In this study, we prepared electrospun polyacrylonitrile (PAN) nanofibers functionalized with dibenzo-18-crown-6 (DB18C6) crown ether and showed the potential of these fibers for the selective recovery of K + from other both mono-and divalent ions in aqueous solutions. Nanofibers were characterized by SEM, FTIR and TGA. SEM results showed that the crown ether addition resulted in thicker nanofibers and higher mean fiber diameters, in a range of 138 to 270 nm. Batch adsorption experiments were conducted in order to evaluate the potential of the crown ether modified nanofibers as an adsorbent for ion removal. The maximum adsorption capacity of the crown ether modified nanofibers for K + was 0.37 mmol g À1 and the nanofibers followed the selectivity sequence of K

Integrating carbon nanotubes (CNTs) in carbon-fiber-reinforced-polymer (CFRP) composites enhances structural and functional properties; however, it often involves chemical functionalization or processes that lead to inhomogeneous dispersion and nonuniform distribution of CNTs that impair the final properties and hinder manufacturing scalability. Herein, we present a novel and scalable processing technique to integrate pristine CNTs (pCNTs) into CFRP composites without the need for chemical functionalization or addition of surfactants. We use cellulose nanocrystals (CNCs) as assisting nanomaterials to uniformly disperse and stabilize pCNTs in water, and then we coat carbon fibers (CFs) with CNC-pCNT prior to resin infusion. Two coating methods are used: simple immersion (I-coating) and simultaneous immersion and sonication (IS-coating). The surface chemistry of coated CFs reveals that I-coating provides a higher quantity of polar oxygen groups in coated CFs containing CNC-pCNT compared to IS-coating. We show that fabricating hybrid CFRPs by incorporating 0.2 wt % CNC–0.2 wt % pCNT in CFRP composites using this simple technique enhances the flexural strength by 33% and the interlaminar shear strength (ILSS) by 35% compared to those of neat CFRPs. Significantly, 0.2CNC-0.2pCNT-CFRPs show ∼25% higher flexural strength and ILSS compared to the largest enhancement in composites with individual functionalized CNTs (fCNTs) or CNCs, demonstrating a synergistic effect of CNC-pCNT in enhancing properties. Moreover, our results indicate that incorporating CNC-pCNT increases the thermal stability of CFs compared to those of fCNTs. These are specifically crucial in composites used in structural applications. These results highlight that the introduced CNC-enabled processing technique is a potential scalable path toward the fabrication of hybrid composites that can enhance properties higher than individual CNTs or CNCs, avoiding costly and/or time-inefficient functionalization processes.

Laminated composites mostly suffer from layer separation and/or delamination, which may affect the stiffness, strength and lifetime of structures. In this study, we aim to produce micronscale thin carbon nanotubes (CNTs) reinforced adhesive nanofibrous interleaves and to explore their effectiveness when incorporated into structural composites. Neat polyvinyl butyral (PVB) and solutions containing low fractions of CNTs from 0.5 to 2 wt.% were electrospun directly onto carbon fiber prepregs. These interlayered laminates were cured above the glass transition temperature (Tg) of PVB to achieve strong interlaminar binding and also to resist crack reinitiation. The effect of CNTs presence and their mass fractions both on total Mixed-Mode I+II fracture toughness (GC) and crack length was investigated under Mixed-Mode I+II loading. Almost 2-fold increase in GC was reported in interlayered composites compared to noninterlayered laminates, associated to toughening effect of adhesive PVB/CNTs nanofibrous interlayers. Furthermore, the post-fracture analysis revealed the aid of CNTs interleaves in retarding delamination and afterward stabilization of crack propagation.

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Dispersing carbon nanomaterials in solvents is effective in transferring their significant mechanical and functional properties to polymers and nanocomposites. However, poor dispersion of carbon nanomaterials impedes exploiting their full potential in nanocomposites. Cellulose nanocrystals (CNCs) are promising for dispersing and stabilizing pristine carbon nanotubes (pCNTs) and graphene nanoplatelets (pGnP) in protic media without functionalization. Here, the underlying mechanisms at the molecular level are investigated between CNC and pCNT/pGnP that stabilize their dispersion in polar solvents. Based on the spectroscopy and microscopy characterization of CNCpCNT/pGnP and density functional theory (DFT) calculations, an additional intermolecular mechanism is proposed between CNC and pCNT/pGnP that forms carbonoxygen covalent bonds between hydroxyl end groups of CNCs and the defected sites of pCNTs/pGnPs preventing re‐agglomeration in polar solvents. This work's findings indicate that the CNC‐assisted process enables new capabilities in harnessing nanostructures at the molecular level and tailoring the performance of nanocomposites at higher length scales.

Cellulose nanocrystals (CNCs) enable the effective coating of carbon fibers (CFs) with pristine carbon nanotubes (CNTs) and graphene nanoplatelets (GnPs). Herein, we articulate the mechanisms that form the interface of CNC-bonded CNT and CNC-bonded GnP-CF reinforced polymer (CFRP) composites that are suitable for structural applications. We show that CNCs provide a suitable platform to engineer the interface of hybrid composites. We demonstrate that the hybrid nanomaterials, i.e., CNC and CNT/GnP, alter the chemical composition of the interface and its properties, and despite the similar elemental composition of the CNT and GnP, the mechanical properties of the produced composites differ. Our results show that the presence of CNC–CNT and CNC–GnP creates a 4 μm interfacial region that leads to a 200 and 145% increase in interfacial shear strength and a 46 and 28% enhancement in interlaminar shear strength, respectively. Furthermore, density functional theory calculations show that the binding energy between the CNC–CNT and CF sizing agent is 14% higher than that of CNC–GnP underlining the effect of chemical and physical interactions in the observed difference in mechanical properties. The understanding gained from this study highlights a path forward bottom-up manufacturing of hybrid composites with an engineered microstructure and properties from the molecular level and nanoscale to higher scales.

Additive manufacturing (AM) enables cost e↵ective production of complex shapes with providing design freedom. Fused deposition modeling (FDM) has been one of the most accessible AM methods which guide thermoplastic filaments to provide accurate and easy production of 3D objects layer by layer fusion. However, this technique has brought some drawbacks associated with limited material choices including relatively weak structural properties, low resolution range, and restrained processability in 3D printers. To overcome these flaws of FDM, herein we described the fabrication of high-performance thermoplastic filaments as an FDM feedstock as a stronger replacement of commodity thermoplastics. For further improvement, carbon nanotubes (CNTs) were incorporated into high performance matrices to provide multifunctionality both by improving mechanical properties and electrical conductivity. To achieve that, composite polyetherimide (PEI) filaments with various CNTs fractions were processed by melt compounding without any solvents or additives. Manufacturing process adopted a sequence of twin and single screw extrusion. Thermal transition and rheological changes due to CNTs incorporation were monitored and morphology, tensile behavior and electrical conductivity of neat PEI and nanocomposite filaments were investigated. The results showed that 5 wt % CNTs reinforced PEI filaments exhibited 55 % higher sti↵ness compared to neat PEI feedstock. Structural analysis supported that these nanofillers were well dispersed in mix state and electrical percolation threshold of CNTs/PEI nanocomposite filaments was found as low as ca. 0.1 wt % CNTs.

Cellulose nanocrystal (CNCs) assisted carbon nanotubes (CNTs) and graphene nanoplatelets (GnP) were used to modify the interfacial region of carbon fiber (CF) and polymer matrix to strengthen the properties of carbon fiber-reinforced polymer (CFRP). Before transferring CNC-CNTs and CNC-GnPs on the CF surface by an immersion coating method, the nanomaterials were dispersed in DI water homogeneously by using probe sonication technique without additives. The results showed that the addition of CNC-CNT and CNC-GnP adjusted the interfacial chemistry of CFRP with the formation of polar groups. Furthermore, according to the single fiber fragmentation test (SFFT), the interfacial shear strength (IFSS) of CNC-GnP 6:1 and CNC-CNT 10:1 added CFRP increased to 55 MPa and 64 MPa due to modified interfacial chemistry by the incorporation of the nanomaterials. This processing technique also resulted in improvement in interlaminar shear strength (ILSS) in CFRPs from 35 MPa (neat composite) to 45 (CNC-GnP 6:1) MPa and 52 MPa (CNC-CNT 10:1).