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: This article is intended for investigating the effects of heat flux and induced magnetic field for the peristaltic flow of two different nanoparticles with the base fluid salt water in the asymmetric vertical permeable channel. The mathematical formulation is presented. The resulting equations are solved exactly. The obtained expressions for pressure gradient, pressure rise, temperature, axial magnetic field, current density and velocity phenomenon are described through graphs for various pertinent parameters. The streamlines are drawn for some physical quantities to discuss the trapping phenomenon.AEJ - Alexandria Engineering Journal 06/2015; 297. DOI:10.1016/j.aej.2015.05.009
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ABSTRACT: Submicron copper reinforced with carbon nanotubes–ruthenium composites as suitable material for thermal management applications has been fabricated by Spark plasma sintering (SPS). The slurry of CNT–Ru was uniformly dispersed into copper matrix by mechanical stirring process using ethanol as a mixing medium. The composites powders were initially annealed for 30 min at 550 °C with heating rate of 5 °C/min under argon. The annealed powders were then consolidated at sintering temperature of 600 °C and 650 °C with a constant pressure of 50 MPa and the holding time of 5 min. The relative density of 98.15% was obtained for Cu-2 vol%CNT while that of Cu-2 vol%CNT-0.5 vol%Ru was of 97.08%. The Vickers hardness values of Cu-2 vol%CNT-0.5 vol%Ru sintered at 650 °C were found to be 130.4 HV. The coefficient of thermal expansion of 2.3 × 10−6/°C was measured for copper reinforced with 2 vol% CNT sample at 100 °C. The thermal conductivity of 323 W/mK and 279 W/mK was measured at 100 °C for Cu and Cu-1CNT-0.5 vol%Ru. The X-ray photoelectron spectroscopy was performed on the samples surface in order to determine the effect of additives on the copper surface. XPS revealed that addition of Ru reduced copper oxidation at the surface.Synthetic Metals 04/2015; 202. DOI:10.1016/j.synthmet.2015.02.001 · 2.22 Impact Factor
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ABSTRACT: a b s t r a c t Highly thermally conductive graphite flakes (G f)/Si/Al composites have been fabricated using G f , Si pow-der and an AlSi 7 Mg 0.3 alloy by an optimized pressure infiltration process for thermal management appli-cations. In the composites, the layers of G f were spaced apart by Si particles and oriented perpendicular to the pressing direction, which offered the opportunity to tailor the thermal conductivity (TC) and coeffi-cient of thermal expansion (CTE) of the composites. Microstructural characterization revealed that the formation of a clean and tightly-adhered interface at the nanoscale between the side surface of the G f and Al matrix, devoid of a detrimental Al 4 C 3 phase and a reacted amorphous Al–Si–O–C layer, contributed to excellent thermal performance along the alignment direction. With increasing volume fraction of G f from 13.7 to 71.1 vol.%, the longitudinal (i.e. parallel to the graphite layers) TC of the composites increased from 179 to 526 W/m K, while the longitudinal CTE decreased from 12.1 to 7.3 ppm/K (match-ing the values of electronic components). Furthermore, the modified layers-in-parallel model better fitted the longitudinal TC data than the layers-in-parallel model and confirmed that the clean and tightly-adhered interface is favorable for the enhanced longitudinal TC.Materials and Design 07/2014; 63:719. DOI:10.1016/j.matdes.2014.07.009 · 3.17 Impact Factor