Tokin Corporation

Etsuo Otsuki

Tsutomu Otsuka

Akio Hasebe

Hiroshi Momotani

Tamiko Takeuchi

In a method for charging a secondary battery having a positive electrode, a negative electrode, and an electrolyte, a pulsed current is supplied to the secondary battery to make the pulsed current flow between the positive electrode and the negative electrode through the electrolyte to thereby charge the secondary battery. The pulsed current comprises positive pulse current which has a positive pulse amplitude corresponding to a first current density of 1 .mu.A/cm.sup.2 to 100 mA/cm.sup.2 in the positive electrode. However, the pulsed current may include a negative pulse current following after each positive pulse and having a negative amplitude corresponding to a second current density not greater than a quarter of the first current density.

Method and apparatus for charging a secondary battery by supplying

A rare earth metal-iron-boron permanent magnet is produced by a sintering method using a magnetic powder prepared from an ingot of R.sub.2 Fe.sub.14 B and another powder prepared from a rapidly-quenched alloy ribbon of R-T-B. R is least one element selected from the group consisting of yttrium and rare earth metals and T is at least one element selected from the group consisting of transition metals. During sintering almost all the rapidly-quenched alloy powder melts to form a liquidus phase which cements the magnetic particles at a sintering temperature. The liquidus phase generates a magnetic crystalline phase and a solid solution phase upon cooling from the sintering temperature. A comparatively large amount of rapidly-quenched alloy powder is used to produce a magnet having a reduced amount of solid solution phase. In addition to this, the rapidly-quenched alloy can readily be finely ground and the rapidly-quenched alloy powder can therefore be uniformly mixed with the magnetic alloy powder so that a magnet having excellent magnetic properties can be produced wherein the magnetic particles are uniformly dispersed in the small amount of the solid solution phase. The magnet also has a reduced oxygen content.

Method for producing a rare earth metal-iron-boron permanent magnet by

A rare earth metal-iron-boron permanent magnet is produced by the sintering method using a magnetic powder prepared from an ingot of R.sub.2 Fe.sub.14 B and another powder prepared from a rapidly-quenched alloy ribbon of R-T-B. R is at least one selected from yttrium and rare earth metals and T is at least one selected from transition metals. The rapidly-quenched alloy powder almost all melts to form a liquidus phase which cements the magnetic particles at a sintering temperature. The liquidus phase generates a magnetic crystalline phase and the solid solution phase upon cooling from the sintering temperature. A comparatively large amount of rapidly-quenched alloy powder is used to produce a magnet having a reduced amount of solid solution phase. In addition to this, the rapidly-quenched alloy can readily be finely ground and the rapidly-quenched alloy powder can therefore be uniformly mixed with the magnetic alloy powder so that the magnet having excellent magnetic properties can be produced wherein the magnetic particles are uniformly dispersed in the small amount of the solid solution phase. The magnet has a reduced oxygen content.

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Miyagi, Japan

Etsuo Otsuki