| Permanent magnet nanoparticles have attracted considerable attention in recent years because of their potential application in the high technology industry such as computer, data storage, biomedical technology and remotely controllable micro-nanomachine. Nano permanent magnetic material gradually become hot research topic in the field of magnetic material. Compared with conventional permanent magnets, they possess unique nanostructure and therefore excellent magnetic properties, good thermal stability, desirable corrosion resistance,and strong mechanical strength. However, only Nd-Fe-B, Sm-Co, Ce-Co, Pr-Co and Tb-Fe-B have been prepared by surfactant assisted ball milling (SABM) technology at room temperature. There are few reports on fabrication of Sm2Fe17Nx nanoflakes by surfactant assisted ball milling. In fact, like other rare earth-transition metal (RE-TM), Sm2Fe17Nx also has excellent intrinsic magnetic properties, such as high curie temperature (750K), high saturation magnetization (1.56T at300K) and extremely high uniaxial magnetocrystalline anisotropy(>MAm-1at300K). Its high uniaxial anisotropy, which is vital in establishing coercivity, makes it a promising material for permanent magnet fabrication. In this thesis, three main subjects were selected and investigated.1. Powder metallurgy method was used to explore the best technological parameters for preparation of Sm2Fe17Nx coarse powder. The composition, structure, and magnetic properties of the Sm2Fe17Nx coarse powder were studied by means of XRD, SEM, VSM, and O/N analysis. The best technological parameters for preparation of Sm2Fe17Nx coarse powder was determined. More than40%of Sm was added before Sm-Fe smelting. Sm2Fe17was broken to30microns by mechanical grinding and then put it into a vacuum furnace. Finally the stove was put into purity nitrogen with3atm and insulated at530℃for6h.2. In this paper, oil amine is used as surfactant and2-methyl pentane (82%) was chosen as solvent for room and low temperature ball milling, permanent magnetic nanoparticles prepared by ball milling has good uniformity narrow particle size distribution. The composition, structure, and magnetic properties of the magnets were studied by means of XRD, SEM and VSM. The results showed that nanoflakes prepared by low temperature ball milling have more fine and uniform particles. Compared with the samples milled at room temperature, the cryomilled Sm2Fe17Nx nanoflakes are finer and more homogeneous. Moreover, the value of their Mr, Ms, and Mr/Ms are all higher than that of samples milled at room temperature for4-6h, of which largest rate of increment are54%,18%, and16%, respectively.3. In this paper, oleic acid is used as surfactant and2-methyl pentane (82%) was chosen as solvent for room and low temperature ball milling, and effects of low temperature on the particle size and distribution, morphology, magnetic properties of the magnets were systematically studied. The results showed that the anisotropic nanoflakes were also obtained when oleic acid as surfactant. Compared with room temperature ball milling, the samples were prepared by low temperature ball milling on the morphology was similar, but the average particle size was more small, about1microns. The samples were prepared by low temperature ball milling has remarkably higher coercivity, about13kOe. The samples were prepared by low temperature ball milling has better orientation and remarkably higher I(006)/I(220). Through the analysis of nitrogen content and the calculation Fe content, sample were prepared by low temperature ball milling has higher nitrogen content and lower iron content at the same time of ball mill, it suggests that low temperature ball milling can inhibit decomposition of Sm2Fe17Nx. |
PDF Full Text Request