• Korean Journal of Materials Research
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• v.17 no.7
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• pp.382-385
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• 2007

[ $LaFeO_3$ ] powders were prepared as the oxidation catalyst materials to reduce the emission of particulate matters from diesel engine and their catalytic effects on the oxidation of carbon were investigated. Solution combustion method was employed for the powder synthesis, which uses highly exothermic and selfsustaining reactions. In this study $LaFeO_3$ powders were synthesized at $400^{\circ}C$ as varying the ratio ($\Phi$) of fuel (citric acid) and oxidizer (metal nitrate), and their phase and carbon ignition property were examined. As $\Phi$ decreases, the crystallinity of synthesized $LaFeO_3$ powders enhanced. By calcining at $700^{\circ}C$, all the powders synthesized at various $\Phi$ fully crystallized. The calcined $LaFeO_3$ powders showed carbon ignition temperature as low as $501{\sim}530^{\circ}C$, which implied the decrease of the ignition temperature by $120{\sim}150^{\circ}C$.

• Journal of Welding and Joining
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• v.17 no.5
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• pp.107-115
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• 1999

The objective of this research was to study the formation of the thick hardened layer with the addition of metal powder(Cu) and ceramics powders(TiC) on the aluminum 5083 alloys by plasma transferred arc process(PTA process) and to characterize the effect of overlaying conditions on the overlaid layer formation. This was followed by investigating the microstructures of the overlaid layers and mechanical properties such as hardness and wear resistance. The overlaid layer containing copper powder was alloyed and intermetallic compound($CuAl_2$) was formed. The overlaid layers with high melting point TiC powders, however, did not react with base metal. Wear resistance of the alloyed layer was remarkably improved by the formation of $CuAl_2$, precipitate phase, which prevented wear of base aluminum alloys and at higher wear speed, accelerated sliding of the counter part. Wear resistance of the composite layer was also remarkably improved because TiC powder act as a load barring element and Fe debris fragments detached from the counter part act as a solid lubricant on the contact surface.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.18-24
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• 2004

Ni-Zn ferrite powder was synthesized from metal nitrates, Fe(N $O_3$)$_3$$.$9 $H_2$O, Ni(N $O_3$)$_2$$.$6 $H_2$O, Zn(N $O_3$)$_2$$.$6 $H_2$O by wet direct process to make high permeability material. The composition of the ferrite powder is (N $i_{0.284}$F $e_{0.053}$Z $n_{0.663}$)F $e_2$ $O_4$. Ni-Zn ferrite powder is compounded by precipitating metal nitrates with NaOH in vessel at 90$^{\circ}C$ synthetic temperature for 8 hours. Calcination temperature and sintering temperature were 700$^{\circ}C$ and 1150$^{\circ}C$-1250$^{\circ}C$ respectively for 2 hours. The same compound powder was extracted from metal oxide by wet ballmilling. We compared the properties of powder and the electromagnetic characteristics of the sintered cores obtained from the two different processes. Wet direct process produces smaller particle size with narrower distribution and higher purified ferrite which cores has high permeability and high magnetization.

• Korean Journal of Materials Research
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• v.14 no.4
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• pp.293-299
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• 2004

Transition metal ions doped $TiO_2$ nanostructured powders were prepared with simply heating aqueous $TiOCl_2$ solutions, contained various metal ions (Ni, Al, Fe, Zr, and Nb) of 1.47 mol% added as metal-chlorides, at $100^{\circ}C$ for 4 hrs by homogeneous precipitation process under suppressing conditions of water vaporization. The characterizations for prepared $TiO_2$ powders were carried out to observe doping of metal ions, their concentrations and microstructures using XRD, UV-VIS (DRS), XPS, SEM, TEM and ICP. Also, photo-oxidative abilities were evaluated by decomposition of 4-chlorophenol (4CP) under ultraviolet light irradiations. No secondary oxide phases were formed in all the $VTiO_2$ powders, showing doping with various transition metal ions. When adding ions ($Ni^{2+}$ or$ Al^{3+ }$ and $Zr^{4+}$ ) having valance states or ionic radii greatly different from those of $Ti^{4+}$ , the $TiO_2$ powders of mixed anatase and rutile phases were formed, whereas in the case of additions of $^Fe{3+ }$ and $Nb^{ 5+}$ as well as no addition of metal ion the powders with pure rutile phase alone were formed. Among the prepared $TiO_2$ powders, Ni$^{2+}$ doped $TiO_2$ powders, containing a small amount of anatase phase, showed excellent photo-oxidative ability in 4CP decomposition because of relative decreases in electron-hole recombination and poisoning of $TiO_2$ surface during the photoreaction.n.

• Particle and aerosol research
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• v.6 no.1
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• pp.29-35
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• 2010

Transition metals such as V, Fe, and Ni were used to synthesize doped zinc oxide nanoparticles from mixed liquid precursors by using the flame spray pyrolysis (FSP). The effects of dopants on the powder properties such as morphology, specific surface area, crystal structure, and light adsorption were analyzed by TEM, BET, XRD, and UV-Vis diffuse reflection spectrum (DRS), respectively. The results showed that hexagonal wurtzite structured ZnO:M (M = V, Fe, Ni) nanoparticles were successfully synthesized by the FSP. The transition metal-doping resulted in the decrease in its particle size and crystallite size. The UV-vis absorption spectra of ZnO:M nanoparticles were also red-shifted. ZnO:V showed the highest MB degradation of 99.4% under the UV irradiation after 3 hrs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.278-283
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• 2019

3 kinds of fine powder, Fe-2%Ni alloy powder(N Ltd.) and Fe+2%Ni mixed powder(B Ltd. and S Ltd.), were fabricated into sintered compacts of bending strength specimens and ring type specimens by metal injection molding, debinding and controlling sintering conditions (reduction and sintering atmospheres, sintering temperature, sintering time and cooling rates). Density and magnetic properties of the sintered compacts were evaluated with the following conclusions. (1) When each compact was hold at 1123K for 3.6ks in H2 and sintered at 1623K for 14.4ks in Ar, the density of N, B and S Ltd.'s sintered compacts were measured as 96, 99 and 99%, and oxygen/carbon contents were measured as 0.0041%O/0.0006%C, 0.0027%O/0.0022%C, and 0.160%O/0.0026%C, respectively. (2) Magnetic characteristics of B Ltd. compact in Ar with the best results showed $B_{25}=14.3KG$, $B_r=7.75KG$, and $H_c=2.1Oe$, but not enough as those made by melting process. (3) Magnetic properties of B Ltd. compact which were sintered at 1673K for 14.4ks in Ar gas, and cooled at $0.83Ks^{-1}$ to 1123K and then cooled at $0.083Ks^{-1}$ down to room temperature were measured as $B_{25}=14.8KG$, $B_r=8.3KG$, and $H_c=1.3Oe$, almost similar to those made by melting process. Objected soft magnetic materials properties were obtained through sintering process by controlling sintering conditions (reduction condition, sintering atmosphere, sintering temperature and sintering time) and cooling rates.

• Transactions of Materials Processing
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• v.32 no.2
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• pp.67-73
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• 2023

To overcome a climate change, manufacturing complex-shaped electric mobility parts becomes one of the important issues for enhancing a performance of motor with reducing their weight. Therefore, development of laser-based additive manufacturing shed on light due to their flexible manufacturing capacity that can be suitable to solve the poor formability of Fe-Si alloys for electric mobility parts. Although there are several studies existed to optimize the performance of additively manufactured Fe-Si alloys, the post-annealing effect was not well investigated yet though this is important to control the texture and mechanical properties of additively manufactured parts. In the present work, annealing effect on the mechanical property and microstructure of additively manufactured Fe-4.5Si alloy was investigated. Because of the ordered phase initiation after annealing, the hardness of additively manufactured Fe-4.5Si alloy increased up to 1173 K while a hardness drop occurs at the 1273 K condition due to the micro-crack initiation. The response surface methodology result represents the 1173 K-5 h sample is an optimal condition to maximize the mechanical property of additively manufactured alloy without micro-cracks.

• Journal of the Korean Society of Safety
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• v.20 no.4 s.72
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• pp.34-39
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• 2005

To evaluate characteristics of explosion hazard of Methyl Ethyl Ketone Peroxide, MCPVT was used for this study. In result maximum explosion pressure and maximum explosion pressure rising velocity of MEK-PO were $12.1kgf/cm^2\;and\;106.81kgf/cm^2/s$. As a result or adding metal powder to estimate hazard of explosion, the maximum explosion pressure and maximum explosion pressure rising velocity according to adding Fe powder in MEK-PO increased. In opposite, those decreased resulting in adding Ca powder in MEK-PO.

• Journal of the Korean Chemical Society
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• v.53 no.4
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• pp.407-414
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• 2009

The solid complexes of Cu(II), Ni(II), Co(II), Mn(II) and Fe(III) with 4-hydroxy-3-(1-{2-(2-hydroxybenzylidene)- amino phenylimino}-ethyl)-6-methy-pyran-2-one (H2L) derived from o-phenylenediamine, 3-acetyl- 6-methyl-(2H) pyran, 2,4 (3H)-dione (dehydroacetic acid or DHA) and salicylic aldehyde have been synthesized and characterized by elemental analysis, conductometry, magnetic susceptibility, UV-visible, IR, $^1H$-NMR spectra, X-ray diffraction, thermal analysis, and screened for antimicrobial activity. The IR spectral data suggest that the ligand behaves as a dibasic tetradentate ligand with ONNO donor atoms sequence towards central metal ion. From the microanalytical data, the stoichiometry of the complexes has been found to be 1:1 (metal: ligand). The physico-chemical data suggests square planar geometry for Cu(II) and Ni(II) complexes and octahedral geometry for Co(II), Mn(II) and Fe(III) complexes. The x-ray differaction data suggests orthorhombic crystal system for Cu(II) complex, monoclinic crystal system for Ni(II), Co(II) and Fe(III) and tetragonal crystal system for Mn(II) complex. Thermal behaviour (TG/DTA) of the complexes was studied and kinetic parameters were determined by Coats-Redfern method. The ligand and their metal complexes were screened for antibacterial activity against Staphylococcus aureus and Escherichia coli and fungicidal activity against Aspergillus Niger and Trichoderma.

• 연구논문집
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• s.29
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• pp.141-149
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• 1999

Brazing of Fe-Cr-Al alloy was carried out at $1200^{\circ}C$ in vacuum furnace using nickel-based filler metals : BNi-5 powder(Ni-Cr-Si-Fe base alloy} and MBF-50 foil (Ni-Cr-Si-B). The effect of boron content on the stability of oxide scale on the brazed joint was investigated by means of cyclic oxidation test performed at $1050^{\circ}C$ and $1200^{\circ}C$. Apparently, the joints brazed with MBF-50 containing boron showed relatively stable oxidation rates compared to boron-free BNi-5 at both temperatures. However, it was considered that the slower weight loss of MBF-50 brazed specimen wasn’t resulted from the low oxidation rate but from the spallation of oxide layer. The oxide layer consisted of thick spinel oxide on the surface and $Al_2 O_3$ internal oxide layer along the interface between mother alloy and braze, the mother alloy was also eroded seriously by the formation of spinel oxides such as $FeCr_2 O_4$ and $NiCr_2 O_4$ on the surface, likely to be induced by the change of oxide forming mechanism due to diffusion of boron from the braze. On the contrary, the joint brazed with BNi-5 showed the good oxidation resistance during the cyclic oxidation test. It seems that the oxidation can be retarded by the formation of stable $Al_2 O_3$ layer at the surface.