• Korean Journal of Materials Research
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• v.10 no.7
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• pp.471-477
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• 2000

Corrosion behavior of Fe-Ni-Cr alloy in molten salts of LiCl and LiCl-$Li_2O was investigated in the tempera-ture range of $650~850^{\circ}C$. In the molten salt of LiCl, and internal oxidation of Fe occurred in the KSA(Kaeri Superalloy)-1 alloy without containing Cr, while a dense protective oxide scale of $LiCrO_2$ was formed in the KSA-4, Incoloy 800H and KSA-5 alloys. In the mixed molten salt of LiCl-$Li_2O$, internal oxidation of Fe and Cr took place in the KSA-1 and KSA-4 alloys, respectively. Non-protective porous oxide scales consisting of $LiCrO_2$ and Ni were formed in the Incoloy 800H and KSA-5. The corrosion rate of the alloys increased with the increase in Cr content and the corrosion rate followed the parabolic law for the alloy containing Cr content less than 8%, and the linear law for the alloy containing Cr content more than 8%. Such a corrosion behavior of the alloy in the mixed molten salt of LiCl-$Li_2O$ was interpreted in terms of the basic fluxing mechanism of protective oxide scale of $Cr_2O_3$.

• Bulletin of the Korean Chemical Society
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• v.26 no.4
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• pp.634-640
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• 2005

The reaction of cis-[Cr([14]-decane)(OH$_2)_2]^+$ ([14]-decane = rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-teraazacyclotetradecane) with auxiliary ligands {$L_a$ = citrate(cit)} leads to a new dimeric complex cis-[{Cr([14]-decane)($\mu$-cit)}$_2](ClO_4)_2$. This binuclear complex has been structurally characterized by a combination of elemental analysis, conductivity, IR and Vis spectroscopy, mass spectrometry, and X-ray crystallography. Analysis of the crystal structure of cis-[{Cr([14]-decane)($\mu$-cit)})($_2]^+$ reveals that each chromium has a distorted octahedral coordination environment and citrato ligands are monodentate to the two chromium atoms via the carboxyl groups. For dimeric complex the bridging geometry is as follows: Cr$\ldots$Cr = 7.361 $\AA$; Cr-O(average) = 1.958 (8) $\AA$; Cr-N range = 2.108 (9)-2.147(9) $\AA$; N(1)-Cr-N(3) (equatorial position) = 98.0(4)$^{\circ}$; N(2)-Cr-N(4) (axial position) = 166.4(4)$^{\circ}$; O(1)-Cr-N(2) = 98.1(4)$^{\circ}$; O(3)-Cr-N(4) = 96.6(3)$^{\circ}$; O(1)-Cr-O(3) = 90.4$^{\circ}$. The FAB mass spectrum of the dimeric complex displays peak due to the molecular ions cis-[{Cr([14]-decane)($\mu$-cit)})($_2]^+$ at m/z 1053.

• Korean Journal of Materials Research
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• v.4 no.6
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• pp.704-709
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• 1994

The $(LaS)_xCrS_2(x \approx 1.20$) of the incommensurate misfit layer was systhesized from reactant mixture of$La_S_3$,Cr and S at 1273K. Powder X-ray diffration of $(LaS)_xCrS_2(x \approx 1.20$) was indexed as a complex structure consisted with a monoclinic LaS-sublattice, a triclinic $CrS_{2}$-sublattice and their superlattice. The temperature dependence of sublattice dimension was investigated by the X-ray diffraction analysis at low temperature. The magnetic susceptibility of $(LaS)_xCrS_2(x \approx 1.20$) was measured between 77K and room temperature using a Faraday balance method. $(LaS)_xCrS_2(x \approx 1.20$) was paramagnetic on a $\sigma$-H plot at room temperature. The observed effective magnetic moment( p dr) was in fair agreement with the value calculated by spin-only contribution for $Cr^{3+}$ and spin and orbital contribution for $La^{3+}$.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.184-188
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• 2002

Unsaturated $Cr(CO)_x(1{\leq}x{\leq}5)$molecules were generated in the gas phase from photolysis of $Cr(CO)_6$vapor in He using an unfocussed weak UV laser pulse and their reactions with $O_2$ and $N_2O$ have been studied. The formation and disappearance of the ground state CrO molecules were identified by monitoring laser-induced fluorescence(LIF) intensities vs delay time between the photolysis and probe pulses. The photolysis laser power dependence as well as the delay time dependence of LIF intensities from the CrO orange system showed different behavior as those from ground state Cr atoms, suggesting that the ground state CrO molecules were generated from the reaction between $O_2/N_2O$ and photo-fragments of $Cr(CO)_6$ by one photon absorption. The depletion rate constants for the ground state CrO by $O_2$ and $N_2O$ are $5.4{\pm}0.2{\times}10^{-11}$ and $6.5{\pm}0.4{\times}10^{-12}cm^3molecule^{-1}s^{-1}$, respectively.

• Korean Journal of Materials Research
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• v.11 no.4
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• pp.324-328
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• 2001

CrN films were deposited onto STD61 steel substrates using an arc-ion plating apparatus, with and without ion-nitriding pretreatment, and their oxidation was studied between 700 and $900^{\circ}C$ for 40hr in air. The oxidation behavior was examined by thermogravimetric analyses, X-ray diffraction. EDS and SEM. The deposited CrN films consisted of CrN and $Cr_2$N phases. The CrN films increased the oxidation resistance of the substrate by forming a protective $Cr_2$$O_3$ layer. The ion-nitriding pretreatment has not affected the oxidation resistance of the CrN film.

• Korean Journal of Crystallography
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• v.3 no.1
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• pp.44-52
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• 1992

The effect of sintering atmosphere on the final properties and phase change of Ti (C, N) Cr3c2 ceramics was investigated. In the case of sintering in vacuum and N2 atmosphere, densely packed sintered body was obtained. In Ar atmosphere, however, densification was much decreased compared to sintering in vacuum and Na. XRD analysis showed that in vacuum atmosphere Cr3c2 phase was changed to Cr7c3 Phase whereas in N2 and Ar atmosphere phase change was not occurred. That is, for vacuum sintering, the formation of defects in Ti(C, N) structure occurred through de-nitridation process, and it promotes the diffusion of C in Cr3c2 and raises the densification effects. But in the case of N2 atmosphere, densification phenomenon was considered to be due to sintering mechanism that enabled formation of free carbon and removal of oxygen by free carbon and existence of carbon in the grain boundary.

• Korean Journal of Materials Research
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• v.13 no.1
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• pp.36-42
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• 2003

The oxidation behaviors of Y-Cr bilayer deposited on ferritic steel by magnetron-sputtering for application of the Fe-Cr alloys as interconnectors of planar-type solid oxide fuel cells (SOFCs) were studied. After oxidation at $800^{\circ}C$ for 40 hours, the major phase of $Y_2$$O_3$and the minor phase of $YCrO_3$, $Mn_{1.5}$ $Cr_{1.5}$ $O_4$and Cr$_2$SiO$_4$were formed in the Y/Cr bilayered samples, while the major phase of Cr$_2$O$_3$and the minor phase of $Y_2$$O_3$were formed as the major phase in the Cr/Y bilayered samples. The Log(ASR/T) that expresses electric resistance of the Y/Cr coated specimen with nonconducting $_Y2$$O_3$oxide showed high value of -2.80 Ω$\textrm{cm}^2$$K^{-1}$ / and that of the Cr/Y coated specimen with conducting $Cr_2$$O_3$oxide appeared to be -4.11 Ω$\textrm{cm}^2$$^{K}$ . The electric resistance of the Y/Cr coated specimen was largely increased due to the formation of high resistance oxide scales. However, the Cr/Y coated specimen did not show any increase in the electric resistance and had the long-term stability of oxidation because there was no formation of the secondary phases with low conductivity.

• Journal of the Korean Magnetics Society
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• v.10 no.6
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• pp.269-273
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• 2000

Fe-l7Cr-2M(M=Si, Nb, Mo) alloy powder was prepared by plasma electrode rotating atomizer and than the alloy powder was formed and sintered. The particle shape of the Fe-l7Cr-2M(M=Si, Nb, Mo) alloy power is spherical. The saturation magnetization of the sintered Fe-17Cr-2Mo and Fe-l7Cr-2Nb alloy are 155 emu/g. The saturation magnetization of the sintered Fe-l7Cr-2Si alloy is less than that of the sintered Fe-l7Cr-2Mo and Fe-l7Cr-2Nb alloy. The amplitude relative permeability of the sintered Fe-l7Cr-2M(M=Si, Nb, Mo) alloy has the maximum value in the range of 3∼5 Oe applied field at forming pressure 12 ton/cm$^2$, sintering temperature 1200$^{\circ}C$, and frequency 1 kHz. Power loss of the sintered Fe-l7Cr-2Nb alloy is 40 mW/cc at applied field, H$\sub$a/=5 Oe, and frequency, f=1 kHz. The power loss of the sintered Fe-l7Cr-2Nb alloy is a half of that of the sintered Fe-l7Cr-2Si and Fe-l7Cr-2Mo alloy.

• Journal of the Korean Ceramic Society
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• v.33 no.11
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• pp.1285-1291
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• 1996

Using Cr2O3 Al and graphite powders as starting materials Cr3C2 was synthesized by combustion synthesis process according to the following reaction : 3Cr3C2 +4C+6Allongrightarrow2Cr3C2 +3Al2O3. The synthesis was conducted at 2 atm in an argon atmosphere. in this study main-product was monolithic phase of Cr3C2 /Cr7C3 mixture and sub-product was slag state of $\alpha$-Al2O3. Single phase of Cr3C2 was obtained when crushed main-product was heat-treated at 120$0^{\circ}C$ for 3h in vacuum state with addition of 2.5wt% C. The obtained Cr3C2 powder can be used as plasma-arc deposit material because the flowability index of powder with the size of 9-50${\mu}{\textrm}{m}$ was 66.

• Journal of the Korean Chemical Society
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• v.34 no.6
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• pp.534-538
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• 1990

Chromium(Ⅵ) compound, [$C_9H_7$NH]$_2Cr_2O_7$ has been prepared by the reaction of isoquinoline with chromium trioxide under the presence of water. [$C_9H_7$NH]$_2Cr_2O_7$ is nonhydroscopic and dissolved in water very well. Structure of [$C_9H_7$NH]$_2Cr_2O_7$ is identified by FTIR spectra and elemental analysis data. The ability of [$C_9H_7$NH]$_2Cr_2O_7$ for the oxidation of alcohols were examined in methylene chloride. [$C_9H_7$NH]$_2Cr_2O_7$ was found as efficient oxidizing agent for the conversion of allyl, primary and secondary alcohols to the corresponding aldehydes or ketones.