Coatings

The fabrication of bio-composite-derived bovine amniotic membrane (BAM) with hydroxyapatite (HAp) is an approach to combining organic and inorganic bio-material to improve the properties of both materials. This research aims to combine, fabricate and characterise the bio-composite of BAM–HA. The combination of bio-composite is made from BAM and HAp in a ratio of 30:70, 35:65, and 40:60. Dried BAM is immersed in saline and then blended until it forms an amniotic slurry with a jelly-like consistency. At this stage, HAp is added so that it can bind to BAM. After the mixture is homogeneous, the freeze-drying process is carried out. After fabrication, all the bio-composites were characterised using Fourier transform infrared spectrometry (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and porosity analysis, and biological activity was conducted using fibroblasts. The bio-composite has functional groups of amides I, II, III, A, B, OH, CO₃²⁻ and PO₄³⁻ according to the results of the FTIR. The XRD analysis showed the presence of HAP crystals. This functional group and the crystal HAP indicate that these two materials are bound. An SEM examination revealed a variety of porous patterns on the surface area. The bio-composite with BAM and HAp at a ratio of 35:65 has a higher mean pore size of 155.625 µm with mean porosity of 89.23% and can maintain the fibroblast viability of 95.14%. In conclusion, the study successfully combined both bio-materials BAM and HAp, which have potential synergistic effects on soft and hard tissue regeneration. The ratio of 35:65 showed good characteristics and was non-toxic. Full article

The purpose of this paper is to reveal the corrosion behavior of J55 and N80 carbon steels in formation water under oil wells at different partial pressures, explore the formation process of corrosion product films under supercritical CO₂ conditions, and analyze the reasons why the microstructure of carbon steel affects the corrosion behavior. The results show that the corrosion rate gradually increases with the increase in CO₂ partial pressure. When the pressure exceeds 10 MPa, the corrosion rate of J55 increases slightly, and that of N80 decreases slightly. Under different partial pressures, the surface composition of the corrosion product film of J55 steel is FeCO₃, and that of N80 steel is FeCO₃ with a small amount of Fe₃C. The analysis shows that the corrosion product films of two kinds of carbon steels can be divided into three layers under the condition of supercritical CO₂. There are holes in the middle layer, which are formed first, and then the inner layer and the outer layer are formed at the same time. It is believed that the difference in the morphology and distribution of Fe₃C is the reason why the corrosion rate of J55 steel is lower than that of N80 steel. Fe₃C in J55 steel is lamellar, which can anchor FeCO₃, promote the formation of corrosion product films, and improve the compactness of corrosion product films. However, the Fe₃C in N80 is granular and dispersed in the ferrite matrix, which makes it easy to fall off the surface, form pits, and destroy the integrity of the corrosion product film. Full article

Polyaniline/Au nanocomposites were synthesized by a novel method. Aniline monomers were loaded in the hydrophobic cavities of beta-cyclodextrin, and a polymerization reaction occurred at the interface of the beta-cyclodextrin cavities and the liquid phase of chloroauric acid. UV-vis absorbance indicated that the nanocomposite covered the range of visible light and NIR (near infrared). The photo-excitation experiment was carried out with typical wavelengths in the visible light (405 nm, 532 nm, and 650 nm) and NIR (780 nm, 808 nm, 980 nm, and 1064 nm) regions (10–200 mW) based on Au inter-digital electrodes on flexible polymer substrates casting a thick film. The nanocomposites exhibited photo-current switching behavior in visible light and NIR. The ratio of on/off was enormously dependent on the power and wavelength of incident light. The robust interface coupling between Au and PANi of the nanocomposite promoted the separation and transfer of electron/hole. The mechanism of carrier generation, separation, and transfer at interfaces of Au/conjugated polymer/non-conjugated small organic molecules by light inducement was discussed at the electron level. The results illustrate that the nanocomposites quickly produced free electrons and holes by low-power incident light, could prevent the recombination of electron/hole pairs to a certain extent, and could overcome the interface barriers between metal, conjugated polymer, and small organic molecules for transfer. This provides a simple and practical approach for developing multi-functional nanocomposites that have the potential act as intelligent nano-carriers, photo-current switches, NIR detectors, and for information storage. Full article

In this study, we aimed to improve our understanding of the response mechanisms associated with the formation of CdS thin films. CdS thin film remains the most valuable option for many researchers, since it has shown to be an effective buffer material for film-based polycrystalline solar cells (CdTe, CIGSe, CZTS). We performed experimental and numerical simulations to investigate the effect of different thiourea concentrations on the characteristics of the CdS buffer layer. The experimental results reveal that an increase in thiourea concentrations had a direct effect on the optical results, with bandgap values ranging from (2.32 to 2.43) eV. XRD analysis confirmed that all deposited films were polycrystalline, except for [1/0.75], where there is no CdS formation. Electrical studies indicated that CdS with a molar ratio of [Cd]/[S] of 1 had the maximum carrier concentration (3.21 × 10¹⁴ cm⁻³) and lowest resistivity (1843.9 Ω·cm). Based on the proposed mechanism, three kinds of mechanisms are involved in the formation of CdS layers. Among them, the ion-by-ion mechanism has a significant effect on the formation of CdS films. Besides, modelling studies reveal that the optic-electrical properties of the buffer layer play a crucial role in influencing the performance of a CIGS solar cell. Full article

Personal protective equipment (PPE) has been adapted as biological threats have emerged, such as increasingly drug-resistant bacteria and the emergence of new viruses such as Covid-19. PPE must be increasingly resilient to prevent the proliferation of pathogens, but using sustainable raw materials and environmentally friendly technologies. The aim of this study is to show a new way of modifying the surface of various types of fabrics to enable their efficient use as PPE. The Ag/DLC coating was successfully deposited by sputtering onto several types of textiles using different chemical compositions of Ag/DLC (0, 8, 10, and 12Ag). As a crucial parameter, wettability was evaluated, showing that silver addition increases the hydrophobicity character of the coated fabrics, namely in cotton, changing from hydrophilic to hydrophobic. Antibacterial activity and cytotoxicity were evaluated on all coatings, revealing that they are efficient in eliminating the spread of bacteria (Staphylococcus aureus and Klebsiella pneumoniae) and pose no risk to the human body. The results presented here are promising in protecting healthcare workers, with the next steps being to study the efficiency of these coatings against viruses. In addition, this study reveals an opportunity to use sustainable fabrics, such as cotton, with high efficiency in protection against pathogens, instead of synthetic fiber textiles. Full article

The paper proposes a surface plasmon resonance (SPR) biosensor utilizing MXene and a Molybdenum Disulfide (MoS₂) material layer, placed on the Ag metal-based conventional biosensor to detect disease in human teeth. The SPR biosensor works on the principle of attenuated total reflection. The transverse matrix method was utilized for the reflectivity calculation. The thickness of the Ag layer, MXene, and MoS₂ were taken as 45, 0.993, and 0.375 nm, respectively. Single-layer MoS₂ and two layers of MXene were taken, and the highest sensitivity of the sensor for the enamel, dentin, and cementum was obtained at 83.219 deg/RIU, 91.460 deg/RIU, and 104.744 deg/RIU. MoS₂ was used to enhance the biocompatibility of the analyte with the sensing layer. The aqueous solution had been considered as sensing medium. Full article

Water can trigger freeze–thaw cycles, acid rain corrosion, and microbial colonisation, all of which destroy stone. Water is one of the most influential factors in the destruction of outdoor stone heritage. Therefore, materials with excellent hydrophobic properties and durability are urgently required to effectively retard long-term stone weathering. In this study, two nanoparticles, TiO₂ and SiO₂, were used to modify dodecyltrimethoxysilane (DTMS), a waterproof coating commonly used for stone heritage protection, to fabricate nanocomposite superhydrophobic coatings. The micromorphology, water repellence (water contact angle and capillary water absorption), suitability to protect stone heritage (color change and water vapor permeability), and durability (thermal, light, and chemical stability) of DTMS and nanocomposite coatings were evaluated. The scanning electron microscope (SEM) images revealed that adding 0.5% (w/w) SiO₂ produced nanoscale roughness on the sandstone surface, leading to superhydrophobicity. The results of ultraviolet -visible (UV–Vis) spectrophotometer showed that adding 0.01% TiO₂ shielded more than 90% of UV light but accelerated the decrease in the contact angle under UVA irradiation. The addition of SiO₂ was able to avoid the detrimental effect of TiO₂ under UV light. The thermogravimetric analysis (TGA) results showed that both SiO₂ and TiO₂ nanoparticles improved the thermal stability of the coatings. In particular, the fabricated nanocomposite coating, SiO₂ and TiO₂ co-modified DTMS, had excellent water repellence, low color change and outstanding durability, and retained about 85% of the water vapor permeability of the stone, showing promise for stone protection. Full article

The thermal insulation and integrity of the thermal barrier coating is hampered by the formation of mixed oxide at intermediate bond coat. The existing reported work correlates growth of mixed oxide to the microstructural and phase changes. The track mostly used to study these changes is scanning electron microscopy, X-ray diffraction, and electrochemical testing. Oxide growth is principally an electrochemical process; hence a thirst exists to study this aspect by using advanced electrochemical techniques. In this study scanning electrochemical microscopy is used to reveal the electrochemical activity in the closest vicinity of the surface. A raster scan of 500 µm area was carried out by microelectrode in an electrolyte at a distance of 5 µm above the surface to record the current profile. The activity at the surface was confirmed by current distance curves. The tip of the microelectrode was approached from 60 µm height to 2 µm above the surface. The current–distance curves for the coating without heat-treatment show an active surface while the heat-treated one show non active surface. The average coating electrochemical response was further studied by polarization curves impedance spectroscopy. The X-ray photoelectron spectroscopy results show that oxidation and formation of the mixed oxide increase with polarization. Full article

The paper summarizes the current development of high-velocity oxygen–fuel coupled physical vapor deposition (HVOF-PVD) duplex coatings as protective candidates. Following a detailed historical overview of HVOF and PVD technologies, the fabrication methods for duplex protective coatings are presented. The duplex coating superimposes the synergistic advantages of coatings deposited by HVOF and PVD, where the traditional weaknesses of each technique are modified to a great certain extent. Subsequently, the relation between structural characteristics of the duplex coatings and their mechanical, tribological, and corrosive behavior is described in detail. It is demonstrated that the duplex coatings show more excellent overall performance than coatings deposited by both HVOF and PVD separately. Finally, we summarize the protective performance and promising potential of HVOF-PVD duplex coating for applications as well as the research prospects of challenges in future. Full article

In this paper, the related experiments were carried out on microcapsules, with the aim of making the prepolymer react with the core emulsion by in situ polymerization using urea–formaldehyde resin as the wall material and waterborne acrylic wood coating as the core material. The prepared microcapsules were added to the waterborne acrylic wood coating and brushed on wood boards. Then, the gloss, hardness, adhesion, impact resistance and color difference were compared with paint surfaces without microcapsules. When the ratio of the microcapsule core-to-wall material was different from the increase in microcapsule content, the gloss of the coating decreased continuously; the decreasing range was basically the same, and the gloss values of the three core-wall ratio microcapsules were rather similar. With the increase in microcapsule content, the impact resistance of the coating first increased and then decreased. With the increase in microcapsule content, the color difference of the coating also increased continuously. The color difference of the coating with a microcapsule core-wall ratio of 0.67 changed the least, and the coating performance was good. When the core-wall ratio of the microcapsules was 0.67, and the proportion of microcapsules in the paint was 7.0%, the comprehensive properties of this coating were good. This research is of great significance to the future protection and development of wood. Full article

The present paper is part of an ongoing research project carried out to find methods to transpose traditional motifs from Romanian textile heritage to furniture ornamentation, as an additional method of preserving the motifs besides conventional conservation. Modern technology, such as Computer Numerical Control (CNC) routing or laser engraving can revive furniture ornamentation, eliminating manual labor and long execution time. Three methods were applied to transpose a bicolored motif from a traditional Romanian blouse from Transylvania onto the surface of maple wood furniture. The first method utilized was nitrogen laser engraving, in which ten power settings between 10 W and 150 W were applied and color measurements were carried out on the resulting engraved surfaces. Following the International Commission on Illumination (CIELab) system analysis, two laser power settings were selected to engrave the ornament on a maple wood surface for an accurate reproduction. The second method employed a staining solution applied on flat wood surface, followed by routing the model on a CNC machine and further coating with lacquer. The third method consisted of CNC routing the model on the wood surface, then coloring the engraved ornament followed by surface sanding to remove color from the flat wood surface and, finally, lacquering. The ornaments transposed onto maple wood surfaces were aesthetically assessed, the technologies were analyzed, and the details of the processed ornaments were highlighted by Stereo Microscope investigation. The conclusions showed that each method adds value to the wood surface by original ornamentation and can be applied as furniture decoration. Full article

Antibacterial and pH-responsive composite films for active food packaging were fabricated based on polyvinyl alcohol (PVA), cassava starch, ethyl lauroyl arginate (LAE), and mulberry anthocyanin. With the incorporation of LAE and mulberry anthocyanin, the PVA/starch blend films exhibited a less compact and more heterogeneous surface structure. The tensile strength and elongation at break of the active films were not significantly affected when the mulberry anthocyanin content was less than 20%. Moreover, the incorporation of mulberry anthocyanin effectively improved the UV barrier property of the blend films. Notably, while mulberry anthocyanin showed obvious color changes in buffer solutions with different pH values, the changes were indistinguishable for the PVA/starch/mulberry anthocyanin films. By contrast, the color changes of the PVA/starch/LAE/mulberry anthocyanin films were more noticeable, indicating the addition of LAE increased the pH sensitivity of the blend films. Furthermore, the PVA/starch/LAE/mulberry anthocyanin films efficiently inhibited the growth of both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) due to the strong antibacterial activity of LAE. According to the spoilage test, the active films containing 5% mulberry anthocyanin and 5% LAE effectively indicated and slowed down the spoilage process of dairy milk. Our results demonstrate that PVA/starch/LAE/mulberry anthocyanin films have high potential as bioactive packaging materials applied in the food industry. Full article

For the micro-milling of hard and brittle materials, to avoid crack formation, a tool with ductile milling mode is required. Composite electrodeposition technology was used to prepare a Ni–diamond coating on the surface of brass. The surface microstructure, composition and surface roughness of the coating were studied with a scanning electron microscope, X-ray diffractometer and roughness tester. The adhesion strength was studied by scratch test, the wear resistance was analyzed by wear test, and the corrosion resistance was investigated by Tafel curves and electrochemical impedance spectra (EIS). It was found that the distribution of diamond particles of the Ni–diamond coating was relatively uniform, and the content was relatively high. The internal stress of the coating prepared by the composite electrodeposition technology was very low. With the incorporation of the diamond particles, the surface roughness of the coating tended to decrease. The wear experiment showed that the wear scar diameter of the corresponding glass ball for the Ni coating was 1.775 mm and the roughness was 13.88 ± 2.811 µm, while that for the Ni–diamond coating was 2.680 mm and 8.35 ± 0.743 µm, respectively, indicating that the tool coating with uniform diamond particles had a strong ability to process workpieces with significantly improved surface quality. The particle press-in mechanism not only improved the wear resistance of the coating, but helped to prolong the service life of the tool. The results of the EIS test and Tafel curves showed that the Ni–diamond coating had a lower corrosion current, and the corrosion resistance of the coating surface was improved. The experimental results showed that the micro-diamond coating prepared by the composite electrodeposition technology had good bonding strength, low internal stress, and significantly improved wear resistance and corrosion resistance. Full article

In this study, waterborne hybrid organic-inorganic zinc rich coatings (ZRC) with different aluminum flake amounts were tested at low thickness in 3 wt% NaCl aqueous solution. Open circuit potential and impedance response evolution over time were measured experimentally to evaluate their anticorrosion properties. Microstructure of the investigated coatings and composition of the corrosion products were also determined by electron microscopy, X-ray diffraction and infrared spectroscopy, while the stability of the coatings was investigated via inductively coupled plasma optical emission spectroscopy. The results showed that the absence of aluminum flakes leads to a less stable matrix, unable to retain sufficient corrosion inhibitors, resulting in a shorter protection time. For an intermediate concentration of aluminum particles, good corrosion properties were observed. Corrosion products play an important role in the protection mechanism, with simonkolleite and hydrozincite accumulating over time, forming a protective layer on the substrate for several weeks. High amounts of aluminum also lead to the formation of corrosion products, but without providing a barrier effect, while rapidly consuming zinc, leading to rapid formula failure. These results indicate that the use of a controlled amount of aluminum flakes can significantly improve the corrosion protection capability of this type of coating. Full article

This article presents the results of a study on polymer coatings containing poly ethoxylated bisphenol A diacrylate (Bis-AEA10) with aluminum silicon nitride oxide (Sialon) and aluminum nitride (AlN). The polymer coatings were obtained by the photopolymerization technique. Investigations were carried out to determine the effect of the AlN and Sialon content on the UV-curing kinetics, as well as on the mechanical (hardness), thermal (T_g, thermal stability), physicochemical (water contact angle), and structural properties of the polymer coatings. Polymerization rates were characterized as functions of double-bond conversion using the photo-Differential Scanning Calorymetry technique (photo-DSC). The results obtained showed that a small addition of sialon filler (3–5 wt.%) to Bis-AEA10 increases the photopolymerization rate of the varnish, while the addition of more Sialon decreases the rate of photopolymerization. However, for the systems containing AlN filler, the maximum polymerization rate was observed for samples containing 10 wt.% filler. In the case of a varnish composition containing AlN, the maximum polymerization rate is characterized by the system containing 10 wt.% of AlN. This shows that the AlN filler has a good influence on the polymerization process. In either case, the final double bond conversion was high (80%–95%). Mechanical tests have shown that introducing the filler into the polymer matrix increases its hardness. The content of Sialon and AlN in the coatings causes an increase (up to 4–5 wt.%) and a decrease (>4–5 wt.%) in the glass transition temperature. The effect of the addition of fillers on the physicochemical properties of the coating surface has also been investigated and characterized by the water contact angle method. The addition of 20 wt.% Sialon and AlN increased the contact angle of the samples by approximately 40% and 31%, respectively, resulting in coatings with hydrophobic surface properties. Full article

An in situ Mg-Al hydrotalcite (LDH) film was prepared using a one-step hydrothermal method on the surface of a medical magnesium alloy. The importance and influence of the reaction parameters on the corrosion resistance of the LDH coatings were optimized and investigated through an orthogonal array and range analysis. The reaction parameters included the temperature, reaction time, pH, and concentration of the aluminum source. The relationship between the parameters and corrosion resistance performance of each coating was compared with the chemical composition, electrochemical corrosion current, and hydrogen evolution rate. Suitable reaction parameters were obtained. The morphology, element distribution, adhesion strength, and electrochemical properties of the preferred coatings were further analyzed and evaluated to optimize the treatment process. The results showed that temperature had the most significant impact on the quality of the LDH coating; a suitably high temperature, a longer reaction time, a higher aluminum source concentration, and a high pH were conducive to forming high-quality LDH coatings. There was an inverse relationship between the corrosion resistance and the LDH-to-Mg(OH)₂ content ratio of the coatings. The optimal reaction parameters for this Mg-Al LDH coating on the substrate were 130 °C for 8 h at a pH of 13 using a 10 mM Al³⁺ solution. Full article

This study examines the formation of hard layers containing Ni-B and Cr-B on the surface of 80/20 nickel–chromium alloy. The work evaluates the mechanical properties of the boride layers using instrumented nanoindentation. In addition, the growth kinetics of the coatings were assessed by applying a kinetic model that relates the layer thickness with the experimental parameters of temperature and treatment time. First, the boride layers were achieved using the powder-pack boriding process in a conventional furnace. The treatment time was set at 2, 4, and 6 h at temperatures of 900, 950, and 975 °C, respectively. The microstructure of the layers was analyzed by X-ray diffraction. The thickness of the layers showed a closed correlation with the experimental parameters of time and temperature, and was established between 38.97 and 156.49 µm for 2 h to 900 °C and for 6 h to 975 °C, respectively. The hardness and Young’s modulus values agree with those presented in the literature for boriding nickel alloys, being in the range of 1.3 GPa on average and 240 to 270 GPa, respectively. The resulting layers exhibited a characteristic diffusion zone where the hardness values decrease gradually without the typical high hardness gradient observed on borided steels. Full article

In order to study the influencing factors of friction coefficient in an M-B model, based on the basic model of fractal theory, the distribution function and probability distribution density of the micro-convex body truncation area are derived by using mathematical and statistical means, and a new model of critical truncation area and friction coefficient in fractal surface contact process are proposed. Considering the differences between the actual contact area and the truncated area during plastic deformation of the micro-convex body, a correction factor is introduced. Focusing on the mechanism of the elastic-plastic transition phase, and finally a friction coefficient model based on the fractal dimension, the normal force and correction factor is derived. Finally, the friction coefficient of fractal surface is simulated and verified by taking nickel as an example, and it is proved that the new model is correct in predicting the change trend of friction coefficient in the M-B model. Full article

The preparation technology of graphene-based coatings on cobalt-based cemented carbides and the friction properties of graphene-based coatings were researched. Based on cooling rate, growth temperature, and methane flow rate, Raman spectroscopy was used to evaluate the influence of chemical vapor deposition (CVD) on graphene-based coatings. The results show that at the growth temperature of 1000 °C, the cooling rate of 15 °C/min and methane flow rate of 10 sccm are more favorable for the growth of pure graphene coating with fewer layers on a cemented carbide surface. As methane flow boosts, the number of graphene layers increases and amorphous carbon is generated. The resulting tribological properties demonstrate that the friction coefficient of graphene-based coatings decreases as the friction load increases. The above results indicate that the graphene-based coating on a cemented carbide surface can be prepared by regulating its composition and defects through technological parameters, and it is viable to use graphene-based coating as anti-wear coating for cutting tools. The results provide a reference for the preparation and properties of cemented carbide surface graphene. Full article