• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.155-155
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• 2014

The oxide film was formed in hydrogen induced cracking (HIC) environment by potentio-dynamic method. Corrosion potentials and rates of the X-65 and X-80 line pipe steels were -0.3495 $V_{SHE}$, $2.833{\times}10^{-3}A/cm^2$ and 0.2716 $V_{SHE}$ and $2.533{\times}10^{-3}A/cm^2$, respectively. Surface composition analysis of the oxide film contained sulfur. Thermodynamic analysis of the HIC solution chemistry suggested that the oxide phase consisted of iron sulfate. Dynamic nano-indentation method applied to determine nano-hardnesses of the oxide film and base metal hardness.

• Journal of Surface Science and Engineering
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• v.51 no.4
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• pp.197-201
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• 2018

Dynamic nano-indentation method was applied to characterize thin electroformed Ni-P layers. The Ni-P layers were produced in a sulphamic acid bath at $50^{\circ}C$ in $0.02A/cm^2$ for 10-60 minutes. The chemical analyses by XRD and EDX showed that the Ni-P layers were very fine grains with mainly $Ni_3P$ with Ni. The surface roughness determined by atomic force microscopy increased with thickness, which was relative to the surface morphology. The nano-hardness and the stiffness of the thin Ni-P layers with thickness of 1.9, 6.2 and $7.5{\mu}m$ were 5.52, 6.52 and 6.77 [GPa] and 56.7, 76.2 and 108.0 [${\mu}N/nm$], respectively. The elastic modulus of the Ni-P layer increased with thickness such as 37.29, 54.50 and 78.76 [GPa], respectively. The surface roughness of the electroplated Ni-P layers with diverse thickness was 8.66, 18.56 and 35.22 [nm], respectively. The enhanced nano-mechanical properties were related to mainly residual stress of the Ni-P layers.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.201.1-201.1
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• 2016

전주된 Invar (Fe-35%Ni) 박판 위에 증착된 Cu 박막은 스퍼터 전력량이 증가할수록 증착속도가 증가하였다. Cu/Invar 박판이 Invar 박판보다 면저항 값이 34%로 작았다. Invar 박판 위에 Cu가 증착되면 최대자화와 투자율은 각각 40.3, 65.0 [%] 감소하였다. Cu 박막의 탄성하강강성도, 마찰계수, 피로한계는 각각 45, 0.130, 0.093 이었다. 동적 나노 압침법으로 얻은 Invaar/Cu 박막의 하중-시간-변위 곡선의 가장 큰 차이는 탄성하강강성도(elastic stiffness) 이었다. 미세경도와 나노경도의 실험적 관계식은 $Y[GPa]=9.18{\times}10^{-3}X[Hv]$ 이었다. 나노압침선단의 하중분포를 이차원 선형 및 비선형 유한요소해석을 통하여 1.0 [mN] 의 정적하중을 가한 Cu 박막은 486 [mN] 으로 예측되었다. 이는 표면탐침현미경으로 관찰한 압흔의 변형정도와 유사한 경향을 보였다.

• Nuclear Engineering and Technology
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• v.49 no.3
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• pp.576-580
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• 2017

A dynamic nanoindentation method was applied to study an Fe-18 at.% Gd alloy as a neutron-absorbing material prepared by vacuum arc-melting and cast in a mold. The Fe-18 at.% Gd cast alloy had a microstructure with matrix phases and an Fe-rich primary dendrite of $Fe_9Gd$. Rietveld refinement of the X-ray spectra showed that the Fe-18 at.% Gd cast alloy consisted of 35.84 at.% $Fe_3Gd$, 6.58 at.% $Fe_5Gd$, 16.22 at.% $Fe_9Gd$, 1.87 at.% $Fe_2Gd$, and 39.49 at.% ${\beta}-Fe_{17}Gd_2$. The average nanohardness of the primary dendrite phase and the matrix phases were 8.7 GPa and 9.3 GPa, respectively. The fatigue limit of the matrix phase was approximately 37% higher than that of the primary dendrite phase. The dynamic nanoindentation method is useful for identifying local phases and for analyzing local mechanical properties.