• Title/Summary/Keyword: 나노분말 합성

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The particle properties and luminescence properties of Gd2O3:Eu using solution-combustion with various Eu content were analysis (X선 검출기를 위해 특수용매 액상법으로 합성한 Gd2O3:Eu의 Europium(Eu) 함량에 따른 입자특성과 발광특성의 분석)

  • Kim, Sung-Hyun;Kim, Young-Bin;Jung, Suk-Hee;Kim, Min-Woo;Oh, Kyung-Min;Park, Ji-Gun
    • Journal of the Korean Society of Radiology
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    • v.2 no.3
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    • pp.11-18
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    • 2008
  • In this study, the particle properties and luminescence properties of Gd2O3 nano powder with various Eu content were studied. Gd2O3:Eu nano powder was fabricated using special solvent which mixed the alcohol and the distilled water at specific ratio. This solvent by the solution method showed short fabrication time because solution time of Gd and Eu was reduced. From this experiment with Gd2O3:Eu, the particle properties og nano powder phosphor way analysed using SEM (scanning electron microscope) and EDX(Energy Dispersive X-ray). Also the luminescence properties of nano powder was measured using PL(Photoluminescence) and CL (CathodeLuminescence). The size of powder was 30nm~40nm. The magnitude of powder showed the best peak at 620nm. Among 1,3,5wt% of Eu content, the more Eu content was added in powder, the more photons wre generated. Also it shows luminescence efficiency was improved adding 5% of Eu content.

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Synthesis and characterization of Mg-Si thermoelectric compound subjected to mechanical alloying (기계적 합금화에 의한 Mg-Si계 열전화합물의 합성 및 평가)

  • Lee, Chung-Hyo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.17 no.3
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    • pp.121-127
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    • 2007
  • We have applied mechanical alloying (MA) to get $Mg_2Si$ thermoelectric material with nano-sized grains. An optimal milling and heat treatment conditions to obtain the single phase of $Mg_2Si$ compound with fine microstructure were investigated by X-ray diffraction and differential scanning calorimetry (DSC) measurement. The $Mg_{66.7}Si_{33.3}$ MA samples ball-milled for $20{\sim}180\;hrs$ exhibit two broad exothermic heat releases around $220^{\circ}C$ and $570^{\circ}C$. On the other hand, MA sample ball-milled far 260 hrs exhibits only a sharp exothermic peak at $230^{\circ}C$ Single phase Mg2Si powder can be obtained by MA of $Mg_{66.7}Si_{33.3}$ mixture for 60 hours and subsequently heated up to $620^{\circ}C$. Sintering of the MA powders was performed in a spark plasma sintering (SPS) machine using graphite dies at $800{\sim}900^{\circ}C$ under 50 MPa. The shrinkage of sintering sample during SPS was significant at about $200^{\circ}C$. All compact bodies have a high relative density above 94% with metallic glare on the surface.

Superconductor Preparation by use of YBa2Cu3Ox powder and BaPbO3 Additive (YBa2Cu3Ox 분말과 첨가제 BaPbO3를 이용한 초전도체 제작)

  • Chu, Soon-Nam;Park, Jung-Cheul
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.15 no.8
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    • pp.1771-1776
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    • 2011
  • In this paper, as an attempt to improve the preparation conditions of $YBa_2Cu_3Ox$ superconducting bulk samples, the properties of $YBa_2Cu_3Ox$ superconductor depending on the particle size of YBCO powder and $BaPbO_3$ as an additive have been investigated, and a study on the effects of additive to the density, grain alignment, and porosity of samples that affect the critical current of superconductor has been performed. In order to prepare superconductor, $YBa_2Cu_3Ox$ powder synthesized by sol-gel method, showing a size distribution of 0.2~1 ${\mu}m$ was used. The $BaPbO_3$ added to promote grain growth and to decrease porosities and weak links between grain boundaries of $YBa_2Cu_3Ox$ superconductors. In the samples prepared by sol-gel synthesized powder with 10, 20, and 30 wt% conductive $BaPbO_3$ additives, the sample with 20 wt% $BaPbO_3$ obtained the highest critical current of 4.74 A, showing 20 wt% higher critical current than that with solid state synthesized powder.

Microstructures and Dielectric Properties of $BaTiO_3$ Ceramics Sintered with Glass Frit (Glass frit를 첨가한 $BaTiO_3$ 세라믹스의 유전 특성과 미세구조 변화 관찰)

  • Woo, Duck-Hyun;Son, Yong-Ho;Yoon, Man-Soon;Ur, Soon-Chul;Kweon, Soon-Yong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.172-172
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    • 2009
  • $BaTiO_3$는 perovskite 구조를 가지는 대표적인 강유전체 재료로서 MLCC(Multi Layer Ceramic Capacitor), PTC thermistor등에 널리 사용되어지고 있다. 최근 고용량 MLCC 의 상업화와 함께 나노크기를 갖는 tetragonal phase의 $BaTiO_3$ 입자를 합성하기 위한 다양한 제조방법이 제시되고 있다. 또한 유전 특성과 온도특성 및 신뢰성을 향상시키기 위해 많은 첨가제들이 연구되어지고 있다. 따라서 이 번 연구에서는 선행 연구를 통해 얻어진 high energy mill을 이용한 고상반응법으로 제조된 $BaTiO_3$를 사용하였으며, 제조된 $BaTiO_3$ 분말에 glass frit를 첨가하여 소결온도 및 유전특성의 변화를 관찰하였다. 제조된 $BaTiO_3$ 분말은 200nm이하의 구형화와 균일한 입자크기를 보였으며, 선행연구를 통해 최적화된 glass frit의 양인 2.53wt%를 첨가하였고 1170, 1200, $1230^{\circ}C$에서 소결하여 소결온도에 따른 변화를 관찰하였다. 실험방법으로는 원료를 혼합하기 위하여 24시간 ball-mill을 이용하여 혼합하였으며, $\Phi15$로 성형하여 소결을 진행하였다. 실험진행 결과 모든 시편에서의 비유전율은 glass frit가 첨가되지 않은 조성보다 높게 나타났으며, $1200^{\circ}C$에서 소결한 시편의 비유전율($\varepsilon_r$)은 2300으로 glass frit가 첨가되지 않은 조성과 비교하여 21% 증가하여 최대치를 나타냈다. 또한 소결온도 $1200^{\circ}C$ 이상에서의 모든 시편에서는 95% 이상의 상대밀도를 나타내어, glass frit가 소결조제로써의 역할을 하는 것으로 나타났다. 따라서 본 연구를 통해 glass frit첨가로 인한 소결온도 감소 및 유전특성이 증가하는 것을 확인 하였다.

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Synthesis and Electromagnetic Wave Absorbing Property of BaTiO3@Fe Nanofibers with Core-Shell Structure (코어-쉘 구조를 갖는 BaTiO3@Fe 나노섬유의 합성 및 전자파 흡수 특성)

  • Lee, Young-In;Jang, Dae-Hwan;Sung, Ki-Hoon;Lee, Kyuman;Choa, Yong-Ho
    • Journal of Powder Materials
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    • v.23 no.1
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    • pp.38-42
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    • 2016
  • $BaTiO_3$-coated Fe nanofibers are synthesized via a three-step process. ${\alpha}-Fe_2O_3$ nanofibers with an average diameter of approximately 200 nm are first prepared using an electrospinning process followed by a calcination step. The $BaTiO_3$ coating layer on the nanofiber is formed by a sol-gel process, and a thermal reduction process is then applied to the core-shell nanofiber to selectively reduce the ${\alpha}-Fe_2O_3$ to Fe. The thickness of the $BaTiO_3$ shell is controlled by varying the reaction time. To evaluate the electromagnetic (EM) wave-absorbing abilities of the $BaTiO_3@Fe$ nanofiber, epoxy-based composites containing the nanofibers are fabricated. The composites show excellent EM wave absorption properties where the power loss increases to the high frequency region without any degradation. Our results demonstrate that the $BaTiO_3@Fe$ nanofibers obtained in this work are attractive candidates for electromagnetic wave absorption applications.

Study on Surface Modification of Ti Substrate to Improve the Dispersion of Catalytic Metals on Synthesis of Carbon Nanotubes (탄소나노튜브 합성 시 촉매 금속의 분산도 향상을 위한 Ti Substrate의 표면 개질 연구)

  • Kwak, Seoung Yeol;Kim, Ho Gyu;Byun, Jong Min;Park, Ju Hyuk;Suk, Myung-Jin;Oh, Sung-Tag;Kim, Young Do
    • Journal of Powder Materials
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    • v.21 no.1
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    • pp.28-33
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    • 2014
  • This paper describes the surface modification effect of a Ti substrate for improved dispersibility of the catalytic metal. Etching of a pure titanium substrate was conducted in 50% $H_2SO_4$, $50^{\circ}C$ for 1 h-12 h to observe the surface roughness as a function of the etching time. At 1 h, the grain boundaries were obvious and the crystal grains were distinguishable. The grain surface showed micro-porosities owing to the formation of micro-pits less than $1{\mu}m$ in diameter. The depths of the grain boundary and micro-pits appear to increase with etching time. After synthesizing the catalytic metal and growing the carbon nano tube (CNT) on Ti substrate with varying surface roughness, the distribution trends of the catalytic metal and grown CNT on Ti substrate are discussed from a micro-structural perspective.

Synthesis of Perforated Polygonal Cobalt Oxides using a Carbon Nanofiber Template (탄소나노섬유 모형을 이용한 천공된 다각형 코발트 산화물 합성)

  • Sin, Dong-Yo;An, Geon-Hyoung;Ahn, Hyo-Jin
    • Journal of Powder Materials
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    • v.22 no.5
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    • pp.350-355
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    • 2015
  • Perforated polygonal cobalt oxide ($Co_3O_4$) is synthesized using electrospinning and a hydrothermal method followed by the removal of a carbon nanofiber (CNF) template. To investigate their formation mechanism, thermogravimetric analysis, field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy are examined. To obtain the optimum condition of perforated polygonal $Co_3O_4$, we prepare three different weight ratios of the Co precursor and the CNF template: sample A (Co precursor:CNF template- 10:1), sample B (Co precursor:CNF template-3.2:1), and sample C (Co precursor:CNF template-2:1). Among them, sample A exhibits the perforated polygonal $Co_3O_4$ with a thin carbon layer (5.7-6.2 nm) owing to the removal of CNF template. However, sample B and sample C synthesized perforated round $Co_3O_4$ and destroyed $Co_3O_4$ powders, respectively, due to a decreased amount of Co precursor. The increased amount of the CNF template prevents the formation of polygonal $Co_3O_4$. For sample A, the optimized weight ratio of the Co precursor and CNF template may be related to the successful formation of perforated polygonal $Co_3O_4$. Thus, perforated polygonal $Co_3O_4$ can be applied to electrode materials of energy storage devices such as lithium ion batteries, supercapacitors, and fuel cells.

Synthesis of Pt@TiO2 Nano-composite via Photochemical Reduction Method (광화학 환원방법을 이용한 Pt@TiO2 나노 복합체 합성)

  • Kim, Ji Young;Byun, Jong Min;Kim, Jin Woo;Kim, Young Do
    • Journal of Powder Materials
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    • v.21 no.2
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    • pp.119-123
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    • 2014
  • Pt has been widely used as catalyst for fuel cell and exhausted gas clean systems due to its high catalytic activity. Recently, there have been researches on fabricating composite materials of Pt as a method of reducing the amount of Pt due to its high price. One of the approaches for saving Pt used as catalyst is a core shell structure consisting of Pt layer on the core of the non-noble metal. In this study, the synthesis of Pt shell was conducted on the surface of $TiO_2$ particle, a non-noble material, by applying ultraviolet (UV) irradiation. Anatase $TiO_2$ particles with the average size of 20~30 nm were immersed in the ethanol dissolved with Pt precursor of $H_2PtCl_6{\cdot}6H_2O$ and exposed to UV irradiation with the wavelength of 365 nm. It was confirmed that Pt nano-particles were formed on the surface of $TiO_2$ particles by photochemical reduction of Pt ion from the solution. The morphology of the synthesized Pt@$TiO_2$ nano-composite was examined by TEM (Transmission Electron Microscopy).

Synthesis and Characterization of SnO2-CoO/carbon-coated CoO Core/shell Nanowire Composites (SnO2-CoO/carbon-coated CoO core/shell 나노선 복합체의 합성 및 구조분석)

  • Lee, Yu-Jin;Koo, Bon-Ryul;Ahn, Hyo-Jin
    • Journal of Powder Materials
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    • v.21 no.5
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    • pp.360-365
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    • 2014
  • $SnO_2-CoO$/carbon-coated CoO core/shell nanowire composites were synthesized by using electrospinning and hydrothermal methods. In order to obtain $SnO_2-CoO$/carbon-coated CoO core/shell nanowire composites, $SnO_2-Co_3O_4$ nanowire composites and $SnO_2-Co_3O_4$/polygonal $Co_3O_4$ core/shell nanowire composites are also synthesized. To demonstrate their structural, chemical bonding, and morphological properties, field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were carried out. These results indicated that the morphologies and structures of the samples were changed from $SnO_2-Co_3O_4$ nanowires having cylindrical structures to $SnO_2-Co_3O_4/Co_3O_4$ core/shell nanowires having polygonal structures after a hydrothermal process. At last, $SnO_2-CoO$/carbon-coated CoO core/shell nanowire composites having irregular and high surface area are formed after carbon coating using a polypyrrole (PPy). Also, there occur phases transformation of cobalt phases from $Co_3O_4$ to CoO during carbon coating using a PPy under a argon atmosphere.

Formation of Nano-oxides on Porous Metallic Glass Compacts using Hydrothermal Synthesis (수열합성 공정을 이용한 금속 다공체의 나노 산화물 형성)

  • Park, H.J.;Kim, Y.S.;Hong, S.H.;Kim, J.T.;Cho, J.Y.;Lee, W.H.;Kim, Ki Buem
    • Journal of Powder Materials
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    • v.22 no.4
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    • pp.229-233
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    • 2015
  • Porous metallic glass compact (PMGC) are developed by electro-discharge sintering (EDS) process of gas atomized $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ metallic glass powder under of 0.2 kJ generated by a $450{\mu}F$ capacitor being charged to 0.94 kV. Functional iron-oxides are formed and growth on the surface of PMGCs via hydrothermal synthesis. It is carried out at $150^{\circ}C$ for 48hr with distilled water of 100 mL containing Fe ions of 0.18 g/L. Consequently, two types of iron oxides with different morphology which are disc-shaped $Fe_2O_3$ and needle-shaped $Fe_3O_4$ are successfully formed on the surface of the PMGCs. This finding suggests that PMGC witih hydrothermal technique can be attractive for the practical technology as a new area of structural and functional materials. And they provide a promising road map for using the metallic glasses as a potential functional application.