Porosity in plasma-sprayed coatings is vital for most engineering applications. Porosity has its merits and demerits depending on the functionality of the coating and the immediate working environment. Consequently, the formation mechanisms and development of porosity have been extensively explored to find out modes of controlling porosity in plasma-sprayed coatings. In this work, a comprehensive review of porosity on plasma-sprayed coatings is established. The formation and development of porosity on plasma-sprayed coatings are governed by set spraying parameters. Optimized set spraying parameters have been used to achieve the most favorable coatings with minimum defects. Even with the optimized set spraying parameters, defects like porosity still occur. Here, we discuss other ways that can be used to control porosity in plasma-sprayed coating with emphasis to atmospheric plasma-sprayed chromium oxide coatings. Techniques like multilayer coatings, nanostructured coatings, doping with rare earth elements, laser surface re-melting and a combination of the above methods have been suggested in adjusting porosity. The influences of porosity on microstructure, properties of plasma-sprayed coatings and the measurement methods of porosity have also been reviewed.

Thermal barrier coatings (TBCs) play a vitally important role in protecting the hot parts of a gas turbine from high temperature and corrosion effectively. More and more attention has been paid to the performance modification of ZrO₂-based ceramics and seeking for new ceramic materials to meet requirements of gas turbine TBCs. The working principle, merits, and demerits of main technologies for coating preparation are elaborated in this paper, and the properties of new ceramic materials are reviewed. It is found that the thermal conductivity, thermal stability, mechanical properties, and other performances of traditional ZrO₂-based ceramics could be improved effectively by doping modification. The emphases for new ceramic materials research were put on pyrochlores, magnetoplumbites, rare-earth tantalates, etc. Rare-earth tantalates with great potentials as new top ceramic materials were described in detail. In the end, the development directions of advanced top ceramic coatings, combining doping modification with preparation technology to regulate and control structure property of high-performance ceramic material, were put forward.

The extended immersion of ships in seawater frequently results in biofouling, a condition characterized by the accumulation of marine organisms such as barnacles and algae. To combat this issue, the application of anti-fouling coatings to the hull surfaces of vessels has emerged as one of the most effective strategies. In response to the increasing global emphasis on environmental sustainability, there is a growing demand for anti-fouling coatings that not only demonstrate superior anti-fouling efficacy but also adhere to stringent environmental standards. The traditional use of organotin-based self-polishing anti-fouling coatings, known for their high toxicity, has been prohibited due to environmental concerns. Consequently, there is a progressive shift toward the development and application of environmentally friendly anti-fouling coatings. This paper reviews the toxicity and application limitations associated with conventional anti-fouling coatings. It provides a comprehensive overview of recent advancements in the field, including the development of novel self-polishing anti-fouling coatings, low surface energy coatings, biomimetic coatings, and nanostructured coatings, each leveraging distinct anti-fouling mechanisms. The paper evaluates the composition and performance of these emerging coatings and identifies key technical challenges that remain unresolved. It also proposes a multi-faceted approach to addressing these challenges, suggesting potential solutions for enhancing the effectiveness and environmental compatibility of anti-fouling technologies. The paper forecasts future research directions and development trajectories for marine anti-fouling coatings, emphasizing the need for continued innovation to achieve both environmental sustainability and superior anti-fouling performance.

Icing as a regular natural phenomenon in life poses a serious threat to human production and life, traditional mechanical deicing, chemical deicing, and other methods have the shortcomings of high pollution, high energy consumption, and low efficiency, which limits their applicability and effectiveness of the scene of the above methods. With the expansion of global economic activities in recent years, the solution to the icing problem has become imminent. As a result, researchers have gradually deepened their studies related to anti-icing. Inspired by the lotus leaf effect, hogwash, polar, marine shellfish, and other natural organisms, anti-icing/deicing coatings can be designed functional biomimetic through both surface micro-nano structures and the physicochemical properties of the material. Superhydrophobic design is based on Young’s wetting equations, Wenzel’s wetting equations, and the Cassie-Baxter model of the superhydrophobic behavior of the interface formed by the liquid droplets and the surface, which prevents the droplets from spreading out and penetration to form heat exchange. The physicochemical properties are based on the slow-release behavior of chemical mediators inside the coating with properties such as super-lubrication and anti-freezing, which reduce the residence time and nucleation temperature of droplets on the surface. The coating effectively blocks the occurrence of icing behavior by passive means such as ultra-low interfacial wetting, interfacial slip, and lowering the freezing point of droplets, which has become a hot research direction. Meanwhile, the active anti-icing of photo-thermal, electro-thermal, phase change and other effects with the passive anti-icing to play a synergistic and complementary role for further enhance the anti-icing effect of the coating. To clarity the design mechanism and preparation process of the anti-icing/ice-removing surfaces, the article firstly classifies and introduces the coatings functioned according to the different mechanisms of action, and sums up the biomimetic super-hydrophobic design, the sacrificial type physicochemical characteristic. The article firstly classifies and introduces the functional types of coatings according to different mechanisms of action, and the latest research progress on the mechanism design of anti-icing coatings and their performance modification such as bionic superhydrophobic design, sacrificial physicochemical property design, microregion modulus control design and multifactorial coupling design were summarized. The problems of single-functionality and imbalance of performance of the existing coating mechanism design were analyzed and discussed, the view of the development trend and outlook of the development and application of icephobic coatings were put forward.

Hollow glass microsphere-reinforced epoxy hollow spheres (HGMS–EHSs) were prepared by a “rolling ball method” using expanded polystyrene beads, HGMSs, and epoxy resin (EP). The three-phase epoxy syntactic foam (epoxy/HGMS–EHS–HGMS composite) was fabricated by combining HGMS–EHS as a lightweight filler with EP and HGMS by a “molding method”. The HGMS–EHS and epoxy curing agent systems were well mixed by scanning electron microscopy. Experiments show that higher HGMS–EHS stack volume fraction, lower HGMS–EHS layer number, higher HGMS–EHS diameter, lower HGMS–EHS density, higher HGMS volume fraction, and lower HGMS density result in a decrease in the density of the three-phase epoxy syntactic foam. However, the above factors have the opposite effect on the compressive strength of the three-phase epoxy syntactic foam. Therefore, in order to obtain the “high-strength and low-density” three-phase epoxy syntactic foam, the influence of various factors should be considered comprehensively to achieve the best balance of compressive strength and density of the three-phase epoxy syntactic foam. This can provide some advice for the preparation of buoyancy materials for deep sea operations.