• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.798-803
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• 2018

In order to use Si as an anode material for lithium-ion battery, the particle size was controlled to less than $0.5{\mu}m$ and carbon was coated on the surface with the thickness less than 10 nm. The carbon fiber was grown on the Si surface with 50~150 wt%, and the carbon coating was carried out once again. The Si composite material was mixed with dissimilar metals to increase the conductivity, and graphite was mixed to improve cyclic life characteristics. The physical and electrochemical characteristics of composite materials were measured with XRD, SEM, TEM and coin cell. The discharge capacity of Si/PC/CNF/PC was lower than that of Si/PC (Pyrolytic Carbon)/CNF (Carbon Nano Fiber). However, the cyclic life of Si/PC/CNF/PC was higher. Initial discharge capacity of 1512 mA h g-1 at 0.2 C rate and initial efficiency of 78% were shown. It also showed a capacity retention of 94% in 10 cycles.

• Journal of the Korean Ceramic Society
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• v.55 no.5
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• pp.498-503
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• 2018

Using the thermal ablation method, the oxidation behavior of $SiC_f/SiC$ composites was investigated in air and in the temperature range of $1,300^{\circ}C$ to $2,000^{\circ}C$. At the relatively low temperature of $1,300^{\circ}C$, passive oxidation, which formed amorphous phase, predominantly occurred in the thermal ablation test. When the oxidation temperature increased, SiO (g) and CO (g) were formed by active oxidation and the dense oxide layer changed to a porous one by vaporization of gas phases. In the higher temperature oxidation test, both active oxidation due to $SiO_2$ decomposition on the surface of the oxide layer and active/passive oxidation transition due to interfacial reaction between oxide and base materials such as SiC fiber and matrix phase simultaneously occurred. This was another cause of high temperature degradation of $SiC_f/SiC$ composites.

• Journal of the Korean Society of Safety
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• v.19 no.4 s.68
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• pp.25-30
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• 2004

Unidirectional fiber-metal matrix composites have superior mechanical properties along the longitudinal direction. However, the applicability of continuous fiber reinforced MMCs is somewhat limited due to their relatively poor transverse properties. Therefore, the transverse properties of MMCs are significantly influenced by the properties of the fiber/matrix interface. In this study, the interfacial stress states of transversely loaded unidirectional fiber reinforced metal matrix composites investigated by using elastic-plastic finite element analysis. Different fiber volume fractions $(5-60\%)$ were studied numerically. The interface was treated as thin layer (with different properties) with a finite thickness between the fiber and the matrix. The fiber is modeled as transversely isotropic linear-elastic, and the matrix as isotropic elastic-plastic material. The analyses were based on a two-dimensional generalized plane strain model of a cross-section of an unidirectional composite by the ANSYS finite element analysis code.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.1
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• pp.23-30
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• 2014

The wear characteristics of $SiC_f$/SiC composites were evaluated according to the alignment direction of the fibers, and the elastic wave-generated friction was detected and analyzed in wearing. The friction coefficient and wear loss were similar in the longitudinal and the transverse direction of the fibers. However, these values were lower in the vertical direction of the fibers because of the brittle nature of the fiber. The friction coefficient and the wear loss were directly proportional to each other. The dominant frequencies were 58.6 kHz for monolithic SiC and 117.2 and 136.7 kHz for $SiC_f$/SiC composites, respectively.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.569-575
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• 2000

Fabrication of carbon fiber reinforced composites was carried out by hand lay-up method. Carbon nanofibers and SiC nanofibers were used as filler in the composites fabrication. Carbon nanofibers, one of the new carbon materials, have 5∼500 nm in diameter and 5-10 nm in length. SiC nanofibers were modified by silicon monoxide vapor with carbon nanofibers. The composites were carbonized at 1000$^{\circ}C$ in a nitrogen atmosphere, and then densified by molten pitches impregnated in vacuum. Multiple cycles of liquid pitch impregnation and carbonization were carried out to obtain a desired density. The composites were characterized by density, microstructure. The inter-laminar shear strength (ILSS) test was performed for mechanical properties. For the new application, the microwave reflective proeprty of composites was investigated. Dielectric constant and permeability spectrum were measured in 12∼18 GHz frequency ranges. On the basis of the wave propagation theory in a lossy media, the reflection loss from the composite inter-layer was predict as a function of frequency.

• Journal of Ceramic Processing Research
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• v.21 no.1
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• pp.113-118
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• 2020

The fabrication of continuous carbon fiber-reinforced carbon-silicon carbide matrix (Cf/C-SiC) cross-ply composites is highly attractive from a practical viewpoint due to their homogeneous microstructures and isotropic mechanical properties. However, the properties of Cf/C-SiC composites depend significantly on their processing conditions and temperatures, especially the pyrolysis conditions and temperatures. In this study, cross-ply Cf/C-SiC composites were fabricated using different pyrolysis protocols with phenolic resin via a liquid silicon infiltration. The effects of the pyrolysis conditions on the microstructures of the composites and their mechanical properties as well as on crack formations were evaluated at room temperature. Pyrolysis was performed at 600 ℃ for 1 h in a nitrogen atmosphere at different heating rates. The flexural strength varied from a minimum of 47 ± 3 MPa to a maximum of 62 ± 6 MPa (~ 35% increase) depending on the pyrolysis conditions.

• Composites Research
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• v.22 no.5
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• pp.15-23
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• 2009

The lubricant tribological characteristics of $Al_2O_3$ fiber and SiC particle hybrid metal matrix composites (MMCs) fabricated by squeeze casting method was investigated using a pin-on-disk wear tester. The wear tests of the MMCs were performed according to fiber/particle hybrid ratio in the planar-random (PR) and normal (N) orientations sliding against a counter steel disk at a fixed speed and $25\;kg_f$ loading under different sliding distances and temperatures. The test results showed that the wear behavior of MMCs varied with fiber orientation and hybrid ratio. At room temperature, the lubricant wear behavior of F20P0 unhybrid PR-MMCs was superior to that of N-MMCs while the hybrid composites exhibited the reverse lubricant wear behavior. It was also revealed that the wear resistance of PR-MMCs was superior to that of the N-MMCs due to the joint action of reinforcements and lubricant film between the friction surfaces at an elevated temperature of $100^{\circ}C$ for both fiber only and hybrid cases. In case of $150^{\circ}C$, although the trend of weight loss was similar to that of others, the wear resistance of PR-MMCs was better than that of N-MMCs for hybrid MMCs.

• Journal of the Korean Ceramic Society
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• v.27 no.8
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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.

• Korean Journal of Materials Research
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• v.14 no.9
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• pp.649-654
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• 2004

In this paper, the fracture toughness and mechanisms of failure in a random SiC-whisker/$Al_{2}O_3$ ceramic composite were investigated using in situ observations during mode I(opening) loading. $SiC_{w}/Al_{2}O_3$ composite was obtained by hot press sintering of $Al_{2}O_3$ powder and SiC whisker as the matrix and reinforcement, respectively. The whisker and powder were mixed using a turbo mill. The composite was produced at SiC whisker volume fraction of $0.3\%$. Compared with monolithic $Al_{2}O_3$, fracture toughness enhancement was observed in $SiC_{w}/Al_{2}O_3$ composite. This improved fracture toughness was attributed to SiC whisker bridging and crack deflection. $SiC_{w}/Al_{2}O_3$ composite exhibited typically brittle fracture behavior, but a fracture process zone was observed in this composite. This means that the load versus load-line displacement curve of $SiC_{w}/Al_{2}O_3$ composite from a fracture test may involve a small non-linear region near the peak load.

• Composites Research
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• v.23 no.2
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• pp.10-16
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• 2010

$Al_2O_3$ fiber and SiC particle hybrid metal matrix composites (MMCs) were manufactured by squeeze casting method investigated for their tribological properties. The pin specimens had different ratios of fiber to particle content but their total weight fraction was constant at 20 wt. %. Tribological tests were performed with a pin-on-disk friction and wear tester. The investigation of the dry tribological characteristics of hybrid MMCs were carried out at room temperature and elevated temperature of$100^{\circ}C$ and$150^{\circ}C$. The morphologies of worn surfaces were examined by scanning electron microscope (SEM) to observe tribological characteristics and investigate wear behavior. The results revealed that the wear resistance improved with the content of SiCp increased of the planar random (PR) MMCs at room temperature. At the elevated temperature, it revealed that the wear resistance of normal (N) MMCs was superior to that of the PR-MMCs due to PR-fibers were easily pulled out holistically from the worn surface. Meanwhile, the coefficient of friction decreased with the temperature increasing.