• Journal of the Korean Magnetics Society
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• v.7 no.5
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• pp.250-257
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• 1997

The microstructure and magnetic properties of Fe-Nb-B-N thin film alloys, which produced by rf magnetron sputtering method in $Ar+N_2$ mixed gas atmosphere, were investigated. The $Fe_{70}Nb_{14}B_{11}N_5$ films, annealed at 59$0^{\circ}C$, exhibit soft magnetic properties: $4{\pi}M_s=16.5kG$ , $H_c=0.13Oe$ and ${\mu}_{eff}$ (1~10 MHz)=5, 000. The frequency stability of the Fe-Nb-B-N films has also been found to be good up to 10 MHz. The Fe-Nb-B-N thin film alloys annealed at 59$0^{\circ}C$ consist of three phase; fine crystalline $\alpha$-Fe phase with grain size of about 5~10 nm, Nb-B rich amorphous phase and Nb-nitride precipitates with the size of less than 3 nm. Annealed Fe-Nb-B films have two phases; $\alpha$-Fe grains with the size of about 10 nm and Nb-B rich amorphous phase. The addition of N decreased $\alpha$-Fe grain size due to the precipitation of NbN. The good magnetic properties of the Fe-Nb-B-N film alloys are due to fine $\alpha$-Fe grains resulting from the precipitation of NbN.

• Journal of the Korean Magnetics Society
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• v.4 no.1
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• pp.7-11
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• 1994

Ferromagnetic resonance experiment was performed to study the variations of micromagnetic structure with heat treatment of melt spun $Fe_{76}Cu_{1}Nb_{3}Si_{14}B_{6}$ alloy for 1h at every $50^{\circ}C$ in the temperature range of $400^{\circ}C-700^{\circ}C$. The variations of micromagnetic structure was discussed qualitatively in terms of the variations of line width ${\Delta}H_{p-p}$ and resonance magnetic field $H_{res}$. With increasing armealing temperature to $400^{\circ}C$, ${\Delta}H_{p-p}$ decreases and $H_{res}$ increases due to the decrease in magnetic anisotropy resulting from structural relaxation during heat treatment. With increasing annealing temperature from 400 to $500^{\circ}C$, ${\Delta}H_{p-p}$ increases and $H_{res}$ decreases due to the increase in magnetic anisotropy resulting from the formation of nanocrystalline particles embedded in an amorphous matrix. With increasing armealing temperature from 500 to $550^{\circ}C$, ${\Delta}H_{p-p}$ decreases and $H_{res}$ increases due to the decrease in magnetic anisotropy resulting from the formation of homogeneous nanocrystalline structure with a minor amorphous phase. Further increase in armealing temperature above $550^{\circ}C$ C causes ${\Delta}H_{p-p}$ to increase and $H_{res}$ to decrease due to the increase in magnetic anisotropy due to the formation of inhomogeneous grain structure and intermetallic compounds.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.1
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• pp.32-36
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• 2021

This study was investigated in carbon diffusion behavior of laser-carburized TiZrN coating layer and the changes of mechanical properties. The carbon paste was deposited on TiZrN coatings, and the laser was irradiated to carburize into the coatings. The XRD peak corresponding to the (111) plane shifted to a lower angle after the carburization, showing the lattice expansion by doped carbon. The decreased grain size implied the compression by the grain boundary diffusion of carbon. The XPS spectra for the bonding states of carbon was analyzed that carbon was substitute to nitrogen atoms in TiZrN, as carbide, through the thermal energy of laser. In addition, the combination of sp2 and sp3 hybridized bonds represented the formation of an amorphous carbon. The cross-sectional TEM image and the inverse FFT of the TiZrN coating after carburizing were observed as the wavy shape, confirming the amorphous phase located in grain boundaries. After the carburization, the hardness increased from 34.57 GPa to 38.24 GPa, and the friction coefficient decreased by 83 %. In particular, the ratio of hardness and elastic modulus (H/E) which is used as an index of the elastic recovery, increased from 0.11 to 0.15 and the wear rate improved by 65 %.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.6
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• pp.1095-1100
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• 2021

In this study, ITZO thin films were deposited on glass, sapphire, and PEN substrates by RF magnetron sputtering, and their electrical and optical properties were investigated. The resistivity of the ITZO thin film deposited on the glass and sapphire substrates was 3.08×10-4 and 3.21×10-4 Ω-cm, respectively, showing no significant difference, whereas the resistivity of the ITZO thin film deposited on the PEN substrate was 7.36×10-4 Ω-cm, which was a rather large value. Regardless of the type of substrate, there was no significant difference in the average transmittance of the ITZO thin film. Figure of Merits of the ITZO thin film deposited on the glass substrate obtained using the average transmittance in the absorption region of the amorphous silicon thin film solar cell and the absorption region of the P3HT : PCBM organic active layer were 10.52 and 9.28×10-3 Ω-1, respectively, which showed the best values. Through XRD and AFM measurements, it was confirmed that all ITZO thin films exhibited an amorphous structure and had no defects such as pinholes or cracks, regardless of the substrate type.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.58-63
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• 2022

Graphite has been used as an anode material for lithium-ion batteries for the past 30 years due to its low de-/lithiation voltage, high theoretical capacity of 372 mAh/g, low price, and long life properties. Recently, all-solid-state lithium-ion batteries (ASSLB), which are composed of inorganic solid materials with high stability, have received great attention as electric vehicles and next-generation energy storage devices, but research works on graphite that works well for ASSLB systems are insufficient. Therefore, we induced the performance improvement of ASSLB anode electrode graphite material by removing the amorphous carbon present in the carbon material surface, acting as a resistive layer from the graphite. As a result of X-ray diffraction (XRD) analysis using heat treated graphite in air at 400, 500, and 600 ℃, the full width at half maximum (FWHM) at (002) peak was reduced compared to that of bare graphite, indicating that the crystallinity of graphite was improved after heat treatment. In addition, the discharge capacity, initial coulombic efficiency (ICE) and cycle stability increased as the crystallinity of graphite increased after heat treatment. In the case of graphite annealed in air at 500 ℃, the high capacity retention rate of 331.1 mAh/g and ICE of 86.2% and capacity retention of 92.7% after 10-cycle measurement were shown.

• Journal of the Korean Electrochemical Society
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• v.9 no.1
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• pp.34-39
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• 2006

Electrochemical properties of Cu foil current collector with a $Li_{0.5}La_{0.5}TiO_3$ Cu a Si thin film deposited by r.f sputtering as an anode for Li free battery were evaluated. The Cu foil current collectors were lied in and out of plasma during sputtering process. The X-ray diffraction results indicated that the as-deposited Si and $Li_{0.5}La_{0.5}TiO_3$ thin films in and out of plasma did not show any crystalline difference. The $Li_{0.5}La_{0.5}TiO_3$ film in plasma and Si film out of plasma showed better cyclability since crystalline $Li_{0.5}La_{0.5}TiO_3$ has much higher ionic conductivity and crystalline Si film is much sensitive far volume change during charge-discharge process. These results suggested that the deposition of amorphous Si on Cu foil current collector is much better for fabrication of Li free battery and it can be useful for the unique battery with a cycling number constraint of below 10.

• Economic and Environmental Geology
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• v.35 no.6
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• pp.491-508
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• 2002

While about 80% of Jeju soils are classified as Andisols, the soils derived from volcanic ash in Dangsanbong are not Andisols. There is a significant difference of precipitation in localities of Jeju island. The study area is characterized by the lowest amount of annual rainfall in Jeju Island, and by the layered silicates as dominant solid phase in clay fraction. The purpose of this study was to characterize the mineralogy of the non-Andie soils in detail, especially hydroxy-interlayered silicates. Two major soil horizons are recognized in the soil profile developed in the Dangsanbong area, which can be designated as A and C. The soil pH($H_{2}0$), ranges from 6.6 to 7.3 increasing with depth, is higher than that of typical Andisols(pH<6.0). While the pH(NaF), ranges from 9.49 to 9.81, indicates that significant amount of amorphous phases might be present as exchanging complexes. It is estimated to about 1.542.88 wt% by using chemical selective dissolution. The organic content of surface horizon is about 2 wt%. This soil are composed of quartz, feldspar and olivine as major constituents with minor of silicate clays. Quartz is frequently observed in A and distinctly decreases in its amount with depth, while olivine is dominant phase in C and rarely observed in A. In the <0.2$\mu\textrm{m}$ size fraction, smectite and kaolinite/smectite interstratification are dominant with minor of illite. The amounts of smectite decrease with depth, while the amounts of kaolinite/smecite interstratification increase with depth, which indicates the trend of mineral transformation with increasing the degree of weathering. The proportion of kaolinite in kaolinite/smectite interstratification is about 85%, and is not changed significantly through the profile. In the 2-0.2$\mu\textrm{m}$size fraction, vermiculite, smectite, illite and kaolinite are major components with minor of chlorite. Most of chlorite are interstratified with smectite. Chlorite which is not interstratified with smectite occurs only in surface horizon. The proportion of the chlorite in the chlorite/smectite interstratification is 59-70(%) and increases with depth. Hydroxy-interlayered vermiculite(HIV) with hydroxy-Fe/AI in their interlayers occurs in both A and C horizon. The amounts of hydroxy-Fe/AI decrease with depth. Hydroxy-interlayered smectite(HIS) of which interlayers might be composed of hydroxy-Mg/Al occurs only in C horizon. As the results of mineralogical investigation for the soil profile in the study area, clay minerals might be changed and evolved through the following weathering sequences: 1) Smectite Kaolinite, HIS, Vermiculite, 2) Vermiculite HIV Chlorite.

• Journal of the Mineralogical Society of Korea
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• v.20 no.3
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• pp.147-153
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• 2007

Kaolinite [$Al_2Si_2O_5(OH)_4$] was successfully synthesized by a hydrothermal process from amorphous $Al(OH)_3$ and $SiO_2$ at $230^{\circ}C$ under the pressure of $30 kg/cm^2$. The experiments were performed varying temperatures ($180{\sim}280^{\circ}C$), pressure ($10{\sim}60kg/cm^2$), chemistry ($Al_2O_3/SiO_2 = 0.5{\sim}0.38$) and pH ($0.3{\sim}9.5$) of the solution. The autoclaving was carried out in a closed stainless steel vessel. Kaolinite appears from the starting composition of $Al_2O_3/SiO_2= 0.5$ with boehmite and was stable as a single phase with the composition of $Al_2O_3/SiO_2=0.45$. Boehmite was a stable phase below $200^{\circ}C$ for the 240 h period of autoclaving, but kaolinite appeared even in 20 h at $230^{\circ}C$. The single kaolinite phase of a good crystallinity was observed at pH ranging 2 to 6. That indicates that pH is one of the most critical parameters for the successful formation of kaolinite. The optimal molar ratio of $Al_2O_3$ to $SiO_2$ was determined to be 0.45. The XRD pattern of the synthesized kaolinite coincided with that of natural one and its morphology was the cluster type of the kaolinite crystals (diameter = ${\sim}3{\mu}m$), irrespective of starting material, composition and temperature.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1149-1154
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• 2014

To observe the tunneling phenomenon of oxide semiconductor transistor, The Indium-gallum-zinc-oxide thin film transistors deposited on SiOC as a gate insulator was prepared. The interface characteristics between a dielectric and channel were changed in according to the properties of SiOC dielectric materials. The transfer characteristics of a drain-source current ($I_{DS}$) and gate-source voltage ($V_{GS}$) showed the ambipolar or unipolar features according to the Schottky or Ohmic contacts. The ambipolar transfer characteristics was obtained at a transistor with Schottky contact in a range of ${\pm}1V$ bias voltage. However, the unipolar transfer characteristics was shown in a transistor with Ohmic contact by the electron trapping conduction. Moreover, it was improved the on/off switching in a ambipolar transistor by the tunneling phenomenon.

• Applied Chemistry for Engineering
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• v.21 no.4
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• pp.440-444
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• 2010

$SnO_2$ powders were prepared from the calcination of stannic acids precipitated from the aqueous solution of $SnCl_4$ with ammonium nitrate as a precipitator at $90^{\circ}C$. For the comparison of properties, the stannic acids were prepared from the homogeneous precipitation method using urea as a precipitator at the same temperature. The stannic acid from ammonium nitrate at a thermal gravity analysis showed the weight loss until $700^{\circ}C$ and the percentage of total weight loss was 16.5%. The crystallization of stannic acid into $SnO_2$ finished in the calcination at $600^{\circ}C$ for 2 h. The crystallite size of $SnO_2$ increased with the increase of calcination temperature and initial concentration of $SnCl_4$ solution. In case of the same calcination condition, $SnO_2$ prepared from homogeneous precipitation using urea had a relatively smaller crystallite size rather than $SnO_2$ prepared from ammonium nitrate.