High-entropy alloys (HEAs) are advanced materials characterized by their unique and complex compositions. Characterized by a mixture of five or more elements in roughly equal atomic ratios, these alloys diverge from traditional alloy formulations that typically focus on one or two principal elements. This innovation has paved the way for subsequent studies that have expanded our understanding of HEAs, highlighting the role of high mixing entropy in stabilizing fewer phases than expected by traditional phase prediction methods like Gibbs’s rule. In this review article, we trace the evolution of HEAs, discussing their synthesis, stability, and the influence of crystallographic structures on their properties. Additionally, we highlight the strength–ductility trade-off in HEAs and explore strategies to overcome this challenge. Moreover, we examine the diverse applications of HEAs in extreme conditions and their promise for future advancements in materials science.

The present paper is a narrative review focused on a few important aspects and moments of trends surrounding materials and methods in sustainable nuclear energy, as an expression of applied chemistry support for more efficiency and safety. In such context, the paper is focused firstly on increasing alloy performance by modifying compositions, and elaborating and testing novel coatings on Zr alloys and stainless steel. For future generation reactor systems, the paper proposes high entropy alloys presenting their composition selection and irradiation damage. Nowadays, when great uncertainties and complex social, environmental, and political factors influence energy type selection, any challenge in this field is based on the concept of increased security and materials performance leading to more investigations into applied science.

A natural deep eutectic solvent (NADES)-based electropolymerization strategy was developed to deposit polypyrrole (PPy) and Naproxen-doped PPy films onto a biomedical Ti–20Zr–5Ta–2Ag high-entropy alloy. Using cyclic voltammetry, chronoamperometry, and chronopotentiometry, coatings were grown potentiostatically (1.2–1.6 V) or galvanostatically (0.5–1 mA) to fixed charge values (1.6–2.2 C). Surface morphology and composition were assessed by optical microscopy, SEM and FTIR, while wettability was quantified via static contact-angle measurements in simulated body fluid (SBF). Electrochemical performance in SBF was evaluated through open-circuit potential monitoring, potentiodynamic polarization, and electrochemical impedance spectroscopy. Drug-release kinetics were determined by UV–Vis spectrophotometry and analyzed using mathematical modelling. Compared to uncoated alloy, PPy and PPy–Naproxen coatings increased hydrophilicity (contact angles reduced from ~31° to 90% over 8 days), with diffusion exponents indicating Fickian (n ≈ 0.51) and anomalous (n ≈ 0.67) transport for potentiostatic and galvanostatic coatings, respectively. These multifunctional PPy–Naproxen films combine robust corrosion protection with controlled therapeutic delivery, supporting their potential biomimetic role as smart coatings for next-generation implantable devices.

Over time, micro- and nano-coatings have evolved from simple passive protective layers into complex, functional surface systems capable of dictating interactions at the material–environment interface

Functional coatings have evolved from their early role as passive barriers against corrosion and wear into engineered interfaces that actively mediate the interaction between a bulk material and its environment. This review traces the evolution of coating technologies from traditional macroscopic protective layers to nanoscale and multifunctional systems, and finally to smart and stimuli-responsive architectures. Advanced deposition and surface modification techniques are examined, including atomic layer deposition, physical vapor deposition, electrochemical and sol–gel approaches. The discussion is structured around two complementary application domains: extreme energy environments, focusing on coatings developed for advanced nuclear systems, and modern medical implants, including bioactive and antimicrobial surfaces and drug-delivery interfaces. The review highlights that, despite the differences between reactor and biomedical environments, both sectors share a common set of design principles and challenges, including interfacial adhesion, mechanical durability, the dual role of nanostructuring, and the trade-off between architectural complexity and operational reliability. Long-term stability, scalability, and standardized validation remain key barriers to deployment, while data-driven design and the deliberate integration of multiple functions emerge as the principal directions for future development.