• 열처리공학회지
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• 제36권6호
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• pp.389-395
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• 2023

Damping capacities of Mg-2.5%Al and Mg-2.5%Zn (in atomic) solid solutions were comparatively investigated in order to clarify the influence of solutionized Al and Zn elements on the damping characteristics of Mg. In this study, solid solutions with similar grain size were obtained by solution treatment at 678 K for different times (24 h for Mg-2.5%Al and 36 h for Mg-2.5%Zn), followed by water quenching at RT. The Mg-2.5%Al and Mg-2.5%Zn solid solutions showed similar damping capacities in the strain-amplitude independent region of 1 × 10^-6 ~ 1 × 10^-5 and in the strain-amplitude dependent region below 6 × 10^-4, over which the Mg-2.5%Zn solid solution possessed better damping capacity than the Mg-2.5%Al solid solution. The damping tendencies depending on strain-amplitude for the two solid solutions were analyzed and discussed in terms of similar length between weak pinning points (solutes) and different solute/dislocation interaction forces in Granato-Lücke model.

• Journal of the Korean Wood Science and Technology
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• 제9권3호
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• pp.7-15
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• 1981

우리나라에 대량조림(大量造林)되어 있는 일본잎갈나무는 기계(機械)펄프의 수율(收率)과 백색도(白色度)가 낮아 펄프재(材)로 이용(利用)되지 못하고 있다. 일본잎갈나무의 펄프재(材) 자원화(資源化)와 해예동력(解穢動力) 절약(節約)을 위하여 제지용 Asplund 펄프제조(製造)에서 셀롤로오스 안정제(安定劑)로서 $MgSO_4$, $ZnSO_4$, $Al_2(SO_4)_3$, KI을 택하고 고농도(高濃度) 과산화수소표백(過酸化水素漂白)과 과초산표백(過酢酸漂白)에서 그의 효과(效果)를 조사(調査)하고, ��의 알카리전처리(前處理)와 셀룰로오스안정제(安定劑)를 첨가(添加)한 알카리 전처리가 Asplund 펄프의 기존과산화수소표백(旣存過酸化水素漂白)에 미치는 영향(影響)을 조사(調査)한 결과(結果) 다음과 같이 요약(要約)된다. 1. 0.5%의 셀룰로오스안정제(安定劑)는 염기(塩基)의 종류(種類)에 따라 PH가 다르고($MgSO_4$=PH 5.72, $ZnSO_4$=PH 4.95, $Al_2(SO_4)_3$=pH 2.85), PH에 따라 침전 PH 범위($MgSO_4$=PH6~13, $ZnSO_4$=PH5~12, $Al_2(SO_4)_3$=PH3~10)와 최대(最大)침전 PH($MgSO_4$=PH9~10, $ZnSO_4$=PH6~7, $Al_2(SO_4)_3$=PH3~4)가 달랐다. 2. 일본잎갈나무 Asplund펄프의 고온고농도(高溫高濃度) 과산화수소(過酸化水素) 및 과초산표백(過酢酸漂白)에서 유효(有效)한 셀룰로오스안정제(安定劑)로는 KI, $MgSO_4$, $ZnSO_4$였으나 그의 효과(效果)는 미미하였다. 3. ��의 알카리전처리는 무처리보다 기존과산화수소표백(過酸化水素漂白)에 효과적(效果的)이었으며, 펄프의 강도(强度)와 백색도(白色度)를 향상(向上)시켰으나 수율(收率)은 저하(低下)시켰다. 그러나 셀룰로오스안정제(安定劑) 첨가(添加)는 황산염(黃酸塩)으로 인한 PH저하(低下)를 초래하여 탄산(炭酸)소다 전처리수준(水準)이었으며 ��의 알카리전처리에 첨가(添加)한 셀룰로오스안정제중(安定劑中)에서 해섬후(解纖後)의 과산화수소표백(過酸化水素漂白)에 유효한(有效)한 ��은 $ZnSO_4$, $Al_2(SO_4)_3$와 KI였다. 4. 따라서 산화조건에 효과적(效果的)인 안정제(安定劑)는 KI, $MgSO_4$이나 환원조건에서는 착염(錯塩)인 Zn, Al 염(塩)과 KI가 효과적(效果的)인 것으로 생각된다.

• 한국세라믹학회지
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• 제50권3호
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• pp.195-200
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• 2013

Here, we report preparation of cyan ceramic nano-pigment for inkjet printing and the Ni substitutional effects on the cyan color. $MgAl_2O_4$ was selected as the crystalline host network for the synthesis of nickel-based cyan ceramic nano-pigments. Various compositions of $Ni_xMg_{1-x}Al_2O_4$ ($0{\leq}x{\leq}1$) powders were prepared using the polymerized complex method. The powder was then preheated at $400^{\circ}C$ for 5 h and finally calcined at $1000^{\circ}C$ for 5 h. XRD patterns of $Ni_xMg_{1-x}Al_2O_4$ showed a single phase of the spinel structure in all the compositions. The particle sizes ranged from 20 to 50 nm in TEM observations. The characteristics of the color tones of $Ni_xMg_{1-x}Al_2O_4$ were analyzed by UV-Visible spectroscopy and CIE $L^*a^*b^*$ measurement. CIE $L^*a^*b^*$ measurement results indicate that the pigment color changes from light cyan to deep cyan due to the decrease of the $a^*$ and $b^*$ values with an increase of an Ni substitutional amount. In addition, the thermal stability and the binding nature of $Ni_xMg_{1-x}Al_2O_4$ are also discussed using TG-DSC and FT-IR results respectively.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.727-730
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• 2009

Highly active and stable nano-sized Ni catalysts supported on MgO-$Al_2O_3$ calcined from hydrotalcite-like materials have been successfully developed with a strong metal to support interaction (SMSI) to enhance the coke resistance in combined $H_2O$ and $CO_2$ reforming of $CH_4$ (CSCRM) for syngas ($H_2$/CO=2) production. The change of the surface area and NiO crystallite size with varying the pre-calcination temperature of support and Mgo content was investigated in relation to the coke resistance. As increasing the pre-calcination temperature, the surface area decreases and the metal to support interaction becomes weak. As a consequence, the coke deposition was more severe on catalysts pre-calcined at high temperature. It was concluded that highly dispersed Ni metal in the surface of Ni/MgO-$Al_2O_3$ catalyst (MgO=30 wt%) pre-calcined at $800^{\circ}C$ had a strong metal to support interaction (SMSI) resulting in an increase of coke resistance and high activity.

• 한국재료학회지
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• 제31권11호
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• pp.642-648
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• 2021

The precipitation effect of Al-6%Si-0.4%Mg-0.9%Cu-(Ti) alloy (in wt.%) after various heat treatments was studied using a laser flash device (LFA) and differential scanning calorimetry (DSC). Solid solution treatment was performed at 535 ℃ for 6 h, followed by water cooling, and samples were artificially aged in air at 180 ℃ and 220 ℃ for 5 h. The titanium-free alloy Al-6%Si-0.4%Mg-0.9%Cu showed higher thermal diffusivity than did the Al-6%Si-0.4%Mg-0.9%Cu-0.2%Ti alloy over the entire temperature range. In the temperature ranges below 200 ℃ and above 300 ℃, the value of thermal diffusivity decreased with increasing temperature. As the sample temperature increased between 200 ℃ and 400 ℃, phase precipitation occurred. From the results of DSC analysis, the temperature dependence of the change in thermal diffusivity in the temperature range between 200 ℃ and 400 ℃ was strongly influenced by the precipitation of θ'-Al₂Cu, β'-Mg₂Si, and Si phases. The most important factor in the temperature dependence of thermal diffusivity was Si precipitation.

• 한국세라믹학회지
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• 제27권4호
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• pp.501-512
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• 1990

Al2O3 and 0.25wt% MgO-doped Al2O3 powders were made from the alcohol solution of Al(NO3)3.9H2O and Mg(NO3)2.6H2O by spray pyrolysis method. Each powder was prepared at 900 and 100$0^{\circ}C$. Powders prepared at 90$0^{\circ}C$ were amorphous phase, but prepared at 100$0^{\circ}C$ wre mainly ${\gamma}$-Al2O3 crystalline form. Particle size of the MgO-doped Al2O3 powders was in the range of 0.2-2${\mu}{\textrm}{m}$, but undooped powders shwoed comparatively wider range of particle size. All the powders prepared at 900 and 100$0^{\circ}C$ were transformed to $\alpha$-Al2O3 crystalline form by calcination at 110$0^{\circ}C$ for 1hr. Each powder was sintered at 1600, 1650 and 1$700^{\circ}C$ for 2hrs. MgO-doped Al2O3 body sintering at 1$650^{\circ}C$ showed 99% of relative density but undooped Al2O3 showed 95% of relative density, even sintered at higher temperature of 1$700^{\circ}C$.

• 생명과학회지
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• 제11권2호
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• pp.153-158
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• 2001

To investigate the effects of soil acidification on growth of Impatiens balsamina L. plants were transplanted to acidified soils with H$_2$SO$_4$ solution. The concentrations of soluble Ca, Mg, K, Al and Mn in the acidified soils increased with increment of H$^{+}$ addition to the soil. In both species, the plant height and root length were inhibited by soil acidification, showing much severer inhibition in Impatiens balsamina L. than in Tagetes patula L., As the soil pH decreases, the growth of underground parts decreased greatly than that of above ground parts in both species. Total dry weight decreased with increased Al concentration as well as lowered soil pH in both plants. There was a strong positive correlation between relative total dry weight and molar (Ca+Mg+K) / Al ratio of the soil. The results suggest that molar(Ca+Mg+K)/ Al ratio of the soil may be useful indicator for assessing the critical load of acid deposition in herb species.s.

• 한국수소및신에너지학회논문집
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• 제21권6호
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• pp.500-506
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• 2010

The metal monolith catalyst coated with 15wt% Ni/$MgAl_2O_4$ is applied to the natural gas steam reforming for hydrogen production. To address the improvement of adherence between metal monolith and catalyst coating layer, the pre-calcination temperature as well as the coating conditions of $Al_2O_3$ sol are optimized. When the Fe-Cr alloy monolith is pre-calcined at $900^{\circ}C$ for 6 h, $Al_2O_3$ layer was formed uniformly on the entire surface of the metal substrate. It is seen that the formation of $Al_2O_3$ layer on the monolith surface is essential for the uniform coating of $Al_2O_3$ sol onto the monolith substrate. The monolith catalyst coated with 10wt% $Al_2O_3$ sol shows high $CH_4$ conversion and good thermal stability as compared with the monolith catalyst without $Al_2O_3$ sol coating under severe reaction conditions with high GHSV of 30,000 $h^{-1}$ at $700^{\circ}C$. In addition, the metal monolith catalyst shows higher catalytic activity and better thermal conductivity than 15wt% Ni/$MgAl_2O_4$ pellet catalyst.

• 열처리공학회지
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• 제36권4호
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• pp.198-205
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• 2023

We investigated the effects of Al and Mg on the microstructure and hardness of the coating layer of galvanized steel sheets, by thermodynamic calculations, X-ray diffraction, scanning electron microscopy, and Vickers hardness tests of Zn-0.2Al, Zn-6Al-2Mg, and Zn-10Al-5Mg coating layers. Regardless of the alloy composition of the galvanizing bath, a Fe-Al layer was observed between the coating layer and steel sheet. The Zn-0.2Al coating layer consists of major h.c.p. Zn phase and minor f.c.c. Al phase. The fraction of f.c.c. Al phase (containing a significant amount of Zn) of the coating layer increases with increasing the chemical composition of Al of the galvanizing bath. The h.c.p. MgZn₂ phase was formed in the Al/Mg-containing Zn-6Al-2Mg and Zn-10Al-5Mg coating layers, forming Zn-Al-MgZn₂ eutectic microstructure. The primary MgZn₂ phase was additionally formed in the Zn-10Al-5Mg coating layers containing high concentrations of Al and Mg. The Vickers hardness values of Zn-0.2Al, Zn-6Al-2Mg, and Zn-10Al-5Mg coating layers were 59.1 ± 1.2 HV, 161.2 ± 5.7 HV, and 215.5 ± 40.3 HV, respectively. The addition of Al and Mg increased the hardness of the coating layer by increasing the fraction of the Al phase (containing Zn) and MgZn₂ intermetallic compound, which were harder than the Zn phase.

• 신재생에너지
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• 제4권4호
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• pp.80-87
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• 2008

Steam reforming of LPG was investigated over spc-Ni/MgAl catalyst in a temperature range of $600{\sim}850^{\circ}C$, feed molar ratio of $H_2O/C=1.0{\sim}3.0$, space velocity of $10,000{\sim}90,000h^{-1}$ and at atmospheric pressure. spc-Ni/MgAl catalyst was prepared by a co-precipitation method, whereas Ni/MgO and $Ni/Al_2O_3$ catalysts were prepared by an incipient wetness method. The characteristics of catalysts were analyzed by N2 Physisorption, CO chemisorption, XRD, TOF-SIMS, SEM and TEM techniques. The Ni/MgO and $Ni/Al_2O_3$ catalysts were deactivated by the formation of carbon. However, the spc-Ni/MgAl catalyst showed higher conversion and $H_2$ selectivity than the other catalysts, even though carbon was formed on the surface of the catalyst during the reaction under the tested reaction conditions.