Wicking characteristics of porous media using short copper micro/nanofibers

Abstract

• Chemical reduction with surface modification enhanced wicking characteristics. • Short copper fibers with 150 nm diameter were used to create porous media. • Combination of two methods estimated contact angle hysteresis in porous medium. • Critical saturation in drying characteristics was high for small pore porous media. Porous media using short copper micro/nanofibers were created and their wicking characteristics of permeability K, capillary performance K/r eff , effective pore radius r eff , and porosity and drying characteristics were evaluated for loop heat pipe (LHP) applications. Different measurement methods were employed to evaluate the characteristics, and the features of each measurement method were discussed. Fibers with diameters of 120 µm, 15 µm, and 150 nm were used. For the wicking characteristics of the 15-µm porous sample, the optimal sintering conditions with respect to the temperature increasing rate, sintering temperature, and holding time were specified. The wicking characteristics were enhanced via chemical reduction, inducing a mechanical surface modification. The differences in the drying characteristics of the prepared porous samples were demonstrated. The wicking characteristics were plotted using K/r eff –1/r eff maps, and the obtained results were compared with those reported in the literature. Porous media with a submicron-scale pore radius were fabricated; these media could transfer heat to more than several meters using an LHP.