Nanocomposite magnets

Zeng H, Li J, Liu JP, Wang ZL, Sun S. Exchange-coupled nanocomposite magnets by nano-particle self-assembly. Nature 2002 420 395-398. 

Generally, isotropic permanent magnets with a remanence ration JJJS > 0.5 are referred as remanence enhanced materials. However, the theoretical limit for the remanence of noninteracting grains depends on the crystal symmetry, the crystallographic orientation of the easy directions, and the volume fraction and the saturation polarization of the phases. The remanence ratio a two-phase nanocomposite magnet is... 

Since the successful preparations of Nd2Fei4B/Fe3B and Nd2Fei4B/Fe nanocomposites magnets were first reported by the Philips group in the late 1980s [72], the RE-TM nanocomposites have been extensively studied [73-75]. Until recently, these materials were prepared under the form of ribbons or powders only. They were isotropic. Recent research focused on the preparation of textured materials [76] and of other potential materials, in particular based on the FePt system [77]. 

Rare-earth iron boron nanocomposite magnets... 

The discovery by Coehoom et al. [119, 120] of a significant coercivity in nanocomposite magnetic materials which associate exchange coupled soft and hard magnetic nanograins, constitutes a spectacular properties of mag-... 

Zeng, H., et al. (2002), Exchange-coupled nanocomposite magnets via nanoparticle self-assembly, Nature, 420, 395-398. 

Mag netosensitive Polyfunctional Nanocomposites Magnetic Fluids Biofunctionalized Mag netosensitive Nanocomposites Biofunctionalized Magnetic Fluids... 

Fig. 23. Comparison between recoil hysteresis curves of a Fe3B/Nd2Fe,4B nanocomposite magnet and an ordinary single-phase Nd2Fe,4B magnet (MQP-B) (Hirosawa 1999).

Fig. 25. The remanence vs. coercivity of rare-earth isotropic nanocomposite magnets (Hirosawa 1999).

The Sumitomo Special Metal Co., Ltd. research team has been able to control the magnetic properties of Nd-Fe-B nanocomposite magnets by using some of the additives mentioned above. The relation between and Hcj of the magnets is shown in fig. 26. These values are quite good for industrial applications. 

On the other hand, the industrialization of Sm-Fe-based nanocomposite magnets will be realized by the manufacturing activities of Siunitomo Metal Mining Co., Ltd., TDK Co., Ltd., Hitachi Metal Ind. Co., Ltd., Toshiba Co., Ltd. and other companies in Japan. 

Fig. 30. Relation between weight gain and dviration of treatment of a NdjFci B sintered magnet and a Fe3B/Nd2Fe,4B nanocomposite magnet.

Li M, Chen Z, Yam VWW et al (2008) Multi functional ruthenium(II) polypyridine complex-based cshell magnetic silica nanocomposites magnetism, luminescence, and electrochemiluminescence. ACS Nano 2 905-912... 

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