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•A novel superhydrophobic Al2O3/cerium hexadecanoate double-layer coating was designed.•The composite coating was fabricated by combining plasma electrolytic oxidation and ...electrodeposition.•The high emissivity double-layer surface enabled a significant LED temperature drop.•The composite coating showed superior self-cleaning, anti-corrosion and adhesion strength.
To enhance the heat dissipation and anti-corrosion performance simultaneously, a superhydrophobic Al2O3/cerium hexadecanoate (Al2O3/CH) composite coating with high adhesion strength has been fabricated by plasma electrolytic oxidation and subsequent electrodeposition. The Al2O3/CH composite coating with a contact angle of 165.5° shows excellent water repelling and self-cleaning ability owing to the micro/nano structure and low surface energy. The composite coating enhances the corrosion potential of pure Al from −0.742 to −0.730 V and lowers the corrosion current density by two orders of magnitude. Thanks to the high emissivity in the wavelength range from 2.5 to 25 μm, the Al2O3/CH coated sample enables the operation temperature of a 5 W LED to drop approximately by 9.3 °C compared with Al substrate. In addition, the Al2O3/CH composite coating exhibits higher adhesion strength than that of the CH single layer. Therefore, the superhydrophobic coating is expected to be a promising candidate for heat dissipation and anti-corrosion applications.
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The effects of hydrate inhibitors on the adhesion of sintered hydrate deposits on pipe walls are still unexplored. Herein, a custom-built adhesion strength measurement apparatus was ...utilized to quantify the adhesion strengths of sintered cyclopentane (CyC5) hydrate deposits with thermodynamic inhibitors (ethylene glycol, glycerol) and low-dosage inhibitors (dodecylbenzene sulfonic acid (DBSA), sorbitan oleate (Span 80)). It was found that the hydrate adhesion strengths decreased by 69.82%-97.06% and 40.24%-94.36% with the concentration of ethylene glycol and glycerol increased from 2 wt% to 6 wt%, respectively. For DBSA and Span 80, the hydrate adhesion strength increased with concentration less than 0.01 wt% due to the acceleration on hydrate growth. The further increment of concentration leads to a dramatic reduction in adhesion strengths. Furthermore, the relatively large deviations with the predicted strengths led to the discussions of the effects of change in hydrate formation rate, crystal morphology, and also the adaption of the fitting model. Two modified models were proposed to give a better prediction/explanation of the hydrate adhesion with thermodynamic inhibitors and low-dosage inhibitors, respectively. This work provides a fundamental understanding of the adhesion mechanism of hydrate deposits with hydrate inhibitors, which is important in advancing the management of hydrate formation for preventing plugging in pipelines.
•EVA films of 18, 24 and 33% VA content by weight are prepared to fabricate mini-modules, which are subjected to DH ageing for 1000 h at 85 °C & 85% RH.•The Pmax, Gc and resistivity reduce and ΔYI ...increases for the modules containing EVA33 after ageing but remains unaltered for EVA24 and EVA18.•It has been found that the films of EVA18 and EVA24 are resilient compared to EVA33.
The photovoltaic (PV) module manufacturers use ethylene vinyl acetate that contains 28 to 33% by weight vinyl acetate (VA) for the encapsulation application. However, it has been found in various field surveys that EVA degrades during its operation in the field. The resilience of ethylene vinyl acetate against environmental stressors can be enhanced by optimising its vinyl acetate (VA) content as has been seen in the few studies done on free-standing EVA films. However, no such comparative study has been carried out on EVA films placed in a module mimicking the actual structure of a PV module. Therefore, in this work EVA films containing 18, 24 and 33% VA content by weight are prepared with the necessary additives to fabricate mini-modules. These mini-modules have been subjected to damp-heat (DH) ageing for 1000 h at 85 °C temperature and 85% relative humidity (RH) according to IEC 61,215 standard. The power output, adhesion strength and volume resistivity reduce and YI increases for the modules containing EVA33 after ageing. However, no significant changes are observed for the above-mentioned properties for the modules containing EVA24 and EVA18. This study presents findings of 1000 h of DH ageing as per IEC standards for mini-modules containing different EVA films and observed that the films of EVA18 and EVA24 are resilient compared to EVA33. Moreover, the findings on mini-modules have a few differences with prior studies done on free-standing EVA the films.
Layer-by-layer assembly (LbL) of trilayer coatings of polyelectrolytes and nanoclays (NC) were produced on poly(lactic acid) based (PLAb) films. The focus of this study was on the optimization of the ...wetting properties of the PLAb substrate, and the adhesion properties of the prepared coating. Coatings produced by an optimized method, by combining UVC-treatment of the substrate and adjusting surface tension of the coating solutions, were compared to coatings made by typically used water-based solutions. Even though LbL-coatings with a high adhesion strength to its substrate is of outmost importance for most applications, this is often not evaluated. In this study, the adhesion of the coatings on the PLAb substrate was assessed using the cross-cut test according to ISO 2409, in which the adhesion is classified on a scale between 0 and 5, where a lower number reflects better adhesion. The coating prepared by the optimized procedure was categorized as class 0, while the control film was classified as 4. These results reveal the importance of the optimization of both the surface free energy of the substrate, and the surface tension of the dipping solutions. The surface morphology and roughness properties of the optimized films were further investigated with scanning electron microscopy (SEM), confocal optical microscopy (COM) and atomic force microscopy (AFM), showing a uniform distribution of NC on the substrate with increasing number of trilayers. X-ray photoelectron spectroscopy (XPS) confirmed the homogenous surface composition of polyelectrolytes and NC. Finally, the oxygen transmission rate (OTR) decreased considerably (by 99.7%), from 97.2 cc/(m2·day) for pristine PLAb substrate to 0.3 cc/(m2·day) for the 20-trilayer coated substrate.
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•Greatly improved oxygen barrier properties of a poly(lactic acid) based material.•Surface evaluations on nano- and microscale reveal a uniform barrier coating.•The optimized coating has a superior adhesion strength.
A self-designed tester is used to study the ash adhesion strength of straw biomass and the effect of dolomite additive. TG-DSC, SEM-EDX, XRD and thermodynamic equilibrium are applied to analyze the ...thermal behaviors, mineral transformation and liquid phase formations of ash samples. The results indicate that the adhesion strength of rice straw ash appears at 600 °C, increases rapidly above 700 °C, and reaches 21.83 kPa at 1000 °C. The melting related to KCl causes the ash adhesion strength of rice straw at low temperature. The more viscous silicate melts result in a rapid rise in ash adhesion strength with increasing temperature. Dolomite additive can inhibit the melting of KCl and increase the appearance temperature of ash adhesion strength. Dolomite promotes the formation of high melting point minerals such as orthoclase, CaMgSi2O6, wollastonite, periclase and magnesium silicate in ash, reduces the liquid phase and controls the growth of ash adhesion strength. When the addition ratio is more than 5%, dolomite has a better inhibitory effect on the ash adhesion strength of straw. When 5% dolomite is added, the appearance temperature of ash adhesion strength increases by 200 °C, and the ash adhesion strength decreases by 58.54% at 1000 °C.
•The ash adhesion strength between straw ash and metal surface appears at 600 °C.•The melting of KCl and silicates leads to the ash adhesion strength.•Dolomite additive can effectively reduce the adhesion strength of straw ash.•The ash adhesion strength was measured by a new self-designed tester.
With the development of ultradeep oil and gas reservoirs, the service environment for tubing and casings is increasingly worse, resulting in higher requirements for the internal coatings, while ...reduced graphene oxide (rGO) is conducive to enhancing the corrosion resistance of the coatings to a certain extent. In this paper, rGO was first modified by the coupling agent KH-550 (namely, MrGO), and the physical and chemical properties (dispersibility, thermal stability, contact angle, and adhesion) of the MrGO/epoxy coatings with different MrGO contents (0.5 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, and 4 wt.%) were analysed. The corrosion resistance behaviour was studied by electrochemical techniques in CO2-Cl- environments. The results showed that the coupling agent KH-550 was better grafted with rGO and that the diffusivity of MrGO in the MrGO/epoxy coatings was significantly improved. With an increase in the MrGO content, the physical and chemical properties of the MrGO/epoxy coatings were considerably enhanced, and the corrosion resistance first increased and then decreased; among them, the thermal stability, friction coefficient, impact performance, adhesion, and corrosion resistance of the MrGO/epoxy coatings were best when the content of MrGO was 3 wt.%. Finally, a novel corrosion resistance mechanism was proposed for the MrGO/epoxy coatings. Thus, this work provides theoretical support for the development of new heavy corrosion coatings.
Mechanically softening materials have been intensively investigated to reduce ice adhesion strength based on the adhesion failure mechanism. Achieving icephobic surfaces with both low ice adhesion ...strength and mechanical robustness is challenging. The surface stiffening-induced stress concentration sites on elastomer should be possible to improve the mechanical robustness and lower the ice adhesion strength simultaneously, as it can build material inhomogeneity (stiffness mismatch) and geometry irregularity-induced cracks on the surface layer of elastic materials. To reveal this hypothesis, the stress concentration sites are introduced to obtain the robust low ice adhesion surface (RLAS) by implementing rigid nanocomposites with the elastic modulus of GPa scales (e.g. silica nanoparticles, SiO2NPs, ca. 68.9 GPa) into the surface layer of elastomers (e.g. polydimethylsiloxane, PDMS, ca. 2.7 MPa). The effects of the material inhomogeneity (stiffness mismatch) and geometry irregularity-induced stress concentration sites on the reduction of ice adhesion strength are revealed. The minimum ice adhesion strength of the RLAS is down to 10.5 kPa, and its ice adhesion strength remains at 13.8 kPa after 25 icing/deicing cycles. Originating from abundant potential crack initiation sites and stiff nanoparticles, our designed nano-composite materials remarkably lower the ice adhesion strength and are over 2-fold mechanically stiffer than pure elastomer. This strategy offers an unconventionally hardening surface approach for designing icephobic materials with combined durability and robustness.
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•This work proposed a stiffening surface strategy to reduce ice adhesion strength.•Stress concentration sites were built by material inhomogeneity and geometry irregularity.•The durable ice adhesion strength of the optimal sample retains ca. 13.8 kPa.
Adhesion of cells on biomaterials plays an essential role in modulating cellular functions. Although hydration of biomaterials occurs under biological conditions, it is challenging to systematically ...evaluate the correlation of hydrated water content in biomaterials with the cell adhesion strength. In this report, we investigated the effect of bound water content on the adhesion strength of cells on poly(2-methoxyethyl acrylate) (PMEA) analogue substrates. Water-insoluble PMEA analogues were synthesized to fabricate substrates with a systemically controlled bound water content. To assess the surface properties of their substrates, contact angle measurement, atomic force microscopy (AFM), and fluorescence measurement were conducted. To reflect the effect of bound water of PMEA analogues, the relationship between the bound water content and cell adhesion behavior was evaluated under serum-free condition. From the single cell force spectrometry (SCFS) and microscopic analysis, it revealed that the increment of bound water content on the substrates decreased cell adhesion strength and cell spreading on the substrates. The bound water content exhibited a good correlation with adhesion strength, spreading area, circularity, and aspect ratio of cells. Our findings indicate that the bound water content could contribute to the development of a novel biomaterial and evaluation of cell behaviors on biomaterials.
For coordinating cell functions, such as growth, mobility, and differentiation, modulating the adhesion strength between cells and their environments is important. Although the hydration to biomaterials has been reported to be closely related to a antifouling property, the effect of hydration water on the cell adhesion behavior is not well understood. We present the first demonstration of essential relationship between cell adhesion strength and hydrated water on a biomaterials surface using the water-insoluble polymers with different hydrated water content. The results reveal that the hydrated water content of polymer substrates strong correlation with adhesion strength of cells. Collectively, the hydrated water content of the biomaterials will be a predominant factor affecting the cell adhesion strength and behavior.
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Environmental friendly sodium alginate (SA) cannot be used as a binder in aqueous batteries due to its high solubility in water. A water-insoluble polyvinylidene difluoride (PVDF) binder has been ...widely applied for an aqueous battery, in which the toxic and expensive organic solvent of N-methy-2-pyrrolidone (NMP) is required during the coating process. Herein, we report that the water-soluble SA can be utilized as a binder in aqueous Zn batteries because SA could cross-link with the Zn2+ ion to form a water-insoluble and mechanically super strong binder for electrodes. Aqueous Zn||LiFePO4 cells are assembled to demonstrate the performance of the SA binder for LiFePO4 cathodes. Due to the high adhesion strength of cross-linked Zn-SA, LiFePO4 with the SA binder displays a high capacity retention of 93.7% with a high Coulombic efficiency of nearly 100% after 100 cycles at a 0.2 C rate, while the capacity of LiFePO4 with the PVDF binder quickly decays to 84.7% after 100 cycles at 0.2 C. In addition, the LiFePO4 cathode with the SA binder also has smaller redox polarization, faster ion diffusion rate, and more favorable electrochemical kinetics than that with the PVDF binder.
