• 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.

• 한국재료학회지
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• 제31권6호
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• pp.339-344
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• 2021

Composite materials offer distinct and unique properties that are not naturally inherited in the individual materials that make them. One of the most attractive composites to manufacture is the aluminum alloy matrix composite, because it usually combines easiness of availability, light weight, strength, and other favorable properties. In the current work, Powder Metallurgy Method (PMM) is used to prepare Al2024 matrix composites reinforced with different mixing ratios of yttrium oxide (Y₂O₃) particles. The tests performed on the composites include physical, mechanical, and tribological, as well as microstructure analysis via optical microscope. The results show that the experimental density slightly decreases while the porosity increases when the reinforcement ratio increases within the selected range of 0 ~ 20 wt%. Besides this, the yield strength, tensile strength, and Vickers hardness increase up to a 10 wt% Y₂O₃ ratio, after which they decline. Moreover, the wear results show that the composite follows the same paradigm for strength and hardness. It is concluded that this composite is ideal for application when higher strength is required from aluminum composites, as well as lighter weight up to certain values of Y₂O₃ ratio.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2006년도 추계학술발표회 초록집
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• pp.90-90
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• 2006

• 한국세라믹학회지
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• 제26권3호
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• pp.438-444
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• 1989

The role of TiC and the effect of Y2O3 addition on the densification, microstructure and mechanical properties of Al2O3-TiC composite have been studied. The amount of Y2O3 has been varied from 0 to 2 wt.% while keeping the TiC content at 10, 20 or 30 wt.%. The powder compacts have been sintered at 1,75$0^{\circ}C$ for various times in 1 atm Ar atmosphere and hot isostatically pressed (HIPed) at 1,$600^{\circ}C$ for 0.5h under 1,500atm Ar. Considerable increase in sintered density(over 95%) has been achieved by adding 0.5 wt.% Y2O3 in specimens containing high TiC volume. More addition of Y2O3 does not affect the densification. With increasing the sintering time from 0.5 to 4h, slight increase in density results. The growth of Al2O3 grain has been enhanced by Y2O3 addition ; this tendency is reduced with increasing TiC content because of grain boundary dragging effect of TiC particles. The hardness of specimens increases considerably by an addition of 0.5wt.% Y2O3 owing to the density increase. Further addition of Y2O3 has no effect on hardness. Fracture toughness augments with TiC content by crack deflection around the particles. By adding 0.5wt.% Y2O3, all the specimens can be densified to isolated pore stage and thus can be HIPed to full densification and better mechanical property. In particular, the fracture toughness of Al2O3-30 TiC specimen increases about 50% by HIPing. Fully dense Al2O3-30 TiC with good mechanical properties can be prepared by normal Sintering/HIPing process.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.69-69
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• 2003

• 한국분말재료학회지
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• 제4권2호
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• pp.106-112
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• 1997

$Cu-Al_20_3 $ composite powders were prepared by hydrogen reduction of $Cu^{2+}$ from ammoniacal copper sulfate solution on alumina core using autoclave. The copper reduction rate and the properties of copper layer were investigated using Scanning Electron Microscope(SEM), X-ray diffractometer, size and chemical analyzers. The reduction rate of $Cu^{2+}$ showed the maximum value when the molar ratio of [$NH_3$]/[$Cu^{2+}$] was 2. In order to prevent the agglomeration of Cu powder and ethane reduction rate, $Fe^{2+}$ and anthraquinone which act as catalysis were added in the solution. Catalysis was effectively chanced with the addition of two elemerts at a time. Optimum conditions obtained in this study were hydrogen reduction temperature of 205$^{\cire}C$, stirring speed of 500 rpm and hydrogen partial pressure of 300 psi. Obtained $Cu-Al_20_3 $ composite Powders were found to have the uniform and continuous copper coating layer of nodule shape with 3~5 $\mu$m thickness.

• 한국세라믹학회지
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• 제25권3호
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• pp.284-292
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• 1988

Alumina-zirconia composite powders for the purpose of improving fracture toughness and thermal shock resistance of alumina were prepared by the emulsion-kerosene drying method. The average particle size of composite powders was less then 1 $\mu\textrm{m}$ and their shapes were spherical. It was shown that the average particle size of composite powders decreased with the concentration of metal-salt in solution and the amount of span 80 added when preparing emulsions. The structure of all zirconia in composite powders heat-treated at 1200$^{\circ}C$ was a tetragonal form at room temperature. This result implied that fine zirconia particles were homogeneously dispersed in the alumina matrix.

• 한국세라믹학회지
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• 제37권9호
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• pp.909-914
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• 2000

반응금속 침투법으로 제조한 $Al_2$O$_3$/Al 복합체의 파괴특성과 손상 내구성을 침투방향성에 따라 관찰하였으며, 복합체는 $Al_2$O$_3$단일상보다 향상된 파괴인성과 Al 단일상보다 높은 경도값을 나타내었다. Vickers 압입법을 사용한 복합체의 손상형태에서는 침투방향에 따른 각각의 미세구조에 의해 상이한 특성을 나타내었으며, 헤르찌안 압입법을 사용한 복합체의 손상거동은 $Al_2$O$_3$과 Al의 중간거동을 나타내었다. 헤르찌안 압입 후 강도저하시험으로 복합체가 갖는 우수한 결함저항성을 관찰할 수 있었으며, 높은 헤르찌안 하중에서는 복합체의 강도저하 특성이 복합체의 미세구조에 의존함을 관찰할 수 있었다. 이와 함께 복합체에서의 반응금속 침투방향성, 미세구조 그리고 손상 내구성 사이 상호연관성에 대해 논의하였다.

• 한국재료학회지
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• 제9권6호
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• pp.609-614
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• 1999

The effect of the amount of $SiO_2$dopant on the behavior of $AlO_2$$O_3$-composite formation by melt oxdation of Al-alloy was examined in this paper. The $SiO_2$powder was spread on the top surface of the Al-1Mg-3-Si-5Zn-1Cu alloy in th alumina crucible. The selected amount of each powder was 0.03, 0.10, 0.16g/$\textrm{cm}^2$. The oxidation behavior was determined by observing the weight gain after the heat treatment for 10 hours at 1373K. The macroscopic structure of formed oxide layer was examined by an optical microscope. The top surface and the cross-section of the grown oxide layer were investigated by SEM and analysed by EDX. The $SiO_2$ powder was determined to enhance oxidation by thermit reaction with Al which reduced the growth incubation period of the oxidation layer. As the amount of the $SiO_2$dopant increased, the growth rate decreased due to the precipitated Si which blocked the Al-alloy channel in the composite materials. However, more uniform layer was obtained due to the occurrance of the enhanced oxidation reaction in the whole alloy surface compared to the case of addition of less amount of dopant.

• 한국세라믹학회지
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• 제38권5호
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• pp.412-417
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• 2001

본 연구는 습식법으로 수산화 알루미늄과 티타니아를 출발물질로 하여 $Al_2$O$_3$-TiO$_2$복합분체를 제조하였으며, 2 mol의 Al(OH)$_3$분말에 대하여 TiO$_2$분말량을 1, 3, 5, 7, 9, 11 wt%로 첨가하여 $Al_2$O$_3$-TiO$_2$복합분체의 특성을 조사하였다. 제조된 $Al_2$O$_3$-TiO$_2$계 복합분체는 $700^{\circ}C$~140$0^{\circ}C$까지 하소하여 XRD 분석을 한 결과 100$0^{\circ}C$까지는 TiO$_2$(rutile)상과 η-Al$_2$O$_3$상이 공존하다가 110$0^{\circ}C$부터 130$0^{\circ}C$까지는 η-Al$_2$O$_3$에서 $\alpha$-Al$_2$O$_3$로의 상전이가 일어나서 $\alpha$-Al$_2$O$_3$상과 TiO$_2$(rutile)상이 나타났으며 하소온도 140$0^{\circ}C$, TiO$_2$첨가량이 5 wt%일 때부터 $Al_2$TiO$_{5}$가 생성되기 시작하였다. TiO$_2$첨가량에 따른 비표면적값은 첨가량이 7 wt%까지는 감소하였으나 그 이상 첨가시 증가하였다. 입도분석 결과 평균입경은 15.74~23.21$mu extrm{m}$로서 TiO$_2$첨가량이 3 wt%일 때 가장 작은 값을 가졌으며 TiO$_2$첨가량은 5 wt% 이상부터 점차 감소하였다.