• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.118-122
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• 2001

The ${\beta}-SiC+TiB_2$ ceramic electroconductive composites were pressureless-sintered and annealed by adding 12wt% $Al_2O_3+Y_2O_3$(6 : 4wt%) powder as a function of sintering temperature. The relative density is over 78.83% of the theoretical density and increased with increasing sintering temperature. The phase analysis of the composites by XRD revealed of $\alpha$-SiC(6H), $TiB_2$, $Al_5Y_2O_{12}$ and $\beta$-SiC(15R). Flexural strength showed the highest of 140 MPa for composites sintered at $1900^{\circ}C$. The vicker's hardness increased with increasing sintering temperature and showed the highest of 4.07 GPa at $1900^{\circ}C$. Owing to YAG, the fracture toughness showed the highest of 4.07 $MPa{\cdot}m^{1/2}$ for composites at $1900^{\circ}C$. The electrical resistivity was measured by the Pauw method from $25^{\circ}C$ to $700^{\circ}C$. The electrical resistivity of the composites showed the PTCR(Positive Temperature Coefficient Resistivity).

• 한국세라믹학회지
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• 제30권6호
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• pp.492-498
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• 1993

The pretreatment condition for uniform distribution of SiC whisker in A2O3-SiCw composites has been determined and the mechanical properties of the composites with various whisker contents have been measured. Good dispersion of the whisker can be obtained in a solution of pH=10.45 by ball milling and ultrasonic treatment. The relative density of hot pressed composites decreases with the whisker content up to 40vol%, but is found to be satisfactory, over 98% for all samples. The mechanical property of the composites is sensitive to the whisker dispersion. Uniform distributjion of the whisker is critical in order to guarantee good mechanical property.The samples containing 20~30vol% whisker show the best mechanical property within the studied range.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 유기절연재료 전자세라믹 방전플라즈마 연구회
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• pp.15-18
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• 2001

The composites were fabricated 61 vol% $\beta$-SiC and $39vol%TiB_2$ powders with the liquid forming additives of 8, 12, 16wt% $Al_2O_3+Y_2O_3$ by hot pressing at $1730^{\circ}C$ and subsequent pressed annealing and pressureless annealing at $1750^{\circ}C$ for 4 hours to form YAG. The result of phase analysis of composites by XRD revealed $\alpha$-SiC(6H), $TiB_2$, and YAG($Al_5Y_3O_{12}$) crystal phase. The relative density of composites were increased with increasing $Al_2O_3+Y_2O_3$ contents. The fracture toughness showed the highest value of $7.77MPa{\cdot}m^{1/2}$ for composites added with 12wt% $Al_2O_3+Y_2O_3$ additives at room temperature. The electrical resistivity and the resistance temperature coefficient showed the lowest of $7.3{\times}10^{-4}{\Omega}{\cdot}cm$ and $3.8{\times}10^{-3}/^{\circ}C$, respectively, for composite added with 12wt% $Al_2O_3+Y_2O_3$ additives at room temperature. The electrical resistivity of the composites was all positive temperature coefficient resistance(PTCR) in the temperature range of $25^{\circ}C$ to $700^{\circ}C$.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.46-49
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• 2003

Aluminum based metal matrix composites(MMCs) are well known for their high specific strength, stiffness and hardness. They are gaining further importance because of their high wear resistance. In this study, Al/Saffil-20%, Al/Saffil-5%/Al2O3(particle type)-15% and Al/Saffil-5%/SiC(particle type)-15% hybird MMCs' wear behavior were characterized by the pin-on-disk test under various normal load The superior wear resistance was exhibited at Al/Saffil-5%/SiC(particle type)-15% MMCs. And this MMCs' predominant wear mechanism is subsurface cracking in the low load wear regime. Others(Al/Saffil-20%, Al/Saffil-5%/Al2O3(particle type)-15%) showed the similar wear resistance with each other at the same test condition. In the low load & room temperature condition, the wear resistance was improved due to the high hardness of the ceramic reinforcements. As the test load increased, the wear properties were governed by the wear properties of matrix.

• 한국세라믹학회지
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• 제30권9호
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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.

• 한국세라믹학회지
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• 제27권8호
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• pp.1043-1049
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• 1990

In this work, strength of ceramic fibers and monofilament composites were evaluated on the basis of Weibull's theory. The fibers used were β-SiC and γ-Al2O3 monofilament composites was fabricated by coating Al on the fiber surface by the use of vacuum evaporation method. Average tensile strength of ceramic fibers showed the tendency to linearly decrease with increasing gauge length. Also, Weibull moduli of ceramic fibers were decreased with increasing gauge length, Weibull modulus of β-SiC was 3.5 for 6-50mm, 2.8 for 100-200mm. Weibull modulus of γ-Al2O3 was 6.5 for 20-50mm, 6 for 100mm. Fibers in monofilament retained their original as-produced strength to exposure temperature of 400℃. However, tensile strength of both monofilament composites approved to remarkably degrade due to interfacial reaction-induced flaws on the fiber surface after thermal exposure of 600℃. In this case, Weibull modulus of monofilament composites was 2.7 for β-SiC and 5.2 for γ-Al2O3 respectively.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권9호
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• pp.510-515
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• 2000

The mechanical and electrical properties of the hot-pressed and annealed $\beta-SiC-TiB_2$ electroconductive ceramic composites were investigated as a function of the liquid forming additives of Al_2O_3+Y_2O_34. The result of phase analysis of composites by XRD revealed $\alpha-SIC(6H)\;TiB_2,\; and YAG(Al5Y3O12) crystal phase. The relative density and the mechanical properties of composites were increased with increasing $Al_2O_3+Y_2O_34 contents because YAG of reaction between $Al_2O_3\; and\; Y_2O_3$ was increased. The Flexural strength showed the highest value of 432.5MPa for composites added with 12wt% $Al_2O_3+Y_2O_34 additives at room temperature. Owing to crack deflection crack bridging phase transition and TAG of fracture toughness mechanism the fracture toughness showed 7.1MPa.m1/2 for composites added with 12wt% $Al_2O_3+Y_2O_34 additives at room temperature. The electrical resistivity and the resistance temperature coefficient showed the lowest of $6.0\times10-4\Omega.cm\; and\; 3.1\times10-3/^{\circ}C4 respectively for composite added with 12wt% \Omega additives at room temperature. The electrical resistivity of the composites was all positive temperature coefficient resistance (PTCR) in the temperature range of $25^{\circ}C\; to\; 700^{\circ}C$.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 춘계학술발표대회 논문집
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• pp.29-33
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• 2001

In the present study, AZ91Mg/$\textrm{Al}_2\textrm{O}_3$ short fiber+SiC particulates hybrid metal matrix composites(MMCs) were fabricated by squeeze casting method. Different particulate sizes of 45, 29 and $9\mu\textrm{m}$ were hybridized with 5% volume fraction to investigate the effect of SiC particulates size on microstructure, mechanical and thermal properties such as hardness, flexural strength, wear resistance and thermal expansion. Results show that the microstructure of the hybrid composites were quite satisfactory, namely revealing relatively uniform distribution of reinforcements. Some aggregation of SiC particulates caused by particle pushing was observed especially in the hybrid composites containing in fine particulates($9\mu\textrm{m}$). The hardness and flexural strength were improved by decreasing particulates size, whereas wear resistance improved by increasing particulates size because of large particulates restricting matrix wear from contacted stress. Regardless of particulates size, thermal expansion of composites was the same. This may be because the content of particulates was in all cases 5 volume fraction.1

• 한국재료학회:학술대회논문집
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• 한국재료학회 1994년도 춘계 학술발표 강연 및 논문 개요집
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• pp.76-76
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• 1994

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제52권2호
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• pp.80-84
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• 2003

The mechanical and electrical properties of the hot-pressed and pressureless annealed SiC-Ti $B_2$electroconductive ceramic composites were investigated as functions of the liquid additives of $Al_2$ $O_3$+ $Y_2$ $O_3$. The result of phase analysis for the SiC-Ti $B_2$ composites by XRD revealed $\alpha$-SiC(6H), Ti $B_2$, and YAG(A $l_{5}$ $Y_3$ $O_{12}$ ) crystal phase. The relative density of SiC-Ti $B_2$ composites was increased with increased $Al_2$ $O_3$+ $Y_2$ $O_3$ contents. The fracture toughness showed the highest value of 6.04 Mpa $m^{\frac{1}{2}}$ for composites added with l2wt% A1$_2$ $O_3$+ $Y_2$ $O_3$ additives at room temperature. The electrical resistivity showed the lowest value of 6.2$\times$10$^{-3}$ $\Omega$ㆍcm for composite added with l6wt% $Al_2$ $O_3$+ $Y_2$ $O_3$ additives at room temperature. The electrical resistivity of the SiC-Ti $B_2$ composites was all positive temperature cofficient resistance(PTCR) in the temperature ranges from $25^{\circ}C$ to $700^{\circ}C$.