• Journal of the Korean institute of surface engineering
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• v.42 no.1
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• pp.1-7
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• 2009

Resistive heating sources are widely used to prepare thin films by vapor deposition because they are cheap, and easy to install and handle in vacuum system. Graphite is one of materials used to make the resistive heating source, but until now only limited applications have been possible as it reacts easily with evaporating materials at high temperature. In this study, evaporation characteristics of aluminum have been investigated by using graphite boat thermally treated with BN powder. The employed graphite boat has been prepared by spray-coating BN power onto the cavity surface of the boat and thermal treatment with aluminum in vacuum at the temperature of more than $1400^{\circ}C$. The voltage-current characteristics as well as resistivity changes of the graphite boat have been investigated during aluminum evaporation according to the applied voltage and time. The evaporation aspect has been picturized during flash evaporation for 40 seconds based on the characterization results. The evaporation rate of the graphite boat has been compared with that of BN boat. The graphite boat showed some different characteristics compared with BN boat, in that the evaporation occurred at the last stage of flash evaporation. The film appearance according to the applied voltage has been compared, and also the reflectance of the resulting film has been investigated according to the film thickness. It has been found that the graphite boat thermally treated with BN powder can be used for aluminum evaporation without problem.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.382-382
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• 2009

염료감응형 태양전지의 구성체 중 전극으로 연구 되어 지고 있는 $TiO_2$는 기존에 대량 생산이 가능한 spin coating법, screen printing법, spray법의 연구가 이루어져 왔으나 고 효율 태양전지에 쓰이는 전극 시스템에 비해 고 분산성을 지닌 $TiO_2$페이스트를 제조 하는데 어려움이 있다. 그리고 플렉시블 디스플레이 소자의 응용을 위해서는 소자 공정 온도인 $250^{\circ}C$ 이하의 공정 온도가 요구 되어 지므로 고온공정인 CVD법은 이에 적합하지 않다. 이에 본 연구는 진공 증착 방법인 광원자층증착법을 이용하여 $150^{\circ}C$이하의 저온공정온도에서도 적용이 가능한 $TiO_2$ 박막을 185nm의 UV light를 조사하여 glass 기판위에 제조 하고 그에 따른 박막의 물성 분석을 하였다. Mo source로는 titanium tetraisopropoxide(TTIP)와 reactant gas 로는 $H_2O$를 사용하였으며 불활성 기체인 Ar 가스는 purge 가스로 각각 사용하였다. $100^{\circ}C{\sim}250^{\circ}C$ 공정온도를 변수로 $TiO_2$ 박막을 제조 하였으며 제조된 $TiO_2$ 박막의 물성 분석을 위해 FESEM, TEM을 이용하여 표면 및 두께를 분석하였다. 또한 $100^{\circ}C$ 400 cycles에서 약 12nm 막 두께를 관찰 할 수 있었으며 그 결과 박막의 성장률이 $0.3{\AA}$/cycle 임을 확인 할 수 있었다. 그리고 UV-VIS을 이용하여 박막의 좌외선에 대한 흡수도 및 투과도 분석을 하였다. 또한 XPS 성분 분석을 통하여 $100^{\circ}C$의 저온 공정에서 형성된 박막이 $TiO_2$임을 확인 하였다. 이러한 결과에서 185nm의 UV light에 의한 광원자층 증착법으로 $100^{\circ}C$의 저온에서도 $TiO_2$ 박막이 증착 되는 것을 확인 할 수 있었다.

• Biomolecules & Therapeutics
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• v.16 no.4
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• pp.425-430
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• 2008

The objectives of this study were to prepare PLGA film onto the surface of the capsular tension ring (CTR) for controlled drug release and investigate the influence of plasticizers, the test drug and measurement conditions on flexibility of the film. Film solutions were prepared by dissolving PLGA, plasticizer (triethyl citrate, TEC or polyethylene glycol, PEG), test drug (dexamethasone) in ethyl acetate then films were prepared by spray coating and evaporation method. Then, the flexibility of PLGA film was determined by elongation test. The addition of plasticizer, PEG or TEC to PLGA copolymer caused a depression of glass transition temperature ($T_g$) and the elasticity of PLGA films increased. The addition of dexamethasone to the PLGA/TEC matrix decreased the flexibility of film. Dimensional factors of the PLGA films such as width and thickness were significantly influenced on flexibility of films and film length and elongation speed had no considerable influence on elongation of films. In this study, sufficiently flexible and stable PLGA films capable of being coated onto CTR could be prepared. This PLGA films can be used as a platform for local drug delivery.

• Journal of the Korean Ceramic Society
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• v.55 no.4
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• pp.344-351
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• 2018

The effects of bond coat species on the growth behavior of thermally grown oxide (TGO) layer in thermal barrier coatings (TBCs) was investigated through furnace cyclic test (FCT). Two types of feedstock powder with different particle sizes and distributions, AMDRY 962 and AMDRY 386-4, were used to prepare the bond coat, and were formed using air plasma spray (APS) process. The top coat was prepared by APS process using zirconia based powder containing 8 wt% yttria. The thicknesses of the top and bond coats were designed and controlled at 800 and $200{\mu}m$, respectively. Phase analysis was conducted for TBC specimens with and without heat treatment. FCTs were performed for TBC specimens at $1121^{\circ}C$ with a dwell time of 25 h, followed by natural air cooling for 1 h at room temperature. TBC specimens with and without heat treatment showed sound conditions for the AMDRY 962 bond coat and AMDRY 386-4 bond coat in FCTs, respectively. The growth behavior of TGO layer followed a parabolic mode as the time increased in FCTs, independent of bond coat species. The influences of bond coat species and heat treatment on the microstructural evolution, interfacial stability, and TGO growth behavior in TBCs are discussed.

• Korean Journal of Materials Research
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• v.20 no.2
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• pp.51-54
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• 2010

Transparent conductive films of single wall carbon nanotube (SWCNT) were prepared by spray coating method. The effect of acid treatment on the SWCNT films was investigated. The field emission scanning electron microscope (FESEM) shows that acid treatment can remove dispersing agent. The electrical and optical properties of acid-treated films were enhanced compared with those of as deposited SWCNT films. Nitric acid ($HNO_3$), sulfuric acid ($H_2SO_4$), nitric acid:sulfuric acid (3:1) were used for post treatment. Although all solutions reduced sheet resistance of CNT films, nitric acid can improve electrical characteristics efficiently. During acid treatment, transmittance was increased continuously with time. But the sheet resistance was decreased for the first 20 minutes and then increased again. Post-treated SWCNT films were transparent (85%) in the visible range with sheet resistance of about $162{\Omega}/sq$. In this paper we discuss simple fabrication, which is suitable for different types of large-scale substrates and simple processes to improve properties of SWCNT films.

• Fire Science and Engineering
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• v.24 no.4
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• pp.41-46
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• 2010

High strength concrete (HSC) has been mainly used in large SOC structures. HSC have superior property as well as improvement in durability compared with normal strength concrete. In spite of durability of HSC, explosive spalling in concrete front surface near the source of fire occurs serious problem in structural safety. Therefore, this study is concerned with experimentally investigation of fire resistance at high temperature due to fireproof material covering thickness in addition to concrete cover. From the test result, it was appeared that the use of fireproof material results in good performance for fire resistance and spalling prevention, and the optimal fireproof covering thickness is 1~3mm. On the other hand, the temperature was rapidly increased by explosive spalling within 30 minutes and showed very little rise caused by evaporation heat after then. It was also found that the void channel was remained at high temperature as PP fiber melts at about $200^{\circ}C$, and the pore pressure in concrete was decreased.

• Journal of Periodontal and Implant Science
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• v.35 no.4
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• pp.1039-1052
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• 2005

IMZ는 "intramobile cylinder implant system" (IMZ)로 독일에서 가장 오래되고 많이 사용되어진 임플란트 중 하나이다. 이 임플란트에 관한 장기적 성공률과 생존률에 대한 연구는 대개 80% 이상을 보고하고 있다. 그러나, 연세대학교 치과병원 치주과에서 식립된 83개의 임플란트에서는 이전의 연구와는 다른 결과를 나타내었다. 1. IMZ 임플란트의 생존률은 67.5% 였다. 2. 변연 치조골 소실에 대한 성공 기준을 적용한 결과 성공률은 49.4%로 나타났다. 3. 발거된 총 27개의 임플란트 중에서 임플란트 주위 골소실을 가지는 경우는 17개, 내부구조 파절은 4개, 식립체 파절은 5개로 보고되었다. 4. 10년 이상 생존된 임플란트에서 변연골 소실의 평균치는 2.82mm였다. IMZ 임플란트는 장기적으로 높은 실패율을 보고하였다. 이는 cylindrical design, titanium plasma flame spray coating, prosthodontic complication 등의 요소에 기인한 것으로 사료된다. 임플란트는 그 형태, 표면 처리 등 여러 가지 요인들에 의해 실패가 나타날 수 있으며 본 연구를 통해 임플란트의 개발 및 선택에 바탕이 될 수 있을 것으로 생각된다.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.5
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• pp.618-628
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• 2016

The development of new concepts of liners is required in order to effectively neutralize the enemy's attack power concealed in the armored vehicles. A multiple-layer liner is one of possibilities and has a mechanism for explosion after penetrating the target which is known as "Behind Armor Effect." The multiple-layer explosive liner should have sufficient kinetic energy to penetrate the protective structure and explosive material react after target penetration. With this in mind, double-layer liner materials were obtained by cold spray coating methods and these material properties were experimentally characterized and used in this simulation for double-layer liners. In this study, numerical simulations in the three different layer types, i.e., single, A/B, A/B/A in terms of the layer location were verified in terms of finite element mesh sizes and numerical results for the jet tip velocity, kinetic energy, and the corresponding jet deformation characteristics were analysed in detail depending on the structure of layer types.

• Polymer(Korea)
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• v.36 no.2
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• pp.163-168
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• 2012

Recently, along with technology development of endoscopic equipment, the stent technology has been developed for the convenience of operation, shortening of recovery times, and reduction of patient's pain. In this study, paclitaxel-eluting metal stents for treatment of biliary benign stenosis were developed through an electrospray-coating method. Polyether-based polyurethane (PELLETHANE 2363-80AE$^{(R)}$)) and paclitaxel were coated onto the surface of a metallic stent and Pluronic F127 was used as an additive. As a result, physicochemical characterization of paclitaxel via SEM, FTIR, contact angle and XRD techniques revealed the information of solid state of paclitaxel-loaded PU film. The in vitro release profile showed a slower release rate with a higher content of paclitaxel.

• Journal of the Korean Society of Safety
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• v.31 no.3
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• pp.16-21
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• 2016

Carbon Fiber Reinforced Plastic(CFRP) composite with a higher specific strength and rigidity is more excellent than conventional metallic materials or other organic polymer of FRP. It has been widely used in vehicles, aerospaces and high technology industries which are associated with nuclear power fields. However, CFRP laminated composite has several disadvantages as like a delamination, matrix brittleness and anisotropic fibers that are the weak points of the crack initiation. In this present work, the reinforced silicon carbide(SiC) particles were added to the interlayer of CFRP laminates in order to mitigate the physical vulnerability affecting the cracking and breaking of the matrix in the CFRP laminated composite because of excellent specific strength and thermal shock resistance characteristics of SiC. The 1wt% of SiC particles were spread into the CFRP prepreg by using a spray coating method. After that, CFRP prepregs were laminated for the specimen. Also, the twill woven type CFRP prepreg was used because it has excellent workability. Thus the mechanical and fracture behaviors of the twill woven CFRP laminated composite reinforced with SiC particles were investigated with the acoustic emission(AE) method under a fracture test. The results show that the SiC particles enhance the mechanical and fracture characteristics of the twill CFRP laminate composite.