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급속응고중 외부자장에 의한 Nd-Fe-Co(-Zr)-B계 합금의 자기이방성 향상
이우영(C. J. Yang),최승덕(S. D. Choi),양충진(W. Y. Lee) 한국자기학회 1992 韓國磁氣學會誌 Vol.2 No.3
Melt-spun Nd₁₄Fe_(76)Co₄B_6 and Nd_(10.5)Fe_(79)Co₂Zr_(1.5)B_7 ribbons were prepared under an externally applied magnetic field. Magnetic properties in terms of anisotropy were evaluated by discussing the effect of textured structure of the ribbon samples as well as its powders. About 32 % increase in (BㆍH)max and 18.8 % increase in Br were observed along the perpendicular direction of the ribbon plane which is more prominent for the Nd-Fe-Co-Zr-B than for the Nd-Fe-Co-B alloy. The enhancement of magnetic anisotropy was monitored by measuring the anisotropy constant of each alloy as a function of quenching rate of the ribbon. It was found that for the melt-spun ribbbon quenched at slow rate(less than 7 ㎧) the magnetic field effect was overwhelmed by the heat gradient effect through the ribbon thickness while the field effect was prominent at intermediate quenching rate (more than 7~11 ㎧). The reproducible maximum energy product, (BㆍH)max=16.4 MGOe can be obtained from the Nd-Fe-Co-Zr-B alloy.
급속냉각된 Nd - Fe(-Co)와 Sm - Co(-Fe)계 Laves 화합물의 미세조직과 자기특성
이우영(W.Y.Lee),최승덕(S.D.Choi),양충진(C.J.Yang) 한국자기학회 1991 韓國磁氣學會誌 Vol.1 No.1
Laves phases of NdFe₂, Nd(Fe_(0.5)Co_(0.5))₂, SmCo₂, and Sm(Fe_(0.5)Co)₂ stoichiometry were prepared using a rapid solidification technology. Low temperature magnetic properties show ferromagnetic behaviors for the Nd(Fe_(0.5)Co_(0.5))₂, SmCo₂ and Sm(Fe_(0.5)Co_(0.5))₂ Laves compounds while a sort of spin reorientation has been suggested for the supposed composition of NdFe₂ alloy. This rapidly solidified NdFe₂ alloy is believed to consist of metastable rhombohedral NdFe_7 phase plus fine particles of Nd-rich phase. Some evidence of phase transition from the mixture of unstable NdFe_7 compound plus Nd-rich to Nd₂Fe_(17) plus Fe-Nd-O phase was obtained after annealing the NdFe₂ alloy. The pseudo-binary Laves compound, Sm(Fe_(0.5)Co_(0.5))₂, exhibits a high coercivity of 4 kOe at room temperature with Curie temperature of 400℃ while the Nd(Fe_(0.5)Co_(0.5))₂ compound shows a magnetic moment of 2.8μ_B/f.u.
Crystal Structure and Low Temperature Magnetic Properties of Melt - Spun Sm₂Co7B₃ Compound
양충진(C.J.Yang),최승덕(W.Y.Lee),이우영(S.D.Choi) 한국자기학회 1993 韓國磁氣學會誌 Vol.3 No.4
Low temperature magnetic properties and crystal structures of melt-spun Sm₂Co_7B₃ compound were characterized. The magnetic measurements in the temperature range 77 K~450 K indicated that a spin-reorientation took place at about 150~160 K. A large anisotropy was observed(Ha = 135 kOe at 300 K, 725 kOe at 77 K) for Sm2Co7B3 although the magnetic moment is rather low. The crystal structure of the Sm₂Co_7B₃ compound was analyzed in detail by Rietveld analysis of powder diffraction pattern, and it was revealed that B(4h) atoms are not placed in the Sm(2e) layer but in between the Sm(2e) and Co(6i₁) layers.
사출성형용 Nylon 6계 Nd - Fe - Co - Zr - B 펠렛의 자기특성
최승덕(S. D. Choi),이우영(W. Y. Lee),양충진(C. J. Yang) 한국자기학회 1993 韓國磁氣學會誌 Vol.3 No.1
Nylon 6 based magnetic pellets for injection molding were produced using plasma arc melt-spun Nd_(10.5)Fe_(79)Co₂Zr_(1.5)B_7 powders. Two sorts of bonded magnets made of two different sizes of particles (38~75㎛ and 75~150㎛) were prepared to determine critical volume fraction of magnet powders, and the magnetic properties of the magnets were discussed as a function of density. For the nylon 6 based Nd-Fe-Co-Zr-B pellets made of 38~75㎛ particles, the critical volume fraction of powders 0.7 was obtained with the pellet density which is 90% of theoretical density while the magnets of 75~150㎛ showed the density of 87% of the theoretical value with the same volume fraction. The nylon 6 magnets with the addition of 0.5wt.% silicon oil only exhibited the best magnetic properties to have iHc=8.8 kOe, Br=5.1 kG and (BH)max=5.2 MGOe which are of world class. An empirical relationship in predicting the magnet density with a known fraction (Vs) of loading powders was obtained such as ρ(g / ㎤) = 1.1 + K Vs where the K ranges over 5.3~5.6 being dependent upon the particle size loaded.