• 환경위생공학
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• 제15권1호
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• pp.95-101
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• 2000

This study was investigated to the reaction of alumina sintering with alkaline. The soluble $NaAlO_2$ was made after the commercial ${\alpha}-Al_2O_3$ was calcinated with NaOH. The reaction of alumina was carried out to be based on the effects of calcination temperature, time, and the mixing ratio of ${\alpha}-Al_2O_3/NaOH$. The alumina was calcined over $500^{\circ}C$ with NaOH powder after it was sieved with 170/270 mesh. The calcined alumina with NaOH powder was dissolved into $25^{\circ}C$ distilled water and filtrated, and HCI was added to adapt pH 6.5~7.5. The residue was separated with vacuum pump for filtration after it was adapted to proper pH, and aluminum compound was precipitated with $Al(OH)_3$. The investigation was carried out with the variables; the calcination temperature($500-900^{\circ}C$), the calcination time (30~90 min), and the concentration of HCI when leaching(0.5~3.0N) respectively. In this investigation, the main product of ${\alpha}-Al_2O_3$ and NaOH was $NaAlO_2$ and the maximum conversion ratio was 91.4% under the optimum conditions as followed ; the ratio of NaOH/${\alpha}-Al_2O_3$ was 1.5 and the calcination conditions were $800^{\circ}C$ and 90 min.

• 한국세라믹학회지
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• 제28권6호
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• pp.465-470
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• 1991

AlN powder was synthesized by carbothermal reduction and nitridation of aluminum hydroxides precipitated in 5∼11 pH range from Al2(SO4)3$.$18H2O aqueous solution. Nitridation reactivity of hydroxide, which depends on precipitation pH, reaction temperature and time, was examined by XRD analysis at 1200∼1350$^{\circ}C$ and compared with that of commercial ${\alpha}$-Al2O3. Hydroxides obtained at higher pH could be more easily nitridated and, considering DTA/TG and BET results, the reason seems to be specific surface area difference of reactants depending on the content of decomposed structural water and the transition rate from transition-Al2O3 to ${\alpha}$-Al2O3.

• 자원리싸이클링
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• 제15권2호
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• pp.3-9
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• 2006

용융전로슬래그로부터 일반 포틀랜드 시멘트로의 전환에 관한 기초 연구의 일환으로, 전로슬래그의 $Al_{2}O_{3}$ 농도에 따를 고체 CaO 입자와 용융슬래그간의 계면반응을 알아보고자 하였다. 염기도($B=CaO/SiO_2$)를 1과 2로 조정한 전로슬래그에 소정의 $SiO_2$와 $5{\sim}15wt%\;Al_{2}O_{3}$를 첨가제로 첨가하여 MgO도가니에 넣고 $1500^{\circ}C$에서 30분간 가열 용해하여 균질화 한 후, 같은 온도의 소결 CaO펠렛을 투입하여 $10{\sim}30$분간 반응시켰다. 반응 후 급냉한 시편을 도가니의 직경방항으로 절단해서 펠렛 단면의 CaO직경 변화를 측정하여 슬래그중 $Al_{2}O_{3}$첨가에 따른 CaO의 용해속도를 조사하고, 계면 생성층을 SEM/EDX로 관찰하였다. 그 결과, 슬래그의 염기도가 2인 경우, 염기도가 1인 경우 보다 생성층 $C_{3}S$상의 두께는 $Al_{2}O_{3}$를 15wt.%까지 첨가함에 따라 3.5배 증가하였으며, $C_{6}AF_{2}$ 또는 $C_{4}AF$양도 2배 정도 증가됨을 알 수 있었다.

• 한국결정성장학회지
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• 제16권3호
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• pp.116-120
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• 2006

반도체 드라이 에처 시스템의 웨이퍼 정전기 척에 적용하기 위해 플라즈마 스프레이 방법으로 Al-60 계열 기판에 코팅한 $Al_2O_3$ 코팅 막의 특성을 조사하였다. 시편 뒷면에 냉각봉이 장착되었을 때와 없을 때, 용사거리와 분말공급량을 변형하면서 $Al_2O_3$ 막 코팅을 하여 시편을 제작 하였다. 시편 뒷면에 냉각봉이 없을 때는 크랙과 기공이 많이 발생하였다. 시편 뒷면에 냉각봉을 장착하고 분말공급량을 15g/min로 한 경우에 용사거리 60, 70, 80mm에 따른 $Al_2O_3$ 코팅에서는 크랙과 기공은 거의 찾아볼 수 없었다. 용사거리 변화에 따른 $Al_2O_3$ 막 코팅의 표면형태 변화는 없었다. 같은 공정조건에서 분말 공급량을 20g/min로 한 경우에도 크랙은 볼 수 없었으나 약간의 기공이 생겼고, 분말공급량을15g/min로 하였을 때 보다 작은 입자들이 많이 증착되었다. 시편 뒷면에 냉각봉이 없을 때가 시편 뒷면에 냉각봉이 장착된 경우에 비하여 증착 속도가 빨랐다.

• 한국세라믹학회지
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• 제27권4호
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• pp.465-472
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• 1990

The effects of Al2O3 and Cr2O3 addition on the mechanical properties and microstructures of Y-TZP ceramics obtained by co-precipitation method of ZrO2＋3m/o Y2O3, following pressureless sintering at 150$0^{\circ}C$ for 2h were investigated. The addition of Al2O3 and Cr2O3 improved the Y-TZP sinterability and the Al2O3 addition showed the better effect on Y-TZP sintering than that of the Cr2O3 addition. The density and microstructure had the better effect on the bending strength of specimen more than stressinduced phase transformation (SIPT) of ZrO2 from tetragonal to monoclinic phase. The hardness of the specimens was found to be depend on the relative density and the fracture toughness of Y-TZP was found to rely on the amount of SIPT. The grian size of Cr2O3-doped Y-TZP was observed to be relatively smaller and had a narrower distribution than that of Al2O3-doped Y-TZP. If decomposition reaction of Cr2O3 can be controlled at high temperatures, it is anticipated that the mechanical properties of Y-TZP can be much improved by the Cr2O3 addition.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.418.2-418.2
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• 2016

$Al_2O_3$ passivation layer has excellent passivation properties at p-type Si surface. This $Al_2O_3$ layer forms thin $SiO_2$ layer at the interface. There were some studies about inserting thermal oxidation process to replace naturally grown oxide during $Al_2O_3$ deposition. They showed improving passivation properties. However, thermal oxidation process has disadvantage of expensive equipment and difficult control of thin layer formation. Wet chemical oxidation has advantages of low cost and easy thin oxide formation. In this study, $Al_2O_3$/$SiO_2/Si(100)$ interface was formed by wet chemical oxidation and PA-ALD process. $SiO_2$ layer at Si wafer was formed by $HCl/H_2O_2$, $H_2SO_4/H_2O_2$ and $HNO_3$, respectively. 20nm $Al_2O_3$ layer on $SiO_2/Si$ was deposited by PA-ALD. This $Al_2O_3/SiO_2/Si(100)$ interface were characterized by capacitance-voltage characteristics and quasi-steady-state photoconductance decay method.

• 공업화학
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• 제9권1호
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• pp.101-106
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• 1998

제올라이트를 담체로 사용하여 활성금속으로 코발트와 몰리브덴을 담지시킨 촉매와 상용공정에 사용되는 $NiMo/{\gamma}-Al_2O_3$촉매를 제조하여, 저온에서의 DBT 탈황활성과 선택성에 대하여 비교하였다. 고정층 고압 연속흐름반응기에서 수행된 탈황반응에서, 저온 영역인 $200^{\circ}C$와 $225^{\circ}C$에서는 제조된 $NiMo/{\gamma}-Al_2O_3$촉매보다 CoMo/zeolite 촉매에서 탈황활성이 더 높았으며, $275^{\circ}C$ 이상의 고온 영역에서는 $NiMo/{\gamma}-Al_2O_3$촉매의 탈황활성이 더 높게 나타났다. $NiMo/{\gamma}-Al_2O_3$촉매에서는 biphenyl과 cyclohexylbenzene이 주생성물인데 비하여 zeolite를 담체로 사용한 촉매의 경우 알킬화반응이 일어나 생성물 분포가 매우 다름을 보여주고 있으며, 알킬화반응과 수소첨가반응의 두 가지 경로를 통해서 최종 생성물질인 alkylcyclohexane을 생성하는 것으로 추정된다. 제올라이트 담체상에서 molybdenum은 flesh 촉매에서 $MoO_3$형태로 존재하고 있으며, aged 촉매상에서는 $MoO_3$와 $MoS_2$형태로 황화되어 있음을 알 수 있었다.

• 공학논문집
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• 제2권1호
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• pp.139-145
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• 1997

촉매연소용 촉매담체인 $\gamma$-$Al_2O_3$의 열안정화에 미치는 Ba의 첨가 효과에 대하여 연구하였다. Ba의 첨가는 $Ba(No_3)_3$.$6H_2O$를 $\gamma$-$Al_2O_3$ 분말에 wet impergnation시키는 방법으로 행하였다. Ba는 $\gamma$-$Al_2O_3$의 소결을 억제함으로써 $\gamma$-$Al_2O_3$의 열안정화에 효과적인 첨가제임을 확인하였으며 최적의 첨가량은 전체 열처리 조건에서 5 mol%임을 알 수 있었다. 이러한 Ba첨가에 의한 열안정화 효과는 이온반경이 큰 $Ba^{2+}$이온이 $\Al^{3+}$이온의 자리에 치환하여 $\Al^{3+}$이온의 표면 확산을 억제하는 효과에서 기인하는 것으로 사료된다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.279-279
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• 2007

Synthesis and dielectric properties of glass-ceramic composites with zinc borosilicate glass(here after ZBS glass) were investigated as functions of $ZnAl_2O_4$ phase synthesis method, glass addition (50~60 vol%) and sintering temperature ($600{\sim}950^{\circ}C$ for 2 hrs). The 50 vol% ZBS glass-$Al_2O_3$ and 60 vol% ZBS glass-$ZnAl_2O_4$ ensured successful sintering below $900^{\circ}C$. But the composition of 100-x-y vol% ZBS glass-x vol% $Al_2O_3-y$ vol% ZnO exhibited poor sinterability below $900^{\circ}C$ and the swelling phenomenon occurred in this composite with the large amount of ZBS glass. The sintering behavior of Glass-ceramic composites was affected by the crystallization of $ZnAl_2O_4$ which was formed by the reaction between ZBS glass and $Al_2O_3$. Dielectric constant (${\varepsilon}_r$), $Q{\times}f$ value and temperature coefficient of resonant frequency (${\tau}_f$) of the composite with 50 and 60 vol% ZBS glass contents demonstrated $ZBS-Al_2O_3({\varepsilon}_r=5.7)$, $ZBS-ZnAl_2O_4({\varepsilon}_r=5.8)$ which is applicable to substrate requiring an low dielectric properties.

• The Korean Journal of Ceramics
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• 제1권2호
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• pp.86-90
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• 1995

Theoretical predictions for thermodynamically stable phases which formed when alkali(sodium and potassium) vapors reacted with alumina-chromia refractories under coal gasifying atmosphere were confirmed experimentally using a laboratory-scale coal gasifying reaction system and a commercial alumina-chromia refractory using SEM, XRD, and EDAX. Alkali concentration profiles in the refractory as a function of time were also determined. The results showed that the compounds that formed were $X_2O{\cdot}Al_2O_3, X_2O{\cdot}Cr_2O_3, X_2O{\cdot}5Al_2O_3, X_2O{\cdot}7Al_2O_3, X_2O{\cdot}11Al_2O_3(X=Na^+ \;or\; K^+)$, depending upon the alkali concentration and time of exposure at high temperatures. The presence of sulfur in gasifying atmospheres did not appear to affect the alkali reaction produces. Alkali pentration into the alumina-chromia refractory was deep and the formation of the $Na_2O{\cdot}Al_2O_3/K_2O{\cdot}Al_2O_3$ compunds resulted in the serious deformation of the refractory due to the large volume expansion at the reaction surface. The hot face of the alumina-chromia refractory in service under an alkali environment is prone to failure by alkali attack.