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An experimental study was conducted to compare various strategies for UAV propeller icing mitigation. With a propeller model with an untreated hydrophilic blade as the comparison baseline, three icing protection systems (IPSs) were evaluated systematically: 1) a passive method with the propeller blade coated with a super-hydrophobic surface (SHS) coating; 2) an active IPS design to forcefully heat the entire blade surface; and 3) a hybrid IPS design with only limited surface heating along the blade leading edge and the SHS-coated blade. While the passive method with the SHS-coated blade was found to be only marginally effective under the glaze icing condition, it became ineffective or even further deteriorated the propeller performance under the mixed and rime icing conditions. While the active IPS design to forcefully heat the entire blade surface was found to be able to prevent ice accretion on most of the blade surface, some minor “ice crowns” were still observed to accrete near the blade tip. The hybrid IPS design was demonstrated to keep the entire blade surface ice-free under all the icing conditions with substantially less power consumption (i.e., [Formula: see text] power saving), rendering it a compelling UAV propeller icing mitigation strategy. 

We report a comparative study to evaluate the effects of surface coatings with different hydrophobicities and icephobicities on the performance of a hybrid anti-/de-icing system that integrates surface heating with hydro-/ice-phobic coating for aircraft icing mitigation. While a flexible electric film heater wrapped around the leading edge of an airfoil/wing model was used to heat the airfoil frontal surface to prevent ice accretion near the airfoil leading edge, three different kinds of coatings were applied to coat the airfoil model at three distinct spanwise locations, which included an icephobic coating with an outstanding icephobicity but a weak hydrophobicity; a superhydrophobic surface (SHS) coating with outstanding water repellency but a moderate icephobicity; and a commonly used hydrophilic coating with poor hydrophobicity and poor icephobicity. Surface wettability was found to play a more important role than icephobicity in affecting the performance of the hybrid anti-/de-icing systems. In comparison to the approach of forceful heating the hydrophilic airfoil surface, the hybrid approach with the SHS coating was found to be able to achieve about 90% energy savings in keeping the entire airfoil surface ice-free; the corresponding energy savings for the hybrid system with the icephobic coating was only about 10%. 

Herein, we report a novel method to obtain oxygenated chemicals and high-quality lignin from biomass in one-pot using a single step process. Plasma electrolysis of red oak was conducted by applying high-voltage alternating current electricity in γ-valerolactone using sulfuric acid as the electrolyte. Red oak was completely solubilized to produce levoglucosenone and furfural as the two major monomers with the respective yields of up to 44.9 mol% and 98.0 mol%. During the conversion, an oxidized lignin was also simultaneously produced in high purity. The valorization potential of the plasma electrolysis-derived lignin evaluated using the pyrolysis method showed that depolymerization of this lignin could produce significantly higher yields of phenolic monomers than the natural lignin or the lignin isolated during conventional solvolysis. Our investigation showed that benzylic carbon of the natural lignin was selectively modified during plasma electrolysis to limit the formation of interunit C–C bonds, significantly improving the subsequent lignin valorization to aromatic monomers. Overall, this study demonstrated a simple green approach to improve chemical production without using costly catalysts or tedious biomass fractionation. This study also presented a novel and highly efficient way to modify lignin for enhanced valorization.