Coatings

In order to explore the effect of ZrH₂ on the electron emission performance of rare earth tungsten electrodes (W-La-Y), different proportions of ZrH₂ were added to rare earth tungsten in this study, and samples of three proportions were obtained by ball milling and vacuum hot-pressing sintering. The electron emission performance, phase evolution and surface valence state of the samples were analyzed, respectively. The test results of electrode emission performance show that increasing the mass fraction of ZrH₂ in the range of 0% to 0.1% can continuously improve the electrode emission performance. At 1600 °C, 0.1% ZrH₂ can increase the zero-field current emission density from 0.36 to 0.90 A/cm². X-ray diffraction (XRD), the comprehensive thermalgravimetric and differential thermal analysis (TG-DTA) and X-ray photoelectron spectroscopy (XPS) results showed that the ZH₂ added to rare earth tungsten electrodes would react with impurity oxygen in the electrode and consume impurity oxygen, thus reducing the inhibitory effect of impurity oxygen on the electron emission of the electrode and improving its electron emission performance. Full article

Plating bath composition, temperature, current density, and pH have a great influence on the properties of a Co-Mo alloy coating. However, these conclusions are obtained from the perspective of test results. Most of the factors that affect the properties of the coating operate by interfering with the electrodeposition process. Therefore, it is of great significance to study the kinetics of the electrodeposition process. To further study the influence of process parameters on the deposition process of Co-Mo alloy coatings, cyclic voltammetry (CV), scanning linear voltammetry (LSV), and electrochemical impedance testing (EIS) were used to study the deposition kinetics of Co-Mo alloy coatings. The results show that with the increase in sodium molybdate content in the plating solution, more Mo elements are involved in the deposition process. At the same time, a higher Mo element content can reduce the dissolution of the coating as the anode and improve the service life of the coating, but too high a Mo element content will lead to cracks on the surface of the coating. The deposition temperature will affect the processes of reduction deposition and oxidation dissolution of the coating. The pH of the plating bath will directly affect the reduction reaction process of MoO₄²⁻ ions in the plating bath. With the increase in the pH value, the reduction reaction rate of MoO₄²⁻ ions decreases, and the cathodic reduction reaction current density decreases. At the same time, the peak current density of anodizing decreases with the decrease in the pH value of the plating solution, indicating that the alkaline plating solution has an inhibitory effect on the plating dissolution process. Full article

In this paper, the influence of water glass types, the modulus of water glass, the alkali content, the water consumption, and plant fibers on the mechanical strengths of alkali-activated blast furnace slag powder (BFS) is investigated. Moreover, the fiber types and pretreatment on the plant fibers and the measuring temperature on the performance of alkali-activated BFS are further considered. Results indicate that BFS activated by potassium silicate shows higher mechanical strengths than that activated by sodium silicate. The alkali-activated BFS with alkali treatment on fibers is the most advantageous. The modulus of alkali leads to decreasing the compressive strength. A total of 35% water consumption is the most beneficial to the specimens’ flexural and compressive strengths. Samples with 14% potassium silicate show the maximum mechanical strength. Alkali-activated BFS with 1% wheat straw fibers in addition by total volume represents the maximum mechanical strength. The alkali-activated BFS with alkali treatment on fibers is the most advantageous. The addition of potassium silicate can improve the flexural and compressive strengths by the maximum values of 30.4% and 16.8% compared to specimens with sodium silicate. A total of 35% water consumption can increase the flexural and compressive strengths by 33.8% and 32.7%. Full article

Hexagonal ZrB₂ belongs to the group of ultra-high temperature ceramics representing an important class of materials with the potential to meet the high demands of today’s industry. However, this potential is limited by inherent brittleness and poor tribological properties. Here, the combination of density functional theory and experiment is used to investigate the effect of silver alloying on the mechanical and tribological properties of hexagonal ZrB₂ thin films. Calculations indicate strong insolubility of Ag atoms in the ZrB₂ metal sublattice and a significant effect on the mechanical properties, pointing out an improvement in ductility and tribological properties but at the cost of reduced hardness. The experiments confirmed the theoretical predictions of the strong insolubility of silver, where the magnetron-sputtered Zr_1−xAg_xB_2+Δ films form a segregated nanostructure consisting of separated hexagonal ZrB₂ and cubic Ag phases. With increased Ag content, values of Young’s modulus decrease from E^ZrB2.31 = 375 GPa to E^{Zr0.26Ag0.74B0.89} = 154 GPa, followed by a decrease in hardness from H^ZrB2.31 = 30 GPa to a value of H^{Zr0.26Ag0.74B0.89} = 4 GPa. The suppression of crack formation is also shown with the material flow around cube corner indents, indicating enhanced ductility. The improvement of tribological properties was also confirmed when the coefficient of friction (COF) was reduced from COF^ZrB2.31 ~0.9 to a value of COF^{Zr0.26Ag0.74B0.89} ~0.25 for all counterpart materials—steel (100Cr6), Si₃N_4, and WC/Co. Full article

Multi-Principal-Element or High-Entropy Alloys (MPEAs/HEAs) have gained increasing interest in the past two decades largely due to their outstanding properties such as superior mechanical strength and corrosion resistance. However, research studies on their processability are still scarce. This work assesses the effect of different machining conditions on the machinability of these novel alloys, with the objective of advancing the introduction of MPEA systems into industrial applications. The present study focuses on the experimental analysis of finish-milling conditions and their effects on the milling process and resulting surface finish of CoCrFeNi, Al_0.3CoCrFeNi and Al_0.3CoCrFeNiMo_0.2 alloys fabricated via Spark Plasma Sintering. Ball-nose-end milling experiments have been carried out various milling parameters such as cutting speed, feed per cutting edge, and ultrasonic assistance. In situ measurements of cutting forces and temperature on the tool edge were performed during the experiments, and surface finish and tool wear were analyzed afterwards. The results exhibited decreasing cutting forces by means of low feed per cutting edge and reduced process temperatures at low cutting speed, with the use of ultrasonic-assisted milling. It was shown that the machinability of these modern alloys through conventional, as well as modern machining methods such as ultrasonic-assisted milling, is viable, and common theories in machining can be transferred to these novel MPEAs. Full article

This study investigated the effect of the mixing ratio of TiO₂ nanoparticles (P25) and titanium alkoxide (T-sol) on various properties of TiO₂ films. The specific surface area of the TiO₂ film was determined using BET analysis, while the microstructure and thickness were analyzed by field emission scanning electron microscopy (FE-SEM) and atomic force microscopy (AFM), respectively. Transmittance and pencil hardness tests were conducted to evaluate the transparency and durability of the coating layer, respectively. The results showed that, as the P25 content increased, the specific surface area of the TiO₂ film also increased, but this effect decreased as the ratio of T-sol to P25 increased. Additionally, the thickness and surface roughness (Ra) of the coating layer increased as the P25 content increased, with the thickness increasing from 210 to 950 nm and Ra increasing from 51 to 88 nm. However, the transmittance of the coating layer decreased as the P25 content increased, indicating that the films became less transparent. Furthermore, the pencil hardness of the coating layer decreased as the P25 content increased, indicating that the films became less durable. Finally, the oil contact angle decreased as the P25 content increased, indicating that the films became more hydrophilic. Full article

Copper alloys with a combination of good electrical conductivity and mechanical properties are widely used in automotive electronics, large-scale integrated circuits, and other fields. In this study, a new type of Cu–Ni–Si alloy with added trace elements of Co and Cr was fabricated. Hot compression tests of this alloy at different temperatures and strain rates were conducted using a Gleeble-1500D simulator. Then, the microstructure transformation and precipitation behaviors of the Cu-1.1–Ni-0.7–Co-0.45–Si-0.3Cr alloy were studied during a hot deformation process. The results show that the hot deformation behavior of the Cu-1.1–Ni-0.7–Co-0.45–Si-0.3Cr alloy includes continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX). The intensity of the texture in the microstructure is decreased, and the randomness of the texture in the microstructure is increased together with the recrystallization progress. The degree of recrystallization of the new Cu-1.1–Ni-0.7–Co-0.45–Si-0.3Cr alloy is increased when the hot deformation temperature rises. Additionally, the results indicate that there are two types of precipitates which are formed in the alloy during the hot deformation process. These two precipitates can pin dislocations and grain boundaries, and therefore, they significantly improve the hot compression resistance of the Cu-1.1–Ni-0.7–Co-0.45–Si-0.3Cr alloy. Full article

The purpose of this research is to prepare GH4 169 alloy specimens by laser metal deposition, by investigating the changes in powder morphology, powder particle size, and elemental content during the cycling process. As well as the pore defects and microstructure of deposited samples prepared from recycled powder, we analyzed the changes in powder properties during the cycling process and the effects of using recycled powder on the organization and properties of LMD-deposited specimens. It was shown that the average particle size of the powder increased with the increase in the size of powder recycling, from 59.861 µm in the original powder to 64.144 µm after four cycles, with the phenomenon of powder burnout and satellite ball. The elemental content of the powder changed with the increase in the number of cycles, among which the elemental content of Nb increased significantly from 4.31 wt% of the original powder to 7.97 wt% after four cycles, the proportion of Laves phase in the deposited samples increased, the porosity and pore size increased, the tensile strength of the specimen decreased from 1046 MPa of the original powder to 936 MPa, the tensile strength decreased by 10.5%, and the elongation was increased to 27% from 11% of the original powder. Powder recycling can lead to powder aging and reduce the mechanical properties of the laser metal deposited formed parts. Full article

The modern coating market is dominated by acrylic, polyurethane, and polyester polymer resins produced from unsustainable fossil resources. Herein, we propose the preparation of resins from biobased components to produce functional and solvent-free wood coatings with enhanced performance properties. Acrylated rapeseed, linseed, and grapeseed oils were prepared via a one-step synthesis and used as a basis for the control of resin viscosity and fatty acid content. A combination of vegetable oil acrylates was used as a matrix and the biobased monomer propoxylated glycerol triacrylate (GPT) was selected to tailor the properties of the UV crosslinked network. During polymerization, the GPT monomer induced a two-phase microstructure as indicated by an SEM analysis. The possibility of generating a tailored microstructure in the final material was examined in this study. The addition of GPT increased the storage modulus by up to five-fold, crosslink density by up to two-fold at 20 °C, and glass transition temperature by up to 10.2 °C. Pull-off adhesion tests showed a strength of 1.21 MPa. In addition, the photo-oxidation effect on samples, i.e., aging, was assessed with microhardness, sliding friction, and optical microscopy. Coatings showed a microhardness value up to 250 MPa, while a coefficient of friction (μ) was in the range of 0.21 to 0.88. Full article

Potentiodynamic and potentiostatic polarization tests in the potential range between open circuit potential (OCP) − 0.1 V and OCP + 4 V were carried out in aluminate–phosphate electrolytes with an aluminate concentration of 0.2 mol/L and varying phosphates contents between 0 and 0.1 mol/L. The pH was adjusted between 11.5 and 12.0 due to phosphate and optional KOH addition. A high-strength, dual-phase steel, which is relevant for lightweight construction, served as the substrate material. The layer microstructure was investigated by optical and scanning electron microscopy. Energy-dispersive X-ray spectroscopy and Raman spectroscopy were used for element and phase analyses. We found that iron hydroxides or oxides are initially formed independently of the electrolyte composition at low potentials. At around 1 V vs. standard hydrogen electrode (SHE), the current density suddenly increases as a result of oxygen evolution, which causes a significant reduction in the pH value. Precipitation leads to the formation of porous layers with thicknesses of 10 µm to 20 µm. In the case of a pure aluminate solution, the layer mainly consists of amorphous alumina. When adding phosphate to the electrolyte, the layer additionally contains the hydrous phosphate evansite. At the highest phosphate content in the electrolyte, the highest P content and the most pronounced crack network were observed. Full article

Ternary heterojunction photocatalysts can improve the transport and separation of photogenerated electrons and holes, which could promote their reduction and oxidation properties for environmental and energy applications. In this research, the ternary photocatalyst Ti₃C₂@TiO₂/g-C₃N₄ was successfully synthesized via direct electrostatic self-assembly during hydrothermal process. Ti₃C₂ MXene was used to optimize the interfacial carrier transport and separation between the interfaces. The obtained ternary heterostructured photocatalyst had a higher photocatalytic degradation performance for removing rhodamine B (RhB) and 4-chlorophenol (4-CP). The synergistic effect of heterojunction between g-C₃N₄ and TiO₂ and Schottky barrier presented among TiO₂ and Ti₃C₂ suppressed the recombination of the photogenerated electron–hole pairs. Moreover, the Ti₃C₂ can serve as an active site for the adsorption and activation of organic pollutants resulting from sufficient functional groups (F⁻ here). Full article

Nitrogen-doped TiO₂ films exhibit good photocatalytic ability in the visible (VIS) light region. This study reports the fabrication of these films using arc ion plating (AIP) in different ratios of nitrogen partial pressure (P_N2) to oxygen partial pressure (P_O2) without substrate heating and/or applied bias. This approach allows a significant broadening of the range of possible substrates to be used. X-ray diffraction (XRD) patterns indicate that these films deposited at room temperature are amorphous, and surface electron microscope (SEM) and atomic force microscope (AFM) images show that they have rough surfaces. Their transmittance and optical properties are measured with a spectrometer and ellipsometer, respectively. In addition, the bandgap energies of these amorphous films are derived by the ellipsometer from the Tauc–Lorentz (TL) model. The results indicate that the N-doped TiO₂ film with a P_N2/P_O2 ratio of 1/4 attains the narrowest bandgap and the highest absorbance in the visible region. It can be attributed to the prominent Ti–N peaks observed in the sample’s Ti and N X-ray photoelectron spectroscopy (XPS) spectra. In addition, verified with the methylene blue (MB) test, this sample exhibits the best photocatalytic performance for its narrowest energy gap. Full article

A Y₂O₃ coating was prepared using the atmospheric plasma spraying (APS) technique. On exposing the coating to CF₄/O₂/Ar plasma, a fluorine contamination layer (YO_xF_y) was formed, which was the main cause of process drift and contamination particle generation on the APS–Y₂O₃ coating surface. To remove the YO_xF_y layer on the coating surface, a piranha solution, which is a mixture of sulfuric acid and hydrogen peroxide, was employed for cleaning. The piranha solution was found to be an excellent medium for removing the YO_xF_y layer. The amount of contamination particle generated could be reduced by approximately 37% after cleaning with a 3:1 piranha solution compared with before cleaning. Full article

The high activity of metallic zinc particles with water, and consequently the short pot lift of a mixed waterborne organic zinc-rich paint, are the most well-known problem for their application. In this study, zinc powders were modified by silane-crosslinked potassium silicate and the paint’s pot life was prolonged. Electron microscopy analysis showed that the zinc spheres in the waterborne paint were encapsulated by the shell consisted of silane-crosslinked potassium silicate and resin. The modification allowed the paint stay fluid after storage for 36 h. Nevertheless, the thickened shell was found to deteriorate the cathodic protection provided by the zinc particles. As a repair strategy, the post-heat treatment performing on the coating could awaken the protective effect of zinc powders. The anti-corrosion performance of the repaired coatings was confirmed by electrochemical tests and salt spray tests. Full article

The results of systematic studies of the electrospark alloying process with the introduction of dispersed materials into plasma of low-voltage pulsed discharges are presented. Technological methods have been developed for supplying the powder material straight into the treatment zone through a hollow electrode of an anode or from the side, with the electrode-anode periodically contacting the substrate of cathode. It has been established that under the same energy regimes, when powder materials were introduced into the discharge zone, the increase in the mass of the cathode per time unit increases from 10 to 15 times or more. This study presents the process of synthesis of carbide phases (TiC and WC) during electrospark alloying of steel substrates with electrodes made of Ti, W, and graphite, with additional supply powders of these materials into the processing zone. A process has been developed for the synthesis of ternary compounds, so-called MAX-phases: Ti₂AlC, Ti₂AlN and Ti₃SiC₂ by electrospark alloying with powder compositions TiAlC, TiAlN and TiSiC. These MAX phases exhibit a unique combination of properties that are characteristic of both metals and ceramics. Energy modes of the processing were optimized, which resulted in high-quality coatings with the maximum content of carbide phases and ternary compounds. It has been established that the energy of electrical pulses during electrospark alloying, when powders of materials are fed into the interelectrode gap, ranges from 0.8 to 3.0 J, depending on their thermal physical properties. High wear and corrosion resistant characteristics of C45 structural steel with such electrospark coatings are obtained. The wear of steel with coatings in comparison with uncoated steel decreased by an average of 5.5–6.0 times. It was estimated the high corrosion resistance of 40X13 steel coated with TiC and WC in 3% NaCl solution. The corrosion current for these coatings is 0.044 and 0.075 A/cm², respectively, and is significantly less than for coatings made of TiAlC, TiAlN, and TiSiC compositions. X-ray phase and optical metallographic microscopy analyses enabled the display of the amorphous-crystalline nature of the coatings. Full article

An asphalt mastic has thixotropic characteristics that significantly influence its fatigue and healing performance. Therefore, understanding the thixotropy of an asphalt mastic is clearly of great importance. However, research in this area is still in the early stages. This study focuses on self-heating as one of the biasing performances of asphalt material by analyzing the viscosity, stress, and hysteresis loops the of asphalt mastics under cyclic shear loading. Twelve types of asphalt mastics fabricated with asphalt, as well as different types of mineral filler, were selected to examine thixotropy. In addition, the filler/asphalt ratio was examined via the hysteresis technique to analyze the hysteresis loop and the viscosity–shear rate. The thixotropic potential function was also studied from the energy viewpoint. The results show that asphalt mastics with different asphalt binders, mineral fillers, and filler volume fractions showed hysteresis loops for shear stress versus shear rate diagrams. With an increase in the loading times of the cyclic load, the area of the hysteresis loop gradually decreases, and the hysteresis area most likely features a relatively stable value. The thixotropy of the asphalt can be significantly reduced by adding filler, and different types of mineral filler can slightly influence the thixotropy. The viscosity decreases with an increase in the shear rate, and it gradually recovers with a decrease in the shear rate. The greater the filler/asphalt ratio, the greater the viscosity, and the faster the viscosity’s descent is with the prolongation of time. Due to the existence of a higher amount of filler content, the recovery of a viscosity crack is more difficult. For asphalt mastics with high filler/asphalt ratios, the thixotropic mechanism can be explained via particle agglomeration and the depolymerization theory. For asphalt mastics with low and medium filler/asphalt ratios, the thixotropic mechanism can be explained via the particle chain theory. The damage and recovery of the internal structure of an asphalt mastic can be characterized by the structural failure potential function and the structural recovery potential function, respectively. Full article

There has been an increase in interest in developing functional polymer composites based on green chemistry principles. The purpose of this study was to investigate the preparation of functional epoxy/carbon nanotube nanocomposites using ball milling methods. In contrast to mechanical mixing, ball milling promoted good dispersion of CNTs within the epoxy matrix, thereby improving their mechanical properties and electrical conductivity. In epoxy nanocomposites with ball milling, Young’s modulus and tensile strength were increased by 653% and 150%, respectively, when CNT loading was 1.0 vol%. Additionally, the ball milling of CNTs improves their dispersion, resulting in a low percolation threshold at 0.67 vol%. The epoxy/CNT film sensor that was produced using the ball milling approach not only exhibited high reliability and sensitivity to mechanical strains and impact loads, but also possessed the ability to self-detect damage, such as cracks, and accurately locate them. This study marks a notable milestone in the advancement of functional epoxy/CNT composites through the ball milling approach. Full article