球磨法制备纳米TiC及其生成机理

采用高能球磨法制备纳米TiC颗粒,通过对不同球磨时间试样进行X射线衍射分析、扫描电镜及透射电镜进行形貌观察,得出球磨过程中TiC的生成机理。结果表明,球磨过程中,首先石墨和钛粉细化,石墨形成片状而钛粉形成细小颗粒;随着球磨时间的延长,片状石墨包裹钛粉;当磨球碰撞时达到Ti和C反应温度,Ti和C发生反应产生TiC,反应放出的热量维持反应的进行。制备的TiC粒度为10～100nm。     

Effect of nano-TiC dopant size on magnetic properties and corrosion resistance of hot-deformed NdFeB

Effects of dopant size on the magnetic properties and corrosion behavior of hot-deformed NdFeB with the intergranular additions of nano-TiC were investigated using X-ray diffraction (XRD), X-ray photoelectron spectrometer (XPS), scanning electron microscopy (SEM), electrochemical and magnetic measurement technologies. Additions of 50 nm-TiC, unlike 30 nm- and 40 nm-TiC, are found to increase the magnetic energy product and comprehensive magnetic properties, due in main to the improvement of magnet orientation by more strip-shaped Nd-rich phases. Nano-TiC dopants especially with a size of 40 nm can increase the electrochemical corrosion resistance of magnets. It is attributed to the hindrance of additives on the reaction channel formation and their barrier effect on the oxidations of Nd and Fe. For 40 nm-TiC doped magnet, the charge transfer resistance in electric double layer structure reaches 15000 Ω?cm² that is one order of magnitude higher than other cases, which is responsible for the lowest corrosion current density and accordingly the best anti-corrosion properties.