• Bulletin of the Korean Chemical Society
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• v.25 no.10
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• pp.1564-1566
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• 2004

• Advanced Composite Materials
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• v.17 no.1
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• pp.25-40
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• 2008

The research and development in soundproof materials for preventing noise have attracted great attention due to their social impact. Noise insulation materials are especially important in the field of soundproofing. Since the insulation ability of most materials follows a mass rule, the heavy weight materials like concrete, lead and steel board are mainly used in the current noise insulation materials. To overcome some weak points in these materials, fiber reinforced composite materials with lightweight and other high performance characteristics are now being used. In this paper, innovative insulation sheet materials with carbon and/or glass fabrics and nano-silica hybrid PU resin are developed. The parameters related to sound performance, such as materials and fabric texture in base fabric, hybrid method of resin, size of silica particle and so on, are investigated. At the same time, the wave analysis code (PZFlex) is used to simulate some of experimental results. As a result, it is found that both bundle density and fabric texture in the base fabrics play an important role on the soundproof performance. Compared with the effect of base fabrics, the transmission loss in sheet materials increased more than 10 dB even though the thickness of the sample was only about 0.7 mm. The results show different values of transmission loss factor when the diameters of silica particles in coating materials changed. It is understood that the effect of the soundproof performance is different due to the change of hybrid method and the size of silica particles. Fillers occupying appropriate positions and with optimum size may achieve a better effect in soundproof performance. The effect of the particle content on the soundproof performance is confirmed, but there is a limit for the addition of the fillers. The optimization of silica content for the improvement of the sound insulation effect is important. It is observed that nano-particles will have better effect on the high soundproof performance. The sound insulation effect has been understood through a comparison between the experimental and analytical results. It is confirmed that the time-domain finite wave analysis (PZFlex) is effective for the prediction and design of soundproof performance materials. Both experimental and analytical results indicate that the developed materials have advantages in lightweight, flexibility, other mechanical properties and excellent soundproof performance.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.12
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• pp.1-9
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• 2003

In this paper, a novel Ni silicide technology with Cobalt interlayer and Titanium Nitride(TiN) capping layer for sub 100 nm CMOS technologies is presented, and the device parameters are characterized. The thermal stability of hi silicide is improved a lot by applying co-interlayer at Ni/Si interface. TiN capping layer is also applied to prevent the abnormal oxidation of NiSi and to provide a smooth silicidc interface. The proposed NiSi structure showed almost same electrical properties such as little variation of sheet resistance, leakage current and drive current even after the post silicidation furnace annealing at $700^{\circ}C$ for 30 min. Therefore, it is confirmed that high thermal robust Ni silicide for the nano CMOS device is achieved by newly proposed Co/Ni/TiN structure.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1871-1876
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• 2013

In this study, we developed and characterized the shielding properties of dose reduction fiber (DRF, Buffalo Co.) sheet during brain and chest CT examinations. The DRF sheet was composed of $1{\sim}500{\mu}m$ oxide Bismuth ($Bi_2O_3$) and 5 ~ 50 nm nano-barium sulfate ($BaSO_4$). Phantom and clinical studies were performed for characterization of the DRF shielding properties. In clinical study, we measured doses of eye, chest, abdomen and reproductive system of 60 patients in 3 hospitals during brain and chest CT examinations. We could determined the shielding effect of the DRF by comparing the doses when we used the DRF sheet or not. When we used the sheet during CT examination, the scattered dose were reduced about 20~50%. So, we suggest that the fiber should be used in radiological examinations for reducing patients doses.

• Composites Research
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• v.33 no.4
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• pp.191-197
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• 2020

In this study, a hybrid metals such as copper (Cu) and nickel (Ni) coated carbon fibers (Ni-Cu/CFs) was prepared by wet laid method to develop a randomly oriented sheet material for high-efficiency electromagnetic interference shielding with the enhanced durability. The prepared sheet materials show a high electromagnetic interference shielding efficiency of 69.4 to 93.0 dB. In addition, the hybrid metals coated Ni-Cu/CFs sheets showed very high durability with harsh chemical/thermal environments due to the effective corrosive and mechanical resistances of Ni surface. In this context, the Ni-Cu/CF sheet possesses longer service life than the Cu/CF sheet, that is, 1.7 times longer.

• Journal of the Microelectronics and Packaging Society
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• v.26 no.3
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• pp.37-41
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• 2019

Sheet resistance reduction in the Ag nanowire (NW) coated films is accomplished with slight improvement of optical properties for the application of transparent conducting electrodes by using $O_2$ plasma treatment. The sheet resistance was optimized after 30 seconds $O_2$ plasma treatment, showing the 27 % of maximum decrease of sheet resistance. It is found that the $O_2$ plasma treatment get rid of the residual organic materials at the junction of Ag NWs. However, the Ag NWs may be also snapped by the excessive $O_2$ plasma treatment can showing the collapses of Ag NWs networks. Furthermore, the optical properties such as optical transmittance and haze were monotonically improved with the $O_2$ plasma treatment time until 90 seconds.

• Journal of the Korean Applied Science and Technology
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• v.37 no.6
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• pp.1597-1604
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• 2020

In this study, a synthesized poly(amino acid) self-assembly grafted with valine molecules was investigated on the skin activity of skin growth factors. The amphiphilic grafted poly(amino acid) derivatives were successfully synthesized by varying of degree of substitution(DS) and polymerization (DP) with valine molecules forming a β-sheet structure. Then, the pro-collagen biosynthesis of EGF(epidermal growth factor) was improved by 20%, and the inhibitory ability of tyrosinase activity was increased by 6.5 times by self-assembling of EGF with the poly(amino acid)s having β-sheet structures. This strategy of preparing protein self-assembly with poly(amino acid) derivatives will help improve the stability of protein growth factors and use it in medicals as well as cosmeceuticals through skin improvement.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.379-382
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• 2007

The MEMS (Micro Electro Mechanical Systems) process is used in a micro/nano pattern manufacturing method. This method is based on the lithography technology. But the MEMS process has some problems such as complicated process, long processing time and high production costs. Many researchers are doing research in substitute manufacturing method to work out a solution to these problems. In this paper, we apply a dieless incremental forming technology to a substitute method of MEMS process. This dieless forming technology is using in the commercial scale sheet forming such as a prototype of automobile sheet parts. 5-axes CNC (Computerized Numeric Control) method are applied in this system to get a micro-scale dieless forming results. These 5-axes system are composed of precision AC servo motor stages (4-axes) and PZT actuator (1-axis). A PZT actuator is used in a precision actuating axis because it can be operated in the nano scale stroke resolution. This micro dieless incremental forming system has the advantage of minimization in manipulating distance and working space. As equipment and tools become smaller in size, minute inertia force and high natural frequency can be obtained. Therefore, high precision forming performance can be obtained. This allows the factory to quickly provide the customer with goods because the manufacturing system and process are reduced. To construct this micro manufacturing system, many technologies are necessary such as high stiffness frame, high precision actuating part, structural analysis, high precision tools and system control. To achieve the optimal forming quality, the micro dieless forming system is designed and made with high stiffness characteristic.

• Membrane and Water Treatment
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• v.9 no.5
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• pp.327-334
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• 2018

The nano/micro composites with highly porous surface area have attracted of great interest, particularly the synthesis of porous and thin film sheets of high performance. In this paper, an easy method of cost-effective synthesis of thin film ceramic fiber membranes based on Hydroxyapatite, and activated carbon by turned into studied to be applied within the service-facilitated the transport of radioactive waste such as $^{90}Sr$, $^{137}Cs$ and $^{60}Co$) as activated product of radioisotopes from ETRR-2 research reactor and dissolved in 3M $HNO_3$, across a thin flat-sheet supported liquid membrane (TFSSLM). Radionuclides are transported from alkaline pH values. The presence of sodium salts in the aqueous media improves in $HNO_3$, the lowering of permeability because the initial $HNO_3$ concentration is improved. The study some parameters on the thin sheet ceramic supported liquid membrane. EDTA as stripping phase concentration, time of extraction and temperature were studied. The study of maximum permeability of radioisotopes for all parameters. The pertraction of a radioactive waste solution from nitrate medium were examined at the optimized conditions. Under the optimum experimental 98.6-99.9% of $^{90}Sr$, 79.65-80.3% of $^{137}Cs$ and $^{60}Co$ 45.5-55.5% in 90-110 min with were extracted in 10-30 min, respectively. The process of diffusion in liquid membranes is governed by the chemical diffusion process.

• Korean Journal of Metals and Materials
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• v.46 no.2
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• pp.69-79
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• 2008

A composition consisting of 10 nm-Ni/1 nm-Pd/(30 nm or 70 nm-poly)Si was thermally annealed using rapid thermal for 40 seconds at $300{\sim}1100^{\circ}C$ to improve the thermal stability of conventional nickel monosilicide. The annealed bilayer structure developed into $Ni(Pd)Si_x$, and the resulting changes in sheet resistance, microstructure, phase, chemical composition, and surface roughness were investigated. The silicide, which formed on single crystal silicon, could defer the transformation of $NiSi_2$, and was stable at temperatures up to $1100^{\circ}C$. It remained unchanged on polysilicon substrate compared with the sheet resistance of conventional nickel silicide. The silicides annealed at $700^{\circ}C$, formed on single crystal silicon and 30 nm polysilicon substrates exhibited 30 nm-thick uniform silicide layers. However, silicide annealed at $1,000^{\circ}C$ showed preferred and agglomerated phase. The high resistance was due to the agglomerated and mixed microstructures. Through X-ray diffraction analysis, the silicide formed on single crystal silicon and 30 nm polysilicon substrate, showed NiSi phase on the entire temperature range and mixed phases of NiSi and $NiSi_2$ on 70 nm polysilicon substrate. Through scanning probe microscope (SPM) analysis, we confirmed that the surface roughness increased abruptly until 36 nm on 30 nm polysilicon substrate while not changed on single crystal and 70 nm polysilicon substrates. The Pd-inserted nickel monosilicide could maintain low resistance in a wide temperature range and is considered suitable for nano-thick silicide processing.