• Title, Summary, Keyword: Al

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The Spontaneous Infiltration Mechanism of Molten Al Alloy to AI$_2$O$_3$ Preform (AI$_2$O$_3$ Preform에 대한 용융 Al 합금의 자발적 침윤 기구)

  • 이동윤;박상환;이동복
    • Journal of the Korean Ceramic Society
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    • v.35 no.7
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    • pp.685-690
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    • 1998
  • The wetting behavior and the characteristic of spontaneous infiltration of pure Al and Al-(Si)-Mg alloys on {{{{ { {Al }_{ 2} O}_{3 } }} in vacuum argon and nitrogen atmosphere were investigated to find out the spontaneous in-filtration mechanism. The wetting of molten Al and Al alloys on {{{{ { {Al }_{ 2} O}_{3 } }} was only possible in cacuum at-mosphere but the sponataneous infiltration of molten Al-(Si)-Mg alloys was successfully made on {{{{ { {Al }_{ 2} O}_{3 } }} pre-form in nitrogen atmoshpere. The difference of wettability and spontaneous infiltration of molten Al and Al alloys on {{{{ { {Al }_{ 2} O}_{3 } }} were found to be related to formation of the Mg-N compound coated layer on {{{{ { {Al }_{ 2} O}_{3 } }} particles which was believd to increase wettability of molten Al alloys on {{{{ { {Al }_{ 2} O}_{3 }.

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Fabrication and Mechanical Property of $Al_2$O$_.3$/Al Composite by Pressureless Infiltration (무가압 침윤법에 의한 $Al_2$O$_.3$/Al 복합재료 제조와 기계적 특성)

  • 이동윤;박상환;이동복
    • Journal of the Korean Ceramic Society
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    • v.35 no.3
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    • pp.303-309
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    • 1998
  • The fabrication of Al2O3/Al composite by pressureless infiltration was investigated by the change of Mg and Si content in Al alloy infiltration process and infiltration atmosphere. The effect of alloying elements infiltration atmosphere and interfacial reactants between Al alloy matrix and Al2O3 particles were in-vestigated in terms of bendingstrength and harness test,. The fabrication of Al2O3/Al composite by the vestigated in terms of bending strength and hardness test. The fabrication of Al2O3/Al composite by the pressureless infiltration was done in nitrogen atmosphere with Mg in Al alloy. It was successfully fabricated at $700^{\circ}C$ according to Mg contents in Al alloy and infiltration condition. Because Mg in the Al alloy and ni-trogen atmosphere of infiltratio condition produced Mg-N compound(Mg3N2) it decreased the wetting an-gle between molten Al alloy and Al2O3 particles by coating on surface of Al2O3 particles. The fracture strength of Al2O3/Al-Mg composite was 800MPa and Al2O3/Al-Si-Mg composite was 400MPa. Si in Al alloy decreased the interfacial strength between Al alloy matrix and Al2O3 particles.

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Solid Solution Phenomena of Al+Al3Ti Alloy and Al+10wt.%Ti Alloy using Mechanical Alloying Process (기계적 합금화법에 의해 제조된 Al+Al3Ti합금 및 Al+10wt.%Ti합금의 고용현상)

  • Kim, Hye-Sung;Lee, Jung-Ill;Kim, Gyeung-Ho;Kum, Dong-Wha;Shur, Dong-Soo
    • Journal of the Korean Society for Heat Treatment
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    • v.9 no.2
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    • pp.121-129
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    • 1996
  • The solubility of Ti in Al matrix was determined by X-ray diffraction method on two different mechanical alloying systems, i.e Al+$Al_3Ti$ and Al+Ti alloys. Starting powder compositions of two systems were chosen for final volume fraction of $Al_3Ti$ phase being 25%. The solubility of Ti in ${\alpha}$-Al was estimated by the lattice parameter measurement of Al. For Al+$Al_3Ti$ mixture, it appeared that some of $Al_3Ti$ particles decomposed during milling and maximum solubility of Ti in Al was about 0.99%. The majority of $Al_3Ti$ particles were dispersed uniformly in Al matrix, having approximate size of 100~200 nm. On the other hand, higher Ti solubility of 1.24 wt.% was found in Al+Ti system, with starting composition of Al+10 wt.%Ti. After 15 hours of milling, Ti phase was identified as 20 nm sized particles embedded in Al matrix. The annealing of mechanically alloyed powders from Al+$Al_3Ti$ and Al+10 wt.%Ti systems was followed in the temperature range of 200 to $600^{\circ}C$ to study thermal stability of supersaturated solution of Al(Ti). After annealing, the lattice parameter of Al reverted back to that of pure Al, and the peak intensity ratio of $Al_3Ti$/Al was increased more than the original value before annealing. These results suggest that Ti dissolve into alpha-Al solutions during milling, and by annealing, $Do_{22}-Al_3Ti$ phase forms from Al(Ti) solution.

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Antioxidation mechanism of Al metal powders on $Al_2O_3-C$ refractory ($Al_2O_3-C$계 내화물에서 알루미늄 금속분말의 산화억제 메카니즘)

  • 류정호;임창성;오근호
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.8 no.1
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    • pp.97-105
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    • 1998
  • Antioxidation mechanism of Al metal powders on $Al_2O_3-C$ refractory was investigated in temperature range from 800 to $1400^{\circ}C$. The addition of 5 wt% Al metal powders suppressed the oxidation of carbon in $Al_2O_3$-C sample. The carbons were distributed uniformly on the surface and the interface of the $Al_2O_3$-C-Al. Reaction products of $Al_4C_3$ and AIN were found with a composition of Al-C at temperatures between 800 and $1200^{\circ}C$ and transformed to $Al_2O_3$ above $1400^{\circ}C$. Cavity structures related to the to the formation of $Al_4C_3$ were observed for the AI-C after heating at $1000^{\circ}C$ ofr 1 hour. Thermodynamic mechanism was considered to discuss the formation $Al_4C_3$, AlN and their transformation to $Al_2O_3$, which leads to the effect of oxidation resistance.

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Aluminum Toxicity on Corn Seedlings (옥수수 유묘(幼苗)에 대(對)한 알미늄 독성(毒性))

  • Lee, Yong-Seok
    • Korean Journal of Soil Science and Fertilizer
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    • v.10 no.2
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    • pp.75-78
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    • 1977
  • Corn (Zea may, L.) was grown alternatively in nutrient solution and hydroxy Al or Al-citrate solution to identify the form of Al which induces Al toxicity on Corn seedlings. Corn seedlings exposed to hydroxy Al solution was very toxic but Al-citrate solution did not show any toxic symptoms. At pH 7 with Al-citrate solution, severe Fe, deficiency was induced probably by the decrease of stability constant of Al-and Fe-oganic complexes and subsequent precipitation of Al-and Fe-as a hydroxide form. Addition of humic acid ameliorated the Al toxicity somewhat at pH 4.7 with hydroxy-Al solution but at pH 7 it induced more severe Fe deficiency.

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Characterization of Oxide Scales Formed on Fe3Al, Fe3Al-Cr, Fe3Al-Cr-Mo, Ni3Al and Ni3Al-Cr Alloys (Fe3Al, Fe3Al-Cr, Fe3Al-Cr-Mo, Ni3Al 및 Ni3Al-Cr 합금표면에 형성된 산화물 특성분석)

  • Shim, Woung-Shik;Lee, Dong-Bok
    • Korean Journal of Materials Research
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    • v.12 no.11
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    • pp.845-849
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    • 2002
  • Alloys of $Fe_3$Al, $Fe_3$Al-6Cr, $Fe_3$Al-4Cr-1Mo, $Ni_3$Al, and $Ni_3$Al-2.8Cr were oxidized at $1000^{\circ}C$ in air, and the oxide scales formed were studied using XRD. SEM, EPMA, and TEM. The oxide scales that formed on $Fe_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$ containing a small amount of dissolved Fe and Cr ions, whereas those that formed on $Ni_3$Al-based alloys consisted primarily of $\alpha$-$Al_2$$O_3$, together with a small amount of $NiAl_2$$O_4$, NiO and dissolved Cr ions. For the entire alloys tested, nonadherent oxide scales formed, and voids were inevitably existed at the scale-matrix interface.

Preparation of Aluminum Nitride from an Alkoxide and its Properties (알콕사이드로부터 AlN분말의 합성 및 분말 특성)

  • 이홍림;박세민;조덕호
    • Journal of the Korean Ceramic Society
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    • v.26 no.1
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    • pp.100-108
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    • 1989
  • Aluminum hydroxides were prepared by the alkoxide hydrolysis method using Al-isopropoxide as a starting material and NH4OH as a catalytic agent. When Al-isopropoxide was hydrolyzed in a H2O-NH3 system, only Al(OH)3 was obtained over all pH values. However, AlOOH was formed besides Al(OH)3 when Al-isopropoxide was hydrolyzed in a H2O-NH3-isopropyl alcohol system. The AlOOH/Al(OH)3 ratio was increased as the isopropyl alcohol content was increased. The hydroxides, Al(OH)3 and AlOOH, obtained in this study and the commerical products, $\alpha$-Al2O3 and AlOOH were subjected to the carbothermal reduction and nitridation reaction to product AlN powder, using carbon black as a reducing agent under N2 atmosphere at various temperatures. AlN was synthesized from the obtained Al(OH)3 and the commercial AlOOH at 145$0^{\circ}C$, however, synthesized from the obtained AlOOH and the commercial alpha-alumina at 135$0^{\circ}C$. The temperature difference is assumed to be attributed to the reactivity of those powders. AlN powder prepared from the Al-isopropoxide was observed to have the narrower particle size distribution than that prepared from the commercial $\alpha$-Al2O3 or AlOOH.

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Growth Characteristics of AlN by Plasma-Assisted Molecular Beam Epitaxy with Different Al Flux (플라즈마분자선에피탁시법을 이용한 알루미늄 플럭스 변화에 따른 질화알루미늄의 성장특성)

  • Lim, Se Hwan;Lee, Hyosung;Shin, Eun-Jung;Han, Seok Kyu;Hong, Soon-Ku
    • Korean Journal of Materials Research
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    • v.22 no.10
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    • pp.539-544
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    • 2012
  • We have grown AlN nanorods and AlN films using plasma-assisted molecular beam epitaxy by changing the Al source flux. Plasma-assisted molecular beam epitaxy of AlN was performed on c-plane $Al_2O_3$ substrates with different levels of aluminum (Al) flux but with the same nitrogen flux. Growth behavior of AlN was strongly affected by Al flux, as determined by in-situ reflection high energy electron diffraction. Prior to the growth, nitridation of the $Al_2O_3$ substrate was performed and a two-dimensionally grown AlN layer was formed by the nitridation process, in which the epitaxial relationship was determined to be [11-20]AlN//[10-10]$Al_2O_3$, and [10-10]AlN//[11-20]$Al_2O_3$. In the growth of AlN films after nitridation, vertically aligned nanorod-structured AlN was grown with a growth rate of $1.6{\mu}m/h$, in which the growth direction was <0001>, for low Al flux. However, with high Al flux, Al droplets with diameters of about $8{\mu}m$ were found, which implies an Al-rich growth environment. With moderate Al flux conditions, epitaxial AlN films were grown. Growth was maintained in two-dimensional or three-dimensional growth mode depending on the Al flux during the growth; however, final growth occurred in three-dimensional growth mode. A lowest root mean square roughness of 0.6 nm (for $2{\mu}m{\times}2{\mu}m$ area) was obtained, which indicates a very flat surface.

Synthesis of AlN Powders from AlOOH (AlOOH로부터 AlN분말의 합성)

  • Lee, Jae-Bum;Kim, Seon-Tai
    • Korean Journal of Materials Research
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    • v.16 no.12
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    • pp.771-776
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    • 2006
  • In this study, we report a method to synthesize the aluminum nitride (AlN) powders from aluminum oxyhydroxide (AlOOH). AlOOH powders were prepared from the aluminum hydroxide ($Al(OH)_3$) by heattreatment at the reaction temperature of $350^{\circ}C$. Simple heat treatment of AlOOH in the flow of $NH_3$ gas leads to the formation of hexagonal AlN powders through intermediate conversion of ${\delta}-,\;{\gamma}-$ and ${\alpha}-Al_2O_3$. The FTIR transmission spectra show a broad peak related to Al-N bonds centered around 690 $cm^{-1}$ confirming the presence of AlN. The major peaks in Raman spectra were observed in 250 $cm^{-1}$ and 659 $cm^{-1}$. From the results, synthesized powders from the AlOOH powders were confirmed AlN powders.

Preparation of AlN Powder by Combustion Reaction in the System of Al-AlN-NH4Cl (Al-AlN-NH4Cl 계에서 연소반응에 의한 AlN 분말의 제조)

  • Min, Hyun-Hong;Won, Chang-Whan
    • Journal of the Korean Ceramic Society
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    • v.43 no.7
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    • pp.445-450
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    • 2006
  • The preparation of AlN powder by SHS in the system of $Al-AlN-NH_4Cl$ was investigated in this study. In the preparation of AlN powder, the effect of gas pressure and the composition such as Al, AlF, and additive in mixture on the reactivity were investigated. At 60 atm of the initial inert gas pressure in reactor, the optimum composition for the preparation of pure AlN was 35 wt%Al+5 wt% $NH_4Cl+60wt%$AlN. The AlN powder synthesized in this condition was a single phase AlN with a whisker morphology.