• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.172-176
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• 2005

Four nano-sized Fe-nano particle samples synthesized by Chemical Vapor Condensation (CVC) were analyzed using $M\ddot{o}ssbauer$ spectroscopy, XRD, BET and TEM. The samples were consisted as functions of carrier gas and decomposition temperature. The synthesized nanoparticles consisted of two- or three-layers with the circular shape. The average particle size was increased with increasing the decomposition temperature. At $500^{\circ}C$ for the decomposition temperature, $Fe_3C$ was formed more under the environment of CO carrier gas than that of $CH_4$. However, at $1,100^{\circ}C$, almost of Fe-nano particles were transformed into $Fe_3C$ with using both carrier gas.

• Journal of Powder Materials
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• v.14 no.2 s.61
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• pp.116-122
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• 2007

It is well known that thermal plasma process has lots of advantages such as high temperature and good quality for synthesis of nano particles. In this research, we attempt the synthesis of nano unitary and composite powder (Ag, Mg-Al, Zr-V-Fe) using transferred thermal plasma. Nano particles of metal alloy, ranging from 20 nm to 150 nm, have been synthesized by this process.

• Journal of Surface Science and Engineering
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• v.50 no.3
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• pp.212-218
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• 2017

$Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrite powders were prepared by self-propagating high temperature synthesis followed by classifying with an ultrasonic wet-magnetic separation unit to get high pure nano-sized particles. The $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ ferrites were well formed by using several powders like iron, nickel oxide, zinc oxide and magnesium oxide at 0.1 MPa of oxygen pressure. The ultrasonic wet-magnetic separation of pre-mechanical milled ferrite powders resulted in producing the powders with average size of 800 nm. The addition of a surfactant during the wet-magnetic separation process improved productivity more than twice. The coercive force, maximum magnetization and residual magnetization of the $Mg_xNi_yZn_{1-x-y}Fe_2O_4$ nano-powders with 800 nm size were 3651 A/m, $53.92Am^2/kg$ and $4.0Am^2/kg$, respectively.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.95.1-95.1
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• 2000

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.11a
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• pp.144-144
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• 2002

• Advances in environmental research
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• v.5 no.1
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• pp.1-18
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• 2016

Magnetic nano-based sorbents have been synthesized for the recovery of two rare earth elements (REE: Nd(III) and Yb(III)). The magnetic nano-based particles are synthesized by a one-pot hydrothermal procedure involving co-precipitation under thermal conditions of Fe(III) and Fe(II) salts in the presence of chitosan. The composite magnetic/chitosan material is crosslinked with epichlorohydrin and modified by grafting alanine and serine amine-acids. These materials are tested for the binding of Nd(III) (light REE) and Yb(III) (heavy REE) through the study of pH effect, sorption isotherms, uptake kinetics, metal desorption and sorbent recycling. Sorption isotherms are well fitted by the Langmuir equation: the maximum sorption capacities range between 9 and 18 mg REE $g^{-1}$ (at pH 5). The sorption mechanism is endothermic (positive value of ${\Delta}H^{\circ}$) and contributes to increase the randomness of the system (positive value of ${\Delta}S^{\circ}$). The fast uptake kinetics can be described by the pseudo-second order rate equation: the equilibrium is reached within 4 hours of contact. The sub-micron size of sorbent particles strongly reduces the contribution of resistance to intraparticle diffusion in the control of uptake kinetics. Metal desorption using acidified thiourea solutions allows maintaining sorption efficiency for at least four successive cycles with limited loss in sorption capacity.

• Korean Journal of Materials Research
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• v.29 no.4
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• pp.221-227
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• 2019

This study examines the role of the nano- and micro-particle ratio in dispersion stability and mechanical properties of composite resins for SLA(stereolithography) 3D printing technology. VTES(vinyltriethoxysilane)-coated $ZrO_2$ ceramic particles with different nano- and micro-particle ratios are prepared by a hydrolysis and condensation reaction and then dispersed in commercial photopolymer (High-temp) based on interpenetrating networks(IPNs). The coating characteristics of VTES-coated $ZrO_2$ particles are observed by FE-TEM and FT-IR. The rheological properties of VTES-coated $ZrO_2/High-temp$ composite solution with different particle ratios are investigated by rheometer, and the dispersion properties of the composite solution are confirmed by relaxation NMR and Turbiscan. The mechanical properties of 3D-printed objects are measured by a tensile test and nanoindenter. To investigate the aggregation and dispersion properties of VTES-coated $ZrO_2$ ceramic particles with different particle ratios, we observe the cross-sectional images of 3D printed objects using FE-SEM. The 3D printed objects of the composite solution with nano-particles of 80 % demonstrate improved mechanical characteristics.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.155.2-155.2
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• 2014

Plasma Enhanced Atomic Layer Deposition(PEALD)와 Atomic Layer Deposition(ALD) Techniques는 '정확한 두께 조절' 및 '우수한 균일도'를 가지는 신뢰할 수 있는 진공 기술이다. 본 연구에서는 다공성 구조를 가지는 기판을 대상으로 PEALD와 ALD Techniques을 이용한 $Al_2O_3$ 형성 공정의 증착 특성을 비교하였다. 각 공정은 공통적으로 Tris-Methyl-Aluminium(TMA)을 첫번째 전구체로 사용하였고 purge gas로는 Nitrogen를 사용하였다. 그리고 두번째 전구체로 PEALD 공정에서는 Oxygen Plasma를 사용하였고 ALD 공정에서는 Water를 사용하였다. 복잡한 다공성 구조를 가지는 기판은 $TiO_2$ Nano-Particle paste과 colloidal Silver paste를 소결시켜 제작하여 사용하였다. 각 공정의 차이점을 비교하기 위해서 배기단에 Capacitor Diaphram Gauge(CDG)와 Residual Gas Analyzer(RGA)를 통해서 압력과 잔류 가스를 모니터하였다. 그리고 각 공정을 통해서 porous한 Nano-Particles Network에 형성된 $Al_2O_3$막의 특성을 비교하기 위해서 FE-SEM과 EDX를 통해서 관찰하였다. 또한 좀 더 자세한 비교 분석을 위해서 $Al_2O_3$ 막이 형성된 porous한 Nano-Particles Networks의 각 각의 particles들을 분산시켜 TEM과 AFM를 통해서 관찰하였다. 나아가 전기적 물성의 차이점을 비교하기 위해서 IV 및 CV를 측정하였다. 위의 일련의 비교 실험을 통해서 'PEALD과 ALD을 이용한 다공성 기판의 증착 특성'에 대하여 고찰하였다.

• Journal of Powder Materials
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• v.13 no.4 s.57
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• pp.285-289
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• 2006

Co-Fe-Ni-B-Si-Cr based amorphous strips containing nitrogen were manufactured via melt spinning, and then devitrified by crystallization treatment at the various annealing temperatures of $300^{\circ}C{\sim}540^{\circ}C$ for up to 30 minutes in an inert gas $(N_2)$ atmosphere. The microstructures were examined by using XRD and TEM and the magnetic properties were measured by using VSM and B-H meter. Among the alloys, the amorphous ribbons of $Co_{72.6}Fe_{9.8}Ni_{5.5}B_{2.4}Si_{7.1}Cr_{2.6}$ containing 121 ppm of nitrogen showed relatively high saturation magnetization. The alloy ribbons crystallized at $540^{\circ}C$ showed that the grain size of $Co_{72.6}Fe_{9.8}Ni_{5.5}B_{2.4}Si_{7.1}Cr_{2.6}$ alloy containing 121 ppm of nitrogen was about f nm, which exhibited paramagnetic behavior. The formation of nano-grain structure was attributed to the finely dispersed Fe4N particles and the solid-solutionized nitrogen atoms in the matrix. Accordingly, it can be concluded that the nano-grain structure of 5nm in size could reduce the core loss within the normally applied magnetic field of 300A/m at 10kHz.

• Bulletin of the Korean Chemical Society
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• v.26 no.2
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• pp.281-284
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• 2005

The Fe/MgO catalysts with different Fe loadings (1, 4, 6, 15 and 30 wt% Fe) were prepared by a wet impregnation with iron nitrate as precursor. All of the catalysts were characterized by BET surface analyzer, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and X-ray photoelectron spectroscopy (XPS). The maximum removal capacity of $H_2S$ was obtained with 15 wt% Fe/MgO catalyst which had the highest BET surface area among the measured catalysts. XRD of Fe/MgO catalysts showed that well dispersed Fe particles could be present on Fe/MgO with Fe loadings below 15 wt%. The crystallites of bulk $\alpha$-$Fe_2O_3$ became evident on 30 wt% Fe/MgO, which were confirmed by XRD. TPR profiles showed that the reducibility of Fe/MgO was strongly related to the loaded amounts of Fe on MgO support. Therefore, the highest removal efficiency of $H_2S$ in wet oxidation could be ascribed to a good dispersion and high reducibility of Fe/MgO catalyst. XPS studies indicated that the $H_2S$ oxidation with Fe/MgO could proceed via the redox mechanism ($Fe^{3+}\;{\leftrightarrow}\;Fe^{2+}$).