• Bulletin of the Korean Chemical Society
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• v.27 no.6
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• pp.853-856
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• 2006

Dion-Jacobson phases $CsCa_2Nb_2FeO_9$ and $CsCa_2Nb_2AlO_9$ were reinvestigated by the Rietveld analysis of powder X-ray diffraction (XRD) method, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). These nominal compounds, previously known as the oxygen-deficient layered perovskites with the sequences of $NbO_6-MO_4-NbO_6$ in tripled slab, in fact, were mixed phases of n = 3 Dion-Jacobson phases and impurities such as $Ca_2NbFeO_6$ and $Ca_3Al_2O_6$. The difference of morphology and chemical in-homogeneity between Dion-Jacobson phases and impurities could be clearly identified by scanning electron microscopy with energy-dispersive X-ray spectroscopy. The chemical composition of $CsCa_2Nb_2FeO_9$ was calculated into $Cs_{0.59}Ca_{2.64}Nb_{2.92}Fe_{0.81}$ in small agglomerate crystals and $Cs_{0.95}Ca_{1.97}Nb_{3.08}Fe_{0.15}$ in long plate-like crystals.

• Analytical Science and Technology
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• v.8 no.1
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• pp.85-90
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• 1995

Corrosion characteristics of 4 kinds of the Fe-Al damping alloys has been studied in the 3.5% NaCl solution and compared with a cold rolled mild steel and pure Ti, No passivation, besides Ti, was observed in the Fe-Al damping alloys and a cold rolled mild steel. Corrosion rate was decreased with lower carbon concentration. In the case of Mn addition for improving damping capacity, corrosion rate was decreased in scrap iron but was not decreased in electrolytic iron. It has been shown that corrosion rate of Fe-Al damping alloys lays between that of the pure Ti and that of a cold rolled mild steel.

• Journal of Surface Science and Engineering
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• v.44 no.1
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• pp.13-20
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• 2011

This study investigated the high temperature oxidation behavior of Fe-22%Cr-5.8%Al alloy and the oxidation kinetics of the alloy were discussed. Bulk samples were prepared by VAM (vacuum arc melting) and hot forging. High temperature oxidation testes were isothermally conducted up to 100 hours in 79%$N_2$+21%$O_2$ environment at three different temperatures ($900^{\circ}C$, $1000^{\circ}C$, $1100^{\circ}C$). The weight gain was measured after oxidation according to oxidation time (2, 4, 6, 8, 10, 15, 20, 25, 30, 60, 80, 100 hours). The weight gain significantly increased with increasing oxidation temperature. As the temperature increased, the oxidized samples showed sequential formation of $Al_2O_3$, Cr-rich oxide, Fe-rich oxide. The activation energy of high temperature oxidation was obtained as 306.63 KJ/mol. $Al_2O_3$ were developed on the surface in the early stage of oxidation, representing protective role of oxidation. However, Fe-based and Cr-based oxides leaded to breakaway of oxide layer, thus resulted in the significant increase of additional oxidation.

• Journal of Sensor Science and Technology
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• v.16 no.6
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• pp.462-466
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• 2007

Aluminum nitride (AlN) thin films were deposited on Si substrates by using polycrystalline (poly) 3C-SiC buffer layers, in which the AlN film was grown by pulsed reactive magnetron sputtering. Characteristics of grown AlN films were investigated experimentally by means of FE-SEM, X-ray diffraction, and FT-IR, respectively. The columnar structure of AlN thin films was observed by FE-SEM. X-ray diffraction pattern proved that the grown AlN film on 3C-SiC layers had highly (002) orientation with low value of FWHM (${\Theta}=1.3^{\circ}$) in the rocking curve around (002) reflections. These results were shown that almost free residual stress existed in the grown AlN film on 3C-SiC buffer layers from the infrared absorbance spectrum. Therefore, the presented results showed that AlN thin films grown on 3C-SiC buffer layers can be used for various piezoelectric fields and M/NEMS applications.

• Transactions of Materials Processing
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• v.12 no.4
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• pp.370-375
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• 2003

Determination of the interface heat transfer coefficient was investigated in non-isothermal bulk forming of glass-coated Ti-6Al-4V. FE analysis and experiments were conducted. Equipment consisting of AISI Hl3 die was instrumented with thermocouples located at sub-surface of the bottom die. Die temperature changes were investigated in related to the process variables such as reduction, lubricant and initial die temperature. The calibration approach based on heat conduction and FE analysis using an inverse algorithm were used to evaluate the interface heat transfer between graphite-lubricated die and glass-coated workpiece. The coefficients determined were affected mainly by the contact pressure. The validation of the coefficients was made by the comparison between experimental data and FE analysis results.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.3
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• pp.141-146
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• 2010

$LiFePO_4$ doped with Cr showed improved electrochemical properties as a cathode material of lithium-ion batteries compared to the undoped. The improvement was thought that the doping would raise the electronic conductivity of the compounds. The electrical conductivity of $LiFe_{0.965}Cr_{0.03}B_{0.005}PO_4$ and $LiFe_{0.965}Cr_{0.03}Al_{0.005}PO_4$ powder was measured in the temperature range from 30 to $80^{\circ}C$. The doped powders were synthesized via mechanochemical milling and subsequent heat treatment at 675~$750^{\circ}C$ for 5~10h. The doping enhanced grain growth and electrical conductivity. The electrical conductivity of the $LiFe_{0.965}Cr_{0.03}Al_{0.005}PO_4$ powder at $30^{\circ}C$ was $1{\times}10^{-8}S/cm$, which was higher two orders of magnitude than that of the undoped.

• Journal of Powder Materials
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• v.9 no.1
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• pp.25-31
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• 2002

The efects of mechanical aloying conditions and the type of reducing agent on the solid state reductionof haematite $Fe_2O_3$ have been investigated at room temperature. Aluminium titanium zinc and copper were used as reducing agent. Nanocomposites of metal-oxide in which oxide particles with nano size were dispersed in Fe matrix were obtained by mechanical alloying of $Fe_2O_3$ with aluminium and titanium respectively However the reduction of $Fe_2O_3$ by coppe was not occurred Composite materials of iron with $Al_2O_3$ and $TiO_2$ were obtained from the system of $Fe_2O_3-Al$ and $Fe_2O_3-Ti$ after ball milling for 20 hrs and 30 hrs respectively. And the system of $Fe_2O_3-Zn$ resulted in the formationof FeO with ZnO after ball milling of 120 hrs. The final grain sizes of iron estimated by X-ray diffraction line-width measurement were in the ranges of 24~33 nm.

• Microbiology and Biotechnology Letters
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• v.26 no.3
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• pp.206-212
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• 1998

The effects of the pretreatment with coagulants on the recovery efficiency of poly (3-hydroxybutyrate, PHB) synthesized in Alcaligenes eutrophus were investigated. Al-base or Fe-base coagulants, and the dispersion method of 30% hypochlorite solution and chloroform were used as coagulants and PHB recovery method, respectively The recovery efficiency of PHB from the cells harvested with Al-base coagulants at the range from 0 to 1000 mg-Al/L was similar to that from cells harvested without the coagulants. At these conditions, the concentrations of residual aluminium in the purified PHB were below 250 mg-Al/kg-PHB, indicating the effect of residual aluminum on the characteristics of the purified PHB can be insignificant. When the dosage of coagulants was over 1000 mg-Al/L, the PHB recovery remarkably decreased with increasing the coagulant dosage. However, the PHB recovery could be enhanced by the use of 50% hypochlorite solution instead of 30% hypochlorite solution. Even though the reduction of PHB recovery efficiency was not found by using Fe-base coagulants, the purified PHB was stained pale red due to residual iron, These results suggest that the use of Al-base coagulants did not exert bad influence on neither PHB recovery efficiency and PHB purity.

• Ocean and Polar Research
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• v.26 no.2
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• pp.231-243
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• 2004

Sequential extraction was carried out on twenty two subsamples of three ferromanganese crusts from three seamounts (Lemkein, Lomilik, and Litakpooki) near the Marshall Islands in the western Pacific. The extraction was designed to fractionate Fe-Mn crust forming elements into low defined groups: (1) exchangeable and carbornate, (2) Mn-oxide, (3) Fe-oxyhyd.oxide, and (4) residual fraction. X-ray diffraction result shows that target material were well removed by each extraction step except for CFA in phosphatized crusts generation. According to chemical analysis of each leachate, most of elements in the Fe-Mn crusts are bound with two major phases. Mn, Ba, Co, Ni, Zn, (Fe, Sr, Cu, and V) are strongly bounded with Mn-oxide $({\delta}-MnO_2)$ phase, whereas Fe, Ti, Zr, Mo, Pb, Al, Cu,(V, P, and Zn) show chemical affinity with Fe-oxyhydroxide phase. This result indicates that significant amount of Al, Ti, and Zr can not be explained by detrital origin. Ca, Mg, K, and Sr mainly occur as exchangeable elements and/or carbonate phase. Outermost layer 1 and inner layer 2 which are both young crusts generations are similar in chemical speciations of elements. However, some of Fe-oxyhydroxide bounded elements (Pb, Y, Mo, Ba, Al, and V) in phosphatized innermost layer 3 are released during phosphatization and incorporated into phosphate (Pb, Y, Mo, and Ba) or Mn-oxide phase (Al and V). Our sequential extraction results reveal that chemical speciations of elements in the hydrogenetic crusts are more or less different from interelemental relationship calculated by statistical method based on bulk chemistry.

• Bulletin of the Korean Chemical Society
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• v.29 no.5
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• pp.974-978
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• 2008

Removal of heavy metal ions ($Cd^{2+}$ and $Zn^{2+}$) by electrocoagulation (ECG) was investigated in an acidic condition, which is necessary for re-using or discharging the mediated electrochemical oxidation (MEO) media. Effects of various parameters such as electrolytes, current densities, and electrode materials were examined for a metal-contaminated MEO system using $Fe^{2+}/Fe^{3+}$ pairs as a mediator. It was found that ECG with Al electrodes is greatly affected by the presence of $Fe^{2+}$. [$Cd^{2+}$] and [$Zn^{2+}$] remain constant until [$Fe^{2+}$] reaches a certain concentration level (ca. 10 mM). This preferential removal of $Fe^{2+}$ during ECG with Al electrodes is not alleviated by controlling current densities, potential programs, and solution mixing. ECG with Fe electrodes, on the other hand, resulted in relatively fast removal of $Cd^{2+}$ and $Zn^{2+}$ under coexistence of $Fe^{2+}$, indicative of the different role between $Fe^{n+}$ generated from an electrode and $Fe^{2+}$ initially present in a solution. When ECG was performed with Fe electrodes until [$Fe^{n+}$] became the same as the concentration of initially present $Fe^{2+}$, [$Cd^{2+}$] and [$Zn^{2+}$] were reduced to one-tenth of the initial concentrations, suggesting the possibility of a continuous use of the medium for a subsequent MEO process.