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강과 알루미늄의 레이저 접합에 관한 연구 Part 1 : 접합 변수의 최적 조건에 관한 연구
박태완,조정호,나석주,Park, Tae-Wan,Cho, Jung-Ho,Na, Suck-Joo 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.5
Steel has been mainly used in the automotive industry, because of good mechanical properties, weldability and so on. However, there has been increase in using aluminum to reduce the weight of vehicle. This leads to improve fuel efficiency and to reduce air pollution. A steel-aluminum hybrid body structure is recently used not only to reduce the weight of vehicle but also to increase safety. In this paper, the laser beam joining method is suggested to join steel and aluminum. To avoid making brittle intermetallic compounds(IMC) that reduce mechanical properties of the joint area, only aluminum is melted by laser irradiation and wetted on the steel surface. The brittle IMC layer is formed with small thickness at the interface between steel and aluminum. By controlling the process parameters, brittle IMC layer thickness is suppressed under 10 micrometers which is a criterion to maintain good mechanical properties.
열보조 나노 전사 프린팅을 통한 금속 박막의 표면 주름 나노패턴 형성 방법
박태완,박운익 대한금속·재료학회 2021 대한금속·재료학회지 Vol.59 No.12
Nanopatterning methods for pattern formation of high-resolution nanostructures are essential for the fabrication of various electronic devices, including wearable displays, high-performance semiconductor devices, and smart biosensor systems. Among advanced nanopatterning methods, nanotransfer printing (nTP) has attracted considerable attention due to its process simplicity, low cost, and great pattern resolution. However, to diversify the pattern geometries for wide device applications, more effective and useful nTP based patterning methods must be developed. Here, we introduce a facile and practical nanofabrication method to obtain various three-dimensional (3D) ultra-thin metallic films via thermally assisted nTP (T-nTP). We show how to generate surface-wrinkled 3D nanostructures, such as angular line, concave-valley, and convex-hill structures. We also demonstrate the principle for effectively forming 3D nanosheets by T-nTP, using Si master molds with a low aspect ratio (A/R ≤ 1). In addition, we explain how to obtain a 3D wavy structure when using a mold with high A/R (≥ 3), based on the isotropic deposition process. We also produced a highly ordered 3D Au nanosheet on flexible PET over a large area (> 15 μm). We expect that this T-nTP approach using various Si mold shapes will be applied for the useful fabrication of various metal/oxide nanostructured devices with high surface area.
Ni 박막 위 20 nm급 고정렬 Pt 크로스-바 구조물의 형성 방법
박태완,정현성,조영래,이정우,박운익 대한금속·재료학회 2018 대한금속·재료학회지 Vol.56 No.12
Since catalyst technology is one of the promising technologies to improve the working performance of next generation energy and electronic devices, many efforts have been made to develop various catalysts with high efficiency at a low cost. However, there are remaining challenges to be resolved in order to use the suggested catalytic materials, such as platinum (Pt), gold (Au), and palladium (Pd), due to their poor costeffectiveness for device applications. In this study, to overcome these challenges, we suggest a useful method to increase the surface area of a noble metal catalyst material, resulting in a reduction of the total amount of catalyst usage. By employing block copolymer (BCP) self-assembly and nano-transfer printing (n-TP) processes, we successfully fabricated sub-20 nm Pt line and cross-bar patterns. Furthermore, we obtained a highly ordered Pt cross-bar pattern on a Ni thin film and a Pt-embedded Ni thin film, which can be used as hetero hybrid alloy catalyst structure. For a detailed analysis of the hybrid catalytic material, we used scanning electron microscope (SEM), transmission electron microscope (TEM) and energy-dispersive X-ray spectroscopy (EDS), which revealed a well-defined nanoporous Pt nanostructure on the Ni thin film. Based on these results, we expect that the successful hybridization of various catalytic nanostructures can be extended to other material systems and devices in the near future.
나노-마이크로 패턴의 형성에 미치는 기판의 표면 거칠기 영향
박태완,변명환,정현성,박운익 대한금속·재료학회 2020 대한금속·재료학회지 Vol.58 No.1
The ability to form high quality nano-/micro- patterns is very important for the nanofabrication of high-density electronic devices. However, remaining challenges have yet to be resolved, including low quality roughness, low pattern resolution, and the highly complex process. In this study, we suggest a novel and simple method for creating high quality patterns, controlling the surface roughness of the target substrates with a polishing process. We systematically investigated the effect of surface roughness on pattern generation, using a nanotransfer printing (nTP) process on target Al2O3 substrates. We successfully formed highly ordered nanoscale functional patterns on well-defined surfaces, using a mirror-polishing process, compared to normally-polished substrates. In addition, we demonstrated well-printed Sn nanopatterns on various metal (Cu and Fe) substrates. Close-up scanning electron microscope (SEM) images clearly show welldefined patterns on the mirror-polished substrates. Based on these results, we expect that by mechanically modifying substrate surfaces, the yield and quality of pattern formation can be improved, and that this approach can be extended to other patterning methods.
박태완,정현성,방지원,박운익,Park, Tae Wan,Jung, Hyunsung,Bang, Jiwon,Park, Woon Ik 한국표면공학회 2018 한국표면공학회지 Vol.51 No.6
Nanopatterning is one of the essential nanotechnologies to fabricate electronic and energy nanodevices. Therefore, many research group members made a lot of efforts to develop simple and useful nanopatterning methods to obtain highly ordered nanostructures with functionality. In this study, in order to achieve pattern formation of three-dimensional (3D) hierarchical nanostructures, we introduce a simple and useful patterning method (nano-transfer printing (n-TP) process) consisting of various linewidths for diverse materials. Pt and $WO_3$ hybrid line structures were successfully stacked on a flexible polyimide substrate as a multi-layered hybrid 3D pattern of Pt/WO3/Pt with line-widths of $1{\mu}m$, $1{\mu}m$ and 250 nm, respectively. This simple approach suggests how to fabricate multiscale hybrid nanostructures composed of multiple materials. In addition, functional hybrid nanostructures can be expected to be applicable to various next-generation electronic devices, such as nonvolatile memories and energy harvesters.