• 한국정밀공학회지
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• 제21권11호
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• pp.149-154
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• 2004

For a present study, we investigated fatigue behavior of cracked aluminum repaired by unidirectional graphite/epoxy composite material. Three different specimens were used in the fatigue tests: cracked aluminum, cracked aluminum repaired by graphite/epoxy composite patch, and plasma-treated aluminum repaired by graphite/epoxy composite patch. The surface of the aluminum was treated using a DC plasma. The results showed that the fatigue crack growth behavior of cracked aluminum was significantly improved by repairing the cracked area with a composite patch. Specifically, the specimen repaired by composite patch showed about 300％ more fatigue lift than the cracked aluminum. In particular, the plasma-treated aluminum repaired by composite patch showed almost 12 ％ more fatigue life than the cracked aluminum repaired by graphite/epoxy composite patch. The increased fatigue life of plasma-treated case was attributed to the surface roughness of aluminum by plasma treatment.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1071-1074
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• 2006

Fabrication and investigation of composite made of graphite, SiC, mullite and aluminum as the additive are the aim of this project. Aluminum acts as an anti-oxidant. SiC is a non-metallic anti-oxidant that increases composite strength. Different compositions with influent percents of aluminum have been selected to determine product specifications by XRD, SEM and STA methods. Results show that the composition of 40wt% graphite-20% SiC- 20% mullite-20% aluminum is a more robust and occurs at elevated temperatures than other graphite combustion composites.

• Journal of Mechanical Science and Technology
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• 제19권10호
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• pp.1932-1938
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• 2005

Graphite foams consist of a network of interconnected graphite ligaments and are beginning to be applied to thermal management of electronics. The thermal conductivity of the bulk graphite foam is similar to aluminum, but graphite foam has one-fifth the density of aluminum. This combination of high thermal conductivity and low density results in a specific thermal conductivity about five times higher than that of aluminum, allowing heat to rapidly propagate into the foam. This heat is spread out over the very large surface area within the foam, enabling large amounts of energy to be transferred with relatively low temperature difference. For the purpose of graphite foam thermosyphon design in electronics cooling, various effects such as graphite foam geometry, sub-cooling, working fluid effect, and liquid level were investigated in this study. The best thermal performance was achieved with the large graphite foam, working fluid with the lowest boiling point, a liquid level with the exact height of the graphite foam, and at the lowest sub-cooling temperature.

• 한국표면공학회지
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• 제42권1호
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• pp.1-7
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• 2009

Resistive heating sources are widely used to prepare thin films by vapor deposition because they are cheap, and easy to install and handle in vacuum system. Graphite is one of materials used to make the resistive heating source, but until now only limited applications have been possible as it reacts easily with evaporating materials at high temperature. In this study, evaporation characteristics of aluminum have been investigated by using graphite boat thermally treated with BN powder. The employed graphite boat has been prepared by spray-coating BN power onto the cavity surface of the boat and thermal treatment with aluminum in vacuum at the temperature of more than $1400^{\circ}C$. The voltage-current characteristics as well as resistivity changes of the graphite boat have been investigated during aluminum evaporation according to the applied voltage and time. The evaporation aspect has been picturized during flash evaporation for 40 seconds based on the characterization results. The evaporation rate of the graphite boat has been compared with that of BN boat. The graphite boat showed some different characteristics compared with BN boat, in that the evaporation occurred at the last stage of flash evaporation. The film appearance according to the applied voltage has been compared, and also the reflectance of the resulting film has been investigated according to the film thickness. It has been found that the graphite boat thermally treated with BN powder can be used for aluminum evaporation without problem.

• 한국해양공학회지
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• 제17권5호
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• pp.76-81
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• 2003

Friction welding of GCD45 spheroidal graphite cast iron and 2024 aluminum alloy has been studied, especially in terms of the joint faces and strength of friction welding. For appropriate results of the friction welding of GCD45 graphite cast iron and 2024 aluminum alloy, an insert of A1050 pure aluminum metal was used. The joint strength of the A1050 pure aluminum insert approached the maximum strength of 165.7Mpa, compared to 128MPa for the joint between GCD45 graphite cast iron and A1050 pure aluminum without the insert metal. Maximum strength, 165.7Mpa, was possible for the following optimum conditions: 20MPa for the friction pressure, P1, 60MPa for the upsetting pressure, P2, 1 second for the friction time, t1, 3000rpm for the rotation, N, and 0.3 seconds for the brake time, tB.

• 한국분말재료학회지
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• 제23권3호
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• pp.195-201
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• 2016

Composite materials consisting of pure aluminum matrix reinforced with different amounts of graphite particles are successfully fabricated by mechanical ball milling and spark plasma sintering (SPS) processes. The shrinkage rates of the composite powders vary with the amount of graphite particles and the lowest shrinkage value is observed for the composite with the highest amount of graphite particles. The current slopes of time increase with increase in the amount of graphite particles whereas the current slopes of temperature show the opposite trend. The highest thermal conductivity is achieved for the composite with the least amount of graphite particles. Therefore, the thermal properties of the composite materials can be controlled by controlling the amount of the graphite particles during the SPS process.

• 한국주조공학회지
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• 제29권5호
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• pp.204-212
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• 2009

The effects of addition of magnesium only and the simultaneous addition of magnesium and aluminum on the graphite morphology of the cast iron with the composition of 3.6wt.% and 2.5wt.%Si poured into shell stack mold were investigated. The nodularity and mechanical properties of the specimen with smaller cross-section were higher than those with langer one, when copper was not added. When the magnesium only was added, the nodularity was decreased with decreased residual magnesium content and the C. V, graphite was obtained with the magnesium content in the range of 0.010~0.015wt.%. When the magnesium and aluminum were added together, the nodularity was decreased with decreased residual magnesium and increased aluminum contents. When copper was added, the volume fraction of pearlite in the matrix, strength and hardness were higher and elongation was lower for specimen with smaller cross-section. The volume fraction of pearlite, strength and hardness were increased and the elongation was decreased with increased copper content for the specimen with C, V, graphite.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.35-38
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• 2004

Graphite nanofiber (GNF) and carbon nanotube (CNT) are novel fiber reinforcing materials which have outstanding physical and mechanical properties. Aluminum matrix composites reinforced graphite nanofiber were fabricated by conventional powder metallurgy (PM) method. The composites were prepared through ultrasonication, ball milling, and hot isostatic pressing. A uniform distribution of GNF in aluminum matrix could be obtained. To measure the mechanical properties of GNF-Al composites testings were done in indentation and compression. The compressive strength was enhanced according to reinforcing graphite nanofiber while the hardness was decreased. This study makes the high performance composites for future applications.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1386-1388
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• 2003

In this study. the fatigue behavior of cracked aluminum repaired by unidirectional graphite/epoxy composites was experimentally investigated. The aluminum used was 7075-T6 and the patch used was four plied unidirectional ([0]$_4$) composites. The composite patch was adhesively bonded to the cracked aluminum using secondary bonding procedure. Two different specimens of cracked aluminum and cracked aluminum repaired with patch were used in the fatigue tests. Load ratio and the frequency applied in the fatigue tests were 0 and 10 Hz, respectively. The results showed that the fatigue behavior of cracked aluminum was improved by repairing the cracked area with composite patch. Specifically, the specimen repaired by composite patch showed 30% more improved fatigue behavior than regular specimen.

• 한국군사과학기술학회지
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• 제7권1호
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• pp.47-58
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• 2004

Loss factors of A356, Mn-Cu alloy and aluminum matrix composites reinforced with $SiC_p$ and Ni-coated graphite particles at various contents have been investigated using clamped-free cantilever beam method. The loss factors of half-power bandwidth of the specimens were measured over a wide range of frequencies from 50 to 3300Hz. Among the specimens, Al-10%$SiC_p$-10%$C_p$ showed the highest loss factor at the mode I, while Mn-Cu alloy showed the highest loss factors at the modes II and III. Consequently, at the mode I the Al-10%$SiC_p$--10%$C_p$ showed the loss factor of 0.00093, which is 2.64 and 1.58 times higher than those of A356 and Mn-Cu alloy, respectively.