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3 pages, 184 KiB

Open AccessEditorial

Recent Advances in Surface Functionalisation

by Jorge Salguero, Juan Manuel Vazquez, Moises Batista and Irene del Sol

Coatings 2023, 13(3), 530; https://doi.org/10.3390/coatings13030530 - 28 Feb 2023

Cited by 1 | Viewed by 1551

Abstract

Surfaces and interfaces have become a highly relevant topic in recent years, mainly due to their technological importance in the design and development of high-performance components [...] Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

Research

Jump to: Editorial

16 pages, 7030 KiB

Open AccessArticle

Facile Preparation of Smart Sponge Based on a Zeolitic Imidazolate Framework for the Efficient Separation of Oily Wastewater

by Yuping Zhang, Xinxin Chen, Pei Yuan, Haie Chen and Songwei Li

Coatings 2024, 14(8), 1058; https://doi.org/10.3390/coatings14081058 - 18 Aug 2024

Viewed by 835

Abstract

The fabrication of durable materials with excellent oil-adsorption capacity and separation performance for the treatment of oily wastewater is meaningful based on the special property of smart responsiveness. Herein, a solvent-responsive melamine sponge (MS) was developed via silanization and the in situ growth [...] Read more.

The fabrication of durable materials with excellent oil-adsorption capacity and separation performance for the treatment of oily wastewater is meaningful based on the special property of smart responsiveness. Herein, a solvent-responsive melamine sponge (MS) was developed via silanization and the in situ growth of a zeolitic imidazolate framework-8 (ZIF-8). Detailed characterization of the resultant composite MS was conducted using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), and X-ray diffraction (XRD). The multiscale hierarchical MS substrate exhibited highly hydrophobic properties in the pH range of 1–11, along with a satisfactory adsorption capacity in the range of 65.4–134.2 g/g for different oils. The modified surface transformed from superhydrophobic/superlipophilic to superhydrophilic/underwater superoleophobic upon ethanol wetting, reverting to its original superhydrophobic state upon drying. The separation flux of the MS substrate was above 1.5 × 10⁴ L/m²h for both oil and water removal, and the separation efficiency was greater than 98.7%. The absence of obvious changes in separation performance after 50 successive immiscible oil−water separations indicated the excellent durability and robustness of the anchored ZIF-8 nanoparticles on the surface of the modified MS substrate. More importantly, oil-in-water emulsion separation was successfully carried out via the ZIF-8 MS composite, showing high separation efficiency (over 99.1%). The developed smart sponge, which had high oil-adsorption capacity, excellent chemical stability, and fire resistance, has a wide range of potential practical applications in the convenient treatment of oily wastewater. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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23 pages, 8368 KiB

Open AccessArticle

Correlation between Surface Texture, Wettability and Mechanical Strength of Polylactic Acid Parts Fabricated by Fused Filament Fabrication

by Fermín Bañón-García, Carolina Bermudo Gamboa, José Andrés López-Fernández, Francisco Javier Trujillo-Vilches and Sergio Martín-Béjar

Coatings 2024, 14(8), 1033; https://doi.org/10.3390/coatings14081033 - 14 Aug 2024

Viewed by 825

Abstract

This research investigates the generation and evaluation of various geometric surface textures on PLA components produced via fused filament fabrication (FFF). Textures, including grooves, pyramids, and cylinders, were created at different depth levels on the PLA surfaces. The surface quality of these textures [...] Read more.

This research investigates the generation and evaluation of various geometric surface textures on PLA components produced via fused filament fabrication (FFF). Textures, including grooves, pyramids, and cylinders, were created at different depth levels on the PLA surfaces. The surface quality of these textures was assessed using a 3D optical system, focusing on area parameters such as Sa and Sz. The wettability of each texture was evaluated through contact angle and sliding angle tests, revealing the ability to modulate contact angles and achieve either hydrophobic or hydrophilic surfaces depending on the texture type. Subsequently, pairs of textured PLA pieces were bonded using a cyanoacrylate adhesive following standardised protocols, and shear tests were conducted to determine the maximum shear stress at bond (τ_max) of each texture. Notably, textured surfaces generally exhibited hydrophobic properties that reduce the adhesion between the adhesive and the piece, leading to reduced maximum shear stress at bond values compared to non-textured surfaces. However, groove textures notably increased τ_max values. The results were analysed to establish correlations between surface quality, wettability, and shear strength. This comprehensive evaluation aims to elucidate the influence of surface texture on the mechanical performance and adhesive properties of FFF-manufactured PLA components. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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23 pages, 41220 KiB

Open AccessArticle

Surface Coating with Foliar Fertilizers

by Yojana J. P. Carreón, Angel A. Pereyra Zarate, Alondra E. Pérez Sánchez, Orlando Díaz-Hernández and Jorge González-Gutiérrez

Coatings 2024, 14(8), 1007; https://doi.org/10.3390/coatings14081007 - 8 Aug 2024

Viewed by 1152

Abstract

Foliar fertilization, an effective agricultural practice, involves the application of nutrients directly through droplets on plant leaves. The mechanisms of mass transport and deposition that arise from the drying of a drop determine the distribution of mass on a surface. Understanding these processes [...] Read more.

Foliar fertilization, an effective agricultural practice, involves the application of nutrients directly through droplets on plant leaves. The mechanisms of mass transport and deposition that arise from the drying of a drop determine the distribution of mass on a surface. Understanding these processes is crucial for optimizing foliar fertilization, ensuring even nutrient distribution, and improving crop yields and quality. This study experimentally investigates deposit formation from the evaporation of fertilizer droplets in various configurations: sessile, vertical, and pendant. We explored the effects of initial droplet volume, vapor pressure, and sorbitol presence on the final deposit morphology. The results reveal distinctive morphological patterns. Sessile drops exhibit two types of deposits—central crystal accumulation with fibrous structures or entirely fibrous structures. In contrast, vertical drops display two zones—fibrous structures at the bottom and small aggregates at the top. On the other hand, pendant drops predominantly feature intertwined crystals with peripheral fibrous structures. We found that high vapor pressures (RH = 60%) inhibit deposit formation within 72 h. Furthermore, the study measures relative evaporation time, showing that sessile droplets exhibit the longest evaporation times, followed by vertical and pendant droplets. Texture analysis, based on GLCM entropy, reveals that deposits generated under low vapor pressure (RH = 20%) show no significant differences in their entropy values, regardless of the droplet configuration and its initial volume. However, at intermediate vapor pressure (RH = 40%), entropy values vary significantly with droplet volume and configuration, being higher in sessile drops and lower in vertical ones. Additionally, we investigated the impact of sorbitol on the coating of sessile fertilizer droplets. We find that configurational entropy decreases exponentially with sorbitol concentration, inducing a morphological transition from fibrous structures to dispersed small aggregates. These findings highlight the complexity of pattern formation in fertilizer deposits and their potential implications for optimizing surface coating processes. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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12 pages, 4958 KiB

Open AccessArticle

Surface Modification of AM60 Mg-Al Alloy with Vanadium and V₂O₅ Sputtered Deposits: Activity in Marine Ambience

by Gerardo Sánchez, Lucien Veleva and Eduardo Flores

Coatings 2024, 14(8), 955; https://doi.org/10.3390/coatings14080955 - 1 Aug 2024

Cited by 1 | Viewed by 1022

Abstract

Vanadium (~450 nm) and V₂O₅ (~350 nm) were deposited by DC magnetron sputtering on an AM60 substrate to improve its degradation resistance in marine ambience. According to Raman and XPS analysis, the vanadium nanofilm mainly consists of amorphous [...] Read more.

Vanadium (~450 nm) and V₂O₅ (~350 nm) were deposited by DC magnetron sputtering on an AM60 substrate to improve its degradation resistance in marine ambience. According to Raman and XPS analysis, the vanadium nanofilm mainly consists of amorphous

V_{2} O_{3}

, while

V_{2} O_{5}

comprises two sheets of

V O_{5}

and

V O_{4}

units. After 30 days of immersion of the coated AM60 in a marine model solution (SME), the shift of the pH of the SME to more alkaline values was less pronounced for

V_{2} O_{5}

-AM60 because of the HCl acid formation during the partial dissolution of

V_{2} O_{5}

in the presence of NaCl, and thus, a higher concentration of

{Mg}^{2 +}

ions

~ 100 mg L^{- 1}

was released from the Mg (AM60) matrix. The lower concentration of

~ 40 mg L^{- 1}

from the V-AM60 surface was attributed to the possible intercalation of the released Mg ions (cations) into the conductive tunnels of

V_{2} O_{3}

as the main component of the vanadium sputtered deposit. This oxide has been reported as a material for high-capacitive energy storage. In this way, the V-deposit provided longer partial protection for the AM60 surface (Mg matrix) from localized pitting attacks. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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15 pages, 4076 KiB

Open AccessArticle

Analyzing the Debinding Step of Ti64 Parts Fabricated by 3D Printing Extrusion

by Ana Silvia González-Pedraza, Didier Bouvard, Jean-Michel Missiaen, Luis Olmos, Héctor Javier Vergara-Hernández, Jose Lemus-Ruiz and Julio César Villalobos

Coatings 2024, 14(6), 715; https://doi.org/10.3390/coatings14060715 - 5 Jun 2024

Viewed by 861

Abstract

The aim of this work is to analyze the effect of the heating rate used during the debinding step on the consolidation of parts fabricated by additive manufacturing using the 3D printing extrusion of Ti64 samples. The cylindrical samples print by extruding MIM [...] Read more.

The aim of this work is to analyze the effect of the heating rate used during the debinding step on the consolidation of parts fabricated by additive manufacturing using the 3D printing extrusion of Ti64 samples. The cylindrical samples print by extruding MIM pellets of Ti64 mixed with a binder. Dilatometry tests follow the densification of the samples by using three different heating rates during the heating stage. All the samples then undergo the same thermal cycle of sintering. SEM and XRD analyze the microstructure. Microhardness and compression tests evaluate the mechanical properties of the sintered samples. We analyze the corrosion behavior under Hank’s solution. The results indicated that the heating rate used during the debinding step affects the densification by reducing this as the heating rate increases. After sintering, a lower relative density is reached, resulting in decreased mechanical properties and corrosion resistance. The Young’s modulus and yield strength correspond well with those of the Ti64 samples prepared by other techniques with similar porosities. Despite the remaining porosity, the parts fabricated by SLM had worse corrosion behavior than ours. The main conclusion is that the isothermal step during debinding is not necessary to ensure complete binder elimination, which will reduce the process time and thus, the fabrication costs of parts by this technique. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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12 pages, 6568 KiB

Open AccessArticle

Rapid Detection and Elimination of Subsurface Mechanical Damage for Improving Laser-Induced Damage Performance of Fused Silica

by Qingzhi Li, Yubin Zhang, Ting Shao, Zhaohua Shi, Jin Huang, Xin Ye, Liming Yang and Wanguo Zheng

Coatings 2024, 14(4), 466; https://doi.org/10.3390/coatings14040466 - 12 Apr 2024

Viewed by 887

Abstract

The fabrication of SSD-free fused silica optics is a crucial objective for high-power laser applications. To treat the surface of polished fused silica, a combination of RIE/RIBE and deep-controlled etch (DCE) techniques are typically employed. Currently, it is important to consider and study [...] Read more.

The fabrication of SSD-free fused silica optics is a crucial objective for high-power laser applications. To treat the surface of polished fused silica, a combination of RIE/RIBE and deep-controlled etch (DCE) techniques are typically employed. Currently, it is important to consider and study the ideal etching depth and precision while using combined etching techniques to remove the identified SSD. Herein, we present a novel approach to identify the distribution of SSD in fused silica, which corresponds to a specific grinding/polishing process condition. Our method involves using a mobile RIBE to perform cone cutting and remove material from the polished fused silica surface. Afterward, we etch the optical element’s surface with HF to visualize the subsurface cracks and understand their relationship with the RIBE depth. Through a systematic investigation of the combined etching technique, we establish a correlation between the depth of RIBE and DCE and the performance of laser damage. The combined etching technique can be implemented as a dependable approach to treat the surface/subsurface defects in fused silica and has the potential to improve laser damage resistance significantly. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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17 pages, 8868 KiB

Open AccessEditor’s ChoiceArticle

Effect of Conformal Coating on Electrochemical Migration Behavior of Multi-Layer Ceramic Capacitor for Automotives Based on Water Drop Test

by Young-Ran Yoo, Seokyeon Won and Young-Sik Kim

Coatings 2024, 14(3), 359; https://doi.org/10.3390/coatings14030359 - 18 Mar 2024

Cited by 1 | Viewed by 1622

Abstract

A large amount of multi-layer ceramic capacitor (MLCC) is mounted inside a printed circuit board (PCB) constituting electronic components. The use of MLCC in electric vehicles and the latest mobile phones is rapidly increasing with the latest technology. Environments in which electronic components [...] Read more.

A large amount of multi-layer ceramic capacitor (MLCC) is mounted inside a printed circuit board (PCB) constituting electronic components. The use of MLCC in electric vehicles and the latest mobile phones is rapidly increasing with the latest technology. Environments in which electronic components are used are becoming more diverse and conformal coatings are being applied to protect mounted components from these environments. In particular, MLCCs in electronic components mainly have voltage applied. They might be used in environments where humidity exists for various reasons. In a humid environment, electrochemical migration (ECM) will occur, with the cathode and anode on the surface of the MLCC encountering each other. This can result in product damage due to a short circuit. In this study, the effects of voltage, NaCl concentration, and distance between electrodes on a non-mount MLCC, surface mount MLCC, and solder pad pattern were evaluated using a water drop test (WDT). Based on the analysis of the effects of the presence of conformal coating, applied voltage, concentration of NaCl, and the distance between electrodes, a mechanism model for ECM behavior in MLCCs was proposed. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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10 pages, 4781 KiB

Open AccessArticle

Electrofrictional Hardening of the 40Kh and 65G Steels

by Zhuldyz Sagdoldina, Yuri Tyurin, Nurbol Berdimuratov, Olga Stepanova, Nurtoleu Magazov and Daryn Baizhan

Coatings 2023, 13(11), 1820; https://doi.org/10.3390/coatings13111820 - 24 Oct 2023

Cited by 1 | Viewed by 1289

Abstract

This study investigated the influence of electrofrictional treatment on the structure and hardness of the surface layers of the 40Kh and 65G steels. Based on the results of scanning electron microscopy, it was determined that during the electrofrictional hardening (EFH) of 40Kh steel, [...] Read more.

This study investigated the influence of electrofrictional treatment on the structure and hardness of the surface layers of the 40Kh and 65G steels. Based on the results of scanning electron microscopy, it was determined that during the electrofrictional hardening (EFH) of 40Kh steel, a hardened surface layer, with a microhardness of 873 ± 37 HV0.1, was formed. This layer consisted of two zones: a surface-quenched zone, with a structure of fine needle-like martensite and austenite; and a heat-affected zone (transition layer), with a structure of martensite and high-dispersion pearlite (troostite), smoothly transitioning into the original ferrite–pearlite structure. After EFH, a layer with a thickness of ~150 μm containing carbides in the martensite was formed on the surface of the 65G steel, which smoothly transitions into the heat-affected zone with a structure of needle-like martensite. The microhardness of the 65G steel in its initial state was 277 ± 20 HV0.1, and after EFH, it reached 811 ± 23 HV0.1. The results of the microstructure analysis of the 40Kh and 65G steels after EFH were consistent with the results of X-ray phase analysis. It was established that the phase composition of the 40Kh and 65G steels in their initial states consisted of an α-Fe phase with a body-centered cubic (BCC) lattice, and after EFH, both steels formed strengthening phases: residual austenite (γ-Fe) and martensite (α′-Fe). During EFH, under high temperature and pressure conditions, carbon from the cast iron electrode was alloyed with iron, contributing to the formation of cementite on the surface of the 65G steel. These obtained data allowed us to conclude that electrofrictional treatment is an effective method for the surface hardening of 40Kh and 65G steels. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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16 pages, 6260 KiB

Open AccessArticle

Effect of Microstructure on Electroless Ni Plating Behavior on Super Duplex Stainless Steel SAF2507 in Li-Ion Batteries

by Byung-Hyun Shin, Dohyung Kim, Doo-In Kim, Wookjin Lee and Se-Hun Kwon

Coatings 2023, 13(10), 1807; https://doi.org/10.3390/coatings13101807 - 20 Oct 2023

Cited by 3 | Viewed by 1401

Abstract

The demand for Li-ion batteries has significantly increased in recent years, driven by the growing need for electric vehicles and electronic devices like smartphones. Among various materials, super duplex stainless steel (SDSS) is considered a suitable material for Li-ion batteries due to its [...] Read more.

The demand for Li-ion batteries has significantly increased in recent years, driven by the growing need for electric vehicles and electronic devices like smartphones. Among various materials, super duplex stainless steel (SDSS) is considered a suitable material for Li-ion batteries due to its excellent strength and corrosion resistance. However, SDSS is sensitive to heat-treatment conditions, necessitating research on heat treatment and Ni plating for battery case usage. While extensive research has been conducted on SDSS and its heat-treatment conditions, there is a research gap concerning the Ni plating of SDSS. This study addresses this gap by performing Ni plating on heat-treated SDSS. Ni plating can be executed via two methods: electroless and electro-Ni plating. To achieve a uniform plating layer, Ni plating was conducted after heat treatment at temperatures ranging from 1000 °C to 1300 °C, followed by an analysis of the behavior of electroless Ni plating. The heat-treated SDSS displayed three primary characteristics: secondary phase precipitation, solution annealing, and ferritization (ferrite fractions of 61% and 73%). The presence of secondary phases led to a slower Ni plating rate due to its lower reactivity with Ni. Post-solution annealing, the texture of SDSS exhibited the thickest Ni plating layer at the same plating time. As the volume fraction of ferrite increased from 50% to 73% on electrochemical impedance spectroscopy, the resistance of the Ni plating layer decreased from 45 kOhms to 13 kOhms. The lowest resistance was observed when the ferrite fraction reached 73%, attributed to the lower reactivity of ferrite compared to austenite. Both secondary phases and ferrite contributed to reducing the thickness of the electroless Ni plating layer. Therefore, optimizing the volume fraction of SDSS using solution annealing proves beneficial for optimizing Ni plating and enhancing corrosion resistance. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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8 pages, 11708 KiB

Open AccessArticle

Surface Smoothing by Gas Cluster Ion Beam Using Decreasing Three-Step Energy Treatment

by Vasiliy Pelenovich, Xiaomei Zeng, Xiangyu Zhang, Dejun Fu, Yan Lei, Bing Yang and Alexander Tolstoguzov

Coatings 2023, 13(5), 942; https://doi.org/10.3390/coatings13050942 - 17 May 2023

Cited by 5 | Viewed by 1657

Abstract

A three-step treatment of Si wafers by gas cluster ion beam with decreasing energy was used to improve the performance of surface smoothing. First, a high energy treatment at 15 keV and an ion fluence of 2 × 10¹⁶ cm⁻² was [...] Read more.

A three-step treatment of Si wafers by gas cluster ion beam with decreasing energy was used to improve the performance of surface smoothing. First, a high energy treatment at 15 keV and an ion fluence of 2 × 10¹⁶ cm⁻² was used to remove initial surface features (scratches). Next, treatments at 8 and 5 keV with the same fluences reduced the roughness that arose due to the formation of morphological features induced by the surface sputtering at the first high energy step. The surface morphology was characterized by the atomic force microscopy. The root mean square roughness R_q and 2D isotropic power spectral density functions were analyzed. For comparison, the smoothing performances of single-step treatments at 15, 8, and 5 keV were also studied. The lowest roughness values achieved for the single and three-step treatments were 1.06 and 0.65 nm, respectively. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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15 pages, 5553 KiB

Open AccessArticle

Solid-to-Liquid Ratio Influenced on Adhesion Strength of Metakaolin Geopolymer Coating Paste Added Photocatalyst Materials

by Liyana Jamaludin, Rafiza Abd Razak, Mohd Mustafa Al Bakri Abdullah, Petrica Vizureanu, Andrei Victor Sandu, Shayfull Zamree Abd Rahim and Romisuhani Ahmad

Coatings 2023, 13(2), 236; https://doi.org/10.3390/coatings13020236 - 19 Jan 2023

Cited by 4 | Viewed by 1782

Abstract

Coating materials are used on surfaces such as steel and ceramic to offer protection, corrosion resistance, wear and erosion resistance, a thermal barrier, or aesthetics. Although organic coating materials such as epoxy resins, silane, and acrylic are widely used, there are restrictions and [...] Read more.

Coating materials are used on surfaces such as steel and ceramic to offer protection, corrosion resistance, wear and erosion resistance, a thermal barrier, or aesthetics. Although organic coating materials such as epoxy resins, silane, and acrylic are widely used, there are restrictions and drawbacks associated with their use, including the ease with which cracking, hazardous and harmful human health and environment, peeling, and deterioration occur. Organic matrices also have the capacity to release vapor pressure, which can lead to the delamination of coatings. Geopolymer coating materials offer an environmentally friendly solution to this concern to encourage sustainable growth. The simplicity with which geopolymers can be synthesized and their low emission of greenhouse gases such as CO₂, SO₂, and NO_x are advantages of geopolymers. The advent of geopolymer coatings with photocatalytic properties is advantageous for the decomposition of pollution and self-cleaning properties. The aim of this paper is to study the optimum solid-to-liquid ratio of metakaolin geopolymer paste added TiO₂ and ZnO by adhesion strength. Through iterative mixture optimization, we investigated the effects of different design parameters on the performance of a metakaolin-based geopolymer as a coating material. The assessed material was a metakaolin which was activated by an alkali activator (a mixture of sodium hydroxide and sodium silicate), with the addition of titanium dioxide and zinc oxide as photocatalyst substances. Varying proportions of solid-to-liquid ratio were tested to optimize the best mix proportion related to the coating application. Adhesion analyses of geopolymer coating paste were evaluated after 7 days. According to the findings, the optimal parameters for metakaolin geopolymer coating material are 0.6 solid-to-liquid ratios with the highest adhesion strength (19 MPa) that is suitable as coating material and enhanced the properties of geopolymer. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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19 pages, 4506 KiB

Open AccessArticle

Droplet Spreading Characteristics on Ultra-Slippery Solid Hydrophilic Surfaces with Ultra-Low Contact Angle Hysteresis

by Yajie Song, Qi Wang, Yushan Ying, Zhuo You, Songbai Wang, Jiang Chun, Xuehu Ma and Rongfu Wen

Coatings 2022, 12(6), 755; https://doi.org/10.3390/coatings12060755 - 31 May 2022

Cited by 12 | Viewed by 3691

Abstract

Dynamic interactions of the droplet impact on a solid surface are essential to many emerging applications, such as electronics cooling, ink-jet printing, water harvesting/collection, anti-frosting/icing, and microfluidic and biomedical device applications. Despite extensive studies on the kinematic features of the droplet impact on [...] Read more.

Dynamic interactions of the droplet impact on a solid surface are essential to many emerging applications, such as electronics cooling, ink-jet printing, water harvesting/collection, anti-frosting/icing, and microfluidic and biomedical device applications. Despite extensive studies on the kinematic features of the droplet impact on a surface over the last two decades, the spreading characteristics of the droplet impact on a solid hydrophilic surface with ultra-low contact angle hysteresis are unclear. This paper clarifies the specific role of the contact angle and contact angle hysteresis at each stage of the droplet impact and spreading process. The spreading characteristics of the droplet impact on an ultra-slippery hydrophilic solid surface are systematically compared with those on plain hydrophilic, hydroxylated hydrophilic, and plain hydrophobic surfaces. The results reveal that the maximum spreading factor (β_max) of impacting droplets is mainly dependent on the contact angle and We. β_max increases with the increase in We and the decrease in the contact angle. Low contact angle hysteresis can decrease the time required to reach the maximum spreading diameter and the time interval during which the maximum spreading diameter is maintained when the contact angles are similar. Moreover, the effect of the surface inclination angle on the spreading and slipping dynamics of impacting droplets is investigated. With the increase in the inclination angle and We, the gliding distance of the impacting droplet becomes longer. Ultra-low contact angle hysteresis enables an impacting droplet to slip continuously on the ultra-slippery hydrophilic surface without being pinned to the surface. The findings of this work not only show the important role of the surface wettability in droplet spreading characteristics but also present a pathway to controlling the dynamic interactions of impacting droplets with ultra-slippery hydrophilic surfaces. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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17 pages, 16790 KiB

Open AccessArticle

The Effects of Zinc Oxide/Silicon Dioxide Composite Coating on Surface Wettability and the Mechanical Properties of Paper Mulching Film

by Anling Li, Yangyang Jia, Fangyuan Zhang, Yiming Zhao and Fengwei Zhang

Coatings 2022, 12(5), 555; https://doi.org/10.3390/coatings12050555 - 20 Apr 2022

Cited by 5 | Viewed by 3976

Abstract

In order to improve the hydrophobic and mechanical properties of paper mulch film, ZnO/SiO₂ composite coated paper mulch film was prepared with a brush coating method. Hydrophobicity and durability of the original paper mulch film and the coated paper mulch film were [...] Read more.

In order to improve the hydrophobic and mechanical properties of paper mulch film, ZnO/SiO₂ composite coated paper mulch film was prepared with a brush coating method. Hydrophobicity and durability of the original paper mulch film and the coated paper mulch film were measured by static contact angle and mechanical torsion tests, and the mechanical properties of the two kinds of paper mulch films were measured by tensile and tear tests at different temperatures. The two kinds of paper mulch films were characterized by their micro-morphology and surface element distribution. The results show that the contact angle of the ZnO/SiO₂ composite coated paper mulch film reaches 161.46°, and the contact angle can still reach 153.15° after 80 mechanical torsion cycles, which shows good superhydrophobic and hydrophobic durability. Compared with the original paper mulch film, the mechanical properties of the coated paper mulch film are also improved to some extent. Combined with the surface micro-morphology, it is found that a ZnO/SiO₂ composite coating fills the pores between fibers in the paper mulch film and promotes the adhesion between fibers, thus improving the hydrophobicity, durability, and mechanical properties of the paper mulch film. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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28 pages, 9255 KiB

Open AccessArticle

Study of Wear and Redistribution Dynamic Forces of Wheel Pairs Restored by a Wear-Resistant Coating 15Cr17Ni12V3F

by Vitaliy V. Savinkin, Zaure Zh. Zhumekenova, Andrei Victor Sandu, Petrica Vizureanu, Sergey V. Savinkin, Sergey N. Kolisnichenko and Olga V. Ivanova

Coatings 2021, 11(12), 1441; https://doi.org/10.3390/coatings11121441 - 24 Nov 2021

Cited by 4 | Viewed by 2344

Abstract

The relevance of this study lies in the need to research the wear process of the elements of dynamic systems and to establish the dependence of the geometric and structural characteristics of wheels restored by plasma surfacing with a coating of 15Cr17Ni12V3F on [...] Read more.

The relevance of this study lies in the need to research the wear process of the elements of dynamic systems and to establish the dependence of the geometric and structural characteristics of wheels restored by plasma surfacing with a coating of 15Cr17Ni12V3F on dynamic, cyclically varying loads. The study was aimed to establish the dependencies between the deviation of the wear area, the formation of contact and fatigue stresses, and the change in the phase structure of the wheel defect. It is important to justify the permissible limits of wear of the transverse profile in the contact zone of a wheel and ridge. The object of the study was the dynamic interaction of the “wheel–ridge–rail contact surface” system. To achieve the goal, the following methodology was adopted: kinematic analysis, strength calculation, the use of mathematical analysis in dynamic system modelling, virtual modelling in the SOLIDWORKS software environment of the GearTrax application, experiment planning, and model correction through the results of metallographic studies. The results of the study are presented as reasonable prediction criteria that consider contact cycles during the formation of fatigue stresses at the stage of defect origin. The process of the dynamic interaction of the contact worn profile of a wheel with a railway rail is explored. Polynomial equations are proposed to substantiate the optimal design and technological parameters of designing a railway carriage wheel. The permissible limits of wear of the transverse profile in the contact zone of the wheel and the ridge are justified while taking the coefficient of the reduction of contact stresses in the metal into account. The dependences of the change in static load on the utilization factor of the railway carriage load capacity are established. The dependences of changes in fatigue stresses on the design deviation of the contact area of wheel wear are established. It is confirmed that the stress concentration under cyclic loads is formed in the ferritic layers of the material structure before the appearance of wear. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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16 pages, 5204 KiB

Open AccessArticle

The Low-Temperature Ring during Droplet Impact on a Superhydrophilic Surface

by Huixia Ma, Jiang Chun, Feng Zhou, Kai Qiao, Rui Jiang, Shumei Zhang and Tingting Hao

Coatings 2021, 11(9), 1043; https://doi.org/10.3390/coatings11091043 - 30 Aug 2021

Cited by 4 | Viewed by 2189

Abstract

Droplet impact on the solid surfaces is widespread in nature, daily life, and industrial applications. The spreading characteristics and temperature evolution in the inertial spreading regime are critical for the heat and mass transfer process on the solid-liquid interface. This work investigated the [...] Read more.

Droplet impact on the solid surfaces is widespread in nature, daily life, and industrial applications. The spreading characteristics and temperature evolution in the inertial spreading regime are critical for the heat and mass transfer process on the solid-liquid interface. This work investigated the spreading characteristics and temperature distribution of the thin liquid film in the inertial rapid spreading regime of droplet impact on the heated superhydrophilic surfaces. Driven by the inertial and capillary force, the droplet rapidly spreads on the superhydrophilic surface, resulting in a high temperature center in the impact center surrounded by a the low-temperature ring. The formation of the unique the low-temperature ring on the heated superhydrophilic surface is due to the much smaller time scale of rapid spreading than that of heat transfer from the hot solid surface to the liquid film surface. CFD numerical simulation shows that the impacting droplet spreads and congests in the front of liquid film, leading to the formation of vortex velocity distribution in the liquid film. Increasing We number and wall temperature can accelerate the heat transfer rate of liquid film and shorten the existence time of the low-temperature ring. The findings of the the low-temperature ring on the superhydrophilic surface provide the guidelines to optimization of surface structures and functional coatings for enhancing heat transfer in various energy systems. Full article

(This article belongs to the Special Issue Recent Advances in Surface Functionalisation)

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