Study On Preparation And Magnetic Properties Of Nano Iron Nitride

In recent years,nano iron nitride material has attracted considerable attention in material field around the world because of its excellent magnetic properties,inoxidizability,and abrasive resistance,which is considered to have great potential for application as a new kind of magnetic materials.It plays an important role in the mechanical,aerospace,chemicals,electronics,metallurgy,energy,medical and other fields.In this research,the influence of synthesis parameters on the preparation of nano iron nitride powder has been systematically investigated with nano Fe(OH)3 as the precursor with the patented technology ‘a preparation method for nano Fe4 N powder and the high pressure gas-solid reaction bed’ and the NH3/H2 high pressure combined method of reduction and nitriding.The phase,composition,morphology,magnetic properties,and thermostability have been preliminarily characterized by X-ray diffraction(XRD),transmission electron microscope(TEM),vibrating sample magnetometer(VSM),and thermogravimetry(TG)to investigate the influence of temperature,time,ammonia hydrogen ratio,and pressure during reaction process on the preparation.At the same time,the molecular dynamics(MD)simulation and LAMMPS has been used to study the effect of temperature on the particle size of Fe4 N at the atomic scale.Results show that the ammonia hydrogen ratio plays an important role in the composition of the product.The relatively ideal ammonia hydrogen ratio for the preparation of nano Fe4 N powder is 3:1.The product would be single-phase Fe3 N when the ratio is all ammonia.The nano Fe4 N powder with the average grain size of 35 nm has been prepared successfully at 673 K and 0.4 MPa for2.5 h with the ammonia hydrogen ratio 3:1 by the combination of MD simulation and experiment.The nano Fe3 N powder with the average grain size of 45 nm has been prepared successfully at 873 K and 0.6 MPa for 5 h with the ammonia hydrogen ratio1:3 by the experiment.TG analysis show that the thermostability of nano Fe4 N powder is good.The results of magnetic detection show that the hysteresis loop of nano Fe4 N powder with the average grain size of 35 nm is thin and narrow,and which is a fairly desirable soft magnetic material with Ms=169.80 emu/g.Results show that with the increase of temperature,the saturation magnetization increases first and then decreases slowly,reaching a maximum at 673 K,and the intrinsic coercivity and magnetic induction coercivity increase continuously.As the reaction time increases,the saturation magnetization remains stable firstly and decreases slowly after the time reaches 4 h,while the intrinsic coercivity and the magnetic induction coercivity fluctuate all through.As the pressure increases,the saturation magnetization,intrinsic coercivity and magnetic induction coercivity increase at first and then decrease,and the maximum value appears at about 0.4 Mpa.The parameters have no significantinfluence on the residual magnetization.Hence,by the accurate controlling of several parameters in the experiment process,the saturation magnetization,residual magnetization,intrinsic coercivity and magnetic induction coercivity of nano Fe4 N powder can be optimized.In general,this process could reduce the reaction temperature and shorten the reaction time,which lays a foundation for the further study on the preparation of nano-sized iron nitride materials and the application of electromagnetic fields,and which is of important significance to the industrial production of nano Fe4 N powder.