Preparation And Characterization Of Ultra-fine Iron Powder And Boron Powder

The specific surface area of the powder materials whose particle size reach the micron even nano level, would be greatly increased, which cause the surface energy and surface activity of the particles to rapidly improved and a lot of changes to the surface and interfacial properties. Ultra-fine powder materials have a more extensive and important applications in various fields of the national economy and play an extremely important role in the development of new materials. In this thesis, the ultra-fine iron powder and boron powder were prepared by electrolysis and high-energy ball milling respectively, and the preparation process and the product were researched.Polished stainless steel plate and titanium plate were treated as an anode and a cathode respectively.Preparing ultrafine iron powder by the following conditions that electrolyte formula of0.1mol/L of FeSO4·7H2O,25g/L K2SO4andlg/L PVP, current density of350A/m2, the pH of range2.4to3.6and electrolysis temperature of40-50℃then using oleic acid to coate and modify iron powder surface. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to study the structure and morphology of the iron powder. The study found that the iron powder was a-Fe which had a high purity and no other impurity phase. The iron powder had a dendritic or rod morphology in a good dispersion with a diameter of about1～5um long and a length of10～20μm, belonging to the micron superfine powder. TG analysis of wrapped iron powder showed that oleic acid had a preferable wrapped effect on the ultrafine iron powder and could prevent iron powder from oxidation under a certain extent. Fe-N compound was prepared by electrolytic iron powder nitriding experiments, therefore electrolytic prepared iron powder can be used as the raw material of the preparation of the novel magnetic recording material of iron nitride compound.Planetary ball mill were used to prepare ultrafine boron powder in this study. The analysis and characterization of the product prepared by using the analyzing test means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and spectroscopy,etc. Results arc as follows:1) The preparation conditions for boron powder that a ball to powders ratio of30:1,a large ball to small ball ratio of2:3and milling at about680rpm for16h were determined through the comparative analysis of the the milling product prepared under different conditions, whose milling raw materials were B2O3and Mg. The boron powder samples prepared by the above milling process with a element boron content of86.12wt%and a size of less than500nm was not high-grade boron powder;2) Adding a small amount of additive A to the raw materials under the same ball milling process that have a certain degree of dispersing effect and may reduce the system temperature, which could prevent the growth of the boron particles and inhibit the generation of impurities. The study found that the boron powder samples prepared had a purity of95.1wt%.Most of the boron powder size were less than100nm, reached a nano-level. The BET and thermal analysis showed that the specific surface area of boron powder was Sw=190.21m2/g, the starting reaction temperature of boron powder with oxygen was only123℃. The boron powder prepared by adding an additive had the characteristics of high activity.The powder preparation process used in this paper is simple, room temperature operation, low production costs and suitable for industrial mass production. The research of preparation and characterization of the products provide a theoretical basis for industrial production and application of ultra-fine iron powder and boron powder.