Graphene Nanoplatelets Content Research Articles

Joule-Heating Effect of Thin Films with Carbon-Based Nanomaterials.

Smart textiles have become a promising area of research for heating applications. Coatings with nanomaterials allow the introduction of different functionalities, enabling doped textiles to be used in sensing and heating applications. These coatings were made on a piece of woven cotton fabric through screen printing, with a different number of layers. To prepare the paste, nanomaterials such as graphene nanoplatelets (GNPs) and multiwall carbon nanotubes (CNTs) were added to a polyurethane-based polymeric resin, in various concentrations. The electrical conductivity of the obtained samples was measured and the heat-dissipating capabilities assessed. The results showed that coatings have induced electrical conductivity and heating capabilities. The highest electrical conductivity of (9.39 ± 1.28 × 10−1 S/m) and (9.02 ± 6.62 × 10−2 S/m) was observed for 12% (w/v) GNPs and 5% (w/v) (CNTs + GNPs), respectively. The sample with 5% (w/v) (CNTs + GNPs) and 12% (w/v) GNPs exhibited a Joule effect when a voltage of 12 V was applied for 5 min, and a maximum temperature of 42.7 °C and 40.4 °C were achieved, respectively. It can be concluded that higher concentrations of GNPs can be replaced by adding CNTs, still achieving nearly the same performance. These coated textiles can potentially find applications in the area of heating, sensing, and biomedical applications.

Energy absorption and vibration of smart auxetic FG porous curved conical panels resting on the frictional viscoelastic torsional substrate

In recent years, the utilization of various methods to absorb vibration in widely-used structures has gained significant attention to control and reduce the destructive effect of the resonance phenomenon. The increased useful lifetime and reduced maintenance and repair costs are the advantages of vibration absorption. Besides, utilization of energy absorbers is one of the most effective strategies for reducing energy supply costs for different parts of the structure, such as sensors. In this regard, a numerical study is performed in this research to evaluate the energy absorption by vibrations' absorption in a conical three-layered panel located on a viscoelastic substrate. This three-layered panel is composed of three parts: piezoelectric upper layer reinforced with Graphene nanoplatelets (GPLs), auxetic core, and functionally graded material (FGM) porous lower layer. The substrate includes spring element, shear, torsion, and substrate-structure friction factor. Hamilton's principle and energy method have been used to extract the governing equations to model the first-order shear deformation theory (FSDT) for the presented structure. The Differential Cubature Method (DCM) and the Newmark method have been used to solve the governing equations. Results show that by applying the negative voltage to the sandwich conical panel, the in-plane compression forces and natural frequency are increased, while the maximum dynamic deflection is decreased. Furthermore, increasing the inherent damping coefficient increases the damping decrement. Meanwhile, the nonlinear scattering and increased dispersion concentration of GPLs near the upper and lower surfaces of the piezoelectric layer will increase the frequency and energy absorption. Besides, the increased friction factor of the viscoelastic substrate and sandwich cone leads to more absorption energy.

Investigation of the effect of Graphene Nanoplatelet content on Flexural Behavior, Surface Roughness and Water Absorption of a Graphene Nanoplatelets Reinforced Epoxy Nanocomposites

In the present work, the effect of Graphene nanoPlatelets (GnP) content on the flexural, surface roughness, and water absorption behavior of a GnP reinforced epoxy composite was investigated. Different wt.% of GnP (0.25, 0.5, 0.75, and 1 wt.%) was added into the epoxy matrix through the sonication method followed by the ball milling. The results indicate a significant enhancement in the flexural properties of the epoxy nanocomposite with the addition of GnP in the epoxy matrix. The optimum enhancement in the properties was obtained at 0.25 wt.% GnP incorporated epoxy composites. The increase in flexural strength and flexural modulus results were noticed as 42.7% and 49.2% when compared with neat epoxy. The surface roughness value for the loading of 0.25 wt.% of GnP into the epoxy showed a drop of 48.7% when compared with that of the neat epoxy sample. The loading of 0.25 wt.% of GnP into the epoxy also reduces the water absorption from 0.125% for the neat epoxy sample to 0.067% for the composite sample. The Scanning Electron Microscope (SEM) images of the fractured surface (flexural samples) of the GnP embedded epoxy composites show the river like pattern, which is the result of the better dispersion of the GnP in the epoxy matrix and thus shows improvement in flexural behaviour of such composite materials.

Influence of graphene nanoplatelets geometrical characteristics on the properties of polylactic acid composites

The influence of graphene nanoplatelets (GNP) surface area and size on the dispersion, electrical percolation behavior, electrical conductivity, thermal conductivity, electromagnetic interference (EMI) attenuation, and EMI attenuation mechanisms of GNP/polylactic acid (PLA) were investigated. The GNP/PLA composite's electrical percolation threshold decreased with the increase in GNP surface area and decrease in GNP size. The higher number of GNP particles associated with the decrease in GNP size and increase in GNP surface area facilitated the creation of a conductive network at a lower GNP content. However, at a GNP loading of 30 wt%, the GNP/PLA composites' electrical, EMI SE, and thermal conductivity decreased with the increase in GNP surface area and decrease in GNP size. At high nanofiller loading, the contact resistance between the nanofiller particles is more important than the nanofiller aspect ratio or size. The smaller filler size means more particles and more filler/filler resistance points. The most exciting finding is the dependence of EMI attenuation mechanisms on the GNP surface area. EMI attenuation by absorption was found to increase with the increase in GNP surface area.

A comparative experimental study on damping properties of epoxy nanocomposite beams reinforced with carbon nanotubes and graphene nanoplatelets

Abstract Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) are extremely ideal nanofillers for applications in damping polymer. This work explores the damping behavior of polymer nanocomposite beams made of epoxy resin reinforced with CNTs and GNPs experimentally. Beam specimens for the vibration tests together with dynamic mechanical analysis (DMA) are fabricated with different weight ratios of CNTs and GNPs, upon which DMA and free vibration tests are conducted. Scanning electron microscope images are also obtained to check the dispersion of nanofillers in microscale. It is found that the first-order loss factor of composite beam specimens shows a rise of 41.1% at 0.4 wt% CNT content compared with that of pure epoxy, while the first-order loss factor of composite beam specimens with 0.025 wt% GNP content increases up by 128.9%. The maximum value of the first-order loss factor of nanocomposite beams with GNP reinforcement is 62.2% higher than that with CNTs.

Influence of graphene nanoplatelet concentration on the electrical, mechanical, and piezoresistive properties of glass fiber/epoxy composites

AbstractThis paper reports the effect of weight concentration of graphene nanoplatelets (GNPs) on the electrical, mechanical, thermo‐mechanical, and piezoresistive properties of unidirectional glass fiber/epoxy composite laminates. The neat (without GNPs) and multiscale laminates (with GNPs) were fabricated with different GNPs contents (0.25, 0.50, 0.75, and 1.00 wt%) using a simple and feasible process based on spray coating followed by vacuum assisted resin infusion. The morphological analysis on glass fiber surfaces evidenced the presence of an effective GNP network formation which tends to be denser as GNPs content increases. As a result, the electrical conductivity and gauge factor measured on top and bottom surfaces of specimens were greatly increased in laminates. Short beam shear and flexural test results showed that the addition of GNPs to the laminates causes a significant reduction in their interlaminar shear strength, flexural strength, and strain to failure with respect to the neat laminate. However, the flexural modulus of laminates does not suffer any apparent change in its reference value and the glass transition temperature was slightly increased in samples with 1.00 wt% GNPs. The fractographic analysis revealed that delamination was the main damage mechanism detected upon mechanical testing, suggesting that relative high concentrations of GNPs cause that interlaminar regions of laminated composites become weaker. In spite of this, excellent strain self‐sensing capabilities and internal damage detection were observed during flexural electromechanical tests performed in beam‐type specimens with higher GNP content.

Graphene nanoplatelets reinforced Polyamide-11 nanocomposites thermal stability and aging for application in flexible pipelines

Novel nanocomposites of polyamide-11 (PA11) reinforced with commercial graphene nanoplatelets (GNP) in amounts of 1.0, 2.5, and 5.0 wt.% were prepared and characterized for their thermal stability and aging performance. The processing of the nanocomposites was carried out by mixing PA11 in the molten state employing a double screw mini-extruder at 200 °C under 60 rpm screw speed, with a residence time of 7 min. The incorporation of GNP increased the thermal stability of PA11, particularly in the amount of 1.0 wt.%, as observed by thermogravimetric analysis. X-ray diffraction indicated that the composites' crystallinity increased with 1.0 and 2.5 wt.% of GNP. Evidence of agglomerates formation in the sample with 5.0 wt.% of GNP suggests it to be less dispersed in the PA11 matrix and associated with reduction in crystallinity. The dynamic mechanical analysis showed that GNP promoted an increase in the storage and loss moduli. The increase of GNP in the PA11 matrix enhanced the water contact angle and, therefore, provided greater hydrophilicity of the nanocomposite. The GNP reinforcement prevents the decrease in the molar mass of PA11, estimated by the corrected inherent viscosity (CIV) measured with aging time into water at 85 °C, when compared to the performance of neat PA11. All nanocomposites had CIV values above 1.20 dL/g before and after the aging test. Therefore, using the lowest GNP content of 1.0 wt.% proved to be the more efficient for application in flexible oil/gas pipelines.

Enhanced Thermal and Mechanical Properties of 3D Printed Highly Porous Structures Based on γ‐Al2O3 by Adding Graphene Nanoplatelets

AbstractOne of the main challenges to widen the potential applications of 3D printed highly porous ceramic structures in catalysis, energy storage or thermal management resides in the improvement of both their mechanical resistance and thermal conductivity. To achieve these goals, highly hierarchical γ‐alumina (γ‐Al2O3) scaffolds containing up to 18 vol% of graphene nanoplatelets (GNP), including channels of controlled size and shape in the millimeter scale and meso‐porosity within the rods, are developed by robocasting from boehmite‐based aqueous inks without other printing additives. These 3D structures exhibit high porosity (85%) and specific surface area of 100 m2 g−1. The incorporation of 12 vol% GNP leads to an enhanced mechanical response of the scaffolds, increasing the compressive strength and the elastic modulus up to ≈80% as compared with data for plain γ‐Al2O3 scaffolds. The thermal conductivity is measured by the transient plane source method using specifically designed 3D structures with external sidewalls and additional top/bottom covers to assure a good contact at the outer surfaces. The thermal conductivity of 3D porous structures augments with the GNP content, reaching a maximum value four times higher for the scaffolds containing 18 vol% GNP than that attained for the 3D monolithic γ‐Al2O3.

Fabrication of TiC-graphene dual-reinforced self-lubricating Al matrix hybrid nanocomposites with superior mechanical and tribological properties

TiC-graphene dual-reinforced Al matrix hybrid nanocomposites (AMHNs) were synthesised by powder metallurgy. Microstructures, compressive and tribological properties of the AMHNs with different fractions of graphene nanoplatelets (GNPs) were studied and compared with Al2024 alloy, and TiC or GNPs singly reinforced Al composites. The results show the microstructures and distributions of TiC and GNPs are homogenised with the increasing content of GNPs. The compressive properties and wear resistance of the composites are improved efficiently by synergistic influences of TiC and GNPs. Significantly, Al-5.0 wt% TiC-1.0 wt% GNPs has the most superior compressive properties and highest wear resistance with a wear rate of 4.62 × 10−4 mm3/Nm, which is a 94.4% reduction compared with that of unreinforced Al alloy.

Chemically Edge-Carboxylated Graphene Enhances the Thermal Conductivity of Polyetherimide–Graphene Nanocomposites

In this work, we demonstrate that edge oxidation of graphene can enable larger enhancement in thermal conductivity (k) of graphene nanoplatelet (GnP)/polyetherimide (PEI) composites relative to oxidation of the basal plane of graphene. Edge oxidation offers the advantage of leaving the basal plane of graphene intact, preserving its high in-plane thermal conductivity (kin > 2000 W m-1 K-1), while, simultaneously, the oxygen groups introduced on the graphene edge enhance interfacial thermal conductance through hydrogen bonding with oxygen groups of PEI, enhancing the overall polymer composite thermal conductivity. Edge oxidation is achieved in this work by oxidizing graphene in the presence of sodium chlorate and hydrogen peroxide, thereby introducing an excess of carboxyl groups on the edge of graphene. Basal plane oxidation of graphene, on the other hand, is achieved through the Hummers method, which distorts the sp2 carbon-carbon network of graphene, dramatically lowering its intrinsic thermal conductivity, causing the BGO/PEI (BGO = basal-plane oxidized graphene or basal-plane-functionalized graphene oxide) composite's k value to be even lower than pristine GnP/PEI composite's k value. The resulting thermal conductivity of the EGO/PEI (EGO = edge-oxidized graphene or edge-functionalized graphene oxide) composite is found to be enhanced by 18%, whereas that of the BGO/PEI composite is diminished by 57%, with respect to the pristine GnP/PEI composite with 10 wt % GnP content. Two-dimensional Raman mapping of GnPs is used to confirm and distinguish the location of oxygen functional groups on graphene. The superior effect of edge bonding presented in this work can lead to fundamentally novel pathways for achieving high thermal conductivity polymer composites.

Influence of ratio of multi-walled carbon nanotubes and graphene on microstructure and mechanical properties of copper-graphite composites fabricated by spark plasma sintering

ABSTRACT Copper-graphite composites synergetic reinforced by nano-carbon (multi-walled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs)) and ceramic particle reinforced phases (Al2O3 particles and hexagonal boron nitride (HBN)) with alloying elements were fabricated through Spark Plasma Sintering for friction material. The surface modification of MWCNTs and GNPs treated with gallic acid and rutin solutions with ultrasonic treatment can improve the dispersibility. The interfacial bonding between the matrix and the reinforcing phase in the composites was mainly mechanical, and the diffusion layer can be observed. The content of MWCNTs and GNPs remained 1 wt.%; as the proportion of MWCNTs increased, the mechanical properties of nano-carbon and ceramic particles reinforced Cu-graphite composites gradually increased. With the content of 0.8 wt.%MWCNTs-0.2 wt.%GNPs, the composites had the best performance, and the relative density, hardness and compressive strength were 96.01%, 42.75 HV and 202.37 MPa, respectively. According to the morphology of compression fracture, the fracture type was a brittle fracture. It can be determined that the strengthening mechanisms of the composites were mainly load transfer, particle strengthening and fine grain strengthening.

Synergistic toughening on hybrid epoxy nanocomposites by introducing engineering thermoplastic and carbon-based nanomaterials

In this study, epoxy-anhydride thermoset was initially modified with polyethersulfone (PESU) at 0‐15 wt% loading. The various mass ratios at 0.50 wt% total content of graphene nanoplatelets (GNPs)/carbon nanotubes (CNTs) were further introduced to comprehensively study the simultaneous incorporation of different tougheners on morphological, thermal, and mechanical properties of engineering thermoplastic modified epoxy. The binary blend of PESU/epoxy reveals two-phase morphologies due to reaction induced phase separation, showing particulate morphology at 5 wt% PESU and co-continuous morphology at 10‐15 wt% PESU. It was found that the presence of PESU at 5 wt% not only improved thermal stability but also provide the optimum mechanical properties, showing 35% and 40% increasing in tensile strength and fracture toughness, respectively. From fracture surface analysis, crack deflection from the PESU dispersed particles was observed as a main toughening mechanism for this binary blend. With introducing GNPs and/or CNTs, hybrid nanocomposite based on 5 wt% PESU modified epoxy matrix showed similar morphology and thermo-mechanical properties to the binary blends. Additionally, the remarkable Young's modulus were observed in all hybrid PESU/carbon-based nanofillers toughened epoxy composites. PESU and GNPs dispersed phase contribute greatly in enhancing fracture toughness (KIc) of hybrid PESU/nanofillers system. KIc of PESU/epoxy blends with 0.5 wt% GNPs was measured at 0.86 MPa m1/2, counting as ∼60% and ∼18% improvement from pristine epoxy and 0.5 wt% GNPs modified neat epoxy, respectively. Apart from crack deflection of PESU, GNPs cluster effectively deviates and bifurcates the crack path, indicating the synergistic effect on PESU/GNPs epoxy nanocomposite. Interestingly, these two tougheners also dominates the toughening mechanism in PESU/GNPs/CNTs epoxy nanocomposites. Meanwhile, the influence of CNTs on fracture toughness was not clearly demonstrated on hybrid nanocomposite system.

Ultrasensitive and highly stretchable sensors for human motion monitoring made of graphene reinforced polydimethylsiloxane: Electromechanical and complex impedance sensing performance

Highly stretchable sensors based on graphene nanoplatelet (GNP) reinforced polydimethylsiloxane (PDMS) are manufactured for human motion monitoring purposes. The strain sensing analysis shows ultra-high gauge factor (GF) values from 40 to 300 at low strain levels up to 106 at high deformations at tensile conditions, and a decreasing sensitivity as GNP content increases. The compressive behavior shows an initial decrease of the electrical resistance, due to the prevalence of in-plane mechanisms, followed by a stable increase, due to the prevalence of out-of-plane mechanisms. In this regard, the Electrical Impedance Spectroscopy (EIS) analysis shows an increase of the complex impedance with increasing compressive strain. The equivalent RC-LRC circuit allows to explain the electrical mechanisms governing the compressive behavior, where the LRC element denotes the contact and intrinsic resistance and the RC element the tunnelling effect. Finally, a proof of concept of human motion monitoring proves the capability of the scalable and easy-manufactured sensors to detect frowning, raising eyebrows, blinking, breathing, blowing and, even, vocal cord motion, where each phoneme follows a unique pattern, with a robust electrical response.

Wearable Sensors Based on Graphene Nanoplatelets Reinforced Polydimethylsiloxane for Human Motion Monitoring: Analysis of Crack Propagation and Cycling Load Monitoring

The use of graphene and other carbon nanoparticles is now of interest for developing chemical (gas and compounds detectors) and physical sensors. In this work, a graphene nanoplatelet (GNP)-PDMS sensor is proposed. More specifically, its strain-sensing capabilities under consecutive cycles as well as the crack propagation mechanisms are widely analyzed. First, an analysis of the electrical properties shows that the increase of the GNP content leads, as expected, to an increase of the electrical conductivity, ranging from values around 10−3 to 1 S/m for 5 and 11 wt.% samples. The analysis of crack propagation monitoring capabilities shows an exceptional sensitivity of the proposed flexible sensors, with a highly exponential behavior of the electrical resistance due to the prevalent breakage of the electrical pathways as crack propagation occurs. Furthermore, the analysis of the electrical response under cyclic load proves a very high robustness, with a similar response when comparing different cycles and an electrical sensitivity that increases when decreasing the GNP content (from 15–25 to 25–50 at 7 and 11 wt.% GNP content, respectively), a fact that is explained by the prevalence of tunneling mechanisms at low contents. Finally, a proof-of-concept of human motion monitoring by the detection of neck, wrist and facial movements is successfully achieved, indicating the high applicability of the proposed sensors.

Mechanical and corrosion properties of graphene nanoplatelet–reinforced Mg–Zr and Mg–Zr–Zn matrix nanocomposites for biomedical applications

Magnesium (Mg)-based biomaterials have gained acceptability in fracture fixation due to their ability to naturally degrade in the body after fulfilling the desired functions. However, pure Mg not only degrades rapidly in the physiological environment, but also evolves hydrogen gas during degradation. In this study, Mg0.5Zr and Mg0.5ZrxZn (x = 1–5 wt.%) matrix nanocomposites (MNCs) reinforced with different contents (0.1–0.5 wt.%) of graphene nanoplatelets (GNP) were manufactured via a powder metallurgy technique and their mechanical and corrosion properties were evaluated. The increase in GNP concentration from 0.2 wt.% to 0.5 wt.% added to Mg0.5Zr matrices resulted in decreases in the compressive yield strength and corrosion resistance in Hanks’ Balanced Salt Solution (HBSS). On the other hand, a higher concentration (4–5 wt.%) of Zn added to Mg0.5Zr0.1GNP resulted in an increase in ductility but a decrease in compressive yield strength. Overall, an addition of 0.1 wt.% GNPs to Mg0.5Zr3Zn matrices gave excellent ultimate compressive strength (387 MPa) and compressive yield strength (219 MPa). Mg0.5Zr1Zn0.1GNP and Mg0.5Zr3Zn0.1GNP nanocomposites exhibited 29% and 34% higher experimental yield strength, respectively, as compared to the theoretical yield strength of Mg0.5Zr0.1GNP calculated by synergistic strengthening mechanisms including the difference in thermal expansion, elastic modulus, and geometry of the particles, grain refinement, load transfer, and precipitation of GNPs in the Mg matrices. The corrosion rates of Mg0.5Zr1Zn0.1GNP, Mg0.5Zr3Zn0.1GNP, Mg0.5Zr4Zn0.1GNP, and Mg0.5Zr5Zn0.1GNP measured using potentiodynamic polarization were 7.5 mm/y, 4.1 mm/y, 6.1 mm/y, and 8.0 mm/y, respectively. Similarly, hydrogen gas evolution tests also demonstrated that Mg0.5Zr3Zn0.1GNP exhibited a lower corrosion rate (1.5 mm/y) than those of Mg0.5Zr1Zn0.1GNP (3.8 mm/y), Mg0.5Zr4Zn0.1GNP (1.9 mm/y), and Mg0.5Zr5Zn0.1GNP (2.2 mm/y). This study demonstrates the potential of GNPs as effective nano-reinforcement particulates for improving the mechanical and corrosion properties of Mg–Zr–Zn matrices.

Experimental and Simulation Studies of Temperature Effect on Thermophysical Properties of Graphene-Based Polylactic Acid.

Overheating effect is a crucial issue in different fields. Thermally conductive polymer-based heat sinks, with lightweight and moldability features as well as high-performance and reliability, are promising candidates in solving such inconvenience. The present work deals with the experimental evaluation of the temperature effect on the thermophysical properties of nanocomposites made with polylactic acid (PLA) reinforced with two different weight percentages (3 and 6 wt%) of graphene nanoplatelets (GNPs). Thermal conductivity and diffusivity, as well as specific heat capacity, are measured in the temperature range between 298.15 and 373.15 K. At the lowest temperature (298.15 K), an improvement of 171% is observed for the thermal conductivity compared to the unfilled matrix due to the addition of 6 wt% of GNPs, whereas at the highest temperature (372.15 K) such enhancement is about of 155%. Some of the most important mechanical properties, mainly hardness and Young’s modulus, maximum flexural stress, and tangent modulus of elasticity, are also evaluated as a function of the GNPs content. Moreover, thermal simulations based on the finite element method (FEM) have been carried out to predict the thermal performance of the investigated nanocomposites in view of their practical use in thermal applications. Results seem quite suitable in this regard.

Room Temperature‐Sintering Conductive Ink Fabricated from Oleic‐Modified Graphene for the Flexible Electronic Devices

AbstractGraphene, a novel 2D nanomaterial, has been intensively studied and utilized in many fields of applications. Graphene‐based conductive ink has attracted many scientific researchers due to its flexibility, durability, and, most importantly, high electrical conductivity. However, the low dispensability and high curing temperature have hindered the use of graphene ink in many practical applications. In this work, graphene nanoplatelets (GNPs) were modified with oleic acid to improve dispensability. Then, the modified GNPs were employed as a major component in the conductive ink‘s formulation. The effects of the oleic acid, binder, and GNPs contents on the conductivity of the prepared ink were studied. The results showed that at the ink‘s formulation of 0.75 % binder and 6 % GNPs (modified with 2.5 % oleic acid), the lowest resistance with the value of 22 Ω.cm and sheet resistance of 7.56 Ω cm2 was obtained. Remarkably, the high conductivity of the modified conductive ink on the substrate could also be observed after curing at room temperature, which is advantageous for practical application. The viscosity of the resultant conductive ink could also be adjusted by changing the amount of solvent in the ink‘s formulation for application of the ink in the pen, painting, or inkjet printing.

Fabrication of PLA/PCL/Graphene Nanoplatelet (GNP) Electrically Conductive Circuit Using the Fused Filament Fabrication (FFF) 3D Printing Technique.

For the purpose of fabricating electrically conductive composites via the fused filament fabrication (FFF) technique whose properties were compared with injection-moulded properties, poly(lactic acid) (PLA) and polycaprolactone (PCL) were mixed with different contents of graphene nanoplatelets (GNP). The wettability, morphological, rheological, thermal, mechanical, and electrical properties of the 3D-printed samples were investigated. The microstructural images showed the selective localization of the GNPs in the PCL nodules that are dispersed in the PLA phase. The electrical resistivity results using the four-probes method revealed that the injection-moulded samples are insulators, whereas the 3D-printed samples featuring the same graphene content are semiconductors. Varying the printing raster angles also exerted an influence on the electrical conductivity results. The electrical percolation threshold was found to be lower than 15 wt.%, whereas the rheological percolation threshold was found to be lower than 10 wt.%. Furthermore, the 20 wt.% and 25 wt.% GNP composites were able to connect an electrical circuit. An increase in the Young’s modulus was shown with the percentage of graphene. As a result, this work exhibited the potential of the FFF technique to fabricate biodegradable electrically conductive PLA-PCL-GNP composites that can be applicable in the electronic domain.

Thermoelectrical properties of graphene knife-coated cellulosic fabrics for defect monitoring in Joule-heated textiles

Knife-coating can confer new properties on different textile substrates efficiently by integrating various compounds into the coating paste. Graphene nanoplatelets (GNP) is one of the most used elements for the functionalization of fabrics in recent years, providing electrical and thermal conductivity to fabrics, later used to develop products such as sensors or heated garments. This paper reports thermoelectrically conductive textiles fabrication through knife-coating of cellulosic fabrics with a GNP load from 0.4 to 2 wt% within an acrylic coating paste. The fabric doped with the highest GNP content reaches a temperature increase of 100°C in few seconds. Besides, it is found out that the thermographic images obtained during the electrical voltage application provide maps of irregularities in the dispersion of conductive particles of the coating and defects produced throughout their useful life. Therefore, the application of a low voltage on the coated fabrics allows fast and effective heating by Joule’s effect, whose thermographic images, in turn, can be used as structural maps to check the quality of the GNP doped coating. The temperature values and the heating rate obtained make these fabrics suitable for heating devices, anti-ice and de-ice systems, and protective equipment, which would be of great interest for industrial applications.

Flexible high dielectric polystyrene/ethylene‐α‐octene copolymer/graphene nanocomposites: Tuning the morphology and dielectric properties by graphene's surface polarity

AbstractThe current research focuses on suggesting a new potential application of polymeric materials for capacitor applications by focusing on polystyrene (PS)/ethylene‐α‐octene copolymer (EOC) blends. Polymeric materials have high dielectric strength (≈ 200 for PS), good processability, and flexibility. However, their low dielectric constants make them not suitable for capacitor applications. Therefore, suggesting a method for enhancing their dielectric constant accompanied by low tan δ proposes an excellent substitute for commonly used ceramic dielectrics. The current article investigates the control of the dielectric properties of PS/EOC blends by manipulating the graphene nanoplatelets (GNPs) surface polarity. Results confirm that the localization site of the GNPs is mainly controlled by their surface polarities; this matter leads to the change of the morphology from sea/island for the pure blend to co‐continuous for the blend containing the most polar GNPs resulting in the best dielectric properties. This manipulation of the morphology by low concentration of GNPs (1.5 wt%) and therefore, dielectric properties result in high dielectric constant ≈ 55.8 at 10 MHz and low tan δ = 0.007, accompanied by high flexibility, which is the main drawback of ceramic capacitors, makes it a fantastic option for capacitor applications.