• 비파괴검사학회지
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• 제21권6호
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• pp.612-617
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• 2001

본 연구에서는 Al-Si 합금 열간단조품 내부 판상 결함을 탐지하기 위한 초음파평가 기법을 확립하였다. 이를 위하여 내부에 존재하는 여러 가지 판상 결함의 초음파 특성을 실험적으로 구하였으며, 펄스-반사법을 적용하여 초음파 탐상신호에 대한 내부 판상 결함의 각도 등이 초음파 수신신호의 형태에 미치는 영향을 평가하였다. 한편 결함위치에 따른 초음파 신호특성을 규명하기 위하여 단조품 가장자리 부위에 존재하는 내부 판상 결함의 초음파 수신신호 특성을 평가하였으며, 본 시험편에 대한 초음파 투과법 적용 한계에 대하여 고찰하였다. 나아가 500개 이상의 파단 실험을 통해 제시된 초음파 평가기법의 신뢰성을 확인하였다.

• 한국재료학회지
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• 제19권12호
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• pp.699-702
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• 2009

Due to the importance of the SiGe/Si heterostructure in the fields of thermoelectric and electronic applications, SiGe/Si heterostructures have been extensively investigated. For practical applications, thermal stability of the heterostructure during the thermoelectric power generation or fabrication process of electronic devices is of great concern. In this work, we focused on the effect of thermal annealing on the defect configuration in the SiGe/Si heterostructure. The formation mechanism of planar defects in an annealed SiGe/Si heterostructure was investigated by transmission electron microscopy. Due to the interdiffusion of Si and Ge, interface migration phenomena were observed in annealed heterostructures. Because of the strain gradient in the migrated region between the original interface and the migrated interface, the glide of misfit dislocation was observed in the region and planar defects were produced by the interaction of the gliding misfit dislocations. The planar defects were confined to the migrated region, and dislocation pileup by strain gradient was the origin of the confinement of the planar defect.

• 한국결정성장학회지
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• 제9권6호
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• pp.558-562
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• 1999

승화 성장법을 적용하여 성장된 6H-SiC 결정에 대하여, KSV 이론과 성장 계면에서의 미사면(vicinal plane)상의 step 성장 양상을 근거로 하여, 성장 계면에서의 물질 흡착의 거동과 결함의 생성간의 상호 관계를 고찰하고, micropipes와 내부 결함의 생성 원인을 논하였다. micropipe와 면결함등의 결함들은 ledge 혹은 kink에 침입된 불순물에 의하여 step 성장의 진행이 방해받는 부분에 형성되었다. 따라서, SiC 결정에서 이들 결함의 생성은 SiC 결정 성장 계면에 형성되는 결정학적 step 성장면과 분자 또는 원자들의 격자 이동에 관련이 있음을 알 수 있었다.

• 한국결정성장학회지
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• 제10권6호
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• pp.373-377
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• 2000

승화 성장법으로 성장된 6H-SiC 단결정에 대하여 etching을 행하여 형성된 etch pit의 형상과 결함과의 관계에 대하여 고찰하였다. (0001) 기저면에서는 육각형의 전형적인 etch pit이 형성되었다. micropipe에 의해서도 유사한 형태의 pit이 형성되었으며, 면결함에 형성된 etch pits을 통하여 SiC 결정의 내부에 형성된 planar defects도 성장 결정과 동일한 구조를 가지면서 형성됨을 알 수 있었다.

• 한국정밀공학회지
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• 제16권2호통권95호
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• pp.225-233
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• 1999

This paper describes a versatile finite element technique which has been used to investigate of wide range of structural defects of practical importance. The procedure automatically remeshes the three-dimensional finite element model during the stages of crack growth. Problems analyzed to date include the surface cracks in leak-before-break situations, the development of quarter-elliptical corner defects, planar semi-elliptical surface defects and the fatigue growth of defects.

• 한국공작기계학회논문집
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• 제13권5호
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• pp.87-95
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• 2004

From the results of AE(Acoustic Emission) source location occurred by the spot exciting as suggested in this research, it has been confirmed that AE technique is quite fruitful in figuring out the location of the occurrence, form, size and direction of the defects. As the results of examining the distribution of event for the angle of crack $\alpha$ to Xs and Ys, as the increases from $0^{\circ}$ ~ $90^{\circ}$, gradually changes its width from the axis Xs to the axis Ys. So event appears approximately similar in its size at the angle of crack $\alpha$=$45^{\circ}$, yet opposite when $\alpha$ is lager. It is believed that this is a phenomenon where its crack legnth $\alpha$, assumed as a planar defect, is to be prcjected toward the direction with a larger size. Thus, it is expected that the application of the experimental method suggested in this study would make it possible to identify the location of the defect in the material in the nondestructive way.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 15TH KACG TECHNICAL MEETING-PACIFIC RIM 3 SATELLITE SYMPOSIUM SESSION 4, HOTEL HYUNDAI, KYONGJU, SEPTEMBER 20-23, 1998
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• pp.35-40
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• 1998

There have two kinds of defects, planar defects and vertical defects which were called micropipes in SiC bulk crystals grown by a sublimation method. We could decrease these defects by adding a little piece of Si in the SiC powder or using Ta cylinder in the crucible. so were report the dependence of these defects in a wafer on silicon/carbon ratio in this paper. The chemical species sublimed from SiC powder is affected by carbon from the graphite wall of the crucible. It is important to control the chemical species on the substrate.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.369-375
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• 2002

The results of source location in terms of AE signal occurred by the spot exciting as suggested in this research, it has been confirmed that AE technique is quite fruitful in figuring out the location of the occurrence, form, size and direction of the defects. Thus, it is expected that the application of the experimental method suggested in this study would make it possible to identify, in the nondestructive way, the location of the defect in the material.

• 한국공작기계학회논문집
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• 제15권2호
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• pp.87-92
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• 2006

This paper supplements shortcoming of radioactivity check by detecting defect of SWP weld zone using ultrasonic wave. Manufacture 2 stage robot detection systems that can follow weld bead of SWP by method to detect weld defects of SWP that shape of weld bead is complex for this as quantitative. Also, through signal processing ultrasonic wave defect signal system of GUI environment that can grasp easily existence availability of defect because do videotex compose. Ultrasonic wave signal of weld defects develops artificial intelligence style sightseeing system to enhance pattern recognition of weld defects and the classification rate using neural net. Classification of weld defects that do fan Planar defect and that do volume defect of by classify.

• 한국결정성장학회지
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• 제8권1호
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• pp.29-35
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• 1998

고품질의 6H-SiC 단결정을 성장하기 위하여 기판, 원료 및 성장에 사용되는 도가니에 대한 고순도 처리공정을 통하여 고순도화하여 결정성장을 시행하였다. 특히, 원료에 대해서는 순화처리전후의 XRD 분석을 행하여 고순도화된 원료의 상태를 확인하였다. 성장된 6H-SiC 단결정의 크기는 직경이 33mm, 길이는 11mm이었고, 기판으로의 사용 및 내부결함에 대한 관찰을 위하여 결정을 절단 및 연마하여 직경 33mm, 두께 0.5mm인 wafer를 제작하였으며, 광학현미경 및 Raman 분석을 이용하여 순화공정을 통해 제작된 wafer의 내부결함밀도 및 결정성을 측정하였다. 분석결과, micropipe 및 planar defect의 밀도는 각각 100개/$\textrm{cm}^2$, 30개/$\textrm{cm}^2$으로 순화처리를 통한 내부결함의 감소로 인해 고품질의 6H-SiC 단결정의 성장이 가능하였다