• 한국산학기술학회논문지
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• 제13권12호
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• pp.6187-6195
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• 2012

네오디뮴 폐자석 침출액으로부터 희유금속인 네오디뮴을 회수하기 위해서는 네오디뮴과 같이 침출되는 철의 부가가치를 높이는 연구가 필요하다. 본 연구에서는 네오디뮴과 같이 침출되는 철의 유용자원화를 위한 기초연구로 철 나노분말 제조하는 실험을 수행하였다. 본 연구는 $FeCl_3$ 용액을 철 분말 원료로, 분산제는 $Na_4O_7P_2$와 Polyvinylpyrrolidone를 이용하였고, 환원제로는 $NaBH_4$, 철 나노분말 핵생성 촉진제 시드(seed)로 염화팔라듐을 사용하였다. 제조한 철 나노분말을 XRD, 전자현미경(SEM) 및 PSA 등을 이용하여 분말의 형상 및 크기 등을 분석하였다. 철과 $NaBH_4$의 농도비가 1 : 5이며, 반응시간이 30분 이상인 경우에서 철 분말이 제조되었으며, 이때 철 분말은 구형이었으며, 입도는 약 50 nm ~ 100 nm 크기였다. 분산제 $Na_4O_7P_2$의 경우 100 mg/L에서 철이온의 제타포텐셜이 음의 값을 가지므로 100 mg/L로 일정하게 하고, PVP와 Pd의 농도를 다양하게 하였을 경우, $FeCl_3$와 PVP와 Pd의 질량비 1 : 4 및 1 : 0.001에서, 분산이 양호하고, 입도 100 nm 크기인 철 나노분말을 합성하였다.

• 한국가스학회지
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• 제16권6호
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• pp.143-147
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• 2012

티타니아($TiO_2$) 나노분말의 우수한 광촉매 활성은 이를 친환경 소재로서 많은 주목을 받도록 하였다. 특히, 최근 들어 이러한 $TiO_2$의 광촉매 활성을 향상시키기 위하여 $TiO_2$ 나노분말에 금속 혹은 비금속 원소를 도핑하는 방법이 널리 시도되고 있다. 화염법, 화학기상합성법, 졸-젤법, 공침법, 이온 주입법 등 다양한 방법들이 사용되고 있으며 합성법에 따라 원소들의 도핑 거동이 달라지므로 $TiO_2$의 전자구조 및 표면성질들이 합성법의 영향을 받게 되며 광촉매 활성 역시 달라진다. $TiO_2$의 광촉매 활성은 합성법 자체에 영향을 받는 것 외에 후속의 열처리에 의해서도 달라질 수 있다. 본 연구에서는 우수한 광촉매 활성을 가진 $TiO_2$ 나노분말 소재를 제조하기 위하여 화학기상합성법(chemical vapor synthesis, CVS)으로 텅스텐(W) 원소가 도핑된 $TiO_2$ 나노분말을 제조하고 물성 및 광촉매 특성을 조사하였다. 일부의 $TiO_2$ 나노분말은 $300^{\circ}C{\sim}700^{\circ}C$ 범위에서 열처리한 후 물성 및 광촉매 특성의 변화를 조사하였다.

• Bulletin of the Korean Chemical Society
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• 제29권8호
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• pp.1495-1498
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• 2008

$TiO_2$ nanopowders were synthesized by new sol-gel combustion hybrid method using acetylene black as a fuel. The dried gels exhibited autocatalytic combustion behaviour. $TiO_2$ nanopowders with an anatase structure and a narrow size distribution were obtained at 400-600 ${^{\circ}C}$. Their crystal structures were examined by powder Xray diffraction (XRD) and their morphology and crystal size were investigated by scanning electron microscopy (SEM). The crystal size of the nanopowders was found to be in the range of 15-20 nm. $TiO_2$ powders synthesized at 500 ${^{\circ}C}$ and 600 ${^{\circ}C}$ were applied to a dye solar cell. An efficiency of 5.2% for the conversion of solar energy to electricity ($J_{sc}$ = 11.79 mA/$cm^2$, $V_{oc}$ = 0.73 V, and FF = 0.58) was obtained for an AM 1.5 irradiation (100 mW/$cm^2$) using the $TiO_2$ nanopowder synthesized by the sol-gel combustion hybrid method at 500 ${^{\circ}C}$.

• 한국전기전자재료학회논문지
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• 제25권8호
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• pp.626-631
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• 2012

$SnO_2$ nanoparticles were synthesized by flame spray pyrolysis, which were directly deposited on Pt interdigitated substrates. Gas sensing performance was evaluated for various gases such as $H_2$, CO, $H_2S$, and $NH_3$, and it was compared with that of commercial $SnO_2$ nanopowder. The synthesis of $SnO_2$ nanoparticles was also conducted in various solvents. As a result, the primary particle size was changed with the solvent of precursor solution, and their $H_2$ sensing properties were significantly affected.

• 한국분말재료학회지
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• 제17권2호
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• pp.101-106
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• 2010

In this study, we successfully synthesized a nano-sized lanthanum-modified lead-titanate (PLT) powder with a perovskite structure using a high-energy mechanochemical process (MCP). In addition, the sintering behavior of synthesized PLT nanopowder was investigated and the sintering temperature that can make the full dense PLT specimen decreased to below $1050^{\circ}C$ by using $Bi_2O_3$ powder as sintering agent. The pure PLT phase of perovskite structure was formed after MCP was conducted for 4 h and the average size of the particles was approximately 20 nm. After sintered at 1050 and $1150^{\circ}C$, the relative density of PLT was about 93.84 and 95.78%, respectively. The density of PLT increased with adding $Bi_2O_3$ and the specimen with the relative densitiy over 96% were fabricated below $1050^{\circ}C$ when 2 wt% of $Bi_2O_3$ was added.

• 한국분말재료학회지
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• 제21권3호
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• pp.222-228
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• 2014

Much research into fuel cells operating at a temperature below $800^{\circ}C$. is being performed. There are significant efforts to replace the yttria-stabilized zirconia electrolyte with a doped ceria electrolyte that has high ionic conductivity even at a lower temperature. Even if the doped ceria electrolyte has high ionic conductivity, it also shows high electronic conductivity in a reducing environment, therefore, when used as a solid electrolyte of a fuel cell, the powergeneration efficiency and mechanical properties of the fuel cell may be degraded. In this study, gadolinium-doped ceria nanopowder with $Al_2O_3$ and $Mn_2O_3$ as a reinforcing and electron trapping agents were synthesized by ultrasonic pyrolysis process. After firing, their microstructure and mechanical and electrical properties were investigated and compared with those of pure gadolinium-doped ceria specimen.

• 한국세라믹학회지
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• 제42권12호
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• pp.821-826
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• 2005

Gadolinia-doped ceria nanopowder was prepared by glycine-nitrate combustion method with different glycine/nitrate mixing ratio. The characteristics of the synthesized powder were investigated by X-ray diffraction method, transmission electron microscopy, thermal gravity, differential thermal analysis and thermo-mechanical analysis. The smallest powder was obtained with glycine/nitrate ratio 1.00 and the lowest organic and water vapor contained powder was made with glycine/nitrate ratio 1.75. According to dilatometry, fast densification was occurred around $1000^{\circ}C$ and shows full density over $1300^{\circ}C$. Finally near-fully dense ceria electrolyte was fabricated with conventional sintering technique. Glycine-nitrate process yields fine nanopowders which enable low temperature sintering and fabrication of fully dense and nanostructured oxide electrolyte.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.781-783
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• 2010

전북대학교 고온 플라즈마 응용 연구 센터 구축사업단은 교육과학기술부 기초연구사업 중 고가연구장비 구축사업을 통하여 고부가가치 재료 연구 및 시험생산이 가능한 소재공정용 60kW 와 200kW ICP(RF) 플라즈마 발생장치를 구축하고 있다. 나노분말소재의 합성과 플라즈마 용사 코팅이 가능한 대형 ICP(RF) 플라즈마 장치 구축을 통하여 차세대 전자 부품 소재의 개발 및 고온 플라즈마 기술의 산업화에 이바지 하고자 한다.

• 한국재료학회지
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• 제25권1호
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• pp.48-53
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• 2015

$TiH_2$ nanopowder was made by high energy ball milling. The milled $TiH_2$ and CNT powders were then simultaneously synthesized and consolidated using pulsed current activated sintering (PCAS) within one minute under an applied pressure of 80 MPa. The milling did not induce any reaction between the constituent powders. Meanwhile, PCAS of the $TiH_2$-CNT mixture produced a Ti-TiC composite according to the reaction ($0.92TiH_2+0.08CNT{\rightarrow}0.84Ti+0.08TiC+0.92H_2$, $0.84TiH_2+0.16CNT{\rightarrow}0.68Ti+0.16TiC+0.84H_2$). Highly dense nanocrystalline Ti-TiC composites with a relative density of up to 99.7% were obtained. The hardness and fracture toughness of the dense Ti-8 mole% TiC and Ti-16 mole% TiC produced by PCAS were also investigated. The hardness of the Ti-8 mole% TiC and Ti-16 mole% TiC composites was higher than that of Ti. The hardness value of the Ti-16 mole% TiC composite was higher than that of the Ti-8 mole% TiC composite without a decrease in fracture toughness.

• 한국재료학회지
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• 제30권5호
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• pp.252-261
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• 2020

We prepare ZnO nanoparticles by environmentally friendly synthesis using Cyathea nilgiriensis leaf extract. Various phytochemical constituents are identified through the assessment of ethanolic extract of plant Cyathea nilgiriensis holttum by GC-MS analysis. The formation of ZnO nanoparticles is confirmed by FT-IR, XRD, SEM-EDX, TEM, SAED and PSA analysis. TEM observation reveals that the biosynthesized ZnO nanopowder has a hexagonal structure. The calculated average crystallite size from the high intense plane of (1 0 1) is 29.11 nm. The particle size, determined by TEM analysis, is in good agreement with that obtained by XRD analysis. We confirm the formation of biomolecules in plant extract by FT-IR analysis and propose a possible formation mechanism of ZnO nanoparticles. Disc diffusion method is used for the analyses of antimicrobial activity of ZnO nanoparticles. The synthesized ZnO nanoparticles exhibit antimicrobial effect in disc diffusion experiments. The biosynthesized ZnO nanoparticles display good antibacterial performance against B. subtilis (Gram-positive bacteria) and K. pneumonia (Gram-negative bacteria). Bio-synthesized nanoparticles using green method are found to possess good antimicrobial performance.