The Synthesis,Structure And Magnetic Property Study Of Iron/Iron Carbide Nanocomposites

Iron carbide ranks amongst the oldest materials known to mankind. The presenceof6.69wt%C in Fe3C in fact changes its properties dramatically: iron carbide is ce-ramic-like in mechanical behavior and chemically much more inert than pure iron.Iron carbide nanoparticles would indeed be suitable for a variety of applications, frombiomedicine (e.g., as a magnetically guided transporter for drugs or as a contrast agentfor magnetic resonance imaging) to electronics (e.g.,as a magnetic recording material)and from the production of novel ferrofluids to the design of novel catalysts (e.g., forthe Fischer-Tropsch process). More specifically, iron carbide is to be considered asthe most suitable candidate to enhance the functionality of metallic iron (e.g., due toits higher resistance against oxidation) and iron oxide (e.g., due to its superior mag-netic properties and hardness) in a myriad of applications. At a time when the litera-ture presents countless procedures for the production of iron carbide nanoparticles,getting a synthetic pathway to produce basic Fe3C nanoparticles in a reproducible,simple, and fast manner is still a challenge.In this thesis,we review relevant studies of iron carbide at home andabroad.Especially we summarise the various synthetic methods and their several ap-plications.It has been reported that both melamine and urea can be used as carbonsource and nitrogen source,thus we choose them as carbon source for the synthesis ofhigh percentage of iron carbide nanocomposites. The method of synthesis is sol geland the essence of it is mixing carbon source and nitrogen source and revulsant to getgel precursor.Final product was successfully fabricated through calcining in ultrapurenitrogen atmosphere.Transmission electron microscope (TEM) and X-ray diffractionanalysis (XRD) have been used for structural characterization; magnetic hysteresiscurve used as the functional characterization;we also make the possible explanationsto the mechanism of two kinds of carbon source and give the comparative study. Themain work of the thesis is as follows: We mixed carbon source and nitrogen source (ferric chloride) and CTAB bysol-gel method to get the precursor compounds. After calcining the precursor com-pounds the final product Fe/Fe3C nanocomposites was prepared.For melamine as thecarbon source,the temperature range of getting products wais600-680℃and for ureait was650-700℃. It has been carried on the thorough exploration and research to theconditions of the synthesis of iron carbide from three aspects of calcining temperature,carbon and nitrogen source proportion and the amount of CTAB. Synthesis conditionsof the iron carbide, the magnetic property of products and the possible formationmechanism are given.The Br in the CTAB which playing the role of inducer leads theprecursor mixture of iron source to get the iron,which is conductive to combine withthe carbon in the carbon source for getting iron carbide.Comparing with melamine,inthe reaction process a part of urea combined with iron source gets the easily decom-posed iron nitrides,the content of iron carbide reduces,the corresponding functionalityalso decreases.