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Abstract: Strong polymer–MWCNT interactions in millimeter-high MWCNT/poly(vinyl alcohol) composite mats of vertically aligned tubes are reported. SEM and TEM imaging revealed extensive polymer sheathing to have occurred homogeneously over the nanotubes in the mats without influencing their morphology, alignment or physical characteristics. A 7- to 10-fold increase in the apparent nanotube diameter due to poly(vinyl alcohol) sheathing was measured. Thermogravimetric analysis showed that the composite mats were thermally more stable than the pure polymer. Differential scanning calorimetry results were compatible with a crystallinity increase of the polymer phase due to the presence of CNTs of the order of 18%. Potential applications of the produced composites include filters, components for sandwich panels and sensors. [Copyright &y& Elsevier]

The macro- and micro-mechanics of large scale bridging in SiC/MAS-L composites were assessed by tensile testing of DEN specimens with in situ LRM measurements. The macromechanical behavior was analyzed in terms of crack growth resistance and bridging laws using an elastic displacement correction approach. A dedicated Raman calibration curve was established for the specific composite fiber, which served in the transformation of wavenumber shifts collected from bridging fibers in the composite to bridging strain, and to stress via the elastic modulus of the fibers. Bridging strain profiles were established along the ligament of the specimen and their shape was discussed in conjunction with local notch effects. Actual bridging strain values up to 0.8% were calculated which compared well with their macromechanical counterparts within the intact-fiber regime. The individual contributions of intact and pulled-out fibers to the total fracture behavior of the composite were distinguished and are discussed in the article. [Copyright &y& Elsevier]

The initial mode of damage in multidirectional composites is the accumulation of matrix cracks in the off-axis plies. Remote laser Raman spectroscopy, using aramid (Kevlar 49®) fibers as Raman strain sensors, has been employed to monitor the local strains in cracked crossply composites. The strain magnification in the 0° ply caused by 90° matrix cracking are measured at different levels of loading. A relationship between the values of strain magnification and the distance between the position of the fibers sensors vis-à-vis the crack front has been established. The effect of damage progression within the 0° plies on the remaining/surviving glass fibers is modeled satisfactorily and verified against predictions on the basis of a generalized plane strain model by assuming that the 90° ply “expands” in relative size against the 0° ply thickness. [ABSTRACT FROM AUTHOR]

As an emerging class of materials, nanocarbons have attracted significant interest for practical applications due to their remarkable mechanical, electrical and thermal properties coupled with high surface areas and tunable surface chemistry. However, challenges like high aspect ratios and poor dispersibility in polymer matrices hinder their widespread use in technological applications. The problems are most prominently resolved with the use of free-standing nanocarbon sheets. The present paper reviews recent advancements in fabricating and utilizing free-standing sheets consisting of various nanocarbons: carbon nanotubes and 2D materials like graphene, graphene oxide, and reduced graphene oxide. It initially delves into the nanomechanics of these sheets, focusing on inter-particle cross-linking and nacre-like microstructures. Energy storage applications are also examined, with emphasis on the role of nanocarbon-based sheets in the enhancement of specific energy capacity and performance retention of batteries, electric double layer supercapacitors, and pseudocapacitors. In the field of electromagnetic interference shielding, the sheets' superior electrical conductivity and microstructures, which amplify internal reflections in the GHz and THz regions, are showcased. Their potential in heat dissipation, owing to their high thermal conductivity and large surface area, is also explored. Additionally, they are reviewed for membrane-based separation processes, specifically gas separation, reverse osmosis, forward osmosis, and pervaporation, highlighting properties like ion selectivity and chlorine resistance. The last discussion concerns the role of nanocarbon-based sheets in catalysis where they can enhance reaction efficiencies and promote sustainable solutions. Either as catalysts and/or supports, with key features such as high surface area, electrical conductivity, and adaptable functionalities, they showcase significant potential in various catalytic processes like electrocatalysis and environmental remediation. [Display omitted] • Mechanical strengthening via cross-linking of nanocarbons and nacre microstructure. • Nanocarbon-based energy storage devices with increased capacity and stability. • EMI shielding applications of nanocarbon sheets in the GHz and THz range. • Methods to increase in-plane and cross-plane thermal conductivity of the sheets. • Use of nanocarbon sheets in RO, NF, FO and gas separation applications. [ABSTRACT FROM AUTHOR]

Graphene and other two-dimensional materials (2DMs) have been shown to be promising candidates for the development of flexible and highly-sensitive strain sensors. However, the successful implementation of 2DMs in practical applications is slowed down by complex processing and still low sensitivity. Here, we report on a novel development of strain sensors based on Marangoni self-assemblies of graphene and of its hybrids with other 2DMs that can both withstand very large deformation and exhibit highly sensitive piezoresistive behaviour. By exploiting the Marangoni effect, reference films of self-assembled reduced graphene oxide (RGO) are first optimized, and the electromechanical behaviour has been assessed after deposition onto different elastomers demonstrating the potential of producing strain sensors suitable for different fields of application. Hybrid networks have been then prepared by adding hexagonal boron nitride (hBN) and fluorinated graphene (FGr) to the RGO dispersion. The hybrid integration of 2D materials is demonstrated to become a potential solution to increase substantially the sensitivity of the produced resistive strain sensors without compromising the mechanical integrity of the film. In fact, for large quasi-static deformations, a range of gauge factor values up to 2000 were demonstrated, while retaining a stable performance under cyclic deformations. [ABSTRACT FROM AUTHOR]

The very serious problem of temperature and humidity regulation, especially for small and medium-sized museums, galleries, and private collections, can be mitigated by the introduction of novel materials that are easily applicable and of low cost. Within this study, archive boxes with innovative technology are proposed as "smart" boxes that can be used for storage and transportation, in combination with a nanocomposite material consisting of polyvinyl alcohol (PVA) and graphene oxide (GO). The synthesis and characterization of the PVA/GO structure with SEM, Raman, AFM, XRD, Optical Microscopy, and profilometry are fully discussed. It is shown that the composite material can be integrated into the archive box either as a stand-alone film or attached onto fitting carriers, for example, those made of corrugated board. By applying the PVA/GO membrane this way, even with strong daily temperature fluctuations of ΔT = ±24.1 °C, strong external humidity fluctuations can be reduced by −87% inside the box. Furthermore, these humidity regulators were examined as Volatile Organic Compounds (VOCs) adsorbers since gas pollutants like formic acid, formaldehyde, acetic acid, and acetaldehyde are known to exist in museums and induce damages in the displayed or stored items. High rates of VOC adsorption have been measured, with the highest ones corresponding to formic acid (521% weight increase) and formaldehyde (223% weight increase). [ABSTRACT FROM AUTHOR]

Laser‐fabrication of graphene from cellulose‐based feedstock materials often requires extensive preprocessing. This work demonstrates laser fabrication of porous, 3D graphene from a new class of marine‐based sustainable materials–chitosan biopolymers. The biopolymer films contain only chitosan, acetic acid, glycerol, and water. Fourier transform infrared spectroscopy studies indicate that the cured chitosan films still retain a significant water content (≈30%), enabling production of flexible films. A simple 3‐step laser fabrication process is presented using low‐cost infrared (CO2, 2.1 W) and visible (405 nm, 0.5 W) hobbyist laser engravers, with measured sheet resistance values as low as 40 ohms sq.−1. Transient electrochemical detection of an inner sphere redox molecule is demonstrated using a graphene‐like carbon working electrode fabricated on a water‐soluble chitosan substrate. [ABSTRACT FROM AUTHOR]

As the power‐conversion efficiency (PCE) of organic–inorganic lead halide perovskite solar cells (PSCs) is approaching the theoretical maximum, the most crucial issue concerns long‐term ambient stability. Here, the application of PCN‐224 quantum dots (QDs) is reported, a typical Zr‐based porphyrinic metal–organic framework (MOF), to enhance the ambient stability of PSCs. PCN‐224 QDs with abundant Lewis‐base groups (e.g., CO, C−N, CN) contribute to high‐quality perovskite films with enlarged grain size and reduced defect density by interaction with under‐coordinated Pb2+. Meanwhile, PCN‐224 QDs enable the well‐matched energy level at the perovskite/hole transport layer (HTL) interface, thereby facilitating hole extraction and transport. More importantly, PCN‐224 QDs‐treated HTL can capture Li+ from bis(trifluoromethanesulfonyl)imide additive, leading to the reduced aggregation and less direct contact with moisture for hygroscopic Li‐TFSI. Moreover, PCN‐224 QDs mitigated Li+ ion migration into the perovskite layer, thus avoiding the formation of deleterious defects. The resultant devices yield a champion PCE of 22.51%, along with substantially improved durability, including humidity, thermal and light soaking stabilities. The findings provide a new approach toward efficient and stable PSCs by applying MOF QDs. [ABSTRACT FROM AUTHOR]

Ultrathin carbon nanomembranes (CNMs) are two-dimensional materials (2DM) of a few nm thickness with sub-nm intrinsic pores that mimic the biofiltration membranes found in nature. They enable highly selective, permeable, and energy-efficient water separation and can be produced at large scales on porous substrates with tuned properties. The present work reports the mechanical performance of such CNMs produced by p-nitrobiphenyl phosphonic acid (NBPS) or polyvinylbiphenyl (PVBP) and their composite membranes of microporous supporting substrates, which constitute indispensable information for ensuring their mechanical stability during operation. Measuring the nanomechanical properties of the ultrathin material was achieved by atomic force microscopy (AFM) on membranes both supported on flat substrates and suspended on patterned substrates ("composite membrane"). The AFM analysis showed that the CNMs presented Young's modulus in the range of 2.5–8 GPa. The composite membranes' responses were investigated by tensile testing in a micro-tensile stage as a function of substrate thickness and substrate pore density and diameter, which were found to affect the mechanical properties. Thermogravimetric analysis was used to investigate the thermal stability of composite membranes at high temperatures. The results revealed the structural integrity of CNMs, while critical parameters governing their mechanical response were identified and discussed. [ABSTRACT FROM AUTHOR]

As the power‐conversion efficiency (PCE) of organic–inorganic lead halide perovskite solar cells (PSCs) is approaching the theoretical maximum, the most crucial issue concerns long‐term ambient stability. Here, the application of PCN‐224 quantum dots (QDs) is reported, a typical Zr‐based porphyrinic metal–organic framework (MOF), to enhance the ambient stability of PSCs. PCN‐224 QDs with abundant Lewis‐base groups (e.g., CO, C−N, CN) contribute to high‐quality perovskite films with enlarged grain size and reduced defect density by interaction with under‐coordinated Pb2+. Meanwhile, PCN‐224 QDs enable the well‐matched energy level at the perovskite/hole transport layer (HTL) interface, thereby facilitating hole extraction and transport. More importantly, PCN‐224 QDs‐treated HTL can capture Li+ from bis(trifluoromethanesulfonyl)imide additive, leading to the reduced aggregation and less direct contact with moisture for hygroscopic Li‐TFSI. Moreover, PCN‐224 QDs mitigated Li+ ion migration into the perovskite layer, thus avoiding the formation of deleterious defects. The resultant devices yield a champion PCE of 22.51%, along with substantially improved durability, including humidity, thermal and light soaking stabilities. The findings provide a new approach toward efficient and stable PSCs by applying MOF QDs. [ABSTRACT FROM AUTHOR]

The combination of two-dimensional materials (2D) into heterostructures enables their integration in tunable ultrathin devices. For applications in electronics and optoelectronics, direct growth of wafer-scale and vertically stacked graphene/hexagonal boron nitride (h-BN) heterostructures is vital. The fundamental problem, however, is the catalytically inert nature of h-BN substrates, which typically provide a low rate of carbon precursor breakdown and consequently a poor rate of graphene synthesis. Furthermore, out-of-plane deformations such as wrinkles are commonly seen in 2D materials grown by chemical vapor deposition (CVD). Herein, a wrinkle-facilitated route is developed for the fast growth of graphene/h-BN vertical heterostructures on Cu foils. The key advantage of this synthetic pathway is the exploitation of the increased reactivity from inevitable line defects arising from the CVD process, which can act as active sites for graphene nucleation. The resulted heterostructures are found to exhibit superlubric properties with increased bending stiffness, as well as directional electronic properties, as revealed from atomic force microscopy measurements. This work offers a brand-new route for the fast growth of Gr/h-BN heterostructures with practical scalability, thus propelling applications in electronics and nanomechanical systems. [ABSTRACT FROM AUTHOR]

[Display omitted] • CVD graphene/PEI nanolaminates were produced via iterative lift-off/float-on technique. • Significantly enhanced mechanical behaviour and electrical conductivity were achieved. • The nanolaminates show impressive joule heating efficiency. • Quick response, low power consumptions and high areal power densities are shown. Graphene, with its superior physical properties, has been considered as the perfect candidate for the production of lightweight, high-strength composite materials with interesting multi-functionalities. The use of large-sized, high-quality CVD graphene monolayers alternated to ultra-thin polymer films in a laminate configuration has been recently proposed as an efficient route to overcome many of the limitations faced by the use of discontinuous sheets of graphene in nanocomposites. Here we report on the production of CVD graphene/polyetherimide (Gr/PEI) nanolaminates with very low graphene volume fractions (up to 0.165 vol%), using a modified iterative and automatic lift-off/float-on procedure. The produced freestanding Gr/PEI nanolaminates present not only a significant enhancement of mechanical and electrical properties but, very interestingly, show impressive Joule heating efficiency. In fact, upon the application of an electrical potential, they can reach temperatures higher than 250 °C, with heating rates up to 325 °C/s. The produced heaters show a very uniform distribution of the temperature even when bend and are characterized by low power consumptions (up to 16 Watt) and high areal power densities (up to ca. ∼1.28 W/cm2), thus suggesting their possible application in thermal management. [ABSTRACT FROM AUTHOR]

Ultra-sensitive and responsive humidity sensors were fabricated by deposition of graphene oxide (GO) on laser-induced graphene (LIG) electrodes fabricated by a low-cost visible laser scribing tool. The effects of GO layer thickness and electrode geometry were investigated. Sensors comprising 0.33 mg/mL GO drop-deposited on spiral LIG electrodes exhibited high sensitivity up to 1800 pF/% RH at 22 °C, which is higher than previously reported LIG/GO sensors. The high performance was ascribed to the high density of the hydroxyl groups of GO, promoted by post-synthesis sonication treatment, resulting in high water physisorption rates. As a result, the sensors also displayed good stability and short response/recovery times across a wide tested range of 0–97% RH. The fabricated sensors were benchmarked against commercial humidity sensors and displayed comparable performance and stability. Finally, the sensors were integrated with a near-field communication tag to function as a wireless, battery-less humidity sensor platform for easy read-out of environmental humidity values using smartphones. [ABSTRACT FROM AUTHOR]

Push-to-pull (PTP) testing is employed to probe the uniaxial tensile response of freestanding monolayer graphene. Various analytical approaches are employed to estimate the elastic modulus of end-clamped graphene samples, combining in-situ Raman spectroscopy and scanning electronic microscope (SEM) measurements. The utilization of spatially resolved Raman-derived strains for assessing the elastic properties of monolayer graphene leads to results consistent with previous experimental and theoretical values of the elastic modulus (approximately 1 TPa). Molecular dynamics (MD) simulations of (pristine and defective) freestanding graphene sheets uniaxially loaded under varying clamping conditions are performed to support the experimental observations. The computational results indicate that the mechanical responses of the sheets are affected by the type, the spatial profile, and the heterogeneity of the clamping. When uniaxial pulling of end-clamped graphene is applied by a substrate adhering to the graphene sheet through van der Waals forces (as in PTP testing), the elastic modulus may be highly underestimated due to often inhomogeneous stress distribution and slippage processes. The MD simulations predict that the elastic modulus of pristine monolayer graphene is approximately 1 TPa, whereas its fracture strength can reach values of up to 110 GPa. Overall, this study underscores the limitations of traditional analyses of PTP experiments (utilizing indentation readouts and SEM imaging) and proposes new potential avenues (involving Raman measurements) for future research on the elastic properties of 2D materials. [Display omitted] • Push-to-pull uniaxial straining is coupled with SEM and Raman spectroscopy. • In-situ Raman spectroscopy quantifies the deformation states of 2D materials. • Measurement of ultra-high elastic modulus (1 TPa) of monolayer graphene. • MD simulations reveal the influence of defects and clamping. [ABSTRACT FROM AUTHOR]

Abstract: Mats of vertically-aligned multiwall carbon nanotubes were grown in an thermal CVD reactor with simultaneous feed of the catalyst and carbon precursors. Mats were soaked into epoxy resin solutions without any prior chemical modification and then cured to produce composite plates of z-axis nano-reinforcement. Direct observations of the epoxy–CNT interactions at the nanoscale revealed that epoxy interacted naturally with the MWCNTs without affecting their physical characteristics, alignment, or the mat’s morphology. The compressive behavior of the pristine and composite mats was consistent with mechanical predictions accounting for an elastic regime followed by elastic instability and compaction. Strong evidence of reinforcement in the MWCNT/epoxy composites was indicated by increased strength, stiffness and toughness values with respect to the as-grown mats and pure polymer. The elastic instability strain of the composites was of the order of 0.4. [Copyright &y& Elsevier]

Abstract: The current study reports on the fatigue behaviour, micromechanics of reinforcement and stress transfer efficiency of the interface of an autoclave-processed Cf-epoxy laminate. Throughout fatigue loading at a maximum strain below the critical fatigue limit of the matrix material, testing was interrupted at discrete fatigue levels of 100, 103, 104 and 105 cycles to allow for laser Raman microscopy measurements of the axial stresses developing along natural and induced discontinuities on fibres in the composite. The established axial stress profiles were regressed to establish the corresponding interfacial shear stress (ISS) profiles at each fatigue level. The effect of fatigue on the stress transfer efficiency of the interface was calculated through the evolution of three interfacial performance parameters (maximum ISS, length required for its attainment and transfer length) as a function of loading cycles. Additional measurements on “random” locations helped identify the main damage mechanisms developing at the microscale. [Copyright &y& Elsevier]

Abstract: The failure of polymer matrix composites upon exposure to the environment has been assessed in the present study. In order to investigate the combined action of temperature, humidity and UV radiation on polymers and composites, an environmental ageing chamber has been constructed and tested. The accelerated environmental ageing was based on two kinds of alternating cycles, which provided humidity, temperature and ultraviolet radiation. The materials examined were isophthalic polyester and isophthalic polyester reinforced with a glass fiber random mat onto which glass fibers were knitted at 0°/90° (GFRPC) at a total volume fraction of approximately 20%. Dynamic mechanical analysis, for a range of temperatures and frequencies under tensile and three-point bending loadings, revealed that the aged materials gained in stiffness, whereas a small deterioration in strength was found. Scanning electron microscopy studies performed before and after environmental chamber conditioning revealed that some microcracks had occurred on the surface of the specimens. Nevertheless, the length of these microcracks was less than the critical value of 0.1mm, required for crack propagation. [Copyright &y& Elsevier]

The mechanically as well as the thermally induced chain conformational transformations in syndiotactic polypropylene (sPP) were monitored using both Raman and FT-IR spectroscopic techniques. Samples of syndiotactic polypropylene of helical crystalline conformations were elongated at different elongations up to 600%, while Raman and infrared spectra were simultaneously recorded. Quantitative analysis of these spectra using the ratio of helical to trans-planar content known as the ‘Transformation Index’ calculated from both Raman and infrared methods revealed that the relative proportion of the helical to the trans-planar conformation dramatically alters when the 100% elongation is reached, while any residual helical proportion has vanished above 500% elongation. Furthermore, we report for the first time an overall comprehensive Raman study of the helical to the trans-planar transformation of sPP during elongation up to 600% and consequent relaxation. In addition, a study of the thermal treatment of an sPP sample in the trans-planar conformation also took place. Furthermore, molecular orientation studies with the use of polarized infrared spectroscopy have been performed in order to monitor the changes in the orientation of the molecular chains during the application of stress. Both Raman and infrared experiments have demonstrated that when the tension is removed, a mixed stage of conformations is observed. Finally, the use of the above-mentioned techniques allows the monitoring of the thermally induced phase transformation from trans-planar configurations to helical in the temperature range between 60 and 90 °C. These spectroscopic findings are in agreement with differential scanning calorimetry thermal studies, which also confirm the thermally induced phase transformation. [Copyright &y& Elsevier]

The mechanical performance of fiber‐reinforced composites is seriously affected by their exposure to the environment. The combined action of elevated temperatures, humidity, and UV radiation (aging) on aramid fibers/epoxy resin composites is examined by employing Raman spectroscopy in tandem with mechanical loading. The imposed conditions drastically affect the interface of the composites altering the performance of the material under tensile loads. Although the maximum values of interfacial shear strength for the aged material are similar to that of the pristine material; however, they appear at lower strain levels, which is attributed to the significant decrease of the shear modulus of the epoxy matrix combined with the failure of aramid fibers to sustain the external loading due to the aging process. At high strains, the interface fails at lower strain levels (compared to the pristine sample) due to significant increase of micro‐cracking and micro‐voids on the surface of the aged composites. The formation of such flaws is the primary reason for the reduced mechanical performance and early failure of the composite material. [ABSTRACT FROM AUTHOR]

SF 6 and SF 6 –N 2 gas mixtures are well known insulators used in industry applications, but SF 6 has to be recovered due to its high global warming potential. In this study, the adsorption of the pure SF 6 and N 2 fluids and the separation of their mixture with SF 6 :N 2 = 1:9 composition, using three-dimensional porous carbon nanotube networks and pillared graphene materials has been studied by employing Monte Carlo and Molecular Dynamics simulations at ambient temperature and pressure up to 20 bar. The results obtained reveal a significant SF 6 uptake and high adsorption selectivity for SF 6 over N 2 , compared to the best performing materials in the literature. The selectivity for SF 6 decreases in the case of pillared graphene and strongly depends on the nanotube pillar and graphene layer distances. The saturation capacity of the investigated materials is also achieved at very different pressure ranges, as it has been reflected on the calculated adsorption isotherms. Due to this fact, the translational diffusion coefficients of the adsorbed SF 6 and N 2 molecules in each material are significantly different at ambient conditions. The results obtained might be used as a springboard towards the rational design of carbon-based materials for the capture of the very potent greenhouse gas SF 6. Image 1 • The adsorption and separation of pure SF 6 and SF 6 /N 2 mixtures have been studied. • PNN show high adsorption selectivity for SF 6 combined with a large SF 6 uptake. • At ambient conditions, PNN achieve high SF 6 selectivity, comparable or higher than the values reported in the literature. • The selectivity for SF 6 decreases for pillared graphene's and depends on their structural properties. • SF 6 packing in pores affects the translational mobility of N 2. [ABSTRACT FROM AUTHOR]

Abstract: The crystallization of calcium carbonate was investigated on pristine and non-covalently modified carbon nanotubes (CNTs) using the vapor diffusion technique in a calcium chloride solution. Non-covalent modification was accomplished by treating the carbon nanostructures with the amphiphilic copolymer poly(isoprene-b-acrylic acid). Calcium carbonate crystals grown on the surface and in the interstitial channels of CNT buckypapers were observed in both cases. Scanning electron microscopy analysis of the untreated CNTs showed the characteristic rhombohedral morphology of calcite crystals, while in the case of modified material spherical and ellipsoidal crystals, consisted of nanocrystallites, were observed. X-ray diffraction analysis showed the presence of calcite crystals in both cases. [Copyright &y& Elsevier]

Carbon is a simple, stable and popular element with many allotropes. The carbon family members include carbon dots, carbon nanotubes, carbon fibers, graphene, graphite, graphdiyne and hard carbon, etc. They can be divided into different dimensions, and their structures can be open and porous. Moreover, it is very interesting to dope them with other elements (metal or non‐metal) or hybridize them with other materials to form composites. The elemental and structural characteristics offer us to explore their applications in energy, environment, bioscience, medicine, electronics and others. Among them, energy storage and conversion are extremely attractive, as advances in this area may improve our life quality and environment. Some energy devices will be included herein, such as lithium‐ion batteries, lithium sulfur batteries, sodium‐ion batteries, potassium‐ion batteries, dual ion batteries, electrochemical capacitors, and others. Additionally, carbon‐based electrocatalysts are also studied in hydrogen evolution reaction and carbon dioxide reduction reaction. However, there are still many challenges in the design and preparation of electrode and electrocatalytic materials. The research related to carbon materials for energy storage and conversion is extremely active, and this has motivated us to contribute with a roadmap on 'Carbon Materials in Energy Storage and Conversion'. [ABSTRACT FROM AUTHOR]

As being only one atom thick, most of the device applications require graphene to be partially or fully supported by a substrate, which is typically silicon dioxide (SiO 2). According to a common understanding, graphene interacts with SiO 2 through weak, long-range van der Waals forces, emerging between instantaneous/induced dipoles, in contrast to the experimental evidence that reveals a surprisingly high interaction between graphene and SiO 2. In order to get further insight into this phenomenon, we carried out diverse physical measurements on SiO 2 substrates, prepared via different fabrication protocols, with and without graphene on top. As a result, the role of the oxide surface charges is recognized for the first time as a main factor causing graphene to strongly interact with SiO 2. Our findings provide guidelines for designing 2D materials interaction with a substrate through modulation of surface charges. This, in turn, can facilitate the development of new graphene based microelectronic devices. Image 1 [ABSTRACT FROM AUTHOR]

In this work we present a fabrication process for sculpturing wrinkled structures into soft polymers by thermal treatment of graphene flakes. This is accomplished by the imposition of a biaxial compressive stress field to the graphene flakes by controlled heating of graphene/polymer composites. The wrinkling patterns (amplitude, wavelength) are linearly related to the thickness of the graphene as in the case of a stiff film deposited on a compliant substrate. The orientation of the wrinkles is controlled by the geometry of the flakes, such as that long and narrow flakes exhibit perfectly parallel wrinkles perpendicular to the longer edge, while more equilateral specimens are wrinkled without any preferred orientation in the flake interior. Kelvin probe measurements showed that this type of wrinkling does not affect the surface potential of the graphene flakes. The universality of the technique is validated by sculpturing two different polymers, using mechanically exfoliated flakes as well as large graphene prepared by chemical vapor deposition. We thus demonstrate that the present approach is an excellent method for patterning the surface of soft matter in a number of applications with nanoscale features of lateral dimensions as low as ∼50 nm. Image 1 [ABSTRACT FROM AUTHOR]

The interface quality between the reinforcement and the host matrix plays a key role in the mechanical performance of Carbon Fibre/Epoxy Resin (CFRP) composites. In most cases, an adequately strong interfacial bond is induced chemically either by the oxidation of the carbon fibre (CF) surface and/or by means of mechanical interlocking (friction). Here, a mild chemical process involving CF's functionalization via an epoxidation reaction at room temperature (RT) is being proposed. By immersing the CF in an organic solution (chloroperoxybenzoic acid in dichloromethane), the outer surface is functionalized with oxygen moieties, such as epoxy rings, at optimized grafting densities. The room-temperature method described here is more advantageous that other oxidative treatments since it is cost-effective, environmentally friendly and does not damage the fibre surface. Furthermore, as detected by Laser Raman microscopy a considerable 2.3-fold increase of the maximum interfacial shear stress was observed for the treated CF/Epoxy systems as compared to the pristine-untreated-samples. [ABSTRACT FROM AUTHOR]

Graphene was successfully employed as a catalyst for the activation of sodium persulfate, towards the effective degradation of propylparaben, an emerging micro-pollutant, representative of the parabens family. A novel process is proposed which utilizes a commercial graphene nano-powder as the catalyst and sodium persulfate as the oxidizing agent. It was found that over 95% of micro-pollutant degradation occurs within 15 min of reaction time. The effects of catalyst loading (75 mg/L to 1 g/L), sodium persulfate (SPS) concentration (10 mg/L to 1 g/L), initial solution pH (3–9) and initial paraben concentration (0.5 mg/L to 5 mg/L) were examined. Experiments were carried out in different aqueous conditions, including ultrapure water, bottled water and wastewater in order to investigate their effect on the degradation rate. The efficiency of the process was lower at complex water matrices signifying the role of organic matter as scavenger of the oxidant species. The role of radical scavengers was also investigated through the addition of methanol and tert-butanol in several concentrations, which was found to be important only in relatively high values. An experiment in which propylparaben was substituted by methylparaben was conducted and similar results were obtained. The consumption of SPS was found to be high in all pH conditions tested, surpassing 80% in near neutral environment. However, the results indicate that the sulfate radicals formed react with water in alkaline conditions, which are the optimal for the reaction, producing hydroxyl radicals which appear to be the dominant species leading to the rapid degradation of propylparaben. To the best of our knowledge, this is the first time pristine graphene has been implemented as an activator of sodium persulfate for the effective oxidation of micro-pollutants. [ABSTRACT FROM AUTHOR]

Mechanical properties of graphene prepared by chemical vapour deposition (CVD) are not easily comparable to the properties of nearly perfect graphene prepared by mechanical cleavage. In this work, we attempt to investigate the mechanical performance of CVD graphene (simply supported or embedded in polymer matrix), transferred by two different techniques, under uniaxial loading with simultaneous in situ monitoring by Raman microspectroscopy. The level of charge transfer doping and strain is assessed using the vector analysis modified for uniaxial strain. The strain distribution across the samples varies significantly, owing to the growth and transfer process, which induces wrinkles and faults in the CVD graphene. In simply supported specimens, the stress transfer efficiency is generally very low and the changes in Raman spectra are dominated by variations in the charge transfer originating from the realignment of the domains on the substrate upon the application of strain. In contrast, samples covered with an additional polymer layer exhibit an improved stress transfer efficiency, and the alterations of charge doping levels are negligible. In fully embedded specimens, the variations in stress transfer efficiencies are caused by the size of the effective graphene domains defined by cracks, folds and/or wrinkles. [ABSTRACT FROM AUTHOR]

High quality graphene was produced by electrochemical exfoliation of graphite. The obtained material was dispersible in several organic solvents and when applied on a Si/SiO 2 substrate it formed thin sheets mostly of 1–3 layers with lateral dimensions ranging between 1 and 10 μm. The number of defects in these sheets was quite low as detected by Raman spectroscopy. Graphene was transferred on FTO electrodes by its dispersion in isopropanol and produced thin transparent films, which were combined with electrochemically deposited PEDOT and were used as counter electrodes in dye-sensitized solar cells. The synergy between the two materials was remarkable and the obtained hybrid electrocatalyst outperformed standard Pt nanoparticle electrocatalyst. [ABSTRACT FROM AUTHOR]

High volume fraction carbon nanotubes (CNTs) composites were fabricated by using the buckypaper approach. CNTs were modified by an epoxidation treatment to achieve high degree of chemical bonding with the epoxy matrix. The fabricated buckypapers exhibited high porosity, allowing the epoxy resin to fully penetrate inside the structure of the film. The hybrid material was found to exhibit specific strength of the same order of magnitude as aluminium-based industrial sheets. The usage of micro-Raman spectroscopy to assess the stress transfer from the polymer to the individual or bundled CNTs upon loading revealed that the enhanced mechanical integrity of such materials is due to the friction and contact forces of a huge number (∼10 23 m −3 ) of inter-bundle junctions. The proposed fabrication procedure can be easily extended towards the preparation of laminated composites at the industrial scale. [ABSTRACT FROM AUTHOR]

Vertically-aligned carbon nanotube–reinforced SiC composites (VACNT/SiC) were prepared via a combined chemical vapor deposition/chemical vapor infiltration process. Thermal oxidation tests, showed the material to undergo virtually no mass loss up to 1400 °C in air, hence indicating excellent oxidation resistance of the composites within the target temperature range of advanced ceramics applications. Microstructural observation demonstrated complete absence of matrix cracks in the surface of VACNT/SiC. A large number of VACNTs having undergone pull-out were observed, a finding which indicated the tubes׳ survival after exposure to the oxidative environment of 1400 °C in air. [ABSTRACT FROM AUTHOR]

[Display omitted] • Whey protein/bacterial nanocellulose film blend was developed from food by-products. • Raman spectroscopy confirmed the uniform distribution of bacterial nanocellulose in film. • Bacterial nanocellulose addition reduced water vapor permeability of films. • Bacterial nanocellulose addition increased films tensile strength & Young's modulus. • Reinforced edible films were developed within the guidelines of Circular Economy. Edible films were developed using whey protein concentrate (WPC) and a natural bio-polymer, namely bacterial cellulose (BC). BC was produced via fermentation from orange peels and subsequently acid-hydrolyzed to obtain BC nanowhiskers (BCNW) with high crystallinity (XRD analysis). Morphology of BCNW was analyzed by SEM, TEM, and AFM. WPC/BCNW film composites, containing different amounts of BCNW (0.5–15%, w/w) were developed and characterized. WPC/BCNW film composite was analyzed by Raman spectroscopy, indicating the successful incorporation and the homogenous distribution of BCNW into the WPC film matrix. Mechanical characterization showed that BCNW behaved as a reinforcing filler in the WPC film, increasing tensile strength and Young's modulus by 32% and 80%, respectively. In addition, water vapor permeability was reduced by 33.9% upon the addition of 0.5% BCNW. This study presented a sustainable approach towards the production of WPC films with improved tensile and water barrier properties, suggesting its potential application as a packaging material. [ABSTRACT FROM AUTHOR]

Graphene-related materials (GRMs) are subject to intensive investigations and considerable progress has been made in recent years in terms of safety assessment. However, limited information is available concerning the hazard potential of GRM-containing products such as graphene-reinforced composites. In the present study, we conducted a comprehensive investigation of the potential biological effects of particles released through an abrasion process from reduced graphene oxide (rGO)-reinforced composites of polyamide 6 (PA6), a widely used engineered thermoplastic polymer, in comparison to as-produced rGO. First, a panel of well-established in vitro models, representative of the immune system and possible target organs such as the lungs, the gut, and the skin, was applied. Limited responses to PA6-rGO exposure were found in the different in vitro models. Only as-produced rGO induced substantial adverse effects, in particular in macrophages. Since inhalation of airborne materials is a key occupational concern, we then sought to test whether the in vitro responses noted for these materials would translate into adverse effects in vivo. To this end, the response at 1, 7 and 28 days after a single pulmonary exposure was evaluated in mice. In agreement with the in vitro data, PA6-rGO induced a modest and transient pulmonary inflammation, resolved by day 28. In contrast, rGO induced a longer-lasting, albeit moderate inflammation that did not lead to tissue remodeling within 28 days. Taken together, the present study suggests a negligible impact on human health under acute exposure conditions of GRM fillers such as rGO when released from composites at doses expected at the workplace. [Display omitted] • Graphene related materials are extensively used to reinforce polymers. • Abrasion of composite materials is an important end-of-life scenario to be assessed prior to their commercial use. • This study provides a qualitative and quantitative analysis of the released materials after abrasion. • The hazard of abraded thermoplastics is assessed focusing on the most likely exposure routes. • Life cycle considerations and impact of reduced graphene oxide in the context of reinforced polymers are addressed. [ABSTRACT FROM AUTHOR]

A method that utilises atomic trajectories and velocities from molecular dynamics simulations has been suitably adapted and employed for the implicit calculation of the phonon dispersion curves of graphene. Classical potentials widely used in the literature were employed. Their performance was assessed for each individual phonon branch and the overall phonon dispersion, using available inelastic x-ray scattering data. The method is promising for systems with large scale periodicity, accounts for anharmonic effects and non-bonding interactions with a general environment, and it is applicable under finite temperatures. The temperature dependence of the phonon dispersion curves has been examined with emphasis on the doubly degenerate Raman active Γ-E2g phonon at the zone centre, where experimental results are available. The potentials used show diverse behaviour. The Tersoff-2010 potential exhibits the most systematic and physically sound behaviour in this regard, and gives a first-order temperature coefficient of χ = −0.05 cm−1/K for the Γ-E2g shift in agreement with reported experimental values. [ABSTRACT FROM AUTHOR]

Exfoliated monolayer graphene flakes were embedded in a polymer matrix and loaded under axial compression. By monitoring the shifts of the 2D Raman phonons of rectangular flakes of various sizes under load, the critical strain to failure was determined. Prior to loading care was taken for the examined area of the flake to be free of residual stresses. The critical strain values for first failure were found to be independent of flake size at a mean value of -0.60% corresponding to a yield stress up to -6 GPa. By combining Euler mechanics with a Winkler approach, we show that unlike buckling in air, the presence of the polymer constraint results in graphene buckling at a fixed value of strain with an estimated wrinkle wavelength of the order of 1-2 nm. These results were compared with DFT computations performed on analogue coronene/ PMMA oligomers and a reasonable agreement was obtained. [ABSTRACT FROM AUTHOR]

Abstract: Graphene oxide has been synthesized by oxidation of graphite flakes and has been deposited on transparent conductive electrodes by casting of its aqueous suspension. Then it was annealed at different temperatures to produce thermally reduced graphene oxide and thus to be employed as counter electrode in quasi-solid-state dye-sensitized solar cells. A variety of techniques has been employed, namely, XPS, TGA, XRD, Raman, FE-SEM and electrochemical analysis to characterize the different phases of graphene oxide reduction, to determine the temperature of completion of thermal reduction and to optimize graphene oxide film thickness. Employment of thermally reduced graphene oxide as electrocatalyst on counter electrodes gave satisfactory current and voltage but very poor fill factor. Then the conductive polymer PEDOT has been deposited on the graphene oxide film by simple and rapid one-step potentiostatic electrodeposition. The mixed PEDOT/reduced-graphene-oxide film demonstrated a behavior comparable with Pt nanoparticulate electrocatalyst. [Copyright &y& Elsevier]

A polyamide (PA) 12-based thermoplastic composite was modified with carbon nanotubes (CNTs), CNTs grafted onto chopped carbon fibers (CFs), and graphene nanoplatelets (GNPs) with CNTs to improve its thermal conductivity for application as a heat sink in electronic components. The carbon-based nanofillers were examined by SEM and Raman. The laser flash method was used to measure the thermal diffusivity in order to calculate the thermal conductivity. Electrical conductivity measurements were made using a Keithley 6517B electrometer in the 2-point mode. The composite structure was examined by SEM and micro-CT. PA12 with 15 wt% of GNPs and 1 wt% CNTs demonstrated the highest thermal conductivity, and its processability was investigated, utilizing sequential interdependence tests to evaluate the composite material behavior during fused filament fabrication (FFF) 3D printing processing. Through this assessment, selected printing parameters were investigated to determine the optimum parametric combination and processability window for the composite material, revealing that the selected composition meets the necessary criteria to be processable with FFF. [ABSTRACT FROM AUTHOR]

Abstract: The mechanical behaviour of PET cord-rubber composites has been investigated by adopting a multi-scale approach by combining standard tensile testing and laser Raman microscopy (LRM). Tensile tests were performed on cord-rubber composite and on its constituents to gain information on the mechanical response at the macro-scale. The behaviour at smaller scales was assessed by means of LRM, which has already been established as a technique that can yield values of stress or strain of reinforcement at the micro-scale. The effects of cord content, composite configuration and sample length have been examined. In particular, the efficiency of stress/strain transfer to the embedded cord has been evaluated and correlated to the micromechanical behaviour through the ‘finite fibre length effect’ observed at the macro-scale. [Copyright &y& Elsevier]

Abstract: A versatile approach is developed to fabricate strong multi walled carbon nanotube/epoxy composites, based on the buckypaper approach. The crucial factors affecting their mechanical performance are the porosity of the carbon nanotube preform, the presence of reactive functional groups onto the CNT surface and the pressure-assisted impregnation. This fabrication procedure can be easily extended towards the preparation of CNT-based composites in industrial scale. [Copyright &y& Elsevier]

Abstract: A simple and efficient approach to exfoliate graphene sheets in solution was reported. The principle of this strategy involved the utilization of binary solvent mixtures which exhibit moderate miscibility. At certain composition, these solvent mixtures showed much more efficient graphene exfoliation, greater than in the case of neat solvents. By adopting a combination of short-time sonication and gradual centrifugation, the resulting suspensions were found to be highly enriched in mono- and few-layer graphene sheets. The structure and morphology of nanosheets were characterized using imaging techniques and spectroscopies. Statistical analysis from imaging techniques showed that 90% of graphene aggregates were less than five layers thick with a monolayer fraction of about 10%. [Copyright &y& Elsevier]

Abstract: A chemical vapor deposition (CVD) process for the production of continuous-high quality-graphene layers based on camphor decomposition on polycrystalline Ni foil, is demonstrated. In situ X-ray diffraction at the pyrolysis temperature of the Ni foil indicates the presence of dominant Ni <111> grains which play an important role in the carbon nucleation and growth. The topography of the grown graphene layers is studied by scanning electron microscopy and atomic force microscopy which show that the Ni surface is covered by continuous and wrinkled graphene carpets. Raman spectroscopy reveals the high quality of the graphene film which appears to be only a few monolayers thick. X-ray photoelectron spectroscopy indicates the existence of graphitic layers and the absence of any spectral features associated with carbides (NixC). The proposed CVD process is a sufficient method for large scale production of graphene films. [Copyright &y& Elsevier]

Abstract: The electrochemical modification of carbon nanotube films (buckypapers) in three different electrolytes consisting of two acids and a basic solvent at very low concentrations was studied. The electrolysis was performed at 1A up to a maximum of 12h. Four different characterization techniques have been employed for assessing the effectiveness of the proposed process. The results presented are very encouraging for the development of electrochemical oxidation as the main surface modification method for carbon nanotubes. It was found that the use of nitric acid electrolyte leads to scalable and controllable oxidation as compared to the basic electrolyte which was also effective but appeared to damage the graphitic structure of nanotubes during longer treatments. [Copyright &y& Elsevier]

Abstract: Carbon nanotubes have long been recognized as the stiffest and strongest man-made material known to date. In addition, their high electrical conductivity has roused interest in the area of electrical appliances and communication related applications. However, due to their miniscule size, the excellent properties of these nanostructures can only be exploited if they are homogeneously embedded into light-weight matrices as those offered by a whole series of engineering polymers. We review the present state of polymer nanocomposites research in which the fillers are carbon nanotubes. In order to enhance their chemical affinity to engineering polymer matrices, chemical modification of the graphitic sidewalls and tips is necessary. In this review, an extended account of the various chemical strategies for grafting polymers onto carbon nanotubes and the manufacturing of carbon nanotube/polymer nanocomposites is given. The mechanical and electrical properties to date of a whole range of nanocomposites of various carbon nanotube contents are also reviewed in an attempt to facilitate progress in this emerging area. [Copyright &y& Elsevier]

Abstract: Carbon nanotube thin sheets – buckypapers – were prepared from multi-walled carbon nanotubes oxidised with different oxidation agents. Prepared buckypapers were characterized by mechanical testing, surface conductivity and mercury porosimetry. It was found that their mechanical properties were increased by increasing the power of oxidation agents. Nitric acid-treated buckypapers showed the highest structural integrity and surface conductivity. [Copyright &y& Elsevier]

• Combination of 2D and 3D techniques for CFRPs' integrity analysis and heal ability. • Surface restoration on micro composites from artificial scratch through SEM analysis. • Recovery rate up to 50% on damaged CFRP reinforced by SH-capsules through DCB test. • Isolation and study of crack by advanced functions of m-CT. In the present study, the healing efficiency of microcapsules containing dicyclopentadiene (DCDP) was investigated on carbon fibre reinforced polymers (CFRPs) via morphological and mechanical characterisation. Micro-computed tomography (m-CT) has been used to observe in three dimensions (3D) the dynamic process of crack propagation and give CFRPs qualitative and quantitative structural and compositional information. Microcapsules with Poly(urea-formaldehyde) as shell and DCPD as healing agent in core were prepared by in situ polymerization in an oil-in-water emulsion. The morphology and thermal properties of microcapsules were examined via Optical Microscopy, Scanning Electron Microscopy (SEM), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Vacuum bagging was proved an efficient technique for the CFRPs' manufacturing that microcapsules can endure. The morphology of heal progression of cracks, induced at the surface of microplastics, was observed through SEM, while for the mechanical response double cantilever beam (DCB) test was selected to evaluate heal efficiency. The reduction of the crack volume in the CFRPs internal structures was up to 45%, while the mechanical restoration exceeded 50% proving microcapsules' efficiency. [ABSTRACT FROM AUTHOR]

In this study, Polyurea/Formaldehyde (PUF) microcapsules containing Dicyclopentadiene (DCPD) as a healing substance were fabricated in situ and mixed at relatively low concentrations (<2 wt%) with a thermosetting polyurethane (PU) foam used in turn as the core of a sandwich structure. The shape memory (SM) effect depended on the combination of the behavior of the PU foam core and the shape memory polymer composite (SMPC) laminate skins. SMPC laminates were manufactured by moulding commercial carbon fiber-reinforced (CFR) prepregs with a SM polymer interlayer. At first, PU foam samples, with and without microcapsules, were mechanically tested. After, PU foam was inserted into the SMPC sandwich structure. Damage tests were carried out by compression and bending to deform and break the PU foam cells, and then assess the structure self-healing (SH) and recovery capabilities. Both SM and SH responses were rapid and thermally activated (120 °C). The CFR-SMPC skins and the PU foam core enable the sandwich to exhibit excellent SM properties with a shape recovery ratio up to 99% (initial configuration recovery). Moreover, the integration of microcapsules (0.5 wt%) enables SH functionality with a structural restoration up to 98%. This simple process makes this sandwich structure ideal for different industrial applications. [ABSTRACT FROM AUTHOR]

Nanocomposites based on the biomimetic brick and mortar architecture are gathering great attention recently due to the outstanding properties of the natural analogues. Thanks to the very high in-plane orientation of nanoplatelets and the low matrix content, these materials exhibit good mechanical performance combined with excellent functional properties based on the nanoplatelets characteristics. Key feature of these materials is the presence of a regular nanostructure that consists of alternated nanoplatelet and matrix layers. Such architecture is commonly attained by means of bottom-up manufacturing processes able to control the alternation of the two phases at the nanoscale. This differs markedly from the top-down manufacturing processes, which are suitable for an industrial scale up but fail to meet the expected requirements. In the present work, nacre-like graphene nanoplatelets (GNPs)/epoxy films at different filler content have been prepared by a top-down manufacturing technology and their mechanical properties in tension have been experimentally evaluated. The elastic modulus has been found to exhibit a maximum between 53 and 67 vol% filler content and then it starts dropping at higher loadings. This was attributed to the depletion of the polymeric matrix which disrupts the continuity of the matrix layer thus inducing incomplete GNP surface coverage. As a result, the effective area for stress-transfer is considerably reduced and this impairs the reinforcement efficiency. In order to explain this behaviour, a model is proposed for predicting the stress transfer characteristics in brick and mortar systems by paying attention to possible non-uniform matrix distribution over the nanoplatelets. The proposed analysis captures well the observed effects and paves the way for the development and further improvement of this new class of engineering materials. [Display omitted] [ABSTRACT FROM AUTHOR]