| Nano toughened SrFe12O19 materials are prepared firstly with raw materials of the nanometer Fe2O3 and SrCO3 by the mechanical methods. On this basis, the nano toughened Sr1-xLaxFe12-yCoyO19 permanent magnet materials are successfully made by adding the element La and Co to the SrFe12O19 materials and secondary doping. Furthermore, in this paper, the effects of secondary doping materials, the addition amount of La and Co, grain size of raw materials, sintering temperature, are systematically investigated, on the fracture toughness and magnet performance of the nano toughened Sr1-xLaxFe12-yCoyO19 permanent magnet materials.The results show that when the SrFe12O19 materials synthesized with the nanometer Fe2O3and SrCO3 are sintered at 1060?, the fracture toughness can reach 2.75MPa·m-0.5, the sintering temperature is 200? lower than using the traditional process. After ball milling, magnetic field press and secondary sintering, the nano toughened SrFe12O19 permanent magnet materials have good mechanical properties and magnetic properties. The best sintering temperature of secondary sintering is at1150??1180?, about 60?90? lower than the sintering temperature with the traditional process to prepare ferrite permanent magnetic materials. After the TEM and SEM analysis to the microstructure, the nano toughened SrFe12O19 permanent magnet materials prepared with the nanometer Fe2O3 and SrCO3 have fine grain size, and uniform particle size distribution, and most grain size is between 0.40?m and 0.65?m, which completely meets the best grain size requirements of high performance ferrite permanent magnetic materials. The reason why fracture toughness is increased is mainly attributed to that the low sintering temperature of preparing the nanometer toughened SrFe12O19 permanent magnet can satisfy the uniformity control of the composition and grain refinement.Based on the above research, the nanometer toughened Sr1-xLaxFe12-yCoyO19 permanent magnet materials are prepared. And quantitative research about the effect of amount of La and Co on the magnet performance and fracture toughness of it has been made. The results show that La can improve Br and Hcj of Sr1-xLaxFe12-yCoyO19 permanent magnet and Co can substantially improve Hcj of the magnet. When using the combined addition of La and Co (X for0.04?0.05, y for0.05?0.06), the high performance ferrite permanent magnet with Br for 435mT, Hcj for 296kA·m-1, and (BH)max for 35.6kJ·m-3 can be prepared, with the fracture toughness of 2.55MPa·m-0.5,35% higher than that prepared by using the traditional process.In order to further optimize the magnetic properties, during the materials'ball milling process, nanometer CaO, SiO2, Al2O3, Pr6O11 and other substances has been added, and the doping mechanism of Sr1-xLaxFe12-yCoyO19 permanent magnet has been analyzed. Research shows that huge specific surface area of the nanometer additive CaCO3+SiO2 could significantly increase particles interface of the ferrite during sintering, thereby increasing the magnetic anisotropy and the coercive force. The ions Pr3+ can partly replace Sr2+. The ions Pr3+ have 4f2 electron configuration, while the electron 4f is shielded by the outer electron shell. The ion magnetic moment is not influenced by freezing of the orbital angular momentum, thereby Br of the sample increasing significantly.In present study, the manufacturing process of nano toughened Sr1-xLaxFe12-yCoyO19 permanent magnet materials is similar to the industrial method of conventional permanent magnet materials. Therefore, the optimization mechanism of magnetic properties can become the theoretical and technological foundation to produce advanced industrialize permanent ferrite. |
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