• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2005년도 추계학술발표회
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• pp.781-782
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• 2005

• 한국생산제조학회지
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• 제24권1호
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• pp.15-22
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• 2015

In the present paper we report the results of a study into Friction Stir Welds (FSWs) made in 13 mm-thick 12%-Cr steel plates. Based on residual strains obtained by diffraction techniques, eigenstrain analysis was performed using the Eigenstrain Reconstruction Method (ERM), which is a novel methodology for the reconstruction of full-field residual strain and stress distributions within engineering components. Significant eigenstrain distributions were found at around Thermo-Mechanically Affected Zone (TMAZ) where the most severe plastic deformation was occurred. Microstructure analysis was used to elucidate this phenomenon showing that the grain structure in TMAZ was bent and not successfully recrystallised, resulting in severe deformation behaviour. The reconstructed residual strain distributions by the ERM agree well with the experimental results. It was found that the approach based on theory of eigenstrain is a powerful basis for reconstructing the full-field residual strain/stress distributions in engineering components and structures.

• 한국결정성장학회지
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• 제5권2호
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• pp.189-196
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• 1995

중성자 회절에 의해 고순도 $TeO_2$ 유리의 단범위 구조를 조사하였다. $Te{\cdot}O$의 결합길이$d_{Te-O}$)와 산소원자를 둘러싼 Te 원자의 배위수($N_{Te-O}$)를 결정하기 위해 고해상도 RDF 곡선의 $Q_{max}$ = 20, 23, 25, 28, 30의 첫 번째 peak를, pairdistribution함수 모두 Gaussian 형식을 따른다는 가정하에 least-squae법으로 peak 분리를 했다. 이 결과를 토대로, 고순도$TeO_2$유리는 하나의 Te 원 자에 4개의 산소가 배위되어 있는$TeO_4$의 단위구조로 이루어져 있으며, 각 2개의 산소원자는 평균 결합길이가 각각 1.916 $\AA$과 2.123 $\AA$으로 Te 원자에 결합하고 있는 것으로 밝혀졌다.

• 한국광물학회지
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• 제15권2호
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• pp.140-144
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• 2002

한국원자력연구소의 연구용 원자로인 하나로에 설치되어 있는 4축 단결정 회절장치에서 사용할 수 있는 고온시료환경장치의 개발이 완료되었다. 이 장치를 이용하여 구조가 알려진 시료에 대해 고온실험을 수행함으로써 장치의 성능을 시험하였다. 이번 연구를 통하여 현재 개발된 고온시료환경장치가 900 K 이상의 고온에서 장시간의 실험에 안정함을 알 수 있었다. $LaTaO_3$단결정(상전이 온도 약 900 K)에 대해 상온과 913 K에서 중성자 회절실험을 수행하여 X-ray 회절실험으로는 정확한 위치를 측정하기 어려운 Li의 위치를 측정하였고 고온에서 Li 원자가 무질서 상태로 존재함을 확인하였다.

• Applied Microscopy
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• 제32권1호
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• pp.9-15
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• 2002

NACT 복합 페브로스카이트 화합물에 대한 미세조직 관찰을 X-ray diffractometer, neutron diffraction 그리고 TEM으로 관찰하였다. $0.3{\leq}x{\leq}0.9$일 때 NACT는 양이온의 1 : 1 chemical ordering 뿐만 아니라 산소팔면체의 antiphase와 inphase tilting을 보여준다. 따라서 APB와 ferroelastic domain 경계가 미세구조에 나타나 있다. X값이 0.3보다 작아지면, chemical ordering은 나타나지 않고 단지 산소팔면체의 antiphase tilting 만이 나타난다. 미세구조에는 tangled dislocation과 2차상이 또한 발견되었다.

• 한국세라믹학회지
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• 제44권3호
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• pp.175-181
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• 2007

Molecular dynamics simulation (MD) of $(62-x)CaO{\cdot}38Al_{2}O_{3}{\cdot}xBaO$ glasses has been carried out using empirical potentials with the covalent term. The simulations closely reproduce the total neutron correlation functions of glass with 5 mol% BaO and physical properties of these glasses such as elastic constants. For these glasses, aluminum is tetrahedrally coordinated by oxygen, but there is a part of five-fold and six-fold coordination of aluminum. There are no major changes to the mid-range structure of glass, as barium is substituted for calcium. To predict the barium coordination number, we have used the bond valence (BV) theory and also compared the results of simulation with Bond valence. The coordination number for oxygen around barium atoms is close to 8 and the average distance of barium and oxygen is nearly 2.80 A. The viscosity of these glasses increases with the content of barium oxide substituted for calcium oxide.

• Journal of Magnetics
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• 제13권3호
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• pp.97-101
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• 2008

We investigated the exchange bias fields at the NiFe/FeMn and FeMn/CoFe interfaces in 18.9-nm NiFe/15.0-nm FeMn/17.6-nm CoFe trilayer thin films as the annealing temperature was varied from room temperature to $250^{\circ}C$ in a vacuum for 1 hour in a magnetic field of 150 Oe. Interestingly, magnetic hysteresis (M-H) measurements showed that NiFe/FeMn/CoFe trilayer thin films exhibited a completely contrasting variation of the exchange bias fields at both the NiFe/FeMn and FeMn/CoFe interfaces with annealing temperatures. High-angle X-ray diffraction (XRD) measurements indicated the absence of any discernible effect of thermal treatment on the NiFe(111) and FeMn(111) peaks. The compositional depth profile obtained from X-ray photoelectron spectroscopy (XPS) results presented the asymmetric compositional depth profiles of the Mn and Fe atoms throughout the FeMn layer. We contend that this asymmetric compositional depth profile and the preferential Mn diffusion into the NiFe layer, compared to that into the CoFe layer, are conclusive experimental evidence of the contrasting variation of the exchange bias fields at two interfaces having a common polycrystalline FeMn(111) layer.

• Nuclear Engineering and Technology
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• 제47권3호
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• pp.323-331
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• 2015

Zirconium alloys are widely used in nuclear reactors as structural materials. During the operation, they are exposed to fast neutrons. Ion irradiation is used to simulate the damage introduced by neutron irradiation. In this article, we briefly review the neutron irradiation damage of zirconium alloys, then summarize the effect of ion irradiation on microstructural evolution, mechanical and corrosion properties, and their relationships. The microstructure components consist of dislocation loops, second phase precipitates, and gas bubbles. The microstructure parameters are also included such as domain size and microstrain determined by X-ray diffraction and the S-parameter determined by positron annihilation. Understanding the relationships of microstructure and properties is necessary for developing new advanced materials with higher irradiation tolerance.

• Bulletin of the Korean Chemical Society
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• 제24권5호
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• pp.573-578
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• 2003

The structural, magnetic, and transport properties of a mono-layered manganite $La_{0.7}Sr_{1.3}MnO_{4+{\delta}}$ were investigated using variable temperature neutron powder diffraction as well as magnetization and transport measurements. The compound adopts the tetragonal I4/mmm symmetry and exhibits no magnetic reflection in the temperature region of 10 K ≤ T ≤ 300 K. A weak ferromagnetic (FM) transition occurs about 130 K, which almost coincides with the onset of a metal-insulator (M-I) transition. Extra oxygen that occupies the interstitial site between the [(La,Sr)O] layers makes the spacing between the [MnO₂] layers shorten, which enhances the inter-layer coupling and eventually leads to the M-I transition. We also found negative magneto resistance (MR) below the M-I transition temperature, which can be understood on the basis of the percolative transport via FM metallic domains in the antiferromagnetic (AFM) insulating matrix.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 14TH KACG TECHNICAL MEETING AND THE 5TH KOREA-JAPAN EMGS (ELECTRONIC MATERIALS GROWTH SYMPOSIUM)
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• pp.39-43
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• 1998

Single crystals of{{{{ { Zn}_{ 1-x} {Mn }_{x }{Te} }}}} with x=0.3-0.6 were prepared by the standard Bridgeman method. Diffuse neutron diffraction intensities due to the short range magnetic ordering is found in the vicinities of 1 1/2 0 reciprocal point and its equivalent point, indicating that the magnetic correlation of the clusters is the type III antiferromangetic one do the F-type Bravais class crystals, being identical with that of {{{{{ Cd}_{ 1-x} {Mn }_{x }Te }}}}. Neutron inelastic scattering measure-ment has been performed for {{{{{ Zn}_{ 0.6} { Mn}_{ 0.4}Te }}}} sample using the cold neutron spectrometer. AGNES. High resolution measurement with the energy resolution of {{{{ TRIANGLE E= +- .01meV}}}} was carried out in the temperature range from 10K to the ambient. Critical scattering, closely related with the spin glass transition, has been observed for the first time in this semimagnetic semi-conductor. The critical scattering is observed at temperatures in the vicinity of the spin glass transition temperature, 17K. The scattering is observed as a kind of quasielastic scattering in the reciprocal range where the elastic magnetic diffuse scattering has been observed, e.g., 11/20 reciprocal point, indicating the spin fluctuation has dynamic components in this material. Photoconductivity has been discovered below 150K in {{{{{ Zn}_{ 0.4} {Mn }_{0.6 } Te}}}}. The electric AC conductivity has been increased dramatically under the laser light with the wave lengths of {{{{ lambda =6328,5145 and4880 }}}}$\AA$ ,respectively. After the light was darkened, the conductivity was reduced to the original level after about 2000 seconds at 50K, being above the spin glass transition temperature. This phenomenon is the typical persistent photoconductivity; PPC which was similarly found in {{{{ { Zn}_{ 1-x} { Mn}_{x} Te}}}}.