• 한국자기학회:학술대회 개요집
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• 한국자기학회 2004년도 하계학술연구발표회 논문개요집
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• pp.150-151
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• 2004

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.29.1-29.1
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• 2009

Fabrication of good quality P-type GaN remained as a challenge for many years which hindered the III-V nitrides from yielding visible light emitting devices. Firstly Amano et al succeeded in obtaining P-type GaN films using Mg doping and post Low Energy Electron Beam Irradiation (LEEBI) treatment. However only few region of the P-GaN was activated by LEEBI treatment. Later Nakamura et al succeeded in producing good quality P-GaN by thermal annealing method in which the as deposited P-GaN samples were annealed in N2 ambient at temperatures above $600^{\circ}C$. The carrier concentration of N type and P-type GaN differs by one order which have a major effect in AlGaN based deep UV-LED fabrication. So increasing the P-type GaN concentration becomes necessary. In this study we have proposed a novel method of activating P-type GaN by electrochemical potentiostatic method. Hydrogen bond in the Mg-H complexes of the P-type GaN is removed by electrochemical reaction using KOH solution as an electrolyte solution. Full structure LED sample grown by MOCVD serves as anode and platinum electrode serves as cathode. Experiments are performed by varying KOH concentration, process time and applied voltage. Secondary Ion Mass Spectroscopy (SIMS) analysis is performed to determine the hydrogen concentration in the P-GaN sample activated by annealing and electrochemical method. Results suggest that the hydrogen concentration is lesser in P-GaN sample activated by electrochemical method than conventional annealing method. The output power of the LED is also enhanced for full structure samples with electrochemical activated P-GaN. Thus we propose an efficient method for P-GaN activation by electrochemical reaction. 30% improvement in light output is obtained by electrochemical activation method.

• 한국수소및신에너지학회논문집
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• 제19권6호
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• pp.545-551
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• 2008

Fe/$Al_2O_3$ composite granules were prepared by combining sol-gel/oil drop method. The shape of granules were mainly determined by composition and concentration of aluminum precursor. The composite granule with the lowest aluminum concentration was synthesized with 0.75M boehmite solution. The prepared granules were tested as a catalyst in the plug-flow reactor for Fischer-Tropsch synthesis. Before the reaction, catalysts were activated by hydrogen reduction and synthesis gas treatment. The activation conditions and aluminum concentration have affected catalytic performance significantly.

• 대한화학회지
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• 제13권2호
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• pp.157-164
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• 1969

Aoolphane was treated with 30% Hydrochloric acid at $18^{\circ}C$ for two hows with stirring in order to obtain the insoluble form of SiO2 gel and to extract quantitatively both $Al_2O_3$as and $Fe_2O_3AlCl_3{\cdot}6H_2O Fe$ and $Cl_3{\cdot}6H_2O$ forms, respectively, at the same time. $SiO_2$ gel was filtered and to the filterate Ammonia was added to precipitate $Al(OH)_3[Fe(OH)_3 Contaminated ]$ The precipitate was separated by filteration and the filterate was recovered as the form of $NH_4Cl$. The precipitate was treated with 200g (NaOH)/l Concentration of NaOH a little excessively to the equivalent at $65~70^{\circ}C$ as $Fe(OH)_3$ formed was insoluble, it was filtered of and to the filterate containing $NaAl(OH)_4(OH_2)_2$Carbon dioxide gas was bubbled at $50^{\circ}C~90^{\circ}C$ to obtain the precipitate with excellent filterability and crystallinity. The product was certified to be Dawsonite $(NaAl(OH)_2CO_3)$ by X-Ray diffraction analysis at below $40^{\circ}C$, when $CO_2$ gas was bubbled into the relatively lower concentration of $NaAl(OH)_4(OH_2)_2$ solution, the precipitate of very fine particles was formed, which was hard to filter and with the Composition of $\alpha-Al_2O_3-H_2O$ (Boehmite).

• 한국재료학회지
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• 제15권8호
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• pp.518-520
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• 2005

Effects of the $O_2/Ar$ flow ratio in the sputtering process on the crystallinity, surface roughness, carrier concentration, carrier mobility, and optical properties of Al-doped ZnO thin films deposited on sapphire (001) substrates by RF magnetron sputtering were investigated. XRD spectra showed a preferred orientation along the c-axis and a minimum FWHM of the (002) XRD intensity peak for the $O_2/Ar$ flow ratio of 0.5. The (101)peak also appeared and the degree of preferred orientation decreased as the $O_2/Ar$ flow ratio increased from 0.5 to 1.0. AFM analysis results showed that the surface roughness was lowest at the $O_2/Ar$ flow ratio of 0.5 and tended to increase owing to the increase of the grain size as the $O_2/Ar$ flow ratio increased further. According to the Hall measurement results the carrier concentration and carrier mobility of the fan decreased and thus the resistivity increased as the $O_2/Ar$ flow ratio increased. The transmittance of the ZnO:Al film deposited on the glass substrate was characteristic of a standing wave. The transmittance increased as the $O_2/Ar$ flow ratio in-RF magnetron sputtering increased up to 0.5. Considering the effects of the $O_2/Ar$ flow ratio on the surface roughness, electrical resistivity and transmittance properties of the ZnO:Al film the optimum $O_2/Ar$ flow ratio was 0.5 in the RF magnetron sputter deposition of the ZnO:Al film.

• Journal of Welding and Joining
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• 제31권6호
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• pp.96-106
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• 2013

In this study, the effect of laser source($CO_2$ and Nd:YAG) on the microstructure and tensile properties of laser welded Al-Si coated boron steel(1.2mmt) was investigated with before and after hot-stamping. In case of as welds condition, fracture occurred in base metal unrelated to the laser source. It could be explained that tensile strength of fusion zone composed of martensite and bainite is higher than that of base metal that contains a lot of ferrite despite dilution of Al and Si from coating layer to fusion zone. In case of hot-stamping condition, the fracture occurred in fusion zone irrelevant to laser source and the tensile strength was lower than hot stamped base metal. In the $CO_2$ laser welds, $Fe_3$(Al,Si) formed near the bond line was transformed into ferrite during hot-stamping. Therefore tensile strength of bond line is lower than that of base metal and center of fusion zone and the fracture occurred in the bond line. On the other hand, in the Nd:YAG laser welds, the higher concentration of Al formed the ferrite in the fusion zone during hot-stamping treatment. Also, the thickness of centerline was thinner than that of base metal. Therefore, it is considered that fracture occurred in centerline of fusion zone due to effect of concentration stress, and it leaded to a lower tensile strength and elongation.

• KEPCO Journal on Electric Power and Energy
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• 제5권1호
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• pp.39-43
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• 2019

에너지 고갈 문제에 대한 대처 방안으로 수소에너지는 직간접적인 긍정적 효과를 가져온 반면, 사용시 안정성이 매우 중요한 사항이기 때문에 수소가스에 대한 정확하고 빠른 감지를 가능하게 하는 센서 기술이 요구된다. 본 연구에서는 AlGaN/GaN 이종접합 반도체 플렛폼을 활용하여 Pd 촉매 기반의 수소센서를 개발하였으며 감도를 높이기 위하여 식각 구조를 도입하였다. 온도 및 바이어스 전압이 센서의 반응도에 미치는 영향을 수소가스 위험도 최하한선 농도인 4% 수소 농도에 노출된 경우에 대하여 세심하게 분석하였다. AlGaN/GaN 이종접합의 우수한 특성에 식각 구조가 도입된 결과 56%의 높은 반응도와 0.75 초의 빠른 응답 속도 성능을 달성하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2001년도 춘계학술발표회 초록집
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• pp.3-3
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• 2001

Recently TiN, TiAlN, CrN hardcoatings have adapted many industrial application such as die, mold and cutting tools because of good wear resistant and thermal stability. However, in terms of high speed process, general hard coatings have been limited by oxidation and thermal hardness drop. Especially in the case of PCB drill, high speed cutting and without lubricant process condition have not adapted these coatings until now. Therefore more recently, superhard nanocomposite coating which have superhard and good thermal stability have developed. In previous works, WC-TiAlN new nanocomposite film was investigated by cathodic arc ion plating system. Control of AI concentration, WC-TiAlN multi layer composite coating with controlled microstructure was carried out and provides additional enhancement of mechanical properties as well as oxidation resistance at elevated temperature. It is noted that microhardness ofWC-TiA1N multi layer composite coating increased up to 50 Gpa and got thermal stability about $900^{\circ}C$. In this study WC-TiAlN nanocomposite coating was deposited on PCB drill for enhancement of life time. The parameter was A1 concentration and plasma cleaning time for edge sharpness maintaining. The characteristic of WC-TiAlN film formation and wear behaviors are discussed with data from AlES, XRD, EDS and SEM analysis. Through field test, enhancement of life time for PCB drill was measured.

• 대한환경공학회지
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• 제30권11호
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• pp.1111-1115
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• 2008

아산 호서대 지역에서 대기 중 미세먼지를 측정하여 PM$_{2.5}$와 PM$_{10}$의 이온성분과 중금속성분 분석을 통해 농도 특성을 분석하고 황사 발생에 따른 농도특성 변화를 관찰하였다. 황사시 미세먼지의 입경별 평균농도는 비황사시에 비해 큰 증가를 보였으나, PM$_{2.5}$ 비율은 79.7%에서 40.1%로 감소하였다. 이러한 원인은 2.1 $\mu$m를 기준으로 조대 입자와 미세 입자로 구분하여 질량농도를 분석한 결과 황사시 조대 입자가 크게 증가하여 PM$_{2.5}$ 비율이 상대적으로 낮아지기 때문인 것을 알 수 있었다. 황사시 이온 성분 농도의 변화는 미세입자 영역에서 큰 변화를 보이지 않았으나 조대입자 영역에서는 Ca$^{2+}$이온이 약 40배 정도 증가하였고 Na$^+$, SO$_4{^{2-}}$이온 순으로 높은 증가율을 나타내었다. 또한, 중금속 성분의 분석 결과 황사시 Mn, Fe, Zn, Al 순으로 증가폭이 컸으나 질량농도로 보았을 때 Al이 가장 큰 증가량을 보였다.

• 한국산림과학회지
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• 제97권3호
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• pp.266-273
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• 2008

소나무, 상수리나무 묘목의 생장 및 영양상태에 미치는 토양산성화의 영향을 조사하고 묘목의 생장과 토양용액 중의 (Ca+Mg+K)/Al 몰비와의 관계를 검토하였다. 인위적으로 산성화 시킨 산림토양에서 생육한 소나무, 상수리나무 묘목의 생장저해에는 토양용액 중의 pH 저하와 이에 따른 토양용액으로의 Al 용출 및 묘목의 지하부에 있어서 Al 농도의 증가에 따른 지상부의 Ca 등의 식물 필수원소의 감소 등이 관여하고 있음을 시사하였다. 토양산성화에 따른 묘목의 생장저하 수준은 토양의 Al 농도뿐만 아니라 Al과 Ca, Mg 및 K과의 무기영양소 균형도에 의해 결정되며, 두 수종 모두 토양용액 중의 (Ca+Mg+K)/Al 몰비가 6.0 이하가 되면 건물생장이 현저하게 저하하고 그 비가 0.8인 경우 건물생장이 대조구 값에 비하여 소나무 묘목에서 약 60%, 상수리나무 묘목에서 약 50% 저하하였다. 앞으로, 산성우 등의 산성강하물에 의한 토양산성화가 수목의 생장 및 영양상태에 미치는 영향을 평가할 경우, 토양용액 중의 (Ca+Mg+K)/Al 몰비는 삼림생태계 피해예측에 대한 산성강하물의 한계부하량의 평가에 있어 중요한 지표가 될 수 있다고 판단된다.