Study And Application Of Nd Or Dy Doped Fe₃C Magnetic Nanomaterials

Iron carbides have high saturation magnetization,good mechanical properties,high chemical stability,corrosion resistance,and excellent biocompatibility,so they have excellent performance in the fields of magnetism,catalysis,and biomedicine which has attracted widespread attention of researchers in recent years.We prepared Fe₃C magnetic materials and rare earth Nd or Dy-doped Fe₃C materials by sol-gel method,studied their synthesis conditions,structural properties,and magnetic properties;prepared and studied Fe₃C/CoFe₂O₄ nanomagnets with exchange coupling;Fe₅C₂ magnetic materials with a cubic shape were synthesized and studied;the applications of these materials were explored.The main content works of this paper are as follows:1.A melamine-based sol-gel method was used to prepare the precursor.The precursor was calcined in an inert atmosphere to synthesize a composite magnetic material of Fe₃C and carbon nanotubes?CNTs?.Firstly,the synthesis conditions of the material were determined by adjusting the calcination temperature;secondly,the morphology of the material was characterized by transmission electron microscopy;finally,the magnetic properties of the sample were tested using a vibrating sample magnetometer.The results show that the prepared Fe₃C nanoparticles are encapsulated in carbon nanotubes,and the Fe₃C nanoparticles have a layer of carbon shell.The synthesized Fe₃C/CNTs composite magnetic materials exhibit soft magnetic properties,and as the synthesis temperature increases,the saturation magnetization of the products changes regularly.2.Nd or Dy doped Fe₃C magnetic materials were synthesized by sol-gel method.By changing the doping concentration of rare earth ions,the effects of these two rare earth metal elements on the structure,morphology and magnetic properties of Fe₃C were investigated.The results show that the incorporation of Nd or Dy has little effect on the structure of Fe₃C,but the incorporation of Dy influences the morphology of the material.In addition,for magnetic properties,the doping of Nd reduces the saturation magnetization of the material,while the doping of Dy increases the saturation magnetization of the material.3.The Fe₃C/CoFe₂O₄ nanocomposites with exchange coupling were prepared by a simple two-step method.This two-step process includes the preparation of iron carbide nanoparticles from ethylenediamine carbonized Fe₃O₄ and the co-precipitation method to prepare Fe₃C/CoFe₂O₄ nanocomposites.The structure and morphology of the nanocomposites were studied by X-ray powder diffraction and transmission electron microscopy.The magnetic properties of the composites were also studied.The results show that CoFe₂O₄ nanoparticles are tightly wrapped around Fe₃C nanoparticles.The magnetic test data show that when the content of CoFe₂O₄ is 1 mmol,the Fe₃C/CoFe₂O₄nanocomposite exhibits excellent magnetic properties.Currently,the exchange coupling effect of the nanocomposite reaches the maximum.4.The cubic iron carbides were successfully prepared by ethylenediamine carbonization,and their structure,morphology,and magnetic properties were studied.Importantly,Fe₅C₂ and Fe₃C can be obtained by changing the calcination temperature.The prepared iron carbide materials have a regular cubic shape and are protected by a thin carbon shell.The magnetic test results show that the prepared Fe₅C₂ and Fe₃C materials all show good soft magnetic properties and both have high saturation magnetization values.5.Finally,the application was explored,and the performance and stability of hydrogen production from electrolytic water of cubic iron carbide materials were tested.The results showed that the synthesized Fe₅C₂-Fe₃C@NC catalyst showed effective hydrogen evolution reaction?HER?catalytic activity.Not only that,the Fe₅C₂-Fe₃C@NC catalyst also exhibits good cycle stability and low Tafel slope.This work provides new ideas for developing efficient alternatives to precious metal catalysts.