Diamond Nanothreads Research Articles

Theoretical prediction electronic properties of Group-IV diamond nanothreads

We have investigated the atomic and electronic structures, and carrier mobility on Group-IV diamond nanothreads (DNTs-C, DNTs-SiC, DNTs-Si and DNTs-Ge) using density functional theory. It is shown that all of Group-IV diamond nanothreads are wide gap semiconductors (>3eV). The highest electron (hole) mobility value is even up to ∼1.15×105 (1.38×103) cm2V-1s-1. Due to the huge difference mobility in hole and electron, DNTs-Si and DNTs-Ge can be considered as p-type semiconductors, and DNTs-C can be considered as n-type semiconductor. Our results suggest that Group-IV diamond nanothreads is a new material that can be applied in optoelectronics and nanoelectronic devices in some special conditions, such as high-temperature devices, wide-gap semiconductors, transparent conductors and so on.

Mechanical properties of diamond nanothread reinforced polymer composites

One-dimensional diamond nanothread (DNT) has drawn intensive research interests and become a promising candidate for nanocomposites reinforcement. This paper explores the mechanical properties of DNT reinforced poly (methyl methacrylate) (PMMA) composite under tensile deformation via molecular dynamics simulation. The study shows that the Young's modulus and yielding stress of PMMA composite are enhanced by 85% and 15% with the incorporation of DNT. Remarkably, DNT which is a hydrogenated carbon nanotube (CNT) is proved to strengthen PMMA composite more effectively than CNT for a similar structure. The outstanding strengthening of DNT is attributed to interfacial interaction and mechanical interlocking between DNT and PMMA matrix. A pull-out simulation is conducted to examine the interfacial shear strength of DNT-PMMA interface and comparison studies are made with that of CNT-PMMA interface. The results reveal that DNT has higher load transference within PMMA composite than CNT, by presenting 34% above CNT in interfacial shear strength. It is also demonstrated that DNT morphology can significantly affect the interfacial interaction and mechanical interlocking with PMMA matrix, leading to distinguished reinforcement efficiency for PMMA composite. These findings will shed light to DNT application in nanocomposites and provide an important insight into reinforcing mechanism.

Diamond nanothread based resonators: ultrahigh sensitivity and low dissipation.

The recently synthesized ultrathin diamond nanothreads (NTHs) exhibit a variety of intriguing properties and are probably the most successful of many encouraging applications to be designed as resonators due to their ultrahigh sensitivity and low dissipation. Herein, we report via molecular dynamics that diamond nanothreads possess not only ultrahigh mass sensitivity but also a very high quality factor. On the one hand, the studied diamond nanothreads demonstrate an extreme mass resolution of ∼0.58 yg (1 yg = 10-24 g), which is almost one order of magnitude higher than that of carbon nanotubes (∼10 yg) with the same length. Moreover, the sensing performance of NTHs is highly tunable owing to their tailorable structures. On the other hand, NTHs exhibit a very low intrinsic energy dissipation and thus a high quality factor which is generally two times that of carbon nanotubes. These intriguing features suggest that diamond nanothreads could be highly attractive candidates for fabricating nano-sized mechanical resonators with outstanding performance.

Kinetic theory for the formation of diamond nanothreads with desired configurations: a strain-temperature controlled phase diagram.

Diamond nanothreads (DNTs) are a brand-new one-dimensional carbon nanomaterial that was synthesized recently by compressing benzene. Compared with sp2 carbon nanotubes, DNTs may possess a much higher interfacial load-transfer ability. However, previous studies have shown that the mechanical properties of DNTs are highly sensitive to the composition of Stone-Wales (SW) transformed sites. Up to now, it remained unclear what roles SWs play in the structure stability and how to engineer its molecular structure for novel mechanical properties. Using ab initio calculations, here we show that the most stable structure of a DNT is composed of alternative SW and hydrogenated carbon nanotube (3,0) units, suggesting that SW plays an essential role in stabilizing DNT. Interestingly, we found that the SW transition barrier is a nearly linear function of the applied strain, enabling strain engineering of its molecular structure. To do so, we propose a strain-temperature-stretching rate phase diagram to guide the construction of desired molecular structures to achieve superplastic behavior of DNTs. Our findings not only enrich our understanding of this novel carbon material, but also provide a strategy to control its structural and mechanical properties for novel applications, such as energy absorption, energy storage and materials reinforcement.

Molecular Dynamics Study of Kumihimo Carbon Fiber Composed of Diamond Nanothreads

Molecular Dynamics Study of Kumihimo Carbon Fiber Composed of Diamond Nanothreads

Morphology- and dehydrogenation-controlled mechanical properties in diamond nanothreads

Recently synthesized diamond nanothreads (DNTs), collecting desired properties of both inorganic nanostructures and hydrocarbon molecular structures, are an interesting group of carbon-based materials. Using full atomistic first-principles based ReaxFF molecular dynamics (MD) simulations, a comprehensive study on tensile and bending mechanical characteristics of fifteen energy-favorable DNTs is performed. All the DNTs show unique tensile and bending mechanical properties that markedly vary with morphology and arrangement of carbon polygons. A straight DNT composed of purely carbon hexagons shows brittle fracture in the temperature range of 1–2000 K, whereas with regard to another hexagon-dominated DNT and helically coiled DNT with the largest coiled radius, a thermal-induced brittle-to-ductile transition is uncovered at 2000 K. Particularly, the coiled DNT subjected to tensile loading/unloading shows a clear mechanical hysteresis loop. Dehydrogenation does not change the morphologies and stability of DNTs, but significantly affect the tensile mechanical responses; the tensile stiffness, toughness and ductility can be enhanced by approximately 1-fold, 2-folds and 3-folds as much of their pristine counterparts, respectively, however, the failure strain is reduced at any degree of dehydrogenation. Similarly, bending stiffness also closely connects with dehydrogenation. A transition of bending stiffness in two specific dehydrogenation-free DNTs occurring at critical curvatures is detected as a consequence of local bond transformations. Moreover, bending stiffness in different bending directions can differ by around 8-folds, originating from the distinct surface morphologies. The findings provide a critical knowledge of mechanical properties of DNTs for practical applications.

The best features of diamond nanothread for nanofibre applications

Carbon fibres have attracted interest from both the scientific and engineering communities due to their outstanding physical properties. Here we report that recently synthesized ultrathin diamond nanothread not only possesses excellent torsional deformation capability, but also excellent interfacial load-transfer efficiency. Compared with (10,10) carbon nanotube bundles, the flattening of nanotubes is not observed in diamond nanothread bundles, which leads to a high-torsional elastic limit that is almost three times higher. Pull-out tests reveal that the diamond nanothread bundle has an interface transfer load of more than twice that of the carbon nanotube bundle, corresponding to an order of magnitude higher in terms of the interfacial shear strength. Such high load-transfer efficiency is attributed to the strong mechanical interlocking effect at the interface. These intriguing features suggest that diamond nanothread could be an excellent candidate for constructing next-generation carbon fibres.

Functionalized diamond nanothreads from benzene derivatives.

Diamond nanothreads (DNTs) are fully sp3-bonded one-dimensional carbon nanostructures, synthesized recently through compression of crystalline benzene. They possess outstanding mechanical strength, suitable for the development of novel nanostructured reinforced materials. In this article, we use density functional theory calculations to investigate the feasibility and physical properties of functionalized DNTs. We show that the stacking and covalent bonding of benzene derivative molecules (toluene, aniline, phenol and fluorobenzene) may lead to stable configurations analogous to benzene-derived DNTs, with functional groups (-CH3, -NH2, -OH, -F) covalently attached to the surface. The same principle was also applied to pyridine, an aromatic heterocyclic compound, resulting in DNTs containing N heteroatoms within the sp3 C-C chain. We show that the mechanical properties remain practically unaltered compared to the original material, and that the electronic properties can be tuned upon functionalization. The presence of polar functional groups on DNT surfaces are expected to affect their compatibility with other materials and solvents, enabling the development of novel processes and technological applications using DNTs.

First-principles calculation of the mechanical properties of diamond nanothreads

The synthesis of novel one-dimensional carbon nanostructures named diamond nanothreads (DNT) has been recently reported, and subsequent studies employing molecular dynamics (MD) simulations demonstrated that they possess remarkable mechanical properties. In this paper we present the results of Density Functional Theory calculations of the mechanical properties for several DNT configurations, confirming that they indeed exhibit a high ideal strength (as high as 15.7 nN or 2.6 × 107 N m/kg) and stiffness (as high as 168 nN or 2.8 × 108 N m/kg), similarly to other carbon nanostructures. We compare these results with previously reported and additional MD calculations, and show that traditional interatomic potentials predict these properties with deviations up to ∼50%. A detailed analysis of the dependence of atomic structure on strain shows the reasons for these discrepancies. We also show that the most known DNT configuration (the (3,0) sp3-nanotube) exhibits a negative radial Poisson ratio.

Phonons, Localization, and Thermal Conductivity of Diamond Nanothreads and Amorphous Graphene.

Recently, the domains of low-dimensional (low-D) materials and disordered materials have been brought together by the demonstration of several new low-D, disordered systems. The thermal transport properties of these systems are not well-understood. Using amorphous graphene and glassy diamond nanothreads as prototype systems, we establish how structural disorder affects vibrational energy transport in low-dimensional, but disordered, materials. Modal localization analysis, molecular dynamics simulations, and a generalized model together demonstrate that the thermal transport properties of these materials exhibit both similarities and differences from disordered 3D materials. In analogy with 3D, the low-D disordered systems exhibit both propagating and diffusive vibrational modes. In contrast to 3D, however, the diffuson contribution to thermal transport in these low-D systems is shown to be negligible, which may be a result of inherent differences in the nature of random walks in lower dimensions. Despite the lack of diffusons, the suppression of thermal conductivity due to disorder in low-D systems is shown to be mild or comparable to 3D. The mild suppression originates from the presence of low-frequency vibrational modes that maintain a well-defined polarization and help preserve the thermal conductivity in the presence of disorder.

The morphology and temperature dependent tensile properties of diamond nanothreads

The ultrathin one-dimensional sp3 diamond nanothreads (NTHs), as successfully synthesised recently, have greatly augmented the interests from the carbon community. In principle, there can exist different stable NTH structures. In this work, we studied the mechanical behaviours of three representative NTHs using molecular dynamics simulations. It is found that the mechanical properties of NTH can vary significantly due to morphology differences, which are believed to originate from the different stress distributions determined by its structure. Further studies have shown that the temperature has a significant impact on the mechanical properties of the NTH. Specifically, the failure strength/strain decreases with increasing temperature, and the effective Young’s modulus appears independent of temperature. The remarkable reduction of the failure strength/strain is believed to be resulted from the increased bond re-arrangement process and free lateral vibration at high temperatures. In addition, the NTH is found to have a relatively high bending rigidity, and behaves more like flexible elastic rod. This study highlights the importance of structure-property relation and provides a fundamental understanding of the tensile behaviours of different NTHs, which should shed light on the design and also application of the NTH-based nanostructures as strain sensors and mechanical connectors.

Diamond Nanothread as a New Reinforcement for Nanocomposites

This work explores the application of a new 1D carbon nanomaterial, the diamond nanothread (DNT), as a reinforcement for nanocomposites. Owing to the existence of Stone–Wales transformation defects, the DNT intrinsically possesses irregular surfaces, which is expected to enhance the noncovalent interfacial load transfer. Through a series of in silico pull‐out studies of the DNT in polyethylene (PE) matrix, it is found that the load transfer between DNT and PE matrix is dominated by the noncovalent interactions, in particular the van der Waals interactions. Although the hydrogenated surface of the DNT reduces the strength of the van der Waals interactions at the interface, the irregular surface of the DNT can compensate for the weak bonds. These factors lead to an interfacial shear strength of the DNT/PE interface comparable with that of the carbon nanotube/PE interface. The results show that the DNT/PE interfacial shear strength remains high even as the number of Stone–Wales transformation defects decreases. It can be enhanced further by increasing the PE density or introduction of functional groups to the DNT, both of which greatly increase the noncovalent interactions.

Generalized Debye-Peierls/Allen-Feldman model for the lattice thermal conductivity of low-dimensional and disordered materials

We present a generalized model to describe the lattice thermal conductivity of low-dimensional (low-D) and disordered systems. The model is a straightforward generalization of the Debye-Peierls and Allen-Feldman schemes to arbitrary dimensions, accounting for low-D effects such as differences in dispersion, density of states, and scattering. Similar in spirit to the Allen-Feldman approach, heat carriers are categorized according to their transporting capacity as propagons, diffusons, and locons. The results of the generalized model are compared to experimental results when available, and equilibrium molecular dynamics simulations otherwise. The results are in very good agreement with our analysis of phonon localization in disordered low-D systems, such as amorphous graphene and glassy diamond nanothreads. Several unique aspects of thermal transport in low-D and disordered systems, such as milder suppression of thermal conductivity and negligible diffuson contributions, are captured by the approach.

From brittle to ductile: a structure dependent ductility of diamond nanothread.

As a potential building block for the next generation of devices/multifunctional materials that are spreading in almost every technology sector, one-dimensional (1D) carbon nanomaterial has received intensive research interests. Recently, a new ultra-thin diamond nanothread (DNT) has joined this palette, which is a 1D structure with poly-benzene sections connected by Stone-Wales (SW) transformation defects. Using large-scale molecular dynamics simulations, we found that this sp(3) bonded DNT can transition from brittle to ductile behaviour by varying the length of the poly-benzene sections, suggesting that DNT possesses entirely different mechanical responses than other 1D carbon allotropes. Analogously, the SW defects behave like a grain boundary that interrupts the consistency of the poly-benzene sections. For a DNT with a fixed length, the yield strength fluctuates in the vicinity of a certain value and is independent of the "grain size". On the other hand, both yield strength and yield strain show a clear dependence on the total length of DNT, which is due to the fact that the failure of the DNT is dominated by the SW defects. Its highly tunable ductility together with its ultra-light density and high Young's modulus makes diamond nanothread ideal for the creation of extremely strong three-dimensional nano-architectures.

Thermal conductivity of a new carbon nanotube analog: The diamond nanothread

Based on the non-equilibrium molecular dynamics simulations, we have studied the thermal conductivities of a novel ultra-thin one-dimensional carbon nanomaterial – diamond nanothread (DNT). Unlike single-wall carbon nanotube (CNT), the existence of the Stone-Wales (SW) transformations in DNT endows it with richer thermal transport characteristics. There is a transition from wave-dominated to particle-dominated transport region, which depends on the length of poly-benzene rings. However, independent of the transport region, strong length dependence in thermal conductivity is observed in DNTs with different lengths of poly-benzene ring. The distinctive SW characteristic in DNT provides more to tune the thermal conductivity not found in the homogeneous structure of CNT. Therefore, DNT is an ideal platform to investigate various thermal transport mechanisms at the nanoscale. Its high tunability raises the potential to design DNTs for different applications, such as thermal connection and temperature management.

Mechanical properties and defect sensitivity of diamond nanothreads.

One of the newest carbon allotropes synthesized are diamond nanothreads. Using molecular dynamics, we determine the stiffness (850 GPa), strength (26.4 nN), extension (14.9%), and bending rigidity (5.35 × 10(-28) N·m(2)). The 1D nature of the nanothread results in a tenacity of 4.1 × 10(7) N·m/kg, exceeding nanotubes and graphene. As the thread consists of repeating Stone-Wales defects, through steered molecular dynamics (SMD), we explore the effect of defect density on the strength, stiffness, and extension of the system.