• Bulletin of the Korean Chemical Society
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• 제14권4호
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• pp.439-444
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• 1993

The aerobic oxidation of the Fe(II) complex of 1,4,8,11-tetraazacyclotetradecane, [Fe(cyclam)$(CH_3CN)_2](ClO_4)_2$, in MeCN in the presence of a few drops of $HClO_4$ leads to low spin Fe(III) species [Fe(cyclam)$(CH_3CN)_2](ClO_4)_3$. The Fe(III) cyclam complex is further oxidized in the air in the presence of a trace of water to produce the deep green binuclear bismacrocyclic Fe(II) complex $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$. The Fe(II) ions of the complex are six-coordinated and the bismacrocyclic ligand is extensively unsaturated. $[Fe_2(C_{20}H_{36}N_8)(CH_3CN)_4](ClO_4)_4{\cdot}2CH_3CN$ crystallizes in the monoclinic space group $P2_1/n$ with a= 13.099 (1) ${\AA}$, b= 10.930 (1) ${\AA}$, c= 17.859 (1) ${\AA}$, ${\beta}$= 95.315 $(7)^{\circ}$, and Z= 2. The structure was solved by heavy atom methods and refined anisotropically to R values of R= 0.0633 and $R_w$= 0.0702 for 1819 observed reflections with F > $4{\sigma}$ (F) measured with Mo K${\alpha}$ radiation on a CAD-4 diffractometer. The two macrocyclic units are coupled through the bridgehead carbons of ${\beta}$-diimitie moieties by a double bond. The double bonds in each macrocycle unit are localized. The average bond distances of $Fe(II)-N_{imine}$, $Fe(II)-N_{amine}$, and $Fe(II)-N_{MeCN}$ are 1.890 (5), 2.001 (5), and 1.925 (6) ${\AA}$, respectively. The complex is diamagnetic, containing two low spin Fe(II) ions in the molecule. The complex shows extremely intense charge transfer band in the near infrared at 868 nm with ${\varepsilon}$= 25,000 $M^{-1}cm^{-1}$. The complex shows a one-electron oxidation wave at +0.83 volts and two one-electron reduction waves at -0.43 and-0.72 volts vs. Ag/AgCl reference electrode. The complex reacts with carbon monoxide in $MeNO_2$ to form carbonyl adducts, whose $v_{CO}$ value (2010 $cm^{-1}$) indicates the ${\pi}$-accepting property of the present bismacrocyclic ligand.

• 한국세라믹학회지
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• 제29권7호
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• pp.511-516
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• 1992

In this study, SiC powder and Si powder were used as the raw materials. Mixture was prepared with addition of Al2O3 and Fe2O3 at 0.1~0.5wt% respectively. After this step, the mixture was pressed and nitrided for 30 hrs at 140$0^{\circ}C$ under NH3-N2 atmosphere. Mechanical properties of sintered specimens were investigated from measurement of porosity, bulk density and three point bending test. nitration reaction extent was observed at the change of mass before and after reaction, and the microstructure and the change of $\alpha$-Si3N4 and $\beta$-Si3N4 were observed by XRD and SEM. In the current work, the results are as follows 1. When Fe2O3 added, the nitridation increased with the content of Fe2O3, and the bending strength was increased from 0.1 wt% to 0.3 wt%, and decreased to 0.5 wt%. 2. When Al2O3 added, the nitridation and the bending strength increased little by little with the content of Al2O3 3. The bending strength of the specimen added with Fe2O3 were higher than that with Al2O3. Because the specimens contained Fe2O3 had much more the whisker type crystal of Si3N4 contributing to strength than contained Al2O3.

• 생약학회지
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• 제47권3호
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• pp.204-210
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• 2016

Phytochemical investigation of the 80% MeOH extract from the stems of Lagerstroemia indica resulted in the isolation of eighteen compounds; four norsesquiterpenes, fourteen phenolic derivatives. Their chemical structures were characterized by spectroscopic methods to be tachioside (1), isotachioside (2), 2,4,6-trimethoxyphenyl ${\beta}$-D-glucopyranoside (3), gallic acid 4-methyl ether (4), protocatechuic acid (5), gallic acid (6), vanillic acid (7), vanillin (8), 2-methoxy-5-hydroxymethyl-phenyl-1-O-(6"-galloyl)-${\beta}$-D-glucopyranoside (9), 2,4,6-trimethoxyphenol-1-O-${\beta}$-D-(6'-O-galloyl)-glucopyranoside (10), 4-hydroxy-3-methoxyphenyl-1-O-(6'-O-galloyl)-${\beta}$-D-glucopyranoside (11), vomifoliol (12), vomifoliol 9-O-${\beta}$-D-glucopyranoside (13), 6R,9R-3-oxo-${\alpha}$-ionol-9-O-${\beta}$-D-glucopyranoside (14), dihydrophaseic acid 4'-O-${\beta}$-D-glucopyranoside (15), ${\beta}$-hydroxypropiovanillone 3-O-${\beta}$-D-glucopyranoside (16), myrciaphenone A (17), and coumaric acid (18). Compounds 1-5 and 7-18 were isolated for the first time from this plant. Compounds 1-18 were investigated for their antioxidant properties using DPPH and ABTS radical scavenging capacity assay, $Fe^{2+}$ chelating, and FRAP assay. It was found that 4, 6, and 11 possessed the highest antioxidant capacities.

• 대한화학회지
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• 제22권5호
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• pp.311-316
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• 1978

Fe(III)과 Xylenol Orange (XO 또는 $H_6A$)의 반응을 분광광도법으로 연구하였다. Fe(III)과 XO는 조성이 Fe(III) : XO = 2 : 1 및 1 : 1 인 두가지 착물을 형성함을 확인하였다. 2 : 1 착물은 XO보다 Fe(III)를 많이 포함한 산성에서 안정하고, 1 : 1 착물은 XO가 많이 포함된 약산성용액에서 안정하다. 흡수극대는 590nm(2 : 1)와 500nm(1 : 1)이고 몰흡광계수는 각각 $3.18{\pm}0.04{\times}10^4,\;1.32{\pm}0.03{\times}10^4$이다. pH값을 변화시키면서 측정한 두 착물의 안정도상수는 $log{\beta}_{21}=18.69{\pm}0.03,\;log{\beta}_{212}=42.08{\pm}0.09,\;log{\beta}_{11}=4.17{\pm}0.04,\;and\;log{\beta}_{113}=34.47{\pm}0.07$이었다.

• 한국분말재료학회지
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• 제6권1호
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• pp.111-118
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• 1999

Ni(Fe)Al powders containing a homogeneous distribution of the in-situ formed AIN and $Al_2O_3$ dispersoids have been produced by mechanical alloying process in a controlled atmosphere using high energy attrition mill. The powders have been successfully consolidated by hot extrusion process. The phase information investigated by TEM and XRD analysis reveals that Fe can be soluble up to 20% to the NiAl phase ($\beta$) at room temperature after MA process. Subsequent thermomechanical treatment under specific condition has been tried to induce secondary recrystallization (SRx) to improve high temperature properties, however, the clear evidence of SRx was not obtained in this material. Mechanical properties in term of strength at room temperature as well as at high temperatures have been improved by the addition pf AIN, and the room temperature ductility has been shown to be improved after heat treatment, presumably due to the precipitation of second phase of $\alpha$ in this material.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1994년도 추계 학술발표 강연 및 논문 개요집
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• pp.1-1
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• 1994

;The electronic state calculations for various types of ceramic materials have beell performed by the use of $DV-X\;{\alpha}$ cluster method. The molecular orbital levels and wave functions for model clusters have been computed to study the electronic properties ami chemical bonding of the ceramics. For ${\beta}-sialon(Si_{6-z}Al_zO_zN_{8-z})$ which is a high temperature structural material based on ${\beta}-Si_3N_4$, we have made model cluster calculations to estimate the strength of chemical bonding between atoms by the Mulliken population analysis. It is found that the covalent bonding between Si and N atoms is very strong in pure ${\beta}-Si_3N_4$, but the covalency around solute atom is considerably weakened when Si atom is substituted by AI. This tendency is enhanced by an additional substitution of oxygen atom for N. The result calculated can well explain the experimental data of changes in mechanical properties such as the reductions of Young's modulus and Vickers hardness with increment of z-value in ${\beta}-sialon$. Various model clusters for transition metal oxides which show many interesting physical and chemical properties have also been calculated. High-valent perovskite-type iron oxides EMFe0_3E(M=Ca and Sr) possess very interesting magnetic and chemical properties. In these oxides, iron exists as $Fe^{4+}$ state, but the experimental measurement of Mossba~er effect suggests that disproportionation $2Fe^{4+}=Fe^{3+}+Fe^{5+}$ takes place for $CaFe0_3$ at low temperatures. The model cluster calculations for these compounds indicated the existence of considerably strong covalent bonding of Fe-O. The calculations of hyperfine interaction at iron neucleus show very good agreement with the experimental Mossbauer measurements. The result calculated also implies that the disproportionation reaction is strongly possible by assuming the quenching of breathing phonon mode at low temperatures.tures.

• 한국세라믹학회지
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• 제28권12호
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• pp.996-1004
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• 1991

In this study, we tried to synthesis iron hydroxide suitable for longitudinal magnetic recording media from waste acid, which is a by-product of an iron works factory. Effects of initial pH of reactants, reaction temperature, reaction time for the synthesis of acicular iron hydroxide were studied in relation to particle properties of iron hydroxide and magnetic properties of maghemite powders. As the pH in reactant solution increased, $\beta$-FeOOH(pH=4.5), mixture of $\beta$-FeOOH and $\alpha$-FeOOH(4.5$\alpha$-FeOOH and Fe3O4(6.4$\alpha$-FeOOH (pH>13) was found to from in order. Especially, $\alpha$-FeOOH formed above pH 13 was single phase with superior acicularity. The temperature range over which the single-phase goethite can be formed increased as the initial pH of reactants increased (pH 13:10~5$0^{\circ}C$, pH 13.2:10~7$0^{\circ}C$, pH 13.5:0~8$0^{\circ}C$). The goethite formed between 40~6$0^{\circ}C$ has superior characteristics because the acicularity increased with increasing temperature but at high temperature (>6$0^{\circ}C$) Fe3O4 (pH=13) was found to start to form. Generally, single phase of goethite was found to form after one hour when an optimized condition. The particle size of goethite did not change as the reaction time increased over one hour. Accordingly, the magnetic properties of ${\gamma}$-Fe2O3 produced from goethite were not altered.

• Bulletin of the Korean Chemical Society
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• 제21권1호
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• pp.65-68
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• 2000

A $\mu-oxo$ diiron(III) complex and two bis( $\mu-alkoxo)$ diiron(III) complexes with biomimetic tripodal ligand containing mixed N/O donor atoms were synthesized using a mononuclear iron(III) complex as starting material. Depending on the amounts and kinds of bases used, we obtained various kinds of diiron (III) complexes. The reaction of $[$Fe^{III}$(Hbbea)Cl_2]Cl$, 1, with an equivalent amount of $KO_2$ or NaOAc produced $[$Fe^{III}$_2O(Hb-bea)_2Cl_2]Cl_2$, 2. An additional equivalent amount of NaOBz or NaOAc converts complex 2 to complex 3 or complex 4 depending on the base used. The addition of two equivalent amounts of NaOBz orNaOAc directly converts complex 1 to $[$Fe^{III}$_2(bbea)_2(OBz)_2]Cl_2$, 3, or $[$Fe^{III}$_2(bbea)_2(OAc)_2]Cl_2$, 4, depending on the base used. Crystal data are as follows: [$Fe^{III}_2O(Hbbea)_2Cl_2]Cl_2$, 2: monoclinic space group $$P2_1/n$$, a = 8.421 (1) $\AA$, b = 18.416 (2) $\AA$, c = 13.736 (1) $\AA$, $\beta$ = 104.870 $(7)^{\circ}$, V = 2058.9 (4) $\AA^3$, Z = 2, R1 = 0.0469 and wR2 = 0.1201 for reflections with I > 2 ${\sigma}$(I).

• Corrosion Science and Technology
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• 제17권2호
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• pp.60-67
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• 2018

The compounds associated with corrosion, in metallic archaeological samples of carbon steel of insular origin were evaluated to establish their degree of deterioration and structural damage against air pollution. The iron phases present in samples of archaeological artifacts were detected by Raman spectroscopy and confocal Raman microcopy. These samples mainly exhibited ing mainly ${\beta}$-FeO(OH) type goethite oxyhydroxides and small amounts of akaganeite ${\alpha}$-FeO(OH) lepidocrocite ${\gamma}$-FeO(OH) due to dominant chloride in a marine environment and non-stoichiometric oxyhydroxides Fe (II + / III +) as indicators of early corrosion. Some parts showed the presence of magnetic maghemite indicating high corrosion. ${\gamma}$-FeO(OH) is a precursor of phases associated with advanced marine corrosion. By studying its decomposition by Raman spectroscopy, it was synthesized with the following sequence: ${\gamma}-FeO(OH){\rightarrow}{\alpha}-FeO(OH)+{\gamma}-FeO(OH)$, ${\rightarrow}{\gamma}-Fe_2O_3+Fe_3O_4$. Ferric compounds provided evidence for the effect of intensity of laser on them, constituting a very useful input for the characterization of oxidation of iron in this type of artifacts. Thus, destructive analysis techniques should be avoided in addition to the use of small amounts of specimen.

• Applied Microscopy
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• 제24권3호
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• pp.78-86
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• 1994

A TEM study on proeutectoid ${\alpha}$ reaction at sub-eutectoid temperatures has been made in hypoeutectoid Ti-3.gw/o Co and Ti-5.2w/o Fe alloys. Widmanstatten ${\alpha}$ plates were formed in both alloys within the ${\beta}$ matrix with some modification of degenerate forms. These degenerate plates were formed by the sympathetic nucleation of ${\alpha}$ plates at ${\alpha}:{\beta}$ interphase boundaries. Three types of sympathetic nucleation, i.e., edge-to-edge, face-to-edge, face-to-face, were found in both alloys. The edge-to-edge sympathetically nucleated crystals formed a low-angle boundary between two crystals. The ${\alpha}:{\beta}$ interphase boundaries were found to be partially coherent interfaces which consist of regularly spaced misfit dislocations. The growth of these interphase boundaries were accomplished by the lateral movement of growth ledges. The intersection points of two ${\alpha}$ plates or the low angle boundaries which had formed by edge-to-edge sympathetic nucleation played a role as the potential sources of growth ledges during the growth of plate. The interfacial structures and the spatial morphologies of the degenerate proeutectoid ${\alpha}$ plates would be expected to influence the nucleation and growth of the succeeding eutectoid decomposition process.