• Nuclear Engineering and Technology
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• 제53권12호
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• pp.4052-4059
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• 2021

The microstructure of the fuel pellet plays an essential role in fission gas buildup and release and is critical for the safe and continued operation of nuclear power stations. Structural analysis of uranium dioxide (UO₂)-molybdenum (Mo) composite fuel pellets prepared at a range of sintering temperatures from 1300 to 1800 ℃ was performed. Mo micro and nanoparticles were used in making the composite pellets. A systematic investigation into the influence of processing parameters during Spark Plasma Sintering (SPS) of the pellets on the microstructure, texture, grain size, and grain boundary characters of UO₂-Mo is presented. UO₂-Mo composite show significant differences in the fraction of general boundaries and also special/coincident site lattice (CSL) boundaries. EBSD orientation maps demonstrated that <111> texturing was observed in the pellets fabricated at 1500 ℃. The experimental investigations suggest that UO₂-Mo composite pellets have favorable microstructural features compared to the UO₂ pellet.

• 전기전자학회논문지
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• 제23권2호
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• pp.534-537
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• 2019

광학적 손실은 태양전지 표면에 조사되는 빛이 태양전지 내부로 흡수되지 않고 표면에서 반사되어 발생하는 손실이다. 이러한 빛의 반사로 인한 광학적 손실을 줄이고 태양전지의 변환 효율을 높이기 위한 연구가 활발하게 진행되고 있다. 본 논문에서는 유리기판 표면을 습식 식각을 사용하여 표면을 거칠게 형성해 식각된 표면의 구조적 특성을 평가하였고, 분광기를 통해 식각된 표면의 광학적 특성을 분석하였다. 식각을 통해 형성되는 분화구 모양의 거친 표면은 입사되는 빛을 태양전지 내부로 재흡수하여 빛의 반사를 줄어들었고, 이에 따라 투과되는 빛이 증가하였음을 확인하였다.

• 소성∙가공
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• 제28권5호
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• pp.239-246
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• 2019

Various surface texturing techniques have been studied because of the effective applicability of micro or nano scale surface patterns. Particularly, the most promising types of patterns include the hierarchical patterns, which consists of micro/nano structures. Different processes such as MEMS, laser machining, micro cutting and micro grinding have been applied in the production of hierarchical patterns on various material surfaces. This study demonstrates the process of hot imprinting to induce the hierarchical patterns on the Al alloy surfaces. Wire electrical discharge machining (WEDM) process was used to imprint molds with micro scale sinusoidal pattern. In addition, the sinusoidal pattern with rough surface morphology was obtained as a result of the discharge craters. Consequently, the hierarchical patterns consisting of the sinusoidal pattern and the discharge craters were prepared on the imprinting mold surface. Hot imprinting process for the Al plates was conducted on the prepared mold, and the replication performance was analyzed. As a result, it was confirmed that the hierarchical patterns of the mold were effectively duplicated on the surface of Al plate.

• 한국초전도ㆍ저온공학회논문지
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• 제8권3호
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• pp.37-40
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• 2006

Oxide buffer layers for YBCO coated conductors were fabricated using MOD processing and development of microstructure and texture were investigated. A $CeO_2$ buffer layers were formed on RABiTS tape. Acetate-based precursor solution was employed to synthesize the precursor solution. Subsequently, the precursor solution was stabilized and modified with triethanolamine. $CeO_2$ precursor gel film was coated and annealed in $Ar/H_2$ atmosphere at high temperature. An annealed $CeO_2$ film shows mixed orientation with high (001) texturing. It was shown that (111) texture of $CeO_2$ layers were enhanced by multiple coating. This degradation was attributed to development of microcracks in the multiply coated $CeO_2$ films. Also discussed are the synthesis and the characterization of $La_2Zr_2O_7$ (LZO) buffer layers on RABiTS tape. A biaxially textured LZO buffer layer was fabricated with MOD processing method using metal alkoxide based precursor solution. It was shown that the LZO film were epitaxially grown on RABiTS tape and crack-free & uniform surface was obtained after annealing in $Ar/H_2$ atmosphere.

• ETRI Journal
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• 제44권1호
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• pp.85-93
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• 2022

We propose an efficient method for synthesizing mesh-based realistic computer-generated hologram (CGH). In a previous nonanalytic mesh-based CGH synthesis, the angular spectrum of the two-dimensional (2D) plane is calculated using the fast Fourier transform (FFT) with the same size as the resolution of the final hologram. Because FFT increases the computation time as the size of the input matrix increases, the previous method has a problem: The higher the resolution of the hologram, the greater the computational load, thereby delaying synthesis time. In this study, when calculating the angular spectrum of the 2D plane in mesh-based CGH synthesis, we propose a method to calculate the angular spectrum by defining the 2D plane with an arbitrary size smaller than the resolution of the final hologram. The resolution adjustment method reduces the computation time and can be applied to occlusion culling and texturing for the realistic effect of mesh-based CGH. We describe the principle, error analysis, application of realistic effect, and experimental results of the proposed method.

• Nuclear Engineering and Technology
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• 제56권6호
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• pp.2367-2374
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• 2024

In this paper, based on the need for high-strength connections between all-tungsten-oriented plasma materials and thermal sinking materials of copper and its alloys in nuclear fusion devices, a study on the effect of tungsten surface laser micro structuring on the interfacial bonding properties of W/Cu joints was carried out. In the experiment, the connectors were prepared by vacuum fusion infiltration technology, and the effects of microgroove structure on the mechanical and thermal conductivity of W/Cu connectors were investigated under different parameters (including microgroove pitch, microgroove depth, and microgroove taper). The maximum shear strength is 126.0 MPa when the pitch is 0.15 mm and the depth is 34 ㎛. In addition, the negative taper structure, i.e., the width of the entrance of the microstructure is smaller than the width of the interior of the microstructure, is also investigated. The shear tests show that there is an approximately linear relationship between the shear strength of W/Cu and taper. Compared with the positive taper, the shear strength of the samples with the same morphological density and depth of the tungsten surface is significantly higher.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 춘계학술대회 초록집
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• pp.73.1-73.1
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• 2010

태양광 시장은 세계적인 금융 위기 속에서도 점점 그 규모가 확대되고 있다. 시장의 규모가 확대되고 있음에도 불구하고 금융 위기를 겪으면서 생산자 중심의 시장에서 수요자 중심의 시장으로 바뀌게 되었다. 이에 따라 더 적은 비용으로 높은 출력의 제품만이 경쟁력을 가지게 됨으로써 효율이 더욱 이슈화되었다. 여러 태양전지 중 가장 점유율이 높은 결정질 태양전지는 일반적인 양산 공정만으로 효율을 높이는데 한계가 있으므로 selective emitter, back contact, light induced plating 등의 새로운 공정을 도입하여 효율을 높이려는 경향이 나타나고 있다. 본 연구에서는, ALD 장치를 사용하여 결정질 태양전지의 후면을 passivation 함으로써 효율을 높이는 방법을 모색하였다. 부동화 층으로는 $Al_2O_3$를 사용하였으며 셀을 제조하여 평가하였다. 실험방법은 p-type의 웨이퍼를 이용하여 습식으로 texturing 후 $POCl_3$ 용액으로 p-n junction을 형성하였고 anti-reflection 막인 SiNx는 PECVD를 사용하여 R.I 2.05, 80nm 두께로 증착하였다. 그런 다음 후면의 n+ layer를 제거하기 위하여 SiNx에 영향을 미치지 않는 용액을 사용하여 후면을 식각하였다. BSF 층은 screen printer로 Al paste를 printing하여 형성하였고 Al etching용액으로 여분의 Al제거한 후 ALD 장치를 이용하여 $Al_2O_3$를 증착하였다. 마지막으로 전극을 형성한 후 laser로 isolation하여 효율을 평가하였다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.430.2-430.2
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• 2016

The front transparent conductive oxide (TCO) films in thin fill solar cell should exhibit high transparency, conductivity, good surface morphology and excellent light scattering properties. The light trapping phenomenon is limited due to random surface structure of TCO films. The proper control of surface structure and uniform cauliflower TCO films may be appropriate for efficient light trapping. We report light trapping scheme of ICP-RIE glass texturing by SF6/Ar plasma for high roughness and haze ratio of ITO films. It was observed that the variation of etching time, pattern size and Ar flow ratio during ICP-RIE process were important factors to improve the diffused transmittance and haze ratio of textured glass. The ICP-RIE textured glass showed low etching rates due to the presence of metal elements like Al, B, F and Na. The ITO films deposited on textured glass substrates showed the high RMS roughness and haze ratio in the visible wavelength region. The change in surface morphology showed negligible influence on electrical and structural properties of ITO films. The ITO films with high roughness and haze ratio can be used to improve the performance of thin film solar cells.

• Journal of Periodontal and Implant Science
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• 제39권3호
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• pp.293-301
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• 2009

Purpose: The purpose of this study is to show the total survival rate of implants with maxillary sinus floor elevation and the effects that reach the survival rate by classifying types of graft materials, implant surface, operation method, bone height. Methods: In a total of 131 patients, 251 implants with sinus floor elevation were installed simultaneously or after regular healing. Various bone grafts (autograft, xonograft, allograft, alloplast) and implant surface (MTX-HA implant, chemical etching implant, Titanium oxide surface implant, resorbable blasting media implant, resorbable blast texturing implant, HA-coated implant) were used. All implants were investigated clinically and radiographically, being with 1 to 5 years follow-up period after installation. Results: The survival rate of 251 implants with maxillary sinus floor elevation was 94%. The types of implant, surface, graft material, bone height have no statistically signi-ficant differencies. Conclusions: It can be suggested that maxillary sinus floor elevation may have predictable result with various bone graft materials and implant surface.

• 감성과학
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• 제17권4호
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• pp.71-78
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• 2014

PET 중공필라멘트 복합 DTY(Draw Textured Yarns)와 ATY(Air-jet Textured Yarns)는 경량의 스포츠 의류를 포함한 고감성 의류용으로 많이 사용되고 있다. 본 연구는 중공섬유 복합 DTY와 ATY 복합사 직물의 수분 및 열이동에 관계되는 쾌적특성에 중공 복합사 및 직물의 구조 특성이 어떠한 영향을 미치는 가에 대한 분석이다. 기공의 크기가 큰 중공 복합 직물의 흡수성이 우수하였고 커버팩터는 영향을 미치지 않았다. 또한 ATY사 직물이 DTY사 직물에 비해 흡수성이 우수하였다. 반면, 건조특성은 기공 사이즈가 미세한 직물이 기공사이즈가 큰 직물보다 건조시간이 짧았으며 낮은 커버팩터와 기공 사이즈가 작은 하이멀티사 직물이 중공 복합직물에 비해 건조 특성이 우수하였다. 직물의 기공 사이즈는 공기투과도와 열전도도 특성에 가장 중요한 인자였다. 직물의 큰 기공도는 중공 복합 직물의 기공도와 열전도도에 비선형적인 반비례 상관관계를 나타냈다.