• Journal of the Korean Society for Heat Treatment
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• v.28 no.4
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• pp.171-180
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• 2015

The variation in microstructure and texture during continuous annealing was examined in a series of 1.6% Mn-0.1% Cr-0.3% Mo-0.005% B steels with carbon contents in the range of 0.010 to 0.030%. It was found that microstructure of hot band consisted of ferrite and pearlite as a consequence of high coiling temperature, and eutectoid carbon content was between 0.011% and 0.016%. Martensite ranged in volume fraction from 1.5% to 4.0% when annealed at $820{\circ}C$ according to the typical continuous annealing cycle. The critical martensite content for the continuous yielding was about 4% from stress-strain curves. The continuous yielding was obtained in the 0.030% carbon steel and 0.010% to 0.020% carbon steels revealed some yield point elongation ranging from 0.8% to 2.2% in as-annealed conditions. Higher tensile strength in the higher carbon steel is due to both increase in the martensite volume fraction and ferrite grain refinement. Decreasing the carbon content to 0.01% strengthened the intensities of ${\gamma}$-fiber textures, resulting in the increase in the $r_m$ value, which was caused by the lower volume fraction of martensite. The higher carbon steels showed the lower $r_m$ value of about 1.0.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.247-247
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• 2011

플라즈마 분자선 에피택시(plasma-assisted molecular beam epitaxy)법을 이용하여 다공질 실리콘(porous silicon)에 ZnO 박막을 성장하였다. 성장 후, 아르곤 분위기에서 10분 간 다양한 온도(500~700$^{\circ}C$)로 열처리하였다. 다공질 실리콘 및 열처리 온도가 ZnO 박막의 특성에 미치는 영향을 scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL)을 이용하여 분석하였다. 실리콘 기판에 성장된 ZnO 박막은 일반적은 섬구조(island structure)로 성장된 반면, 다공질 실리콘에 성장된 ZnO 박막은 산맥과 같은 구조(mountain range-like structure)로 성장되었다. 열처리 온도가 증가함에 따라 ZnO 박막의 grain size는 증가하였다. 실리콘 기판 위에 성장된 ZnO 박막은 wurtzite 구조를 나타내는 여러 개의 회절 피크가 관찰된 반면, 다공질 실리콘에 성장된 ZnO 박막은 c-축 배향성(c-axis preferred orientation)을 나타내는 ZnO (002) 회절 피크만이 나타났다. 다공질 실리콘에 성장된 ZnO 박막의 구조적 및 광학적 특성이 실리콘 기판에 성장된 ZnO 박막의 특성보다 우수하게 나타났다. 뿐만 아니라, 열처리 온도가 증가함에 따라 다공질 실리콘에 성장된 ZnO 박막의 PL 강도비(intensity ratio)가 실리콘 기판에 성장된 ZnO 박막의 강도비보다 월등하게 증가하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.8
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• pp.455-460
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• 2016

A textured front surface is required in high efficiency silicon solar cells to reduce reflectance and to improve light trapping. Wet etching with alkaline solution is usually applied for mono crystalline silicon solar cells. However, alkali texturing method is not appropriate for multi-crystalline silicon wafers due to grain boundary of random crystallographic orientation. Accordingly, acid texturing method is generally used for multi-crystalline silicon wafers to reduce the surface reflectance. To reduce reflectivity of multi-crystalline silicon wafers, double texturing method with combination of acid and reactive ion etching is an attractive technical solution. In this paper, we have studied to optimize RIE condition by different RF power condition (100, 150, 200, 250, 300 W).

• Journal of the Korean Ceramic Society
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• v.32 no.7
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• pp.799-808
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• 1995

Transparent conductive films of aluminium doped zinc oxide (AZO) have been prepared by using the DC magnetron sputtering with the ZnO : Al (Al2O3 2 wt%) oxide target oriented to c-axis. Electrical and optical properties depended upon the O2/Ar gas ratio. The optical transmittance and sheet resistance of the AZO coated glass was 60~65% and 75Ω/$\square$, respectively at the O2/Ar gas ratio of 0. With the increase of the oxygen partial pressure to 2.0$\times$10-2, they were increased to the values of 81% and 1kΩ/$\square$, respectively. The films with the resistivities of 1.2~1.4$\times$10-3 Ω.cm, mobilities of 11~13 $\textrm{cm}^2$/V.sec and carrier concentrations of 3.5$\times$1020~4.0$\times$1020/㎤ were produced at the optimum O2/Ar gas ratio, which was 0.5$\times$10-2~1.0$\times$10-2. According to XRD analysis, the films have only one peak corresponding to the (002) plane, which indicates that there is a strong preferred orientation of the films. The grain size of ZnO films were calculated to 200~320 $\AA$, which was increased with the O2/Ar gas ratio and Ar gas flowrate.

• Journal of the Korean Ceramic Society
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• v.32 no.7
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• pp.809-816
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• 1995

Ti1-xAlxN films were successfully deposited on high speed steel and silicon wafer by plasma-assisted chemical vapor deposition using a TiCl4/AlCl3/N2/Ar/H2 gas mixture. Plasma process enabled N2 gas to nitride AlCl3, which is not possible in sense of thermodynamics. XPS analyses revealed that the deposited layer contained Al-N bond as well as Ti-N bond. Ti1-xAlxN films were polycrystalline and had single phase, B1-NaCl structure of TiN. Interplanar distance, d200, of (200) crystal plane of Ti1-xAlxN was, however, decreased with Al content, x. Al incorporation into TiN caused the grain size to be finer and changed strong (200) preferred orientation of TiN to random oriented microstructure. Those microstructural changes with Al addition resulted in the increase of micro-hardness of Ti1-xAlxN film up to 2800Kg/$\textrm{mm}^2$ compared with 1400Kg/$\textrm{mm}^2$ of TiN.

• Corrosion Science and Technology
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• v.10 no.4
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• pp.143-150
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• 2011

Copper electroplating has been applied to various fields such as decorative plating and through-hole plating. Technical realization of high strength copper preplating for wear-resistant tools and molds in addition to these applications is the aim of this work. Brighters and levelers, such as MPSA, Gelatin, Thiourea, PEG and JGB, were added in copper sulfate electrolyte, and the effects of these organic additives on the hardness were evaluated. All additives in this work were effective in increasing the hardness of copper electrodeposits. Thiourea increased the hardness up to 350 VHN, and was the most effective accelarator in sulfate electrolyte. It was shown from the X-ray diffraction analysis that preferred orientation changed from (200) to (111) with increasing concentration of organic additives. Crystallite size decreased with increasing concentration of additive. Hardness was increased with decreasing crystallite size, and this result is consistent with Hall-Petch relationship, and it was apparent that the hardening of copper electrodeposits results from the grain refining effect.

• Journal of the Korean Magnetics Society
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• v.11 no.1
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• pp.8-13
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• 2001

Effects of casting Processes and lubricant addition were studied to improve remanence of 31RE-68TM-lB based sintered magnet by using axial pressing process. Strip casting was effective to get the fine and homogeneous microstructure without ${\alpha}$-Fe segregation. The strip cast flake resulted in narrower particle size distribution after jet milling with respect to the conventional cast ingot. During pressing step with a magnetic field, the particle alignment was increased by appropriate addition of liquid lubricant. In this study, it was revealed that narrow particle size distribution and appropriate addition of liquid lubricant were essential to improve the grain alignment and thus the remanence of Nd-Fe-B sintered magnet.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.2
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• pp.32-36
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• 2001

We investigate the surface order, defects and morphology of hexagonal columnar mesophases, Having a crown ether at one end which forms the center of the column and three fluorinated tails at the other, The orientation of the columns was successfully controlled by surface anchoring: Columns were aligned perpendicularly to an evaporated carbon surface, and the planar alignment do asymmetric compounds was induced by a water surface. TEM images show that there is a high degree of perfection in the packing do the cylinders. The hexagonal columnar mesophase (F(sub)h) was confirmed by direct images and the corresponding electron diffractions, where ordered cylindrical moieties are packed on a hexagonal lattice. The column of 12F8-ABG-15C5 was much straighter, compared with that of 12F8-AG-B15C5, resulting from the degrees of regular stacking. Elementary edge dislocation, grain boundary and +1/2 disclination have been observed, although the defects are generally rare.

• Journal of the Korean Ceramic Society
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• v.43 no.9 s.292
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• pp.582-587
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• 2006

Decomposition behavior of $ferro-Si_3N_4$was investigated with varying temperature and holding time in mud components for high temperature refractory applications. Porosities gradually increased with increasing temperature and holding time due to the carbothermal reduction of $Si_3N_4\;and\;SiO_2$. Silicon monoxide (SiO) as a intermediate resulted from evaporation of $Si_3N_4\;and\;SiO_2$ reacted with C sources to generate needle-like ${\beta}-SiC$ and Fe in $Si_3N_4$ acted as a catalyst in order to enhance growth of SiC grain with the preferred orientation. SiC generation yield increased with increasing holding time, all of the $Si_3N_4\;and\;SiO_2$ affected on SiC formation up to 2h. However, SiC generation was only dependent on residual $SiO_2$ over 2h, because the carbothermal reduction reaction of $Si_3N_4$ was no longer possible at that time.

• Journal of the Korean Ceramic Society
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• v.35 no.1
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• pp.88-96
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• 1998

The structural and electrical properties of titanium dioxide(TiO2) thin films deposited on p-type (100) si and 4$^{\circ}$off(100) Si substartes by metalorganic chemical vapor deposition (MOCVD) have been studied with post rapid thermal annealing. TiO2 thin films of anatase phase were grown at 300-500$^{\circ}C$ using titanium post rapid thermal annealing at a temperature of 800$^{\circ}C$ for 30sec. rutile phase was observed in the condition of the deposition temperature over 350$^{\circ}C$ in the ambient air atmosphere and at 500$^{\circ}C$ in cacuu,. SEM and AFM study show-ed surface roughness were increased slightly from 40${\AA}$to 55${\AA}$ after annealing due to grain growth and phase transformation. From capacitane-voltage measurement of Al/TiO2./p-Si structure after annealing we obtained ideal capacitance-voltage characteristics of MOS structure with dielectric constant of 16-22 in case of (100) Si and about 30- in case of 4$^{\circ}$off(100) Si but showed the higher leakage current.