• Journal of Welding and Joining
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• 제22권5호
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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.

• 한국분말재료학회지
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• 제25권1호
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• pp.25-29
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• 2018

Porous Cu with a dispersion of nanoscale $Al_2O_3$ particles is fabricated by freeze-drying $CuO-Al_2O_3$/camphene slurry and sintering. Camphene slurries with $CuO-Al_2O_3$ contents of 5 and 10 vol% are unidirectionally frozen at $-30^{\circ}C$, and pores are generated in the frozen specimens by camphene sublimation during air drying. The green bodies are sintered for 1 h at $700^{\circ}C$ and $800^{\circ}C$ in $H_2$ atmosphere. The sintered samples show large pores of $100{\mu}m$ in average size aligned parallel to the camphene growth direction. The internal walls of the large pores feature relatively small pores of ${\sim}10{\mu}m$ in size. The size of the large pores decreases with increasing $CuO-Al_2O_3$ content by the changing degree of powder rearrangement in the slurry. The size of the small pores decreases with increasing sintering temperature. Microstructural analysis reveals that 100-nm $Al_2O_3$ particles are homogeneously dispersed in the Cu matrix. These results suggest that a porous composite body with aligned large pores could be fabricated by a freeze-drying and $H_2$ reducing process.

• 한국세라믹학회지
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• 제33권10호
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• pp.1147-1155
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• 1996

• Korean Chemical Engineering Research
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• 제55권3호
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• pp.436-442
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• 2017

Fischer-Tropsch 합성(F-T 합성)은 석탄, 바이오매스, 천연가스 등을 개질하여 얻은 합성 가스(CO, $H_2$)를 촉매를 이용하여 탄화수소로 전환 하는 기술이다. Fischer-Tropsch 합성에 이용되는 촉매는 활성 금속, 조촉매, 지지체로 구성되는데 이들의 종류와 조성은 반응의 활성 및 생성물 선택도에 영향을 미친다. 본 연구에서는 ${\gamma}-Al_2O_3$와 $SiO_2$ 혼합 지지체의 조성이 Fiscsher-Tropsch 반응의 활성과 생성물 선택도에 미치는 영향을 알아 보기위해, ${\gamma}-Al_2O_3/SiO_2$ 혼합 지지체를(100/0 wt%, 75/25 wt%, 50/50 wt%, 25/75 wt%, 0/100 wt%) 이용하여 함침(impregnation)법으로 철 촉매를 제조하였다. 촉매의 물리적 특성은 질소 물리 흡착 법과 X-선 회절 분석법을 통해 분석 하였고, 고정층 반응기에서 Fischer-Trosch 반응을 $300^{\circ}C$, 20bar에서, 60시간 동안 수행 하였다. 촉매의 물리적 특성 분석 결과 촉매의 BET 표면적은 ${\gamma}-Al_2O_3$의 조성이 감소함에 따라 감소하였으며, 촉매 기공의 부피 및 평균 크기는 지지체 조성이 ${\gamma}-Al_2O_3/SiO_2$ (50/50 wt%)인 경우를 제외 하고 증가하는 경향을 보였다. 또한, X-선 회절 분석법을 통해 ${\alpha}-Fe_2O_3$의 입자 크기를 계산한 결과 ${\gamma}-Al_2O_3$의 조성이 감소함에 따라 입자 크기가 감소 하였다. Fischer-Tropsch 합성 결과 ${\gamma}-Al_2O_3$의 조성이 감소함에 따라 CO 전환율은 감소 하였으며, C1-C4의 선택도는 ${\gamma}-Al_2O_3$의 조성이 25 wt%일 때 까지 감소하였으며 이와 반대로, C5+의 선택도는 ${\gamma}-Al_2O_3$의 조성이 25 wt%일 때 까지 증가 하였다.

• 한국결정성장학회지
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• 제7권2호
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• pp.259-270
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• 1997

$\alpha-Al_2O_3$와 비정질 $TiO_2$부터 $Al_2TiO_5$를 합성하기 위한 고체상태반응의 반응속도를 $1200~1300^{\circ}C$ 온도 범위에서 연구하였다. 반응속도는 $Al_2O_3$분말을 코팅한 50 mol%의. $TiO_2$와 일정한 온도에서 여러 시간동안 가열하여 생성된 혼합물에 의하여 결정되었다. MgO안의 반응물과 미반응물의 양은 X-선 회절분석에 의하여 결정되었다. $Al_2TiO_5$의 부피율과 peak intensity비의 자료로부터 $Al_2O_3$와 $TiO_2$의 pseudobrookite(Tialite)형태로의 반응은 $1280^{\circ}C$와 $1300^{\circ}C$ 사이에서 시작되었다. 고체상태반응 활성화 에너지는 Arrhenius식에 의하여 결정되었다. 활성화 에너지는 622.4 kJ/mol이다.

• 한국세라믹학회지
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• 제37권5호
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• pp.459-465
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• 2000

3CaO.3Al2O3.CaSO4(C4A3)clinker was prepared by solid state reaction and then its hydration property was investigated. C4A3 clinker was fired at various temperatures in the range of 700~135$0^{\circ}C$. The hydration of it was studied by XRD, DSC, Solid-state 27Al MAS NMR and SEM. According to the results, the Ca4A3 clinker was produced by reacting calcium aluminates with CaSO4 and Al2O3 and C4A3 was formed as a main phase after calcining at 120$0^{\circ}C$. The hydration products were mainly calcium monosulfoaluminate hydrate and Al(OH)3, and they were produced after 2hrs of hydration. However the hydration rate was about 74% at 3days.

• 한국분말재료학회지
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• 제9권3호
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• pp.161-166
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• 2002

Processing and properties of $Al_2O_3$ composites with Ni-Fe content of 10 and 15 wt% were investigated. Homogeneous powder mixtures of $Al_2O_3$/Ni-Fe alloy were prepared by the solution-chemistry route using $Al_2O_3$, $Ni(NO_3)_2{\cdot}6H_2O$ and $Fe(NO_3)_3{\cdot}9H_2O$ powders. Microstructural observation of composite powder revealed that Ni-Fe alloy particles with a size of 20nm were homogeneously dispersed on $Al_2O_3$ powder surfaces. Hot-pressed composites showed enhanced fracture toughness and magnetic response. The properties are discussed based on the observed microstructural characteristics.

• The Korean Journal of Ceramics
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• 제4권3호
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• pp.207-212
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• 1998

By comparison of the experimental results in two systems of ZnO varistors, it's appear that Sb2O3 is the indispensable element for twining in ZnO varistors and the Zn7Sb2O12 spinel acts as the nucleus to form twins. Al2O3 is not the origin of twining in ZnO varistor, but it was found that Al2O3 could strengthen the twining and form a deformation twining by ZnAl2O4 dragging and pinning effect. The inhibition ratios of grain and nonuniformity of two systems ZnO varistors increase with the increase of Al2O3 content. The twins affect the inhibition of grain growth, the mechanism could be explained follow as: twins increase the mobility viscosity of ZrO grain and grain boundary, and drag ZrO grain and liquid grain boundary during the sintering, then the grain growth is inhibited and the microstructure becomes more uniform.

• 한국표면공학회지
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• 제34권2호
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• pp.105-114
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• 2001

$Al_2$$O_3$ coatings were deposited on M2 high speed steels by the plasma enhanced chemical vapor deposition (PECVD) process, using a gas mixture of AlC1$_3$, $H_2$, $CO_2$ and Ar $Al_2$$O_3$ coatings had interference color and showed amorphous phase. $A1_2$X$A1_3$/($Ti_{0.5}$ /$Al_{0.5}$ )N double layer coatings were produced in the sequence of substrate $NH_3$ plasma pretreatment, ($Ti_{0.5}$$Al_{0.5}$)N depoition process, $Al_2$$O_3$ deposition process. $Al_2$ $O_3$/( $Ti_{0.5}$A $l_{0.5}$)N double layer coatings showed NaCl structure in ( $Ti_{0.5}$A $l_{0.5}$)N layer and amorphous phase in A1$_2$ $O_3$ layer. It was shown that $Al_2$ $O_3$ columns continuously grew onto ( $Ti_{0.5}$A $l_{0.5}$)N columns. ( $Ti_{0.5}$A $l_{0.5}$)N single coating and $Al_2$ $O_3$/( $Ti_{0.5}$A $l_{0.5}$)N double layer coating were oxidized at $700^{\circ}C$, 80$0^{\circ}C$, 90$0^{\circ}C$ for 1hr, 3hr in atmosphere. At 80$0^{\circ}C$, single layer coatings were oxidized, which were examined substrate oxide particle. But $Al_2$ $O_3$/ ( $Ti_{0.5}$A $l_{0.5}$)N double layer coatings maintained the asdeposited state. Therefore, $Al_2$ $O_3$/ ( $Ti_{0.5}$A $l_{0.5}$)N double layer coatings have moreexcellent oxidation resistance than ( $Ti_{0.5}$A $l_{0.5}$)N single layer coatings.X> 0.5/)N single layer coatings.s.

• 한국세라믹학회지
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• 제41권8호
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• pp.610-617
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• 2004

평균입자크기가 20 ${\mu}$이고, 두께가 0.2∼0.3 ${\mu}m$인 ${\alpha}-Al_2O_3$ 판상체를 제조하기 위하여 전구물질로써 황산알루미늄과 황산나트륨을 사용하여 수산화알루미늄을 제조하였다. 이때 첨가되는 인산나트륨의 양이 ${\alpha}Al_2O_3$ 판상체의 입자크기, 형상, 그리고 두께에 어떠한 영향을 미치는지에 대하여 관찰하였다. 인산나트륨을 첨가하지 않았을 경우, 대부분의 ${\alpha}-Al_2O_3$ 판 상체가 육각판상모양을 띠고 있었으나 그 두께가 1.0 ${\mu}m$ 이상으로 진주안료 기질로는 적합하지 않았다. 반면, 인산나트륨이 첨가되었을 경우, ${\alpha}-Al_2O_3$ 판상체의 두께를 감소시켜 각형비를 증가시키는 현상을 초래하였다.