表面活性剂辅助球磨制备的各向异性Nd-Fe-B粉末形貌与性能

Morphology and magnetic properties of anisotropic Nd-Fe-B powders by surfactant-assisted ball milling

利用表面活性剂辅助球磨技术,以Nd14.5Dy1.5Fe76Nb2B6铸锭为原料制备了各向异性Nd-Fe-B纳米粉末,研究了球磨工艺对粉末性能的影响。结果表明:当球磨转速从375r/min减小到300r/min时,粉末的矫顽力明显提高,进一步降低转速,粉末矫顽力下降。当球磨转速为300r/min,球磨7h,球料比10∶1,油酸量40%,正庚烷量40%时,制得的纳米粉末矫顽力达到358.28kA/m。在球磨过程中,粉末先破碎成较大的块体和片状,随着球磨的继续,粉末细化为主,薄化为辅,最后破碎成尺寸均一的小颗粒。球料比越大,粉末的撞击越强,粉末破碎的越明显,效率越高,片状化越明显。此外,采用沉降法得到了不同粒径的粉末,研究了粉末粒度对性能的影响。随着粉末粒度的降低,矫顽力也随之降低。

Anisotropic Nd-Fe-B powders were prepared by surfactant-assisted ball milling （SABM） using Nd14.5Dy1.5Fe76Nb2B6 ingots as the starting material. Influences of processing parameters on the magnetic properties were investigated. The results show that coercivity increases clearly with decreasing milling speed from 375r/min to 300r/min. A maximum coercivity of 358.28kA/m was obtained for milling time of 7h, the ball to powder ratio of 10∶1, concentration of OA and n-heptane of 40%and 40%, respectively. Milling time and ball to powder ratio have significant effects on the morphology of the powders. The raw materials are broken into blocks and flakes firstly in the milling process. Afterwards, most of the powders are refined and some are thinned continuously. Finally they broke into homogeneous particles. The larger the ball to powder ratio is, the more strongly they collide, and the higher the broken efficiency is. In addition, the selected powders are separated by sedimentation and the effect of particle size on the coercivity of Nd-Fe-B nanoparticles was analyzed. The result shows that the coercivity decreases with decreasing particle size.