• 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.

• Korean Journal of Materials Research
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• v.21 no.5
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• pp.288-294
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• 2011

Simultaneous Ni and C codeposition by electrolysis was investigated with the aim of obtaining better corrosion resistivity and surface conductivity of a metallic bipolar plate for application in fuel cells and redox flow batteries. The carbon content in the Ni-C composite plate fell in a range of 9.2~26.2 at.% as the amount of carbon in the Ni Watt bath and the roughness of the composite were increased. The Ni-C composite with more than 21.6 at.% C content did not show uniformly dispersed carbon. It also displayed micro-sized defects such as cracks and crevices, which result in pitting or crevice corrosion. The corrosion resistance of the Ni-C composite in sulfuric acid is similar with that of pure Ni. Electrochemical test results such as passivation were not satisfactory; however, the Ni-C composite still displayed less than $10^{-4}$ $A/cm^2$ passivation current density. Passivation by an anodizing technique could yield better corrosion resistance in the Ni-C composite, approaching that of pure Ni plating. Surface resistivity of pure Ni after passivation was increased by about 8% compared to pure Ni. On the other hand, the surface resistivity of the Ni-C composite with 13 at.% C content was increased by only 1%. It can be confirmed that the metal plate electrodeposited Ni-C composite can be applied as a bipolar plate for fuel cells and redox flow batteries.

• Journal of Welding and Joining
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• v.15 no.6
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• pp.96-104
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• 1997

The present study was aimed to correlate the microstructure and the hardness as well as the wear resistance of the metal-ceramic particulated composite layer on the pure Al plate. The composite layers were constructed by the addition of TiC particles on the surface of Al-Cu alloyed layers by PTA overlaying process. Initially, the Al-Cu alloyed layers were achieved by the deposition of Al-(25 ~ 48%) Cu alloys on the pure Al plate by TIG process. It was revealed that TiC particles were uniformly dispersed without any reaction with matrix in the composite layer. The volume fraction of TiC particles (TiC V F) increased from 12% to 55% with increasing the number of pass of composite layer. Hardnesses of (Al-48%Cu + TiC (3&4layers)) composite layer were Hv450 and Hv560, respectively, due to the increase of TiC V/F. Hardnesses of (Al-Cu + TiC) composite layers decreased gradually with insreasing temperature from 100$^{\circ}$C to 400$^{\circ}$C, and hardnesses at 400$^{\circ}$C were then reached to 1/5 - 1/10 of room temperature hardness depending on the construction of composite layers. The Specific wear of (Al + Tic) layer and Al-48%Cu alloyed layer decreased to 1/10 of the of pure Al, while the specific wear of (Al-48%Cu + TiC (4 layers)) composite layer exhibited 1/15 of that of steel such as SS400 and STS304.

• Composites Research
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• v.26 no.2
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• pp.111-115
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• 2013

Aluminum-based composites containing $C_{60}$-fullerenes are produced by hot rolling of ball-milled powder. The grain size of aluminum is effectively reduced to ~100 nm during ball-milling processes, leading to grain refinement strengthening of the composite. Furthermore, $C_{60}$-fullerenes are gradually dispersed during ball-milling processes and hence the strength of the composite increases with the volume of $C_{60}$-fullerenes. The composite containing 10 vol% $C_{60}$-fullerenes with a grain size of ~ 100 nm exhibits ~1 GPa of compressive strength.

• Journal of the Korean Ceramic Society
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• v.30 no.4
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• pp.316-324
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• 1993

Three types of dispersed, coated and mechanically mixed SiC reinforced Al2O3 composite powders were used to investigate the effect of composite powder type on sintering characteristics and properties of Al2O3-SiC composites. Sinterability of coated type composite powders was superior to that of other composite powders when they were pressureless sintered at 1500~1$700^{\circ}C$ for 2h in Ar atmosphere. However, sinterabilities (>98% TD) of each type of composite powders were similar when they were hot pressed at 180$0^{\circ}C$ for 1h under 30MPa in N2 atmosphere. SiC powders were randomly distributed in the specimen prepared from dispersed type composite powders, whereas homogeneously distributed for coated type specimens. It was found that SiC powders inhibited the grain growth of Al2O3, and fracture toughness was increased by the increment of crack growth resistance due to residual stress by secondary SiC particles within Al2O3 grains.

• Proceedings of the KAIS Fall Conference
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• 2001.05a
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• pp.91-94
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• 2001

Powder Metallurgy method have been used to fabricate TiC base composite with ferrous binder. TiC base composite has versatile hardness and is usable as sintered, or after heat treatment as required by the given applications. Smooth, round TiC grains impart high wear resistance and lubricity as well known characteristics of this composite. Annealed composite can be formed by conventional machining and be hardened up to 70 H$\_$R/C in vacuum. The optimizing fabrication process enables this composite to improve mechanical properties in heat, wear and corrosion environments. This study has examine the relationship between fabrication condition and mechanical property in TiC-Cr-Mo-Fe Composite.

• Journal of Powder Materials
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• v.21 no.6
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• pp.415-421
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• 2014

W-10vol.%ZrC composites reinforced by micrometric and nanosized ZrC particles were prepared by hot-pressing of 25 MPa for 2 h at $1900^{\circ}C$. The effect of ZrC particle size on microstructure and mechanical properties at room temperature and elevated temperatures was investigated by X-ray diffraction analysis, scanning electron microscope and transmission electron microscope observations and the flexural strength test of the W-ZrC composite. Microstructural analysis of the W-ZrC composite revealed that nanosized ZrC particles were homogeneously dispersed in the W matrix inhibiting W grain growth compared to W specimen with micrometric ZrC particle. As a result, its flexural strength was significantly improved. The flexural strength at room temperature for W-ZrC composite using nanosized ZrC particle being 740 MPa increased by around 2 times than that of specimen using micrometric ZrC particle which was 377 MPa. The maximum strength of 935 MPa was tested at $1200^{\circ}C$ on the W composite specimen containing nanosized ZrC particle.

• Journal of the Korean Society of Safety
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• v.33 no.1
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• pp.1-6
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• 2018

The effects of the fiber direction, specimen size and temperature on the compressive strength of carbon fiber reinforced silicon carbide composite (C/SiC composite) manufactured by liquid silicon infiltration(LSI) is investigated. Tests were conducted in accordance with ASTM C 695 at room temperature and elevated temperatures. Experiments are conducted with two different specimens considering grain direction. With grain (W/G) specimens have a carbon fibers parallel to the load direction, but across grain (A/G) specimens have a perpendicular carbon fibers. To verify the specimen size effect of C/SiC composite, two types of specimens are manufactured. One has a one to two ratio of diameter to height and the other has a one to one ratio. The compressive strength of C/SiC composite increased as temperature rise. As specimens are larger, compressive strength of A/G specimens increased, however compressive strength of W/G decreased.

• 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.

• Journal of Korea Foundry Society
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• v.18 no.6
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• pp.593-603
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• 1998

Commercial ductile iron was coated with titanium and aluminum powders by low pressure plasma spraying and then irradiated with a $CO_2$ laser to produce anti-corrosive TiC composite layer. TiC carbides were precipitated homogeneously in a laser alloyed layer by in-situ reaction between carbon existed in the base metal and titanium with thermal sprayed coating. The formation of gas pores and brittle limited mixing zone with ledeburite microstructure in TiC composite layer were surpressed by the complementary alloying of aluminum. The hardness of TiC composite layer obtained by addition of titanium and aluminum was between 600 and 660 Hv, which was three times as high as the hardness of ferritic ductile iron. From the results of isothermal oxidation at 1123k for 24 hours in air, high temperature oxidation resistance of the TiC composite layer with aluminum was improved and doubled when compared with the TiC composite layer without aluminum.