Study On The Preparation Of Nitride In High Magnetic Field And By Mechanical Alloying

Nitrides are widely used as a variety of functional materials, such as magnetic recording medium and vibration-absorptive materials, due to its excellent properties on anticorrosion, wear resistance, oxidation resistance and outstanding magnetic properties However, there are still a lot of urgent problems concerning how to improve their preparation methods. For instance, the preparation periodicity is too long and it is of big difficulty to obtain products with high purity. Therefore, exploration for creative preparation processing and application of auxiliary facilities are essential.In this work, our investigations mainly focused on the study on the effect of high magnetic field (H=12T) as well as mechanical alloying on the formation of nitride. Samples were characterized by means of XRD,SEM,Mossbauer spectroscopy and OM (Being equipped with the customized depth-measuring software). The main results are as follows:1. Effect of magnetic field on formation of nitride(1) When nitriding occurred in the direction perpendicular to the magnetic field direction at 550℃for 2 h, the phase composition of the compound layer remained the same as that without a magnetic field, which consists ofε-Fe2-3N andγ'-Fe4N and was with a thickness of 8.64μm (being slightly thinner than that without a magnetic field-8.853μm). But the X-Ray diffraction patterns showed that the volume percentage ofε-Fe2-3N was smaller in the magnetical sample than that in non-magnetical sample which indicated that high magnetic field restricted s formation.(2) When nitriding occurred in the direction perpendicular to the high magnetic field direction at lower temperatures (T=494℃,450℃,410℃and 400℃), as the decrease of nitriding temperature, the degree that nitriding occurred weakened gradually. However, it was clear that high magnetic field inhibited the precipitation of bothγ'-Fe4N andε-Fe2-3N.(3) There was a different result when the direction of magnetic field changed during nitriding at 550℃. In the diffusion layer, the quantitative relationship of volume fraction of long-needledγ'-Fe4N nitride was:that in the direction parallel to the magnetic field (H=12T) was the biggest, that without the magnetic field was medium, and that in the direction perpendicular to the magnetic field was the smallest.2. Study on mechanical alloying of Fe and nitride powders and thermodynamic stabilityNitride powder was firstly obtained by nitriding of pure iron powder at 550℃for 2h, and then a mixture of pure iron powder and nitride powder was milled for different time. When the mess ratio was 4:3 (iron:nitride), it could be found that the X-Ray diffraction patterns of resultant powder still kept the existence of nitride peakes afer milling for 16h. But when the mess ratio became to 5:2 (iron:nitride), the diffraction peaks of nitrides disappeared due to the formation of supersaturedα-Fe with nitrogen. When the resultant powder was annealed, nitride precipitated again.