• 한국전기전자재료학회논문지
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• 제11권10호
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• pp.796-803
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• 1998

Intrinsic and proximity gettering are popular processes to get higher cumulative production yield and usually adopt multi-step annealing and high energy ion implantation, respectively. In order to test the combined processed of these, high energy \ulcornerAs\ulcorner ion implantation and 2-step annealing process were adopted. After the ion implantation followed by 2-step annealing, the wafers were cleaved and etched with Wright etchant. The morphology of cross section on samples was inspected by FESEM. The concentration profile of As was measured by SRP. The location and type of secondary defects inspected by HRTEM were dependent on the 1st annealing temperatures. That is, a line of dislocation located at $1.5mutextrm{m}$ apart from the surface at $600^{\circ}C$ lst annealing was changed to some dislocation lines or loops nearby the surface at 100$0^{\circ}C$. The density of dislocation line was reduced but the size of the defects was enlarged as the temperature increased.

• Composites Research
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• 제22권3호
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• pp.9-17
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• 2009

본 논문에서는 분자동력학 방법을 이용하여 Ag 필름/Cu기판에 대한 나노인덴테이션 특성을 파악하였다. 필름의 강성과 경도는 필름의 두께에 관계되어있으며, 임계범위 내에서, 그래인 크기가 증기하면 강성과 경도도 증가하는 것을 확인하였다. 5nm 두께 이하의 Ag필름/Cu기판의 강성과 경도는 벌크 Ag의 경우에 비해 낮은 값을 나타내었다. 특히 4nm 두께 이하의 Ag필름/Cu기판의 인덴테이션에 있어서, 전위 집적과 불일치 전위사이의 상호작용에 의해 계면상에서 꽃모양의 전위 루프가 발생 하였다. 이는 인덴테이션 하중과 변위 커브에서 하중이 저하되는 것과 관계있는 것으로 사료되고 있다.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.337-343
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• 2020

Oxide dispersed strengthened (ODS) steel is an important candidate for Gen-IV reactors. Oxide embedded in Fe can help to trap irradiation defects and enhances the strength of steel. It was observed in this study that the size of oxide has a profound impact on the depinning mechanism. For smaller sizes, the oxide acts as a void; thus, letting the dislocation bypass without any shear. On the other hand, oxides larger than 2 nm generate new dislocation segments around themselves. The depinning is similar to that of Orowan mechanism and the strengthening effect is likely to be greater for larger oxides. It was found that higher shear deformation rates produce more fine-tuned stress-strain curve. Both molecular dynamics (MD) simulations and BKS (Bacon-Knocks-Scattergood) model display similar characteristics whereby establishing an inverse relation between the depinning stress and the obstacle distance. It was found that (110)_oxide || (111)_Fe (oriented oxide) also had similar characteristics as that of (100)_oxide || (111)_Fe but resulted in an increased depinning stress thereby providing greater resistance to dislocation bypass. Our simulation results concluded that critical depinning stress depends significantly on the size and orientation of the oxide.

• Nuclear Engineering and Technology
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• 제51권2호
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• pp.501-509
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• 2019

In this paper a body-centered cubic(BCC) crystal plasticity model based on microscopic dislocation mechanism is introduced and numerically implemented. The model is coupled with irradiation effect via tracking dislocation loop evolution on each slip system. On the basis of the model, uniaxial tensile tests of unirradiated and irradiated RPV steel(take Chinese A508-3 as an example) at different temperatures are simulated, and the simulation results agree well with the experimental results. Furthermore, crystal plasticity damage is introduced into the model. Then the damage behavior before and after irradiation is studied using the model. The results indicate that the model is an effective tool to study the effect of irradiation and temperature on the mechanical properties and damage behavior.

• Nuclear Engineering and Technology
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• 제54권3호
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• pp.991-996
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• 2022

Microstructures of monolithic high purity SiC and SiC with sintering additives after neutron irradiation to a fluence of 2.0-2.5 × 10²⁴ n/m² (E > 0.1 MeV) at 333-363 K and after post-irradiation annealing up to 1673 K were observed using a transmission electron microscopy. Results showed that no black spot defects or dislocation loops in SiC grains were found after the neutron irradiation for all of the specimens owing to the moderate fluence at low irradiation temperature. Thus, it is confirmed that these specimens were swelled mostly by the formation of point defects. Black spots and small dislocation loops were discovered only after the annealing process in PureBeta-SiC and CVD-SiC, where the swelling almost diminished. Anomalous-shaped YAG grains were found in SiC ceramics containing sintering additives. These grains contained dense black spots defects and might lose crystallinity after the neutron irradiation, while these defects may annihilate by recrystallization during annealing up to 1673 K. Amorphous grain boundary phase was also presented in this ceramic, and a large part of it was crystallized through post-irradiation annealing and could affect their recovery behavior.

• 한국재료학회지
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• 제11권7호
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• pp.615-621
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• 2001

본 연구에서는 고변형된 이중 에피층에서 두 가지 종류의 반원 전위 루프 ($60^{\circ}$및 쌍격자 전위)의 생성 속도물 예측하는 모델을 제안한다. 모델링 시, 에피층 표면에서 발생하는 결함과 이곳에 집중되는 응력 효과를 고려하였으며, Matthew의 식을 발전시켜 에피층 두께에 따른 잔류 변형율을 변수로 사용하였다. 모델링을 통한 계산 결과에 의하면, 응력 집중 현상은 고변형된 이종에피층에서 전위 및 결정 결함 현상을 설명하는 데 매우 중요하였다. 또한,본 연구를 퉁하여, 응력 집중 현상이 에피층 성장 초기에 생성되는 전위 형태를 결정하는 주요한 인자 중 하나임을 단면 투과 전자 현미경 결과와의 비교를 통해 확인할 수 있었다.

• 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.

• 한국결정성장학회지
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• 제15권2호
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• pp.45-50
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• 2005

규소 표면의 기계적 손상은 산화 공정 중에 규소 표면에 여러 가지 형태의 결함들을 발생 시킨다. 규소 표면에 손상을 주는 마모 입자가 커짐에 따라 OISF보다는 etch pit의 형상이 동굴형인 선 결함(line defects)들이 많이 발생된다. 이들 결함들은 실리콘 결정을 성장시키는 단계에서 형성되는 결함들과는 상호 관련이 없다. 방향성 응고법으로 성장된 규소 결정속에 존재하는 결함들은 주로 twin과 stacking fault들이며 응고과정에서 발생이 예상되는 응력에 의한 전위는 거의 발견되지 않았다. 따라서 Czochralski 법으로 성장된 단 결정 규소뿐 아니라 방향성 응고법으로 성장된 다 결정 규소 기판도 표면의 결함들을 이용하여 extrinsic gettering을 통한 규소 결정 내부의 불순물 제거의 가능성이 높다.

• 한국자기학회지
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• 제8권5호
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• pp.249-254
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• 1998

자기측정법에 의한 조사손상 평가 가능성을 조사하기 위하여 SA508 CI.3강 모재금속의 중성자 조사 및 열처리 온도에 따른 자기특성(자기이력곡선, Barkhausen Noise(BN) 진폭, BN 에너지)과 경도 변화를 측정 비교하였다. 중성자 조사에 따라 자화율, BN 진폭, BN 에너지는 감소하였고 보자력과 경도는 증가하였으며, 포화자화 값은 변화하지 않았다. 열처리된 조사시편의 경우, 열처리 온도 증가에 따라 BN 에너지는 증가하였으며, 경도는 감소하였다. 결함과 전위혹은 자벽 이동과의 상호작용에 의한 경도 및 자기특성의 일관성 있는 변화는 원자로 압력용기 재료의 조사손상 평가와 관련 자기적 측정법 응용 가능성을 보여주었다.

• 한국음향학회:학술대회논문집
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• 한국음향학회 1999년도 학술발표대회 논문집 제18권 2호
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• pp.401-406
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• 1999

In relation to a non-destructive evaluation of irradiation damages of micro-structure interstitial, void and dislocation, the changes in the hysteresis loop, Barkhausen noise amplitude and the harmonics frequency due to a neutron irradiation were measured and evaluated. The Mn-Mo-Ni low alloy steel of RPV was irradiated to a neutron fluence of $2.3\times10^{19}\;n/cm^2\;(E\geq1\;MeV)\;at\;288^{\circ}C$. The saturation magnetization of neutron irradiated metal did not change. The neutron irradiation caused the coercivity to increase, whereas susceptibility to decrease. The amplitude of Barkhausen noise parameters associated with the domain wall motion were decreased by a neutron irradiation. The spectrum of Barkhausen noise is analysed with an applied frequency of 4 Hz and 8 Hz, sampling time of $50\;{\mu}sec\;and\;20\;{\mu}sec$. The harmonic frequency shows 4 Hz, 8 Hz, 12 Hz; and 16 Hz reflected from an unirradiated specimen. On the contrary, the harmonic frequency disappeared on the irradiated specimen.