• Journal of Welding and Joining
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• v.10 no.4
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• pp.240-249
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• 1992

The objective of this study is to investigate the characteristics of welded joints on the Zircaloy-4 resistance upset welding for HWR(Heavy Water reactor)fuel rods. To estimate the characteristics of welded joints, the various tests were performed on the test coupons systematically with a wide range of each welding parameters in terms of a tensile test, burst test, knoop hardness test and metallography. Major results obtained in this study are as follows: 1. The tube and machined with 120.deg. projection was the reliable weld joint design for the nuclear fuel rod end cap welding. 2. As the weld current and the amount of upset increased linearly with increasing welding main heat input, it could make an estimate of their variation in accordance with the phase shift control. 3. It was found that an increase in squeeze force has an effect on the upset contour of welded joint because the amount of upset were increased by the change of squeeze force.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.410-415
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• 2003

Electrolytic In-process Dressing (ELID) technique for metal bonded diamond grinding wheel has been developed for mirror surface grinding of hard and brittle materials. This study process optical glass in using Electrolytic In-process Dressing. In using to main variable wheel speed (400rpm~2000rpm),feed rate (5$\mu\textrm{m}$/min~25$\mu\textrm{m}$/min),depth of cut (3$\mu\textrm{m}$~5$\mu\textrm{m}$),dressing and spray. We measured surface roughness in representative brittle materials

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.316-323
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• 2012

The aim of this study is to investigate the effect of post heat treatment on bonding properties of roll cladded Ti/MS/Ti materials. First grade Ti sheets and SPCC mild steel sheets were prepared and then Ti/MS/Ti clad materials were fabricated by a cold rolling and post heat treatment process. Microstructure and point analysis of the Ti/MS interfaces were performed using the SEM and EDX Analyser. Diffusion bonding was observed at the interfaces of Ti/MS. The thickness of the diffusion layer increased with post heat treatment temperature and the diffusion layer was verified as having $({\epsilon}+{\zeta})+({\zeta}+{\beta}-Ti)$ intermetallic compounds at $700^{\circ}C$ and an $({\zeta}+{\beta}-Ti)$ intermetallic compound at $800^{\circ}C$, respectively. The micro Knoop hardness of mild steel decreased with post heat treatment temperature; however, those of Ti decreased at a range of $500{\sim}600^{\circ}C$ and showed a uniform value until $800^{\circ}C$ and then increased rapidly up to $900^{\circ}C$. The micro Knoop hardness value of the diffusion layer increased up to $700^{\circ}C$ and then saturated with post heat treatment. A T-type peel test was used to estimate the bonding forces of Ti/Mild steel interfaces. The bonding forces decreased up to $800^{\circ}C$ and then increased slightly with post heat treatment. The optimized temperature ranges for post heat treatment were $500{\sim}600^{\circ}C$ to obtain the proper formability for an additional plastic deformation process.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.5
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• pp.307-311
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• 2009

In this study, TiCrN films were deposited on STS 316 Land Si (100) wafer by inductively coupled plasma (ICP) assisted D.C. magnetron sputtering. The effect R.F. power for ICP discharge on the mechanical properties of TiCrN films was investigated. XRD, XPS and FE-SEM were used for the structure analysis. Also the Micro-Knoop hardness tester and profilometer were used for measuring hardness of coatings and film stress respectively. As increasing the R.F. power for ICP discharge, thickness of coating was decreased from 1633 nm to 1288 nm but hardness was increased about $Hk_{5g}$ 4200 at 400 W. All of the XRD patterns showed (111), (200) and (220) peaks of TiCrN films. Surface morphology was studied using the profilometer. FE-SEM was used to know morphology and cross-section of the films. Structure of the films was changed dense as increased ICP power.

• Journal of Periodontal and Implant Science
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• v.34 no.4
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• pp.733-746
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• 2004

The present study aimed to examine the effects of topical application of alendronate with a collagen membrane on the healing of the calvarial defect in rats, which has a good experimental design for the healing of tissue destruction, To study the effect of alendronate on bone healing, the collagen membrane containing $200{\mu}g$ alendronate was inserted in the defects of the right side and collagen membrane treated with physiologic saline was inserted in the defects of the left side. After 1, 2 and 4 weeks, observation of histologic feature after H&E staining, cell counting after TRAP staining, and hardness measurement(Knoop) were performed. In histologic finding, similar features were shown for both test and control groups each week. In cell counting only the 1 week test groups showed significant reduction of TRAP(+)cells than control groups(p<0.01) and the control groups showed statistically significant difference for 1, 2, 4weeks(p<0.05). In hardness measurement, The 2 week test groups showed significant higher hardness than control groups.(p<0,05) and not 4 weeks. There was significant increase of hardness for both groups as time goes by.(p<0.0l) Therefore local application of alendronate with collagen membrane was somewhat effective in reducing osteoclastic activity and increasing hardness in the early stage of healing. Further investigation concerning the actual effect of alendronate for bony healing will be necessary to apply the clinical cases

• Restorative Dentistry and Endodontics
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• v.41 no.3
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• pp.196-201
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• 2016

Objectives: The aim of this in vitro study was to evaluate the effect of incorporating three different nanobiomaterials into bleaching material on microhardness of bleached enamel. Materials and Methods: The crowns of 24 extracted sound human molars were sectioned. Sixty enamel specimens ($2{\times}3{\times}4 mm$) were selected and divided into five groups (n = 12): Group 1 received no bleaching procedure (control); Group 2 underwent bleaching with a 40% hydrogen peroxide (HP) gel; Groups 3, 4, and 5 were bleached with a 40% HP gel modified by incorporation of bioactive glass (BAG), amorphous calcium phosphate (ACP) and hydroxyapatite (HA), respectively. The enamel microhardness was evaluated. The differences in Knoop microhardness data of each group were analyzed by one-way ANOVA, followed by post hoc Tukey tests. Results: Significant differences were observed between the study groups. The enamel microhardness changes in Groups 1, 3, 4, and 5 were significantly lower than that of Group 2 (p < 0.001). Conclusions: Within the limitations of this study, it can be concluded that incorporation of each one of the three tested biomaterials as remineralizing agents might be effective in decreasing enamel microhardness changes subsequent to in-office bleaching.

• Corrosion Science and Technology
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• v.6 no.5
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• pp.251-256
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• 2007

Plasma nitriding is a surface treatment process which is increasingly used to improve wear, fatigue and corrosion resistance of industrial parts. Active screen plasma nitriding (ASPN) has both the advantages of the classic cold wall and the hot wall conventional dc plasma nitriding (DCPN) method and the parts to be nitrided are no longer directly exposed to the plasma. In this study, AS plasma nitriding has been used to nitride the UNS S31803 duplex stainless steel, AISI 304 and AISI 316 austenitic stainless steel, and AISI 420 martensitic stainless steel. Treated specimenswere characterized by means of microstructural analysis, microhardness measurements and electrochemical tests in NaCl aerated solutions. Hardness of the nitride cases of AISI 420 stainless steel by Knoop test can get up to 1300 HK0.1. From polarization tests, the corrosion current densities of AISI 420 and UNS S31803specimens ASPN at $420^{\circ}C$ were generally lower than those of their untreated substrates. The corrosion resistance of UNS S31803 duplex stainless steel can be enhanced by plasma nitriding at $420^{\circ}C$ Cowing to the formation of the S-phase.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.195.1-195.1
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• 2013

Cu는 금속 박막재료로서 높은 전기전도성을 지니고 있을 뿐만 아니라 Ag, Al, Pt 등 보다 비용이 저렴하여, 높은 전기전도성을 필요로 하는 박막 재료로써 폭넓게 사용되고 있다. 그러나, 낮은 기계적 특성을 지니고 있어서 interconnect와 같은 작은 단면적의 배선재료로 사용될 경우, 높은 전류밀도에 따른 electromigration 현상에 의하여 hillock 또는 void의 형성 등 박막재료의 변형이 생기게 되어서 전자소자의 수명이 단축된다는 단점이 있다. TiN은 금속재료 못지않은 높은 전기 전도성을 지니고 있을 뿐만 아니라, 금속재료에 비하여 높은 기계적 특성과 녹는점을 지니고 있어 다양한 분야로 사용되고 있다. 본 연구에서는 Cu와 TiN composite 박막을 soda-lime glass위에 증착하여 낮은 비저항 뿐만 아니라 Cu와 비교하여 기계적 특성이 향상된 박막을 제작하고자 하였다. Cu와 TiN composite 박막 증착을 위하여 DC reactive magnetron co-sputtering 장비를 사용하였으며, Cu와 Ti 타겟 power, Ar:N2 유량비(Flow rate)을 변화시켜 Cu와 Ti의 조성비 및 TiN의 결정성을 조절하였고, 이를 통하여 박막의 TiN 조성에 따른 낮은 비저항 값과 순수한 Cu 박막과 비교하여 높은 기계적 특성을 지닌 Cu-TiN 박막을 증착하였다. Cu-TiN composite 박막의 구조 및 조성은 SEM (Scanning Electron Microscope), EDS (Energy Dispersive Spectrometer), XPS (X-ray Photoelectron Spectroscopy)장비를 사용하여 분석하였으며, 전기전도도는 4-point probe를 사용하여 측정하였고, Knoop hardness 측정방법을 사용하여 박막의 기계적 특성을 측정하였다.

• Journal of the Korean Ceramic Society
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• v.30 no.4
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• pp.289-298
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• 1993

Properties in terms of the variation of the glass compositions, which were density (p), molar volume(Vm), atom/ion packing density (Dp), refractive index (nD), transformation temperature (Tg), dilatometric softening point (Td), thermal expansion coefficient (α), Young's modulus (E), and knoop hardness (KHN) were investigated in CaO-SiO2 glasses and CaO-P2O5-SiO2 glasses containing less than 10mole% of P2O5. Those properties were measured by density measurement kit, Abbe refractometer, dilatometer, ultrasonic pulse echo equipment, and micro hardness tester. When CaO content was increased in CaO-SiO2 glasses, p, Dp, nD, Tg, Td, α, E and KHN were increased, while Vm was decreased. When P2O5 was added to the CaO-SiO2 glasses with constant CaO/SiO2 ratio as 1.07, p, Dp, nD, Tg, Td, α, E and KHN were decreased, while Vm was increased. When the amount of P2O5 in glasses was kept constant, the changes of the properties with variation of CaO content in the CaO-P2O5-SiO2 glasses were very similar to those of CaO-SiO2 glasses. These phenomena could be explained by the structural role of P2O5 in the CaO-P2O5-SiO2 glasses, which was polymerization of siicate structures and resulted in [PO4] monomer structure in glasses. Due to this structural characteristics, the bond strength and packing density were changed with compositions. Proportional relationships between 1) np and Dp, 2) Tg, Td, α and CaO content, 3) E and Vm-1, and 4) KHN and P2O5 content were evaluated in this investigation.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.275.2-275.2
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• 2014

현재 자동차 분야에서 차량 경량화의 한 수단으로 자동차용 유리를 고강도 투명 플라스틱 소재인 Polycarbonate(PC)로 대체하고자 하는 연구가 이루어지고 있다. 하지만, PC의 낮은 내마모 특성과 자외선에 의한 열화 및 변색 현상은 해결하여야 할 문제점으로 지적되고 있으며, 에너지 소비 저감을 위하여 적외선 영역 반사율(reflectance)이 높은 저방사(low emissivity) 특성이 요구되고 있다. 본 연구에서는, ICP-assisted reactive magnetron sputtering 장비를 이용하여 투과율(transmittance)이 확보되고, 고경도 특성을 갖는 Al-Si-N와 300 nm 파장 이하의 자외선 차단 특성이 있는 SiN:H 그리고 저방사 특성을 위해 Al을 증착하였고, 박막의 증착 순서는 SiN:H 박막을 가장 아래에 증착하고 그 위에 Al/Al-Si-N 박막을 다층으로 형성하였다. 박막의 chemical state와 crystallinity를 확인하기 위하여 XPS(X-ray Photoelectron Spectroscopy), XRD (X-ray Diffraction)를 이용하여 분석하였다. Knoop ${\mu}$-hardness tester와 Taber tester를 이용하여 경도 및 내마모 특성을 분석하였다. 제작된 샘플의 Al-Si-N 박막 경도는 Si 비율에 따라 다른 경도 특성을 갖는데, 실제 Si/(Al+Si) 비율이 24%에서 최대 31 GPa의 경도 값을 갖는 것을 확인하였다. UV-Vis Spectrometer를 이용하여 250 nm~700 nm 파장의 투과율을 측정하였고, 자외선 영역의 경우 SiN:H 박막에 의해 300 nm 이하의 파장에서 2% 이하의 투과율을 확인하였다. 그리고 FT-IR(Fourier Transform Infrared Spectroscopy)를 이용하여 $2.5{\mu}m{\sim}15{\mu}m$ 파장의 반사율을 이용하여 방사율을 측정하였는데, 3*(Al/Al-Si-N) 구조의 다층 박막의 경우 방사율은 0.27로 측정되었다.