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Polyethersulfonbasierte Hohlfasermembranen mit einer hydrophil funktionalisierten Trennschicht wurden hergestellt und untersucht. In die Trennschicht wurde ein amphiphiles Triblockcopolymer mit verschiedenen Konzentrationen integriert. Um eine gesteigerte Hydrophilie und damit assoziiertes verringertes Fouling zu erreichen, bestehen die Blockcopolymere aus zwei äußeren Poly(ethylenoxid)-Blöcken. Diese flankieren den inneren Polyethersulfonblock, welcher der Verankerung des Additivs in die Membran dient. Gesteigerte Hydrophilie, gepaart mit Permeanzen von 2000 L m−2h−1bar−1 und einem Rückhalt von 100 kDa, kennzeichnete die vielversprechendste Membran dieser Studie.

Bovine serum albumin (BSA) or fetal bovine serum (FBS), as the protein component, is usually added into solution to study the influence of proteins on Mg degradation. However, the specific character of proteins used and the interaction between organic molecules in FBS do not draw enough attention. This study investigated the influence of BSA, fibrinogen (Fib) and FBS on Mg degradation in Hanks’ balanced salt solution without (HBSS) or with calcium (HBSSCa) and Dulbecco\'s modified eagle medium Glutamax-I (DMEM). The results reveal that the effect of BSA, Fib and FBS on the degradation rate of Mg is time- and media-dependent, as a result of the overlap of protein adsorption, binding/chelating to ions and interaction between organic molecules. The binding/chelating of proteins and/or the possible effect of proteins on the kinetics of products formation lead to the formation of different degradation precipitates on Mg surface in HBSS. The interaction between proteins and Ca2+/PO43− accelerates the formation of Ca-P salts in HBSSCa and DMEM, thereby impeding the degradation of Mg. Moreover, the interplay between organic molecules and the specific character of proteins are highlighted by the cooperative (in media + FBS) or competitive (in DMEM + BSA + Fib) effect of proteins in the presence of more kinds of proteins and the different effect of BSA and Fib on the degradation of Mg. Therefore, the addition of proteins to testing medium is necessary for in vitro tests and DMEM + 10% FBS is recommended as the in vitro testing medium to present an in vivo-like degradation for Mg.

Several typical organic components, l-ascorbic acid (l-AA), l-glutamine (l-Gln), l-alanyl-l-glutamine (l-Ala-l-Gln) and fetal bovine serum (FBS) were chosen to elucidate the effects of organic components on the degradation of pure Mg under cell culture conditions. The results revealed that the influence of organic components on the degradation of pure Mg is time-dependent and they play an important role in the formation of the degradation layer. The addition of organic components favors the precipitation of nesquehonite rather than hydromagnesite in the “outer” layer, while in the “inner” layer the organic components accelerates the formation of phosphate (Mg-PO4, Ca-P salts) during immersion.

Chemistry of surface and thin films

Friction spot joints of aluminum alloy 2024-T3 and carbon-fiber-reinforced polyphenylene sulfide (CF-PPS) were produced with PPS film interlayer. Mechanical grinding, sandblasting and sandblasting combined with plasma activation were performed on the composite part to enhance the interface adhesion. The surface features – roughness, wettability and chemical activation – were correlated with the ultimate lap shear force of the joints. The composite surface with the highest surface roughness (sandblasting: 5.3 ± 0.6 µm) led to joints approximately 95% stronger (3068 ± 192 N) than the joints with the lowest surface roughness (mechanical grinding: 0.6 ± 0.1 µm, 1573 ± 84 N). The increase in surface roughness enlarged the effective contact surface area, leading to a better micro-mechanical interlocking between PPS film and composite. Although functional groups were identified in the plasma-treated specimens using X-ray photoelectron spectroscopy, no contribution to the mechanical strength of the joints were observed. The fracture surface analysis supported the conclusion that sandblasting was the most effective treatment, maximizing the mechanical performance of the joints. Impressions containing pieces of carbon fibers were identified on the interlayer surface. It indicates effective micro-mechanical interlocking at the interface of interlayer-composite achieved with the sandblasted specimens.

Four binary cast Mg-Ga alloys containing 1, 2, 3 and 4 wt% Ga were studied in terms of microstructure and degradation behavior. The alloys present two types of intermetallics: (i) the second phase Mg5Ga2, which volume increases with the amount of Ga in the alloy, and (ii) inclusions containing impurities. For the first time, the binary Mg-Ga system is analyzed paying particular attention to the effect of secondary phases (Mg5Ga2) and impurities on the localized corrosion mechanism using AFM/SKPFM. Inclusions containing impurities reveal a high Volta potential difference, enough to form an active galvanic couple. However, localized electrochemical activities decrease with time leading to uniform degradation. For short immersion times, there is no clear influence of the element Ga on the corrosion behavior, measured by electrochemical and hydrogen evolution tests. However, for longer immersion times, increasing the amount of Ga in the alloy shows a clear negative effect. Electrochemical measurements reveal that higher Ga containing alloys form faster an oxide layer which is not stable.

Surface species responsible for low pH values of zero charge point and high sorption capacity of mesoporous TiO2 powder obtained by TiC oxidation with nitric acid were studied by FTIR, EPR and XPS methods. It was found that during the titania synthesis the oxide surface was modified by nitrate-nitrite, carboxylic groups, NOx and ·С≡ radicals which determined adsorption properties of the TiO2 powder. published

The high oxidizing power of photogenerated holes in titania coupled with the chemical stability of TiO2 material allow to use it for many applications that exploit solar energy. (...) published

This article provides a contribution towards the mechanistic understanding of surface phenomena observed during corrosion of Mg-based substrates particularly in the low anodic polarization range. The concept considers recent literature explaining cathodic hydrogen evolution from noble acting areas even during global anodic polarization. Heavy metal impurities in the ppm range or intermetallics are always present even in highly pure magnesium. Their potential effect was investigated here in more detail. Experimental results contribute to understanding the role of iron impurities during dark area formation and suggest a way of linking the observed phenomena to recent literature. The shown enhanced cathodic activity of dark areas especially at the corrosion front and the superfluous hydrogen are linked to an iron re-deposition mechanism due to iron reduction. The proposed mechanism is based on results obtained from innovative characterisation techniques using magnetic fields, diffraction experiments and transmission electron microscopy, which show the formation of iron rich zones, especially at the corrosion front offering “in statu nascendi” metallic Fe films acting as active cathodes for hydrogen reduction.

In this work, nanocontainers based on layered double hydroxide (LDH) loaded with two different corrosion inhibitors, namely 2-mercaptobenzothiazole (MBT) and cerium(III) nitrate, were prepared. MBT was intercalated into LDH galleries in anionic form by anion-exchange, while Ce3+ was fixed between polyelectrolyte layers on the surface of LDH-MBT nanoplatelets by the Layer-by-Layer (LbL) method. Both inhibitors were found in the modified LDHs (LDH-Mod) by X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy. The release studies performed by UV-vis spectrophotometry indicated that the main triggering conditions for release of MBT from LDHs changed when LDH nanoplatelets were covered with polyelectrolytes. Furthermore, electrochemical impedance spectroscopy and DC polarization were used to investigate the effect in combining MBT− and Ce3+ within the same nanocontainer, for the corrosion protection of 2024-T3 aluminium alloy directly in solution as well as in a hybrid sol–gel coating. The obtained results open prospects for application of these systems as additives in multifunctional smart coatings.

In a screening test, typical traditional alloying elements for magnesium (Al, Mn, Zn, Y) were added to Mg10Gd alloy to study their influence on its corrosion resistance. The Mg10Gd1Mn alloy was identified as the most promising ternary alloy system. While addition of Gd alone disturbs the passive film formation the presence of Mn is beneficial for recovery of the passivity. Performance of the Mg10Gd1Mn alloys is comparable to high purity Mg.

In the present study, the potential of poly(ether imide) as corrosion protective coating for magnesium alloys was evaluated using the spin coating technique. The influence of different parameters on the coating properties was evaluated and the corrosion behaviour of the coatings was investigated using electrochemical impedance spectroscopy. The best corrosion protection was obtained preparing the coatings under N2 atmosphere, using 15% wt. solution in N’N’- dimethylacetamide (DMAc) which resulted in a coating of approximately 2 μm thickness, with an initial impedance of 109 Ω cm2 and of 105 Ω cm2 after 240 h of exposure to a 3.5% NaCl solution.

It is critical for the aeronautical industry that the next generation of smart coatings allows the early detection and continuous monitoring of corrosion. Once corrosion is detected, preventive actions can be taken in order to mitigate its costs. Our strategy relies on functional coatings capable of detecting metallic corrosion early on. After appropriate selection of sensing compounds and subsequent loading into nanostructured materials, these are incorporated into coating formulations giving them corrosion sensing functionality. Based on this concept we focused on the compatibility between nanocontainers and coating formulations. Thus, a new sensing coating was investigated using immersion and salt-spray tests, release and leaching studies, viscoelastic properties, curing, thermal stability, hardness, mechanical properties and corrosion resistance. The results embody a new generation of coatings with sensing ability, and have implications for self-healing and anti-fouling coatings as well. published