• Korean Journal of Materials Research
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• v.29 no.10
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• pp.647-655
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• 2019

In order to analyze the effect of hot asymmetric rolling on the microstructure and texture of aluminum alloy and to investigate the effect of the texture on the formability and plastic anisotropy of aluminum alloy, aluminum 6061 alloy is asymmetrically rolled at room temperature, $200^{\circ}C$, $350^{\circ}C$, and $500^{\circ}C$, and the results are compared with symmetrically rolled results. In the case of asymmetric rolling, the equivalent strain (${\varepsilon}_{eq}$) is greatest in the upper roll part where the rotational speed of the roll is high and increases with increasing rolling temperature. The increase rate of the mean misorientation angle with increasing temperature is larger than that during symmetrical rolling, and dynamic recrystallization occurs the most when asymmetrical rolling is performed at $500^{\circ}C$. In the case of hot symmetric rolling, the {001}<110> rotated cube orientation mainly develops, but in the case of hot asymmetric rolling, the {111}<110> orientation develops along with the {001}<100> cube orientation. The hot asymmetric rolling improves the formability (${\bar{r}}$) of the aluminum 6061 alloy to 0.9 and reduces the plastic anisotropy (${\Delta}r$) to near zero due to the {111}<110> shear orientation that develops by asymmetric rolling.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.27 no.3
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• pp.159-167
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• 2021

The need for biodegradable plastic continues to increase, improvement of physical properties is necessary for actual use in the market. In this study, composite film was produced by adding peroxide additives to bioplastic according to concentration to investigate changes in the melt index, elongation, morphology, and TGA of the composite film. The addition of peroxide compatibilizer showed superior elongation of film and TGA compared to those of control. The added amount of compatibilizer affected the extrusion process, and it was revealed that adding an appropriate amount of peroxidizer is important. Analysis of the composite film's morphology revealed a heterogeneous dispersion sequence due to different rates of crystallization depending on the resin, and surface physical properties were best in the group added with 4% peroxide. The results above showed that the test group added with 4% peroxide compatibilizer was superior in the production of composite biodegradable film.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.95-99
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• 2018

High thermal conductivity films with electrically insulating properties have a great potential for the effective heat transfer as substrate and thermal interface materials in high density and high power electronic packages. There have been lots of studies to achieve high thermal conductivity composites using high thermal conductivity fillers such alumina, aluminum nitride, boron nitride, CNT and graphene, recently. Among them, hexagonal-boron nitride (h-BN) nano-sheet is a promising candidate for high thermal conductivity with electrically insulating filler material. This work presents an enhanced heat transfer properties of ceramic/polymer composite films using h-BN nano-sheets and PVA polymer resins. The h-BN nano-sheets were prepared by a mechanical exfoliation of h-BN flakes using organic media and subsequent ultrasonic treatment. High thermal conductivities over $2.8W/m{\cdot}K$ for transverse and $10W/m{\cdot}K$ for in-plane direction of the cast films were achieved for casted h-BN/PVA composite films. Further improvement of thermal conductivity up to $13.5W/m{\cdot}K$ at in-plane mode was achieved by applying uniaxial compression at the temperature above glass transition of PVA to enhance the alignment of the h-BN nano-sheets.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.4
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• pp.83-89
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• 2020

For the past few decades, as part of efforts to protect the environment where fossil fuels, which have been a key energy resource for mankind, are becoming increasingly depleted and pollution due to industrial development, ecofriendly secondary batteries, hydrogen generating energy devices, energy storage systems, and many other new energy technologies are being developed. Among them, the lithium-ion battery (LIB) is considered to be a next-generation energy device suitable for application as a large-capacity battery and capable of industrial application due to its high energy density and long lifespan. However, considering the growing battery market such as eco-friendly electric vehicles and drones, it is expected that a large amount of battery waste will spill out from some point due to the end of life. In order to prepare for this situation, development of a process for recovering lithium and various valuable metals from waste batteries is required, and at the same time, a plan to recycle them is socially required. In this study, we introduce a nanoscale pattern transfer printing (NTP) process of Li2CO3, a representative anode material for lithium ion batteries, one of the strategic materials for recycling waste batteries. First, Li2CO3 powder was formed by pressing in a vacuum, and a 3-inch sputter target for very pure Li2CO3 thin film deposition was successfully produced through high-temperature sintering. The target was mounted on a sputtering device, and a well-ordered Li2CO3 line pattern with a width of 250 nm was successfully obtained on the Si substrate using the NTP process. In addition, based on the nTP method, the periodic Li2CO3 line patterns were formed on the surfaces of metal, glass, flexible polymer substrates, and even curved goggles. These results are expected to be applied to the thin films of various functional materials used in battery devices in the future, and is also expected to be particularly helpful in improving the performance of lithium-ion battery devices on various substrates.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.62 no.4
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• pp.285-292
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• 2017

We investigated physicochemical properties of puffed snacks with intermediate and high amylose rice varieties. The intermediate amylose rice varieties 'Sindongjin' and high amylose rice varieties newly developed for food processing, 'Dodamssal' and 'Goami4' were tested for this study. The crude fat and crude protein contents of the rice cultivars ranged 1.47-3.08% and 6.30-7.63%, respectively. The resistant starch and amylose contents of Dodamssal and Goami4 were higher than those of Sindongjin. The hardness of rice was the highest in Sindongjin and Dodamssal. Also, Hardness of puffed snacks decreased by 72.07% for Sindongjin, 88.21% for Dodamssal and 66.67% for Goami4 compared to raw rice samples. The sensory evaluation showed that the highest scores in taste, texture and overall acceptability of puffed snacks were obtained in Dodamssal. The results of this study indicate that Dodamssal was suitable varieties for puffed snacks. Also, the physicochemical properties of Dodamssal were improved by the extrusion process. Therefore Dodamssal can be used for the industrial production of puffed snacks.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.644-649
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• 2017

In the automobile industry, there is growing demand for lightweight vehicles due to environmental problems and rising oil prices. Therefore, aluminum alloys and special materials are being used to reduce the weight of vehicles, but there are still many difficulties to overcome in terms of cost and strength. Therefore, the application of advanced high strength steel (AHSS)is increasing. AHSS has good strength and formability.Safety regulations are becoming stricter, and 1.2-GPa super-high-strength steels are gradually being applied for the center pillar and roof rails. Thus, the application of different kinds of steels in automobile bodiesis also increasing gradually. This study evaluates the resistance point weldability and the characteristics of a welded part of SGAFC1180 1.2t steel. A simulation was used to observe the nugget formation and its growth behavior. The prediction performance showed a similar tendency within an error rate of 10%. Also, the effect of this behavior on the process resistance and dynamic resistance was investigated,along with the correlation between the shear tensile strength and nugget diameter.

• Clean Technology
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• v.29 no.2
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• pp.126-134
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• 2023

Direct catalytic decomposition is a promising method for controlling the emission of nitrous oxide (N₂O) from the semiconductor and display industries. In this study, a γ-Al₂O₃ catalyst was developed to reduce N₂O emissions by a catalytic decomposition reaction. The γ-Al₂O₃ catalyst was prepared by an extrusion method using boehmite powder, and a N₂O decomposition test was performed using a catalyst reactor that was approximately 25.4 mm (1 in) in diameter packed with approximately 5 mm of catalysts. The N₂O decomposition tests were carried out with approximately 1% N₂O at 550 to 750 ℃, an ambient pressure, and a GHSV=1800-2000 h^-1. To confirm the N₂O decomposition properties and the effect of O₂ and steam on the N₂O decomposition, nitrogen, air, and air and steam were used as atmospheric gases. The catalytic decomposition tests showed that the 1% N₂O had almost completely disappeared at 700 ℃ in an N₂ atmosphere. However, air and steam decreased the conversion rate drastically. The long term stability test carried out under an N₂ atmosphere at 700 ℃ for 350 h showed that the N₂O conversion rate remained very stable, confirming no catalytic activity changes. From the results of the N₂O decomposition tests and long-term stability test, it is expected that the prepared γ-Al₂O₃ catalyst can be used to reduce N₂O emissions from several industries including the semiconductor, display, and nitric acid manufacturing industry.

• Applied Chemistry for Engineering
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• v.19 no.1
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• pp.98-104
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• 2008

This research was performed to evaluate the extraction characteristics of heavy metals for soil washing of mine tailings-contaminated soil according to particle size distribution and the chemical distributional existence of the metals. As the soil particle size was decreased, the extracted concentrations of heavy metals was increased except Fe and Mn. Most of all heavy metals were extracted within 6 h by soil washing with 0.05 M EDTA. Extraction efficiency of metals was decreased for Pb, Cu, and Zn with decreasing of particle size. Significant difference was not observed in extraction efficiency for Cd according to particle size distribution. Extraction efficiency for Cd was the highest as 86~91%, while the lowest as 5~14% for Fe. Most metals of the soil without soil washing was distributed as reducible, oxidizable, and residual fractions. Pb, Zn, and Cd existed as reducible (Fe/Mn oxide) and residual fractions and Cu existed as oxidizable and residual fractions after soil washing treatment with 0.05 M EDTA. As the soil particle size was decreased, residual fraction was increased for Pb and Cu. About 90% of reducible fraction in Pb, Zn, and Cd was removed by soil washing with 0.05 M EDTA. As the results, it was founded that soil particle size was the important parameter to effect on distributional fraction and extraction efficiency of metals in mine tailings-contaminated soil.

• Korean Journal of Food Science and Technology
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• v.46 no.1
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• pp.19-24
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• 2014

This study was carried out to identify the volatile organic compounds (VOCs) in polyethylene terephthalate (PET) bottles and to determine the extent to which VOCs migrate into mineral water during the bottling process and storage. A greater amount of nonanal and decanal was generated from the PET bottles than from the PET preforms. Benzene, ethylbenzene, nonanal, and vinyl benzoate were identified from the PET bottles when the incubation temperature of the headspace solid-phase microextraction (HS-SPME) sampler was set to 60, 80, and $100^{\circ}C$. As the incubation temperature increased, the concentrations of nonanal, vinyl benzoate, and decanal increased significantly. When the high-density polyethylene (HDPE) PET bottle caps were extracted with dichloromethane, the level of Irgafos 168 was found to be $206{\pm}20.1\mu}g/g$. The concentration of 2,4-di-tert-butylphenol in water was $4.80{\pm}0.2{\mu}g/L$. Therefore, it is necessary to avoid exposing PET and HDPE resins to high temperatures during the manufacturing process and storage of bottled water.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.26.2-26.2
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• 2010

최근에는 차세대 조명용 후보광원인 고출력 백색 LED를 개발하기 위한 경쟁이 치열하며, 이를 위해 업체가 고심하고 있는 가장 큰 문제 중의 하나가 칩에서 발생하는 열을 어떻게 관리하는가 하는 방열의 문제이다. 따라서, LED의 가장 큰 특징인 장수명을 손해보지 않기 위해서는 칩에서 발생되고 있는 열을 외부에 확산시키기 위한 기술 개발이 필수적이다. 다양한 방열소재 중 W-Cu 복합재는 W의 낮은 열팽창계수와 Cu의 높은 열전도도로 인해 방열소재로써 유망한 소재로 주목받고 있으나, 우수한 열적 특성을 발현하기 위해서는 고치밀화를 갖는 W-Cu 복합재 제조가 우선적으로 필요하다. W-Cu 복합체는 일반적으로 액상소결법을 통해 균일한 미세조직을 얻을 수 있으나, 열팽창계수를 낮추기 위해 Cu 함량이 적어지게 되면 치밀화가 어려우며 이를 해결하기 위해 나노입자를 갖는 분말을 이용하고자 하는 연구가 많이 진행되고 있다. 본 연구에서는 W과 Cu 산화물을 이용하는 것이 구성성분끼리의 편석이 발생하지 않으며, 소결성도 우수하여 양산화에 가장 접근한 방법으로 알려져 있다. 그러나, 지금까지의 얻어진 W-Cu 복합체의 경우, 분말상태에서의 얻어진 나노입자가 승온시에 마이크로 크기로 과도한 입자성장이 일어나기 때문에 소결 후에도 나노크기를 유지하기 어려울 뿐만 아니라, 구성상끼리의 응집체가 형성된다. 본 연구에서는 액상소결후에 W 입자가 Cu 기지내에 균일하게 분산되는 동시에 나노크기의 입자를 가지는 고분산 W-Cu 소결체를 얻고자 하였다. 이를 위해 금속산화물 분말의 분쇄를 위해 효과적인 방법으로 알려진 습식상태에서의 고에너지 볼밀링을 통하여 혼합된 텅스텐과 구리 산화물 분말의 수소환원공정을 통해 얻어진 100nm 이하의 입자를 가지는 W-20wt%Cu 나노복합분말을 출발분말로 사용하였다. W-20wt%Cu 나노복합분말의 성형체를 $1050^{\circ}C-1250^{\circ}C$의 온도범위에서 소결거동을 조사하였다. 그 결과, $1100^{\circ}C$ 온도에서 이론밀도에 가까운 소결밀도를 나타내었으며, 이는 기존에 비해 $100^{\circ}C$ 정도 치밀화 온도를 낮추는 결과이다. 소결체의 미세구조 관찰결과, 소결 후 약 200nm의 텅스텐 입자가 Cu내에 균일하게 분산되어 있었다. 제조된 W-Cu 시편에 대해서는 LED 응용성을 조사하기 위해 열전도도와 열팽창계수 등을 평가하였다.