• Nuclear Engineering and Technology
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• 제56권1호
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• pp.114-122
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• 2024

Irradiation-induced defects and the precipitates in the wrapper material of the Indian Fast Breeder Test Reactor (FBTR), SS 316 are analyzed using the synchrotron source-based Angle Dispersive X-Ray Diffraction (ADXRD) technique with X-rays of energy 17.185 keV (wavelength ~0.72146 Å). The differences and similarities in the high displacement damage samples as a function of dpa (displacement per atom) and dpa rate in the range of 2.9 × 10^-7- 9 × 10^-7 dpa/s are studied. Ferrite and M₂₃C₆ are commonly observed in the present set of high displacement damage 40-74 dpa SS 316 samples irradiated at temperatures in the range of 400-483 ℃. Also, the dislocation density has increased as a function of the irradiation dose. The X-ray diffraction peak profile parameters quantified such as peak shift and asymmetry show that the irradiation-induced defects are sensitive to the dpa rate-irradiation temperature combinations. The increase in yield strength as a function of displacement damage is also correlated to the dislocation density.

• 한국재료학회지
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• 제25권5호
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• pp.221-225
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• 2015

In-situ neutron diffraction has been employed to examine the effect of strain path on lattice strain evolution during monotonic and cyclic tension in an extruded Mg-8.5wt.%Al alloy. In the cyclic tension test, the maximum applied stress increased with cycle number. Lattice strain data were acquired for three grain orientations, characterized by the plane normal to the stress axis. The lattice strain in the hard {10.0} orientation, which is unfavorably oriented for both basal slip and {10.2} extension twinning, evolved linearly throughout both tests during loading and unloading. The {00.2} orientation exhibited significant relaxation associated with {10.2} extension twinning. Coupled with a linear lattice strain unloading behavior, this relaxation led to increasingly compressive residual strains in the {00.2} orientation with increasing cycle number. The {10.1} orientation is favorably oriented for basal slip, and thus showed a soft grain behavior. Microyielding occurred in the monotonic tension test and in all cycles of the cyclic test at an applied stress of ~50 MPa, indicating that strain hardening in this orientation was not completely stable from one cycle to the next. The lattice strain unloading behavior was linear in the {10.1} orientation, leading to a compressive residual strain after every cycle, which, however, did not increase systematically from one cycle to the next as in the {00.2} orientation.

• Bulletin of the Korean Chemical Society
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• 제33권12호
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• pp.4059-4062
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• 2012

The effect of a conductive agent on the structural and electrochemical properties of $Li_4Ti_5O_{12}$(LTO) spinel was investigated through neutron diffraction during Li intercalation and electrochemical measurements. The charging process of LTO is known as transformation of the white $(Li_3)_{8a}[LiTi_5]_{16d}O_{12}$ into a dark-colored $(Li_{3-X})_{8a}[Li_{X+Y}]_{16c}[LiTi_5]_{16d}O_{12}$ by incorporating the inserted Li into octahedral 16c sites, and the Li in tetrahedral 8a sites shifted to 16c sites. The occupancy of the tetrahedral 8a site varied with the existence of carbon in the electrode. Without carbon, the lattice parameter and cell volume of LTO decreased more notably than in the carbon-containing LTO electrode during Li insertion process. These phenomena might be attributed that the Li occupancy of the tetrahedral 8a of the LTO electrode without carbon was less than that of the carbon-containing LTO electrode.

• 한국자기학회지
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• 제15권2호
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• pp.142-147
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• 2005

고속 중성자 조사한 원자로 압력 용기의 취하현상을 상온에서 X-선 회절 실험과 액체 질손 온도에서 M$\ "{o}$ssbauer 분광법으로 조사하였다. 시료의 중성자 조사량은 $10^{12},\;10^{13},\;10^{14},\;10^{15},\;10^{16},\;10^{17},\;10^{18}\;n/{\cal}cm^2$이다. X-선 회절 패턴에서 중성자 조사하지 않은 시료는 bcc 형태를 나타내었으나, 중성자 조사량이 $10^{17}\;n/{\cal}cm^2$ 이상인 시료에서는 bcc 구조가 사라지는 심각한 손상을 보였다. 모든 시료의 $M\ddot{o}ssbauer$ 스펙트럼은 두개 혹은 그 이상의 sextet의 중첩을 보였다. 모든 $M\ddot{o}ssbauer$ 스펙트럼은 본문에서는 3조의 sextet로 fitting 하였다. 이성질체 이동치와 사중극자 분열치는 거의 영에 가까운 값을 나타내었다. 액체 질소 온도에서 중성자 조사량이 $10^{17}\~10^{18}\;n/{\cal}cm^2$인 시료에서 S1 sextet의 초미세 자기장과 흡수 면적이 급격히 상승하는 현상을 관측하였으며, 상온에서 또한 이 현상을 관측하였다. 이는 중성자 조사에 의한 시료 내부의 $^{55}Mn$ 혹은 $^{56}Fe$이 $^{57}Fe$의 천이에 의한 $^{57}Fe$의 $M\ddot{o}ssbauer$ 핵종의 증가에 기인하는 것으로 추측된다.

• Transactions on Electrical and Electronic Materials
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• 제9권6호
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• pp.265-272
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• 2008

In this paper, AC losses of long wire Bi-2223 tapes with different twist pitch of superconducting core were fabricated, measured and analyzed. These samples produced by a powder-in-tube method are multi-filamentary tape with Ag matrix. Also, it's produced by non-twist. The critical current measurement was carried out under the environment in Liquid nitrogen and in zero field by 4-prob method. And the Magnetic measurement was carried out under the environment of applied time-varying transport current by transport method. From experiment, the susceptibility measurements were conducted while cooling in a magnetic field. Flux loss measurements were conducted as a function of ramping rate, frequency and field direction. The AC flux loss increases as the twist-pitch of the tapes decreased, in agreement with the Norris Equation. Neutron-diffraction measurements have been carried out investigate the crystal structure, magnetic structures, and magnetic phase transitions in Bi-2223([Bi, Pb]:Sr:Ca:Cu:O).

• Journal of Welding and Joining
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• 제21권6호
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• pp.64-70
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• 2003

Multipass welds of the 316L stainless steel have been widely employed in the pipes of Liquid Metal Reactor. Owing to localized heating and subsequent rapid cooling by the welding process, the residual stress arises in the weld of the pipe. In this study, the residual stresses in the 316L stainless steel pipe welds were calculated by the finite element method using ANSYS code. Also, the residual stresses both on the surface and in the interior of the thickness were measured by HRPD(High Resolution Powder Diffractometer) instrumented in HANARO Reactor. The experimental data and the calculated results were compared and the characteristics of the distribution of the residual stress discussed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.298-303
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• 2000

Principles of residual stress measurements by neutron diffraction and the residual stress instrument installed at 30MWt HANARO reactor in KAERI are considered. In-depth residual stress distribution was measured in aluminum VAMAS round robin sample and welded stainless steel plate, which showed high ability of the instrument for the stress measurements in components.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1325-1326
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• 2006

Tungsten-molydiside $W_xMo_{1-x}Si_2$ was synthesized by self-propagating high temperature synthesis (SHS). The SHS product with the initial composition of (0.5Mo+0.5W+2Si) contains 23.9% $MoSi_2$, 40.89% $WSi_2$ with remaining 9.11% Mo, 9.16% Si and 16.94%W. Lattice parameters of the $MoSi_2$ and $WSi_2$ determined by Rietvelt analysis were a=0.3206 nm, c=0.7841 nm and a=0.3212 nm, c=0.7822 nm, respectively.

• 한국분말재료학회지
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• 제10권3호
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• pp.164-167
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• 2003

The mechanical alloying effect has been studied on the three Cu-based alloy systems with a positive heat of mixing. The extended bcc solid solution has been formed in the Cu-V system and an amorphous phase in the Cu-Ta system. However, it is round that a mixture of nanocrystalline Cu and Mo Is formed in the Cu-Mo system. The neutron diffraction has been employed at a main tool to characterize the detailed amorphization process. The formation of an amorphous phase in Cu-Ta system can be understood by assuming that the smaller Cu atoms preferentially enter into the bcc Ta lattice during ball milling.

• E2M - 전기 전자와 첨단 소재
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• 제8권6호
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• pp.715-720
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• 1995

기계적 합금화법에 의한 비정질화 과정을 Ni-Ta계 및 Cu-Ta계에 대하여 조사하였다. Ni-Ta합금계는 혼합엔탈피가 음이나, Cu-Ta계는 혼합엔탈피가 양인 열역학적으로 대조적인 합금계이다. 볼밀 중 발생하는 원자구조 변화를 중성자회절법을 이용하여 관찰하였다. 두 합금게에 있어서 기계적 합금화에 의한 비정질상이 생성되었다. 비정질 Cu-Ta합금의 local원자구조를 혼합엔탈피가 크게 음인 Ni-Ta계의 결과와 비교하였다. 그 결과, 대조적 특성을 가진 두 합금계임에도 불구하고 원자크기가 작은 Ni 및 Cu가 bcc Ta의 결정격자 속으로 우선적으로 침입함으로써 비정질화가 진행됨을 알 수 있었다.