Preparation And Magnetic Properties Of Nanocomposite Magnets

Bulk NdFeB alloys and Ribbon were prepared by Rapid cooling. The effects of alloy compositions and heat treatment on microstructure, magnetic properties of alloys were investigated by optical microscopy (OM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM). The major results as follows:1. In the Nd2o-xFe76+xB4and Nd2o-xFe66+xB4Al10alloys, As Nd content increased, the grains size of alloys decrease, the coercivity of alloys increase, from512Oe to1430Oe, and558Oe to3003Oe, respectively.2. In the Nd2oFe76-xB4Alx alloys, Comparing with Nd2oFe76B4alloys, the grains size of Nd2oFe76-xB4Alx alloys is much smaller. And with Al content increasing from2to10, the grains size of alloys decrease, the coercivity and saturation magnetization of alloys increase from458Oe to3003Oe, and decreased from90.54to56.76emu/g, respectively.3. Replace Fe with little Ti in Nd2oFe76-xTixB4alloys, the volume fraction of eutectic structure increases. The microstructure of Nd2oFe76-xTixB4alloys become to be classic herringbone structure which cause to decrease the crystal interface areas when x increased to3. From the result of XRD, the volume fraction of Nd2Fen increased and the volume fraction of Nd2Fe14B decreased with increasing Ti content. The phenomenon above contributes to coercivity decreased from1430Oe to727Oe.4. In the Nd2oFe76B4alloys, grain is coarse before the Heat treatment, and these is no apparently change after heat treatment at1023K, as the temperature increases up to1073K, the grain size become smaller, the crystal dimension continually increases with the temperature increasing to1123K. And the alloy owns the smallest grain after1073*20min.5. It’s easier to obtain small size of eutectic structure and higher coercivity in Nd2oFe68B4Al8alloys after high temperature and short time heat treatment condition as comparing with the microstructures of Nd2oFe68B4Al8alloys after1073K*20min and1373K*2min heat treatment condition. The coercivity of Nd2oFe68B4Al8alloy after1373K*2min heat treatment condition increases from2126Oe to8932Oe.6. The velocity of melting spun has a great influence in microstructure and magnet of i2Zr2alloy. It appears the volume fraction of crystalline state increases at higher velocity, otherwise decreases, While the velocity increases from7m/s to25m/s, the (BH)max increases first, and then decreases. The Nd8Fe83B5Ti2Zr2alloy has the biggest (BH)max at the velocity of13m/s, while it is not conducive to obtain best magnetic property at the too high or too low velocity.The nanocomposite magnets Nd8Fe87B5was prepared by melting spun at the velocity of13m/s, it appears the enhancement remanence characteristic of nanocomposite magnets, that The saturation magnetization is125.54emu/g, the coercivity is3353.25Oe,the remanence is70.3emu/g.7. The Nd9Fe73B14Zr4alloy was prepared at the velocity of40m/s by melting spun, it can be typed to be amorphous as spun from the results of XRD; The ribbon of Nd9Fe73B14Zr4is soft magnet after923K*5min heat treatment, and transform to be hard magnetic with increasing the heat temperature. The coercivity increased and then decreased with increasing heat temperature, and reached a highest value at943K, equaled to5841Oe. So was (BH)max, equaled to59.75kJ/m3at953K.