Search Results (1,700)

The role of the long-period stacking ordered (LPSO) phase on the microstructure and corrosion properties of micro-arc oxidation (MAO) ceramic coatings was systematically investigated in this study. Optical microscopy and scanning electron microscopy (SEM) were employed to characterize the MAO coatings, while their corrosion behavior was evaluated through electrochemical measurements and immersion tests in a 3.5 wt.% NaCl solution. The results reveal that the sample containing the LPSO phase exhibited an increased coating thickness. However, the coating formed on the LPSO-containing Mg alloy presented a highly porous morphology with numerous large micropores. This defective microstructure compromised the protective barrier function of the ceramic layer, ultimately resulting in inferior corrosion resistance compared to coatings on its LPSO-free counterparts. Full article

Magnetron-sputtered coatings consisting of multiple alternating layers of chromium and amorphous carbon (Cr/a-C)ml were deposited on HS6-5-2 steel with an intermediate chromium layer by varying deposition rates. Three series of coatings, S1, S2, and S3, with thicknesses of 1.74, 1.15, and 1.14 μm and average chromium contents of 89.3, 66.0, and 59.7 wt.% Cr, respectively, were obtained. Open-circuit potential, cyclic potentiodynamic measurements, and electrochemical impedance spectroscopy were used to characterize their corrosion resistance in 3.5% NaCl. The surfaces were observed with optical and scanning electron microscopy before and after the corrosion tests, and changes in the elemental composition were monitored by energy-dispersive spectroscopy. The protective properties of coatings from series S2 and S3 are similar and significantly better than those of S1. They are characterized by a corrosion current below 1 μA cm^–2 and a stable passive state up to over 0.9 V_Ag/AgCl. The coatings have cathodic behavior towards the substrate, and when the coatings are damaged, galvanic corrosion causes deep pits. Coatings deposited at lower rates and with higher carbon content demonstrate significantly enhanced corrosion resistance in 3.5% NaCl. All three series of Cr/(Cr/a-C)ml@HS6-5-2 exhibit identical corrosion behavior after compromising the coatings’ integrity. Full article

Metallized papers or cardboards, used when high barrier properties are required in packaging, are usually coated with white ink prior to printing to ensure accurate colors and high print quality. The coating provides well-controlled sorption properties at a certain thickness, allowing for better printability and reduced penetration of ink components into the substrate. The white ink used for coating ensures the dimensional stability of the substrate after the drying process is complete. This research compares how different numbers of white base coat layers affect the print quality of multicolor offset prints onto metallized cardboard after rubbing. A high print quality assessment after rubbing was obtained based on spectrophotometric and gloss measurements. A comparison of the number of white base coat layers on metallized cardboard indicated that multicolor prints with two base coat layers have lower reflectance, better color stability, and high print quality after rubbing. Gloss measurements showed that prints with one layer of white base coat exhibited higher gloss values, while rubbing led to a moderate increase in gloss for all samples. Ultimately, a thicker layer of white base coat enhances mechanical resistance while maintaining acceptable optical properties in multicolor prints on metallized cardboards. Full article

The article examines the effect of different types of two-layer nanostructured coatings (cVIc and nACVIc) deposited on three types of steel substrates, 45S20, C45E, and 42CrMo4, to determine the resistance to adhesive wear of the substrate/coating system. The samples underwent different heat treatments, including normalising, quenching, and quenching and tempering, followed by PVD (physical vapour deposition) treatment at temperatures of 450 °C (cVIc) and 460 °C (nACVIc). The thickness of the cVIc layers for all three steels ranged from 0.9 to 3.4 μm, while the thickness of the nACVIc layers on all steels was slightly greater, ranging from 1.9 to 3.1 μm. Tribological tests were conducted using the pin-on-disc method, and the results were statistically analysed. Results indicate that steel grade, heat treatment, and PVD coating significantly affect adhesive wear resistance, with the type of PVD coating showing the strongest influence. For all three steels, quenched and uncoated samples exhibited the lowest adhesion wear index values. Normalised and quenched with or without tempering steels coated with cVIc layer exhibit higher resistance to adhesive wear due to better adhesion of the layer compared to the nACVIc coating. Full article

Subsea pipelines are critical lifelines for marine resource development, yet they face severe threats from accidental ship anchor impacts. This study addresses the scientific challenge of quantifying the “protection margin” of artificial rock-dumping layers, moving beyond traditional passive structural response to a “Critical Failure Intervention” logic. Based on the energy criteria of DNV-RP-F107, a critical velocity required to trigger Concrete Weight Coating (CWC) failure for a bare pipe was derived and established as the Safety Factor baseline (S = 1). Two groups of scaled model tests (1:15) were conducted using a Hall anchor to simulate impact scenarios, where impact forces were measured via force sensors beneath the pipeline under varying backfill thicknesses and configurations. Results show that artificial backfill provides a significant protective redundancy; a 10 cm coarse rock layer increases the safety factor to 3.69 relative to the H₀ baseline, while a multi-layer configuration (sand bedding plus coarse rock) elevates S to 27. Analysis reveals a non-linear relationship between backfill thickness and cushioning efficiency, characterized by diminishing marginal utility once a specific thickness threshold is reached. These findings indicate that while thickness is critical for extreme impacts, the protection efficiency optimizes at specific depths, providing a quantifiable framework to reduce small-particle layers in engineering projects without compromising safety. Full article

Background/Objectives: The use of zirconia implants is gaining traction as a potential alternative to titanium. Although having excellent properties, the zirconia surface has limited osteogenic potential. The purpose of this study was to produce, for the first time, mechanically stable, thick micron-scale hydroxyapatite coatings on zirconia implant material using radiofrequency (RF) magnetron sputtering. Methods: Zirconia samples were coated with HA using an RF magnetron sputtering device at a temperature of 125 °C for 20 h with 155 W of power. The procedure included rotating the substrate at a speed of 10 rpm while an argon gas flow was maintained continuously. Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX) analysis, atomic force microscopy, and Vickers hardness measurements were used to evaluate the coat’s characteristics. Results: A smooth hydroxyapatite coating layer that was consistent and free of cracks was observed in all FESEM pictures. The EDX study revealed that the substrate surface contains HA particles, and the ratio of calcium (Ca) to phosphorus (P) was 16.58 to 11.31, which is very close to the ratio in original HA. FESEM cross-section pictures showed good adhesion between the coating and substrate without any gaps, and the coating thickness was 5 µm on average. A statistically significant difference was found in the roughness analysis between the samples of uncoated Zr and HA-coated Zr (p-value < 0.05). Conclusions: Zirconia implant material can be coated with a uniform layer of HA, displaying good adhesion and a thickness of a few micrometers when using magnetron sputtering for an extended period of time. Full article

The development of functional polymer films on porous paper substrates is inherently constrained by substrate-induced defects that hinder film continuity and barrier performance. In this study, process-controlled amylose–Poly(Vinyl alcohol) (PVA) coatings incorporating ZnO nanoparticles (ZnO NPs) were fabricated via aqueous deposition to investigate the process-structure-property relationship governing oxygen barrier behavior on paper. The moisture resistance of the coating was also evaluated. Single-layer coatings exhibited severe barrier failure due to insufficient film formation and pervasive pinhole defects. In contrast, systematic multi-layer deposition enabled the formation of continuous polymer films. A pronounced non-linear reduction in oxygen transmission rate was observed once the dry coating thickness exceeded approximately 5 µm. Under these conditions, the oxygen transmission rate decreased to approximately 15 cc/m²·day·atm at 20 °C and 65% relative humidity. This transition was correlated with the elimination of substrate-induced defects, as confirmed by morphological analysis. In addition to enhanced barrier performance, ZnO NP-loaded coatings demonstrated strong and broad-spectrum antimicrobial activity against both Escherichia coli and Staphylococcus aureus, indicating their multifunctional potential for active packaging applications. Supporting evaluations further indicated adequate mechanical flexibility and high repulpability, highlighting the suitability of the coating for sustainable paper-based packaging. Overall, this work identifies a quantitative critical film thickness that serves as process-specific design guideline for engineering high-performance functional polymer coatings on porous paper substrates. Full article

To mitigate the attenuation of color-change sensitivity in cholesteric liquid crystals (CLCs) post-microencapsulation, this study developed MXene-reinforced thermochromic textiles. Monolayer/few-layer MXene nanosheets were fabricated via an etching-intercalation-dispersion approach, while cholesteric liquid crystal microcapsules (CLCMs) were synthesized through a solvent evaporation method. Cotton fabrics were pretreated with polydopamine (PDA), followed by the fabrication of poly(diallyldimethylammonium chloride) (PDAC)/MXene composite coatings via layer-by-layer (LbL) self-assembly and subsequent hydrophobic modification. Systematic characterizations (scanning electron microscopy, SEM; atomic force microscopy, AFM) and performance evaluations revealed that MXene nanosheets have an average thickness of 1.54 nm, while CLCMs display a uniform spherical morphology. The resultant textiles exhibit a reversible red-green-blue color transition over the temperature range of 26.5–29.5 °C, with sensitivity comparable to pristine CLCs and excellent hydrophobicity. This work overcomes the long-standing bottleneck of inadequate color-change sensitivity in conventional liquid crystal microcapsule textiles, offering a novel strategy for the advancement of smart wearable color-changing materials. Full article

A TiAlCrSiNbY coating was fabricated on γ-TiAl alloy by arc ion plating. The coating exhibits a dense, crack-free microstructure with a thickness of 5 ± 0.5 μm and strong interfacial bonding with the substrate. The characteristic power law correlations between mass gain and oxidation time were obtained for the uncoated and the coated samples at 850 °C with rate exponents of 2.38 and 2.14, respectively. After oxidation at 850 °C for 200 h, a continuous and dense oxide layer primarily composed of α-Al₂O₃ with a low oxidation reaction rate was formed, and the mass gain of the coated sample was 1/9 times that of the uncoated sample. Additionally, the addition of Cr and Nb in the TiAlCrSiNbY coating can increase the activity of Al and promoted the formation of stable and dense Al₂O₃ oxide films, the presence of a strong high-temperature stability Ti₅Si₃ phase inhibited the affinity of Ti and O, which maintained structural integrity and enhanced high-temperature oxidation resistance. Full article

This study presents a statistically robust quality-engineering evaluation of an industrial cathodic electrodeposition (CED) process applied to large electric-charging station components. In contrast to predominantly laboratory-scale studies, the analysis is based on 1250 thickness measurements, enabling reliable assessment of process uniformity, positional effects, and long-term stability under real production conditions. The mean coating thickness was specified at 21.84 µm with a standard deviation of 3.14 µm, fully within the specified tolerance window of 15–30 µm. One-way ANOVA revealed statistically significant but technologically small inter-station differences (F(49, 1200) = 3.49, p < 0.001), with an effect size of η² ≈ 12.5%, indicating that most variability originates from inherent within-station common causes. Shewhart X^¯–R–S control charts confirmed process stability, with all subgroup means and dispersions well inside the control limits and no evidence of special-cause variation. Distribution tests (χ², Kolmogorov–Smirnov, Shapiro–Wilk, Anderson–Darling) detected deviations from perfect normality, primarily in the tails, attributable to the superposition of slightly heterogeneous station-specific distributions rather than fundamental non-Gaussian behaviour. Capability and performance indices were evaluated using Statistica and PalstatCAQ according to ISO 22514; the results (Cp = 0.878, Cpk = 0.808, Pp = 0.797, Ppk = 0.726) classify the process as conditionally capable, with improvement potential mainly linked to reducing positional effects and centering the mean closer to the target thickness. To complement the statistical findings, an AIAG–VDA FMEA was conducted across the entire value stream. The highest-risk failure modes—surface contamination, incorrect bath chemistry, and improper hanging—corresponded to the same mechanisms identified by SPC and ANOVA as contributors to thickness variability. Proposed corrective actions reduced RPN values by 50–62.5%, demonstrating strong potential for capability improvement. A predictive machine-learning model was implemented to estimate layer thickness and successfully reproduced the global trend while filtering process-related noise, offering a practical tool for future predictive quality control. Full article

Niobium nitride (δ-NbN) coatings were deposited on AISI 316L austenitic steel using reactive DC magnetron sputtering. This study investigates the effects of air oxidation on the surface morphology, topography, roughness, nanohardness, adhesion, and wear resistance of NbN coatings. Their microstructure and thickness were analyzed by scanning electron microscopy (SEM), while surface morphology and roughness were assessed using atomic force microscopy (AFM), and surface topography was assessed by an optical profilometer. Nanohardness was measured using a Berkovich indenter. Adhesion was evaluated via progressive-load scratch testing and Rockwell indentation (VDI 3198 standard). Wear resistance was assessed using the “ball-on-disk” method. Both as-deposited and oxidized NbN coatings improved the mechanical performance of the substrate surface. Air oxidation led to the formation of an orthorhombic Nb₂O₅ surface layer, which increased surface roughness and reduced hardness. However, the brittle oxide also contributed to a lower coefficient of friction. Despite reduced adhesion and increased surface development, the oxidized coating exhibited a significantly lower wear rate than the uncoated steel, though several times higher than that of the non-oxidized NbN. Considering its good wear and corrosion performance, along with the bioactivity confirmed in earlier research, the oxidized NbN coating can be considered a promising candidate for biomedical applications. Full article

A kinetic and thermodynamic multi-phase model has been developed to describe the adsorption of gases on ice surfaces and their subsequent diffusional loss into the bulk ice phase. This model comprises a gas phase, a solid surface, a sub-surface layer, and the ice bulk. The processes represented include gas adsorption on the surface, solvation into the sub-surface layer, and diffusion in the ice bulk. It is assumed that the gases dissolve according to Henry’s law, while the surface concentration follows the Langmuir adsorption equilibrium. The flux of molecules from the sub-surface layer into the ice bulk is treated according to Fick’s second law. Kinetic and thermodynamic quantities as applicable to the uptake of small carbonyl compounds on ice surfaces at temperatures around 200 K have been used to perform model calculations and corresponding sensitivity tests. The primary application in this study is acetic acid. The model simulations are applied by fitting the experimental data obtained from coated-wall flow-systems (CWFT) measurements, with the best curve-fit solutions providing reliable estimations of kinetic parameters. Over the temperature range from 190 to 220 K, the estimated desorption coefficient, k_des, varies from 0.02 to 1.35 s⁻¹, while adsorption rate coefficient, k_ads, ranges from 3.92 and 4.17 × 10⁻¹³ cm³ s⁻¹, and the estimated diffusion coefficient, D, changes by more than two orders of magnitude, increasing from 0.03 to 13.0 × 10⁻⁸ cm² s⁻¹. Sensitivity analyses confirm that this parameter estimation approach is robust and consistent with underlying physicochemical processes. It is shown that for shorter exposure times the loss of molecules from the gas phase is caused exclusively by adsorption onto the surface and solvation into the sub-surface layer. Diffusional loss into the bulk, on the other hand, is only important at longer exposure times. The model is a useful tool for elucidating surface and bulk process kinetic parameters, such as adsorption and desorption rate constants, solution and segregation rates, and diffusion coefficients, as well as the estimation of thermodynamic quantities, such as Langmuir and Henry constants and the ice film thickness. Full article

Hydrogenated tetrahedral amorphous carbon (ta-C:H) thin films were modified using 266 nm picosecond laser pulses to investigate structural transformations at low and moderate fluences. Nitrogen-doped hydrogenated tetrahedral amorphous carbon layers 20–40 nm thick were deposited on silicon (Si) and silicon dioxide on silicon (SiO₂/Si) substrates and irradiated with picosecond pulses at 0.5–1.6 J cm⁻² using a raster-scanned beam. Structural changes in morphology, composition, and bonding were evaluated via optical microscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Even below 1.0 J cm⁻², localized color shifts and slight swelling indicated early structural rearrangements without significant material removal. Above 1.0–1.2 J cm⁻², the films were largely ablated, although a persistent 3–6 nm carbon layer remained on both substrate types. XPS showed an increase in sp²-bonded carbon by roughly 15%–20% in optimally modified regions, and Raman spectroscopy revealed defect-activated D-bands and the formation of multilayer defective graphene or reduced-graphene-oxide-like flakes at ablation boundaries. These results indicate that picosecond ultraviolet irradiation enables controllable graphitization and thinning of ta-C:H films while maintaining uniform processing over centimeter-scale areas, providing a route to thin, conductive, partially graphitized carbon coatings for optical and electronic applications. Full article

Background/Objectives: Laser has a prominent place in pharmaceutical industry, especially in the marking of solid dosage forms (SDFs). To combat falsified medicines, this study evaluates QR code marking on the surface of tablets as a supplement to serialization on packaging, using an ultrafast laser to achieve industrially relevant marking speeds while preserving the functional integrity of double film-coated ibuprofen tablets. Methods: Tablets were directly compressed and coated with a double film: the inner layer was a gastro-resistant coating (Acryl-EZE^® MP), while the outer one was a coloured, TiO₂-containing (TC) or TiO₂-free (TF) immediate-release coating (Opadry^®). QR codes were ablated on the tablet surface using various laser parameters (e.g., pulse energy and scanning speed), and the effects were physically, chemically, and microscopically examined to evaluate their properties after this processing. Results: No significant differences were observed between TC and TF coatings. In addition, the readability of QR code is strongly influenced by laser settings and coating types. Furthermore, the used laser has achieved the expected fast marking speed and high-precision coding, which may be economically feasible for pharmaceutical companies. According to the profilometry findings, the ablation depth could be compensated for with an appropriate coating thickness to enable the desired release properties. This was confirmed by the results of SEM, Raman analysis, and in vitro dissolution test. Conclusions: Ultrafast Ti:Sa laser-based QR code marking directly onto the dosage form offers increasing benefits in the healthcare field. However, it may undesirably affect the behavior of the dosage form. This requires careful consideration of formulation and laser processing conditions before application, especially in the case of delayed-release (DR) systems. Full article

Coatings are often applied in the materials industry to impart hydrophobic properties to the produced materials. Commonly used coatings contain plastics as well as perfluorinated compounds, which pose challenges for environmental sustainability due to their persistence and end-of-life impacts. Coatings based on natural wax, such as rapeseed, soy, palm or beeswax, constitute a key bio-based and more sustainable alternative. These waxes exhibit high hydrophobicity while also being biodegradable, offering opportunities to replace fossil-derived coatings within circular-economy material systems. Wax coating constitutes a protective layer that undergoes biodegradation after a certain amount of time. This paper presents the results of studies concerning the development of a wax coating characterized by a coarse microstructure that increases water resistance, and an appropriate susceptibility to biodegradation. It was revealed that all the analysed coatings were susceptible to biodegradation, although their rates varied markedly depending on wax type and form. The biodegradation of palm wax in bulk form and as a thick layer was 17% and 80%, respectively, after 180 days. Palm wax exhibited a pronounced ability to bind inorganic and organic matter deposits, which reduced the degradation rate. When applied as a thin coating, palm wax did not form such a barrier. Palm wax significantly influences coating durability because its surface undergoes morphic changes induced by bio-surfactants secreted by microorganisms. These changes the adhesion of organic and inorganic matter particles, and the layer thus established limits the diffusion of oxygen, enzymes and microorganisms to the wax coating. The tests demonstrated that the addition of palm wax to wax mixtures allows the degradation rate to be controlled, and that its inhibitory effect is strongly dependent on the geometry of the material. Full article