• Journal of the Korean institute of surface engineering
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• v.31 no.3
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• pp.142-150
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• 1998

Stainless steel is being used widely for various purposes due to its good corrosion resistance. There has been much research to produce colored stainless steel by several methods such as anodizing and ion plating. In this experiment, we coated TiN(C,O,H)films SUS304 substraate with the DC magnetron spttering system made by Leybold Heraeus and studied the interlater structure and abhesive strength of the films as a function of additional gases, acetylene, hydrogen and oxygen. When the acetylene gas was added into the chamber, the specimen with the interlayer phase had good adhesion due to the toughness of the $\gamma'-Fe_4N$ plase induced from a solid solution of carbon atoms, while low adhesion appeared on the specimen of the non interlayer phase. The formation of the interlayer phase($\gamma'-Fe_4N$) was due to hydrogen embrittlement and internal stress induced by $\gamma'-Fe_4N$ formation in the interlayer. We could fine the interlayer phase ($\gamma'-Fe_4N$) at the interface between the film and the substrate of the TEM image when $\gamma'-Fe_4N$ was detected by the X-ray duffraction metheod.

• Bulletin of the Korean Chemical Society
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• v.32 no.2
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• pp.467-471
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• 2011

Spin exchange interactions of $(C_2N_2H_{10})[Fe(HPO_3)F_3]$ were examined by performing a spin dimer analysis based on extended Huckel tight binding method and a mapping analysis based on first principles density functional theory. Spin exchange interactions occur through the super-superexchange paths $J_1$ and $J_2$ in $(C_2N_2H_{10})[Fe(HPO_3)F_3]$. In the super-superexchange path $J_2$ magnetic orbital interactions between eg-block levels are much stronger than those from $t_{2g}$-block levels. Both electronic structure calculations show that the spin exchange interaction through the super-superexchange path $J_2$ is much stronger than that of $J_1$.

• Journal of the Korean Ceramic Society
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• v.28 no.2
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• pp.93-100
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• 1991

For determination the optimum manufacturing condition Fe4N powder for magnetic recording media, we have studied the following important conditions : the effect of particle size of metal powder on the nitridation, the condition of nitridation on the formation and magnetic properties of Fe4N, and stability of Fe4N powder against temperature and change on standing. The results can be summarized as : 1) Single phase Fe4N is formed at 50v/o of ammonia concentration during the nitridation reaction, 2) Single phase Fe4N is formed above 40$0^{\circ}C$, 15min regardless of the metal powder sizes, 3) Coercivity and saturation magnetization of Fe4N powder almost constant value until 20 day-passing from preparation date.

• Journal of the Korean Magnetics Society
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• v.16 no.5
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• pp.240-244
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• 2006

In this paper, magnetic properties and annealing behavior of spin valve structures using Mo(MoN) layers as underlayers were studied varying the thickness of the underlayers. The spin valve structure was consisted of Si substrate/$SiO_2(2,000{\AA})/Mo(MoN)(t{\AA})/NiFe(21\;{\AA})/CoFe(28\;{\AA})/Cu(22\;{\AA})/CoFe(18\;{\AA})/IrMn(65\;{\AA})/Ta(25\;{\AA})$. Also, MoN films were deposited on Si substrates and their thermal annealing behavior was analyzed. The resistivity of the MoN film increased as the $N_2$ gas flow rate was increased. After annealing at $600^{\circ}C$, XRD results did not show peaks of silicides. XPS results indicated MoN film deposited with 5 sccm of $N_2$ gas flow rate was more stable than the film deposited with 1 sccm of $N_2$ gas flow rate. The variations of MR ratio and magnetic exchange coupling fold were small for the spin valve structures using Mo(MoN) underlayers up to thickness of45 ${\AA}$. MR ratio of spin valves using MoN underlayers deposited with various $N_2$ gas flow rate was about 7.0% at RT and increased to about 7.5% after annealing at $220^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased to about 3.5%. Variation of $N_2$ gas flow rate up to 5 sccm did not change the MR ratio and $H_{ex}$ appreciably.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.4
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• pp.289-301
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• 1995

The effect of Air/$C_3H_8$ gas addition on the compound layer growth of steels nitrocarburised in $NH_3+Air+C_3H_8$ mixed gas atmospheres was investigated. It is considered that amount of residual $NH_3$ was varied according to alternation of Air/$C_3H_8$ mixing ratio and volume content. The compound layer formed from nitrocarburising was composed of ${\varepsilon}-Fe_{2-3}$(C, N) and ${\gamma}^{\prime}-Fe_4$(C, N). According as Air/$C_3H_8$ mixing ratio increased, the superficial content of ${\gamma}^{\prime}-Fe_4$(C, N) within the compound layer was increased, at the same time the growth rate of compound layer and porous layer was increased. In the case of alloy steel at the fixed gas composition, the growth rate of compound layer and porous layer was worse than carbon steel and compound layer phase composition structure primarily consisted of E phase. As the carbon content of materials was increasing in the given gas atmospheres, the growth rate of compound layer and porous layer was increased and the superficial content of ${\varepsilon}-Fe_{2-3}$(C, N) within the compound layer was increased.

• Journal of the Korean Magnetics Society
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• v.17 no.2
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• pp.95-98
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• 2007

In this paper, the magnetic properties and the annealing behavior of spin valve structures with Mo(MoN) underlayers were studied for various underlayer thickness. The spin valve structure was Si substrate/Mo(MoN)$(t{\AA})/NiFe(21{\AA})/CoFe(28{\AA})/Cu(22{\AA})/CoFe(18{\AA})/IrMn(65{\AA})/Ta(25 {\AA})$. Mo and MoN films were deposited on Si substrates and their thermal annealing behavior was analyzed. The deposition rate of the MoN thin film was decreased and tile resistivity of the MoN thin films were increased as the $N_2$ gas flow was increased. The variations of MR ratio and magnetic exchange coupling field of spin valve structure were smaller with MoN underlayers than that with Mo underlayers up to thickness of $51{\AA}$. MR ratio of spin valves with Mo underlayers was 2.86% at room temperature and increased up to 2.91 % after annealing at $200^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased about 2.16%. The MR ratio of spin valves structure with MoN underlayers for $N_2$ gas flow 1 sccm was 5.27% at room temperature and increased up to 5.56% after annealing at $200^{\circ}C$. Upon annealing at $300^{\circ}C$, the MR ratio decreased about 4.9%.

• Korean Journal of Materials Research
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• v.22 no.11
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• pp.620-625
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• 2012

A general synthetic method to make $Fe_3O_{4-{\delta}}$ (activated magnetite) is the reduction of $Fe_3O_4$ by $H_2$ atmosphere. However, this process has an explosion risk. Therefore, we studied the process of synthesis of $Fe_3O_{4-{\delta}}$ depending on heat-treatment conditions using $FeC_2O_4{\cdot}2H_2O$ in Ar atmosphere. The thermal decomposition characteristics of $FeC_2O_4{\cdot}2H_2O$ and the ${\delta}$-value of $Fe_3O_{4-{\delta}}$ were analyzed with TG/DTA in Ar atmosphere. ${\beta}-FeC_2O_4{\cdot}2H_2O$ was synthesized by precipitation method using $FeSO_4{\cdot}7H_2O$ and $(NH_4)_2C_2O_4{\cdot}H_2O$. The concentration of the solution was 0.1 M and the equivalent ratio was 1.0. ${\beta}-FeC_2O_4{\cdot}2H_2O$ was decomposed to $H_2O$ and $FeC_2O$4 from $150^{\circ}C$ to $200^{\circ}C$. $FeC_2O4$ was decomposed to CO, $CO_2$, and $Fe_3O_4$ from $200^{\circ}C$ to $250^{\circ}C$. Single phase $Fe_3O_4$ was formed by the decomposition of ${\beta}-FeC_2O_4{\cdot}2H_2O$ in Ar atmosphere. However, $Fe_3C$, Fe and $Fe_4N$ were formed as minor phases when ${\beta}-FeC_2O_4{\cdot}2H_2O$ was decomposed in $N_2$ atmosphere. Then, $Fe_3O_4$ was reduced to $Fe_3O_{4-{\delta}}$ by decomposion of CO. The reduction of $Fe_3O_4$ to $Fe_3O_{4-{\delta}}$ progressed from $320^{\circ}C$ to $400^{\circ}C$; the reaction was exothermic. The degree of exothermal reaction was varied with heat treatment temperature, heating rate, Ar flow rate, and holding time. The ${\delta}$-value of $Fe_3O_{4-{\delta}}$ was greatly influenced by the heat treatment temperature and the heating rate. However, Ar flow rate and holding time had a minor effect on ${\delta}$-value.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1703-1707
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• 2018

Ferromagnetic ${\tau}-phase$ $Mn_{54}Al_{46}C_{2.44}$ particles were synthesized, and its composites with commercial $Sm_2Fe_{17}N_3$ and synthesized $Fe_{65}Co_{35}$ powders were fabricated. Smaller grain size than the single domain size of the $Mn_{54}Al_{46}C_{2.44}$ without obvious grain boundaries and secondary phases is the origin for the low intrinsic coercivity. It was confirmed that the magnetic properties of the $Mn_{54}Al_{46}C_{2.44}$ can be enhanced by magnetic exchange coupling with the hard magnetic $Sm_2Fe_{17}N_3$ and soft magnetic $Fe_{65}Co_{35}$. The high degrees of the exchange coupling were verified by calculating first derivative curves. Thermo-magnetic stabilities of the composites from 100 to 400 K were measured and compared. It was demonstrated that the $Mn_{54}Al_{46}C_{2.44}$ based composites containing $Sm_2Fe_{17}N_3$ and $Fe_{65}Co_{35}$ could be promising candidates for future permanent magnetic materials with the proper control of purity, magnetic properties, etc.

• Journal of The Korean Astronomical Society
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• v.55 no.2
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• pp.23-36
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• 2022

We present a method to determine nitrogen abundance ratios with respect to iron ([N/Fe]) from molecular CN-band features observed in low-resolution (R ~ 2000) stellar spectra obtained by the Sloan Digital Sky Survey (SDSS) and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Various tests are carried out to check the systematic and random errors of our technique, and the impact of signal-to-noise (S/N) ratios of stellar spectra on the determined [N/Fe]. We find that the uncertainty of our derived [N/Fe] is less than 0.3 dex for S/N ratios larger than 10 in the ranges T_eff = [4000, 6000] K, log g = [0.0, 3.5], [Fe/H] = [-3.0, 0.0], [C/Fe] = [-1.0, +4.5], and [N/Fe] = [-1.0, +4.5], the parameter space that we are interested in to identify N-enhanced stars in the Galactic halo. A star-by-star comparison with a sample of stars with [N/Fe] estimates available from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) also suggests a similar level of uncertainty in our measured [N/Fe], after removing its systematic error. Based on these results, we conclude that our method is able to reproduce [N/Fe] from low-resolution spectroscopic data, with an uncertainty sufficiently small to discover N-rich stars that presumably originated from disrupted Galactic globular clusters.

• Journal of the Korean Ceramic Society
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• v.29 no.12
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• pp.942-948
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• 1992

Ultrafine iron oxide powder, {{{{ gamma }}-Fe2O3 and $\alpha$-Fe2O3, were prepared by the thermal decomposition of organometallic compounds. The formation process of powder includes the thermal decomposition and oxidation of the organometallic precursors, Fe(N2H3COO)2(N2H4)2 (A) and N2H5Fe(N2H3COO)3.H2O (B). The organometallic precursors, A and B, were synthesized by the reaction of ferrous ion with hydrazinocarboxylic acid, and characterized by quantitative analysis and infrared spectroscopy. The mechanistic study for the thermal decomposition was performed by DAT-TG. The iron oxide powder was obtained by the heat treatment of the precursors at 20$0^{\circ}C$ and $600^{\circ}C$ for half an hour in air. The phases of the resulting product were proved {{{{ gamma }}-Fe2O3 and $\alpha$-Fe2O3 respectively. The particle shape was equiaxial and the particle size was less than 0.1 ${\mu}{\textrm}{m}$. Magnetic properties of the {{{{ gamma }}-Fe2O3 powder obtained from A and B was 234 Oe of coercivity, 64.26 emu/g of saturation magnetization, 23.59 emu/g of remanent magnetization and 24.1 Oe, 47.27 emu/g, 3.118 emu/g respectively. The value of $\alpha$-Fe2O3 powder was 1.494 Oe, 0.4862 emu/g, 0.1832 emu/g and 1,276 Oe, 0.4854 emu/g, 0.1856 emu/g respectively.