• Korean Journal of Materials Research
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• v.17 no.9
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• pp.458-462
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• 2007

The effect of oxygen in the synthesis of oxide nanowires by using carbothermal reduction process have been studied thermodynamically and kinetically. By using laboratory air, ZnO nanowires could be fabricated in the carbothermal reduction process and a metal oxidation process. As the processing pressure decreases, the diameter of the nanowires decreases and the oxygen vacancy increases. As the processing pressure increases, the oxygen vacancy decreases and the shape of the ZnO becomes plate-like.

• Tribology and Lubricants
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• v.32 no.3
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• pp.75-81
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• 2016

Future electronics such as electronic paper and foldable cellphone are required to be flexible and transparent and should have a high performance. In order to fabricate the flexible electronics using flexibility transfer process, techniques for transferring various devices from rigid substrate onto flexible substrate by elastomeric stamp, have been developed. Adhesion between the elastomeric stamp and various devices is crucial for successful transfer process. The adhesion can be controlled by the thickness of the stamp, separation velocity, contact load, and stamp surface treatment. In this study, we fabricated the bump shape stamp consisting of a UV-curable polymer and investigated the effects of curing condition, separation velocity, and contact load on the adhesion characteristics of bumps. The bumps with hemispherical shape were fabricated using a dispensing process, which is one of the ink-jet printing techniques. Curing conditions of the bumps were controlled by the amount of UV irradiation energy. The adhesion characteristics of bumps are evaluated by adhesion test. The results show that the pull-off forces of bumps were increased and decreased as UV irradiation energy increased. For UV irradiation energies of 300 and 500 mJ/cm², the pull-off forces were increased as the separation velocity increased. The pull-off forces also increased with the increase of contact load. In the case of UV irradiation energy above 600 mJ/cm², however, the pull-off forces were not changed. Therefore, we believe that the bump shape stamp can be applied to roll-based transfer process and selective transfer process as an elastomeric stamp.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.333-338
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• 2003

Nano-imprint lithography(NIL) is a polymer embossing technique, capable of transferring nano-scale patterns onto a thin film of thermoplastics such as polymethyl methacrylate(PMMA) using this parallel process. Feature size down 10 nm have been demonstrated. In NIL, the pattern is formed by displacing polymer material, which can be squeeze flow of a viscous liquid. Due to the size of the pattern, a thorough understood of the process through experiments may be very different. Therefore we nead to resort to numerical simulation on the embossing process. Generally, there are two ways of numerical simulation on nano-scale flow, namely top-down and bottom-up approach. Top-down approach is a way to simulate the flow assuming that polymer is a continuum. On the contrary, in the bottom-up approach, simulation is peformed using molecular dynamics(MD). However, as latter method is not feasible yet. we chose the top-down approach. For the numerical analysis, two dimensional moving grid was used since the moving grid can predict the flow front. Effects of surface tension as well as the slip at the boundary were also considered.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.63-63
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• 2003

The nanotopography of silicon wafers has emerged as an important factor in the STI process since it affects the post-CMP thickness deviation (OTD) of dielectric films. Ceria slurry with surfactant is widely applied to STI-CMP as it offers high oxide-to-nitride removal selectivity. Aiming to control the nanotopography impact through ceria slurry characteristics, we examhed the effect of surfactant concentration and abrasive size on the nanotopography impact. The ceria slurries for this study were produced with cerium carbonate as the starting material. Four kinds of slurry with different size of abrasives were prepared through a mechanical treatment The averaged abrasive size for each slurry varied from 70 nm to 290 nm. An anionic organic surfactant was added with the concentration from 0 to 0.8 wt %. We prepared commercial 8 inch silicon wafers. Oxide Shu were deposited using the plasma-enhanced tetra-ethyl-ortho-silicate (PETEOS) method, The films on wafers were polished on a Strasbaugh 6EC. Film thickness before and after CMP was measured with a spectroscopic ellipsometer, ES4G (SOPRA). The nanotopogrphy height of the wafer was measured with an optical interferometer, NanoMapper (ADE Phase Shift)

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1075-1079
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• 2005

The Pseudo MOSFET measurements technique has been used for the electrical characterization of the nano SOI wafer. Silicon islands for the Pseudo MOSFET measurements were fabricated by selective etching of surface silicon film with dry or wet etching to examine the effects of the etching process on the device properties. The characteristics of the Pseudo MOSFET were not changed greatly in the case of thick SOI film which was 205 nm. However the characteristics of the device were dependent on etching process in the case of less than 100 nm thick SOI film. The sub 100 nm SOI was obtained by thinning the silicon film of standard thick SOI wafer. The thickness of SOI film was varied from 88 nm to 44 nm by chemical etching. The etching process effects on the properties of pseudo MOSFET characteristics, such as mobility, turn-on voltage, and drain current transient. The etching Process dependency is greater in the thinner SOI wafer.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.9
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• pp.799-804
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• 2014

Hard turning is a machining process for hardened materials with high surface quality so that grinding process can be eliminated. Therefore, the hard turning is capable of reducing machining time and improving productivity. In this study, hardened AISI4140 (high-carbon chromium steel) that has excellent yield strength, toughness and wear resistance was finish turned using CBN tools. Wear characteristics of CBN tool was analyzed in dry and MQL mixed with nano-particle (Nano-MQL). The dominant fracture mechanism of CBN tool is diffusion and dissolution wear on the rake surface resulting in thinner cutting edge. Abrasive wear by hard inclusion in AISI4140 was dominant on the flank surface. Nano-MQL reduced tool wear comparing with the dry machining but chip evacuation should be considered. A cryogenically treated tool showed promising result in tool wear.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.7 s.238
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• pp.998-1004
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• 2005

A nano-stereolithography (NSL) process has been developed for fabrication of 3D shell structures which can be applied to various nano/micro-fluidic devices. By the process, a complicated 3D shell structure on a scale of several microns can be fabricated using lamination of layers with a resolution of 150 nm in size, so it does not require the use of my sacrificial layer or any supporting structure. A layer was fabricated by means of solidifying liquid-state monomers using two-photon absorption (TPA) induced using a femtosecond laser processing. When the polymerization process is finished, unsolidified liquid state resins can be removed easily by dropping several droplets of ethanol fur developing the fabricated structure. Through this work, some 3D shell structures, which can be applied to various applications such as nano/micro-fluidic devices and MEMS system, were fabricated using the developed process.

• Journal of Powder Materials
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• v.13 no.2 s.55
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• pp.124-128
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• 2006

In recent years, equal channel angular pressing (ECAP) has been the subject of intensive study due to its capability of producing fully dense samples having a ultrafine grain size. In this paper, the ECAP process was applied to metallic powders in order to achieve both powder consolidation and grain refinement. In the ECAP process for solid and powder metals, knowledge of the internal stress, strain and strain rate distribution is fundamental to the determination of the optimum process conditions for a given material. The properties of the ECAP processed solid and powder materials are strongly dependent on the shear plastic deformation behavior during ECAP, which is controlled mainly by die geometry, material properties, and process conditions. In this study, we investigated the consolidation, plastic deformation and microstructure evolution behaviour of the powder compact during ECAP.

• Journal of the Korean Electrochemical Society
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• v.8 no.1
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• pp.42-46
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• 2005

It has been known that the synthesis of the cathode materials for the lithium rechargeable batteries by the sol-gel process has many advantages over the conventional solid-state method. It has been, however, a continuing issue that new additional steps should be introduced to commercialize this process. In this work, spray drying was introduced to the existing sol-gel process as a continuous mass production method of the pre-heat treatment precursor materials. The precursors of $LiCoO_2$ and $LiNi_{0.8}Co_{0.2}O_2$ were continuously produced through spray drying from the solution containing stoichiometric amount of lithium, cobalt, and nickel sources as well as a chelating agent. The process variables, such as pH of the starting solution, spray drying conditions, and calcination conditions were optimized. The XRD pattern for the synthesized material indicated a good crystallinity with a layered structure.

• Journal of Welding and Joining
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• v.27 no.6
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• pp.43-48
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• 2009

In this study, Cu-based bulk metallic glass (BMG) coatings were deposited by atmospheric plasma spraying (APS) process with different process conditions (with- and without hydrogen gas). As adding the hydrogen gas, thermal energy in the plasma flame increased and induced difference in the melting state of the Cu-based BMG particles. The microstructure and mechanical properties of the coatings were analyzed using a scanning electron microscope (SEM) with an energy dispersive spectroscopy (EDS) and nano-indentation tester in the light of phase analysis. It was elucidated by the nano-indentation tests that un-melted region was a mainly amorphous phase which showed discrete plasticity observed as the flow serrations on the load.displacement (P - h) curves, and the curves of solidified region showed lower flow serrations as amorphous phase mingled with crystalline phase. Oxides produced during the spraying process had the highest hardness value among the phases and were well mixed with other phases resulted from the increase in melting degree.