• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.53-53
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• 2007

반도체 소자의 고집적화, 미세화 화로 인해 반도체의 동작속도를 증가시키기 위하여 Cu를 이용한 금속배선이 주목받게 되었으나, 높은 압력으로 인한 보은 Cu 영역에서 과잉 디슁 현상과 에로젼을 유도하고 반도체 웨이퍼위의 low-k 물질에 손상을 줌에 따라 메탈라인 브리징과 단락을 초래할 있어, Cu의 단락인 islands를 남김으로서 표면 결항을 제거하지 못한다는 단점을 가지고 있었다. 그래서 이러한 문제점을 해결하기 위하여 기존의 CMP에 전기화학을 결합시킴으로서 낮은 하력에서의 Cu평탄화를 달성할 수 있는 ECMP (electrochemical mechanical polishing)기술이 필요하게 되었다. 따라서 본 논문에서는 전기화학적 기계적 연마(ECMP)작용을 위해, I-V 특성 곡선을 이용하여 패시베이션 막의 active, passive, transient, trans-passive영역의 전기화학적 특성을 비교 분석하였으며, Cu막의 표면 형상을 알아보기 위해 scanning electron microscopy (SEM) 측정과 energy dispersive spectroscopy (EDS)와 X-ray Diffraction (XRD) 분석을 통해 금속 화학적 조성을 조사하였다.

• Korean Journal of Metals and Materials
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• v.48 no.9
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• pp.807-812
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• 2010

In this paper, the Ultrasonic Nanocrystalline Surface Modification (UNSM) surface treatment process was used to induce compressive residual stress and nanocrystalline structure by severe plastic deformation on the UNSM-treated surface. The test results for AISI304 stainless steel demonstrated that the grain size was found to be 23 nm, the dislocation density was increased by $0.2085{\times}10^{18}\;m^{-2}$, and the volume fraction of martensite is defined as 27.6% from austenite so that the surface hardness of the surface is increased from 200 Hv up to 515 Hv. The initial tensile residual stress is changed from 300 MPa to a compressive residual stress of 500 MPa after UNSM treatment. In addition, UNSM was applied under five various conditions, and the results of those conditions were defined as a function of depth quantitative.

• Journal of Food Hygiene and Safety
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• v.34 no.4
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• pp.317-324
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• 2019

This study focuses on the role of nanotechnology in the field of food industries. Bioactive components with antimicrobial activity against food pathogens are encapsulated into nanoparticles (NPs) to improve and extend their efficiency in food preservation. However, these NPs should be biocompatible and nontoxic for humans. Advancement in this field has resulted in the development of NPs for food packaging in some industries. The most commonly used group of NPs in the food industry is metal oxide. As metal oxide NPs such as zinc oxide and titanium dioxide exhibit antimicrobial activity in food materials, the NPs can be used for food preservation with enhanced functional properties. The application and effects of nanotechnology in correlation with the nutritional and sensory properties of foods were briefly discussed with a few insights into safety regulations on nano-based food formulation and preservation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.80-85
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• 2021

In the fourth industrial revolution, the demand for metal three-dimensional (3D) printing technology is rapidly increasing. Metal 3D printing is an efficient method for manufacturing products because the method reduces material waste compared to subtractive manufacturing. In addition, products with complex shapes, such as turbine blades, can be easily produced using metal 3D printing because the method offers a high degree of freedom. However, due to the long production time of metal 3D printing, mass production is impossible, and post-processing is necessary due to its low precision. Therefore, it is necessary to develop a new hybrid process that can efficiently process metals and to develop a metal 3D-printing-based hybrid processing system technology to secure high processing precision and manufacture complex shapes. In this study, the structural stability of a metal 3D printer based hybrid machining center was analyzed through structural analysis before its development. In addition, we proposed a design modification that can reduce the weight and increase the stiffness of the hybrid machining center by performing shape lightning based on the structural analysis results.

• Korean Journal of Metals and Materials
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• v.48 no.4
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• pp.369-375
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• 2010

Ti-6Al-4V ELI alloy, which is commonly used as a biomaterial, is associated with a high elastic modulus and poor biocompatibility. This alloy presents a variety of problems on several areas. Therefore, the development of good non-toxic biocompatible biomaterials with a low elastic modulus is necessary. Particularly, hydroxyapatite (HA) is an attractive material for human tissue implantation. This material is widely used as artificial bone due to its good biocompatibility and similar composition to human bone. Many scientists have studied the fabrication of HA as a biomaterial. However, applications of bulk HA compact are hindered by the low strength of HA when it is sintered. Therefore, HA has been coated on Ti or Ti alloy to facilitate good bonding between tissue and the HA surface. However, there are many problems when doing this, such as the low bonding strength between HA and Ti due to the different thermal expansion coefficients and mechanical properties. In this study, a Ti-HA composite with a porous surface was successfully fabricated by pulse current activated sintering (PCAS) and a subsequent leaching process.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.5
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• pp.36-52
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• 2021

As the application of nano-satellites constellation increases worldwide in the wake of New Space era, there is growing demand for the development of thrusters for precise attitude and orbit control of small satellites. Field Emission Electric Propulsion(FEEP) thruster uses a liquid metal as a propellant and accelerates the ionized liquid metal through a strong electric field at the tip of the metal surface. FEEP thruster technology is suitable for nano-satellites which require various missions for attitude and orbit control, because it provides thrust ranging from 1 µN to 1 mN with high specific impulse up to about 10,000 s and can be miniaturized due to its simple structure. In this paper, the basics of FEEP thrusters are introduced, then the current status of research and development of FEEP thrusters are presented.

• Composites Research
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• v.36 no.3
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• pp.154-161
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• 2023

This study explored the feasibility of replacing a metal link with a carbon fiber/epoxy composite link and assessed its capacity to withstand a given load condition using failure criteria. The micromechanics of failure (MMF) criterion was employed to predict the failure mode of the composite material, and mechanical tests were conducted to obtain reference strength parameters for MMF. The findings revealed that the stress distribution was concentrated near the hole, and weaknesses were found around the hole and at the end of the link under bending conditions. Based on the failure index, matrix tensile failure was predicted at the end of the link, and fiber compression failure occurred near the hole. The methods and results obtained from this study can provide valuable guidelines for assessing the safety of composite materials under specific load conditions when replacing metal parts with carbon fiber/epoxy composites to achieve weight reduction.

• Journal of Korean Ophthalmic Optics Society
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• v.7 no.2
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• pp.163-167
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• 2002

Improved optical switching property of electrochromic nickel hydroxide/nickel glass thin film is reported. Nickel metal film was deposited on glass by e-beam evaporation before following electrochemical redox cycling to form nickel hydroxide for electrochromic activation. Without ITO (indium tin oxide) layer as electrical conductor, this electrode showed more rapid coloration rate than nickel hydroxide film on ITO substrate in the change of the electric voltage and optical transmittance. XPS analysis confirmed the existence of ultra-thin nickel metal layer (${\sim}10{\AA}$) between electrochemically grown nickel hydroxide and the glass substrate. It is concluded that the remained nickel metal nano-layer attribute to the conduction layer and the enhanced response time.

• Korean Chemical Engineering Research
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• v.51 no.2
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• pp.171-180
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• 2013

Metal organic frameworks (MOFs) are a class of crystalline organic-inorganic hybrid compounds formed by coordination of metal clusters or ions with organic linkers. MOFs have recently attracted intense research interest due to their permanent porous structures, large surface areas and pore volume, high-dispersed metal species, and potential applications in gas adsorption, separation, and catalysis. $CO_2$ adsorption in MOFs has been investigated in two areas of $CO_2$ storage at high pressures and $CO_2$ adsorption at atmospheric pressure conditions. In this short review, $CO_2$ adsorption/separation results using MOFs conducted in our laboratory was explained in terms of four contributing effects; (1) coordinatively unsaturated open metal sites, (2) functionalization, (3) interpenetration/catenation, and (4) ion-exchange. Zeolitic imidazolate frameworks (ZIFs) and covalent organic frameworks (COFs) were also considered as a candidate material.

• The korean journal of orthodontics
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• v.33 no.5 s.100
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• pp.351-358
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• 2003

Nickel and chromium are two major metals used in the alloys of most orthodontic appliances. But these metals are known to cause hypersensitivity, dermatitis, and asthma. In addition, a significant carcinogenic and mutagenic potential has been demonstrated for compounds containing these metals. The purpose of this study was to find out how much nickel and chromium was released from orthodontic appliances, and which factors would influence the release. The simulated orthodontic appliances were constructed for a half of a mandibular arch and incubated in $0.05\%$ NaCl solution at $37^{\circ}C$. Nickel and chromium release was quantified with an Inductively Coupled Plasma (ICP) spectroanalyzer. The results were as follows : 1. From simulated orthodontic appliances, nickel was released $9.83-70.0{\mu}g/day$ but the release of chromium was not detectable in Limit of 10ppb. 2. The amount of nickel release was significantly different between the types of appliances. 3. The galvanic condition increased the amount of nickel release, which was not statistically significant. 4. The sand blasting increased the amount of nickel release, which was also not statistically significant.