• Title/Summary/Keyword: 나노분말 합성

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Synthesis and Characterization of Si-C-N Precursor by Using Chemical Vapor Condensation Method (화학기상응축법을 이용한 Si-C-N Precursor 분말의 합성 및 특성평가)

  • Kim, Hyoung-In;Kim, Dae-Jung;Hong, Jin-Seok;So, Myoung-Gi
    • Journal of the Korean Ceramic Society
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    • v.39 no.8
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    • pp.783-788
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    • 2002
  • In this study, nano-sized Si-C-N precursor powders were synthesized by Chemical Vapor Condensation Method(CVC) using TMS(Tetramethylsilane: Si($CH_3)_4$), $NH_3$ and $H_2$ gases under the various reaction conditions of the reaction temperature, TMS/$NH_3$ ratio and TMS/$H_2$ ratio. XRD and FESEM were used to analysis the crystalline phase and the average particle size of the synthesized powders. It was found that the obtained powders under the considering conditions were all spherical amorphous powder with the particle size of 87∼130 nm. The particle size was decreased as the reaction temperature increased and TMS/$NH_3$ and TMS/$H_2$ ratio decreased. As the results of EA analysis, it was found that the synthesized powders had been formed the powders composed of Si, N, C and H. Through FT-IR results, it was found that the synthesized powders were Si-C-N precursor powders with Si-C, Si-N and C-N bonds.

Synthesis and electrochemical characterization of nano structure $CeO_2$ (나노 구조의 $CeO_2$ 합성과 전기화학적 특성 분석)

  • Cho, Min-Young;Lee, Jae-Won;Park, Sun-Min;Roh, Kwang-Chul;Choi, Heon-Jin
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.462-462
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    • 2009
  • $CeO_2$는 고체 산화물 연료전지 (SOFC, soild oxide fuel cell)의 전해질 재료와 CMP(Chemical Mechanical Polishing) 슬러리 재료, 자동차의 3원 촉매, gas sensor, UV absorbent등 여러 분야에서 사용되고 있다. 본 연구에서는 위의 활용범위 외에 $CeO_2$의 구조적 안정성과 빠른 $Ce^{3+}/Ce^{4+}$의 전환 특성을 이용하여 lithium ion battery의 anode 재료로서 전기화학적 특성을 알아보고자 실험을 실시하였다. $CeO_2$ 합성에 사용되는 전구체인 cerium carbonate의 형상 및 크기, 비표면적과 같은 물리화학적 특성이 $CeO_2$ 분말의 특성에 직접적인 영향을 주기 때문에 전구체의 합성 단계에서 입자의 특성을 조절하였다. 전구체 합성의 출발원료로 cerium nitrate hexahydrate 와 ammonium carbonate를 사용하였고 반응온도 및 농도 등을 변화시켜 입자의 형상 및 결정상을 fiber형태의 orthorombic $Ce_2O(CO_3)_2{\cdot}H_2O$와 구형의 hexagonal $CeCO_3OH$의 세리아 전구체를 합성하였다. 이를 $300^{\circ}C$에서 30분 동안 하소하여 전구체의 입자형상을 유지하는 cubic $CeO_2$를 합성하고 X-ray diffraction, FE-SEM, micropore physisorption analyzer 분석을 통하여 입자의 결정상과 형상, 비표면적 등을 비교 분석하고 $Li/CeO_2$ couple의 충,방전 용량과 수명특성을 비교 분석하여 $CeO_2$의 전기화학적 특성을 알아보았다.

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Fabrication of $TiO_2$ Electrode Containing Scattering Particles in Dye-Sensitized Solar Cells (산란 입자를 포함하는 염료감응 태양전지용 $TiO_2$ 전극 제조)

  • Lee, Jin-Hyoung;Lee, Tae-Kun;Kim, Cheol-Jin
    • Journal of the Microelectronics and Packaging Society
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    • v.18 no.2
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    • pp.57-62
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    • 2011
  • The energy conversion efficiency of DSSCs (Dye-Sensitized Solar Cells) is dependent on the powder size, the structure, and the morphology of $TiO_2$ electrode. The higher efficiency is obtained with high surface area of the nanoanatase-$TiO_2$ powder adsorbed onto a lot more of the dye. Also, the enhancement of light scattering increases the efficiency with high adsorption of the dye. Powder size, crystalline phase, and shape of $TiO_2$ obtained by hydrothermal method have 15-20 nm, anatase and round. $TiO_2$ electrode has fabricated with the mixture of scattering $TiO_2$ particle with 0.4 ${\mu}m$ in nano-sized powder. Conversion efficiency of series of DSSCs was measured with volume fraction of scattering particle. Photovoltaic characteristics of DSSCs with 10% scattering particles are 3.51 mA for Jsc (short circuit current), 0.79 V for Voc(open circuit potential), filling factor 0.619 and 6.86% for efficiency. Jsc was improved by 11% and enhancement of efficiency by 0.77% compared with that of no scattering particles. The confinement of inserted light by light scattering particles has more increase of the injection of exiton(electron-hole pair) and decrease of moving path in electron. Efficiencies of DSSCs with more than 10% for scattering particles have reduced with increasing the pore in the $TiO_2$ electrode.

Characterization of SiC nanowire Synthesized by Thermal CVD (열 화학기상증착법을 이용한 탄화규소 나노선의 합성 및 특성연구)

  • Jung, M.W.;Kim, M.K.;Song, W.;Jung, D.S.;Choi, W.C.;Park, C.J.
    • Journal of the Korean Vacuum Society
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    • v.19 no.4
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    • pp.307-313
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    • 2010
  • One-dimensional cubic phase silicon carbide nanowires (${\beta}$-SiC NWs) were efficiently synthesized by thermal chemical vapor deposition (TCVD) with mixtures containing Si powders and nickel chloride hexahydrate $(NiCl_2{\cdot}6H_2O)$ in an alumina boat with a carbon source of methane $(CH_4)$ gas. SEM images are shown that the growth temperature (T) of $1,300^{\circ}C$ is not enough to synthesize the SiC NWs owing to insufficient thermal energy for melting down a Si powder and decomposing the methane gas. However, the SiC NWs could be synthesized at T>$1,300^{\circ}C$ and the most efficient temperature for growth of SiC NWs is T=$1,400^{\circ}C$. The synthesized SiC NWs have the diameter with an average range between 50~150 nm. Raman spectra clearly revealed that the synthesized SiC NWs are forming of a cubic phase (${\beta}$-SiC). Two distinct peaks at 795 and $970 cm^{-1}$ in Raman spectra of the synthesized SiC NWs at T=$1,400^{\circ}C$ represent the TO and LO mode of the bulk ${\beta}$-SiC, respectively. XRD spectra are also supported to the Raman spectra resulting in the strongest (111) peaks at $2{\Theta}=35.7^{\circ}$, which is the (111) plane peak position of 3C-SiC. Moreover, the gas flow rate of 300 sccm for methane is the optimal condition for synthesis of a large amount of ${\beta}$-SiC NW without producing the amorphous carbon structure shown at a high methane flow rate of 800 sccm. TEM images are shown two kinds of the synthesized ${\beta}$-SiC NWs structures. One is shown the defect-free ${\beta}$-SiC NWs with a (111) interplane distance of 0.25 nm, and the other is the stacking-faulted ${\beta}$-SiC NWs. Also, TEM images exhibited that two distinct SiC NWs are uniformly covered with $SiO_2$ layer with a thickness of less 2 nm.

Synthesis and Microstructure of Fe(C) Nanocapsules by Chemical Vapor Condensation (화학기상응축공정으로 제조한 Fe(C) 나노캡슐의 합성 및 미세구조)

  • Lee Jung-Han;Kim Sung-Duk;Kim Jin-Chun;Choi Chul-Jin;Lee Chan-Gyu
    • Journal of Powder Materials
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    • v.11 no.6 s.47
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    • pp.515-521
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    • 2004
  • Fe(C) nanocapsules were prepared by the chemical vapor condensation(CVC) process using the pyrolysis of iron pentacarbonyl $(Fe(CO)_5)$. Their characterizations were studied by means of X-ray diffraction, X-ray photoelectron spectrometer and transmission electron microscopy. The long-chained Fe(C) nanocapsules hav-ing the mean size of under 70 nm could be obtained below $1100^{\circ}C$ in different gas flow rates. The particle size of the powders was increased with increasing decomposition temperature, but it was decreased with increasing CO gas flow rate. The Fe powders produced at $500^{\circ}C$ consisted of three layers of ${\alpha}$-Fe/$Fe_3C$/amorphous phases, but it had two phase core-shell structure which consited of $Fe_3C$ phase of core and graphite of shell at $1100^{\circ}C$.

Mechanical Properties and Fabrication of Nanostructured ReSi1.75 by High Frequency Induction Heated Combustion Synthesis (고주파유도가열 연소합성에 의한 나노구조 ReSi1.75 제조 및 기계적 성질)

  • Kim, Byung-Ryang;Kim, Su-Chul;Shon, In-Jin
    • Journal of Powder Materials
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    • v.16 no.1
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    • pp.16-21
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    • 2009
  • Nanostructured $ReSi_{1.75}$ was synthesized to have high density via rapid and cost effective process named as high-frequency induction heated combustion synthesis(HFIHCS) method. For the process, mechanically activated Re-Si powder was used, which had been prepared by mechanical ball milling of Re and Si powders with mixing ratio of 1:1.75. Both combustion synthesis and densification were accomplished simultaneously by applying electric current and mechanical pressure of 80 MPa during the process. The average grain size, hardness, and fracture toughness of the compound were 210 nm, 1085 $kg/mm^2$ and 4 $MPa{\cdot}m^{1/2}$, respectively. The experimental results show that HFIHCS is a promising process for synthesis of nanostructured $ReSi_{1.75}$ which has a potential for both high temperature and thermo-electric applications.

Synthesis and Characterization of WS2 Nanoparticles by Chemical Vapor Condensation (화학기상응축공정에 의한 WS2 나노입자의 합성 및 특성평가)

  • Lee, Dong-Won;Kim, Ju-Hyeong;Tolochko, O.;Yun, Jung-Yeul;Kim, Byung-Kee
    • Journal of Powder Materials
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    • v.15 no.4
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    • pp.314-319
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    • 2008
  • Nano-sized tungsten disulfide ($WS_2$) powders were synthesized by chemical vapor condensation (CVC) process using tungsten carbonyl ($W(CO)_6$) as precursor and vaporized pure sulfur. Prior to the synthesis of tungsten disulfide nanoparticles, the pure tungsten nanoparticles were produced by same route to define the optimum synthesis parameters, which were then successfully applied to synthesize tungsten disulfide. The influence of experimental parameters on the phase and chemical composition as well as mean size of the particles for the produced pure tungsten and tungsten disulfide nanoparticles, were investigated.

Synthesis of the Multifunctional Core/Intermediate/Shell Nanoparticles: Tunable Magnetic and Photoluminescence Properties (자성 및 발광 특성이 조절 가능한 다기능 코어/중간체/쉘 나노 입자 합성)

  • Kim, Mun-Kyoung;Kim, Seyun;Moon, Kyoung-Seok;Shin, Weon Ho;Jeong, Hyung Mo
    • Journal of Powder Materials
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    • v.26 no.6
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    • pp.463-470
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    • 2019
  • Fe3O4/SiO2/YVO4:Eu3+ multifunctional nanoparticles are successfully synthesized by facile stepwise sol-gel processes. The multifunctional nanoparticles show a spherical shape with narrow size distribution (approximately 40 nm) and the phosphor shells are well crystallized. The Eu3+ shows strong photoluminescence (red emission at 619 nm, absorbance at 290 nm) due to an effective energy transfer from the vanadate group to Eu. Core-shell structured multifunctional nanoparticles have superparamagnetic properties at 300 K. Furthermore, the core-shell nanoparticles have a quick response time for the external magnetic field. These results suggest that the photoluminescence and magnetic properties could be easily tuned by either varying the number of coating processes or changing the phosphor elements. The nanoparticles may have potential applications for appropriate fields such as laser systems, optical amplifiers, security systems, and drug delivery materials.

Synthesis of γ-Fe2O3 Nanoparticles by Low-pressure Ultrasonic Spraying (저압 초음파 분무 공정을 이용한 γ-Fe2O3 나노입자의 합성)

  • Lee, Chang-Woo;Kim, Soon-Gil;Choa, Yong-Ho;Lee, Jai-Sung
    • Journal of Powder Materials
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    • v.14 no.1 s.60
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    • pp.19-25
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    • 2007
  • This study was focused on the optimization of low-pressure ultrasonic spraying process for synthesis of pure ${\gamma}-Fe_2O_3$ nanoparticles. As process variables, pressure in the reactor, precursor concentration, and reaction temperature were changed in order to control the chemical and microstructural properties of iron oxide nanoparticles including crystal phase, mean particle size and particle size distribution. X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies revealed that pure ${\gamma}-Fe_2O_3$ nanoparticles with narrow particle size distribution of 5-15 nm were successfully synthesized from iron pentacarbonyl ($Fe(CO)_{5}$) in hexane under 30 mbar with precursor concentrations of 0.1M and 0.2M, at temperatures over $800^{\circ}C$. Also magnetic properties, coercivity ($H_c$) and saturation magnetization ($M_s$) were reported in terms of the microstructure of particles based on the results from vibration sampling magnetometer (VSM).

Photocatalytic and Adsorption Properties of WO3 Nanorods Prepared by Hydrothermal Synthesis (수열합성법으로 제조된 나노막대 구조 WO3의 광촉매 효과 및 염료 흡착 반응)

  • Yu, Su-Yeol;Nam, Chunghee
    • Journal of Powder Materials
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    • v.24 no.6
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    • pp.483-488
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    • 2017
  • Transition-metal oxide semiconductors have various band gaps. Therefore, many studies have been conducted in various application fields. Among these, methods for the adsorption of organic dyes and utilization of photocatalytic properties have been developed using various metal oxides. In this study, the adsorption and photocatalytic effects of $WO_3$ nanomaterials prepared by hydrothermal synthesis are investigated, with citric acid added in the hydrothermal process as a structure-directing agent. The nanostructures of $WO_3$ are studied using transmission electron microscopy and scanning electron microscopy images. The crystal structure is investigated using X-ray diffraction patterns, and the changes in the dye concentrations adsorbed on $WO_3$ nanorods are measured with a UV-visible absorption spectrophotometer based on Beer-Lambert's law. The methylene blue (MB) dye solution is subjected to acid or base conditions to monitor the change in the maximum adsorption amount in relation to the pH. The maximum adsorption capacity is observed at pH 3. In addition to the dye adsorption, UV irradiation is carried out to investigate the decomposition of the MB dye as a result of photocatalytic effects. Significant photocatalytic properties are observed and compared with the adsorption effects for dye removal.