Condensation Heat-Transfer Performance of Thermally Stable Superhydrophobic Cerium-Oxide Surfaces

Abstract

We introduce a thin (<200 nm) superhydrophobic cerium-oxide surface formed by a one-step wet chemical process to enhance the condensation heat-transfer performance with improved thermal stability compared to silane-treated surfaces. The developed cerium-oxide surface showed a superhydrophobic characteristic with a low (<5°) contact angle hysteresis because of the unique surface morphology and hydrophobicity of cerium oxide. The surface was successfully incorporated to popular engineering materials including copper, aluminum, and steel. Thermal stability of the surfaces was investigated by exposing them to hot (∼100 °C) steam conditions for 12 h. The introduced ceria surfaces could maintain active dropwise condensation after the thermal stability test, whereas silane-treated surfaces completely lost their hydrophobicity. The heat-transfer coefficient was calculated using the thermal network model incorporating the droplet size distribution and morphology obtained from the microscopic measurement. The analysis shows that the suggested cerium-oxide surfaces can provide approximately 2 times and 5 times higher heat-transfer coefficient before and after the thermal stability test, respectively, mainly because of the decrease in the thermal conduction resistance across droplets. The results indicate that the introduced nanostructured cerium-oxide surface is a promising condenser coating to enhance the droplet mobility and the resulting condensation heat-transfer performance for various thermal and environmental applications, especially those being exposed to hot steam conditions.

High-Temperature Carbonized Ceria Thermophotovoltaic Emitter beyond Tungsten

“…The Ce 3d spectrum was composed of pairs of spin–orbit doublets denoted by V and V 0 . In particular, the group of satellite peaks, V 0 , was associated with Ce 3d 3/2 , demonstrating the existence of tetravalent Ce­(IV) ions. − In addition, the XPS scan of C 1s exhibited the typical nature of pyrolytic carbon, revealing both carbon–carbon and carbon–oxygen bonds, unlike graphite and graphene. − Considering the above SEM, EDS, and XPS results, we postulate that the carbonated film was composed of agglomerated ceria and pyrolytic carbon dots, as illustrated in Figure g. Initially, ceria nanoparticles were mixed with citric acid.…”

“…All the peaks were accurately indexed to the fluorite structure of crystalline bulk ceria. − Notably, the line width of the peak assigned to (111) was steadily reduced by an increase in the annealing temperature (Figure b, inset). A pronounced neighboring peak emerging at 1500 and 1600 °C resulted from cerium­(III) oxide (Ce 2 O 3 ) (111) surfaces, indicating that Ce 2 O 3 nanoparticles were actively synthesized by the reduction of ceria nanoparticles at these temperatures. − It is well known that CeO 2 /Ce 2 O 3 nanocomposites boost the absorption at green-red wavelengths, which accounts for dramatic changes in the reflectivity spectra and color of the bare ceria wafers when annealed at >1300 °C (Figure S1). More importantly, the Scherrer equation related the broadening of the peaks to the crystallite size of the annealed ceria wafers, as presented in Figure b (Methods) .…”

Advances in vapor dropwise condensation heat transfer

“…. Shim等人 [96] 通过一步湿 法化学工艺在Cu, Al和钢表面上形成厚度小于200 nm 的CeO涂层, 表面超疏水且接触角滞后小于5°. 实验发 现, CeO涂层的传热系数比硅烷处理的表面高5倍.…”

Review of Micro–Nanoscale Surface Coatings Application for Sustaining Dropwise Condensation

“…In a study by Khan [100], CeO thin film coatings (~300 nm) were developed by sputtering and tested for 100 h. Results showed sustained DWC without deterioration of the structure and enhancement of htc by 10 times (>100 kWh/m 2 •K) as compared to htc in the case of FWC (<10 kWh/m 2 •K). Recently, Shim et al [101] developed a CeO coating of less than 200 nm thickness on Cu, Al, and steel surfaces by a one-step wet chemical process. This process resulted in the formation of superhydrophobic surfaces with contact angle hysteresis less than 5 • .…”