The Study Of Sm(Co, M)₇(Cnts)_0.05(M=Hf, Cu, Fe, And Zr) Magnets

SmCo matrix permanent magnetic materials of TbCu₇-type have been widely studied because of their potential application as high temperature permanent magnets. Cu, Fe, Zr were added into the SmCo6.9Hf0.1CNTs0.05 alloy by substituting Co in order to stabilizing the TbCu₇ structure and improving the properties of the magnets. The ribbons are prepared by melt-spinning at 50 m/s. The sintered magnets were prepared by powder metallurgy method. The phase everlution, microstructure and magnetic properties of all samples were investigated using XRD, SEM, VSM and DTA.The grain boundary phase will pin strongly the Sm(Co,Hf)7 matrix phase in the SmCo6.9Hf0.1(CNTs)x ribbons with x=0.05. And the SmCo6.9Hf0.1(CNTs)0.05 ribbons have the best magnetic properties: Hci=18.5kOe, Ms2T=74.2 and Mr=59.6emu/g.In SmCo_6.0Cu_0.9Hf_0.1(CNTs)_0.05 ribbon, The Cu atoms replace some of the Co atoms in the TbCu₇-type structure, On the one hand, it result in increasing of anisotropy field, which cause the coercivity of the magnet increase, on the other hand, it result in reduce of total magnet moment,which reduce the saturation magnetization and remanent magnetizaiton of ribbon. In SmCo6.1Fe0.8Hf0.1(CNTs)0.05 ribbon, The Fe atoms go into the structure of Sm2Co17 which exhibits more magnetic moment and lower anisotropy field. Therefore, the Ms and Mr of the ribbon are increased and the Hci of the ribbon is decreased. Some of the Zr atoms in the SmCo6.6Zr0.3Hf0.1(CNTs)0.05 ribbon go into TbCu₇-type structure, increasing the anisotropy field but others may combine with CNTs in the boundary, which decrease the coercivity of the magnet.The deposition temperature of 1:7 phase decreased among ribbons added M through thermomagnetic analysis and difference temperature analysis. In addition, ribbons which added Fe contain 2:17phase.The ribbons were milled, sintered and aged to obtaining the cellular tissue. However,the magnets are composed of Sm2Co17, Co2Hf, Co and Sm2O3. The Oxidation result in decrease of the magnetic properties. There are two ways. One way is that the powder are exposed in the air for long time, the other way is that the Oxygen in the sintering furnace combine with the magnet composition at 1200°C.