• Corrosion Science and Technology
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• 제18권1호
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• pp.16-23
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• 2019

Steels for automotive fuel tank require unique properties such as corrosion resistance for fuel, welding for joining, forming for press, and painting for exterior. Recently, automakers have been requiring excellent seam weldable steels to enhance manufacturing productivity of fuel tank. Thus, POSCO developed a new type of functional steels coated with nano-composite thin layer on Zn-Ni plating steels. The nano-composite coating solution was prepared by mechanical fine dispersion of solutions consisting of polymeric resin and nano-composite materials in aqueous media. The composite solution was coated on the plating steel surface by using roll coater and cured through induction furnace. These new developed plating steels were evaluated for quality performances such as seam and spot weldability, press formability, and corrosion resistance. These new functional steels coated with nano-composite layer exhibited excellent seam weldability and press formability. Detailed discussion of coating solution and experimental results suggest that nano-sized composite dispersion as coating layer plays a key role in enhancing the quality performance.

• 한국재료학회지
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• 제29권10호
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• pp.639-646
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• 2019

Ink-jet printing is a manufacturing process technology that directly prints a digitalized design pattern onto a substrate using a fine ink jetting system. In this study, environmentally friendly yellow aqueous ceramic ink is synthesized by mixture of distilled water, yellow ceramic pigment and additives for ink-jet printing. The graft polymer, which combines electrostatic repulsion and steric hindrance mechanism, is used as a surfactant for dispersion stability of aqueous ceramic ink. Synthesized ceramic ink with graft polymer surfactant shows better dispersion stability than did ceramic ink with PAA surfactant; synthesized ink also shows desirable ink-jet printability with the formation of a single ink droplet during printability test. Finally, ceramic ink printed on glass substrate and ceramic ink with graft polymer surfactant shows a high contact angle without surface treatment on glass substrate. Consequently, it is confirmed that the ceramic ink with graft polymer surfactant can achieve high printing resolution without additional surface treatment process.

• 한국산학기술학회논문지
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• 제20권12호
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• pp.230-236
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• 2019

최근 콘크리트 품질과 관련된 이슈로 시멘트의 원가절감 및 잔골재의 품질저하로 인해 콘크리트 표면의 들뜸, 레이턴스의 과다로 인한 표면 스케일링 및 소성수축의 증가로 인한 균열발생 등의 표면품질 하자 발생사례가 지속적으로 증가되고 있으며, 사회적인 이슈로 인해 미세먼지 및 배기가스로 인한 환경문제를 해결하고자 도로구조물의 광촉매 적용이 시도되고 있다. 이에 본 연구에서는 현장에서 편리하게 적용될 수 있는 양생 방법 중 작업 속도 및 효율성에서 우수한 양생제를 개발하고자 하였으며, 이와 더불어 표면층의 광촉매 코팅을 위한 나노사이즈의 이산화티탄(TiO2)의 혼입 및 분산방안을 평가하여 광촉매 작용이 가능한 다기능성 피막양생제를 개발가능성을 검토하고자 하였다. 실험결과 실리콘계 및 실란계는 굳지않은 콘크리트 표면에서 신속하게 피막을 형성하는 성능을 보이기 때문으로 양생제로서의 원료로 검토를 진행하여 기존의 양생제보다 피막성능이 우수한 고성능 피막 양생제를 개발하였다. 나노물질의 적용을 위한 분산방안을 검토하기 위해 분산된 시료를 4주간 옥외폭로하여 분리유무를 통한 안정성을 평가한 결과 초음파 분산기의 성능이 가장 우수한 것으로 확인되었다.

• Composites Research
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• 제26권4호
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• pp.218-222
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• 2013

본 연구에서는 제강 과정의 부산물로 발생하는 슬래그의 구조용 충전제로써의 사용 가능성을 검토하였다. 고분자 기지 슬래그 복합재료를 제작하여 슬래그 입자의 크기(8~12 ${\mu}m$ and 12~16 ${\mu}m$), 체적 비(0-30 vol.%)에 따른 슬래그 복합재료의 기계적 특성에 대한 실험적 연구를 수행하였다. 복합재료 물성에 영향을 주는 요인인 입자 분산 도와 계면상태를 고찰하기 위해 각각 시편에 대하여 조직사진을 촬영하였다. 인장 시험 결과 슬래그 복합재료의 재료강성은 슬래그 체적비가 증가할수록 증가하였고 인장 강도는 체적비가 증가할수록 감소하였다. 슬래그 복합재료의 재료강성은 슬래그 입자의 크기의 변화에 따른 뚜렷한 경향성을 띄지 않았고 인장강도는 입자의 크기가 작을수록 높은 값을 가졌다. 조직 사진 촬영 결과 슬래그 복합재료가 양호한 계면상태를 보였고, 낮은 체적 비에서는 좋은 분산 도를 나타냈지만 체적비가 높아지면 입자들의 뭉침 현상이 발생하는 것을 알 수 있었다.

• 한국입자에어로졸학회지
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• 제9권4호
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• pp.231-238
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• 2013

Carbon nanotubes (CNTs) are one of the nanomaterials that were discovered by Iijima in 1991 for the first time. CNTs have long cylindrical and axi-symmetric structures. CNTs are made by rolling graphene sheets. Because of their large length-to-diameter ratio, they are called nanotubes. CNTs are categorized as single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) based on the shell structures. CNTs are broadly used in various fields, such as scanning probe microscopy, ultra fine nano balance and medicine, due to their extraordinary thermal conductivity, electrical and mechanical properties. Because long, straight CNTs have the same shape as asbestos, which cause cancer in cells lining the lung, there have been many studies on the effects of MWCNTs on human health that have been conducted. Stable atomization of CNTs is very important for the estimation of inhalation toxicity. In the present study, electro-static assisted axial atomizer (EAAA), which is the instrument that uses MWCNTs and aerosolizes them by transforming the single fiber shape using ultrasonic dispersion and electric field, was invented. EAAA consists of a ultrasonic bath for dispersion of MWCNTs and a particle generator for atomizing single fibers. The performance evaluation was conducted in order to assess the possibilities of 6-hour straight atomization with stability, which is the suggested exposure time in a day for the estimation of inhalation toxicity.

• 한국분말재료학회지
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• 제21권1호
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• pp.16-20
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• 2014

In order to fabricate the porous $Al_2O_3$ with dispersion of nano-sized Cu particles, freeze-drying of camphene/$Al_2O_3$ slurry and solution chemistry process using Cu-nitrate are introduced. Camphene slurries with 10 vol% $Al_2O_3$ was frozen at $-25^{\circ}C$. Pores were generated by sublimation of the camphene during drying in air. The sintered samples at 1400 and $1500^{\circ}C$ showed the same size of large pores which were aligned parallel to the sublimable vehicles growth direction. However, the size of fine pores in the internal walls of large pores decreased with increase in sintering temperature. It was shown that Cu particles with the size of 100 nm were homogeneously dispersed on the surfaces of the large pores. Antibacterial test using fungus revealed that the porous $Al_2O_3$/1 vol% Cu composite showed antifungal property due to the dispersion of Cu particles. The results are suggested that the porous composites with required pore characteristics and functional property can be fabricated by freeze-drying process and addition of functional nano particles by chemical method.

• Journal of Pharmaceutical Investigation
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• 제26권4호
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• pp.299-308
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• 1996

In order to develop the controlled release of a drug from the suppsitories, in vitro drug release and in vivo absorption in rabbits were investigated. Various suppository forms with hollow cavities, into which drugs in the form of fine powder or solid dispersion system(SDS) could be placed, were utilized. The polyvinyl alcohol(PVA) hydrogel as a base, and propranolol HCl(PPH) as a model drug were employed. In vitro drug dissolution studies showed that the dissolved amounts(%) of PPH from PPH-methylcellulose(MC)-SDS and PPH-ethylcellulose(EC)-SDS reached 100% and 63% in 4.5-hours, respectively. In the relative strength test for PVA hydrogel, PVA hydrogel became harder and more rigid when the number of freezing-thawing cycles and the ratio of PVA 2000 were increased. In vitro drug release profile revealed that the release rate(%) of PPH from PPH-EC-SDS and PPH-MC-SDS hollow type suppositories were sustained. The release amount(%) of PPH from PPH-EC-SDS hollow type suppositories was not affected by storage time, but since the use of hydrophilic MC made PPH diffuse into the hydrogel after it absorbed the water of base, the various release patterns were appeared as the storage time went by. In vivo absorption experiments with rabbits showed that PPH-EC-SDS(PPH : EC=1:3) hollow type suppository delayed the absorption of PPH, significantly. The $C_{max}$, $AUC_{0{\rightarrow}8}$ and MRT of PPH powder hollow type suppository were $196.37{\pm}5.63\;ng/ml$, 1105.26 ng/ml/min and 8.66 min, respectively. The $C_{max}$, $AUC_{0{\rightarrow}8}$ and MRT of PPH-EC-SDS(PPH : EC=1:3) were $91.30{\pm]14.14\;ng/ml$, 554.69 ng/ml/min, 235.99 min, respectively.

• 한국재료학회지
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• 제29권4호
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• pp.271-276
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• 2019

Oxide-dispersion-strengthened (ODS) alloy has been developed to increase the mechanical strength of metallic materials; such an improvement can be realized by distributing fine oxide particles within the material matrix. In this study, the ODS layer was formed in the surface region of Zr-based alloy tubes by laser beam treatment. Two kinds of Zr-based alloys with different alloying elements and microstructures were used: KNF-M (recrystallized) and HANA-6 (partial recrystallized). To form the ODS layer, $Y_2O_3$-coated tubes were scanned by a laser beam, which induced penetration of $Y_2O_3$ particles into the substrates. The thickness of the ODS layer varied from 20 to $55{\mu}m$ depending on the laser beam conditions. A heat affected zone developed below the ODS layer; its thickness was larger in the KNF-M alloy than in the HANA-6 alloy. The ring tensile strengths of the KNF-M and HANA-6 alloy samples increased more than two times and 20-50%, respectively. This procedure was effective to increase the strength while maintaining the ductility in the case of the HANA-6 alloy samples; however, an abrupt brittle facture was observed in the KNF-M alloy samples. It is considered that the initial microstructure of the materials affects the formation of ODS and the mechanical behavior.

• 한국건설순환자원학회논문집
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• 제11권2호
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• pp.97-104
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• 2023

본 연구에서는 순환잔골재 사용량 증대를 목적으로 순환잔골재만 혼입한 고강도 모르타르를 제조하고 이의 물성을 분석하여, 순환잔골재의 구조용 골재로서의 활용가능성을 파악하고자 하였다. 시멘트, 실리카퓸 및 고로슬래그 미분말을 함유한 물결합 재비 0.2 시멘트 모르타르에, 나노실리카를 추가로 혼입하고 이의 치환율을 변화시켜, 나노실리카 혼입량 변화가 순환잔골재 모르타르의 물성 변화에 미치는 영향을 분석하였다. 시험체 제작 시 결합재 내부에서의 나노실리카 분산도 향상을 위해, 초음파 처리한 수분산된 나노실리카 수용액을 활용하였고, 나노실리카의 혼입률은 1 %까지 변화시켜 모르타르 플로우, 공극률 및 압축강도의 변화를 평가하였다. 실험 결과에 따르면, 나노실리카의 혼입률이 증가할수록 모르타르 플로우는 감소하였으며, 나노실리카 혼입률 0.75 %까지는 혼입율을 높일수록 공극률은 감소하고 압축강도는 증가하였으나, 치환율 1 %에서는 공극률의 상승 및 압축강도의 저하가 관찰되어, 나노실리카 혼입률 0.75 %가 성능 최적화를 위해 가장 적절한 혼입 비율인 것을 확인할 수 있었다.

• 한국결정성장학회지
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• 제9권1호
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• pp.23-28
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• 1999

Au 미립자가 분산된 $TiO_{2}$ 박막을 졸겔담금법과 열처리공정으로 실리카 유리기판위에 제조하였다. $TiO_{2}$ 박막제조는 titanium tetraisopropoxide-EtOH-HCl-$H_{2}O$-hydrogen tetrachloroaurat (III) tetrahydrate계를 이용하였다. 고농도로 Au 화합물을 함유하면서 투명한 코팅용액을 형성하는 조건을 검토하였다. Au 금속미립자의 크기를 조절하기 위하여 광환원공정을 채택하였다. UV 조사에 따른 Au 입자의 변화와 $TiO_{2}$ 매트릭스의 상전이과정을 XRD, SEM, TEM and UV-visible spectrophotometer로 관찰하였다. 분산제로서 CPCl (Cetylpyridinium chloride monohydrate)의 효과를 평가하였다.