• 한국재료학회지
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• 제21권1호
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• pp.28-33
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• 2011

This paper describes the fabrication of AlN thin films containing iron and iron nitride particles, and the magnetic and electrical properties of such films. Fe-N-Al alloy films were deposited in Ar and $N_2$ mixtures at ambient temperature using Fe/Al composite targets in a two-facing-target DC sputtering system. X-ray diffraction results showed that the Fe-N-Al films were amorphous, and after annealing for 5 h both AlN and bcc-Fe/bct-$FeN_x$ phases appeared. Structure changes in the $FeN_x$ phases were explained in terms of occupied nitrogen atoms. Electron diffraction and transmission electron microscopy observations revealed that iron and iron nitride particles were randomly dispersed in annealed AlN films. The grain size of magnetic particles ranged from 5 to 20 nm in diameter depending on annealing conditions. The saturation magnetization as a function of the annealing time for the $Fe_{55}N_{20}Al_{25}$ films when annealed at 573, 773 and 873 K. At these temperatures, the amount of iron/iron nitride particles increased with increasing annealing time. An increase in the saturation magnetization is explained qualitatively in terms of the amount of such magnetic particles in the film. The resistivity increased monotonously with decreasing Fe content, being consistent with randomly dispersed iron/iron nitride particles in the AlN film. The coercive force was evaluated to be larger than $6.4{\times}10^3Am^{-1}$ (80 Oe). This large value is ascribed to a residual stress restrained in the ferromagnetic particles, which is considered to be related to the present preparation process.

• 한국결정성장학회지
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• 제9권5호
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• pp.516-520
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• 1999

유형성 볼밀을 사용하여 순수한 철분말 암모니아가스 분위기 중에서 기계적 합금화(MA) 처리를 하였다. 그 결과 질소함량이 23 at% 까지 준안정 질화철 분말을 얻을 수 있었다. 질화철 분말의 생성상은 질소 함량이 14.5 at% N 이하의 경우 bcc과포화 고용체가, 20.8 at% N에서는 고온에서 안정한 비평형 hcp 결정 분말이었다. MA법으로 제조한 Fe-N계 분말의 포화 자화는 질소농도가 증가함에 따라 단조로운 감소를 보였으며 보고된 bct 질화철에서의 포화자화값 증가와 대조적인 결과를 나타냈다. 질소원자 주위의 상세한 를 조사하기 위하여 중성자 회절 실험을 행하였다. 그 결과, 9.5 at% N의 질화철 분말의 경우 질소원자 주위의 철원자의 배위수는 3.9이었으며, 이러한 결정구조해석 결과로부터 질소원자는 철원자로 이루어진 4면체의 중심에 위치하고 있는 것으로 판단되었다.

• 한국표면공학회지
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• 제36권6호
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• pp.455-460
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• 2003

Microstructural and magnetic properties of nanocrystalline Fe-46 wt%Ni and Fe-36 wt%Ni alloys were investigated. Alloys were prepared by the electrodeposition process. The electrolytes were iron sulfate/nickel chloride-based and iron chloride/nickel sulfamate-based solutions. Fe-46 wt%Ni alloy was FCC structure with grain size of 10 nm, but FCC and BCC phases were found in Fe-36 wt%Ni alloy and its grain size was smaller. Effective permeability of Fe-36 wt%Ni alloy was higher than that of Fe-46 wt%Ni alloy in the high frequency range because of large electrical resistivity and small eddy current loss resulted from grain size decrease. Up to $300^{\circ}C$ of annealing temperature, grain growth of Fe-Ni alloys slowly occured. Conversely, annealing above $450^{\circ}C$ led to a drastic grain growth. In that case, effective permeability was decreased at the temperature lower than $300^{\circ}C$ but at $300^{\circ}C$ or higher effective permeability was increased. At the high frequency of 1 MHz, electrodeposited Fe-Ni alloys had higher effective permeability with an decrease in the grain size.

• 보존과학회지
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• 제35권6호
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• pp.631-640
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• 2019

본 연구는 전통제철법인 정련 및 단접을 적용한 사철강괴(SI)의 미세조직을 파괴분석법인 현미경분석과 비파괴분석법인 중성자 영상 분석을 통해 분석결과를 비교하였다. 시료는 전통제철법으로 생산한 사철강괴이며, 파괴분석용의 SI-A와 비파괴분석용의 9 ㎠의 SI-B를 제작하였다. 파괴분석으로 금속현미경과 주사전자현미경이 이용되었으며, 비파괴분석으로 일본 훗카이도 대학의 소형 중성자원 이용시설을 통한 중성자 영상 분석을 이용하였다. 파괴분석결과 미세한 ferrite 및 pearlite가, 시료의 가장자리에서 Widmanstätten ferrite와 조대한 ferrite가 관찰되었다. 또한 비파괴분석법인 중성자 영상 분석 결과 체심입방격자 구조의 grain size가 3 ㎛ 정도의 α-Fe인 ferrite와 층상의 pearlite가 관찰되었다. 이렇듯 중성자 영상 분석을 이용하면 비파괴로 연구대상의 재료과학적 특성을 확인할 수 있고 문화재에 적용 시 최적의 연구결과를 얻을 수 있음을 확인하였다.

• Journal of Magnetics
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• 제6권3호
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• pp.94-100
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• 2001

Fe-Co-Ni particles with an average size of 45 and 135 nm are characterized in terms of magnetic phase transformation and magnetic properties at room temperature. BCC structure of Fe-Co-Ni spherical particles can be synthesized from Fe-Co-Ni-Al-Cu precursor films by heating at 600-80$0^{\circ}C$ for the phase separation of Fe-Co rich Fe-Co-Ni particles, followed by a post heating at $600^{\circ}C$ for 5 hours. The average size of nanoparticles was directly determined by the thickness of precursor films. Exchange interactive hysteresis was observed for the nano-composite (Fe-Co-Ni)+(Fe-Ni-Al) films resulting from the short exchange interface between ferromagnetic Fe-Co-Ni particles surrounded by almost papramagnetic Ni-Al-Fe matrix. Arraying the isolated Fe-Co-Ni nano-particles in a random arrangement on $Al_2O_3$substrate the particle assembly showed a behavior of dipole interactive ferromagnetic clusters depending on their volume and inter-particle distance.

• 한국주조공학회지
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• 제32권3호
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• pp.138-143
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• 2012

This steel has been synthesized integrating concepts from Austempering Ductile Cast Iron (ADI) technology. While ADI has excellent mechanical and physical properties, the Young's modules of ADI is approximately 20% lower than steel. In addition, the presence of graphite nodules in ADI can be sites of crack initiation, where fracture takes place at graphite matrix interface. Because of this limitations of ADI, there has been a growing interest in austempered steels as structural materials in resent years. In this investigation, a new steel with microstructure composed of ferrite and austenite and with simultaneous high tensile strength (1,150 MPa) and high ductility (33%) was developed. The goal of this investigation is to obtain a better understanding of deformation and transformation behaviour in high carbon retained austenite(${\gamma}_{HC}$) and over-saturated ferrite(${\alpha}$) during the plastic deformation. A detailed study of the microstructure of this steel was carried out by means of X-ray diffraction (XRD) and electron back scattering diffraction (EBSD) technic. In this way it was shown that BCC phase (BCC) took up the larger part of the nominal strain whereas the a part of retained austenite responded to the mechanincal load by partial martensite transformation, and misorientation change in the retained austenite after plastic strain could be attributed to the large elongation.

• 한국자기학회지
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• 제19권3호
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• pp.81-84
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• 2009

상관효과 U가 전자구조와 자성에 미치는 영향을 검토하기 위하여 대표적 자성물질인 철의 덩어리, 단층 및 사슬 구조에 대해 연구하였다. 이를 위하여 U = 3 eV로 택하여, 총 퍼텐셜 보강 평면파동 에너지 띠 방법을 이용하여 LDA+U 및 GGA+U 근사 하에 전자구조 계산을 수행하였다. 비교를 위하여 LDA 및 GGA를 이용한 계산도 수행하였다. 그 결과 U의 효과를 포함시켰을 때 덩어리 철의 경우 자기모멘트가 $0.3{\mu}_B$ 증가하여 실험값이나 LDA 및 GGA 계산에 비해 과다하게 계산되는 것으로 나타났으나, 단층이나 사슬의 경우는 그렇게 큰 차이를 보이지 않았다. 이로부터 전자구조 계산 시대상 계에 따라 U의 효과를 적절히 고려하여야 함을 알았다.

• 한국자기학회지
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• 제9권4호
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• pp.190-195
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• 1999

최대 출력 3.5kW인 고주파에 의한 알곤 플라즈마 분위기에서 제작한 Fe1-xCox(x=0.2와 0.4)계와 25$\mu\textrm{m}$의 철 박막의 자기적인 성질을 상온에서의 X선 회절과 진동시료자력계를 이용한 자기이력곡선 측정 방법을 사용하여 연구하였다. arc로에서 제작된 시룐느 삼단계 처리 가공하였다. 첫째는 수압기로 9,000N/$\textrm{cm}^2$의 압력을 가하여 알약 형태로 만들었다. 이 단계는 압연기로 눌러 얇은 sheet로 만들었다. 삼단계는 시료는 질소 가스 분위기에서 90$0^{\circ}C$로 열처리하였다. 일단계 시료의 X선 회절결과는 시료가 균질이며 각 시료는 철과 동일한 bcc 결정구조를 갖는 단일결저상(single crystal phase)임을 보였다. 철 박막은 43 Oe의 항자력과 인가자기장에 대한 자화, 즉 초기 기울기는 0.328 emu/gOe를 나타냈다. 이단계 시료에서는 Co량이 증가함에 따라 항자력과 포화자화값은 증가하였다. 반면 초기 기울기는 감소하였다. 이는 항자력의 증가로 인해서 계면이동이 억제되었음을 의미한다. 삼단계 시료에서 두 시료 모두 포화자화값은 증가하였다. 반면 이들 시료의 항자력은 감소하였다. 3단계 시료의 포화자화의 열처리로 인한 시료의 X선 회절강도 변화와 연관이 있어 보인다. 또한 몇 개의 자기 매개변수를 단순모형을 써서 계산하여 다른값과 비교하였다.

• Journal of Magnetics
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• 제11권2호
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• pp.87-89
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• 2006

CoFeV thin film alloys were fabricated by electrodeposition, and the dependences of their magnetic properties on the current density were investigated using an X-ray diffractometer and a vibrating sample magnetometer. The deposited Co increased from about 45 to 60 wt.% with increasing current density until $25mA/cm^2$ whereas the deposited Fe decreased from about 55 to 40 wt.% with increasing current density until $25mA/cm^2$. The deposited V, about 2 wt.%, was independent of the current density. The current efficiencies of electrodeposition decreased linearly from about 40 to 29% with increasing current density. The X-ray diffraction measurement showed that all peaks of the CoFeV films were consistent with those of a typical Co hcp and Fe bcc mixed phase. An increase in the current density decreased the grain size and increased the lattice constant. The saturation magnetization increased from about 2.2 to 2.5 T with increasing current density. The coercivity measured in the perpendicular direction decreased from 260 to 120 Oe with increasing current density; a drastic drop of 60 Oe occurred at $5mA/cm^2$. The coercivity measured in the in-plane direction remained almost unchanged, at about 20 Oe, with increasing current density.

• 한국분말재료학회지
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• 제29권4호
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• pp.325-331
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• 2022

Beta-titanium alloys are used in many industries due to their increased elongation resulting from their BCC structure and low modulus of elasticity. However, there are many limitations to their use due to the high cost of beta-stabilizer elements. In this study, biocompatible Ti-Mo-Fe beta titanium alloys are designed by replacing costly beta-stabilizer elements (e.g., Nb, Zr, or Ta) with inexpensive Mo and Fe elements. Additionally, Ti-Mo-Fe alloys designed with different Fe contents are fabricated using powder metallurgy. Fe is a strong, biocompatible beta-stabilizer element and a low-cost alloying element. The mechanical properties of the Ti-Mo-Fe metastable beta titanium alloys are analyzed in relation to the microstructural changes. When the Fe content increases, the tensile strength and elongation decrease due to brittle fracture despite a decreasing pore fraction. It is confirmed that the hardness and tensile strength of Ti-5Mo-2Fe P/M improve to more than 360 Hv and 900 MPa, respectively.