• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1193-1194
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• 2006

The magnetic ferrite nanoparticles were synthesized and coated by silica precursor in controlling the coating thicknesses and sizeses. The surface modification was performed with amino-functionalized organic silanes on silica coated magnetic nanoparticles. The use of functionalized self-assembled magnetic ferrite nanoparticles for nucleic acid separation process give a lot of advantages rather than the conventional silica based process.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.49-55
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• 2020

In order to improve the electromagnetic shielding rate of Carbon Fiber (CF), it was produced using the nickel nano-powder impregnating method. Using two types of nickel powder having thicknesses of 50 ㎛ and 100 ㎛, and a thermoplastic elastomer resin, a compound containing 10-20% nickel content was mixed and then manufactured through an extruder. The CF coated with the compound was woven and manufactured using a 1-ply specimen. The final nickel content of the specimen was verified using TGA and the distribution of nickel powder on the CF surface was verified using SEM. The metal shows a high shielding rate in the low-frequency band, but the shielding rate decreases at higher-frequency bands. The CF improves at the higher frequency band, and metals reflect electromagnetic waves while carbon absorbs electromagnetic waves. The study of shielding materials, which are stronger and lighter than metal, by using CF lighter than metal and enabling the shielding rate from low-frequency band to high-frequency band, confirmed that the larger the area coated with nickel nano-powder, the better the electromagnetic shielding performance. In particular, CF coated with a thickness of 100 ㎛ has a shielding rate similar to that of copper and can also be used for EV/HEV automotive cables and other applications in the future.

• Journal of Powder Materials
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• v.19 no.3
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• pp.226-231
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• 2012

In this research, the coating behavior of Mg and Fe desulfurization powder fabricated by low energy and conventional planetary mill equipment was investigated as a function of milling time, which produces uniform Fe coated powders due to milling energy. Since high energy ball milling results in breaking the Fe coated Mg powders into coarse particles, low energy ball milling was considered appropriate for this study, and can be implemented in desulfurization industry widely. XRD and FE-SEM analyses were carried out to investigate the microstructure and distribution of the coating material. The thickness of the Fe coating layer reaches a maximum of 14 ${\mu}m$ at 20 milling hours. The BCC structures of Fe particles are deformed due to the slip system of Fe coated Mg particles.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.377-378
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• 2006

Thermal management technology is a critical element in all new chip generations, caused by a power multiplication combined with a size reduction. A heat sink, mounted on a base plate, requires the use of special materials possessing both high thermal conductivity (TC) and a coefficient of thermal expansion (CTE) that matches semiconductor materials as well as certain packaging ceramics. In this study, nano tungsten coated copper powder has been developed with a wide range of compositions, 90W-10Cu to 10W-90Cu. Powder technologies were used to make samples to evaluate density, TC, and CTE. Measured TC lies among theoretical values predicted by several existing models.

• Journal of Powder Materials
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• v.18 no.4
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• pp.322-326
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• 2011

Inkjet printing was successfully done using Cu nano powder ink after these Cu nano powders were dry-coated with 1-octanethiol for oxidation prevention. 1-octanethiol, which is Self-Assembled Multi-layers (SAMs), was coated approximately 10-nm thick on the surface of Cu nano powders. 1-Octanol, which has the same chain length as that for 1-octanethiol, was used as a solvent to make the ink for inkjet printing. As a result, the fabricated ink was dispersed for about 4 weeks, and after printing and heat treatment at $350^{\circ}C$ for 4 hours, the resistivity for the printed pattern was measured to be $1.15{\times}10^{-5}{\Omega}{\cdot}cm$.

• Journal of Powder Materials
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• v.12 no.6 s.53
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• pp.413-421
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• 2005

Copper is able to work as a current collector under wide range of hydrocarbon fuels without coking in Solid oxide fuel cells (SOFCs). The application of copper in SOFC is limited due to its low melting point, which result in coarsening the copper particle. This work focuses on the sintering of copper powder with ceria coating layer. Ceria-coated powder was prepared by thermal decomposition of urea in $Ce(NO_3)_3\cdot6H_2O$ solution, which containing CuO core particles. The ceria-coated powder was characterized by XRD, ICP, and SEM. The thermal stability of the ceria-coated copper in fuel atmosphere $(H_2)$ was observed by SEM. It was found that the ceria coating layer could effectively hinder the grain growth of the copper particles.

• 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.

• Journal of Powder Materials
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• v.18 no.6
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• pp.546-551
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• 2011

Ag spot-coated Cu nanopowders were synthesized by a hydrothermal-attachment method (HA) using oleic acid capped Ag hydrosol. Cu nano powders were synthesized by pulsed wire exploding method using 0.4 mm in diameter of Cu wire (purity 99.9%). Synthesized Cu nano powders are seen with comparatively spherical shape having range in 50 nm to 150 nm in diameter. The oleic acid capped Ag hydrosol was synthesized by the precipitation-redispersion method. Oleic acid capped Ag nano particles showed the narrow size distribution and their particle size were less than 20 nm in diameter. In the case of nano Ag-spot coated Cu powders, nanosized Ag particles were adhered in the copper surface by HAA method. The components of C, O and Ag were distributed on the surface of copper powder.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.221-226
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• 1998

The processing conditions for the mass production of platelet WS$_2$ lubricant powder were optimized. The mixture of tungsten and sulfur powders was sealed in a vacuum of 10$^{-3}$ torr and heat-treated at 850$\circ$C for 2 h. The internal pressure of reaction chamber was maintained at certain level by controlling the release valve automatically. The reaction product was the platelet WS$_2$ powder with an average size of 15 $\mu$m. The synthesized WS$_2$ powder was then coated on the wiper-blade of automobiles and the commercial deep-grooved ball bearing using wet and dry coating methods, respectively. High lubricity and wear resistance of wet coated wiper-blade were confirmed by the life test of 70,000 cycles. The life-time of the ball bearing assembled after WS$_2$ coating onto each part increased 50 times compared to the non-coated ball bearing.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1110-1111
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• 2006

[ $Ti_3SiC_2$ ] was coated with $Al_2O_3$, MgO and $SiO_2$ respectively by sol-gel method and cured at 900 and $1200^{\circ}C$. The coated oxides did not react with $Ti_3SiC_2$ at $900^{\circ}C$ but reacted with it to form $TiC_x$ at $1200^{\circ}C$. The specimen coated with $SiO_2$ at $900^{\circ}C$ formed a dense protecting layer and showed the best oxidation resistance at $800^{\circ}C$ in air. However, the dense protecting layers did not form in $Al_2O_3$ and MgO coated specimens cured even at $900^{\circ}C$. MgO coated specimen showed the worst improvement in the oxidation resistance because the reactivity of MgO with $Ti_3SiC_2$ was highest. On the other hand, the electrical conductivities were measured in MgO and $Al_2O_3$ coated specimens to have TiCx but could not be measured in the $SiO_2$ coated ones because of the nonconductive dense protected layers.