• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.778-781
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• 1995

The mixed ferrite $Ni_{x}Co_{1-x}Fe_{2}O_{4}$ have been investigated by X-ray and $M\"{o}ssbauer$ spectoscpy. From the results of X-ray diffraction measurement the structure for this system is spinel, and the lattice constant is in accord with Vegard's law. $M\"{o}ssbauer$ spectra of $Ni_{x}Co_{1-x}Fe_{2}O_{4}$ have been taken at various temperature ranging from 13 to 800 K. The isomer shifts indicate that the valence states of the irons at both A(tetrahedral) and B(octahedral) sithe are found to be in ferric high-spin states. The variation of magnetic hyperfine fields at the A and B sites are explained on the basis on A-B and B-B supertransferred hyperfine interactions. It is found that Debye temperatures for the A and B sites of $CoFe_{2}O_{4}$ and $NiFe_{2}O_{4}$ are found to be ${\theta}_{A}=734{\pm}5K,\;{\theta}_{B}=248{\pm}5K,\;and\;{\theta}_{A}=378{\pm}5K,\;{\theta}_{B}=357{\pm}5K$, respectively. Atomic migration of $Ni_{0.3}Co_{0.7}Fe_{2}O_{4}$ starts near 450 K and increases rapidly with increasing temperature to such a degree that 61 % of the ferric ions at the A site have moved over to the B site by 700 K.

• Journal of Magnetics
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• v.11 no.2
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• pp.87-89
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• 2006

CoFeV thin film alloys were fabricated by electrodeposition, and the dependences of their magnetic properties on the current density were investigated using an X-ray diffractometer and a vibrating sample magnetometer. The deposited Co increased from about 45 to 60 wt.% with increasing current density until $25mA/cm^2$ whereas the deposited Fe decreased from about 55 to 40 wt.% with increasing current density until $25mA/cm^2$. The deposited V, about 2 wt.%, was independent of the current density. The current efficiencies of electrodeposition decreased linearly from about 40 to 29% with increasing current density. The X-ray diffraction measurement showed that all peaks of the CoFeV films were consistent with those of a typical Co hcp and Fe bcc mixed phase. An increase in the current density decreased the grain size and increased the lattice constant. The saturation magnetization increased from about 2.2 to 2.5 T with increasing current density. The coercivity measured in the perpendicular direction decreased from 260 to 120 Oe with increasing current density; a drastic drop of 60 Oe occurred at $5mA/cm^2$. The coercivity measured in the in-plane direction remained almost unchanged, at about 20 Oe, with increasing current density.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.3
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• pp.456-464
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• 1997

The effect of the additives on the Zn-Ni alloy electrocrystallization from a chloride bath was investigated by means of electrochemical methodes, scanning electron microscopy and measurement of surface appearance, X-ray diffraction patterns. The additives tested were the surfactant of naphtalene-derivative, saccharin and aliphatic alcohol. The resistance of electrodeposit increased by adding the additives, whereas the effect of additives on resistance was different with current density. The nickel content of alloy deposit was increased by the addition of alcohol, while decreased by the surfactant. The surface roughness, appearance and morphology of deposit were also influenced by the type of additive. The fine, compact grains and good surface roughness could be obtained from the surfactant or alcohol -added bath, and the surfactant or saccharin improved the surface appearance.

• Journal of the Korean institute of surface engineering
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• v.42 no.6
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• pp.280-286
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• 2009

In this study, the corrosion property of copper alloy tubes in seawater has been investigated. Three copper alloys of nominal composition Cu-20Zn-2Al(Al-Brass), Cu-30Ni(CN70/30) and Cu-10Ni(CN90/10) were considered. The samples were immersed in 3%NaCl flowing solution at $90^{\circ}C$ for 30, 50 and 80 days. Corrosion rate of copper alloy tubes in 3%NaCl flowing solution was investigated by weight-loss measurements and electrochemical test. The CN70/30 showed lowest corrosion rate among three copper alloy tubes. Because of passive films formation, corrosion rates of three types of copper tubes were decrease with time. Surface characteristics of copper alloy tubes were analyzed by optical micrograph(OM), scanning electronic microscopy (SEM), energy dispersive X-ray analysis(EDAX) and X-ray diffraction patterns(XRD). CN70/30 showed partly pitting problem on the surface owing to high Fe content, even though having high resistant against corrosion. Cracks appeared on the surface of CN90/10 and CN70/30 after more than 50 days immersion, which could be derived from high nickel contents.

• Bulletin of the Korean Chemical Society
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• v.33 no.2
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• pp.398-402
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• 2012

ZnSe/$SiO_2$ coaxial nanowires were synthesized by a two-step process: thermal evaporation of ZnSe powders and sputter-deposition of $SiO_2$. Two different types of nanowires are observed: thin rod-like ones with a few to a few tens of nanometers in diameter and up to a few hundred of micrometers in length and wide belt-like ones with a few micrometers in width. Room-temperature photoluminescence (PL) measurement showed that ZnSe/$SiO_2$ coaxial nanowires had an orange emission band centered at approximately 610 nm. The intensity of the orange emission from the $SiO_2$-sheathed ZnSe nanowires was enhanced significantly by annealing in a reducing atmosphere whereas it was degraded by annealing in an oxidizing atmosphere. The origins of the PL changes by annealing are discussed based on the energy-dispersive X-ray spectroscopy analysis results.

• Bulletin of the Korean Chemical Society
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• v.31 no.2
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• pp.331-334
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• 2010

In the present study, carbon supports mixed with purified multi-walled carbon nanotubes (MWNTs) and carbon blacks (CBs) were used to improve the cell performance of direct methanol fuel cells (DMFCs). Additionally, the effect of $O_2$ plasma treatment on CBs/MWNTs supports was investigated for different plasma RF powers of 100, 200, and 300 W. The surface and structural properties of the CBs/MWNTs supports were characterized by FT-IR, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and inductive coupled plasma-mass spectrometer (ICP-MS). The electrocatalytic activity of PtRu/CBs/MWNTs catalysts was investigated by cyclic voltammetry measurement. In the experimental results, the oxygen functional groups of the supports were increased with increasing plasma RF power, while the average Pt particle size was decreased owing to the improvement of dispersibility of the catalysts. The electrochemical activity of the catalysts for methanol oxidation was gradually improved by the larger available active surface area, itself due to the introduction of oxygen functional groups. Consequently, it was found that $O_2$ plasma treatments could influence the surface properties of the carbon supports, resulting in enhanced electrocatalytic activity of the catalysts for DMFCs.

• Korean Journal of Materials Research
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• v.26 no.4
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• pp.222-227
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• 2016

Tin oxides have been studied for various applications such as gas detecting materials, transparent electrodes, transparent devices, and solar cells. p-type SnO is a promising transparent oxide semiconductor because of its high optical transparency and excellent electrical properties. In this study, we fabricated p-type SnO thin film using rf magnetron sputtering with an SnO/Sn composite target; we examined the effects of various oxygen flow rates on the SnO thin films. We fundamentally investigated the structural, optical, and electrical properties of the p-type SnO thin films utilizing X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV/Vis spectrometry, and Hall Effect measurement. A p-type SnO thin film of $P_{O2}=3%$ was obtained with > 80% transmittance, carrier concentration of $1.12{\times}10^{18}cm^{-3}$, and mobility of $1.18cm^2V^{-1}s^{-1}$. With increasing of the oxygen partial pressure, electrical conductivity transition from p-type to n-type was observed in the SnO crystal structure.

• Korean Journal of Materials Research
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• v.19 no.10
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• pp.555-561
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• 2009

Expanded graphite (EG) is synthesized by chemical intercalation of natural graphite (NG) and rapid expansion at high temperature, with titanium n-butoxide (TNB) used as titanium source by a sol-gel method to prepare EG-TiO$_2$ composite. The performances of the prepared EG-TiO$_2$ composite are characterized by BET surface area measurement, scanning electron microscopy (SEM), X-ray diffraction patterns (XRD) and energy dispersive X-ray analysis (EDX). To compare the photocatalytic activities of the EG-TiO$_2$ composite, three kinds of dye solutions, methylene blue (MB), methylene orange (MO) and rhodamine B (RhB), and two kinds of light source, UV light and visible light (VL), are used. Comparing the results, it can be clearly seen that the degradation of all of the dye solutions under irradiation by UV light is much better than that under irradiation by visible light, and the decomposition of MB solution was better than that of both of MO and RhB solution.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.369-372
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• 2009

In the present study, the effect of chemical treatment on graphite nanofibers (GNFs) supports with various concentrated nitric acids was investigated for methanol oxidation. To optimize the electrocatalytic activity, PtRu catalysts were deposited on GNF supports by impregnation method. The surface and structural properties of the GNF supports were characterized by X-ray photoelectron spectroscopy (XPS), element analyzer (EA), and X-ray diffraction (XRD). The morphology of the catalysts was observed by means of transmission electron microscopy (TEM). The electrocatalytic activity of PtRu/GNF catalysts was investigated by cyclic voltammetry measurement. As a result, the oxygen functional groups were introduced on the GNF supports and were gradually increased with increasing of concentrated nitric acid, causing the smaller particle size and higher loading level. And the electrocatalytic activity of the catalysts for methanol oxidation was gradually improved. Consequently, it was found that chemical treatments could influence on surface properties of the carbon supports, resulting in enhancing the electrocatalytic activity of the catalysts for DMFCs.

• Textile Coloration and Finishing
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• v.28 no.1
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• pp.33-39
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• 2016

The crystal structure of nylon 56 fibers post extended by drawing process was investigated by synchrotron x-ray scattering measurement. In as-cast fiber, distinct (004) and (020) diffraction peaks were observed and they were related to initial metastable alignment of nylon molecules. With increase in the drawing ratio, (110) peak intensity was increased in vertical direction with decreasing (020) peak. At the same time, (004)' peak evolved position tilted to 29 degrees from the (004) peak. This evolution is directly related to stable crystalline phase of nylon 56 originated from additional formation of hydrogen bondings between N-H and C=O by post drawing process. We also compared density variation, stress-strain curves of the fiber as a function of drawing ratio and strain. The variations of density and tanacity also supported the increase of stable structure of nylon 56.