Microstructured Ceramic-Coated Carbon Nanotube Surfaces for High Heat Flux Pool Boiling

Stable surfaces with high boiling heat flux are critical to many thermal and energy conversion systems, and it is well-known that the microscale texture and wettability of a surface influences its critical heat flux (CHF). We investigate pool boiling on microstructured ceramic-coated carbon nanotube (CNT) surfaces. CNT microstructures are patterned with precise dimensions over large areas, and a ceramic coating by atomic layer deposition (ALD) imparts stability in the presence of capillary forces and thermal stresses that occur during boiling, achieving a measured CHF as high as 245 W cm–2. We also show that the nanoporosity of the ceramic–CNT microstructures has a negligible influence on the CHF because surface rewetting is dominated by microscale imbibition. The high CHF values achieved on our surfaces are attributed to the micropatterning and the nanoscale surface texture of the CNTs, which accelerate liquid imbibition upon bubble departure. Our findings also suggest further enhancements in CHF can be made by optimizing the microstructure pattern and improving its wettability. Therefore, micropatterned ceramic−CNT composites are a potentially attractive substrate for industrial applications of pool boiling.