RESUMO
Sustainable high-performance steam condensation is critical to reducing the size, weight, and cost of water and energy systems. It is well-known that dropwise condensation can provide a significantly higher heat-transfer coefficient than filmwise condensation. Tremendous efforts have been spent to promote dropwise condensation by achieving a nonwetting state on superhydrophobic surfaces and a slippery state on liquid-infused surfaces, but these surfaces suffer from severe durability challenges. Here, we report sustainable high-performance dropwise condensation of steam on newly developed durable quasi-liquid surfaces, which are easily made by chemically bonding quasi-liquid polymer molecules on solid substrates. As a result, the solid/water interface is changed to a quasi-liquid/water interface with minimal adhesion and extraordinary durability. The quasi-liquid surface with ultralow contact angle hysteresis down to 1° showed a heat-transfer coefficient up to 70 and 380% higher than those on conventional hydrophobic and hydrophilic surfaces, respectively. Furthermore, we demonstrated that the quasi-liquid coating exhibited a sustainable heat-transfer coefficient of 71 kW/(m2 K) at a heat flux of 420 kW/m2 under a prolonged period of 39 h in continuous steam condensation. Such a quasi-liquid surface has the potential to sustain high-performance dropwise condensation of steam and address the long-standing durability challenge in the field.
RESUMO
Surfaces with ultralow adhesion to liquids and solids have attracted broad interests in both fundamental studies and engineering applications from passive removal of highly wetting liquids and water harvesting to anti-/de-icing. The current state-of-the-art superomniphobic surfaces (rely on air lubricant) and liquid-infused surfaces (rely on liquid lubricant) suffer from severe issues for liquid repellency and ice removal: air/liquid lubricant loss or topography damage. Here, we create a durable quasi-liquid surface by tethering flexible polymer on various solid substrates. The untethered end of the polymer has mobile chains that behave like a liquid layer and greatly reduce the interfacial adhesion between the surface and foreign liquids/solids. Such a quasi-liquid surface with a 30.1 nm flexible polymer layer shows ultralow contact angle hysteresis (≤1.0°) to liquids regardless of their surface tensions. The highly wetting perfluorinated liquids like FC72 and Krytox101, as well as complex fluids like urine and crude oil, can be repelled from the surface. Moreover, wind can remove accreted ice from the surface in harsh conditions due to the negligible ice adhesion. We have demonstrated that the quasi-liquid surface shows robust performances in repelling highly wetting liquids, harvesting water, and removing ice, respectively.
RESUMO
A comparative adsorption kinetics, isotherms, dissolution and surface complexation of 3,4-dihydroxybenzoic acid (3,4-DHBA) and 1,2-dihydroxybenzene (catechol) at the hematite/electrolyte interface were investigated. The kinetics at pH 10 and 298.15K suggested that the adsorption behaviour of 3,4-DHBA and catechol onto hematite surface is similar and attain same equilibration time of 60 min. The adsorption kinetics data of 3,4-DHBA and catechol fit the pseudo-second-order kinetic equation of nonlinear form best. The adsorption density of 3,4-DHBA at pH≥9 increases and thereby mimics the behaviour of catechol. The solubility of hematite depends on both pH of the suspension and concentration of adsorbate. The inner-sphere complex is formed by 3,4-DHBA and catechol onto hematite surface but the mode orientation is likely to be different in the pH range 5-8 and 9-10. The advance microscopic scanning in conjunction with the vibration spectroscopy would provide better pictorial presentation of the mode of orientation of 3,4-DHBA and catechol onto hematite surface at different pH.