• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 춘계학술발표회 논문집
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• pp.245-246
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• 2012

Al 농도를 0 부터 2 at.% 까지 조절하여 도핑된 $Cd_{0.5}Zn_{0.5}O$ 박막을 석영 기판 위에 성장하였다. Al 도핑된 $Cd_{0.5}Zn_{0.5}O$ 박막의 구조적, 광학적 특성을 조사하기 위해 field-emission scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), 그리고 ultraviolet-visible (UV) spectroscopy을 사용하였다. 광학적 밴드갭은 Al 도핑 농도가 증가함에 따라 2.874 (0 at.%), 2.874 (0.5 at.%), 3.029 (1.0 at.%), 3.038 (1.5 at.%), 3.081 eV (2.0 at.%)로 증가하였다. Urbach energy는 도핑 농도에 따라 각각 464 (0 at.%), 585 (0.5 at.%), 571 (1.0 at.%), 600 (1.5 at.%), 470 meV (2.0 at.%)이었다. 또한, Al 농도가 증가함에 따라 $Cd_{0.5}Zn_{0.5}O$ 박막의 표면, 구조적 및 광학적 특성이 크게 변화되었다.

• 한국재료학회지
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• 제30권8호
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• pp.399-405
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• 2020

In the present investigation we show the effect of Al doping on the length, size, shape, morphology, and sensing property of ZnO nanorods. Effect of Al doping ultimately leads to tuning of electrical and optical properties of ZnO nanorods. Undoped and Al-doped well aligned ZnO nanorods are grown on sputtered ZnO/SiO₂/Si (100) pre-grown seed layer substrates by hydrothermal method. The molar ratio of dopant (aluminium nitrate) in the solution, [Al/Zn], is varied from 0.1 % to 3 %. To extract structural and microstructural information we employ field emission scanning electron microscopy and X-ray diffraction techniques. The prepared ZnO nanorods show preferred orientation of ZnO <0001> and are well aligned vertically. The effects of Al doping on the electrical and optical properties are observed by Hall measurement and photoluminescence spectroscopy, respectively, at room temperature. We observe that the diameter and resistivity of the nanorods reach their lowest levels, the carrier concentration becomes high, and emission peak tends to approach the band edge emission of ZnO around 0.5% of Al doping. Sensing behavior of the grown ZnO nanorod samples is tested for H₂ gas. The 0.5 mol% Al-doped sample shows highest sensitivity values of ~ 60 % at 250 ℃ and ~ 50 % at 220 ℃.

• 한국결정성장학회지
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• 제21권5호
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• pp.205-209
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• 2011

ZnO는 반도전성과 초전도성을 나타내며 광학적으로도 독특한 재료로 가스센서, 태양전지, 광학도파관 등 여러 방면에 널리 활용되고 있다. 본 논문에서는 이러한 ZnO에 Al을 첨가함에 따라 광학적 특성에 어떠한 영향을 미치는지 알아보기 위하여 ZnO에 Al 첨가량 변화에 따른 나노구조체를 제작하여 특성을 비교하였다. ZnO 용액은 PVP, ethanol, zinc acetate를 이용하여 Sol의 형태로 제작하였으며, Al첨가용액을 넣어 Al이 첨가된 ZnO Sol을 제작하였다. 제작된 Sol을 전기 방사법을 이용하여 나노구조체를 제조하였다. 제조된 섬유들을 각각 300, 500, $700^{\circ}C$로 열처리 한 후 나노 구조체를 XRD, XPS, SEM을 이용하여 분석하였다. 또한 TGA, DSC를 이용하여 온도변화에 따른 질량 및 열량의 변화를 측정하였다. UVvis를 이용하여 ZnO와 Al이 첨가된 ZnO의 흡광도를 측정 비교하였다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.408-409
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• 2007

Al-doped p-type ZnO films were fabricated on n-Si (100) and homo-buffer layers in pure oxygen at $450^{\circ}C$ by RF magnetron sputtering. Target was ZnO ceramic mixed with 2wt% $Al_2O_3$. XRD spectra show that the Al-doped ZnO thin films have ZnO crystal structure and homo-buffer layers are beneficial to Al-doped ZnO films to grow along c-axis. Hall Effect experiments with Van der Pauw configuration show that p-type carrier concentrations are ranged from $1.66{\times}10^{16}\;to\;4.04{\times}10^{18}cm^{-3}$, mobilities from 0.194 to $2.3cm^2V^{-1}s^{-1}$ and resistivities from 7.97 to $18.4{\Omega}cm$. P-type sample has density of $5.40cm^{-3}$ which is smaller than theoretically calculated value of $5.67cm^{-3}$. XPS spectra show that O1s has O-O and Zn-O structures and A12p has only Al-O structure. P-ZnO:Al/n-ZnO:Al junctions were fabricated by magnetron sputtering. V-I curves show that the p-n junctions have rectifying characteristics.

• 한국기계기술학회지
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• 제20권6호
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• pp.818-823
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• 2018

In this study, the effect of pre-aging treatment for inhibition of natural aging of Al-4.8Zn-1.3Mg alloy by extrusion process was investigated. Firstly, the as-cast microstructure of Al-4.8Zn-1.3Mg alloy billet and its evolution during homogenization($460^{\circ}C$, $4h+510^{\circ}C$, 5h) were investigated by means of optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), hardness analysis. The as-cast microstructures of Al-4.8Zn-1.3Mg alloy reveal $Mg_2Zn$, $Al_5Cu$, $Al_{13}Cu$ formed between dendrities. After homogenization, MgZn, $Al_4Cu$, $Al_{13}Cu$ phases precipitated into the matrix. In addition, standard deviation of homogenized billet was improved than as-cast billet from 2.62 to 0.99. According to pre-aging($100^{\circ}C$, 1h) Al-4.8Zn-1.3Mg alloy by extrusion process, yield strength and tensile strength deviation improved more than condition by natural aging.

• Journal of Welding and Joining
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• 제23권6호
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• pp.93-98
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• 2005

The purpose of this study is to investigate the characteristics of pb-free $Zn-(3\~6)\%Al-(1\~6)\%Cu$ solder alloys for ultra high temperature(>573K) which applied to air craft, space satellite, automotive, oil, gas well exploration and data logging of geo-thermal wells. Melting range, solderability, electric resistivity, microstructure and mechanical properties were examined with solder alloys casted in Ar gas atmosphere. $Zn-4\%Al-(1\~3)\%Cu,\;Zn-5\%Al-(2\~4)\%Cu\;and\;Zn-6\%Al-(3\~5)\%Cu$ alloys satisfied the optimum melting range of 643 to 673k for ultra high temperature solder. A melting temperature increased with increasing Cu content, but decreased with increasing Al content. The spreadability was improved with increasing hi content. But the content of Cu had no effect on the spreadability. The electric resistivity was lowered with increasing Al and decreasing Cu content. In all Zn-Al-Cu solder alloys, primary dendritic $\varepsilon$ phase(Zn-Cu), dendritic $\eta$ phase(Zn-Cu-Al), $\alpha(Al-Zn)-\eta$ eutectic and eutectoid phase were observed. The addition of Al increased the volume fraction of eutectic and eutectoid phase and it decreased f phases. Also, the addition of Cu increased slightly the volume fraction of e, the eutectic and eutectoid phases. With increasing total content of Al and Cu, a hardness and a tensile strength were linearly increased, but anelongation was linearly decreased.

• Corrosion Science and Technology
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• 제2권4호
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• pp.165-170
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• 2003

Atmospheric corrosion behaviors of Zn, Zn-5%Al and Zn-55%A l coated steels have been investigated under cyclic wet-dry environments containing chloride ions. The wet-dry cycle was carried out by alternate exposure to immersion in 0.5 M (or 0.05 M) NaCl solutions and drying at $25^{\circ}C$ and 60 %RH. The polarization resistance $R_p$ and solution resistance $R_s$ were monitored by AC impedance technique. From the obtained $1/R_p$ and $1/R_s$ values, the corrosion rate of the coatings and the Time of Wetness (TOW) were estimated, respectively. Effects of chloride ions and TOW on the corrosion rates of Zn, Zn-5%Al, Zn-55%Al coatings and appearance of red rust (onset of underlying steel corrosion) under wet-dry cycles are discussed on the basis of the corrosion monitoring data.

• Corrosion Science and Technology
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• 제23권4호
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• pp.289-295
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• 2024

Zn-Mg-Al alloy hot-dip galvanized steel sheet has high corrosion resistance. Compared to conventional Zn coating with the same coating thickness, the high corrosion resistance Zn-Mg-Al coating is more corrosion-resistant. Various coating compositions are commercially produced and applied in diverse fields. However, these steel sheets typically contain up to 3 wt% magnesium. In recent years, there has been a growing demand for higher corrosion resistance in harsh corrosive environments. Therefore, variations in Mg and Al contents were investigated while evaluating primary properties and performance. As a result, we developed new alloy-coated steel with ultra-high corrosion resistance. A Zn-5 wt%Mg-Al coated steel sheet was evaluated for its corrosion resistance and various properties. As the amount of Mg added increased, the corrosion loss tended to decrease. The corrosion resistance of the coated steel sheet in a particular composition, the Zn-5 wt%Mg-Al coating sheet, was about 1.5 to 2 times higher than that of the conventional Zn-3 wt%Mg-Al coating sheet. Ultimately, this ultra-high corrosion-resistance coated steel sheet will provide a robust solution to conserve Zn resources and contribute to a low-carbon society.

• 한국건축시공학회지
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• 제21권6호
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• pp.539-550
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• 2021

일반 전기 아크에 의한 금속용사공법에 비해 시공속도와 효율성능이 우수한 플라즈마 아크 용사장비를 개발하여 이 플라즈마 용사장비에 의한 코팅의 부식특성 평가가 요구되었다. 본 연구에서는 일반 탄소강에 Zn 및 Zn-15Al을 플라즈마 아크 금속 용사법으로 코팅한 후 해수 환경과 유사한 3.5wt.% NaCl 용액에 침지하여 내식성을 평가하였다. SEM 및 XRD에 의한 표면 형상 분석 시험 결과, Zn 코팅이 다공성이고 침상 형태로 되어 있어 용액의 침투가 용이하여 부식 속도가 빠른 것을 알 수 있었다. 반면, Zn-15Al 코팅은 균일하고 조밀한 형태를 보여 부식을 억제하는 것으로 나타났다.

• Corrosion Science and Technology
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• 제21권3호
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• pp.221-229
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• 2022

To understand effects of cooling rates of coating layer on microstructures and corrosion behaviors of hot-dip alloy coated steel sheets (Zn-5%Al-2%Mg) in a neutral aqueous condition with chloride ion, a range of experimental and analytical methods were used in this study. Results showed that a faster cooling rate during solidification decreased the fraction of primary Zn, and increased the fraction of Zn-Al phase. In addition, interlamellar spacing became refined under a faster cooling rate. These modifications of the coating structure had higher open circuit potentials (OCP) with smaller anodic and cathodic current densities in the electrochemical potentiodynamic polarization. Surface analyses after a salt spray test showed that the increase in the Zn-Al phase in the coating formed under a faster cooling rate might have contributed to the formation of simonkolleite (Zn₅(OH)₈Cl₂·H₂O) and hydrotalcite (ZnAl₂(OH)₆Cl₂·H₂O) with a protective nature on the corroded outer surface, thus delaying the formation of red rust.