• Journal of the Korean Ceramic Society
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• 제55권4호
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• pp.392-399
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• 2018

$C_f/SiC$ composites were prepared via a process combining chemical vapor infiltration (CVI) and precursor infiltration pyrolysis (PIP), wherein silicon carbide matrices were infiltrated into 2.5D carbon preforms. The obtained composites exhibited porosities of 20 vol % and achieved strengths of 244 MPa in air at room temperature and 423 MPa at $1300^{\circ}C$ under an Ar atmosphere. Carbon fiber pull-out was rarely observed in the fractured surfaces, although intermediate layers of pyrolytic carbon of 150 nm thickness were deposited between the fiber and matrix. Fatigue fracture was observed after 1380 cycles under 45 MPa stress at $1000^{\circ}C$. The fractured samples were analyzed by transmission electron microscopy to observe the distributed phases.

• Journal of the Korean Ceramic Society
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• 제34권9호
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• pp.993-1001
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• 1997

The (0.8PPV+0.2DMPPV) copolymer and silica/borosilicate composites were synthesized by sol-gel process. The organic-inorganic hybrid solution was prepared by using of (0.8PPV+0.2DMPPV) copolymer precursor solution as a raw material for organic components and TEOS and TMB for glass components. Then by drying the solution in vacuum at 5$0^{\circ}C$ for 7days and subsequent heat treatment in vacuum at 15$0^{\circ}C$~30$0^{\circ}C$ for 2h~72h with heating rate of 0.2$^{\circ}C$/min and 1.8$^{\circ}C$/min, the organic-inorganic composites were synthesized. Microstructural evolution of the composites was characterized by DSC, IR spectrocopy, UV/VIS spectroscopy, and TEM. Elimination of the polymer precursor and degradation of the polymer were observed by DSC and Si-O and trans C=C absorption peaks were identified by IR spectra. The polymer was found to be successfully incorporated into the glass matrix and it was confirmed by the absorption peaks from the polymer in the UV/VIS spectra and the TEM results. The absorption peak of the composites was found to shift toward short wavelength side compared to that of the pure polymer and the amount of the blue shift increased with increasing the heat treatment temperature and heat treatment time and with decreasing the heating rate.

• Journal of the Korean Ceramic Society
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• 제38권4호
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• pp.314-318
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• 2001

SiC-TiC composites have been fabricated by using a mechanochemical processing of a mixture of Si, Ti, and C at room temperature and subsequent hot pressing. TiC powders have been obtained by the mechanochemical processing of a mixture of Ti and C whereas SiC powders has not been obtained from a mixture of Si and C. By using the exothermic reaction between Ti and C, SiC-TiC powder could be obtained from the mixture of Si, Ti, and C using the mechanochemical processing for more than 12h. The X-ray diffraction analysis has shown that the powder subjected to the mechanochemical processing consisted of the particles having crystallite size below 10nm. Fully densified SiC-TiC composites have been obtained by hot-pressing of the powder at 1850$\^{C}$ for 3h and it has shown comparable mechanical properties to those of the SiC-TiC composites prepared from the commercially available SiC and TiC powders. Flexural strength of 560 MPa and fracture toughness of 4.8 MP$.$am$\_$1/2/ have been shown for the SiC-TiC composites with composition corresponding to 0.75:0.25:1 mole ratio of Si:Ti:C.

• Journal of the Korean Ceramic Society
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• 제46권5호
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• pp.484-487
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• 2009

$SiC_f$/SiC composites with whiskers and pyrolytic carbon (PyC) coated whiskers in the matrix were fabricated for enhancement of the fracture behaviors by the whisker growing assisted chemical vapor infiltration (WA-CVI) process, respectively. $SiC_f$/SiC composites were also prepared by the conventional CVI process as reference material. The mechanical properties and fracture behaviors were analyzed by comparison of the two types of composites prepared by WA-CVI and conventional CVI. The densities of $SiC_f$/SiC composites were in the range of $2.6{\sim}2.65g/cm^3$. The flexural strengths of composite with whiskers and with those coated by PyC were 650 MPa and 600 MPa, respectively. The tensile strength of composites with whiskers was ${\sim}285$ MPa.

• Journal of the Korean Ceramic Society
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• 제40권3호
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• pp.229-233
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• 2003

By using an oxynitride glass as a sintering additive, the effects of BN content on microstructure and mechanical properties of the hot-pressed and subsequently annealed SiC-BN composites were investigated. The microstructures developed were analyzed by image analysis. The morphology of SiC grains was strongly dependent on BN content in the starting composition. The aspect ratio of SiC decreases with increasing BN content and the average diameter of SiC shows a maximum at 5 wt% BN and decreases with increasing BN content in the starting powder. The fracture toughness increased with increasing BN content while the strength decreased with increasing BN content. The strength and fracture toughness of SiC or SiC-TiC composites were strongly dependent on the morphology of SiC grains, but the strength and fracture toughness of SiC-BN composites were strongly dependent on BN content rather than morphology of SiC grains. These results suggest that fracture toughness of SiC ceramics can be tailored by manipulating BN content in the starting composition. Typical fracture toughness and strength of SiC-10 wt% BN composites were 8 MPa$.$m$\^$1/2/ and 445 MPa, respectively.

• Journal of the Korean Ceramic Society
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• 제26권5호
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• pp.617-624
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• 1989

Piezoelectric composites of O-3 connectivity were prepared by thermosetting barium titanate-phenolic resin composite under various cruing pressure. Among three kinds of pore in O-3 type ceramic-polymer composite, such as matrix pores, particle pores, and ceramic-polymer interface pores, the effect of interface porosity on the dielectric and piezoelectric constant was investigated. In pure barium titanate ceramics, the porosity factor of dielectric and piezoelectric constants were 5.7 and 5.0, respectively. However, in BaTiO3-polymer composite, the interface porosity factor of the piezoelectric constant was greater than that of the dielectric constant, interface porosity factor b in d33 was 9.8 and in r 4.6. On the other, piezoelectric voltage constant g33 was independent of the porosity of barium titanate ceramics. But in composite system, the piezoelectric voltage constant g33 was decreased with interface porosity.

• The Korean Journal of Ceramics
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• 제4권3호
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• pp.227-230
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• 1998

Alumina($Al_2O_3$)-Titanium Diboride($TiB_2) particulate composites were fabricated by hot pressing of the powder mixture that was prepared from Self-propagating High Temperature Synthesis (SHS) product and commercial powders. Their propeties were examined in order to find feasibility of using SHS for making the high performance ceramic composite. $TiB_2 particles obtained by grinding the SHS product were finer than the commercial powders. Hot pressed sample containing the SHS products exhibited higher strength than the one prepared from the commercial powders.

• Journal of the Korean Ceramic Society
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• 제27권1호
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• pp.102-108
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• 1990

WC-Co composites are widely used as cutting or drilling tools because of their high hardness, strength, and fracture toughness. The working temperature is, however, generally in the range of 300-$700^{\circ}C$ so thermal shock fracture of WC-Co can occur. In this study, the strength, fracture toughness and fracture surface of 16wt% Co bonded tungsten carbide composites before and after thermal shock were observed.

• Journal of Applied Reliability
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• 제1권1호
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• pp.17-33
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• 2001

The characteristics of Weibull distribution are investigated as a function of shape parameter. The statistical estimation methods of the shape parameter and statistical comparison methods of two or more shape parameters are studied. Assuming Weibull distribution, statistical analysis of bending-strength data of alumina titanium carbide ceramic matrix composites machined two different methods are performed.

• Proceedings of the KIEE Conference
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1252_1253
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• 2009

The composites were fabricated by adding 0, 15, 20, 25[vol.%] Zirconium Diboride(hereafter, $ZrB_2$) powders as a second phase to Silicon Carbide(hereafter, SiC) matrix. The physical, mechanical and electrical properties of electroconductive SiC ceramic composites by spark plasma sintering(hereafter, SPS) were examined. Reactions between $\beta$-SiC and $ZrB_2$ were not observed in the XRD analysis The relative density of mono SiC, SiC+15[vol.%]$ZrB_2$, SiC+20[vol.%]$ZrB_2$ and SiC+25[vol.%]$ZrB_2$ composites are 90.97[%], 74.62[%], 77.99[%] and 72.61[%] respectively. The XRD phase analysis of the electroconductive SiC ceramic composites reveals high of SiC and $ZrB_2$ and low of ZrO2 phase. The electrical resistivity of mono SiC, SiC+15[vol.%]$ZrB_2$, SiC+20[vol.%]$ZrB_2$ and SiC+25[vol.%]$ZrB_2$ composites are $4.57{\times}10^{-1}$, $2.13{\times}10^{-1}$, $1.53{\times}10^{-1}$ and $6.37{\times}10^{-2}[{\Omega}{\cdot}cm]$ at room temperature, respectively. The electrical resistivity of mono SiC, SiC+15[vol.%]$ZrB_2$, SiC+20[vol.%]$ZrB_2$ and SiC+25[vol.%]$ZrB_2$ are Negative Temperature Coefficient Resistance(hereafter, NTCR) in temperature ranges from 25[$^{\circ}C$] to 100[$^{\circ}C$]. It is convinced that SiC+20[vol.%]$ZrB_2$ composite by SPS can be applied for heater above 1000[$^{\circ}C$].