• 한국가스학회지
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• 제19권5호
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• pp.75-80
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• 2015

나노 및 마이크로 크기의 알루미늄(Al) 분진은 매우 높은 연소열을 가지고 있어서 로켓 추진체와 폭발물 등을 제조하는 원료로 많이 사용되고 있다. 본 연구에서는 서로 다른 크기의 입자경 (70 nm, 100 nm, $6{\mu}m$, $15{\mu}m$)을 가진 알루미늄 분진을 사용하여 열분해 위험성을 실험적으로 검토하였다. 이를 위해 열중량분석장치(TGA)를 사용하여 승온속도의 변화에 따른 열분해특성을 조사하고 입경이 다른 나노 및 마이크로 크기의 Al에서의 중량개시온도(Temperature of weight gain)로부터 발화온도를 추정하였다. 승온속도가 동일한 조건에서 Al분진의 중량개시온도는 입경이 증가할수록 또한 공기중 승온속도가 증가할수록 증가하는 경향을 나타냈다. 이러한 실험결과로부터 Al분진의 열분해 위험성은 분진 입자경의 증가와 함께 감소할 것으로 추정되었다.

• 한국분말재료학회지
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• 제28권3호
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• pp.253-258
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• 2021

There is increasing demand for the development of a new material with high strength, high stiffness, and good electrical conductivity that can be used for high-voltage direct current cables. In this study, we develop aluminum-based composites containing C₆₀ fullerenes, carbon nanotubes, or graphene using a powder metallurgical route and evaluate their strength, stiffness, coefficient of thermal expansion, and electrical conductivity. By optimizing the process conditions, a material with a tensile strength of 800 MPa, an elastic modulus of 90 GPa, and an electrical conductivity of 40% IACS is obtained, which may replace iron-core cables. Furthermore, by designing the type and volume fraction of the reinforcement, a material with a tensile strength of 380 MPa, elastic modulus of 80 GPa, and electrical conductivity of 54% IACS is obtained, which may compete with AA 6201 aluminum alloys for use in all-aluminum conductor cables.

• 한국기계가공학회지
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• 제13권4호
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• pp.13-20
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• 2014

In this paper, the effects of a nonionic surfactant on the etch uniformity and the etch profile during the wet-etching process of high-purity aluminum were investigated for the fabrication of uniform micropattern arrays. To improve the surface roughness of a high-purity aluminum plate, a mechanical lapping process and an electrolytic polishing process were used. After electrolytic polishing process, the surface roughness, Ra, of the high-purity aluminum plate was improved from $1.25{\mu}m$ to $0.02{\mu}m$. A photoresist was used as an etching mask during the aluminum etching process, where the mixture of phosphoric acid, acetic acid, nitric acid, a nonionic surfactant and water was used as the aluminum etchant. Different amounts of the Triton X-100 nonionic surfactant were added to the aluminum etchant to investigate the effect of a nonionic surfactant during the wet-etching process of high-purity aluminum. The etch rate and the etch profile were measured by an optical interferometer and a scanning electron microscope.

• 한국정밀공학회지
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• 제32권1호
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• pp.63-68
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• 2015

Micro/nano patterns for optical concentration and diffusion have been studied in the various fields such as displays, optics, and sensors. Conventional micro patterns were continuous and linear shapes due to using linear-type light sources, however, recently non-continuous patterns have been applied as point sources are used for dot-type light sources such as LEDs and OLEDs. In this study, a hybrid machining technology combining an indentation machining method and an AAO process was developed for manufacturing the non-continuous micro patterns having nano patterns. First, mirror-like surfaces ($R_a<20nm$) of pure Aluminum substrates were obtained by optimizing cutting conditions. Then, The letter of 'K' consisting of the arrays of the micro patterns was manufactured by the indentation machining method which has a similar principle to indentation hardness testing. Finally, nano patterns were machined by AAO process on the micro patterns. Conclusively, a specific letter having nano-micro hybrid patterns was manufactured in this study.

• 한국재료학회지
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• 제21권1호
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• pp.39-45
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• 2011

In this study, the heat flow of the plant scale aluminum extrusion process was investigated to establish optimum continuous heat treatment conditions. During the extrusion of 6061 aluminum alloy, processing parameters such as the extrusion pressure, speed and temperature histories of billets were logged as a function of time. The surface temperature of the billets increased at constant ram speed, while it decreased with decreases of the ram speed. In order to maintain the billet temperature within a solutionizing temperature range prior to the succeeding water quenching step, the ram speed or the temperature of the blower should be controlled. The temperature histories of the billets during the extrusion and hot air blowing processes were successfully simulated by using the velocity boundary model in ANSYS CFX. The methodology to design an optimum process by using a commercial simulation program is described in this study on the basis of the metallurgical validation results of the microstructural observation of the extrudates. The developed model allowed the advantages of taking into account the motion of the extrudate coupled with the temperature change based on empirical data. Calculations were made for the extrudate passing through the isothermal chamber maintained at appropriate temperature. It was confirmed that the continuous heat treatment system is beneficial to the productivity enhancement of the commercial aluminum extrusion industry.

• 한국정보통신학회논문지
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• 제14권4호
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• pp.923-928
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• 2010

양극산화 알루미늄(anodic aluminum oxide, AAO) 나노템플레이트는 제작이 쉬우며, 저비용, 대면적 제작이 가능하다는 장점으로 인해 이를 나노 전자소자 제작에 응용하려는 많은 연구가 이루어지고 있다. 이러한 나노템플레이트를 이용하면 기공의 직경이나 밀도를 변화킴으로써 나노구조의 물질의 크기나 밀도를 제어할 수 있다. 따라서 본 논문에서는 나노 전자소자 제작에 응용할 수 있는 AAO 나노템플레이트를 2단계 양극산화법에 의해 제조하였다. 이를 위해 기존의 알루미늄 판 대신 실리콘 웨이퍼 상에 DC 마그네트론 스퍼터법으로 $2{\mu}m$ 두께의 알루미늄 박막을 증착하였고, 전해액으로 사용한 옥살산 용액의 온도 및 양극산화 전압에 따른 다공성 알루미나 막의 미세구조를 조사하였다. 전해액 온도가 $8^{\circ}C$에서 $20^{\circ}C$로 높아짐에 따라 다공성 알루미나 막의 성장속도는 86.2 nm/min에서 179.5 nm/min으로 증가하였다. 최적 조건에서 제작된 AAO 나노 템플레이트의 기공 직경 및 깊이는 각각 70 nm와 $1\;{\mu}m$이었다.

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권1호
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• pp.15-21
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• 2013

In this paper, a MEMS tunable capacitor was successfully designed and fabricated using an aluminum nitride film and a gold suspended membrane with two air gap structure for commercial RF applications. Unlike conventional two-parallel-plate tunable capacitors, the proposed tunable capacitor consists of one air suspended top electrode and two fixed bottom electrodes. One fixed and the top movable electrodes form a variable capacitor, while the other one provides necessary electrostatic actuation. The fabricated tunable capacitor exhibited a capacitance tuning range of 375% at 2 GHz, exceeding the theoretical limit of conventional two-parallel-plate tunable capacitors. In case of the contact state, the maximal quality factor was approximately 25 at 1.5 GHz. The developed fabrication process is also compatible with the existing standard IC (integrated circuit) technology, which makes it suitable for on chip intelligent transceivers and radios.

• 산업기술연구
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• 제39권1호
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• pp.33-39
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• 2019

This paper addresses effects of nanoscale structures on structural colors of micropatterned transparent substrate by light diffraction. Structural colors is widely investigated because they present colors without any chemical pigments. Typically structural colors is presented by diffraction of light on a micropatterned surface or by multiple interference of light on a surface containing a periodic or quasi-periodic nano-structures. In this paper, each structural colors induced by quasi-periodic nano-structures, periodic micro-structures, and nano/micro dual structures is measured in order to investigate effects of nanoscale and microscale structures on structural colors in the transparent substrate. Using pre-fabricated pattern mold and hot-embossing process, nanoscale and microscale structures are replicated on the transparent PMMA(Poly methyl methacrylate) substrate. Nanoscale and microscale pattern molds are prepared by anodic oxidation process of aluminum sheet and by reactive ion etching process of silicon wafer, respectively. Structural colors are captured by digital camera, and their optical transmittance spectrum are measured by UV/visible spectrometer. From experimental results, we found that nano-structures provide monotonic colors by multiple interference, and micro-structures induce iridescent colors by diffraction of light. Structural colors is permanent and unchangeable, thus it can be used in various application field such as security, color filter and so on.

• 한국재료학회지
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• 제23권2호
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• pp.89-97
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• 2013

The study of grinding behavior characteristics on aluminum powders and carbon nano tubes (CNTs) has recently gained scientific interest due to their useful effect in enhancing advanced nano materials and components, which significantly improves the property of new mechatronics integrated materials and components. We performed a series of dry grinding experiments using a planetary ball mill to systematically investigate the grinding behavior during Al/CNTs nano composite fabrication. This study focused on a comparative study of the various experimental conditions at several variations of rotation speeds, grinding time and with and without CNTs. The results were monitored for the particle size distribution, median diameter, crystal structure from XRD pattern and particle morphology at a given grinding time. It was observed that pure aluminum powders agglomerated with low rotation speed and completely enhanced powder agglomeration. However, Al/CNTs composites were achieved at maximum experiment conditions (350 rpm, 60 min.) of this study by a mechanical alloy process for Al/CNTs mixed powders because the grinding behavior of Al/CNTs composite powder was affected by addition of CNTs. Indeed, the powder morphology and crystal size of the composite powders changed more by an increase of grinding time and rotation speed.

• 한국표면공학회지
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• 제54권1호
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• pp.25-29
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• 2021

The fabrication of nanopore membrane by deposition of Al2O3 film using electron-beam evaporation, which is fast, cost-effective, and negligible dependency on substance material, is investigated for potential applications in water purification and sensors. The decreased nanopore diameter owing to increased wall thickness is observed when Al2O3 film is deposited on anodic aluminum oxide membrane at higher deposition rate, although the evaporation process is generally known to induce a directional film deposition leading to the negligible change of pore diameter and wall thickness. This behavior can be attributed to the collision of evaporated Al2O3 particles by the decreased mean free path at higher deposition rate condition, resulting in the accumulation of Al2O3 materials on both the surface and the edge of the wall. The reduction of nanopore diameter by Al2O3 film deposition can be applied to the nanopore membrane fabrication with sub-100 nm pore diameter.