Performances of the STA material. (IMAGE)
Caption
a, Lifetime τ of a water drop with initial volume 17 µl placed on samples A, B and STA, as a function of the sample temperature T. Colours in the background emphasize the Leidenfrost transition (characterized by a jump in τ) on both control samples A and B. This transition is not observed on STA (blue data), even at a temperature as high as 1,000 °C. b, Phase diagram of the different behaviours: on both samples A and B, drops wick at low temperature (blue), and either successively wick and levitate (mixed state, orange) at higher temperature or directly levitate (Leidenfrost state, red). By contrast, wicking persists in the whole range of temperatures on STA. c, For each experiment in a, we measure the solid–liquid area in which the mean value A provides an estimate of the average heat flux q = mL/τA. Plotting q as a function of T shows that STA outperforms A and B at large T, despite a larger A (typically 1 cm2 throughout the drop lifetime). d, Variation of the surface temperature when the samples are subjected to impacts of water drops every 6 s. e, Same experiment as in d but for impacts of water drops every 0.25 s. The cumulative cooling (imposed for 400 s) strongly decreases the substrate temperature, whch can reach 100 °C on STA. f, Cooling performance of STA at water fluxes Q of 2–20 ml min–1: the higher Q, the quicker the cooling, and the lower the temperature reached by the material. At high Q, the top surface of a red-hot sample quickly becomes grey, as shown in the inset; scale bars, 1 cm. Error bars in a–c indicate the standard deviations in the experiments, as estimated from at least five independent measurements.
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