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The continuous growth in the use of preimpregnated semielaborated products to manufacture continuous carbon fiber-reinforced polymer parts has led the industry to face an important challenge in the management of the prepreg scrap, as the amount of waste produced can reach almost 75% due to the inefficiency of the cutting phase. In this context, this industry is pushed to move toward a circular economy approach by conferring a new use to their waste. The main problem arises from the fact that shortening carbon fiber leads to nonefficient mechanical reinforcement and that other thermal or chemical recycling approaches are environmentally hazardous. In this work, mechanical recycling of carbon fiber prepregs from expired virgin prepregs or scrap from an automated manufacturing operation is proposed as an economical and environmentally efficient method to obtain multifunctional coatings with Joule effect heating capabilities, which are demanded by different industries as a high-value product. As a coating, mechanical performance is not so relevant; nevertheless, obtaining high electrical conductivity by the incorporation of proper size and distributed short recycled carbon fiber can lead to a self-heating coating that could be used for anti- and deicing purposes or any other thermally activated function with very low power consumption. In this way, electrical conductivities up to 2 S/m were obtained, which allowed for achieving temperatures of 200 °C by the Joule effect in all samples in less than 17 s by the application of voltages below 48 V for bulk materials and 100 V for the coating., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

The pursuit of efficient, profitable, and ecofriendly materials has defined solar cell research from its inception to today. Some materials, such as copper nitride (Cu 3 N), show great promise for promoting sustainable solar technologies. This study employed reactive radio-frequency magnetron sputtering using a pure nitrogen environment to fabricate quality Cu 3 N thin films to evaluate how both temperature and gas working pressure affect their solar absorption capabilities. Several characterization techniques, including X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), Raman spectroscopy, scanning electron microscopy (SEM), nanoindentation, and photothermal deflection spectroscopy (PDS), were used to determine the main properties of the thin films. The results indicated that, at room temperature, it is possible to obtain a material that is close to stoichiometric Cu 3 N material (Cu/N ratio ≈ 3) with (100) preferred orientation, which was lost as the substrate temperature increases, demonstrating a clear influence of this parameter on the film structure attributed to nitrogen re-emission at higher temperatures. Raman microscopy confirmed the formation of Cu-N bonds within the 628-637 cm -1 range. In addition, the temperature and the working pressure significantly also influence the film hardness and the grain size, affecting the elastic modulus. Finally, the optical properties revealed suitable properties at lower temperatures, including bandgap values, refractive index, and Urbach energy. These findings underscore the potential of Cu 3 N thin films in solar energy due to their advantageous properties and resilience against defects. This research paves the way for future advancements in efficient and sustainable solar technologies.

The influence of the average surface area of different graphene nanoplatelets (GNP) on the thermo-electrical behaviour, associated with Joule heating, and the attenuation of electromagnetic signals of epoxy composites has been studied, analysing the effect of the morphology obtained as a function of the dispersion time by ultrasonication and the GNP content added. Gravity moulding was used as the first stage in the scaling-up, oriented to the industrial manufacture of multilayer coatings, observing a preferential self-orientation of nanoparticles and, in several conditions, a self-stratification too. The increase of sonication time during the GNP dispersion provides a decrease in the electrical conductivity, due to the GNP fragmentation. Instead, the thermal conductivity is enhanced due to the higher homogeneous distribution of GNPs into the epoxy matrix. Finally, the lower surface area of GNPs reduces the thermal and electrical conductivity due to a greater separation between nanosheets. Regarding the study of the attenuation of electromagnetic waves, it has been discovered that in the frequency range from 100 Hz to 20 MHz, this attenuation is independent of the direction of analysis, the type of graphene, the sonication time, and the state of dispersion of the nano-reinforcement in the matrix. Furthermore, it has also been observed that the conservation of the constant shielding values for the three types of GNPs are in a range of average frequencies between 0.3 and 3 MHz.