Thick Coatings Research Articles

X‐Ray Fluorescence Determination of the Chemical Composition and Coating Thickness of Artifact Surfaces Using the Intensity Ratio of α‐ and β‐Lines

ABSTRACTThe potential capabilities of the x‐ray spectral analysis method and the efforts of many researchers have ensured its widespread use in industry and scientific research. X‐ray fluorescence analysis (XRF) is one of the non‐destructive methods widely used to determine the chemical composition of automobile catalysts, solar panels, coins, jewelry, and so forth. In recent years, the problems of studying gold and silver objects of artistic value have attracted great interest. This paper presents a review of work on determining the chemical composition and thickness of single‐layer and multi‐layer coatings of artifacts and other objects of study with surfaces of complex configuration using the ratio of the intensities of characteristic x‐ray radiation of α‐ and β‐lines.

Hydroxyapatite Nanocoatings Deposited by Means of Resonant Matrix-Assisted Pulsed Laser Evaporation

Hydroxyapatite (HAp) is one of the most widely studied materials for utilization in the development of artificial implants. Research is mainly aimed at the production and modification of HAp coatings for simplification of the deposition process, cost reduction, and increase in biocompatibility. In this paper, the authors deposited HAp synthetic microparticles by means of matrix-assisted pulsed laser evaporation (MAPLE) on Ti6Al4V alloy plate substrates and obtained uniform HAp coatings without further treatment or modifications. The authors utilized a tunable pulsed laser to adjust its wavelength to the selected solvents, in order to optimize the process for deposition speed and quality. The following solvents were used as matrices: deionized water, isopropyl alcohol, and a 3:2 mixture of isopropanol:acetonitrile. Obtained coatings were examined by means of scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and profilometry in order to evaluate coating quality, uniformity, and structural integrity. MAPLE deposition allowed the acquisition of approx. 200 nm thick coatings for water and isopropanol matrices and approx. 320 nm for isopropanol:acetonitrile matrix, which indicates an increase in deposition rate by 37%. The obtained coatings meet requirements for further biocompatibility testing, material modification, and composite synthesis.

Micromorphology evolution and properties of strontium-zinc-phosphate chemical conversion coatings on Ti:Effect of Zn2+ and Ca2+ in the reaction solution

Bioactive strontium zinc phosphate (SrZn2(PO4)2, SZP) coatings have attracted much attention in the surface modification of medical metal materials. And the micro-morphologies of that coating have an important influence on cellular function and osseointegration. This study prepared a variety of micro-morphology SrZn2(PO4)2 coatings on titanium (Ti) using the phosphate chemical conversion (PCC) method. The effect of Zn2+ concentration in the reaction solution on the micro-morphology and properties of the SZP coatings was studied. The results showed that the SZP crystal size increased with increasing concentration of Zn2+ in the reaction solution, which also led to a more regular morphology of the coatings on Ti. A corresponding increase in the thickness, hydrophilicity, and roughness of the SZP coatings was also observed because of the increase in Zn2+ concentration. The bond strength of the coatings showed an initial increase followed by a slight decline with rising Zn2+ concentration. Moreover, the addition of Ca2+ in the reaction solution also significantly affected the micro-morphology of the SZP coatings, changing the crystal morphology from rectangular blocky to shuttle-shaped lamellar. The wettability, bonding strength, porosity, and ion release rate of the coatings were also increased because of the addition of Ca2+. This study elucidated the mechanism of Zn2+ and Ca2+ ions in the reaction solution on the morphology and properties of SZP coatings. The findings provided a novel approach to controlling and optimizing the micro-morphology of phosphate coatings to enhance their osteogenic activity.

Sparse-deconvolution terahertz near-field microprobe tomography enabling non-destructive inspection of small solid dosage forms

Terahertz (THz) pulsed imaging is a powerful tool for investigating solid dosage forms. However, traditional far-field systems struggle with physically small samples and strongly bent surfaces due to inherently limited lateral resolution. The present study introduces a novel approach using photo-conductive near-field microprobes (PC-NFMs) with a THz time-domain spectroscopy module to overcome the limitations of far-field setups concerning their achievable lateral resolution. In addition, a modified sparse deconvolution algorithm for advanced THz signal processing is presented, enabling the reconstruction of fainting interfaces in scattering media. This approach is particularly valuable for specialized dosage forms with extremely thick coatings, such as the investigated controlled-release dosage form, aiding as a worst-case scenario. While most pharmaceutical coatings are <100 µm thick, our method’s ability to analyze thicker coatings up to nearly 400 µm at an extraordinarily high spatial resolution of 87 µm in the x-direction and 175 µm in the y-direction sets it apart from approaches presented so far. This versatility makes the approach relevant for standard pharmaceutical products and niche, specialized dosage forms, including mini tablets.

Residual Stress Analysis in High‐Speed Physical Vapor Deposition Coatings

Several studies focus on impact of residual stress in coatings, predominantly those synthesized by conventional physical vapor deposition (PVD) techniques like arc PVD and magnetron sputtering. High‐speed PVD (HS‐PVD) is based on hollow cathode gas flow sputtering, enabling the deposition of thick coatings s &gt; 20 μm in contrast to the mentioned processes, where coating thickness is limited due to compressive residual stresses. Therefore, the effect of residual stresses on HS‐PVD coatings and adhesion was analyzed for the first time. The aim is to evaluate the influence of diverse substrate materials, different coating systems, and process parameters on the residual stress states in HS‐PVD coatings. Different coating systems like AlCrN and AlCrO are deposited at different reactive gas flows, coating times, and bias voltages. The residual stress of oxide coatings, deposited on cemented carbide and steel X40CrMoV5–1, is analyzed using X‐ray diffraction (XRD) and the sin2ψ method. For AlCrN coatings, in addition to the XRD method, the residual stresses are measured by focused ion‐beam‐digital image correlation ring‐core method to investigate different measuring methods. Both coating systems show higher adhesion strength with increasing thickness. Lower residual compressive stresses are unexpectedly observed at higher coating thickness using both analysis methods.

FSUNet: lightweight full-scale information fusion UNet for seed coat thickness measurement

FSUNet: lightweight full-scale information fusion UNet for seed coat thickness measurement

GET 203-2024 state primary special standard of complex refractive index and length in the field of measuring the thickness of optical coatings

GET 203-2024 state primary special standard of complex refractive index and length in the field of measuring the thickness of optical coatings

Two species of Polycelis (Platyhelminthes, Tricladida, Planariidae) newly recorded for the Qinling Mountains and the Loess Plateau in China, with a comparative discussion on their karyotypes

The paper details new geographic records of two species of the genus Polycelis Ehrenberg,1831 (Platyhelminthes, Tricladida, Planariidae) for the Qinling Mountains and the Loess Plateau in China and provides redescriptions of these species based on an integrative taxonomic study involving morphology, karyology, and histology. This new information considerably expands our knowledge on these species, for which until now only limited data was available. The species Polycelis asiatica Selinova, 1985 is characterized by the following features: 63–80 eyes; sperm ducts that exhibit an intrabulbar knee-shaped bend towards the ventral surface before opening separately and symmetrically into the antero-dorsal portion of a large seminal vesicle; the latter is ventrally displaced, thus creating a narrow ventral lip on the penis papilla; dorsal wall of the seminal vesicle is provided with several well-developed folds; more or less bulbous penis papilla protrudes from the dorsal wall of the male atrium and is provided with a slender and flexible tip; chromosome complement diploid with 30 metacentric chromosomes, 8 submetacentric chromosomes, and 2 subtelocentric chromosomes. The species Polycelis eudendrocoeloides (Zabusova, 1929) is characterized by: 49–80 eyes; highly reduced and blunt penis, provided with a kind of flagellum that projects into the seminal vesicle; a relatively thick coat of circular and longitudinal muscles around the entire male atrium; generally, a very large intrabulbar seminal vesicle, extending from near the ventral body surface to occupy the major part of both the penis bulb and the dorso-ventral space of the body; diploid chromosome complement consisting of 36 metacentric chromosomes.

Corrosion resistance and biocompatibility of silica coatings on AZ31 magnesium alloy via magnetron sputtering

Magnesium alloys have promising prospects in biodegradable implants, but premature degradation is the main factor limiting their application. We prepared silicon coatings of different thicknesses on the surface of AZ31 magnesium alloy using the RF magnetron sputtering method. The phase, microstructure, and elemental composition of the coatings were characterized by XRD, SEM, and EDS, respectively. The corrosion resistance of the coatings in simulated body fluids was tested using immersion corrosion and electrochemical corrosion tests. Results showed that the silicon coating sputtered for 3 hours had the best corrosion potential and current, with a corrosion current density of 6.5614E-6 (A/cm2), which is two orders of magnitude lower than that of the AZ31 substrate. The extract of the sample in RPMI-1640 medium was co-cultured with human umbilical vein endothelial cells (HUVEC), and its cytotoxicity was evaluated by the CCK-8 assay. It was found that the silicon coating sputtered for 3 hours had the least toxicity, and the endothelial cells had a high proliferation rate. Therefore, the magnetron sputtered Si coating on AZ31 magnesium alloy exhibits good corrosion resistance and biocompatibility.

Microstructure evolution and high temperature air oxidation behaviour of thick Cr coatings at 1200°C

The thick Cr coated Zr-4 alloys were prepared by magnetron sputtering deposition and their microstructure evolution and high-temperature air oxidation behaviour were investigated. Oxidation tests showed that the thick Cr coatings can improve the high-temperature air oxidation resistance of Zr-4 alloy even if the α-Zr(O) layer was formed at some regions. The mechanism of high-temperature air oxidation was also discussed in detail, and these experimental results could provide data for establishing a reliable prediction model of this degradation.

Boronize Coatings Studied with a New Mass Transfer Model.

This study examined the development of Fe2B (diiron boronize) coatings on the surface of 35NiCrMo4 steel through the thermochemical surface hardening process called boronizing. The morphology and thickness of the boronize coatings were assessed using Scanning Electron Microscopy (SEM) and optical microscopy (OM). A novel mathematical mass transfer model was developed to estimate the diffusion coefficients of boron in hard coating. The presence of uniformly distributed boronize coatings with a typical sawtooth pattern on the surface of the substrate was confirmed. The boronize coating's chemical composition and phase constituents were analyzed utilizing X-ray energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD). The study confirmed the presence of a single-phase boronize coating (Fe2B). Furthermore, microhardness tests indicated that the boronized specimen's surface demonstrated an average hardness of approximately 1953 HV. The wear study were conducted using the pin-on-disk method under dry debonding conditions at room temperature to estimate the coefficient of friction (COF) of the boronized (average ≈ 0.35) and untreated (0.725) specimens. The results revealed approximately 200% improvement in wear resistance due to the boronized coating. The empirical validation of the mathematical model was carried out for two additional boronizing conditions at 1223 K for 3 h and 1273 K for 1.5 h, resulting in an estimated percentage error of around 2.5% for both conditions. Additionally, an ANOVA analysis was performed, taking into account the temperature and time factors. The findings indicate that both factors exert a substantial influence on the dependent variable (u), with temperature (T) contributing 64.68%, time (t) contributing 27.37%, and the interaction of both factors (T × t) contributing 5.13%.

Effect of Glyphosate on Behavioral Changes in a Fresh Water Fish, Labeio Rohita in Sarju River of Gonda, Uttar Pradesh

The present study showed that the glyphosate is toxic and causes behavioral changes in Labeio rohita. The LC50, values of glyphosate conducted to be as 0.018 ml/l; 0.015; m1/1; 0.012 m1/1 and 0.010 m1/1 at 24, 48, 72 and 96 hours. A thick coat of mucus over the body and loss of stability noticed may be due to none functioning of the brain. The colors of the tested fishes appeared little pale as compared to the normal fishes. Hyper excitability followed by lethargy was observed by the jerky and random movement of fishes just after the addition of toxicants. Due to the low rate of oxygen uptake, fishes came to the surface to engulf air frequently. Herbicides, commonly employed to control unwanted vegetation in crops, can enter water bodies through runoff, leading to unintended consequences for aquatic ecosystems.

Effect of Coating Treatment on the Properties of Extruded Mg-1.0Zn-0.3Zr-1.0Y-2.0Sn Alloys

The impact of fluoride-based coatings on the microstructure and mechanical integrity of extruded Mg-1.0Zn-0.3Zr-1.0Y-2.0Sn alloys was assessed utilizing optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), immersion testing, electrochemical analysis, and tensile testing. It was observed that the magnesium alloys could be immersed in hydrofluoric acid (HF) for varying durations to achieve coatings of distinct thicknesses, with the coating thickness stabilizing at approximately 8 μm after a 48 h immersion period. The application of the fluoride coating significantly enhanced the corrosion resistance of the alloys, with a corrosion rate (CRH) of 0.13 ± 0.012 mm/y. Upon a 20-day immersion in simulated body fluid (SBF), the degradation rates of the yield strength (YS), tensile strength (UTS), and elongation (EL) for the cast alloys were recorded as 62%, 59%, and 64%, respectively. For the extruded alloys, these rates escalated to 77%, 76%, and 95%. In contrast, the fluorine-coated alloys exhibited significantly lower degradation rates of 28%, 23%, and 39% after a 25-day immersion in SBF. Upon extrusion, the specimens exhibit a diminished corrosion resistance and a more substantial decline in mechanical properties compared to their as-cast state. Upon the application of the coating, there is a discernible reduction in the rate of mechanical property degradation observed in the specimens. This indicates that the fluorinated coating can mitigate the corrosion rate and enhance the corrosion resistance of magnesium alloys.

Influence of BN microstructure on oxidation of SiC/BN/SiC composites

AbstractThis study investigates the effects of boron nitride (BN) coating characteristics on the subsurface oxidation behavior of SiC/SiC composites in high‐temperature, water‐rich environments. Three types of coatings were examined: a crystalline stoichiometric BN, an amorphous BN, and a Si‐doped amorphous BN, the latter two containing 5–10 at% of oxygen and carbon. High‐resolution imaging and chemical analysis techniques were used to probe microstructural changes after oxidation at 1000°C for 1 or 12 h in flowing 20 vol% H2O, focusing on effects of coating thickness. Complementary chemical thermodynamic calculations and models for reaction‐ and transport‐controlled recession were used to interpret the experimental findings. Crystalline BN coatings produce open recession channels without forming borosilicate glass, a consequence of carbothermal reduction arising from C/CO produced through concomitant SiC oxidation. The combination of active oxidation and the relatively thick coatings in this system (ca. 1 µm) leads to a recession rate controlled by the intrinsic BN volatilization rate rather than the rate of gas transport. In contrast, amorphous coatings, both undoped and Si‐doped, readily oxidize to form borosilicate glasses that replace the BN. Broadly, the recession lengths increase with coating thickness. In the early stages, while the glass is boria‐rich and thus permeable to environmental oxidants, recession is controlled by the BN oxidation rate. As boria volatilizes, the silica concentration in the glass increases, eventually reaching the saturation limit and precipitating solid silica on the internal surfaces, essentially arresting further recession.

The Role of Seed Characteristics on Water Uptake Preceding Germination

Seed germination is a complex process involving imbibition, activation and subsequent growth. In addition to re-establishing metabolic activity, water uptake helps stabilize macromolecules and biochemical reactions, resulting in radicle protrusion. Factors affecting water uptake include seed composition, water availability and seed coat permeability. Water entry sites vary with species and occur primarily through the hilum, micropyle or lens. In addition, seed size influences water uptake, where larger seeds are usually less permeable. The seed coat plays a significant role in regulating the water absorption process. Several seed coat characteristics, including color, thickness and differences in the anatomical structure, such as the presence of pores, cuticles and radicle pockets, alter water permeability. Similarly, the presence of either physical or physiological seed dormancy negatively affects water uptake. This review emphasizes that understanding seed characteristics, such as size, shape and seed coat permeability, and their relationships is essential for breeding and selecting seeds with desirable traits, as they directly influence water uptake, leading to improved germination and growth.

Using Thin Ultra-High-Molecular-Weight Polyethylene Coatings to Reduce Friction in Frost-Resistant Rubbers.

Frost-resistant rubbers retain their highly elastic properties over a wide temperature range. They are used in various friction units (e.g., seals), but their high friction coefficient and low wear resistance lead to the need for frequent replacement. In this paper, we propose applying thin (several hundred microns) UHMWPE coatings to formed rubber rings. The application technology depends on the required coating thickness. Friction tests of the coatings and pure UHMWPE were performed using the ball-on-disk (unidirectional sliding) scheme for various loads and velocities. In the experiments, the friction coefficients and temperatures near the contact area were determined. Friction tracks were studied using microscopy methods. The sliding contact of the ball and the two-layer material was modeled to obtain the dependences of the deformation component of friction on the sliding velocity for coatings of different thicknesses. UHMWPE is sensitive to frictional heating, so the thermal problem of determining the temperature in the contact area was also solved. It is shown that the minimum friction coefficient occurs for coatings with a thickness of 600 μm. At the same time, in the case of the 300 μm coating, the surface of the friction track is practically no different from the initial one. Thus, the studied combination of polymers provides antifrictional properties and wear resistance to the surface layer while maintaining the damping properties of rubber.

Experimental and Modeling Analysis of the Tensile Properties of Heavy-Duty Coatings for Steel Structures

Coatings are essential for protecting steel structures from corrosion and mechanical stresses, especially under challenging environmental conditions. To this end, this study systematically examines the effects of temperature (20 °C to 50 °C), strain rate (6.67 × 10−4 s−1 to 1.67 × 10−2 s−1), and intermediate coat thickness (140 μm to 700 μm, the layer between the primer and topcoat) on the uniaxial tensile properties of heavy-duty coatings for steel structures. Experimental and theoretical analyses were conducted to quantitatively assess the influence of these factors on the mechanical properties of the coatings. A multifactor constitutive model was developed based on the Sherwood–Frost model by integrating material characteristics and fitting experimental data, incorporating response functions for temperature, strain rate, and intermediate coat thickness. The results reveal that increased temperature causes temperature-induced softening, while higher strain rates lead to strain rate-dependent strengthening of the coatings. In contrast, the effect of layer thickness on mechanical properties follows a non-monotonic trend, influenced by the structural and material characteristics of the coatings, with the most significant mechanical response occurring at 560 μm thickness. These findings suggest that optimal coating design must consider multiple factors to enhance mechanical performance. Additionally, the correlation coefficients (r) between the model predictions and experimental results are 0.97 or higher, indicating the model’s effectiveness in predicting and optimizing the mechanical performance of heavy-duty coatings under complex conditions.

An Assessment of Coating Thickness on the Microstructure and Mechanical Behavior of IN625 Coating on Ni-Based Superalloy Substrate Deposited by High Velocity Air Fuel Technique

An Assessment of Coating Thickness on the Microstructure and Mechanical Behavior of IN625 Coating on Ni-Based Superalloy Substrate Deposited by High Velocity Air Fuel Technique

Physical and microstructural properties of YSZ + Cr2O3 thermal barrier coatings developed using HVOF technique

A composite coating material of Yttria-Stabilized Zirconia (YSZ) and Chromium Oxide (Cr2O3) was developed on the surface of Al-6061 substrates. The coating consisting of equal measures of the composite material of YSZ and Cr2O3 was successfully obtained using the High-Velocity Oxy Fuel (HVOF) technique. The surface roughness and coating thickness of the composite coatings are evaluated. The surface roughness (Ra) was evaluated showing an average of 6.0848 µm using the Surface Roughness Tester (SRT). The coating thickness was evaluated showing an average of 220.8 µm using the Coating Thickness Tester (CTT). The surface roughness and the coating thickness obtained are comparable to typical physical properties of Thermal Barrier Coatings (TBC’s). The microstructural evaluation of the coated specimens was performed through the Scanning Electron Microscope (SEM), showing the clear unification of materials The determination of the elemental composition of surface coatings was performed through the EDAX tests, which clearly established the elements in the coatings. This article is indicative of the achievement of TBC’s consisting of composite materials though HVOF technique as an alternative to TBC’s obtained through surface coats and bond coats.

Effect of bath temperature on corrosion resistance of electroless Ni-P coating on 5A90 Al-Li alloy

Abstract The Al-Li alloy exhibits outstanding characteristics, including remarkable specific strength, elevated specific stiffness, and heightened susceptibility to localized corrosion. Electroless Ni-P coating is extensively applied over the appearance of aluminum alloys to enhance their corrosion resistance. Electroless Ni-P coating was applied to 5A90 Al-Li alloy at various plating temperatures for the study presented in this publication. The coating’s surface, composition, and cross-sectional morphology were examined using SEM/EDS. The corrosion behavior of coating was studied using the potentiodynamic polarization curve. Results showed that coating on the surface of 5A90 Al-Li alloy was uniform and smooth. Ni and P elements were evenly distributed in the coating. The thickness of coatings at 80°C, 85°C, 90°C and 95°C was about 3.98 μm, 5.5 μm, 11.2 μm, and 10.29 μm, respectively. As the temperature of the bath increased, the corrosion resistance of the coating first increased and afterward decreased. The corrosion resistance of the coating might be correlated with its thickness.