• Title/Summary/Keyword: $Al_2O_3/SiC$

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Fabrication of $Al_2O_3/SiC$ Composite Through Oxidation of SiC (SiC의 산화에 의한 $Al_2O_3/SiC$ 복합체의 제조)

  • 김경환;이홍림;이형민;홍기곤
    • Journal of the Korean Ceramic Society
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    • v.34 no.5
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    • pp.535-543
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    • 1997
  • The surface of SiC particles were partially oxidized to produce SiO2 layers on the SiC particles to prepare Al2O3/SiC composite by formation of mullite bonds between the grains of Al2O3 and SiC during sintering at 1$600^{\circ}C$. This process is considered to enable the sintering of Al2O3/SiC composite at lower temperature and also to relieve the stress, produced by thermal expansion mismatch between Al2O3 and SiC. In fact, Al2O3/SiC composite prepared by oxidation of SiC was observed to be more effectively sintered and densified at lower temperature. Maximum density, flexural strength and microhardness were obtained with 5.65 vol% of mullite content in Al2O3/SiC composite.

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Fabrication of $Al_2O_3$/SiC Hybrid-Composite ($Al_2O_3$/SiC Hybrid-Composite의 제조)

  • Lee, Su-Yeong;Im, Gyeong-Ho;Jeon, Byeong-Se
    • 연구논문집
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    • s.26
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    • pp.103-112
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    • 1996
  • $Al_2O_3/SiC$ Hybrid-Composite has been fabricated by conventional powder process. The addition of $\alpha-Al_2O_3$ as seed particles in the transformation of $\gamma-Al_2O_3 to $\alpha-Al_2O_3$ provided a homogeneity of the microstructure, resulting in increase of mechanical properties. The grain growth of $Al_2O_3$ are significantly surpressed by the addition of nano-sized. SiC particles, increasing in fracture strength. The addition of SiC plates to $Al_2O_3$ nano-composite decreased the fracture strength, but increased the fracture toughness. Coated SiC plates with nitrides such as BN and /SiC$Si_3N_4$ enhanced fracture toughness much more than uncoated SiC plates by inducing crack deflection.

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R-Curve Behavior and Mechanical Properties of Al2O3 Composites Containing SiC and TiC Particles (SiC와 TiC 입자를 함유하는 Al2O3 입자복합체의 균열저항거동과 기계적 성질)

  • Na, Sang-Woong;Lee, Jae-Hyung
    • Journal of the Korean Ceramic Society
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    • v.39 no.4
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    • pp.413-419
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    • 2002
  • Particulate composites of $Al_2O_3$/TiC/SiC, $Al_2O_3$/TiC and $Al_2O_3$/SiC have been fabricated by hot pressing and their R-curve behaviors and mechanical properties were investigated. $Al_2O_3$ containing 30 vol% TiC particles showed higher toughness by 8% than that for monolithic alumina and its fracture strength was increased significantly by approximately 30%. On the other hand, the addition of 30 vol% SiC of $3{\mu}m$ in $Al_2O_3$ decreased the fracture strength slightly but induced a rising R-curve behavior owing to the strong crack bridging of SiC particles. In case of $Al_2O_3$/TiC/SiC, arising R-curve behavior was also observed and the fracture toughness reached 6.6 MPa${\cdot}\sqrt{m}$ at the crack length of $1000{\mu}m$, which was lower than that of $Al_2O_3$/SiC, however, while the fracture strength was higher by about 20%. The fracture toughness seemed to be decreased as smaller TiC particles roughened the SiC interface and pullout of the SiC particles for crack bridging became less active.

The effect of the addition of TiO2 in the preparation of (Al2O3-SiC)- SiC composite powder by SHS Process (SHS법을 이용한 복합분말(Al2O3-SiC) 제조시 TiO2첨가의 영향)

  • Yun, Gi-Seok;Yang, Beom-Seok;Lee, Jong-Hyeon;Won, Chang-Hwan
    • Korean Journal of Materials Research
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    • v.12 no.1
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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 $5{\mu}m$.

Properties of Al2O3-SiCw Composites Fabricated by Three Preparation Methods (제조방법에 따른 Al2O3-SiCw 복합체의 특성)

  • Lee, Dae-Yeop;Yoon, Dang-Hyok
    • Journal of the Korean Ceramic Society
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    • v.51 no.5
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    • pp.392-398
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    • 2014
  • $Al_2O_3$-SiC composites reinforced with SiC whisker ($SiC_w$) were fabricated using three different methods. In the first, $Al_2O_3-SiC_w$ starting materials were used. In the second, $Al_2O_3-SiC_w$-SiC particles ($SiC_p$) were used, which was intended to enhance the mechanical properties by $SiC_p$ reinforcement. In the third method, reaction-sintering was used with mullite-Al-C-$SiC_w$ starting materials. After hot-pressing at $1750^{\circ}C$ and 30 MPa for 1 h, the composites fabricated using $Al_2O_3-SiC_w$ and $Al_2O_3-SiC_w-SiC_p$ showed strong mechanical properties, by which the effects of reinforcement by $SiC_w$ and $SiC_p$ were confirmed. On the other hand, the mechanical properties of the composite fabricated by reaction-sintering were found to be inferior to those of the other $Al_2O_3$-SiC composites owing to its relatively lower density and the presence of ${\gamma}-Al_2O_3$ and ${\gamma}-Al_{2.67}O_4$. The greatest hardness and $K_{1C}$ were 20.37 GPa for the composite fabricated using $Al_2O_3-SiC_w$, and $4.9MPa{\cdot}m^{1/2}$ using $Al_2O_3-SiC_w-SiC_p$, respectively, which were much improved over those from the monolithic $Al_2O_3$.

Mechanical Properties of 2024/(Al2O3.SiC)p Composite Reinforced with Al2O3.SiC Particle Prepared by SHS Process (자전연소법으로 제조한 Al2O3.SiC 입자로 보강된2024/(Al2O3.SiC)p 복합재료의 기계적특성)

  • 맹덕영
    • Journal of Powder Materials
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    • v.7 no.1
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    • pp.35-41
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    • 2000
  • Al2O3$.$SiC particle was prepared was prepared by the self-propagting high temperature sYthesis(SHS) process from a mixture of SiO2, Al and C powders, The fabricated Al2O3$.$SiC particle was applied to 2024Al/(Al2O3$.$SiC)pcomposite as a reinforcement. Aluminum matix composites were fabricares by the powder extrusion method using the synthesized Al2O3$.$SiC particle and commercial 2024Al powder. Theoptimum preparation conditions for Al2O3$.$SiC partticle by SHS process were described. The influence of the Al2O3$.$SiC voiume fraction on the mechanical was composite was also discussed. Despite adiabatic temperature was about 2367K, SHs reaction was completed not by itself, but by using pre-heating. Mean particle size of final particle synthesized was 0.73 ${\mu}$m and most of the particle was smaller than 2${\mu}$m. Elastic modulus and tensile strength of the composite increased with increase the volume fraction of reinforcement but, tensile strength depreciated at 30 vol% of reinforcement.

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The Effect of Nitride Coating on SiC Platelet in $Al_2O_3/SiC$ Hybrid-Composite ($Al_2O_3/SiC$ Hybrid-Composite에서 SiC에 질화물 코팅의 영향)

  • 이수영;임경호;전병세
    • Journal of the Korean Ceramic Society
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    • v.34 no.4
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    • pp.406-412
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    • 1997
  • Al2O3/SiC hybrid-composite has been fabricated by the conventional powder process. The addition of $\alpha$-Al2O3 as seed particles in the transformation of ${\gamma}$-Al2O3 to $\alpha$-Al2O3 provided a homogeneity of the microstructure. The grain growth of Al2O3 are significantly surpressed by the addition of nano-size SiC particles. Dislocation were produced due to the difference of thermal expansion coefficient between Al2O3 and SiC and piled up on SiC particles in Al2O3 matrix, resulting in transgranular fracture. The high fracture strength of the composite was contributed to the grain refinement and the transgranular fracture mode. The addition of SiC platelets to Al2O3/SiC nano-composite decreased the fracture strength, but increased the fracture toughness. Coated SiC platelets with nitrides such as BN and Si3N4 enhanced fracture toughness much more than non-coated SiC platelets by enhancing crack deflection.

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Mechanical Properties and Wear Behaviour of $Al/SiC/Al_{2}O_{3}$ Composite Materials ($Al/SiC/Al_{2}O_{3}$복합재료의 기계적 성질 및 마멸특성)

  • 임흥준;김영한;한경섭
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.10
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    • pp.2498-2508
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    • 1993
  • $Al/SiC/Al_{2}O_{3}$ hybrid composites are fabricated by squeeze infiltration method. From the misconstructive of $Al/SiC/Al_{2}O_{3}$ hybrid composites fabricated by squeeze infiltration method, uniform distribution of reinforcements and good bondings are found. Hardness value of $Al/SiC/Al_{2}O_{3}$ hybrid composites increases linearly with the volume fraction of reinforcement because SiC whisker and $Al_{2}$O$_{3}$ fiber have an outstanding hardness. Optimal aging conditions are obtained by examining the hardness of $Al/SiC/Al_{2}O_{3}$ hybrid composites with different aging time. Tensile properties such as Young's modulus and ultimate tensile strength are improved up to 30% and 40% by the addition of reinforcements, respectively. Failure mode of $Al/SiC/Al_{2}O_{3}$ hybrid composites is ductile on microstructural level. Through the abrasive wear test and wear surface analysis, wear behaviour and mechanism of 6061 aluminum and $Al/SiC/Al_{2}O_{3}$ hybrid composites are characterized under various testing conditions. The addition of SiC whisker to $Al/SiC/Al_{2}O_{3}$ composites gives rise to improvement of the wear resistance. The wear resistance of $Al/SiC/Al_{2}O_{3}$ hybrid composites is superior to that of Al/SiC composites. The wear mechanism of aluminum alloy is mainly abrasive wear at low speed range and adhesive and melt wear at high speed range. In contrast, that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is abrasive wear at all speed range, but severe wear when counter material is stainless steel. As the testing temperature increases, wear loss of aluminum alloy decreases because the matrix is getting more ductile, but that of $Al/SiC/Al_{2}O_{3}$ hybrid composites is hardly varied. Oil lubricant is more effective to reduce the wear loss of aluminum alloy and $Al/SiC/Al_{2}O_{3}$ hybrid composites at high speed range.

Study on the R-curve Behaviour in $Al_2O_3-ZrO_2-SiC$ Whisker Comosite ($Al_2O_3-ZrO_2-SiC$ Whisker 복합재료에서의 R-curve 거동에 관한 연구)

  • Kim, Hyun-Ha;Park, Hyun;Choi,Sung-Churl
    • Journal of the Korean Ceramic Society
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    • v.30 no.9
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    • pp.731-739
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    • 1993
  • R-curve measurements were performed on Al2O3(matrix)-ZrO2-SiC whisker composite and Al2O3-ZrO2, Al2O3-SiC whisker composites in the favor of comparing the effect of ZrO2 and SiC whisker, as a second phase, to Al2O3 matrix. Al2O3-SiC whisker and Al2O3-ZrO2-SiC whisker were fabricated by hot pressing at 1$700^{\circ}C$, 15MPa and Al2O3-ZrO2 by pressureless sintering at 1$600^{\circ}C$. A controlled flaw/strength technique was utilized to determine fracture resistance as a function of crack extension and R-curve behaviour was determined from the relationship which is KR=K0(Δa)m. R-curveresults were KR=6.173$\times$Δa0.031 for Al2O3-ZrO2, KR=18.796$\times$Δa0.172 for Al2O3-SiC whisker and KR=11.96$\times$Δa0.110 for Al2O3-ZrO2-SiC whisker composite. From the analysis of R-curve and expeirmental data above three composites, it is found that R-curve behaviour of Al2O3-ZrO2-SiC whisker composite was dominated initially by the strengthening effect of ZrO2 and after, some extended crack were influenced by the effect of SiC whisker. Analysis of SEM and X-ray data revealed that whisker bridging in the crack wake and whisker pull-out mechanisms were the main mechanism for the R-curve behaviour.

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Synthesis and Properties of $Al_2O_3-SiC$ Composites from Alkoxides II. Synthesis of Coated Type $Al_2O_3-SiC$ Composite Powders (알콕사이드로부터 $Al_2O_3-SiC$ 복합재료의 제조 및 특성 II. 피복형 $Al_2O_3-SiC$ 복합분말의 합성)

  • 이홍림;김규영
    • Journal of the Korean Ceramic Society
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    • v.30 no.3
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    • pp.243-249
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    • 1993
  • Coated type Al2O3-SiC composite powders were synthesized by surface modification method. Transformation temperature to $\alpha$-Al2O3 of Al2O3 monolith was 115$0^{\circ}C$ whereas increased to 1200, 1250, 130$0^{\circ}C$ with increment of SiC content to 5, 15, 25wt%. Transformation temperature to $\alpha$-Al2O3 was lowered by $\alpha$-Al2O3 seeding. FTIR data analysis and electron micrographs showed that Al2O3 particles were effectively coated on SiC particles.

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