No abstract available

No abstract available

[en] We report thermally activated transport resonances for biases below the superconducting energy gap in a carbon nanotube quantum dot (QD) device with a superconducting Pb and a normal metal contact. These resonances are due to the superconductor's finite quasi-particle population at elevated temperatures and can only be observed when the QD life-time broadening is considerably smaller than the gap. This condition is fulfilled in our QD devices with optimized Pd/Pb/In multi-layer contacts, which result in reproducibly large and “clean” superconducting transport gaps with a strong conductance suppression for subgap biases. We show that these gaps close monotonically with increasing magnetic field and temperature. The accurate description of the subgap resonances by a simple resonant tunneling model illustrates the ideal characteristics of the reported Pb contacts and gives an alternative access to the tunnel coupling strengths in a QD.

[en] Nanocarbons represented especially by carbon nanotubes (CNTs) and graphene have been of great interest during the last two decades, both from a fundamental point of view and for future applications. The most eye-catching features of carbon nanostructures (CNSs) are their electronic, mechanical, optical and chemical characteristics, which open a way for versatile applications. Among those future prospects, actuators are one of the promising technologies. Since 1999 when the first macroscopic actuator containing CNTs was reported, the interest of utilizing these materials as well as other CNSs in active systems has been triggered all over the world. This paper gives a thorough review as well as in-depth descriptions of the many aspects of nanocarbon-based actuators. The review covers aspects of worldwide research and development of nanocarbon ionic actuators up to 2012. Materials which are covered by this review include CNTs and their composites, carbon nanofibres (CNFs), graphene and its derivatives, microporous carbon materials (for example carbide derived carbons (CDCs) and carbon aerogels) as well as the possible combinations of these materials. The considered aspects cover the following fields: synthesis and characterization of the investigated materials, the actuation mechanism as well as modelling and simulation. Applications comprising system integration and device development are also reviewed within this paper. (paper)

[en] Stretchable and compressible strain sensors play an essential role in various fields with uses ranging from automotive components to medical devices. This study reports on the fabrication and characteristics of stretchable strain and pressure sensors constructed using a carbon nanotube and graphene composite. The sensors were used for gait analysis, an important step in the diagnosis and management of movement disorders. The stretchable and compressible strain sensors were used to measure peak knee sagittal angles and forces under the feet when walking. Gait analysis is usually performed within a laboratory. However, in this research we propose a shift to gait assessments conducted via long-term daily monitoring using wearable devices. (paper)

[en] Graphene quantum dots (GQDs) have been successfully deposited onto aligned carbon nanotubes (CNTs) by a benign electrochemical method and the capacitive properties of the as-formed GQD/CNT hybrid arrays were evaluated in symmetrical supercapacitors. It was found that supercapacitors fabricated from GQD/CNT hybrid arrays exhibited a high capacitance of 44 mF cm⁻², representing a more than 200% improvement over that of bare CNT electrodes. (paper)

[en] Water permeation across a single-walled carbon nanotube has been studied in the presence of static electric fields (SEFs) with different directions under hydrostatic pressures. With the angle between the SEF direction and tube axis increasing from 0^∘ to 90^∘, the water flux decreases gradually until almost vanishes, and the maximum value at 0^∘ is approximately four times the case without SEFs. The phenomenon is attributed to the alignment of the polar water molecules along the SEF direction. We also show that water permeation properties are dependent on the field strength due mainly to thermal fluctuations of water molecules.

[en] This study investigates the flow of viscous micropolar nanofluids. Single-walled carbon nanotubes are taken as the solid constituent. Dynamic viscosity is temperature dependent. The flow take place across two parallel squeezing plates with an unsteady magnetic field normal to the surface of the plates. The effects of thermal radiation are also determined. The problem is modeled with the help of micropolar fluid theory. The governing equations are nonlinear coupled partial differential equations, which are non-dimensionalized and then transform to ordinary differential equations by suitable similarity transformations. These highly nonlinear coupled ordinary differential equations are then solved with an implicit finite difference scheme called the Keller box method. This method has second order accuracy and is unconditionally stable. Graphical results are plotted for quantities of physical interest such as velocity, temperature, Nusselt number, and skin friction. The study is focused on the flow behavior of fluid keeping dynamic viscosity sensitive to temperature. It has been concluded that the skin friction coefficient and angular velocity profile rises while the linear velocity of the fluid body decreases with the magnitude of the variable viscosity parameter. (paper)

[en] Concern over the health effects from the inhalation of carbon nanotubes (CNTs) has been building for some time, and adverse health effects found in animal studies include acute and chronic respiratory damage, cardiac inflammation, and cancer including mesothelioma, heretofore only associated with asbestos exposure. The strong animal evidence of toxicity requires that the occupational hygiene community develops strategies for reducing or eliminating worker exposures to CNTs; part of this strategy involves the setting of occupational exposure limits (OELs) for CNTs. A number of government agencies and private entities have established OELs for CNTs; some are mass-based, while others rely on number concentration. We review these various proposed standards and discuss the pros and cons of each approach. We recommend that specific action be taken, including intensified outreach to employers and employees concerning the potential adverse health effects from CNT inhalation, the development of more nuanced OELs that reflect the complex nature of CNT exposure, a broader discussion of these issues among all interested parties, and further research into important unanswered questions including optimum methods to evaluate CNT exposures. We conclude that current animal toxicity evidence suggests that strong action needs to be taken to minimize exposures to CNTs, and that any CNT OEL should be consistent with the need to minimize exposures.

[en] In this work, the role of optical wavelength on the photo induced strain in carbon nanotubes (CNT) is probed using a Fiber Bragg Grating (FBG), upon exposure to infrared (IR) (21 με mW"−"1) and visible (9 με mW"−"1) radiations. The strain sensitivity in CNT is monitored over a smaller range (10"−"3 to 10"−"9 ε) by exposing to a low optical power varying in the range 10"−"3 to 10"−"6 W. In addition, the wavelength dependent response and recovery periods of CNT under IR (τ_r_i_s_e = 150 ms, τ_f_a_l_l = 280 ms) and visible (τ_r_i_s_e = 1.07 s, τ_f_a_l_l = 1.18 s) radiations are evaluated in detail. This study can be further extended to measure the sensitivity of nano–scale photo induced strains in nano materials and opens avenues to control mechanical actuation using various optical wavelengths. (paper)