• 대한금속재료학회지
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• 제49권11호
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• pp.853-859
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• 2011

Compressive deformation behavior of Al-10Si-5Fe-1Zr (wt%) alloy preform fabricated by SPS(spark plasma sintering) of gas atomized powder was investigated in the temperature range from 380 to $480^{\circ}C$ and at strain rates from $1.0{\times}10^{-3}$ to $1.0{\times}10^{0}s^{-1}$. Stress-strain curves showed a peak stress (${\sigma}_p$) during initial stage of deformation, followed by a steady state flow at all temperatures and strain rates tested. The (${\sigma}_p$) decreased with both increase in temperature and decrease in strain rate. Nearly full densification was found to occur in the compressively deformed specimens irrespective of test condition. TEM observation revealed a restricted grain growth during steady state flow.

• Membrane and Water Treatment
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• 제13권4호
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• pp.183-189
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• 2022

This study seeks towards an optimal way to control sulfate ions in semiconductor wastewater effluent with potential eco-toxicity. We developed a system based on ettringite (Ca₆Al₂(SO₄)₃(OH)₁₂·26H₂O). The basic idea is that the pH of the water is raised to approximately 12 with Ca(OH)₂. After, aluminium salt is added, leading to the precipitation of ettringite. Lab-scale batch and continuous experiment results with real semiconductor wastewater demonstrated that 1.5 and 1 of stoichiometric quantities for Ca²⁺ and A³⁺ with pH above 12.7 could be considered as the optimal operation condition with 15% of sludge recycle to the influent. A mixed AlCl₃ + Fe reagent was selected as the beneficial Al³⁺ source in ettringite process, which resulted in 80% of sludge volume reduction and improved sludge dewaterability. The results of continuous experiment showed that with precipitation as ettringite, sulfate concentration can be stably reduced to less than 50 mg/L in effluent from the influent 2,050 ± 175 mg/L on average (1,705 ~ 2,633 mg/L).

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.1630-1636
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• 2009

Nine alkali-activated (AA) mortars were mixed and cured at water or air-dried conditions to explore the significance and limitation for the application of the combination of Ba and Ca ions as an alkali-activator. Ground granulated blast-furnace slag (GGBS) was used for source materials, and calcium hydroxide (Ca(OH)₂) and barium hydroxide (Ba(OH)₂) were employed as alkali activators. Test results clearly showed that the water curing condition was more effective than the air-dried curing condition for the formation of the denser calcium silicate hydrate (C-S-H) gels that had a higher molar Si/Ca ratio, resulting in a higher strength development. At the same time, the introduction of Ba(OH)₂ led to the formation of 2CaO·Al₂O₃·SiO₂·8H₂O (C₂ASH₈) hydrates with higher molar Si/Al and Ca/Al ratios. Based on the test results, it can be concluded that the developed cementless mortars have highly effective performance and high potential as an eco-friendly sustainable building material.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2013년도 춘계학술대회 논문집
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• pp.150-150
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• 2013

Al-Mg films were prepared onto steel sheet according to deposition condition by eco-friendly electron beam vacuum evaporation method. The influence of Al-Mg films on corrosion resistance was evaluated by salt spray test and electrochemical method etc.. From the experimented results, it was found that the Al-Mg films which showed good corrosion resistance tend to have fine structure with homogenious composition distribution. In addition, it was shown that the property of coating films can be improve by controlling thickness ratio and uniform distribution of intermetallic compounds in Al-Mg films.

• 한국재료학회지
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• 제17권8호
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• pp.447-451
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• 2007

We investigated the dependence of the various annealing conditions and thickness ($6\sim45nm$) of the Ti-doped $Al_2O_3$ coating on the electrochemical properties and the capacity fading of Ti-doped $Al_2O_3$ coated $LiCoO_2$ films. The Ti-doped-$Al_2O_3$-coating layer and the cathode films were deposited on $Al_2O_3$ plate substrates by RF-magnetron sputter. Microstructural and electrochemical properties of Ti-doped-$Al_2O_3$-coated $LiCoO_2$ films were investigated by transmission electron microscopy (TEM) and a dc four-point probe method, respectively. The cycling performance of Ti-doped $Al_2O_3$ coated $LiCoO_2$ film was improved at higher cut-off voltage. But it has different electrochemical properties with various annealing conditions. They were related on the microstructure, surface morphology and the interface condition. Suppression of Li-ion migration is dominant at the coating thickness >24.nm during charge/discharge processes. It is due to the electrochemically passive nature of the Ti-doped $Al_2O_3$ films. The sample be made up of Ti-doped $Al_2O_3$ coated on annealed $LiCoO_2$ film with additional annealing at $400^{\circ}C$ had good adhesion between coating layer and cathode films. This sample showed the best capacity retention of $\sim92%$ with a charge cut off of 4.5 V after 50 cycles. The Ti-doped $Al_2O_3$ film was an amorphous phase and it has a higher electrical conductivity than that of the $Al_2O_3$ film. Therefore, the Ti-doped $Al_2O_3$ coated improved the cycle performance and the capacity retention at high voltage (4.5 V) of $LiCoO_2$ films.

• Ecology and Resilient Infrastructure
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• 제8권3호
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• pp.135-142
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• 2021

친환경 제방 건설 소재로 연구되고 있는 바이오폴리머는 토양의 강도 증진 효과가 알려져 있으나, 아직 식생에 미치는 영향에 대한 연구는 부족하다. 본 연구에서는 토양의 aluminum (Al) 스트레스 조건에서 잔탄검 (xanthan gum) 혼합에 따른 Camelina sativa L. (Camelina)의 뿌리 생장을 분석하였다. Al 스트레스 조건과 더불어 xanthan gum 0.05% 혼합구에서 생육한 Camelina가 비혼합구보다 뿌리 생장이 증가하였다. 같은 조건에서 aluminum activated malate transporter 1 (ALMT1) 유전자 발현이 xanthan gum 혼합구 및 비혼합구에서 모두 유도되었지만, xanthan gum 혼합구가 비혼합구보다 낮은 수준의 발현을 보여주었다. 추가적으로 용액에서 xanthan gum과 Al 이온의 결합을 확인하였으며, morin 염색과 ICP-OES 분석을 통해 Camelina 뿌리의 Al 함량을 측정한 결과 xanthan gum 혼합구에서 비혼합구 보다 뿌리의 Al 함량이 낮았다. 이러한 결과들은 xanthan gum과 Al 결합으로 인해 뿌리의 피해를 감소시키고 궁극적으로 식물의 생존 및 생육에 긍정적 효과를 미치는 것으로 보인다.

• 대한금속재료학회지
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• 제48권10호
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• pp.936-941
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• 2010

Al-Zn based alloys are the most common types of wrought Al alloys. Although Al-Zn alloys have high strength, they cannot be applied to a conventional casting process. In this study, Al-Zn-based alloys applicable to a die casting process were developed successfully. The developed Al-45 wt% Zn-based alloys showed a fine equiaxed grain structure and high strength. A fine equiaxed grain having an average size of $25{\mu}m$ was obtained by the die casting process. The UTS and elongation of the new alloy are 475 MPa and ~3.5%, respectively. In addition, we elucidate the effect of a Zn addition on variations in different mechanical properties and the microstructure characteristics of (Al96.3-xZnxCu3Si0.4Fe0.3) x=20, 30, 40, and 45 wt% alloys fabricated by a die casting process.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 추계학술대회 논문집
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• pp.37-38
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• 2007

This paper reports the characteristics of piezoelectric microspeakers that are audible in open air with high quality piezoelectric AlN thin film according to the materials properties. When we use a tensile-stressed silicon nitride diaphragm as a supporting layer, the Sound Pressure Level (SPL) is relatively small. However, the SPL of the fabricated microspeakers that have compressive-stressed composite diaphragm show higher output pressure than those of tensile-stressed diaphragm. It produces more than 60dB from 100Hz to 15kHz and the highest SPL is about 100dB at 9.3kHz with 20 Vpeak-to-peak sinusoidal input biases and at 10 mm distances from the fabricated microspeakers to the reference microphone.

• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1301-1304
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• 2010

The Indium modified mesoporous zeolite AlMCM-41 were synthesized by hydrothermal method and characterized by powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) techniques. The Knoevenagel condensation of aldehyde with malononitrile or ethyl cyanoacetate was carried out at reflux condition in ethanol by using heterogeneous In/AlMCM-41 catalyst. This method is fast, efficient, easy work-up and eco-friendly to afford the corresponding Knoevenagel adducts. The catalyst was recovered and reused for several cycles with consistent activity.

• 한국주조공학회지
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• 제30권6호
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• pp.205-209
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• 2010

This study evaluates the influence of strontium addition and holding time on mechanical properties for Al-10.5wt%Si-2wt%Cu secondary die-casting alloy and the measured electrical conductivity of modified alloys. A general improvement in the mechanical properties of the alloy was observed after adding the strontium. Ultimate tensile strength, elongation and electrical conductivity of modified alloys were improved by increasing strontium content and holding time. From these results, the optimal strontium content and holding time were identified on the mechanical properties of Al-10.5wt%Si-2wt%Cu secondary die-casting alloys.