• Korean Journal of Materials Research
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• v.16 no.11
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• pp.681-686
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• 2006

Plasma nitrocarburising and plasma post oxidation were performed to improve the wear and corrosion resistance of S45C and SCM440 steel by a plasma ion nitriding system. Plasma nitrocarburizing was conducted for 3h at $570^{\circ}C$ in the nitrogen, hydrogen and methane atmosphere to produce the ${\varepsilon}-Fe_{2-3}$(N, C) phase. Plasma post oxidation was performed on the nitrocarburized samples with various oxygen/hydrogen ratio at constant temperature of $500^{\circ}C$ for 1 hour. The very thin magnetite ($Fe_3O_4$) layer $1-2{\mu}m$ in thickness on top of the $15{\sim}25{\mu}m$ ${\varepsilon}-Fe_{2-3}$(N, C) compound layer was obtained by plasma post oxidation. A salt spray test and electrochemical testing revealed that in the tested 5% NaCl solution, the corrosion characteristics of the nitrocarburized compound layer could be further improved by the application of the superficial magnetite layer. Throttle valve shafts were treated under optimum plasma processing conditions. Accelerated life time test results, using throttle body assembled with shaft treated by plasma nitrocarburising and post oxidation, showed that plasma nitrocarburizing and plasma post oxidation processes could be a viable technology in the very near future which can replace $Cr^{6+}$ plating.

• Proceedings of the Korean Magnestics Society Conference
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• 2017.05a
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• pp.211-211
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• 2017

• Proceedings of the Korean Magnestics Society Conference
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• 2016.05a
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• pp.158-158
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• 2016

• Proceedings of the Korean Magnestics Society Conference
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• 2016.11a
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• pp.156-156
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• 2016

• Journal of the Korean Magnetics Society
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• v.10 no.2
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• pp.49-52
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• 2000

The changes of magnetic properties in neutron irradiated F $e_{81}$ $B_{13.5}$S $i_{3.5}$ $C_2$ amorphous ribbon were studied by X-ray diffraction, hysteresis loop, temperature dependence of magnetization and complex permeability. The fluences of thermal ( $n_{th}$) and fast ( $n_{f}$) neutron were 6.95$\times$10$^{18}$ $n_{th}$ c $m^{-2}$ and 4.56$\times$10$^{16}$ $n_{f}$c $m^{-2}$ , respectively. The changes of XRD Profiles were not observable at the neutron irradiated sample. The complex permeability spectra showed that the permeability from domain wall motion decreased due to the increase of pinning force against domain motion by the neutron irradiation, and the relaxation frequency of rotational magnetization moved to higher frequency region. The measurement of hysteresis loop showed the increase of magnetic softness, related to rotational magnetization, but saturation magnetization was decreased in neutron irradiation sample. The Curie temperature was decreased in the neutron irradiated sample.e.e.e.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.186-195
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• 2016

We investigated phytoplankton and vertical inorganic nutrients at two stations around water of Ulleungdo and Dokdo in the East Sea, Korea. Nutrient addition experiments (+N, +P, +NP and +Fe) were also conducted to determine the growth response and nutrient consumption of the phytoplankton assemblage using the surface water of St. UD3 and St.50. In the field, although inorganic nutrients were low in the euphotic layer, these nutrients were increased at depths below 100 m. The total phytoplankton abundances in St. UD3 and St.50 were $4.9{\times}10^5cells\;L^{-1}$ and $1.9{\times}10^5cells\;L^{-1}$, respectively. The dominant species at St. UD3 was observed to be Raphidophyta Heterosigma akashiwo, Cryptophyta Crytomonas spp., and diatom Leptocylindrus danicus, while L. danicus and H. akashiwo including small diatom species Chaetoceros socialis were dominant at St. 50. In the nutrient addition experiments, phytoplankton growth (in vivo flourescence) in the +N and +NP treatment was 2-3 times higher than that in the +P treatment, indicating that the natural phytoplankton can respond to pulsed nutrient loading events. In addition, in vivo fluorescence in +Fe treatment was not statistically (p>0.05) different from that of the non-Fe treatments, indicating that the phytoplankton growth response in +Fe treatment was not significant. Dominant H akashiwo and L. danicus in the field showed a rapid response in nutrient additional bio-algal assay, particularly L. danicus in the +Fe treatments.

• Journal of the Korean Magnetics Society
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• v.10 no.1
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• pp.16-21
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• 2000

Magnetic properties and crystallographic properties of $Cu_{0.95}Ge_{0.95}Fe_{0.1}O_3$ were studied by using x-ray diffraction, superconducting quantum interference device (SQUID) and Mossbauer spectroscopy. Our sample has orthorhombic structure and the lattice constants are a = 4.795 $\AA$, b = 8.472 $\AA$, c = 2.932 $\AA$. The spin-Peierls (SP) transition temperatures of our sample is 13 K. The Mossbauer spectra consisted with two Zeeman sextets and one doublet due to $Fe^{3+}$ions. The Zeeman sextets come from tetrahedral $Fe^{3+}$ions and the doublets come from octahedral $Fe^{3+}$ions. The jump up of magnetic hyperfine field of 2nd Zeeman sextet and the increasing of the values of quadrupole splitting and isomer shift of doublet below SP transition temperature could be interpreted related with the atomic displacements. The N el temperature is 715 K, the Debye temperature are 540 K for octahedral site and 380 K for tetrahedral site, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.120-123
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• 1997

In this paper, we deal with the effect on magnetic properties when Nd is added to Sr ferrite bonded magnet. First, we choose SrO$_{n}$.Fe$_2$O$_3$(n=5.9), which is nonstoichiomatric composition, as specimen ferrite. Then, we add 5wt% polyvinyl alcohol and calcinate at 12$25^{\circ}C$ under $N_2$ environment for carbon coating on chemical compound specimen. After that we obtain 1.2${\mu}{\textrm}{m}$ single domain powder through grinding process for 18 hours. The single domain Sr ferrite Powder is well mixed with silage coupling and calcium stearate of 1wt% Then, it is kneaded by using polyamide12 as a binder and is pelleted. After adding Nd-Fe-B powder to the pelleted specimen, we injection-mould it under magnetic field by using anisotropic mould. Especially, when we add l3wt% Nd-Fe-B powder to the polyamide12, we obtain excellent magnetic propertiecs which are $_{B}$H$_{C}$=2.65KOe, Br=3.16KG and (BH)$_{max}$=2.61MGOeOeOeOeOe

• Journal of the Korean Magnetics Society
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• v.7 no.1
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• pp.49-54
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• 1997

The effect of Co and annealing temperature on the magnetic properties, phase change and microstructure of melt-spun $(Nd_{14.73}Fe_{78.67}B_{6.60})_{100-x}Co_x$ (X=0, 1, 2, 3) ribbons has been studied. The Co containing ribbons were found to have higher coercivity ($_iH_c$) than the ribbons without Co. Intrinsic coercivity of 20.3 kOe has been obtained by addition of 2 at%Co. This effect by Co addition is also represented in the case of hot pressed and die-upseted magnets. The maximum intrinsic coercivities of hot press and die-upset $(Nd_{14.73}Fe_{78.67}B_{6.60})_{100- x}Co_x$ (X=0, 1, 2, 3) magnets are 16.9 kOe and 15.2 kOe when X=2.

• Journal of Soil and Groundwater Environment
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• v.17 no.2
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• pp.7-14
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• 2012

Batch tests were carried out to evaluate the thermal treatment of low volatile organic compounds in low-permeability soil. The chemical oxidation by sodium persulfate catalyzed by heat and Fe (II) was evaluated. Enhanced persulfate oxidation of n-decane (C-10), n-dodecane (C-12), n-tetradecane (C-14), n-hexadecane (C-16), and phenanthrene was observed with thermal catalyst, indicating increased sulfate radical production. Slight enhancement of the pollutants oxidation was observed when initial sodium persulfate concentration increased from 5 to 50 g/L. However, the removal efficiency greatly decreased as soil/water ratio increased. It indicates that mass transfer of the pollutants as well as the contact between the pollutants and sulfate radical were inhibited in the presence of solids. In addition, more pollutants can be adsorbed on soil particles and soil oxidant demand increased when soil/water ratio becomes higher. The oxidation of the pollutants was significantly improved when catalyzed by Fe(II). The sodium persulfate consumption increased at the same time because the residual Fe(II) acts as the sulfate radical scavenger.