Preparation Of Carbon Encapsulated Iron Nanoparticles And Nitrogen-and Iron-doped Graphene By Arc Discharge

In this thesis, the anodes were prepared by the compacting method with a certainmass ratio of mixture of iron(III) oxide and graphite powders as the raw materials.The carbon encapsulated iron nanoparticles (CEINPs) and nitrogen-and iron-dopedgraphene were prepared by DC arc discharge. The products were characterized bySEM, TEM, HRTEM, EDX, XRD, XPS, TG-DSC and PPMS. The effects of intaketemperature of argon, the atmosphere of discharge chamber, the diameter of anodeand the methods of preparing anode on the morphology, structure and yield of theproducts were investigated. The possible processesof formation of the CEINPs werediscussed briefly.When the intake temperature of argon was at room temperature, the CEINPs withcomposite shells and good core-shell structure were prepared. The shells of CEINPsare mainly composed of the innermost non-graphite, middle incomplete graphite, andoutermost disordered carbon structures, containing C, Fe, and O elements, and theirthicknesses are between1.7nm and7.9nm. The average diameter of the CEINPs isabout17.4nm; the stable temperature of product B1in air reaches260oC, the totalcontent of Fe element is79.5wt.%. The saturation magnetization (Ms) and coercivity(Hc) of the product B1are109.3emu/g and167Oe respectively. When the intaketemperature of argon was at800oC, the CEINPs with very thin shells and goodcore-shell structure were prepared successfully. The thicknesses of the carbon shellsof CEINPs are in the range of ca.0.5-5.3nm, i.e., they can be as thin as only twolayers of graphite; the average diameter of the CEINPs is about24.7nm; the stabletemperature of product B2is below245oC in air, the total content of Fe element is77.0wt.%. The Ms and Hc of the product B2are107.4emu/g and143Oe respectively.The homogeneity of compositions of anode, the content of iron, the microelectric fieldand micromagnetic field of iron element, the discharge chamber atmosphere andintake temperature, and gradients of temperature and concentration between the arcdischarge zone and the inner wall of cooling copper tube play important role on themorphology, microstructure and sizes of the CEINPs.The different discharge chamber atmospheres of argon and nitrogen havesignificant effects on the shell thicknesses and sizes of CEINPs and magnetic property of the products B, and also have some influences on their elemental compositions andthermodynamic stabilities. The size of diameter of anode has a certain influence onthe contents of nanoparticles in the products B.The methods of preparing anode (the homogeneity of composition of the wholeanode) have significant effects on the shell microstructures of CEINPs of the productsB and the yield of the products C, i.e., the compacted anode (the whole compositionof anode is uniform) is advantageous to form CEINPs with good shells of graphitelayers and can greatly increase the yield of nitrogen-and iron-doped graphene.The results of this paper have important practical and theoretical significances ondeveloping the applied researches of CEINPs and nitrogen-and iron-doped graphene,and preparing novel nanomaterials by arc discharge.