ABSTRACT
With the development of industry and global warming, passive radiative cooling textiles have recently drawn great interest owing to saving energy consumption and preventing heat-related illnesses. Nevertheless, existing cooling textiles often lack efficient sweat management capacity and wearable comfort under many practical conditions. Herein, a hierarchical cooling metafabric that integrates passive radiation, thermal conduction, sweat evaporation, and excellent wearable comfort is reported through an electrospinning strategy. The metafabric presents excellent solar reflectivity (99.7%, 0.3-2.5 µm) and selective infrared radiation (92.4%, 8-13 µm), given that the unique optical nature of materials and wettability gradient/micro-nano hierarchical structure design. The strong moisture-wicking effect (water vapor transmission (WVT) of 2985 g m-2 d-1 and directional water transport index (R) of 1029.8%) and high heat-conduction capacity can synergistically enhance the radiative cooling efficiency of the metafabric. The outdoor experiment reveals that the metafabric can obtain cooling temperatures of 13.8 °C and 19.3 °C in the dry and sweating state, respectively. Meanwhile, the metafabric saves ≈19.3% of annual energy consumption compared with the buildings with HAVC systems in Shanghai. The metafabric also demonstrates desirable breathability, mechanical strength, and washability. The cost-effective and high-performance metafabric may offer a novel avenue for developing next-generation personal cooling textiles.
ABSTRACT
Fog harvesting is a sustainable approach to dealing with the global freshwater crisis. A range of strategies in microstructure design and wettability remodeling for fog management are clearly explained. However, the influence of thermodynamic endothermic and exothermic processes on fog harvesting is rarely explored. Here, a thermodynamically induced interfacial condensation-enhanced fog-harvesting fabric (AWF-6) is developed that also incorporates asymmetric geometry and surface chemistry. By coupling the high thermal conductivity interface supported by boron nitride nanosheets (BNNS), the Laplace pressure difference generated by nanoneedles, and the wettability gradient constructed by stearic acid (STA), the fabric achieves a water collection rate (WCR) of 1538.4 mg h cm-2 , which is the maximum value in state-of-the-art cotton-based fog harvesting devices (FHDs). Furthermore, the potential application of AWF-6 in agricultural irrigation is demonstrated. This study shows a thermodynamic proposal for building next-generation fibrous FHDs.
ABSTRACT
In this work, an ethanol/water/glycerol ternary coagulation bath system was used to fabricate a hydrophobic PVDF membrane, which will have a considerable impact on the micromorphology. This change will further affect the performance of the membrane. After introducing glycerol into the coagulation bath, the precipitation process was finely regulated. The obtained results implied that glycerol could inhibit solid-liquid separation and promoted liquid-liquid separation. A pleasant discovery was that the mechanical properties of the membrane were improved because of the more fibrous polymers formed by liquid-liquid separation. Besides, a more uniform pore size can be achieved. A fascinating symmetrical interconnected fibrous and spherulitic structure was depicted by membranes fabricated with a coagulation bath consisting of 6% water, 34% ethanol, and 60% glycerol. This membrane had a high water contact angle of 146.6° and a small mean pore size of 0.46 µm. Enhanced tensile strength and elongation at break evidenced that the membrane enjoyed good robustness and flexibility. This facile approach provided the possibility to prepare membranes with tailored pore size and the required strength.
ABSTRACT
Except the good separation performance, the membranes used for oil-water mixture separation should be fabricated with as little wastewater produced as possible. Thus, we proposed a green tactic--water vapor induced phase inversion to prepare the high-strength and superhydrophilic/underwater superoleophobic nonwoven fabric-based cotton/PA6/PAN membranes which is based on the polymer/solvent/nonsolvent ternary system analysis. Differing from adding additives in polymer solution or coagulation bath, above proposed strategy has an "subtractive effect" with the advantages of constructing three-dimensional porous structure and greatly reducing the organic wastewater produced during preparation process. Moreover, the obtained cotton/PA6/PAN membranes exhibited unexpected performances for separating oil-in-water emulsions. An ultrahigh permeation flux of up to 478,000 L m-2 h-1 bar-1 with a separation efficiency of > 99.9% was obtained under the driving pressure of 1.6 KPa, which was one order of magnitude higher than the conventional separation membranes with similar properties. In addition, it is surprising that the cotton/PA6/PAN membranes can also extract water from the slick oil/water immiscible mixture. Therefore, it is expected that the cotton/PA6/PAN membranes can be used in practical oily wastewater purification.
