Search Results (695)

Aluminum–graphene nanoplatelet (Al/GNP) composites have attracted significant attention as lightweight structural materials, yet their mechanical performance is strongly influenced by interfacial reactions and the formation of carbides. In this study, Al/GNP composites containing 0.1–1.1 wt.% graphene were produced via powder metallurgy and hot extrusion at 400 °C and 500 °C. Hot extrusion at the higher temperature enables the controlled in situ formation of aluminum carbide (Al₄C₃). A comprehensive microstructural characterization using SEM and HRTEM was combined with tensile testing to elucidate the influence of carbide size on mechanical behavior. Hot extrusion at 500 °C promotes the formation of uniformly distributed, nanoscale Al₄C₃ carbides whose size, morphology, and aspect ratio depend on graphene content. Composites containing nano-sized carbides exhibit a markedly improved strength–ductility balance compared to carbide-free counterparts, with optimal performance achieved at 0.3 and 0.7 wt.% GNPs. The enhancement is attributed to synergistic strengthening mechanisms involving improved interfacial bonding, efficient load transfer, nanoscale dispersion strengthening, and carbide–dislocation interactions. The results indicate that the controlled formation of nanoscale Al₄C₃ is not detrimental; rather, it contributes to the optimization of the mechanical properties of Al/GNP composites. Unlike most previous studies that treat carbide formation as a detrimental effect, this work demonstrates that its controlled nanoscale evolution can be used as a deliberate strengthening strategy through its influence on microstructural mechanisms. Full article

Polydimethylsiloxane (PDMS) films doped with graphene nanoplatelets (GNP) with an embossed surface-relief grating were investigated as photothermal actuated sensors. The films were initially characterized using controlled environmental heating where the wavelength of a diffracted white-light probe beam measured at a fixed angle increased monotonically with temperature due to thermal expansion of the grating. An asymmetric double sigmoidal function tracked the shift in peak diffraction wavelength. The observed thermal response is consistent with the thermal expansion of a freestanding PDMS composite film. When a continuous-wave (CW) laser was incident on the film, intensity-dependent photothermal expansion caused a transient deformation in the grating. The photomechanical behavior of the grating, tracked by the diffracted probe beam with a miniature spectrometer, was then shown to act as a laser power meter. These results demonstrate that photomechanical materials can be used as add-ons to existing optical spectroscopy devices for power-sensing applications. Full article

This study investigates the effects of the co-curing process and nanoparticle reinforcement on the mechanical performance of plain-woven glass fiber-reinforced plastic (GFRP) adhesive joints, aiming to address the limitations of traditional fastening methods and the inherent brittleness of epoxy adhesives. Specifically, spherical silica (SiO₂) and plate-like graphene nanoplatelets (GNPs) were incorporated into the epoxy matrix at varying concentrations (0.25 to 1.0 wt.%) to evaluate the influence of particle geometry on joint integrity. Experimental results demonstrated that the co-curing technique yields superior mechanical properties compared to secondary bonding, exhibiting improvements of 35% in shear strength (from 10.97 MPa to 14.83 MPa) and 12% in flexural strength (from 72.57 MPa to 81.28 MPa) due to enhanced chemical interlocking. Furthermore, the addition of nanoparticles significantly improved joint performance, with the optimal content identified at 0.75 wt.% for both particle types. Notably, GNPs outperformed SiO₂, enhancing shear and flexural strengths compared to the neat co-cured baseline. Ultimately, the 0.75 wt.% GNP-reinforced material exhibited a shear strength of 21.22 MPa and a flexural strength of 104.09 MPa. Morphological analysis revealed that while SiO₂ contributes to reinforcement primarily via crack deflection, the high-aspect-ratio GNPs provide superior energy dissipation through crack bridging and pull-out mechanisms. Consequently, this study suggests that the co-curing process combined with an optimal concentration of GNPs presents a highly effective strategy for maximizing the reliability and structural efficiency of composite joints in weight-critical applications. Full article

The rising environmental impact of building energy consumption has intensified the demand for sustainable energy solutions. Latent heat thermal energy storage (LHTES) using phase-change materials (PCMs) offers a highly effective approach to improve energy efficiency; however, the intrinsically low thermal conductivity of most PCMs limits their practical performance. This study explores the thermophysical properties of a commercially available bio-based PCM (CrodaTherm^TM 60) enhanced with graphene nanoplatelets (GNPs) to improve heat transfer performance. Nano-enhanced PCMs (NePCMs) were prepared using a two-step process combining magnetic stirring and ultrasonication, incorporating GNPs at 2, 4, and 6 wt.%. Solid-phase density measurements of the NePCMs and viscosity measurements of the pure PCM were also conducted to support material characterisation. The results indicate distinct behaviours for the two nanoparticle sizes. At 6 wt.% nanoparticle loading, for 2 nm particles, the thermal conductivity increases by up to 13.9%, whereas for 6–8 nm particles, the enhancement is 148.9% of the pure PCM. Additionally, a reduction in latent heat is observed, with a proportional relationship to mass loading, as expected. These findings underscore the need for improved nanoparticle dispersion and formulation strategies to optimise both thermal performance and stability. Full article

Biodegradable nanocomposite materials possessing self-healing behavior are emerging as an attractive option of being used in advanced mechatronic systems. The current study is focused on a thorough examination of the micromechanical properties of graphene–reinforced polylactic acid (PLA)/polycaprolactone (PCL) composite samples, followed by estimation of their self-healing behavior upon heating. Polymer blend–based nanocomposite materials were prepared using the green and reliable in terms of good nanofiller dispersion melt extrusion method. 3D printed nanocomposite specimens with impeccable flatness were subjected to fine microscratch testing by applying a constant force experimental mode. The surface resistance of the three-component polymer materials against the lateral movement of the stylus fulfilling the scratch and the impact of the dual-phase PLA/PCL ratio on the nanocomposite mechanical performance were estimated by calculation of the coefficient of friction (COF = F_x/F_z). COF values in the range of 0.8–1.4 indicated excellent nanocomposite resilience against scratch. Creating a heterogeneous polymer system that combines phase-separated soft and hard domains with close melt and glass transition temperatures, respectively, may facilitate the physical flow of macromolecular chains into voids or free volume areas. This aspect can be critical in the achievement of thermally–induced self-healing properties of the composite material. Scanning electron microscopy (SEM) imaging of the microscratches, made before and after Joule heating of the polymer samples, revealed a significant degree of surface recovery and a sensible reduction in the width of the adjusted scratch grooves. Full article

The 4D printing of thermo-responsive shape-memory multicomponent polymer composites, which possess the ability to change shape by exposure to heat, has attracted much attention in recent years because of their scientific and technological significance. In the present study, we investigate shape memory performance of a polylactic acid-polycaprolactone-graphene nanocomposite activated directly by increasing the environmental temperature and indirectly, by Joule heating. The incorporation of graphene within the shape-memory biopolymer blend allowed formation of a programmable conduction path, whose electric properties are intimately coupled to thermo-mechanical processes. Advanced rheological, thermal, and thermo-mechanical properties were evaluated and related to the structure of nanocomposite. The electrically and thermally stimulated shape memory and self-healing behavior of the nanocomposite based on polycaprolactone/poly(lactic) acid blend reinforced with graphene nanoplatelets (PCL/PLA/GNP) were investigated. The shape memory tests revealed a good reversibility of 76% between the temporary and permanent states of the samples bent to 180 degrees and a high healing efficiency of 96% if stimulated by Joule heating. The highly electroactive nanocomposite demonstrated a great potential for 4D-printing of objects with complex structures, shapes, and electrically-stimulated shape-memory and self-healing functions. The nanocomposite is biodegradable, recyclable, and reusable, which may reduce the carbon footprint of the rapidly developing additive technology. Full article

Polymer–ceramic hybrid composites are emerging as attractive candidates for lightweight, corrosion-resistant absorber components in solar thermal collectors; however, their adoption is constrained by the intrinsically low thermal conductivity of polymers, processing-induced anisotropic heat transport, interfacial thermal resistance at tube/laminate joints, and durability challenges under outdoor exposure. This review provides a collector-centered synthesis of polymer–ceramic hybrid materials, emphasizing the translation of composite properties into collector-level outcomes rather than conductivity enhancement alone. A structure–property–performance mapping approach is presented to connect directional thermal conductivity ((k_in-plane), (k_perp)), thermal diffusivity, heat capacity, coefficient of thermal expansion, and service temperature with collector performance parameters such as heat removal effectiveness, overall heat losses, and stagnation behavior. Ceramic fillers (e.g., boron nitride, aluminum nitride, silicon carbide, alumina) are examined for stable conduction-network formation, coating compatibility, and long-term reliability, while carbon fillers (graphite, graphene nanoplatelets, carbon nanotubes) are evaluated for combined heat spreading and solar absorption benefits, with attention to emissivity penalties. Hybrid ceramic–carbon architectures and multilayer absorber designs are identified as the most promising routes to balance thermal transport, optical selectivity (high solar absorptance and low thermal emittance), manufacturability, and durability under UV, humidity, and thermal cycling. Full article

This study investigates the synergistic effect of functionalized carbon nanotubes (CNTs), graphene nanoplatelets (GNPs), and carbon fibers (CFs) on the mechanical performance of cement-based composites through a multivariate optimization approach. All carbon allotropes were covalently functionalized via acid treatment to enhance dispersion and interfacial bonding with the cement matrix. A face-centered central composite design (FCCD) combined with response surface methodology (RSM) was employed to systematically evaluate the influence of the three reinforcements, each varied between 0.033 wt.% and 0.067 wt.%, with a total carbon content not exceeding 0.2 wt.% of cement. The statistical analysis revealed a negligible correlation between reinforcement content and flexural strength (explained variance ≈ 1%), whereas fracture energy and compressive strength showed stronger dependencies, with explained variances of 25% and 66%, respectively. The maximum experimental fracture energy reached 18.1 J, corresponding to an increase of nearly 800% compared to plain cement, obtained at the highest combined reinforcement content. Compressive strength improved up to 48 MPa (≈32% higher than the reference), with the model predicting potential enhancements up to 40% under optimized compositions. The regression analysis highlighted the dominant role of quadratic and interaction terms, indicating that mechanical performance is governed more by synergistic effects than by the linear contribution of individual components. These findings demonstrate that controlled co-dispersion of multiple functionalized carbon allotropes enables significant enhancement of cement mechanical properties at very low total carbon contents, providing a cost-effective strategy for the design of high-performance cementitious composites. Full article

Continuous plantar-pressure monitoring is important for objective gait analysis and early detection of abnormal loading; however, many existing solutions remain laboratory-bound (force plates and instrumented walkways) or rely on costly in-shoe multilayer sensor arrays. Here, we developed and optimized a fully screen-printed pressure-sensing insole based on carbon–polymer nanocomposite layers, with an emphasis on manufacturability and process control to bridge the gap between proof-of-concept force-sensitive resistor (FSR)-based insoles and scalable printed-electronics manufacturing workflows. Composite pastes containing carbon fillers (graphene nanoplatelets, carbon black, and graphite) were formulated to improve sensor repeatability and sensitivity. Sensors were characterized under compression loads from 100 N to 1300 N, showing a sensitivity of 10.5 ± 2.8 Ω per 100 N and a sheet-to-sheet coefficient of variation of 22.1% in resistance response. The effects of paste composition, screen mesh density, electrode layout, and lamination on sensitivity and repeatability were systematically evaluated. In addition, correlation analysis of resistance values from integrated quality-control meanders proved useful for monitoring screen-printing process stability. The final insole integrates printed carbon sensing pads and contacts, a dielectric spacer, and an adhesive layer in a thin, flexible format suitable for integration with wearable electronics. In practical static-load tests, repeated manual placement of weights yielded coefficients of variation as low as 4% at 500 g and a detection limit of ~0.1 N, comparable to a very light finger touch. These results demonstrate that low-cost screen-printed electronics can provide robust pressure sensing for wearable plantar-pressure monitoring. Full article

We present an investigation to develop innovative composite fibrous electrodes optimized for a supercapacitor with a “green” low-cost aqueous electrolyte, superconcentrated potassium formate, which raises the maximum energy storage device voltage beyond the water electrolysis limit. Three types of electrospun nanofiber mats are investigated for optimum pseudocapacitance with this electrolyte: polyaniline (PANI)/polyacrylonitrile (PAN) fibers, without or with 1 wt% or 10 wt% graphene nanoplatelets (GNP). These nanofiber mats are considered as standalone electrodes or in bilayer formations with a phenolic-derived activated carbon fabric. Supercapacitor cells with these electrodes are tested electrochemically via electrical impedance spectroscopy, cyclic voltammetry and galvanostatic charge–discharge at different current densities. The supercapacitor with hybrid electrode bilayers of activated carbon fabric and electrospun fiber mat consisting of PANI:PAN at 50:50 w/w with 10 wt% GNP exhibited the best performance with an energy and a power density of 39 Wh/kg and 6057 W/kg of electrodes, respectively. Full article

Cement-based construction in cold regions faces severe challenges due to the dramatic retardation of hydration and strength development under sub-zero temperatures. Joule curing as a novel curing method showed certain advantages in solving this problem, while the curing efficiency was low for Joule curing under severely cold temperatures. This study systematically investigates the performance of graphene nanoplatelet (GNP)-modified electrically conductive cementitious composites under sub-zero temperature curing conditions. Joule curing method was employed to ensure a high-quality curing at ambient temperatures of −20 °C, −40 °C, and −60 °C. The results demonstrate that GNP incorporation significantly enhances electro-thermal performance. For the electrical conductivity of the specimens, the specimens containing 0.5 wt% GNP showed a much stable electric resistance development under severely cold environment, illustrating the value of 1169 Ω after 1 day Joule curing at the environmental temperature of −60 °C, which was 36% lower than the Ref. group. As for the curing temperature, the specimen with 0.5 wt% GNP effectively maintained the internal temperature within 50–60 °C during the 24 h curing period, even under extreme conditions. Mechanical tests reveal that the GNP-modified specimens exhibit remarkable strength retention, with the 0.5% GNP composite maintaining 86.3% of its compressive strength and 95.9% of its flexural strength at −60 °C compared to standard curing values. Microstructural characterization through XRD and TG analyses confirms that while the crystalline phase composition remains unchanged across different curing regimes, the hydration degree directly correlates with the mechanical performance, explaining the observed strength variations. MIP analysis further proved the advantage of Joule curing on refining the microstructure for the specimens. The findings establish that GNP modification, combined with Joule curing, presents an effective strategy for winter concrete construction, ensuring adequate strength development through enhanced electrical conductivity and controlled internal curing temperature, without altering the fundamental hydration chemistry. Full article

Friction stir spot welding (FSSW) is a novel variant of Friction Stir welding (FSW), developed by Mazda Motors and Kawasaki Heavy Industries to join similar and dissimilar materials in a solid state. It is an economic and environmentally friendly alternative to resistance spot welding (RSW). The FSSW technique, however, includes some structural defects imbedded within the weld joint, such as keyhole formation, hook crack, and bond line oxidation challenging the joint strength. The unique properties of nanomaterials in the reinforcement of metal matrices motivated researchers to enhance the FSSW joints’ strength. Previous studies successfully fabricated nano-reinforced FSSW joints. At different volumetric ratios of nano-reinforcement, nanoparticles may agglomerate due to inefficient stirring of the welding tool pin, forming stress concentration sites and brittle phases, affecting tensile and fatigue strength under static and cyclic loading conditions, respectively. This work investigated how the welding tool pin affects stirring efficiency by controlling the distribution of a nano-reinforcing material within the joint stir zone (SZ), and thus the tensile and fatigue strength of the FSSW joints. Sheets of AA6061-T6 of 1.8 mm thickness were used as a base material. In addition, graphene nanoplatelets (GNPs) with lateral sizes of 1–10 µm and thicknesses of 3–9 nm were used as nano-reinforcements. GNP-reinforced FSSW specimens were prepared and successfully fabricated. Optical microscope (OM) and field emission scanning electron microscope (FE-SEM) methods were employed to visualize the GNPs’ incorporation into the SZs of the FSSW joints. Micrographs of as-welded specimens showed lower formations of scattered, clustered GNPs achieved by the threaded pin tool compared to continuous agglomerations observed when the cylindrical pin tool was used. Tensile test results revealed a significant improvement of about 30% exhibited by the threaded pin tool compared to the cylindrical pin tool, while fatigue test showed an improvement of 46–24% for the low- and high-cycle fatigue, respectively. Full article

Poly(lactic acid) (PLA)-based nanocomposites containing a mixture of graphene nanoplatelets (GNP) and carbon nanotube (CNT) as hybrid fillers were prepared using a solution-assisted sonication process followed by melt processing. The effects of the filler dispersion on dielectric properties and microwave absorbing (MWA) performance were systematically investigated. Two ionic liquids (ILs), trihexyl-(tetra-decyl)phosphonium bis (trifluoromethanesulfonyl)imide (IL1) and 11-carboxyundecyl-triphenylphosphonium bromide (IL2), were employed as dispersing agents for the carbonaceous fillers. Incorporation of IL-treated fillers resulted in enhanced dielectric permittivity and improved MWA performance of the PLA composites. The MWA properties were evaluated in X- band and Ku-band. A minimum reflection loss (RL) of −34 dB and an effective absorption bandwidth (EAB) of 2.1 GHz were achieved for the composite containing GNP/CNT/IL2 (HB3) at a weight ratio of 2.5:0.5:0.5 wt% with one 3 mm thick layer. The superior performance of IL2 is attributed to π-π and π-cation interactions between its phenyl-containing cation and the carbonaceous fillers, as well as improved compatibility with the PLA matrix due to carboxyl groups. Additionally, three-layered composite structures, combining PLA/GNP as the outer layer with IL-assisted hybrid fillers in the core and PLA/CNT at the bottom layer, achieved an extended EAB of 4.5 GHz for GNP/HB2/CNT arrangement and 4.35 GHz for the GNP/HB3/CNT arrangement, driven by enhanced scattering and internal reflection of microwaves. These results demonstrate the potential of IL-assisted hybrid filler dispersion in PLA for developing biodegradable materials with multifunctional applications as charge storage capacitors and microwave absorbing materials for sustainable electronics. Full article

The growing accumulation of plastic and electronic waste highlights the urgent need for sustainable and biodegradable polymers. However, developing intrinsically conductive biodegradable polymers remains challenging, particularly for packaging and sensing applications. Poly(lactic acid) (PLA) is intrinsically non-conductive, and enhancing its functionality without compromising structural integrity is a key research goal. In this study, PLA-based filaments were developed using melt extrusion, incorporating cellulose nanocrystals (CNCs), graphene nanoplatelets (GNPs), and carbon nanotubes (CNTs), individually and in hybrid combinations with total filler contents between 1 and 5 wt%. The inclusion of CNC enhanced the dispersion of GNP and CNT, promoting the formation of interconnected conductive networks within the PLA matrix, allowing the percolation threshold to be reached at a lower fillers concentration. Hybrid formulations showed a balance melt strength and processability suitable for fused deposition modelling (FDM) 3D printing and prototypes successfully made. This study also provides the first systematic evaluation of temperature-dependent thermal conductivity of PLA-based composites at multiple temperatures (25, 5, and −20 °C), relevant to typical food and medical supply chains conditions. Full article

This article provides a comprehensive review of the literature on the use of graphene-based nanomaterials (graphene oxide, reduced graphene oxide, and graphene nanoplatelets) and nanosilica (SiO₂) in architectural paint and coatings. The aim was to quantitatively assess their effect on dirt pickup resistance, hydrophobicity, and mechanical properties. In a systematic search across ScienceDirect, Scopus, and Web of Science (2010–2025), 20 studies that met the set inclusion criteria were identified. We extracted and generalized data with random-effects models (REML) based on standardized mean differences, conducting subgroup and meta-regression analyses to assess filler type, loading, and binder system impact. The results reveal that graphene-based fillers and SiO₂ improve coating performance at the same time, and hybrid graphene-SiO₂ systems may provide a synergistic improvement depending on the binder matrix. Our results present the first quantitative evidence of graphene-SiO₂ interaction in the coating formulations, identify remaining research gaps, and indicate methods for designing next-generation facade paints with better dirt repellence, durability, and sustainability. Full article