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Faculty of Mechanical Engineering, Lj. (FSLJ)
  • Surface chemistry and morphology transition induced by critical heat flux incipience on laser-textured copper surfaces
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    Stability of functionalized surfaces is an often-neglected topic in phase-change heat transfer research. Here, we examine the chemical and morphological changes of textured surfaces on the molecular ... and atomic level after the critical heat flux incipience during saturated pool-boiling of water. SEM imaging, EDS, AES and XPS analyses are used to examine the surface changes. Copper samples were laser textured via ablation using a nanosecond fiber laser under air or argon atmosphere. Multiscale microcavities, which serve as preferential nucleation sites, were produced on the samples, which exhibited significantly enhanced heat transfer performance in pool-boiling tests. Repeated formation of a vapor film and accompanying temperatures of up to 320°C during the tests resulted in changes of the surface chemistry and nanomorphology. It was determined that Cu (II) oxide and hydroxide transform into Cu (I) oxide and Cu metal as a result of repeated low-temperature annealing of the surface when a vapor film is formed during the transition towards film boiling. This additionally causes a wettability transition of the functionalized surfaces from hydrophilic towards hydrophobic. Both effects importantly influence the solid-liquid-vapor interface during phase-change heat transfer. Overall, surfaces functionalized via laser texturing exhibited significantly enhanced stability and boiling heat transfer performance.
    Source: Applied Surface Science. - ISSN 0169-4332 (Vol. 490, Oct. 2019, str. 220-230)
    Type of material - article, component part ; adult, serious
    Publish date - 2019
    Language - english
    COBISS.SI-ID - 16653083

source: Applied Surface Science. - ISSN 0169-4332 (Vol. 490, Oct. 2019, str. 220-230)

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