Trapping Molecules in a Covalent Graphene-Nanotube Hybrid

This study employs molecular dynamics simulations to examine the physisorption behavior of hydrocarbon molecules on a covalent graphene-nanotube hybrid nanostructure. The results indicate that the adsorbed molecules undergo self-diffusion into the nanotubes without the need for external driving forces, primarily driven by significant variations in the binding energy throughout different regions. Notably, these molecules remain securely trapped within the tubes even at room temperature, thanks to a "gate" effect observed at the neck region, despite the presence of a concentration gradient that would typically hinder such trapping. This mechanism of passive mass transport and retention holds implications for the storage and separation of gas molecules.

Construction and application of carbon aerogels in microwave absorption

Electromagnetic pollution that threatens human health, the ecological environment and electronic equipment has been recognized as a serious environmental issue. In view of this, microwave absorbing materials (MAMs) are urgently required in modern society. Compared with traditional MAMs, carbon aerogels have inherent advantages in microwave absorption because of their high porosity and controllable conductive networks. Moreover, they are self-supporting 3D architectures with tailorable shapes, which satisfy most application scenarios. Therefore, carbon aerogels have aroused great interest in recent years and are being developed as promising absorption materials. In this review, we emphasize recent developments in carbon-aerogel-based MAMs constructed with some typical carbon nanomaterials, including graphene, carbon nanotubes and pyrolytic carbon. Their preparation methods, especially some newly developed strategies, are introduced as well as their influence on the structures and properties of aerogels. With a brief analysis of classic microwave absorption processes, we propose the requirements and strategies for modifying carbon aerogels to achieve ideal microwave absorption performance. Finally, we provide comprehensive comparisons of the MA performances of various carbon aerogels that show application potential and set forth the challenges and prospects of this kind of MAM.

Modeling the effect of chirality on thermal transport in a pillared-graphene structure

The anisotropic heat transport in graphene-CNT based materials provoked the development of three-dimensional pillared-graphene (PG) systems. In this study, we performed non-equilibrium molecular dynamics simulations to analyze PG thermal conductivity and thermal boundary conductance. For the first time, we have considered the influence of pillar chirality and the temperature effect on PG heat transport. We analyzed the influence of pillar chirality and pillar length on the in- and out-of-plane transport properties. For the temperature-dependent analysis, the chosen temperatures were in the range of 100 K to 500 K. To elucidate the mechanism underlying the heat transport, we investigated the phonon density of states (DOS) in the different regions of PG systems. The overlap factor was calculated to quantify the mismatch in the phonon DOS profiles. Across the pillar region, the overlap factor correlates directly with the thermal boundary conductance. When heat is transported in an out-of-plane direction, the zig-zag PG system performs better than the armchair PG system. The atomic arrangement at the graphene-CNT interface plays an inevitable role in limiting heat transport in PG systems. The calculated phonon energy in the zig-zag PG interface is higher than that in the armchair PG interface.

Electronic properties and behavior of carbon network based on graphene and single-walled carbon nanotubes in strong electrical fields: quantum molecular dynamics study

Using the self-consistent-charge density-functional tight-binding method (SCC-DFTB) and extended lagrangian DFTB-based molecular dynamics, we performedin silicostudies of the behavior of graphene-nanotube hybrid structures that are part of a branched 3D carbon network in strong electrical fields. It has been established that strong fields with strength ranging from 5 to 10 V nm^-1cause oscillating deformations of the atomic framework with a frequency in the range from 1.22 to 1.38 THz. It has been revealed that the oscillation frequency is determined primarily by the topology of the atomic framework of graphene-nanotube hybrid, while the electric field strength has an effect within 1%-2%. A further increase in electric field strength reduces the oscillation frequency to 0.7 THz, which accompanies the partial destruction of the atomic framework. The critical value of the electric field strength when the graphene is detached from the nanotube is ∼20 V nm^-1.

Influence of Defect Number, Distribution Continuity and Orientation on Tensile Strengths of the CNT-Based Networks: A Molecular Dynamics Study

Networks based on carbon nanotube (CNT) have been widely utilized to fabricate flexible electronic devices, but defects inevitably exist in these structures. In this study, we investigate the influence of the CNT-unit defects on the mechanical properties of a honeycomb CNT-based network, super carbon nanotube (SCNT), through molecular dynamics simulations. Results show that tensile strengths of the defective SCNTs are affected by the defect number, distribution continuity and orientation. Single-defect brings 0 ~ 25% reduction of the tensile strength with the dependency on defect position and the reduction is over 50% when the defect number increases to three. The distribution continuity induces up to 20% differences of tensile strengths for SCNTs with the same defect number. A smaller arranging angle of defects to the tensile direction leads to a higher tensile strength. Defective SCNTs possess various modes of stress concentration with different concentration degrees under the combined effect of defect number, arranging direction and continuity, for which the underlying mechanism can be explained by the effective crack length of the fracture mechanics. Fundamentally, the force transmission mode of the SCNT controls the influence of defects and the cases that breaking more force transmission paths cause larger decreases of tensile strengths. Defects are non-negligible factors of the mechanical properties of CNT-based networks and understanding the influence of defects on CNT-based networks is valuable to achieve the proper design of CNT-based electronic devices with better performances.

A method for designing tunable chiral mechanical carbon networks for energy storage

A method is proposed for designing tunable chiral nano-networks using partly hydrogenated graphene ribbons and carbon nanotubes (CNTs). In the network, the hydrogenated graphene ribbons (HGRs) act as basic components, which connect each other via CNT joints. Each component contains two HGR segments and an internal graphene joint (G-J2) or CNT joint (CNT-J2). Since the two HGR segments are hydrogenated at opposite surfaces, they may wind in chiral about the internal joint to form a scroll (G-J2-scroll or CNT-J2-scroll) or about the two end joints to form CNT-J4-scrolls. In general, a G-J2-scroll is formed more easily than both a CNT-J4-scroll and a CNT-J2-scroll. Because of scrolling, the surface energy is reduced. This reduction is converted to and stored as deformation potential energy. By means of molecular-dynamics simulations, we studied the final configurations of two types of networks from the same components, the maximum shrinkage, and their capacity of energy storage for potential application of energy storage or as large-deformable components in a nano-device. The results indicate that the network reaches a stable state when the shrinkage reaches 70% of the two in-plane dimensions.

Tunable ductility of a nano-network from few-layered graphene bonded with benzene: a molecular dynamics study

Developing novel graphene-based materials with unique mechanical properties is of significance to meet the requirements in new applications. The pristine graphene shows a brittle fracture when the stretching strain on it exceeds the critical value. Further, it fails to bear the external load. Herein, to enhance the ductility of the pristine graphene, we proposed a corrugated sandwich carbon network based on few-layered graphene, in which the two surface layers are bonded with several corrugated core layers via benzene molecules. The effects of factors such as the geometry, temperature, and strain rate on the ductility of the carbon network were evaluated using the uniaxial tension tests by molecular dynamics simulations. Results show that the new carbon material has more than one peak fracture strain in stretching. The second peak fracture strain is proportional to the length difference between the surface layers and core layers. Hence, the carbon network has a tunable ductility, which suggests a flexible design of such novel materials in a nanostructure/nanodevice with large deformation.

Mechanical properties of graphene-CNT van der Waals heterostructures: a molecular dynamics study

We find stiffness properties of van der Waals heterostructures made of graphene and carbon nanotubes (CNTs) using molecular dynamics (MD) simulations. The variation of the stiffness tensor is studied at different temperatures for structures with changing CNT density, and orientations. Orthotropic structures with unidirectional CNTs have high stiffness ∼300-500 GPa, in one direction. Structures with transverse isotropy show stiffness of ∼150-350 GPa along two mutually perpendicular directions. The orthotropic structures also show greater stiffness with increasing CNT density, while the others are insensitive to it. In general,the stiffness constant values are decrease as temperatures increase. The results can aid in determining useful heterostructure configuration for a particular application and in finding overall stiffness of devices having additional components.

An MD-based systematic study on the mechanical characteristics of a novel hybrid CNT/graphene drug carrier

This paper is aimed to assess the mechanical properties of a hybrid graphene-carbon nanotube carrier embedded with doxorubicin (DOX). Utilizing molecular dynamics simulation, the results reveal that by increasing the temperature from 309 to 313 K, the elastic modulus of the GS/CNT/DOX carrier decreases from 0.8 to 0.74 TPa. Also, it is shown that the presence of chitosan molecules enhances the mechanical characteristics of the proposed nanocarrier. Taking the chirality of the graphene sheet into account, the results indicate that by increasing the size of the graphene sheet, the failure stress is slightly increased for the armchair type. However, this value decreases as the size of the zigzag sample increases. Additionally, the influence of aspect ratio on the elastic modulus, fracture stress, and fracture strain of these systems is systematically examined. It has been shown that the failure stress may change significantly with increasing this parameter, especially for carrier systems having zigzag carbon nanostructures. Moreover considering various voids content in the CNT structure, the weakening effect of defects is systematically explored. Also, the dependence of the mechanical features of the proposed hybrid carrier on the presence of DOX molecules is studied via MD simulations. Finally, we have investigated the role of CNT physical characteristics including its size and chirality on the results. Graphical abstract.

Development of graphene-based enzymatic biofuel cells: A minireview

Enzymatic biofuel cells (EBFCs) have attracted increasing attention due to their potential to harvest energy from a wide range of fuels under mild conditions. Fabrication of effective bioelectrodes is essential for the practical application of EBFCs. Graphene possesses unique physiochemical properties making it an attractive material for the construction of EBFCs. Despite these promising properties, graphene has not been used for EBFCs as frequently as carbon nanotubes, another nanoscale carbon allotrope. This review focuses on current research progress in graphene-based electrodes, including electrodes modified with graphene derivatives and graphene composites, as well as free-standing graphene electrodes. Particular features of graphene-based electrodes such as high conductivity, mechanical flexibility and high porosity for bioelectrochemical applications are highlighted. Reports on graphene-based EBFCs from the last five years are summarized, and perspectives for graphene-based EBFCs are offered.

Thermal transport of carbon nanomaterials

The diversity of thermal transport properties in carbon nanomaterials enables them to be used in different thermal fields such as heat dissipation, thermal management, and thermoelectric conversion. In the past two decades, much effort has been devoted to study the thermal conductivities of different carbon nanomaterials. In this review, different theoretical methods and experimental techniques for investigating thermal transport in nanosystems are first summarized. Then, the thermal transport properties of various pure carbon nanomaterials including 1D carbon nanotubes, 2D graphene, 3D carbon foam, are reviewed in details and the associated underlying physical mechanisms are presented. Meanwhile, we discuss several important influences on the thermal conductivities of carbon nanomaterials, including size, structural defects, chemisorption and strain. Moreover, we introduce different nanostructuring pathways to manipulate the thermal conductivities of carbon-based nanocomposites and focus on the wave nature of phonons for controlling thermal transport. At last, we briefly review the potential applications of carbon nanomaterials in the fields of thermal devices and thermoelectric conversion.

Thermally Reduced Graphene Oxide/Carbon Nanotube Composite Films for Thermal Packaging Applications

Thermally reduced graphene oxide/carbon nanotube (rGO/CNT) composite films were successfully prepared by a high-temperature annealing process. Their microstructure, thermal conductivity and mechanical properties were systematically studied at different annealing temperatures. As the annealing temperature increased, more oxygen-containing functional groups were removed from the composite film, and the percentage of graphene continuously increased. When the annealing temperature increased from 1100 to 1400 °C, the thermal conductivity of the composite film also continuously increased from 673.9 to 1052.1 W m⁻¹ K⁻¹. Additionally, the Young’s modulus was reduced by 63.6%, and the tensile strength was increased by 81.7%. In addition, the introduction of carbon nanotubes provided through-plane thermal conduction pathways for the composite films, which was beneficial for the improvement of their through-plane thermal conductivity. Furthermore, CNTs apparently improved the mechanical properties of rGO/CNT composite films. Compared with the rGO film, 1 wt% CNTs reduced the Young’s modulus by 93.3% and increased the tensile strength of the rGO/CNT composite film by 60.3%, which could greatly improve its flexibility. Therefore, the rGO/CNT composite films show great potential for application as thermal interface materials (TIMs) due to their high in-plane thermal conductivity and good mechanical properties.

Controlling the electronic properties of 2D/3D pillared graphene and glass-like carbon via metal atom doping

We present the results of investigation of the nanopore filling of planar layered and bulk pillared graphene (PGR) as well as films and 3D samples of glass-like porous carbon (GLC) with potassium atoms. The patterns of charge transfer, electronic structure, and shift of the Fermi level during the filling of nanopores with potassium atoms are established. It is found that the greatest charge transfer from potassium atoms to the carbon framework is observed in PGR with a density of 1.1-1.4 g cm^-3 (that is, with a nanopore volume of 1300-1800 nm³) regardless of the framework topology. The maximum charge transfer occurs already when the mass fraction of potassium is 12 wt%. At the same potassium concentration, a maximum shift of the Fermi level to zero by ∼3 eV occurs in a bilayer PGR film with a density of 1.4 g cm^-3. Thus, our work shows for the first time that the electronic properties of nanoporous materials doped with alkaline earth metals (in particular, potassium) can be controlled by varying the volume of doped nanopores, i.e. by controlling the density of the nanoporous material. We first demonstrated that the potassium doping of PGR would be more effective than potassium doping of GLC. It is established that 2D samples of PGR and GLC completely reproduce the electronic properties of the bulk samples and even surpass them in some parameters. To carry out research, we developed a new method for nanopore filling with dopant atoms based on both the randomness of the nanopore filling and the energy advantage of this process. This method allows us to reliably determine the maximum possible mass fraction (wt%) of dopant atoms of any porous material.

Hydrogenation-controlled mechanical properties in graphene helicoids: exceptional distribution-dependent behavior

Mechanical properties of pristine GHs along with patterned and randomly hydrogenated GHs have been investigated for various geometries and H-coverages.

Large tunability in the mechanical and thermal properties of carbon nanotube-fullerene hierarchical monoliths

Carbon based materials have attracted much attention as building blocks in technologically relevant nanocomposites due to their unique chemical and physical properties. Here, we propose a new class of hierarchical carbon based nano-truss structures consisting of fullerene joints attached with carbon nanotubes as the truss forming a three-dimensional network. Atomistic molecular dynamics simulations allow us to systematically demonstrate the ability to simultaneously control the mechanical and thermal properties of these structures, elucidating their unique physical properties. Specifically, we perform uniaxial tensile and compressive loading to show that by controlling the length of the carbon nanotube trusses, the mechanical properties can be tuned over a large range. Furthermore, we utilize the Green-Kubo method under the equilibrium molecular dynamics simulations framework to show that the thermal conductivities of these structures can be manipulated by varying the densities of the overall structures. This work provides a computational framework guiding future research on the manipulation of the fundamental physical properties in these organic-based hierarchical structures composed of carbon nanotubes and fullerenes as building blocks.

Coupled Chiral Structure in Graphene-Based Film for Ultrahigh Thermal Conductivity in Both In-Plane and Through-Plane Directions

The development of high-performance thermal management materials to dissipate excessive heat both in plane and through plane is of special interest to maintain efficient operation and prolong the life of electronic devices. Herein, we designed and constructed a graphene-based composite film, which contains chiral liquid crystals (cellulose nanocrystals, CNCs) inside graphene oxide (GO). The composite film was prepared by annealing and compacting of self-assembled GO-CNC, which contains chiral smectic liquid crystal structures. The helical arranged nanorods of carbonized CNC act as in-plane connections, which bridge neighboring graphene sheets. More interestingly, the chiral structures also act as through-plane connections, which bridge the upper and lower graphene layers. As a result, the graphene-based composite film shows extraordinary thermal conductivity, in both in-plane (1820.4 W m^-1 K^-1) and through-plane (4.596 W m^-1 K^-1) directions. As a thermal management material, the heat dissipation and transportation behaviors of the composite film were investigated using a self-heating system and the results showed that the real-time temperature of the heater covered with the film was 44.5 °C lower than a naked heater. The prepared film shows a much higher efficiency of heat transportation than the commonly used thermal conductive Cu foil. Additionally, this graphene-based composite film exhibits excellent mechanical strength of 31.6 MPa and an electrical conductivity of 667.4 S cm^-1. The strategy reported here may open a new avenue to the development of high-performance thermal management films.

Mechanical properties of hollow and water-filled graphyne nanotube and carbon nanotube hybrid structure

By performing molecular dynamics simulations, a GNT/CNT hybrid structure constructed via combing (6, 6) graphyne nanotube (GNT) with (6, 6) carbon nanotube (CNT) has been designed and investigated. The mechanical properties induced by the percentage of GNT, water content and electric field were examined. Calculation results reveal that the fracture strain and strength of hollow hybrid structure are remarkably smaller than that of perfect (6, 6) CNT. In addition, the Young's modulus decreases monotonously with the increase of percentage of GNT. More importantly, the tunable mechanical properties of hybrid structure can be achieved through filling with water molecules and applying an electric field along tensile direction. Specifically, increasing water content from 0.0 to 8.70 mmol g^-1 in the absence of electric field could result in fracture strain and strength reducing by 15.09% and 12.87%, respectively. Besides, enhancing fracture strain and strength of water-filled hybrid structure with water content of 8.70 mmol g^-1 can also be obtained with rising electric field intensity. These findings would provide a valuable theoretical basis for designing and fabricating a nanodevice with controllable mechanical performances.

Pillared graphene as an ultra-high sensitivity mass sensor

Hybrid structure of graphene sheets supported by carbon nanotubes (CNTs) sustains unique properties of both graphene and CNTs, which enables the utilization of advantages of the two novel materials. In this work, the capability of three-dimensional pillared graphene structure used as nanomechanical sensors is investigated by performing molecular dynamics simulations. The obtained results demonstrate that: (a) the mass sensitivity of the pillared graphene structure is ultrahigh and can reach at least 1 yg (10⁻²⁴ g) with a mass responsivity 0.34 GHz · yg⁻¹; (b) the sizes of pillared graphene structure, particularly the distance between carbon nanotube pillars, have a significant effect on the sensing performance; (c) an analytical expression can be derived to detect the deposited mass from the resonant frequency of the pillared graphene structure. The performed analyses might be significant to future design and application of pillared graphene based sensors with high sensitivity and large detecting area.

Hierarchical Cobalt Hydroxide and B/N Co-Doped Graphene Nanohybrids Derived from Metal-Organic Frameworks for High Energy Density Asymmetric Supercapacitors

To cater for the demands of electrochemical energy storage system, the development of cost effective, durable and highly efficient electrode materials is desired. Here, a novel electrode material based on redox active β-Co(OH)₂ and B, N co-doped graphene nanohybrid is presented for electrochemical supercapacitor by employing a facile metal-organic frameworks (MOFs) route through pyrolysis and hydrothermal treatment. The Co(OH)₂ could be firmly stabilized by dual protection of N-doped carbon polyhedron (CP) and B/N co-doped graphene (BCN) nanosheets. Interestingly, the porous carbon and BCN nanosheets greatly improve the charge storage, wettability, and redox activity of electrodes. Thus the hybrid delivers specific capacitance of 1263 F g⁻¹ at a current density of 1A g⁻¹ with 90% capacitance retention over 5000 cycles. Furthermore, the new aqueous asymmetric supercapacitor (ASC) was also designed by using Co(OH)₂@CP@BCN nanohybrid and BCN nanosheets as positive and negative electrodes respectively, which leads to high energy density of 20.25 Whkg⁻¹. This device also exhibits excellent rate capability with energy density of 15.55 Whkg⁻¹ at power density of 9331 Wkg⁻¹ coupled long termed stability up to 6000 cycles.

Compressive Strength Enhancement of Vertically Aligned Carbon Nanotube Forests by Constraint of Graphene Sheets

We fabricated a 3D sandwich hybrid material composed of graphene and vertically aligned carbon nanotube forests (VACNTs) using chemical vapor deposition. The graphene was first synthesized on Cu foil. Then it was transferred to a substrate which had a pre-deposited catalyst Fe film and a buffer film of Al₂O₃ for the growth of VACNTs. The VACNTs were grown underneath the graphene and lifted up the graphene. The graphene, with its edges anchored on the Al₂O₃, provided a constrained boundary condition for the VACNTs and hence affected the growth height and mechanical strength of the VACNTs. We prepared three groups of samples: VACNTs without graphene, VACNTs with graphene transferred once (1-Gr/VACNTs), and VACNTs with graphene transferred twice (2-Gr/VACNTs). A nano-indentation system was used to measure the reduced compressive modulus (Er) and hardness (H). The Er and H of Gr/VACNTs increased with the number of transfers of the anchored graphene. The 2-Gr/VACNTs had the largest Er and H, 23.8 MPa and 912 KPa, which are 6.6 times and 5.2 times those of VACNTs without the anchored graphene, respectively. In this work, we have demonstrated a simple method to increase the mechanical properties and suppress the height of VACNTs with the anchored graphene and number of transfers.

Ultrahigh Thermal Rectification in Pillared Graphene Structure with Carbon Nanotube-Graphene Intramolecular Junctions

In this letter, graded pillared graphene structures with carbon nanotube-graphene intramolecular junctions are demonstrated to exhibit ultrahigh thermal rectification. The designed graded two-stage pillared graphene structures are shown to have rectification values of 790.8 and 1173.0% at average temperatures 300 and 200 K, respectively. The ultrahigh thermal rectification is found to be a result of the obvious phonon spectra mismatch before and after reversing the applied thermal bias. This outcome is attributed to both the device shape asymmetry and the size asymmetric boundary thermal contacts. We also find that the significant and stable standing waves that exist in graded two-stage pillared graphene structures play an important role in this kind of thermal rectifier, and are responsible for the ultrahigh thermal rectification of the two-stage ones as well. Our work demonstrates that pillared graphene structure with SWCNT-graphene intramolecular junctions is an excellent and promising phononic device.

Synthesis of ultralow density 3D graphene-CNT foams using a two-step method

Here, we report a highly scalable two-step method to produce graphene foams with ordered carbon nanotube reinforcements. In our approach, we first used solution assembly methods to obtain graphene oxide foam. Next, we employed chemical vapor deposition to simultaneously grow carbon nanotubes and thermally reduce the 3D graphene oxide scaffold. The resulting structure presented increased stiffness, good mechanical stability and oil absorption properties. Molecular dynamics simulations were carried out to further elucidate failure mechanisms and to understand the enhancement of the mechanical properties. The simulations showed that mechanical failure is directly associated with bending of vertical reinforcements, and that, for similar length and contact area, much more stress is required to bend the corresponding reinforcements of carbon nanotubes, thus explaining the experimentally observed enhanced mechanical properties.

Modelling of graphene functionalization

This perspective describes the available theoretical methods and models for simulating graphene functionalization based on quantum and classical mechanics.

Template-directed growth and mechanical properties of carbon nanotube–graphene junctions with nano-fillets: molecular dynamic simulation

Nano-fillet enhances both the stability and mechanical properties of carbon nanotube–graphene junctions synthesized by a templating method.

Thermal conductivity from hierarchical heat sinks using carbon nanotubes and graphene nanosheets

The in-plane (kip) and through-plane (ktp) thermal conductivities of heat sinks using carbon nanotubes (CNTs), graphene nanosheets (GNs), and CNT/GN composites are extracted from two experimental setups within the 323-373 K temperature range. Hierarchical three-dimensional CNT/GN frameworks display higher kip and ktp values, as compared to the CNT- and GN-based heat sinks. The kip and ktp values of the CNT/GN-based heat sink reach as high as 1991 and 76 W m(-1) K(-1) at 323 K, respectively. This improved thermal conductivity is attributed to the fact that the hierarchical heat sink offers a stereo thermal conductive network that combines point, line, and plane contact, leading to better heat transport. Furthermore, the compression treatment provided an efficient route to increase both kip and ktp values. This result reveals that the hierarchical carbon structures become denser, inducing more thermal conductive area and less thermal resistivity, i.e., a reduced possibility of phonon-boundary scattering. The correlation between thermal and electrical conductivity (ε) can be well described by two empirical equations: kip = 567 ln(ε) + 1120 and ktp = 20.6 ln(ε) + 36.1. The experimental results are obtained within the temperature range of 323-373 K, suitably complementing the thermal management of chips for consumer electronics.

Mechanical properties of bulk carbon nanostructures: effect of loading and temperature

Carbon-based bulk nanostructures are believed to entail certain advantages over their parent low-dimensional materials and are promising candidates for supercapacitors due to their unique properties such as extremely high specific surface area and high conductivity. Herein the mechanical and structural properties of four types of carbon nanopolymorph-based nanomaterials were calculated using molecular dynamics simulations. Bulk carbon nanostructures composed of structural units of bent graphene flakes, short carbon nanotubes, fullerenes and their mixture were considered. The effect of the loading scheme and temperature was studied and constitutive relationships describing the deformation of the materials were given. The simulation results revealed that the effect of the loading scheme significantly depends on the type of structural units, and was slightly affected by the temperature especially for high densities. The constitutive equations obtained in this work can be applied to describe the mechanical behavior of new bulk carbon nanostructures.

Growth mechanisms and mechanical properties of 3D carbon nanotube–graphene junctions: molecular dynamic simulations

Two mechanisms of seamlessly C–C bonded junction formation: (i) CNT growth over the holes that are smaller than 3 nm. (ii) CNT growth inside the holes that are larger than 3 nm.

Graphene/single-walled carbon nanotube hybrids: one-step catalytic growth and applications for high-rate Li-S batteries

The theoretically proposed graphene/single-walled carbon nanotube (G/SWCNT) hybrids by placing SWCNTs among graphene planes through covalent C-C bonding are expected to have extraordinary physical properties and promising engineering applications. However, the G/CNT hybrids that have been fabricated differ greatly from the proposed G/SWCNT hybrids because either the covalent C-C bonding is not well constructed or only multiwalled CNTs/carbon nanofibers rather than SWCNTs are available in the hybrids. Herein, a novel G/SWCNT hybrid was successfully fabricated by a facile catalytic growth on layered double hydroxide (LDH) at a high temperature over 950 °C. The thermally stable Fe nanoparticles and the uniform structure of the calcined LDH flakes are essential for the simultaneously catalytic deposition of SWCNTs and graphene. The SWCNTs and the CVD-grown graphene, as well as the robust connection between the SWCNTs and graphene, facilitated the construction of a high electrical conductive pathway. The internal spaces between the two stacked graphene layers and among SWCNTs offer room for sulfur storage. Therefore, the as obtained G/SWCNT-S cathode exhibited excellent performance in Li-S batteries with a capacity as high as 650 mAh g(-1) after 100 cycles even at a high current rate of 5 C. Such a novel G/SWCNT hybrid can serve not only as a prototype to shed light on the chemical principle of G/CNT synthesis but also as a platform for their further applications in the area of nanocomposites, heterogeneous catalysis, drug delivery, electrochemical energy storage, and so on.

Nanoparticle manipulation by thermal gradient

A method was proposed to manipulate nanoparticles through a thermal gradient. The motion of a fullerene molecule enclosed inside a (10, 10) carbon nanotube with a thermal gradient was studied by molecular dynamics simulations. We created a one-dimensional potential valley by imposing a symmetrical thermal gradient inside the nanotube. When the temperature gradient was large enough, the fullerene sank into the valley and became trapped. The escaping velocities of the fullerene were evaluated based on the relationship between thermal gradient and thermophoretic force. We then introduced a new way to manipulate the position of nanoparticles by translating the position of thermostats with desirable thermal gradients. Compared to nanomanipulation using a scanning tunneling microscope or an atomic force microscope, our method for nanomanipulation has a great advantage by not requiring a direct contact between the probe and the object.