Advanced Materials Research Vols. 79-82

Abstract: Styrene-acrylic emulsion was synthesized by pre-emulsification and semi-continuous emulsion polymerization, with styrene and butyl acrylate as monomers. The effects of initiator dosage and ratio of polymer to cement on durability of polymeric sulphoaluminate cement were investigated. SEM, pore structure and resistance to sulfate attack were also studied. The results show that the total porosity of the polymer sulphoaluminate hardened cement paste is lowest when P/C is 7.5%. Innocuous pores of the hardened paste are the least when P/C is 5.0%. It shows that polymer particles can spread around the cement paste, and polymer particles, aggregates, hydration products and pores come into being a compact mass. Flexural strength is higher when initiator dosage is 5‰ than that is 4‰. Flexural strength is the highest when initiator dosage is 5‰ and P/C is 7.5%, in other words, the performance of resistance to sulfate attack is best when initiator dosage is 5‰ and P/C is 7.5%.

Abstract: The composite antibacterial agents were prepared with Medical stone containing Cu2+ and Zn2+ by liquid ion-exchange reaction. The ion exchange capacity of the as-prepared Medical stone composite antibacterial agents (MSAA) products were investigated by ICP-AES, and the antibacterial activities of the agents were tested by Bacteriastasis ratio, and the structures were characterized by XRD and SEM. The results show that the conditions of preparation, such as pH, concentrations of copper and zinc ions, reaction time and reaction temperature, have important influences on the ion exchange of MSAA. The maximum ion exchange capacity have been obtained when 0.2mol/l Cu2+ and 0.6 mol /l Zn2+ reacted with Medical stone powers in the solution with pH values of 8 for 8 hours at 50 °C. Meanwhile good antibacterial activities and safety are also gained. The reasons for causing the above results are that copper and zinc ions can enter the framework of Medical stone through ion exchanging and adsorption, and are released slowly owing to its porosity.

Abstract: In this study, the V-doped TiO2 was synthesized by sol-gel method and we evaluate the photocatalytic degrading efficiency of V-TiO2 complexes on azo dye wastewater under irradiation with visible light (λ= 419 nm). The results showed that the Anatase structure and nano size of V-TiO2 complexs were formed and they had better photo-response to visible light than pure TiO2. The efficiency of decoloriztion or destruction efficiency was less than 6 % using TiO2 alone but efficiency of 0.10VT-I was up to 90% after irradiated with visible light for 240 min. These evidences also reveal that the system of V-TiO2 complexes can directly utilize the sunlight and can be used to treat organic pollutants in the practical wastewate treatment factories.

Abstract: Biofouling on underwater engineered structures, especially on ship hulls, results in increased operational and maintenance costs. The traditional methods of protecting marine structures have been the use of toxic antifoulants, such as lead, mercury and tributyltin compounds (TBT). Such heavy metals have proven to be effective in deed, but severe shellfish deformities and the bioaccumulation of heavy metals in ducks, seals and fish lead to the global ban of toxic antifoulants. Therefore, our antifouling strategy is to develop minimally adhesive, mechanically stable and nontoxic fouling release coatings which degrade fouling an organism’s ability to adhere to surfaces. Herein we report on the synthesis and characterization of a novel cross-linkable copolymer grafted a semifluorinated aromatic side chain which was prepared by copolymerization with methyl methacrylate and glycidyl methacrylate. Bulk and surface properties were assessed through 1H NMR and 19F NMR spectra, contact angle measurement. The cross-linkable copolymer was rationally designed for use as coating to prevent marine bioufouling. Apart from the use of methyl methacrylate and glycidyl methacrylate which contained epoxide ring serving as a cross-linked group, the other important monomer―a semifluorinated group substituted styrene monomer was selected to construct a low surface energy material. Finally, the antifouling potential of the designed polymer surface was evaluated employing the fouling diatom Nitzschia in our laboratory. Experimental results indicated the combination of the low surface energy group (semifluorinated segments) and linker group (epoxide ring) allowed the cross-linkable polymer surface possessing a little better antifouling properties than that a standard poly(dimethyl siloxane) (PDMS) coating.

Abstract: Biofouling, which is the result of marine organisms settling, attaching, and growing on submerged marine surfaces, is a usually-seeing phenomenon for the ocean-going ships and submarines. And, it can decrease the range, speed, and maneuverability of these vessels and increase the fuel consumption. Contrarily, the sharks remain largely free of bioadhesion despite spending their entire lives submerged. The sharks have placoid scales, which consist of rectangular base embedded in the skin with tiny spines that poke up from the surface. It is found that this special structure can make great deal of function for antifouling. In our report, parallel works for antifouling mechanisms were motivated by Triakidae shark feeding, observations on shark skin, and the experiments of benthic diatoms adhesion and Mytilus edulis byssus attachment. And, the optical configurations were acquired by using 3D video microscope and environment scanning electron microscope (ESEM). The results showed that, the benthic diatoms adhesion on the naked skin of living sharks was obviously fewer than the dead ones, and could not be found on the surface of placoid scales. As the time progressed, the rate of Mytilus edulis byssus attachment reduced gradually. It was thought that, the water turbulent boundary on the surface was changed greatly and innumerable minimal vortex was generated when the water flow on the shark skin. The strong exchange of momentum in a turbulent boundary layer would produce high-speed lumps approaching the surface, which could develop strong shear stress. Benthic diatoms and mussel could not attached firmly or be cleared easily when the shear stress became stronger than the adhesion power of these organisms. After finding the real working mechanism of antifouling for sharks, it could be used to direct the progresses of synthesizing biomimetic coatings or materials with antifouling performance in the future.

Abstract: Imidazoline derivative inhibitors are successfully used in oil-gas field for CO2 and H2S corrosion. The inhibition performance and inhibition mechanism of imidazoline with thioureido to prevent corrosion of steel in saltwater saturated with CO2 were studied by polarization curves and electrochemical impedance spectroscopy (EIS), in the meantime, quantum chemical analysis was used to analysis the results. The results of electrochemical measurements indicated that the inhibitor belonged to mixed-type inhibitor which mainly inhibited anodic process and worked as “negative catalysis”. The inhibition efficiencies increased then decreased with the increase in inhibitor concentration. The electrochemical results have also been supplemented by quantum chemical analysis. It was found that the chemical adsorption of the imidazoline with thioureido molecule on Q235 steel depended on the imidazoline ring and thioureido, thus the inhibitor had good corrosion inhibition.

Abstract: In natural seawater environment, temperature and chlorine ion are important factors for organic coating degradation. The alternating pressure of seawater can also affect the lifetime in deep-sea environment and probably is conducive to synergistic effects with other ageing factors. The present work is to investigate the effect of alternating pressure of seawater on protective properties of epoxy organic coating on 907A steel substrate, and evaluates the organic coating degradation process after pressure tests at atmospheric pressure. EIS was used to study the degradation process of the organic coating in natural seawater. The results demonstrated that the impedance of coating under alternating pressure of seawater conditions decreased faster than that at atmospheric pressure. With the increase of alternating pressure cycles, the entire degradation process of organic coating was accelerated. It is concluded that alternating pressure of seawater has to be considered as an aggressive factor like temperature or chlorine ion.

Abstract: In this study, we synthesized a new inorganic antibacterial material, of which Cu2+ was selected to be the antibacterial ion, cerous nitrate served as the additives, and the white carbon black was chosen as the carrier, which was prepared by a sol-gel method. The as-synthesized antibacterial material was characterized by inductively coupled plasma, particle size measurement instrument, scanning electron microscope and enumeration tests. The result showed that the amount of antibacterial ions and bacteriostasis rate of this new material are higher than those for the common Cu-inorganic antibacterial material without rare earths. In addition, the particle size of this material can be extended down to 20 μm with a narrow size distribution. Other advantages of this material are its loose and dispersive structure.

Abstract: The effects of pH value and chloride ions concentration of the solution on pitting susceptibility and semiconducting properties of passive films formed on 18Cr-18Mn-2Mo-0.9N high nitrogen austenitic stainless steel (HNSS) were investigated using potentiodynamic polarization and capacitance measurement methods, respectively. The anodic polarization curves show that HNSS exhibits excellent pitting corrosion resistance in the solution with different pH values and chloride ions concentration, and the pitting corrosion resistance of HNSS decreases a little with decreasing the pH value or increasing the chloride ions concentration of the solution. The passive films formed on HNSS in the solution with pH values ranging from 1 to 9 or chloride ions concentration from 3.5 wt% to 20 wt% NaCl behave as n-type semiconductors. With increasing the pH value or decreasing the chloride ions concentration, the shallow donor and deeper donor densities decrease and the flat bland potential decreases, and the thickness of space charge layer increases. The deeper donor increases and then the second positive slope of straight linear region disappears with decreasing the pH value or increasing the chloride ions concentration of the solution, which can be attributed to the formation of Cr6+ is depressed.

Abstract: Ternary Ni-W-P coating was synthesized from a sulfate nickel bath. The planting rate is about 10µm/h, and the bath shows a reasonable stability. The coating shows a good adhesion to the substrate. The microhardness and corrosion resistance of the Ni–W–P deposits were found to be better when compared to plain Ni–P deposits. Also, the Ni-W-P coating with a high W content exhibits a better hardness and corrosion resistance than that with a low W content.