• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.1140-1142
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• 1993

It has been prepared by a coprecipitation method for Ferroxplana $Ni_2Y\;(Ba_2Ni_2Fe_{12}O_{22}$ magnetic particles, which is one of the Hexagonal ferrite. The coprecipitates were synthesized by adding aqueous solution of $BaCl_2{\cdot}2H_2O,\;NiCl_2{\cdot}6H_2O\;and\;FeCl_2{\cdot}4H_2O$ (of which the mole ratio is $Ba^{2+}:Ni^{2+}:Fe^{2+}$=1:1:6) to a mixture of NaOH and $Na_2CO_3$ solution. The shape of Ferroxplana $Ni_2Y$ magnetic particles obtained at the calcined temperature 1,100($^{\circ}C$) was hexagonal plate-like, average particle size was 2(${\mu}m$), and aspect ratio was more than 7.

• Korean Journal of Materials Research
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• v.14 no.11
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• pp.813-820
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• 2004

The electrolytic reduction of spent oxide fuel involves the liberation of oxygen in a molten LiCl electrolyte, which is a chemically aggressive environment that is very corrosive for typical structural materials. So, it is essential to choose the optimum material for the process equipment handling molten salt. In this study, corrosion behavior of Haynes 263, 75, and Inconel X-750, 718 in molten salt of $LiCl-Li_{2}O$ under oxidation atmosphere was investigated at $650^{\circ}C\;for\;72\sim360$ hours. At $3\;wt\%\;of\;Li_{2}O$, Haynes 263 alloy showed the highest corrosion resistance among the examined alloys, and up to $8\;wt\%\;of\;Li_{2}O$, Haynes 75 exhibited the highest corrosion resistance. Corrosion products were formed $Li(Ni,Co)O_2,\;LiNiO_2\;and\;LiTiO_2\;and\;Cr_{2}O_3$ on Haynes 263, $Cr_{2}O_3,\;NiFe_{2}O_4,\;LiNiO_2,\;Li_{2}NiFe_{2}O_4,\;Li_{2}Ni_{8}O_10$ and Ni on Haynes 75, $Cr_{2}O_3,\;(Al,Nb,Ti)O_2,\;NiFe_{2}O_4,\;and\;Li_{2}NiFe_{2}O_4$ on Inconel X-750 and $Cr_{2}O_3,\;NiFe_{2}O_4\;and\;CrNbO_4$ on Inconel 718, respectively. Haynes 263 showed local corrosion behavior and Haynes 75, Inconel X-750, 718 showed uniform corrosion behavior.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.10
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• pp.873-877
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• 2007

In order to apply a complex multilayer chip LC filter, this study has estimated the interfacial reaction and coupling properties of dielectric materials $Pb(Fe_{1/2}Nb_{1/2})O_3$ and Ni-Zn-Cu ferrite materials through low-temperature co-sintering (LTCS). PFN powders were fabricated using double calcinated at $700^{\circ}C$ and then $850^{\circ}C$. While the perovskite phase rate was found to be 91 %, after heat treatment at $900^{\circ}C$ for 6h, the perovskite phase rate and density exhibited a value of 100 % and 7.46$g/cm^3$, respectively. The PFN/Ni-Zn-Cu ferrite, PFN/CUO (or $Pb_2Fe_2O_5$) and ferrite/CuO (or $Pb_2Fe_2O_5$) were mechanically coupled through interfacial reactions after the specimen was co-sintered at $900^{\circ}C$ for 6 h. No intermediate layer exists for the mutual coupling reaction. This result indicates the possibility of low-temperature co-sintering without any interfacial reaction layer for a multilayer chip LC filter.

• Journal of Powder Materials
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• v.29 no.2
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• pp.132-151
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• 2022

The CoCrFeMnNi high-entropy alloy (HEA), which is the most widely known HEA with a single face-centered cubic structure, has attracted significant academic attention over the past decade owing to its outstanding multifunctional performance. Recent studies have suggested that CoCrFeMnNi-type HEAs exhibit excellent printability for selective laser melting (SLM) under a wide range of process conditions. Moreover, it has been suggested that SLM can not only provide great topological freedom of design but also exhibit excellent mechanical properties by overcoming the strength-ductility trade-off via producing a hierarchical heterogeneous microstructure. In this regard, the SLM-processed CoCrFeMnNi HEA has been extensively studied to comprehensively understand the mechanisms of microstructural evolution and resulting changes in mechanical properties. In this review, recent studies on CoCrFeMnNi-type HEAs produced using SLM are discussed with respect to process-induced microstructural evolution and the relationship between hierarchical heterogeneous microstructure and mechanical properties.

• Journal of Magnetics
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• v.15 no.4
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• pp.159-164
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• 2010

The Zn, Co and Ni substituted manganese ferrite powders, $Mn_{1-x}$(Zn, Co, Ni)$_xFe_2O_4$, were fabricated by the solgel method, and their crystallographic and magnetic properties were studied. The Zn substituted manganese ferrite, $Zn_{0.2}Mn_{0.8}Fe_2O_4$, had a single spinel structure above $400^{\circ}C$, and the size of the particles of the ferrite powder increased when the annealing temperature was increased. Above $500^{\circ}C$, all the $Mn_{1-x}$(Zn, Co, Ni)$_xFe_2O_4$ ferrite had a single spinel structure and the lattice constants decreased with an increasing substitution of Zn, Co, and Ni in $Mn_{1-x}$(Zn, Co, Ni)$_xFe_2O_4$. The Mossbauer spectra of $Mn_{1-x}Zn_xFe_2O_4$ (0.0$\leq$x$\leq$0.4) could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. For x = 0.6 and 0.8 they showed two Zeeman sextets and a single quadrupole doublet, which indicated they were ferrimagnetic and paramagnetic. And for x = 1.0 spectrum showed a doublet due to a paramagnetic phase. For the Co and Ni substituted manganese ferrite powders, all the Mossbauer spectra could be fitted as the superposition of two Zeeman sextets due to the tetrahedral and octahedral sites of the $Fe^{3+}$ ions. The variation of the Mossbauer parameters are also discussed with substituted Zn, Co and Ni ions. The increment of the saturation magnetization up to x = 0.6 in $Mn_{1-x}Co_xFe_2O_4$ could be qualitatively explained using the site distribution and the spin magnetic moment of substituted ions. The saturation magnetization and coercivity of the $Mn_{1-x}$(Zn, Co, Ni)$_xFe_2O_4$ (x = 0.4) ferrite powders were also compared with pure $MnFe_2O_4$.

• Journal of Powder Materials
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• v.6 no.4
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• pp.294-300
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• 1999

This study was carried out to investigate the possibility whether Metal Injection Molding (MIM) process could be applied to 95wt.%W-3.5wt.%Ni-1.5wt.%Fe heavy alloy in order to obtain an intricate shape. Methylcellulose was used in the injection molding for binder. $FeCl_2-4H_2O$ was added in solvent substituting Fe powder and $FeCl_2$ was doped on W-Ni premixed powder. When $FeCl_2-4H_2O$ was added in solvent, the binder separation occurred for injection molding so that the matrix content was changed. Such problem was solved when $FeCl_2$ was doped. In this study. the debinding process did not affect residual carbon content. The sintered microsouctures as addition methods of Fe element and the sintering temperature from $1420^{\circ}C$ to $1470^{\circ}C$, which are around the temperature of liquid phase formation, were observed.

• Clean Technology
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• v.21 no.1
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• pp.39-44
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• 2015

This study investigated the effects of six metal oxide nanoparticles (NPs: CuO, NiO, TiO₂, Fe₂O₃, Co₃O₄, ZnO) on seed germination and germination index (G.I) for five types of seeds: Brassica napus L., Malva verticillata L., Brassica olercea L., Brassica campestris L., Daucus carota L. NPs of CuO, ZnO, NiO show significant toxicity impacts on seed activities [CuO (6-27 mg/L), ZnO (16-86 mg/L), NiO (48-112 mg/L)], while no significant effects were observed at > 1000 mg/L of TiO₂, Fe₂O₃, Co₃O₄. Tested five types of seed showed different sensitivities on seed germination and root activity, especially on NPs of CuO, ZnO, NiO. Malva verticillata L. seed was highly sensitive to toxic metal oxide NPs and showed following EC₅₀s : CuO 5.5 mg/L, ZnO 16.4 mg/L, NiO 53.4 mg/L. Mostly following order of toxicity was observed, CuO > ZnO > NiO > Fe₂O₃ ≈ Co₃O₄ ≈ TiO₂, where slightly different toxicity order was observed for carrot, showing CuO > NiO ≈ ZnO > Fe₂O₃ ≈ Co₃O₄ ≈ TiO₂.

• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.156-161
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• 1998

We have measured changes of the non-stoichiometry, $\Delta\delta$, in Fe-doped nicked oxide , by thermogravimetry for four iron fractions, x=0.01, 0.031, 0.057 and 0.10, and three temperatures, T=1273, 1373 and 1473 K. The obtained data can be modelled by a defect structure in which substitutional trivalent iron ions, FeNi, are compensated by cation vacancies, $V_{Ni}$", and (4:1)-clusters. These clusters consist of tetravalent interstitial iron, $Fe_i\;^4$

• Journal of Magnetics
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• v.9 no.4
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• pp.121-124
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• 2004

NiO thickness dependences of perpendicular magnetic anisotropy (PMA) in the $NiO/[CoFe/Pt]_5$ multilayers for exchange biasing and $[CoFe/Pt]_4/Pt/[CoFe/Pt]_4$ for interlayer exchange coupling were investigated. Perpendicular magnetization curve was obtained by out-of-plane extraordinary Hall measurement. Magnetic force microscopy (MFM) has been used for the investigation of magnetic domains on thin films. We confirmed that the interlayer exchange coupling (IEC) as a function of NiO thickness at room temperature existed with a period of two monolayers.

• Korean Journal of Environment and Ecology
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• v.12 no.3
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• pp.271-278
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• 1998

Heavy metal concentrations in rocks and soils from serpentinite(SP) and in plants (Pinus densiflora: PD and Pinus rigida: PR) were examined at Baekdong mine in Hongsung, Chungnam. Parent rocks were compared with amphibole schist(AS) and gneiss(GN) and plants divided the above grounds and roots were examined, respectively. In rocks, Ni, Cr, Co, Fe concentrations in SP were higher than those in AS and GN. The concentrations of top soils had the similar differences to their rocks; especially Ni, Cr, Co, Fe concentrations were the highest in SP, Zn and Sc concentrations, however, were the highest in AS. Average Ni, Cr, Co, Au, As, Sb, W concentrations of PD were the highest in SP and especially Ni, Cr, Co concentrations were accorded with changes of rocks and top soils. Zn and Sc concentrations in AS were higher and Fe and Mo concentrations in GN were higher than those in SP. Compared with two plants in the same serpentinite sites, most elements of PR were higher than those of PD. Therefore, these suggested PR absorbed much heavy metal than PD. Most element concentrations of roots in two plants and three rocks were higher than those of the above ground. Relative ratios (average plant concentration/soil concentration) of Ni, Cr, Co, Zn, Sc, Fe in AS and GN were higher than those of SP. Especially, relative ratios of most elements except Zn in GN were the highest.