非晶質 Fe Si P 合金의 結晶化過程

孫紅在,申鉉澈,金澤基 忠南大學校 産業技術硏究所 1986 산업기술연구논문집 Vol.1 No.2

The thermal stability and crystallization process of amorphous Fe Si P alloys were studied by D.S.C and x-ray diffractometer. The results are as follows; 1) The amorphous forming range of Fe Si P alloys is O x 8. 2) Phase transformation by the crystallization occurs as follows ⅰ) x=2,4 ; amorphous → α-Fe(b.c.c) + Fe₃P(b.c.t) ⅱ) x=6,8 ; amorphous → amorphous + FeP → Fep + Fe₂P(h.c.p) → Fe₃P(b.c.t) + α-Fe(b.c.c). 3) The crystallization temperature and activation energy for crystallization are increased with increasing Si contents and presented max 718K, 110Kcal/mole at x=4, respectively and then decreased with increasing Si contents.

비정질 (Fe1-x Co x) 80 B20 합금의 결정화 과정에 대한 속도론적 연구

김택기,김윤배,오병현 대한금속재료학회(대한금속학회) 1985 대한금속·재료학회지 Vol.23 No.1

The thermal stability for the amorphous (Fe_(l-x)Co_x)_(80)B_(20) alloys has been studied systematically through DTA, X-ray diffraction pattern and the electrical resistance change response to temperature and time variations. The results obtained are as follows; 1) The crystallization temperature of amorphous (Fe_(l-x)Co_x)_(80)B_(20) alloy is independent of the concentration of Co and it is about 710˚K. 2) The crystallization process of amorphous (Fe_(l-x)Co_x)_(80)B_(20) alloy occurs in two steps; In the composition range of 0.1≤x≤0.5, amorphous (Fe_(l-x)Co_x)_(80)B_(20)→α phase (Fe, Co; bcc)+Fe₃B(bct) →α phase (Fe, Co; bcc)+Fe₂B(fct)+Co₂B(fct), and in the composition of x = 0.6 amorphous (Fe_(l-x)Co_x)_(80)B_(20)→α phase (Fe, Co; bcc) +Fe₃B(bct)+Co₃B(fct) →αphase (Fe, Co; bcc)+Fe₂B(fct)+Co₂B(fct), and in the composition of x = 0.7 amorphous (Fe_(l-x)Co_x)_(80)B_(20)→αphase (Fe, Co; bcc) +Co₃B(fco)→αphase (Fe, Co; bcc)+Fe₂B(fct)+Co₂B(fct) 3) The crystallization of amorphous (Fe_(l-x)Co_x)_(80)B_(20) is the diffusion-controlled nucleation and growth process, and the crystallization activation energy of amorphous (Fe_(l-x)Co_x)_(80)B_(20) alloy is independent of the composition of Co and it is about 70㎉/mole.

비정질 Fe80 Si x- P20-x 합금의 결정화 과정

김택기,임영언,손홍재 대한금속재료학회(대한금속학회) 1986 대한금속·재료학회지 Vol.24 No.12

The thermal stability and crystallization process of amorphous Fe_(80)Si_xP_(20-x) alloys were studied by DSC and x-ray diffractometer. The crystallizations of the amorphous Fe_(80)Si_xP_(20-x) occurred in one step when 2≤x ≤4 as amorphous → α-Fe (b.c.e) + Fe₃P (b.c.t). However, when 6≤x≤10 the crystallization was completed in two stage as amorphous → amorphous + Fe₃P (b.c.t) → Fe₃P (b.c.t) + Fe₂P (h.c.p). Then, Fe₃P + Fe₂P transformed into Fe₃P (b.c.t) + α-Fe. The activation energy for crystallization was about 115㎉/㏖ for x≥4 at % and the activation energy for 1st step, about 20 ㎉/mole larger than that of 2nd step.

비정질 자성 재료

김택기 대한금속재료학회(대한금속학회) 1980 대한금속·재료학회지 Vol.18 No.4

새로운 α-Fe 기 NdFeB 초미세결정립 자석의 자기특성

김택기,김윤배,조용수 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.8

The α-Fe based Nd-Fe-B magnet with 4at% Nd content have been investigated for the development of the new type rare earth magnets. Amorphous Nd₄Fe_(85.5)B_(10.5) alloy prepared by rapid quenching technique crystallized to form only two phases, α-Fe as main phase and Nd₂Fe_(14)B as secondary phase. However, the alloy showed a poor magnetic properties (₁H₁= 12 kOe, B₁= 1.2 T). The additions of Mo and Cu to Nd₄Fe_(85.5)B_(10.5) alloy reduced the average grain size and increased the coercivity up to 2.6 kOe. Furthermore, the substitution of Co far Fe in Nd₄Fe_(82)B_(10)Mo₃Cu₁ alloy to 16 at% entirely improved the magnetic properties. The optimally annealed Nd₄Fe_(74)C_5B_(10)Mo₃Cu₁ alloy showed the best magnetic properties among the perpared alloys. The coercivity, remanence and energy products, of the alloy was 2.75 kOe. 1.42 T and 13 MGOe respectively.

Fe-25Cr-14Co-2Si-1.5 Ti 합금의 자기적 특성에 미치는 열처리 효과

김택기,김윤배,송세안 대한금속재료학회(대한금속학회) 1986 대한금속·재료학회지 Vol.24 No.4

To study the effect s of heat treatment on the magnetic properties of ductile Fe-Cr-Co permanent magnets, a composition of Fe-25Cr-l4Co-2Si-1.5Ti alloy was prepared by induction melting, and the optimum heat treatment procedure and the microstructures of the alloy were investigated. After step aging treatments, it was concluded that aging at high temperature effects largely on the squareness of the demagnetization currve and aging at low temperature effects largely on the coercive force. The sample which was thermomagnetically treated for 10 minutes at 675℃ showed clearly the evidence of spinodal decomposition of the FeCo-rich phases from the Cr-rich matrix.

비정질 (Fe, Co) 80 (Si, B, P) 20 합금의 자기적 특성

김택기,황인엽,조용수 대한금속재료학회(대한금속학회) 1989 대한금속·재료학회지 Vol.27 No.11

The magnetic properties of amorphous Fe_(80-x)Co_xSi_6B_(14)(10≤X≤70, X ; 10at% interval) and Fe_(80-x)Co_xSi_9B_9P₂(10≤X≤70, X, 15 at% interval) have been investigated. The amorphous alloys were fabricated into ribbons by a single-roller rapid quenching technique. The saturation magnetization and its temperature-dependence, coercive force and power loss were studied. The saturation magnetization of the amorphous Fe_(80-x)Co_xSi_9B_9P₂alloy shows similar tendency to that of amorphous Fe_(80-x)Co_xSi_6B_(14) alloy except Fe-rich composition at room temperature. The average effective magnetic moment per transition metal atom in both alloys is 2.10-141 μ_B, and decreases with Co content, but increases slightly with Co content from X=40. The coercive force and power loss are 0.31-0.11 Oe and 33-49 mW/Kg at 0.5 Tesla and 60 Hz, respectively, and decrease with Co content.

강자성 Mn-Sb 박막의 자기 광학적 효과

김택기 공주교육대학교 초등연구원 1973 公州敎大論叢 Vol.10 No.-

The polycrystalline MnSb films of 800 A thickness Were deposited on glass substrates kept at room temperature under 1 X 10-5 Torr.. The magnetic and magneto-optic properties of these films in terms of atomic ratio were investigated. The saturation magnetization, Ms, and coercive force, He, of these films were measured with self-made hysteresis loop tracer. The Kerr rotation angles, ellipticities and absorption coeficients in terms of specific wave length (from 4,000 A to 7,200 A) and atomic ratio were obtained with ellipsometric method. In the Mn-Sb films the maximum value of Ms, 700 gauss, and mimimum value of He, 180 Oe, were obtained in the case 50% Sb in Mn. In this case the Kerr rotation angle was 1.3x 10~2 rad. at λ=4,200 A, the minimum value of ellipticity was 1.4X10-2 rad. λ = 4,800 A. Therefore the Mn-Sb compound thin films which atomic ratio is 1 : 1 are most adequate of the memory element in computer.

저진공증착 Fe막의 자성

김택기 공주교육대학교 초등연구원 1970 公州敎大論叢 Vol.7 No.2

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방사선 동시계수기의 제작

김택기 공주교육대학교 초등연구원 1968 公州敎大論叢 Vol.5 No.-

The radiation counter is one of the important instruments for the understanding of much natural phenomena. Many physicists have aleady made many kinds of radiation counters. In recnt days, many physicsts have intented to improve Geiger-Muller^ counter (1928): especially its apparatus and counting method. W. Borthe improved the G-M counter, and made the first simultaneous counter of radiation. B. Rossi and [L.M.Mott-Smith improved Borthe’s model. This writer has made the simultaneous counter of radiation to improve Rossi’ s circuit. The structure of this simultanteous counter of radiation is divided into the 4 major part: 1) G-M tube (fig-1) 2) Discriminator and amplifier(circuit-l) 3) Scaler (scale-of-26: circuit-2) 4) High voltage source of electricity and 300V. constant source of electricity (circuit-3 and circuit-4) The characteristices of the apparatus can be described as follow: 1) The pulse sent from the G-M tube to scaler can make the complete rectangular wave. 2) It can get to the fixed and unchangeable signal output without the signal imput being concerned. 3) We can freely regulate the pulse duration time. 4) In the case of using the single counter, the counting efficiency is reduced. In the case of using this simultaneons counter of radiation, however, we can conveniently get the true value without any error by the geometrical efficiency, the absorption of radiation, the infule- nces of dispersion, and sensitivity of detector. 5) It uses the scale-of-26 method which is less convenient than the decimal method, becaouse the circuit of scaler is simple. 6) This simultaneous counter of radiation contributes confidence/safety, stability and handy handling to its practical use.