Wicking Study of Nanostructured Titania Surfaces for Flat Heat Pipes
C. Ding, P. Bogorzi, M. Sigurdson, G. Soni, C. Meinhart, N.C. MacDonald
University of California, Santa Barbara, US
Keywords: wick, Titania, Nanostructure, heat pipe, NST
Abstract:We report a wicking material based on nanostructured TiO2 (NST) for the application of flat heat pipes. This wicking material is formed by oxidizing Ti pillar structures in H2O2 solution. The NST surfaces shows nano-scale walls (~30nm thick) and pores (~150nm in diameter). The NST structures are self assembled on the high-aspect-ratio Ti pillar arrays when oxidized in H2O2 solution. The micro pillar arrays were fabricated using a bulk Ti micromachining technique developed at UCSB in MACD-MEMS group. The test results indicate that the spread speed is proportion to the reverse of the travel distance of the water in the wick. The water travels 2cm within less than 2 seconds in the wick. By doing least square fitting analysis on the spread speed data, we found the wicking velocity Vs distance relationship fit well with the modified Washburn equation. Also we provide a prototype of a titanium-based flat heat pipe which has this wicking material hermetically packaged. The first prototype of our Ti-based flat heat pipe gives a very decent thermal conductivity (~ 350W/K-m), and it offers a potential for higher heat carrying capacity and thermal conductivity with improved design of the wicking material.