• Journal of Ocean Engineering and Technology
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• v.13 no.4 s.35
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• pp.37-44
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• 1999

Hardness characteristics and microstructures of $Nb/MoSi_2$ laminate composites were evaluated from the variation of fabricating conditions such as preparation temperature, applied pressure and pressure holding time. $Nb/MoSi_2$ laminate composites composed of $MoSi_2$ powder and Nb sheets were fabricated by the hot press. From experimental results, it was found that the lamination from Nb sheet and $MoSi_2$ powder was an excellent strategy to improve hardness characteristics of monolithic $MoSi_2$. However, interfacial reaction products like(Nb, Mo)$SiO_2\;and\;Nb2Si_3$ formed at the interface of $Nb/MoSi_2$ and increased with fabricating temperature.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.29-34
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• 2002

[ $Nb/MoSi_2-ZrO_2$ ] laminate composites have been successfully fabricated by alternately stacking $MoSi_2-ZrO_2$ powder layer and Nb sheet, followed by hot pressing in a graphite mould. The fabricating parameters were selected as hot press temperatures. The instrumented Charpy impact test was carried out at the room temperature in order to investigate the relationship between impact properties and fabricating temperatures. The interfacial shear strength between $MoSi_2-ZrO_2$ and Nb, which is associated with the fabricating temperature and the growth of interfacial reaction layer, is also discussed. The plastic deformation of Nb sheet and the interfacial delamination were macroscopically observed. The $Nb/MoSi_2-ZrO_2$ laminate composites had the maximum impact value when fabricated at 1623K, accompanying the increase of fracture displacement and crack propagation energy. The interfacial shear strength of $Nb/MoSi_2-ZrO_2$ laminate composites increased with the growth of interfacial reaction layer, which resulted from the increase of fabricating temperature. there is an appropriate interfacial shear strength for the enhancement of impact value of $Nb/MoSi_2-ZrO_2$ laminate composites. A large increase of interfacial shear strength restrains the plastic deformation of Nb sheet.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.311-312
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• 2005

Applying a designed test coupon pattern for fabricating resistors various resistors were formed using PTF(polymer thick film) pastes. Aspect ratio from 0.25 to 4 were selected for fabricating resistors. Formed resistors were cured at $170^{\circ}C$ and $240^{\circ}C$. Electrical properties of fabricated resistors were measured and their values analyzed in relation to cure temperature and formed geometry via printing. Also effects of substrates used for fabricating resistors were observed.

• Progress in Superconductivity
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• v.7 no.2
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• pp.152-157
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• 2006

New precursor solution with dichloroacetic acid (DCA) was developed for fabricating high $J_c$ REBCO film. DCA based-precursor solution was coated on $LaAlO_3$(001) substrate by dip coating method. Processing parameters such as oxygen partial pressure, water vapor, ramping rate and pyrolysis temperature were controlled in order to obtain a good epitaxial film. The film with thickness of 0.5 micrometer was obtained by single coating and no crack was observed at calcined films. Oxygen partial pressure was controlled in the range of $100{\sim}1,000$ ppm and conversion heat treatment was carried out at the temperature range of $705-765^{\circ}C$. A critical transition temperature ($T_c$) of 90 K and a critical transport current density ($J_c$) of $>0.5\;MA/cm^2$ (77 K and self-field) were obtained for the GdBCO film. It is thought that fluorine-free MOD solution using DCA is promising precursor solution for fabricating high quality REBCO films.

• Journal of Ocean Engineering and Technology
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• v.25 no.4
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• pp.66-71
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• 2011

The flexural strength of $MoSi_2$ based composites reinforced with Nb sheets has been investigated, based on the detailed examination of their microstructure and fractured surface. Both sintered density and porosity of Nb/$MoSi_2$ composites were also examined. Nb/$MoSi_2$ composites were fabricated by different conditions such as temperature, applied pressure and its holding time, using a hot-press device. The volume fraction of Nb sheet in this composite system was fixed as 10%. The characterization of Nb/$MoSi_2$ composites were investigated by means of optical microscopy, scanning electron microscope and three point bending test. Nb/$MoSi_2$ composites represented a dense morphology at the interfacial region, accompanying the creation of two types of reaction layer by the chemical reaction of Nb and $MoSi_2$. Nb/$MoSi_2$ composites possessed an excellent density at the fabricating temperature of $1350^{\circ}C$, corresponded to about 95% of theoretical density. The flexural strength of Nb/$MoSi_2$ romposites were greatly affected by the pressure holding time at the same fabricating temperature, owing to the large suppression of porosity in the microstructure. Especially, Nb/$MoSi_2$ composites represented a good flexural strength of about 310 MPa at the fabricating condition of $1350^{\circ}C$, 30MPa and 60min, accompanying the pseudo-ductile fracture behavior by the deformation of Nb sheet and the interfacial delamination.

• Journal of Ocean Engineering and Technology
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• v.16 no.6
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• pp.60-64
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• 2002

This paper describes the machining characteristics of the MoSi$_2$--based composites through the process of electric discharge drilling with various tubular electrodes. In addition to hardness characteristics, microstructures of Nb/MoSi$_2$laminate composites were evaluated from the variation of fabricating conditions, such as preparation temperature, applied pressure, and pressure holding time. MoSi$_2$-based composites have been developed in new materials for jet engines of supersonic-speed airplanes and gas turbines for high-temperature generators. These high performance engines may require new hard materials with high strength and high temperature-resistance. Also, with the exception of grinding, traditional machining methods are not applicable to these new materials. Electric discharge machining (EDM) is a thermal process that utilizes a spark discharge to melt a conductive material. The tool electrode is almost -unloaded, because there is n direct contact between the tool electrode and the work piece. By combining a non-conducting ceramic with more conducting ceramic, it was possible to raise the electrical conductivity. From experimental results, it was found that the lamination from Nb sheet and MoSi$_2$ powder was an excellent strategy to improve hardness characteristics of monolithic MoSi$_2$. However, interfacial reaction products, like (Nb, Mo)SiO$_2$and Nb$_2$Si$_3$formed at the interface of Nb/MoSi$_2$, and increased with fabricating temperature. MoSi$_2$composites, with which a hole drilling was not possible through the conventional machining process, enhanced the capacity of ED-drilling by adding MbSi$_2$, relative to that of SiC or ZrO$_2$reinforcements.

• Proceedings of the Korean Vacuum Society Conference
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• 2009.08a
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• pp.297-297
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• 2009

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1732-1734
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• 1999

In order to study the fabricating condition of phosphor layers of thin film EL devices, some discharge characteristics with several targets in the parallel-plate magnetron sputtering system will be studied. Plasma parameters, such as electron density and temperature, are also studied since they may be considered as one of the very important factors of fabricating condition of thin film EL device.

• Journal of Sensor Science and Technology
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• v.31 no.6
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• pp.428-432
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• 2022

In this study, we describe the improvement of the resolution of a paper-based sensor by fabricating a high-concentration ninhydrin part using a low-temperature drying method to detect proline with high resolution. In the conventional paper-based sensor for detecting proline, the ninhydrin part is fabricated at room temperature, and in this process, the ninhydrin solution spreads around the ninhydrin part. Therefore, the concentration of the ninhydrin part becomes lower than that of the applied solution, lowering the resolution of the sensor. The proposed paper-based sensor better improved the sensitivity of the sensor compared to the existing sensor by fabricating a high-concentration ninhydrin part through drying the ninhydrin solution using a low-temperature drying method. Owing to the experiment, the intensity of the green color of the paper-based sensor with the integrated ninhydrin part fabricated at 10 ℃ is approximately 20% lower than the paper-based sensor with an integrated ninhydrin part fabricated at room temperature, indicating better sensor resolution. Therefore, the paper-based sensor with an integrated ninhydrin part fabricated at a high concentration could be useful for diagnosing drought.

• Journal of Mechanical Science and Technology
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• v.14 no.8
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• pp.823-829
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• 2000

[ $Nb/MoSi_2$ ]laminate composites have been successfully fabricated by hot pressing in a graphite mould. Lamination of Nb foil and $MoSi_2$ layer showed a sufficient improvement in the absorbed impact energy compared to that of monolithic $MoSi_2$ material. The impact value of $Nb/MoSi_2$ laminate composites obviously is reduced when sintered at temperatures higher than 1523K, even if the composite density contributing to impact load increased along with fabricating temperatures. Impact value of laminate composites was also drastically decreased with the growth of reaction layer after the heat treatment. However, it was effective to increase the pressure at the same sintering temperature for the improvement of the impact value.