Fabrication and effective thermal conductivity of multi-walled carbon nanotubes reinforced Cu matrix composites for heat sink applications
ABSTRACT A novel particles-compositing method was used for the first time to disperse different contents of multi-walled carbon nanotubes (CNTs) in micron sized copper powders, which were subsequently consolidated into CNT/Cu composites by spark plasma sintering (SPS). Microstructural observations showed that the homogeneous distribution of CNTs and dense composites could be obtained for 0–10 vol.% CNT contents. The CNT clusters were appeared in the powder mixture with 15 vol.% CNTs, which resulted in an insufficient densification of the composites. The effective thermal conductivity of the composites was analyzed both theoretically and experimentally. The addition of CNTs showed no enhancement in overall thermal conductivity of the composites due to the interface thermal resistance associated with the low phase contrast of CNT to copper and the random tube orientation. Besides, the composite containing 15 vol.% CNTs led to a rather low thermal conductivity due possiblely to the combined effect of unfavorable factors induced by the presence of CNT clusters, i.e. large porosity, lower effective conductivity of CNT clusters themselves and reduction of SPS cleaning effect. The CNT/Cu composites may be a promising thermal management material for heat sink applications.
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ABSTRACT: a b s t r a c t The thermal stability of ultrafine-grained (UFG) microstructures in pure copper samples and copper–car-bon nanotube (CNT) composites processed by High Pressure Torsion (HPT) was compared. The UFG microstructure in the sample consolidated from pure Cu powder exhibited better stability than that developed in a casted Cu specimen. The addition of CNTs to the Cu powder further increased the stability of the UFG microstructure in the consolidated Cu matrix by hindering recrystallization, however it also yielded a growing porosity and cracking during annealing. It was shown that the former effect was stron-ger than the latter one, therefore the addition of CNTs to Cu has an overall benefit to the hardness in the temperature range between 300 and 1000 K. A good agreement between the released heat measured dur-ing annealing and the calculated stored energy was found for all samples.Composites Part A Applied Science and Manufacturing 01/2013; 51:71–79. · 2.74 Impact Factor
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ABSTRACT: AlN/Al composites are a potentially new kind of thermal management material for electronic packaging and heat sink applications. The spark plasma sintering (SPS) technique was used for the first time to prepare the AlN/Al composites, and attention was focused on the effects of sintering parameters on the relative density, microstructure and, in particular, thermal conductivity behavior of the composites. The results showed that the relative density and thermal conductivity of the composites increased with increasing sintering temperature and pressure. The composites sintered at 1550°C for 5 min under 70 MPa showed the maximum relative density and thermal conductivity, corresponding to 99% and 97.5 W·m−1·K−1, respectively. However, the thermal conductivity of present AlN/Al composites is still far below the theoretical value. Possible reasons for this deviation were discussed. Keywordsmetallic matrix composites–aluminum nitride–spark plasma sintering–density–thermal conductivityRare Metals 30(2):189-194. · 0.49 Impact Factor
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ABSTRACT: Diamond reinforced copper (Cu/diamond) composites were prepared by pressure infiltration for their application in thermal management where both high thermal conductivity and low coefficient of thermal expansion (CTE) are important. They were characterized by the microstructure and thermal properties as a function of boron content, which is used for matrix-alloying to increase the interfacial bonding between the diamond and copper. The obtained composites show high thermal conductivity (>660 W/(m·K)) and low CET (<7.4×10−6 K−1) due to the formation of the B13C2 layer at the diamond-copper interface, which greatly strengthens the interfacial bonding. Thermal property measurements indicate that in the Cu-B/diamond composites, the thermal conductivity and the CTE show a different variation trend as a function of boron content, which is attributed to the thickness and distribution of the interfacial carbide layer. The CTE behavior of the present composites can be well described by Kerner’s model, especially for the composites with 0.5wt% B. Keywordscomposite materials–pressure infiltration–thermal conductivity–coefficient of thermal expansionInternational Journal of Minerals Metallurgy and Materials 18(4):472-478. · 0.48 Impact Factor