• Title/Summary/Keyword: Al_2\

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Effect of $SiO_2$ and $Al_2O_3$ on Characteristics of Yttria-Stabilized Zirconia Ceramics (아트리아 안정화 지르토니아 소결체의 특성에 $SiO_2$$Al_2O_3$ 가 미치는 영향)

  • 손정덕;최시영;조상희
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.27 no.6
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    • pp.886-894
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    • 1990
  • Sinterbility, microstructure, mechenical and electrical properties of yttriastabilized zirkconiz (92 mole % ZrO2 + 8 mole % Y2O3) doped with 0.5 mole % SiO2 and 0-2.O mole% Al2O3 were studied as a functin of Al2O3 addition. Sintered density increased with increasing Al2O3 addition up to o.5 mole%but decreased up to 1.0mole% Al2O3. Vickers hardness is proportional to sintered density. The specimen added 0.5mole% Al2O3 and 0.5mole% SiO2 exhibited a maximum conductivity. And the specimen added 0.5 mole % Al2O3 and 0.5 mole% SiO2 was measured a maximum electromotive force for a characteristics of oxyzen partial pressure.

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A Study on the Precipitation Behavior of $Al_2Ti$ Phase in $L1_0$-TiAl and $L1_2-(Al,Cr)_3Ti$ ($L1_0$-TiAl 및 $L1_2-(Al,Cr)_3Ti$ 중에 $Al_2Ti$상의 석출거동에 관한 연구)

  • Han, Chang-Suk
    • Journal of the Korean Society for Heat Treatment
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    • v.21 no.1
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    • pp.20-25
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    • 2008
  • Structural studies have been performed on precipitation hardening and microstructural variations found in Ti-Al-Cr ternary $L1_0$- and $L1_2$-phase alloys using transmission electron microscopy. Both the $L1_0$ and $L1_2$ phase alloys harden by aging at 973 K after solution annealing at higher temperatures. The amount of age hardening of the $L1_2$ phase alloy is larger than that of the $L1_0$ phase alloy. The phase separation between $L1_0$ and $L1_2$ phase have not been observed by aging at 973 K. But $Al_2Ti$ was formed in each matrix alloy during aging. The crystal structure of the $Al_2Ti$ phase is a $Ga_2Zr$ type in the $L1_0$ and a $Ga_2Hf$ type in the $L1_2$ phase, respectively. At the beginning of aging the fine coherent cuboidal $Al_2Ti$-phase are formed in the $L1_0$ phase. By further aging, two variants of $Al_2Ti$ precipitates grow along the two {110} habit planes. On the other hand, in the $L1_2$ phase, the $Al_2Ti$ phase forms on the {100} planes of the $L1_2$ matrix lattice. After prolonged aging the precipitates are rearranged along a preferential direction of the matrix lattice and form a domain consisting of only one variant. It is suggested that the precipitation of $Al_2Ti$ in each matrix alloy occurs to form a morphology which efficiently relaxes the elastic strain between precipitate and matrix lattices.

Microstructure and Tribological Characteristics of AlSi-Al$_2$O$_3$ Composite Coating Prepared by Plasma Spray (플라즈마 용사에 의한 AlSi-Al$_2$O$_3$ 복합재료 코팅층의 미세조직 및 마찰.마모특성)

  • Min Joon-Won;Yoo Seung-Eul;Kim Young-Jung;Suhr Dong-Soo
    • Journal of Welding and Joining
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    • v.22 no.5
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    • pp.46-52
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    • 2004
  • AlSi-Al$_2$O$_3$ composite layer was prepared by plasma spray on steel substrate. The composite powder for plasma spray was prepared by simple mechanical blending. The wear resistance of the composite layers and matrix aluminum alloy were performed in terms of size distribution of ceramic particles. Friction coefficients of AlSi were decreased with incorporation of $Al_2$O$_3$. The tribological properties of coated layers were affected by the size of incorporated $Al_2$O$_3$ particle. The reinforcement of $Al_2$O$_3$ particle into aluminum alloy matrix decreased the friction coefficient as well as wear loss.

Mullitization of Al-Kaolin Mixture (Al-Kaolin 혼합물의 Mullite화 반응)

  • 박정현;조정식;배원태
    • Journal of the Korean Ceramic Society
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    • v.20 no.2
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    • pp.123-128
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    • 1983
  • This research is aimed to synthesize the mullite by adding Al powder of $Al_2O_3$ to kaolin. Specimens fired at 1400, 1450 and 150$0^{\circ}C$ were compared in their X-ray diffraction patterns quantitative analysis of mullite formed and fine microstructures with those containing reactive $Al_2O_3$ activated $Al_2O_3$ as alumina source The experiment of Al oxdiation was also performed by measuring the weight increase of specimens. Two different shapes of mullites acicular and chunky were observed by SEM and the yield of mullites were in-creased by the order of adding activated $Al_2O_3$ reactive $Al_2O_3$ and Al powder to kaolin.

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The Oxidation and Sintering of $Al-Al_2O_3$ Powder Mixture by using Microwave (Hybrid) Heating (마이크로파 혼합 가열에 의한 $Al-Al_2O_3$ 분말성형체의 산화와 소결)

  • 박정현;안주삼
    • Journal of the Korean Ceramic Society
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    • v.32 no.3
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    • pp.331-340
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    • 1995
  • Microwave (Hybrid) Heating (MHH) was used to oxidize and sinter Al-Al2O3 powder mixture. For 25 v/o Al specimen and 35 v/o Al specimen, the total processing to produce low-shrinkage reaction bonded alumina was carried out within 1 hour even though conventional furnace process took more than 10 hours. Compared with conventional fast firing process, MHH process increased more than 40% oxidation at the same temperature, and these high oxidation rates were thought to be caused by the surface ohmic current on Al particles.

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Characteristics of AlN thin films for SAW filters based on substrates (기판의 종류에 따른 SAW 필터용 AlN 박막의 특성)

  • Ko, Bong-Chul;Nam, Chang-Woo
    • Journal of Sensor Science and Technology
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    • v.16 no.3
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    • pp.240-245
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    • 2007
  • AlN thin film for SAW filter application was deposited on (100) silicon, sapphire, $Si_{3}N_{4}$/Si, and $Al_{2}O_{3}$/Si substrates by reactive magnetron sputtering method, respectively. The structural characteristics were dependent on the structure of substrates. Scanning Electron Microscope (SEM), X-ray Diffraction (XRD) and Atomic Force Microscope (AFM) have been used to analyze structural properties and preferred orientation of AlN thin films. Preferred orientation and SAW characteristic of AlN were improved by insertion of $Al_{2}O_{3}$ buffer layer. Insertion loss of SAW devices using AlN/Si and AlN/$Al_{2}O_{3}$/Si were about 33.27 dB and 30.20 dB, respectively.

Excited-state Intramolecular Proton Transfer of 1,5- and 1,8-Dihydroxyanthraquinones Chemically Adsorpted onto SiO2, SiO2-Al2O3, and Al2O3 Matrices

  • Cho, Dae-Won;Song, Ki-Dong;Park, Seong-Kyu;Jeon, Ki-Seok;Yoon, Min-Joong
    • Bulletin of the Korean Chemical Society
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    • v.28 no.4
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    • pp.647-651
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    • 2007
  • In order to investigate the excited-state intramolecular proton transfer (ESIPT) process of dihydroxyanthraquinones (DHAQ; 1,5-DHAQ and 1,8-DHAQ) in organic-inorganic hybrid matrices, transparent SiO2, SiO2- Al2O3, and Al2O3 matrices chemically bonded with DHAQ were prepared using a sol-gel technique. The absorption maxima of 1,5- and 1,8-DHAQ in SiO2 matrices are observed at around 420 nm, whereas those of DHAQ in both SiO2-Al2O3 and Al2O3 matrices are markedly shifted to longer wavelength compared with those in SiO2 matrix. This indicates that DAHQ forms a chemical bond with an Al atom of Al2O3. The DHAQ in SiO2 matrix shows a markedly Stokes-shifted emission which is originated from the ESIPT in DHAQ. Based on the emission lifetimes of DHAQ, the ESIPT of DHAQ was found to be strongly affected by the chemical interaction with Al atom in the Al2O3-related matrices.

High temperature air-oxidation of CrAlSiN thin films (CrAlSiN 박막의 대기중 고온산화)

  • Hwang, Yeon-Sang;Won, Seong-Bin;Chunyu, Xu;Kim, Seon-Gyu;Lee, Dong-Bok
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2013.05a
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    • pp.53-54
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    • 2013
  • Nano-multilayered CrAlSiN films consisting of crystalline CrN nanolayers and amorphous AlSiN nanolayers were deposited by cathodic arc plasma deposition. Their oxidation characteristics were studied between 600 and $1000^{\circ}C$ for up to 70 h in air. During their oxidation, the amorphous AlSiN nanolayers crystallized. The formed oxides consisted primarily of $Cr_2O_3$, ${\alpha}-Al_2O_3$, $SiO_2$. The outer $Al_2O_3$ layer formed by outward diffusion of Al ions. Simultaneously, an inner ($Al_2O_3$, $Cr_2O_3$)-mixed layer formed by the inward diffusion of oxygen ions. $SiO_2$ was present mainly in the lower part of the oxide layer due to its immobility. The CrAlSiN films displayed good oxidation resistance, owing to the formation of oxide crystallites of $Cr_2O_3$, ${\alpha}-Al_2O_3$, and amorphous $SiO_2$.

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Synthesis of CaO-Al2O3 System Clinker Using CaCO3 and Al2O3 (CaCO3와 Al2O3를 이용한 CaO-Al2O3계 클링커 합성)

  • Lee, Yun-Su;Lee, Han-Seung
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2018.05a
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    • pp.238-239
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    • 2018
  • This paper presents the synthesis results of CaO-Al2O3 system clinker using the CaCO3 and the Al2O3 according to the synthesis methods dependent on the temperature. The purpose of this study is the formation of the CaO-Al2O3 system clinker containing high ratio of CaO·2Al2O3 (CA2). The maximum sintering temperature for the synthesis of CaO-Al2O3 compounds was 1250℃, 1300℃ and 1400℃. The CaO-Al2O3 compounds was sintered at the maximum sintering temperature for three hours. After sintering, the compounds was analyzed using X-ray diffraction method. The 12CaO·7Al2O3 (C12A7) and CaO·Al2O3 (CA) increased as elevating the maximum sintering temperature whereas the CA2 decreased. Especially, at the 1250℃ of maximum sintering temperature, the un-reacted CaO and Al2O3 was identified.

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Preparation of Alumina Powder from Aluminum Salts by Precipitation Method (알루미늄 염으로부터 침전법에 의한 알루미나 분체의 제조)

  • Rhee, Jhun;Choi, Sang-Wook;Jo, Dong-Soo;Lee, Jong-Gil;Kim, Seung-Tae
    • Journal of the Korean Ceramic Society
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    • v.30 no.12
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    • pp.1045-1053
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    • 1993
  • Alumina hydrates were prepared by the neutralization of AlCl3.6H2O solution with NH3 gas diluted with N2 gas. The values of pH in reaction solution influenced the formation of alumina hydrates minerals. Amorphous alumina hydrates, for example, were formed at ${\gamma}$-Al2O3longrightarrow$\delta$-Al2O3longrightarrow$\theta$-Al2O3longrightarrow$\alpha$-Al2O3. (2) Bayeritelongrightarrowamorphouslongrightarrow${\gamma}$-Al2O3longrightarrow$\delta$-Al2O3longrightarrowη-Al2O3longrightarrow$\theta$-Al2O3longrightarrow$\alpha$-Al2O3. On the other hand, the shape of alumina hydrates whichw ere prepared by the reacton of Al2(SO4)3.16H2O solution and NH3 gas was spherical, the progress of its phase transformation with increasing temperature was amorphouslongrightarrow${\gamma}$-Al2O3longrightarrow$\alpha$Al2O3 in sequence.

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