• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.04a
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• pp.9-10
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• 2000

An important business-field of world-wide steel-industry is the coating of thin metal-sheets with zinc, zinc-aluminum and aluminum based materials. These products mostly go into automotive industry. in particular for the car-body. into building and construction industry as well as household appliances. Due to mass-production, the processing is done in large continuously operating plants where the mostly cold-rolled metal-strip as the substrate is handled in coils up to 40 tons unwind before and rolled up again after passing the processing plant which includes cleaning, annealing, hot-dip galvanizing / aluminizing and chemical treatment. In the liquid Zn, Zn-AI, AI-Zn and AI-Si bathes a combined action of corrosion and wear under high temperature and high stress onto the transfer components (rolls) accounts for major economic losses. Most critical here are the bearing systems of these rolls operating in the liquid system. Rolls in liquid system can not be avoided as they are needed to transfer the steel-strip into and out of the crucible. Since several years, ceramic roller bearings are tested here [1.2], however, in particular due to uncontrollable Slag-impurities within the hot bath [3], slide bearings are still expected to be of a higher potential [4]. The today's state of the art is the application of slide bearings based on Stellite\ulcorneragainst Stellite which is in general a 50-60 wt% Co-matrix with incorporated Cr- and W-carbides and other composites. Indeed Stellite is used as the bearing-material as of it's chemical properties (does not go into solution), the physical properties in particular with poor lubricating properties are not satisfying at all. To increase the Sliding behavior in the bearing system, about 0.15-0.2 wt% of lead has been added into the hot-bath in the past. Due to environmental regulations. this had to be reduced dramatically_ This together with the heavily increasing production rates expressed by increased velocity of the substrate-steel-band up to 200 m/min and increased tractate power up to 10 tons in modern plants. leads to life times of the bearings of a few up to several days only. To improve this situation. the Mechanical Alloying (MA) TeChnique [5.6.7.8] is used to prOduce advanced Stellite-based bearing materials. A lubricating phase is introduced into Stellite-powder-material by MA, the composite-powder-particles are coated by High Energy Milling (HEM) in order to produce bearing-bushes of approximately 12 kg by Sintering, Liquid Phase Sintering (LPS) and Hot Isostatic Pressing (HIP). The chemical and physical behavior of samples as well as the bearing systems in the hot galvanizing / aluminizing plant are discussed. DependenCies like lubricant material and composite, LPS-binder and composite, particle shape and PM-route with respect to achievable density. (temperature--) shock-reSistibility and corrosive-wear behavior will be described. The materials are characterized by particle size analysis (laser diffraction), scanning electron microscopy and X-ray diffraction. corrosive-wear behavior is determined using a special cylinder-in-bush apparatus (CIBA) as well as field-test in real production condition. Part I of this work describes the initial testing phase where different sample materials are produced, characterized, consolidated and tested in the CIBA under a common AI-Zn-system. The results are discussed and the material-system for the large components to be produced for the field test in real production condition is decided. Outlook: Part II of this work will describe the field test in a hot-dip-galvanizing/aluminizing plant of the mechanically alloyed bearing bushes under aluminum-rich liquid metal. Alter testing, the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed. Part III of this project will describe a second initial testing phase where the won results of part 1+11 will be transferred to the AI-Si system. Part IV of this project will describe the field test in a hot-dip-aluminizing plant of the mechanically alloyed bearing bushes under aluminum liquid metal. After testing. the bushes will be characterized and obtained results with respect to wear. expected lifetime, surface roughness and infiltration will be discussed.

• Journal of the Korean Vacuum Society
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• v.17 no.3
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• pp.226-233
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• 2008

The nucleation and evolution process of Ge nano-islands on Si(001) surfaces grown by chemical vapor deposition have been explored using atomic force microscopy (AFM). The Ge nano-islands are grown by exposing the substrates to a mixture of gasses GeH4 and H2 at pressure of 0.1-0.5Torr and temperatures of $600-650^{\circ}C$. The effect of growth conditions such as temperature, Ge thickness, annealing time on the shape, size, number density, and surface distribution was investigated. For Ge deposition greater than ${\sim}5$ monolayer (ML) with a growth rate of ${\sim}0.1ML/sec$ at $600^{\circ}C$, we observed island nucleation on the surface indicating the transition from strained layer to island structure. Further deposition of Ge led to shape transition from initial pyramid and hut to dome and superdome structure. The lateral average size of the islands increased from ${\sim}20nm$ to ${\sim}310nm$ while the number density decreased from $4{\times}10^{18}$ to $5{\times}10^8cm^{-2}$ during the shape transition process. In contrast, for the samples grown at a relatively higher temperature of $650^{\circ}C$ the morphology of the islands showed that the dome shape is dominant over the pyramid shape. The further deposition of Ge led to transition from the dome to the superdome shape. The evolution of shape, size, and surface distribution is related to energy minimization of the islands and surface diffusion of Ge adatoms. In particular, we found that the initially nucleated islands did not grow through long-range interaction between whole islands on the surface but via local interaction between the neighbor islands by investigation of the inter-islands distance.

• Korean Journal of Materials Research
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• v.6 no.7
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• pp.700-708
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• 1996

Electroless plating technique was utilized to flip chip bonding to improve surface mount characteristics. Each step of plating procedure was studied in terms pf pH, plating temperature and plating time. Al patterned 4 inch Si wafers were used as substrstes and zincate was used as an activation solution. Heat treatment was carried out for all the specimens in the temperature range from room temperature to $400^{\circ}C$ for $30^{\circ}C$ minutes in a vacuum furnace. Homogeneous distribution of Zn particles of size was obtained by the zincate treatment with pH 13 ~ 13.5, solution concentration of 15 ~ 25% at room temperature. The plating rates for both Ni-P and Au electroless plating steps increased with increasing the plating temperature and pH. The main crystallization planes of the plated Au were found to be (111) a pH 7 and (200) and (111) at pH 9 independent of the annealing temperature.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.135-135
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• 2018

천이금속 질화물 코팅은 우수한 기계적 특성들로 인해 공구 코팅으로 많이 사용 되어왔다. 그 중에서도 특히 Cr계 경질 코팅은 높은 경도와 낮은 표면조도, 우수한 마찰특성 등 뛰어난 기계적 특성을 나타내므로 공구 코팅으로의 적용 가능성이 크다. 그러나 최근 공구산업의 발전으로 인해 공구가 더욱 가혹한 환경에서 사용됨에 따라, 공구의 수명을 향상시키고 보호하기 위해 코팅의 높은 밀착력이 요구되고 있으며, 모재와 코팅 사이에 중간층을 합성함으로써 공구의 밀착력을 향상시키는 연구가 활발히 진행되고 있다. 이전 연구에서 모재/중간층/코팅간의 경도와 탄성계수 비율(H/E ratio)의 구배가 코팅의 밀착력에 큰 영향을 미치는 것으로 확인되었다. 그러므로, WC 모재와 Cr계 코팅의 중간값의 H/E ratio를 갖는 중간층의 합성을 통해 코팅의 밀착력을 향상시킬 수 있을 것으로 판단된다. 본 연구에서는, 코팅의 밀착력을 향상시키기 위해 다양한 중간층을 증착한 CrZrN, CrAlN 코팅을 비대칭 마그네트론 스퍼터링 장비를 이용하여 합성하였다. 모재로는 디스크 형상의 WC-6wt.%Co 시편을 사용하였고 Cr, Zr, Si, Al single 타겟을 이용하여 Cr, CrN, CrZrN, CrZrSiN 등의 중간층이 증착된 코팅을 합성했다. 코팅의 합금상, 경도 및 탄성계수, 미세조직 및 조성, 표면 조도을 확인하기 위해 X-ray diffractometer (XRD), Fischer scope, field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy를 사용하였고, 코팅의 밀착 특성을 분석하기 위해 scratch tester와 optical microscopy (OM)를 이용하였다. 코팅의 내열성을 확인하기 위해 코팅을 furnace에 넣어 공기중에서 500, 600, 700, 800, 900, $1,000^{\circ}C$로 30분 동안 annealing 한 후에 nano-indentation을 사용하여 경도를 측정하였다. CrZrN 및 CrAlN 코팅을 나노 인덴테이션으로 분석한 결과, 모든 코팅의 경도(33.4-35.8 GPa)와 탄성계수(384.1-391.4 GPa)는 중간층의 종류에 상관없이 비슷한 값을 보인 것으로 확인됐다. 그러나, 코팅의 마찰계수는 중간층의 종류에 따라 다른 값을 보였다. CrZrN 코팅의 경우 CrN 합금상 중간층을 갖을 때 가장 낮은 값을 보였으며, CrAlN 코팅의 경우 CrN/CrZrSiN 중간층을 증착하였을때 마찰계수는 0.34로 CrZrN 중간층을 증착하였을 때(0.41)에 비해 낮은 값을 보였다. 또한, 코팅의 마모율 및 마모폭도 비슷한 경향을 보인 것으로 보아, CrN/CrZrSiN 중간층을 합성한 CrAlN 코팅의 내마모성이 상대적으로 우수한 것으로 판단된다. 코팅의 밀착력의 경우도 마찰계수와 비슷한 경향을 보였다. 이것은 중간층의 H/E ratio가 코팅의 내마모성에 미치는 영향에 의한 결과로 사료된다. H/E ratio는 파단시의 최대 탄성 변형율로써, 모재/중간층/코팅의 H/E ratio 구배에 따라 코팅 내의 응력의 완화 정도가 변하게 된다. WC 모재 (H/E=0.040)와 CrAlN 코팅(H/E=0.089) 사이에서 CrN, CrZrSiN 중간층의 H/E ratio는 각각 0.076, 0.083으로 모재/중간층/코팅의 H/E ratio 구배가 점차 증가함을 확인 할 수 있었고, 일정 응력이 지속적으로 가해지면서 진행되는 마모시험중에 CrN과 CrZrSiN 중간층이 WC와 CrAlN 코팅 사이에서 코팅 내부의 응력구배를 완화시키는 역할을 함으로써 CrAlN 코팅의 내마모성이 향상된 것으로 판단된다. 모든 코팅을 열처리 후 경도 분석 결과, CrN/CrZrSiN 중간층을 증착한 CrAlN 코팅은 $1,000^{\circ}C$까지 약 28GPa의 높은 경도를 유지한 것으로 확인 되었고, 이는 CrZrSiN 중간층 내에 존재하는 SiNx 비정질상의 우수한 내산화성에 의한 결과로 판단된다.

• Journal of the Korean Magnetics Society
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• v.27 no.4
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• pp.123-128
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• 2017

The magnetic isotropy property from the magnetoresistance (MR) curve and magnetization (MH) loop for the PtMn based spin valve (SV) multilayer films fabricated with different the bottom structure after post-annealing treatment was investigated. The exchange biased coupling field ($H_{ex}$), coercivity ($H_c$), and MR ratio of Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/Ta(4 nm) SV multilayer film without antiferromagnetic PtMn layer are 0 Oe, 25 Oe, and 3.3 %, respectively. MR curve for the Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/PtMn(6 nm)/Ta(4 nm) SV multilayer film showed $H_{ex}=2Oe$, $H_c=316Oe$, and MR (%) = 4.4 % with one butterfly MR curve having by the effect of antiferromagnetic PtMn layer. MR curve for the dualtype Glass/Ta(10 nm)/CoFe(6 nm)/Cu(2.5 nm)/CoFe(3 nm)/PtMn(6 nm)/CoFe(3 nm)/Cu(2.5 nm)/CoFe(6 nm)/Ta(4 nm) SV multilayer film showed $H_c=37.5Oe$ and 386 Oe, MR = 3.5 % and 6.5 % with two butterfly MR curves and square-like hysteresis MH loops. The anisotropy property in CoFe spin valve-PtMn multilayer is neglected by the effects of a very small value of $H_{ex}$ and a very slightly shape magnetic anisotropy. This result is possible to explain the effect of magnetization configuration spin array of the bottom SV film and the top SV film of PtMn layer.

• Journal of the Speleological Society of Korea
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• no.95
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• pp.35-49
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• 2009

Ever since the beginning of time, caves not only have offered a place to live for humans but they have also been used as cultural spaces. That is, in the event of making some sounds in a location within the cave, the sound that is created is greatly magnified and sounds out as if it is being amplified from a giant megaphone. This, as we well know it, is known as the resonance effect. Here, the cave itself appears to function as a massive wind instrument. Especially in cases like the Altamira Cave (Spain) where cave paintings were found, the point where the cave drawings were found has commonalities in that it is a wide space and that it is usually discovered together with flutes and drums that are made with mammoth bones. We need to focus on this point. We can infer from these facts that the prehistoric people have carried out cultural activities along with their incantation rituals within those caves. In the meantime, amongst the Korean traditional arts, in the case of pansori which is a representative vocal genre, there have been examples where caves were used as practicing locations for those people who are training to perfect their singing. This is known as toguldoggong(土窟獨功) which literally means 'obtaining one's own art by oneself in the earth cave by practicing incessantly'. This process along with pokpodoggong (瀑布獨功) (same as above except that the location is by the waterfall) is the final training stage in order to become a recognized virtuoso on the part of the apprentice. This could be compared to the final annealing and finishing process of producing a metalwork. This has been a long tradition followed by most Korean traditional artists in order to perfect their sound which is harmonious with nature within natural surroundings. By honing in on this point, I have come to think about this matter repeatedly while coaching the university students in vocal singing. In short, I came to the conclusion that "the making of natural sounds will be obtained naturally within natural surroundings like caves!" Consequently, The Society for Studying Cave Sounds was inaugurated on January 1992 along with some of my students. We made use of times like vacations to go around exploring caves all over Jeju and carried out investigations of sounds along with cave exploration on an experimental basis. After 5 years, in September of 1997, we were able to host the first ever cave concert domestically at the Whale Nostril Cave(東岸鯨窟) on Wu-do. After that, we have been hosting the cave concert once every year. We have achieved a record of a total of 14 cave concerts until 2009 of this year. Out of these, 2 were held in Seokhwaeam Cave in Kangwon Province, another two were held in Manjang Cave which is a lava cave, and the remaining 10 were held in the Whale Nostril Cave of Wu-do. Along with that, I have carried out a special recording for the production of a cave music CD in May of 1999. This paper was written and organized by using the main materials that were derived from the experiences of using caves as concert halls in the past. It is hoped that this cave concert will offer a very unique experience to tourists who come to Jeju every year and give them the best possible superior natural sound effect that only Jeju caves can offer.

• Journal of the Korean Electrochemical Society
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• v.13 no.2
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• pp.116-122
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• 2010

A $Cu_3Si$ film electrode is obtained by Si deposition on a Cu foil using DC magnetron sputtering, which is followed by annealing at $800^{\circ}C$ for 10 h. The Si component in $Cu_3Si$ is inactive for lithiation at ambient temperature. The linear sweep thermammetry (LSTA) and galvano-static charge/discharge cycling, however, consistently illustrate that $Cu_3Si$ becomes active for the conversion-type lithiation reaction at elevated temperatures (> $85^{\circ}C$). The $Cu_3Si$ electrode that is short-circuited with Li metal for one week is converted to a mixture of $Li_{21}Si_5$ and metallic Cu, implying that the Li-Si alloy phase generated at 0.0 V (vs. Li/$Li^+$) at the quasi-equilibrium condition is the most Li-rich $Li_{21}Si_5$. However, the lithiation is not extended to this phase in the constant-current charging (transient or dynamic condition). Upon de-lithiation, the metallic Cu and Si react to be restored back to $Cu_3Si$. The $Cu_3Si$ electrode shows a better cycle performance than an amorphous Si electrode at $120^{\circ}C$, which can be ascribed to the favorable roles provided by the Cu component in $Cu_3Si$. The inactive element (Cu) plays as a buffer against the volume change of Si component, which can minimize the electrode failure by suppressing the detachment of Si from the Cu substrate.

• Journal of the Korean Society of Food Science and Nutrition
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• v.40 no.8
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• pp.1141-1149
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• 2011

The objective of this study was to analyze quality changes during storage of fresh-cut produce (leafy vegetables and condiment vegetables) as a function of packaging and storage temperature. Fresh-cut produce was washed using a three step cleaning process and was packed in vacuum packaging (green onion, hot pepper, onion, baechu) and perforated film packaging (buchu and perilla leaf). The effects of packaging method and storage temperature on quality of fresh-cut produce were determined by analyzing total plate counts, E. coli, coliform groups, moisture content, pH, Aw, surface color, and exterior quality during storage at 4 and 10$^{\circ}C$. According to the results, surface color change and microbial growth were delayed during storage at 4$^{\circ}C$. Additionally, E. coli was not detected during storage. Generally, moisture content decreased in the perforated film packaging. Changes in surface quality such as skin browning, softening of tissue and chlorosis at 4$^{\circ}C$ were inhibited, whereas rapid vacuum annealing and changes in color and flavor were observed in the sample stored at 10$^{\circ}C$. The result indicated that overall quality of the fresh-cut produce at 4$^{\circ}C$ was well maintained. The perforation in packing materials did not significantly increase the number of microorganisms on buchu and perilla leaf. The proper packaging methods and temperature may beneficial effect on microbial safety, quality and thus result in longer shelf-life fresh-cut vegetables during distribution.

• Resources Recycling
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• v.26 no.6
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• pp.29-37
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• 2017

Nuclear fuel cladding tube is fabricated by pilgering and annealing process. In order to remove impurity and oxygen layer on the surface, pickling process is carried out. When Zirconium(Zr) is dissolved and saturated in acid solution during the pickling process, all the waste acid including Zr is disposed. Therefore, $BaF_2$ is added into the waste acid to extract Zr and $Ba_2ZrF_8$ is subsequently formed. To recycle Zr by electrowinning process, $Ba_2ZrF_8$ is used as electrolyte, but it has high melting point ($1053^{\circ}C$). $ZrF_4$ should be added into $Ba_2ZrF_8$ to decrease the melting point. In this paper, it was investigated that $Ba_2ZrF_8$ was separated to $BaF_2$ and $ZrF_4$ by vacuum distillation. Firstly, $BaF_2$ with different particle size ($1{\mu}m$, $35{\mu}m$, $110{\mu}m$) was added into the waste acid and the respective precipitation property was estimated. $BaF_2$ obtained by vacuum distillation was shattered by ball-milling with different time. The precipitation efficiency was compared with $1{\mu}m$ of ${BaF_2}^{\prime}s$ one, which was not used as precipitation agent.

• Journal of the Korean Magnetics Society
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• v.18 no.3
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• pp.109-114
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• 2008

The samples were synthesized by using a solid state reaction. The X-ray diffraction pattern for $Ti_{0.96}Co_{0.02}Fe_{0.02}O_2$ showed a pure rutile phase with tetragonal structure, Mixtures of the proper proportions of the elements sealed in evacuated quartz ampoule were heated at $870{\sim}930^{\circ}C$ for one day and then slowly cooled down to room temperature at a rate of $10^{\circ}C$/h. In order to obtain single phase material, it was necessary to grind the sample after the first firing and to press the powders into pellets before annealing them for a second time in evacuated and sealed quartz ampoule. Magnetic properties have been investigated using the vibrating sample magnetometer (VSM). Room temperature magnetic hysteresis (M-H) curve showed an obvious ferromagnetic behavior and the magnetic moment per Fe atom under the applied of 0.8 T was estimated to be about $1.5\;{\mu}_B$/CoFe. But the magnetic moment per Fe atom under the applied of 0.8 T was estimated to be about $0.02\;{\mu}_B$/CoFe without Ti-getter. Size of particles is about $1\;{\mu}m$ using the transmission electron microscope (TEM). The ingredients of sample are distributed irregular in particles. Only Fe get shown on the surface of particles.