• Analytical Science and Technology
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• v.5 no.1
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• pp.103-110
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• 1992

Chemical homogeneity and dispersoid formation in mechanically alloyed Al-Ti composite metal powders were investigated in order to fabricate the high temperature Al-Ti alloys. The homogeneity of composite particles was able to be obtained by MA milling time more than 10 hours with the milling velocity of 400 rpm. The amounts of titanium, carbon and oxygen elements in MA Al-Ti alloys by chemical analysis were 8.2, 1.135 and 0.233 wt.%, respectively. The amount of carbon analyzed corresponds to 90 pet. of carbon contained the PCA of stearic acid. TEM analysis has revealed the presence of the rounded $Al_3Ti$ dispersoids with the size of 250nm and the $Al_4C_3$ dispersoids of cylindrical shape with a size of 50nm in thickness and 150nm in length. Also, the some rounded $Al_2O_3$ dispersoids with a size of about 20nm were found in grain boundaries as well as in matrix.

• Korean Journal of Materials Research
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• v.31 no.8
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• pp.439-444
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• 2021

The oxidation resistance of the diffusion aluminide bond coat (BC) is compromised largely by interdiffusion (ID) effects on coated turbine blades of aeroengines. The present study is designed to understand the influence of ID on βNiAl coatings or BC. In this regard, nickel substrate and CMSX-4 superalloy are deposited. In total, four sets of BCs are developed, i.e. pure βNiAl (on Ni substrate), simple βNiAl (on CMSX-4 substrate), Zr-βNiAl (on CMSX-4 substrate) and Pt-βNiAl (on CMSX-4 substrate). The main aim of this study is to understand the interdiffusion of Al, Zr and Pt during preparation and oxidation. In addition, the beneficial effects of both Zr and platinum are assessed. Pure βNiAl and simple βNiAl show Ni-out-diffusion, whereas for platinum inward diffusion to the substrate is noticed under vacuum treatment. Interestingly, Zr-βNiAl shows the least ID in all BCs and exhibit stability under both vacuum and oxidation treatments. However, its spallation resistance is slightly lower than that of Pt-βNiAl BC. All BCs show similar oxide growth trends, except for Zr-βNiAl, which exhibits two-stage oxidations, i.e. transient and steady-state. Moreover, it is suggested that the localized spallation in all BCs is caused by βNiAl - γ'-Ni₃Al transformation.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.216.1-216.1
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• 2015

본 연구에서는 용액 공정 기반 AZTO (Aluminum-Zinc-Tin Oxide, AlZnSnO) 박막 트랜지스터를 제작하여 Al (Aluminum) 도핑과 열처리 온도의 가변을 통한 특성 향상을 확인하였다. ZTO 용액의 Zn:Sn 비율(4:7)을 고정하고 Al 도핑(0~8.3%)과 열처리 온도($350{\sim}550^{\circ}C$)를 가변하였다. 실험 결과 Al 도핑이 증가할수록 드레인 전류는 감소하고 문턱 전압이 양의 방향으로 이동하면서 포화 이동도와 아문턱 기울기가 감소하였다. 열처리 온도가 증가할 때는 드레인 전류가 증가하고 문턱 전압은 음의 방향으로 이동하며 이동도와 아문턱 기울기가 증가하였다. Al 도핑은 강한 금속-산소 결합에 의해 oxygen vacancy와 전자 농도가 감소하게 하여 드레인 전류, 이동도, 아문턱 기울기의 감소와 양의 방향 문턱 전압 이동을 야기한다. 열처리 온도가 높아지면 반도체 층의 분자 구조가 더 밀집되고 oxygen vacancy 가 증가하며, 이는 전자 농도의 증가로 이어져 Al 도핑의 효과와 반대의 경향을 보인다. 실험 결과를 통해 Al:Zn:Sn=0.5:4:7의 비율과 $350^{\circ}C$ 열처리 조건에서 문턱 전압과 이동도, 아문턱 기울기, 전류 온오프 비($I_{on}/I_{off}$)가 각각 3.54V, $0.16cm^2/Vs$, 0.43 V/dec, $8.1{\times}10^5$으로 우수한 특성을 확인하였다.

• Journal of Korea Foundry Society
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• v.30 no.2
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• pp.76-82
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• 2010

Effect of reaction time and sludge formation on the thickness of die soldering reaction layer has been studied in Al-9Si-0.3Mg casting alloy. Ternary ${\alpha}_{bcc}-Al_8Fe_2Si$ and ${\alpha}_{hcp}-Al_8Fe_2Si$ intermetallic compounds formed at the interface of SKD61 tool steel by interaction diffusion of Al, Fe and Si atoms after 0.5hr and 6hr immersion time, respectively. Binary ${\eta}-Fe_2Al_5$ additionally formed at the interface of SKD61 tool steel after 10hr immersion time. Thickness of soldering reaction layer in die surface increased as immersion time increased from 0.5hr to 24hr. Sludge formation was ascertained in the samples which were immersed in the melts more than 10hr. Reaction of die soldering after sludge formation was more accelerated than that of before sludge formation due to a decrease in Fe content, followed by higher diffusion rate of Al in the melt by sludge formation.

• Applied Science and Convergence Technology
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• v.27 no.3
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• pp.56-60
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• 2018

The optical properties of the digital-alloy $(In_{0.53}Ga_{0.47}As)_{1-z}/(In_{0.52}Al_{0.48}As)_z$ grown by molecular beam epitaxy as a function of composition z (z = 0.4, 0.6, and 0.8) have been studied using temperature-dependent photoluminescence (PL) and time-resolved PL (TRPL) spectroscopy. As the composition z increases from 0.4 to 0.8, the PL peak energy of the digital-alloy $In(Ga_{1-z}Al_z)As$ is blueshifted, which is explained by the enhanced quantization energy due to the reduced well width. The decrease in the PL intensity and the broaden FWHM with increasing z are interpreted as being due to the increased Al contents in the digital-alloy $In(Ga_{1-z}Al_z)As$ because of the intermixing of Ga and Al in interface of InGaAs well and InAlAs barrier. The PL decay time at 10 K decreases with increasing z, which can be explained by the easier carrier escape from InGaAs wells due to the enhanced quantized energies because of the decreased InGaAs well width as z increases. The emission energy and luminescence properties of the digitalalloy $(InGaAs)_{1-z}/(InAlAs)_z$ can be controlled by adjusting composition z.

• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1149-1153
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• 2002

CH4/CO2 dry reforming was carried out to make syn gas on the Ni/Al2O3 catalysts calcined at different temperatures. The Ni/Al2O3 (850 $^{\circ}C)$ catalyst gave good activity and stability w hereas the Ni/Al2O3 $(450^{\circ}C)$ catalyst showed lower activity and stability. The NiO/Al2O3 catalyst calcined at $850^{\circ}C$ for 16 h (Ni/Al2O3 $(850^{\circ}C))$ formed the spinel structure of nickel aluminate, which was confirmed by TPR. The carbon formation rate on the Ni/Al2O3 $(850^{\circ}C)$ catalyst was very low till 20 h, and then steeply increased with reaction time without decreasing the activity for CH4 reforming. The Ni/Al2O3 $(450^{\circ}C)$ catalyst showed high carbon formation rate at the initial reaction time and then, the rate nearly stopped with continuous decreasing the activity for CH4 reforming. Even though the amount of carbon deposition on the Ni/Al2O3 $(850^{\circ}C)$ catalyst was higher than that on the Ni/Al2O3 $(450^{\circ}C)$ catalyst, the activity for CH4ing was also high, which could be attributed to the different type of the carbon formed on the catalyst surface.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.123-126
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• 2002

Samples of Nb/Al-Al$O_{x}$/Nb tunnel junction with the size of 50$\mu$m $\times$ 50$\mu$m were fabricated by employing self-aligning and reactive ion etching technique. In the samples with high-quality, $V_{m}$ value (the product of the critical current and subgap resistance measured at 2 mV) was 34 mV at the critical current density $J_{c}$ = 500 A/$cm^{2}$ and $V_{g}$ value (the gap voltage) was 2.8 mV. In the higher $J_{c}$, voltage fluctuation in the current rising at the gap voltage was observed. The $V_{m}$ and $J_{c}$ value were 8 mV and 900 A/$cm^{2}$, respectively.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.650-653
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• 2004

We have synthesized some phosphors in the system MO-$Al_2O_3-SiO_2$(M=Sr, Ba) by combinatorial polymerized-complex method. Composition and synthetic temperature of phosphors in the liblary was screened from the emission intensities of individual samples under 365nm excitation. As we were screened the higher luminescent candidate composition (or candidate host lattice) at 365nm excitation, investigated whether good radiation was possible at the 405 or 465nm excitation by give the host lattice to be discovered more various change. From libraries about 2 systems, the compound to be expected in long wavelength among the compound to be screened are $Sr_4Al_{14}O_{25}$, $Sr_3Al_2O_6$, $SrAl_2Si_2O_8$, and $BaAl_2Si_2O_8$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.8
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• pp.1322-1331
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• 1997

A method of strength evaluation applying fracture mechanics in the adhesively bonded joints of Al/Steel dissimilar materials was investigated in this paper. Various shapes of adhesively bonded Al/Steel scarf joints focussing on fracture criterion of mixed mode crack were prepared for the static tests. Also, stress intensity factors of the interface cracks in adhesively bonded joints of Al/Steel dissimilar materials were analyzed with 2-dimensional elastic program of boundary element method(BEM), and the experiment of fracture toughness were carried out under various mixed mode conditions. From the results, the fracture criterion and method of strength evaluation by the fracture toughness in adhesively bonded joints of Al/Steel dissimilar materials were proposed.

• Journal of the Korean Society for Heat Treatment
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• v.8 no.3
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• pp.222-228
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• 1995

Mechanical alloying behaviour was investigated after adding 6, 8, 12wt% Fe powder into A1 matrix, respectively, in order to develop Al alloy. And the mechanical characteristics of the alloy which was produced by the above method were studied. The hardness and ultimata tensile strength of the material with different compositions were found to be increased with annealing temperatures and holding times. Intermetallic compound of $Al_3Fe$ and carbide of $Al_4C_3$ phases, which were generated from the different compositions during annealing, were found. It was suggested that enhancement of mechanical properties of Al-Fe alloy system was due to the presence of these preapitates that constrained grain growth and blocked dislocation movement in the alloy system.