Increased secretion of bacterial pyomelanin caused by light accelerates corrosion of low alloy steel.

Microorganisms in the waterline zone can secrete pigments to avoid damage caused by ultraviolet radiation, some of which have corrosive effects. In this work, we found that the secretion of pyomelanin by P3 strain of Pseudoalteromonas lipolytica significantly increases under strong lighting conditions, accelerating the corrosion of the material. Molecular mechanisms indicate that strong light, as a stressful environmental factor, enhances the expression of melanin secretion-related genes to prevent bacteria from being damaged by ultraviolet radiation. Therefore, this work proposes a new corrosion mechanism in the waterline zone, pigment-producing microorganisms are also involved in the waterline corrosion process.

Corrosion Behavior of Ni/NiCr/NiCrAlSi Composite Coating on Copper for Application as a Heat Exchanger in Sea Water.

This study introduces a novel Ni/NiCr/NiCrAlSi composite coating to enhance the corrosion resistance of copper, particularly for its use in marine heat exchangers. Utilizing characterization techniques such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS), the paper investigates the coating's composition, structure, and corrosion resistance in 3.5 wt.% NaCl aqueous solutions. A significant focus is placed on the role of aluminum within the NiCrAlSi layer, examining its influence on the coating's structure and corrosion behavior. The results indicate that the NiCrAlSi layer with an aluminum content of 5.49 at.% exhibits the most improved corrosion resistance, characterized by the highest corrosion potential and a corrosion current density that is more than one order of magnitude lower compared to the Ni/NiCr coating. The effectiveness of this composite coating is attributed to its multilayer structure and the synergistic effect of alloying elements Cr, Al, and Si, which collectively inhibit corrosive medium penetration. These insights present the Ni/NiCr/NiCrAlSi coating as a promising candidate for copper protection in sea water environments, merging enhanced durability with cost-effectiveness.

Highly Orientated Sericite Nanosheets in Epoxy Coating for Excellent Corrosion Protection of AZ31B Mg Alloy.

The growing demands for material longevity in marine environments necessitate the development of highly efficient, low-cost, and durable corrosion-protective coatings. Although magnesium alloys are widely used in the automotive and aerospace industries, severe corrosion issues still hinder their long-term service in naval architecture. In the present work, an epoxy composite coating containing sericite nanosheets is prepared on the AZ31B Mg alloy using a one-step electrophoretic deposition method to improve corrosion resistance. Due to the polyetherimide (PEI) modification, positively charged sericite nanosheets can be highly orientated in an epoxy coating under the influence of an electric field. The sericite-incorporated epoxy coating prepared in the emulsion with 4 wt.% sericite exhibits the highest corrosion resistance, with its corrosion current density being 6 orders of magnitude lower than that of the substrate. Electrochemical measurements and immersion tests showed that the highly orientated sericite nanosheets in the epoxy coating have an excellent barrier effect against corrosive media, thus significantly improving the long-term anti-corrosion performance of the epoxy coating. This work provides new insight into the design of lamellar filler/epoxy coatings with superior anticorrosion performance and shows promise in the corrosion protection of magnesium alloys.

Anti-Fouling and Anti-Biofilm Performance of Self-Polishing Waterborne Polyurethane with Gemini Quaternary Ammonium Salts.

Biofilms are known to be difficult to eradicate and control, complicating human infections and marine biofouling. In this study, self-polishing and anti-fouling waterborne polyurethane coatings synthesized from gemini quaternary ammonium salts (GQAS), polyethylene glycol (PEG), and polycaprolactone diol (PCL) demonstrate excellent antibiofilm efficacy. Their anti-fouling and anti-biofilm performance was confirmed by a culture-based method in broth media, with the biofilm formation factor against Gram-positive (S. aureus) and Gram-negative bacterial strains (E. coli) for 2 days. The results indicate that polyurethane coatings have excellent anti-biofilm activity when the content of GQAS reached 8.5 wt% against S. aureus, and 15.8 wt% against E. coli. The resulting waterborne polyurethane coatings demonstrate both hydrolytic and enzymatic degradation, and the surface erosion enzymatic degradation mechanism enables them with good self-polishing capability. The extracts cyto-toxicity of these polyurethane coatings and degradation liquids was also systematically studied; they could be degraded to non-toxic or low toxic compositions. This study shows the possibility to achieve potent self-polishing and anti-biofilm efficacy by integrating antibacterial GQAS, PEG, and PCL into waterborne polyurethane coatings.

FeS2 Nanoparticles Encapsulated in S/N Co-Doped Carbon Nanofibers With a Three-Dimensional Multi-Channel Structure for Lithium-Ion Batteries.

Pyrite (FeS2) is one of the potential candidates for advanced rechargeable Li-ion batteries (LIBs) owing to its inherent capacity (849 mAh g-1), environmental friendliness, and abundant natural resources. However, the volume expansion of FeS2 and the dissolution of polysulfide in the electrochemical reaction severely limit its application in the field of energy conversion and storage. Herein, FeS2 nanoparticles are encapsulated in S/N co-doped three-dimensional multi-channel structural carbon nanofibers (FeS2@CNFs) through the electrospinning method. As a cathode material for LIBs, FeS2@CNFs demonstrated excellent rate property and cyclic stability. The 3FeS2@CNFs (weight ratio of FeS2 is 30%) present the initial capacity of 1,336.7 mAh g-1 and the remaining 856.5 mAh g-1 at 0.02A g-1 after 100 circles. The favorable electrochemical properties have confirmed that carbon nanofibers can enhance the electroconductivity of electrodes, reduce the volume collapse of FeS2, and remit the dissolution of polysulfide during the Li+ ions insertion/de-insertion process. In addition, co-doped S/N can supply abundant active sites for electrochemical reactions, providing enough space for Li+ ion storage. The results indicate that 3FeS2@CNFs is a cathode with a developmental prospect for LIBs.

Design of Multi-Functional Superhydrophobic Coating via Bacterium-Induced Hierarchically Structured Minerals on Steel Surface.

The fabrication of an eco-friendly, multi-functional, and mechanically robust superhydrophobic coating using a simple method has many practical applications. Here, inspired by shell nacre, the micro- or nano-scale surface roughness that is necessary for superhydrophobic coatings was formed via Bacillus subtilis-induced mineralization. The biomineralized film coated with hexadecyltrimethoxysilane (HDTMS) exhibited superhydrophobicity with water contact angles of 156°. The biomimetic HDTMS/calcite-coating showed excellent self-cleaning, anti-icing, and anti-corrosion performances. Furthermore, mechanically robust superhydrophobicity could be realized by hierarchically structured biomineralized surfaces at two different length scales, with a nano-structure roughness to provide water repellency and a micro-structure roughness to provide durability. Our design strategy may guide the development of "green" superhydrophobic coatings that need to retain effective multi-functional abilities in harsh marine environments.

Properties and Corrosion Resistance Mechanism of a Self-Healing Propane-1,2,3-Triol-Loaded Polysulfone Microcapsule Coating Loaded with Epoxy Resin.

Propane-1,2,3-triol-loaded polysulfone (PSF) microcapsules were prepared by the solvent evaporation method. The particle size of the microcapsules is about 140 µm. The shell wall thickness is about 17 µm approximately. The microcapsules have high thermal stability and antiwear performance. The self-healing coating was prepared by adding the prepared capsule into the epoxy resin coating. After electrochemical and corrosion immersion experiments, the resistance modulus of the coating added to the microcapsules was higher than the others in a 3.5 wt % NaCl corrosion solution, and it had the lowest corrosion current density, so the self-healing microcapsule coatings showed excellent healing ability and corrosion inhibition function for microcracks. This was attributed to the formation of a hydrophobic film after propane-1,2,3-triol was released from the damaged microcapsules.

Study of pitting corrosion inhibition effect on aluminum alloy in seawater by biomineralized film.

Metallic materials can be easily corroded in marine environments, in which pitting corrosion is very common. In this study, we investigated the effect of Bacillus subtilis, isolated from the South China Sea on the corrosion behavior of 2A14 aluminum alloy in seawater. Surface analysis of the alloy in the presence of the bacteria was used to observe corrosion morphology and the corrosion products studied. Electrochemical method was used to analyze the corrosion susceptibility of the alloy in seawater in the presence of the bacteria. Surface analysis suggested that a protective film with CaMg(CO3)2 was gradually formed on the surface of the alloy in the presence of the bacteria. The electrochemical results showed that the radius of the impedance arc of the alloy immersed in seawater with bacteria increased gradually with time. The bacteria promoted the formation of the CaMg(CO3)2 film, which blocked seawater from the alloy and consequently, inhibited pitting corrosion.

Bacillus subtilis Inhibits Vibrio natriegens-Induced Corrosion via Biomineralization in Seawater.

The marine bacterium, Vibrio natriegens, grows quickly in a marine environment and can significantly accelerate the corrosion of steel materials. Here, we present an approach to inhibit V. natriegens-induced corrosion by biomineralization. The corrosion of steel is mitigated in seawater via the formation of a biomineralized film induced by Bacillus subtilis. The film is composed of extracellular polymeric substances (EPS) and calcite, exhibiting stable anti-corrosion activity. The microbial diversity and medium chemistry tests demonstrated that the inhibition of V. natriegens growth by B. subtilis was essential for the formation of the biomineralized film.

Effect of Conducting Polyaniline/Graphene Nanosheet Content on the Corrosion Behavior of Zinc-Rich Epoxy Primers in 3.5% NaCl Solution.

The corrosion behavior of zinc-rich epoxy primers or paints (ZRPs) with different conducting polyaniline-grafted graphene (PANI/Gr) contents was investigated. Conductivity of the formed PANI/Gr nanosheets was significantly improved by employing the Gr as the inner template to synthesize the PANI. The protective properties and electrochemical behavior of coatings with artificial defects were investigated by monitoring the free corrosion potential versus time and by using localized electrochemical impedance spectroscopy (LEIS). A synergetic enhancement of the physical barrier role of the coating and the zinc sacrificial cathodic protection was achieved in the case of ZRP including PANI/Gr nanosheets. In addition, the ZRP mixed with the PANI/Gr at a content of 0.6% exhibited the best anticorrosion performance across the range of investigated PANI/Gr contents.

Marine Bacteria Provide Lasting Anticorrosion Activity for Steel via Biofilm-Induced Mineralization.

Steel corrosion is a global problem in marine engineering. Numerous inhibitory treatments have been applied to mitigate the degradation of metallic materials; however, they typically have a high cost and are not environmental friendly. Here, we present a novel and "green" approach for the protection of steel by a marine bacterium Pseudoalteromonas lipolytica. This approach protects steel from corrosion in seawater via the formation of a biofilm followed by the formation of an organic-inorganic hybrid film. The hybrid film is composed of multiple layers of calcite and bacterial extracellular polymeric substances, exhibiting high and stable barrier protection efficiency and further providing an in situ self-healing activity. The process involving the key transition from biofilm to biomineralized film is essential for its lasting anticorrosion activity, which overcomes the instability of biofilm protection on corrosion. Therefore, this study introduces a new perspective and an option for anticorrosion control in marine environments.

Copper Sulfide-Based Plasmonic Photothermal Membrane for High-Efficiency Solar Vapor Generation.

Solar vapor generation has attracted tremendous attention as one of the most efficient ways of utilizing solar energy. It is highly desirable to develop low-cost, eco-friendly, and high-efficiency solar absorbers for practical applications of solar vapor generation. Herein, a three-dimensional plasmonic covellite CuS hierarchical nanostructure has been synthesized as the light-absorbing material via a facile one-pot hydrothermal method for structurally integrated solar absorbers with microporous poly(vinylidene fluoride) membrane (PVDFM) as the supporting material. A broadband and highly efficient light absorption has been achieved in the wavelength of 300-2500 nm, along with high water evaporation efficiencies of 90.4 ± 1.1 and 93.3 ± 2.0% under 1 and 4 sun irradiation, respectively. Meanwhile, stable performance has been demonstrated for over 20 consecutive runs without much performance degradation. To the best of our knowledge, this is the highest performance among the copper sulfide-based solar absorbers. With the additional features of low-cost and convenient fabrication, this plasmonic solar absorber exhibits a tremendous potential for practical solar vapor generation.

Efficient synthesis of tungsten oxide hydrate-based nanocomposites for applications in bifunctional electrochromic-energy storage devices.

In this work, we realized the large-scale synthesis of WO3 · H2O nanoflakes (NFs), g-C3N4/WO3 · H2O nanocomposite (NC) and graphene (G)/WO3 · H2O NC via a sonochemical process with tungsten salt as the precursor, g-C3N4 or G sheets as the supports, and distilled water as the solvent. Both the g-C3N4/WO3 · H2O NC and G/WO3 · H2O NC exhibited much better electrochromic (EC) performance (higher coloration efficiencies and faster response times) than that of the WO3 · H2O NFs. Using the WO3 · H2O-based materials as electrode materials, EC batteries that integrate the energy storage and EC functions in one device have been assembled. The energy status of the EC batteries could be visually indicated by the reversible color variations. Compared with the plain WO3 · H2O-based EC batteries, the NC-based EC batteries possessed a lower color contrast between the charged and discharged conditions but much longer discharge durations. The EC batteries could be quickly charged in a few seconds by adding H2O2, and the charged batteries exhibited significantly-enhanced discharging durations in comparison with the initial ones. The g-C3N4/WO3 · H2O NC-EC batteries charged by a small amount of H2O2 could produce a long discharging duration up to 760 min.

Promoting Barrier Performance and Cathodic Protection of Zinc-Rich Epoxy Primer via Single-Layer Graphene.

The effect of single-layer graphene sheets (Gr) on the corrosion protection of zinc-rich epoxy primers (ZRPs) was investigated. Scanning electron microscopy (SEM) with an energy dispersive spectrometer (EDS) were used to characterize morphology and composition of the coatings after immersion for 25 days. The cross-sectional SEM images and X-ray photoelectron spectroscopy (XPS) confirmed that the addition of single-layer graphene facilitated assembling of zinc oxides on the interface between the coating and the steel. The open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) measurements revealed that both the cathodic protection and barrier performance of the ZRP were enhanced after addition of 0.6 wt. % Gr (Gr0.6-ZRP). In addition, the cathodic protection property of the Gr0.6-ZRP was characterized quantitatively by localized electrochemical impedance spectroscopy (LEIS) in the presence of an artificial scratch on the coating. The results demonstrate that moderate amounts of single-layer graphene can significantly improve corrosion resistance of ZRP, due to the barrier protection and cathodic protection effects.

Adhesion of Bacillus subtilis and Pseudoalteromonas lipolytica to steel in a seawater environment and their effects on corrosion.

In a marine environment, Bacillus subtilis and Pseudoalteromonas lipolytica are commonly found in the biofilms adherent to low-alloy engineering steel, and they have distinct effects on corrosion. In the present work, this phenomenon was investigated through the study of various materials characterization methods, electrochemical techniques, and contact angle measurements. It was found that the surface film formed on the steel in the presence of B. subtilis was compact, uniform, free of cracks, and hydrophobic. However, the film formed in the presence of P. lipolytica was loose, rough, heterogeneous, and hydrophilic. The main components of the films formed in the presence of B. subtilis and P. lipolytica were polysaccharides/TasA amyloid fibers and proteins/carboxylic acid, respectively. The composition, structure, and properties of the surface films formed on the steel were associated with different effects on corrosion. The presence of B. subtilis enhances the steel's resistance to corrosion, whereas corrosion was increased by the presence of P. lipolytica. In short, the compact and hydrophobic biofilm of B. subtilis appears to inhibit the corrosion of steel, while the loose, hydrophilic film of P. lipolytica tends to induce pitting corrosion.

Radio frequency negative permittivity in random carbon nanotubes/alumina nanocomposites.

While metal is the most common conductive constituent element in the preparation of metamaterials, one-dimensional conductive carbon nanotubes (CNTs) provide alternative building blocks. Here alumina (Al2O3) nanocomposites with multi-walled carbon nanotubes (MWCNTs) uniformly dispersed in the alumina matrix were prepared by hot-pressing sintering. As the MWCNT content increased, the formed conductive MWCNT networks led to the occurrence of the percolation phenomenon and a change of the conductive mechanism. Two different types of negative permittivity (i.e., resonance-induced and plasma-like) were observed in the composites. The resonance-induced negative permittivity behavior in the composite with a low nanotube content was ascribed to the induced electric dipole generated from the isolated MWCNTs. The frequency dispersions of such negative permittivity can be fitted well by the Lorentz model, while the observed plasma-like negative permittivity behavior in the composites with MWCNT content exceeding the percolation threshold could be well explained by the low frequency plasmonic state generated from conductive nanotube networks using the Drude model. This work is favorable to revealing the generation mechanism of negative permittivity behavior and will greatly facilitate the practical applications of metamaterials.

MnO2/g-C3N4 nanocomposite with highly enhanced supercapacitor performance.

A novel sandwich-like MnO2/g-C3N4 nanocomposite (NC) based on the integration of high-density MnO2 nanorods (NRs) onto the surfaces of two-dimensional (2D) g-C3N4 sheets has been successfully fabricated through a facile soft chemical route at low temperature. The MnO2/g-C3N4 NC electrode enhanced the supercapacitor (SC) performance, benchmarked against both the bare MnO2 NRs electrode and the MnO2/graphene oxide (GO) NC electrode, exhibiting high specific capacitance of 211 F/g at a current density of 1 A/g, with good rate capacity and cycling stability. The sandwich-like hybrid structure, the unique 2D structure of the g-C3N4 sheets and the presence of nitrogen in the g-C3N4 all contributed to the promising SC performance of the MnO2/g-C3N4 NC. This work demonstrated the advantages of the g-C3N4 sheets over the commonly-used GO sheets in the design of novel hybrid composite for enhanced capacitance performance of MnO2-based electrochemical SCs, and the results could be extended to other electrode materials for SCs.

Fabrication and Application of a New-Type Photothermal Conversion Nano Composite Coating.

Photothermal conversion nanomaterials attract much attention for their high light/heat transform efficiency and controllable light absorption. In this work, the CuS semiconductor nanomaterials were prepared through the deposition method in the presence of citrate sodium and were characterized by TEM, XRD and UV-vis spectra. A new type of nano composite coating was obtained from acrylic resin by adding the CuS nanoparticles and other nanomaterials which could absorb the light of various infrared bands. The test showed that when exposed to infrared light, the plastic greenhouse model equipped with photothermal conversion coating gave out a more significant temperature rising than that of the common plastic greenhouse. The properties of photothermal conversion and heat insulation of photothermal conversion coating reach the best when the addition quantities of CuS and ZrC nanoparticles are 2%.

Facile Synthesis of [Cu(SCH3 )]∞ Nanowires with High Charge Mobility.

[Cu(SCH3 )]∞ nanowires with lengths on the order of hundreds of micrometers were obtained with a facile method from the reaction of Cu(NO3 )2 ⋅3 H2 O, dimethyl sulfoxide (DMSO), and water under hydrothermal conditions within a large range of DMSO/water ratios and at various temperatures. These highly crystalline, thermally stable (under vacuum) nanowires are p-type conducting and have a hole mobility as high as 2 cm2 V-1 S-1 , which is 102 -105  times higher than previously reported values. The high hole mobility may demonstrate their promising future in various electronic-device applications.

Prolonging the duration of preventing bacterial adhesion of nanosilver-containing polymer films through hydrophobicity.

A superhydrophobic coating composed of silver nanoparticles was developed on copper from fluorinated multilayered polyelectrolyte films to examine its performance in preventing microbial adhesion. Antibacterial and antibiofouling experiments for this novel coating were conducted with SRB. From the disk diffusion tests (for 48 h), it was found that, compared to the traditional coating composed of nanosilver, this novel coating significantly improved antibacterial performance and long-term effectiveness. The oxidation states of the immobilized silver in polyelectrolyte multilayer films were investigated with X-ray photoelectron spectroscopy (XPS), and the stability of the immobilized silver was evaluated through a leaching test. It was found that if silver was exposed to aqueous environments some ionic silver species would be produced and released. The ion release kinetics showed that the duration of sustained release of antibacterial Ag ions from the novel coatings was prolonged, which was why they had more long-term antibacterial performance.