Coatings

The search for lightweight and low-cost anticorrosion coatings is particularly important in coastal environments with high salt and humidity. Graphene-based anticorrosion coatings are currently unable to provide long-lasting corrosion protection for metals because of their “corrosion-promoting activity”, and graphene-like materials, such as molybdenum disulfide (MoS₂), are beginning to be anticipated its ability to protect against metals. This paper reported a simple method for preparing polypyrrole (PPy)-modified MoS₂ nanomaterials from natural bulk MoS₂. Their corrosion resistance behavior as fillers for epoxy (EP) resins was investigated in 3.5 wt.% NaCl solution. After the preparation of the MoS₂ nanosheet dispersion by liquid-phase sonication using ethanol aqueous solution, the polypyrrole-coated molybdenum disulfide nanomaterials (MoS₂@PPy) were directly obtained by adding pyrrole monomer to it in the presence of the initiator ammonium persulfate. Tafel polarization curves showed that the corrosion current of the MoS₂@PPy/EP coating was 0.006 µA/cm² after 15 days of immersion in 3.5 wt.% NaCl solution, much lower than that of pure EP coating (19.134 µA/cm²), effectively improving the anticorrosive properties of the coating. Overall, this study offered a practical method for the application of natural bulk MoS₂ for corrosion protection. Full article

We report an investigation into 1,4-Bis-N,N-(trimethylsilyl)piperazine (BTMSP) as a novel precursor for the synthesis of silicon carbonitride films by chemical vapor deposition (CVD). The thermal stability, temperature dependence of vapor pressure and thermodynamic constants of the evaporation process of BTMSP were determined by static tensimetry with a glass membrane zero manometer. The transformation of the compound in low-power (25 W) plasma conditions was investigated by optical emission spectroscopy. It was shown that BTMSP undergoes destruction, accompanied by H and CH elimination and CN formation. SiCN(H) films were deposited in a hot-wall plasma-enhanced CVD reactor. The optical properties of the films were studied by spectral ellipsometry (refractive index: 1.5–2.2; absorption coefficient: 0–0.12) and UV–Vis spectroscopy (transmittance: up to 95%; optical bandgap: 1.6–4.9 eV). Information on the aging behavior of the films is also provided. The transformation of the films occurred through water adsorption and the formation of Si–O bonds with the degradation of Si–H, N–H and Si–CH_x–Si bonds. Full article

The femur supports the entire body weight, and any damage or necrosis to this bone can significantly impair normal walking. Therefore, repairing the femur is essential to restoring its function. However, due to variations in human bone structure, standardized prostheses often deliver poor repair outcomes. We used the medical three-dimensional (3D) auxiliary software Mimics to design personalized femoral prostheses to address this issue. The femoral prosthesis filler was porous, and all aspects of the prosthesis were thoroughly studied and analyzed before direct molding using 3D printing technology. The personalized femoral prosthesis filler and bone plate designed using 3D printing technology have positive effects, and the matching between the femoral prosthesis, bone plate, and filler is satisfactory. The pore structure of the 3D-printed femoral prosthesis filler and the bone plate is clear and of high quality, which shortens the research and development cycle and reduces costs, providing a foundation for the direct application of 3D-printed personalized prostheses. Full article

Microbial fuel cell (MFC) technology can potentially recover bioelectricity from wastewater. However, its practical applications have been limited because of its low power density and since the energy generated from an MFC cannot be stored. In this study, manganese dioxide (MnO₂) coupled with carbon nanotubes (CNT) was chosen to in situ modify carbon felt (CF) as a capacitive bioanode (CF/CNT/MnO₂) to improve the power generation and energy storage of MFCs. The maximum power density of the MFC with the MnO₂-CNT-modified bioanode reached 3471.6 mW m³, which was 1.96 times higher than that of the CF/CNT anode (1772.6 mW m⁻³). During the experiment of charging for 30 min and discharging for 30 min, the MFC with a capacitive bioanode had a total charge of 8777.1 C m⁻², 2.74 times higher than that of the CF/CNT anode. The excellent electricity-producing and energy storage performance of the MFC equipped with the CF/CNT/MnO₂ anode is attributed to the composite materials, which can be due to their better biocompatibility, large capacitance, and high specific surface area. This study provides a new way to improve the performance of electricity generation and energy storage of MFCs. Full article

In this work we have synthesized Ti₃C₂T_X MXene powder and studied its structure. Composite electrochemical coatings (CECs) of Ni-Ti₃C₂T_X MXene were obtained from a sulfate– chloride bath in the galvanostatic regime. The microstructure of CEC was researched using X-ray phase analysis and scanning electron microscopy methods. It has been established that a Ni–Ti₃C₂T_X MXene CEC microhardness rises by about 1.80 times compared with electrolytic Ni without a dispersed phase. For corrosion research, different corrosive media is applied. The corrosion–electrochemical behavior of Ni–Ti₃C₂T_X MXene CECs by the chronovoltamperometry method in 0.5 M H₂SO₄ solution has been investigated. Trials in 3.5% NaCl have shown that Ti₃C₂T_X MXene inclusion into the matrix of the electrochemical Ni results in a decrease in the corrosion rate by 1.60–1.75 times. These effects are due to the addition of Ti₃C₂T_X MXene into the nickel matrix and the formation of CECs with a strengthening fine-grained structure. Full article

Atomic layer deposition (ALD) has emerged as a promising technology for the development of the next generation of low-power semiconductor electronics. The wafer-scaled growth of two-dimensional (2D) crystalline nanostructures is a fundamental step toward the development of advanced nanofabrication technologies. Ga₂O₃ is an ultra-wide bandgap metal oxide semiconductor for application in electronic devices. The polymorphous Ga₂O₃ with its unique electronic characteristics and doping capabilities is a functional option for heterointerface engineering at metal-semiconductor 2D heterojunctions for application in nanofabrication technology. Plasma-enhanced atomic layer deposition (PE-ALD) enabled the deposition of ultra-thin nanostructures at low-growth temperatures. The present study used the PE-ALD process for the deposition of atomically thin crystalline ß-Ga₂O₃ films for heterointerface engineering at 2D metal-semiconductor heterojunctions. Via the control of plasma gas composition and ALD temperature, the wafer-scaled deposition of ~5.0 nm thick crystalline ß-Ga₂O₃ at Au/Ga₂O₃-TiO₂ heterointerfaces was achieved. Material characterization techniques showed the effects of plasma composition and ALD temperature on the properties and structure of Ga₂O₃ films. The following study on the electronic characteristics of Au/Ga₂O₃-TiO₂ 2D heterojunctions confirmed the tunability of this metal/semiconductor polarized junction, which works as functional electron channel layer developed based on tunable p-n junctions at 2D metal/semiconductor interfaces. Full article

The most economical way to move liquids and gaseous hydrocarbons is by using pipelines. According to several international organizations and oil companies, the use of fossil fuels will continue in the following decades. For this reason, it is important to continue studying different corrosion mechanisms and their origins. One of the mechanisms that provoke small leaks, affecting pipeline hermeticity, is pitting corrosion. It is well-known that non-metallic inclusion dissolution can trigger pit nucleation. As pitting corrosion is recognized to be random in nature, it is also interesting to study the random nature of the inclusions present in API 5L X60 steel. Probability distributions commonly used to describe pitting corrosion characteristics are appropriate for studying inclusion characteristics. The size of inclusions plays a key role in pit nucleation because small inclusions tend to generate more defects, especially when these inclusions are compounds of MnS, and the steel is immersed in a corrosive solution. The results of this research work show that there is a close relationship between the random nature of pitting corrosion and inclusions. Full article

In this study, an Inconel625-Ni60-Ni60/25%WC (Inconel625-Ni/WC) composite coating was fabricated on Cr12MoV steel by first-stage laser cladding, followed by second-stage laser remelting with various laser powers, and the better laser energy density of 25.0 J/mm² for laser remelting test was obtained by macroscopic morphology and microhardness analysis. The effects of laser remelting on the microstructure, microhardness, wear resistance, and impact resistance of the composite coating was systematically investigated by combining various characterization methods. The results showed that laser remelting did not cause the composite coating to produce new phases. The microstructure of the Ni/WC layer in the remelted composite coating was denser and finer, and the average grain size of the surface layer was reduced by 11.69%. The impact depth of laser remelting was about 2.0 mm. The average microhardness of the Ni/WC layer in the remelted composite coating increased by 5.9%, and the average wear rate of the surface was reduced by 50.12% compared with that before laser remelting. The wear surface of remelted composite coating exhibited abrasive wear, and the wear resistance was significantly improved. In addition, the impact toughness value of the remelted composite coating reached 5.15 J/cm², which increased by 87.96% compared with that before laser remelting. The impact resistance of the composite coating was further improved. Full article

LiFePO₄ is a type of cathode material with good safety and long service life. However, the problems of the low Li ion diffusion rate and low electron conductivity limit the application of LiFePO₄ in the field of electric vehicles. In this paper, FePO₄ with different grain sizes was prepared via the air oxidation precipitation method and then sintered to prepare LiFePO₄. The refined grain can shorten the diffusion distance of Li⁺, accelerate the diffusion of Li⁺, and improve the diffusion coefficient of Li⁺. The results show that LiFePO₄ with a smaller grain size has better electrochemical performance. The discharge capacity of the first cycle is 151.3 mAh g⁻¹ at 1 C, and the capacity retention rate is 95.04% after 230 cycles. Its rate performance is more outstanding, not only at 0.2 C, where the discharge capacity is as high as 155 mAh g⁻¹, but also at 10 C, the capacity fade is less, and it can still reach 131 mAh g⁻¹. The air oxidation precipitation method reduces the production cost, shortens the production process, and prepares FePO₄ with small grains, which provides a reference for further improving the properties of precursors and LiFePO₄. Full article

Recently, the near-infrared-II (NIR-II, 1000–1350 nm) region has been extensively applied in deep-tissue photothermal therapy (PTT) on account of it having stronger tissue penetration and a higher maximum permissible exposure (MPE) than the near-infrared-I (NIR-I, 650–950 nm) region. In this study, we developed a rapid and convenient in situ polymerization strategy to fabricate polypyrrole nanosheets (PPy NSs) within a few minutes using manganese dioxide nanosheets (MnO₂ NSs) as both the oxidant and the self-sacrificed template. The fabricated PPy NSs exhibited excellent NIR-II absorption, which conferred its high photothermal conversion efficiency (66.01%) at 1064 nm and its photoacoustic (PA) imaging capability. Both in vivo and in vitro studies have shown that that PPy NSs possess good biological safety and excellent PTT efficacy and PA imaging performances. Thus, the as-synthesized PPy NSs could effectively achieve PA imaging-guided photothermal tumor ablation under 1064 nm excitation. Our work provides a novel and promising method for the rapid preparation of PPy NSs without the addition of exogenous oxidants and subsequent template removal, which could be regarded as potential photothermal agents (PTAs) to integrate the diagnosis and treatment of cancer. Full article

Flax fibers have found widespread use in eco-composite materials because of their remarkable mechanical properties compared to glass fibers. However, their low stability limits their use on a larger scale when employed in hot or humid environments. Therefore, the surfaces should be modified before the composite process to provide the best interfacial interactions and increase the dispersion of natural fibers. To tackle this problem, two kinds of modifications can be considered: wet and dry modifications. This research explores different methods to improve the adhesion between flax fibers and the poly lactic acid (PLA) polymer. Morphological and chemical modifications in the presence of acetone, alkali (as a wet modification), and with air atmospheric pressure plasma (as a dry modification) are compared in this research. The results revealed that altering the chemical characteristics on the surface significantly changed the mechanical properties of the final composite. More specifically, the Fourier transform infrared spectroscopy (FTIR) data indicate that wax-related peaks (2850 and 2920 cm⁻¹) were eliminated by both wet and dry treatments. Dynamic mechanical analysis (DMA) results also highlighted that a better bond between the flax fibers and the PLA matrix is obtained with the plasma modification. Full article

In order to further enhance the reinforcing effectiveness of polypropylene (PP) fibers on pavement concrete, waterborne epoxy (WBE) was introduced in this research and its effect on the flexural properties and freeze–thaw resistance of PP-fiber-reinforced concrete was evaluated. Compressive-strength tests, flexural-strength tests, three-point bending tests, freeze–thaw cycling tests and a scanning electron microscopic observation were carried out to analyze mainly the influence of WBE on the flexural properties and freeze–thaw resistance of PP-fiber-reinforced concrete. WBE contents of 0, 5%, 10%, 15% and 20% by weight of the cement were employed. The experimental results indicated that WBE was beneficial to improving the flexural properties of PP-fiber-reinforced concrete. With increasing content of WBE, the flexural strength and the peak load showed significant increases. Although a slight degradation in the abovementioned flexural parameters was observed when the WBE content was above 15%, the deflection at the peak, the fracture energy and the fracture toughness still showed an upward trend. In addition, the freeze–thaw resistance of PP-fiber-reinforced concrete was improved remarkably with the increasing addition of WBE content, leading to smaller mass loss and higher residual flexural strength. Moreover, microstructural images revealed that with the addition of WBE, the PP fiber/concrete interfacial bonding was effectively improved, and the concrete matrix tended to be denser as well, which provided higher resistance for crack initiation and propagation. In consideration of maximally improving the flexural properties of PP-fiber-reinforced pavement concrete, and while ensuring the compressive strength and meeting the freeze–thaw requirements, it was recommended that the content of WBE in PP-fiber-reinforced concrete should be 15%. Full article

This study is aimed to compare, through laboratory experimentations, the efficiency of UV-C irradiation and an essential-oils-based product as tools to reduce the biofilm identified in a semi-hypogeum room located in the archaeological park of Baia, Italy. During this study, the autotrophic component of the original biofilm, mostly composed of Chlorophyceae and Cyanophycean, was isolated in the laboratory, while simultaneously, the composition of the pigments used for the fresco paintings was examined in situ through X-ray fluorescence. These examinations were necessary for the creation of test samples that were similar to the original surfaces and used for subsequent experiments. The plaster testers were contaminated with artificial biofilm, exposed to UV-C at a distance of 80 cm for a fixed time interval and treated with ESSENZIO©, a product based on oregano and thyme essential oils, to eradicate the biological species. The treatment’s effectiveness was then assessed by employing optical microscopy and spectrometric techniques applied to the areas previously occupied by the biofilm on the different test samples. To obtain an additional parameter to evaluate the treatments efficacy, the concentrations of the photosynthetic pigments were also measured by spectrophotometry. Results showed that biofilms were successfully removed by the irradiation of the surfaces and by the essential-oils-based product at a dilution of 50% in demineralized water with a time of application of 1 h and 30 min; in addition, no visible change of the pigments used on the testers were observed, demonstrating the high efficiency of the treatments against biodeteriogens. The two methods and their different mechanisms of action have provided interesting aspects that suggest a combined strategy to contrast and prevent biological growth in archaeological contexts. Full article

An Fe-based coating was thermally sprayed onto the surface of AZ91 magnesium alloy via the High-Velocity-Oxygen-Fuel (HVOF) method. The thermally sprayed coating with a thickness of 530 ± 25 µm and a porosity of 0.7 ± 0.1% did not show any macrostructural defects and did not cause any degradation of the AZ91 alloy. Laser remelting of the surface layer of the sprayed coating resulted in the recrystallization of the structure and the disappearance of presented pores, splat boundaries, and other defects. This led to an increase in the hardness of the remelted layer from the original 535 ± 20 HV0.3 up to 625 ± 5 HV0.3. However, during the laser remelting at a laser power of 1000 W, stress cracking in the coating occurred. The tribological properties were evaluated by the ball-on-plate method under dry conditions. Compared to the uncoated AZ91 magnesium alloy, a higher value of friction coefficient (COF) was measured for the as-sprayed coating. However, there was a decrease in wear rate and weight loss. The remelting of the surface layer of the as-sprayed coating led to a further decrease in the wear rate and weight loss. Based on the obtained data, it has been shown that the application of laser-remelted thermally sprayed Fe-based coatings on AZ91 Mg alloy improves hardness and tribological properties compared to bare Mg alloy and as-sprayed Fe-based coatings. Full article

In this work, we fabricated lap joints between embossed projection phosphorus bronze and flat brass through resistance projection welding (RPW). The experimental results indicated that the bronze projection moves into the softer brass without being deformed during the welding process. The tensile shear loads of the joint reached a maximum value of 273.6 N at a welding current of 5.5 kA. Under this circumstance, a reaction layer, including a columnar crystal solidification layer and a diffusion layer, is formed at the interface beside the boundary of bronze. The EDS line scan shows an elemental transition diffusion layer of about 1.5 μm between the H62 brass columnar crystal and XYK-6 phosphorus bronze. The fracture occurred on the XYK-6 side, passing through the bump instead of the welding interface, resulting in intactness of the welding interface. The results revealed that resistance projection welding is an effective method for welding copper alloys, suggesting the bright prospects of this technology in welding electrical parts. Full article

The hot corrosion behavior of Co-9Al-9.5W-xSi (where x = 0%, 0.1%, 0.5%, at.%) alloys in a salt mixture at 900 °C was investigated. The effect of Si on hot corrosion resistance was examined using corrosion kinetics. The surface morphology of the corrosion products was explored via SEM with EDS and the phase constituents were examined using XRD. The results revealed that hot corrosion occurred as a combination of both sulfidation and oxidation behavior. With the increase in Si content, the hot corrosion resistance of the alloy was capable of remarkable advancement. Corrosion scales on the three Co-based alloys were mostly comprised of Co₃O₄, CoO, CoAl₂O₄, CoWO₄, and Al₂O₃. The hot corrosion mechanism for the Co-based alloy in the presence of 75 wt.% Na₂SO₄ and 25 wt.% NaCl deposits were analyzed. Full article

Lead-based ternary-chalcogenide thin films of the (PbTe)_1−x(PbS)_x system were obtained using the plasma-enhanced chemical-vapor-deposition (PECVD) technique under conditions of a nonequilibrium low-temperature argon plasma of an RF discharge (40.68 MHz) at a reduced pressure (0.01 Torr). High-purity elements were directly used as starting materials, namely Pb, S and Te. Plasma–chemical synthesis was carried out on the surface of c-sapphire and silicon substrate. The physicochemical properties of the films were studied using various analytical methods. The dependence of the Seebeck coefficient, resistivity and power factor on the structural properties and composition has been studied. The thermoelectric characteristics were found to be dependent on film composition. Upon the selection of optimal sulfur concentration, one can increase the power factor compared to single-phase PbS or PbTe films. Full article

This paper aims to study the possibility of improving the chemical and surface characteristics of the Ti6Al4V alloy by depositing phosphate layers on its surface. Accordingly, an innovative phosphating solution was developed and used in a chemical conversion process to obtain Ca–Zn phosphate layers on the base material surface. Moreover, the chemical composition of the phosphate solution was chosen considering the biocompatibility of the chemical elements and their possibility of contributing to the formation of phosphate compounds. The obtained layer was characterized by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and potentiodynamic polarization tests. The wetting of the Ca–Zn sample surface was also investigated using water and two liquids similar to body fluids, namely, Ringer and Dulbecco solutions. According to the surface energy study, the polar component is almost two times larger compared with the dispersive one. The SEM and EDS tests revealed a uniformly coated surface with intercalated crystals leading to a rough surface. Furthermore, the XRD results showed not only the presence of hopeite and scholzite but also of phosphophyllite. By the vibrations of the PO₄⁻³ groups, the FTIR test confirmed the presence of these phases. The potentiodynamic tests revealed that the samples coated with the Ca–Zn phosphate layer present better corrosion resistance and a lower corrosion rate compared with the uncoated ones. Full article

X-rays are commonly employed in medical institutions for diagnostic examinations, which often results in radiation exposure for both patients and medical personnel during treatments and procedures. Hands are typically the most exposed body parts, with scattered rays causing secondary exposure. To address this issue, a lightweight functional radiation protection fabric that guarantees the activity of medical personnel is required. In this study, a shielding fabric was fabricated with nanofibers using a mixture of tungsten and polyurethane to resolve the weight reduction problem of such nanofibers. To improve the shielding performance, the change in the performance arising from the spinning pattern in the nanofiber electrospinning manufacturing process was compared and tracked. The patterns reproduced via electrospinning included honeycomb, matrix-orthogonal, double-circle, and spider web patterns. Through this, a nanofiber fabric was produced, and the shielding performance was evaluated. The honeycomb pattern fabric exhibited the best shielding rate of 89.21% at an effective X-ray energy of 60.3 keV, and the double-circle pattern exhibited the lowest shielding rate of 62.55% at the same energy. Therefore, it was observed that the pattern arising from the nanofiber spinning conditions affects the dispersion of the shielding material, which affects the shielding performance. When 0.3 mm tungsten nanofiber fabric is compared with its lead equivalent of 0.25 mm, a difference of 8.7% was observed, suggesting that the nanofiber can be used in medical institutions. Future research will explore the potential of protective fabrics that minimally impact medical personnel’s mobility but provide enhanced protection against radiation exposure. Full article