• Korean Journal of Materials Research
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• v.12 no.5
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• pp.334-340
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• 2002

$TiO_2$-coated fly ash was synthesized by dropping method of coating agent in order to get $TiO_2$ coating layer with high photocatalytic activity on the surface of coal fly ash. The properties of the $TiO_2$ coating layer such as morphology, crystal structure, crystal size and photocatalytic activity were compared with those of the $TiO_2$-coated fly ash prepared by the traditional method of precipitation. $TiCl_4$ aqueous solution was used as a titanium stock solution and $NH_4HCO_3$ was used as a precipitant. The $TiO_2$ coating layer obtained by dropping method of coating agent was more uniform than that coated by precipitation. However, the crystal of $TiO_2$ coated by dropping method of coating agent was easy to grow by heat treatment because of the small primary particle size and bulky morphology, and its photocatalytic activity was consequently lower than that of the $TiO_2$ coated by precipitation. The $TiO_2$ coating layer obtained by both methods had a crystal structure of anatase, and the temperature of phase transformation into rutile was 90$0^{\circ}C$. The minimum crystal size of $TiO_2$ for the highest photocatalytic activity was found to be about 10nm.

• Journal of the Korean institute of surface engineering
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• v.49 no.2
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• pp.202-210
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• 2016

This study was intended to investigate the effect of the amount of magnesium addition and heat treatment in the Al-Mg coating film in order to improve corrosion resistance of aluminum coating. Al-Mg alloy films were deposited on cold rolled steel by physical vapor deposition sputtering method. Heat treatment was fulfilled in an nitrogen atmosphere at the temperature of $400^{\circ}C$ for 10 min. The morphology was observed by SEM, component and phase of the deposited films were investigated by using GDLS and XRD, respectively. The corrosion behaviors of Al-Mg films were estimated by exposing salt spray test at 5 wt.% NaCl solution and measuring polarization curves in deaerated 3 wt.% NaCl solution. With the increase of magnesium content, the morphology of the deposited Al-Mg films changed from columnar to featureless structure and particle size was became fine. The x-ray diffraction data for deposited Al-Mg films showed only pure Al peaks. However, Al-Mg alloy peaks such as $Al_3Mg_2$ and $Al_{12}Mg_{17}$ were formed after heat treatment. All the sputtered Al-Mg films obviously showed good corrosion resistance compared with aluminum and zinc films. And corrosion resistance of Al-Mg film was increased after heat treatment.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.447-447
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• 2010

일찍이 $SiO_2$ (Silicon dioxide) 박막은 다양한 분야에서 유전층, 부식 방지층, passivation층 등의 역할을 해왔다. 그리고 이러한 박막 공정은 대부분 진공의 환경에서 그 공정이 이루어지고 있다. 하지만 이러한 진공 system은 chamber, loadlock 그리고 펌프 등의 다양한 진공장비로 인한 생산 비용 증가, 공정의 복잡성뿐만 아니라 공정의 대면적화에 어려움을 지니고 있다. 그리고 최근 flexible display의 제조 공정에서 polymer 혹은 plastic 기판을 제조 공정에 적용시키기 위해 저온 공정이 필수적으로 요구 되고 있다. 이러한 기술적 한계를 뛰어 넘기 위해 최근 많은 연구가들은 atmospheric pressure plasma enhanced chemical vapor deposition (AP-PECVD)에 대해 지속적으로 다양한 연구를 하고 있다. 본 연구에서는 remote-type의 modified pin-to-plate dielectric barrier discharge (DBD) 시스템을 이용한 $SiO_2$ 무기 박막 증착에 관해 연구하였다. $O_2$/He/Ar의 gas와 5 kV AC power (30 kHz)의 전원장치를 통해 고밀도 대기압 플라즈마를 발생시켰고, silicon precursor로는 hexamethyldisilazane (HMSD)를 사용하였다. 먼저 HMDS와 $O_2$ gas의 flow rate 변화에 따른 증착률을 조사하였고 그 다음으로 박막의 조성 및 표면 특성을 조사하였다. HMDS의 유량이 100 ~ 300 sccm으로 증가함에 따라 증착속도는 증가했다. 하지만 FT-IR을 통해 HMDS의 유량이 증가하면 반응에 참여할 산소 분자의 부족으로 인해 $-(CH_3)_X$의 peak intensity가 증가하고, -OH의 peak intensity가 점차 감소함을 관찰 할 수 있었다. 또한 증착된 박막의 표면에 particle과 불균일한 surface morphology 등을 SEM image를 통해 관찰 하였다. 산소 유량이 탄소와 관련된 많은 불순물들의 제거에 도움이 됨에도 불구하고 14 slm 이상의 산소가 반응기 내로 주입되게 되면 대기압 플라즈마의 discharge가 불안정하게 되어 공정효율을 저하시키는 요소가 되었다. 결과적으로 HMDS (150 sccm)/$O_2$ (14 slm)/He (5 slm)/Ar (3 slm)의 조건에서 약 42.7 nm/min 증착률을 가지며, 불순물이 적고 surface morphology가 깨끗한 $SiO_2$ 박막을 증착할 수 있었다.

• Korean Chemical Engineering Research
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• v.57 no.6
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• pp.804-811
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• 2019

This study was performed the real motion and DEM simulation of ball motion using three different types of grinding media with different size and materials in media formation for optimization of process conditions in a traditional ball mill (media ball mill). In the simulation, the rotational speed of the mill, the material of the medium, the velocity of the medium, and the coefficient of friction between the media and the wall of pot were fixed into the actual experimental conditions. The motion of various kinds of grinding media was quantitatively measured by setting the grinding zone defined in the present study on the photographs taken and the snapshot images analyzed in the simulation. In addition, we observed the quantitatively measured value and the changed morphology of the sample and examined the correlation. Therefore, it is suggested to optimize the grinding media which has the greatest influence on the grinding zone under specific experimental conditions.

• Korean Journal of Materials Research
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• v.31 no.9
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• pp.481-487
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• 2021

ZnO particles are successfully synthesized at 150 ℃ for 30 min using zinc acetate as the Zn source and 1,4-butanediol as solvent using a relatively facile and convenient glycol process. The effect of ammonium hydroxide amounts on the growth behavior and the morphological evolution of ZnO particles are investigated. The prepared ZnO nanoparticle with hexagonal structure exhibits a quasi-spherical shape with an average crystallite size of approximately 30 nm. It is also demonstrated that the morphology of ZnO particles can be controlled by 1,4-butanediol with an additive of ammonium hydroxide. The morphologies of ZnO particles are changed sequentially from a quasi-spherical shape to a rod-like shape and a hexagonal rod shape with a truncated pyramidal tip, exhibiting preferential growth along the [001] direction with increasing ammonium hydroxide amounts. It is demonstrated that much higher OH^- amounts can produce a nano-tip shape grown along the [001] direction at the corners and center of the (001) top polar plane, and a flat hexagonal symmetry shape of the bottom polar plane on ZnO hexagonal prisms. The results indicate that the presence of NH⁴⁺ and OH^- ions in the solution greatly affects the growth behaviors of ZnO particles. A sharp near-band-edge (NBE) emission peak centered at 383 nm in the UV region and a weak broad peak in the visible region between 450 nm and 700 nm are shown in the PL spectra of the ZnO synthesized using the glycol process, regardless of adding ammonium hydroxide. Although the broad peak of the deep-level-emission (DLE) increases with the addition of ammonium hydroxide, it is suggested that the prominent NBE emission peaks indicate that ZnO nanoparticles with good crystallization are obtained under these conditions.

• Korean Journal of Metals and Materials
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• v.46 no.6
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• pp.329-337
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• 2008

During the continuous casting of boron-bearing steel, the corner cracks on the slab are formed by deformation with low strain rate and rapid cooling at the unbending temperature within the range of 800- $1000^{\circ}C$. Especially, the rapid cooling in the corner of slab during the continuous casting leads to as corner cracking. Therefore, in this study, the hot tensile tests applied to the different cooling rates were taken into account in order to study the effect of cooling rate on the hot ductility of boron-bearing steel. The results revealed that increasing cooling rate deteriorate the hot ductility of boron- bearing steel. Rapid decreasing of the hot ductility is caused by formation of a film-like ferrite and precipitate at the austenite grain boundaries. The morphology of the precipitates in the boron-bearing steel was monitored by PTA (Particle Tracking Autoradiography) and TEM, we observed MnS and BN compound and their morphology was quite different depending on the cooling rates. When the cooling rate is increased, rodshape MnS and BN precipitates can be formed along the austenite grain boundaries. It can cause that weakening the boundary region and decreasing the hot ductility of boron-bearing steel.

• Polymer(Korea)
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• v.39 no.1
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• pp.78-87
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• 2015

With aiming to prepare microcapsules having a particle size of $30-50{\mu}m$, thermally expandable capsules with relatively uniform particle sizes consisting of a n-octane/poly(acrylonitrile-co-methyl methacrylate) core/shell structure were synthesized using SPG membrane emulsification and suspension polymerization. Four steric stabilizers and five crosslinking agents were employed. When poly(vinyl alcohol) as a stabilizer was used, the prepared capsules showed a smooth and regular morphology and the liquid hydrocarbon (n-octane) was well encapsulated in the core. When 1,4-butnaediol methacrylate (BDDMA) was used as a crosslinker, the uniform capsules with the average diameter of $36.8{\mu}m$ were synthesized. The capsules prepared with 0.05 mol% BDDMA showed the best encapsulation efficiency.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.6
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• pp.238-244
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• 2007

Nano-sized ZnO crystals were successfully incorporated using ion exchange method in TMA-A zeolite synthesized by the hydrothermal method. The optimal composition for the synthesis of TMA-A zeolite was resulted in a solution of $Al(i-pro)_3$:2.2 TEOS:2.4 TMAOH:0.3 NaOH:200 $H_2O$. 0.3g of TMA-A zeolite and 5mol of $ZnCl_2$ solution were employed for the preparation of ZnO incorporated TMA-A zeolite. The ZnO incorporated TMA-A zeolite precursors, prepared from the process of mixing, stirring, centrifugal separation and drying, were calcined at temperatures from 400 to $600^{\circ}C$ for 3 h. The crystallization process of ZnO incorporated TMA-A zeolite was analyzed by X-ray diffraction (XRD). The Brunaur-Emett-Teller (BET) surface area of the ZnO incorporated TMA-A zeolite was measured. Subsequently, the morphology and the particle size depending on the temperature and time were observed using scanning electron microscopy(SEM), transmission electron microscopy(TEM) and particle size analyzer.

• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.515-519
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• 2015

Complexes composed of hydrogen tetrachloroaurate (III) trihydrate ($HAuCl_4{\cdot}3H_2O$) and DNA were first formed for the synthesis of gold nanoparticle using a DNA template, which were validated using UV-Vis spectroscopy. The morphology of complexes were also characterized by scanning electron microscopy (SEM). DNA-mediated gold nanoparticles were synthesized by the chemical reduction of DNA-Au(III) complexes using hydrazine ($N_2H_4$) and sodium borohydride ($NaBH_4$) as reducing agents. The effects of reducing agent types and their concentration on the formation of gold nanoparticles were investigated. The results showed that hydarazine was the most effective for the reduction of DNA-Au(III) complex. The DNA-mediated gold nanoparticles were characterized SEM, particle size analyzer (PSA), and transmission electron microscopy (TEM). Gold nanoparticles with 55~80 nm in diameter were formed by the aggregation of smaller gold nanoparticles (~nm), which was confirmed in the DNA matrix.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.487-487
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• 2009

One of the critical consumables in chemical mechanical polishing (CMP) is a specialized solution or slurry, which typically contains both abrasives and chemicals acting together to planarize films. In single abrasive slurry (SAS), the solid phase consists of only one type of abrasive particle. On the other hand, mixed abrasive slurry (MAS) consists of a mixture of at least two types of abrasive particles. In this paper, we have studied the CMP characteristics of mixed abrasive slurry (MAS) retreated by adding of $CeO_2$ abrasives within 1:10 diluted silica slurry (DSS). The slurry designed for optimal performance should produce reasonable removal rates, acceptable polishing selectivity with respect to the underlying layer, low surface defects after polishing, and good slurry stability. The modified abrasives in MAS are evaluated with respect to their particle size distribution, surface morphology, and CMP performances such as removal rate and non-uniformity. As an experimental result, we obtained the comparable slurry characteristics compared with original silica slurry in the viewpoint of high removal rate and low non-uniformity.