Aikaterini-Flora Trompeta

The growing volume of fiber-reinforced polymer composite waste creates an urgent need for efficient recycling technologies. While solvolysis effectively breaks down thermoset matrices for fiber reinforcement recovery, the process generates hydrocarbon-rich liquid by-products that require further management. This study validates the use of these liquid recycling streams—derived from the solvolysis of unsaturated polyester and epoxy resins—as sustainable carbon precursors for the growth of carbon nanomaterials. Synthesis was performed via catalytic chemical vapor deposition (CVD) at 850 °C using iron nanoparticles impregnated on a zeolite substrate. Morphological analysis confirmed the production of one-dimensional nanostructures (carbon nanotubes/nanofibers), with average diameters below 100 nm. Raman spectroscopy revealed a high degree of graphitization, with I_D/I_G ratios ranging from 0.25 to 0.58, which is comparable to structures synthesized from conventional precursors. Thermogravimetric analysis (TGA) demonstrated high thermal stability and carbon purity reaching up to 90.3%. These findings demonstrate a viable upcycling pathway that enhances the economic attractiveness of composite recycling by transforming waste into advanced nanomaterials.

The growth of urban areas and climate change affect the performance of water management, increasing the rate of flooding and decreasing the quality of available water. To address this issue, the sustainable urban drainage systems (SUDs) and conventional urban drainage systems (UDIs) must be promoted. In both systems, grey infrastructure plays an important role, in the form of reinforced concrete tanks, filters, and water treatment plants. Nowadays, the use of reinforced concrete is a major contributor of the environmental impact of human activities environmental impacts. This study aims to assess the potential of nanoparticle-based concrete to mitigate the environmental impacts of water management facilities. To achieve this target, a comparative Life Cycle Assessment (LCA) analysis was performed on a multi walled carbon nanotubes (MWCNTs) based concrete, and a conventional one. To evaluate the corresponding benefits, a Functional Unit has been defined representing a frequently used element in water management facilities. The conducted review found no similar research. It is noted that the functional units used in published studies on nanoproducts are usually defined for the production of mass units. This study, found that using MWCNT-based concrete reduced the weight of the steel reinforcement by 47%. This reduction in steel outweighs the environmental impacts corresponding to used MWCNTs. The impact scores obtained are significantly lower for the MWCNT-based concrete. Therefore, the use of this material is recommended in Water management facilities, only on an environmental basis. Further investigation is recommended into the economic viability of this use.

The initial segment unfolds by expounding upon the foundational concepts of nanotechnology, tracing its historical evolution, delving into its normative framework of reference, and elucidating its diverse applications across various sectors, navigating the inherent challenges associated with nanotechnology.

In this paper, we explore a straightforward two-step method to produce high-purity, vertically aligned multi-walled carbon nanofibres (MWCNFs) via chemical vapor deposition (CVD). Two distinct solutions are utilized for this CVD method: a catalytic solution consisting of ferrocene and acetonitrile (ACN) and a carbon source solution with camphor and ACN. The vapors of the catalytic solution inserted in the reaction chamber through external boiling result in a floating catalyst CVD approach that produces vertically aligned CNFs in a consistent manner. CNFs are grown in a conventional CVD horizontal reactor at 850 °C under atmospheric pressure and characterized by Raman spectroscopy, scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Coating the MWCNTs with polymethyl methacrylate (PMMA) while still on the Si substrate retains the structure and results in a flexible, conductive thin film suitable for flexible electrodes. The film is 62 μm thick and stable in aqueous solutions, capable of withstanding further processing, such as electropolymerization with polyaniline, to be used for energy storage applications.

In this paper, we explore a straightforward two-step method to produce high purity, vertically aligned multi-walled carbon nanotubes (MWCNTs) via chemical vapor deposition (CVD). Two distinct solutions are utilized for this CVD method: a catalytic solution consisting of ferrocene and acetonitrile (ACN), and a carbon source solution with camphor and ACN. The vapors of the catalytic solution inserted in the reaction chamber through external boiling, result in a floating catalyst CVD approach that produces vertically aligned MWCNTs in a consistent manner. MWCNTs are grown in a conventional CVD horizontal reactor, at 850°C under atmospheric pressure, and characterized by Raman spectroscopy, Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). Coating the MWCNTs with polymethyl methacrylate (PMMA) while still on the Si substrate, retains the structure and results in a flexible, conductive thin film suitable for electrodes. The film is 62 μm thick and stable in aqueous solutions, capable of withstanding further processes such as electropolymerization with polyaniline, to be used for energy storage applications.

High electrical conductivity, along with high piezoresistive sensitivity and stretchability, are crucial for designing and developing nanocomposite strain sensors for damage sensing and on-line structural health monitoring of smart carbon fiber-reinforced polymer (CFRP) composites. In this study, the influence of the geometric features and loadings of carbon-based nanomaterials, including reduced graphene oxide (rGO) or carbon nanofibers (CNFs), on the tunable strain-sensing capabilities of epoxy-based nanocomposites was investigated. This work revealed distinct strain-sensing behavior and sensitivities (gauge factor, GF) depending on both factors. The highest GF values were attained with 0.13 wt.% of rGO at various strains. The stability and reproducibility of the most promising self-sensing nanocomposites were also evaluated through ten stretching/relaxing cycles, and a distinct behavior was observed. While the deformation of the conductive network formed by rGO proved to be predominantly elastic and reversible, nanocomposite sensors containing 0.714 wt.% of CNFs showed that new conductive pathways were established between neighboring CNFs. Based on the best results, formulations were selected for the manufacturing of pre-impregnated materials and related smart CFRP composites. Digital image correlation was synchronized with electrical resistance variation to study the strain-sensing capabilities of modified CFRP composites (at 90° orientation). Promising results were achieved through the incorporation of CNFs since they are able to form new conductive pathways and penetrate between micrometer-sized fibers.

This review article gathers the most recent recycling technologies for thermoset and thermoplastic polymers. Results about existing experimental procedures and their effectiveness are presented. For thermoset polymers, the review focuses mainly on fibre-reinforced polymer composites, with an emphasis on epoxy-based systems and carbon/glass fibres as reinforcement, due to the environmental concerns of their end-of-life management. Thermal processes (fluidised bed, pyrolysis) and chemical processes (different types of solvolysis) are discussed. The most recent combined processes (microwave, steam, and ultrasonic assisted techniques) and extraordinary recycling attempts (electrochemical, biological, and with ionic liquids) are analysed. Mechanical recycling that leads to the downgrading of materials is excluded. Insights are also given for the upcycling methodologies that have been implemented until now for the reuse of fibres. As for thermoplastic polymers, the most state-of-the-art recycling approach for the most common polymer matrices is presented, together with the appropriate additivation for matrix upcycling. Mechanical, chemical, and enzymatic recycling processes are described, among others. The use of fibre-reinforced thermoplastic composites is quite new, and thus, the most recent achievements are presented. With all of the above information, this extensive review can serve as a guide for educational purposes, targeting students and technicians in polymers recycling.

In the present study, a series of carbon-based nanocomposites based on recycled thermoplastic polyurethane (TPU) matrix and MWCNT fillers synthesized in a laboratory environment were prepared at various loadings and assessed in terms of their functional thermal, dielectric, and rheological properties, as well as their ohmic heating capability, for self-healing applications in extrusion-based 3D printing technologies. The synthesis of nanomaterials focused on the production of two different types of carbon nanotubes (CNTs) via the chemical vapor deposition (CVD) method. A comparative assessment and benchmarking were conducted with nanocomposite filaments obtained from commercial nanomaterials and masterbatches with MWCNTs. For all the polymer nanocomposites, samples were prepared at additive contents up to 15 wt.% and filament feedstock was produced via the melt-extrusion process for 3D printing; these were previously characterized by rheological tests. The measurements of thermal and electrical conductivity resulted in a selected composition with promising ohmic heating capability. As a preliminary assessment of the self-healing ability of the above samples, artificial cracks were introduced on the surface of the samples and SEM analysis took place at the crack location before and after applying voltage as a measure of the effectiveness of the material remelting due to the Joule effect. Results indicate a promising material response with a partial restoration of artificial cracks.