When superhydrophobic coatings are icephobic: Role of surface topology

Among different types of anti-icing coatings, superhydrophobic coatings have attracted considerable attention due to their water repellency and low heat-transfer rate. However, condensation on superhydrophobic surfaces at low temperatures usually causes an increase in ice adhesion because of the induced wetting of micro- and nanostructures. By tuning the weight ratio of surface-modified nanoparticles to unmodified ones, five superhydrophobic coatings with different structural features at the microscale were developed. Ice-adhesion strength and ice-nucleation temperature were studied, together with the effect of moisture condensation on ice adhesion. It was found that the ice-adhesion strength and icing temperature of these coatings do not necessarily follow the same order among these surfaces because of different mechanisms involved. Surface roughness is inadequate to describe the necessary surface features that critically affect the anti-icing behavior of the coatings. Detailed topology/geometry has to be considered when designing icephobic coatings. Superhydrophobic coatings can be adopted for icephobic applications once the surface topology is carefully designed

Mechanically robust transparent anti-icing coatings: Roles of dispersion status of Titanate nanotubes

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Ice accretion on automobiles, aerospace components, precision instruments, and photovoltaic devices detrimentally affect their performance and increase the maintenance cost. Despite significant efforts devoted to the investigation of anti-icing coatings in the past decades, mechanically robust and transparent anti-icing coatings are rarely reported. In this study, titanate nanotubes are used as filler to prepare mechanically robust anti-icing coatings with a sol-gel method. Specially, the effect of dispersion status of nanotubes on the transmittance, surface roughness, and water repellency is investigated. The optimized smooth, transparent coating exhibits higher water repellency and better anti-icing performance in terms of ice-adhesion strength, icing delay time, and ice-nucleation temperature than the rough one. Much higher hardness and scratch resistance than that of commercially available icephobic or anti-icing coatings is obtained on the smooth, transparent sample; the coating also presents good adhesion to the substrate

Transparent icephobic coatings using bio-based epoxy resin

© 2017 Elsevier Ltd Ice accretion and accumulation pose serious challenges for maintaining the operation and performance of outdoor facilities in cold climate. Epoxy resin, with a wide range of formulation possibilities, is widely used as protective coatings for outdoor facilities. However, bisphenol A (BPA), a key ingredient of conventional epoxy, is known to interfere with human's natural hormones and cause various disorders in the body system. Reduction or complete elimination of the usage of BPA is therefore high in the agenda of the coatings industries. In this study, a transparent, anti-icing, bio-based ep oxy coating was developed for room-temperature processing. As a result of hydrophobic treatment with addition of silanes, the glass-transition temperature and anti-icing performance of bio-based epoxy resin increased significantly. The optimum coating exhibited good water repellency and ice-adhesion strength as low as 50 kPa at − 20°, which was half of the widely accepted threshold value of 100 kPa for icephobic coatings. The icing delay time was much delayed compared with that of an uncoated glass substrate. To further demonstrate the anti-icing performance of the optimized coating, supercooled-water dripping on coated wooden outdoor floors and wooded boards was conducted at − 15 °C, superior anti-icing performance was observed on the coated substrates

Efficient Amidation from Carboxylic Acids and Azides via Selenocarboxylates: Application to the Coupling of Amino Acids and Peptides with Azides

A facile one-pot procedure for the coupling of carboxylic acid and azide via selenocarboxylate and selenatriazoline has been developed and successfully applied to the coupling of amino acids and peptides with azides. Selenocarboxylates are readily prepared by the reaction of the activated carboxylic acids with LiAlHSeH under mild conditions. The selenocarboxylates formed in situ are used to react directly with azides to form the corresponding amides via a selenatriazoline intermediate. Excellent yields were obtained for electron-deficient azides, and moderate to good yields were obtained for electron-rich azides. The selenocarboxylate/azide amidation reaction is clean and chemoselective. It provides an attractive alternative method to the conventional acylation of amines when an amide bond needs to be formed without going through an amine intermediate

When superhydrophobic coatings are icephobic: Role of surface topology

Among different types of anti-icing coatings, superhydrophobic coatings have attracted considerable attention due to their water repellency and low heat-transfer rate. However, condensation on superhydrophobic surfaces at low temperatures usually causes an increase in ice adhesion because of the induced wetting of micro- and nanostructures. By tuning the weight ratio of surface-modified nanoparticles to unmodified ones, five superhydrophobic coatings with different structural features at the microscale were developed. Ice-adhesion strength and ice-nucleation temperature were studied, together with the effect of moisture condensation on ice adhesion. It was found that the ice-adhesion strength and icing temperature of these coatings do not necessarily follow the same order among these surfaces because of different mechanisms involved. Surface roughness is inadequate to describe the necessary surface features that critically affect the anti-icing behavior of the coatings. Detailed topology/geometry has to be considered when designing icephobic coatings. Superhydrophobic coatings can be adopted for icephobic applications once the surface topology is carefully designed

Transparent icephobic coatings using bio-based epoxy resin

© 2017 Elsevier Ltd Ice accretion and accumulation pose serious challenges for maintaining the operation and performance of outdoor facilities in cold climate. Epoxy resin, with a wide range of formulation possibilities, is widely used as protective coatings for outdoor facilities. However, bisphenol A (BPA), a key ingredient of conventional epoxy, is known to interfere with human's natural hormones and cause various disorders in the body system. Reduction or complete elimination of the usage of BPA is therefore high in the agenda of the coatings industries. In this study, a transparent, anti-icing, bio-based ep oxy coating was developed for room-temperature processing. As a result of hydrophobic treatment with addition of silanes, the glass-transition temperature and anti-icing performance of bio-based epoxy resin increased significantly. The optimum coating exhibited good water repellency and ice-adhesion strength as low as 50 kPa at − 20°, which was half of the widely accepted threshold value of 100 kPa for icephobic coatings. The icing delay time was much delayed compared with that of an uncoated glass substrate. To further demonstrate the anti-icing performance of the optimized coating, supercooled-water dripping on coated wooden outdoor floors and wooded boards was conducted at − 15 °C, superior anti-icing performance was observed on the coated substrates

Mechanically robust transparent anti-icing coatings: Roles of dispersion status of Titanate nanotubes

© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Ice accretion on automobiles, aerospace components, precision instruments, and photovoltaic devices detrimentally affect their performance and increase the maintenance cost. Despite significant efforts devoted to the investigation of anti-icing coatings in the past decades, mechanically robust and transparent anti-icing coatings are rarely reported. In this study, titanate nanotubes are used as filler to prepare mechanically robust anti-icing coatings with a sol-gel method. Specially, the effect of dispersion status of nanotubes on the transmittance, surface roughness, and water repellency is investigated. The optimized smooth, transparent coating exhibits higher water repellency and better anti-icing performance in terms of ice-adhesion strength, icing delay time, and ice-nucleation temperature than the rough one. Much higher hardness and scratch resistance than that of commercially available icephobic or anti-icing coatings is obtained on the smooth, transparent sample; the coating also presents good adhesion to the substrate

Attachment efficiency among fine sediment considering surface heterogeneity

Interactions among natural fine sediment particles are essential to the flocculation process, and are affected significantly by surface heterogeneity. In this study, a series of mathematical sediments are generated to characterize the natural particles with different sizes and surface heterogeneities of micro-morphology and charge distribution. The total particles interactions are calculated with Derjaguin–Landau–Verwey–Overbeek (DLVO) theory to theoretically estimate the attachment efficiency (α), where the irreversible and reversible attachment are distinguished. The results show that approaching particles are easier to attached to after collision with increasing particle size (with a fixed size ratio between particles) or increasing similarity in size of both particles. Meanwhile, the electrostatic interactions increase significantly with the presence and enlargement of surface heterogeneities, especially at large separations, which reduces the more approachable reversible attachment, and thus mitigates the flocculation in aquatic systems. This study gives an insight into the mechanism of attachment among sediment considering surface heterogeneities, and provides a quantitative estimation of attachment efficiency which is adaptable for sediment flocculation modelling.</p

Sensitivity-Tunable Terahertz Liquid/Gas Biosensor Based on Surface Plasmon Resonance with Dirac Semimetal

In this paper, we study the sensitivity-tunable Terahertz (THz) liquid/gas biosensor in a coupling prism-three-dimensional Dirac semimetal (3D DSM) multilayer structure. The high sensitivity of the biosensor originates from the sharp reflected peak caused by surface plasmon resonance (SPR) mode. This structure achieves the tunability of sensitivity due to that the reflectance could be modulated by the Fermi energy of 3D DSM. Besides, it is found that the sensitivity curve depends heavily on the structural parameters of 3D DSM. After parameter optimization, we obtained sensitivity over 100{\deg}/RIU for liquid biosensor. We believe this simple structure provides a reference idea for realizing high sensitivity and tunable biosensor device

Table1_Carbon dioxide partial pressures and emissions of the Yarlung Tsangpo River on the Tibetan Plateau.docx

Rivers are important routes for material and energy transport between terrestrial and marine ecosystems. Recent global-scale assessments of carbon (C) have suggested that C emission fluxes to the atmosphere are comparable to the fluvial C fluxes to the ocean. However, many previous studies only collected data from inland rivers in low altitude regions. Therefore, it remains unclear how plateau rivers affect C flux. In this study, 20 monitoring sites were set up along the Yarlung Tsangpo (YT) River on the Tibetan Plateau and detailed observations were carried out in the wet and dry seasons. The riverine CO2 fluxes exhibited significant seasonal patterns which ranged from 597.12 ± 292.63 μatm in the wet season to 368.72 ± 123.50 μatm in the dry season. The CO2 emission flux (FCO2) obtained from floating chamber method, ranging from 8.44 ± 6.94 mmol m−2 d−1 in sunmmer to 3.62 ± 6.32 mmol m−2 d−1 in winter, with an average value of 6.03 mmol m−2 d−1. Generally, the river was a weak carbon source with respect to the atmosphere. However, the pCO2 and FCO2 were much lower than that for other large rivers around the globe, which were obviously restrained by the weak microbial activities due to the low primary productivity and carbonate buffer activities in the carbonate background. Carbon loss via atmosphere exchange in the YT River on the plateau accounted for 2.2% and 10.6% of the riverine dissolved carbon fluxes (67.77 × 109 mol a−1) according to the floating chamber and thin boundary layer methods, respectively. The YT River probably acts as a “pipeline” to transport weathered nutrients from the plateau to downstream areas. Our results demonstrated the characteristics of a “weak outgassing effect and a high transport flux of carbon” for the plateau river, which is different from rivers on plains. Considering the global relevance of Tibetan Plateau, further studies with enhanced spatiotemporal resolution are needed to better understand the important role of plateau rivers on carbon budgets and climate change over both regional and global cycles.</p