• 한국전기전자재료학회논문지
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• 제35권5호
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• pp.516-521
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• 2022

We investigated the microstructure, crystal structure, dielectric, and elecromechanical strain properties of lead-free BaTiO₃ (BT)-modified (Bi_1/2Na_1/2)TiO₃-SrTiO₃ (BNT-ST) piezoelectric ceramics. Samples were prepared by a conventional ceramic processing route. Temperature dependent dielectric properties confirmed that a phase transition from a nonergodic relaxor to an ergodic relaxor was induced when the BT concentration reached 1.5 mol%, interestingly, where the average grain size reached a maximum value of 4.5 ㎛. At the same time, enhanced electromechanical strain (S_max/E_max = 600 pm/V) was obtained. It is suggested that the induced ferroelectric-relaxor phase transition by the BT modification is responsible for the enhancement of electromechanical strain in 1.5 mol% BT-modified BNT-ST ceramics.

• Journal of the Korean Wood Science and Technology
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• 제30권2호
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• pp.102-107
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• 2002

본 연구는 낙엽송(Larix Kaemferi Carr.)재를 이용하여 100℃부터 180℃까지의 고온영역에서 20℃ 간격으로 처리시간을 10분, 30분, 60분, 90분간으로 하여 처리조는 봄베를 사용하였다. 1) 고온수증기처리의 처리시간이 길고, 처리온도가 높을수록 밀도의 감소도 커졌다. 2) 밀도의 감소에도 불구하고 고온수증기처리재의 수축율이 control재와 비교하여 비슷하거나 높게 나타나는 것은 수증기처리에 의하여 세포벽 내부의 구성성분 및 구조변화에 의하여 야기된 것으로 판단된다. 3) 고온수증기처리에 의하여 추정목재의 틀어짐은 감소되었다.

• 열처리공학회지
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• 제35권6호
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• pp.303-313
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• 2022

The purpose of this study was to test and analyze the effects of the mechanical properties and structural changes of the austenitized and tempered martensite STS 410 stainless steel containing 11.5~13%Cr and 0.10%C on its temper embrittlement. The STS 410 stainless steel test pieces for each 3 hours at 960℃, 1000℃ and then, tempered them for 2 hours at 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃ and 700℃ known as the intervals vulnerable to temper embrittlement to observe the changes of their structures and mechanical properties. In case autenitizing was insufficient due to lower temperature of thermal treatment for solution, unsolved carbides and ferrites remained in the structure after quenching, which meant that the parts could wear out and corrode to embrittle at the room temperature. Elongation and impact energy changes with Tempering conditions showed minimum results in range of 400~500℃. The decrease in elongation and impact energy at 400~500℃ was the hardening effect of the subgrain due to the precipitation of many M₃C or M₇C₃, M₂₃C₆. And STS 410 stainless steel corrosion tested in 10% NaCl solution at 30℃ after tempering treatment. The degree of corrosion sensitization showed increasing tendency with increase of tempering temperature and Cr carbide precipitation were observed in grain boundary.

• Journal of the Korean Wood Science and Technology
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• 제30권4호
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• pp.1-7
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• 2002

본 연구에서는 낙엽송재(Larix Kaemferi Carr.)를 대상으로 100℃부터 130℃까지의 고온영역에서 10℃ 간격으로 처리시간을 10분, 30분, 60분간으로 하여 수증기처리 후 처리재의 물리적 특성 등을 검토하였으며, 오토클레이브를 사용 처리하였다. 휨강도와 압축강도는 처리온도의 증가에 따라 약간씩 감소하는 것으로 나타났다. 그러나 수증기처리한 목재강도와 처리온도 사이에는 명확한 결과가 나타나지 않았다. 120℃에서 130℃의 온도범위에서 세포벽 내의 성분과 조직이 변화하는 것으로 생각되는데, 이것은 응력의 해소에서 기인되는 것으로 생각되었다. 수분흡수성은 고온수증기처리조건에 의한 변화가 없는 것으로 나타났다. 결론적으로 본 실험의 범위에 있어서 목재의 물성은 처리 온도조건보다는 목재밀도의 영향을 많이 받고 있는 것으로 판단되었다.

• 건축역사연구
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• 제31권4호
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• pp.17-28
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• 2022

This study aims to investigate and reveal the spatial structure of Boryeonghyeon by examining the geographical status of its Eupchi (Local administrative center:邑治) through an analysis of the location, tracing locations of governemnt offices including Dongheon(東軒) and Kaeksa(客舍) in the walled town, and checking the lot numbers of Sajikdan(社稷壇), Yeodan(厲壇), and Cheongyeonyeok(靑淵驛) outside it. Buildings of Boryeonghyeon in the walled town in the Joseon Dynasty were almost lost and now, part of the city wall and Haesanru(海山樓) just remains as relic. The walled town consisted of several buildings of government offices as well as Dongheon and Kaeksa which are government organs. Altar and shrine(壇廟) facilities including Shrine of Confucius(文廟), Altar of Land and Grain, and Preceptor's Shrine were placed outside the walled town and Cheongyeonyeok were operated as the facilities for transmission of royal orders. Therefore, the government office facilities in the walled town, altar and shrine facilities outside the fortress, and the location of the post station were required to trace and check each of them. For the checking method, the lot numbers could be checked by checking the original cadastral maps and the then land categories and owners, analyzing the records and circumstances of the relevant township annals(邑誌), and examining analyses on the locations by using a numerical map of one to 5 thousands. The study estimated the locations of government facilities including Dongheon and Kaesa placed in the walled town and was grasped to be the east and west gates with the south gate which remains now in the fortress. And the lot numbers of Sajikdan, Yeodan, Cheongyeonyeok.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2001년도 추계학술발표회 초록집
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• pp.37-37
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• 2001

TiN coatings were applied for VarIOUS application fields, because of a good wear-resistance and a high hardness. Typically, TiN thin films show the hardness of 25GPa and friction coefficient of 0.6. However, in many field, one is looking for a more improved tool which has low friction coefficient and high wear resistance. The main motivation of this study is to characterize the influence of copper dopant content on TiN thin films. Ti-Cu-N thin films were deposited onto D2 steel substrates by PVD processing with various magnetron current densities (Cu contents). In this work, we synthesized titanium nitride films similar with reported typical titanium nitride films and synthesized Ti-Cu-N thin films with the addition of elemental copper which is measured improved hardness more than pure TiN films with copper content variables. This films has preferred oriented films of (111) direction. In addition, It was found that there is a strong correlation between content of various metal and film characteristics such as preferred orientation, grain size, hardness and friction coefficient and so, in future study, improved mechanical properties of TiN films can be controlled by change in target current density. The Ti-Cu-N film will show apparent hardness improvement and mechanical properties enhancement, when doping element is added onto TiN thin films. Film structure, chemical composition, mechanical properties were investigated by means of X-ray diffraction(XRD), scanning electron microscopy(SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy(EDS), wear resistance tester and nanohardness tester.

• 한국표면공학회지
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• 제34권5호
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• pp.414-420
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• 2001

A 30-kV plasma immersion ion implantation setup (P $I^3$) has been equipped with a self-developed 6'-magnetron to perform hard coatings with enhanced adhesion by P $I^3$D(P $I^3$ assisted deposition) process. Using ICP source with immersed Ti antenna and reactive magnetron sputtering of Ti target in $N_2$/Ar ambient gas mixture, the TiN films were prepared on Si substrates at different pulse bias and ion-to-atom arrival ratio ( $J_{i}$ $J_{Me}$ ). Prior to TiN film formation the nitrogen implantation was performed followed by deposition of Ti buffer layer under A $r^{+}$ irradiation. Films grown at $J_{i}$ $J_{Me}$ =0.003 and $V_{pulse}$=-20kV showed columnar grain morphology and (200) preferred orientation while those prepared at $J_{i}$ $J_{Me}$ =0.08 and $V_{pulse}$=-5 kV had dense and eqiaxed structure with (111) and (220) main peaks. X-ray diffraction patterns revealed some amount of $Ti_{x}$ $N_{y}$ in the films. The maximum microhardness of $H_{v}$ =35 GN/ $M^2$ was at the pulse bias of -5 kV. The P $I^3$D technique was applied to enhance wear properties of commercial tools of HSS (SKH51) and WC-Co alloy (P30). The specimens were 25-kV PII nitrogen implanted to the dose 4.10$^{17}$ c $m^{-2}$ and then coated with 4-$\mu\textrm{m}$ TiN film on $Ti_{x}$ $N_{y}$ buffer layer. Wear resistance was compared by measuring weight loss under sliding test (6-mm $Al_2$ $O_3$ counter ball, 500-gf applied load). After 30000 cycles at 500 rpm the untreated P30 specimen lost 3.10$^{-4}$ g, and HSS specimens lost 9.10$^{-4}$ g after 40000 cycles while quite zero losses were demonstrated by TiN coated specimens.s.

• 천문학회보
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• 제46권2호
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• pp.66.3-67
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• 2021

Low-mass stars form by the gravitational collapse of dense molecular cores. Observations and theories of low-mass protostars both suggest that accretion bursts happen in timescales of ~100 years with high accretion rates, so called episodic accretion. One mechanism that triggers accretion bursts is infalling fragments from the outer disk. Such fragmentation happens when the disk is massive enough, preferentially activated during the embedded phase of star formation (Class 0 and I). Most observations and models focus on the gas structure of the protostars undergoing episodic accretion. However, the dust and ice composition are poorly understood, but crucial to the chemical evolution through thermal and energetic processing via accretion burst. During the burst phase, the surrounding material is heated up, and the chemical compositions of gas and ice in the disk and envelope are altered by sublimation of icy molecules from grain surfaces. Such alterations leave imprints in the ice composition even when the temperature returns to the pre-burst level. Thus, chemical compositions of gas and ice retain the history of past bursts. Infrared spectral observations of the Spitzer and AKARI revealed a signature caused by substantial heating, toward many embedded protostars at the quiescent phase. We present the AKARI IRC 2.5-5.0 ㎛ spectra for embedded protostars to trace down the characteristics of accretion burst across the evolutionary stages. The ice compositions obtained from the absorption features therein are used as a clock to measure the timescale after the burst event, comparing the analyses of the gas component that traced the burst frequency using the different refreeze-out timescales. We discuss ice abundances, whose chemical change has been carved in the icy mantle, during the different timescales after the burst ends.

• 한국전기전자재료학회논문지
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• 제36권6호
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• pp.582-587
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• 2023

The effects of the annealing temperature on the structural, morphological, and luminescent properties of SrWO₄:Sm³⁺ thin films grown on quartz substrates by radio-frequency magnetron sputtering were investigated. The thin films were annealed at various annealing temperatures for 20 min in a rapid thermal annealer after growing the thin films. The experimental results showed that the annealing temperature has a significant effect on the properties of the SrWO₄:Sm³⁺ thin films. The crystal structure of the as-grown SrWO₄:Sm³⁺ thin films was transformed from amorphous to crystalline after annealing at 800℃. The preferred orientation along (112) plane and a significant increase in average grain size by 820 nm were observed with increasing the annealing temperature. The average optical transmittance in the wavelength range of 500~1,100 nm was decreased from 72.0% at 800℃ to 44.2% at an annealing temperature of 1,000℃, where the highest value in the photoluminescence intensity was obtained. In addition to the red-shift of absorption edge, a higher annealing temperature caused the optical band gap energy of the SrWO₄:Sm³⁺ thin films to fall rapidly. These results suggest that the structural, morphological, and luminescent properties of SrWO₄:Sm³⁺ thin films can be controlled by varying annealing temperature.

• 한국표면공학회지
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• 제56권6호
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• pp.451-456
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• 2023

Transparent conducting films having a three layered structure of ZnO/Cu/ZnO (ZCZ) were deposited onto the glass substrates by using RF and DC magnetron sputtering at room temperature. The emissivity and opto-electrical properties of the films were investigated with a varying thickness(5, 10, 15 nm) of the Cu interlayer. With increasing the Cu thickness to 15 nm, the films showed a enhanced electrical properties. Although ZnO 30/Cu 15/ZnO 30 nm film shows a lower resistivity of 5.2×10^-5 Ωcm, it's visible transmittance is deteriorated by increased optical absorbtion of the films. In addition, X-ray diffraction patterns indicated that the insertion of Cu interlayer improve the grain size of ZnO films, which is favor for the electrical and optical properties of transparent conducting films. From the observed low emissivity of the films, it is concluded that the ZCZ thin films with optimal thickness of Cu interlayer can be applied effectively for the car's window coating materials.