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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.
합금조성에 따른 Nd - Fe - Co - B 및 Nd - Fe - Co - Zr - B계 본드자석의 자기특성
최승덕(S. D. Choi),이우영(W. Y. Lee),양충진(Choong Jin Yang) 한국자기학회 1991 韓國磁氣學會誌 Vol.1 No.2
In compacting the melt-spun Nd₁₄Fe_(76)Co₄B_6 and Nd_(10.5)Fe_(79)Co₂Zr_(1.5)B_7 magnetic powders, the difference in composition induces a different behavior of closed packing rate as a function of aspect ratio of the powders. The Nd_(10.5)Fe_(79)Co₂Zr_(1.5)B_7 alloy having a low Co/Fe ratio (low density) shows the better green density to have an enhanced closed packing rate. An empirical power equation relating the green density with the compacting pressure was obtained such as p (g /㎤)=5.2~5.6×P^(0.045~0.065)(ton/㎠).<br/> The Nd₁₄Fe_(76)Co₄B_6 alloy having a high Nd/Fe ratio possesses much finer grain size(50~60 ㎚) than that of Nd_(10.5)Fe_(79)Co₂Zr_(1.5)B_7 alloy and shows the higher coercivity(iHc=14~15kOe). The higher Nd/Fe ratio in the melt-spun Nd-Fe-Co-B alloy, where the domain wall pinning mechanism was found to be predominant, assists the formation of Nd-rich grain boundary phase acting as a pinning site. The grain boundary ranges over 12~16 Å thick in the Nd-Fe-Co-B alloy while it ranges over 8~12 Å thick in the Nd-Fe-Co-Zr-B alloy.
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.
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.