Coatings

15 pages, 1596 KiB

Open AccessArticle

Three-Dimensional Micromechanical Simulation and Evaluation of High-Toughness Ultra-Thin Friction Course with X-Ray Computed Tomography

by Cheng Wan, Qiang Yi, Jiankun Yang, Yong Yu and Shuai Fang

Coatings 2024, 14(11), 1423; https://doi.org/10.3390/coatings14111423 - 8 Nov 2024

Abstract

As a novel pavement wear layer material, the micromechanical mechanisms of High-toughness Ultra-thin Friction Course (HUFC) have not been fully elucidated. This paper presents a new method for the three-dimensional micromechanical simulation of high-toughness asphalt mixtures based on a viscoelastic parameter calibration model. [...] Read more.

As a novel pavement wear layer material, the micromechanical mechanisms of High-toughness Ultra-thin Friction Course (HUFC) have not been fully elucidated. This paper presents a new method for the three-dimensional micromechanical simulation of high-toughness asphalt mixtures based on a viscoelastic parameter calibration model. X-ray Computerized Tomography (CT) was employed to scan samples of high-toughness asphalt mixtures to obtain detailed information on the internal structure (aggregate, fine aggregate matrix FAM and voids), and a three-dimensional micromechanical model was constructed based on the real-scale distribution of these components. Aggregates in the high-toughness asphalt mixture were modeled as elastic bodies, while FAM was treated as a viscoelastic material characterized by the Burgers model. Using the Boltzmann linear superposition principle and Laplace transform theory, the viscoelastic properties of FAM were converted into Prony parameters recognizable by finite element software, and the viscoelastic parameters were calibrated. Micromechanical simulations were conducted for three different gradings of high-toughness asphalt mixtures, and the results show that the predicted deformation closely matched the measured deformation. This method accurately reflects the deformation characteristics of different gradings of high-toughness asphalt mixtures, overcoming the limitations of traditional numerical simulations based on homogeneous material models. It represents an advancement and refinement of micromechanical simulation methods for high-toughness asphalt mixtures. Full article

(This article belongs to the Special Issue Surface and Interface Characteristics of Pavements: New Perspectives and Applications)

18 pages, 10249 KiB

Open AccessArticle

Enhancing Interface Performance Through Self-Assembly Mechanisms of APTES on Surface-Modified Tuff Aggregates

by Mingxin Lai, Xiaoying Gao, Lin Kong, Lizong Chen, Guoan Gan, Haixing Lin, Jiakang Zhang, Gen Zhang, Yueling Lin, Hongming Zhu and Xinping Zhang

Coatings 2024, 14(11), 1422; https://doi.org/10.3390/coatings14111422 (registering DOI) - 8 Nov 2024

Abstract

To enhance the adhesion between tuff and asphalt, this study investigates the efficacy of alkalinization treatment technology using a molecular self-assembly layer derived from the silane-coupling agent γ-aminopropyltriethoxysilane (APTES). APTES hydrolysis solutions at varying concentrations were prepared to assess their impact on the [...] Read more.

To enhance the adhesion between tuff and asphalt, this study investigates the efficacy of alkalinization treatment technology using a molecular self-assembly layer derived from the silane-coupling agent γ-aminopropyltriethoxysilane (APTES). APTES hydrolysis solutions at varying concentrations were prepared to assess their impact on the adhesive strength of the aggregate–asphalt interface and water damage resistance. Using surface energy theory, the interface adhesion work of tuff was analyzed, while SEM and EDS were employed to examine changes in surface morphology and composition after treatment. The results demonstrate that an APTES:water:ethanol mass ratio of 5:45:50, along with a curing temperature of 200 °C, significantly improves the bonding strength between tuff and asphalt. The silanol groups on APTES react with hydroxyl groups on the tuff surface to form siloxane bonds (Si-O-Si), anchoring APTES to the tuff. This study elucidates the self-assembly mechanisms of APTES on tuff aggregates and demonstrates the consequent enhancement of interfacial adhesion, providing valuable insights for the application of tuff as tunnel spoil in road engineering. Full article

(This article belongs to the Special Issue Surface Engineering and Mechanical Properties of Building Materials)

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14 pages, 4822 KiB

Open AccessArticle

Study on the Effect of Lignin Removal Rate on the Dielectric Properties of Delignified Materials

by Hui Xu, Fengqi Qiu, Weishuai Han and Zhenhua Xue

Coatings 2024, 14(11), 1421; https://doi.org/10.3390/coatings14111421 - 8 Nov 2024

Abstract

To investigate the relationship between the lignin removal rate change of wood and its dielectric properties, this study employed Mongolian Scotch Pine and Paulownia as the test materials. The acidic sodium chlorite method was used to delignify the treated material, and the lignin [...] Read more.

To investigate the relationship between the lignin removal rate change of wood and its dielectric properties, this study employed Mongolian Scotch Pine and Paulownia as the test materials. The acidic sodium chlorite method was used to delignify the treated material, and the lignin removal rate was determined at a specified reaction time interval to ascertain the dielectric constant and the tangent of the dielectric loss angle. The findings revealed that: As the delignification process progresses, the lignin content declines, accompanied by a reduction in the dielectric constant at elevated frequencies. This decline reaches a plateau near 10 MHz. The results demonstrated that the dielectric constant of the samples decreased with an increase in frequency and exhibited a stabilizing effect near 10 MHz. However, the dielectric constant of delignified wood was significantly higher than that of untreated wood. Additionally, the dielectric constant exhibited a linear relationship with the increase in lignin removal rate, while the tangent of the dielectric loss angle demonstrated a tendency to increase and then decrease. An investigation into the dielectric properties of delignified wood can yield valuable data and a theoretical foundation for the development of wood-based dielectric materials. Full article

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13 pages, 4685 KiB

Open AccessArticle

High-Performance SAW-Based Microfluidic Actuators Composed of Sputtered Al–Cu IDT Electrodes

by Hwansun Kim, Youngjin Lee, Peddathimula Puneetha, Sung Jin An, Jae-Cheol Park and Siva Pratap Reddy Mallem

Coatings 2024, 14(11), 1420; https://doi.org/10.3390/coatings14111420 - 8 Nov 2024

Abstract

To realize highly sensitive SAW devices, novel Al–Cu thin films were developed using a combinatorial sputtering system. The Al–Cu sample library exhibited a wide range of chemical compositions and electrical resistivities, providing valuable insights for selecting optimal materials for SAW devices. Considering the [...] Read more.

To realize highly sensitive SAW devices, novel Al–Cu thin films were developed using a combinatorial sputtering system. The Al–Cu sample library exhibited a wide range of chemical compositions and electrical resistivities, providing valuable insights for selecting optimal materials for SAW devices. Considering the significant influence of electrode resistivity and density on acoustic wave propagation, an Al–Cu film with 65 at% Al was selected as the IDT electrode material. The selected Al–Cu film demonstrated a resistivity of 6.0 × 10⁻⁵ Ω-cm and a density of 4.4 g/cm³, making it suitable for SAW-based microfluidic actuator applications. XRD analysis revealed that the Al–Cu film consisted of a physical mixture of Al and Cu without the formation of Al–Cu alloy phases. The film exhibited a fine-grained microstructure with an average crystallite size of 7.5 nm and surface roughness of approximately 6 nm. The SAW device fabricated with Al–Cu IDT electrodes exhibited excellent acoustic performance, resonating at 143 MHz without frequency shift and achieving an insertion loss of −13.68 dB and a FWHM of 0.41 dB. In contrast, the Au electrode-based SAW device showed significantly degraded acoustic characteristics. Moreover, the SAW-based microfluidic module equipped with optimized Al–Cu IDT electrodes successfully separated 5 μm polystyrene (PS) particles even at high flow rates, outperforming devices with Au IDT electrodes. This enhanced performance can be attributed to the improved resonance characteristics of the SAW device, which resulted in a stronger acoustic radiation force exerted on the PS particles. Full article

(This article belongs to the Special Issue Thin Films and Nanostructures for Electronics)

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5 pages, 178 KiB

Open AccessEditorial

Innovations in Active Food Packaging During the Pandemic and into the ‘New Normal’

by Maria-Ioana Socaciu, Dan Cristian Vodnar and Cristina Anamaria Semeniuc

Coatings 2024, 14(11), 1419; https://doi.org/10.3390/coatings14111419 - 8 Nov 2024

Abstract

COVID-19 significantly impacted global socioeconomic conditions and food security [...] Full article

(This article belongs to the Special Issue Innovations in Active Food Packaging during the Pandemic and into the 'New Normal')

14 pages, 3687 KiB

Open AccessArticle

Construction of a Carbon Monoxide-Releasing Bioactive Hydrogel Coating on the Magnesium Alloy Surface for Better Corrosion Resistance, Anticoagulant Properties, and Endothelial Cell Growth

by Renwei Gao, Lingjie Meng and Changjiang Pan

Coatings 2024, 14(11), 1418; https://doi.org/10.3390/coatings14111418 - 8 Nov 2024

Abstract

In this study, we first fabricated a crosslinked hydrogel coating by polymerizing methacryloyloxyethyl sulfonyl betaine and acrylamide (SBMA) on the magnesium (Mg) alloy surface employing ultraviolet (UV) polymerization. Bivalirudin and CO-releasing molecules (CORM-401) were further grafted onto the hydrogel coating surface to acquire [...] Read more.

In this study, we first fabricated a crosslinked hydrogel coating by polymerizing methacryloyloxyethyl sulfonyl betaine and acrylamide (SBMA) on the magnesium (Mg) alloy surface employing ultraviolet (UV) polymerization. Bivalirudin and CO-releasing molecules (CORM-401) were further grafted onto the hydrogel coating surface to acquire a multifunctional biocompatible coating capable of releasing CO to augment corrosion-resisting properties and biocompatibility. The findings verified that the bioactive hydrogel coating significantly increased the corrosion potential and reduced the corrosion current, thereby improving the anticorrosion performance. Meanwhile, owing to the excellent hydrophilicity, the antifouling performance of the hydrogel coating, and the excellent anticoagulant performance of bivalirudin, the hydrogel coating significantly reduced the fibrinogen adsorption, platelet adhesion and activation, and hemolysis occurrence, displaying excellent ability to inhibit blood clotting. Moreover, endothelial cell (EC) experimental results demonstrated that the hydrogel coating could significantly promote EC growth, displaying great potential to induce re-endothelialization after implantation. Specifically, in the presence of cysteine capable of catalyzing CO release, the anticoagulant performance and ability to promote EC growth were further improved significantly. Therefore, the study offers an effective strategy to prepare a hydrogel coating capable of releasing CO to improve the corrosion-resisting performance and biocompatibility of Mg alloys, which is anticipated to be applied in the surface modification of Mg alloy intravascular stents. Full article

(This article belongs to the Special Issue Advanced Alloy Degradation and Implants, 2nd Edition)

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19 pages, 2609 KiB

Open AccessArticle

Numerical Study on Composite Multilayer Insulation Material for Liquid Hydrogen Storage

by Yi Ding, Dongliang Shao, Suke Jin, Meng Yu, Yubo Wang and Long Jiang

Coatings 2024, 14(11), 1417; https://doi.org/10.3390/coatings14111417 - 8 Nov 2024

Abstract

This study investigated the heat transfer characteristics of composite multilayer insulation (MLI) materials used for the storage and transport of liquid hydrogen at cryogenic temperatures. This research focused on analyzing the effects of thermal boundary temperature, total layer count, and vacuum level on [...] Read more.

This study investigated the heat transfer characteristics of composite multilayer insulation (MLI) materials used for the storage and transport of liquid hydrogen at cryogenic temperatures. This research focused on analyzing the effects of thermal boundary temperature, total layer count, and vacuum level on the heat flux through the insulation material. Based on the layer-by-layer model, a heat transfer model of composite MLI was constructed. This research introduces a novel method for analyzing the heat transfer properties of composite MLI in the liquid hydrogen temperature range. Results indicate that heat flux increases with higher thermal boundary temperatures, with the MLI layers near the cold boundary playing a critical role in overall insulation performance. Additionally, numerical analysis was conducted to examine the impact of different material combinations and variations in vacuum level on heat transfer characteristics. Findings reveal that adding spray-on foam insulation reduces heat flux by 20.76% compared to using MLI alone. Furthermore, increasing the total number of MLI layers effectively mitigates heat flux increase, achieving an optimal heat flux of 0.5377 W/m² with a total of 50 layers. Full article

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11 pages, 3003 KiB

Open AccessArticle

Synthesis of a Hard Anodic Oxide Coating with a Structure Allowing for Its Modification by Nanoparticles

by Anna Kozik, Marek Nowak, Kamila Limanówka and Anna Góral

Coatings 2024, 14(11), 1416; https://doi.org/10.3390/coatings14111416 - 7 Nov 2024

Abstract

A hard anodic oxide coating’s characteristic porous structure allows for its modification by the incorporation of nanoparticles. However, achieving an appropriate microstructure requires an optimal pore arrangement and shape, which is influenced by the electrolyte composition, current densities, temperature, and processing time. To [...] Read more.

A hard anodic oxide coating’s characteristic porous structure allows for its modification by the incorporation of nanoparticles. However, achieving an appropriate microstructure requires an optimal pore arrangement and shape, which is influenced by the electrolyte composition, current densities, temperature, and processing time. To achieve pores with a diameter of about 50 nm and the most regular structure, a range of these parameters were tested. Using a two-stage manufacturing process had a beneficial effect on increasing the microporosity of the coating. The addition of phthalic acid at 0 °C did not increase the pore diameter, but allowed for the process to be carried out at higher temperatures. However, the coating produced at 20 °C had a larger pore diameter, but numerous defects. The coating obtained from the three-component solution had the most regular structure, but the smallest pore diameter. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation, 2nd Edition)

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15 pages, 6565 KiB

Open AccessArticle

Effect of Over-Aging Degree on Microstructures, Precipitation Kinetics, and Mechanical Properties of an Ultra-High-Strength Al-Zn-Mg-Cu Alloy

by Yuyang Liu, Zhihao Zhao and Gaosong Wang

Coatings 2024, 14(11), 1415; https://doi.org/10.3390/coatings14111415 - 7 Nov 2024

Abstract

The effect of over-aging on the precipitation behavior and mechanical properties of an ultra-high-strength Al-Zn-Mg-Cu alloy was investigated using various over-aging treatment regimes. To reveal the influence of over-aging on matrix precipitation, nucleation and coarsening mechanisms were analyzed based on thermodynamic models and [...] Read more.

The effect of over-aging on the precipitation behavior and mechanical properties of an ultra-high-strength Al-Zn-Mg-Cu alloy was investigated using various over-aging treatment regimes. To reveal the influence of over-aging on matrix precipitation, nucleation and coarsening mechanisms were analyzed based on thermodynamic models and calculated precipitation data. Precipitation kinetics at different over-aging degrees were determined through differential scanning calorimetry analysis and the Johnson–Mehl–Avrami–Kolmogorov equations, revealing the activation energy required to precipitate the η’ phase precipitates ranging from 166.08 to 343.28 kJ/mol, and the activation energy required to precipitate the η phase precipitates ranging from 802.03 to 288.42 kJ/mol from the T6 to T73 conditions. In conjunction with a quantitative microstructure analysis, a highly accurate model was developed by systematically calculating the strengthening components of the ultra-high-strength Al-Zn-Mg-Cu alloy under various aging conditions. Full article

(This article belongs to the Special Issue Research and Application of High Entropy Alloys)

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14 pages, 4965 KiB

Open AccessArticle

Effect of Layer Thickness on the Practical Adhesion of Borided Monel 400 Alloy

by Francisco Javier Alfonso-Reyes, José Martínez-Trinidad, Luis Alfonso Moreno-Pacheco, Osvaldo Quintana-Hernández, Wilbert Wong-Ángel and Ricardo Andrés García-León

Coatings 2024, 14(11), 1414; https://doi.org/10.3390/coatings14111414 - 7 Nov 2024

Abstract

This study presents new results on the practical adhesion behavior of a boride layer formed on Monel 400 alloy, developed using the powder-pack boriding (PPBP) at 1223 K for 2, 4, and 6 h of exposure times, obtaining layer thicknesses from approximately 7.9 [...] Read more.

This study presents new results on the practical adhesion behavior of a boride layer formed on Monel 400 alloy, developed using the powder-pack boriding (PPBP) at 1223 K for 2, 4, and 6 h of exposure times, obtaining layer thicknesses from approximately 7.9 to 23.8 µm. The nickel boride layers were characterized using optical microscopy, Berkovich nanoindentation, X-ray diffraction (XRD), and scanning electron microscopy (SEM) to determine microstructure, hardness distribution, and failure mechanisms over the worn tracks. Scratch tests were conducted on the borided Monel 400 alloy according to the ASTM C-1624 standard, applying a progressively increasing normal load from 1 to 85 N using a Rockwell-C diamond indenter, revealing that critical loads (L_C1, L_C2, and L_C3) increased with layer thickness. The tests monitored the coefficient of friction and residual stress in real time. Critical loads were determined based on the correlation between the normal force and visual inspection of the worn surface, identifying cracks (cohesive failure) or detachment (adhesive failure). The results exposed those cohesive failures that appeared as Hertzian cracks, while adhesive failures were chipping and delamination, with critical loads reaching up to 49.0 N for the 6 h borided samples. Also, the results indicated that critical loads increased with greater layer thickness. The boride layer hardness was approximately 12 ± 0.3 GPa, ~4.0 times greater than the substrate, and Young’s modulus reached 268 ± 15 GPa. These findings underscore that PPBP significantly enhances surface mechanical properties, demonstrating the potential for applications demanding high wear resistance and strong layer adhesion. Full article

(This article belongs to the Special Issue Enhanced Mechanical Properties of Metals by Surface Treatments)

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14 pages, 5724 KiB

Open AccessArticle

Simulation Analysis of the Influence of Operating Parameters on the Pressure Profile in the Coating Bead

by Shaofei Pan, Jianneng Chen, Yikun Wei, Chuanyu Wu, Jiangming Jia and Kun Yao

Coatings 2024, 14(11), 1413; https://doi.org/10.3390/coatings14111413 - 7 Nov 2024

Abstract

In-depth analysis of the pressure profile of coating beads of slot die coating is helpful to better understand the behavior of the flow field in a coating bead and to better obtain a stable coating bead. In this study, ANSYS Fluent 19.2 was [...] Read more.

In-depth analysis of the pressure profile of coating beads of slot die coating is helpful to better understand the behavior of the flow field in a coating bead and to better obtain a stable coating bead. In this study, ANSYS Fluent 19.2 was used to simulate slot die coating. The simulation results clearly show the influence of various operating parameters on the state of the coating bead and the pressure profile in the coating bead. The results show that the pressure profile can be clearly changed by changing the flow rate, substrate speed, and downstream die lip length. Simultaneously increasing the substrate speed from 0.08 to 0.12 m/s and the average inlet velocity from 0.02672 to 0.04 m/s results in an increase in maximum pressure from 298 to 538 Pa. Increasing only the substrate speed, from 0.12 to 0.16 m/s, causes the maximum pressure to decrease from 538 to 195 Pa. Increasing only the average inlet flow velocity, from 0.027 to 0.04 m/s, leads to an increase in maximum pressure from 167 to 745 Pa. Extending the downstream die lip length from 0.4 mm to 1 mm results in an increase in maximum pressure from 189 to 471 Pa. Reducing the upstream coating gap from 0.3 to 0.1 mm results in significant changes in the pressure profile in the upstream direction. Changing the contact angle can affect the pressure profile in the coating bead, but this is not clear. Changing the coating liquid density at a Reynolds number less than 1.733 has less effect on the pressure profile. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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19 pages, 4201 KiB

Open AccessArticle

Exploring the Relationship Between Electrical Characteristics and Changes in Chemical Composition and Structure of OSG Low-K Films Under Thermal Annealing

by Mungunsuvd Gerelt-Od, Tatiana G. Kolesnikova, Pavel A. Mokrushev, Alexey S. Vishnevskiy, Konstantin A. Vorotilov, Andrei A. Gismatulin, Vladimir A. Gritsenko and Mikhail R. Baklanov

Coatings 2024, 14(11), 1412; https://doi.org/10.3390/coatings14111412 - 6 Nov 2024

Abstract

The influence of annealing temperature on the chemical, structural, and electrophysical properties of porous OSG low-k films containing terminal methyl groups was investigated. The films were deposited via spin coating, followed by drying at 200 °C and annealing at temperatures ranging from [...] Read more.

The influence of annealing temperature on the chemical, structural, and electrophysical properties of porous OSG low-k films containing terminal methyl groups was investigated. The films were deposited via spin coating, followed by drying at 200 °C and annealing at temperatures ranging from 350 °C to 900 °C. In the temperature range of 350–450 °C, thermal degradation of surfactants occurs along with the formation of a silicon-oxygen framework, which is accompanied by an increase in pore radius from 1.2 nm to 1.5 nm. At 600–700 °C, complete destruction of methyl groups occurs, leading to the development of micropores. FTIR spectroscopy reveals that after annealing at 700 °C, the concentration of silanol groups and water reaches its maximum. By 900 °C, open porosity is no longer observed, and the film resembles dense SiO₂. JV measurements show that the film annealed at 450 °C exhibits minimal leakage currents, approximately 5 × 10⁻¹¹ A/cm² at 700 kV/cm. This can be attributed to the near-complete removal of surfactant residues and non-condensed silanols, along with non-critical thermal degradation of methyl groups. Leakage current models obtained at various annealing temperatures suggest that the predominant charge carrier transfer mechanism is Poole–Frenkel emission. Full article

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21 pages, 8404 KiB

Open AccessArticle

The Interfacial Reaction Traits of (Al₆₃Cu₂₅Fe₁₂)₉₉Ce₁ Quasicrystal-Enhanced Aluminum Matrix Composites Produced by Means of Hot Pressing

by Juan Wang and Zhong Yang

Coatings 2024, 14(11), 1411; https://doi.org/10.3390/coatings14111411 - 6 Nov 2024

Abstract

This study fabricated (Al₆₃Cu₂₅Fe₁₂)₉₉Ce₁ quasicrystal-enhanced aluminum matrix composites using the hot-pressing method to investigate their interfacial reaction traits. Microstructure analysis revealed that at 490 °C for 30 min of hot-pressing, the interface between the [...] Read more.

This study fabricated (Al₆₃Cu₂₅Fe₁₂)₉₉Ce₁ quasicrystal-enhanced aluminum matrix composites using the hot-pressing method to investigate their interfacial reaction traits. Microstructure analysis revealed that at 490 °C for 30 min of hot-pressing, the interface between the matrix and reinforcement was clear and intact. Chemical diffusion between the I-phase and aluminum matrix during sintering led to the formation of Al₇Cu₂Fe, AlFe, and AlCu phases, which, with their uniform and fine distribution, significantly enhanced the alloy’s overall properties. Regarding compactness, it first increased and then decreased with different holding times, reaching a maximum of about 98.89% at 490 °C for 30 min. Mechanical property analysis showed that compressive strength initially rose and then fell with increasing sintering temperature. After 30 min at 490 °C, the reinforcement particles and matrix were tightly combined and evenly distributed, with a maximum compressive strength of around 790 MPa. Additionally, the diffusion dynamics of the transition layer were simulated. The reaction rate of the reaction layer increased with hot-pressing temperature and decreased with holding time. Selecting a lower temperature and appropriate holding time can control the reaction layer thickness to obtain composites with excellent properties. This research innovatively contributes to the preparation and property study of such composites, providing a basis for their further application. Full article

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20 pages, 2735 KiB

Open AccessArticle

Functional Nano-Metallic Coatings for Solar Cells: Their Theoretical Background and Modeling

by Witold Aleksander Jacak

Coatings 2024, 14(11), 1410; https://doi.org/10.3390/coatings14111410 - 6 Nov 2024

Abstract

We have collected theoretical arguments supporting the functional role of nano-metallic coatings of solar cells, which enhance solar cell efficiency via by plasmon-strengthening the absorption of sun-light photons and reducing the binding energy of photoexcitons. The quantum character of the plasmonic effect related [...] Read more.

We have collected theoretical arguments supporting the functional role of nano-metallic coatings of solar cells, which enhance solar cell efficiency via by plasmon-strengthening the absorption of sun-light photons and reducing the binding energy of photoexcitons. The quantum character of the plasmonic effect related to the absorption of photons (called the optical plasmonic effect) is described in terms of the Fermi golden rule for the quantum transitions of semiconductor-band electrons induced by plasmons from a nano-metallic coating. The plasmonic effect related to the lowering of the exciton binding energy (called the electrical plasmonic effect) is of particular significance for metalized perovskite solar cells and is also characterized in quantum mechanics terms. The coupling between plasmons in nanoparticles from a coating with band electrons in a semiconductor substrate significantly modifies material properties (dielectric functions) both of the particles and the semiconductor, beyond the ability of the classical electrodynamics to describe. Full article

(This article belongs to the Special Issue Perovskite Films as Functional Coatings: Synthesis and Applications)

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10 pages, 3891 KiB

Open AccessArticle

Study on Low-Temperature Deposition of Diamond-like Carbon Film on the Surface of Bionic Joint Thread and Its Properties

by Chuanliu Wang and Shaoming Ma

Coatings 2024, 14(11), 1409; https://doi.org/10.3390/coatings14111409 - 6 Nov 2024

Abstract

The double-connection structure of bionic joints of mining drill pipes has solved the problem of drill drop caused by fatigue cracks. However, with low-melting-point elastic–ductile alloy filling in the bionic joint, the thread on the joint cannot be hardened by high-temperature surface hardening [...] Read more.

The double-connection structure of bionic joints of mining drill pipes has solved the problem of drill drop caused by fatigue cracks. However, with low-melting-point elastic–ductile alloy filling in the bionic joint, the thread on the joint cannot be hardened by high-temperature surface hardening treatments such as quenching and nitriding, making it prone to thread gluing or excessive wear. In this paper, the feasibility of diamond-like film deposition on the surface of a bionic drill pipe thread was studied. A tungsten transition film was used to improve the thickness of the film and the interfacial bond strength between the film and the substrate. The test results show that the total thickness of the DLC film is about 3~5 μm, the roughness is less than 2 μm, the hardness of the film reaches 24.4 GPa, the friction coefficient is 0.04, and the critical load is 56 N. SEM and EDS analyses show that the tungsten film and the bionic joint thread form a metallurgical structure. The morphology of the diamond-like carbon film is uniform and dense, and there is no obvious stratification between the substrate material. The joint with a diamond-like coating treatment has a longer service life than joints receiving conventional high-temperature nitriding treatment. Full article

(This article belongs to the Special Issue Nanostructured Films and Their Multi-scale Applications)

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18 pages, 7907 KiB

Open AccessArticle

Fabrication and Characterization of Micro-Arc Oxidation Films on β-Titanium Alloy in Silicate and Silicate/Glycerin Electrolyte

by Lin Chen, Xiaoyue Jin, Wenbin Xue and Jie Wu

Coatings 2024, 14(11), 1408; https://doi.org/10.3390/coatings14111408 - 5 Nov 2024

Abstract

Micro-arc oxidation (MAO) films were fabricated on the Ti-39Nb-6Zr alloy at different voltages in the silicate and silicate/glycerin electrolyte. Their morphology, phase structure and composition were characterized by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray [...] Read more.

Micro-arc oxidation (MAO) films were fabricated on the Ti-39Nb-6Zr alloy at different voltages in the silicate and silicate/glycerin electrolyte. Their morphology, phase structure and composition were characterized by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was found that the glycerin additive in the silicate electrolyte improved the compactness of the MAO film. The corrosion resistance was evaluated, and the influence of glycerin additive in electrolyte on the growth of micro-arc oxidized film was revealed by optical emission spectra. Full article

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13 pages, 4658 KiB

Open AccessArticle

Novel Anodic TiO₂ Synthesis Method with Embedded Graphene Quantum Dots for Improved Photocatalytic Activity

by Ainars Knoks, Liga Grinberga and Janis Kleperis

Coatings 2024, 14(11), 1407; https://doi.org/10.3390/coatings14111407 - 5 Nov 2024

Abstract

Photocatalytic degradation of pollutants have a high potential for sustainable and renewable uses. TiO₂ is a widely studied photocatalyst due to its high chemical and photochemical stability and wide range of applications. However, the wide band gap and low capacity of photo-induced [...] Read more.

Photocatalytic degradation of pollutants have a high potential for sustainable and renewable uses. TiO₂ is a widely studied photocatalyst due to its high chemical and photochemical stability and wide range of applications. However, the wide band gap and low capacity of photo-induced charge separation provide lower catalytic activity; thus, improvement of these properties must be found. The doping of TiO₂ with other elements, such as carbon nanoparticles (CNP) in a quantum dot form, offers a promising pathway to improve the aforementioned properties. In addition, in situ doping methods should be investigated for practical scalability, as they offer the advantage of integrating dopants directly during material synthesis, ensuring a more uniform distribution and better interaction between the dopant and the host material, in turn leading to more consistent photocatalytic properties. Current technologies primarily involve nanoparticle combinations. This work focuses on the development of a novel in situ synthesis methodology by the introduction of three different graphene-based quantum nanodots into anodic TiO₂ and the following investigation of structural, morphological, and photocatalytic properties. Results indicate that the introduction of CNP allows for the shift of a set of parameters, such as the optical band gap, increased photo-induced charge carrier density of TiO₂/CNP composite, and, most importantly, the change of crystalline phase composition depending on added CNP material. Research indicates that not only a higher concentration of added CNP enhances higher photocatalytic activity as tested by the degradation of methylene blue dye, but also the type of CNP determines final crystalline phase. For the first time brookite and rutile phases were obtained in anodic titania synthesized in inorganic electrolyte by introducing hydrothermally treated exfoliated graphene. Full article

(This article belongs to the Special Issue Advanced Research on Energy Storage Materials and Devices)

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33 pages, 9739 KiB

Open AccessArticle

Numerical Modelling and Experimental Validation of Selective Laser Melting Processes Using a Custom Argon Chamber Setup for 316L Stainless Steel and Ti6AI4V

by Gasser Abdelal, Daniel Higgins, Chi-Wai Chan and Brian G. Falzon

Coatings 2024, 14(11), 1406; https://doi.org/10.3390/coatings14111406 - 5 Nov 2024

Abstract

Selective Laser Melting (SLM) is an advanced additive manufacturing technique that demands meticulous control over thermal dynamics to maintain the integrity and performance of manufactured parts. This study presents the development and validation of a thermal model designed to enhance the SLM process [...] Read more.

Selective Laser Melting (SLM) is an advanced additive manufacturing technique that demands meticulous control over thermal dynamics to maintain the integrity and performance of manufactured parts. This study presents the development and validation of a thermal model designed to enhance the SLM process for 316L stainless steel (316L SS) and titanium alloy Ti6Al4V. A specially constructed Argon Chamber Setup, equipped with a 200 W continuous-wave (CW) fibre laser system, was used to create an SLM-representative environment for 316L SS, enabling precise experimental validation of the model. This validation serves as a robust baseline, facilitating the model’s extension to more complex materials like Ti6Al4V, thereby supporting a cost-efficient and safe approach to initial testing. The rigorously validated thermal model offers a comprehensive link between experimental data and numerical simulations in SLM. It supports process optimisation by accurately predicting thermal behaviours, contributing significantly to additive manufacturing advancements. By fine-tuning processing parameters, this model enhances material characteristics, thereby providing practical insights applicable to industrial production and improving the consistency and quality of SLM-manufactured parts. Full article

(This article belongs to the Special Issue Laser Surface Engineering and Additive Manufacturing)

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10 pages, 5131 KiB

Open AccessArticle

Metal Ions’ Dynamic Effect on Metal-Assisted Catalyzed Etching of Silicon in Acid Solution

by Xiaoyu Yang, Ying Liu, Lin Wu, Zhiyuan Liao, Baoguo Zhang, Tinashe Tembo, Yichen Wang and Ya Hu

Coatings 2024, 14(11), 1405; https://doi.org/10.3390/coatings14111405 - 5 Nov 2024

Abstract

Metal-assisted catalyzed etching (MACE) technology is convenient and efficient for fabricating large-area silicon nanowires at room temperature. However, the mechanism requires further exploration, particularly the dynamic effect of various ions in the acid-etching solution. This paper investigated the MACE of silicon wafers predeposited [...] Read more.

Metal-assisted catalyzed etching (MACE) technology is convenient and efficient for fabricating large-area silicon nanowires at room temperature. However, the mechanism requires further exploration, particularly the dynamic effect of various ions in the acid-etching solution. This paper investigated the MACE of silicon wafers predeposited with metal nanofilms in an HF-M(NO₃)x-H₂O etching solution (where M(NO₃)x is the nitrate of the fourth-period elements of the periodic table). The oxidizing ability of Fe³⁺ and NO₃⁻ was demonstrated, and the dynamic influence of metal ions on the etching process was discussed. The results show that the MACE of silicon can be realized in various HF-M(NO₃)_x-H₂O etching solutions, such as KNO₃, Al(NO₃)₃, Cr(NO₃)₃, Mn(NO₃)₂, Ni(NO₃)₂, Co(NO₃)₂, HNO₃, and Ca(NO₃)₂. It is confirmed that the concentration and type of cations in the etching solution affect the etching rate and morphology of silicon. Fe³⁺ and NO₃⁻ act as oxidants in catalytic etching. The fastest etching rate is about 5~6 μm/h in Ni(NO₃)₂, Co(NO₃)₂, and Ca(NO₃)₂ etching solutions. However, a high concentration of K⁺ hinders silicon etching. This study expands the application of MACE etching solution systems. Full article

(This article belongs to the Special Issue Coatings as Key Materials in Catalytic Applications)

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