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Graphene-based nanomaterials possess broad applications because of their excellent multi-functional properties. In this work, a facile self-assembling method was presented for preparing one kind of graphene oxide-based paper/hollow microspheres hybrid. It was found that most of the hollow microspheres can strongly anchored on the surface of graphene oxide paper (GOP) by an in-situ scanning electron microscope peeling testing combining with molecular dynamics (MD) simulation. In addition, the uniform distribution of hollow microspheres on the surface of GOP cannot only provide a better surface wettability, but also can effectively improve the interfacial stress-transfer capability between such hybrid and polymer matrix. Our work provides a guidance for the structural designs of graphene-based nanomaterials and broaden their applications.

Carbon nanotubes (CNTs) are regarded as the next generation of one-dimensional super-strong nanomaterials due to their extraordinary mechanical properties. Recently, much attention has been dedicated into super-strong CNT-based fibers resulting from twisting operation. However, the roles of a promising compression operation on the mechanical enhancement mechanisms of CNT fibers (CNFs) are not clear. Especially, the combined twisting-compression effect has not been known. In this work, with using coarse-grained molecular dynamic simulation method, the tensile mechanical properties and mechanical enhancements of randomly-distributed CNT fibers (RDCNFs) were studied. It was found that the mechanical performances of such RDCNFs could be significantly improved by increasing CNT length or decreasing initial bending degree of CNTs. Furthermore, both specific strength and specific modulus can be effectively tuned by twisting and compressing operations, where self-locking and unhitching mechanisms of CNT knots play critical roles. On the other hand, following theoretical guidance, a super-strong CNF with the maximum specific strength up to 296 mN/tex (∼6.8 GPa) was designed and fabricated. This work provides a theoretically and experimentally support to design super-strong CNT-based fibers and lays a foundation for their future applications.

Carbon nanotube fibers have attracted much interest because of their outstanding multifunctional properties. In this work, double-helix carbon nanotube fibers (DHCNFs) assembled by combined self-twisting and whole-twisting processes are presented, and their mechanical properties were studied based on atomic simulation. We found that the self-twisting of carbon nanotubes (CNTs) can lead to interesting intertube entanglements, with the formation of a helical structure. In addition, the twisting process can cause a remarkable decline of the mechanical properties of CNTs owing to their hollow structure collapse, thus deteriorating the tensile mechanical performances of DHCNFs. Meanwhile, by tuning related twisting parameters, different fracture failure modes, including simultaneous and stepwise breakages, can be found. More importantly, it was revealed that, as nanoenhancements, the helical morphology of DHCNFs can effectively enhance the interlocking effect between CNTs and the matrix, thereby improving the interfacial strength and toughness of DHCNF-reinforced nanocomposites. This work systemically studied the effect of the twisting operation on the mechanical properties of DHCNFs and provided an innovative way of simultaneously enhancing the strength and toughness of CNT-based nanocomposites.

Graphite carbon nitride (GCN), which can be regarded as a nitrogen heteroatom-substituted graphite framework, has attracted great attention as a new 2D layered structure material with semiconductor electronic characteristics. Using molecular dynamics simulations, the in-plane thermal conductivity and cross-plane thermal resistance of two GCN structures (i.e., triazine-based and heptazine-based) are investigated. Our results show that the in-plane thermal conductivities of the triazine-based and heptazine-based GCN monolayers along the armchair direction are 55.39 and 17.81 W m-1 K-1, respectively. The cross-plane thermal resistance decreases with increasing layer number and reaches asymptotic values of 3.6 × 10-10 and 9.3 × 10-10 m2 K W-1 at 40 layers for triazine-based and heptazine-based GCN, respectively. The in-plane thermal conductivity can be effectively manipulated by changing the temperature and applying strain, while it is insensitive to the number of layers, which is in sharp contrast to that of graphene. Moreover, the cross-plane thermal resistance decreases monotonically with temperature and coupling strength, and can be modulated by external strain. Surprisingly, the cross-plane tensile strain can reduce the thermal resistance of the heptazine-based GCN. Our study serves as a guide to groups interested in the physical properties of GCN.

In-plane heterojunctions, obtained by seamlessly joining two or more nanoribbon edges of isolated two-dimensional atomic crystals such as graphene and hexagonal boron nitride, are emerging as nanomaterials for the development of future multifunctional devices. The thermal transport behavior at the interface of these heterojunctions plays a pivotal role in determining their functional performance. Using molecular dynamics simulations, the interfacial thermal conductance of graphene/hexagonal boron nitride (GE/BN) in-plane heterojunctions was investigated. The GE/BN heterostructure has a remarkably high interfacial thermal conductance, and thermal rectification occurs at the interface. The results also show that the interfacial thermal conductance is effectively modulated by strain and defect engineering. The atomic defect location can affect the phonon transmission at the interface. Interestingly, compared with the nitrogen doping effect, the boron doping defect can more effectively facilitate vibrational coupling at the interface in the graphene sheet. Stress distribution and vibrational spectral analyses are performed to elucidate the thermal transport mechanism. The results of this study may provide a foundation for future research attempting to manipulate the interfacial thermal conductance in other two-dimensional heterostructures.

Carbon nanotube (CNT) reinforced nanocomposites (CNTRNs) have been regarded as the most promising substitutes for traditional carbon fiber reinforced composites, due to their excellent multi-functional properties. However, the weak CNT-matrix interface which impairs the mechanical properties of CNTRNs is always an issue, limiting their practical applications. Here, inspired by strong pinning effect of screws, we partially unzipped the CNTs into graphene nanoribbons (GNRs) and a screw-like CNT/GNR hybrid (CGH) nanostructure was proposed to reinforce the nanocomposites. It was found that the fracture strength, Young’s modulus and fracture toughness of CGH reinfroced nanocomposites can be boosted by 155 %, 89 % and 117 %, respectively, comparing to those of CNTRNs. The molecular dynamic simulation on pullout of CGHs from matrix revealed that the CNT-GNR junction can lead to a mechanical interlocking, which can not only hinder the pullout of CGH, but also cause remarkable matrix shear deformation, contributing to energy dissipation to a large extent. In addition, the morphology of CGHs can be tuned by changing structural chirality of CNTs, by which the interfacial properties can be further improved. This work opens a new route to engineer high-performance nanocomposites, and provides an in-depth understanding on the mechanical enhancement of CNT-based nanocomposites.