CNT-ZnO Core-Shell Photoanodes for Photoelectrochemical Water Splitting

Solar-driven water splitting is a promising route toward clean H2 energy and the photoelectrochemical approach attracts a strong interest. The oxygen evolution reaction is widely accepted as the performance limiting stage in this technology, which emphasizes the need of innovative anode materials. Metal oxide semiconductors are relevant in this respect owing to their cost-effectiveness and broad availability. The combination of chemical vapor deposition and atomic layer deposition was implemented in this study for the synthesis of randomly oriented CNT-ZnO core-shell nanostructures forming an adhering porous coating. Relative to a directly coated ZnO on Si, the porous structure enables a high interface area with the electrolyte and a resulting 458% increase of the photocurrent density under simulated solar light irradiation. The photoelectrochemical characterization correlates this performance to the effective electrons withdrawing along the carbon nanotubes (CNTs), and the resulting decrease of the onset potential. In terms of durability, the CNT-ZnO core–shell structure features an enhanced photo-corrosion stability for 8 h under illumination and with a voltage bias.

Electrochemical Behaviour of Ti and Ti-6Al-4V Alloy in Phosphate Buffered Saline Solution

The electrochemical behavior of commercially pure titanium (CP Ti) and Ti-6Al-4V (Grade 5) alloy in phosphate buffered saline solution (PBS, pH = 7.4) at 37 °C (i.e., in simulated physiological solution in the human body) was examined using open circuit potential measurements, linear and potentiodynamic polarization and electrochemical impedance spectroscopy methods. After the impedance measurements and after potentiodynamic polarizationmeasurements, the surface of the samples was investigated by scanning electron microscopy, while the elemental composition of oxide film on the surface of each sample was determined by EDS analysis. The electrochemical and corrosion behavior of CP Ti and Ti-6Al-4V alloys is due to forming a two-layer model of surface oxide film, consisting of a thin barrier-type inner layer and a porous outer layer. The inner barrier layer mainly prevents corrosion of CP Ti and Ti-6Al-4V alloy, whose thickness and resistance increase sharply in the first few days of exposure to PBS solution. With longer exposure times to the PBS solution, the structure of the barrier layer subsequently settles, and its resistance increases further. Compared to Ti-6Al-4V alloy, CP Ti shows greater corrosion stability.

The effect of stadial nitrogenization on the structure and properties of martensitic steel 13X11N2V2MF

A new method of gas nitriding is presented, which produces obtaining high-quality diffusion layers that meet the requirements of the use for various purposes, including aviation ones. Peculiar properties of highly alloyed martensitic steel nitriding after stadial thermo-gas-cyclic nitrogenization under partially dissociated ammonia with air additives have been examined. The results of metallographic studies, diagnostic leach, tests for wear resistance, impact hardness and corrosion stability, depending on the test mode are presented.

Magnetoimpedance of CoFeCrSiB Ribbon-Based Sensitive Element with FeNi Covering: Experiment and Modeling

Soft magnetic materials are widely requested in electronic and biomedical applications. Co-based amorphous ribbons are materials which combine high value of the magnetoimpedance effect (MI), high sensitivity with respect to the applied magnetic field, good corrosion stability in aggressive environments, and reasonably low price. Functional properties of ribbon-based sensitive elements can be modified by deposition of additional magnetic and non-ferromagnetic layers with required conductivity. Such layers can play different roles. In the case of magnetic biosensors for magnetic label detection, they can provide the best conditions for self-assembling processes in biological experiments. In this work, magnetic properties and MI effect were studied for the cases of rapidly quenched Co67Fe3Cr3Si15B12 amorphous ribbons and magnetic Fe20Ni80/Co67Fe3Cr3Si15B12/Fe20Ni80 composites obtained by deposition of Fe20Ni80 1 μm thick films onto both sides of the ribbons by magnetron sputtering technique. Their comparative analysis was used for finite element computer simulations of MI responses with different types of magnetic and conductive coatings. The obtained results can be useful for the design of MI sensor development, including MI biosensors for magnetic label detection.

Vapour Phase Deposition of Thin Siloxane Coatings on the Iron Surface. The Impact of the Layer Structure and Oxygen Adsorption on Corrosion Stability

The mechanism of iron corrosion protection by thin siloxane films was clarified. Quartz crystal microbalance technique (QCM) was applied to control the vapour phase deposition of alkoxysilanes and the formation of thin siloxane films. It was shown that the addition of water vapour increased the thickness of the grafted siloxane films. Crystal-like films spontaneously grow to 10–16 monolayers at 100% RH of Ar flow due to the catalytic effect of the surface. X-ray photoelectron (XPS) and Auger spectroscopies analysed the thin siloxane films and Scanning Kelvin Probe (SKP) showed the formation of iron-siloxane bonds passivating the iron surface. The films showed high hydrophobicity and corrosion inhibition in humid air contaminated by sulphur dioxide. Thick films were less ordered, hydrophilic and accelerated the corrosion of iron. For corrosion protection, the presence of oxygen in the atmosphere is extremely important. In a wet Ar atmosphere, contaminated by sulphur dioxide, the surfaces are not stable and quickly corroded. Oxygen adsorption stabilizes the surface oxide film that correspondingly preserves the anchoring iron-siloxane bonds and enables corrosion protection by the coating.

Evolution of the ε and γ phases in biodegradable Fe–Mn alloys produced using laser powder-bed fusion

The key feature of Fe–Mn alloys is gradual degradability and non-magneticity, with laser power bed fusion (LPBF) parameters influencing the microstructure and chemical composition. Our study focuses on biodegradable Fe–Mn alloys produced by mechanically mixing pure metal feedstock powders as part of the LPBF process. The Mn content and, consequently, the γ-ε phase formation in LPBF samples are directly correlated with an adapted energy–density (E) equation by combining the five primary LPBF parameters. We varied laser power (P) in a range of 200–350 W and scanning speed at 400 and 800 mm/s, and a comprehensive study was performed on samples with similar E. The study also showed an almost linear correlation between the LPBF's laser power and the material's hardness and porosity. The corrosion resistance was significantly reduced (from 13 to 400 μm/year) for the LPBF samples compared to a conventionally produced sample due to the dual-phase microstructure, increased porosity and other defects. The static immersion test showed that the process parameters greatly influence the quantity of oxides and the distribution of their diameters in the LPBF samples and, therefore, their corrosion stability. The most challenging part of the study was reducing the amount of ε phase relative to γ phase to increase the non-magnetic properties of the LPBF samples.

Electrochemical corrosion response of ZrN coated Nickel-Titanium alloy in 0.9% NaCl solution

The biomedical application as metallic body implants of Nickel-Titanium shape memory alloys are of high interest due to its unique property of pseudo elasticity. However, high content of nickel and its potential to release from the surface due to corrosion raises safety concerns about its allergic reactions, toxicity and carcinogenicity. Hence, it is necessary to produce proper passivity to prevent surface layer degradation. In this study, ZrN coating on Nickel-Titanium shape memory alloys was obtained by vacuum cathodic arc physical vapor deposition technique to improve electrochemical corrosion resistance. The electrochemical corrosion response was studied in 0.9% NaCl solution at 370C using Tafel extrapolation method. Surface morphology was studied using SEM/EDAX and XRD. ZrN coating increases corrosion stability and micro hardness. Keywords: Shape memory alloy; pseudoelasticity; vacuum cathodic arc PVD; electrochemical corrosion; micro hardness.

Ceria Particles as Efficient Dopant in the Electrodeposition of Zn-Co-CeO2 Composite Coatings with Enhanced Corrosion Resistance: The Effect of Current Density and Particle Concentration

Novel Zn-Co-CeO2 protective composite coatings were deposited successfully from chloride plating solutions. Two different types of ceria sources were used and compared: commercial ceria powder and home-made ceria sol. Electrodeposition was performed by a direct current in the range of 1–8 A dm−2. Two different agitation modes were used and compared, magnetic stirring and ultrasound-assisted stirring (US). The influence of magnetic stirring on the stability of the related plating baths was evaluated via a dynamic scattering method. The results pointed to better stability of the prepared ceria sol. The morphology of the composite coatings was examined by scanning electron microscopy (SEM), and particle content was determined by energy-dispersive X-ray spectroscopy (EDS). The results showed that the increase in the deposition current density was not beneficial to the coating morphology and particle content. The corrosion behavior of the Zn-Co-CeO2 composite coatings was analyzed and compared by electrochemical impedance spectroscopy and polarization resistance. The ultrasound-assisted electrodeposition at small current densities was favorable for obtaining composite coatings with enhanced corrosion stability. The protection was more effective when US was applied and, additionally, upon utilization of ceria sol as a particle source, which was revealed by higher polarization resistance and greater low-frequency impedance modulus values for sol-derived composite coatings deposited under ultrasound.