ABSTRACTFe-based amorphous coatings (AMC) are deposited on 8090 Al–Li alloy using low-pressure plasma spraying. Coating’s microstructure and interfacial characteristics are investigated. The coating is mainly amorphous in structure. Some crystalline phases were observed between the two splats. The corrosion current density of this coating is two orders of magnitude less compared to 8090. The coating has high density as the average porosity is less than 0.5%. Because of partial melting and quick cooling of the 8090 alloy in the process of molten droplets deposition, there is an amorphous transition zone formed at the interface of AMC/8090 Al–Li alloy, which indicates localized metallurgical bonding. In electrochemical testing, the coating shows an obvious passivation tendency, and crystallization between splats is the main cause of corrosion. Owing to the low oxygen content, the coating exhibits excellent wear resistance.

ABSTRACTIn order to promote the application of TiO2 in surface modification technologies, a detailed understanding of its structure and properties is necessary. For this reason, the reactivity and corresponding surface chemistry of stoichiometric and non-stoichiometric single crystals of titanium dioxide have been widely studied. In Part II of this review, special attention is paid to the role of individual surface sites and the effect of available charge on the adsorption processes on stoichiometric and reduced single crystal rutile and anatase surfaces. In addition, the most appropriate surface science methods used to study the surface chemistry of these surfaces are also highlighted. An understanding of the interaction of H2O and O2 with oxide surfaces is extremely important because these adsorbates form a de facto part of the environment in all technological applications. Moreover, they play an extraordinarily important role in the processes taking place in high-performance devices in the fields of energy, environment, and health. Consequently, special consideration is given to the adsorption and dissociation processes of the most technologically important inorganic adsorbates, such as H2O and O2, on model low Miller index single crystal surfaces of titania. In addition, light-induced reactivity of TiO2 and its application is also considered. Furthermore, the engineering of TiO2 nanocrystals with well-defined facets, their unusual photocatalytic properties, and applications are also briefly considered.

ABSTRACTFor the first time, a dynamic beamshaping technology has been utilized for the efficient production of periodic nanostructures on top of AlTiN coating to enable dry machining without costly and environmentally hazardous cutting fluids. First, a variety of periodic nanostructures with periods in a range of 740–273 nm were produced utilizing different wavelengths. Additionally, beamshaping technology increased productivity by 4008% up to 105 cm2 min−1 by shaping the Gaussian beam into a rectangular beam of 500 × 30 µm. To simulate the application load and resulting heat production during manufacturing, friction analysis was performed at room and elevated temperature to 500°C. The analysis revealed a significant reduction in the friction coefficient – up to 27% and 19% at room temperature and 500°C, respectively. The combination of these results demonstrates that the proposed method can be scaled up for the mass production of functionalized machining tools for dry machining.

ABSTRACTFabrication of the tri metal sulphide Al2S3-Cu2S-Ni17S18 thin film was achieved by physical vapour deposition. The synthesised material was fully characterised by XRD, SEM, EDX, UV-visible spectrophotometer and FTIR. A nanoscale ranged 23.5 nm average crystallite size was obtained for the ternary metal sulphide. A motley of clustered morphological particles was observed by SEM with the confirmation of the desired metals through energy dispersive X-ray. Band gap energy possessed by the ternary metal sulphide was 2.5 eV. The remarkable energy storing capability of the electrode was investigated by cyclic voltammetry, which presented a supercapacitance of 595 F g−1 expressing the pertinence of the synthesised material. Cycling stability of the nanoparticle thin film was also observed through the voltammetric analysis. Furthermore, the environmental applicability of the thin film was investigated by the photocatalytic degradation of pollutants with an impressive degradation rate constant 3.61 × 10−2 min−1 achieved for pesticide.

ABSTRACTDodecyltrimethoxysilane (DTMS)-modified reduced graphene oxide (rGO) nanocomposites were incorporated into polyurethane (PU) sponges by a combination of dip-coating and thermal curing reduction reaction to obtain a novel superhydrophobic DTMS-rGO-PU sponge for effective oil/water separation. The reaction conditions, such as the dip-coating solution concentration, the thermal curing reduction temperature, and the reaction time were demonstrated to be key factors in forming hierarchical DTMS-rGO nanocomposites, which significantly affected the surface wettability of the PU sponge. The resulting DTMS-rGO-PU sponge with a static water contact angle (WCA) of 152.2° displayed superior superhydrophobicity, and achieved an oil–water separation efficiency of 99.89% for various oil/water mixtures. This superhydrophobic sponge also showed minimal deterioration in its high oil adsorption capacity after 100 recycled adsorption operations. Furthermore, the as-prepared DTMS-rGO-PU sponge was proven to be physically and chemically stable and durable in harsh environmental conditions, suggesting its potential for industrial applications in oil spillage management.

ABSTRACTIn this study, the ceramic coating was prepared on Ti6Al4V alloy by scanning micro-arc oxidation (SMAO). The growth features of SMAO coating were investigated by combining the voltage and discharge variation. The result shows that a higher working voltage is obtained during SMAO treatment owing to additional resistance from the electrolyte column. As the SMAO goes on, the discharge region moves to the electrolyte column edge, exhibiting an annular shape. The current density with Gaussian distribution is observed between the stainless-steel tube (cathode) and titanium substrate (anode), which causes the SMAO coating to show a higher thickness in the middle and lower on both sides. Similar to traditional MAO, the SMAO coating has an enhancement in the thickness, pore size and Si content with increasing oxidation time, but coating degradation occurs in the later stage of SMAO. The SMAO coating mainly consists of amorphous SiO2, rutile and anatase phases.

ABSTRACTSlurry impregnation and gaseous Si infiltration were effectively used to produce compact MoSi2-doped Si–HfB2–SiC/Si–SiC (HMSS/SS) coatings with a thickness of 250 μm to protect carbon fibre reinforced carbon (Cf/C) composites from oxygen corrosion at 1700°C. The HMSS/SS coating obtained with a mosaic structure makes it possible to protect Cf/C composites at 1700°C for 276 h and the mass reduction is only 0.99%. The pinning effect of the embedded hafnia, the generated MoB together with the Hf, Mo co-doped Si-based glass layer, which successfully prevented the migration of oxygen, was attributed to the superior oxidation protection ability of the HMSS/SS coatings. This work provides a practical method for successfully extending the service life of Cf/C composites in the aerospace industry.

ABSTRACTThe current investigation focuses on the comparative assessment of each alloying element such as titanium, chromium, boron, and molybdenum on mechanical and solid particle erosion behaviour of Iron amorphous composite coatings. Iron amorphous composite coatings were deposited on 316L steel. Based on mechanical and erosion properties, the ranking of the alloying element was derived using the Fuzzy analytic hierarchy process (FAHP) and Grey relational analysis (GRA). Eight different series of Iron-based composite coatings with varying alloying elements were deposited on 316L steel. The results indicated that titanium showed the maximum hardness and adhesion pull-off strength, boron showed maximum fracture toughness, Molybdenum indicated the lowest porosity and chromium indicated maximum corrosion resistance. The result of FAHP + GRA concluded that the ranking of Fe amorphous composite coatings followed the order as FeCSiMoBCr10Ti (C-2)> FeCSiMoBCr5Ti (C-1) FeCSiMo10BCrTi (C-6)> > FeCSiMo5BCrTi (C-5)> FeCSi10MoBCrTi (C-8) > FeCSiMoB10CrTi (C-4) > FeCSi5MoBCrTi (C-7) > FeCSiMoB5CrTi (C-3).

ABSTRACTThe Cathedral of St. George is located in the Yuriev Monastery, in Novgorod, one of the capitals of ancient Rus (The Great Novgorod). The wall paintings were completed around 1120 CE. The Cathedral or its parts were renovated in different periods. The fragments of the twelfth-century frescoes were deposited under the new floor and in the area around the Cathedral. Archaeological excavations of the Institute of Archaeology of the Russian Academy of Sciences in Moscow brought to light a large number of fragments of frescoes. The Laboratory for Architectural Archaeology and Multidisciplinary Methods in Architectural Research of the Institute began to study the fragments in 2021 and presents here the first results of the research on substrate and preparation layers of the paintings. Our aim was tdistinguishing the different phases of the wall paintings. The plasters used in the twelfth century are different from the later ones and contain different aggregates.

ABSTRACTThe material deposition in aqueous solution, also known as chemical bath deposition (CBD), is a well-established technique for the fabrication of semiconducting thin films. The success of the CBD technique is mainly based on the relatively easy implementation and operation requirements. The CBD has importantly contributed to the development of sensors, optical devices and solar cells applications. In this review, the origins and current state of the art of the CBD technique, the involved physicochemical processes, the growing mechanisms, and the analytical techniques for the estimation of optimal physicochemical conditions for the film deposition are discussed. Emphasis on authors’ experience on CBD of CdS, ZnS, Zn(OH)2, and ZnO films are here highlighted, following methodologies for a high control of the deposited materials, such as the species distribution diagrams and the solubility curves.

ABSTRACTA TiO2/ZnO composite film which served as the bind-free anode for lithium-ion battery was rapidly constructed on Ti foil by the one-step plasma electrolytic oxidation process. The fabricated TiO2-based transition metal oxide composites took advantage of the high theoretical capacity of ZnO and the good structural stability of TiO2, showing a high specific capacity (706.2 mAh g−1 over 400 cycles at 0.1 A g−1) and a good rate capability (capacity reversible after 2.0 A g−1). When the scan rate gradually elevated from 0.2 to 1.0 mV s−1, the pseudocapacitance contribution increased from 63.9% to 81.2%. Besides, the hole-containing morphology of the film guaranteed efficient diffusion and excellent dynamic characteristics for Li + . The whole film preparation process was accompanied by a facile in-liquid plasma discharge with an average electron temperature of 3519 K. This high-efficiency and low-cost approach extends the practical territory of transition metal oxide anodes.

ABSTRACTThe electroless deposition of a novel vanadium-based conversion coating (VCC) on carbon steel was investigated varying parameters as vanadium salt concentration, immersion time, bath pH and temperature. The novelty resides on the deposition of a protective layer from a V4+ solution comprising green reducing agents like ascorbic and citric acids. The VCC was found to be amorphous, composed by closely packed particles rich in vanadium oxides/hydroxides. Corrosion resistance was evaluated by linear polarization resistance, Tafel extrapolation and electrochemical impedance spectroscopy. Such conversion coating provided an optimum corrosion performance for steel substrates immersed in sulphates and chlorides rich solutions. An optimum was achieved with a 0.1 M KVO3 solution held at 45°C, at pH = 3 and a deposition time of 10 min. Higher values of the latter parameters did not provide any further improvements: the formation of cracks during the dehydration process compromised the coating integrity.

ABSTRACTMagnesium alloys are low in density, high in strength and non-toxic, nevertheless, their industrial application is substantially limited owing to their low electrode potential and susceptibility to corrosion. Surface and coating technology is widely used to improve their corrosion resistance. Graphene is one candidate material for anti-corrosion coatings because of its high aspect ratio, outstanding chemical resistance and good physical resistance. Its good barrier properties mean that graphene may have a wide range of applications in magnesium alloy coatings. This paper reviews (i) the potential of graphene for anti-corrosion coatings, (ii) the production methods and types of graphene anti-corrosion coatings, (iii) their properties, (iv) the protection mechanisms and (v) the future development trends of graphene-based corrosion protective coatings on magnesium alloys.

ABSTRACTAs using recyclates in the food sector is currently severely restricted due to the risk of harmful contamination, the reuse of PCR (Post-Consumer Recyclates) could be greatly increased through the development of migration barriers. However, the deposition of functional barrier coatings in PECVD processes (Plasma-Enhanced Chemical Vapour Deposition) on thermoformed PCR polypropylene cups is non-trivial due to complex geometries and difficult surface properties (high roughness, non-polarity, fluctuation of recycylate properties). To develop barriers in this system, material properties of recyclate and virgin material were compared by rheometric and thermal analysis and surface properties of PCR and virgin material cups were analysed morphologically in order to define specific coating challenges. Subsequently, coatings were deposited by PECVD consisting of both, silicon organic intermediate layers (SiOCH) and silicon oxide barrier layers (SiOx). The barrier, measured by the oxygen transmission rate, could be improved by a factor of about 60 compared to uncoated cups.

ABSTRACTThe present work describes the influence of underwater laser shock peening without coating (LSPwC) on selective laser melting manufactured meso-size (outside diameter ≤ 10 mm) helical gears. Five experiments were conducted using energies in the 200 mJ up to 1 J, while the spot size and overlap were kept constant as 1 mm and 90 %, respectively. Responses were measured and compared in terms of surface residual stresses, surface roughness, and microstructure of LSPwC-treated samples. Results show the development of significant compressive residual stresses in the root of the LSPwC processed helical gear, where it changes the state from tensile +45 MPa to compressive −421 MPa. Surface roughness has shown improvement, while volumetric material peak confirms the reduction by over 50%. Microstructure study was performed at the surface and by cross-section using scanning electron microscopy and electron backscatter diffraction analysis. The grain refinement and change in misorientation were observed, confirming plastic deformation.

ABSTRACTThe adhesion strength from the cold-spray coating requires assessing multiple flaws and property distributions. Two approaches have been proposed for determining the adhesion strength of the cold spray-coated substrate. The interfacial shear strength approach combines the fragmentation test with a modified Weibull model. Fragmentation testing can examine materials with geometrical (roughness) and property (strength) variations for cold spray-coated specimens. The results give an insight into local strength and the coating strength distribution. The fracture toughness approach uses an electrical four-point probe to identify crack initiation and calculate the energy release rate of the coating. Sn coatings between 74 and 120 μm show an interfacial shear strength between 25 and 53 MPa and an energy release rate between 15 and 32 J m–2. The measured interfacial shear strength was independent of the coating thickness, while the energy release rate depends on the coating thickness.

ABSTRACTThree kinds of laser surface texture (LST), i.e. square pit-textured surface (SPTS), round pit-textured surface (RPTS) and groove-textured surface (GTS), are fabricated on the flat brass (H65) sample surfaces. The current-carrying tribological behaviour of these surfaces are investigated. It is noticed the COFs of smooth surface, SPTS and RPTS are all greater than 0.6 after the test, while the GTS has the lowest COF, which remains around 0.2 throughout the test. The vibration signals detected from all surfaces indicate the larger COF will not trigger the FIV generation in this state. All the texture surfaces will not cause electrical contact breaks. Worn surface analysis indicates the wear level of GTS is the weakest, with slight damage and debris accumulation occurs along the groove edges. Finite element analysis is performed to calculate the variation of contact force, contact temperature and voltage signal, and the test results can be well explained.

ABSTRACTSealing treatment is an effective, environmentally friendly, and economical coating surface modification technology. To clarify the inorganic silicate sealing mechanism and concentration dependence on corrosion behaviour, HVAF-sprayed Fe-based amorphous metallic coatings (AMCs) were sealed by Na2SiO3 solution with various concentrations, and their microstructure, electrochemical performance, and surface chemistry were characterised in detail. The results showed that Na2SiO3, in the form of a silicon-oxygen bond (Si-O), could effectively bond with the coating surface inside the pore defects. In addition, the optimal concentration was proved to be 1 mol/L, and the corresponding passivation current density could be reduced to (2.38 ± 0.33) × 10−6 A/cm2, which was an order of magnitude lower than that of as-sprayed coating. This was due to the incomplete filling of the sealant at lower concentrations and the release of water vapour at higher concentrations. This work aims to provide guidance for the practical application of silicate sealing treatment.

ABSTRACTThis paper assessed the antifouling activities of a superhydrophobic surface with a contact angle of 161.6° and a sliding angle of 4.1° which can be employed on large scales. The preparation of PDMS/silica nanoparticles composite was first described for the production of superhydrophobic surfaces with different contents of silica nanoparticles. Then, the surface roughness of the produced samples was investigated. Subsequently, the surface reaction against the algae was evaluated at different immersion times. The samples coated with PDMS-to-Silica ratio of 100% exhibited higher stability against algal growth for more than 10 h while samples with a coating ratio of 25% withstood algae for less than 2 h, indicating the influence of surface roughness. Although the withstanding time of this coating cannot compete with the commercial antifouling coatings, it becomes vital when it comes to the use of this coating as a drag-reducing surface in which fouling worsens the effectiveness.

ABSTRACTMetal components in microelectromechanical systems are prone to failure and corrosion due to droplet adhesion in wet environments. Several multi-level structures on the micro-nano scale may induce effective superhydrophobicity to prevent such adhesion. This study proposes a hybrid manufacturing process to generate ‘frame-cone’ textures on the surfaces of metals by combining ultra-fast laser etching and electrodeposition. Periodically distributed frame recesses and pits were coated with nano-submicron Ni coatings with conical shapes, and the pit depth and cone height were controlled by tuning the laser scanning time and current density, respectively. The surface adhesion force was reduced to 22.8 μN, and the static contact angle was maintained at 156.7° using the hybrid process, while the adhesion forces of laser etched samples with the same depth were 164.7 μN. The multi-level ‘frame-cone’ structure stored more air and reduced the contact areas between the bottoms of the pits and droplets. The hybrid process of ultra-fast laser etching and electrodeposition aided in improving the superhydrophobicity, with less damage to the substrate.