• Corrosion Science and Technology
• /
• 제23권2호
• /
• pp.121-130
• /
• 2024

In recent years, Zn-Al-Mg alloy galvanized steel sheets have been widely used as coated steel sheets to support social capital in the infrastructure field. A feature of Zn-Al-Mg alloy-coated steel sheets is that they provide a better corrosion protection period than Zn-coated steel sheets. In this study, the corrosion resistance of a new Zn-Al-Mg alloy-coated steel sheet was investigated and compared to that of conventional commercially available coated steel sheets. The investigation confirmed that increasing the Mg concentration in the Zn-Al-Mg-coated steel sheet improved corrosion resistance, which was more than 10 times that of the galvanized steel sheet specified in JIS G 3302. The study findings also confirmed that the corrosion resistance reached more than twice that of the coated steel sheet specified in JIS G 3323. If such galvanized steel sheets are applied to social infrastructures that are exposed to severely corrosive environments, the service life of the infrastructure might be extended.

• 한국재료학회지
• /
• 제26권11호
• /
• pp.628-634
• /
• 2016

The cold rolling workability and mechanical properties of two new alloys, designed and cast Al-5.5Mg-2.9Si and Al-7Mg-0.9Zn alloys, were investigated in detail. The two alloy sheets of 4 mm thickness, 30 mm width and 100 mm length were reduced to a thickness of 1 mm by multi-pass rolling at ambient temperature. The rolling workability was better for the Al-7Mg-0.9Zn alloy than for the Al-5.5Mg-2.9Si alloy; in case of the former alloy, edge cracks began to occur at 50% rolling reduction, and their number and length increased with rolling reduction; however, in the latter alloy, the sheets did not have any cracks even at higher rolling reduction. The mechanical properties of tensile strength and elongation were also better in the Al-7Mg-0.9Zn alloy than in Al-5.5Mg-2.9Si alloy. Work hardening ability after cold rolling was also higher in the Al-7Mg-0.9Zn alloy than in the Al-5.5Mg-2.9Si alloy. At the same time, the texture development was very similar for both alloys; typical rolling texture developed in both alloys. These differences in the two alloys can primarily be explained by the existence of precipitates of $Mg_2Si$. It is concluded that the Al-7Mg-0.9Zn alloy is better than the Al-5.5Mg-2.9Si alloy in terms of mechanical properties.

• Transactions on Electrical and Electronic Materials
• /
• 제4권3호
• /
• pp.15-18
• /
• 2003

Aluminum oxide ($Al_2O_3$) materials were coated conformally on ZnO nanorods by atomic layer deposition (ALD). The ZnO nanorods were first synthesized on a Si(100) substrate from ball-milled ZnO powders by a thermal evaporation procedure. $Al_2O_3$ films were then deposited on these ZnO nanorods by ALD at a substrate temperature of $300^{\circ}C$ using trimethylaluminum (TMA) and distilled water ($H_2O$). Transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM) images of the deposited ZnO nanorods revealed that amorphous $Al_2O_3$ cylindrical shells surround the ZnO nanorods. These TEM images illustrate that ALD has an excellent capability to coat any shape of nanorods conformally.

• The Korean Journal of Ceramics
• /
• 제7권2호
• /
• pp.85-92
• /
• 2001

Thin films of ZnO and Al doped ZnO were prepared by rf magnetron sputter techniques. When the oxygen fraction in Ar-O$_2$ sputter gas was about 2.0%, the films exhibited the composition of Zn:O=1.05:1. The films prepared at 250 W contain larger grains than the films grown at 100 W. However, high deposition rate seems to deteriorates the crystallinity as well as Al-substitution, resulting in lower concentration of mobile electrons. The Al-doped ZnO films which were deposited at $500^{\circ}C$ show resistance of 1$\times$10$^-2$ Wcm; optical band gap of the films ranges from 3.25 to 3.40 eV. These electrical and optical features are related with microstructural as well as crystalline characteristics of the films.

• 한국표면공학회:학술대회논문집
• /
• 한국표면공학회 2009년도 춘계학술대회 논문집
• /
• pp.122-122
• /
• 2009

금속기판과 액체금속의 젖음성은 일반적으로 액적법 (sessile drop)에 의해 고체와 액체간의 접촉각 측정을 통해서 알 수 있다. 이러한 방법에 의한 젖음성 실험결과는 고체와 액체계면에서의 반응이 무시될 수 있는 경우에 적용가는 하지만 연속용용도금공정과 같이 용융된 금속내부로 강판이 인입되는 과정에서 계면반응이 동적으로 진행되는 과정에서의 젖음성을 모사하기에는 이러한 방법의 신뢰성이 떨어지는 문제점이 있다. 따라서 본 연구에서는 실제 용융도금공정과 유사하게 소둔열처리된 저탄소강판이 환원성분위기내에서 Zn 및 Zn-Al 용융도금욕 내부로 연속적으로 인입되는 과정에서의 젖음력 및 접촉각 등의 측정을 통해 실제 도금공정상의 도금성과 젖음성의 연관성을 규명하고자하였다. 연구결과 일반적인 Zn 도금욕의 경우 젖음성이 양호하지만 Al함량이 높은 경우에는 젖음성이 좋지 못한 것으로 나타났다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
• /
• pp.143-146
• /
• 2003

Al doped Zinc Oxide(ZnO:Al) films, which is widely used as a transparent conductor in optoelectronic devices such as solar cell, liquid crystal display, plasma display panel, thermal heater, and other sensors, were prepared by using the capacitively coupled DC magnetron sputtering method. The influence of the substrate temperature, working gas pressure and discharge power on the electrical, optical and morphological properties were investigated experimentally. The consideration on the effect of doping amounts of Al on the electrical and optical properties of ZnO thin film were also carried out. ZnO:Al films with the optimum growth conditions showed resistivity of $9.42{\times}10^{-4}\;{\Omeg}-cm$ and transmittance of 90.88% for 840nm in film thickness in the wavelength range of the visible spectrum.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
• /
• pp.466-467
• /
• 2005

Al doped zinc oxide films (ZnO:Al) were deposited on glass substrate by RF magnetron sputtering from a ZnO target mixed with 2 wt% $Al_2O_3$. The as-deposited ZnO:Al films were rapid-thermal annealed. Electrical properties and structural evolution of the films, as annealed by rapid thermal process (RTP), were studied and compared with the films annealed by conventional annealing process. RTP, the (002) peak intensity increases and the electrical resistivity decreases by 20%, after RT annealing. The effects of RT annealing on the structural evolution and electrical properties of RF sputtered films were further discussed and compared also with the films deposited by DC magnetron sputtering.

• 에너지공학
• /
• 제11권2호
• /
• pp.136-141
• /
• 2002

석탄가스화 복합발전용 고온건식 탈황제의 반응성을 개선하기 위하여 $Al_2$O$_3$를 지지체로사용한 ZnO/Al$_2$O$_3$ 탈황제를 제조하고 반응특성을 조사하였다. ZnO/Al$_2$O$_3$의 성분함량 및 소성온도에 따른 물리화학적 구조변화를 XRD로 관찰하였고 ZnO의 소결 및 열화로 인한 활성저하를 $Al_2$O$_3$의 함량과 소성온도를 변화시켜 개선할 수 있음을 탈황 및 재생반응실험을 통하여 확인하였다. 마지막으로 첨가제를 함유한 ZnO/Al$_2$O$_3$ 탈황제의 내구성실험에 의한 고온건식 탈황제로의 사용가능성을 실험적으로 확인하였다.

• 열처리공학회지
• /
• 제18권1호
• /
• pp.12-17
• /
• 2005

Effects of Zn and Zr additions on the microstructure and mechanical properties of Al-5%Mg-1%Mn alloys were investigated. As Zn content increased in the Al-Mg-Mn-Zn alloys, the tensile strength and ductility of as-cast alloys rather decreased while the tensile strength of the heat-treated alloys significantly increased mainly due to the precipitation of fine $MgZn_2$ phases. Small amount of Zr was added to the 3%Zn alloy to further enhance the mechanical properties, and it appeared to increase the strength and ductility, especially in as-cast state.

• 한국주조공학회지
• /
• 제17권5호
• /
• pp.419-425
• /
• 1997

용탕단조방법에 의해 제조된 Mg-6Al-xZn(x=0, 1, 2)합금의 기계적 성질에 미치는 시효열처리의 영향을 조사한결과 아래와 같은 결론을 얻었다. (1) 주조조직을 관찰한 결과 미세한 수지상조직을 나타냈으며 초정${\alpha}$, 과포화 ${\alpha}$, ${\beta}$상 등 세가지 상으로 구성되어 있었다. (2) Mg-6Al-xZn합금은 시효경화성을 나타내었으며 Zn의 첨가량이 증가할수록 전시효구간에서 경도값이 높게 나타났다. (3) 시효조직을 관찰한 결과 $200^{\circ}C$의 시효시에는 불연속 석출물이 대부분 차지했으나 $240^{\circ}C$의 시효온도에서는 수지상 경계에서 시작되는 미세분산된 연속석출물이 대부분 이었다. (4) $240^{\circ}C$에서 시효열처리 한 시편은 연속석출물이 석출됨으로서 $200^{\circ}C$에서의 시효열처리된 시편에 비하여 과시효되는 경향이 작았다. (5) T6열처리 후 인장시험 결과 Zn 첨가량에 따라 강도가 증가하였는데 Mg-6Al-2Zn합금의 경우 인장강도는 248.4 MPa을 나타내었으며 Zn양에 따른 연신율의 감소는 나타나지 않았다.