High-entropy films (HEFs) are of considerable interest in surface engineering applications due to their superior properties, such as good corrosion resistance, good thermal stability and excellent high temperature oxidation. Recently, the scientific community has seen an increasing development of the multicomponent coatings, improving their properties compared to conventional films. Technically, different strategies have been exploited to fabricate HEFs. Magnetron-sputtered HEFs have made significant advancements in this field. HEFs have various applications given their interesting performances. This article overviews the development and the outcome of HEFs prepared using the magnetron sputtering technique. The classification of HEFs is reported. The effect of magnetron sputtering parameters on the microstructural, mechanical, electrochemical and thermal properties of HEFs is also discussed. Applications of HEFs are reported in the last section.

Refractory high-entropy films (RHEFs), as multi-component materials, have garnered significant attention due to their potential use in high-temperature applications. RHEFs are endowed with unique microstructural and functional properties due to the use of refractory elements. In this review, we examine the recent state of research on RHEFs deposited by the magnetron sputtering technique. The microstructure of RHEFs has been analyzed/explored and the mechanical properties as well as the main hardening mechanisms of these films are discussed. Furthermore, functional properties such as resistance to corrosion and wear, electrical and irradiation performances, and high-temperature oxidation were evaluated. RHEFs can meet market demand in the field of engineering materials. However, many challenges, such as low ductility at room temperature, remain to be overcome. This review provides an overview of the strengths and weaknesses of RHEFs produced using magnetron sputtering.

The present work is based on the principle of biomass waste valorization. Brewer’s spent grains (BSG) come from breweries as by-products. Their huge amount of production on an industrial scale should focus our attention on their valorization, which creates challenges as well as opportunities. One way to valorize BSG by-products is to convert them into biochar, a functional material with multiple potential applications. With an emphasis on sustainable development and the circular economy, in this work, we focused on a comparative study of the different mechanical processes of BSG grinding and their effect on the resulting biochar formed after pyrolysis. Home appliances such as blenders, coffee mills, and mortar and pestles were used for this purpose. FESEM images confirmed the successful creation of five different morphologies from the same BSG under the same pyrolysis conditions. Interestingly, a novel Chinese tea leaf egg-like biochar was also formed. It was found that a series of physical pretreatments of the biomass resulted in the reduced roughness of the biochar surface, i.e., they became smoother, thus negatively affecting the quality of the biochar. XRD revealed that the biomass physical treatments were also reflected in the crystallinity of some biochar. Via a Raman study, we witnessed the effect of mechanical pressure on the biomass for affecting the biochar features through pressure-induced modifications of the biomass’s internal structure. This induced enhanced biochar graphitization. This is a good example of the role of mechanochemistry. DSC revealed the thermochemical transformation of the five samples to be exothermic reactions. This study opens up an interesting possibility for the synthesis of biochar with controlled morphology, crystallinity, degree of graphitization, and heat capacity.

The LFPECVD (Low-Frequency Plasma-Enhanced Chemical Vapor Deposition) technique is now used on an industrial scale for the deposition of carbon-based coatings for several applications. This short review recalled the main principles of LFPECVD and provided examples of DLC-based films. The main differences between low-frequency (LF) and radio-frequency (RF) discharges were also recalled here and examples of deposition and characterization of carbon-based films were proposed. The influence of the bias voltage or the temperature of the active electrode on the deposition rate and the structure of a-C: H films obtained in cyclohexane/hydrogen mixtures was first discussed. Next, the properties of carbon-based films doped with silicon were described and, finally, it was shown that multilayer architectures make it possible to reduce the stresses without altering their tribological properties.