Synthesis, Microsturcture And Magnetic Roperties Of Strong Textured （Sm,Pr）₁Co₅/Co Nanocomposite Powders

Nanocomposite permanent magnets which consist of hard and soft magnetic phasesin nano-scale are the most promising permanent magnetic materials, which results fromthe truth that its theoretical energy product（（BH）max≥800kJ/m3） is two times larger thanthat maximum energy product in commercial sintered NdFeB. For improving properties ofnanocomposite magnets, it’s quite important to consider that how to array the easy axis ofhard phase for strong texture as well as control the size and distribution of hard-softphases efficiently, which had attracted much attention.In this paper,（Sm,Pr）₁Co₅/Co nanocomposte permanent magnetic powders withstrong texture were synthesized via the combination of surfactant assisted high energy ballmilling and electronless deposition, followed by studies on micro-structure and magneticproperties using scanning electron microscope （SEM）, X-ray diffraction （XRD） andvibrating sample magnetometer （VSM） techniques.（Sm,Pr）₁Co₅nanocrystal flakes were synthesized by oleic acid assisted high energyball milling. After milling for2h, we got nanocrystal flakes with the thickness of100-200nm and length of0.5-8μm. Under the optimized conditions, which includeddroping reactants at the same time,40MHz frequency ultrasound vibrating, pre-treatingwith PVP and HCl, cobalt particles depositing on hard magnetic nanoflakes were compactwith uniformly distribution, whose size could be controlled around10nm. By combiningsoft and hard magnetic phases, not only saturation magnetization increased from77.1emu/g to82.2emu/g, but also remanent magnetization increased from65.4emu/g to68.1emu/g, which resulted from the exchange-coupled effects between hard-soft phases,namely remanent enhancement.（Sm,Pr）₁Co₅/Co nanocomposite permanent magnetic powders with strong texturewere synthesized using nanocrystal flakes prepared by polyvinylpyrrolidone assisted highenergy ball milling for4hours and8hours. With the increase of soft magnetic phase,cobalt deposited on the hard magnetic nanoflekes grown from5-12nm with3wt%Cocontent to20-30nm with10wt%content. When the milling time kept constant, theintensity of texture I（002）/I（111）was down as the content of soft phase increasing and the saturation magnetization would increase with cobalt rise. However, the remanentsaturation magnetization first increased and then decreased, maximizing at certain cobaltcontent. With the decreasing of hard magnetic matrix in size, the intensity of texturedropped more and more slowly and the cobalt content corresponding to maximumremanent magnetization showed a rising trend. For example, the remanent magnetizationmaximized with3wt%Co when milled for4h and maximized with5wt%Co when milledfor8h.