• Korean Journal of Materials Research
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• v.10 no.8
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• pp.575-580
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• 2000

Diamond thin films were deposited on $Si_3N_4$, SiC, TiC and $Al_2O_3$, substrates by the CVD method using Ta(TaC)Filament, and the appearance of the diamond films and their adhesion properties were examined by SEM, optical microscopy, indentation test and compression topple test. Diamond films were deposited at lower $CH_4$ concentration than 5%$CH_4$ for all kinds of the substrate material, but graphitic(amorphous)carbon was observed at 10%$CH_4$. The diamond film of about $12\mu\textrm{m}$ thickness on WC substrate partly peeled off, but the film on $Si_3N_4$ substrate held good adhesion. The indentation test showed that roughly ground surface was very effective for adhesion of diamond films to substrate. The topple test revealed that film thickness was an important factor governing the adhesion of the diamond film.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.606-610
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• 2019

In this study, we demonstrated that the nonenzymatic glucose sensor based on the flexible carbon fiber bundle electrode with BDD nanocomposites (CF-BDD electrode). As a nano seeding method for the deposition of BDD on flexible carbon fiber, electrostatic self-assembly technique was employed. Surface morphology of BDD coated carbon fiber electrode was observed by scanning electron microscopy. And the electrochemical characteristics were investigated by cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. This CF-BDD electrode exhibited a large surface area, a direct electron transfer between the redox species and the electrode surface and a high catalytic activity, resulting in a wider linear range (3.75~50 mM), a faster response time (within 3 s) and a higher sensitivity (388.8 nA/mM) in comparison to a bare CF electrode. As a durable and flexible electrochemical sensing electrode, this brand new CF-BDD scheme has promising advantages on various electrochemical and wearable sensor applications.

• Korean Journal of Materials Research
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• v.9 no.11
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• pp.1049-1054
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• 1999

Two-step growth method is suggested to enhance the alignment of highly oriented diamond films. (100) Si wafers are pretreated with negative biasing of - 200 V at $850^{\circ}C$ for 20 min with 4 % methane in hydrogen plasma. The pretreated wafers are grown under the lst-step growth conditions(2 % CH$_4$ in H$_2$, $810^{\circ}C$) from 2 hr to 35 hr, in order to obtain <100> textured films. The 2nd-step growth(2 % CH$_4$ in H$_2$, $850^{\circ}C$) is carried out to make diamond films having (100) growth planes, which are parallel to the substrate. The alignment of the films after the 1st-step growth, has been analyzed by {111} X-ray pole figure, which is improved abruptly with increasing film thickness. However, the pyramidal surface morphology is inevitable. These morphology is flattened after the 2nd-step growth by developing the (100) facets parallel to the substrate. The alignment of the highly oriented textured films after the two-step growth depends on the thickness of the 1st-step growth film.

• Journal of Powder Materials
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• v.21 no.4
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• pp.260-265
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• 2014

In this study, in order to increase surface ability of hardness and corrosion of magnesium alloy, anodizing and sealing with nano-diamond powder was conducted. A porous oxide layer on the magnesium alloy was successfully made at $85^{\circ}C$ through anodizing. It was found to be significantly more difficult to make a porous oxide layer in the magnesium alloy compared to an aluminum alloy. The oxide layer made below $73^{\circ}C$ by anodizing had no porous layer. The electrolyte used in this study is DOW 17 solution. The surface morphology of the magnesium oxide layer was investigated by a scanning electron microscope. The pores made by anodizing were sealed by water and aqueous nano-diamond powder respectively. The hardness and corrosion resistance of the magnesium alloy was increased by the anodizing and sealing treatment with nano-diamond powder.

• Journal of Powder Materials
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• v.21 no.2
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• pp.114-118
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• 2014

In this study, an aluminum oxide layer for sealing treatment of nano-diamond powder was synthesized by anodizing under constant current. The produced pore size and oxide thickness were investigated using scanning electron microscopy. The pore size increased as the treatment time increased, current density increased, sulfuric acid concentration decreased, which is different from the results under constant voltage, due to a dissolution of the oxide layers. The oxide layer thickness by the anodizing increased as temperature, time, and current density increased. The results of this study can be applied to optimize the sealing treatment process of nano-diamond particles of 4-10 nm to enhance the resistances of corrosion and wear of the matrix.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.337-350
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• 1999

Thick diamond film having ~700${\mu}{\textrm}{m}$ thickness was deposited on polycrystalline molybdenum (Mo) substrate using high power (4kW) microwave plasma enhanced chemical vapor deposition (MPECVD) system. We could achieve free-standing diamond film via detaching as-deposited diamond film from the substrate by rapid cooling them under vacuum. We investigated the variation of photoconductivity after exposing the film surface to either oxygen or hydrogen plasma. At as-grown state, the growth side (the as-grown surface of the film) showed noticeable photoconductivity. The oxygen plasma treatment of this side led to the insulator. After exposing the film surface to hydrogen plasma, on the other hand, we could observe the reappearing of photoconductivity at the growth side. Based on these results, we suggest that the hydrogen plasma treatment may enhance the photoconductivity of free-standing diamond film.

• Journal of Institute of Control, Robotics and Systems
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• v.22 no.11
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• pp.932-936
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• 2016

In this paper, we present a method for the inspection of diamond wheels. In total, six items, including height, radius, and angle, need to be checked during the manufacturing of a diamond wheel. Automatic inspection through image processing is presented in this paper. First, a contour corresponding to the boundary of the diamond wheel is extracted from an image. Next, control points are selected by processing the contour. Seven control points are detected and used for the computation of the required item. Detailed procedures for the computation of the height, radius, and angle using control points are presented in this paper. Experimental results show the feasibility of the presented method.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.72-72
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• 2015

최근 비철소재 가공용 공구의 이형성 향상 코팅 및 자동차 부품의 고온 환경에서 사용할 수 있는 코팅으로 유망한 수소가 없는 비정질 다이아몬드 카본 막 (Non-Hydrogen Diamond Like Carbon films : ta-C)을 양산할 수 있는 코팅 시스템에 대한 연구 결과를 발표하고자 한다. 본 시스템은 Diamet-600이라고 하며 ta-C의 처리폭은 350 mm, 직경 450 mm 8축 공자전 치구에서 400nm/h의 증착률을 가지며, 막의 경도는 최대 65GPa을 달성하였다.

• Resources Recycling
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• v.21 no.1
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• pp.49-59
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• 2012

One of the world's top resource-rich countries, the Democratic Republic of the Congo has ample reserves of cobalt, iron ore, copper and diamond in particular. Importing most of major mineral resources, the Republic of Korea has examined-together with the Congo government since 2008-the possibility of a project where it supports port construction in the Democratic Republic of the Congo and acquires useful minerals such as zinc, cobalt and copper in exchange through slag reprocessing in the local city of Lubumbashi. This study conducted feasibility analysis on the slag reprocessing project in Lubumbashi, Congo and found that the project's payback period stands at 6.7 years, net present value(NPV) at 34 million dollars and internal rate of return(IRR) at 17.4%. According to sensitivity analysis that takes into account uncertainties concerning taxation, fixed cost, operational cost and resource prices, the NPV of the project ranges from -24.8 million dollars to 92.7 million dollars.

• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.2
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• pp.125-133
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• 2014

The purpose of this study was to investigate the effect of various surface treatment methods on the shear bond strength of orthodontic brackets in vitro. Ninety six specimens, 6 mm in diameter and 5 mm in height, were made with composite resin ($Filtek^{TM}$ Z350 XT, 3M ESPE, USA) and treated with an aging procedure. After aging, the specimens were randomly separated in six groups: (1) control with no surface treatment, (2) 37% phosphoric acid gel, (3) 4% hydrofluoric acid gel, (4) sodium bicarbonate particle abrasion, (5) diamond bur, and (6) 1 W carbon dioxide laser for 5s. The metal brackets were bonded to composite surfaces by means of an orthodontic adhesive (Transbond XT, 3M Unitek, USA). Shear bond strength values were evaluated with a universal testing machine (R&B Inc., Korea). Analysis of variance showed a significant difference between the groups. Group 5 had the highest mean shear bond strength (11.9 MPa), followed by group 6 (11.1 MPa). Among the experimental groups, group 2 resulted in the weakest mean shear bond strength (5.22 MPa). The results of this study suggest that the repair shear bond strength of the aged composite resin was acceptable by surface treatment with a carbon dioxide laser.