• Bulletin of the Korean Chemical Society
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• 제28권4호
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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.

• 한국결정성장학회지
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• 제11권4호
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• pp.170-175
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• 2001

It was possible to grow the $Al_{2}O_{3}$ based $Y_{3}A_{5}O_{12}(YAG),ZrO_{2}$ binary and ternary eutectic fibers using micro-pulling down method with a growing rate of 0.1~15 mm/min. While $Al_{2}O_{3}/ZrO_{2}$ showed cellular-lamellar structure, $Al_{2}O_{3}$/YAG and $Al_{2}O_{3}$/YAG/$ZrO_{2}$ternary eutectic fibers showed homogeneous Chinese script lamellar structures. The microstructures of $Al_{2}O_{3}/ZrO_{2}$ binary eutectic fibers changed with solidification rate from lamellar pattern to cellular structure. The interlamellar spacing agreed with the inverse-square-root dependance on pulling rate according to $\lambda$=$kv_p\;{-1/2}$. $Al_{2}O_{3}/ZrO_{2}$ binary eutectic fibers recorded the highest tensile strength of about 1560MPa at room temperature. $Al_2O_3/YAG/ZrO_2$ternary eutectic fiber showed excellent thermal stability to $1200^{\circ}C$ without significant decrease. The maximum strength of ternary eutectic fibers recorded were 1100MPa at $25^{\circ}C$ and 970MPa at $1200^{\circ}C$, respectively.

• 한국세라믹학회지
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• 제33권9호
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• pp.985-994
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• 1996

The initiation and growth of $\alpha$-Al2O3/metal composites by the directed oxidation of molten commercial AlZnMg-alloy at 1223-1423K were investigated. Spontaneous bulk growth did not occur on the alloy alone. but the uniform initiation and growth of the composite were obtained by putting a thin layer of SiO2 particles on the surface of the alloy. Without SiO2 the external surface of the oxide layer was convered by MgO and MgAl2O4. But with the SiO2 reaction initiate the porous ZnO layers were found on the growth surface. The higher process temperature yielded a lower metal content. The oxidation product of $\alpha$-Al2O3 was found to be oriented with c-axis parallel to th growth direction. The growth rates increased with temperature and the apparent activation energy was 111.8 kJ/mol.

• 한국분말재료학회지
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• 제10권2호
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• pp.97-102
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• 2003

The powder-in sheath rolling was applied to the fabrication of $Al/Al_2O_3$ composite. A stainless steel tube with outer diameter of 12 mm and wall thickness of 1 mm was used as a sheath. Mixture of aluminum powder and $Al/Al_2O_3$ particles of which volume content was varied from 5 to 20 vol.% was filled in the tube by tap filling and then rolled to 75% reduction at ambient temperature. The re]]ed specimen was sintered at 56$0^{\circ}C$ for 0.5 hr. The $Al/Al_2O_3$ composite fabricated by the sheath rolling and subsequent sintering showed the relative density higher than 0.96. The tensile strength of the composite increased with the volume content of $Al_2O_3$ particles, and it reached a maximum of 90 MPa which is 1.5 times higher than unreinforced material. The elongation decreased with the volume content of $Al_2O_3$ particles. It is concluded that the powder-in sheath rolling is an effective method for fabrication of $Al/Al_2O_3$ composite.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 하계학술대회 논문집 Vol.5 No.2
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• pp.1278-1282
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• 2004

수열처리법으로 nano-sized $CeO_2$ 입자를 $Al_3O_3$ 입자의 표면에 균일하게 코팅하여 $AL_2O_3/O_2$ composite 연마 입자를 제조하었다. 제조된 $Al_2O_3\CeO_2$ composite 입자의 뭍성을 TEM, XRD, zeta potential analyzer 및 particle size analyzer로 측징하였다. $Al_2O_3/CeO_2$ composite 입자와 구성된 슬러리와 비교 시료로서 $Al_2O_3$와 $CeO_2$ 입자를 혼합한 슬러리를 사용하여 thermal oxide film에 대한 연마특성을 평가하였다. 연마슬러리에 포함된 $A1_2O_3/CeO_2$ composite 입자와 $Al_2O_3$와 $CeO_2$ 혼합입자에서 나노 크기의 세리아 입자가 sub-micron 크기의 알루미나 입자의 표면에 균일하게 코팅되므로서 $Al_2O_3$ 단일 성분의 슬러리에 비해 removal rate(RR)는 106 nm/min, WIWNU는 $8\sim9%$, roughness는 $2.6{\AA}$의 향상된 연마 특성을 나타내었다. 알루미나 입자의 불규칙한 형상 때문에 $Al_2O3/CeO_2$ composite 슬러리와 $Al_2O_3$ 와 $CeO_2$ 혼합슬러리의 연마 특성이 비슷한 수준을 나타내었다.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2006년도 춘계학술발표논문집
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• pp.335-338
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• 2006

전자수송층과 음극 사이에 $Al_2O_3$를 넣은 이중구조 음극을 갖는 유기발광다이오드를 제작하였다. 제작한 디바이스의 구조는 $ITO/NPB(40\;nm)/Alq_3(60\;nm)/Al_2O_3(0-1.5\;nm)/Al(120\;nm)$로 $Al_2O_3$의 두께를 변화시켰다. $Al_2O_3$의 두께가 0.3 nm일 때는 터널링에 의해서 전자주입이 증가하여 전류와 휘도가 모두 좋아졌다. 반면에 $Al_2O_3$의 두께가 0.5 nm일 때는 전류는 감소하지만 정공과 전자의 비율이 더 좋아져서 전류효율이 크게 향상되었다. 또한 $Al_2O_3$는 엑시톤이 음극과의 계면에서 발광하지 않고 소멸하는 것을 막아주어서 휘도를 증가시켰다.

• Composites Research
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• 제13권6호
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• pp.1-8
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• 2000

무가압함침법에 의한 $Al_2O_{3p}$/AC8A 복합재료의 제조와, 제조법과 관련하여 부가적인 Mg의 첨가와 강화상의 부피분율이 $Al_2O_{3p}$/AC8A복합재료의 기계적 성질과 마모저항에 미치는 영향을 조사하였다. 강화상 입자와 기지재료의 일부를 분말로 조합한 혼합분말 속으로 기지금속을 자발적으로 침투시켜 부피분율이 20~40%인 $Al_2O_{3p}$/AC8A 복합재료를 제조할 수 있었다. 그러나 강화상의 부피분율이 40%인 복합재료의 경우 기공율의 상승으로 복합재료의 강도는 저하하였다. Mg의 첨가량이 5~7wt% 일 때 가장 높은 강도를 나타냈으며, 경도는 Mg 첨가량의 증가에 따라 점진적으로 상승하였다. $Al_2O_{3p}$/AC8A복합재료는 저속에서 기지재료에 비해 내마모성이 저하하였으나, 고속에서는 AC8A합금에 비해 약 5.5배의 우수한 내마모성을 나타냈다. 마모기구의 관찰에 의해 부피분율 20% $Al_2O_{3p}$/AC8A복합재료의 경우 연삭마모가 주된 마모기구임을 알 수 있었으며, 부피분율 40% $Al_2O_{3p}$/AC8A복합재료는 높은 기공율로 인한 마모 가중으로 저속에서도 경미한 응착마모가 관찰됐고 마찰 속도가 증가함에 따라 격심한 마모로 진행되었다.

• 한국재료학회지
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• 제26권2호
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• pp.90-94
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• 2016

In this study, to increase the strength and enhance the sintering property of $Al_2O_3$, $Y_2O_3$ and $La_2O_3$ were added; the effects of these additions on the sintering characteristics of $Al_2O_3$ were observed. Adding 1% of $Y_2O_3$ to $Al_2O_3$ repressed the development of abnormal particles and reduced the grain boundary migration of $Al_2O_3$, curbing pores to capture particles; as such, the material showed a fine microstructure. But, when over 2% of $Y_2O_3$ was added, the sintering property was reduced because of abnormal particle grain growth and pore formation in particles. Adding 1% of $Y_2O_3$ and $La_2O_3$ to $Al_2O_3$ led to the development of abnormal particles and formed pores in the particles; when over 3% of $La_2O_3$ was added, the sintering property was reduced because the shape of the $Al_2O_3$ particles changed to angled plates.

• 한국세라믹학회지
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• 제19권4호
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• pp.287-292
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• 1982

Nonohmic properties of ZnO ceramics with various small amounts of additives were studied in relation to experimental methods, additive contant and sintaring temperature. The kinds of additives used to following chemicals were basic additives ($0.5Bi_2O_3$, $0.3BaCO_3$, $0.5MnCO_3$, $0.5Cr_2O_3$, $0.1KNO_3$), $TiO_2$ and $Al(OH)_3$. Expecially, this study has focused on the effectsof $TiO_2$ and $Al(OH)_3$ in ZnO ceramics with the basic additives. SEM studies indicated that the addition of TiO2 promoted grain growth but retarded grain growth with the addition of $Al(OH)_3$. Also, in the case of calcination of ZnO with $TiO_2$ and ZnO with $Al(OH)_3$ previously, grain size of ZnO with $TiO_2$ was larger and that of ZnO with Al(OH)3 was smaller in comparison to the case with out calcination. From the viewpoint of nonohmic exponent and nonohimic resistance, electrical characteristics of ZnO, $TiO_2$ and the basic additives was more effective than that of ZnO, $Al(OH)_3$ and the basic additives. Nonohmic exponent and nonohmic resistance of ZnO, $TiO_2$ and the basic additives was 11-13 and 40-65 respectively.

• 한국재료학회지
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• 제12권6호
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• pp.493-498
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• 2002

$Al_2O_3$ is a promising gate dielectric because of its high dielectric constant, high resistivity and low leakage current. Since $OH^-$ radical in $Al_2O_3$ films deposited by ALD using TMA and $H_2O$ degrades the good properties of $Al_2O_3$, TMA and $O_3$ were used to deposite $Al_2O_3$ films and the effects of $O_3$ on the properties of the $Al_2O_3$ films were investigated. The growth rate of the $Al_2O_3$ film under the optimum condition was 0.85 $\AA$/cycle. According to the XPS analysis results the $OH^-$ concentration in the $Al_2O_3$ film deposited using $O_3$ is lower than that using $H_2O$. RBS analysis results indicate the chemical formula of the film is $Al_{2.2}O_{2.8}$. The carbon concentration in the film detected by AES is under 1 at%. SEM observation confirms that the step coverage of the $Al_2O_3$ film deposited by ALD using $O_3$ is nearly 100%.