Ultra Fine Specialty Products

J.L. Johnson and L.K. Tan, “Fabrication of Heat Transfer Devices by Metal Injection Molding,” published in the proceedings of PM2004, EPMA, Vienna, Austria (October 17-21).

 

​Abstract

    Processing of high thermal conductivity materials, such as Al, Cu, W-Cu, and Mo-Cu by metal injection molding is reviewed. The effects of impurities, especially oxygen and iron, on the sintered density and the thermal conductivity of copper are investigated. Recently, the ability to fabricate combinations of two different materials to obtain unique functionality has been developed. In this paper, this method is used to produce a high density, high conductivity copper casing surrounding a porous copper wick to directly fabricate a heat pipe with complex geometry. The porosity and pore size distribution of the wick are measured and compared to literature values for commercial heat pipes.

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Conclusions

    Oxide-reduced, water-atomized, gas-atomized, and jet-milled Cu powders all give densities near 95% of theoretical at 1050°C. Particle size has little effect on sintered density at this temperature. Oxide reduction is practically complete by 900°C. Thermal conductivity drops significantly with as little as 50 ppm iron. Copper heat pipes can be produced by bi-material metal injection molding and co-sintering a -150/+325 mesh Cu powder with a -13 µm Cu powder. The permeability of the wick is comparable to those of commercial heat pipes.