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In this work, a plasma-assisted solvolysis method is proposed as an alternative method for the oxidative degradation of carbon fiber-reinforced composites (CFRCs). Nitrogen plasma ignition within bubbles in a concentrated nitric acid solution is employed, combining the synergistic effects of traditional nitric acid solvolysis and plasma chemistry. A comprehensive process flowchart, including steps such as composite pretreatment, matrix dissolution, fiber recovery and cleaning, solvent regeneration and reuse, and waste treatment, is also discussed, highlighting their importance in process effectiveness. Moreover, a study on the effect of the composite's mass on the plasma-enhanced solvolysis process is conducted, and the results are exploited for the calculation of critical parameters such as efficiency, recovery rates, capacity, fibers quality, energy consumption, consumption of raw materials, operational and installation costs, and environmental impact. A preliminary comparison to other recycling methods based on the literature findings is also attempted, and preliminary metrics to assess the sustainability of the recycling process are proposed. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) of composite materials is promising to create customizable products with enhanced properties, utilizing materials like carbon fibers (CFs). To increase their circularity, composite recycling has been proposed to re-introduce the recovered components in AM. A careful evaluation of recycling is necessary, considering the sustainability and functionality (i.e., mechanical properties) of the recovered components. Thus, Life Cycle Assessment (LCA) is applied to estimate the environmental impacts of AM via Fused Filament Fabrication (FFF), using virgin or recycled CFs via solvolysis at a laboratory scale. This study aims to provide a detailed Life Cycle Inventory (LCI) of FFF and evaluate the sustainability of using recycled CFs in AM. For both virgin CF manufacturing and CF recycling, electricity consumption was the main contributor to environmental impacts. CF recovery via solvolysis resulted in lower impacts across most impact categories compared to AM with virgin CFs. Different scenarios were examined to account for the mechanical properties of recycled CFs. AM with 75% recycled CFs, compared to 100% virgin CFs undergoing landfilling, resulted in over 22% reduction in climate change potential, even after a 50% loss of recycled CF functionality. Overall, this study offers insights into the LCI of FFF and shows that CF recycling from composites is worth pursuing. [ABSTRACT FROM AUTHOR]

We clarify the difference between the SiH4 consumption efficiency η and the SiH4 depletion fraction D, as measured in the pumping line and the actual reactor of an industrial plasma-enhanced chemical vapor deposition system. In the absence of significant polysilane and powder formation, η is proportional to the film growth rate. Above a certain powder formation threshold, any additional amount of SiH4 consumed translates into increased powder formation rather than into a faster growing Si film. In order to discuss a zero-dimensional analytical model and a two-dimensional numerical model, we measure η as a function of the radio frequency (RF) power density coupled into the plasma, the total gas flow rate, the input SiH4 concentration, and the reactor pressure. The adjunction of a small trimethylboron flow rate increases η and reduces the formation of powder, while the adjunction of a small disilane flow rate decreases η and favors the formation of powder. Unlike η, D is a location-dependent quantity. It is related to the SiH4 concentration in the plasma cp, and to the phase of the growing Si film, whether the substrate is glass or a c-Si wafer. In order to investigate transient effects due to the RF matching, the precoating of reactor walls, or the introduction of a purifier in the gas line, we measure the gas residence time and acquire time-resolved SiH4 density measurements throughout the ignition and the termination of a plasma. [ABSTRACT FROM AUTHOR]

Transparent polycrystalline TiO 2 thin films have been deposited on unheated glass substrates using RF reactive magnetron sputtering. Depositions were carried out at different glancing angles and with different total gas mixture pressures. The variation of these parameters affected the crystal phase composition and the surface morphology. Depending on the glancing angle and the pressure, rutile, mixed anatase/ rutile and pure anatase were deposited at low substrate temperature. Both hydrophilic and hydrophobic TiO 2 were obtained, exhibiting fast photoconversion to superhydrophilic upon UV irradiation. The effect of the materials physicochemical properties on the wettability and rate of the UV induced superhydrophilicity is evaluated.