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High-entropy rare earth titanates (Y 0.2 Gd 0.2 Ho 0.2 Er 0.2 Yb 0.2) 2 Ti 2 O 7 (YHT) have great application potential in the thermal protection coating field. In this work, the YHT coating was successfully prepared by atmospheric plasma spraying. The influence of different spraying powers and coating ablation behavior by plasma flame on the phase composition and microstructure morphology of the coating surface, cross-section and fracture surface were investigated using X-ray diffraction, scanning electron microscopy and atomic force microscope. Results show that the YHT powder has a sufficiently melted state before impacting the metal substrate and the coating can be effectively deposited through optimizing the plasma spraying power. And the YHT coatings undergo slight sintering, leading to the formation and growth of a spherical structure at 1200 °C, while the grain preferential growth, mechanical failure and water-like structure occurred due to strong thermal shock at 1400 °C. In addition, when the coating surface temperatures are 1200 °C and 1400 °C, the corresponding heat insulation temperatures are 590 °C and 620 °C, respectively, indicating that YHT coating has good thermal insulation ability. This study provides a powerful theoretical basis and technical support for the application of high-entropy rare earth titanates YHT as a thermal protection material for high temperature devices. [Display omitted] • High-entropy rare earth titanates coating was first deposited by plasma spraying. • Microstructure evolution of the high-entropy coating was studied in detailed. • Ablation behaviors and mechanism of the high-entropy coating were explored. [ABSTRACT FROM AUTHOR]

[Display omitted] • The high-entropy monoboride ceramic coating was successfully prepared for the first time by atmospheric plasma spraying technology. • The novel design concept-typical precipitation reaction was applied to improve the failure of multiphase coatings caused by interface cracks. • The cooperative effect of the two phases is the main reason for the high wear resistance of high-entropy monoboride ceramic coating. Surface wear-resistant coatings are an effective way to protect tools and provide certain desired properties; however, these coatings often fail prematurely owing to their low plastic deformation ability. High-entropy monoboride (VCrMoWNi)B with an super hardness is a promising material for wear resistance. To balance the high hardness and plastic deformation ability of coating, a novel design concept for the plastic phase precipitate reaction was developed based on the crystallization conditions of the different elements of the composite during deposition of the plasma sprayed high-entropy monoboride (VCrMoWNi)B-Ni 2 B (HEMB-Ni 2 B) composite coating. The microstructure evolution, hardness, and wear resistance mechanism of the HEMB-Ni 2 B coating were thoroughly investigated. Because the second phase Ni 2 B is beneficial for producing plastic deformation and absorbing large strain energy, the cooperation effect between the super hardness of HEMB and large plastic deformation ability of Ni 2 B can significantly enhance the wear resistance of the HEMB-Ni 2 B coating. Particularly, a friction coefficient as low as 0.13 for the HEMB-Ni 2 B coating and outstanding wear resistance are achievable. This study paves the way for the design of high-entropy ceramic coatings with excellent mechanical performance. Moreover, it has a high practical application value in the field of wear resistant coatings. [ABSTRACT FROM AUTHOR]

Metal materials have been used as thin films in many optical applications because of its excellent high reflectivity in the near-infrared range. However, studies on thick metal coatings deposited by plasma spraying have rarely been conducted. The current study investigates the relationship between optical property and microstructure for different metal plasma-sprayed coatings (Al, Cu, and Ag) and discusses the corresponding mechanical properties. The phase structure and surface morphology of as-sprayed powders and corresponding coatings were examined by X-ray diffraction and scanning electron microscopy, respectively. The optical and mechanical properties were characterized by UV–visible-near infrared spectroscopy, Multi-Specimen machine testing and Vickers microhardness testing. Results indicate that the optical behavior of metal plasma-sprayed coatings is related to their phase structure, splat microstructure, and surface roughness. Optimization of powders in molten state and the surface microstructure is proposed as an effective method to improve the optical property of these coatings. The molten state and low porosity also help to improve the mechanical properties of the coating materials. [ABSTRACT FROM AUTHOR]

Perovskite La 1− x Sr x TiO 3+ δ oxide is used in various industrial applications because of its excellent physical and chemical properties, which beneficially affects the lifetime and performance of electronic and optical devices. This study illustrates the effects of the spray parameters on particles molten state, microstructure, and optical reflectivity from room temperature up to 1000 °C of single-phase La 1− x Sr x TiO 3+ δ ( x = 0.1) coating deposited by atmospheric plasma spraying technique. The phase structure and surface morphology of the coating were examined using X-ray diffraction and scanning electron microscopy analysis, respectively, whereas the optical property coating was characterized by UV–visible–near infrared spectroscopy. Results show that plasma spray parameters significantly influenced the microstructure and optical performance of the La 1− x Sr x TiO 3+ δ coating, and oxygen deficiency during spraying considerably reduced the coating reflectivity. A high-reflectivity coating can be prepared by adopting optimized plasma spraying parameters and subsequent heat treatment. [ABSTRACT FROM AUTHOR]

The microstructure of thermal spray powders plays a significant role in the application performance of thermal protection coatings deposited by air plasma spraying. Based on the design of the spray powder structure, the YSZ@Cu core-shell structure powders have the potential to be a thermal conduction anisotropy material for thermal protection coating, owing to the special alternate-layered structure formed during plasma spraying. To study the mechanism of the thermal conduction anisotropy of YSZ/Cu composite coatings, the YSZ coatings, YSZ@Cu coatings and YSZ-Cu coatings were fabricated by YSZ powders, YSZ@Cu core-shell structure powders and YSZ-Cu mechanical mixture powders, respectively. There were YSZ vertical thermal insulation layer and Cu horizontal thermal condition layer in the YSZ@Cu coatings, which provides a structural basis for the realization of thermal conduction anisotropy. Compared with the YSZ-Cu coatings, the temperature difference between the back-surface center area and the edge area of the YSZ@Cu coatings is significantly reduced by approximately 37%, which is attributed to the synergistic effect of alternate-layered comprising the YSZ layer and the high thermal conductivity Cu layer. YSZ@Cu coatings can effectively prevent the rapid rise in local temperature by the analysis of finite-element simulation, which is beneficial for prolonging the service life of the thermal protection coating in a non-uniform temperature field. • To reveal thermal conduction anisotropy, YSZ@Cu core-shell structure powder was used to fabricate composite coatings by APS. • The YSZ@Cu coating has an alternate-layered structure including horizontal thermal conduction and vertical thermal isolation layer. • Based on experimental analysis, the novel YSZ@Cu coating make surface temperature difference reduce by approximately 37%. [ABSTRACT FROM AUTHOR]