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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.

In the present study, the feasibility to achieve localized induction heating and debonding of multi-material composite structures is assessed in testing coupons prepared by Automated Fiber Placement (AFP) and extrusion-based additive manufacturing (AM) technologies. Nano-compounds of Polyether-ketone-ketone (PEKK) with iron oxide nanoparticles acting as electromagnetic susceptors have been processed in a parallel co-rotating twin-screw extruder to produce filament feedstock for extrusion-based AM. The integration of nanocomposite interlayers as discrete debonding zones (DZ) by AFP-AM manufacturing has been investigated for two types of sandwich-structured laminate composites, i.e., laminate-DZ-laminate panels (Type I) and laminate-DZ-AM gyroid structures (Type II). Specimens were exposed to an alternating magnetic field generated by a radio frequency generator and a flat spiral copper induction coil, and induction heating parameters (frequency, power, heating time, sample standoff distance from coil) have been investigated in correlation with real-time thermal imaging to define the debonding process window without compromising laminate quality. For the optimized process parameters, i.e., 2–3 kW generator power and 20–25 mm standoff distance, corresponding to magnetic field intensities in the range of 3–5 kA m−1, specimens were effectively heated above PEKK melting temperature, exhibiting high heating rates within the range of 5.3–9.4 °C/s (Type I) and 8.0–17.5 °C/s (Type II). The results demonstrated that localized induction heating successfully facilitated debonding, leading to full unzipping of the debonding zones in both laminate structures. Further insight on PEKK nanocomposites debonding performance was provided by thermal, morphological characterization and non-destructive inspection via X-ray micro-computed tomography at different processing stages. The developed framework aims to contribute to the development of rapid, on-demand joining, repair and disassembly technologies for thermoplastic composites, towards more efficient maintenance, repair and overhaul operations in the aviation sector and beyond.

Sustainability, safety and service life expansion in the construction sector have gained a lot of scientific and technological interest during the last few decades. In this direction, the synthesis and characterization of smart cementitious composites with tailored properties combining mechanical integrity and self-sensing capabilities have been in the spotlight for quite some time now. The key property for the determination of self-sensing behavior is the electrical resistivity and, more specifically, the determination of reversible changes in the electrical resistivity with applied stress, which is known as piezoresistivity. In this study, the mechanical and piezoresistive properties of mortars reinforced with carbon nanotubes (CNTs) and carbon micro-fibers (CMFs) are determined. Silica fume and a polymer with polyalkylene glycol graft chains were used as dispersant agents for the incorporation of the CNTs and CMFs into the cement paste. The mechanical properties of the mortar composites were investigated with respect to their flexural and compressive strength. A four-probe method was used for the estimation of their piezoresistive response. The test outcomes revealed that the combination of the dispersant agents along with a low content of CNTs and CMFs by weight of cement (bwoc) results in the production of a stronger mortar with enhanced mechanical performance and durability. More specifically, there was an increase in flexural and compressive strength of up to 38% and 88%, respectively. Moreover, mortar composites loaded with 0.4% CMF bwoc and 0.05% CNTs bwoc revealed a smooth and reversible change in electrical resistivity vs. compression loading—with unloading comprising a strong indication of self-sensing behavior. This work aims to accelerate progress in the field of material development with structural sensing and electrical actuation via providing a deeper insight into the correlation among cementitious composite preparation, admixture dispersion quality, cementitious composite microstructure and mechanical and self-sensing properties.

The possibility of directly growing carbon nanofibers (CNFs) and carbon nanotubes (CNTs) on half-Heusler alloys by Chemical Vapour Deposition (CVD) is investigated for the first time, without using additional catalysts, since the half-Heusler alloys per se may function as catalytic substrates, according to the findings of the current study. As a carbon source, acetylene is used in the temperature range of 700–750 °C. The n-type half-Heusler compound Zr0.4Ti0.60.33Ni0.33Sn0.98Sb0.020.33 is utilized as the catalytic substrate. At first, a computational model is developed for the CVD reactor, aiming to optimize the experimental process design and setup. The experimental process conditions are simulated to investigate the reactive species concentrations within the reactor chamber and the activation of certain reactions. SEM analysis confirms the growth of CNFs with diameters ranging from 450 nm to 1 μm. Raman spectroscopy implies that the formed carbon structures resemble CNFs rather than CNTs, and that amorphous carbon also co-exists in the deposited samples. From the characterization results, it may be concluded that a short reaction time and a low acetylene flow rate lead to the formation of a uniform CNF coating on the surface of half-Heusler alloys. The purpose of depositing carbon nanostructures onto half-Heusler alloys is to improve the current transfer, generated from these thermoelectric compounds, by forming a conductive coating on their surface.

Introduction: Significant progress has been made in terms of best practice in research data management for nanosafety. Some of the underlying approaches to date are, however, overly focussed on the needs of specific research projects or aligned to a single data repository, and this “silo” approach is hampering their general adoption by the broader research community and individual labs.Methods: State-of-the-art data/knowledge collection, curation management FAIrification, and sharing solutions applied in the nanosafety field are reviewed focusing on unique features, which should be generalised and integrated into a functional FAIRification ecosystem that addresses the needs of both data generators and data (re)users.Results: The development of data capture templates has focussed on standardised single-endpoint Test Guidelines, which does not reflect the complexity of real laboratory processes, where multiple assays are interlinked into an overall study, and where non-standardised assays are developed to address novel research questions and probe mechanistic processes to generate the basis for read-across from one nanomaterial to another. By focussing on the needs of data providers and data users, we identify how existing tools and approaches can be re-framed to enable “on-the-fly” (meta) data definition, data capture, curation and FAIRification, that are sufficiently flexible to address the complexity in nanosafety research, yet harmonised enough to facilitate integration of datasets from different sources generated for different research purposes. By mapping the available tools for nanomaterials safety research (including nanomaterials characterisation, nonstandard (mechanistic-focussed) methods, measurement principles and experimental setup, environmental fate and requirements from new research foci such as safe and sustainable by design), a strategy for integration and bridging between silos is presented. The NanoCommons KnowledgeBase has shown how data from different sources can be integrated into a one-stop shop for searching, browsing and accessing data (without copying), and thus how to break the boundaries between data silos.Discussion: The next steps are to generalise the approach by defining a process to build consensus (meta)data standards, develop solutions to make (meta)data more machine actionable (on the fly ontology development) and establish a distributed FAIR data ecosystem maintained by the community beyond specific projects. Since other multidisciplinary domains might also struggle with data silofication, the learnings presented here may be transferrable to facilitate data sharing within other communities and support harmonization of approaches across disciplines to prepare the ground for cross-domain interoperability.

This study focuses on the development of a pilot-scale sizing line, including its initial design and installation, operational phases, and optimization of key process parameters. The primary objective is the identification of critical parameters for achieving a uniform sizing onto the fibres and the determination of optimal conditions for maximum production efficiency. This investigation focused on adjusting the furnace desizing temperature for the removal of commercial sizing, adjusting the drying temperature, as well as optimizing the corresponding residence time of carbon fibres passing through the furnaces. The highest production rate, reaching 1 m sized carbon fibres per minute, was achieved by employing a desizing temperature of 550 °C, a drying temperature of 250 °C, and a residence time of 1 min. Furthermore, a range of sizing solutions was investigated and formulated, exploring carbon-based nanomaterial types with different surface functionalizations and concentrations, to evaluate their impact on the surface morphology and mechanical properties of carbon fibres. In-depth analyses, including scanning electron microscopy and contact angle goniometry, revealed the achievement of a uniform coating on the carbon fibre surface, leading to an enhanced affinity between fibres and the polymeric epoxy matrix. The incorporation of nanomaterials, specifically N2-plasma-functionalized carbon nanotubes and few-layer graphene, demonstrated notable improvements in the interfacial shear properties (90% increase), verified by mechanical and push-out tests.

With an ever-increasing material and design space available for Fused Filament Fabrication (FFF) technology, fabrication of complex three-dimensional structures with functional performance offers unique opportunities for product customization and performance-driven design. However, ensuring the quality and functionality of FFF-printed parts remains a significant challenge, as material-, process-, and system-level factors introduce variability and potentially hinder the translation of bulk material properties in the respective FFF counterparts. To this end, the present study presents a methodological framework for assessing the influence of process parameters on FFF strand stability and functional performance through a systematic analysis of FFF structural elements (1D stacks of FFF strands and 3D blocks), in terms of dimensional deviation from nominal geometry and resistivity, corresponding to the printability and functionality attributes, respectively. The influence of printing parameters on strand stability was investigated in terms of dimensional accuracy and surface morphology, employing optical microscopy and micro-computed tomography (mCT) for dimensional deviation analysis. In parallel, electrical resistance measurements were carried out to assess the effect of different process parameter combinations and toolpath patterns on functional performance. In low-level structural elements, strand height (H) was found to induce the greatest influence on FFF strand dimensional accuracy and resistivity, with higher H values leading to a reduction in resistivity of up to 38% in comparison with filament feedstock; however, this occurred at the cost of increased dimensional deviation. At higher structural levels, the overall effect of process parameters was found to be less pronounced, indicating that the translation of 1D strand properties to 3D blocks is subject to a trade-off due to competing mechanisms that facilitate/hinder current flow. Overall, the proposed framework enables the quantification of the influence of process parameters on the selected response variables, contributing to the development of standard operating procedures and recommendations for selecting optimal process parameters to achieve the desired process stability and functional performance in FFF.

Abstract Background The widespread use of nano-biomaterials (NBMs) has increased the chance of human exposure. Although ingestion is one of the major routes of exposure to NBMs, it is not thoroughly studied to date. NBMs are expected to be dramatically modified following the transit into the oral-gastric-intestinal (OGI) tract. How these transformations affect their interaction with intestinal cells is still poorly understood. NBMs of different chemical nature—lipid-surfactant nanoparticles (LSNPs), carbon nanoparticles (CNPs), surface modified Fe3O4 nanoparticles (FNPs) and hydroxyapatite nanoparticles (HNPs)—were treated in a simulated human digestive system (SHDS) and then characterised. The biological effects of SHDS-treated and untreated NBMs were evaluated on primary (HCoEpiC) and immortalised (Caco-2, HCT116) epithelial intestinal cells and on an intestinal barrier model. Results The application of the in vitro SDHS modified the biocompatibility of NBMs on gastrointestinal cells. The differences between SHDS-treated and untreated NBMs could be attributed to the irreversible modification of the NBMs in the SHDS. Aggregation was detected for all NBMs regardless of their chemical nature, while pH- or enzyme-mediated partial degradation was detected for hydroxyapatite or polymer-coated iron oxide nanoparticles and lipid nanoparticles, respectively. The formation of a bio-corona, which contains proteases, was also demonstrated on all the analysed NBMs. In viability assays, undifferentiated primary cells were more sensitive than immortalised cells to digested NBMs, but neither pristine nor treated NBMs affected the intestinal barrier viability and permeability. SHDS-treated NBMs up-regulated the tight junction genes (claudin 3 and 5, occludin, zonula occludens 1) in intestinal barrier, with different patterns between each NBM, and increase the expression of both pro- and anti-inflammatory cytokines (IL-1β, TNF-α, IL-22, IL-10). Notably, none of these NBMs showed any significant genotoxic effect. Conclusions Overall, the results add a piece of evidence on the importance of applying validated in vitro SHDS models for the assessment of NBM intestinal toxicity/biocompatibility. We propose the association of chemical and microscopic characterization, SHDS and in vitro tests on both immortalised and primary cells as a robust screening pipeline useful to monitor the changes in the physico-chemical properties of ingested NBMs and their effects on intestinal cells.

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.

The generation of 3D structures comprises three interlinked phases: material development, the printing process, and post-printing treatment. Numerous factors control all three phases, making the optimization of the entire process a challenging task. Until now, the state of the art has mainly focused on optimizing material processability and calibration of the printing process. However, after the successful Direct Ink Writing (DIW) of a hydrogel scaffold, the post-printing stage holds equal importance, as this allows for the treatment of the structure to ensure the preservation of its structural integrity for a duration that is sufficient to enable successful cell attachment and proliferation before undergoing degradation. Despite this stage’s pivotal role, there is a lack of extensive literature covering its optimization. By studying the crosslinking factors and leveling the post-treatment settings of alginate–gelatin hydrogel, this study proposes a method to enhance scaffolds’ degradation without compromising the targeted swelling behavior. It introduces an experimental design implementing the Response Surface Methodology (RSM) Design of Experiments (DoE), which elucidated the key parameters influencing scaffold degradation and swelling, and established an alginate ratio of 8% and being immersed for 15 min in 0.248 M CaCl2 as the optimal level configuration that generates a solution of 0.964 desirability, reaching a degradation time of 19.654 days and the swelling ratio of 50.00%.

Direct Ink Writing (DIW), which is widely used for developing functional 3D scaffolds that have robust structural integrity for the growth of target tissues/cells, has emerged as an appealing method for biomedical applications. The production of 3D structures involves three separate but interconnected stages (material development, printing process, and post-printing treatment), whose effectiveness is influenced by several factors that therefore make it challenging to optimize the entire procedure. By studying the material processability and leveling the printing settings, this study proposes a three-step method to enhance the ink property design and the printer’s performance. The recommended approach is focused on the thorough study of alginate–gelatin hydrogel properties, which is a commonly used ink in biomedical applications, due to its natural origin through marine flora, as well as the development process parameters and their intercorrelations. Principal Component Analysis in comparison with K-means clustering was applied to reveal material properties that are highly correlated with additive manufacturing (AM) processability, and Taguchi’s Design of Experiments (DOE) determined the printing settings (primary and secondary) for achieving optimum printing accuracy. PCA results were affirmed by K-means clustering and showed that viscosity, m, G′ and G″ govern blends’ printing behavior while application of DOE led to 85% pore area printability.

Machine learning has been an emerging scientific field serving the modern multidisciplinary needs in the Materials Science and Manufacturing sector. The taxonomy and mapping of nanomaterial properties based on data analytics is going to ensure safe and green manufacturing with consciousness raised on effective resource management. The utilization of predictive modelling tools empowered with artificial intelligence (AI) has proposed novel paths in materials discovery and optimization, while it can further stimulate the cutting-edge and data-driven design of a tailored behavioral profile of nanomaterials to serve the special needs of application environments. The previous knowledge of the physics and mathematical representation of material behaviors, as well as the utilization of already generated testing data, received specific attention by scientists. However, the exploration of available information is not always manageable, and machine intelligence can efficiently (computational resources, time) meet this challenge via high-throughput multidimensional search exploration capabilities. Moreover, the modelling of bio-chemical interactions with the environment and living organisms has been demonstrated to connect chemical structure with acute or tolerable effects upon exposure. Thus, in this review, a summary of recent computational developments is provided with the aim to cover excelling research and present challenges towards unbiased, decentralized, and data-driven decision-making, in relation to increased impact in the field of advanced nanomaterials manufacturing and nanoinformatics, and to indicate the steps required to realize rapid, safe, and circular-by-design nanomaterials.

Thermoplastic nanocomposites were fabricated in order to deliver a suitable material for thermal management devices, commonly processed by injection molding or 3D printing. Scalable manufacturing of Carbon Nanotubes (CNTs) and multi-functional polymers with good thermal conductivity and ease of handling was demonstrated in the present study. The standard grade polyethylene reinforced with CNTs, was formed by melt mixing. Polyethylene glycol was used for concentrating CNTs in a masterbatch for its plasticizing properties, ensuring safe handling and even dispersion of CNTs. Through characterization of morphology and thermal properties, an interconnected CNTs network was established, which enhanced the heat transfer at high concentration by changing the main conduction path from polymer crystal lattice to CNTs conductive network. Moreover, it was shown that modification in the matrix crystallinity is key to maximize the phonon and electron conduction interfaces and achieve advances in thermal conductivity beyond 68% and 100% achieved for 15 wt% content of CNTs compared to neat PE and PE@PEG matrices, respectively, within this study.

Carbon fiber reinforced polymer manufacturing is emerging, with multiple studies to focus on the design of interfacial reinforcement to ensure the maximum of composite properties, but also respectively to be able to align with zero defect manufacturing. The controversy on the engineering approach is a data-driven task that can be efficiently tackled by involving Artificial Intelligence in order to establish unbiased structure-property relations. In the present study, nanoindentation mapping data were processed with Machine Learning classification models to identify the interfacial reinforcement. The data preparation included normalization and sorting out of highly similar data with k-means clustering, since nanoindentation on epoxy matrix does not enhance insight on the mechanism of reinforcement. The trained models included neural networks, classification trees, and support vector machines. Realization of models' performance was evaluated on the test dataset as screening to obtain best fitted models for each algorithm. Transfer learning potential was demonstrated by extrapolating the prediction of best trained models to a validation dataset at different indentation depth with support vector machines outperforming the other models. Overall accuracy was 67% on the test dataset, F1 Score was 65% in the prediction of reinforcement mechanism classes and 72% in case of pristine specimen, while accuracy on validation dataset was 72.7%. Prediction metrics were comparable to other case studies of real-world classification problems. Computational time-cost for tuning and training was sustainable and equal to 2.3 min.

In this work we study the fabrication and characterization of hafnium nanoparticles and hafnium nanoparticle thin films. Hafnium nanoparticles were grown in vacuum by magnetron-sputtering inert-gas condensation. The as deposited nanoparticles have a hexagonal close-packed crystal structure, they possess truncated hexagonal biprism shape and are prone to surface oxidation when exposed to ambient air forming core–shell Hf/HfO2 structures. Hafnium nanoparticle thin films were formed through energetic nanoparticle deposition. This technique allows for the control of the energy of charged nanoparticles during vacuum deposition. The structural and nanomechanical properties of the nanoparticle thin films were investigated as a function of the kinetic energy of the nanoparticles. The results reveal that by proper adjustment of the nanoparticle energy, hexagonal close-packed porous nanoparticle thin films with good mechanical properties can be formed, without any additional treatment. It is shown that these films can be patterned on the substrate in sub-micrometer dimensions using conventional lithography while their porosity can be well controlled. The fabrication and experimental characterization of hafnium nanoparticles is reported for the first time in the literature.

This study was focused on the growth of multi-walled carbon nanotubes (MWCNTs) on iron chloride-functionalized silica microspheres. In addition, the microwave absorption potential and the subsequent heat production of the resulting structures were monitored by means of infrared thermometry and compared with pristine commercially available MWCNTs. The functionalized silica microparticle substrates produced MWCNTs without any amorphous carbon but with increased structural defects, whereas their heat production performance as microwave absorbents was comparable to that of the pristine MWCNTs. Two-minute microwave irradiation of the SiO2@CNTs structures resulted in an increase in the material’s temperature from ambient temperature up to 173 °C. This research puts forward a new idea of charge modulation of MWCNTs and sheds light on an investigation for the development of bifunctional materials with improved properties with respect to efficient microwave absorbance.

The present study focuses on the effect of two novel carbon fibre surface treatments, electropolymerisation of methacrylic acid and air pressure plasma, on the mechanical properties and structural integrity of carbon-fibre-reinforced composites under operational conditions. Extensive mechanical testing was applied, both in nano- and macro-scale, to assess the performance of the composites and the interphase properties after ultraviolet/humidity weathering. The results of the mechanical assessment are supported by structure, surface, and chemistry examination in order to reveal the failure mechanism of the composites. Composites with the electropolymerisation treatment exhibited an increase of 11.8% in interlaminar shear strength, while APP treatment improved the property of 23.9%, rendering both surface treatments effective in increasing the fibre-matrix adhesion. Finally, it was proven that the developed composites can withstand operational conditions in the long term, rendering them suitable for a wide variety of structural and engineering applications.

Silver nanoparticles (AgNPs) exert profound physicochemical, biological, and antimicrobial properties, therefore, they have been extensively studied for a variety of applications such as food packaging and cultural heritage protection. However, restrictions in their stability, aggregation phenomena, and toxicity limit their extensive use. Hence, the use of functional substrates that promote the silver nanoparticles’ growth and allow the formation of uniform-sized, evenly distributed, as well as stable nanoparticles, has been suggested. This study reports on the fabrication and the characterization of hydrophilic polymer spheres including nanoparticles with intrinsic antifungal properties. Poly (methacrylic acid) microspheres were synthesized, employing the distillation precipitation method, to provide monodisperse spherical substrates for the growth of silver nanoparticles, utilizing the co-precipitation of silver nitrate in aqueous media. The growth and the aggregation potential of the silver nanoparticles were studied, whereas the antifungal activity of the produced nanostructures was evaluated against the black mold-causing fungus Aspergillus niger. The produced structures exhibit dose-dependent antifungal activity. Therefore, they could potentially be employed for the protection and preservation of cultural heritage artifacts and considered as new agents for food protection from fungal contamination during storage.

This study focuses on the design, development, and validation of two coating systems for corrosion protection of hot dip galvanized steel substrates. The coatings consist of epoxy-based resin reinforced with core-shell microcapsules, either cerium oxide or cuprous oxide core and a polymeric shell doped with cerium ions. The effect of the modification of the epoxy resin with a liquid rubber polymer has also been studied. Corrosion studies via electrochemical impedance spectroscopy (EIS) revealed that the coatings have enhanced barrier properties. Moreover, EIS studies on coatings with artificial scribes, demonstrated an autonomous response to damage and a self-healing effect. Heat-induced material re-flow has also been observed after exposure to temperature higher than the Tg of the system, which offered an additional self-healing mechanism, partially inhibiting the underlying corrosion processes when the liquid rubber is present in the system.

This study aims to examine how core–shell super absorbent polymers (SAPs) can be effective in relation to recycling processes by using them as triggerable materials in coating binders. Super absorbent polymers are partially cross-linked, three-dimensional polymer networks that can absorb and retain water. Coatings based on an acrylic binder, including SAPs, were applied onto plastic substrates of acrylonitrile–butadiene–styrene/polycarbonate. The incorporation of 1 wt.% and 5 wt.% SAPs into the coatings resulted in the debonding of the coatings from the substrates under a steam treatment. The trigger mechanism for the core–shell hydrophilic SAPs relies on the different abilities of the core and shell materials to be swollen. Therefore, under the influence of steam, SAPs can enhance their shape due to water absorption and the breaking of the inorganic shell. This results in the reduction of the attachment between the primer layer and both the top coating and the substrate, thus enabling the detachment of the top coating from the corresponding substrate. The obtained results from this study can be considered as potential formulations for plastic recycling applications in industries.

The management of energy consumption in the building sector is of crucial concern for modern societies. Fossil fuels’ reduced availability, along with the environmental implications they cause, emphasize the necessity for the development of new technologies using renewable energy resources. Taking into account the growing resource shortages, as well as the ongoing deterioration of the environment, the building energy performance improvement using phase change materials (PCMs) is considered as a solution that could balance the energy supply together with the corresponding demand. Thermal energy storage systems with PCMs have been investigated for several building applications as they constitute a promising and sustainable method for reduction of fuel and electrical energy consumption, while maintaining a comfortable environment in the building envelope. These compounds can be incorporated into building construction materials and provide passive thermal sufficiency, or they can be used in heating, ventilation, and air conditioning systems, domestic hot water applications, etc. This study presents the principles of latent heat thermal energy storage systems with PCMs. Furthermore, the materials that can be used as PCMs, together with the most effective methods for improving their thermal performance, as well as various passive applications in the building sector, are also highlighted. Finally, special attention is given to the encapsulated PCMs that are composed of the core material, which is the PCM, and the shell material, which can be inorganic or organic, and their utilization inside constructional materials.

Cementitious structures have prevailed worldwide and are expected to exhibit further growth in the future. Nevertheless, cement cracking is an issue that needs to be addressed in order to enhance structure durability and sustainability especially when exposed to aggressive environments. The purpose of this work was to examine the impact of the Superabsorbent Polymers (SAPs) incorporation into cementitious composite materials (mortars) with respect to their structure (hybrid structure consisting of organic core—inorganic shell) and evaluate the microstructure and self-healing properties of the obtained mortars. The applied SAPs were tailored to maintain their functionality in the cementitious environment. Control and mortar/SAPs specimens with two different SAPs concentrations (1 and 2% bwoc) were molded and their mechanical properties were determined according to EN 196-1, while their microstructure and self-healing behavior were evaluated via microCT. Compressive strength, a key property for mortars, which often degrades with SAPs incorporation, in this work, practically remained intact for all specimens. This is coherent with the porosity reduction and the narrower range of pore size distribution for the mortar/SAPs specimens as determined via microCT. Moreover, the self-healing behavior of mortar-SAPs specimens was enhanced up to 60% compared to control specimens. Conclusively, the overall SAPs functionality in cementitious-based materials was optimized.

The aim of this study is to synthesize an organic core-shell co-polymer with a different glass transition temperature (Tg) between the core and the shell that can be used for several applications such as the selective debonding of coatings or the release of encapsulated materials. The co-polymer was synthesized using free radical polymerization and was characterized with respect to its morphology, composition and thermal behavior. The obtained results confirmed the successful synthesis of the co-polymer copolymer poly(methyl methacrylate)@poly(methacrylic acid-co-ethylene glycol dimethacrylate), PMMA@P(MAA-co-EGDMA), which can be used along with water-based solvents. Furthermore, the Tg of the polymer’s core PMMA was 104 °C, while the Tg of the shell P(MAA-co-EGDMA) was 228 °C, making it appropriate for a wide variety of applications. It is worth mentioning that by following this specific experimental procedure, methacrylic acid was copolymerized in water, as the shell of the copolymer, without forming a gel-like structure (hydrogel), as happens when a monomer is polymerized in aqueous media, such as in the case of super-absorbent polymers. Moreover, the addition and subsequent polymerization of the monomer methyl methacrylate (MAA) into the mixture of the already polymerized PMMA resulted in a material that was uniform in size, without any agglomerations or sediments.

In the present work, an assessment of the corrosion behavior of mild steel in the presence of an organic corrosion inhibitor loaded into hybrid composite materials is performed. Hybrid organic–inorganic nanocontainers based on cerium and titanium oxides were fabricated via a combination of radical polymerization together with the coprecipitation method and sol-gel technique. The corrosion inhibition role of these hybrid materials loaded with an inhibitor is considered. A set of characterization assays addressing morphology, composition and structural aspects of the exposed steels is illustrated, along with electrochemical evaluations. The results reveal enhanced stimuli responsive anticorrosion ability of the produced hybrid materials. Furthermore, upon corrosion, new compounds are formed onto the exposed areas of the treated metals. The conducted experiments shed light on the corrosion mechanisms for steel alloys as well as the actuation of the fabricated composite materials, paving the way for future developments in this area.

Life cycle assessment is a methodology to assess environmental impacts associated with a product or system/process by accounting resource requirements and emissions over its life cycle. The life cycle consists of four stages: material production, manufacturing, use, and end-of-life. This study highlights the need to conduct life cycle assessment (LCA) early in the new product development process, as a means to assess and evaluate the environmental impacts of (nano)enhanced carbon fibre-reinforced polymer (CFRP) prototypes over their entire life cycle. These prototypes, namely SleekFast sailing boat and handbrake lever, were manufactured by functionalized carbon fibre fabric and modified epoxy resin with multi-walled carbon nanotubes (MWCNTs). The environmental impacts of both have been assessed via LCA with a functional unit of ‘1 product piece’. Climate change has been selected as the key impact indicator for hotspot identification (kg CO2 eq). Significant focus has been given to the end-of-life phase by assessing different recycling scenarios. In addition, the respective life cycle inventories (LCIs) are provided, enabling the identification of resource hot spots and quantifying the environmental benefits of end-of-life options.

Bioinspired scaffolds mimicking natural bone-tissue properties holds great promise in tissue engineering applications towards bone regeneration. Within this work, a way to reinforce mechanical behavior of bioinspired bone scaffolds was examined by applying a physical crosslinking method. Scaffolds consisted of hydroxyapatite nanocrystals, biomimetically synthesized in the presence of collagen and l-arginine. Scaffolds were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), microcomputed tomography, and nanoindentation. Results revealed scaffolds with bone-like nanostructure and composition, thus an inherent enhanced cytocompatibility. Evaluation of porosity proved the development of interconnected porous network with bimodal pore size distribution. Mechanical reinforcement was achieved through physical crosslinking with riboflavin irradiation, and nanoindentation tests indicated that within the experimental conditions of 45% humidity and 37 °C, photo-crosslinking led to an increase in the scaffold’s mechanical properties. Elastic modulus and hardness were augmented, and specifically elastic modulus values were doubled, approaching equivalent values of trabecular bone. Cytocompatibility of the scaffolds was assessed using MG63 human osteosarcoma cells. Cell viability was evaluated by double staining and MTT assay, while attachment and morphology were investigated by SEM. The results suggested that scaffolds provided a cell friendly environment with high levels of viability, thus supporting cell attachment, spreading and proliferation.

Carbon Fibres (CFs) are widely used in textile-reinforced composites for the construction of lightweight, durable structures. Since their inert surface does not allow effective bonding with the matrix material, the surface treatment of fibres is suggested to improve the adhesion between the two. In the present study, different surface modifications are compared in terms of the mechanical enhancement that they can offer to the fibres. Two main advanced technologies have been investigated; namely, plasma treatment and electrochemical treatment. Specifically, active screen plasma and low-pressure plasma were compared. Regarding the electrochemical modification, electrochemical oxidation and electropolymerisation of monomer solutions of acrylic and methacrylic acids, acrylonitrile and N-vinyl pyrrolidine were tested for HTA-40 CFs. In order to assess the effects of the surface treatments, the morphology, the physicochemical properties, as well as the mechanical integrity of the fibres were investigated. The CF surface and polymeric matrix interphase adhesion in composites were also analysed. The improvement of the carbon fibre’s physical–mechanical properties was evident for the case of the active screen plasma treatment and the electrochemical oxidation.

The aim of this work is to review a possible correlation of composition, thermal processing, and recent alternative stabilization technologies to the mechanical properties. The chemical microstructure of polyacrylonitrile (PAN) is discussed in detail to understand the influence in thermomechanical properties during stabilization by observing transformation from thermoplastic to ladder polymer. In addition, relevant literature data are used to understand the comonomer composition effect on mechanical properties. Technologies of direct fiber heating by irradiation have been recently involved and hold promise to enhance performance, reduce processing time and energy consumption. Carbon fiber manufacturing can provide benefits by using higher comonomer ratios, similar to textile grade or melt-spun PAN, in order to cut costs derived from an acrylonitrile precursor, without suffering in regard to mechanical properties. Energy intensive processes of stabilization and carbonization remain a challenging field of research in order to reduce both environmental impact and cost of the wide commercialization of carbon fibers (CFs) to enable their broad application.

Nanoindentation was utilized as a non-destructive technique to identify Portland Cement hydration phases. Artificial Intelligence (AI) and semi-supervised Machine Learning (ML) were used for knowledge gain on the effect of carbon nanotubes to nanomechanics in novel cement formulations. Data labelling is performed with unsupervised ML with k-means clustering. Supervised ML classification is used in order to predict the hydration products composition and 97.6% accuracy was achieved. Analysis included multiple nanoindentation raw data variables, and required less time to execute than conventional single component probability density analysis (PDA). Also, PDA was less informative than ML regarding information exchange and re-usability of input in design predictions. In principle, ML is the appropriate science for predictive modeling, such as cement phase identification and facilitates the acquisition of precise results. This study introduces unbiased structure-property relations with ML to monitor cement durability based on cement phases nanomechanics compared to PDA, which offers a solution based on local optima of a multidimensional space solution. Evaluation of nanomaterials inclusion in composite reinforcement using semi-supervised ML was proved feasible. This methodology is expected to contribute to design informatics due to the high prediction metrics, which holds promise for the transfer learning potential of these models for studying other novel cement formulations.

The design and synthesis of new biomaterials with adjustable physicochemical and biological properties for tissue engineering applications have attracted great interest. In this work, chitosan-graft-poly(l-lactide) (CS-g-PLLA) copolymers were prepared by chemically binding poly(l-lactide) (PLLA) chains along chitosan (CS) via the “grafting to” approach to obtain hybrid biomaterials that present enhanced mechanical stability, due to the presence of PLLA, and high bioactivity, conferred by CS. Two graft copolymers were prepared, CS-g-PLLA(80/20) and CS-g-PLLA(50/50), containing 82 wt % and 55 wt % CS, respectively. Degradation studies of compressed discs of the copolymers showed that the degradation rate increased with the CS content of the copolymer. Nanomechanical studies in the dry state indicated that the copolymer with the higher CS content had larger Young modulus, reduced modulus and hardness values, whereas the moduli and hardness decreased rapidly following immersion of the copolymer discs in alpha-MEM cell culture medium for 24 h. Finally, the bioactivity of the hybrid copolymers was evaluated in the adhesion and growth of MC3T3-E1 pre-osteoblastic cells. In vitro studies showed that MC3T3-E1 cells exhibited strong adhesion on both CS-g-PLLA graft copolymer films from the first day in cell culture, whereas the copolymer with the higher PLLA content, CS-g-PLLA(50/50), supported higher cell growth.

Mild or low-carbon steel has an increasing utilization and is widely used for building construction, machinery parts, and pipelines, because it can be machined easily and has enhanced weldability as well as a low price. In any case, the corrosion resistance of mild steel under the conditions in industrial applications or in atmosphere is a thoughtful concern. This study inquires into the application of 2-mecraptobenzothiazole (MBT) and Na2HPO4 as corrosion inhibitors for the protection of API 5L X42 pipeline steel in 3.5 wt % NaCl as well as in water from the Athens city supply system. The electrochemical/morphological characterizations of the aforementioned mild steel proved that the corrosion protection mechanisms can be assigned to the protective layers created onto the metal surface because of the presence of the inhibitors, which prevent chloride’s penetration. The synergistic effect of the MBT and Na2HPO4 corrosion inhibition behavior, in a molar ratio of 1:1, revealed that the additives performed effectively with corrosion inhibition efficiency above 90%.

Epoxy composites are widely used in primary aerospace structures, where high impact damage properties are necessary. However, challenges appear when multiple functionalities, including electrical and thermal conductivity, are needed in parallel with increased mechanical properties. The current study aims at the assessment of a critical concentration of multiwalled carbon nanotubes (MWCNTs), incorporated in epoxy resin, which will indicate a threshold for optimal electrical, thermal and mechanical properties. For the evaluation of this optimal concentration, electrical conductivity, thermal stability and nanomechanical properties (Young modulus and nanohardness) have been assessed, for epoxy nanocomposites with 0 to 15 parts per hundred resin per weight (phr) MWCNTs. Percolation theory was applied to study the electrical conductivity for different contents of MWCNTs in the epoxy nanocomposite system. Thermogravimetric analysis was employed for the assessment of the epoxy composites’ thermal properties. Nanohardness and elastic modulus were measured, and the hardness versus modulus index was calculated. Emphasis was given to the dispersion of MWCNTs in the epoxy matrix, which was assessed by both microscopy techniques and X-ray micro–computed tomography. A correlation between the optimum dispersion and MWCNTs content in terms of electrical conductivity, thermal stability, and nanomechanical properties revealed a threshold concentration at 3 phr, allowing the manufacturing of aerospace structures with multifunctional properties.

This paper deals with the fabrication of Resistive Random Access Memory (ReRAM) based on oxidized carbon nanofibers (CNFs). Stable suspensions of oxidized CNFs have been prepared in water and sprayed on an appropriate substrate, using the dynamic spray-gun deposition method, developed at Thales Research and Technology. This technique allows extremely uniform mats to be produced while heating the substrate at the boiling point of the solvent used for the suspensions. A thickness of around 150 nm of CNFs sandwiched between two metal layers (the metalized substrate and the top contacts) has been achieved, creating a Metal-Insulator-Metal (MIM) structure typical of ReRAM. After applying a bias, we were able to change the resistance of the oxidized layer between a low (LRS) and a high resistance state (HRS) in a completely reversible way. This is the first time that a scientific group has produced this kind of device using CNFs and these results pave the way for the further implementation of this kind of memory on flexible substrates.

Tissue regeneration necessitates the development of appropriate scaffolds that facilitate cell growth and tissue development by providing a suitable substrate for cell attachment, proliferation, and differentiation. The optimized scaffolds should be biocompatible, biodegradable, and exhibit proper mechanical behavior. In the present study, the nanomechanical behavior of a chitosan-graft-poly(ε-caprolactone) copolymer, in hydrated and dry state, was investigated and compared to those of the individual homopolymers, chitosan (CS) and poly(ε-caprolactone) (PCL). Hardness and elastic modulus values were calculated, and the time-dependent behavior of the samples was studied. Submersion of PCL and the graft copolymer in α-MEM suggested the deterioration of the measured mechanical properties as a result of the samples’ degradation. However, even after three days of degradation, the graft copolymer presented sufficient mechanical strength and elastic properties, which resemble those reported for soft tissues. The in vitro biological evaluation of the material clearly demonstrated that the CS-g-PCL copolymer supports the growth of Wharton’s jelly mesenchymal stem cells and tissue formation with a simultaneous material degradation. Both the mechanical and biological data render the CS-g-PCL copolymer appropriate as a scaffold in a cell-laden construct for soft tissue engineering.

The use of materials with very attractive friction and wear properties has raised much attention in research and industrial sectors. A wide range of tribological applications, including rolling and sliding bearings, machining, mechanical seals, biomedical implants and microelectromechanical systems (MEMS), require thin films with high mechanical strength, chemical inertness, broad optical transparency, high refractive index, wide bandgap excellent thermal conductivity and extremely low thermal expansion. Carbon based thin films like diamond, diamond-like carbon, carbon nitride and cubic boron nitride known as “super-hard” material have been studied thoroughly as the ideal candidate for tribological applications. In this study, the results of experimental and simulation works on the nanotribological behavior of carbon films and fundamental mechanisms of friction and lubricity at the nano-scale are reviewed. The study is focused on the nanomechanical properties and analysis of the nanoscratching processes at low loads to obtain quantitative analysis, the comparison obtain quantitative analysis, the comparison of their elastic/plastic deformation response, and nanotribological behavior of the a-C, ta-C, a-C:H, CNx, and a-C:M films. For ta-C and a-C:M films new data are presented and discussed.

The purpose of this study is to assess the integrity of carbon-fibre reinforced plastics (CFRP) comprising of commercial and surface modified CFs through nanomechanical mapping protocol, towards the feasibility of nanoindentation tool as a quality assurance means in a composite manufacturing process. Carbon fibre surface modification was selected for enhancement of the wetting properties of carbon fibres in order to improve the adhesion force between the fibre and the polymer matrix. In all cases, epoxy resin was used as a matrix for the manufacturing of composite samples. Plastic deformation/elastic recovery were recorded (together with viscoelasticity and adhesion-discontinuities and fluctuations during measurement), while elastic modulus values are also mapped. Moreover, the resistance to applied load is assessed and compared for all cases.