlled byadjusting the additive amount of graphene. Compared with pure NiFe2O4NCs, theparticle size of NiFe2O4in the nanocomposites increases as their graphene loadingamount increasing, while their particle distribution uniformity decreaes. Absorbingproperty measurement of pure NiFe2O4and the three amounts of graphene/NiFe2O4nanocomposite reveals the doping of graphene can increase the dielectric loss of thenanocomposites, which is good for their absorbtion of electromagnetic waves. But whengraphene loading amount is over20%, electromagnetic waves absorbing property of thenanocomposites decreases. The possible reason for it is the complex permittivity of theamount accordingly matches with its complex permeability when graphene loadingamount is20%.

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CLC: > Mathematical sciences and chemical > Chemistry > Inorganic Chemistry > Metal elements and their compounds > First Ⅷ group metal elements and their compounds > Iron metal element > Iron Fe
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