Preparation Of Novel Carbon-iron Nanocomposites And Carbon-nitrogen Nanomaterials By DC Arc Discharge

In this thesis, carbon-iron nanocomposites, including carbon-encapsulated ironnanoparticles (CEINPs) and iron/graphene nanocomposites (Fe/GNCs), andcarbon-nitrogen nanomaterials were prepared by DC arc discharge method,respectively. The products were characterized by TEM, HRTEM, SEM, EDX, XRD,Raman spectroscope, XPS, and TG-DSC. The effects of the ratios of raw materialsand methods of preparing anode on the preparations of CEINPs and Fe/GNCs wereinvestigated. The effects of the ratios of raw materials, pumping the arc dischargechamber, utilization of transition metal catalyst, melt down of stainless steel sheets,and methods of preparing anode on the morphology and the content of nitrogen ofcarbon-nitrogen nanomaterials were also investigated. The possible processes offormation of CEINPs and Fe/GNCs were discussed briefly.The anodes were prepared by the filling and compacting method respectively witha mixture of90wt.%iron(III) oxide and10wt.%graphite powders as raw material.The CEINPs with high iron content (82.6wt.%), quasi-spherical, and goodcore-shell structure can be successfully prepared in high yield (22.3wt.%) by DCarc discharge, using the anode prepared by the compacting method with the mold I.The cores of CEINPs mainly consist of-iron and iron carbide with similar contents;the diameters of the cores are in the range of3-37nm and their average diameter isabout20.6nm; the shells consist of about3-7graphitic layers and the interlayerspacing is about0.348nm; the product, mainly composed of CEINPs, shows typicalferromagnetic behavior. And the product CIC, prepared in this experiment, mainlyconsists of multi-layer graphene, and some quasi-spherical particles with high ironcontent are distributed among the graphene nanosheets.The product CIC, which mainly consists of Fe/GNCs, is prepared by DC arcdischarge, using the anode prepared by the compacting method with the mold II. TheFe/GNCs are the iron nanoparticles with diameters of3-6nm inside graphene, butsome quasi-spherical particles with diameters of0.1-2.2m and high iron contentare distributed among the graphene nanosheets. The product CICshows thesuperparamagnetic behavior at room temperature.When the anode prepared by the filling method was used, many iron species nanoparticles in the product B are enwrapped in the carbon material; the carbonmaterial shows imperfect and disordered layer structure. And the product CICmainlyalso consists of multi-layer graphene.The carbon-nitrogen nanomaterials were prepared under six groups of differentexperimental conditions, respectively. The products B and CICare investigatedmainly. The former mainly consists of the particles and flakes, and the latter mainlyconsists of the flakes. The carbon contents in them are very high, but the nitrogencontents are very low, especially in the latter. The nitrogen contents of the particlesin the products B increase with the increase of the particle sizes (within certainrange); both the increase of the amount of high nitrogen compound in raw materialand the melt down of stainless steel sheets are beneficial to improve the nitrogencontents in the products; the utilization of transition metal catalyst has no obviouseffect on the nitrogen contents in the products.The uniformity of compositions of anode, the content of iron, the microelectricfield and micromagnetic field of iron element, the inlet temperature of nitrogen, andgradients of temperature and concentration between the region of arc discharge andthe inner wall of cooling copper tube may play an important role in the formation ofCEINPs and Fe/GNCs.