Heat transfer behavior of as-processed and cleaned picosecond pulse laser processed copper

Mark Anderson, Justin Costa-Greger, Aaron Ediger, Craig Zuhlke, Dennis Alexander, George Gogos, Jeffrey E. Shield

Research output: Contribution to journalArticlepeer-review

Abstract

Improving the heat transfer characteristics of materials can be accomplished by increasing the surface area. This surface roughening can be accomplished efficiently and directly using pulsed-laser processing. Here, laser processing of copper using a picosecond laser pulse technique produced mound-like structures, with surface morphologies and subsurface microstructures dependent on laser pulse count, with higher pulse counts producing a unique layering of Cu and Cu2O in the mounds. Processing in ambient air resulted in the formation of surface oxides. The presence of oxides deleteriously influenced the heat transfer characteristics, with a lower heat transfer coefficient compared to unprocessed Cu. To remove the oxidation, the laser-processed copper was subjected to different acid treatments. It was found that treatment using citric acid resulted in efficient and effective removal of oxides both surface and subsurface. For low pulse count samples, an improvement in the heat transfer characteristics was observed after oxide removal, and outperformed the polished reference sample at heat fluxes above approximately 90 W/cm2. However, the removal of oxides using citric acid was found to actually decrease heat transfer characteristics for high pulse count samples with the onion-like subsurface layers, as oxide removal left behind voids in the structure which were detrimental to heat transfer. Thus, optimized laser surface processing which avoids subsurface onion-like layer formation enhances heat transfer performance.

Original languageEnglish (US)
Article number101105
JournalThermal Science and Engineering Progress
Volume27
DOIs
StatePublished - Jan 1 2022

Keywords

  • Citric acid
  • Copper oxide
  • Heat transfer performance
  • Picosecond laser processing

ASJC Scopus subject areas

  • Fluid Flow and Transfer Processes

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