• Journal of Korea Foundry Society
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• v.20 no.4
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• pp.254-259
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• 2000

Metal matrix composites(MMCs) reinforced with hard particles have many potential application in aerospace structures, auto parts, semiconductor package, heat resistant panels, wear resistant materials and so on. In this work, the effect of SiC partioel sizes(50 and 100 ${\mu}m$) and additional elements such as Si, Cu and Ti on the microstructure and the wear property of $Al-5Mg-X(Si,Cu,Ti)/SiC_p$ composites produced by pressureless infiltration method have been investigated using optical microscopy, scanning eletron microcopy(SEM) with EDS(energy dispersive spectrometry), hardness test, X-ray diffractometer(XRD) and wear test. In present study, the sound $Al-5Mg-X(Si,Cu,Ti)/SiC_p$(50 and 100 ${\mu}m$) composites were fabricated by pressureless infiltration method. The $Al-5Mg-0.3Si-O.1Cu-O.1Ti/SiC_p$ composite with $50 {\mu}m$ size of SiC particle has higher hardness and better wear property than any other composite with $100{\mu}m$ size of SiC particle produced by pressureless infiltration method. The hardness and wear property of $Al-5Mg/SiC_p$(50 and 100 ${\mu}m$) composites were enhanced by the addition of Si, Cu and Ti in Al-5%Mg matrix alloy.

• Journal of Ocean Engineering and Technology
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• v.22 no.4
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• pp.59-64
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• 2008

The mechanical properties of liquid phase sintered (LPS) SiC materials, with the addition of oxide powder, were investigated, in conjunction with a detailed analysis of their microstructures. LPS-SiC materials were fabricated at a temperature of 1820 $^{\circ}C$ under an argon atmosphere, using three different starting sizes of SiC particles. The sintering additive for the fabrication of the LPS-SiC materials was an $Al_2O_3-Y_2O_3$ mixture with a constant composition ratio ($Al_2O_3/Y_2O_3$: 1.5). The particle sizes of the commercial SiC powderswere 30 nm, 0.3 $\mu$m, and 3.0 $\mu$m. The flexural strength of the LPS-SiC materials was also examined at elevated temperatures. A decrease in the starting size of the SiC particles led to an increase in the flexural strength of the LPS-SiC materials, accompanying a highly dense morphology with the creation of a secondary phase. Such a secondary phase was identified as $Y_3Al_2(AlO_4)2$. The flexural strength of the LPS-SiC materials greatly decreased with an increase in the test temperature, due to the creation of a large amount of pores.

• Journal of Korea Foundry Society
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• v.17 no.2
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• pp.170-179
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• 1997

A noble technique has been developed for fabricating in situ formed $TiC_p/Al$ composites. In this process, fairly stable TiC particles were in situ synthesized in liquid aluminum by the interfacial reaction between an Al-Ti melt and SiC, which is a comparatively unstable carbide from the view-point of thermodynamics. It is possible in the present process to generate TiC particles of nearly 1 ${\mu}m$ in diameter, even utilizing SiC of 14 ${\mu}m$ as raw material. However, the dispersion behavior of TiC particles in the matrix depends on the size of the raw material SiC. Decomposing finer SiC makes the dispersion of TiC particles more uniform and the mechanical properties of composites are improved accordingly. The structure of in situ composites and their mechanical properties are affected by the fabrication temperature and the stirring time. It has been found that the most suitable condition for fabrication should be applied depending on the size of the raw material, even if the same kinds of carbide are used. Furthermore, although Al-Ti-Si system intermetallic compounds are detected in a $TiC_p/Al-Si$ composite which is fabricated by conventional melt-stirrng method, these compounds can not be observed in a $TiC_p/Al-Si$ composite made by this in situ production method. Hence the mechanical properties of the in situ $TiC_p/Al-Si$ composite are superior to those of the conventional $TiC_p/Al-Si$ composites.

• Journal of Ocean Engineering and Technology
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• v.10 no.4
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• pp.84-91
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• 1996

A fractal analysis on fracture surface of aluminium-particulate SiC composites was attempted. As the volume fraction of SiC in composites increases, the fractal dimension tends to increase. However, no correlation between the fractal dimension and the fracture toughness in terms of critical energy release rate was observed. Since the fractal dimension represents the roughness of fracture surface, the fracture toughness would be a function of not only fracture surface roughness but also additional parameters. Thus the applicability of fractal analysis to the estimation of fracture toughness must depend on the proper choice and interpretation of additioal paramerters. In this paper, the size of characteristic strctural unit for fracture was considered as an additional parameter. As a result, the size appeared to be a function of only volume fraction of SiC. Finally, a master curve for fracture toughness of aluminium-particulate SiC composites was proposed as a function of fractal dimension and volume fraction of SiC.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.251-251
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• 2008

In this work, appropriate corrugated structure is suggested to increase resonant frequency of resonators. Micro beam resonators based on polycrystalline 3C-SiC films which have a two-side corrugation along the length of beams were simulated by finite element method and compared to a same - size flat rectangular. With the dimension of $36\times12\times0.5{\mu}m^3$, the flat cantilever has resonant frequency of 746 kHz. Meanwhile, with this size only corrugation width of $6{\mu}m$ and depth of $0.4{\mu}m$, the corrugated cantilever reaches the resonant frequency at 1.252 MHz, and is 68% larger than that of flat type.

• Transactions on Electrical and Electronic Materials
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• v.9 no.5
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• pp.193-197
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• 2008

On the purpose of increasing resonant frequency without sacrificing quality factor as well as much decreasing dimensions, corrugated micro beam resonator based on polycrystalline 3C-SiC films is the applicable solution. In this work, appropriate corrugated structure is suggested to increase resonant frequency of resonators. Micro beam resonators based on 3C-SiC films which have a two-side corrugation along the length of beams were simulated by finite element method and compared to a same-size flat rectangular. With the dimension of 36x12x0.5 ${\mu}m^{3}$, the flat cantilever has resonant frequency of 746 kHz. Meanwhile, with this size but corrugation width of 6 ${\mu}m$ and depth of 0.4 ${\mu}m$, the corrugated cantilever reaches the resonant frequency at 1.252 MHz.

• Journal of Powder Materials
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• v.10 no.5
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• pp.325-332
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• 2003

The effect of extrusion temperature on the microstructure and mechanical properties was studied in gas atomized TEX>$Al_{81}Si_{19}$ alloy powders and their extruded bars using SEM, tensile testing and wear testing. The Si particle size of He-gas atomized powder was about 200-800 nm. Each microstructure of the extruded bars with extrusion temperature (400, 450 and 50$0^{\circ}C$) showed a homogeneous distribution of primary Si and eutectic Si particles embedded in the Al matrix and the particle size varied from 0.1 to 5.5 ${\mu}m$. With increasing extrusion temperature from 40$0^{\circ}C$ to 50$0^{\circ}C$, the ultimate tensile strength (UTS) decreased from 282 to 236 ㎫ at 300 K and the specific wear increased at all sliding speeds due to the coarse microstructure. The fracture behavior of failure in tension testing and wear testing was also studied. The UTS of extrudate at 40$0^{\circ}C$ higher than that of 50$0^{\circ}C$ because more fine Si particles in Al matrix of extrudate at 40$0^{\circ}C$ prevented crack to propagate.

• Journal of the Korean Vacuum Society
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• v.2 no.2
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• pp.199-208
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• 1993

The effect of nucleation free energy related to Si surface states on diamond film growth behavior has been studied. Ar first, the three kinds of diamond thin films (A, B, C) were deposited on various Si substrates (A-Si, B-Si, C-Si) whose surfaces were polished with 1 ${\mu}m$ diamond paste, 6 ${\mu}m$ Al_2O_3$ powder and 12 ${\mu}m$ Al_2O_3$ powder respectively. And then, relative nucleation free energy calculated is ${\Delta}G_{A-Si}<{\Delta}G_{B-Si}<{\Delta}G_{C-Si}$. Although there are some difference in grain size, shape and nucleated size, the thin films on A-Si and B-Si were diamond including a small amount of DLC which was confirmed by AES, SEM, XRD, and RHEED. Namely, the diamonds of films (B) were not nucleated in scratches but in dents and larger in grain size compare with the film (C) of which diamond sere nucleated not only scratches but also dents. And, the sphere diamond which is not general shape was grown on C-Si. After all, the sphere was turned out to be the diamond including much graphite as a result of the AES in situ depth profiling. Consequently, the diamond shape and quality grown on Si were Changed from the crystal which the (100) and (110) planes were predominent to the crystal in which (111) plane was predominent, and newt to sphere shape diamond including much graphite according as the nucleation free energy increases.

• Journal of the Korean Ceramic Society
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• v.21 no.1
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• pp.27-32
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• 1984

During the last decade there have been many studies on the new ceramics especially engineering ceramics. Sintered silicon carbide is one of the main materials in engineering ceramics. This study shows the effects of surface treatment and microstructure especially the abnormal grain growth on the strength of sintered SiC. Surface of sintered SiC and treated with 400, 800 and 1200 grit diamond wheel. Grain growth is introduced by increasing the sintering times at 205$0^{\circ}C$. The $\beta$longrightarrow$\alpha$ transformation occurs during the sintering of $\beta$-starting materials and is often accompanied by abnormal grain growth. The overall strength distribution are estimated using the Weibull statistics. The results show that the strength of sintered SiC is limited by extrinsic surface flaws in normal-sintered specimens. And it is sound that the finer the surface finishing and the grain size the higher the strength results. But the strength of abnormal sintering specimens is limited by the abnormally-grown large tabular grains. The Weibull modulus increases with the decreasing grain size and the decreasing grit size of grinding.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.42-48
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• 2018

Silicon has attracted extensive attention due to its high theoretical capacity, low discharge potential and non-toxicity as anode material for lithium ion batteries. In this study, Si-CNT-C composites were fabricated for use as a high-efficiency anode material in a lithium ion battery. Aerosol self-assembly and post-heat treatment processes were employed to fabricate the composites. The morphology of the Si-CNT-C composites was spherical and an average particle size was $2.72{\mu}m$. The size of the composite increased as concentration of Si and CNT increased in the precursor solution. In the Si-CNT-C composites, CNT and C carbonized from glucose were attached to the surface of Si particles. Electrochemical measurement showed that the cycle performance of Si-CNT-C composites was better than that of silicon particles.