• Journal of the Korean Vacuum Society
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• v.19 no.5
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• pp.385-390
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• 2010

We studied the optical characteristics of ZnO:Al and $Al_2O_3$ coated ZnO nanorods. When ZnO:Al is deposited around the undoped ZnO nanorods, thermal diffusion of Al into ZnO gives rise to decrease the binding energy of neutral donor bound exciton whereas an insulating Al2O3 is coated around ZnO, we found that semiconducor-insulator interface states play an important role in optical quenching.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.591-600
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• 1997

Al2O3/Al composites were produced by displacement reaction method, which was carried out by immersing the sintered silica preform, which was prepared from fused silica powder, in molten aluminum. Because the molten aluminum did not penetrate into the silica preform with higher than 20% of porosity when the displacement reaction was accomplished at 100$0^{\circ}C$ for 10 hours in air atmosphere, the optimum range of sintering temperature of silica preform was from 135$0^{\circ}C$ to 140$0^{\circ}C$. The microstructure of this Al2O3/Al composites showed three-dimentionally co-continuous alumina, which provides wear resistance and high stiffness, and aluminium which acts as a toughnening phase. The grain size of the alumina in composites did not change with the particle size of the silica preform. The exact shape of the preform was retained and a net-shaped composite was produced. The representative Al2O3/Al composite prepared in this study showed 3.30mg/㎤ of bulk density, 350-430 MPa of flexural strength, 7.0 MPa.m1/2 of fracture toughness, and good machinability.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.2
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• pp.128-136
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• 2004

The overall objective of this research was to find out the role of rapid mixing conditions in the species of hydrolyzed Al(III) formed by different Al(III) coagulants. When an Al(III) salt is added to water, monomers, polymers, or solid precipitates may form. Different Al(III) coagulants (alum and PACl) show to have different Al species distribution over a rapid mixing condition. During the rapid mixing period, for alum, formation of dissolved Al(III) (monomer and polymer) increases, but for PACl, precipitates of $Al(OH)_{3(s)}$. increases rapidly. Also, for alum, higher mixing speed favoured Al(III) polymers formation over precipitates of $Al(OH)_{3(s)}$ but for PACl, higher mixing speed formed more precipitates of $Al(OH)_{3(s)}$. At A/D and sweep condition, both $Al(OH)_{3(s)}$ and dissolved Al(III) (monomer and polymer) exist, concurrent reactions by both mechanism appear to cause simultaneous precipitation.

• Journal of Powder Materials
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• v.6 no.1
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• pp.42-48
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• 1999

Three mixtures of elemental powders of Al-25at.%Ti, 48at.%Ti and 70at.%Ti were offered to ball milling process for the formation of intermetallic compounds of $Al_3Ti$, AlTi and $Ti_3Al$. Ballmilling or attrition process were carried out at the condition of rotaing speed of 110 or 350 rpm at $10^{-3}$ torr vacuum or argon atmospheres. $Al_3Ti$phases were fully obtained by heat treatment for 1 hors at $600^{\circ}C$ with Al-25at.%Ti composition mixtures milled by 100 hours. The amorphous phase was completely formed at the composition of Al-48at.%Ti mixed powders by milling 100hours at the 50 to 1 weight ratio of ball to powder, and AlTi compounds were obtained by heat treament. In the case of Al-70at%Ti mixed powders milled for 100 hours, $Ti_3Al$ and $Al_3Ti$intermetallic compounds were formed by heat treatment for 1 hour at $600^{\circ}C$. By attrition milling of 350rpm for 10 hours, $Ti_3Al$ phase was formed completley after heat treatment for 1 hour at $600^{\circ}C$.

• Bulletin of the Korean Chemical Society
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• v.34 no.8
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• pp.2335-2339
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• 2013

Relative reactivity of various Al-substituted dialkylalans ($AlR_2(X)$) in reduction of acetone has been studied with density functional theory and MP2 method. Formation of the alan dimers and the alan-acetone adduct, and the transition state for the Meerwein-Ponndorf-Verley (MPV) type reduction of the adduct were calculated to figure out the energy profile. Formation of dimeric alans is highly exothermic. Both the relative free energies for acetone-alan adduct formation and the TS barriers for the MPV type reduction with respect to alan dimers and acetone were calculated and they show the same trend. Based on these energetic data, relative reactivity of alans is expected to be; $AlR_2(Cl)$ > $AlR_2(OTf)$ > $AlR_2(O_2CCF_3)$ > $AlR_2(F)$ > $AlR_2(OMs)$ > $AlR_2(OAc)$ > $AlR_2(OMe)$ > $AlR_2(NMe_2)$. The energy profile is relatively well correlated with the experimental order of the reactivity of Al-substituted dialkylalans. It is noted that the substituents of alans have initial effects on the relative free energies for the carbonyl-adduct formation. Therefore, an $AlR_2(X)$ which forms a more stable carbonyl-adduct is more reactive in carbonyl reduction.

• Journal of Korea Foundry Society
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• v.20 no.2
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• pp.89-96
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• 2000

The effects of modification processing on the refinement of primary Si and the wear behavior of hyper-eutectic Al-Si alloys have been mainly investigated. Refining effects of primary Si in Al-17%Si alloy was more efficient than that of B.390 alloy. Optimum condition of getting the finest primary Si microstructure was when AlCuP modifier is added into the melt at $750^{\circ}C$ and held it at $700^{\circ}C$ for 30 minutes. Wear loss in the specimens of as-cast condition decreases as the size of primary Si decreases, in the order of B.390 alloy, B.390 alloy with AlCuP addition, Al-17%Si alloy and Al-17%Si alloy with AlCuP addition. Wear loss in the aged condition of Al-17%Si alloy, B.390 alloy and B.390 alloy with AlCuP addition decreased due to the increase of compressive residual stress in the matrix by the aging treatment. While, wear loss increased in the aged specimens of Al-17%Si alloy with AlCuP addition and Hepworth addition in which compressive residual stress decreases by the aging treatment. Therefore, it is assumed that higher compressive residual stress in the matrix can reduce the wear loss in composite materials such as hyper-eutectic Al-Si alloys.

• Journal of the Korean institute of surface engineering
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• v.25 no.5
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• pp.235-252
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• 1992

(Ti, Al)N films were deposited on 304 stainless steel sheet by D.C. magnetron sputtering using Al target and Ti plate. The high temperature oxidation of (T, Al)N films with the variation of composition has been investigated. The chemical composition of (Ti, Al)N films with the variation of composition has been investigated. The chemical composition of (Ti, Al)N films was similar to the sputter area ratio of titanium to aluminum target by means of EDS and AES survey. The high temperature oxidation test of (Ti, Al)N showed that (Ti, Al)N has better high temperature resistance than TiN and TiC films. TiC films were cracked at 40$0^{\circ}C$ in air TiN films quickly were oxidised at $600^{\circ}C$, were spalled more than $700^{\circ}C$. But (Ti, Al)N films are relatively stable to$ 900^{\circ}C$. The good resistance to high temperature oxida-tion of (Ti, Al)N films are due to the formation of dense Al2O3 and TiO2 oxide layer. Especially, Al2O3 oxide layer is more important. The results obtained from this study show, it is believe that the (Ti, Al)N film by D.C. magnetron sputtering is promising for the use of high temperature and wear resistance mate-rials.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.170-171
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• 2012

$Fe_2O_3$, Al, Cr과 Si 분말을 고 에너지 볼 밀링해서 나노분말을 제조한 후 고주파유도 가열 활성 연소합성 장치로 1분 이내의 짧은 시간에 합성 및 소결한 $Al_2O_3+4.65(Fe_{0.43}Cr_{0.17}Al_{0.323}Si_{0.077})$, $Al_2O_3$ + 5.33 ($Fe_{0.375}Cr_{0.11}Al_{0.3}Si_{0.075}$), $Al_2O_3$ + 6.15 ($Fe_{0.325}Cr_{0.155}Al_{0.448}Si_{0.072}$), $Al_2O_3$ + 3.3 ($Fe_{0.6}Cr_{0.3}Al_{0.6}$) 소결체 시편을 $700^{\circ}C$의 온도에서 100시간 동안 공기 중에서 산화 및 $N_2-H_20-H_2S$ 혼합 가스 내에서 황화 부식을 실시하였다. 그 결과 산화 및 황화 부식 후에 ${\alpha}-Al_2O_3$가 표면에 생성되어 보호 피막으로 작용하여 우수한 내식성을 보였다.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.6
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• pp.295-302
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• 2022

The present study aims to investigate the effect of Al content on microstructure and hardness of discontinuous precipitates (DPs) formed by continuous cooling (CC) in Mg-8%Al and Mg-9.5%Al alloys. The DPs had a wide range of (α+β) interlamellar spacings, which may well be attributed to the different transformation temperatures during CC. The higher Al content gave rise to the higher level of interlamellar spacings of the DPs, and thicker and larger amount of β phase layer in the DPs. It is noticeable that the Mg-9.5%Al alloy exhibited higher hardness of the DPs than the Mg-8%Al alloy, but the ratio of increase in hardness of the DPs compared to that of the as-cast state was similar regardless of the Al content. The reason was discussed based on the differences in microstructures of the DPs for the Mg-8%Al and Mg-9.5%Al alloys.

• Korean Journal of Materials Research
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• v.33 no.9
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• pp.353-359
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• 2023

This study investigated the growth behavior and characteristics of compounds formed at the interface between a liquid Al-Si-Cu alloy and solid cast iron. Through microstructural analyses, it was observed that various AlFe and AlFeSi phases are formed at the interface, and the relative proportion of each phase changes when small amounts of strontium are added to the Al alloy. The results of the microstructural analysis indicate that the primary phases of the interfacial compounds in the Al-Si-Cu base alloy are Al₈Fe₂Si and Al_4.5FeSi. However, in the Sr-added alloys, significant amounts of binary AlFe intermetallic compounds such as Al₅Fe₂ and Al₁₃Fe₄ formed, in addition to the AlFeSi phases. The inclusion of Sr has a slight diminishing effect on the rate at which the interfacial compounds layer thickens during the time the liquid Al alloy is in contact with the cast iron. The study also discusses the nano-indentation hardness and micro-hardness of the interfacial phases.