• Title/Summary/Keyword: Nano-Sized Particles

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Bio-toxicity of Titanium Dioxide Nano Particles (P-25) in Zebrafish Development Stage (Zebrafish 발생기에서 $TiO_2(P-25)$ 나노 입자의 생물 독성)

  • Yeo, Min-Kyeong;Jo, Yoon-Hee
    • Environmental Analysis Health and Toxicology
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    • v.22 no.3
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    • pp.189-196
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    • 2007
  • [ $TiO_2$ ] is widely used because it is non-toxic. Recently, however, nanometer size $TiO_2$ particles (P-25) have been produced and used to increase the photo catalysis efficiency. Nanometer-sized $TiO_2$ is efficient, but due to its small size ($20{\sim}30\;nm$), it can flow into ecosystems and into cells. Thus, it may affect human health. Additionally, $TiO_2$ can produce a second contaminant, OH-radical, which is a health risk for all living organisms during photo degradation reaction. Hence, when nanometer-sized $TiO_2$ flows into natural streams and attaches to living organisms, it will create health risks. We investigated the biological toxicity of this condition in zebrafish embryos. We observed abnormal morphology, hatching rate, and measured the catalase activity to determine anti-oxidation at 100 post fertilization hours. Zebrafish were somewhat affected by $TiO_2$ nanometer sized particles under UV-A (a condition similar to sunlight). Powdered $TiO_2$ is toxic to the zebrafish fly. Even without light, $TiO_2$ particles attached to embryos and flies, having an effect on both.

Microstructure and Synthesis of Nano Palladium Spot Coated Activated Carbon Powders by Hydrothermal Attachment Method (수열흡착법을 이용한 나노팔라듐 점코팅 활성탄 분말의 합성 및 미세조직)

  • Kim, Hyeong Chul;Han, Jae Kil
    • Journal of Powder Materials
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    • v.19 no.6
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    • pp.424-428
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    • 2012
  • Nano Pd spot-coated active carbon powders were synthesized by a hydrothermal-attachment method (HAA) using PVP capped Pd colloid in a high pressure bomb at $250^{\circ}C$, 450 psi, respectively. The PVP capped Pd colloid was synthesized by the precipitation-redispersion method. PVP capped Pd nano particles showed the narrow size distribution and their particle sizes were less than 8nm in diameter. In the case of nano Pd-spot coated active carbon powders, nano-sized Pd particles were adhered in the active carbon powder surface by HAA method. The component of Pd was homogeneously distributed on the active carbon surface.

Synthesis and Compaction of Al-based Nanopowders by Pulsed Discharge Method

  • Rhee, Chang-Kyu;Lee, Geun-Hee;Kim, Whung-Whoe
    • Journal of Powder Materials
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    • v.9 no.6
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    • pp.433-440
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    • 2002
  • Synthesis and compaction of Al-base nano powders by pulsed discharge method were investigated. The aluminum based powders with 50 to 200 nm of diameter were produced by pulsed wire evaporation method. The powders were covered with very thin oxide layer. The perspective process for the compaction and sintering of nanostructured metal-based materials stable in a wide temperature range can be seen in the densification of nano-sized metal powders with uniformly distributed hard ceramic particles. The promising approach lies in utilization of natural uniform mixtures of metal and ceramic phases, e.g. partially oxidized metal powders as fabricated in our synthesis method. Their particles consist of metal grains coated with oxide films. To construct a metal-matrix material from such powder, it is necessary to destroy the hard oxide coatings of particles during the compaction process. This goal was realized in our experiments with intensive magnetic pulsed compaction of aluminum nanopowders passivated in air.

Self-assembly of Fine Particles Applied to the Production of Antireflective Surfaces

  • Kobayashi, Hayato;Moronuki, Nobuyuki;Kaneko, Arata
    • International Journal of Precision Engineering and Manufacturing
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    • v.9 no.1
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    • pp.25-29
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    • 2008
  • We introduce a new fabrication process for antireflective structured surfaces. A 4-inch silicon wafer was dipped in a suspension of 300-nm-diameter silica particles dispersed in a toluene solution. When the wafer was drawn out of the suspension, a hexagonally packed monolayer structure of particles self-assembled on almost the complete wafer surface. Due to the simple process, this could be applied to micro- and nano-patterning. The self-assembled silica particles worked as a mask for the subsequent reactive ion etching. An array of nanometer-sized pits could be fabricated since the regions that correspond to the small gaps between particles were selectively etched off. As etching progressed, the pits became deeper and combined with neighboring pits due to side-etching to produce an array of cone-like structures. We investigated the effect of etching conditions on antireflection properties, and the optimum shape was a nano-cone with height and spacing of 500 nm and 300 nm, respectively. This nano-structured surface was prepared on a $30\;{\times}\;10-mm$ area. The reflectivity of the surface was reduced 97% for wavelengths in the range 400-700 nm.

The Role of Nano-particles on the Material Properties of Epoxy/Fe2O3 Nano-composites (Epoxy/Fe2O3 나노 복합재의 물성치에 미치는 나노 입자의 역할)

  • Park, Joo-Hyuk;Kim, Jung-Yub
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.5
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    • pp.88-93
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    • 2002
  • The objective of this study is to obtain fundamental understandings involving the manufacturing process of nano-composite via resin transfer molding and explore the role of nano sized $Fe_2O_3$ particles in the epoxy/$Fe_2O_3$ nano-composites. To achieve this goal, following investigations have been conducted: Define the optimum dispersion technique of nano-particles, identify the effect of the nano-particles to the resin viscosity, characterize the key mechanical properties versus particle loading amounts, and explore the usefulness and quality improvement in nano-composites. These efforts will be useful for designers to quantify application payoffs and define a technology development roadmap for manufacturing nano-composites, and will help an engineering design and manufacturing nano-composites more efficiently by providing the design methodology.

Formation of Asperites on the Plate-like Alumina Particles by Molten-salt Method (Molten-salt 방법에 의해 합성되는 판상형 알루미나 분말 표면에 돌기형성 거동)

  • Lee, Yoon Joo;Kim, Bo Yeon;Shin, Dong-Geun;Kim, Soo Ryong;Kwon, Woo Teck;Kim, Younghee
    • Journal of the Korean Ceramic Society
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    • v.51 no.6
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    • pp.560-565
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    • 2014
  • Alumina nano-asperites were grown on plate-like alumina particles of which the surface had been covered with a capping agent to control the asperite formation sites on the particles. Utilized alumina source for asperite was nano sized ${\gamma}$-alumina, which was prepared by calcination of $Al(OH)_3$ at $600^{\circ}C$; silica suspension was used as the capping agent. Plate like alumina particles were covered by silica suspension and continuously heat-treated to $900^{\circ}C$ with nano sized ${\gamma}$-alumina, as the source material, under molten-salt atmosphere. Asperite growing site were controlled by the degree of coating of the capping agent; 10-20 nanosize of ${\theta}$-alumina were formed on the particle surface. On the other hand, alumina particles without capping agent were observed to undergo only step-like crystal growth during heat-treatment.

Effect of Nozzle Tip Size on the Fabrication of Nano-Sized Nickel Oxide Powder by Spray Pyrolysis Process

  • Kim, Donghee;Yu, Jaekeun
    • Korean Journal of Materials Research
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    • v.23 no.9
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    • pp.489-494
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    • 2013
  • In this study, by using nickel chloride solution as a raw material, a nano-sized nickel oxide powder with an average particle size below 50 nm was produced by spray pyrolysis reaction. A spray pyrolysis system was specially designed and built for this study. The influence of nozzle tip size on the properties of the produced powder was examined. When the nozzle tip size was 1 mm, the particle size distribution was more uniform than when other nozzle tip sizes were used and the average particle size of the powder was about 15 nm. When the nozzle tip size increases to 2 mm, the average particle size increases to roughly 20 nm, and the particle size distribution becomes more uneven. When the tip size increases to 3 mm, particles with an average size of 25 nm and equal to or less than 10 nm coexist and the particle size distribution becomes much more uneven. When the tip size increases to 5 mm, large particles with average size of 50 nm partially exist, mostly consisting of minute particles with average sizes in the range of 15~25 nm. When the tip size increases from 1 mm to 2 mm, the XRD peak intensities greatly increase while the specific surface area decreases. When the tip size increases to 3 mm, the XRD peak intensities decrease while the specific surface area increases. When the tip size increases to 5 mm, the XRD peak intensities increase again while the specific surface area decreases.

Synthesis and Microstructure of Porous Al2O3 with Nano-Sized Cu Dispersions (나노크기 Cu 분산입자를 갖는 Al2O3 다공체의 제조 및 미세조직 특성)

  • Yoo, Ho-Suk;Kim, An-Gi;Hyun, Chang-Yong
    • Korean Journal of Materials Research
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    • v.23 no.1
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    • pp.67-71
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    • 2013
  • Porous $Al_2O_3$ dispersed with nano-sized Cu was fabricated by freeze-drying process and solution chemistry method using Cu-nitrate. To prepare porous $Al_2O_3$, camphene was used as the sublimable vehicle. Camphene slurries with $Al_2O_3$ content of 10 vol% were prepared by milling at $50^{\circ}C$ with a small amount of oligomeric polyester dispersant. Freezing of the slurry was done in a Teflon cylinder attached to a copper bottom plate cooled to $-25^{\circ}C$ while unidirectionally controlling the growth direction of the camphene. Pores were subsequently generated by sublimation of the camphene during drying in air for 48 h. The green body was sintered in a furnace at $1400^{\circ}C$ for 1 h. Cu particles were dispersed in porous $Al_2O_3$ by calcination and hydrogen reduction of Cu-nitrate. The sintered samples showed large pores with sizes of about $150{\mu}m$; these pores were aligned parallel to the camphene growth direction. Also, the internal walls of the large pores had relatively small pores due to the traces of camphene left between the concentrated $Al_2O_3$ particles on the internal wall. EDS analysis revealed that the Cu particles were mainly dispersed on the surfaces of the large pores. These results strongly suggest that porous $Al_2O_3$ with Cu dispersion can be successfully fabricated by freeze-drying and solution chemistry routes.