• 한국세라믹학회지
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• 제42권6호
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• pp.384-390
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• 2005

[ ${\alpha}-Al_2O_3$ ] precursor was synthesised by sol-gel method using aluminum sulfate, sodium sulfate and sodium carbonate as law materials. The flaky ${\alpha}-Al_2O_3$ crystals were prepared by heating using precursor about $1,050^{\circ}C$. In this study, the effect of some transition-metal sulfate ($FeSO_4,\;SnSO_4,\;ZnSO_4$) addition have been investigated. When iron sulfate was added, it could see that act on impurities in crystal growth process. In case of tin sulfate, distribution of Platelets was very broad. When flaky ${\alpha}-Al_2O_3$ crystals were prepared zinc sulfate addition, thickness, size, and distribution of platelets was suited to industrial application. The average diameter of flaky ${\alpha}-Al_2O_3$ crystals was about 20 $\mu$m, and its thickness was about 0.3 $\mu$m. Increasing addition of zinc sulfate, thickness of ${\alpha}-Al_2O_3$ platelet was decreased.

• 한국세라믹학회지
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• 제34권11호
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• pp.1187-1197
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• 1997

Dry gel composed of primary particles more homogeneous than starting boehmite powder was prepared by dispersing and gelling the boehmite powder. The transformation temperatures of boehmite powder, dry gel seeded with 0, 1, 3, 5 wt% $\alpha$-Al2O3, and ball milled gel were 1192$^{\circ}C$, 1184$^{\circ}C$, 1141$^{\circ}C$, 1119$^{\circ}C$, 1117$^{\circ}C$, and 1106$^{\circ}C$, respectively. Sintering behavior of dry gel without seed was similar to that of boehmite powder, but the sintered density of dry gel was improved as much as 10%~15% than boehmite powder. In the case of dry gel seeded with 5 wt% $\alpha$-Al2O3, sintering behavior was much improved. The relative density of the gel seeded with 5 wt% $\alpha$-Al2O3 was 96% when sintered at 140$0^{\circ}C$ for 1h. On the other hand, ball milling of the non-seeded sol for 48h resulted in the relative density of 97% when sintered at 130$0^{\circ}C$ for 1h. The size and amount of $\alpha$-Al2O3 particles added by ball milling were 0.107 ${\mu}{\textrm}{m}$ and 0.5 wt%.

• 한국응용과학기술학회지
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• 제9권1호
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• pp.47-54
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• 1992

The natural antioxidant such as e-tocopherol and synthetic antioxidant BHT were used to compare antioxidative effects of those antioxidants from the physico-chemical properties and fatty acid composition changes in the soybean oil due to number of frying. The composition of frying oil were consisted of a group(Fresh oil), B gorup(Fresh oil added with 0.05% ${\alpha}$-tocopherol), C group(Fresh oil added with 0.2% ${\alpha}$-tocopherol), D group(Fresh oil added with 0.1% BHT), E group(Tocopherol removed oil from oil by active alumina column chromatography The results obtained were as follws : 1. The color was determined by the Lovibond colorimeter color intensity increased number of frying oil. 2, The acid value, TBA value and Carbonyl value were increased number of frying oil. 3. Natural antioxidants less effective than BHT but effect of ${\alpha}$-tocopherol was very similar to that of BHT. 4. The order of antioxidative effect was 0.1% BHT, 0.2% ${\alpha}$-tocopherol, 0.05% ${\alpha}$-tocopherol, fresh oil, tocopherol remove oil.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 추계학술대회 논문집 Vol.16
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• pp.136-139
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• 2003

Copper has attractive properties as a multi-level interconnection material due to lower resistivity and higher electromigration resistance as compared with Alumina and its alloy with Copper(0.5%). Among a variety of agents in Copper CMP slurry, $H_2O_2$ has commonly been used as the oxidizer However. $H_2O_2$ is so unstable that it requires stabilization to use as oxidizer Hence, stabilization of $H_2O_2$ is a vital process to get better yield in practical CMP process. In this article the stability of Hydrogen Peroxide as oxidizer of Copper CMP slurry has been investigated. When alumina abrasive was used, $\gamma$-particle Alumina C had a better stability than $\alpha$-particle abrasive. As adding KOH as pH buffering agent, $H_2O_2$ stability in slurry decreased. Urea hydrogen peroxide was used as oxidizer, an enhanced stability was gotten. When $H_3PO_4$ as $H_2O_2$ stabilizer was added, the decrease of $H_2O_2$ concentration in slurry became slower. Even though adding $H_2O_2$ in slurry after bead milling lead to better stability than in advance of bead milling, it had a lower dispersibility.

• 공업화학
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• 제21권5호
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• pp.488-494
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• 2010

W/O 에멀젼법하에 homogenizer를 사용하여 ${\alpha}$-알루미나 분체 제조 시 O : W 부피비, 교반속도, 계면활성제 사용량과 조성 및 종류 등의 변화에 의하여 분체의 입자형상, 응집성, 평균입경과 입도분포 등의 변화를 분석하였다. 계면활성제는 비이온 계면활성제가 사용되었고 단일 및 혼합계면활성제로는 SP80 및 [SP80 & TW80]을 사용하였고 보조계면활성제로는 n-부탄올을 사용하였다. SP80을 사용하였을 경우, 분체의 입자형상은 구형에 근접하였고 평균입경은 주어진 O : W 부피비 변화 및 16000 rpm 이상의 교반속도에서 큰 차이를 보이지 않았다. [SP80 & TW80]을 사용하였을 경우, 구형에 가까운 분체의 입자간 응집 및 합체현상은 $HLB_m$ = 5일 때 낮았고 평균입경은 단일계면활성제를 사용하였을 때 비하여 다소 감소하였다. $HLB_m$ = 5인 [SP80 & TW80]와 함께 0.1 vol% n-부탄올을 사용하였을 경우, 입자간 응집성이 상대적으로 낮고 나노크기의 입도를 갖는 분체 분율을 증가시킬 수 있었다.

• 한국결정성장학회지
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• 제3권2호
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• pp.131-139
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• 1993

결정 구조와 결정 내부의 결함들을 연구하는데 매우 유용한 투과전자현미경법(TEM)과 결정 표면에 존재하는 결함들을 발견하는데 있어 매우 민감한 인지력이 있는 반사현미경법(REM)을 이용하여 알루미나($\alpha$-Al2O3) 단결정내 또는 표면에 존재하는 전위(dislocations)와 쌍정(twins)들의 거동에 대하여 연구하였다.

• 한국분말재료학회지
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• 제12권6호
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• pp.422-427
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• 2005

The $Al_2O_3$ with various phases were prepared by simple ex-situ hydrolysis and spark plasma sintering (SPS) process of Al powder. The nano bayerite $(\beta-Al(OH)_3)$ phase was derived by hydrolysis of commercial powder of Al with micrometer size, whereas the bohemite (AlO(OH)) phase was obtained by hydrolysis of nano Al powder synthesized by pulsed wire evaporation (PWE) method. Compaction as well as dehydration of both nano bayerite and bohemite was carried out simultaneously by SPS method, which is used to fabricate dense powder compacts with a rapid heating rate of $100^{\circ}C$ per min. under the pressure of 50MPa. After compaction treatment in the temperature ranges from $100^{\circ}C\;to\; 1100^{\circ}C$, the bayerite and bohemite phases change into various alumina phases depending on the compaction temperatures. The bayerite shows phase transition of $Al(OH)_3{\to}{\eta}-Al_2O_3{\to}{\theta}-Al_2O_3{\to}\alpha-Al_2O_3$ sequences. On the other hand, the bohemite experiences the phase transition from AlO(OH) to ${\gamma}-Al_2O_3\;at\;350^{\circ}C.$ It shows AlO(OH) ${\gamma}-Al_2O_3{\to}{\delta}-Al_2O_3{\to}{\alpha}-Al_2O_3$ sequences. The ${\gamma}-Al_2O_3$ compacted at $550^{\circ}C$ shows a high surface area $(138m^2/g)$.

• 한국세라믹학회지
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• 제38권11호
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• pp.987-992
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• 2001

내화물 등급의 저가 질화규소 분말을 분석 및 가공한 후, 소결조제을 첨가하여 가스압 소결하였다. 원료분말에는 다량의 free Si가 있었으며 Fe, Al, Ca등의 불순물도 각각 0.72wt%, 0.5wt%, 0.31wt%로 다량 존재하였다. 산소와 탄소의 함량도 각각 3.3wt%와 0.4wt%로 많았으며, 96%의 $\beta$-상과 4%의 $\alpha$-상으로 구성하였다. 원료 분말을 탈철처리 및 질화처리 하여 소결조제인 6wt% yttria와 2wt% alumina를 첨가하고, 1823K-2133 K의 온도 범위에서 1시간씩 소결하여 소결거동을 조사하였다. 또, 2123K에서 2시간동안 소결하여 충분히 치밀화된 소결체를 얻었다. 비교를 위하여 상용 질화규소 분말을 같이 소결하여 소결거동과 기계적 특성 등을 조사하였다. 저가의 분말을 상용 분말보다 치밀화 속도는 늦었다. 충분히 치밀화된 저가 분말의 소결체는 낮은 aspect rtio를 갖는 조대 결정립들이 다수 존재하였으며, 경도, 파괴인성, 꺽임강도, 내열 충격성 등이 상용 분말의 소결체 보다 떨어졌다.

• 한국세라믹학회지
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• 제26권1호
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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.

• 한국세라믹학회지
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• 제43권4호
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• pp.242-246
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• 2006

[ ${\alpha}-Al_2O_3$ ] nanopowders were fabricated by the thermal decomposition and synthetic of Ammonium Aluminum Carbonate Hydroxide (AACH). Crystallite size of 5 to 8 nm were fabricated when reaction temperature of AACH was low, $8^{\circ}C$, and the highest $[NH_4{^+}][AlO(OH)_n{(SO_4){^-}}_{3-n/2}][HCO_3]$ ionic concentration to pH of the Ammonium Hydrogen Carbonate (AHC) aqueous solution was 10. The phase transformation fem $NH_4Al(SO_4)_2$, rhombohedral $(Al_2(SO_4)_3)$, amorphous-, ${\theta}-,\;{\alpha}-Al_2O_3$ was examined at each temperature according to the AACH. A Time-Temperature-Transformation (TTT) diagram for thermal decomposition in air was determined. Homogeneous, spherical nanopowders with a particle size of 70 nm were obtained by firing the 5 to 8 m crystallites, which had been synthesized from AACH at pH 10 and $8^{\circ}C,\;at\;1150^{\circ}C$ for 3 h in air.