Slippery liquid-infused porous surfaces (SLIPSs) prepared with phase invariant materials (e.g., Krytox GPL oil) have been increasingly researched as low adhesion engineered functional surfaces in the last decade. However, phase change materials (PCMs) have been scarcely adopted, although they are potential candidates due to their inherent lubricant characteristics as well as temperature-dependent phases empowering unique thermoresponsive switchable wettability. Here, paraffin wax (an organic PCM) has been applied on hydrophobized nanoporous copper substrate to realize the phase-change SLIPSs (PC-SLIPSs) fabricated via spin-coating followed by thermal annealing, which overcomes earlier limitations encountered on the PC-SLIPSs. Advantages of these PC-SLIPSs are: the prompting of a low adhesion Wenzel (LAW) state opposed to earlier completely-pinned Wenzel state in the solid phase, and the optimized slippery state without excess of PCM in the liquid phase. Further, in order to characterize the intimate interactions between liquid droplets and the different phases of the PC-SLIPSs, i.e., solid, mush, and liquid phases, the contact line dynamics have been comprehensively investigated, unveiling the water droplet adhesion and depinning phenomenon as the function of thermo-responsive wetting states.Lastly, the PC-SLIPSs have also been tested for water vapor condensation, demonstrating the feasibility of dropwise condensation and the shift of droplet size distribution in both the solid and liquid phases. The results suggest that such engineered surfaces have great potential to prompt and tune dropwise condensation via thermo-responsive switchable wettability for heat transfer and water harvesting applications.
In the present study, calorimetric measurements were conducted to determine CO 2 behavior in aqueous solutions of 30 and 50 wt % N-methyl diethanolamine (MDEA) and 40 + 10 wt % MDEA−piperazine (PZ) at 323.15 and 353.15 K at pressures from 0.5 to 4 MPa. The effects of temperature, pressure, MDEA concentration, and addition of PZ on the heat of absorption and CO 2 solubility were investigated based on the calorimetric results, which were verified to be consistent with the vapor−liquid equilibrium data. No apparent effect of MDEA concentration was observed, while the heat of absorption was influenced by the temperature and pressure. The heat of absorption of the solution with PZ was enhanced, but the enhancement decreased with the increase of CO 2 loading. The CO 2 solubilities in aqueous solutions of 50 wt % MDEA and 40 + 10 wt % MDEA−PZ were compared in the experimental range, and the results showed no effect of PZ on the CO 2 capture capacity. In addition, the absorption processes with and without PZ were simulated using Aspen Plus on the basis of the electrolyte non-random two-liquid model and a further study on the effect of the composition of MDEA and PZ in the solution was also conducted. The reaction mechanism was derived to give insights into the contribution of all reactions to the integral heat of absorption.
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