In this review, recent progress in the mechanical, thermal and interfacial properties of graphene/CNT multiphase polymer composites is examined. Progress in the mechanical and thermal properties of CNT (1D) and graphene (2D) nanostructure materials is also reviewed and compared. Furthermore, this review highlights the improvements in the mechanical, thermal and interfacial properties of two- and three-phase composites, owing to the addition of graphene/CNT. In particular, analysis of several notable papers on hybrid composites (graphene/CNT) provides an intensive review of synergetic effects on the overall properties of the corresponding composites. This holistic review describes an improved interface between fibers and a nanofiller-reinforced matrix. Although the presence of nanofillers even at low loadings confers an overall improvement in composite properties, the exact ratios of individual fillers and combined forms remain to be discussed in depth. Finally, potential applications, current challenges and future perspectives for use of these multiphase composites are discussed with regard to their extraordinary capabilities and promising developments in graphene/CNT family-based composite materials.

Carbon nanotube- and graphene-reinforced multiphase polymeric composites: review on their properties and applications

Atomically 2D thin-layered structures, such as graphene nanosheets, graphitic carbon nitride nanosheets (g-C3N4), hexagonal boron nitride, and transition metal dichalcogenides are emerging as fascinating materials for a good array of domains owing to their rare physicochemical characteristics. In particular, graphitic carbon nitride has turned into a hot subject in the scientific community due to numerous qualities such as simple preparation, electrochemical properties, high adsorption capacity, good photochemical properties, thermal stability, and acid-alkali chemical resistance, etc. Basically, g-C3N4 is considered as a polymeric material consisting of N and C atoms forming a tri-s-triazine network connected by planar amino groups. In comparison with most C-based materials, g-C3N4 possesses electron-rich characteristics, basic moieties, and hydrogen-bonding groups owing to the presence of hydrogen and nitrogen atoms; therefore, it is taken into account as an interesting nominee to further complement carbon in applications of functional materials. Nevertheless, g-C3N4 has some intrinsic limitations and drawbacks mainly related to a relatively poor specific surface area, rapid charge recombination, a limited light absorption range, and a poor dispersibility in both aqueous and organic mediums. To overcome these shortcomings, numerous chemical modification approaches have been conducted with the aim of expanding the range of application of g-C3N4 and enhancing its properties. In the current review, the comprehensive survey is conducted on g-C3N4 chemical functionalization strategies including covalent and noncovalent approaches. Covalent approaches consist of establishing covalent linkage between the g-C3N4 structure and the chemical modifier such as oxidation/carboxylation, amidation, polymer grafting, etc., whereas the noncovalent approaches mainly consist of physical bonding and intermolecular interaction such as van der Waals interactions, electrostatic interactions, π-π interactions, and so on. Furthermore, the preparation, characterization, and diverse applications of functionalized g-C3N4 in various domains are described and recapped. We believe that this work will inspire scientists and readers to conduct research with the aim of exploring other functionalization strategies for this material in numerous applications.

Emerging Chemical Functionalization of g-C3N4: Covalent/Noncovalent Modifications and Applications.

We report the preparation of epoxy-based composites with enhanced dielectric properties and thermal conductivity, by employing intelligently designed core/shell Alumina/Polydopamine (indicated as AO*) and strawberry-like core/shell structured Alumina/Polydopamine/Silver (indicated as AO*@Ag) particles as fillers. The introduction of the core-shell AO* and AO*@Ag particles into the epoxy matrix can distinctly enhance both the dielectric permittivity and dielectric breakdown strength of composites, as compared to that incorporating AO particles as fillers. For example, the dielectric breakdown strength of AO*@Ag/epoxy with 22.9 vol% filler loading is up to 65.5 kV/mm, representing an improvement of 24% compared with AO/epoxy composite at the same filler loading (52.8 kV/mm), while it has enhanced dielectric permittivity at room temperature at low frequency. Additionally, the strawberry-like core/shell particle-filled composites still take on a high thermal conductivity.

Dielectric properties and thermal conductivity of epoxy composites using quantum-sized silver decorated core/shell structured alumina/polydopamine

This paper provides an overview of recent advances in research on the interfacial characteristics of carbon nanotube–polymer nanocomposites. The state of knowledge about the chemical functionalization of carbon nanotubes as well as the interaction at the interface between the carbon nanotube and the polymer matrix is presented. The primary focus of this paper is on identifying the fundamental relationship between nanocomposite properties and interfacial characteristics. The progress, remaining challenges, and future directions of research are discussed. The latest developments of both microscopy and scattering techniques are reviewed, and their respective strengths and limitations are briefly discussed. The main methods available for the chemical functionalization of carbon nanotubes are summarized, and particular interest is given to evaluation of their advantages and disadvantages. The critical issues related to the interaction at the interface are discussed, and the important techniques for improving the properties of carbon nanotube–polymer nanocomposites are introduced. Additionally, the mechanism responsible for the interfacial interaction at the molecular level is briefly described. Furthermore, the mechanical, electrical, and thermal properties of the nanocomposites are discussed separately, and their influencing factors are briefly introduced. Finally, the current challenges and opportunities for efficiently translating the remarkable properties of carbon nanotubes to polymer matrices are summarized in the hopes of facilitating the development of this emerging area. Potential topics of oncoming focus are highlighted, and several suggestions concerning future research needs are also presented.

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A review of the interfacial characteristics of polymer nanocomposites containing carbon nanotubes

A novel class of carbon nanotube (CNT)-based nanomaterials has been surging since 1991 due to their noticeable mechanical and electrical properties, as well as their good electron transport properties. This is evidence that the development of CNT-reinforced polymer composites could contribute in expanding many areas of use, from energy-related devices to structural components. As a promising material with a wide range of applications, their poor solubility in aqueous and organic solvents has hindered the utilizations of CNTs. The current state of research in CNTs—both single-wall carbon nanotubes (SWCNT) and multiwalled carbon nanotube (MWCNT)-reinforced polymer composites—was reviewed in the context of the presently employed covalent and non-covalent functionalization. As such, this overview intends to provide a critical assessment of a surging class of composite materials and unveil the successful development associated with CNT-incorporated polymer composites. The mechanisms related to the mechanical, thermal, and electrical performance of CNT-reinforced polymer composites is also discussed. It is vital to understand how the addition of CNTs in a polymer composite alters the microstructure at the micro- and nano-scale, as well as how these modifications influence overall structural behavior, not only in its as fabricated form but also its functionalization techniques. The technological superiority gained with CNT addition to polymer composites may be advantageous, but scientific values are here to be critically explored for reliable, sustainable, and structural reliability in different industrial needs.

Fabrication, Functionalization, and Application of Carbon Nanotube-Reinforced Polymer Composite: An Overview.

Carbon nanotubes (CNTs) are considered as high potential filler material to improve the mechanical properties of epoxy nanocomposites. The CNTs are functionalized by attaching melamine to improve the dispersibility in epoxy matrix and to enhance the interfacial bonding between CNTs and matrix. The tensile tests and single edge notch bending (SENB) tests were performed for CNT/Epoxy and M-CNT/Epoxy nanocomposites at various weight fraction of functionalized CNTs. The M-CNT/Epoxy nanocomposites with addition of 2wt% functionalized CNTs exhibited enhancements of Young's modulus by 64% and ultimate tensile strength by 22%. Furthermore, a significant increase of fracture toughness by 95% was observed for 2wt% M-CNT/Epoxy nanocomposite. The homogeneity of CNTs in epoxy matrix has been analyzed and related to the improvement of modulus and strength. The phenomena of crack propagation has been investigated and related to the improvement of fracture toughness.

Improvement of modulus, strength and fracture toughness of CNT/Epoxy nanocomposites through the functionalization of carbon nanotubes

Low-dimension carbon nanomaterials, such as carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), are effective mechanical reinforcements in polymer composites. Epoxy matrix composites were fabricated by functionalizing CNT and GNP nanofillers using melamine and nondestructive ball milling. This noncovalent functionalization prevents agglomeration of nanofiller and produces direct C N bonds with the epoxy matrix. Compared to pristine CNTs and GNPs/epoxy nanocomposites, melamine-functionalized CNT (M-CNT)/epoxy and melamine-functionalized GNP (M-GNP)/epoxy nanocomposites exhibited considerably higher tensile strengths and fracture toughness (single edge notch bending, SENB). At 2 wt%, both M-CNT/epoxy and M-GNP/epoxy nanocomposites exhibited enhanced Young's modulus values (M-CNT: 64% and M-GNP: 71%) and ultimate tensile strengths (M- CNT: 22% and M-GNP: 23%). Fracture toughness increased by 95% with the 2 wt% M-CNT/epoxy and by 124% with the 2 wt% M-GNP/epoxy nanocomposite. The reinforcing effects of the two-dimensional M-GNPs were greater than those of the one-dimensional M-CNTs due to differences in pull-out mechanisms and bridging effects. Crack propagation in the nanocomposites, as it relates to fracture toughness, was also investigated.

Comparison to mechanical properties of epoxy nanocomposites reinforced by functionalized carbon nanotubes and graphene nanoplatelets

Functionalization of carbon nanotubes for fabrication of CNT/epoxy nanocomposites

Fabrication and mechanical properties of carbon fiber/epoxy nanocomposites containing high loadings of noncovalently functionalized graphene nanoplatelets

The strengthening mechanism of graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) at general fiber reinforced polymer (FRP) composite were investigated by interlaminar shear failure. We proposed 6 steps of interlaminar shear behavior of laminates at FRPs impregnated with epoxy resins. The GNPs and CNTs were functionalized by melamine to form M-CNTs and M-GNPs, which improved their dispersion in the epoxy matrix of the CFRPs and enhanced the interfacial strength. As a result, the resistance to crack propagation at the interface of fiber and polymer matrix increased. The interlaminar shear deformation behavior was characterized performing an interlaminar shear strength (ILSS) test, and the six failure stages were observed by scanning electron microscopy. Differences between load–displacement curves and the effects of GNPs and CNTs on shear deformation were analyzed. The incorporation of 2 wt% of M-CNTs increased the ILSS value of the CF/M-CNT/epoxy nanocomposite by 61%. The same loading but with M-GNPs increased the ILSS of the CF/M-GNP/epoxy nanocomposite by 219%. The greater reinforcing effect of the M-GNPs than the M-CNTs was attributed to differences in delamination resistance at the interface between the fibers and the epoxy. The phenomenon of crack propagation was investigated and related to the improved ILSS values.

Jaemin Cha

Papers

Improvement of modulus, strength and fracture toughness of CNT/Epoxy nanocomposites through the functionalization of carbon nanotubes

Comparison to mechanical properties of epoxy nanocomposites reinforced by functionalized carbon nanotubes and graphene nanoplatelets

Functionalization of carbon nanotubes for fabrication of CNT/epoxy nanocomposites

Fabrication and mechanical properties of carbon fiber/epoxy nanocomposites containing high loadings of noncovalently functionalized graphene nanoplatelets

Strengthening effect of melamine functionalized low-dimension carbon at fiber reinforced polymer composites and their interlaminar shear behavior