Yasutaka Fukuda

Planar inductor with ferrite layers for DC-DC converter

We fabricated planar inductors with ferrite layers by a screen printing, photolithography, and electroplating process. The screen printing method made it possible to obtain a coil spacing filled with ferrite. In this structure, the perpendicular leakage magnetic flux preferentially passes through the coil spacing and bypasses the copper conductor line, a path that is expected to reduce eddy current loss. Trial samples of a planar inductor with ferrite layers achieved a high-quality Q factor of 40-70 at 5 MHz. Magnetic field analysis revealed that the eddy current loss of the conductor line was only 2.4% of total loss.

Corrosion-resistance Nd-TM-B magnet

A search for compatibility between magnetic properties and corrosion resistance was made by studying a pseudoternary system, Nd-(Fe/sub 1-x-y/Co/sub x/Ni/sub y/)-B, of melt-spun ribbons and sintered bodies. It was found that the double substitutions with 0.2 >

Analytical electron microscopy of corrosion-resistant Nd-(Fe, Co, Ni, Ti)-B magnets

Abstract The microstructures of cast ingot, annealed ingots and sintered bodies of Nd 15 (Fe 0.585 Co 0.3 Ni 0.1 Ti 0.015 ) 77 B 8 alloy were investigated with analytical electron microscopes to clarify the changes of the phases with successive processing. Five phases were identified in the specimens, namely Nd 2 (Fe 0.6 Co 0.3 Ni 0.1 ) 14 B, Nd(Fe 1− x−y Co x Ni y ) 4 B, Nd(Ni 1− x Co x ), Nd(Fe 1− x−y Co x Ni y ) 2 and TiB 2 . In addition, (Nd 1− y TM y ) 2 O 3 (TM  Fe, Ni, Co) phase was also identified in the sintered specimen. An Nd-rich phase was not observed in the present specimens. The phases, except the main magnetic phase (Nd 2 TM 14 B), were different in crystal structure from those in ternary Nd-Fe-B magnets. The majority of NdTM 4 B dissolved to supply B atoms to TiB 2 during the sintering. Some of the Nd(Ni 1− x Co x ) phase reacted with O atoms absorbed during the milling and/or sintering process, and formed Nd 1− y TM y ) 2 O 3 precipitate during the sintering. The remaining Nd(Ni 1− x Co x ) phase precipitated as thin precipitates at grain boundaries. It is suggested that the phases enriched with Ni and the absence of the Nd-rich phase give rise to the high corrosion resistance of Nd-(Fe, Co, Ni, Ti)-B magnets.

Magnetic properties of monocrystalline Nd2(Fe, Co, Ni)14B

Abstract Single crystals of Nd 2 (Fe 1− x−y Co x Ni y ) 14 B were prepared in an IR-imaging furnace by applying the floating zone-melting technique. Their saturation magnetization and anisotropy field were measured over the temperature range 4.2–300 K. It has been found that double substitution of Co and Ni atoms for Fe atoms in the Nd 2 Fe 14 B compound restores the values of saturation magnetization and anisotropy field which are lost by single substitution of Ni atoms for Fe atoms. This phenomenon is understood by a model of ordered substitution of Co and Ni atoms in the iron sublattice.

Development of the Mass Production Technology for Large Scale Mn-Zn Ferrite Single Crystals

Kawatetsu Mining Company Ltd. has developed large sized Mn-Zn ferrite single crystals mainly usea as me magnetic heads of the Video Tape Recorder, by innovating the structure of the 3 heater zone vertical Bridgman furnace and by optimizing the growth conditions. The weight of the single crystal is 28 kg, which is 110 mm in diameter and 630 mm in length, approximately 7 times as heavy as those conventionally supplied.Distinctive features of the developed Mn-Zn ferrite single crystal are the uniformity of the composition within +/-0.5 mol%, lower included platinum particles in the crystal and elimination of cracks along with almost the full length of the crystal. In this report, the control of the variation of the composition along with the growth direction, the restriction of the dissolution of the platinum in melt and the suppression of the cracks, which had been main problems to be overcome during the development, are described.

Magnetic Properties of Thin Sheets (50 μm) of Nd-(FeCoNiTi)-B Sintered Magnets

The magnetic properties of Nd-(FeCoNiTi)-B and Nd-Fe-B type sintered magnets in thin sheet form were investigated from the standpoint of the deterioration in coercivity caused by machining. It was found that the thickness of a deteriorated layer of an Nd-(FeCoNiTi)-B type magnet is smaller than that of an Nd-Fe-B type magnet. This phenomenon is explained in terms of the toughness and fine-grained structure of Nd-(FeCoNiTi)-B magnets. It is suggested that Nd-(FeCoNiTi)-B magnets may be used in the form of 50 μm thick sheets.

Corrosion Resistance of RE-(FeCoNi)-B Sintered Magnets.

Nd-Fe-B系磁石のFeをCoとNiで複合置換した磁石が磁気特性と耐食性が両立する希土類ホウ化物磁石として提案されている。その磁石の高温多湿大気環境下・塩水噴霧下および溶液申での腐食挙動を明らかにし,従来の希土類磁石と比較検討した。粉末焼結法を用いて,Nd-Co-B系状態図にしたがう組成のNd-(Fe,Ca,Ni)-B磁石とそのNdをDy,PrやLaで置換した磁石を試料として用意した。希土類がNdやDyの試料では,70℃ で95%の相対湿度の環境で1000時間まで発錆はなく,35℃の塩水噴霧に対しても表面に薄い被膜が出来るだけで,従来のSm-Co磁石と同等の耐食性を示した。定電位法でアノード分極曲線を酸性溶液,中性溶液,アルカリ性溶液において測定した結果,腐食電位の改善に及ぼすNiの顕著な効果が明らかになった。また,アルカリ性溶液ではNiは不働態領域を発現させることを見いだした。標記磁石のこのような良好な耐食性には主相のNd2(Fe,Co,Ni)14Bの結晶粒の周囲に粒界相として存在するNd(Ni,Co)相が大きな役割を果していると考えられる。

Magnetic Properties and Corrosion Characteristics of Nd-(Fe,Co,Ni)-B Pseudo-Ternary System

Melt-spun ribbons and sintered materials with the composition Nd<inf>15</inf>(Fe<inf>1-x-y</inf>Co<inf>x</inf>Ni<inf>y</inf>).<inf>77</inf>B<inf>8</inf> were investigated with respect to the saturation magnetization, coercivity, Curie temperature and corrosion characteristics. It was found that simultaneous substitution of Co and Ni atoms for Fe atoms enhances the intrinsic coercivity of sintered magnets in the composition range 0.2¿x¿0.4 and 0.0¿y¿0.2, and also improves the corrosion resistance. A further addition of Ti atoms to the system increases the coercivity and makes the demagnetization curve rectangular. For example, the (BH)<inf>max</inf> and intrinsic coercivity in Nd<inf>15</inf>(Fe<inf>0.585</inf>Co<inf>0.30</inf>Ni<inf>0.10</inf> Ti<inf>0.015</inf>)<inf>77</inf>B<inf>8</inf> are as high as 33.8 MGOe and 10.4 kOe respectively.