• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.219-219
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• 2013

The effect of an electron blocking layer (EBL) on V-I curves in GaN/InGaN multiple quantum well is investigated. For the first time, we found that curves were intersected at 3.012 V and analyzed the reason for intersection. The forward voltage in LEDs with an p-AlGaN EBL is larger than without p-AlGaN EBL at low injection current because the Mg doping efficiency for p-GaN layer was higher than that of p-AlGaN layer. However, the forward voltage in LEDs with an p-AlGaN EBL is smaller than without p-AlGaN EBL at high injection current because the carriers overflow from the active layer when injection current increases in LEDs without p-AlGaN EBL and in case of LED with p-AlGaN EBL, the carriers are blocked by EBL.

• 한국주조공학회지
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• 제17권2호
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• pp.180-187
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• 1997

The influence of solidification condition on the segregation of SiC particles in the $Al-xSi/6wt%SiC_p$(x: 6, 10, 14, 18${\cdot}$wt%) composites was investigated in the study. The results are as follows: 1) During the counter-gravity unidirectional solidification of $Al-Si/SiC_p$ composites melt, most of the SiC particles are pushed to the top of the casting. 2) The SiC particles pushing in the $Al-Si/SiC_p$ composite melts are not observed, when the interface velocity of melts increases more than 1.41 ${\mu}m/sec$. 3) The SiC particles are entrapped in the interdendrite regions, when the sizes of SiC particles in the $Al-Si/SiC_p$ composites are large than ${\varphi}22{\mu}m$.

• 한국진공학회지
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• 제19권2호
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• pp.134-140
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• 2010

Metal-organic chemical vapour deposition (MOCVD)법으로 성장된 $In_{0.5}(Ga_{1-x}Al_x)_{0.5}P$/GaAs 이중 이종접합 구조의 특성을 contactless electroreflectance (CER) 분광법으로 조사하였다. CER 측정은 변조전압($V_{ac}$), 온도 및 dc 바이어스 전압($V_{bias}$)의 함수로 수행하였다. 상온에서는 5개의 신호가 관측되었는데, 이 신호들은 각각 GaAs, $In_{0.5}Ga_{0.5}P$, $In_{0.5}(Ga_{0.73}Al_{0.27})_{0.5}P$, $In_{0.5}(Ga_{0.5}Al_{0.5})_{0.5}P$ 및 $In_{0.5}(Ga_{0.2}Al_{0.8})_{0.5}P$ 전이에 관련된 것이다. CER 스펙트럼의 온도 의존성으로부터 Varshni 계수 및 평탄인 자를 구하였다. 그리고 인가전압에 따른 신호의 진폭은 순방향 바이어스 전압 인가시 점차로 감소하나, 역방향 바이어스 전압 인가시에는 반대의 경향을 보였다.

• 동력기계공학회지
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• 제5권4호
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• pp.74-81
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• 2001

The infiltration behavior of molten Al-alloy, microstructures, hardness, and the interfacial reactions of $SiC_p/Al$ composites fabricated by the pressureless infiltration technique were investigated. It was made clear that both the weight fraction of SiC reinforcement and additive Mg content considerably influenced on the infiltration behavior of the molten Al-alloy matrix. Complete infiltration of molten Al-alloy achieved under the conditions that weight fraction of SiC content is more than 30wt%, and additive Mg content is more than 9wt%. Interfacial region of Al-alloy matrix and SiC reinforcement phase, $Mg_2Si$ was formed by the reaction between Mg and SiC. Another reaction product AlN was also formed by the reaction between Al-alloy matrix and gas atmosphere nitrogen.

• 반도체디스플레이기술학회지
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• 제20권4호
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• pp.125-129
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• 2021

We investigated the electronic property and atomic structure for chalcopyrite (CH) Al_xGa_1-xAs semiconductor by using first-principles FPLMTO method. The CH-Al_xGa_1-xAs exhibits a p-type semiconductor with a direct band-gap. For low Al concentration unoccupied hole-carriers are induced, but for high Al concentration it is formed a localized bonding or anti-bonding state below Fermi level. The hybridization of Al(3s)-Ga(4s, or 4p) is larger than that of Al(3s)-As(4s, or 4p). And the Al film on As-terminated surface, Al/AsGa(001), is more energetically favorable one than that on Ga-terminated (001) surface. Consequently, the band-gap of CH-Al_xGa_1-xAs system increases exponentially with increasing Al concentration. The change of lattice parameter is shown two different configurations with increasing Al concentration. The calculated lattice parameters for CH-Al_xGa_1-xAs system are compared to the experimental ones of zinc-blend GaAs and AlAs.

• 열처리공학회지
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• 제5권4호
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• pp.233-239
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• 1992

A study of the precipitation process of Al-Li binary alloy at low ageing temperature has been carried by electrical resistivity measurement. Two types of G.P.zones were formed during ageing at low temperature. G.P. (1) zone and G.P. (2) zone have been formed primarily at ageing temperature below $60^{\circ}C$ and at ageing temperature range of $80^{\circ}C$ to $100^{\circ}C$, respectively. Therefore the precipitation process of Al-Li binary alloy was as follows; G.P.(1) zone ${\rightarrow}$ G.P.(2) zone ${\rightarrow}{\delta}^{\prime}{\rightarrow}{\delta}$ G.P. (1) zone might be affected by excess vacancies, but G.P. (2) zone might be affected by secondary defects. clusters and Li-vacancy pairs. The activation energy for formation of G.P. (2) zone is 0.87eV. It is lower than that of Al-Cu alloy.

• 한국분말재료학회지
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• 제11권3호
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• pp.259-264
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• 2004

Aluminum based metal matrix composite reinforced with SiC particles was fabricated by the powder-in sheath rolling method. A stainless steel tube with outer diameter of 12 mm and wall thickness of 1mm was used as a sheath. Mixture of aluminum powder and SiC particles of which volume content was varied from 5 to 20vol.% was filled in the tube by tap filling and then rolled to 75% reduction at ambient temperature. The rolled specimen was sintered at 56$0^{\circ}C$ for 0.5hr. The tensile strength of the (SiC)$_{p}$/Al composite increased with the volume content of SiC particles, and at 20vol.% it reached a maximum of 100㎫ which is 1.6 times higher than unreinforced material. The elongation decreased with the volume content of $Al_{2}$O$_{3}$ particles. The mechanical properties of the (SiC)$_{p}$/Al composite fabricated by the powder-in sheath rolling is compared with that of (Al$_{2}$O$_{3}$)$_{p}$/Al composite by the same process.ess.

• 상하수도학회지
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• 제24권1호
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• pp.15-24
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• 2010

Coagulation can be used for pretreatment of NF membrane filtration. Foulants such as organic matter and particulate can be removed effectively with the process while high flux recovery is maintained. Recently various types of polyaluminium coagulants including polyaluminium chloride(PAC) are commercially available for water treatment. This study examines effects of polymeric Al and hydrolysis products of PAC on nanofiltration membrane performance. Dominant hydrolysis products were polymeric Al, $Al(OH)_3$, and ${Al(OH)_4}^{-1}$ at acidic, neutral, and alkaline pH conditions, respectively. Under acidic pH condition, flux decline was increased with increasing PAC concentrations, possibly due to polymeric Al adsorption on membrane pore and/or surfaces. For neutral and alkaline pH conditions, little flux decline was observed with increasing PAC concentrations except the highest ${Al(OH)_4}^{-1}$ concentration, with which rapid flux decline was shown. Removal of ionic matters was also varied with pH conditions in this study. Especially, conductivity removal was substantially low and $Ca^{2+}$ concentration in the permeate was quite high at neutral pH condition.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1994년도 춘계 학술발표 강연 및 논문 개요집
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• pp.76-76
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• 1994

• 한국양식학회지
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• 제16권2호
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• pp.76-83
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• 2003

본 연구에서는 상향류식 연속 역세여과 연구를 통하여 양어장 순환수 처리 후 박테리아 및 바이러스 등을 효과적으로 처리하는 기술 개발과 여과사에 금속염을 코팅시켜 생물막의 형성을 도모하는 연구를 수행하였다. 여과사를 코팅한 경우 중성 pH에서 zeta potential 양(+)이 됨을 알 수 있었고 zeta potential이 양(+)에 근접할수록 column test에서 바이러스 제거효율이 증가함을 알 수 있었다. 따라서 여과사를 금속염으로 코팅을 하는 경우가 안한 경우 보다 음이온을 띤 부유물 제거에 탁월한 효능이 있음을 보여주었다. pH에 따른 여과재료의 흡착율에서 Al coating과 Al+Fe coating은 반응 시간 30분까지 효과적으로 흡착이 일어나는 것을 볼수 있었고 이 후의 반응시간에서 파과 곡선형태를 보여주었다. 회분식 형태로 운영한 여과재료를 이용한 탈착실험에서 Non, Al, Fe및 Al+Fe coating모두에서 pH 9.95에서 용출(leaching)되는 농도가 가장 높았으며 각각의 농도는 7.47, 4.80, 20.89 및 7.23 mg/L로 각각 나타났다. 이번 연구에서 Al coating의 경우 pH에 따른 영향은 거의 나타나지 않았으며, pH가 증가함에 따라 약간 감소하는 것을 알수 있었고 Fe coating에서는 pH의 영항이 없었으며, Al+Fe coating에서는 pH가 증가함에 따라 탁도도 역시 일정하게 증가하는 것으로 나타났다.