Study And Applications Of Mn Or Ni Doped Fe3C Magnetic Nanomaterials

Fe₃C can find applications in the fields of magnetism, medicine, electrochemistry and so on. It have been shown that bulk Fe₃C has a high theorical saturated magnetization（Ms） value of 150 emu g-1 and can be also regarded as the catalyst of oxygen reduction reaction（ORR） with highly catalytic activity. However, due to the harsh synthesis conditions from the special structure of Fe₃C, it is necessary to develop a flexible and facile route to prepare Fe₃C and enhance its applications. Based on the previous theoretical and experimental research on Fe₃C, we design a series of metal-organic precursors based on Sol-gel method and successfully prepared Fe₃C, Mn doped Fe₃C((Fe_1-xMn_x)₃C), Ni doped Fe₃C((Fe_1-xNi_x)₃C) and N-Enriched Fe₃C（Fe₃C/C-N_x） magnetic nanomaterials via the carbothermic reduction in high temperature. The detailed works are as followed:1. We systemically develope a novel route to prepare single-phase Fe₃C nanomaterials and confirmed their optimized fabrication conditions. The measuring results show that the as-synthesized Fe₃C nanomaterials possess core-shell structures which are encapsulated by graphite carbon. Besides, all the as-synthesized materials demonstrate the soft magnetic behavior, the particle sizes and M s values will be changed with the increase of calcination temperatures and heating rates.2. To further study the effect of transition metal doping on the structure and magnetism of Fe₃C, we fabricate(Fe_1-xMn_x)₃C and(Fe_1-xNi_x)₃C magnetic nanomaterials. The maximum doping concentrations are 20% and 10% for Mn and Ni, respectively. The optimized fabrication conditions are also fixed. The measuring results show that the structure of Fe₃C can not be changed by the doping of Mn or Ni, but the crystallization temperature, morphology and magnetic properties may be affected.3. The structure and magnetism among the Fe₃C,(Fe_1-xMn_x)₃C and(Fe_1-xNi_x)₃C magnetic nanomaterials are compared. We believe that the doping of Mn and Ni can substitute portion of the Fe atoms in the crystal cell. The key factors for the change of crystal parameters, morphology and magnetic properties of Fe₃C are the differences of diameter and magnetic moment among Fe, Mn and Ni atoms.4. At last, a series of Fe₃C/C-N_x magnetic nanomaterials are prepared and used as ORR catalyst in alkaline solution. Among the series, Fe₃C/C-N750 demonstrates the comparable catalytic activity with commercial Pt/C catalyst, superior stability and methanol-resist property. These advantages make the Fe₃C/C-N750 as the optimal substitute of commercial Pt/C catalyst. Besides, Fe₃C and(Fe_1-xNi_x)₃C are also utilized to adsorb methylene blue（MB）, both of them can realize the quick adsorption and separation of MB in the water which make them have potential application in wastewater treatment.