Earticle

본 연구는 철제유물의 부식두께에 대해 비파괴 및 파괴분석 결과와 비교하여, 비파괴적 인 중성자 회절법을 이용한 철제유물의 부식 측정의 적용 가능성을 확인하였다. 중성자 회절을 이용한 부식두께는 각 분석법을 적용한 결과와 비교했을 때 오차범위가 약 6%이며, 이는 선행 연구 결과와 비교하였을 때 철제유물의 부식두께를 측정함에 있어 적용성이 큼을 확인하였다. 또한, 파괴분석 결과와 비교하였을 때, TM의 특성을 고려하면 비파괴적인 중성자 회절법을 이용하여 DPL의 두께를 추정할 수 있음을 확인하였다. 이렇듯 중성자를 이용하여 파괴하지 않고 철제유물의 부식두께 및 내부구조를 추정하는 방법은 철제유물의 부식을 이해하는 데 있어 큰 도움을 줄 수 있으므로 그 활용 가능성이 큼을 확인하였다.

This study compared the corrosion thickness of iron artifacts using both non-destructive and destructive analytical methods. More specifically, the study evaluated the effectiveness of non-destructive neutron diffraction in measuring corrosion. Neutron diffraction analysis indicated a measurement error of approximately 6% when compared to the results of the other methods, confirming its applicability in assessing corrosion thickness in iron artifacts. The results were in line with those of previous studies. In addition, a results comparison with destructive analysis confirmed that the corrosion thickness of DPL(Dense Product Layer) could be estimated using the non-destructive neutron diffraction method when considering the characteristics of TM(Transformed Medium). This method of estimating the corrosion thickness and internal structures of iron artifacts through neutron analysis and without causing damage significantly enhances our understanding of iron corrosion while verifying its potential for use in practical applications.

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.

상온 거대자기저항 물질로 많은 연구가 이루어지고 있는 double perovskite (A$_2$BB'O$_{6}$) 계 물질은 B-site의 전이금속 윈자 종류에 따라 다양한 특성이 나타나는 것으로 보고되고 있다$^{[1]-[4]}$ . 그 중 Sr$_2$FeMoO$_{6}$ 시료가 MR 특성 및 전자기적 특성이 가장 우수한 것으로 알려져 있으나, Figure 1에 보이는 것과 같이, Sr$_2$CrMoO$_{6}$ 시료가 가장 높은 전이온도를 갖음으로 훌륭한 소자로의 응용 가능성을 보이고 있다. (중략)

Alternating current (AC) losses of two Bi-2223 ([Bi, Pb]: Sr: Ca: Cu: O = 2:2:2:3) tapes [(Tape I, un-twist-pitch) and the other with a twist-pitch of 10 mm (Tape II)] were measured and compared. These samples, produced by the powder-in-(Ag) tube (PIT) method, are multi-filamentary. Also, it's produced by non-twist and different twist pitch (8, 10, 13, 30, 50 and 70 mm). The critical current measurement was carried out under the environment in liquid Nitrogen and in zero-field by 4-probe method. 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)

최근 Y. Masumoto[1]등에 의하여 Co가 도핑된 anatase 구조의 TiO$_2$ 물질에서 상온 강자성 현상이 보고된 이후, 이에 대한 관심이 고조되면서 다른 연구 그룹들에 의해 실험적으로 상온 강자성을 성공하였다는 보고[2,3]가 있으나 현재 그 메커니즘에 대하여 명확한 해석이 되어있지 않고 있기 때문에 이것이 정말 자성반도체의 성질인지 아니면 clustering에 의한 것인지 아직 확실히 밝혀져 있지는 않다. (중략)

Fatigue crack growth experiments were carried out on a 304 L stainless steel compact-tension(CT) specimen under load control mode. Neutron diffraction was employed to quantitatively measure the residual strains/stresses and the evolution of stress fields in the vicinity of a propagating fatigue-crack tip. Three principal stress components (i.e. crack growth, crack opening, and through-thickness direction stresses) were examined in-situ under loading as a function of distance from the crack tip along the crack-propagation path. The stress/strain fields, measured both at the mid-thickness and near the surface of the CT specimen, were compared. The results show that much higher compressive residual stress fields developed in front of the crack tip near the surface than developed at the mid-thickness area. The change of the stresses ahead of the crack tip under loading is more significant at the mid-thickness area than it is near the surface.

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).

The catalytic activity of ceria originates from oxygen vacancies. Ce2O3 is the most oxygen-deficient end-member of nonstoichiometricceria, CeO2-x. A new method of synthesizing air-stable Ce2O3 from the micron- and nano-sized CeO2 powderwas developed. The key part of this synthetic process is to reduce the sample in a low-pressure H2 gas (10 Torr) under vacuumat 1300°C. The percentage of the Ce2O3 phase in the reduced sample ranges from 55% ~ 96 wt.% according to the powdersize and reduction time. Hydrogen incorporation in reduced ceria was confirmed by secondary ion mass spectrometry depthprofile analysis and vibrational spectroscopic techniques, such as Raman and Fourier transform infrared spectroscopy. Thesurface region (zero depth) showed the highest H concentration that decreased with increasing profiling depth. The locationsof hydrogen incorporated in the Ce2O3 phase in the reduced sample were revealed by calculating the nuclear densitydistribution. The maximum entropy method-based pattern fitting and Dysnomia program were combined to calculate thenuclear density map using the neutron diffraction data.

The thermal stress distribution of WC and Ni binder phases In WC-26st.%Ni and WC-6wt.%Ni composites has been investigated over the temperature range 100-900 K using a time-of-flight neutron diffractometer. To determine the stress distribution, the breadths of WC and Ni peaks in the reference powder and the composites were analyzed. The peak breadths were corrected for particle size effect using a procedure based on the integral peak breadth method of particle size-strain analysis. The result shows a broad range of strain, and thus stress, is present in the WC and Ni binder phases of the composites. The strain distribution of both phases broadens as the temperature decreases, and some fraction of total strain distribution of the WC phase remains tensile regardless of the temperature. The strain distribution of the WC phase broadens as the binder content increases, and that of Ni binder phase broadens as the binder content decreases, which means the strain distribution broadens as the absolute value of residual stress increase.

The structural change during electrochemical cycling in full-cell system has been investigated by neutron diffraction methodand the full-cell consists of spinel-lithium manganese oxide cathode and graphite anode. The structural variation has beenmonitored by in-situ neutron diffraction technique at different state of charges (SOCs), and the obtained data were comparedwith ex-situ powder neutron diffraction patterns. Phase transitions for lithiated/delithiated graphite can clearly explain thatthe intercalated lithium ions in graphite are not perfectly extracted during a delithiaion process. The content of LiC12 phaseincreases as an increase in electrochemical cycle numbers, and the lattice parameter of LiMn2O4 also decreases due to thereduction of the amounts of Li ions, which can be reversibly intercalated/deintercalated into/from the structure.

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

The three-dimensional orientation distribution function of a conical shaped tungsten liner prepared by the thermo-mechanical forming process was analyzed by 1.525$\AA$ neutrons to carry out the Rietveld refinement. The pole figure data of three reflections, (110)(220) and (211) were measured. The orientation distribution functions for the normal and radial directions were calculated by the WIMV method. The inverse pole figures of the normal and radial directions were obtained from their orientation distribution functions. The Rietveld refinement was performed with the RIETAN program that was slightly modified for the description of preferred orientation effect. We could successfully do the Rietveld refinement of the strongly textured tungsten liner by applying the pole density of each reflection obtained from the inverse pole figure to the calculated diffraction pattern. The correction method of preferred orientation effect based on the inverse pole figures showed a good improvement over the semi-empirical texture correction based on the direct usage of simple empirical functions.