High temperature thermal radiation property measurements on large periodic micro-structured nickel surfaces fabricated using a femtosecond laser source

Abstract

Microstructures enable many kinds of surface modifications with unique physical characteristics. The difficulties in fabricating microstructures on large metallic surfaces, however, may limit their wide use. This work measured the thermal radiation characteristics of large, three-dimensional microstructured metal surfaces where the microstructures were fabricated by a femtosecond laser to investigate the influence of the surface microstructures on the thermal radiation properties at elevated temperatures. The microstructured nickel surfaces with the microholes having the periods of 100 μm (aligned array) and 71 μm (staggered array) were fabricated by different femtosecond laser pulses (200 and 2000) and fluences (0.138 J/cm2 and 0.276 J/cm2). The microhole diameter was close to 20 μm and the depth was 50–120 μm with large aspect ratios above 2.5. Measurements of the thermal radiation properties of a polished bare nickel surface and surfaces with microholes showed that the topography greatly affected the surface radiation properties with increased emissivities (maximum increase of 55%) at temperatures from 700 K to 1200 K. It mainly arises from the multiple reflections inside the microholes and even cavity resonance inside some of the microholes. The work provides a valuable reference for fabricating 3D periodic microstructures on large metallic surfaces and shows how the engineered microstructure surfaces affect the thermal radiation at elevated temperatures.