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Abstract: Carbon nanotubes (CNTs) possess outstanding properties and a unique physicochemical architecture, which may serve as an alternative platform for the delivery of various therapeutic molecules. This review focuses on recent progress in the field of CNTs for biomedical applications. After a short, general physico-chemical introduction to CNTs, we introduce different methods for CNT surface modification, facilitating their dispersions in physiological solutions, on the one hand, and binding a wide range of molecules or drug-loaded liposomes, on the other. We summarize imaging evidences on the structure of CNT-drug conjugates and their relevant uptake mechanisms by the cell. Lastly, we review current repots on CNT toxicity and new developments in CNT-based medical applications: photo-thermal therapy, drug delivery and gene therapy. [Copyright &y& Elsevier]

Abstract: The combination of cryo-TEM and staining is employed for studying protein-enabled dispersion of carbon nanotubes in aqueous solution. The same staining agent is used for both positive- and negative-staining. We are able to image the adsorbed layer of protein or polysaccharide on the nanotube but not the individual molecule. The process is not artifact-free due to change in ionic strength of the solution. However, our results are in line with other, not related, experimental techniques. The obtained information could be used to update models suggested based on, e.g., scattering data. [Copyright &y& Elsevier]

Abstract: Single walled carbon nanotubes (SWNTs) with an anisotropic morphology (rod) are currently being employed as fillers in polymer matrix to produce novel nanocomposites with enhanced properties and performance in a wide variety of applications. We investigate the effect of the addition of second isotropic (spherical) filler, antimony tin oxide (ATO) particles to the anisotropic SWNT-polymer composites. Cryogenic transmission electron microscope (cryo-TEM) and scanning electron microscope (SEM) were employed to image the aqueous dispersions of the SWNTs–ATO–Latex solution and composite thin films respectively. The SEM imaging of these films shows that SWNTs (rods) tend to aggregate in the presence of ATO clusters, indicating depletion interactions between the rods and the spheres. The difference in the value of electrical conductivity of the films measured along the radial and the tangential directions to the spinning lines is probably due to the preferred orientation of the SWNTs in the matrix during the spin coating process. [Copyright &y& Elsevier]

Abstract: High aspect ratio (>1000) CdS nanostructures were prepared via ultrasound treatment of parent nanowires (NWs) dispersed in sodium dodecyl sulfate (SDS) aqueous solution. The CdS parent NWs were prepared using ordered mesoporous silica, SBA-15, as a template. The elongated nanostructures (ENS), namely, NWs, nanoribbons and nanotubes, form stable dispersions in aqueous solutions. Electron microscopy and X-ray diffraction techniques were used to characterize both the parent NWs and the ENS. While the structure of the parent NWs is crystalline cubic, the ENS are amorphous. We show that the amorphous ENS bud from the parent bundled NWs. Ultrasound power and duration, presence of commensurate surfactant and calcination temperature of the templating SBA-15 are critical parameters in the formation of ENS in aqueous solution. [Copyright &y& Elsevier]

Abstract: Rapid strides realized in the field of ordered mesoporous silica (OMS) with a well-defined pore shape and nanometric sizes, provide new gateways for the preparation of nanostructured materials having controlled shape and size with a very narrow distribution. The focus of the current review is on the synthesis of nanostructures templated by OMS either in bulk or in thin film form. The importance of electron microscopy as an indispensable technique in the structural characterization of OMS templated nanostructures, including cryo-TEM, electron tomography and HR-SEM, is highlighted in this review. [Copyright &y& Elsevier]

The in-situ exfoliation of graphite in molten NaCl–KCl salt at 750 °C yielded a homogeneous composite, from which graphene nanoplatelets (GnP) could be easily and completely separated. The GnP product displayed relatively large-size particles (12 μm, TEM, SEM, laser diffraction) and low defect density (Raman, XPS), indicating the superiority of the molten salt exfoliation approach over the conventional liquid-phase approach for producing GnP. The mechanism of GnP production involves the formation of cavities in the molten salt, such that impregnation of the graphite by the molten material facilitated gentle exfoliation of the graphite to GnP. The methodology for the in-situ production of GnP in molten salt is highly applicable in the field of thermal energy storage, where molten inorganic salts are one of the most widely used heat-transfer fluids, such as phase-change materials. In graphite-GnP-salt composite, the thermal conductivity is enhanced by more than one order of magnitude compared to the neat salt matrix, which is essential for efficient thermal energy storage applications. [Display omitted] • In-situ exfoliation of graphite in molten NaCl–KCl yields a homogeneous composite. • Graphite exfoliation mechanism involves controllable cavity-rich melt impregnation. • Graphene nanoplatelets (GnP) product can be completely separated from the composite. • The salt-GnP composite is highly applicable for thermal management applications. [ABSTRACT FROM AUTHOR]

The effect of loading a polymer matrix with more than one filler was investigated for nanocarbon-based fillers of different dimensionalities, namely, 1D carbon nanotubes (CNTs) and 2D graphene nanoplatelets (GNPs). Since both fillers have superior intrinsic mechanical, electrical and thermal properties, their use in tandem enhanced the properties of the resulting composites. The robustness , i.e., the range of nanofiller concentrations at which a substantial enhancement is achieved (considered as a weakness in single filler systems), was dramatically increased in the hybrid system as well as the thermal and electrical conductivities due to the formation of a CNT-GNP 3D structure. These measurements were in keeping with the Kreiger-Dougherty and the effective medium models, respectively. The overall performance of the hybrid composite was compared to single filler systems (using an index of performance) demonstrating the superiority of the hybrid composite in multifunctionality and robustness. [Display omitted] • Hybrid-filler has superior performance and robustness vs single-filler composite. • CNT-GNP hybrid shows enhanced fracture toughness and thermal conductivity. • 3D-filler structure (CNT-GNP) enhances the multifunctionality of the hybrid composite. • A dimensionless number determines the overall system performance. [ABSTRACT FROM AUTHOR]

Phase Change Materials (PCM) possess high heat storage density, but commonly have low thermal conductivity that results in poor heat transfer. Another common problem is the shape stabilization of the storage medium. These problems could be solved by loading the medium with thermally conductive fillers, such as graphite, and encapsulating it in a thermally conductive polymer matrix shell, hence enhancing the thermal properties of both. We suggest a ternary system in which a graphite-epoxy composite provides an encapsulating scaffold to the paraffin, which is also loaded with graphite-based filler. Various graphite-based fillers differing in sizes and geometry were explored, aiming at optimizing their intrinsic properties, such as defect density, and consequently enhancing the thermal properties of the PCM as a whole. It was demonstrated that by judicious choice of the filler, enhancement is achieved for the thermal conductivity of: (1) the shell (epoxy-graphite flakes composite) by 4000% compared to the neat epoxy; (2) the medium (paraffin-graphite flakes composite) by > 2000% compared to the neat paraffin; and (3) the integrated PCM system (paraffin-epoxy-graphite flakes composite) by 1000% compared to that of neat paraffin. The PCM composite is completely preserved during phase change cycling. • Various graphite-based fillers differing in size and geometry were explored for PCM. • Graphite flakes (GF) were found to be the best filler for the overall properties. • Ternary paraffin-GF-epoxy thermally conductive shape-stabilized system was achieved. • Properties of the ternary system were completely preserved during thermal cycling. [ABSTRACT FROM AUTHOR]

The miniaturization, integration and compatibilization of electronic devices dictate the need for efficient thermal management to prevent heat accumulation, which may reduce the operation speed and shorten their life time. Addressing this challenge requires the development of novel polymer-based composite materials with enhanced thermal conductivity. Here, we report a compression-based (25–250 bars) approach for the preparation of polymer composites loaded with carbon-based hybrid fillers, i.e., graphene nanoplatelets and graphite flakes. The carbon-based fillers contribute significantly to the thermal conductivity of the composite while boron nitride nanoparticles inhibit the electrical conductivity to avoid short circuits. An optimal thermal conductivity of 27.5 W (m K)−1 is obtained for the compressed system (measured under atmospheric pressure) for epoxy polymer loaded with 30 wt% graphene nanoplatelets and 40 wt% graphite flakes compared to 0.2 W (m K)−1 of the neat thermoset polymer. Image 1 [ABSTRACT FROM AUTHOR]

Abstract We explored the mechanical and the rheological properties of cement reinforced with graphene oxide (GO, STANDARD GRAPHENE INC.) in the presence of a superplasticizer. The GO enhanced the compressive and flexural strengths of the cement matrix by 40% and 70%, respectively, at extremely low GO concentrations (<0.05 wt%). An optimal nanomaterial concentration (ONC) was observed, above which the properties deteriorate due to the formation of voids in the composite. In a comparison of different nanofiller-reinforced systems, the superiority of the cement + GO + superplasticizer system over other previously reported systems was shown by comparing the nanofiller reinforcement efficiency and a figure of merit that combines the nanocomposite's mechanical and rheological properties. [ABSTRACT FROM AUTHOR]

Aggressive miniaturization in the electronics industry demands more efficient thermal management for electronic devices. Employing the excluded volume approach, we enhanced thermal conductivity (TC) and manipulated heat dissipation in a polymer composite loaded with a thermally conductive filler—graphene nanoplatelets (GNP)—alone or supplemented with a high-volume filler (diamonds). This yielded a maximum bulk TC of 4.5 W m−1K−1 (no compression). The heat dissipation direction could be controlled by compressing (≥50 bars) the wet composite before curing, resulting in an enhancement of the cross-plane thermal conductivity (for thermal-interface materials) to 12.3 W m−1K−1. For non-compressed samples, in-plane thermal conductivity (for circuit board conformal coatings) was dominant (8 Wm−1K−1). Our holistic approach meets diverse thermal management needs. [Display omitted] • The direction of the heat dissipation could be manipulated by compression. • Composites' preparation for various thermal management applications is provided. • Generating excluded volume enhances the thermal conductivity of polymer composites. • Compressed graphene-diamonds composites yield high vertical thermal conductivity. [ABSTRACT FROM AUTHOR]

Abstract The integration of carbon nanotubes (CNTs) into a polymer matrix strongly affects the rheological behavior that in turn may hamper the overall performance of the resulting composite. Research in this topic has focused on bulk rheological properties, while here we employ NMR diffusion experiments to explore the mobility (diffusivity) of epoxy molecules when loaded with CNTs. Rheology and light microscopy indicate percolation of CNT aggregates. Those aggregates cage a substantial amount of epoxy molecules while small angle X-ray scattering indicates some rearrangement of epoxy molecules in the vicinity of the nanotubes. NMR diffusion experiments distinguish between the slow diffusion of the caged molecules and that of the free ones, and relate the fraction of the former to the macroscopic system viscosity. The demonstrated surface-induced slowing-down of diffusion is attributed to strong intermolecular π-π interactions among the epoxy molecules, and between them and the CNT surface. These findings demonstrate the utility of NMR diffusion experiments as an additional method applied to nanocomposites. Graphical abstract Image 1 Highlights • NMR diffusion aid rationalizing the rheological trends in filler-loaded resins. • CNTs influence the rheological behavior by forming a percolating network of aggregates. • The diffusive motion of epoxy molecules confined within the aggregates is strongly reduced. • The fraction of aggregate-confined epoxy correlated with the increase in the mixture's viscosity. • The slowing-down of diffusion is attributed to strong CNT-epoxy intermolecular π-π interactions. [ABSTRACT FROM AUTHOR]

Size and morphology distributions are critical to the performance of nano-drug systems, as they determine drug pharmacokinetics and biodistribution. Therefore, comprehensive and reliable analyses of these properties are required by both the US Food and Drug Administration (FDA) and European Medicines Agency (EMA). In this study, we compare two most commonly used approaches for assessing the size distribution and morphology of liposomal nano-drug systems, namely, dynamic light scattering (DLS) and cryogenic-transmission electron microscopy (cryo-TEM); an automated quantitative analysis method was developed for the latter method. We demonstrate the advantages and disadvantages of each of these two approaches for a commercial formulation of the anti-cancer drug doxorubicin - Doxil®, in which the drug is encapsulated, mostly in the form of nano-rod crystals. With increasing drug concentration, these nano-rods change the shape of the liposomes from spherical , before drug loading, to prolate (oval), post drug loading. Cryo-TEM analysis provides a detailed size distribution of both the liposomes (minor and major axes) and the nano-rod drug. Both these values are relevant to the drug performance. In this study, we show that at elevated drug concentration (2.75 mg/ml) the drug grows mainly along the major axis and that this high concentration can result, in some cases, in liposome rupture. We show that the combination of cryo-TEM and DLS constitutes a reliable tool for demonstrating the stability of the formulation in human plasma at body temperature, a characteristic that is crucial for achieving therapeutic efficacy. [ABSTRACT FROM AUTHOR]

The kinetics of hydrogen storage in magnesium can be accelerated by nanocarbon additives. In this study, we show that loading magnesium by graphene nanoplatelets (GNP) enhances the kinetics by more than an order of magnitude. The GNP presence reduces the Mg agglomeration, induced by de/hydriding, and accelerates the kinetics by connecting between Mg particles. The GNP were prepared by top-down graphite ball-milling in the presence of various organic protective agents. We found that both the molecular structure of the protective agent and the milling energy dictated the GNP properties, namely, size, thickness, defect density and specific surface area. We demonstrated how manipulation of the GNP size has a major effect on the hydrogen storage kinetics in magnesium-GNP composites. [ABSTRACT FROM AUTHOR]

Reduction in water vapor permeability is both fundamentally important and a practical necessity in the polymer industry for packaging and protective applications. The barrier of polymers is significantly improved by inclusion of impermeable lamellar fillers, increasing the diffusion path of gas or water vapor molecules. The most common “barrier-modifier” for polymers is clay, which is less effective for reducing water vapor permeability since it absorbs water, swells and also degrades other properties (e.g., mechanical strength). In this study we focus on graphene as the barrier filler in polyurethane, examining the influence of its lateral size and concentration on both water vapor permeability and the mechanical properties. We demonstrated optimal barrier and mechanical enhancements at low graphene loading of 2 and 1 wt%, respectively. We tested few lateral dimension of graphene and found that the larger size (25 μm) exhibited an optimal barrier enhancement (50% reduction). In addition we found correlation between the onset of the barrier and an increase in the polymer viscosity. [ABSTRACT FROM AUTHOR]

A comparative study was conducted on composite materials having various nanocarbon fillers of different dimensionalities, namely, 1D carbon nanotubes (CNTs), 2D graphite nanoplates (GNPs), and 3D graphite. Comprehensive mechanical, electrical and rheological studies illustrated the complexity of selecting the optimal nanocarbon filler. We found that the mechanical performance of the composite is optimal near the percolation threshold concentration of the filler for all the nanocarbons. The 1D CNTs strongly affected the electrical conductivity and reinforcement of the composite, yielding a narrow range of optimal performance at the lowest filler concentration (0.15 wt%), albeit at the cost of high viscosity. The 2D GNPs demonstrated a wider range of reinforcement with a milder influence on the viscosity at a moderate GNP concentration (3.5 wt%). The 3D graphite filler exhibited similar behavior to that of GNPs, although at a much higher concentration (25 wt%). We introduced a robustness factor as a measure of the filler concentration range at which a valuable reinforcing effect is achieved; this factor increases with the filler dimensionality. These contradicting dimensionality effects are condensed into a figure of merit that takes into account the rheological effect, the mechanical enhancement, and the filler concentration and robustness. [ABSTRACT FROM AUTHOR]

• PCM-based heat sink with plate fins and spreader for transient thermal management. • Different heat sink materials and two PCM types with similar melting temperatures. • Heat spreading, temperature evolution and detailed melting patterns in the sink. • Advantageous performance of Field's metal vs. organic paraffin in heat accumulation. • Dimensional analysis generalizing power inputs and material properties. The use of phase change materials (PCMs) has gained much attention for applications of transient thermal management of electronic systems due to their high latent heat and ability to absorb heat near-isothermally. Because of their low thermal conductivity, PCMs are usually integrated with heat sinks to be used more efficiently. In this study a PCM-based heat sink with a generic structure of plate fins was investigated experimentally and numerically. The intentionally simple fin topology allowed focusing on the effects of various material properties rather than the commonly investigated geometry effects. Hence, two types of heat sink material, copper and aluminum, were examined, and two PCMs with similar melting temperatures but distinctly different thermal properties – a metallic alloy (Field's metal) and an organic paraffin (n-Octacosane), were used. Experimental findings allowed for validation of the numerical approach, used for a comprehensive parametric numerical study. The latter facilitated a more detailed investigation of the transient heat transfer processes, such as melting patterns and heat accumulation analyses, where the superior thermal properties of the metallic PCM manifested in more efficient latent heat accumulation, resulting in reduced system peak temperatures. It was found that systems with Field's metal were able to accommodate up to 80% of the energy in the form of latent heat, which is 10 percentage points higher than achieved using the organic paraffin. A dimensional analysis accounting for power inputs and material properties was conducted, and a generalized behavior was achieved for a normalized time in terms of Fourier and Stefan numbers, and thermal diffusivities ratio. [ABSTRACT FROM AUTHOR]

Mg-nanocarbon composites demonstrate fast reversible hydriding kinetics. The kinetics is strongly correlated with the structure of the added nanocarbon allotrope. We conducted a systematic exploration of the reversible hydriding kinetics of Mg upon addition of nanocarbons with different dimensionalities, namely, 1D carbon nanotubes, 2D graphene nanoplatelets and 3D activated carbon. Our findings showed that the Mg (de)hydriding rate could be tuned by the dimensionality and defect density of the nanocarbon. The resulting kinetic enhancement was explained in terms of the hydrogen spillover mechanism. The use of nanocarbons offers an alternative to the utilization of high concentrations of expensive transition-metal catalysts for hydrogen storage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nano-additives accelerated the self-healing of the textile reinforced concrete (TRC). • Decorating the textile surface with micro silica particles accelerated the self-healing process and enhanced TRC tensile strength and toughness. • Salt-cured TRC samples showed more fine cracks than tap-water-cured which promotes the self-healing process. Textile reinforced concrete (TRC) is an attractive alternative to the classic steel rebar reinforcement since the textile is stronger, more flexible, and non-corrosive compared to steel. Moreover, the TRC approach promotes the formation of multiple thin cracks pattern upon loading instead of a few wide cracks in rebar reinforcement. We found that the self-healing of these multiple thin cracks was accelerated by modifying the concrete matrix (addition of crystalline additive and alumina nanofibers) and by decorating the carbon-based textile with micro silica particles. Exposing the TRC samples to a saturated NaCl environment (as in coastal constructions) improved the bonding strength between the textile and the matrix, hence increasing the self-healing capability (compared to samples cured in tap water). [ABSTRACT FROM AUTHOR]

The loading of individual carbon nanotubes (CNTs) in matrices provides state-of-the-art nanocomposite reinforcement at low CNT concentrations. The dispersion of the CNTs in the matrix is often assisted by surfactants (termed also dispersants), which de-bundle the CNT agglomerates. Despite the critical role of the dispersants in this process, their effect on the properties of the nanocomposite has not been sufficiently studied. In the current study, we elucidate the influence of freeze-dried dispersant-CNT on the performance of polymeric and cementitious nanocomposites. We show that the dispersant (Pluronic) is crucial for exfoliating the CNTs in both types of nanocomposite, whereas it also acts as a plasticizer – thus lowering the mixture's effective viscosity – in cementitious matrices. We identify the optimal nanomaterial concentration (ONC) in each nanocomposite system, namely, the critical filler concentration in which optimal mechanical properties are obtained, and above which they degrade dramatically due to the formation of air voids that can initiate mechanical failure. Importantly, the effect of the dispersant on the nanocomposite system – and, accordingly, the origin of the resulting air voids – is different between polymeric and cementitious matrices. In polymers , a high filler concentration increases the viscosity, and, consequently, entraps air voids in the matrix during mixing. In cement , by contrast, the dispersant stabilizes the air and leads to the formation of foam in the matrix. Taken together, our findings indicate that the behavior of the dispersant throughout the composite preparation process – both in the fresh mixture and in the hardened state – should be considered when employing dispersants for use in applicative composite systems. [ABSTRACT FROM AUTHOR]

The growing availability of nanotubes and the increased knowledge about their loading in polymers have prompted the incorporation of nanotubes in cementitious matrices. The effects of loading straight tungsten di-sulfide nanotubes (WS 2 NT) or waved carbon nanotubes (CNT) in cementitious matrices was explored. Their inclusion in these composites at exceptionally low concentrations (0.063 vol% and 0.15 vol% for WS 2 NT and CNT, respectively) enhanced the composite’s mechanical properties, including compressive and flexural strengths (25–38%). Thermal analysis and electron microscopy indicated that nanotube incorporation in cementitious matrices also accelerated hydration reaction kinetics. It was shown that straight WS 2 NTs bridged pores and cracks more effectively than the waved CNTs, which resist crack propagation via an anchoring mechanism. A comparison to representative cement nanocomposite systems shows that nanotubes (aspect ratio≫1), offer better reinforcement efficiencies than particulate nanomaterials, yielding high mechanical properties enhancement at low concentration. [ABSTRACT FROM AUTHOR]

The extraordinary mechanical properties of graphene prompt its incorporation into a wide range of polymeric nanocomposite materials (NCMs). However, similar to other nanomaterials (NMs), the reinforcement efficiency of graphene and its derivatives is hindered by their agglomeration and poor compatibility with the polymer matrix. In this paper, edge-functionalized graphene nanoribbons (EF-GNR) are incorporated in brittle epoxy polymer matrix. The functionalization process by polyvinylamine (PVAM) chains occurs only at the edges, preserving the in-plane sp 2 of the graphene; thereby the PVAM EF-GNRs are both compatible and strong. The produced NCMs exhibit a wide range of enhanced mechanical properties including fracture toughness, flexural strength and shear strength at low EF-GNR loading (0.15 wt%). The effect of the edge functionalization is indeed critical, demonstrating superior mechanical properties by the EF-GNR loaded NCMs compared to pristine-GNR loaded composites. Finally, a comparative overview of various carbon NM-loaded NCMs indicates that EF-GNR possess high reinforcement efficiency (enhancement % per NM loading %) making it an attractive filler for polymer systems. [ABSTRACT FROM AUTHOR]

We explored the hydrogen storage kinetics of Pd-Mg composites upon addition of different carbonaceous spillover agents (activated carbon and a wide spectrum of carbon nanotube types). We found that the hydrogen (loading or release) kinetics is strongly dependent on the nanocarbon morphology and configuration (e.g., length, diameter and Pd distribution). We therefore define a figure of merit quantifying the de/hydriding performance of previously reported systems and the system investigated in the present study. It demonstrates that the fastest kinetics is obtained for our Pd-decorated carbon nanotubes having the largest diameter. We found a clear structure-function relation between the spillover agent properties and the Mg de/hydriding rates, which could be applied in replacing the heavy and expensive transition metal catalyst by lightweight nanocarbon additive. [ABSTRACT FROM AUTHOR]

Nanotubes are considered as promising nano-reinforcement in cement-based materials. The main challenge towards achieving a significant enhancement in cement properties is an effective dispersion of the agglomerated nanotubes. In this paper, we demonstrate a novel dispersion method of Tungsten di-Sulfide NanoTubes (WS 2 NTs) that results in substantial flexural and compressive strength enhancements at optimal nanotube concentration as low as 0.15 wt%. The reinforcement by WS 2 NTs remains significant after a variety of curing processes, suggesting a genuine nanoscale reinforcing effect. Finally, by employing a comprehensive fractography we found that the WS 2 NTs inhibit crack propagation by bridging with a pullout failure mechanism. [ABSTRACT FROM AUTHOR]

Reinforcing a fine-grained cement-based matrix with a textile fabric is an emerging approach in civil engineering, termed Textile Reinforced Mortar (TRM). We propose to load the ultra-high-performance matrix with nano-additives, i.e., a crystalline admixture (CA) or CA plus alumina nanofibers. The mix was designed to yield flow values - in the fresh state - suitable for retrofitting, and to provide high compressive strength. Examination of the durability of the TRM elements exposed to salty environments unexpectedly showed enhanced tensile strength (<81%). This is owing to the growth of salt crystals at the matrix–textile interface resulting in stronger bond strength, as imaged by scanning electron microscopy, identified by acoustic emission measurements, and validated by pull-off tests. • The developed textile reinforced mortar composites were durable in a salty environment. • Nano-additives enhanced the mortar's compressive strength and the stress at the first crack of the textile reinforced mortar. • Textile–mortar matrix bond strength was enhanced in samples cured in NaCl solution. • Salt-cured vs. tap-water-cured textile reinforced mortars showed more fine cracks with higher energy. [ABSTRACT FROM AUTHOR]

Abstract: The utilization of highly branched polymer (e.g., epoxy resins) in engineering applications is often limited by their brittle nature (low fracture toughness). Loading the polymer matrix by fillers such as individual nanotubes is a promising alternative to enhance fracture toughness without compromising other mechanical properties. However, to fully understand the nanotubes toughening role and correctly characterize the nanocomposite failure mechanisms, a complete exfoliation of the nanotubes aggregates into individual nanotubes is essential. In this work, we embed only individual nanotubes in the polymer matrix using a novel dispersion method. The individual nanotube concentration in the composite is accurately determined. We achieve a record fracture toughness enhancement and, for the first time, demonstrate a coherent quantitative correlation between the fracture toughness and the surface roughness. Finally, comprehensive statistical investigation of the nanotube failure mechanisms shows that carbon nanotubes fail via fracture mechanism, while tungsten di-sulfide nanotubes via pullout mechanism. The failure mechanism could be predicted by the slope of the surface roughness vs. fracture toughness curve. [Copyright &y& Elsevier]

Abstract: Biological sensing is explored through novel stable colloidal dispersions of pyrrole-benzophenone and pyrrole copolymerized silica (PPy-SiO2-PPyBPh) nanocomposites, which allow covalent linking of biological molecules through light mediation. The mechanism of nanocomposite attachment to a model protein is studied by gold labeled cholera toxin B (CTB) to enhance the contrast in electron microscopy imaging. The biological test itself is carried out without gold labeling, i.e., using CTB only. The protein is shown to be covalently bound through the benzophenone groups. When the reactive PPy-SiO2-PPyBPh-CTB nanocomposite is exposed to specific recognition anti-CTB immunoglobulins, a qualitative visual agglutination assay occurs spontaneously, producing as a positive test, PPy-SiO2-PPyBPh-CTB-anti-CTB, in less than 1h, while the control solution of the PPy-SiO2-PPyBPh-CTB alone remained well-dispersed during the same period. These dispersions were characterized by cryogenic transmission microscopy (cryo-TEM), scanning electron microscopy (SEM), FTIR and X-ray photoelectron spectroscopy (XPS). [Copyright &y& Elsevier]

Abstract: Single-walled and multi-walled carbon nanotubes (SWNTs and MWNTs) were characterised as-produced, after exfoliation and purification, and imbedded in the polymer matrix of nanocomposites by using various microscopic techniques. Transmission electron microscopy (TEM) shows thickness distribution as well as catalyst presence of as-produced carbon nanotubes (CNTs); scanning electron microscopy (SEM) and atomic force microscopy (AFM) are helpful tools to better understand the influence of post-treatment during exfoliation and purification, e.g. on the length distribution of CNTs; and finally SEM operated in charge contrast mode offers the potential to monitor the organisation of CNT networks in the polymer matrix of conductive nanocomposites. [Copyright &y& Elsevier]

Abstract: The morphology of conductive nanocomposites consisting of low concentration of single-wall carbon nanotubes (SWNT) and polystyrene (PS) has been studied using atomic force microscopy (AFM), transmission electron microscopy (TEM) and, in particular, scanning electron microscopy (SEM). Application of charge contrast imaging in SEM allows visualization of the overall SWNT dispersion within the polymer matrix as well as the identification of individual or bundled SWNTs at high resolution. The contrast mechanism involved will be discussed. In conductive nanocomposites the SWNTs are homogeneously dispersed within the polymer matrix and form a network. Beside fairly straight SWNTs, strongly bended SWNTs have been observed. However, for samples with SWNT concentrations below the percolation threshold, the common overall charging behavior of an insulating material is observed preventing the detailed morphological investigation of the sample. [Copyright &y& Elsevier]

Abstract: Coatings and engineering plastics often require high impact strength. This property can be achieved with tougheners. For the present paper, core-shell impact modifiers were synthesized using ethylene–propylene copolymers (EPM), ethylene–propylene-diene copolymers (EPDM) or a mixture of both types (EP(D)M) as core material, as well as poly(methyl methacrylate) (PMMA) as shell material. EP(D)M-based polymers were dispersed in water using an Ultra-Turrax® and a high pressure homogenizer. The prepared artificial latexes were used, either without further treatment or after crosslinking, as seed latexes in the emulsion polymerization of methyl methacrylate (MMA). The free radical seeded emulsion polymerization of MMA was investigated in the presence of an oil-soluble initiator, i.e. cumene hydroperoxide (CHP), combined with a redox system, i.e. sodium formaldehyde sulfoxylate hydrate (SFS), disodium salt of ethylenediamine tetra-acetic acid (EDTA), iron (II) sulfate heptahydrate (FeSO4). This initiation system promotes polymerization of MMA near the surface of the seed particles, partially suppressing homogeneous secondary nucleation and polymerization in the aqueous phase. Kinetic and thermodynamic considerations were used to predict the particle morphology. The monomer type, the monomer-to-rubber ratio, the monomer feed type, and crosslinking of the seed latex particles were investigated, to optimize the polymerization kinetics and the properties of the resulting dispersions. The particle morphology was determined by cryo-transmission electron microscopy (cryo-TEM). Monomer-flooded conditions led to the formation of inverted core-shell particles, whereas starved–feed MMA or MMA/styrene mixtures gave rise to partially engulfed structures, i.e. snowman-like. Crosslinking of the EP(D)M seed particles was found to be required to provide the desired core-shell structures. Finally, the obtained core-shell structured particles were used to toughen a PMMA matrix. The tensile properties of the modified PMMA matrix were investigated. The micro-morphology of modified PMMA was studied by scanning electron microscopy (SEM). Tensile tests as well as TEM and SEM analyses demonstrated that the main mechanism of deformation operating in the EP(D)M-toughened PMMA matrix is shear yielding, accompanied by debonding and cavitation processes. [Copyright &y& Elsevier]

Textile reinforced concrete (TRC) has recently gained significant attention in the field of construction. The textile is made of multifilament yarns that exhibit telescopic pull-out behavior reducing its reinforcing efficiency. The remedy lies in epoxy coating, which facilitates full utilization of all filaments within the yarn during loading. Nevertheless, the obtained interfacial bonding between the hydrophilic cementitious matrix and hydrophobic epoxy coating is rather weak. In this study, several coating strategies were employed to enhance the interface bonding by modifying the textile surface with graphene oxide or cement powder. The effect of these coatings on the pull-out behavior of a single multifilament yarn from a cementitious matrix was systematically investigated and compared to that of plain or neat epoxy-coated yarns. The pull-out mechanism was found to involve adhesion followed by friction. The best adhesion between the epoxy-coated yarn and the cementitious matrix was obtained for cement powder sprinkled over freshly coated epoxy yarn, yielding an enhancement in chemical debonding energy of 472% compared to a plain yarn. The highest slippage energy (indicating friction) was obtained for a coated epoxy surface decorated with a small amount of cement or graphene oxide particles, which provided improved mechanical anchoring. [ABSTRACT FROM AUTHOR]

High thermal-conductivity coatings have garnered much attention in fields such as the automotive and aerospace industries. Commonly used filler-loaded coatings are limited either by the high viscosity of the coating paint or by the intrinsic properties of the filler. In this study, we used graphene as a high thermal conductivity filler to enhance the properties of paint used in the automotive industry. The effects of filler size on the thermal conductivity and viscosity of stable liquid dispersion (paint) are studied and modeled in graphene nanoplatelet-loaded paint (2.47 vol%), which exhibits enhanced thermal conductivity of 160% (1.6 vs. 0.6 W (m K)−1 for the neat commercial paint) and low viscosity. Furthermore, the filler with the optimum performance (in the paint) is studied in solid state, where it elicits a 720% enhancement in thermal conductivity (14.4 vol%). • Water-based paint coating with enhanced thermal conductivity was developed. • Graphene is employed in enhancing the thermal conductivity of the paint. • Larger size graphene of lower aspect ratio yields optimal behavior. • Dispersion quality and defect density of the graphene are critical for performance. • Concentration and aspect-ratio-based modeling provide insight into the findings. [ABSTRACT FROM AUTHOR]

• Carbon allotropes of various dimensionalities are explored in reinforcing cement. • Effect of nanofillers on fresh and hardened states of cement composites is investigated. • Compatibility and dimensionality of nanofillers play a crucial role in reinforcing cement composites. Carbon-based nanofillers (NFs) have a marked effect on the mechanical and rheological properties of polymeric and cementitious composites. In this study, we explored the role of four nanocarbon materials as NFs, namely, graphene nano-platelets (GNP) and carbon nanotubes (CNT) and their hydrophilic derivatives, graphene oxide (GO) and functionalized CNT (f-CNT), respectively. We investigated how the NF dimensionality and hydrophilicity affect the various properties of NF-cement composites in fresh (e.g., workability) and hardened (e.g., strength) states. This will enable one to judiciously choose an appropriate NF for a specific application. In that respect, the additive polycarboxylate ether (PCE) is employed both as a surfactant for the NF dispersion in the cementitious matrix and as a superplasticizer, reducing the composite mixture viscosity to enhance its workability. The addition of GO, CNT or f-CNT fillers (in the presence of 0.2 wt% PCE) demonstrated workability deterioration for all NF concentrations while that of the GNP-loaded system was much less affected. Among the four explored NF-loaded systems, GO (0.025 wt%) was the best reinforcing agent with enhancement of 60% in flexural and ~30% in compressive strengths. Nevertheless, GNP presents a cost-effective alternative, although a little inferior to GO in its mechanical performance. [ABSTRACT FROM AUTHOR]

• Graphene and boron nitride nanoplatelets were used as fillers to create epoxy nanocomposite via rod- coating technique. • The influence of the fillers on the barrier and thermal properties of the composite was studied. • Graphene nanoplatelets based nanocomposite presented 80% reduction in water vapor permeability due to nanofiller alignment. • The thermal conductivity enhancement was higher when loaded with Graphene nanoplatelets (2.18 W/(m∙K)). Enhancement of barrier properties of coating materials are essential for potting sensitive electronic devices to prevent moisture penetration, in addition to enhancement of thermal conductivity required to facilitate efficient thermal management. The barrier of polymers is significantly improved by inclusion of impermeable 2D fillers. Clays, which are the most common "barrier-modifier" for polymers, are less effective for reducing water vapor permeability since they absorb water and swells. In this communication we focus on the addition of Graphene and Boron Nitride Nano Platelets (GNP and BNNP) as an alternative to clay, both are known to be impermeable to most gases and liquids. Alignment of the fillers within the matrix has a substantial effect on the barrier properties. Therefore, the nanocomposite was applied on a surface by a rod coating method. The larger aspect ratio (˜700) of the GNP filler (compared to BNNP) results in an alignment perpendicular to the vapor flow upon rod-coating. As a result, the GNP-loaded polymer film provided more substantial barrier enhancement (80% reduction in permeability) than the BNNP-loaded film (60% reduction). Moreover, the thermal conductivity enhancement of the pristine epoxy matrix (0.2 W/(mK)) was higher when loaded with GNPs (2.18 W/(mK)) than with the BNNPs (0.57 W/(mK)), most probably due to the high intrinsic thermal conductivity and larger aspect ratio of the former. [ABSTRACT FROM AUTHOR]