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Research Papers: Micro/Nanoscale Heat Transfer

Particle Aspect-Ratio Effects on the Thermal Conductivity of Micro- and Nanoparticle Suspensions

[+] Author and Article Information
Anna S. Cherkasova

Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, NJ 08854-8054

Jerry W. Shan

Department of Mechanical and Aerospace Engineering, Rutgers University, Piscataway, NJ 08854-8054jshan@jove.rutgers.edu

J. Heat Transfer 130(8), 082406 (Jun 04, 2008) (7 pages) doi:10.1115/1.2928050 History: Received October 05, 2007; Revised February 22, 2008; Published June 04, 2008

The influence of particle anisotropy on the effective thermal conductivity of a suspension is experimentally investigated. Suspensions of micron-sized, silicon-carbide particles with varying aspect-ratio distributions were prepared and measured. It is shown that the conductivity of the silicon-carbide suspensions can be quantitatively predicted by the effective medium theory of Nan (1997, “Effective Thermal Conductivity of Particulate Composites With Interfacial Thermal Resistance  ,” J. Appl. Phys.81(10), pp. 6692–6699), provided the volume-weighted aspect ratio of the particles is used. Recent experimental data on multiwalled-nanotube-in-oil suspensions by Yang (2006, “Thermal and Rheological Properties of Carbon Nanotube-in-Oil Dispersions  ,” J. Appl. Phys., 99(11), 114307) are also analyzed and shown to be in at least qualitative agreement with the effective-medium-theory prediction that the thermal conductivity of suspensions is enhanced by large aspect-ratio particles.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Image of SiC in EG suspension before (a) and after (b) 28h of milling

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Figure 2

Aspect-ratio distribution for SiC whiskers in EG before (a) and after (b) 28h of milling

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Figure 3

Optical micrograph (a) and size distribution (b) for SiC spheres in EG

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Figure 4

Relative thermal conductivity enhancement in the suspensions containing SiC spherical particles (solid squares) and whiskers (solid circles) compared to the data calculated with the aid of Maxwell (dashed line) and EMT (solid line). Data by Xie for spheres and cylinders are shown with hollow squares and circles correspondingly. EMT prediction for a=3.7 is shown with dotted line for comparison with the data on cylinders of Xie

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Figure 5

Measured thermal conductivities of 2.5% volume suspensions of SiC in EG with whiskers of different aspect ratio. For comparison, the Maxwell model, and EMT predictions for different magnitudes of kp, are shown.

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Figure 6

Thermal conductivity of a 2.5% SiC-in-oil suspension with log-normal aspect ratio distribution (σ=0.5)

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Figure 7

Thermal conductivity of a 2.5% SiC-in-oil suspension with log-normal aspect ratio distribution (σ=2.0)

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Figure 8

Thermal conductivities of MWNTs in PAO with different aspect ratio of nanotubes. The solid squares indicate the measurements of Yang , while the solid line shows the EMT model.

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