A flexible and elastic carbon coil (see figure) has been fabricated using a continuous yarn of carbon nanotube arrays. The processed yarn is both elastic and pliable and can be freely manipulated and molded to any desired shape that is retained after heat treatment. Owing to their highly ordered macroscopic structures, the good electrical and thermal conductivity of the nanotube components, and their good mechanical properties, these carbon nanostructures may find extensive use in a wide range of applications.

We report the direct synthesis of strong, highly conducting, and transparent single-walled carbon nanotube (SWNT) films. Systematically, tests reveal that the directly synthesized films have superior electrical and mechanical properties compared with the films made from a solution-based filtration process: the electrical conductivity is over 2000 S/cm and the strength can reach 360 MPa. These values are both enhanced by more than 1 order. We attribute these intriguing properties to the good and long interbundle connections. Moreover, by the help of an extrapolated Weibull theory, we verify the feasibility of reducing the interbundle slip by utilizing the long-range intertube friction and estimate the ultimate strength of macroscale SWNTs without binding agent.Because of their optical transparency and unique electric properties together with mechanical flexibility, film-like single-walled carbon nanotubes (SWNTs) are attractive not only for fundamental researches but also potential applications. For example, large optical nonlinearity, 1 subpicosecond optical response 2,3 and bolometric infrared photoresponse 4 have been observed in SWNT films, and the feasibilities of using SWNT films or networks as sensors, 5,6 diodes, 7 and field effect transistors 8 have already been demonstrated. Recently, highly conducting transparent SWNT films (tSWNTs) have also been fabricated by a kind of controlled filtration-deposition process, 9 which could be used as transparent electrodes for GaN/InGaN or flexible organic lightemitting diodes. 10,11 However, almost all of the above reports focused on the post-treated SWNT films, which are obtained through solution-based filtration processes. As known, to obtain high conductivity, SWNTs must be well purified and dispersed from sootlike morphology, which usually costs several days and leaves unrecyclable chemical residues. Besides, the comparative low strength of these films is one of the challenges for their applications, especially in the field of high-strength enforcement sheets.Here we report the direct synthesis of strong, highly conducting, and transparent films through a further developed floating catalyst CVD (FCCVD) technique that is based on the methods of producing large-scale nonwoven SWNTs. 12 As catalyst source, ferrocene/sulfur powder is heated to 65-85°C and flowed into a reaction zone by the mixture of 1000 sccm argon and 1-8 sccm methane. The growth rates of the films are mainly determined by the sublimation rate of the catalysts. Under typical conditions, after 30 min growth, thin films with a thickness of 100 nm will form in the high-temperature zone (over 600°C) of the quartz tube and can be easily peeled off. This type of large-area freestanding film can be easily handled for further researches. Raman scattering and HRTEM images show that most CNTs in the films are single-walled carbon nanotubes. In this paper, we systematically investigated the properties of the directly

Carbon nanotubes have unprecedented mechanical properties as defect-free nanoscale building blocks, but their potential has not been fully realized in composite materials due to weakness at the interfaces. Here we demonstrate that through load-transfer-favored three-dimensional architecture and molecular level couplings with polymer chains, true potential of CNTs can be realized in composites as initially envisioned. Composite fibers with reticulate nanotube architectures show order of magnitude improvement in strength compared to randomly dispersed short CNT reinforced composites reported before. The molecular level couplings between nanotubes and polymer chains results in drastic differences in the properties of thermoset and thermoplastic composite fibers, which indicate that conventional macroscopic composite theory fails to explain the overall hybrid behavior at nanoscale.To build composites with superior strength and flawtolerance, nanoscale reinforcements have natural advantages than their micrometer-sized counterparts because of their paucity of structural defects and high aspect ratio.1 However, a huge challenge still lies in the manufacturing of a highperformance nanocomposite because of the agglomeration tendency of the nanometer-sized fillers and poor load transfer efficiency between the matrix and reinforcements. A good example is carbon nanotube (CNT) reinforced composites. Although individual CNTs have Young's modulus of 1 TPa and strength over 60 GPa, 2,3 to date CNT reinforced polymer composites fabricated by mixing polymers and nanotubes have shown only moderate enhancement in modulus and even more limited improvements in strength. 4 Even in the cases where CNTs are optimally dispersed at high volume fraction, their moduli and strengths are at least 2 orders of magnitude lower than what was theoretically predicted by composite theory. [5][6][7] Essentially, the mechanical performance of CNT reinforced composites relies on the load-bearing status of the CNTs in the matrix. However, two inherent problems of CNTs shadow their promise as efficient load-bearers. One is their waviness. A multiwalled carbon nanotube with a diameter of 10 nm is 10 12 times easier to be bent than a

A B S T R A C TMechanical properties and in vitro biocompatibility of graphene/hydroxyapatite (HA) composite synthesized using spark plasma sintering (SPS) are reported in this study. Raman spectroscopy corroborated that graphene nanosheets (GNSs) survived the harsh processing conditions of the selected SPS processing parameters. A 1.0 wt.% GNS/HA composite exhibits $80% improvement in fracture toughness as compared to pure HA. GNS pull-out, grain bridging by GNS, crack bridging and crack deflection are the major toughening mechanisms that resist crack propagation. In vitro osteoblast growth tests illustrate that the added GNSs contribute to the improvement of both osteoblast adhesion and apatite mineralization. Therefore, the GNS/HA composite is expected to be a promising material for load-bearing orthopedic implants.Ó 2013 Elsevier Ltd. All rights reserved. IntroductionGraphene, a monolayer of sp 2 -hybridized carbon atoms arranged in a two-dimensional lattice, has drawn much attention in the composite field as reinforcement for structural composites due to its combination of excellent mechanical properties (e.g., tensile strength 130 GPa and Young's modulus 0.5-1 TPa) and very high specific surface area (up to 2630 m 2 g À1 ) [1][2][3]. In particular, the high specific surface area of graphene, inherent to its two-dimensional lattice geometry, imparts strong interfacial bonding with the matrix phase and effective load transfer from the matrix to graphene [4]. Graphene nanosheets (GNSs) with a thickness of approximately 1-10 nm, also called as graphene nanoplatelets (GNPs) or graphene platelets (GPLs), are generally composed of a few graphene layers and display compatible properties similar to that of monolayer graphene. Furthermore, it is worth to note that GNSs are much easier to produce and handle. Very recently, GNSs have been widely employed as nanofillers to polymers [5,6], metals [7,8] and ceramics [9][10][11] to produce composites with tailored mechanical properties.Due to its chemical composition (Ca/P ratio of 1.67) and crystal structure that are similar to the apatite in human skeletal system, hydroxyapatite (HA), with excellent bioactivity and osteoconductivity, is suitable for osteoblast adhesion and proliferation, new bone growth and integration [12], and therefore is recognized as one of the most promising orthopedic biomaterials. However, the intrinsic brittleness of HA, i.e., low fracture toughness and low toughness-induced poor wear resistance, still restricts its clinical applications. Therefore, toughening of HA with a second phase such as alumina, yttria stabilized zirconia, titania and carbon nanotubes (CNTs) has been extensively explored to overcome the deficiencies of pure HA [13].Among HA based composites, much recent attention has been devoted to the CNT/HA composites.

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Silicon nitride with helical structure was prepared on a large scale by CVD. On the microscale, these coiled Si3N4 ceramics still possess superelasticity and can recover their original shapes after cyclic loadings without noticeable deformations. These results suggest helical microcoils could have potential in microdevices for MEMS, motors, electromagnets, generators, and related equipment.

The present paper aims to develop a robust spherical indentation-based method to extract material plastic properties. For this purpose, a new consideration of piling-up effect is incorporated into the expanding cavity model; an extensive numerical study on the similarity solution has also been performed. As a consequence, two semi-theoretical relations between the indentation response and material plastic properties are derived, with which plastic properties of materials can be identified from a single instrumented spherical indentation curve, the advantage being that this approach no longer needs estimations of contact radius with given elastic modulus. Moreover, the inconvenience in using multiple indenters with different tip angles can be avoided. Comprehensive sensitivity analyses show that the present algorithm is reliable. Also, by experimental verification performed on three typical materials, good agreement of the material properties between those obtained from the reverse algorithm and experimental data is obtained.

The relationship between hardness (H), reduced modulus (Er), unloading work (Wu), and total work (Wt) of indentation is examined in detail experimentally and theoretically. Experimental study verifies the approximate linear relationship. Theoretical analysis confirms it. Furthermore, the solutions to the conical indentation in elastic-perfectly plastic solid, including elastic work (We), H, Wt, and Wu are obtained using Johnson’s expanding cavity model and Lamé solution. Consequently, it is found that the We should be distinguished from Wu, rather than their equivalence as suggested in ISO14577, and (H∕Er)∕(Wu∕Wt) depends mainly on the conical angle, which are also verified with numerical simulations.