•Al coatings with good adhesion were deposited on sintered NdFeB by multi arc ion plating.•Al coatings on NdFeB magnets showed excellent resistance to corrosion without affecting magnetic property.Herein, pure Al coatings have been deposited on sintered NdFeB via multi-arc ion plating method. The effect of target current and working pressure on the microstructure and properties of these coatings have been investigated using scanning electron microscopy, laser scanning confocal microscopy, X-ray diffraction, tensile testing, electrochemical tests and neutral salt spray. The results showed that the Al coating on NdFeB magnets achieved higher deposition rate of 4.85 μm/h, a maximum adhesive strength of 24 MPa and a corrosion current density of two orders of magnitude less than that of bare NdFeB substrates when processed using a target current of 60 A and a working pressure of 1.0 Pa. Electrochemical impedance spectroscopy and neutral salt spray tests further proved the excellent corrosion protection performance of such thin films with a thickness of 5 μm without any significant perturbation on the magnetic properties of the substrate.

•Bi-layered TiAlN based tandem absorbers were prepared by DC magnetron reactive sputtering.•A high value of absorptance (0.92) and very low emittance (0.06) at 70 °C were achieved.•The porous surface of the tandem absorber suppresses the surface reflection.•Tandem absorbers are promising for high temperature solar thermal power generation applications.Bi-layered TiAlN based tandem absorbers deposited on Cu and Si substrates using DC magnetron reactive sputtering system have been reported. The TiAlN layer was graded with SiO2 to suppress the surface reflections. A high value of absorptance (0.92) and very low emittance (0.06) at 70 °C was achieved because of columnar TiAlN structure and porous surface of the tandem absorber. UV–Visible spectroscopy, scanning electron microscopy, transmission electron microscopy, micro-Raman spectroscopy and X-ray photoelectron spectroscopy techniques were employed to test the thermal stability. The tandem absorber showed high thermal stability in air at 550 °C. XPS results confirmed that the TiAlN layer also acts as a diffusion barrier for Cu and therefore the absorption property was not degraded even on heating at high temperature for 4 h.

Biological fouling in marine environments creates numerous problems for engineered structures. Microbial attachment to a solid surface and biofilm formation initiates the process of biofouling. Therefore, detecting the initial bacterial attachment and understanding the mechanism of biofilm formation are important for controlling biofouling. In the present study, the mechanisms of bacterial attachment and biofilm formation of two marine isolated bacteria, namely Pseudoalteromonas sp. and Pseudoalteromonas flavipulchra on Ti-coated samples were examined through different electrochemical, surface analysis and thermodynamic methods. The results revealed that the rate of bacterial attachment and mechanism of biofilm formation varied for different species of bacteria. The amount of exopolysaccharide production could affect the bacterial attachment rate. Open circuit potentiometry has been found to be a valid and simple technique for continuous real-time monitoring of the biofilm formation compared to other electrochemical and thermodynamic techniques. Finally, two different models have been suggested to explain initial adhesion and biofilm formation of bacteria of different species.

•Cr2O3 coatings are first used on sintered NdFeB magnets by magnetron sputtering.•Cr2O3 coating by IBAD has excellent properties due to crystal structure obtained.•Effect of oxygen flux on microstructure and properties is discussed.The coatings of Cr2O3 were deposited on sintered NdFeB magnets by direct current (DC) pulse magnetron sputtering with and without ion beam at different O2 pressures. The coatings were compact and had a thickness of 1.8–2.2 μm. The coatings achieved a hardness up to 29 GPa and a wear rate of 1.78 × 10−7 mm3/Nm when ion-beam-assisted-deposition (IBAD) was used. Excellent anti-corrosion properties were obtained in the coating prepared by IBAD while the good magnetic properties of NdFeB substrate were retained. Electrochemical measurements revealed that the corrosion current density of the sample decreased from 4.66 × 10−6 A/cm2 (bare NdFeB) to 2.87 × 10−7 A/cm2 when O2 flux was 17 sccm during IBAD process.

•A novel bacterium with the highest corrosion inhibitory effect is introduced.•From EIS, corrosion resistance of carbon steel increased by more than sixty fold.•An inhibitory layer covered the entire surface in the first hours of attachment.•Extracellular polymeric substances of bacterium have a corrosion inhibitory effect.Degradation of metals due to corrosion causes serious economic problems throughout the world, and different corrosion protection techniques are being used to extend the service life of metallic structures. It has been suggested that some microorganisms can inhibit electrochemical corrosion of metals. Here we isolated a new marine inhibitory bacterium, Vibrio neocaledonicus sp., and EIS results showed that the corrosion resistance of carbon steel increased by more than sixty fold in the presence of this bacterium. This is the highest corrosion inhibitory effect reported for bacteria and is comparable with some industrial coatings such as electroless Ni. This bacterium affected corrosion by the formation of an inhibitory layer on the metal surface in the first hours of attachment, with the consumption of oxygen by electron transport proteins. Extracellular polymeric substances produced by this bacterium also have a corrosion inhibitory effect. Thus we propose a new, natural, non-toxic, and cost-effective system for controlling corrosion processes using this bacterium or extracellular polymeric substances produced by this bacterium.

Electroless deposition technology has been considered as a kind of common ways to obtain cobalt alloy films. However, in order to get cobalt alloy films, high temperature (353 K) is necessary during the electroless deposition process which will increase costs and energy consumption. Ultrasonic was introduced during electroless plating process to obtain cobalt alloy films at lower initial temperature. It was found that the cobalt thin films could be prepared at lower initial temperature (323 K) with the introduction of ultrasonic. Therefore, different powers of ultrasonic were applied during the electroless deposition process to prepare CoP thin films on copper substrates from an alkaline bath in this investigation. The effects of different powers of ultrasonic on deposition rate, surface morphology, anticorrosion performance and magnetic property of films were studied. It was found that the deposition rate increased gradually with the rise in ultrasonic powers due to cavitation phenomenon. All the CoP films presented the typical spherical nodular structures with the impact of ultrasonic. Smaller and regular shaped structures could be observed when the films were deposited with higher power of ultrasonic which contributed directly to enhancement of anticorrosion performance. Saturation magnetization and coercivity of thin films increased gradually with the rise in ultrasonic powers during the electroless deposition process due to the higher amounts of cobalt.

•A method was suggested for studying a serious of Al-based alloys systematically.•The amorphous ranges of Al–M (Ti, Cr, W, Mo) alloys were identified.•The hardness of binary alloy coatings seems to be influenced by their structure.Al–M (M = Ti, Cr, Mo, W) alloy coatings were subjected to DC magnetron sputtering by a rapid method to analyze the evolution of coating structures with composition. Pure Al and M targets were used to deposit coating arrays across the entire binary range of Al–M alloys. All Al–M alloys exhibited a specific amorphicity range. Al–Ti and Al–Cr alloys were completely amorphous, whereas Al–Mo and Al–W alloys possessed a range of amorphous–crystalline mixtures. Results revealed that Al–Ti alloys had the widest amorphicity range. Nanoindentation tests indicated that the hardness and modulus of amorphous alloys were higher than those of solid solutions for Al–M alloys.

Ti/Al multilayers deposited on sintered NdFeB magnets by direct current magnetron sputtering with ion-beam assistance were studied in this report. Ti layers with a hexagonal close packed structure were obtained in the Ti/Al multilayers. The columnar structure growth of Al layers was successfully interrupted by the intercalated Ti layers. The Ti/Al multilayers showed more compact and uniform surfaces than the Al single layer. The corrosion current densities of the sintered NdFeB magnets coated with Ti/Al multilayers were much lower than that of the Al single layer. The Ti/Al multilayers also presented improved hardness.Highlights► Ti/Al multilayers were deposited on the NdFeB magnets by magnetron sputtering. ► The columnar structure growth was successfully interrupted in Ti/Al multilayers. ► The Ti/Al multilayers presented improved corrosion resistance and hardness.

•A little Ce could promote the magnets for a better corrosion resistance.•With increased Ce contents, the corrosion resistances of magnets decrease.•As the corrosion developed, the magnetic properties decreased.For the balanced consumption of rare-earth elements, cerium (Ce) was partially used for NdFeB magnets instead of Nd. The corrosion behaviour of the (Nd,Ce)FeB magnet with different Ce contents in 3.5% NaCl solution was investigated by SEM, XRD, EDS and electrochemical tests. After immersion, the weight loss was calculated and the magnetic properties of the samples were measured. Results showed that Ce affected the corrosion of the (Nd,Ce)FeB magnet. Compared with the NdFeB magnet without Ce but of the same grade as the magnetic energy product, (Nd,Ce)FeB magnet showed better corrosion resistance. With increased Ce content, the corrosion resistances and magnetic properties of (Nd,Ce)FeB magnets were investigated.