Trends in Coatings and Surface Technology

The advancement in material science, industrial evolution, and growing environmental concerns make it essential for continuous updates in coating and surface technology. To keep pace with the ongoing industrial evolution, there are also several key trends going on in coating and surface technology. The coatings with various key features such as multifunctionality, thermal sustainability, antibacterial, anti-viral, wear and corrosion resistant, sustainable, and eco-friendly are the focal point for the research. Hence the development in coating and surface technology is driven to achieve these features.

This Special Issue on “Trends in Coating and Surface Technology” is a comprehensive collection of the latest research and advancements, highlighting the potential role of modern coating and surface technologies in various fields of science and industries. This Special Issue presents a selection of high-quality articles reflecting the trends in coating and surface technology. It comprises eighteen contributions, covering different coating techniques, different approaches for surface modification, and different types of coatings to be utilized for diverse applications.

This Special Issue includes six articles that showcase different approaches to coating technology to be utilized on different coating materials for distinct applications. Sandra Lepak-Kuc et al. [1] presented an ecofriendly, biodegradable composite based on biopolymer and graphene nanoplatelets. This composite is deposited via spray coating technology and showcases good electrical conductivity, biocompatibility, stability, and physiochemical properties. With these properties, these biodegradable conductive coatings emerge as sustainable materials that can be used in printed conductive structures. Xiangyong Zeng et al. [2] presented a novel method of hot filament chemical vapor deposition technology to deposit spherical diamond particles on Si₃N₄ powder that improves the tribological and griding properties of lubricants. These diamond particles play a vital role in decreasing the surface roughness of Si₃N₄ powder. Therefore, this approach can be beneficial for the production of abrasive materials with an improved performance and can be used further for industrial applications. Chao Chen et al. [3] utilized a laser cladding technique to prepare high-chromium cast iron (HCCI) coatings with multicomponent carbides. These improve the hardness and wear resistance of low-alloy steel substrates. The approach of incorporating multielement dopants to form multicomponent carbides emerge out to be very effective for enhancing laser cladded coatings performance. Effect of substrate bias voltage on microstructure and mechanical properties of Cr-Nb-Ti-Zr-N-O ceramic presented by Sayed Alireza Ataie et al. [4]. These multielement films deposited via reactive sputtering at different bias voltage. The substrate bias voltage effects the structural and mechanical properties of the film. This article explains how crystallinity is affected by the substrate bias and demonstrates a particular bias value at which the film, with minimal defects and good mechanical performance, can be used for hard coating applications. A cold spraying technique has been used by Xiao Chen et al. [5] for the preparation of HA/Ti composite coatings. Their study on the effect of gas pressure and gas temperature variation, both numerically and experimentally, has been presented to provide valuable insights into optimizing cold spraying conditions for improving the mechanical properties and bonding strength of HA composite coatings. The sol gel technique was explored by Asad ur Rehman Khan et al. [6] for the synthesis of zirconium-doped zinc oxide (ZZO) nanostructures for use as transparent conductive oxides in optoelectronic devices. The zirconium-doping in zinc oxide results in nanostructures with high optical transmittance, wide band gap, low resistivity, and high carrier concentrations.

This Special Issue also features articles on the behaviors of different coatings and their characteristic analyses. Vasil Kostov et al. [7] present Cu–Sb-based alloys, specifically with copper content between 18 and 30 wt.%, showing promising potential for green applications, such as CO₂ reduction catalysts, anodic materials for metal-ion batteries, and solar cell components. The study demonstrated that decreasing copper content increases the roughness and chemical heterogeneity of the alloy, largely due to the formation of antimony crystal clusters, but does not significantly impact their hardness or electrochemical behavior. Nattakorn Borwornpornmetee et al. [8] contributes to the understanding of how thermal vacuum annealing at 300, 600, and 900 °C impacts the performance of Fe3Si films, offering novel findings on the evolution of their wetting and mechanical characteristics with temperature variation. Mohammadamin Sadeghi et al. [9] introduces the tribological behavior of gadolinium-doped diamond-like carbon (Gd-DLC) coatings in the presence of ionic liquid additive in polyalphaolefin (PAO) 8 lubricant under different lubrication regimes compared to europium-doped DLC (Eu-DLC) and pure DLC coatings. Gd-DLC achieved a higher hardness, better thin-film adhesion, and greater resistance to plastic deformation, resulting in a lower coefficient of friction (CoF) in all lubrication regimes. José Antunes et al. [10] demonstrates the deposition of Ag/DLC coatings via sputtering with varying silver content onto different fabrics, which results in the hydrophobicity of textiles, particularly in cotton, converting it from hydrophilic to hydrophobic. The coatings exhibited strong antibacterial activity against Staphylococcus aureus and Klebsiella pneumoniae without posing cytotoxic risks, which makes them a promising application in healthcare for pathogen-resistant personal protective equipment (PPE). Junfei Xu et al. [11] present the enhanced protective mechanism of CoCrNiAlY–YSZ–LaMgAl11O19 (LMA) double-layer ceramic coatings with an aluminum plating. The un-aluminized coatings at high temperatures generate significant radial thermal stress on the LMA layer’s surface, leading to axial crack initiation; however, post-aluminum plating reduces the thermal stress and improves the overall protection of the coating. Despite the risk of radial microcracks due to shear stress, the aluminum plating provides significant enhancement and protection to the ceramic coating system.

This Special Issue includes articles on the synthesis of distinct surfaces, such as textile electrodes introduced by Dajana Doci and Melisa et al. [12], that can be used in place of traditional Ag/AgCl gel electrodes for ECG measurements. This study demonstrated the durability of textile electrodes, exhibiting high abrasion resistance and maintaining signal quality even after washing and abrasion tests, and can be used for long-term ECG monitoring with better comfort and durability compared to conventional electrodes. Kazuya Yamamoto et al. [13] present a novel approach for fabricating flexible, functional materials entirely based on chitin through the preparation of nanochitin (ChNF) films grafted with oligochitin dihexanoate chains. By reducing the crystallinity of chitin through the introduction of oligochitin dihexanoate, the resulting films exhibit enhanced flexibility compared to the brittle parent ChNF film. Linxin Dai et al. [14] successfully present the green synthesis of carbon-encapsulated magnetic Fe₃O₄ nanoparticles using hydrothermal carbonization from rattan holocelluloses. By employing ionic liquid pretreatment and hydrothermal carbonization, the resulting nanoparticles exhibit tunable structures and enhanced saturation magnetization, up to 42.6 emu/g. This innovative approach opens new possibilities for producing carbon-encapsulated iron oxide nanoparticles, paving the way for advancements in magnetic materials. Fan Zhang et al. [15] article indicates the effectiveness of BA-g-CNCs for the formation of high internal phase emulsions without cross-linking, especially at optimal conditions of 13% BA and 1.75% BA-g-CNCs. Additionally, BA-g-CNCs exhibit self-emulsifying properties and enhance mechanical performance, making them promising candidates for applications in coatings for fabrics, leather, paper, and controlled encapsulation, as well as other functional material science fields.

This Special Issue also covers research on the factors that affect surface morphology and coating quality. Lulu Wang et al. [16] highlight the significant impact of interface curvature on the evolution of thermal mismatch stresses, thermally grown oxide (TGO) behavior, and crack formation during thermal cycling in ceramic-metal coating systems. The findings reveal that the growth of TGO and the resulting stress distribution are highly sensitive to interfacial curvature, with tensile stresses shifting from the crest to the near-peak and ramp regions as oxidation progresses. Chenchun Chiu et al. [17] provide a comprehensive analysis of the effects of film cooling holes and CMAS infiltration on the thermomechanical behavior of thermal barrier coating systems (TBCs) in gas turbines. By developing a three-dimensional thermo-fluid–solid coupling model, the research reveals that film cooling holes significantly reduce interfacial residual stress around the TC/BC interface by 60% through a 40% temperature reduction. Xiaozhen Li et al. [18] present a novel regression method to address the challenges posed by surface morphology on the accuracy of indentation hardness measurements, particularly in small-scale structures like thin films and coatings. Traditional methods, such as mechanical polishing and increasing indentation depth, have limitations in these contexts. Through finite element simulations, the study demonstrated that the new regression approach effectively eliminates the influence of surface undulation, providing accurate hardness measurements. This method simplifies the testing process, reduces workload, and significantly enhances measurement precision, offering a valuable alternative to conventional techniques.

In conclusion, the Special Issue highlights the wide array of advancements in coatings and surface technology. From distinct surface coating to different surface coating techniques, it showcases the ongoing progress in surface engineering. This Special Issue highlights the remarkable achievements in this field, which will contribute to the future growth of coating and surface technology. Furthermore, it presents insights into trending surface modification techniques for future applications.