• Korean Journal of Materials Research
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• v.9 no.4
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• pp.428-433
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• 1999

An objective of this study is to compare the characteristics of coating layer of plasma sprayed fine $Al_2O_3$ and those of layer by commercial $Al_2O_3$(Metco 105). The microstructure of fine $Al_2O_3$ coating layer was denser compared with commercial $Al_2O_3$ coating layer. The surface roughness$(R_a)$ of the layer by the fine $Al_2$O$_3$ was lower compared with that of commercial $Al_2O_3$. Thickness of splat for fine $Al_2O_3$ was $1.4\mu\textrm{m}$ while the commercial $Al_2O_3$ was $3.53\mu\textrm{m}$. The main phase existing in coating layer was of $\gamma-Al_2O_3$ and the fraction of $\alpha-Al_2O_3$ in fine $Al_2O_3$ coating layer was 8.39% and that of commercial $Al_2O_3$ was 13.79%. Microhardness was no great difference between the fine and commercial $Al_2O_3$ but deviation of the fine $Al_2O_3$ coating layer was relatively large. Accordingly, the strength of splat of the coating was expected that fine $Al_2O_3$was lower than commercial $Al_2O_3$ powder.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.4
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• pp.147-152
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• 2011

ZnO nanorods fabricated on a Zn substrate pre-coated with ZnO as a seed layer by the hydrothermal method were studied mainly as a function of ZnO precursor concentration. Characteristic features by using field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) were investigated to define the changed micro-structure and crystalline phase of the ZnO nanorods according to the experimental conditions. The nanorod morphology strongly depended on the precursor concentration. For example, ZnO nanorods vertically aligned with a hexagonal (002) oriented structure with a diameter of 600~700 nm and length of $6.75{\mu}m$ were clearly observed at the highest concentration of 0.015 M. The strong hexagonal structure was believed to be associated with the highest photoluminescene (PL) intensity and a promising voltage value of ca. 6.069 V at $1000{\mu}A$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.2
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• pp.69-73
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• 2010

The microstructural change of the $Sm_{0.5}Sr_{0.5}CoO_3$ (SSC) electrode for a cathode material of solid oxdie fuel cells (SOFCs) deposited by the electrostatic spray deposition (ESD) technique was characterized. Samarium chloride hexahydrate $(SmCl_3{\cdot}6H_2O)$, strontium chloride hexahydrate $(SrCl_2{\cdot}gH_2O)$, cobalt nitrate hexahydrate $(Co(No_3)_2{\cdot}6H_2O)$ as starting materials and methyl alcohol as solvent were used to make precursor solution. The suitable porous SSC films for a cathode of SOFCs were deposited on Si substrate and it is observed that the microstructure was strongly dependent on processing parameters such as deposition time, substrate temperature, and applied voltage. Scanning Electron Microscope (SEM) and X-ray Diffractometer (XRD) measurement were used to investigate the microstructure and crystallinity of the SSC films. The ESD technique is shown to be an efficient method in which the SOFCs' cathode film can be fabricated with the desired phases and microstructure.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.1
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• pp.37-43
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• 2013

Conductivity of LSGMC materials were affected by secondary phase segregation, composition and synthetic route. $La_{0.8}Sr_{0.2}Ga_{0.8}Mg_{0.1}Co_{0.1}O_{3-{\delta}}$ (LSGMC) powders were prepared using the glycine nitrate process to produce high surface area and compositionally homogeneous powders. The powders were synthesized with different 0.5, 1, 1.5, 2, 2.5 of glycine/cation molar ratios. A single perovskite phase from the synthesized powders was characterized with X-ray diffraction patterns. The obtained sintered pellets showed the dense grain microstructure. In case of 1.5 molar ratio, its density was higher than the others. The electrical conductivity measured at $800^{\circ}C$ was observed to be 0.131 $Scm^{-1}$. In addition, the linear thermal expansion behavior was indicated between $25^{\circ}C$ and $800^{\circ}C$.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.33-37
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• 2004

Cu$_{0.1}$Fe$_{0.9}$Cr$_2$S$_4$ has been studied with Mossbauer spectroscopy, x-ray diffraction, vibrating sample magnetometer (VSM), and magnetoresistance (MR) measurement. The crystal structure was determined to be a cubic spinel with lattice parameter a$_{0}$=9.9880 $\AA$. The MR measurements show a semiconductor behavior below 110 K and metal behaved above 100 K. The temperature dependence of magnetization of Cu$_{0.1}$Fe$_{0.9}$Cr$_2$S$_4$ was reported. In addition to a large irreversibility between the zero-field-cooling (ZFC) and the field-cooling (FC) magnetization at applied field H=100 Oe, a cusp-like anomaly was observed in both the FC and ZFC curves. It shifted toward the lower temperature region with increasing magnetic field, and then showed convex type maximum at 110 K, under the applied field of 5 kOe. The Mossbauer spectra were measured from 15 K to room temperature. The asymmetric line broadening was observed for the sample Cu$_{0.1}$Fe$_{0.9}$Cr$_2$S$_4$, and it was considered to be dynamic Jahn-Teller relaxation. The charge state of Fe ions was ferrous in character. The unusual reduction of magnetic hyperfine field below 110 K was interpreted in terms of cancellation effect between the mutually opposite orbital current field (H$_{L}$) and Fermi contact field (H$_{C}$).

• Journal of the Korean Magnetics Society
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• v.17 no.2
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• pp.86-89
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• 2007

[ $FeCr_2Se_4$ ] prepared under the high pressure (3 GPa) has been studied with x-ray, neutron diffraction techniques, superconducting quantum interference device (SQUID) magnetometer, resistance, and Mossbauer spectroscopy. The temperature dependence of resistance is explained by Mott-VRH and small polaron model for the regions I (T<20 K) and II (T>42 K), respectively. Neutron diffraction results show an antiferromagnetic spin-lattice coupling near the Neel temperature. So finally the distance of atom is enlarged in region (110$FeCr_2Se_4$ shows convex type of temperature dependence.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.115-121
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• 2013

We fabricated thin film transistors (TFTs) using TiInZnO(TiIZO) thin films as active channel layer. The thin films of TiIZO were deposited at room temperature by RF-magnetron co-sputtering system from InZnO(IZO) and Ti targets. We examined the effects of titanium addition by X-ray diffraction, X-ray photoelectron spectroscopy and the electrical characteristics of the TFTs. The TiIZO TFTs were investigated according to the radio-frequency power applied to the Ti target. We found that the transistor on-off currents were greatly influenced by the composition of titanium addition, which suppressed the formation of oxygen vacancies, because of the stronger oxidation tendency of Ti relative to that of Zn or In. A optimized TiIZO TFT with rf power 40W of Ti target showed good performance with an on/off current ratio greater than $10^5$, a field-effect mobility of 2.09 [$cm^2/V{\cdot}s$], a threshold voltage of 2.2 [V] and a subthreshold swing of 0.492 [V/dec.].

• Clean Technology
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• v.19 no.3
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• pp.257-263
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• 2013

The zinc phosphate-coated mica (ZP/mica) pigments were prepared using phosphoric acid, zinc nitrate and mica as starting materials, and used as anticorrosive pigments. The scanning electron microscopy (SEM) and x-ray diffraction (XRD) techniques were used to observe the morphology and crystal structure of prepared pigments. The prepared pigments were incorporated into an epoxy binder to prepare coating and the corrosion inhibition performance of the pigments was evaluated using electrochemical impedance spectroscopy (EIS). It was found that the anticorrosive performance of the ZP/mica pigment prepared at $70^{\circ}C$ was the better than that prepared at $20^{\circ}C$. The formation of ZnO, in addition to $Zn_3(PO_4)_2{\cdot}2H_2O$, was observed on ZP/mica pigment prepared at $70^{\circ}C$. The excellent anticorrosive performance of ZP/mica pigment could be ascribed to the synergistic effect with electrochemical anticorrosive mechanism from zinc compounds on mica and barrier anticorrosive mechanism from lamellar mica.

• Korean Journal of Materials Research
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• v.10 no.1
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• pp.77-82
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• 2000

A surface of polytetrafluoroethylene(PTFE) was modified with changing ion doses by 1 keV $Ar^+$ ion irradiation and Cu films having thickness $5000\;{\AA}$ were deposited on the modified PTFE. The SEM study showed that the surface texture of modified PTFE was in the form of cones whose height increased depending on ion doses. Through XPS spectra, it was found that the intensity of F ls peaks decreased with ion doses by preferential sputtering of F atoms and the C-C and / or C-F chains were formed by the crosslinking in the newly unstable chains. Cu films were deposited uniformly along the filaments formed on the modified PTFE. In x-ray diffraction (XRD) spectra of deposited Cu films on modified PTFE, a preferred orientation along (111) and (200) planes was found and the peak intensity of (111) plane increased as surface roughness of modified PTFE increased. The resistivity of Cu films was changed from $2.7{\mu}{\Omega}cm$ of unmodified PTFE to $4.3{\mu}{\Omega}cm$ of modified PTFE at ion dose of $1{\times}10^{16}/\textrm{cm}^2$ and the abrupt increase of resistivity in the modified PTFE at ion dose of $1{\times}10^{17}/\textrm{cm}^2$ was due to being cut off the film which resulted from the increased surface roughness.

• Journal of the Korean Magnetics Society
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• v.11 no.2
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• pp.58-62
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• 2001

The L $i_{0.5}$F $e_{2.5-x}$A $l_{x}$ $O_4$ systems (x=0, 0.3, 0.6, 0.9, 1.2, 1.5) were investigated by X-ray diffraction and Mossbauer spectroscopy. The structure of all the samples is cubic spinel type and lattice constant decrease with increasing Al content x. The Moissbauer spectra reveal two sextet for 0$\leq$x$\leq$0.6, two sextet and a doublet for 0.9$\leq$x$\leq$1.2, and a doublet for x=1.5. The cation distribution of the samples is (L $i_{1-a}$$^{+}$F $e_{a}$ $^{3+}$)$^{A}$[L $i_{a-0.5}$$^{+}$A $l_{2.5-a-x}$$^{+}$F $e_{2.5-a-x}$$^{3+}$]$^{B}$ $O_4$$^{2-}$ and substituted $Al^{3+}$ ions decrease the covalency of F $e^{3+}$- $O^{2-}$ bond in B-sites and A-B super-exchange interactions.tions.s.tions.ons.s.