Characterization of Electrolessly Plated Graphite Foams with Particle Additions

Michael Asaro,Jennifer Mueller,Patrick Dykema

doi:10.21061/jumr.v3i0.0804

Abstract

With a low density and high bulk thermal conductivity, graphite foams are ideal for thermal management systems such as computer heat sinks, radiators, and heat exchangers.Previous work has shown it is possible to improve the foams performance by opening the porosity with nanoparticle additions in the foams precursor, an oil based mesophase pitch.[1] The open porosity allows more fluid, such as air or water, to pass through the foam and carry heat away.The original study, performed by Jennifer Mueller at Oak Ridge National Labs (ORNL), considered the concentrations of nanoparticle’s used.The present study looked to determine the effects of using different types of nanoparticles at a range of sizes from the nano- to micro- level.The study began by adding, respectively, silver, ceria, alumina, tungsten, and nickel to different batches of mesophase pitch at a single weight percent concentration to create graphite foams with a significant amount of continuous porosity.The pitch was foamed, carbonized, and graphitized.The final foam products were then measured in a variety of ways including thermal conductivity, permeability, and scanning electron microscope (SEM).As a side project, an electroless copper plating solution was passed through the foams to determine if a continuous and uniform copper coating could be built up.The copper coating that was eventually obtained coated the foam walls without filling the open porosity and may help to increase the foams solderability, strength, durability, and corrosion resistance.

Highlights

Graphite foams are an excellent material for use in thermal management systems such as computer heat sinks, radiators, and heat exchangers
Previous work has shown that the addition of carbon nanoparticles to the foam precursor, an oil based mesophase pitch, will act as nucleation sites for pore windows during the foaming process
3.1 Particle Additions The foams that were processed at higher processing pressures had a higher pressure drop, meaning there was less open porosity, compared to the foams processed at lower pressures for a given material (Figure 4)

Summary

Introduction

Graphite foams are an excellent material for use in thermal management systems such as computer heat sinks, radiators, and heat exchangers. The graphite ligaments themselves have a thermal conductivity of >1700 W/mK.[2] As can be seen, they are usually aligned parallel to the pore structure, which gives the bulk foam a thermal conductivity on par with aluminum. Previous work has shown that the addition of carbon nanoparticles to the foam precursor, an oil based mesophase pitch, will act as nucleation sites for pore windows during the foaming process.

Results

Conclusion