Isao Sakai

Hydrogen storage properties of new ternary system alloys: La2MgNi9, La5Mg2Ni23, La3MgNi14

The hydrogen storage properties of the new ternary system alloys, La2MgNi9, La5Mg2Ni23, La3MgNi14, were investigated. As a result, the negative electrode of the La5Mg2Ni23 alloy (La0.7Mg0.3Ni2.8Co0.5) showed a large discharge capacity (410 mAh/g), 1.3 times larger than that of AB5 type alloys. These ternary system alloys were found to be mainly composed of stacked AB5 and AB2 structure subunits in a superstructure arrangement.

Mn substitution effect on magnetostriction temperature dependence in Tb0.3Dy0.7Fe2

Magnetostriction temperature dependencies in Tb0.3Dy0.7 (Fe1−xMnx)2 were investigated. Mn substitution lowers the spin reorientation temperature, at which magnetostriction shows a sharp drop. Moreover, Mn containing compounds show larger magnetostriction than that for a Mn‐free compound at low temperature. Mossbauer measurements show that easy magnetization direction for the Mn containing compound is in the 〈111〉 direction at 300 K, while it is in the 〈100〉 at 77 K. These results indicate that the tetragonal distortion λ100 increases by Mn addition in Tb0.3Dy0.7Fe2.

Nd-Fe-B-Co-Al based permanent magnets with improved magnetic properties and temperature characteristics

Magnetic properties of Nd-Fe-B-Co-Al alloy magnets have been studied with respect to both boron and aluminum concentration. Both cobalt and aluminum substitution for iron is remarkably effective for increasing magnetic hardness in the low boron concentration region. The following magnetic properties were attained for Nd 15 Fe 62.5 B 5.5 Co 16 Al 1 : Br=13.2KG, iHc=11.0kOe, (BH) max =41.0MGOe and T c =500°C. The reversible temperature coefficient of remanence in the above magnet was -0.071%/°., approximately one-half that for the Nd 15 Fe 77 B 8 magnet. It was observed that Laves phase Nd(Fe, Co) 2 precipitates in cobalt containing magnets. The authors think that the addition of aluminum makes this Nd(Fe, Co) 2 magnetic phase non-magnetic; which is considered to be the cause of coercivity increase.

Magnetic field generator useful for a magnetic resonance imaging instrument

A magnetic field generator comprises a permanent magnet, and pole pieces magnetically connected to the permanent magnet. The pole pieces are disposed to face each other to generate a magnetic field between them, and have a specific resistance of 20 μΩ-cm or more. The permanent magnet comprises a sintered alloy including iron as a main component, a rare earth element including yttrium, cobalt, and boron. The permanent magnet includes, as its main part, a strong magnetic Fe-rich phase of a tetragonal system, as well as a non-magnetic Laves phase, and preferably has a maximum energy product of 38 MGOe or more.

Effect of Ga addition to NdFeCoB on their magnetic properties

It was found that the Ga addition to NdFeCoB magnets was very effective for improving their magnetic properties. Magnets with high boron concentration had a high coercive force and magnets with low boron concentration had a high‐energy product. The following magnetic properties were obtained: (1) Nd14.5FebalCo16Ga1B9.5:Br=12.0 kG, IHc=15.3 kOe, (BH)max=34 MGOe, Tc=500 °C (2) Nd14.5FebalCo16Ga1B5.5:Br=13.1 kG, IHc=12.2 kOe, (BH)max=40 MGOe, Tc=500 °C. It was also found that NdFeCoGaB magnets with very low boron concentration still had a relatively high coercive force.

Nd‐Fe‐B‐Co‐Al based permanent magnets with improved magnetic properties and temperature characteristics

Magnetic properties have been studied with respect to the boron concentration on Nd‐Fe‐B based magnets. The combined addition of cobalt and aluminum in a Nd‐Fe‐B magnet is remarkably effective for increasing magnetic hardness in the region of low boron concentration. The following magnetic properties were attained for Nd15Fe62.5B5.5Co16Al1 :Br=13.2 kG, iHc=11.0 kOe, (BH)max=41.0 MGOe, and Tc=500 °C. The reversible temperature coefficient of the remanence of the magnet is −0.071%/deg, approximately one‐half of the Nd15Fe77B8 magnet.

Magnetic properties of Nd-Fe-B magnets with both Co and Al addition

Magnetic properties of Nd-Fe-B based magnets with both cobalt and aluminum addition have been investigated with respect to cobalt and aluminum concentration. Structural analyses were carried out for the sintered bodies. In cobalt containing alloys, Nd(Fe,Co) 2 phase was clearly observed by X-ray diffractometer, SEM and TEM, especially for the magnet with more than 30 at % cobalt. The coercive force behavior versus aluminum content for cobalt containing magnets can be divided into two stages. The first stage in which coercive force increases abruptly with the small amount addition of aluminum may result from Nd(Fe,Co) 2 phase being nonmagnetic by the addition of aluminum. The quantity of this Nd(Fe,Co) 2 phase increases with increasing cobalt content. It was shown that the greater the quantity of cobalt in the sintered body, the greater the addition of aluminum becomes necessary for obtaining high coercive force.

Coercive force of Co added Nd-Fe-B based powders prepared by crushing sintered magnets

An anisotropic resin-bonded magnet was prepared by crushing sintered Nd-Fe-B magnets with Co-Al or Co-Ga. The following magnetic properties for the composition of Nd/sub 14.5/Fe/sub 63/Co/sub 16/Ga/sub 1/B/sub 5.5/ were obtained: (BH)/sub max/=114 kJ/m/sup 3/, B/sub r/=0.89 T, and iH/sub c/=810 kA/m. Co addition is shown to play a significant role in improving the magnetic properties of the crushed powder. The surface layer damaged by crushing becomes thinner in the powder containing Co. In the Co-added sintered magnets, the main crack brought about by Vickers indentation is comparatively easy to propagate through the grain boundaries, and microcrack branchings are rarely observed. These mechanical properties are closely related to the thickness of the damaged surface layer. Al or Ga addition to the Nd-Fe-Co-B system is very effective for obtaining a high coercive force of the powder. >

Nd-Fe-B System Magnets with High Curie Temperature

Magnetic Properties of Nd-Fe-B based magnets with Co-Al or Co-Ga addition were investigated. Co-Al or Co-Ga addition increases Curie temperature and coercive force, hence, improves temperature coefficient of magnetic induction, and makes it possible to use the Nd-Fe-B magnets at a higher temperature. The coercive force of the magnets with Co and Ga increases with increasing B content, while it hardly changes with B content for Co and Al containing magnets. Also, the magnets with Co and Ga have a high coercive force of about 12 kOe even at low boron content of 3.5 at % which is far lower than that of Nd2Fe14B. Itwas shown that intrinsic coercive force IHc for Nd-Fe-B system magnets with various composition changes with temperature with a relation of IHc1/2∝T2/3.