• 한국세라믹학회지
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• 제24권1호
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• pp.9-16
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• 1987

Physical and electrical properties of ${\beta}$-Al2O3 were investigated as function of Na2O content from 6.67 wt.% to 13.19 wt.%. The majority phase is ${\beta}$-Al2O3 and the small amount of ${\beta}$"-Al2O3 exists in the specimens sintered at 1600$^{\circ}$for 30 mins. In the case of specimens with 8.54 wt.% Na2O sintered at 1600$^{\circ}C$, the relative amount of ${\beta}$-Al2O3 phase increases and that of ${\beta}$"-Al2O3 phase decreases with increasing sintering time, and then ${\beta}$"-Al2O3 phase does not exist if sintering time is over 8 hrs. As the Na2O content is increased, the 3-Point MOR and the resistivity are decreased. However, density and 3-Point MOR with increasing sintering time are decreased due to increasing the enclosed pore trapped inside of the exaggerated grains. As the sintering time is increased, the average grain size and the duplexity of microstructure are increased, and the resistivity is slightly decreased.

• 한국결정성장학회지
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• 제15권6호
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• pp.225-228
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• 2005

본 연구에서는 장잔광성 $SrAl_2O_4:Eu^{2+},\;Dy^{3+}$ 단결정을 베르누이법으로 성장시켰다. 성장된 $SrAl_2O_4:Eu^{2+},\;Dy^{3+}$ 단결정은 지름이 5 mm, 길이는 55 mm이다. 상온(300 K)과 저온(15 K)에서 각각 photoluminescence를 측정한 결과, 상온에서는 ${\lambda}=526nm$에서만 나타났으나, 저온에서는 454nm 영역과 526nm 영역에서 발광피크를 나타내었다. 이는 형광도료로 사용되는 분말과 유사한 결과이다. 결정성장 시 적외선 광고온계로 녹는점을 측정한 결과는 $1968^{\circ}C$였다. 결정을 성장시키는 최적의 조성은 $SrCO_3:Al(OH)_3:Eu_2O_3:Dy_2O_3$ = 1 : 2 : 0.015 : 0.02이고 $H_2:O_2$의 혼합비는 약 4 : 1이다. 성장속도는 시간당 5mm이다. 성장된 단결정의 결정구조는 XRD로 측정하였다.

• Bulletin of the Korean Chemical Society
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• 제33권8호
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• pp.2513-2516
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• 2012

This study examined the effects of the epoxidized castor oil (ECO) and $Al_2O_3$ content on the thermal stability and fracture toughness of the diglycidylether of bisphenol-A (DGEBA)/ECO/$Al_2O_3$ ternary composites using a range of techniques. The thermal stability of the composites was decreased by the addition of ECO and $Al_2O_3$ nanoparticles. The fracture toughness of the composites was improved significantly by the addition of ECO and $Al_2O_3$ nanoparticles. The composite containing 3 wt % $Al_2O_3$ nanoparticles showed the maximum flexural strength. Scanning electron microscopy (SEM) revealed tortuous cracks in the DGEBA/ECO/$Al_2O_3$ composites, which prevented deformation and crack propagation.

• 한국세라믹학회지
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• 제22권5호
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• pp.76-84
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• 1985

Mechanical property enhancing mechanisms of $Al_2O_3-ZrO_2$ two phase ceramic composites were studied for several compositions of different $ZrO_2$/$Al_2O_3$ ratio. Microstructural analysis of $Al_2O_3-ZrO_3$(pure) composites indicated that pre-existing microcrack due to larger $ZrO_2$ particle at grain boundary extended along alumina grain boundaries within process zone. Microcracks also nucleated when very small $ZrO_2$ particles at the grain boundaries transformed to monoclinic phase at near of main crack tip. These types of microcracks could contribute to the toughening achieved by creating additional crack surface area during crack propagation. Microstructural analyses also showed that the average grain size and abnormal grain size of $Al_2O_3$ were decreased with increasing $ZrO_2$ vol% in $Al_2O_3$ matrix. As a result it could be concluded as follows In TEX>$Al_2O_3-ZrO_3$(pure) system 1. Microcrack nucleation (stress-induced microcracking) and extension was effective mechanism for absorpiton of fracture energy 2, More narrow distribution and smaller grain size of $Al_2O_3$ due to $ZrO_2$particles mainly contributed to main-tatin the strength and hardness.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2013년도 춘계학술대회 논문집
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• pp.53-54
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• 2013

Nano-multilayered CrAlSiN films consisting of crystalline CrN nanolayers and amorphous AlSiN nanolayers were deposited by cathodic arc plasma deposition. Their oxidation characteristics were studied between 600 and $1000^{\circ}C$ for up to 70 h in air. During their oxidation, the amorphous AlSiN nanolayers crystallized. The formed oxides consisted primarily of $Cr_2O_3$, ${\alpha}-Al_2O_3$, $SiO_2$. The outer $Al_2O_3$ layer formed by outward diffusion of Al ions. Simultaneously, an inner ($Al_2O_3$, $Cr_2O_3$)-mixed layer formed by the inward diffusion of oxygen ions. $SiO_2$ was present mainly in the lower part of the oxide layer due to its immobility. The CrAlSiN films displayed good oxidation resistance, owing to the formation of oxide crystallites of $Cr_2O_3$, ${\alpha}-Al_2O_3$, and amorphous $SiO_2$.

• 한국세라믹학회지
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• 제39권7호
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• pp.704-709
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• 2002

ZrO$_2$가 분산된 $Al_2$O$_3$/ZrO$_2$ 복합체의 기계적 성질을 향상시키기 위하여 분산되는 ZrO2의 입자크기를 공침법에 의해 초미립으로 균질하게 분산시키기 위한 방안을 고찰하여 보았다. 일반적으로 $Al_2$O$_3$와 ZrO$_2$ 분말의 기계적혼합에 의해 제조되는 경우 분산되는 ZrO$_2$ 출발입자의 크기도 크고 소결시에도 비교적 빠르게 성장하므로 본 연구에서는 상용의 이소결성 $\alpha$-Al$_2$0$_3$ 분말(Sumitomo:AES-11(0.5$mu extrm{m}$)) 및 저온 소결용 초미립 알루미나(Taimei Chemical(0.22$\mu\textrm{m}$))에 ZrOC1$_2$. 8$H_2O$ 와 Y(NO$_3$)$_3$를 pH 9.5의 조건에서 공침하여 $\alpha$-Al$_2$0$_3$입자 표면에 초미립의 미세한 Zr(OH)$_4$ 침전 입자가 부착되도록 하였다. 이를 150$0^{\circ}C$-1$600^{\circ}C$의 온도에서 소결하여 작은 크기의 ZrO$_2$ 입자가 균질하게 분산된 $Al_2$O$_3$/ZrO$_2$ 복합체를 제조하였으며 이의 기계적성질을 관찰하였다.

• 한국세라믹학회지
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• 제52권1호
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• pp.19-22
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• 2015

The joining behavior of YSZ ceramics to the glasses used in the $9Al_2O_3-24ZrO_2-51SiO_2-16R_2O$ and $9Al_2O_3-24ZrO_2-51SiO_2-7La_2O_3-9R_2O$ (wt%) glass systems was investigated. The glass transition and softening temperatures were determined to be $430^{\circ}C$ and $760^{\circ}C$, respectively. The behavior of the contact angle was inversely proportional to an increase in the temperature. The Zr element in YSZ acted as a nucleation agent and contributed to the bonding behavior at the interface.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 추계학술대회 논문집
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• pp.307-310
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• 1998

In this paper, $Al_2$O$_3$/MgO belayer was prepared with Electron-beam evaporation and the properties of the film was investigated in order to improve the property of MgO film, which is used for the protection layer in PDP(Plasma Display Panel). $Al_2$O$_3$/MgO belayer were improved of roughness and it were condensed by annealing, and the result of XPS analysis for $Al_2$O$_3$/MgO belayer unchanged binding energy. To investigate electric characteristics, discharge properties of $Al_2$O$_3$/MgO belayer were compared with discharge minimum voltage for MgO monolayer through Ar discharge experiments.

• 한국표면공학회지
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• 제42권2호
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• pp.86-94
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• 2009

Various types of multilayer coatings including Al/$Al_2O_3$ structure have been prepared on Nd-Fe-B permanent magnet to modify the morphology of the coating and to enhance the corrosion resistance of the magnet. Magnetron sputtering has been employed to make the multilayer coatings. $Al_2O_3$sputtering conditions were optimized in reactive sputtering by varying the deposition parameters. The formation of $Al_2O_3$ film was confirmed from the binding energy shift measured by electron spectroscopy for chemical analysis. 3 types of coating structures were designed and prepared by magnetron sputtering. The coating structures consist of (1) single Al coating, (2) modified coatings having oxide or plasma treated layer in the middle of coating structure, and (3) Al/$Al_2O_3$ multilayer coatings. Surface and cross-sectional morphologies showed that Al/$Al_2O_3$ multilayer grew as a layered structure, and that very compact Zone 3 like structure were formed. X-ray diffraction peak showed that the crystal orientations of multilayer coatings were similar to that of the bulk powder pattern. Hardness increased drastically when the Al thickness was around 1im in the Al/$Al_2O_3$ multilayer. From the salt spray test and pressure cooker test, it has been shown that the multilayer coatings showed good corrosion resistance compared to Al single or modified layer coatings.

• 열처리공학회지
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• 제20권5호
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• pp.231-236
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• 2007

High velocity oxy-fuel (HVOF) spraying was used to coat Ti(Al,O)/$Al_2O_3$ powder onto the SS41 steel plate. Macrostructure of the coated specimen has been investigated by scanning electron micrograph (SEM). High temperature oxidation behavior of the coated specimen and SS41 steel have been studied. From the results of SEM observation, Ti(Al,O)/$Al_2O_3$ powder was coated well onto the substrate SS41 steel. Porosity onto the coated layer was only 0.38%. The oxidation results showed that Ti(Al,O)/$Al_2O_3$ powder coated SS41 steel have improved little oxidation resistance at $900^{\circ}C$ in air, but improved remarkably oxidation resistance at $800^{\circ}C $ in air compare to the substrate SS41 steel.