• Title/Summary/Keyword: $NiO/Fe_3O_4$

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Preparation and Characterization of Palladium Nanoparticles Supported on Nickel Hexacyanoferrate for Fuel Cell Application

  • Choi, Kwang-Hyun;Shokouhimehr, Mohammadreza;Kang, Yun Sik;Chung, Dong Young;Chung, Young-Hoon;Ahn, Minjeh;Sung, Yung-Eun
    • Bulletin of the Korean Chemical Society
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    • v.34 no.4
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    • pp.1195-1198
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    • 2013
  • Nickel hexacyanoferrate supported palladium nanoparticles (Pd-NiHCF NPs) were synthesized and studied for oxygen reduction reactions in direct methanol fuel cell. The NiHCF support was readily synthesized by a comixing of $Ni(OCOCH_3)_2$ and equimolar $K_3[Fe(CN)_6]$ solution into DI water under rigorous stirring. After the preparation of NiHCF support, Pd NPs were loaded on NiHCF via L-ascorbic acid reduction method at $80^{\circ}C$. Pd-NiHCF NPs were electrochemically active for oxygen reduction reaction in 0.1 M $HClO_4$ solution. X-ray absorption near edge structure analysis was conducted to measure the white line intensity of Pd-NiHCF to verify the OH adsorption. As a comparison, carbon supported Pd NPs exhibited same white line intensity. This study provides a general synthetic approach to easily load Pd NPs on porous coordination polymers such as NiHCF and can provide further light to load Pd based alloy NPs on NiHCF framework.

Geologic Report on the Goobong Limestone Mine (구봉석회석광산의 지질조사보고(地質調査報告))

  • Lee, Dai Sung
    • Economic and Environmental Geology
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    • v.3 no.1
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    • pp.17-24
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    • 1970
  • The purpose of this report is to prepare a data for the economic evaluation on the Goobong Limestone Mine which is located at the south-eastern corner of the Yongchun Quadrangle scaled in 1:50,000. The accessibility from the mine to railroad was considered in two ways. One is to Dodam Station on Central Railway Line and the other is to reach Songjung-ni village which is near Sangyong Station on Hamback Railway Line. The distance of the former way is 26.7km and the later is 24.2km. Geologically the mine is situated near the base of the Greast Limestone Series which strikes generally $N25^{\circ}{\sim}30^{\circ}E$. The series comprises six different formations from older to younger; Pungchon Limestone Formation and Whajol Formation of Cambrian age, and Dongjum Quartzite Formation, Dumudong Formation, Maggol Limestone Formation and Goseong Formation of lower to middle Ordovician age. 82 samples; 48 from Pungchon Limestone Formation, 11 from Dumudong Formation, 15 from Maggol Limestone Formation and 8 from Goseong Formation, were taken from the series in the crossed direction to the general trend of the series as shown in geological map. They were chemically analyzed on the components of CaO, MgO, $SiO_2$, $R_2O_3(Al_2O_3+Fe_2O_3)$ and ignition loss as shown in table 2, table 3, table 4, and table 5. As seen from the tables, among the formations of the series, middle to upper parts of the Pungchon Limestone Formation and middle and upper parts of the Dumudong Formation have chemical composition as available source for the raw material of cement industry, not only that but also the part of the Pungchon Formation was highly evaluated as source for the flux of iron smelting and the raw material of carbide manufacturing because of its high purity of calcium carbonate.

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A Study on the Oxidation Resistance of Aluminum Cast Iron by Aluminum Content (알루미늄 함량에 따른 알루미늄 주철의 내산화성에 관한 연구)

  • Kim, Dong-Hyuk
    • Journal of Korea Foundry Society
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    • v.40 no.6
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    • pp.135-145
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    • 2020
  • Aluminum cast iron has excellent oxidation resistance, sulfurization resistance, and corrosion resistance. However, the ductility at room temperature is insufficient, and at temperatures above 600?, the strength drops sharply and practicality is limited. In the case of heat-resistant cast iron, high-temperature materials containing Cr and Ni account for 30 to 50% or more. However, these high-temperature materials are expensive. Aluminum heat-resistant cast iron is considered as a substitute for expensive heat-resistant materials. Oxidation due to the aging temperature and holding time conditions increases more in 0 wt.% Al-cast iron than in 2 and 4 wt.% Al-cast iron according to oxidized weight and gravimetric oxide layer thickness measurements. As a result of observing the cross-section of the oxide layer, it was found to contain 0 wt.% of Al-cast iron silicon oxide-containing SiO2 or Fe2SiO4 oxide film. In cast iron containing aluminum, the thickness of the internal oxide layer due to aluminum increases as the aging temperature and retention time increase, and the amount of the iron oxide layer generated on the surface decreases.

Preparation and Characterization of Ferrite Supported on Porous Ceramic Fiber Composites for Co2 Decomposition (이산화탄소 분해용 페라이트 담지 다공성 세라믹 섬유복합체 제조와 물성)

  • Lee, Bong-Soo;Kim, Myung-Soo;Choi, Seung-Chul;Oh, Jae-Hee;Lee, Jae-Chun
    • Journal of the Korean Ceramic Society
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    • v.39 no.8
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    • pp.801-806
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    • 2002
  • The decomposition and/or conversion of carbon dioxide to carbon have been studied using oxygen-deficient ferrites for the reduction of $CO_2$ emission to the atmosphere. In this work, the homogeneous precipitation method using urea decomposition was employed to induce in situ precipitation of Ni ferrite($Ni_{0.4}Fe_{2.6}O_4$) on the porous ceramic fiber support (50 mm diameter${\times}$10 mm thickness). Effects of ferrite loading conditions on the CO2 decomposition efficiency were discussed in this paper. Removal of residual chloride ions and urea by solvent exchange from the porous media after ferrite deposition apparently helps to form spinel ferrite, but does not increase the efficiency of $CO_2$ decomposition. Porous ceramic fiber composites containing 20 wt% (1g) ferrite samples showed 100% efficiency for $CO_2$decomposition during the first three minutes, but the efficiency decreased rapidly after the elapsed time of ten minutes. The characteristic reduction time for the $CO_2$ decomposition efficiency was estimated as about 3∼7 min.

High-frequency Magnetic Properties of Ni-Zn-Co Ferrites Used for Mangetic Shielding in NFC (NFC의 자기 차폐용 Ni-Zn-Co 페라이트 자성체의 고주파 자기특성)

  • Ryu, Yo-Han;Kim, Sung-Soo
    • Journal of Powder Materials
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    • v.21 no.6
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    • pp.429-433
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    • 2014
  • This study investigated the magnetic properties and frequency dispersion of complex permeability of Ni-Zn-Co ferrites used for magnetic shielding in near field communication (NFC) system. The sintered specimens of $(Ni_{0.7}Zn_{0.3})_{1-x}Co_xFe_2O_4$ composition were prepared by the conventional ceramic processing. The coercive force and saturation magnetization were measured by vibrating sample magnetometer. The complex permeability was measured by RF impedance analyzer in the range of 1 MHz~1.8 GHz. The coercive force increased and saturation magnetization decreased with increasing the Co substitution. The real and imaginary parts of complex permeability decreased and the resonance frequency increased with Co substitution, which was attributed to the increase in crystal anisotropy field and reduction in saturation magnetization. The effect of Co substitution could be found in reducing the magnetic loss to nearly zero at the operating frequency of NFC (13.56 MHz).

Influence of Sintering Temperature on Magnetic Properties of Ni-Zn-Cu Ferrites Used for Mangetic Shielding in NFC (NFC의 자기차폐용 Ni-Zn-Cu 페라이트의 자기특성에 미치는 소결온도의 영향)

  • Ryu, Yo-Han;Kim, Sung-Soo
    • Journal of Powder Materials
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    • v.23 no.2
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    • pp.132-135
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    • 2016
  • This study investigates the influence of sintering temperature on the magnetic properties and frequency dispersion of the complex permeability of Ni-Zn-Cu ferrites used for magnetic shielding in near-field communication (NFC) systems. Sintered specimens of $(Ni_{0.7}Zn_{0.3})_{0.96}Cu_{0.04}Fe_2O_4$ are prepared by conventional ceramic processing. The complex permeability is measured by an RF impedance analyzer in the range of 1 MHz to 1.8 GHz. The real and imaginary parts of the complex permeability depend sensitively on the sintering temperature, which is closely related to the microstructure, including grain size and pore distribution. In particular, internal pores within grains produced by rapid grain growth decrease the permeability and increase the magnetic loss at the operating frequency of NFC (13.56 MHz). At the optimized sintering temperature ($1225-1250^{\circ}C$), the highest permeability and lowest magnetic loss can be obtained.

Influence of Heat-treatment Temperature on Microwave Absorbing Properities of Ni-Zn Ferrite (Zi-Zn Ferrite의 전파흡수특성에 미치는 열처리온도의 영향)

  • 조성백;권경일;최경구;김성수;김재묵
    • Journal of the Korean Ceramic Society
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    • v.29 no.3
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    • pp.177-182
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    • 1992
  • The effect of heat-treatment temperature on the microwave absorbing properties was investigated in Ni0.8Zn0.2Fe2O4 specimens. The composite specimens were prepared by modling and curing the mixture of prereacted ferrite powder and silicone rubber. The measurement of complex permeability and permittivity was made by the reflection/transmission method. The most sensitive material constants with heat-treatment temperature is the imaginary (loss) component of permeability. The higher the heat-treatment temperature, the greater the magnetic loss. The composite specimens with high magnetic loss exhibited superior microwave absorbing properties. The quantitative estimation of microwave absorbing properties were made by plotting the observed material constants on the calculated solution map of impedance-matching.

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Formation of Nano-oxides on Porous Metallic Glass Compacts using Hydrothermal Synthesis (수열합성 공정을 이용한 금속 다공체의 나노 산화물 형성)

  • Park, H.J.;Kim, Y.S.;Hong, S.H.;Kim, J.T.;Cho, J.Y.;Lee, W.H.;Kim, Ki Buem
    • Journal of Powder Materials
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    • v.22 no.4
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    • pp.229-233
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    • 2015
  • Porous metallic glass compact (PMGC) are developed by electro-discharge sintering (EDS) process of gas atomized $Zr_{41.2}Ti_{13.8}Cu_{12.5}Ni_{10}Be_{22.5}$ metallic glass powder under of 0.2 kJ generated by a $450{\mu}F$ capacitor being charged to 0.94 kV. Functional iron-oxides are formed and growth on the surface of PMGCs via hydrothermal synthesis. It is carried out at $150^{\circ}C$ for 48hr with distilled water of 100 mL containing Fe ions of 0.18 g/L. Consequently, two types of iron oxides with different morphology which are disc-shaped $Fe_2O_3$ and needle-shaped $Fe_3O_4$ are successfully formed on the surface of the PMGCs. This finding suggests that PMGC witih hydrothermal technique can be attractive for the practical technology as a new area of structural and functional materials. And they provide a promising road map for using the metallic glasses as a potential functional application.

Seasonal Variation and Statistical Analysis of Particulate Pollutants in Urban Air (도시대기립자상물질중 오염성분의 계절적 변동 및 통계적 해석)

  • 이승일
    • Journal of environmental and Sanitary engineering
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    • v.9 no.2
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    • pp.8-23
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    • 1994
  • During the period from Mar., 1991 to Feb., 1992 66 tSP samples were collected by Hi volume air sampler at 1 sampling site in Seoul and the amount of concentration of 21 components(SO$_{4}$$^{2-}$, NO$_{3}$$^{-}$, NH$_{4}$$^{+}$, Cl$^{-}$, Al, Ba, Ca, Cd, Cr, Cu, Fe, It Mg, Mn, Na, Ni, Pt Si, Ti, Zn, Zr ) were measured. And monthly and seasonal variation were surveyed and the principal component analysis( PCA ) were carried out with respect to these amount of pollutants, minimum of visibility and radiation on a horizontal surface. The total amount of soluble ion in water was high in order o(SO$_{4}$$^{2-}$> NO$_{3}$$^{-}$> N%'>Cl$^{-}$ and metal ion was high in order of Na> Ca>Si> Fe> Al> K> Mg> Zn> Pb> Cu>Ti> Mn > Ba> Cr> Zr> Ni> Cd. There was Seasonal variation in concentration for SO$_{4}$$^{2-}$, NH$_{4}$$^{+}$, Cl$^{-}$, Na, Al, Ca, Bt Mg, Fe and Si. It was assumed that the components of the highest concentration on April were depend on yellow sand and the frequency of wind velocity and direction. As the results of PCA, the amount of pollution components was able to characterized with two principal components(Z$_{1}$, Z$_{2}$ ). The first principal components Z$_{1}$ was considered to be a factor indicating the pollutants originated from natural generation and The second principal components Z$_{2}$ was considered to be a factor indicating the pollutants originated from human work. The monthly concentration of pollutants in ISP, minimum of visibility and radiation on a horizontal surface was possible to evaluate by the use of these two principal components Z$_{1}$ and Z$_{2}$ .

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Stainless Steel Surface Oxidized in Strong Oxidizing Solution

  • Kyoung-Chul Lee;Kyoung-Hee Ham;Woon-Sun Ahn
    • Bulletin of the Korean Chemical Society
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    • v.12 no.5
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    • pp.520-524
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    • 1991
  • Stainless steel 304 2B and BA are oxidized in 2.5 M $CrO_3/$ 5.0 M $H_2SO_4$ solution, and elemental composition and oxidized state of the surface region is analyzed as a function of the surface depth using X-ray photoelectron spectroscopy. It is found that Fe and Cr are preferentially oxidized and diffuse outward following the oxidation. Element Ni, the third major component of the steel is not oxidized and remains deep under the surface. It is also found that the oxidized Fe dissolves considerably into the solution thereby enriching the gas-oxide interface with Cr.