• Journal of the Korean Society for Heat Treatment
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• v.27 no.4
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• pp.175-179
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• 2014

IGZO thin films were prepared by radio frequency (RF) magnetron sputtering on glass substrates and then annealed in vacuum for 30 minutes at 100, 200 and $300^{\circ}C$, respectively. The thickness of films kept at 100 nm by controlling the deposition rate. While the optical transmittance and sheet resistance of as deposited films were 91.9% and $901{\Omega}/{\Box}$, respectively, the films annealed at $300^{\circ}C$ show the optical transmittance of 95.4% and the sheet resistance of $383{\Omega}/{\Box}$. The experimental results indicate that vacuum-annealed IGZO film at $300^{\circ}C$ is an attractive candidate for the transparent thin film transistor (TTFT) in large area electronic applications.

• Journal of the Korean Ceramic Society
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• v.34 no.8
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• pp.834-842
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• 1997

Controlled Ca impurity implanted inner crack-like pore in the high purity alumina single crystal, sapphire, had been created by micro-fabrication technique, which includes ion implantation, photo-lithography, Ar ion milling, and hot press technique. The morphological change and the healing of cracklike pore in Ca doped high purity single crystal alumina, sapphire, during high temperature heat treatment in vacuum were observed using optical microscopy. The dot-like surface roughening was developed and hexagon like crystal appeared on inner surface of crack-like pore after heat treatment. Bar type crystals, probably CaO.6Al2O3, were observed on the inner surface after 1 hour heat treatment at 1, 50$0^{\circ}C$, but this bar type crystal disappeared after 1 hour heat treatment at 1, $600^{\circ}C$. This disappearance means that there should be a little increase of Ca solubility limit to alumina at this temperatures.

• Journal of the Korean Society for Heat Treatment
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• v.34 no.6
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• pp.272-280
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• 2021

The influence of acetylene flow rates on the carburizing behavior of an AISI 4115 steel in 1 ton-class mass production-type vacuum carburizing furnace has been studied through microstructure, carbon concentration, hardness analyses. The AISI 4115 steels were carburized with various flow rates (20, 32.7, 60 l/min) and locations in the furnace (top, center, bottom) at 950℃. The acetylene flow rate played an important role in controlling the carburizing properties of carburized samples, such as effective case depth and uniformity carburizing according to location in the furnace. At an acetylene flow rate of 20 l/min, the carburized samples had a shallow average hardened layer (0.645 mm) compared to the target hardening depth (1 mm) due to low carbon flux and spatial uniformity of carburization (17.8%) in the furnace. At a flow rate of 60 l/min, the carburized samples showed an average hardened layer (1.449 mm) deeper than the target hardening depth and had the spatial uniformity of carburization (98.8%). In particular, at a flow rate of 32.7 l/min, the carburized samples had an average hardened layer (1.13 mm) close to the target hardening depth and had the highest carburizing uniformity (99.1%). As a result, an appropriate flow rate of 32.7 l/min was derived to satisfy the target hardening depth and to have spatial uniform hardened layer in the furnace.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.2
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• pp.149-154
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• 1995

The alloying of 6.5wt % Silicon in iron decreases the magnetization and the anisotropy and minimizes the iron loss noticeably. But it is very difficult to make thin sheets because of its poor ductility which is due to an ordering reaction (body centered cubic to CsCI type crystal structure). However the ordering reaction can be suppressed by rapid solidification method. The cooling rate of rapidly solidified Fe-6.5wt % Si alloy is about $10^3K/s$ and rapidly solidified structure are fine structure, cellular structure, dendrite and equiaxed grain from surface. The precipitates of $DO_3$ Phase emerges on $B_2$ matrix and the coercive force was 0.51 Oe (50cycle, 15KGauss) in Fe-6.5wt% Si alloy which was processed by heat treatment of $1150^{\circ}C$ for 1hr in high vacuum.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.283-283
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• 2013

Because of beautiful glossy and color, the value of gold leverage is very high in Europe. To improve the quality of gold alloys, we performed heat treatment on 14 K white gold alloys by variously changing age-hardening conditions. Age-hardening behavior and the related phase transformation changes were studied to elucidate the hardening mechanism of 14 K white gold alloy. For solid solution treatment [ST], casted gold alloy specimens were treated at high temperature ($750^{\circ}C$) for 30 minutes, and the specimens dropped to water to quench them. For Age-hardening treatment [AT], the specimens were treated at various temperatures ($250{\sim}300^{\circ}C$). After the heat treatment, we observed the phenomenon to increase hardness from 126 Hv to 166 Hv by Vicker's hardness tester. Through electron probe micro-analysis (EPMA) mapping analysis, we investigated that irregular particles were changed uniformly. In the SEM and OM images, two phases of matrix and particle-likestructures were observed, and the precipitation of these elements from the matrix progressed during age-hardening. By transmission electron microscope and X-ray diffraction observation, it was revealed that the formation of the Au3Cu superstructure contributed to the age-hardening at $270^{\circ}C$ in the gold alloy. After the heat treatment, this analysis shows that casted gold alloys were to improve hardness and to moderate surface defects at specific temperatures and duration.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.171.1-171.1
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• 2016

재료의 표면 강화 방법 중의 하나인 질화공정을 이용하여 탄소강 S45C 소재의 질화 거동에 대하여 연구하였다. $520^{\circ}C$ 온도에서 질화 공정을 진행하여 공정시간에 따른 Kn값을 수소 센서로 측정하여 공정시간에 따른 N-potential의 변화와 그에 따른 화합물층 성장 및 화합물층의 상변화에 대해 관찰하였다. 화합물 층의 미세구조 변화는 광학현미경 및 주사전자현미경을 통해 관찰하였다. 가스 질화 처리 후 표면경도는 약 600Hv의 경도값이 측정되었고, 공정 시간이 늘어남에 따라 화합물층 및 경화깊이가 증가되고 표면 화합물이 성장하여 porous가 감소하는 것을 확인 할 수 있다. 경화깊이는 1440분 일 때 약 0.5mm 경화 깊이를 얻었고, 화합물층의 성장은 ${\varepsilon}$상(Fe2-3N)과 ${\gamma}$'상(Fe4N)으로 두 개의 상으로 형성되는 것을 관찰할 수 있었다. 시험 결과를 바탕으로 S45C 소재의 탄소 함량에 따른 lehrer diagram을 열역학 적으로 계산하고 화합물층의 형성 기구에 대해 비교 분석하였다.

• Journal of the Korean Ceramic Society
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• v.34 no.9
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• pp.993-1001
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• 1997

The (0.8PPV+0.2DMPPV) copolymer and silica/borosilicate composites were synthesized by sol-gel process. The organic-inorganic hybrid solution was prepared by using of (0.8PPV+0.2DMPPV) copolymer precursor solution as a raw material for organic components and TEOS and TMB for glass components. Then by drying the solution in vacuum at 5$0^{\circ}C$ for 7days and subsequent heat treatment in vacuum at 15$0^{\circ}C$~30$0^{\circ}C$ for 2h~72h with heating rate of 0.2$^{\circ}C$/min and 1.8$^{\circ}C$/min, the organic-inorganic composites were synthesized. Microstructural evolution of the composites was characterized by DSC, IR spectrocopy, UV/VIS spectroscopy, and TEM. Elimination of the polymer precursor and degradation of the polymer were observed by DSC and Si-O and trans C=C absorption peaks were identified by IR spectra. The polymer was found to be successfully incorporated into the glass matrix and it was confirmed by the absorption peaks from the polymer in the UV/VIS spectra and the TEM results. The absorption peak of the composites was found to shift toward short wavelength side compared to that of the pure polymer and the amount of the blue shift increased with increasing the heat treatment temperature and heat treatment time and with decreasing the heating rate.

• Journal of Welding and Joining
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• v.19 no.2
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• pp.191-199
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• 2001

The oxidation and recrystallization behaviors of Ni-base single crystal superalloy, CMSX-2 were investigated to determine the condition of the preparation for transient liquid phase (TLP) bonding operations. The faying surfaces of CMSX-2 were worked by the shot peening, fine cutting and mechanical polishing treatments and the degree of working of treated surfaces was evaluated by the hardness test and X-ray diffraction method CMSX-2 was heat-treated at 1,173∼1.589k for 3.6ks in vacuum of 4mPa. The mechanically polished surface was slightly oxidized after heat treatment even in the vacuum atmosphere of 4mPa. The thickness of an oxide film increased with increasing the heating temperature and the surface roughness of the faying surface. Recrystallization occurred at the surface after heat treatment at above 1,423K when the hardness was increased more than Hv600 by the shot peening treatment while the mechanically polished or fine cut surfaces didn't recrystallized. Based on these results, it was clearfied that the mechanically polishing with fine abrasive grit could be used for the preparation of faying surface of CMSX-2 before bonding operation.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.4
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• pp.210-216
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• 2009

Stainless steel EGR cooler of diesel engine is widely used to prevent the corrosion due to the content of sulfur in diesel fuel. The strength of brazed joint between stainless steel materials is very important. It is essential to observe the spreading ratio of the filler metals under the condition of deoxidation or vacuum during heating process. In this experiment, spreading ratio was tested to find the optimum brazing condition for stainless steel using brazing filler metals of FP-613, BNi-2 and BNi-5 on sus304 and sus410. Anti-corrosion tests were also performed on the above filler metals with solution of 5% $H_2SO_4$, 65% $HNO_3$ and 5% $NH_4OH$. Consequently FP-613 has good ability for anti-corrosion with 30% of chromium content compared with other filler metals. The optimum brazing conditions are occurred at $960^{\circ}C$ for 90 min. and at $1090^{\circ}C$ for 50 min. at the same degree of vacuum, $2{\sim}3{\times}10^{-3}$ Torr.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.650-650
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• 2013

Although imprinted nanopatterns of organic polymer can be modified by the heat treatment [1], it generally requires high process temperatures and is material-dependent since the heat-induced mass loss of the organic polymer is greatly affected by its chemical characteristics. When oxygen is added during the annealing process, one can reduce the process temperature as well as the dependence of the materials. With the oxygen, line width reduction of a polymer (SU-8) patterns could be accomplished at temperature of as low as $250^{\circ}C$ which was not possible in the heat only process. This oxidative line width reduction can be dramatically promoted with the introduction of oxygen plasma. The oxygen plasma, with its highly-reactive oxygen species, vigorously etches away the organic materials, proven to be extremely effective line with reduction method. It is, however, very hard to control the extent and homogeneity of the etching, particularly of very fine patterns. Here, we report an effective and reliable line width reduction method of imprinted nanopatterns by combined plasma and heat treatment. The merits of this process include the reduction of process temperature, time and material-dependence.