• 대한전자공학회논문지TE
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• 제39권1호
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• pp.1-8
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• 2002

단사정 ZrO/sub 2/(ZrO2(m)) 또는 Y/sub 2/O/sub 3/를 5.35wt% 첨가한 정방정 ZrO2(ZrO/sub 2/(t))를 A1/sub 2/O/sub 3/에 첨가하여 물리적 및 전기전도도의 영향을 연구하였다. ZrO/sub 2/(m)과 ZrO/sub 2/(t)의 첨가는 A1/sub 2/O/sub 3/의 소결밀도를 증가 시켰다. ZrO2(t)의 첨가함에 따라 비커스 경도 또한 증가했으며, 그 량이 20wt%에서 최대가 되었다. 시편의 경도는 소결밀도에 의존함을 알 수 있었다. A1/sub 2/O/sub 3/-ZrO/sub 2/계의 경도는 ZrO/sub 2/(t)의 첨가에 의해 개선 되었고, ZrO/sub 2/(m)의 첨가가 ZrO/sub 2/(t)의 첨가보다 A1/sub 2/O/sub 3/-ZrO/sub 2/계의 열충격 특성에는 더 많은 영향을 받음을 알 수 있었다. l5wt% 이상의 ZrO/sub 2/(t) 첨가에서 인가전압이 증가 함에 따라 점차로 전기전도도가 증가 하였으나, ZrO/sub 2/(m)의 첨가에서는 영향이 없었다.

• 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.

• 한국전기전자재료학회논문지
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• 제29권12호
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• pp.791-795
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• 2016

The effects of $TiO_2$ addition on the electrical insulation of AlN ceramics with 1 wt% $Y_2O_3$ as a sintering aid have been investigated. Some of $TiO_2$ has reacted with AlN powders and transformed to fine TiN particles during sintering, which was uniformly dispersed along grain boundaries of AlN. At a high electrical field (500 V/mm), the resistivity of AlN ceramics with $TiO_2$ addition of 0.2 wt% increased about 1000 times from $3{\times}10^{10}{\Omega}cm$ to $3.1{\times}10^{13}{\Omega}cm$. Based on the impedance spectroscopy measurement, it was found that $TiO_2$ addition increased dramatically electrical resistivity of AlN grains much more than that of grain boundaries. Thus, $TiO_2$ was believed to dissolve inside AlN grains to suppress ionic conduction of Al vacancies. This suppressed ionic conduction by Ti incorporation into AlN grains seems to contribute to more electrically insulating AlN ceramics.

• 한국세라믹학회지
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• 제34권6호
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• pp.668-676
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• 1997

Al2O3/SiC nanocomposites are fabricated through intensive ball milling to mix fine SiC particles uniformly with the Al2O3 powder. Another role of milling is to reduce particle sizes by crushing particles as well as agglomerates. However, balls are worn during ball milling and the sample powder mixtures pick up to weight loss of the balls. In this study, pressureless sintering was performed to obtain Al2O3/SiC nanocomposites. It was found that the wear rate of zirconia balls during milling was considerable, and the zirconia addition after even a few hours of ball milling could increase the sintering rates of the nanocomposites significantly. Thus, addition of ZrO2 changed the sintering behaviors as well as mechanical properties of Al2O3/SiC nanocomposites.

• 콘크리트학회논문집
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• 제28권2호
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• pp.205-212
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• 2016

본 연구는 고로슬래그 미분말(GGBFS)의 구성성분이 알칼리 활성화 슬래그 시멘트(AASC)에 미치는 영향에 관한 연구이다. 산화알루미늄($Al_2O_3$)을 고로슬래그 미분말 중량에 대해 2~16% 혼합하였다. 활성화제는 KOH를 사용하였고, 물-결합재 비는 0.5이다. 강도 향상은 $Al_2O_3$ 혼합률이 증가함에 따라 수화반응의 향상으로 나타난다. 재령 28일에서 가장 높은 강도는 2M KOH + 16% $Al_2O_3$와 4M KOH + 16% $Al_2O_3$일 때이고 각각 30.8 MPa과 45.2 MPa이였다. 재령 28일에서 2M KOH + 16% $Al_2O_3$의 강도는 2M KOH ($Al_2O_3$ 미첨가) 보다 46% 향상되었다. 또한 4M KOH + 16% $Al_2O_3$의 강도는 4M KOH ($Al_2O_3$ 미첨가) 보다 44% 향상되었다. 결합재에서 $Al_2O_3$ 혼합률이 증가함에 따라 모든 재령에서 강도가 증가하였다. AASC에서 초음파속도(UPV)는 강도와 유사한 경향을 나타내었지만 흡수율과 공극률은 $Al_2O_3$의 혼합률이 증가함에 따라 강도경향과 상반된 경향을 나타내었다. $Al_2O_3$ 혼합률이 높은 시험체에서 반응생성물질의 Al/Ca와 Al/Si가 증가하였다. SEM과 EDX 분석을 통해 $Al_2O_3$의 혼합은 더욱 치밀한 미세조직을 형성한 것을 확인하였다.

• 한국재료학회지
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• 제12권1호
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• pp.48-53
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• 2002

$Al_2O_3-SiC$ and $Al_2O_3-SiC$-TiC composite powders were prepared by SHS process using $SiO_2,\;TiO_2$, Al and C as raw materials. Aluminum powder was used as reducing agent of $SiO_2,\;TiO_2$ and activated charcoal was used as carbon source. In the preparations of $Al_2O_3-SiC$, the effect of the molar ratio in raw materials, compaction pressure, preheating temperature and atmosphere were investigated. The most important variable affecting the synthesis of $Al_2O_3-SiC$ was the molar ratio of carbon. Unreactants remained in the product among all conditions without compaction. The optimum condition in this reaction was $SiO_2$: Al: C=3: 5: 5.5, 80MPa compaction pressure under Preheating of $400^{\circ}C$ with Ar atmosphere. However there remains cabon in the optimum condition. The effect of $TiO_2$ as additive was investigated in the preparations of $Al_2O_3-SiC$. As a result of $TiO_2$ addition, $Al_2O_3-SiC$-TiC composite powder was prepared. The $Al_2O_3$ powder showed an angular type with 8 to $15{\mu}m$, and the particle size of SiC powder were 5~$10{\mu}m$ and TiC powder were 2 to $5{\mu}m$.

• 한국세라믹학회지
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• 제51권5호
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• pp.498-504
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• 2014

Particulate nitride composites have been fabricated by sintering the compacted powder of AlN and 5 - 64.3 mol% $Al_2O_3$, with a small addition of $Y_2O_3$ ($Y_2O_3$/AlN, 1 wt%), in 1-atm nitrogen gas at $1650-1900^{\circ}C$. The composites were characterized in terms of sintering behavior, phase relations, microstructure and thermal shock resistance. AlN, 27R AlN pseudopolytype, and alminium oxynitride (AlON, $5AlN{\cdot}9Al_2O_3$) were found to existin the sintered material. Regardless of batch composition, the AlN-$Al_2O_3$ powder compacts exhibited similar sintering behavior; however, the degree of shrinkage commonly increased with increasing $Al_2O_3$ content, consequently giving high sintered bulk density. By increasing the $Al_2O_3$ addition up to ${\geq}50 mol%$, the matrix phase in the sintered material was converted from AlN or 27R to AlON. Above $1850^{\circ}C$, a liquid phase was formed by the reaction of $Al_2O_3$ with AlN, aided by $Y_2O_3$ and mainly existed at the grain boundaries of AlON. Thermal shock resistance was superior in the sintered composite consisting of AlON with dispersed AlN or AlN matrix phase.

• 한국세라믹학회지
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• 제23권2호
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• pp.7-12
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• 1986

As the other silicate minerals such as kaolinite and pyrophyllite kyanite ($Al_2O_3$.$SiO_2$) is transformed to mullite and free silica or glassy phase at high temperature. Therefore $Al_2O_3$ is commonly added to kyanite in order to increase the mullite-yield. In case of $Al_2O_3$-addition mullite-yield depends on the reactivity of added $Al_2O_3$ with free silica which occurs from transformation of kyanite or exists as accessory minerals. It is well known that addition of activated $Al_2O_3$Al powder is added to kyanite to utilize the aluminothermal reac-tion of Al powder in reaction of mullite-formation.

• 신재생에너지
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• 제3권1호
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• pp.54-59
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• 2007

A sintering aid, $B_{2}O_{3}$ have been included into a $LiAlO_{2}$ electrolyte support by a tape casting method in order to reinforce mechanical strength of the support for molten carbonate fuel cells [MCFCs). Starting idea originates from the low melting point of $B_{2}O_{3}$ ($450^{\circ}C$), which can provide the low temperature consolidation of ceramic materials. The mechanical properties and the microstructure changes of the $B_{2}O_{3}$-included electrolyte support were examined by scanning electron microscope, mercury porosimetry, X-ray powder diffraction [XRD], high temperature differential scanning calorimeter and three-point bending strength measurement. The mechanical strength was clearly improved by addition of $B_{2}O_{3}$. The increase of mechanical strength results from the neck growth of a new $LiAlO_{2}$ phase between $LiAlO_{2}$ particles by the liquid phase sintering. Average pore size and porosity of the electrolyte support reinforced by addition of the sintering aid, $B_{2}O_{3}$, was $0.24{\mu}m$ and 59%, respectively which were suitable microstructure of a matrix for an application of MCFCs.

• 한국세라믹학회지
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• 제25권3호
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• pp.201-206
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• 1988

Mo 입자의 첨가가 Al_2O_3$ 세라믹스의 미세구조와 기계적 성질에 미치는 영향을 알아보기 위하여 평균입경이 2-micron인 Mo와 6-micron인 Mo를 Al_2O_3$에 각 분산시켜 1$600^{\circ}C$, $H_2$ 분위기에서 5시간 소결하였다. Mo는 Al_2O_3$의 입자성장을 억제시켰으며 Mo의 입자가 작을 때 그 효과는 크게 나타났다. 2-micron Mo를 분산한 경우 꺽임강도와 파괴인성은 크게 증가하여하였으며, 6-micron Mo를 분산한 경우 강도는 증가하지 않았으나 파괴인성은 다소 증가하였다. Al_2O_3$-Mo계의 인성증진기구는 균열편향에 의한 파단면의 증가와 미세균열에 의한 균열전파에너지의 분산에 의한 것으로 보인다.