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Sample records for aligned cnt arrays

  1. Actuation-mechanisms of CNT-bucky papers and CNT-arrays

    NASA Astrophysics Data System (ADS)

    Geier, Sebastian; Mahrholz, Thorsten; Wierach, Peter; Sinapius, Michael

    2015-04-01

    In the fields of smart materials there is still a demand for a material featuring high modulus, low density and large strain. Carbon materials catch enormous scientific attention not only since carbon fibers were used for highperformance composite structures. But more and more the scientific attention moves from the macroscale to the nanoscale. This paper focuses with a adaptive point of view on one of the carbon allotropes: carbon nanotubes (CNTs). Beside excellent electromechanical properties another interesting feature was first mentioned 1999 - the active behavior of paper-like mats (bucky-papers) made of CNTs. CNT-papers are electrically activated using a double-layer interaction of ions provided by an electrolyte and the charged, high specific surface area of the paper formed by carbon nanotubes. Until now the detailed mechanism behind the strain/force generation of CNT-based architectures is unknown. A clarification of this principle reveals the potential of carbon tubes to be or not to be a resilient smart material in order to use their strong covalent carbon bonds instead of weak van der Waals force as tube-linking. This paper presents further investigations about the composition of CNT-papers and their performance in contrast to vertical aligned CNT-arrays using an actuated tensile test set-up. For better comparison the experiments of both specimen-types are carried out in dry, wet and wet/charged conditions. Especially in the case of CNT-arrays it is essential to preload the specimens because the curly CNT-structure superimposes the vertical orientation. While the CNT-paper is tested in an aqueous solution of one molar sodium chloride, the hydrophobic character of CNT-arrays requires an ionic liquid (IL) as electrolyte. It is found that the mechanical properties of CNT-papers drop significantly by wetting and can be controlled by charging what indicates an electrostatic dominated effect. In contrast the CNT-arrays show identical results regardless of the

  2. Large-Scale `Linker-Free Assembly' of swCNT-Based Biosensor Arrays

    NASA Astrophysics Data System (ADS)

    Sohn, Donghee; Lee, Byung Yang; Hong, Seunghun

    2008-03-01

    Biosensors based on single-walled carbon nanotubes (swCNTs) have received a great deal of attention due to their potential applications such as genotyping, disease diagnosis, food analysis, etc. However, a lack of reliable mass-production method for such swCNT-based biosensor has been holding back their practical applications. One promising mass-production method for swCNT-based biosensor arrays can be `linker-free assembly' process (Nature Nanotechnology 1, 66 (2006)), where non-polar patterns guide the `selective assembly' and `precision alignment' of carbon nanotubes on bare substrates without using any external forces such as liquid flow, etc. We used this method to fabricate large-scale assembly of swCNT-based integrated devices on virtually general substrates including SiO2, Si, Al, Au, etc. To utilize swCNT devices for biosensors, we functionalized swCNT devices on SiO2 with receptor biomolecules such as enzyme L-glutamate oxidase or biotin. And then, we could detect the target biomolecules (L-glutamate or streptavidin, respectively) with high sensitivity and selectivity by monitoring the conductance change of swCNT junctions in aqueous environment. These studies provide biological implications on neurotransmitters and proteins onto swCNT patterned surface.

  3. Solution-based electric-field-assisted assembly of vertically aligned CNT membranes

    NASA Astrophysics Data System (ADS)

    Castellano, Richard; Akin, Cevat; Shan, Jerry

    2014-11-01

    Carbon-nanotube (CNT) membranes are of interest due to experiments and simulations showing flow through nanotubes to be 3 to 5 orders of magnitude faster than predicted by viscous flow theory. Thus, membranes incorporating vertically aligned CNTs (VACNTs) as through-pores offer promise as highly efficient and permeable membranes for a variety of filter and separation processes. However, current membrane-fabrication techniques utilizing CVD-grown VACNT arrays are costly and difficult to scale up. We are developing a solution-based, electric-field-assisted approach as a cost-effective and scalable method to producing large-area VACNT membranes and composites. Post-growth nanotubes are first dispersed in a polymeric matrix and then aligned with an AC electric field. A DC component induces electrophoresis to the CNTs to significantly increase the VACNT number density. This composite field also introduces complex fluid motion caused by induced-charge electro-osmosis and the electrochemistry of the fluid/electrode interface. We experimentally probe all of these effects and consider factors affecting the number density and spatial uniformity of VACNT membranes. We also consider the basic electrokinetics of nanotube alignment under spatially uniform AC electric fields, making quantitative comparison with classical models of the dynamics of polarizable, 1D particles under the combined effects of electric fields, hydrodynamic drag, and Brownian motion. We conclude by discussing the implications of these fundamental electrohydrodynamic studies for producing large-area membranes containing aligned CNTs.

  4. Measurement of Vertically Aligned Carbon Nanotube Array Compression Response

    NASA Astrophysics Data System (ADS)

    Cao, Changhong

    The use of carbon nanotubes (CNTs) in the form of vertically aligned arrays or films has been of interest due to the super-compressible response and the ability to be used as electrical and thermal contacts. CNT arrays have shown the remarkable ability to react as foam-like structures and exhibit localized, coordinated buckling within specific regions. An understanding of the buckling region evolution and the resulting effects on the bulk CNT array response are important, unanswered fundamental questions necessary for the future application of CNT arrays. Here, we report on the low-cycle compression of bulk vertically aligned CNT arrays to observe initiation and growth of the buckling as a function of compressive strain and the contacting substrate material. A critical strain of ˜5.5% is found above which the buckling region length increased and below which remained at or below the applied strain. The results are corroborated with nanoindentation on the surfaces, which indicate a stiffening of the near surface by 9.4%-16.5% with increasing applied strain. Also, contact counterfaces with different stiffness, lithium niobate and a polymer gel, were compared, which resulted in changes of ˜32% in total array height after cyclic compression. Raman spectroscopy on CNT arrays before and after compressive deformation was performed observing repeatable vibrational shifts in the strained regions. Also, to observe the applicability of CNT arrays as contact sensors, electrical resistance change during compression was measured and found to increase by 4 times in the parallel versus vertical direction. Observation and results of the buckling region nature and relationship with applied strain and contacting substrates are important for applying the nanotube arrays to energy absorbing cushions, tunable dampers, thermal contacts, contact sensing, chemical sensing, or in sliding contact.

  5. Full elastic constitutive relation of non-isotropic aligned-CNT/PDMS flexible nanocomposites

    NASA Astrophysics Data System (ADS)

    Sepúlveda, A. T.; Guzman de Villoria, R.; Viana, J. C.; Pontes, A. J.; Wardle, B. L.; Rocha, L. A.

    2013-05-01

    The elastic response of vertically aligned-carbon nanotube/polydimethylsiloxane (A-CNT/PDMS) nanocomposites is presented in this study and related to the underlying aligned-CNT morphology. Multiwalled carbon nanotubes (MWCNTs) at 1% Vf are embedded in a flexible substrate of PDMS to create a flexible polymer nanocomposite (PNC). The PNC properties are evaluated using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and tensile mechanical tests, and the full linearly elastic constitutive relation is established for such a PNC. The results suggest that the CNTs retain the alignment after wetting and curing of PDMS. PDMS is significantly modified by the reinforcing aligned-CNT fibers, demonstrating non-isotropic (as opposed to the isotropic neat PDMS) elastic properties all different from PDMS (Young's modulus of 0.8 MPa), including an anisotropy ratio of 4.8 and increases in the modulus of A-CNT/PDMS over PDMS by more than 900% and 100%, in the CNT longitudinal and transverse directions, respectively. This study reports the first full constitutive relation that may be useful in modeling PNCs as composites or as elements of hierarchical nanoengineered composites, particularly PDMS-CNT PNCs are envisioned as elements in biomedical devices such as pressure transducers and energy harvesters.

  6. Simulation of water impregnation through vertically aligned CNT forests using a molecular dynamics method.

    PubMed

    Tajiri, Tomohiro; Matsuzaki, Ryosuke; Shimamura, Yoshinobu

    2016-01-01

    The flow rate of water through carbon nanotube (CNT) membranes is considerably large. Hence, CNT membranes can be used in nanofluidic applications. In this work, we performed a molecular dynamics (MD) simulation of the introduction of water into CNTs in the CNT membranes, especially in vertically aligned CNT forests. The results showed that the Knudsen number (Kn) increased with an increasing volume fraction of CNT (VC) and was greater than 10(-3) for each VC. Beyond this value, the flow became a slip flow. Further, the permeability increased as VC increased in the actual state calculated by the MD simulation, whereas the permeability in the no-slip state predicted by the Hagen-Poiseuille relationship decreased. Thus, a clear divergence in the permeability trend existed between the states. Finally, the flow enhancement ranged from 0.1 to 23,800, and the results show that water easily permeates as VC increases. PMID:27562112

  7. Simulation of water impregnation through vertically aligned CNT forests using a molecular dynamics method

    PubMed Central

    Tajiri, Tomohiro; Matsuzaki, Ryosuke; Shimamura, Yoshinobu

    2016-01-01

    The flow rate of water through carbon nanotube (CNT) membranes is considerably large. Hence, CNT membranes can be used in nanofluidic applications. In this work, we performed a molecular dynamics (MD) simulation of the introduction of water into CNTs in the CNT membranes, especially in vertically aligned CNT forests. The results showed that the Knudsen number (Kn) increased with an increasing volume fraction of CNT (VC) and was greater than 10−3 for each VC. Beyond this value, the flow became a slip flow. Further, the permeability increased as VC increased in the actual state calculated by the MD simulation, whereas the permeability in the no-slip state predicted by the Hagen–Poiseuille relationship decreased. Thus, a clear divergence in the permeability trend existed between the states. Finally, the flow enhancement ranged from 0.1 to 23,800, and the results show that water easily permeates as VC increases. PMID:27562112

  8. Aligned carbon nanotube array stiffness from stochastic three-dimensional morphology.

    PubMed

    Stein, Itai Y; Lewis, Diana J; Wardle, Brian L

    2015-12-14

    The landmark theoretical properties of low dimensional materials have driven more than a decade of research on carbon nanotubes (CNTs) and related nanostructures. While studies on isolated CNTs report behavior that aligns closely with theoretical predictions, studies on cm-scale aligned CNT arrays (>10(10) CNTs) oftentimes report properties that are orders of magnitude below those predicted by theory. Using simulated arrays comprised of up to 10(5) CNTs with realistic stochastic morphologies, we show that the CNT waviness, quantified via the waviness ratio (w), is responsible for more than three orders of magnitude reduction in the effective CNT stiffness. Also, by including information on the volume fraction scaling of the CNT waviness, the simulation shows that the observed non-linear enhancement of the array stiffness as a function of the CNT close packing originates from the shear and torsion deformation mechanisms that are governed by the low shear modulus (∼1 GPa) of the CNTs. PMID:26553970

  9. Array tomography: semiautomated image alignment.

    PubMed

    Micheva, Kristina D; O'Rourke, Nancy; Busse, Brad; Smith, Stephen J

    2010-11-01

    Array tomography is a volumetric microscopy method based on physical serial sectioning. Ultrathin sections of a plastic-embedded tissue are cut using an ultramicrotome, bonded in an ordered array to a glass coverslip, stained as desired, and imaged. The resulting two-dimensional image tiles can then be reconstructed computationally into three-dimensional volume images for visualization and quantitative analysis. The minimal thickness of individual sections permits high-quality rapid staining and imaging, whereas the array format allows reliable and convenient section handling, staining, and automated imaging. Also, the physical stability of the arrays permits images to be acquired and registered from repeated cycles of staining, imaging, and stain elution, as well as from imaging using multiple modalities (e.g., fluorescence and electron microscopy). Array tomography makes it possible to visualize and quantify previously inaccessible features of tissue structure and molecular architecture. However, careful preparation of the tissue is essential for successful array tomography; these steps can be time-consuming and require some practice to perfect. Successful array tomography requires that the captured images be properly stacked and aligned, and the software to achieve these ends is freely available. This protocol describes the construction of volumetric image stacks from images of fluorescently labeled arrays for three-dimensional image visualization, analysis, and archiving. PMID:21041400

  10. Highly aligned carbon nanotube arrays fabricated by bias sputtering

    NASA Astrophysics Data System (ADS)

    Hayashi, Nobuyuki; Honda, Shin-ichi; Tsuji, Keita; Lee, Kuei-Yi; Ikuno, Takashi; Fujimoto, Keiichi; Ohkura, Shigeharu; Katayama, Mitsuhiro; Oura, Kenjiro; Hirao, Takashi

    2003-05-01

    Vertically aligned carbon nanotube (CNT) arrays have been successfully grown on Si substrates by dc bias sputtering. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations revealed that the resultant arrays consisted of dense CNTs with diameters of 40-60 nm and lengths of 300-400 nm. The CNTs were found to have a bamboo-like structure at the end of which metallic nanoparticle was formed, indicating tip growth mechanism. The energy enhancement of carbon particles is a key factor for synthesis of CNTs using dc bias sputtering system.

  11. Stacked 3D RRAM Array with Graphene/CNT as Edge Electrodes.

    PubMed

    Bai, Yue; Wu, Huaqiang; Wang, Kun; Wu, Riga; Song, Lin; Li, Tianyi; Wang, Jiangtao; Yu, Zhiping; Qian, He

    2015-01-01

    There are two critical challenges which determine the array density of 3D RRAM: 1) the scaling limit in both horizontal and vertical directions; 2) the integration of selector devices in 3D structure. In this work, we present a novel 3D RRAM structure using low-dimensional materials, including 2D graphene and 1D carbon nanotube (CNT), as the edge electrodes. A two-layer 3D RRAM with monolayer graphene as edge electrode is demonstrated. The electrical results reveal that the RRAM devices could switch normally with this very thin edge electrode at nanometer scale. Meanwhile, benefited from the asymmetric carrier transport induced by Schottky barrier at metal/CNT and oxide/CNT interfaces, a selector built-in 3D RRAM structure using CNT as edge electrode is successfully fabricated and characterized. Furthermore, the discussion of high array density potential is presented. PMID:26348797

  12. Stacked 3D RRAM Array with Graphene/CNT as Edge Electrodes

    PubMed Central

    Bai, Yue; Wu, Huaqiang; Wang, Kun; Wu, Riga; Song, Lin; Li, Tianyi; Wang, Jiangtao; Yu, Zhiping; Qian, He

    2015-01-01

    There are two critical challenges which determine the array density of 3D RRAM: 1) the scaling limit in both horizontal and vertical directions; 2) the integration of selector devices in 3D structure. In this work, we present a novel 3D RRAM structure using low-dimensional materials, including 2D graphene and 1D carbon nanotube (CNT), as the edge electrodes. A two-layer 3D RRAM with monolayer graphene as edge electrode is demonstrated. The electrical results reveal that the RRAM devices could switch normally with this very thin edge electrode at nanometer scale. Meanwhile, benefited from the asymmetric carrier transport induced by Schottky barrier at metal/CNT and oxide/CNT interfaces, a selector built-in 3D RRAM structure using CNT as edge electrode is successfully fabricated and characterized. Furthermore, the discussion of high array density potential is presented. PMID:26348797

  13. Highly uniform hole spacing micro brushes based on aligned carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Yang, Zhi; Zhu, Xingzhong; Huang, Xiaolu; Cheng, Yingwu; Liu, Yun; Geng, Huijuan; Wu, Yue; Su, Yanjie; Wei, Hao; Zhang, Yafei

    2013-11-01

    Highly uniform hole spacing micro brushes were fabricated based on aligned carbon nanotube (CNT) arrays synthesized by chemical vapor deposition method with the assistance of anodic aluminum oxide (AAO) template. Different micro brushes from CNT arrays were constructed on silicon, glass, and polyimide substrates, respectively. The micro brushes had highly uniform hole spacing originating from the regularly periodic pore structure of AAO template. The CNT arrays, serving as bristles, were firmly grafted on the substrates. The brushes can easily clean particles with scale of micrometer on the surface of silicon wafer and from the narrow spaces between the electrodes in a series of cleaning experiments. The results show the potential application of the CNT micro brushes as a cleaning tool in microelectronics manufacture field.

  14. Highly uniform hole spacing micro brushes based on aligned carbon nanotube arrays

    PubMed Central

    2013-01-01

    Highly uniform hole spacing micro brushes were fabricated based on aligned carbon nanotube (CNT) arrays synthesized by chemical vapor deposition method with the assistance of anodic aluminum oxide (AAO) template. Different micro brushes from CNT arrays were constructed on silicon, glass, and polyimide substrates, respectively. The micro brushes had highly uniform hole spacing originating from the regularly periodic pore structure of AAO template. The CNT arrays, serving as bristles, were firmly grafted on the substrates. The brushes can easily clean particles with scale of micrometer on the surface of silicon wafer and from the narrow spaces between the electrodes in a series of cleaning experiments. The results show the potential application of the CNT micro brushes as a cleaning tool in microelectronics manufacture field. PMID:24274897

  15. Metal-modified and vertically aligned carbon nanotube sensors array for landfill gas monitoring applications

    NASA Astrophysics Data System (ADS)

    Penza, M.; Rossi, R.; Alvisi, M.; Serra, E.

    2010-03-01

    Vertically aligned carbon nanotube (CNT) layers were synthesized on Fe-coated low-cost alumina substrates using radio-frequency plasma enhanced chemical vapour deposition (RF-PECVD) technology. A miniaturized CNT-based gas sensor array was developed for monitoring landfill gas (LFG) at a temperature of 150 °C. The sensor array was composed of 4 sensing elements with unmodified CNT, and CNT loaded with 5 nm nominally thick sputtered nanoclusters of platinum (Pt), ruthenium (Ru) and silver (Ag). Chemical analysis of multicomponent gas mixtures constituted of CO2, CH4, H2, NH3, CO and NO2 has been performed by the array sensor responses and pattern recognition based on principal component analysis (PCA). The PCA results demonstrate that the metal-decorated and vertically aligned CNT sensor array is able to discriminate the NO2 presence in the multicomponent mixture LFG. The NO2 gas detection in the mixture LFG was proved to be very sensitive, e.g.: the CNT:Ru sensor shows a relative change in the resistance of 1.50% and 0.55% for NO2 concentrations of 3.3 ppm and 330 ppb dispersed in the LFG, respectively, with a wide NO2 gas concentration range measured from 0.33 to 3.3 ppm, at the sensor temperature of 150 °C. The morphology and structure of the CNT networks have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. A forest-like nanostructure of vertically aligned CNT bundles in the multi-walled form appeared with a height of about 10 µm and a single-tube diameter varying in the range of 5-35 nm. The intensity ratio of the Raman spectroscopy D-peak and G-peak indicates the presence of disorder and defects in the CNT networks. The size of the metal (Pt, Ru, Ag) nanoclusters decorating the CNT top surface varies in the range of 5-50 nm. Functional characterization based on electrical charge transfer sensing mechanisms in the metal-modified CNT-chemoresistor array demonstrates high sensitivity by

  16. Metal-modified and vertically aligned carbon nanotube sensors array for landfill gas monitoring applications.

    PubMed

    Penza, M; Rossi, R; Alvisi, M; Serra, E

    2010-03-12

    Vertically aligned carbon nanotube (CNT) layers were synthesized on Fe-coated low-cost alumina substrates using radio-frequency plasma enhanced chemical vapour deposition (RF-PECVD) technology. A miniaturized CNT-based gas sensor array was developed for monitoring landfill gas (LFG) at a temperature of 150 degrees C. The sensor array was composed of 4 sensing elements with unmodified CNT, and CNT loaded with 5 nm nominally thick sputtered nanoclusters of platinum (Pt), ruthenium (Ru) and silver (Ag). Chemical analysis of multicomponent gas mixtures constituted of CO(2), CH(4), H(2), NH(3), CO and NO(2) has been performed by the array sensor responses and pattern recognition based on principal component analysis (PCA). The PCA results demonstrate that the metal-decorated and vertically aligned CNT sensor array is able to discriminate the NO(2) presence in the multicomponent mixture LFG. The NO(2) gas detection in the mixture LFG was proved to be very sensitive, e.g.: the CNT:Ru sensor shows a relative change in the resistance of 1.50% and 0.55% for NO(2) concentrations of 3.3 ppm and 330 ppb dispersed in the LFG, respectively, with a wide NO(2) gas concentration range measured from 0.33 to 3.3 ppm, at the sensor temperature of 150 degrees C. The morphology and structure of the CNT networks have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. A forest-like nanostructure of vertically aligned CNT bundles in the multi-walled form appeared with a height of about 10 microm and a single-tube diameter varying in the range of 5-35 nm. The intensity ratio of the Raman spectroscopy D-peak and G-peak indicates the presence of disorder and defects in the CNT networks. The size of the metal (Pt, Ru, Ag) nanoclusters decorating the CNT top surface varies in the range of 5-50 nm. Functional characterization based on electrical charge transfer sensing mechanisms in the metal-modified CNT-chemoresistor array

  17. Aligned carbon nanotube array stiffness from stochastic three-dimensional morphology

    NASA Astrophysics Data System (ADS)

    Stein, Itai Y.; Lewis, Diana J.; Wardle, Brian L.

    2015-11-01

    The landmark theoretical properties of low dimensional materials have driven more than a decade of research on carbon nanotubes (CNTs) and related nanostructures. While studies on isolated CNTs report behavior that aligns closely with theoretical predictions, studies on cm-scale aligned CNT arrays (>1010 CNTs) oftentimes report properties that are orders of magnitude below those predicted by theory. Using simulated arrays comprised of up to 105 CNTs with realistic stochastic morphologies, we show that the CNT waviness, quantified via the waviness ratio (w), is responsible for more than three orders of magnitude reduction in the effective CNT stiffness. Also, by including information on the volume fraction scaling of the CNT waviness, the simulation shows that the observed non-linear enhancement of the array stiffness as a function of the CNT close packing originates from the shear and torsion deformation mechanisms that are governed by the low shear modulus (~1 GPa) of the CNTs.The landmark theoretical properties of low dimensional materials have driven more than a decade of research on carbon nanotubes (CNTs) and related nanostructures. While studies on isolated CNTs report behavior that aligns closely with theoretical predictions, studies on cm-scale aligned CNT arrays (>1010 CNTs) oftentimes report properties that are orders of magnitude below those predicted by theory. Using simulated arrays comprised of up to 105 CNTs with realistic stochastic morphologies, we show that the CNT waviness, quantified via the waviness ratio (w), is responsible for more than three orders of magnitude reduction in the effective CNT stiffness. Also, by including information on the volume fraction scaling of the CNT waviness, the simulation shows that the observed non-linear enhancement of the array stiffness as a function of the CNT close packing originates from the shear and torsion deformation mechanisms that are governed by the low shear modulus (~1 GPa) of the CNTs. Electronic

  18. Vertically aligned CNT-Cu nano-composite material for stacked through-silicon-via interconnects.

    PubMed

    Sun, Shuangxi; Mu, Wei; Edwards, Michael; Mencarelli, Davide; Pierantoni, Luca; Fu, Yifeng; Jeppson, Kjell; Liu, Johan

    2016-08-19

    For future miniaturization of electronic systems using 3D chip stacking, new fine-pitch materials for through-silicon-via (TSV) applications are likely required. In this paper, we propose a novel carbon nanotube (CNT)/copper nanocomposite material consisting of high aspect ratio, vertically aligned CNT bundles coated with copper. These bundles, consisting of hundreds of tiny CNTs, were uniformly coated by copper through electroplating, and aspect ratios as high as 300:1 were obtained. The resistivity of this nanomaterial was found to be as low as ∼10(-8) Ω m, which is of the same order of magnitude as the resistivity of copper, and its temperature coefficient was found to be only half of that of pure copper. The main advantage of the composite TSV nanomaterial is that its coefficient of thermal expansion (CTE) is similar to that of silicon, a key reliability factor. A finite element model was set up to demonstrate the reliability of this composite material and thermal cycle simulations predicted very promising results. In conclusion, this composite nanomaterial appears to be a very promising material for future 3D TSV applications offering both a low resistivity and a low CTE similar to that of silicon. PMID:27383767

  19. Vertically aligned CNT-Cu nano-composite material for stacked through-silicon-via interconnects

    NASA Astrophysics Data System (ADS)

    Sun, Shuangxi; Mu, Wei; Edwards, Michael; Mencarelli, Davide; Pierantoni, Luca; Fu, Yifeng; Jeppson, Kjell; Liu, Johan

    2016-08-01

    For future miniaturization of electronic systems using 3D chip stacking, new fine-pitch materials for through-silicon-via (TSV) applications are likely required. In this paper, we propose a novel carbon nanotube (CNT)/copper nanocomposite material consisting of high aspect ratio, vertically aligned CNT bundles coated with copper. These bundles, consisting of hundreds of tiny CNTs, were uniformly coated by copper through electroplating, and aspect ratios as high as 300:1 were obtained. The resistivity of this nanomaterial was found to be as low as ∼10‑8 Ω m, which is of the same order of magnitude as the resistivity of copper, and its temperature coefficient was found to be only half of that of pure copper. The main advantage of the composite TSV nanomaterial is that its coefficient of thermal expansion (CTE) is similar to that of silicon, a key reliability factor. A finite element model was set up to demonstrate the reliability of this composite material and thermal cycle simulations predicted very promising results. In conclusion, this composite nanomaterial appears to be a very promising material for future 3D TSV applications offering both a low resistivity and a low CTE similar to that of silicon.

  20. Remarkably enhanced thermal transport based on a flexible horizontally-aligned carbon nanotube array film

    NASA Astrophysics Data System (ADS)

    Qiu, Lin; Wang, Xiaotian; Su, Guoping; Tang, Dawei; Zheng, Xinghua; Zhu, Jie; Wang, Zhiguo; Norris, Pamela M.; Bradford, Philip D.; Zhu, Yuntian

    2016-02-01

    It has been more than a decade since the thermal conductivity of vertically aligned carbon nanotube (VACNT) arrays was reported possible to exceed that of the best thermal greases or phase change materials by an order of magnitude. Despite tremendous prospects as a thermal interface material (TIM), results were discouraging for practical applications. The primary reason is the large thermal contact resistance between the CNT tips and the heat sink. Here we report a simultaneous sevenfold increase in in-plane thermal conductivity and a fourfold reduction in the thermal contact resistance at the flexible CNT-SiO2 coated heat sink interface by coupling the CNTs with orderly physical overlapping along the horizontal direction through an engineering approach (shear pressing). The removal of empty space rapidly increases the density of transport channels, and the replacement of the fine CNT tips with their cylindrical surface insures intimate contact at CNT-SiO2 interface. Our results suggest horizontally aligned CNT arrays exhibit remarkably enhanced in-plane thermal conductivity and reduced out-of-plane thermal conductivity and thermal contact resistance. This novel structure makes CNT film promising for applications in chip-level heat dissipation. Besides TIM, it also provides for a solution to anisotropic heat spreader which is significant for eliminating hot spots.

  1. Remarkably enhanced thermal transport based on a flexible horizontally-aligned carbon nanotube array film.

    PubMed

    Qiu, Lin; Wang, Xiaotian; Su, Guoping; Tang, Dawei; Zheng, Xinghua; Zhu, Jie; Wang, Zhiguo; Norris, Pamela M; Bradford, Philip D; Zhu, Yuntian

    2016-01-01

    It has been more than a decade since the thermal conductivity of vertically aligned carbon nanotube (VACNT) arrays was reported possible to exceed that of the best thermal greases or phase change materials by an order of magnitude. Despite tremendous prospects as a thermal interface material (TIM), results were discouraging for practical applications. The primary reason is the large thermal contact resistance between the CNT tips and the heat sink. Here we report a simultaneous sevenfold increase in in-plane thermal conductivity and a fourfold reduction in the thermal contact resistance at the flexible CNT-SiO2 coated heat sink interface by coupling the CNTs with orderly physical overlapping along the horizontal direction through an engineering approach (shear pressing). The removal of empty space rapidly increases the density of transport channels, and the replacement of the fine CNT tips with their cylindrical surface insures intimate contact at CNT-SiO2 interface. Our results suggest horizontally aligned CNT arrays exhibit remarkably enhanced in-plane thermal conductivity and reduced out-of-plane thermal conductivity and thermal contact resistance. This novel structure makes CNT film promising for applications in chip-level heat dissipation. Besides TIM, it also provides for a solution to anisotropic heat spreader which is significant for eliminating hot spots. PMID:26880221

  2. Remarkably enhanced thermal transport based on a flexible horizontally-aligned carbon nanotube array film

    PubMed Central

    Qiu, Lin; Wang, Xiaotian; Su, Guoping; Tang, Dawei; Zheng, Xinghua; Zhu, Jie; Wang, Zhiguo; Norris, Pamela M.; Bradford, Philip D.; Zhu, Yuntian

    2016-01-01

    It has been more than a decade since the thermal conductivity of vertically aligned carbon nanotube (VACNT) arrays was reported possible to exceed that of the best thermal greases or phase change materials by an order of magnitude. Despite tremendous prospects as a thermal interface material (TIM), results were discouraging for practical applications. The primary reason is the large thermal contact resistance between the CNT tips and the heat sink. Here we report a simultaneous sevenfold increase in in-plane thermal conductivity and a fourfold reduction in the thermal contact resistance at the flexible CNT-SiO2 coated heat sink interface by coupling the CNTs with orderly physical overlapping along the horizontal direction through an engineering approach (shear pressing). The removal of empty space rapidly increases the density of transport channels, and the replacement of the fine CNT tips with their cylindrical surface insures intimate contact at CNT-SiO2 interface. Our results suggest horizontally aligned CNT arrays exhibit remarkably enhanced in-plane thermal conductivity and reduced out-of-plane thermal conductivity and thermal contact resistance. This novel structure makes CNT film promising for applications in chip-level heat dissipation. Besides TIM, it also provides for a solution to anisotropic heat spreader which is significant for eliminating hot spots. PMID:26880221

  3. Copper-encapsulated vertically aligned carbon nanotube arrays.

    PubMed

    Stano, Kelly L; Chapla, Rachel; Carroll, Murphy; Nowak, Joshua; McCord, Marian; Bradford, Philip D

    2013-11-13

    A new procedure is described for the fabrication of vertically aligned carbon nanotubes (VACNTs) that are decorated, and even completely encapsulated, by a dense network of copper nanoparticles. The process involves the conformal deposition of pyrolytic carbon (Py-C) to stabilize the aligned carbon-nanotube structure during processing. The stabilized arrays are mildly functionalized using oxygen plasma treatment to improve wettability, and they are then infiltrated with an aqueous, supersaturated Cu salt solution. Once dried, the salt forms a stabilizing crystal network throughout the array. After calcination and H2 reduction, Cu nanoparticles are left decorating the CNT surfaces. Studies were carried out to determine the optimal processing parameters to maximize Cu content in the composite. These included the duration of Py-C deposition and system process pressure as well as the implementation of subsequent and multiple Cu salt solution infiltrations. The optimized procedure yielded a nanoscale hybrid material where the anisotropic alignment from the VACNT array was preserved, and the mass of the stabilized arrays was increased by over 24-fold because of the addition of Cu. The procedure has been adapted for other Cu salts and can also be used for other metal salts altogether, including Ni, Co, Fe, and Ag. The resulting composite is ideally suited for application in thermal management devices because of its low density, mechanical integrity, and potentially high thermal conductivity. Additionally, further processing of the material via pressing and sintering can yield consolidated, dense bulk composites. PMID:24143862

  4. Use of Patterned CNT Arrays for Display Purposes

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance D. (Inventor); Schipper, John F. (Inventor)

    2009-01-01

    Method and system for providing a dynamically reconfigurable display having nanometer-scale resolution, using a patterned array of multi-wall carbon nanotube (MWCNT) clusters. A diode, phosphor or other light source on each MWCNT cluster is independently activated, and different color light sources (e.g., red, green, blue, grey scale, infrared) can be mixed if desired. Resolution is estimated to be 40-100 nm, and reconfiguration time for each MWCNT cluster is no greater than one microsecond.

  5. Synthesis and electron emission properties of aligned carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Neupane, Suman

    Carbon nanotubes (CNTs) have become one of the most interesting allotropes of carbon due to their intriguing mechanical, electrical, thermal and optical properties. The synthesis and electron emission properties of CNT arrays have been investigated in this work. Vertically aligned CNTs of different densities were synthesized on copper substrate with catalyst dots patterned by nanosphere lithography. The CNTs synthesized with catalyst dots patterned by spheres of 500 nm diameter exhibited the best electron emission properties with the lowest turn-on/threshold electric fields and the highest field enhancement factor. Furthermore, CNTs were treated with NH3 plasma for various durations and the optimum enhancement was obtained for a plasma treatment of 1.0 min. CNT point emitters were also synthesized on a flat-tip or a sharp-tip to understand the effect of emitter geometry on the electron emission. The experimental results show that electron emission can be enhanced by decreasing the screening effect of the electric field by neighboring CNTs. In another part of the dissertation, vertically aligned CNTs were synthesized on stainless steel (SS) substrates with and without chemical etching or catalyst deposition. The density and length of CNTs were determined by synthesis time. For a prolonged growth time, the catalyst activity terminated and the plasma started etching CNTs destructively. CNTs with uniform diameter and length were synthesized on SS substrates subjected to chemical etching for a period of 40 minutes before the growth. The direct contact of CNTs with stainless steel allowed for the better field emission performance of CNTs synthesized on pristine SS as compared to the CNTs synthesized on Ni/Cr coated SS. Finally, fabrication of large arrays of free-standing vertically aligned CNT/SnO2 core-shell structures was explored by using a simple wet-chemical route. The structure of the SnO2 nanoparticles was studied by X-ray diffraction and electron microscopy

  6. Alignment method for solar collector arrays

    DOEpatents

    Driver, Jr., Richard B

    2012-10-23

    The present invention is directed to an improved method for establishing camera fixture location for aligning mirrors on a solar collector array (SCA) comprising multiple mirror modules. The method aligns the mirrors on a module by comparing the location of the receiver image in photographs with the predicted theoretical receiver image location. To accurately align an entire SCA, a common reference is used for all of the individual module images within the SCA. The improved method can use relative pixel location information in digital photographs along with alignment fixture inclinometer data to calculate relative locations of the fixture between modules. The absolute locations are determined by minimizing alignment asymmetry for the SCA. The method inherently aligns all of the mirrors in an SCA to the receiver, even with receiver position and module-to-module alignment errors.

  7. Electrospun Aligned Fibrous Arrays and Twisted Ropes: Fabrication, Mechanical and Electrical Properties, and Application in Strain Sensors

    NASA Astrophysics Data System (ADS)

    Zheng, Jie; Yan, Xu; Li, Meng-Meng; Yu, Gui-Feng; Zhang, Hong-Di; Pisula, Wojciech; He, Xiao-Xiao; Duvail, Jean-Luc; Long, Yun-Ze

    2015-12-01

    Electrospinning (e-spinning) is a versatile technique to fabricate ultrathin fibers from a rich variety of functional materials. In this paper, a modified e-spinning setup with two-frame collector is proposed for the fabrication of highly aligned arrays of polystyrene (PS) and polyvinylidene fluoride (PVDF) nanofibers, as well as PVDF/carbon nanotube (PVDF/CNT) composite fibers. Especially, it is capable of producing fibrous arrays with excellent orientation over a large area (more than 14 cm × 12 cm). The as-spun fibers are suspended and can be easily transferred to other rigid or flexible substrates. Based on the aligned fibrous arrays, twisted long ropes are also prepared. Compared with the aligned arrays, twisted PVDF/CNT fiber ropes show enhanced mechanical and electrical properties and have potential application in microscale strain sensors.

  8. Electrospun Aligned Fibrous Arrays and Twisted Ropes: Fabrication, Mechanical and Electrical Properties, and Application in Strain Sensors.

    PubMed

    Zheng, Jie; Yan, Xu; Li, Meng-Meng; Yu, Gui-Feng; Zhang, Hong-Di; Pisula, Wojciech; He, Xiao-Xiao; Duvail, Jean-Luc; Long, Yun-Ze

    2015-12-01

    Electrospinning (e-spinning) is a versatile technique to fabricate ultrathin fibers from a rich variety of functional materials. In this paper, a modified e-spinning setup with two-frame collector is proposed for the fabrication of highly aligned arrays of polystyrene (PS) and polyvinylidene fluoride (PVDF) nanofibers, as well as PVDF/carbon nanotube (PVDF/CNT) composite fibers. Especially, it is capable of producing fibrous arrays with excellent orientation over a large area (more than 14 cm × 12 cm). The as-spun fibers are suspended and can be easily transferred to other rigid or flexible substrates. Based on the aligned fibrous arrays, twisted long ropes are also prepared. Compared with the aligned arrays, twisted PVDF/CNT fiber ropes show enhanced mechanical and electrical properties and have potential application in microscale strain sensors. PMID:26646688

  9. Prospective gated chest tomosynthesis using CNT X-ray source array

    NASA Astrophysics Data System (ADS)

    Shan, Jing; Burk, Laurel; Wu, Gongting; Lee, Yueh Z.; Heath, Michael D.; Wang, Xiaohui; Foos, David; Lu, Jianping; Zhou, Otto

    2015-03-01

    Chest tomosynthesis is a low-dose 3-D imaging modality that has been shown to have comparable sensitivity as CT in detecting lung nodules and other lung pathologies. We have recently demonstrated the feasibility of stationary chest tomosynthesis (s-DCT) using a distributed CNT X-ray source array. The technology allows acquisition of tomographic projections without moving the X-ray source. The electronically controlled CNT x-ray source also enables physiologically gated imaging, which will minimize image blur due to the patient's respiration motion. In this paper, we investigate the feasibility of prospective gated chest tomosynthesis using a bench-top s-DCT system with a CNT source array, a high- speed at panel detector and realistic patient respiratory signals captured using a pressure sensor. Tomosynthesis images of inflated pig lungs placed inside an anthropomorphic chest phantom were acquired at different respiration rate, with and without gating for image quality comparison. Metal beads of 2 mm diameter were placed on the pig lung for quantitative measure of the image quality. Without gating, the beads were blurred to 3:75 mm during a 3 s tomosynthesis acquisition. When gated to the end of the inhalation and exhalation phase the detected bead size reduced to 2:25 mm, much closer to the actual bead size. With gating the observed airway edges are sharper and there are more visible structural details in the lung. Our results demonstrated the feasibility of prospective gating in the s-DCT, which substantially reduces image blur associated with lung motion.

  10. Chemical Bath Deposition of Aluminum Oxide Buffer on Curved Surfaces for Growing Aligned Carbon Nanotube Arrays.

    PubMed

    Wang, Haitao; Na, Chongzheng

    2015-07-01

    Direct growth of vertically aligned carbon nanotube (CNT) arrays on substrates requires the deposition of an aluminum oxide buffer (AOB) layer to prevent the diffusion and coalescence of catalyst nanoparticles. Although AOB layers can be readily created on flat substrates using a variety of physical and chemical methods, the preparation of AOB layers on substrates with highly curved surfaces remains challenging. Here, we report a new solution-based method for preparing uniform layers of AOB on highly curved surfaces by the chemical bath deposition of basic aluminum sulfate and annealing. We show that the thickness of AOB layer can be increased by extending the immersion time of a substrate in the chemical bath, following the classical Johnson-Mehl-Avrami-Kolmogorov crystallization kinetics. The increase of AOB thickness in turn leads to the increase of CNT length and the reduction of CNT curviness. Using this method, we have successfully synthesized dense aligned CNT arrays of micrometers in length on substrates with highly curved surfaces including glass fibers, stainless steel mesh, and porous ceramic foam. PMID:26053766

  11. Flexible CNT-array double helices Strain Sensor with high stretchability for Motion Capture.

    PubMed

    Li, Cheng; Cui, Ya-Long; Tian, Gui-Li; Shu, Yi; Wang, Xue-Feng; Tian, He; Yang, Yi; Wei, Fei; Ren, Tian-Ling

    2015-01-01

    Motion capture is attracting more and more attention due to its potential wide applications in various fields. However, traditional methods for motion capture still have weakness such as high cost and space consuming. Based on these considerations, a flexible, highly stretchable strain sensor with high gauge factor for motion capture is fabricated with carbon nanotube (CNT) array double helices as the main building block. Ascribed to the unique flexible double helical CNT-array matrix, the strain sensor is able to measure strain up to 410%, with low hysteresis. Moreover, a demonstration of using this strain sensor for capture hand motion and to control a mechanical hand in real time is also achieved. A model based on finite difference method is also made to help understand the mechanism of the strain sensors. Our work demonstrates that strain sensors can measure very large strain while maintaining high sensitivity, and the motion capture based on this strain sensor is expected to be less expensive, more convenient and accessible. PMID:26530904

  12. Flexible CNT-array double helices Strain Sensor with high stretchability for Motion Capture

    NASA Astrophysics Data System (ADS)

    Li, Cheng; Cui, Ya-Long; Tian, Gui-Li; Shu, Yi; Wang, Xue-Feng; Tian, He; Yang, Yi; Wei, Fei; Ren, Tian-Ling

    2015-11-01

    Motion capture is attracting more and more attention due to its potential wide applications in various fields. However, traditional methods for motion capture still have weakness such as high cost and space consuming. Based on these considerations, a flexible, highly stretchable strain sensor with high gauge factor for motion capture is fabricated with carbon nanotube (CNT) array double helices as the main building block. Ascribed to the unique flexible double helical CNT-array matrix, the strain sensor is able to measure strain up to 410%, with low hysteresis. Moreover, a demonstration of using this strain sensor for capture hand motion and to control a mechanical hand in real time is also achieved. A model based on finite difference method is also made to help understand the mechanism of the strain sensors. Our work demonstrates that strain sensors can measure very large strain while maintaining high sensitivity, and the motion capture based on this strain sensor is expected to be less expensive, more convenient and accessible.

  13. Flexible CNT-array double helices Strain Sensor with high stretchability for Motion Capture

    PubMed Central

    Li, Cheng; Cui, Ya-Long; Tian, Gui-Li; Shu, Yi; Wang, Xue-Feng; Tian, He; Yang, Yi; Wei, Fei; Ren, Tian-Ling

    2015-01-01

    Motion capture is attracting more and more attention due to its potential wide applications in various fields. However, traditional methods for motion capture still have weakness such as high cost and space consuming. Based on these considerations, a flexible, highly stretchable strain sensor with high gauge factor for motion capture is fabricated with carbon nanotube (CNT) array double helices as the main building block. Ascribed to the unique flexible double helical CNT-array matrix, the strain sensor is able to measure strain up to 410%, with low hysteresis. Moreover, a demonstration of using this strain sensor for capture hand motion and to control a mechanical hand in real time is also achieved. A model based on finite difference method is also made to help understand the mechanism of the strain sensors. Our work demonstrates that strain sensors can measure very large strain while maintaining high sensitivity, and the motion capture based on this strain sensor is expected to be less expensive, more convenient and accessible. PMID:26530904

  14. Aligning parallel arrays to reduce communication

    NASA Technical Reports Server (NTRS)

    Sheffler, Thomas J.; Schreiber, Robert; Gilbert, John R.; Chatterjee, Siddhartha

    1994-01-01

    Axis and stride alignment is an important optimization in compiling data-parallel programs for distributed-memory machines. We previously developed an optimal algorithm for aligning array expressions. Here, we examine alignment for more general program graphs. We show that optimal alignment is NP-complete in this setting, so we study heuristic methods. This paper makes two contributions. First, we show how local graph transformations can reduce the size of the problem significantly without changing the best solution. This allows more complex and effective heuristics to be used. Second, we give a heuristic that can explore the space of possible solutions in a number of ways. We show that some of these strategies can give better solutions than a simple greedy approach proposed earlier. Our algorithms have been implemented; we present experimental results showing their effect on the performance of some example programs running on the CM-5.

  15. Algorithms for Automatic Alignment of Arrays

    NASA Technical Reports Server (NTRS)

    Chatterjee, Siddhartha; Gilbert, John R.; Oliker, Leonid; Schreiber, Robert; Sheffler, Thomas J.

    1996-01-01

    Aggregate data objects (such as arrays) are distributed across the processor memories when compiling a data-parallel language for a distributed-memory machine. The mapping determines the amount of communication needed to bring operands of parallel operations into alignment with each other. A common approach is to break the mapping into two stages: an alignment that maps all the objects to an abstract template, followed by a distribution that maps the template to the processors. This paper describes algorithms for solving the various facets of the alignment problem: axis and stride alignment, static and mobile offset alignment, and replication labeling. We show that optimal axis and stride alignment is NP-complete for general program graphs, and give a heuristic method that can explore the space of possible solutions in a number of ways. We show that some of these strategies can give better solutions than a simple greedy approach proposed earlier. We also show how local graph contractions can reduce the size of the problem significantly without changing the best solution. This allows more complex and effective heuristics to be used. We show how to model the static offset alignment problem using linear programming, and we show that loop-dependent mobile offset alignment is sometimes necessary for optimum performance. We describe an algorithm with for determining mobile alignments for objects within do loops. We also identify situations in which replicated alignment is either required by the program itself or can be used to improve performance. We describe an algorithm based on network flow that replicates objects so as to minimize the total amount of broadcast communication in replication.

  16. Controlled growth of super-aligned carbon nanotube arrays for spinning continuous unidirectional sheets with tunable physical properties.

    PubMed

    Liu, Kai; Sun, Yinghui; Chen, Lei; Feng, Chen; Feng, Xiaofeng; Jiang, Kaili; Zhao, Yonggang; Fan, Shoushan

    2008-02-01

    We report controlled syntheses of super-aligned carbon nanotube (CNT) arrays with the desired tube-diameter, number of walls, and length for spinning continuous unidirectional sheets to meet a variety of industrial demands. The tube-diameter distribution of super-aligned arrays is well controlled by varying the thicknesses of catalyst films, and the length of them is tuned by the growth time. Further investigation indicates that the physical properties of the unidirectional sheets, such as electrical transport, optical transmittance, and light emission properties, can be well tuned by the tube-diameter- and length-controlled growth. This work extends the understanding of the super-aligned CNT arrays and will be very helpful in developing further applications. PMID:18269255

  17. Freestanding aligned carbon nanotube array grown on a large-area single-layered graphene sheet for efficient dye-sensitized solar cell.

    PubMed

    Qiu, Longbin; Wu, Qiong; Yang, Zhibin; Sun, Xuemei; Zhang, Yuanbo; Peng, Huisheng

    2015-03-01

    A novel carbon nanomaterial with aligned carbon nanotubes (CNTs) chemically bonded to a single-layered, large area graphene sheet is designed and fabricated, showing remarkable electronic and electrocatalytic properties. When the carbon nanomaterial is used as a counter electrode, the resulting dye-sensitized solar cell exhibits ≈11% enhancement of energy conversion efficiency than aligned CNT array. PMID:24889384

  18. Large-scale submicron horizontally aligned single-walled carbon nanotube surface arrays on various substrates produced by a fluidic assembly method.

    PubMed

    Yan, Y H; Li, S; Chen, L Q; Chan-Park, M B; Zhang, Qing

    2006-11-28

    Single-walled carbon nanotube (CNT) arrays have been assembled on various substrates over mm-scale surface areas by combining fluidic alignment with soft lithography (micropatterning in capillaries) techniques. The feature size of the nanotube patterns reaches down to submicrometre scale. To this end, tailored substrate surface modification and pre-alignment of chopped CNTs in suspension are highly critical. PMID:21727344

  19. Femtosecond laser modification of an array of vertically aligned carbon nanotubes intercalated with Fe phase nanoparticles

    PubMed Central

    2013-01-01

    Femtosecond lasers (FSL) are playing an increasingly important role in materials research, characterization, and modification. Due to an extremely short pulse width, interactions of FSL irradiation with solid surfaces attract special interest, and a number of unusual phenomena resulted in the formation of new materials are expected. Here, we report on a new nanostructure observed after the interaction of FSL irradiation with arrays of vertically aligned carbon nanotubes (CNTs) intercalated with iron phase catalyst nanoparticles. It was revealed that the FSL laser ablation transforms the topmost layer of CNT array into iron phase nanospheres (40 to 680 nm in diameter) located at the tip of the CNT bundles of conical shape. Besides, the smaller nanospheres (10 to 30 nm in diameter) are found to be beaded at the sides of these bundles. Some of the larger nanospheres are encapsulated into carbon shells, which sometime are found to contain CNTs. The mechanism of creation of such nanostructures is proposed. PMID:24004518

  20. Fabrication of Dense Horizontally Aligned Arrays of Single-Wall Carbon Nanotubes from Vertically Aligned Arrays

    NASA Astrophysics Data System (ADS)

    Zheng, Gang; Wang, Xueshen; Li, Qunqing; Xie, Jing; Zhu, Zhendong; Zou, Yuan; Liu, Junku; Jiang, Kaili; Fan, Shoushan

    2011-01-01

    The as-grown vertically aligned single-wall carbon nanotube (SWNT) arrays are transferred from the original silicon substrate to a poly(ethylene terephthalate) (PET) substrate, which acts as a stamp. Thin SWNT films can be applied from the stamp to the target substrate and subsequently treated by an ultrasonic process to reduce their thickness to 6.6 nm. The transferred SWNT thin film retains the advantageous super-alignment and high-density properties of the vertical SWNT arrays. The linear density, transmittance, and square resistance of the thin film are as high as 15 tubes per micrometer, 99% at 550 nm, and 16 kΩ, respectively.

  1. Field emission luminescence of nanodiamonds deposited on the aligned carbon nanotube array

    PubMed Central

    Fedoseeva, Yu. V.; Bulusheva, L. G.; Okotrub, A. V.; Kanygin, M. A.; Gorodetskiy, D. V.; Asanov, I. P.; Vyalikh, D. V.; Puzyr, A. P.; Bondar, V. S.

    2015-01-01

    Detonation nanodiamonds (NDs) were deposited on the surface of aligned carbon nanotubes (CNTs) by immersing a CNT array in an aqueous suspension of NDs in dimethylsulfoxide (DMSO). The structure and electronic state of the obtained CNT–ND hybrid material were studied using optical and electron microscopy and Infrared, Raman, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy. A non-covalent interaction between NDs and CNT and preservation of vertical orientation of CNTs in the hybrid were revealed. We showed that current-voltage characteristics of the CNT–ND cathode are changed depending on the applied field; below ~3 V/µm they are similar to those of the initial CNT array and at the higher field they are close to the ND behavior. Involvement of the NDs in field emission process resulted in blue luminescence of the hybrid surface at an electric field higher than 3.5 V/µm. Photoluminescence measurements showed that the NDs emit blue-green light, while blue luminescence prevails in the CNT–ND hybrid. The quenching of green luminescence was attributed to a partial removal of oxygen-containing groups from the ND surface as the result of the hybrid synthesis. PMID:25797710

  2. Synthesis and Investigation of Millimeter-Scale Vertically Aligned Boron Nitride Nanotube Arrays

    NASA Astrophysics Data System (ADS)

    Tay, Roland; Li, Hongling; Tsang, Siu Hon; Jing, Lin; Tan, Dunlin; Teo, Edwin Hang Tong

    Boron nitride nanotubes (BNNTs) have shown potential in a wide range of applications due to their superior properties such as exceptionally high mechanical strength, excellent chemical and thermal stabilities. However, previously reported methods to date only produced BNNTs with limited length/density and insufficient yield at high temperatures. Here we present a facile and effective two-step synthesis route involving template-assisted chemical vapor deposition at a relatively low temperature of 900 degree C and subsequent annealing process to fabricate vertically aligned (VA) BN coated carbon nanotube (VA-BN/CNT) and VA-BNNT arrays. By using this method, we achieve the longest VA-BN/CNTs and VA-BNNTs to date with lengths of over millimeters (exceeding two orders of magnitude longer than the previously reported length of VA-BNNTs). In addition, the morphology, chemical composition and microstructure of the resulting products, as well as the mechanism of coating process are systematically investigated. This versatile BN coating technique and the synthesis of millimeter-scale BN/CNT and BNNT arrays pave a way for new applications especially where the aligned geometry of the NTs is essential such as for field-emission, interconnects and thermal management.

  3. Improved Synthesis of Aligned Carbon Nanotube Arrays for Optical Applications

    NASA Astrophysics Data System (ADS)

    Paudel, Trilochan; Gao, Yantao; Lan, Yucheng; Macmohan, Gregs; Kempa, Krzysztof; Naughton, Michael; Ren, Zhifeng

    2009-03-01

    Vertically aligned carbon nanotubes were grown on the high temperature glass (Aluminosilicate, Corning 1737) substrates with improved characteristics compared to previous attempts. The glass substrates were first coated with a buffer layer of either Chromium or Titanium, thick enough to facilitate CNT growth, but thin enough as to be largely transparent. On the top of the buffer layer, a monolayer of polystyrene spheres was deposited with close compaction, and then a Nickel catalyst film was evaporated. The polystyrene spheres were then removed to obtain honeycomb Ni patterns. On top of the Ni patterns, vertically aligned carbon nanotubes were grown by the direct current plasma enhanced chemical vapor deposition (dc PECVD). These aligned carbon nanotubes, which can range in height from 0.5 to 10 microns, and in diameter from 50 to 350 nm, can then be coated with various dielectrics to function as components in optical waveguides, including solar cells.

  4. Tailoring the morphology of carbon nanotube arrays: from spinnable forests to undulating foams.

    PubMed

    Zhang, Yingying; Zou, Guifu; Doorn, Stephen K; Htoon, Han; Stan, Liliana; Hawley, Marilyn E; Sheehan, Chris J; Zhu, Yuntian; Jia, Quanxi

    2009-08-25

    Directly spinning carbon nanotube (CNT) fibers from vertically aligned CNT arrays is a promising way for the application of CNTs in the field of high-performance materials. However, most of the reported CNT arrays are not spinnable. In this work, by controlling catalyst pretreatment conditions, we demonstrate that the degree of spinnability of CNTs is closely related to the morphology of CNT arrays. Shortest catalyst pretreatment time led to CNT arrays with the best spinnability, while prolonged pretreatment resulted in coarsening of catalyst particles and nonspinnable CNTs. By controlling the coalescence of catalyst particles, we further demonstrate the growth of undulating CNT arrays with uniform and tunable waviness. The CNT arrays can be tuned from well-aligned, spinnable forests to uniformly wavy, foam-like films. To the best of our knowledge, this is the first systematical study on the correlation between catalyst pretreatment, CNT morphology, and CNT spinnability. PMID:19640000

  5. Nanoelectrode Arrays Based on Low Site Density Aligned Carbon Nanotubes

    SciTech Connect

    Yi, Tu; Lin, Yuehe ); Ren, Zhifeng N.

    2003-01-29

    Nanoelectrode arrays (NEAs) were fabricated from the low site density aligned carbon nanotubes (CNTs). The CNTs were grown by plasma enhanced chemical vapor deposition (PECVD) on Ni nanoparticles made by the electrochemical deposition.

  6. Aligned Carbon Nanotube Array Functionalization for Enhanced Atomic Layer Deposition of Platinum Electrocatalysts

    SciTech Connect

    Dameron, A. A.; Pylypenko, S.; Bult, J. B.; Neyerlin, K. C.; Engtrakul, C.; Bochert, C.; Leong, G. J.; Frisco, S. L.; Simpson, L.; Dinh, H. N.; Pivovar, B.

    2012-04-15

    Uniform metal deposition onto high surface area supports is a key challenge of developing successful efficient catalyst materials. Atomic layer deposition (ALD) circumvents permeation difficulties, but relies on gas-surface reactions to initiate growth. Our work demonstrates that modified surfaces within vertically aligned carbon nanotube (CNT) arrays, from plasma and molecular precursor treatments, can lead to improved catalyst deposition. Gas phase functionalization influences the number of ALD nucleation sites and the onset of ALD growth and, in turn, affects the uniformity of the coating along the length of the CNTs within the aligned arrays. The induced chemical changes for each functionalization route are identified by X-ray photoelectron and Raman spectroscopies. The most effective functionalization routes increase the prevalence of oxygen moieties at defect sites on the carbon surfaces. The striking effects of the functionalization are demonstrated with ALD Pt growth as a function of surface treatment and ALD cycles examined by electron microscopy of the arrays and the individual CNTs. Finally, we demonstrate applicability of these materials as fuel cell electrocatalysts and show that surface functionalization affects their performance towards oxygen reduction reaction.

  7. Effect of the morphology of CNT arrays on the current density of field-emitter matrices

    SciTech Connect

    Galperin, V. A. Zhukov, A. A.; Pavlov, A. A.; Skorik, S. N.; Shaman, Yu. P.; Shamanaev, A. A.

    2014-12-15

    Structured carbon-nanotube arrays synthesized in topological regions formed by electron-beam lithography are studied. The effect of the morphology and topology of the carbon-nanotube arrays on the emission characteristics of the structures being formed are considered.

  8. Large hexagonal arrays of aligned ZnO nanorods

    NASA Astrophysics Data System (ADS)

    Banerjee, D.; Rybczynski, J.; Huang, J. Y.; Wang, D. Z.; Kempa, K.; Ren, Z. F.

    2005-02-01

    Large-scale truly periodic arrays of vertically aligned zinc oxide nanorods were grown on pre-patterned and pre-annealed gold dots on a-plane sapphire substrates via the vapor liquid solid mechanism. Periodic arrays of triangular gold islands were first patterned on the a-plane sapphire substrates by the nanosphere self-assembly technique. Zinc has been found to be an effective interfacial modifier between gold and sapphire to form single catalytic dots from triangular islands. The successful fabrication of zinc oxide nanowires in truly periodic arrays opens up the possibility of achieving enhanced room-temperature ultraviolet lasing and photonic crystal based devices and sensors.

  9. LDRD final report : chromophore-functionalized aligned carbon nanotube arrays.

    SciTech Connect

    Vance, Andrew L.; Yang, Chu-Yeu Peter; Krafcik, Karen Lee

    2011-09-01

    The goal of this project was to expand upon previously demonstrated single carbon nanotube devices by preparing a more practical, multi-single-walled carbon nanotube (SWNT) device. As a late-start, proof-of-concept project, the work focused on the fabrication and testing of chromophore-functionalized aligned SWNT field effect transistors (SWNT-FET). Such devices have not yet been demonstrated. The advantages of fabricating aligned SWNT devices include increased device cross-section to improve sensitivity to light, elimination of increased electrical resistance at nanotube junctions in random mat devices, and the ability to model device responses. The project did not achieve the goal of fabricating and testing chromophore-modified SWNT arrays, but a new SWNT growth capability was established that will benefit future projects. Although the ultimate goal of fabricating and testing chromophore-modified SWNT arrays was not achieved, the work did lead to a new carbon nanotube growth capability at Sandia/CA. The synthesis of dense arrays of horizontally aligned SWNTs is a developing area of research with significant potential for new discoveries. In particular, the ability to prepare arrays of carbon nanotubes of specific electronic types (metallic or semiconducting) could yield new classes of nanoscale devices.

  10. Aligning Arrays of Lenses and Single-Mode Optical Fibers

    NASA Technical Reports Server (NTRS)

    Liu, Duncan

    2004-01-01

    A procedure now under development is intended to enable the precise alignment of sheet arrays of microscopic lenses with the end faces of a coherent bundle of as many as 1,000 single-mode optical fibers packed closely in a regular array (see Figure 1). In the original application that prompted this development, the precise assembly of lenses and optical fibers serves as a single-mode spatial filter for a visible-light nulling interferometer. The precision of alignment must be sufficient to limit any remaining wavefront error to a root-mean-square value of less than 1/10 of a wavelength of light. This wavefront-error limit translates to requirements to (1) ensure uniformity of both the lens and fiber arrays, (2) ensure that the lateral distance from the central axis of each lens and the corresponding optical fiber is no more than a fraction of a micron, (3) angularly align the lens-sheet planes and the fiber-bundle end faces to within a few arc seconds, and (4) axially align the lenses and the fiber-bundle end faces to within tens of microns of the focal distance. Figure 2 depicts the apparatus used in the alignment procedure. The beam of light from a Zygo (or equivalent) interferometer is first compressed by a ratio of 20:1 so that upon its return to the interferometer, the beam will be magnified enough to enable measurement of wavefront quality. The apparatus includes relay lenses that enable imaging of the arrays of microscopic lenses in a charge-coupled-device (CCD) camera that is part of the interferometer. One of the arrays of microscopic lenses is mounted on a 6-axis stage, in proximity to the front face of the bundle of optical fibers. The bundle is mounted on a separate stage. A mirror is attached to the back face of the bundle of optical fibers for retroreflection of light. When a microscopic lens and a fiber are aligned with each other, the affected portion of the light is reflected back by the mirror, recollimated by the microscopic lens, transmitted

  11. Pulsed Growth of Vertically Aligned Nanotube Arrays with Variable Density

    SciTech Connect

    Jackson, Jeremy Joseph; Puretzky, Alexander A; More, Karren Leslie; Rouleau, Christopher M; Eres, Gyula; Geohegan, David B

    2010-01-01

    The density of vertically-aligned carbon nanotube arrays is shown to vary significantly during normal growth by chemical vapor deposition and respond rapidly to changes in feedstock flux. Pulsing the feedstock gas to repeatedly stop and start nanotube growth is shown to induce density variations up to a factor of 1.6 within ~1-2 micron-long layers, allowing the synthesis of new array architectures with distinct regions of controllable length and density variation. The evolution of density within each layer of growth is determined from time-resolved optical reflectivity measurements of the height and optical extinction coefficient of the array as it grows, providing a real-time diagnostic of both density and growth kinetics. Z-contrast scanning transmission electron microscopy of corresponding sections of the arrays is used to independently assess and confirm these density variations.

  12. Energy harvesting from vertically aligned PZT nanowire arrays

    NASA Astrophysics Data System (ADS)

    Malakooti, Mohammad H.; Zhou, Zhi; Sodano, Henry A.

    2016-04-01

    In this paper, a nanostructured piezoelectric beam is fabricated using vertically aligned lead zirconate titanate (PZT) nanowire arrays and its capability of continuous power generation is demonstrated through direct vibration tests. The lead zirconate titanate nanowires are grown on a PZT thin film coated titanium foil using a hydrothermal reaction. The PZT thin film serves as a nucleation site while the titanium foil is used as the bottom electrode. Electromechanical frequency response function (FRF) analysis is performed to evaluate the power harvesting efficiency of the fabricated device. Furthermore, the feasibility of the continuous power generation using the nanostructured beam is demonstrated through measuring output voltage from PZT nanowires when beam is subjected to a sinusoidal base excitation. The effect of tip mass on the voltage generation of the PZT nanowire arrays is evaluated experimentally. The final results show the great potential of synthesized piezoelectric nanowire arrays in a wide range of applications, specifically power generation at nanoscale.

  13. Thermal Conduction in Vertically Aligned Copper Nanowire Arrays and Composites.

    PubMed

    Barako, Michael T; Roy-Panzer, Shilpi; English, Timothy S; Kodama, Takashi; Asheghi, Mehdi; Kenny, Thomas W; Goodson, Kenneth E

    2015-09-01

    The ability to efficiently and reliably transfer heat between sources and sinks is often a bottleneck in the thermal management of modern energy conversion technologies ranging from microelectronics to thermoelectric power generation. These interfaces contribute parasitic thermal resistances that reduce device performance and are subjected to thermomechanical stresses that degrade device lifetime. Dense arrays of vertically aligned metal nanowires (NWs) offer the unique combination of thermal conductance from the constituent metal and mechanical compliance from the high aspect ratio geometry to increase interfacial heat transfer and device reliability. In the present work, we synthesize copper NW arrays directly onto substrates via templated electrodeposition and extend this technique through the use of a sacrificial overplating layer to achieve improved uniformity. Furthermore, we infiltrate the array with an organic phase change material and demonstrate the preservation of thermal properties. We use the 3ω method to measure the axial thermal conductivity of freestanding copper NW arrays to be as high as 70 W m(-1) K(-1), which is more than an order of magnitude larger than most commercial interface materials and enhanced-conductivity nanocomposites reported in the literature. These arrays are highly anisotropic, and the lateral thermal conductivity is found to be only 1-2 W m(-1) K(-1). We use these measured properties to elucidate the governing array-scale transport mechanisms, which include the effects of morphology and energy carrier scattering from size effects and grain boundaries. PMID:26284489

  14. Array of aligned and dispersed carbon nanotubes and method of producing the array

    DOEpatents

    Ivanov, Ilia N; Simpson, John T; Hendricks, Troy R

    2013-06-11

    An array of aligned and dispersed carbon nanotubes includes an elongate drawn body including a plurality of channels extending therethrough from a first end to a second end of the body, where the channels have a number density of at least about 100,000 channels/mm.sup.2 over a transverse cross-section of the body. A plurality of carbon nanotubes are disposed in each channel, and the carbon nanotubes are sufficiently dispersed and aligned along a length of the channels for the array to comprise an average resistivity per channel of about 9700 .OMEGA.m or less.

  15. Array of aligned and dispersed carbon nanotubes and method of producing the array

    DOEpatents

    Ivanov, Ilia N.; Simpson, John T.; Hendricks, Troy R.

    2012-06-19

    An array of aligned and dispersed carbon nanotubes includes an elongate drawn body including a plurality of channels extending therethrough from a first end to a second end of the body, where the channels have a number density of at least about 100,000 channels/mm.sup.2 over a transverse cross-section of the body. A plurality of carbon nanotubes are disposed in each channel, and the carbon nanotubes are sufficiently dispersed and aligned along a length of the channels for the array to comprise an average resistivity per channel of about 9700 .OMEGA.m or less.

  16. Superaligned carbon nanotube arrays, films, and yarns: a road to applications.

    PubMed

    Jiang, Kaili; Wang, Jiaping; Li, Qunqing; Liu, Liang; Li, Changhong; Fan, Shoushan

    2011-03-01

    A superaligned carbon nanotube (CNT) array is a special kind of vertically aligned CNT array with the capability of being converted into continuous fi lms and yarns. The as-produced CNT fi lms are transparent and highly conductive, with aligned CNTs parallel to the direction of drawing. After passing through volatile solutions or being twisted, CNT fi lms can be further condensed into shrunk yarns. These shrunk yarns possess high tensile strengths and Young’s moduli, and are good conductors. Many applications of CNT fi lms and shrunk yarns have been demonstrated, such as TEM grids, loudspeakers, touch screens, etc. PMID:21465707

  17. An active alignment scheme for the MPTS array. [contour sensors

    NASA Technical Reports Server (NTRS)

    Iwasaki, R.

    1980-01-01

    In order to achieve and maintain required flatness of the antenna array, a rotating laser beam used for leveling applications on earth was utilized as a reference system. A photoconductive sensor with a reflective collecting surface determines the displacement and polarity of any misalignment and automatically engages a stepping motor to drive a variable-length mechanism to make the necessary corrections. Once aligned, little power is dissipated since a nulling bridge circuit that centers on the beam is used. A three-point subarray alignment arrangement is described which independently adjusts, in the three orthogonal directions, the height and tilt of subarrays within the MPTS array and readily adapts to any physical distortions of the secondary structure (such as that resulting from severe temperature extremes caused by an eclipse of the Sun). It is shown that only one rotating laser system is required since optical blockage is minimal on the array surface and that it is possible to incorporate a number of redundant laser systems for reliability without affecting the overall performance.

  18. Modelling clustering of vertically aligned carbon nanotube arrays.

    PubMed

    Schaber, Clemens F; Filippov, Alexander E; Heinlein, Thorsten; Schneider, Jörg J; Gorb, Stanislav N

    2015-08-01

    Previous research demonstrated that arrays of vertically aligned carbon nanotubes (VACNTs) exhibit strong frictional properties. Experiments indicated a strong decrease of the friction coefficient from the first to the second sliding cycle in repetitive measurements on the same VACNT spot, but stable values in consecutive cycles. VACNTs form clusters under shear applied during friction tests, and self-organization stabilizes the mechanical properties of the arrays. With increasing load in the range between 300 µN and 4 mN applied normally to the array surface during friction tests the size of the clusters increases, while the coefficient of friction decreases. To better understand the experimentally obtained results, we formulated and numerically studied a minimalistic model, which reproduces the main features of the system with a minimum of adjustable parameters. We calculate the van der Waals forces between the spherical friction probe and bunches of the arrays using the well-known Morse potential function to predict the number of clusters, their size, instantaneous and mean friction forces and the behaviour of the VACNTs during consecutive sliding cycles and at different normal loads. The data obtained by the model calculations coincide very well with the experimental data and can help in adapting VACNT arrays for biomimetic applications. PMID:26464787

  19. Algorithm for Aligning an Array of Receiving Radio Antennas

    NASA Technical Reports Server (NTRS)

    Rogstad, David

    2006-01-01

    A digital-signal-processing algorithm (somewhat arbitrarily) called SUMPLE has been devised as a means of aligning the outputs of multiple receiving radio antennas in a large array for the purpose of receiving a weak signal transmitted by a single distant source. As used here, aligning signifies adjusting the delays and phases of the outputs from the various antennas so that their relatively weak replicas of the desired signal can be added coherently to increase the signal-to-noise ratio (SNR) for improved reception, as though one had a single larger antenna. The method was devised to enhance spacecraft-tracking and telemetry operations in NASA's Deep Space Network (DSN); the method could also be useful in such other applications as both satellite and terrestrial radio communications and radio astronomy. Heretofore, most commonly, alignment has been effected by a process that involves correlation of signals in pairs. This approach necessitates the use of a large amount of hardware most notably, the N(N - 1)/2 correlators needed to process signals from all possible pairs of N antennas. Moreover, because the incoming signals typically have low SNRs, the delay and phase adjustments are poorly determined from the pairwise correlations. SUMPLE also involves correlations, but the correlations are not performed in pairs. Instead, in a partly iterative process, each signal is appropriately weighted and then correlated with a composite signal equal to the sum of the other signals (see Figure 1). One benefit of this approach is that only N correlators are needed; in an array of N much greater than 1 antennas, this results in a significant reduction of the amount of hardware. Another benefit is that once the array achieves coherence, the correlation SNR is N - 1 times that of a pair of antennas.

  20. Ionization Gas Sensor using Aligned Multiwalled Carbon Nanotubes Array

    SciTech Connect

    Kermany, A. R.; Mohamed, N. M.; Singh, B. S. M.

    2011-05-25

    The challenge with current conventional gas sensors which are operating using semiconducting oxides is their size. After the introduction of nanotechnology and in order to reduce the dimension and consequently the power consumption and cost, new materials such as carbon nanotubes (CNTs) are being introduced. From previous works and characterization results, it was proven that the CNTs based gas sensor has better sensitivity, selectivity and faster response time in compared with semiconducting oxides based gas sensors. As in this work, a fabrication and successful testing of an ionization-based gas sensor using aligned Multiwalled CNTs (MWCNTs) as sensing element is discussed, in which MWCNTs array and Al film are used as anode and cathode plates respectively with electrode separation ranging from 80 {mu}m to 140 {mu}m. Aligned MWCNTs array was incorporated into a sensor configuration in the gas chamber for testing of gases such as argon, air, and mixed gas of 2%H{sub 2} in air. Obtained results show that among the three gases, argon has the lowest breakdown voltage whilst air has the highest value and the breakdown voltage was found to decrease as the electrode spacing was reduced from 140 {mu}m to 80 {mu}m for all three gases.

  1. Significantly improving electromagnetic performance of nanopaper and its shape-memory nanocomposite by aligned carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lu, Haibao; Gou, Jan

    2012-04-01

    A new nanopaper that exhibits exciting electrical and electromagnetic performances is fabricated by incorporating magnetically aligned carbon nanotube (CNT) with carbon nanofibers (CNFs). Electromagnetic CNTs were blended with and aligned into the nanopaper using a magnetic field, to significantly improve the electrical and electromagnetic performances of nanopaper and its enabled shape-memory polymer (SMP) composite. The morphology and structure of the aligned CNT arrays in nanopaper were characterized with scanning electronic microscopy (SEM). A continuous and compact network of CNFs and aligned CNTs indicated that the nanopaper could have highly conductive properties. Furthermore, the electromagnetic interference (EMI) shielding efficiency of the SMP composites with different weight content of aligned CNT arrays was characterized. Finally, the aligned CNT arrays in nanopapers were employed to achieve the electrical actuation and accelerate the recovery speed of SMP composites.

  2. Boron Nitride Coated Carbon Nanotube Arrays with Enhanced Compressive Mechanical Property

    NASA Astrophysics Data System (ADS)

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Tan, Dunlin; Zhang, Bowei; Tok, Alfred Iing Yoong; Teo, Edwin Hang Tong

    Vertically aligned carbon nanotube (CNT) array is one of the most promising energy dissipating materials due to its excellent temperature invariant mechanical property. However, the CNT arrays with desirable recoverability after compression is still a challenge. Here, we report on the mechanical enhancement of the CNT arrays reinforced by coating with boron nitride (BN) layers. These BN coated CNT (BN/CNT) arrays exhibit excellent compressive strength and recoverability as compared to those of the as-prepared CNT arrays which totally collapsed after compression. In addition, the BN coating also provides better resistance to oxidation due to its intrinsic thermal stability. This work presented here opens a new pathway towards tuning mechanical behavior of any arbitrary CNT arrays for promising potential such as damper, vibration isolator and shock absorber applications.

  3. Carbon nanotube array actuators

    NASA Astrophysics Data System (ADS)

    Geier, S.; Mahrholz, T.; Wierach, P.; Sinapius, M.

    2013-09-01

    Experimental investigations of highly vertically aligned carbon nanotubes (CNTs), also known as CNT-arrays, are the main focus of this paper. The free strain as result of an active material behavior is analyzed via a novel experimental setup. Previous test experiences of papers made of randomly oriented CNTs, also called Bucky-papers, reveal comparably low free strain. The anisotropy of aligned CNTs promises better performance. Via synthesis techniques like chemical vapor deposition (CVD) or plasma enhanced CVD (PECVD), highly aligned arrays of multi-walled carbon nanotubes (MWCNTs) are synthesized. Two different types of CNT-arrays are analyzed, morphologically first, and optically tested for their active characteristics afterwards. One type of the analyzed arrays features tube lengths of 750-2000 μm with a large variety of diameters between 20 and 50 nm and a wave-like CNT-shape. The second type features a maximum, almost uniform, length of 12 μm and a constant diameter of 50 nm. Different CNT-lengths and array types are tested due to their active behavior. As result of the presented tests, it is reported that the quality of orientation is the most decisive property for excellent active behavior. Due to their alignment, CNT-arrays feature the opportunity to clarify the actuation mechanism of architectures made of CNTs.

  4. A small-area low-power current readout circuit using two-stage conversion method for 64-channel CNT sensor arrays.

    PubMed

    Shin, Young-San; Lee, Seongsoo; Wee, Jae-Kyung; Song, Inchae

    2013-06-01

    In this paper, a small-area and low-power current readout circuit with a novel two-stage conversion method is presented for 64-channel CNT (carbon nanotube) sensor arrays. In the first stage, current of each CNT sensor is amplified by 64 active input current mirrors (AICMs). In the second stage, the amplified current is converted to a voltage level through the shared variable gain amplifier (S-VGA). Then the S-VGA output is digitalized by successive approximation register analog-to-digital converter (SAR-ADC). The proposed readout circuit significantly reduces chip area and power consumption, since VGA is shared over 64 channels and passive elements are used only in S-VGA. Fabricated chip area is 0.173 mm(2) in 0.13 μm CMOS technology. Measured power consumption and linearity error are 73.06 μW and 5.3%, respectively, at the input current range of 10 nA-10 μA and conversion rate of 640 samples/s. A prototype real-time CNT sensor system was implemented using the fabricated readout circuit, and successfully detected alcohol reaction. PMID:23853327

  5. Aligned Silver Nanorod Array as SERS Substrates for Viral Sensing

    NASA Astrophysics Data System (ADS)

    Zhao, Yiping; Shanmukh, Saratchandra; Chaney, Stephen B.; Jones, Les; Dluhy, Richard A.; Tripp, Ralph A.

    2006-03-01

    The aligned silver nanorod array substrates prepared by the oblique angle deposition method are capable of providing extremely high enhancement factors (˜10^9) at near-infrared wavelengths (785 nm) for a standard reporter molecule 1,2 trans-(bis)pyridyl-ethene (BPE). The enhancement factor depends strongly on the length of the Ag nanorods, the substrate coating, as well as the polarization of the excitation laser beam. With the current optimum structure, we demonstrate that the detection limit for BPE can be lower than 0.1 fM. The applicability of this substrate to the detection of bioagents has been investigated by looking several viruses, such as Adenovirus, HIV, Rhinovirus and Respiratory Syncytial Virus (RSV), at low quantities (˜0.5uL). Different viruses have different fingerprint Raman spectrum. The detection of virus presented in infected cells has also been demonstrated.

  6. Automated Optical Extraction from Line Arrays of the Alignment Between Microfabricated Layers

    NASA Technical Reports Server (NTRS)

    Lieneweg, Udo

    1997-01-01

    Machine reading of layer alignment from line arrays in fully fabricated wafers is demonstrated. Misalignment is calculated from the correlation funcation of optical intensity scans through arrays in the two layers.

  7. Graphene/carbon nanotube hybrid-based transparent 2D optical array.

    PubMed

    Kim, Un Jeong; Lee, Il Ha; Bae, Jung Jun; Lee, Sangjin; Han, Gang Hee; Chae, Seung Jin; Güneş, Fethullah; Choi, Jun Hee; Baik, Chan Wook; Kim, Sun Il; Kim, Jong Min; Lee, Young Hee

    2011-09-01

    Graphene/carbon nanotube (CNT) hybrid structures are fabricated for use as optical arrays. Vertically aligned CNTs are directly synthesized on a graphene/quartz substrate using plasma-enhanced chemical vapor deposition (PECVD). Graphene preserves the transparency and resistance during CNT growth. Highly aligned single-walled CNTs show a better performance for the diffraction intensity. PMID:21769950

  8. Controlling the morphology of carbon nanotube arrays: from spinnable forests to undulating foams

    SciTech Connect

    Zhang, Yingying; Zou, Guifu; Stan, Liliana; Hawley, Marilyn E; Sheehan, Chris J; Zhu, Yuntain; Jia, Quanxi; Doorn, Stephen K; Htoon, Han

    2009-01-01

    By controlling catalyst pretreatment conditions, we demonstrate that the degree of spinnability of carbon nanotubes (CNTs) is closely related to the morphology of CNT arrays. Shortest catalyst pretreatment time led to CNT arrays with the best spinnability, while prolonged pretreatment resulted in coarsening of catalyst particles and non-spinnable CNTs. We further demonstrate the growth of undulating CNT arrays with uniform and tunable waviness by controlling the coalescence of catalyst particles. The CNT arrays can be tuned from well-aligned, spinnable forests to uniformly wavy, foam-like films by controlling catalyst pretreatment conditions.

  9. Liquid crystal alignment on zinc oxide nanowire arrays for LCDs applications.

    PubMed

    Chen, Mu-Zhe; Chen, Wei-Sheng; Jeng, Shie-Chang; Yang, Sheng-Hsiung; Chung, Yueh-Feng

    2013-12-01

    The zinc oxide (ZnO) nanowire arrays on the indium tin oxide (ITO) glass substrates were fabricated by using the two-step hydrothermal method. A high transmittance ~92% of ZnO nanowire arrays on ITO substrate in the visible region was obtained. It was observed that the liquid crystal (LC) directors were aligned vertically to the (ZnO) nanowire arrays. The properties of ZnO nanowire arrays as vertical liquid crystal (LC) alignment layers and their applications for hybrid-aligned nematic LC modes were investigated in this work. PMID:24514480

  10. Coated carbon nanotube array electrodes

    DOEpatents

    Ren, Zhifeng; Wen, Jian; Chen, Jinghua; Huang, Zhongping; Wang, Dezhi

    2008-10-28

    The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

  11. Coated carbon nanotube array electrodes

    DOEpatents

    Ren, Zhifeng; Wen, Jian; Chen, Jinghua; Huang, Zhongping; Wang, Dezhi

    2006-12-12

    The present invention provides conductive carbon nanotube (CNT) electrode materials comprising aligned CNT substrates coated with an electrically conducting polymer, and the fabrication of electrodes for use in high performance electrical energy storage devices. In particular, the present invention provides conductive CNTs electrode material whose electrical properties render them especially suitable for use in high efficiency rechargeable batteries. The present invention also provides methods for obtaining surface modified conductive CNT electrode materials comprising an array of individual linear, aligned CNTs having a uniform surface coating of an electrically conductive polymer such as polypyrrole, and their use in electrical energy storage devices.

  12. Clothing polymer fibers with well-aligned and high-aspect ratio carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Sun, Gengzhi; Zheng, Lianxi; An, Jia; Pan, Yongzheng; Zhou, Jinyuan; Zhan, Zhaoyao; Pang, John H. L.; Chua, Chee Kai; Leong, Kah Fai; Li, Lin

    2013-03-01

    It is believed that the crucial step towards preparation of electrical conductive polymer-carbon nanotube (CNT) composites is dispersing CNTs with a high length-to-diameter aspect ratio in a well-aligned manner. However, this process is extremely challenging when dealing with long and entangled CNTs. Here in this study, a new approach is demonstrated to fabricate conductive polymer-CNT composite fibers without involving any dispersion process. Well-aligned CNT films were firstly drawn from CNT arrays, and then directly coated on polycaprolactone fibers to form polymer-CNT composite fibers. The conductivity of these composite fibers can be as high as 285 S m-1 with only 2.5 wt% CNT loading, and reach 1549 S m-1 when CNT loading is 13.4 wt%. As-prepared composite fibers also exhibit 82% retention of conductivity at a strain of 7%, and have improved mechanical properties.It is believed that the crucial step towards preparation of electrical conductive polymer-carbon nanotube (CNT) composites is dispersing CNTs with a high length-to-diameter aspect ratio in a well-aligned manner. However, this process is extremely challenging when dealing with long and entangled CNTs. Here in this study, a new approach is demonstrated to fabricate conductive polymer-CNT composite fibers without involving any dispersion process. Well-aligned CNT films were firstly drawn from CNT arrays, and then directly coated on polycaprolactone fibers to form polymer-CNT composite fibers. The conductivity of these composite fibers can be as high as 285 S m-1 with only 2.5 wt% CNT loading, and reach 1549 S m-1 when CNT loading is 13.4 wt%. As-prepared composite fibers also exhibit 82% retention of conductivity at a strain of 7%, and have improved mechanical properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr34208e

  13. A polarized infrared thermal detector made from super-aligned multiwalled carbon nanotube films.

    PubMed

    Xiao, Lin; Zhang, Yuying; Wang, Yang; Liu, Kai; Wang, Zheng; Li, Tianyi; Jiang, Zhe; Shi, Junpeng; Liu, Liang; Li, QunQing; Zhao, Yonggang; Feng, Zhenghe; Fan, Shoushan; Jiang, Kaili

    2011-01-14

    Carbon nanotube (CNT) films, easily drawn from super-aligned CNT arrays with a large area and a good compatibility with semiconductor technology, have been used as light sensitive materials for infrared (IR) detection. A bolometric CNT detector made from one layer of super-aligned CNT film shows a 15.4% resistance change under 10 mW mm(-2) of IR illumination and a fast characteristic response time of 4.4 ms due to its ultra-small heat capacity per unit area in vacuum at room temperature. Besides the power intensity detection, the anisotropic property of the super-aligned CNT films makes them ideal materials to detect the polarization of IR light simultaneously, which provides great potential in infrared imaging polarimetry. Theoretical analyses have been carried out to investigate the influences of CNT film properties on the responsivity and response time of the detector. PMID:21135478

  14. Nonhomogeneous morphology and the elastic modulus of aligned carbon nanotube films

    NASA Astrophysics Data System (ADS)

    Won, Yoonjin; Gao, Yuan; Guzman de Villoria, Roberto; Wardle, Brian L.; Xiang, Rong; Maruyama, Shigeo; Kenny, Thomas W.; Goodson, Kenneth E.

    2015-11-01

    Carbon nanotube (CNT) arrays offer the potential to develop nanostructured materials that leverage their outstanding physical properties. Vertically aligned carbon nanotubes (VACNTs), also named CNT forests, CNT arrays, or CNT turfs, can provide high heat conductivity and sufficient mechanical compliance to accommodate thermal expansion mismatch for use as thermal interface materials (TIMs). This paper reports measurements of the in-plane moduli of vertically aligned, single-walled CNT (SWCNT) and multi-walled CNT (MWCNT) films. The mechanical response of these films is related to the nonhomogeneous morphology of the grown nanotubes, such as entangled nanotubes of a top crust layer, aligned CNTs in the middle region, and CNTs in the bottom layer. To investigate how the entanglements govern the overall mechanical moduli of CNT films, we remove the crust layer consisting of CNT entanglements by etching the CNT films from the top. A microfabricated cantilever technique shows that crust removal reduces the resulting moduli of the etched SWCNT films by as much as 40%, whereas the moduli of the etched MWCNT films do not change significantly, suggesting a minimal crust effect on the film modulus for thick MWCNT films (>90 μm). This improved understanding will allow us to engineer the mechanical moduli of CNT films for TIMs or packaging applications.

  15. Mechanical properties of aligned carbon nanotube architectures: origin from 3D morphology

    NASA Astrophysics Data System (ADS)

    Stein, Itai Y.; Wardle, Brian L.

    The scale-dependent properties of carbon nanotubes (CNTs) continue to motivate their study for next-generation material architectures. While recent work has shown that aligned CNT arrays can be made on the cm-scale, such systems exhibit properties that are orders of magnitude below those predicted by existing theories. This deviation mainly stems from the rudimentary assumptions made about the CNT morphology: CNTs are either devoid of local curvature (i.e. waviness) or have waviness that is easy to model, e.g. using helices and sine waves. Here, we use a simulation framework comprised of 105 CNTs with realistic 3D stochastic morphologies to elucidate the role morphology plays in the orders of magnitude over-prediction of the effective stiffness of aligned CNT structures. Application to aligned CNT polymer and carbon matrix nanocomposites reveals that the elimination of the torsion deformation mechanism, which dominates the effective compliance of CNT arrays, through CNT interactions with the matrix is responsible for the stiffness enhancement in CNT nanocomposites. This works paves the way to more accurate property prediction of CNT nanocomposites, and further work to predict the transport properties of aligned CNT architectures is planned.

  16. X-band printed phased array antennas using high-performance CNT/ion gel/Ag transistors

    NASA Astrophysics Data System (ADS)

    Grubb, Peter M.; Bidoky, Fazel; Mahajan, Ankit; Subbaraman, Harish; Li, Wentao; Frisbie, Daniel; Chen, Ray T.

    2016-05-01

    This paper reports a fully printed phased array antenna developed on a 125 micron thick flexible Kapton substrate. Switching for the phase delay lines is accomplished using printed carbon nanotube transistors with ion gel dielectric layers. Design of each element of the phased array antenna is reported, including a low loss constant impedance power divider, a phase shifter network, and patch antenna design. Steering of an X-band PAA operating at 10GHz from 0 degrees to 22.15 degrees is experimentally demonstrated. In order to completely package the array with electrical interconnects, a single substrate interconnect scheme is also investigated.

  17. En route to controlled catalytic CVD synthesis of densely packed and vertically aligned nitrogen-doped carbon nanotube arrays

    PubMed Central

    Pattinson, Sebastian W; Geiser, Valérie; Shaffer, Milo S P

    2014-01-01

    Summary The catalytic chemical vapour deposition (c-CVD) technique was applied in the synthesis of vertically aligned arrays of nitrogen-doped carbon nanotubes (N-CNTs). A mixture of toluene (main carbon source), pyrazine (1,4-diazine, nitrogen source) and ferrocene (catalyst precursor) was used as the injection feedstock. To optimize conditions for growing the most dense and aligned N-CNT arrays, we investigated the influence of key parameters, i.e., growth temperature (660, 760 and 860 °C), composition of the feedstock and time of growth, on morphology and properties of N-CNTs. The presence of nitrogen species in the hot zone of the quartz reactor decreased the growth rate of N-CNTs down to about one twentieth compared to the growth rate of multi-wall CNTs (MWCNTs). As revealed by electron microscopy studies (SEM, TEM), the individual N-CNTs (half as thick as MWCNTs) grown under the optimal conditions were characterized by a superior straightness of the outer walls, which translated into a high alignment of dense nanotube arrays, i.e., 5 × 108 nanotubes per mm2 (100 times more than for MWCNTs grown in the absence of nitrogen precursor). In turn, the internal crystallographic order of the N-CNTs was found to be of a ‘bamboo’-like or ‘membrane’-like (multi-compartmental structure) morphology. The nitrogen content in the nanotube products, which ranged from 0.0 to 3.0 wt %, was controlled through the concentration of pyrazine in the feedstock. Moreover, as revealed by Raman/FT-IR spectroscopy, the incorporation of nitrogen atoms into the nanotube walls was found to be proportional to the number of deviations from the sp2-hybridisation of graphene C-atoms. As studied by XRD, the temperature and the [pyrazine]/[ferrocene] ratio in the feedstock affected the composition of the catalyst particles, and hence changed the growth mechanism of individual N-CNTs into a ‘mixed base-and-tip’ (primarily of the base-type) type as compared to the purely

  18. En route to controlled catalytic CVD synthesis of densely packed and vertically aligned nitrogen-doped carbon nanotube arrays.

    PubMed

    Boncel, Slawomir; Pattinson, Sebastian W; Geiser, Valérie; Shaffer, Milo S P; Koziol, Krzysztof K K

    2014-01-01

    The catalytic chemical vapour deposition (c-CVD) technique was applied in the synthesis of vertically aligned arrays of nitrogen-doped carbon nanotubes (N-CNTs). A mixture of toluene (main carbon source), pyrazine (1,4-diazine, nitrogen source) and ferrocene (catalyst precursor) was used as the injection feedstock. To optimize conditions for growing the most dense and aligned N-CNT arrays, we investigated the influence of key parameters, i.e., growth temperature (660, 760 and 860 °C), composition of the feedstock and time of growth, on morphology and properties of N-CNTs. The presence of nitrogen species in the hot zone of the quartz reactor decreased the growth rate of N-CNTs down to about one twentieth compared to the growth rate of multi-wall CNTs (MWCNTs). As revealed by electron microscopy studies (SEM, TEM), the individual N-CNTs (half as thick as MWCNTs) grown under the optimal conditions were characterized by a superior straightness of the outer walls, which translated into a high alignment of dense nanotube arrays, i.e., 5 × 10(8) nanotubes per mm(2) (100 times more than for MWCNTs grown in the absence of nitrogen precursor). In turn, the internal crystallographic order of the N-CNTs was found to be of a 'bamboo'-like or 'membrane'-like (multi-compartmental structure) morphology. The nitrogen content in the nanotube products, which ranged from 0.0 to 3.0 wt %, was controlled through the concentration of pyrazine in the feedstock. Moreover, as revealed by Raman/FT-IR spectroscopy, the incorporation of nitrogen atoms into the nanotube walls was found to be proportional to the number of deviations from the sp(2)-hybridisation of graphene C-atoms. As studied by XRD, the temperature and the [pyrazine]/[ferrocene] ratio in the feedstock affected the composition of the catalyst particles, and hence changed the growth mechanism of individual N-CNTs into a 'mixed base-and-tip' (primarily of the base-type) type as compared to the purely 'base'-type for undoped

  19. Gimbal for aligning laser and lenslet arrays for coherent operation in an external cavity

    SciTech Connect

    Caunt, J.W.; Diadiuk, V. )

    1990-05-20

    We describe a miniature alignment stage designed for use with semiconductor diode laser and lenslet arrays. The device achieves 0.03-mrad angular and 0.3-{mu}m linear precision utilizing metal flexures and piezoelectric transducers in a mechanical arrangement that provides compactness and repeatability not obtainable with other types of components. It has been used successfully to coherently combine output of a linear diode laser array of five elements and can accommodate a 2-D array.

  20. Gimbal for aligning laser and lenslet arrays for coherent operation in an external cavity.

    PubMed

    Caunt, J W; Diadiuk, V

    1990-05-20

    We describe a miniature alignment stage designed for use with semiconductor diode laser and lenslet arrays. The device achieves 0.03-mrad angular and 0.3-microm linear precision utilizing metal flexures and piezoelectric transducers in a mechanical arrangement that provides compactness and repeatability not obtainable with other types of components. It has been used successfully to coherently combine output of a linear diode laser array of five elements and can accommodate a 2-D array. PMID:20563167

  1. Gimbal for aligning laser and lenslet arrays for coherent operation in an external cavity

    SciTech Connect

    Caunt, J.W.; Diadiuk, V.

    1990-05-20

    This reprint describes a miniature alignment stage designed for use with semiconductor diode laser and lenslet arrays. The device achieves 0.03-mrad angular and 0.3-micron linear precision utilizing metal flexures and piezoelectric transducers in a mechanical arrangement that provides compactness and repeatability not obtainable with other types of components. It has been used successfully to coherently combine output of a linear diode laser array of five elements and can accommodate a 2-D array.

  2. PEDOT-CNT-Coated Low-Impedance, Ultra-Flexible, and Brain-Conformable Micro-ECoG Arrays.

    PubMed

    Castagnola, Elisa; Maiolo, Luca; Maggiolini, Emma; Minotti, Antonio; Marrani, Marco; Maita, Francesco; Pecora, Alessandro; Angotzi, Gian Nicola; Ansaldo, Alberto; Boffini, Massimiliano; Fadiga, Luciano; Fortunato, Guglielmo; Ricci, Davide

    2015-05-01

    Electrocorticography (ECoG) is becoming a common tool for clinical applications, such as preparing patients for epilepsy surgery or localizing tumor boundaries, as it successfully balances invasiveness and information quality. Clinical ECoG arrays use millimeter-scale electrodes and centimeter-scale pitch and cannot precisely map neural activity. Higher-resolution electrodes are of interest for both current clinical applications, providing access to more precise neural activity localization and novel applications, such as neural prosthetics, where current information density and spatial resolution is insufficient to suitably decode signals for a chronic brain-machine interface. Developing such electrodes is not trivial because their small contact area increases the electrode impedance, which seriously affects the signal-to-noise ratio, and adhering such an electrode to the brain surface becomes critical. The most straightforward approach requires increasing the array conformability with flexible substrates while improving the electrode performance using materials with superior electrochemical properties. In this paper, we propose an ultra-flexible and conformable polyimide-based micro-ECoG array of submillimeter recording sites electrochemically coated with high surface area conductive polymer-carbon nanotube composites to improve their brain-electrical coupling capabilities. We characterized our devices both electrochemically and by recording from rat somatosensory cortex in vivo. The performance of the coated and uncoated electrodes was directly compared by simultaneously recording the same neuronal activity during multiwhisker deflection stimulation. Finally, we assessed the effect of electrode size on the extraction of somatosensory evoked potentials and found that in contrast to the normal high-impedance microelectrodes, the recording capabilities of our low-impedance microelectrodes improved upon reducing their size from 0.2 to 0.1 mm. PMID:25073174

  3. Dry Oxidation and Vacuum Annealing Treatments for Tuning the Wetting Properties of Carbon Nanotube Arrays

    PubMed Central

    Aria, Adrianus Indrat; Gharib, Morteza

    2013-01-01

    In this article, we describe a simple method to reversibly tune the wetting properties of vertically aligned carbon nanotube (CNT) arrays. Here, CNT arrays are defined as densely packed multi-walled carbon nanotubes oriented perpendicular to the growth substrate as a result of a growth process by the standard thermal chemical vapor deposition (CVD) technique.1,2 These CNT arrays are then exposed to vacuum annealing treatment to make them more hydrophobic or to dry oxidation treatment to render them more hydrophilic. The hydrophobic CNT arrays can be turned hydrophilic by exposing them to dry oxidation treatment, while the hydrophilic CNT arrays can be turned hydrophobic by exposing them to vacuum annealing treatment. Using a combination of both treatments, CNT arrays can be repeatedly switched between hydrophilic and hydrophobic.2 Therefore, such combination show a very high potential in many industrial and consumer applications, including drug delivery system and high power density supercapacitors.3-5 The key to vary the wettability of CNT arrays is to control the surface concentration of oxygen adsorbates. Basically oxygen adsorbates can be introduced by exposing the CNT arrays to any oxidation treatment. Here we use dry oxidation treatments, such as oxygen plasma and UV/ozone, to functionalize the surface of CNT with oxygenated functional groups. These oxygenated functional groups allow hydrogen bond between the surface of CNT and water molecules to form, rendering the CNT hydrophilic. To turn them hydrophobic, adsorbed oxygen must be removed from the surface of CNT. Here we employ vacuum annealing treatment to induce oxygen desorption process. CNT arrays with extremely low surface concentration of oxygen adsorbates exhibit a superhydrophobic behavior. PMID:23629482

  4. Al-doped ZnO aligned nanorod arrays for opto-electronic and sensor applications

    NASA Astrophysics Data System (ADS)

    Holloway, T.; Mundle, R.; Dondapati, H.; Konda, R. B.; Bahoura, M.; Pradhan, A. K.

    2012-04-01

    We report on the growth of vertically aligned Al:ZnO nanorod arrays synthesized by the hydrothermal technique at considerably low temperature on a sputtered Al:ZnO seed layer. The morphology demonstrates that the nanorod arrays maintain remarkable alignment along the c-axis over a large area. The optoelectronic properties of nanorod arrays on Al:ZnO/p-Si seed layer with SiO2 have been illustrated. The photocurrent is significantly reduced in nanorod arrays on AZO/SiO2/p-Si heterojunction due to multiple scattering phenomena associated with the nanorod arrays. The optical properties of the AZO film with and without the AZO nanorod arrays were investigated. Also the effects of an intermediate layer in the AZO/P-Si heterojunction structure with and without the AZO nanorod array present were explored. All the various intermediate layers displayed photovoltaic effect behavior, especially with the AZO/SiO2/P-Si heterojunction structure, which exhibited ideal diode behavior. The optoelectronic properties of nanorod arrays on AZO/P-Si seed layer with SiO2 have been illustrated. The photocurrent is significantly reduced in nanorod arrays on AZO/SiO2/P-Si heterojunction due to multiple scattering phenomena associated with the nanorod arrays. The results have tremendous impact for sensor fabrication, including glucose sensor.

  5. Mobile and replicated alignment of arrays in data-parallel programs

    NASA Technical Reports Server (NTRS)

    Chatterjee, Siddhartha; Gilbert, John R.; Schreiber, Robert

    1993-01-01

    When a data-parallel language like FORTRAN 90 is compiled for a distributed-memory machine, aggregate data objects (such as arrays) are distributed across the processor memories. The mapping determines the amount of residual communication needed to bring operands of parallel operations into alignment with each other. A common approach is to break the mapping into two stages: first, an alignment that maps all the objects to an abstract template, and then a distribution that maps the template to the processors. We solve two facets of the problem of finding alignments that reduce residual communication: we determine alignments that vary in loops, and objects that should have replicated alignments. We show that loop-dependent mobile alignment is sometimes necessary for optimum performance, and we provide algorithms with which a compiler can determine good mobile alignments for objects within do loops. We also identify situations in which replicated alignment is either required by the program itself (via spread operations) or can be used to improve performance. We propose an algorithm based on network flow that determines which objects to replicate so as to minimize the total amount of broadcast communication in replication. This work on mobile and replicated alignment extends our earlier work on determining static alignment.

  6. Terahertz detectors arrays based on orderly aligned InN nanowires

    PubMed Central

    Chen, Xuechen; Liu, Huiqiang; Li, Qiuguo; Chen, Hao; Peng, Rufang; Chu, Sheng; Cheng, Binbin

    2015-01-01

    Nanostructured terahertz detectors employing a single semiconducting nanowire or graphene sheet have recently generated considerable interest as an alternative to existing THz technologies, for their merit on the ease of fabrication and above-room-temperature operation. However, the lack of alignment in nanostructure device hindered their potential toward practical applications. The present work reports ordered terahertz detectors arrays based on neatly aligned InN nanowires. The InN nanostructures (nanowires and nano-necklaces) were achieved by chemical vapor deposition growth, and then InN nanowires were successfully transferred and aligned into micrometer-sized groups by a “transfer-printing” method. Field effect transistors on aligned nanowires were fabricated and tested for terahertz detection purpose. The detector showed good photoresponse as well as low noise level. Besides, dense arrays of such detectors were also fabricated, which rendered a peak responsivity of 1.1 V/W from 7 detectors connected in series. PMID:26289498

  7. Periodically striped films produced from super-aligned carbon nanotube arrays.

    PubMed

    Liu, Kai; Sun, Yinghui; Liu, Peng; Wang, Jiaping; Li, Qunqing; Fan, Shoushan; Jiang, Kaili

    2009-08-19

    We report a novel way to draw films from super-aligned carbon nanotube arrays at large drawing angles. The obtained super-aligned carbon nanotube films have a periodically striped configuration with alternating thinner and thicker film sections, and the width of the stripes is equal to the height of the original arrays. Compared with ordinary uniform films, the striped films provide a better platform for understanding the mechanism of spinning films from arrays because carbon nanotube junctions are easily observed and identified at the boundary of the stripes. Further studies show that the carbon nanotube junctions are bottleneck positions for thermal conduction and mechanical strength of the film, but do not limit its electrical conduction. These films can be utilized as striped and high-degree polarized light emission sources. Our results will be valuable for new applications and future large-scale production of tunable super-aligned carbon nanotube films. PMID:19636102

  8. Remote alignment of large mirror array for RICH detectors

    NASA Astrophysics Data System (ADS)

    Dalla Torre, S.; Levorato, S.; Menon, G.; Polak, J.; Steiger, L.; Sulc, M.; Tessarotto, F.

    2008-09-01

    Image focusing in large RICH detectors is obtained by composite systems of mirror elements. Monitoring and adjusting the alignment of the mirror elements during data taking are important handles to improve the detector resolution. Mirror adjustment via piezoelectric actuators can combine unprecedented accuracy and match some fundamental requirements: the detector material budget can be kept low and the high purity of the gas radiator can be preserved, a prerequisite when UV photons are detected. A system based on this principle, well suited for COMPASS RICH-1 mirrors, is proposed.

  9. Vertically aligned carbon nanofiber nanoelectrode arrays: electrochemical etching and electrode reusability

    PubMed Central

    Gupta, Rakesh K.; Meyyappan, M.; Koehne, Jessica E.

    2014-01-01

    Vertically aligned carbon nanofibers in the form of nanoelectrode arrays were grown on nine individual electrodes, arranged in a 3 × 3 array geometry, in a 2.5 cm2 chip. Electrochemical etching of the carbon nanofibers was employed for electrode activation and enhancing the electrode kinetics. Here, we report the effects of electrochemical etching on the fiber height and electrochemical properties. Electrode regeneration by amide hydrolysis and electrochemical etching is also investigated for electrode reusability. PMID:25089188

  10. Stability Measurements for Alignment of the NIF Neutron Imaging System Pinhole Array

    SciTech Connect

    Fittinghoff, D N; Bower, D E; Drury, O B; Dzenitis, J M; Frank, M; Buckles, R A; Munson, C; Wilde, C H

    2011-03-29

    The alignment system for the National Ignition Facility's neutron imaging system has been commissioned and measurements of the relative stability of the 90-315 DIM, the front and the back of the neutron imaging pinhole array and an exploding pusher target have been made using the 90-135 and the 90-258 opposite port alignment systems. Additionally, a laser beam shot from the neutron-imaging Annex and reflected from a mirror at the back of the pinhole array was used to monitor the pointing of the pinhole. Over a twelve hour period, the relative stability of these parts was found to be within {approx} {+-}18 {micro}m rms even when using manual methods for tracking the position of the objects. For highly visible features, use of basic particle tracking techniques found that the front of the pinhole array was stable relative to the 90-135 opposite port alignment camera to within {+-}3.4 {micro}m rms. Reregistration, however, of the opposite port alignment systems themselves using the target alignment sensor was found to change the expected position of target chamber center by up to 194 {micro}m.

  11. Density controlled carbon nanotube array electrodes

    DOEpatents

    Ren, Zhifeng F.; Tu, Yi

    2008-12-16

    CNT materials comprising aligned carbon nanotubes (CNTs) with pre-determined site densities, catalyst substrate materials for obtaining them and methods for forming aligned CNTs with controllable densities on such catalyst substrate materials are described. The fabrication of films comprising site-density controlled vertically aligned CNT arrays of the invention with variable field emission characteristics, whereby the field emission properties of the films are controlled by independently varying the length of CNTs in the aligned array within the film or by independently varying inter-tubule spacing of the CNTs within the array (site density) are disclosed. The fabrication of microelectrode arrays (MEAs) formed utilizing the carbon nanotube material of the invention is also described.

  12. Phase aligner for the Electronically Scanned Thinned Array Radiometer (ESTAR) instrument

    NASA Technical Reports Server (NTRS)

    Chren, William A., Jr.; Zomberg, Brian G.

    1993-01-01

    A prototype Phase Aligner (PA) or the Electronically Scanned Thinned Array Radiometer instrument has been designed and tested. Implemented in a single Xilinx XC3042PC84-125 Field Programmable Gate Array (FPGA), it is a dual-port register file which allows independent storage and phase coherent retrieval of antenna array data by the Central Processing Unit (CPU). It has dimensions of 4 x 20 bits and can be used at clock frequencies as high as 25 MHz. The ESTAR is a passive synthetic-aperture radiometer designed to sense soil moisture and ocean salinity at L-band.

  13. Single-mode array optoelectronic packaging based on actively aligned planar optical waveguides

    NASA Astrophysics Data System (ADS)

    Kalman, Robert F.; Silva, Edward R.; Knapp, Daniel F.

    1996-03-01

    Packaging of integrated optoelectronic devices (e.g., laser diode arrays and OEICs) is motivated by potential cost savings and the increased functionality of more highly integrated devices. To date, attempts to package integrated optoelectronic devices with arrays of single- mode fibers have tended to exhibit high optical losses. We have developed a single-mode array packaging process based on the use of an intermediate silica-on-silicon planar optical waveguides (POWs) assembly to which optical fibers are attached using V-grooves. By lensing the POWs, we have achieved coupling efficiencies of greater than 50%. The photolithographic registration of the POWs allows a large (greater than or equal to 8) array of POWs with attached fibers to be aligned to an array of optoelectronic devices in a single active alignment procedure. This single active alignment step is well-suited to automation, and our approach is thus well-suited to achieving low cost in a manufacturing environment. We also discuss our positioning and mounting techniques, which provide high-stability coupling in adverse temperature and vibration environments and are compatible with hermetic packaging.

  14. Density Detection of Aligned Nanowire Arrays Using Terahertz Time-Domain Spectroscopy.

    PubMed

    Xiang, Wenfeng; Wang, Xin; Liu, Yuan; Zhang, JiaQi; Zhao, Kun

    2016-12-01

    A rapid technique is necessary to quantitatively detect the density of nanowire (NW) and nanotube arrays in one-dimensional devices which have been identified as useful building blocks for nanoelectronics, optoelectronics, biomedical devices, etc. Terahertz (THz) time-domain spectroscopy was employed in this research to detect the density of aligned Ni NW arrays. The transmitted amplitude of THz peaks and optical thickness of NW arrays was found to be the effective parameters to analyze the density change of NW arrays. Owing to the low multiple scattering and high order of Ni NW arrays, a linear relationship was observed for the transmitted amplitude and optical thickness regarding NW density, respectively. Therefore, THz technique may be used as a promising tool to characterize the density of one-dimensional structures in the large-scale integrated nanodevice fabrication. PMID:27431495

  15. Density Detection of Aligned Nanowire Arrays Using Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Xiang, Wenfeng; Wang, Xin; Liu, Yuan; Zhang, JiaQi; Zhao, Kun

    2016-07-01

    A rapid technique is necessary to quantitatively detect the density of nanowire (NW) and nanotube arrays in one-dimensional devices which have been identified as useful building blocks for nanoelectronics, optoelectronics, biomedical devices, etc. Terahertz (THz) time-domain spectroscopy was employed in this research to detect the density of aligned Ni NW arrays. The transmitted amplitude of THz peaks and optical thickness of NW arrays was found to be the effective parameters to analyze the density change of NW arrays. Owing to the low multiple scattering and high order of Ni NW arrays, a linear relationship was observed for the transmitted amplitude and optical thickness regarding NW density, respectively. Therefore, THz technique may be used as a promising tool to characterize the density of one-dimensional structures in the large-scale integrated nanodevice fabrication.

  16. Structure-thermal property correlation of aligned silicon dioxide nanorod arrays

    NASA Astrophysics Data System (ADS)

    Zhu, Jie; Zhu, Yu; Wu, Xuewang; Song, Helun; Zhang, Yaohui; Wang, Xiaojia

    2016-06-01

    Quantitative characterization of thermal properties of nanorod (NR) arrays appears to be challenging due to the complex combination of high volume of air voids, anisotropy, and structural non-uniformity. This work investigates the structure-thermal property correlation of arrays consisting of either vertically aligned or slanted silicon dioxide (SiO2) NRs, fabricated by the dynamic shadowing growth technique. We apply the frequency-dependent time-domain thermoreflectance method to quantify the thermal properties of SiO2 NR arrays that may possess inhomogeneity along the depth direction. The effective thermal conductivities of four SiO2 NR array films and one reference capping layer for the SiO2 NR array are obtained. The impact of the structure on the effective thermal conductivities of the SiO2 NR array is discussed. The lowest effective thermal conductivity among all samples in this work is found to be 0.13 W m-1 K-1 for the slanted NR array. We attribute the reduction in the effective thermal conductivity of the NR array to the discontinuous nature of SiO2 NRs, which reduces the density of the thermal transport channels and thus prevents heat flux from propagating downwards along the through-plane direction. The results from this work facilitate the potential applications of NR-array-based thermal insulators for micro-thermal devices.

  17. Large format focal plane array integration with precision alignment, metrology and accuracy capabilities

    NASA Astrophysics Data System (ADS)

    Neumann, Jay; Parlato, Russell; Tracy, Gregory; Randolph, Max

    2015-09-01

    Focal plane alignment for large format arrays and faster optical systems require enhanced precision methodology and stability over temperature. The increase in focal plane array size continues to drive the alignment capability. Depending on the optical system, the focal plane flatness of less than 25μm (.001") is required over transition temperatures from ambient to cooled operating temperatures. The focal plane flatness requirement must also be maintained in airborne or launch vibration environments. This paper addresses the challenge of the detector integration into the focal plane module and housing assemblies, the methodology to reduce error terms during integration and the evaluation of thermal effects. The driving factors influencing the alignment accuracy include: datum transfers, material effects over temperature, alignment stability over test, adjustment precision and traceability to NIST standard. The FPA module design and alignment methodology reduces the error terms by minimizing the measurement transfers to the housing. In the design, the proper material selection requires matched coefficient of expansion materials minimizes both the physical shift over temperature as well as lowering the stress induced into the detector. When required, the co-registration of focal planes and filters can achieve submicron relative positioning by applying precision equipment, interferometry and piezoelectric positioning stages. All measurements and characterizations maintain traceability to NIST standards. The metrology characterizes the equipment's accuracy, repeatability and precision of the measurements.

  18. Secondary nanotube growth on aligned carbon nanofibre arrays for superior field emission.

    PubMed

    Watts, Paul C P; Lyth, Stephen M; Henley, Simon J; Silva, S Ravi P

    2008-04-01

    We report substantial improvement of the field emission properties from aligned carbon nanotubes grown on aligned carbon nanofibres by a two-stage plasma enhanced chemical vapour deposition (PECVD) process. The threshold field decreased from 15.0 to 3.6 V/microm after the secondary growth. The field enhancement factor increased from 240 to 1480. This technique allows for superior emission of electrons for carbon nanotube/nanofibre arrays grown directly on highly doped silicon for direct integration in large area displays. PMID:18572626

  19. Periodically Aligned Si Nanopillar Arrays as Efficient Antireflection Layers for Solar Cell Applications

    PubMed Central

    2010-01-01

    Periodically aligned Si nanopillar (PASiNP) arrays were fabricated on Si substrate via a silver-catalyzed chemical etching process using the diameter-reduced polystyrene spheres as mask. The typical sub-wavelength structure of PASiNP arrays had excellent antireflection property with a low reflection loss of 2.84% for incident light within the wavelength range of 200–1,000 nm. The solar cell incorporated with the PASiNP arrays exhibited a power conversion efficiency (PCE) of ~9.24% with a short circuit current density (JSC) of ~29.5 mA/cm2 without using any extra surface passivation technique. The high PCE of PASiNP array-based solar cell was attributed to the excellent antireflection property of the special periodical Si nanostructure. PMID:21124636

  20. Aligned ZnO nanorod arrays growth on GaN QDs for excellent optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Sang, Dandan; Li, Hongdong; Wang, Qinglin

    2016-02-01

    Uniformly aligned ZnO nanorod (NR) arrays grown on GaN quantum dots (QDs) as preferred nucleation sites are imperative for designing field emission emitters, ultraviolet photodetectors and light-emitting diodes for a wide range of new optoelectronic applications. In a recent study (2015 Nanotechnology 26 415601), Qi et al reported a novel method of fabricating ZnO NRs arrays with uniform shape, the density of which is easily tunable by adjusting the density of GaN QDs. This approach opens a door to obtaining a combination of 0D and 1D structures for optoelectronic applications.

  1. Thermal conductivity of vertically aligned carbon nanotube arrays: Growth conditions and tube inhomogeneity

    SciTech Connect

    Bauer, Matthew L.; Pham, Quang N.; Saltonstall, Christopher B.; Norris, Pamela M.

    2014-10-13

    The thermal conductivity of vertically aligned carbon nanotube arrays (VACNTAs) grown on silicon dioxide substrates via chemical vapor deposition is measured using a 3ω technique. For each sample, the VACNTA layer and substrate are pressed to a heating line at varying pressures to extract the sample's thermophysical properties. The nanotubes' structure is observed via transmission electron microscopy and Raman spectroscopy. The presence of hydrogen and water vapor in the fabrication process is tuned to observe the effect on measured thermal properties. The presence of iron catalyst particles within the individual nanotubes prevents the array from achieving the overall thermal conductivity anticipated based on reported measurements of individual nanotubes and the packing density.

  2. Wafer-scale high-throughput ordered growth of vertically aligned ZnO nanowire arrays.

    PubMed

    Wei, Yaguang; Wu, Wenzhuo; Guo, Rui; Yuan, Dajun; Das, Suman; Wang, Zhong Lin

    2010-09-01

    This article presents an effective approach for patterned growth of vertically aligned ZnO nanowire (NW) arrays with high throughput and low cost at wafer scale without using cleanroom technology. Periodic hole patterns are generated using laser interference lithography on substrates coated with the photoresist SU-8. ZnO NWs are selectively grown through the holes via a low-temperature hydrothermal method without using a catalyst and with a superior control over orientation, location/density, and as-synthesized morphology. The development of textured ZnO seed layers for replacing single crystalline GaN and ZnO substrates extends the large-scale fabrication of vertically aligned ZnO NW arrays on substrates of other materials, such as polymers, Si, and glass. This combined approach demonstrates a novel method of manufacturing large-scale patterned one-dimensional nanostructures on various substrates for applications in energy harvesting, sensing, optoelectronics, and electronic devices. PMID:20681617

  3. Steering epitaxial alignment of Au, Pd, and AuPd nanowire arrays by atom flux change.

    PubMed

    Yoo, Youngdong; Seo, Kwanyong; Han, Sol; Varadwaj, Kumar S K; Kim, Hyun You; Ryu, Ji Hoon; Lee, Hyuck Mo; Ahn, Jae Pyoung; Ihee, Hyotcherl; Kim, Bongsoo

    2010-02-10

    We have synthesized epitaxial Au, Pd, and AuPd nanowire arrays in vertical or horizontal alignment on a c-cut sapphire substrate. We show that the vertical and horizontal nanowire arrays grow from half-octahedral seeds by the correlations of the geometry and orientation of seed crystals with those of as-grown nanowires. The alignment of nanowires can be steered by changing the atom flux. At low atom deposition flux vertical nanowires grow, while at high atom flux horizontal nanowires grow. Similar vertical/horizontal epitaxial growth is also demonstrated on SrTiO(3) substrates. This orientation-steering mechanism is visualized by molecular dynamics simulations. PMID:20050692

  4. Highly aligned arrays of high aspect ratio barium titanate nanowires via hydrothermal synthesis

    SciTech Connect

    Bowland, Christopher C.; Zhou, Zhi; Malakooti, Mohammad H.; Sodano, Henry A.

    2015-06-01

    We report on the development of a hydrothermal synthesis procedure that results in the growth of highly aligned arrays of high aspect ratio barium titanate nanowires. Using a multiple step, scalable hydrothermal reaction, a textured titanium dioxide film is deposited on titanium foil upon which highly aligned nanowires are grown via homoepitaxy and converted to barium titanate. Scanning electron microscope images clearly illustrate the effect the textured film has on the degree of orientation of the nanowires. The alignment of nanowires is quantified by calculating the Herman's Orientation Factor, which reveals a 58% improvement in orientation as compared to growth in the absence of the textured film. The ferroelectric properties of barium titanate combined with the development of this scalable growth procedure provide a powerful route towards increasing the efficiency and performance of nanowire-based devices in future real-world applications such as sensing and power harvesting.

  5. Field emission from in situ-grown vertically aligned SnO2 nanowire arrays

    PubMed Central

    2012-01-01

    Vertically aligned SnO2 nanowire arrays have been in situ fabricated on a silicon substrate via thermal evaporation method in the presence of a Pt catalyst. The field emission properties of the SnO2 nanowire arrays have been investigated. Low turn-on fields of 1.6 to 2.8 V/μm were obtained at anode-cathode separations of 100 to 200 μm. The current density fluctuation was lower than 5% during a 120-min stability test measured at a fixed applied electric field of 5 V/μm. The favorable field-emission performance indicates that the fabricated SnO2 nanowire arrays are promising candidates as field emitters. PMID:22330800

  6. Macroscopic alignment of nanoparticle arrays in soft crystals of cubic and cylindrical polymer micelles

    NASA Astrophysics Data System (ADS)

    Pozzo, D. C.; Walker, L. M.

    2008-05-01

    We describe a method to organize nanometer-sized hydrophilic particles into ordered arrays by templating them in the soft, micelle-crystal phases (spherical and cylindrical) of a thermoreversible block copolymer. Small-angle neutron scattering (SANS) with contrast variation is used to show that the dispersed particles (in this case, proteins or silica) form structured arrays by being constrained in the interstitial cavities between the polymer micelles in the ordered micelle crystal. Simple shear is used to macroscopically align both phases of the nanocomposites (micelles and particles) into macro-domains. The temperature-induced order-order transition between templates of spherical and cylindrical micelles is demonstrated as a reversible technique to modify the structure of the templated nanoparticle arrays.

  7. Planarized arrays of aligned, untangled multiwall carbon nanotubes with Ohmic back contacts

    SciTech Connect

    Rochford, C.; Limmer, S. J.; Howell, S. W.; Beechem, T. E.; Siegal, M. P.

    2014-11-26

    Vertically aligned, untangled planarized arrays of multiwall carbon nanotubes (MWNTs) with Ohmic back contacts were grown in nanopore templates on arbitrary substrates. The templates were prepared by sputter depositing Nd-doped Al films onto W-coated substrates, followed by anodization to form an aluminum oxide nanopore array. The W underlayer helps eliminate the aluminum oxide barrier that typically occurs at the nanopore bottoms by instead forming a thin WO3 layer. The WO3 can be selectively etched to enable electrodeposition of Co catalysts with control over the Co site density. This led to control of the site density of MWNTs grown by thermal chemical vapor deposition, with the W also serving as a back electrical contact. As a result, Ohmic contact to MWNTs was confirmed, even following ultrasonic cutting of the entire array to a uniform height.

  8. Planarized arrays of aligned, untangled multiwall carbon nanotubes with Ohmic back contacts

    DOE PAGESBeta

    Rochford, C.; Limmer, S. J.; Howell, S. W.; Beechem, T. E.; Siegal, M. P.

    2014-11-26

    Vertically aligned, untangled planarized arrays of multiwall carbon nanotubes (MWNTs) with Ohmic back contacts were grown in nanopore templates on arbitrary substrates. The templates were prepared by sputter depositing Nd-doped Al films onto W-coated substrates, followed by anodization to form an aluminum oxide nanopore array. The W underlayer helps eliminate the aluminum oxide barrier that typically occurs at the nanopore bottoms by instead forming a thin WO3 layer. The WO3 can be selectively etched to enable electrodeposition of Co catalysts with control over the Co site density. This led to control of the site density of MWNTs grown by thermalmore » chemical vapor deposition, with the W also serving as a back electrical contact. As a result, Ohmic contact to MWNTs was confirmed, even following ultrasonic cutting of the entire array to a uniform height.« less

  9. Aligned silver nanorod arrays as substrates for surface-enhanced infrared absorption spectroscopy.

    PubMed

    Leverette, C L; Jacobs, S A; Shanmukh, S; Chaney, S B; Dluhy, R A; Zhao, Y-P

    2006-08-01

    Preferentially aligned silver nanorod arrays prepared by oblique angle vapor deposition were evaluated as substrates for surface-enhanced infrared absorption (SEIRA) spectroscopy. These nanorod arrays have an irregular surface lattice and are composed of tilted, cylindrically shaped nanorods that have an average length of 868 nm +/- 95 nm and an average diameter of 99 nm +/- 29 nm. The overall enhancement factor for chemisorbed organic films of para-nitrobenzoic acid (PNBA) deposited onto the Ag nanorod arrays analyzed by external reflection SEIRA was calculated to be 31 +/- 9 compared to infrared reflection-absorption spectroscopy (IRRAS) obtained from a 500 nm Ag film substrate. This enhancement is attributed to the unique optical properties of the nanorod arrays as well as the increased surface area provided by the nanorod substrate. SEIRA reflection-absorbance intensity was observed with both p- and s-polarized incident radiation with angles of incidence ranging from 25 degrees to 80 degrees . The largest intensity was achieved with p-polarization and incident angles larger than 75 degrees . Polarization-dependent ultraviolet/visible/near-infrared (UV/Vis/NIR) spectra of the nanorod arrays demonstrate that the red-shifted surface plasmon peaks of the elongated nanorods may be partially responsible for the observed SEIRA response. The SEIRA detection limit for the Ag nanorod arrays was estimated to be 0.08 ng/cm(2). Surface-enhanced Raman scattering (SERS) and SEIRA analysis of chemisorbed PNBA utilizing the same nanorod substrate is demonstrated. PMID:16925927

  10. Nanophotonics of vertically aligned carbon nanotubes: Two-dimensional photonic crystals and optical dipole antennas

    NASA Astrophysics Data System (ADS)

    Wang, Yang

    Carbon nanotubes (CNTs) and related nanostructures represent a novel class of condensed matters with intriguing properties due to their unique atomic structures and nanoscale morphologies. It is of particular interest to examine the interaction behavior and mechanism between the free electron gas within carbon nanotubes and the external electromagnetic wave, which may greatly facilitate the understanding of the physics of nanophotonics at the fundamental level. This dissertation is committed to investigate the optical responses of arrays of vertically aligned CNTs in different configurations, based on their fabrication by Plasma-Enhanced Chemical Vapor Deposition (PECVD) and other techniques involved therein. The mechanisms of the photonic results are categorized into inter-CNT and intra-CNT contributions through data analysis on periodic and random CNT arrays, which then give rise to practical applications in photonic crystals and optical antennas. The growth and fabrication procedure of vertically aligned CNTs with optimized morphology and well-defined arrangement is first elaborated in this dissertation, owing to the tremendous difficulties encountered and efforts paid during the sample fabrication and optimization process, and the dominant effect of sample quality on the final results at the optical characterization stage. To fabricate periodic CNT arrays, a microsphere self-assembly technique is first adopted for catalyst patterning and a parametric study is carried out systematically for CNT growth by PECVD method. For random CNT arrays, the growth conditions are also modified so that small diameter CNTs can be grown and an IC industry-compatible procedure can be developed for practical application purposes. The inter-scatterer optical responses are studied by using hexagonal lattices of vertically aligned CNTs with various lattice constants and CNT morphologies. The diffraction patterns of theses CNT arrays are recorded and compared to theoretical

  11. A passive micromachined device for alignment of arrays of single-mode fibers for hermetic photonic packaging - the CLASP concept

    SciTech Connect

    Seigal, P.K.; Kravitz, S.H.; Word, J.C.; Bauer, T.M.

    1997-02-01

    A micro-machined fiber alignment device, called CLASP (Capture and Locking Alignment Spring Positioner) has been fabricated. It uses a nickel leaf spring to passively capture vertical arrays of single-mode fibers with {approximately} 2 {mu}m accuracy.

  12. Aligned carbon nanotube sheet piezoresistive strain sensors

    NASA Astrophysics Data System (ADS)

    Li, Ang; Bogdanovich, Alexander E.; Bradford, Philip D.

    2015-09-01

    Carbon nanotubes (CNTs) have a unique set of properties that may be useful in the production of next generation structural health monitoring composites. This research introduces a novel CNT based material system for strain and damage sensing applications. An aligned sheet of interconnected CNTs was drawn from a chemical vapor deposition grown CNT array and then bonded to the surface of glass fiber/epoxy composite coupons. Various types of mechanical tests were conducted, accompanied by real-time electrical data acquisition, in order to evaluate the electro-mechanical behavior of the developed sensing material. Specimens were loaded in the longitudinal and transverse CNT sheet orientations to investigate the anisotropy of the piezoresistive effect. The CNT sheets exhibited good sensing stability, linearity, sensitivity and repeatability within a practical strain range; which are crucial sensor features for health monitoring. It was also demonstrated that the CNT orientation in the sheet had a dramatic effect on the sensitivity, thus validating the usefulness of this sensing material for directional strain/damage monitoring. Finally, pre-straining of the CNT sheet sensors was conducted to further enhance the linearity of electro-mechanical response and long-term stability of the sensors during cyclic loading.

  13. Fabricating vertically aligned sub-20 nm Si nanowire arrays by chemical etching and thermal oxidation

    NASA Astrophysics Data System (ADS)

    Li, Luping; Fang, Yin; Xu, Cheng; Zhao, Yang; Zang, Nanzhi; Jiang, Peng; Ziegler, Kirk J.

    2016-04-01

    Silicon nanowires (SiNWs) are appealing building blocks in various applications, including photovoltaics, photonics, and sensors. Fabricating SiNW arrays with diameters <100 nm remains challenging through conventional top-down approaches. In this work, chemical etching and thermal oxidation are combined to fabricate vertically aligned, sub-20 nm SiNW arrays. Defect-free SiNWs with diameters between 95 and 200 nm are first fabricated by nanosphere (NS) lithography and chemical etching. The key aspects for defect-free SiNW fabrication are identified as: (1) achieving a high etching selectivity during NS size reduction; (2) retaining the circular NS shape with smooth sidewalls; and (3) using a directional metal deposition technique. SiNWs with identical spacing but variable diameters are demonstrated by changing the reactive ion etching power. The diameter of the SiNWs is reduced by thermal oxidation, where self-limiting oxidation is encountered after oxidizing the SiNWs at 950 °C for 1 h. A second oxidation is performed to achieve vertically aligned, sub-20 nm SiNW arrays. Si/SiO2 core/shell NWs are obtained before removing the oxidized shell. HRTEM imaging shows that the SiNWs have excellent crystallinity.

  14. Fabricating vertically aligned sub-20 nm Si nanowire arrays by chemical etching and thermal oxidation.

    PubMed

    Li, Luping; Fang, Yin; Xu, Cheng; Zhao, Yang; Zang, Nanzhi; Jiang, Peng; Ziegler, Kirk J

    2016-04-22

    Silicon nanowires (SiNWs) are appealing building blocks in various applications, including photovoltaics, photonics, and sensors. Fabricating SiNW arrays with diameters <100 nm remains challenging through conventional top-down approaches. In this work, chemical etching and thermal oxidation are combined to fabricate vertically aligned, sub-20 nm SiNW arrays. Defect-free SiNWs with diameters between 95 and 200 nm are first fabricated by nanosphere (NS) lithography and chemical etching. The key aspects for defect-free SiNW fabrication are identified as: (1) achieving a high etching selectivity during NS size reduction; (2) retaining the circular NS shape with smooth sidewalls; and (3) using a directional metal deposition technique. SiNWs with identical spacing but variable diameters are demonstrated by changing the reactive ion etching power. The diameter of the SiNWs is reduced by thermal oxidation, where self-limiting oxidation is encountered after oxidizing the SiNWs at 950 °C for 1 h. A second oxidation is performed to achieve vertically aligned, sub-20 nm SiNW arrays. Si/SiO2 core/shell NWs are obtained before removing the oxidized shell. HRTEM imaging shows that the SiNWs have excellent crystallinity. PMID:26953775

  15. Identification of energy dissipation mechanisms in CNT-reinforced nanocomposites

    NASA Astrophysics Data System (ADS)

    Gardea, Frank; Glaz, Bryan; Riddick, Jaret; Lagoudas, Dimitris C.; Naraghi, Mohammad

    2016-03-01

    In this paper we present our recent findings on the mechanisms of energy dissipation in polymer-based nanocomposites obtained through experimental investigations. The matrix of the nanocomposite was polystyrene (PS) which was reinforced with carbon nanotubes (CNTs). To study the mechanical strain energy dissipation of nanocomposites, we measured the ratio of loss to storage modulus for different CNT concentrations and alignments. CNT alignment was achieved via hot-drawing of PS-CNT. In addition, CNT agglomeration was studied via a combination of SEM imaging and Raman scanning. We found that at sufficiently low strains, energy dissipation in composites with high CNT alignment is not a function of applied strain, as no interfacial slip occurs between the CNTs and PS. However, below the interfacial slip strain threshold, damping scales monotonically with CNT content, which indicates the prevalence of CNT-CNT friction dissipation mechanisms within agglomerates. At higher strains, interfacial slip also contributes to energy dissipation. However, the increase in damping with strain, especially when CNT agglomerates are present, does not scale linearly with the effective interface area between CNTs and PS, suggesting a significant contribution of friction between CNTs within agglomerates to energy dissipation at large strains. In addition, for the first time, a comparison between the energy dissipation in randomly oriented and aligned CNT composites was made. It is inferred that matrix plasticity and tearing caused by misorientation of CNTs with the loading direction is a major cause of energy dissipation. The results of our research can be used to design composites with high energy dissipation capability, especially for applications where dynamic loading may compromise structural stability and functionality, such as rotary wing structures and antennas.

  16. Identification of energy dissipation mechanisms in CNT-reinforced nanocomposites.

    PubMed

    Gardea, Frank; Glaz, Bryan; Riddick, Jaret; Lagoudas, Dimitris C; Naraghi, Mohammad

    2016-03-11

    In this paper we present our recent findings on the mechanisms of energy dissipation in polymer-based nanocomposites obtained through experimental investigations. The matrix of the nanocomposite was polystyrene (PS) which was reinforced with carbon nanotubes (CNTs). To study the mechanical strain energy dissipation of nanocomposites, we measured the ratio of loss to storage modulus for different CNT concentrations and alignments. CNT alignment was achieved via hot-drawing of PS-CNT. In addition, CNT agglomeration was studied via a combination of SEM imaging and Raman scanning. We found that at sufficiently low strains, energy dissipation in composites with high CNT alignment is not a function of applied strain, as no interfacial slip occurs between the CNTs and PS. However, below the interfacial slip strain threshold, damping scales monotonically with CNT content, which indicates the prevalence of CNT-CNT friction dissipation mechanisms within agglomerates. At higher strains, interfacial slip also contributes to energy dissipation. However, the increase in damping with strain, especially when CNT agglomerates are present, does not scale linearly with the effective interface area between CNTs and PS, suggesting a significant contribution of friction between CNTs within agglomerates to energy dissipation at large strains. In addition, for the first time, a comparison between the energy dissipation in randomly oriented and aligned CNT composites was made. It is inferred that matrix plasticity and tearing caused by misorientation of CNTs with the loading direction is a major cause of energy dissipation. The results of our research can be used to design composites with high energy dissipation capability, especially for applications where dynamic loading may compromise structural stability and functionality, such as rotary wing structures and antennas. PMID:26866611

  17. Tunable Surface Wettability of ZnO Nanoparticle Arrays for Controlling the Alignment of Liquid Crystals.

    PubMed

    Chung, Yueh-Feng; Chen, Mu-Zhe; Yang, Sheng-Hsiung; Jeng, Shie-Chang

    2015-05-13

    The control of the liquid crystal (LC) alignment is very important for both academic research and practical applications. LC molecules aligned on the ZnO nanoparticle arrays (ZnO NPAs) are demonstrated and the pretilt angles of LCs can be controlled by using ZnO NPAs with different surface wettability. The wettability of ZnO NPAs fabricated by the solution-based hydrothermal method can be controlled by changing the annealing temperature of the as-prepared ZnO NPAs. The measurements of the energy-dispersive spectra and photoluminescence have shown that the chemical properties of ZnO NPAs have been changed with the annealing temperature. Our results show that the pretilt angle of LCs can be tuned continuously from ∼0 to ∼90° as the contact angle of water on ZnO NPAs changes from 33 to 108°. PMID:25895105

  18. Charge trapping in aligned single-walled carbon nanotube arrays induced by ionizing radiation exposure

    SciTech Connect

    Esqueda, Ivan S.; Cress, Cory D.; Che, Yuchi; Cao, Yu; Zhou, Chongwu

    2014-02-07

    The effects of near-interfacial trapping induced by ionizing radiation exposure of aligned single-walled carbon nanotube (SWCNT) arrays are investigated via measurements of gate hysteresis in the transfer characteristics of aligned SWCNT field-effect transistors. Gate hysteresis is attributed to charge injection (i.e., trapping) from the SWCNTs into radiation-induced traps in regions near the SWCNT/dielectric interface. Self-consistent calculations of surface-potential, carrier density, and trapped charge are used to describe hysteresis as a function of ionizing radiation exposure. Hysteresis width (h) and its dependence on gate sweep range are investigated analytically. The effects of non-uniform trap energy distributions on the relationship between hysteresis, gate sweep range, and total ionizing dose are demonstrated with simulations and verified experimentally.

  19. Growth and characterization of vertically aligned carbon nanotubes using PECVD

    NASA Astrophysics Data System (ADS)

    Neupane, Suman; Li, Wenzhi

    2010-03-01

    Vertically aligned carbon nanotubes (CNTs) have been grown by using plasma enhanced chemical vapor deposition technique (PECVD). The density of the CNTs is controlled by the density of the nickel catalyst nanoparticles on silicon (Si) surface. Photolithography and nanosphere lithography have been employed to form a catalyst nanoparticle pattern on Si to grow periodic array of CNTS with controllable size and distribution. The electron emission properties of the CNT array have also been investigated.

  20. Vertically aligned graphitic carbon nanosheet arrays fabricated from graphene oxides for supercapacitors and Li-O2 batteries.

    PubMed

    Zhao, Guangyu; Zhang, Li; Lv, Jixian; Li, Changle; Sun, Kening

    2016-05-11

    Vertically aligned graphitic carbon nanosheet arrays were fabricated from graphene oxide solution by a hydrothermal method. The arrays exhibited a specific capacitance of 240 F g(-1) at 200 A g(-1) as a supercapacitor electrode and a capacity of 6500 mA h g(-1) as a Li-O2 battery cathode. PMID:27090965

  1. A vertically aligned carbon nanotube-based impedance sensing biosensor for rapid and high sensitive detection of cancer cells.

    PubMed

    Abdolahad, Mohammad; Taghinejad, Mohammad; Taghinejad, Hossein; Janmaleki, Mohsen; Mohajerzadeh, Shams

    2012-03-21

    A novel vertically aligned carbon nanotube based electrical cell impedance sensing biosensor (CNT-ECIS) was demonstrated for the first time as a more rapid, sensitive and specific device for the detection of cancer cells. This biosensor is based on the fast entrapment of cancer cells on vertically aligned carbon nanotube arrays and leads to mechanical and electrical interactions between CNT tips and entrapped cell membranes, changing the impedance of the biosensor. CNT-ECIS was fabricated through a photolithography process on Ni/SiO(2)/Si layers. Carbon nanotube arrays have been grown on 9 nm thick patterned Ni microelectrodes by DC-PECVD. SW48 colon cancer cells were passed over the surface of CNT covered electrodes to be specifically entrapped on elastic nanotube beams. CNT arrays act as both adhesive and conductive agents and impedance changes occurred as fast as 30 s (for whole entrapment and signaling processes). CNT-ECIS detected the cancer cells with the concentration as low as 4000 cells cm(-2) on its surface and a sensitivity of 1.7 × 10(-3)Ω cm(2). Time and cell efficiency factor (TEF and CEF) parameters were defined which describe the sensor's rapidness and resolution, respectively. TEF and CEF of CNT-ECIS were much higher than other cell based electrical biosensors which are compared in this paper. PMID:22294045

  2. Vertically Aligned Nanostructured Arrays of Inorganic Materials: Synthesis, Distinctive Physical Phenomena, and Device Integration

    NASA Astrophysics Data System (ADS)

    Velazquez, Jesus Manuel

    The manifestation of novel physical phenomena upon scaling materials to finite size has inspired new device concepts that take advantage of the distinctive electrical, mechanical, and optical, properties of nanostructures. The development of fabrication approaches for the preparation of their 1D nanostructured form, such as nanowires and nanotubes, has contributed greatly to advancing fundamental understanding of these systems, and has spurred the integration of these materials in novel electronics, photonic devices, power sources, and energy scavenging constructs. Significant progress has been achieved over the last decade in the preparation of ordered arrays of carbon nanotubes, II---VI and III---V semiconductors, and some binary oxides such as ZnO. In contrast, relatively less attention has been focused on layered materials with potential for electrochemical energy storage. Here, we describe the catalyzed vapor transport growth of vertical arrays of orthorhombic V2O 5 nanowires. In addition, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is used to precisely probe the alignment, uniformity in crystal growth direction, and electronic structure of single-crystalline V2O5 nanowire arrays prepared by a cobalt-catalyzed vapor transport process. The dipole selection rules operational for core-level electron spectroscopy enable angle-dependant NEXAFS spectroscopy to be used as a sensitive probe of the anisotropy of these systems and provides detailed insight into bond orientation and the symmetry of the frontier orbital states. The experimental spectra are matched to previous theoretical predictions and allow experimental verification of features such as the origin of the split-off conduction band responsible for the n-type conductivity of V2O5 and the strongly anisotropic nature of vanadyl-oxygen-derived (V=O) states thought to be involved in catalysis. We have also invested substantial effort in obtaining shape and size control of metal oxide

  3. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties.

    PubMed

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Huang, Jingfeng; Tan, Dunlin; Zhang, Bowei; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2016-06-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ∼4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (∼60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications. PMID:27227818

  4. Characterization of Hybrid CNT Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Cano, Roberto J.; Kinney, Megan C.; Pressley, James; Sauti, Godfrey; Czabaj, Michael W.; Kim, Jae-Woo; Siochi, Emilie J.

    2015-01-01

    Carbon nanotubes (CNTs) have been studied extensively since their discovery and demonstrated at the nanoscale superior mechanical, electrical and thermal properties in comparison to micro and macro scale properties of conventional engineering materials. This combination of properties suggests their potential to enhance multi-functionality of composites in regions of primary structures on aerospace vehicles where lightweight materials with improved thermal and electrical conductivity are desirable. In this study, hybrid multifunctional polymer matrix composites were fabricated by interleaving layers of CNT sheets into Hexcel® IM7/8552 prepreg, a well-characterized toughened epoxy carbon fiber reinforced polymer (CFRP) composite. The resin content of these interleaved CNT sheets, as well as ply stacking location were varied to determine the effects on the electrical, thermal, and mechanical performance of the composites. The direct-current electrical conductivity of the hybrid CNT composites was characterized by in-line and Montgomery four-probe methods. For [0](sub 20) laminates containing a single layer of CNT sheet between each ply of IM7/8552, in-plane electrical conductivity of the hybrid laminate increased significantly, while in-plane thermal conductivity increased only slightly in comparison to the control IM7/8552 laminates. Photo-microscopy and short beam shear (SBS) strength tests were used to characterize the consolidation quality of the fabricated laminates. Hybrid panels fabricated without any pretreatment of the CNT sheets resulted in a SBS strength reduction of 70 percent. Aligning the tubes and pre-infusing the CNT sheets with resin significantly improved the SBS strength of the hybrid composite To determine the cause of this performance reduction, Mode I and Mode II fracture toughness of the CNT sheet to CFRP interface was characterized by double cantilever beam (DCB) and end notch flexure (ENF) testing, respectively. Results are compared to the

  5. Patterning square and rectangular arrays using shear-aligned block copolymer thin films

    NASA Astrophysics Data System (ADS)

    Kim, So Youn; Davis, Raleigh L.; Register, Richard A.; Gwyther, Jessica; Nunns, Adam; Manners, Ian; Chaikin, Paul M.

    2014-03-01

    Microphase separation of block copolymers in thin films can generate periodic structures: hexagonally packed arrays of dots from spherical or cylindrical phase block copolymers, or periodic stripes from cylindrical or lamellar phase block copolymers. Square or rectangular patterns, however, do not naturally form by spontaneous self-assembly of a simple diblock copolymer, and are a challenge to create. We present a simple way to create nano-square/rectangular arrays by building up a double-layer film of a cylinder-forming diblock, where each layer is sequentially deposited, shear-aligned independently, and cross-linked. Any block copolymer with at least one crosslinkable block can in principle be employed; in this study we use cylinder-forming polystyrene-b-poly(ferrocenylisopropylmethylsilane) and polystyrene-b-poly(hexylmethacrylate). The pitch of the array is tunable by varying polymer molecular weight. Oxygen reactive ion etching is used to reveal the grid structures, and these grids can in turn form nano-wells in the silicon substrate when the cylinder-forming block is very etch-resistant under the conditions used for silicon etching. Additionally, metal dots ordered in square arrays can be created using these grids as templates, via metal evaporation and lift-off.

  6. Time limit for the efficient coupling of relativistic femtosecond laser pulses into aligned nanowire arrays

    NASA Astrophysics Data System (ADS)

    Hollinger, R.; Bargsten, C.; Shlyaptsev, V.; Keiss, D.; Townsend, A.; Rockwood, A.; Wang, Y.; Wang, S.; Rocca, J. J.; Pukhov, A.; Kaymak, V.; London, R.; Tommasini, R.

    2015-11-01

    Recent experiments at Colorado State University have demonstrated volumetric heating of near solid density plasmas to multi-keV temperatures by intense high contrast femtosecond laser irradiation of vertically aligned nanostructures. A key parameter is the time for the heated nanowires to expand and fill the inter-wire gaps with a super-critical density plasma. After this time the laser light can no longer penetrate deep into the array, effectively terminating volumetric heating. We have gained information on the gap closure time for arrays with different wire spacing by monitoring the intensity of He-like lines from arrays of nickel nanowires while varying the laser pulse width from 50 fs to 250 fs. Experiments conducted at constant laser energy show that He-like α line emission from arrays of 80 nm diameter nanowires separated by 205 nm is observed for pulse widths of 200 fs. It is possible to find an optimal wire separation to match the pulse width of the driving laser. The results are relevant to scaling the scheme to high energy laser facilities that are characterized by longer pulses. Work supported by the Office of Fusion Energy Science of the US Dept of Energy, and the DTRA. A.P was supported by DFG project TR18, and R.L. and R.T. by LLNL Contract No. DE-AC52-07NA27344.

  7. Investigation of anisotropic reflectance from densified arrays of vertically aligned carbon nanotube forests (VACNTs)

    NASA Astrophysics Data System (ADS)

    Rana, Masud; Asyraf, M. R. Mohd; Saleh, T.; Muthalif, Asan G. A.

    2016-08-01

    VACNTs is commonly known as darkest absorber on earth owing to their highly inherent porosity. To reduce this porosity, in this letter, we introduce a simple process to densify VACNTs by soaking into water. Later on, the VACNTs was dried at ambient temperature, which made VACNTs more compacted due to their capillary action. Optical characterization of the densified CNT forest was carried out. It was observed that at a fixed incident angle 70° with P-polarized incident light, densified CNT forest shows enhanced reflectance with anisotropic behavior as compared to bare CNT forest.

  8. Microwave purification of large-area horizontally aligned arrays of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Xie, Xu; Jin, Sung Hun; Wahab, Muhammad A.; Islam, Ahmad E.; Zhang, Chenxi; Du, Frank; Seabron, Eric; Lu, Tianjian; Dunham, Simon N.; Cheong, Hou In; Tu, Yen-Chu; Guo, Zhilin; Chung, Ha Uk; Li, Yuhang; Liu, Yuhao; Lee, Jong-Ho; Song, Jizhou; Huang, Yonggang; Alam, Muhammad A.; Wilson, William L.; Rogers, John A.

    2014-11-01

    Recent progress in the field of single-walled carbon nanotubes (SWNTs) significantly enhances the potential for practical use of this remarkable class of material in advanced electronic and sensor devices. One of the most daunting challenges is in creating large-area, perfectly aligned arrays of purely semiconducting SWNTs (s-SWNTs). Here we introduce a simple, scalable, large-area scheme that achieves this goal through microwave irradiation of aligned SWNTs grown on quartz substrates. Microstrip dipole antennas of low work-function metals concentrate the microwaves and selectively couple them into only the metallic SWNTs (m-SWNTs). The result allows for complete removal of all m-SWNTs, as revealed through systematic experimental and computational studies of the process. As one demonstration of the effectiveness, implementing this method on large arrays consisting of ~20,000 SWNTs completely removes all of the m-SWNTs (~7,000) to yield a purity of s-SWNTs that corresponds, quantitatively, to at least to 99.9925% and likely significantly higher.

  9. Microwave purification of large-area horizontally aligned arrays of single-walled carbon nanotubes.

    PubMed

    Xie, Xu; Jin, Sung Hun; Wahab, Muhammad A; Islam, Ahmad E; Zhang, Chenxi; Du, Frank; Seabron, Eric; Lu, Tianjian; Dunham, Simon N; Cheong, Hou In; Tu, Yen-Chu; Guo, Zhilin; Chung, Ha Uk; Li, Yuhang; Liu, Yuhao; Lee, Jong-Ho; Song, Jizhou; Huang, Yonggang; Alam, Muhammad A; Wilson, William L; Rogers, John A

    2014-01-01

    Recent progress in the field of single-walled carbon nanotubes (SWNTs) significantly enhances the potential for practical use of this remarkable class of material in advanced electronic and sensor devices. One of the most daunting challenges is in creating large-area, perfectly aligned arrays of purely semiconducting SWNTs (s-SWNTs). Here we introduce a simple, scalable, large-area scheme that achieves this goal through microwave irradiation of aligned SWNTs grown on quartz substrates. Microstrip dipole antennas of low work-function metals concentrate the microwaves and selectively couple them into only the metallic SWNTs (m-SWNTs). The result allows for complete removal of all m-SWNTs, as revealed through systematic experimental and computational studies of the process. As one demonstration of the effectiveness, implementing this method on large arrays consisting of ~20,000 SWNTs completely removes all of the m-SWNTs (~7,000) to yield a purity of s-SWNTs that corresponds, quantitatively, to at least to 99.9925% and likely significantly higher. PMID:25387684

  10. On the rate dependence of mechanical properties of aligned carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Lu, Y. C.; Zhang, Q.; Dai, L.; Baur, J.

    2015-08-01

    Aligned carbon nanotube arrays are a new form of carbon nanomaterials that have received great interest due to their superior structure and properties. The present work comprehensively examines the rate-dependent mechanical deformation of the vertically aligned carbon nanotube arrays (VA-CNTs) by the use of indentation tests. The small-displacement, elastic property of the VA-CNTs was measured by a spherical indenter. The effective indentation strain rate was varied by adjusting the indenter unloading rate. The instantaneous modulus of the VA-CNTs has been calculated and is found to increase linearly with indentation strain rate. The large-displacement, plastic property of the VA-CNTs was measured by a cylindrical, flat-ended indenter. At large indentation depths, the stress-strain curve of the VA-CNTs reveals distinct plastic deformation. The indentation strain rate was varied by directly changing the indenter velocity. The yield strength ( σ y) of the VA-CNTs also increases linearly with respect to indentation strain rate.

  11. Spray-coating route for highly aligned and large-scale arrays of nanowires.

    PubMed

    Assad, Ossama; Leshansky, Alexander M; Wang, Bin; Stelzner, Thomas; Christiansen, Silke; Haick, Hossam

    2012-06-26

    Technological implementation of nanowires (NWs) requires these components to be organized with controlled orientation and density on various substrates. Here, we report on a simple and efficient route for the deposition of highly ordered and highly aligned NW arrays on a wide range of receiver substrates, including silicon, glass, metals, and flexible plastics with controlled density. The deposition approach is based on spray-coating of a NW suspension under controlled conditions of the nozzle flow rate, droplet size of the sprayed NWs suspension, spray angle, and the temperature of the receiver substrate. The dynamics of droplet generation is understood by a combined action of shear forces and capillary forces. Provided that the size of the generated droplet is comparable to the length of the single NW, the shear-driven elongation of the droplets results presumably in the alignment of the confined NW in the spraying direction. Flattening the droplets upon their impact with the substrate yields fast immobilization of the spray-aligned NWs on the surface due to van der Waals attraction. The availability of the spray-coating technique in the current microelectronics technology would ensure immediate implementation in production lines, with minimal changes in the fabrication design and/or auxiliary tools used for this purpose. PMID:22554272

  12. Nanoscale thermocapillarity enabled purification for horizontally aligned arrays of single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Jin, Sung Hun; Dunham, Simon; Xie, Xu; Rogers, John A.

    2015-09-01

    Among the remarkable variety of semiconducting nanomaterials that have been discovered over the past two decades, single-walled carbon nanotubes remain uniquely well suited for applications in high-performance electronics, sensors and other technologies. The most advanced opportunities demand the ability to form perfectly aligned, horizontal arrays of purely semiconducting, chemically pristine carbon nanotubes. Here, we present strategies that offer this capability. Nanoscale thermos-capillary flows in thin-film organic coatings followed by reactive ion etching serve as highly efficient means for selectively removing metallic carbon nanotubes from electronically heterogeneous aligned arrays grown on quartz substrates. The low temperatures and unusual physics associated with this process enable robust, scalable operation, with clear potential for practical use. Especially for the purpose of selective joule heating over only metallic nanotubes, two representative platforms are proposed and confirmed. One is achieved by selective joule heating associated with thin film transistors with partial gate structure. The other is based on a simple, scalable, large-area scheme through microwave irradiation by using micro-strip dipole antennas of low work-function metals. In this study, based on purified semiconducting SWNTs, we demonstrated field effect transistors with mobility (> 1,000 cm2/Vsec) and on/off switching ratio (~10,000) with current outputs in the milliamp range. Furthermore, as one demonstration of the effectiveness over large area-scalability and simplicity, implementing the micro-wave based purification, on large arrays consisting of ~20,000 SWNTs completely removes all of the m-SWNTs (~7,000) to yield a purity of s-SWNTs that corresponds, quantitatively, to at least to 99.9925% and likely significantly higher.

  13. Design and fabrication of microlens and spatial filter array by self-alignment

    NASA Astrophysics Data System (ADS)

    Yang, Ren; Chan, Kin Foong; Feng, Zhiqiang; Mei, Wenhui

    2003-01-01

    For typically small volume production of MEMS, MOEMS, fine feature PCB, high density chip packaging and display panels, especially for lab tests, low cost and the capability to change the original design easily and quickly are very important for customers and researchers. BALL Semiconductor Inc.'s Maskless Lithography Systems (MLS) feature the Digital Mirror Device (DMD) as the pattern generator to replace photo-masks. This can remove masks from UV lithography, and dramatically reduce the running cost and save time for lab tests and small volume production. At Ball Semiconductor Inc, 1.5μm line/space, 10μm line/space, and 20μm line/space Maskless Lithography Systems were developed. In our MLS, an 848×600 microlens and spatial filter array (MLSFA) was used to focus the light and to filter the noise. In order to produce smaller line-space than 16μm the MLSFA was used to get smaller UV light pad (compared with the SVGA DMD"s micro-mirror: 17μm×17μm) and to filter the noise produced from the DMD, optical lens system, and micro lens array. This MLSFA is one of the key devices for our Maskless Lithography System, and determines the resolution and quality of maskless lithography. A novel design and fabrication process of a single-package MLSFA for our Maskless Lithography System will be introduced. To avoid problems produced by misalignment between a two-piece spatial filter and microlens array, MEMS processing is used to integrate the microlens array with the spatial filter array. In this paper, the self-alignment method used to fabricate exactly matched MLSFA will be presented.

  14. Fabrication of free-standing aligned multiwalled carbon nanotube array for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Bulusheva, L. G.; Arkhipov, V. E.; Fedorovskaya, E. O.; Zhang, Su; Kurenya, A. G.; Kanygin, M. A.; Asanov, I. P.; Tsygankova, A. R.; Chen, Xiaohong; Song, Huaihe; Okotrub, A. V.

    2016-04-01

    We show that a high-temperature CCl4 vapor treatment of vertically aligned multiwalled carbon nanotubes (VA-MWCNTs) grown on silicon substrate allows carefully detach the array from the substrate. Moreover, this procedure partially purifies the VA-MWCNTs from the residual iron catalyst. To improve electrical connectivity of free-standing VA-MWCNTs in an electrochemical cell, the array was placed between the layers of Ni foam. Such assembly demonstrated the better performance in Li-battery as compared to the disordered MWCNTs. After 50 cycles, the specific capacity of VA-MWCNT array synthesized from 0.5 wt% ferrocene solution in toluene was 350 mAh g-1 at a current density of 0.1 A g-1, while the battery with the disordered MWCNTs achieved 197 mAh g-1 only. By the results of electrochemical impedance spectroscopy, the higher capacity of VA-MWCNTs was attributed to larger surface area available for electrolyte and Li ions due to the absence of binder coating.

  15. One-step catalytic growth of carbon nanofiber arrays vertically aligned on carbon substrate

    SciTech Connect

    Li, Xun; State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 ; Xu, Zheng

    2012-06-15

    Highlights: ► Acetylene as carbon resource and copper foil as catalyst. ► Three carbon nanostructures are synthesized by modulating feeding gas compositions. ► NH{sub 3} is a key factor in the growth of VA-CNF arrays. -- Abstract: Vertically aligned carbon nanofiber (VA-CNF) arrays on carbon substrate have been synthesized via one-step chemical vapor deposition process on copper foil, by using acetylene as carbon resource. Three types of carbon nanostructures, viz. bare carbon films, CNFs and VA-CNFs grown on carbon substrate, could be selectively synthesized by only modulating the concentration of C{sub 2}H{sub 2} and NH{sub 3} in the feeding gases. It was found that NH{sub 3} was a key factor in the growth of VA-CNF arrays, which could increase the diffusion capability of copper atoms in carbon materials, therefore promote forming larger spherical Cu NPs catalysts for the growth of VA-CNFs. Furthermore, a growth mechanism in different feeding gas compositions was proposed.

  16. Ultralight anisotropic foams from layered aligned carbon nanotube sheets.

    PubMed

    Faraji, Shaghayegh; Stano, Kelly L; Yildiz, Ozkan; Li, Ang; Zhu, Yuntian; Bradford, Philip D

    2015-10-28

    In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm(-3), the foam structure is over 500 times less dense than bulk graphite. Microscopy revealed that PyC coated the junctions among CNTs, and also increased CNT surface roughness. These changes in the morphology explain the transition from inelastic behavior to foam-like recovery of the layered CNT sheet structure. Mechanical and thermal properties of the foams were tuned for different applications through variation of PyC deposition duration while dynamic mechanical analysis showed no change in mechanical properties over a large temperature range. Observation of a large and linear electrical resistance change during compression of the aligned CNT/carbon (ACNT/C) foams makes strain/pressure sensors a relevant application. The foams have high oil absorption capacities, up to 275 times their own weight, which suggests they may be useful in water treatment and oil spill cleanup. Finally, the ACNT/C foam's high porosity, surface area and stability allow for demonstration of the foams as catalyst support structures. PMID:26419855

  17. Collimator of multiple plates with axially aligned identical random arrays of apertures

    NASA Technical Reports Server (NTRS)

    Hoover, R. B.; Underwood, J. H. (Inventor)

    1973-01-01

    A collimator is disclosed for examining the spatial location of distant sources of radiation and for imaging by projection, small, near sources of radiation. The collimator consists of a plurality of plates, all of which are pierced with an identical random array of apertures. The plates are mounted perpendicular to a common axis, with like apertures on consecutive plates axially aligned so as to form radiation channels parallel to the common axis. For near sources, the collimator is interposed between the source and a radiation detector and is translated perpendicular to the common axis so as to project radiation traveling parallel to the common axis incident to the detector. For far sources the collimator is scanned by rotating it in elevation and azimuth with a detector to determine the angular distribution of the radiation from the source.

  18. Carbon nanotube nanoelectrode arrays

    DOEpatents

    Ren, Zhifeng; Lin, Yuehe; Yantasee, Wassana; Liu, Guodong; Lu, Fang; Tu, Yi

    2008-11-18

    The present invention relates to microelectode arrays (MEAs), and more particularly to carbon nanotube nanoelectrode arrays (CNT-NEAs) for chemical and biological sensing, and methods of use. A nanoelectrode array includes a carbon nanotube material comprising an array of substantially linear carbon nanotubes each having a proximal end and a distal end, the proximal end of the carbon nanotubes are attached to a catalyst substrate material so as to form the array with a pre-determined site density, wherein the carbon nanotubes are aligned with respect to one another within the array; an electrically insulating layer on the surface of the carbon nanotube material, whereby the distal end of the carbon nanotubes extend beyond the electrically insulating layer; a second adhesive electrically insulating layer on the surface of the electrically insulating layer, whereby the distal end of the carbon nanotubes extend beyond the second adhesive electrically insulating layer; and a metal wire attached to the catalyst substrate material.

  19. Parallel Aligned Mesopore Arrays in Pyramidal-Shaped Gallium Nitride and Their Photocatalytic Applications.

    PubMed

    Kim, Hee Jun; Park, Joonmo; Ye, Byeong Uk; Yoo, Chul Jong; Lee, Jong-Lam; Ryu, Sang-Wan; Lee, Heon; Choi, Kyoung Jin; Baik, Jeong Min

    2016-07-20

    Parallel aligned mesopore arrays in pyramidal-shaped GaN are fabricated by using an electrochemical anodic etching technique, followed by inductively coupled plasma etching assisted by SiO2 nanosphere lithography, and used as a promising photoelectrode for solar water oxidation. The parallel alignment of the pores of several tens of micrometers scale in length is achieved by the low applied voltage and prepattern guided anodization. The dry etching of single-layer SiO2 nanosphere-coated GaN produces a pyramidal shape of the GaN, making the pores open at both sides and shortening the escape path of evolved gas bubbles produced inside pores during the water oxidation. The absorption spectra show that the light absorption in the UV range is ∼93% and that there is a red shift in the absorption edge by 30 nm, compared with the flat GaN. It also shows a remarkable enhancement in the photocurrent density by 5.3 times, compared with flat GaN. Further enhancement (∼40%) by the deposition of Ni was observed due to the generation of an electric field, which increases the charge separation ratio. PMID:27347685

  20. Self-alignment of silver nanoparticles in highly ordered 2D arrays

    NASA Astrophysics Data System (ADS)

    Rodríguez-León, Ericka; Íñiguez-Palomares, Ramón; Urrutia-Bañuelos, Efraín; Herrera-Urbina, Ronaldo; Tánori, Judith; Maldonado, Amir

    2015-03-01

    We have synthesized silver nanoparticles in the non-polar phase of non-aqueous microemulsions. The nanocrystals have been grown by reducing silver ions in the microemulsion cylindrical micelles formed by the reducing agent (ethylene glycol). By a careful deposit of the microemulsion phase on a substrate, the micelles align in a hexagonal geometry, thus forming a 2D array of parallel strings of individual silver nanoparticles on the substrate. The microemulsions are the ternary system of anionic surfactant, non-polar solvent (isooctane), and solvent polar (ethylene glycol); the size of synthesized nanoparticles is about 7 nm and they are monodisperse. The study of the microstructure was realized by transmission electron microscopy, high-resolution technique transmission electron microscopy (HR-TEM), and Fourier processing using the software Digital Micrograph for the determination of the crystalline structure of the HR-TEM images of the nanocrystals; chemical composition was determined using the energy-dispersive X-ray spectroscopy. Addition technique polarizing light microscopy allowed the observation of the hexagonal phase of the system. This method of synthesis and self-alignment could be useful for the preparation of patterned materials at the nanometer scale.

  1. Self-alignment of silver nanoparticles in highly ordered 2D arrays.

    PubMed

    Rodríguez-León, Ericka; Íñiguez-Palomares, Ramón; Urrutia-Bañuelos, Efraín; Herrera-Urbina, Ronaldo; Tánori, Judith; Maldonado, Amir

    2015-01-01

    We have synthesized silver nanoparticles in the non-polar phase of non-aqueous microemulsions. The nanocrystals have been grown by reducing silver ions in the microemulsion cylindrical micelles formed by the reducing agent (ethylene glycol). By a careful deposit of the microemulsion phase on a substrate, the micelles align in a hexagonal geometry, thus forming a 2D array of parallel strings of individual silver nanoparticles on the substrate. The microemulsions are the ternary system of anionic surfactant, non-polar solvent (isooctane), and solvent polar (ethylene glycol); the size of synthesized nanoparticles is about 7 nm and they are monodisperse. The study of the microstructure was realized by transmission electron microscopy, high-resolution technique transmission electron microscopy (HR-TEM), and Fourier processing using the software Digital Micrograph for the determination of the crystalline structure of the HR-TEM images of the nanocrystals; chemical composition was determined using the energy-dispersive X-ray spectroscopy. Addition technique polarizing light microscopy allowed the observation of the hexagonal phase of the system. This method of synthesis and self-alignment could be useful for the preparation of patterned materials at the nanometer scale. PMID:25883540

  2. A new angle for probing field-aligned irregularities with the Murchison Widefield Array

    NASA Astrophysics Data System (ADS)

    Loi, Shyeh Tjing; Murphy, Tara; Cairns, Iver H.; Trott, Cathryn M.; Hurley-Walker, Natasha; Feng, Lu; Hancock, Paul J.; Kaplan, David L.

    2016-06-01

    Electron density irregularities in the ionosphere are known to be magnetically anisotropic, preferentially elongated along the lines of force. While many studies of their morphology have been undertaken by topside sounding and whistler measurements, it is only recently that detailed regional-scale reconstructions have become possible, enabled by the advent of widefield radio telescopes. Here we present a new approach for visualizing and studying field-aligned irregularities (FAIs), which involves transforming interferometric measurements of total electron content gradients onto a magnetic shell tangent plane. This removes the perspective distortion associated with the oblique viewing angle of the irregularities from the ground, facilitating the decomposition of dynamics along and across magnetic field lines. We apply this transformation to the data set of Loi et al. (2015a), obtained on 15 October 2013 by the Murchison Widefield Array (MWA) radio telescope and displaying prominent FAIs. We study these FAIs in the new reference frame, quantifying field-aligned and field-transverse behavior, examining time and altitude dependencies, and extending the analysis to FAIs on subarray scales. We show that the inclination of the plane can be derived solely from the data and verify that the best fit value is consistent with the known magnetic inclination. The ability of the model to concentrate the fluctuations along a single spatial direction may find practical application to future calibration strategies for widefield interferometry, by providing a compact representation of FAI-induced distortions.

  3. Horizontally aligned single walled carbon nanotube arrays on quartz for electrochemical biosensing

    NASA Astrophysics Data System (ADS)

    Yang, Yuehai; Wang, Xuewen; Li, Wenzhi; He, Jin

    2014-03-01

    We have fabricated and characterized a simple and high performance electrochemical sensor using horizontally aligned single walled carbon nanotube arrays on transparent single crystal quartz substrates grown by chemical vapor deposition. The electrochemical activities of redox probes Fe(CN)63- / 4 - , Ru(NH3) 6 3 + and protein cytochrome c on these pristine SWCNT thin films have been studied. Because the surface coverage of CNTs is extremely low and aligned, the shape of cyclic voltammograms of these molecules in stationary solution is strongly affected by the mass transport rate of molecules and the interactions between molecules and the SWCNT surface. We also studied the electrochemical flow sensing capability of the device for detecting neurotransmitter dopamine at physiological conditions with the presence of Bovine serum albumin. Good sensitivity, fast response, high stability and anti-fouling capability are observed. Therefore, this device shows great potential for sensing applications in complex solution. This work was supported by a start-up fund (J. H.), NSF (CMMI-1334417) and the American Chemical Society under grant PRF #51766-ND10.

  4. Fabrication of Vertically Aligned Carbon Nanotube or Zinc Oxide Nanorod Arrays for Optical Diffraction Gratings.

    PubMed

    Kim, Jeong; Kim, Sun Il; Cho, Seong-Ho; Hwang, Sungwoo; Lee, Young Hee; Hur, Jaehyun

    2015-11-01

    We report on new fabrication methods for a transparent, hierarchical, and patterned electrode comprised of either carbon nanotubes or zinc oxide nanorods. Vertically aligned carbon nanotubes or zinc oxide nanorod arrays were fabricated by either chemical vapor deposition or hydrothermal growth, in combination with photolithography. A transparent conductive graphene layer or zinc oxide seed layer was employed as the transparent electrode. On the patterned surface defined using photoresist, the vertically grown carbon nanotubes or zinc oxides could produce a concentrated electric field under applied DC voltage. This periodic electric field was used to align liquid crystal molecules in localized areas within the optical cell, effectively modulating the refractive index. Depending on the material and morphology of these patterned electrodes, the diffraction efficiency presented different behavior. From this study, we established the relationship between the hierarchical structure of the different electrodes and their efficiency for modulating the refractive index. We believe that this study will pave a new path for future optoelectronic applications. PMID:26726580

  5. Large-scale growth of density-tunable aligned ZnO nanorods arrays on GaN QDs

    NASA Astrophysics Data System (ADS)

    Qi, Zhiqiang; Li, Senlin; Sun, Shichuang; Zhang, Wei; Ye, Wei; Fang, Yanyan; Tian, Yu; Dai, Jiangnan; Chen, Changqing

    2015-10-01

    An effective approach for growing large-scale, uniformly aligned ZnO nanorods arrays is demonstrated. The synthesis uses a GaN quantum dot (QD) template produced by a self-assembled Stranski-Krastanow mode in metal organic chemical vapor deposition, which serves as a nucleation site for ZnO owing to the QD’s high surface free energy. The resultant ZnO nanorods with uniform shape and length align vertically on the template, while their density is easily tunable by adjusting the density of GaN QDs, which can be adjusted by simply varying growth interruption. By controlling the density of ZnO nanorod arrays, their optical performance can also be improved. This approach opens the possibility of combining one-dimensional (1D) with 0D nanostructures for applications in sensor arrays, piezoelectric antenna arrays, optoelectronic devices, and interconnects.

  6. Direct current injection and thermocapillary flow for purification of aligned arrays of single-walled carbon nanotubes

    SciTech Connect

    Xie, Xu; Islam, Ahmad E.; Seabron, Eric; Dunham, Simon N.; Du, Frank; Lin, Jonathan; Wilson, William L.; Rogers, John A.; Wahab, Muhammad A.; Alam, Muhammad A.; Li, Yuhang; Tomic, Bojan; Huang, Jiyuan; Burns, Branden; Song, Jizhou; Huang, Yonggang

    2015-04-07

    Aligned arrays of semiconducting single-walled carbon nanotubes (s-SWNTs) represent ideal configurations for use of this class of material in high performance electronics. Development of means for removing the metallic SWNTs (m-SWNTs) in as-grown arrays represents an essential challenge. Here, we introduce a simple scheme that achieves this type of purification using direct, selective current injection through interdigitated electrodes into the m-SWNTs, to allow their complete removal using processes of thermocapillarity and dry etching. Experiments and numerical simulations establish the fundamental aspects that lead to selectivity in this process, thereby setting design rules for optimization. Single-step purification of arrays that include thousands of SWNTs demonstrates the effectiveness and simplicity of the procedures. The result is a practical route to large-area aligned arrays of purely s-SWNTs with low-cost experimental setups.

  7. Direct current injection and thermocapillary flow for purification of aligned arrays of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Xie, Xu; Wahab, Muhammad A.; Li, Yuhang; Islam, Ahmad E.; Tomic, Bojan; Huang, Jiyuan; Burns, Branden; Seabron, Eric; Dunham, Simon N.; Du, Frank; Lin, Jonathan; Wilson, William L.; Song, Jizhou; Huang, Yonggang; Alam, Muhammad A.; Rogers, John A.

    2015-04-01

    Aligned arrays of semiconducting single-walled carbon nanotubes (s-SWNTs) represent ideal configurations for use of this class of material in high performance electronics. Development of means for removing the metallic SWNTs (m-SWNTs) in as-grown arrays represents an essential challenge. Here, we introduce a simple scheme that achieves this type of purification using direct, selective current injection through interdigitated electrodes into the m-SWNTs, to allow their complete removal using processes of thermocapillarity and dry etching. Experiments and numerical simulations establish the fundamental aspects that lead to selectivity in this process, thereby setting design rules for optimization. Single-step purification of arrays that include thousands of SWNTs demonstrates the effectiveness and simplicity of the procedures. The result is a practical route to large-area aligned arrays of purely s-SWNTs with low-cost experimental setups.

  8. Aligned Single-Crystalline Perovskite Microwire Arrays for High-Performance Flexible Image Sensors with Long-Term Stability.

    PubMed

    Deng, Wei; Zhang, Xiujuan; Huang, Liming; Xu, Xiuzhen; Wang, Liang; Wang, Jincheng; Shang, Qixun; Lee, Shuit-Tong; Jie, Jiansheng

    2016-03-16

    A simple, low-cost blade-coating method is developed for the large-area fabrication of single-crystalline aligned CH3NH3PbI3 microwire (MW) arrays. The solution-coating method is applicable to flexible substrates, enabling the fabrication of MW-array-based photodetectors with excellent long-term stability, flexibility, and bending durability. Integrated devices from such photodetectors demonstrate high performance for high-resolution, flexible image sensors. PMID:26780594

  9. UV Photodetectors using Vertically-aligned GaN n-core/p-shell Arrays

    NASA Astrophysics Data System (ADS)

    Ha, Jong-Yoon; Krylyuk, Sergiy; Paramanik, Dipak; Debnath, Ratan; Davydov, Albert; King, Matthew; Motayed, Abhishek

    2013-03-01

    The fabrication methods of GaN nanostructures, such as vertically aligned core-shell nano- and micro- pillar arrays, are critical for device applications. We have demonstrated dense arrays of vertically-oriented, individual GaN core-shell structures realized by a combination of top-down etching of the n-type pillars and subsequent p-shell epitaxial growth using selective CVD. The patterned samples were then etched in an inductively coupled plasma system to form GaN pillars. Mg-doped p-type GaN shells were then epitaxially grown over the n-GaN pillars in a custom-built horizontal hot-wall halide vapor phase epitaxy (HVPE) reactor. Room-temperature photoluminescence and Raman spectroscopy measurements indicate strain-relaxation in the etched pillars compared to the as-grown GaN film. Complete devices have been fabricated using dielectric planarization Detailed device characterization was correlated with TEM microstructural analysis. IREAP, University of Maryland, College Park, MD 20742

  10. Influence of carbon nanotube (CNT) on the mechanical properties of the polyethylene teraphthalate (PET)/CNT nanocomposite fibers

    NASA Astrophysics Data System (ADS)

    Farooqui, Mohammed Riyazuddin

    Polyethylene teraphthalate (PET) is one of the mostly used polyester for fiber production. It is spun into filament, string or rope and used as a component of composite materials. In order to enhance their strength and broaden their application, PET fibers are blended with carbon nanotubes (CNT) which are known for high strength and stiffness. However, to produce good quality of PET/CNT nanocomposite fibers two major challenges were faced, one to obtain good distribution of CNT and the other to achieve good alignment of CNT along the fiber direction. In the present work, good distribution of CNT in PET matrix was achieved using twin screw melt extrusion process and the CNT alignment was obtained using melt spinning technique. The present study investigated the effect of process parameters on the mechanical properties of two sets of fibers. The first set of fibers is extruded in the form of large diameter fibers in the range of 220 to 700µm. The second set of fibers was melt spun into fine fibers of diameter in the range of 20 to 50 µm. The extruded fibers showed good improvement in their mechanical properties with respect to CNT content in the range of 0.1 to 7.5wt%. The highest improvement of mechanical properties was achieved with 0.1 wt% CNT content. Using this concentration in the nanocomposite fibers, the tensile strength was enhanced by about 90%, compared to pure PET fibers (51MPa). In addition, this composition significantly enhanced the strain at break by about 173 % and toughness by about 285 %. Other CNT concentration showed moderate improvements. The second set of fibers which were melt spun fibers also showed good enhancement in the strength, stiffness and toughness with respect to CNT content in the range of 0.1 to 2.7wt%. The best improvement in the mechanical properties was observed with 0.1 and 0.5wt% CNT. Incorporating 0.1 and 0.5 wt% CNT in spun PET/CNT nanocomposite fibers of 20 µm diameters showed remarkable increment in the modulus by about

  11. In situ fabrication of inorganic nanowire arrays grown from and aligned on metal substrates.

    PubMed

    Zhang, Weixin; Yang, Shihe

    2009-10-20

    The full potential of nanotechnology can be unleashed only when one is able not only to synthesize a rich variety of nanoscale building blocks but also assemble them into various patterns at the supramolecular and supracluster levels. In particular, the application of nanoparticle and nanowire materials often requires their assembly in the form of thin films, preferably on conductive surfaces for electrical addressing, control, and detection. Although a dazzling array of nanostructures has been fabricated by bottom-up approaches, one of the contemporary challenges is to assemble these nanostructures so that they introduce and realize functionalities. An alluring avenue is to simultaneously accomplish both the nanostructure synthesis and assembly on a useful substrate in a parallel fashion, affording the advantages of simplicity, low cost, and high throughput. In this Account, we review our recent work on growing inorganic nanowires (for example, metal sulfides, metal oxides, and so forth) directly from and on metal substrates in arrays without using templates and catalysts. This method of engineering nanowire arrays on metal substrates integrates the nanowire synthesis and assembly into a parallel process, both in time and in space, by exploiting in situ chemistry on the metal substrates. Both gas-phase and solution-phase approaches have been developed to synthesize the aligned nanowires; here, full advantage is taken of interfacial kinetics of restricted diffusion and surface-specific reactions, often accompanied by new interfacial growth mechanisms. The setting of nanowire arrays on metal substrates has allowed exploration of their application potentials in areas such as field electron emission and chemical sensing. The approaches described here are general, and we predict that they will be extended to more inorganic materials, such as metal halides. Moreover, as more control is achieved with synthetic methods, inorganic nanowire arrays should provide unusual

  12. Raman spectroscopic investigation of the confined optical phonon modes in the aligned CdSe nanorod arrays

    NASA Astrophysics Data System (ADS)

    Nobile, Concetta; Carbone, Luigi; Kudera, Stefan; Manna, Liberato; Cingolani, Roberto; Krahne, Roman; Fonoberov, Vladimir A.; Balandin, Alexander A.; Chilla, Gerwin; Kipp, Tobias; Heitmann, Detlef

    2007-03-01

    Nanocrystal rods have emerged as promising nanostructured material for both fundamental studies of nanoscale effects and for optical and electronic device applications. We investigated the optical phonon excitations in laterally aligned CdSe nanocrystal rod arrays using resonant Raman scattering. Electric-field mediated alignment between interdigitated electrodes has been used to prepare the samples. We report Raman experiments that probe the optical lattice vibrations in ordered arrays of CdSe nanorods with respect to the nanorod orientation. The packing of nanorods into dense arrays leads to the suppression of the surface optical phonon modes. In the longitudinal-optical phonon peak we observe a fine structure that depends on the relative orientation of the nanorods with respect to the incident light polarization. Detailed comparison of the experimental data with the first-principle calculations for corresponding nanostructures, which reveal the symmetry of the phonon potentials for the Raman active modes, provides a qualitative explanation of the experimentally observed phonon modes.

  13. Quality assurance of asymmetric jaw alignment using 2D diode array

    SciTech Connect

    Kim, Sun Mo; Yeung, Ivan W. T.; Moseley, Douglas J.

    2013-12-15

    Purpose: A method using a 2D diode array is proposed to measure the junction gap (or overlap) and dose with high precision for routine quality assurance of the asymmetric jaw alignment.Methods: The central axis (CAX) of the radiation field was determined with a 15 × 15 cm{sup 2} photon field at four cardinal collimator angles so that the junction gap (or overlap) can be measured with respect to the CAX. Two abutting fields having a field size of 15 cm (length along the axis parallel to the junction) × 7.5 cm (width along the axis perpendicular to the junction) were used to irradiate the 2D diode array (MapCHECK2) with 100 MU delivered at the photon energy of 6 MV. The collimator was slightly rotated at 15° with respect to the beam central axis to increase the number of diodes effective on the measurement of junction gap. The junction gap and dose measured in high spatial resolution were compared to the conventional methods using an electronic portal imaging device (EPID) and radiochromic film, respectively. In addition, the reproducibility and sensitivity of the proposed method to the measurements of junction gap and dose were investigated.Results: The junction gap (or overlap) and dose measured by MapCHECK2 agreed well to those measured by the conventional methods of EPID and film (the differences ranged from −0.01 to 0 cm and from −1.34% to 0.6% for the gap and dose, respectively). No variation in the repeat measurements of the junction gap was found whereas the measurements of junction dose were found to vary in quite a small range over the days of measurement (0.21%–0.35%). While the sensitivity of the measured junction gap to the actual junction gap applied was the ideal value of 1 cm/cm as expected, the sensitivity of the junction dose to the actual junction gap increased as the junction gap (or overlap) decreased (maximum sensitivity: 201.7%/cm).Conclusions: The initial results suggest that the method is applicable for a comprehensive quality

  14. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties

    NASA Astrophysics Data System (ADS)

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Huang, Jingfeng; Tan, Dunlin; Zhang, Bowei; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2016-05-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ~4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (~60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications.Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability

  15. Low-temperature growth of well-aligned zinc oxide nanorod arrays on silicon substrate and their photocatalytic application

    PubMed Central

    Azam, Ameer; Babkair, Saeed Salem

    2014-01-01

    Well-aligned and single-crystalline zinc oxide (ZnO) nanorod arrays were grown on silicon (Si) substrate using a wet chemical route for the photodegradation of organic dyes. Structural analysis using X-ray diffraction, high-resolution transmission electron microscopy, and selected area electron diffraction confirmed the formation of ZnO nanorods grown preferentially oriented in the (001) direction and with a single phase nature with a wurtzite structure. Field emission scanning electron microscopy and transmission electron microscopy micrographs showed that the length and diameter of the well-aligned rods were about ~350–400 nm and ~80–90 nm, respectively. Raman scattering spectra of ZnO nanorod arrays revealed the characteristic E2 (high) mode that is related to the vibration of oxygen atoms in the wurtzite ZnO. The photodegradation of methylene blue (MB) using ZnO nanorod arrays was performed under ultraviolet light irradiation. The results of photodegradation showed that ZnO nanorod arrays were capable of degrading ~80% of MB within 60 minutes of irradiation, whereas ~92% of degradation was achieved in 120 minutes. Complete degradation of MB was observed after 270 minutes of irradiation time. Owing to enhanced photocatalytic degradation efficiency and low-temperature growth method, prepared ZnO nanorod arrays may open up the possibility for the successful utilization of ZnO nanorod arrays as a future photocatalyst for environmental remediation. PMID:24812511

  16. Time-dependent contact behavior between diamond and a CNT turf

    NASA Astrophysics Data System (ADS)

    Qiu, A.; Fowler, S. P.; Jiao, J.; Kiener, D.; Bahr, D. F.

    2011-07-01

    The elastic and adhesive properties of nominally vertically aligned carbon nanotube (CNT) turfs have been measured using nanoindentation. The perceived stiffness of a CNT turf is dependent on the unloading rate, which decreases at slower unloading rates. Depth-controlled nanoindentation was used to examine adhesion effects. Adhesive loads between the turf and the probe tip increased as the time the tip is in contact with the turf increased. As these effects could be from either more tubes coming into contact with the tip due to relaxation and motion of CNTs relative to one another or each tube in contact increasing its adhesive behavior and sub-contact stiffness due to tube-tube interactions within the turf, electrical resistance measurements during nanoindentation were carried out. When the tip is held at a fixed nominal depth, the current remains constant while the contact load decreases, suggesting the number of tubes in contact with the tip stays constant with time while the relaxation mechanisms in the turf occur at positions lower than the contact surface. These observations, in conjunction with in situ TEM compression test of CNT arrays, are used to describe the relative effects the various length and time scales may have on the perceived properties measured during experiments, including elastic modulus and adhesion for gecko-like dry adhesives.

  17. High-yield growth of vertically aligned carbon nanotubes on a continuously moving substrate.

    PubMed

    Guzmán de Villoria, R; Figueredo, S L; Hart, A J; Steiner, S A; Slocum, A H; Wardle, B L

    2009-10-01

    Vertically aligned carbon nanotube (CNT) arrays are grown on a moving substrate, demonstrating continuous growth of nanoscale materials with long-range order. A cold-wall chamber with an oscillating moving platform is used to locally heat a silicon growth substrate coated with an Fe/Al2O3 catalyst film for CNT growth via chemical vapor deposition. The reactant gases are introduced over the substrate through a directed nozzle to attain high-yield CNT growth. Aligned multi-wall carbon nanotube arrays (or 'forests') with heights of approximately 1 mm are achieved at substrate speeds up to 2.4 mm s(-1). Arrays grown on moving substrates at different velocities are studied in order to identify potential physical limitations of repeatable and fast growth on a continuous basis. No significant differences are noted between static and moving growth as characterized by scanning electron microscopy and Raman spectroscopy, although overall growth height is marginally reduced at the highest substrate velocity. CNT arrays produced on moving substrates are also found to be comparable to those produced through well-characterized batch processes consistent with a base-growth mechanism. Growth parameters required for the moving furnace are found to differ only slightly from those used in a comparable batch process; thermal uniformity appears to be the critical parameter for achieving large-area uniform array growth. If the continuous-growth technology is combined with a reaction zone isolation scheme common in other types of processing (e.g., in the manufacture of carbon fibers), large-scale dense and aligned CNT arrays may be efficiently grown and harvested for numerous applications including providing interlayers for advanced composite reinforcement and improved electrical and thermal transport. PMID:19752503

  18. Quasi-ballistic carbon nanotube array transistors with current density exceeding Si and GaAs

    PubMed Central

    Brady, Gerald J.; Way, Austin J.; Safron, Nathaniel S.; Evensen, Harold T.; Gopalan, Padma; Arnold, Michael S.

    2016-01-01

    Carbon nanotubes (CNTs) are tantalizing candidates for semiconductor electronics because of their exceptional charge transport properties and one-dimensional electrostatics. Ballistic transport approaching the quantum conductance limit of 2G0 = 4e2/h has been achieved in field-effect transistors (FETs) containing one CNT. However, constraints in CNT sorting, processing, alignment, and contacts give rise to nonidealities when CNTs are implemented in densely packed parallel arrays such as those needed for technology, resulting in a conductance per CNT far from 2G0. The consequence has been that, whereas CNTs are ultimately expected to yield FETs that are more conductive than conventional semiconductors, CNTs, instead, have underperformed channel materials, such as Si, by sixfold or more. We report quasi-ballistic CNT array FETs at a density of 47 CNTs μm−1, fabricated through a combination of CNT purification, solution-based assembly, and CNT treatment. The conductance is as high as 0.46 G0 per CNT. In parallel, the conductance of the arrays reaches 1.7 mS μm−1, which is seven times higher than the previous state-of-the-art CNT array FETs made by other methods. The saturated on-state current density is as high as 900 μA μm−1 and is similar to or exceeds that of Si FETs when compared at and equivalent gate oxide thickness and at the same off-state current density. The on-state current density exceeds that of GaAs FETs as well. This breakthrough in CNT array performance is a critical advance toward the exploitation of CNTs in logic, high-speed communications, and other semiconductor electronics technologies. PMID:27617293

  19. Quasi-ballistic carbon nanotube array transistors with current density exceeding Si and GaAs.

    PubMed

    Brady, Gerald J; Way, Austin J; Safron, Nathaniel S; Evensen, Harold T; Gopalan, Padma; Arnold, Michael S

    2016-09-01

    Carbon nanotubes (CNTs) are tantalizing candidates for semiconductor electronics because of their exceptional charge transport properties and one-dimensional electrostatics. Ballistic transport approaching the quantum conductance limit of 2G 0 = 4e (2)/h has been achieved in field-effect transistors (FETs) containing one CNT. However, constraints in CNT sorting, processing, alignment, and contacts give rise to nonidealities when CNTs are implemented in densely packed parallel arrays such as those needed for technology, resulting in a conductance per CNT far from 2G 0. The consequence has been that, whereas CNTs are ultimately expected to yield FETs that are more conductive than conventional semiconductors, CNTs, instead, have underperformed channel materials, such as Si, by sixfold or more. We report quasi-ballistic CNT array FETs at a density of 47 CNTs μm(-1), fabricated through a combination of CNT purification, solution-based assembly, and CNT treatment. The conductance is as high as 0.46 G 0 per CNT. In parallel, the conductance of the arrays reaches 1.7 mS μm(-1), which is seven times higher than the previous state-of-the-art CNT array FETs made by other methods. The saturated on-state current density is as high as 900 μA μm(-1) and is similar to or exceeds that of Si FETs when compared at and equivalent gate oxide thickness and at the same off-state current density. The on-state current density exceeds that of GaAs FETs as well. This breakthrough in CNT array performance is a critical advance toward the exploitation of CNTs in logic, high-speed communications, and other semiconductor electronics technologies. PMID:27617293

  20. Nanofabrication of arrays of silicon field emitters with vertical silicon nanowire current limiters and self-aligned gates

    NASA Astrophysics Data System (ADS)

    Guerrera, S. A.; Akinwande, A. I.

    2016-07-01

    We developed a fabrication process for embedding a dense array (108 cm‑2) of high-aspect-ratio silicon nanowires (200 nm diameter and 10 μm tall) in a dielectric matrix and then structured/exposed the tips of the nanowires to form self-aligned gate field emitter arrays using chemical mechanical polishing (CMP). Using this structure, we demonstrated a high current density (100 A cm‑2), uniform, and long lifetime (>100 h) silicon field emitter array architecture in which the current emitted by each tip is regulated by the silicon nanowire current limiter connected in series with the tip. Using the current voltage characteristics and with the aid of numerical device models, we estimated the tip radius of our field emission arrays to be ≈4.8 nm, as consistent with the tip radius measured using a scanning electron microscope (SEM).

  1. Nanofabrication of arrays of silicon field emitters with vertical silicon nanowire current limiters and self-aligned gates.

    PubMed

    Guerrera, S A; Akinwande, A I

    2016-07-22

    We developed a fabrication process for embedding a dense array (10(8) cm(-2)) of high-aspect-ratio silicon nanowires (200 nm diameter and 10 μm tall) in a dielectric matrix and then structured/exposed the tips of the nanowires to form self-aligned gate field emitter arrays using chemical mechanical polishing (CMP). Using this structure, we demonstrated a high current density (100 A cm(-2)), uniform, and long lifetime (>100 h) silicon field emitter array architecture in which the current emitted by each tip is regulated by the silicon nanowire current limiter connected in series with the tip. Using the current voltage characteristics and with the aid of numerical device models, we estimated the tip radius of our field emission arrays to be ≈4.8 nm, as consistent with the tip radius measured using a scanning electron microscope (SEM). PMID:27292120

  2. On-chip polarized light emitters based on (6,5) chirality-sorted carbon nanotube aligned arrays

    NASA Astrophysics Data System (ADS)

    Ma, Ze; Liang, Shuang; Liu, Yang; Wang, Fanglin; Wang, Sheng; Peng, Lian-Mao

    2016-02-01

    Electrically driven light-emitters based on carbon nanotubes are highly promising candidates for on-chip optical interconnection and nanophotonics. Here, we fabricated on-chip polarized light-emitters based on (6,5) chirality-sorted carbon nanotube aligned arrays obtained via an evaporation-induced self-assembly method. Electroluminescence results shows an impact excitation dominant mechanism originated from (6,5) defect-brightened dark exciton emission and trion emission. The degree of polarization of the carbon nanotube aligned arrays is characterized quantitatively and the average value is ˜76.8%. The importance of parallelism and orientation of nanotubes when integrated with on-chip waveguides is also discussed.

  3. Determination of the effective Young's modulus of vertically aligned carbon nanotube arrays: a simple nanotube-based varactor

    NASA Astrophysics Data System (ADS)

    Olofsson, Niklas; Ek-Weis, Johan; Eriksson, Anders; Idda, Tonio; Campbell, Eleanor E. B.

    2009-09-01

    The electromechanical properties of arrays of vertically aligned multiwalled carbon nanotubes were studied in a parallel plate capacitor geometry. The electrostatic actuation was visualized using both optical microscopy and scanning electron microscopy, and highly reproducible behaviour was achieved for actuation voltages below the pull-in voltage. The walls of vertically aligned carbon nanotubes behave as solid cohesive units. The effective Young's modulus for the carbon nanotube arrays was determined by comparing the actuation results with the results of electrostatic simulations and was found to be exceptionally low, of the order of 1-10 MPa. The capacitance change and Q-factor were determined by measuring the frequency dependence of the radio-frequency transmission. Capacitance changes of over 20% and Q-factors in the range 100-10 were achieved for a frequency range of 0.2-1.5 GHz.

  4. Vertically Well-Aligned ZnO Nanowire Arrays Directly Synthesized from Zn Vapor Deposition Without Catalyst

    NASA Astrophysics Data System (ADS)

    Van Khai, Tran; Van Thu, Le; Huu, Nguyen The; Lam, Tran Dai

    2016-05-01

    Vertically well-aligned ZnO nanowire (NW) arrays with high density have been successfully synthesized on sapphire substrate by thermal evaporation of the zinc powders without catalysts or additives. The ZnO NWs were characterized by scanning electron microscopy, transmission electronic microscopy (TEM), x-ray diffraction, ultraviolet-visible, photoluminescence, Raman, and x-ray photoelectron spectroscopy. The results showed that the obtained ZnO NWs had diameters in the range of 100-130 nm, lengths over several micrometers and well aligned in the direction perpendicular to the substrate surface. The as-synthesized ZnO NWs, which were single crystalline in a hexagonal structure, showed uniform morphology, faceted planes at the tips of the NWs, and grown along the [001] direction. The as-synthesized NW arrays had a good crystal quality with excellent optical properties, showing a sharp and strong ultraviolet emission at 380 nm and a weak visible emission at around 500 nm.

  5. Low-Cost, Large-Area, Facile, and Rapid Fabrication of Aligned ZnO Nanowire Device Arrays.

    PubMed

    Cadafalch Gazquez, Gerard; Lei, Sidong; George, Antony; Gullapalli, Hemtej; Boukamp, Bernard A; Ajayan, Pulickel M; Ten Elshof, Johan E

    2016-06-01

    Well aligned nanowires of ZnO have been made with an electrospinning technique using zinc acetate precursor solutions. Employment of two connected parallel collector plates with a separating gap of 4 cm resulted in a very high degree of nanowire alignment. By adjusting the process parameters, the deposition density of the wires could be controlled. Field effect transistors were prepared by depositing wires between two gold electrodes on top of a heavily doped Si substrate covered with a 300 nm oxide layer. These devices showed good FET characteristics and photosensitivity under UV-illumination. The method provides a fast and scalable fabrication route for functional nanowire arrays with a high degree of alignment and control over nanowire spacing. PMID:27173007

  6. Dense arrays of highly aligned graphene nanoribbons produced by substrate-controlled metal-assisted etching of graphene.

    PubMed

    Solís-Fernández, Pablo; Yoshida, Kazuma; Ogawa, Yui; Tsuji, Masaharu; Ago, Hiroki

    2013-12-01

    Dense arrays of aligned graphene nanoribbons (GNRs) are fabricated by substrate-controlled etching of large-area single-layer graphene. An adequate choice of etching substrate and catalyst deposition method allows densities up to 25 nanoribbons μm(-1) to be obtained with average widths of 19 nm. The efficacy of the method is evidenced by the high on/off ratios of back-gated transistors made with these GNRs, which can go up to 5000. PMID:24030892

  7. Controlled Deposition and Alignment of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Smits, Jan M. (Inventor); Wincheski, Russell A. (Inventor); Ingram, JoAnne L. (Inventor); Watkins, Anthony Neal (Inventor); Jordan, Jeffrey D. (Inventor)

    2009-01-01

    A carbon nanotube (CNT) attraction material is deposited on a substrate in the gap region between two electrodes on the . substrate. An electric potential is applied to the two electrodes. The CNT attraction material is wetted with a solution defined by a carver liquid having carbon nanotubes (CNTs) suspended therein. A portion of the CNTs align with the electric field and adhere to The CNT attraction material. The carrier liquid and any CNTs not adhered to the CNT attraction material are then removed.

  8. Controlled Deposition and Alignment of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Smits, Jan M. (Inventor); Wincheski, Russell A. (Inventor); Patry, JoAnne L. (Inventor); Watkins, Anthony Neal (Inventor); Jordan, Jeffrey D. (Inventor)

    2012-01-01

    A carbon nanotube (CNT) attraction material is deposited on a substrate in the gap region between two electrodes on the substrate. An electric potential is applied to the two electrodes. The CNT attraction material is wetted with a solution defined by a carrier liquid having carbon nanotubes (CNTs) suspended therein. A portion of the CNTs align with the electric field and adhere to the CNT attraction material. The carrier liquid and any CNTs not adhered to the CNT attraction material are then removed.

  9. Ultra-violet Sensing Characteristic and Field Emission Properties of Vertically Aligned Aluminum Doped Zinc Oxide Nanorod Arrays

    SciTech Connect

    Mamat, M. H.; Malek, M. F.; Musa, M. Z.; Khusaimi, Z.; Rusop, M.

    2011-05-25

    Ultra-violet (UV) sensing behavior and field emission characteristic have been investigated on vertically aligned aluminum (Al) doped zinc oxide (ZnO) nanorod arrays prepared using sol-gel immersion method. Uniform and high coverage density of ZnO nanorod arrays have been successfully deposited on seeded-catalyst coated substrates. The synthesized nanorods have diameter sizes between 50 nm to 150 nm. The XRD spectra show Al doped ZnO nanorod array has high crystallinity properties with the dominancy of crystal growth along (002) plane or c-axis. UV photoresponse measurement indicates that Al doped ZnO nanorod array sensitively detects UV light as shown by conductance increment after UV illumination exposure. The nanorod array shows good field emission properties with low turn on field and threshold field at 2.1 V/{mu}m and 5.6 V/{mu}m, respectively. The result suggested that Al doped ZnO nanorod arrays prepared by low-cost sol-gel immersion method show promising result towards fabrication of multi applications especially in UV photoconductive sensor and field emission displays.

  10. The Alignment System for a Medium-Sized Schwarzschild-Couder Telescope Prototype for the Cherenkov Telescope Array

    NASA Astrophysics Data System (ADS)

    Ribeiro, Deivid; Humensky, Brian; Nieto, Daniel; V Vassiliev Group in UCLA division of Astronomy and Astrophysics, P Kaaret Group at Iowa University Department of Physics and Astronomy, CTA Consortium

    2016-01-01

    The Cherenkov Telescope Array (CTA) is an international project for a next-generation ground-based gamma-ray observatory. CTA, conceived as an array of tens of imaging atmospheric Cherenkov telescopes, comprising small, medium and large-size telescopes, is aiming to improve on the sensitivity of current-generation experiments by an order of magnitude and provide energy coverage from 20 GeV to more than 300 TeV. The Schwarzschild-Couder design is a candidate 9-m diameter medium-sized telescope featuring a novel aplanatic two-mirror optical design capable of a wide field of view with significantly improved imaging resolution as compared to the traditional Davies-Cotton optical design. Achieving this imaging resolution imposes strict mirror alignment requirements that necessitate a sophisticated alignment system. This system uses a collection of position sensors between panels to determine the relative position of adjacent panels; each panel is mounted on a Stewart platform to allow motion control with six degrees of freedom, facilitating the alignment of the optical surface for the segmented primary and secondary mirrors. Alignments of the primary and secondary mirrors and the camera focal plane with respect to each other are performed utilizing a set of CCD cameras which image LEDs placed on the mirror panels to measure relative translation, and custom-built auto-collimators to measure relative tilt between the primary and secondary mirrors along the optical axis of the telescope. In this contribution we present the status of the development of the SC optical alignment system, soon to be materialized in a full-scale prototype SC medium-size telescope (pSCT) at the Fred Lawrence Whipple Observatory in southern Arizona.

  11. Advanced materials based on carbon nanotube arrays, yarns and papers

    NASA Astrophysics Data System (ADS)

    Bradford, Phlip David

    Carbon nanotubes have hundreds of potential applications but require innovative processing techniques to manipulate the microscopic carbon dust into useful devices and products. This thesis describes efforts to process carbon nanotubes (CNTs) using novel methods with the goals of: (1) improving the properties of energy absorbing and composite carbon nanotube materials and (2) increasing understanding of fundamental structure-property relationships within these materials. Millimeter long CNTs, in the form of arrays, yarns and papers, were used to produce energy absorbing foams and high volume fraction CNT composites. Vertically aligned CNT arrays were grown on silicon substrates using chemical vapor deposition (CVD) of ethylene gas over iron nano-particles. The low density, millimeter thick arrays were tested under compression as energy absorbing foams. With additional CVD processing steps, it was possible to tune the compressive properties of the arrays. After the longest treatment, the compressive strength of the arrays was increased by a factor of 35 with a density increase of only six fold, while also imparting recovery from compression to the array. Microscopy revealed that the post-synthesis CVD treatment increased the number of CNT walls through an epitaxial type radial growth on the surface of the as-grown tubes. The increase in tube radius and mutual support between nanotubes explained the increases in compressive strength while an increase in nanotube roughness was proposed as the morphological change responsible for recovery in the array. Carbon nanotube yarns were used as the raw material for macroscopic textile preforms with a multi-level hierarchical carbon nanotube (CNT) structure: nanotubes, bundles, spun single yarns, plied yarns and 3-D braids. In prior tensile tests, composites produced from the 3-D braids exhibited unusual mechanical behavior effects. The proposed physical hypotheses explained those effects by molecular level interactions and

  12. Aligned ZnO/CdTe core-shell nanocable arrays on indium tin oxide: synthesis and photoelectrochemical properties.

    PubMed

    Wang, Xina; Zhu, Haojun; Xu, Yeming; Wang, Hao; Tao, Yin; Hark, Suikong; Xiao, Xudong; Li, Quan

    2010-06-22

    Vertically aligned ZnO/CdTe core-shell nanocable arrays-on-indium tin oxide (ITO) are fabricated by electrochemical deposition of CdTe on ZnO nanorod arrays in an electrolyte close to neutral pH. By adjusting the total charge quantity applied during deposition, the CdTe shell thickness can be tuned from several tens to hundreds of nanometers. The CdTe shell, which has a zinc-blende structure, is very dense and uniform both radially and along the axial direction of the nanocables, and forms an intact interface with the wurtzite ZnO nanorod core. The absorption of the CdTe shell above its band gap ( approximately 1.5 eV) and the type II band alignment between the CdTe shell and the ZnO core, respectively, demonstrated by absorption and photoluminescence measurements, make a nanocable array-on-ITO architecture a promising photoelectrode with excellent photovoltaic properties for solar energy applications. A photocurrent density of approximately 5.9 mA/cm(2) has been obtained under visible light illumination of 100 mW cm(-2) with zero bias potential (vs saturated calomel electrode). The neutral electrodeposition method can be generally used for plating CdTe on nanostructures made of different materials, which would be of interest in various applications. PMID:20446665

  13. Scintillating Fiber Array Characterization and Alignment for Neutron Imaging using the High Energy X-ray (HEX) Facility

    SciTech Connect

    Buckles, R. A., Ali, Z. A., Cradick, J. R., Traille, A. J., Warthan, W. A.

    2009-09-04

    The Neutron Imager diagnostic at the National Ignition Facility (NIF) located at Lawrence Livermore National Laboratory (LLNL) will produce high-resolution, gated images of neutron-generating implosions. A similar pinhole imaging experiment (PINEX) diagnostic was recently deployed at the Z facility at Sandia National Laboratories (SNL). Both the SNL and LLNL neutron imagers use similar fiber array scintillators (BCF-99-555). Despite diverse resolution and magnification requirements, both diagnostics put significant onus on the scintillator spatial quality and alignment precision to maintain optimal point spread. Characterization and alignment of the Z-PINEX scintillator and imaging system were done at NSTec/Livermore Operations in 2009, and is currently underway for the NIF Neutron Imager.

  14. Ultralight anisotropic foams from layered aligned carbon nanotube sheets

    NASA Astrophysics Data System (ADS)

    Faraji, Shaghayegh; L. Stano, Kelly; Yildiz, Ozkan; Li, Ang; Zhu, Yuntian; Bradford, Philip D.

    2015-10-01

    In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm-3, the foam structure is over 500 times less dense than bulk graphite. Microscopy revealed that PyC coated the junctions among CNTs, and also increased CNT surface roughness. These changes in the morphology explain the transition from inelastic behavior to foam-like recovery of the layered CNT sheet structure. Mechanical and thermal properties of the foams were tuned for different applications through variation of PyC deposition duration while dynamic mechanical analysis showed no change in mechanical properties over a large temperature range. Observation of a large and linear electrical resistance change during compression of the aligned CNT/carbon (ACNT/C) foams makes strain/pressure sensors a relevant application. The foams have high oil absorption capacities, up to 275 times their own weight, which suggests they may be useful in water treatment and oil spill cleanup. Finally, the ACNT/C foam's high porosity, surface area and stability allow for demonstration of the foams as catalyst support structures.In this work, we present large scale, ultralight aligned carbon nanotube (CNT) structures which have densities an order of magnitude lower than CNT arrays, have tunable properties and exhibit resiliency after compression. By stacking aligned sheets of carbon nanotubes and then infiltrating with a pyrolytic carbon (PyC), resilient foam-like materials were produced that exhibited complete recovery from 90% compressive strain. With density as low as 3.8 mg cm-3, the foam structure is over 500 times less dense than

  15. Phonon processes in vertically aligned silicon nanowire arrays produced by low-cost all-solution galvanic displacement method

    NASA Astrophysics Data System (ADS)

    Banerjee, Debika; Trudeau, Charles; Gerlein, Luis Felipe; Cloutier, Sylvain G.

    2016-03-01

    The nanoscale engineering of silicon can significantly change its bulk optoelectronic properties to make it more favorable for device integration. Phonon process engineering is one way to enhance inter-band transitions in silicon's indirect band structure alignment. This paper demonstrates phonon localization at the tip of silicon nanowires fabricated by galvanic displacement using wet electroless chemical etching of a bulk silicon wafer. High-resolution Raman micro-spectroscopy reveals that such arrayed structures of silicon nanowires display phonon localization behaviors, which could help their integration into the future generations of nano-engineered silicon nanowire-based devices such as photodetectors and solar cells.

  16. Photoelectrochemical Properties of Vertically Aligned CuInS2 Nanorod Arrays Prepared via Template-Assisted Growth and Transfer.

    PubMed

    Yang, Wooseok; Oh, Yunjung; Kim, Jimin; Kim, Hyunchul; Shin, Hyunjung; Moon, Jooho

    2016-01-13

    Although copper-based chalcopyrite materials such as CuInS2 have been considered promising photocathodes for solar water splitting, the fabrication route for a nanostructure with vertical orientation has not yet been developed. Here, a fabrication route for vertically aligned CuInS2 nanorod arrays from an aqueous solution using anodic aluminum oxide template-assisted growth and transfer is presented. The nanorods exhibit a phase-pure CuInS2 chalcopyrite structure and cathodic photocurrent response without co-catalyst loading. Small particles of CdS and ZnS were conformally decorated onto CuInS2 nanorods using a successive ion layer adsorption and reaction method. With surface modification of CdS/ZnS, the photoelectrochemical properties of CuInS2 nanorod arrays are enhanced via flat-band potential shift, as determined by analyses of onset potential and Mott-Schottky plots. PMID:26645722

  17. Preparation of a novel structured catalyst based on aligned carbon nanotube arrays for a microchannel Fischer-Tropsch synthesis reactor

    SciTech Connect

    Chin, Ya-Huei; Hu, Jianli; Cao, Chunshe; Gao, Yufei; Wang, Yong

    2005-12-15

    A novel catalyst microstructure based on aligned multiwall carbon nanotube arrays was synthesized. Its advanced heat and mass transport characteristics coupled with high surface area led to superior performances for Fischer-Tropsch synthesis in a microchannel chemical reactor. The fabrication of such a novel catalyst structure first involved metalorganic chemical vapor deposition (MOCVD) growth of a dense Al2O3 thin film over FeCrAlY foam substrate to enhance adhesion between catalyst layer and metal substrate. Aligned arrays of multiwall carbon nanotubes were grown over the substrate by catalytic decomposition of ethylene. These nanotube bundles were directly attached to the FeCrAlY substrate through a thin layer of oxide thin film. When the outer surfaces of nanobundles were coated with a catalyst layer, a unique hierarchical catalyst structure with nanoporous interstitials between the bundles was created. Thus, engineered catalysts based on such a novel hierarchical structure minimizes mass transfer encountered in the gas-liquid-solid three phase reactions. In addition, high thermal conductivity of carbon nanotube and the direct attachment of these nanobundles to the metal foam allow efficient heat removal from catalytic sites. The advanced heat and mass transfer on this novel structured catalyst was demonstrated in Fischer-Tropsch synthesis in a microchannel fixed bed reactor. The presence of carbon nanotube arrays improved dispersion of active metals and reduced mass transfer limitation, leading to a factor of four enhancement of Fischer-Tropsch synthesis activity. The improved temperature control with the carbon nanotube arrays also allows the Fischer-Tropsch synthesis being operated at temperatures as high as 265 C without reaction runaway favoring methane formation.

  18. Synthesis of Large Arrays of Well-Aligned Carbon Nanotubes on Glass

    SciTech Connect

    Bush, P. Siegal, M.P.; Huang, Z.P.; Provencio, P.N.; Ren, Z.F.; Wang, J.H.; Xu, J.W.

    1998-11-10

    Free-standing aligned carbon nanotubes have previously been grown above 7000C on mesoporous silica embedded with iron nanoparticles. Here, carbon nanotubes aligned over areas up to several square centimeters were grown on nickel-coated glass below 666oC by plasma-enhanced hot filament chemical vapor deposition. Acetylene (C2H2) gas was used as the carbon source and ammonia (NH3) gas was used as a catalyst and dilution gas. Nanotubes with controllable diameters from 20 to 400 nanometers and lengths from 0.1 to 50 micrometers were obtained. Using this method, large panels of aligned carbon nanotubes can be made under conditions that are suitable for device fabrication.

  19. Large-scale fabrication of vertically aligned ZnO nanowire arrays

    DOEpatents

    Wang, Zhong Lin; Hu, Youfan; Zhang, Yan; Xu, Chen; Zhu, Guang

    2014-09-09

    A generator includes a substrate, a first electrode layer, a dense plurality of vertically-aligned piezoelectric elongated nanostructures, an insulating layer and a second electrode layer. The substrate has a top surface and the first electrode layer is disposed on the top surface of the substrate. The dense plurality of vertically-aligned piezoelectric elongated nanostructures extends from the first electrode layer. Each of the nanostructures has a top end. The insulating layer is disposed on the top ends of the nanostructures. The second electrode layer is disposed on the non-conductive layer and is spaced apart from the nanostructures.

  20. Nanoconfinement induced crystal orientation and large piezoelectric coefficient in vertically aligned P(VDF-TrFE) nanotube array

    PubMed Central

    Liew, Weng Heng; Mirshekarloo, Meysam Sharifzadeh; Chen, Shuting; Yao, Kui; Tay, Francis Eng Hock

    2015-01-01

    Vertically aligned piezoelectric P(VDF-TrFE) nanotube array comprising nanotubes embedded in anodized alumina membrane matrix without entanglement has been fabricated. It is found that the crystallographic polar axes of the P(VDF-TrFE) nanotubes are oriented along the nanotubes long axes. Such a desired crystal orientation is due to the kinetic selection mechanism for lamellae growth confined in the nanopores. The preferred crystal orientation in nanotubes leads to huge piezoelectric coefficients of the P(VDF-TrFE). The piezoelectric strain and voltage coefficients of P(VDF-TrFE) nanotube array are observed to be 1.97 and 3.40 times of those for conventional spin coated film. Such a significant performance enhancement is attributed to the well-controlled polarization orientation, the elimination of the substrate constraint, and the low dielectric constant of the nanotube array. The P(VDF-TrFE) nanotube array exhibiting the unique structure and outstanding piezoelectric performance is promising for wide applications, including various electrical devices and electromechanical sensors and transducers. PMID:25966301

  1. Coaxial carbon/metal oxide/aligned carbon nanotube arrays as high-performance anodes for lithium ion batteries.

    PubMed

    Lou, Fengliu; Zhou, Haitao; Tran, Trung Dung; Melandsø Buan, Marthe Emelie; Vullum-Bruer, Fride; Rønning, Magnus; Walmsley, John Charles; Chen, De

    2014-05-01

    Coaxial carbon/metal oxide/aligned carbon nanotube (ACNT) arrays over stainless-steel foil are reported as high-performance binder-free anodes for lithium ion batteries. The coaxial arrays were prepared by growth of ACNTs over stainless-steel foil followed by coating with metal oxide and carbon. The carbon/manganese oxide/ACNT arrays can deliver an initial capacity of 738 mAh g(-1) with 99.9 % capacity retention up to 100 cycles and a capacity of 374 mAh g(-1) at a high current density of 6000 mA g(-1). The external carbon layer was recognized as a key component for high performance, and the mechanism of performance enhancement was investigated by electrochemical impedance spectroscopy, electron microscopy, and X-ray diffraction analysis. The layer increases rate capability by enhancing electrical conductivity and maintaining a low mass-transfer resistance and also improves cyclic stability by avoiding aggregation of metal-oxide particles and stabilizing the solid electrolyte interface. The resultant principle of rational electrode design was applied to an iron oxide-based system, and similar improvements were found. These coaxial nanotube arrays present a promising strategy for the rational design of high-performance binder-free anodes for lithium ion batteries. PMID:24578068

  2. Nanoconfinement induced crystal orientation and large piezoelectric coefficient in vertically aligned P(VDF-TrFE) nanotube array.

    PubMed

    Liew, Weng Heng; Mirshekarloo, Meysam Sharifzadeh; Chen, Shuting; Yao, Kui; Tay, Francis Eng Hock

    2015-01-01

    Vertically aligned piezoelectric P(VDF-TrFE) nanotube array comprising nanotubes embedded in anodized alumina membrane matrix without entanglement has been fabricated. It is found that the crystallographic polar axes of the P(VDF-TrFE) nanotubes are oriented along the nanotubes long axes. Such a desired crystal orientation is due to the kinetic selection mechanism for lamellae growth confined in the nanopores. The preferred crystal orientation in nanotubes leads to huge piezoelectric coefficients of the P(VDF-TrFE). The piezoelectric strain and voltage coefficients of P(VDF-TrFE) nanotube array are observed to be 1.97 and 3.40 times of those for conventional spin coated film. Such a significant performance enhancement is attributed to the well-controlled polarization orientation, the elimination of the substrate constraint, and the low dielectric constant of the nanotube array. The P(VDF-TrFE) nanotube array exhibiting the unique structure and outstanding piezoelectric performance is promising for wide applications, including various electrical devices and electromechanical sensors and transducers. PMID:25966301

  3. Volumetric Heating of Ultra-High Energy Density Relativistic Plasmas by Ultrafast Laser Irradiation of Aligned Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Bargsten, Clayton; Hollinger, Reed; Shlyaptsev, Vyacheslav; Pukhov, Alexander; Keiss, David; Townsend, Amanda; Wang, Yong; Wang, Shoujun; Prieto, Amy; Rocca, Jorge

    2014-10-01

    We have demonstrated the volumetric heating of near-solid density plasmas to keV temperatures by ultra-high contrast femtosecond laser irradiation of arrays of vertically aligned nanowires with an average density up to 30% solid density. X-ray spectra show that irradiation of Ni and Au nanowire arrays with laser pulses of relativistic intensities ionizes plasma volumes several micrometers in depth to the He-like and Co-like (Au 52 +) stages respectively. The penetration depth of the heat into the nanowire array was measured monitoring He-like Co lines from irradiated arrays in which the nanowires are composed of a Co segment buried under a selected length of Ni. The measurement shows the ionization reaches He-like Co for depth of up to 5 μm within the target. This volumetric plasma heating approach creates a new laboratory plasma regime in which extreme plasma parameters can be accessed with table-top lasers. Scaling to higher laser intensities promises to create plasmas with temperatures and pressures approaching those in the center of the sun. Work supported by the U.S Department of Energy, Fusion Energy Sciences and the Defense Threat Reduction Agency grant HDTRA-1-10-1-0079. A.P was supported by of DFG-funded project TR18.

  4. Embedded arrays of vertically aligned carbon nanotube carpets and methods for making them

    DOEpatents

    Kim, Myung Jong; Nicholas, Nolan Walker; Kittrell, W. Carter; Schmidt, Howard K.

    2015-06-30

    According to some embodiments, the present invention provides a system and method for supporting a carbon nanotube array that involve an entangled carbon nanotube mat integral with the array, where the mat is embedded in an embedding material. The embedding material may be depositable on a carbon nanotube. A depositable material may be metallic or nonmetallic. The embedding material may be an adhesive material. The adhesive material may optionally be mixed with a metal powder. The embedding material may be supported by a substrate or self-supportive. The embedding material may be conductive or nonconductive. The system and method provide superior mechanical and, when applicable, electrical, contact between the carbon nanotubes in the array and the embedding material. The optional use of a conductive material for the embedding material provides a mechanism useful for integration of carbon nanotube arrays into electronic devices.

  5. Ruggedized microchannel-cooled laser diode array with self-aligned microlens

    DOEpatents

    Freitas, Barry L.; Skidmore, Jay A.

    2003-11-11

    A microchannel-cooled, optically corrected, laser diode array is fabricated by mounting laser diode bars onto Si surfaces. This approach allows for the highest thermal impedance, in a ruggedized, low-cost assembly that includes passive microlens attachment without the need for lens frames. The microlensed laser diode array is usable in all solid-state laser systems that require efficient, directional, narrow bandwidth, high optical power density pump sources.

  6. 3D RVE models able to capture and quantify the dispersion, agglomeration and orientation state of CNT in CNT/PP nanocomposites

    NASA Astrophysics Data System (ADS)

    Bhuiyan, Md; Pucha, Raghuram; Kalaitzidou, Kyriaki

    2016-02-01

    The focus of this study is to investigate the capabilities of 3D RVE models in predicting the tensile modulus of carbon nanotube polypropylene (CNT/PP) composites which differ slightly in the dispersion, agglomeration and orientation states of CNT within the PP matrix. The composites are made using melt mixing followed by either injection molding or melt spinning of fibers. The dispersion, agglomeration and orientation of CNT within the PP are experimentally altered by using a surfactant and by forcing the molten material to flow through a narrow orifice (melt spinning) that promotes alignment of CNT along the flow/drawing direction. An elaborate image analysis technique is used to quantify the CNT characteristics in terms of probability distribution functions (PDF). The PDF are then introduced to the 3D RVE models which also account for the CNT-PP interfacial interactions. It is concluded that the 3D RVE models can accurately distinguish among the different cases (dispersion, distribution, geometry and alignment of CNT) as the predicted tensile modulus is in good agreement with the experimentally determined one.

  7. Microwave systems analysis, solar power satellite. [alignment of the antenna array

    NASA Technical Reports Server (NTRS)

    1979-01-01

    Various alternative active approaches to achieving aand maintaining flatness for the microwave power transmission system (MPTS) were studied. A baseline active alignment scheme was developed which includes subarray attachment mechanisms, height and tilting adjustments, service corridors, a rotating laser beam reference system, monopulse pointing techniques, and the design of a beam-centering photoconductive sensor.

  8. Surface diffuse discharge mechanism of well-aligned atmospheric pressure microplasma arrays

    NASA Astrophysics Data System (ADS)

    Ren-Wu, Zhou; Ru-Sen, Zhou; Jin-Xing, Zhuang; Jiang-Wei, Li; Mao-Dong, Chen; Xian-Hui, Zhang; Dong-Ping, Liu; Kostya (Ken, Ostrikov; Si-Ze, Yang

    2016-04-01

    A stable and homogeneous well-aligned air microplasma device for application at atmospheric pressure is designed and its electrical and optical characteristics are investigated. Current-voltage measurements and intensified charge coupled device (ICCD) images show that the well-aligned air microplasma device is able to generate a large-area and homogeneous discharge at the applied voltages ranging from 12 kV to 14 kV, with a repetition frequency of 5 kHz, which is attributed to the diffusion effect of plasma on dielectric surface. Moreover, this well-aligned microplasma device may result in the uniform and large-area surface modification of heat-sensitive PET polymers without damage, such as optimization in hydrophobicity and biocompatibility. In the biomedical field, the utility of this well-aligned microplasma device is further testified. It proves to be very efficient for the large-area and uniform inactivation of E. coli cells with a density of 103/cm2 on LB agar plate culture medium, and inactivation efficiency can reach up to 99% for 2-min treatment. Project supported by the Natural Science Foundation of Fujian Province, China (Grant No. 2014J01025), the National Natural Science Foundation of China (Grant No. 11275261), the Natural Science Foundation of Guangdong Province, China (Grant No. 2015A030313005), and the Fund from the Fujian Provincial Key Laboratory for Plasma and Magnetic Resonance, China.

  9. Vertically aligned ZnO nanorod core-polypyrrole conducting polymer sheath and nanotube arrays for electrochemical supercapacitor energy storage

    PubMed Central

    2014-01-01

    Nanocomposite electrodes having three-dimensional (3-D) nanoscale architecture comprising of vertically aligned ZnO nanorod array core-polypyrrole (PPy) conducting polymer sheath and the vertical PPy nanotube arrays have been investigated for supercapacitor energy storage. The electrodes in the ZnO nanorod core-PPy sheath structure are formed by preferential nucleation and deposition of PPy layer over hydrothermally synthesized vertical ZnO nanorod array by controlled pulsed current electropolymerization of pyrrole monomer under surfactant action. The vertical PPy nanotube arrays of different tube diameter are created by selective etching of the ZnO nanorod core in ammonia solution for different periods. Cyclic voltammetry studies show high areal-specific capacitance approximately 240 mF.cm-2 for open pore and approximately 180 mF.cm-2 for narrow 30-to-36-nm diameter PPy nanotube arrays attributed to intensive faradic processes arising from enhanced access of electrolyte ions through nanotube interior and exterior. Impedance spectroscopy studies show that capacitive response extends over larger frequency domain in electrodes with PPy nanotube structure. Simulation of Nyquist plots by electrical equivalent circuit modeling establishes that 3-D nanostructure is better represented by constant phase element which accounts for the inhomogeneous electrochemical redox processes. Charge-discharge studies at different current densities establish that kinetics of the redox process in PPy nanotube electrode is due to the limitation on electron transport rather than the diffusive process of electrolyte ions. The PPy nanotube electrodes show deep discharge capability with high coulomb efficiency and long-term charge-discharge cyclic studies show nondegrading performance of the specific areal capacitance tested for 5,000 cycles. PMID:25246867

  10. Horizontal transfer of aligned Si nanowire arrays and their photoconductive performance

    PubMed Central

    2014-01-01

    An easy and low-cost method to transfer large-scale horizontally aligned Si nanowires onto a substrate is reported. Si nanowires prepared by metal-assisted chemical etching were assembled and anchored to fabricate multiwire photoconductive devices with standard Si technology. Scanning electron microscopy images showed highly aligned and successfully anchored Si nanowires. Current-voltage tests showed an approximately twofold change in conductivity between the devices in dark and under laser irradiation. Fully reversible light switching ON/OFF response was also achieved with an ION/IOFF ratio of 230. Dynamic response measurement showed a fast switching feature with response and recovery times of 10.96 and 19.26 ms, respectively. PMID:25520603

  11. Large-scale fabrication of vertically aligned ZnO nanowire arrays

    DOEpatents

    Wang, Zhong L; Das, Suman; Xu, Sheng; Yuan, Dajun; Guo, Rui; Wei, Yaguang; Wu, Wenzhuo

    2013-02-05

    In a method for growing a nanowire array, a photoresist layer is placed onto a nanowire growth layer configured for growing nanowires therefrom. The photoresist layer is exposed to a coherent light interference pattern that includes periodically alternately spaced dark bands and light bands along a first orientation. The photoresist layer exposed to the coherent light interference pattern along a second orientation, transverse to the first orientation. The photoresist layer developed so as to remove photoresist from areas corresponding to areas of intersection of the dark bands of the interference pattern along the first orientation and the dark bands of the interference pattern along the second orientation, thereby leaving an ordered array of holes passing through the photoresist layer. The photoresist layer and the nanowire growth layer are placed into a nanowire growth environment, thereby growing nanowires from the nanowire growth layer through the array of holes.

  12. Dendron growth from vertically aligned single-walled carbon nanotube thin layer arrays for photovoltaic devices.

    PubMed

    Bissett, Mark Alexander; Köper, Ingo; Quinton, Jamie Scott; Shapter, Joe George

    2011-04-01

    Single-walled carbon nanotube arrays attached to conductive transparent electrodes have previously shown promise for use in photovoltaic devices, whilst still retaining light transmission. Here, chemical modification of these thin (<200 nm) arrays with PAMAM-type dendrons has been undertaken to enhance the photoresponse of these devices. The effect of modification on the electrode was measured by differential pulse voltammetry to detect the dendrons, and the effect on the nanotubes was measured by Raman spectroscopy. Solar simulator illumination of the cells was performed to measure the effect of the nanotube modification on the cell power, and determine the optimal modification. Electrochemical impedance spectroscopy was also used to investigate the equivalent electronic circuit elements of the cells. The optimal dendron modification occurred with the second generation (G-2.0), which gave a 70% increase in power over the unmodified nanotube array. PMID:21347484

  13. The Surface Interface Characteristics of Vertically Aligned Carbon Nanotube and Graphitic Carbon Fiber Arrays Grown by Thermal and Plasma Enhanced Chemical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance; Nguyen, Cattien; Li, Jun; Han, Jie; Meyyappan, M.

    2002-01-01

    The development of nano-arrays for sensors and devices requires the growth of arrays with the proper characteristics. One such application is the growth of vertically aligned carbon nanotubes (CNTs) and graphitic carbon fibers (GCFs) for the chemical attachment of probe molecules. The effectiveness of such an array is dependent not only upon the effectiveness of the probe and the interface between that probe and the array, but also the array and the underlaying substrate. If that array is a growth of vertically aligned CNTs or GCFs then the attachment of that array to the surface is of the utmost importance. This attachment provides the mechanical stability and durability of the array, as well as, the electrical properties of that array. If the detection is to be acquired through an electrical measurement, then the appropriate resistance between the array and the surface need to be fabricated into the device. I will present data on CNTs and GCFs grown from both thermal and plasma enhanced chemical vapor deposition. The focus will be on the characteristics of the metal film from which the CNTs and GCFs are grown and the changes that occur due to changes within the growth process.

  14. Enhanced field electron emission from aligned diamond-like carbon nanorod arrays prepared by reactive ion beam etching

    NASA Astrophysics Data System (ADS)

    Zhao, Yong; Qin, Shi-Qiao; Zhang, Xue-Ao; Chang, Sheng-Li; Li, Hui-Hui; Yuan, Ji-Ren

    2016-05-01

    Homogeneous diamond-like carbon (DLC) films were deposited on Si supports by a pulsed filtered cathodic vacuum arc deposition system. Using DLC films masked by Ni nanoparticles as precursors, highly aligned diamond-like carbon nanorod (DLCNR) arrays were fabricated by the etching of inductively coupled radio frequency oxygen plasma. The as-prepared DLCNR arrays exhibit excellent field emission properties with a low turn-on field of 2.005 V μm‑1 and a threshold field of 4.312 V μm‑1, respectively. Raman spectroscopy and x-ray photoelectron spectroscopy were employed to determine the chemical bonding structural change of DLC films before and after etching. It is confirmed that DLC films have good connection with Si supports via the formation of the SiC phase, and larger conductive sp2 domains are formed in the as-etched DLC films, which play essential roles in the enhanced field emission properties for DLCNR arrays.

  15. Dye-sensitized solar cells with vertically aligned TiO2 nanowire arrays grown on carbon fibers.

    PubMed

    Cai, Xin; Wu, Hongwei; Hou, Shaocong; Peng, Ming; Yu, Xiao; Zou, Dechun

    2014-02-01

    One-dimensional semiconductor TiO2 nanowires (TNWs) have received widespread attention from solar cell and related optoelectronics scientists. The controllable synthesis of ordered TNW arrays on arbitrary substrates would benefit both fundamental research and practical applications. Herein, vertically aligned TNW arrays in situ grown on carbon fiber (CF) substrates through a facile, controllable, and seed-assisted thermal process is presented. Also, hierarchical TiO2 -nanoparticle/TNW arrays were prepared that favor both the dye loading and depressed charge recombination of the CF/TNW photoanode. An impressive conversion efficiency of 2.48 % (under air mass 1.5 global illumination) and an apparent efficiency of 4.18 % (with a diffuse board) due to the 3D light harvesting of the wire solar cell were achieved. Moreover, efficient and inexpensive wire solar cells made from all-CF electrodes and completely flexible CF-based wire solar cells were demonstrated, taking into account actual application requirements. This work may provide an intriguing avenue for the pursuit of lightweight, cost-effective, and high-performance flexible/wearable solar cells. PMID:24488679

  16. Cross-linking multiwall carbon nanotubes using PFPA to build robust, flexible and highly aligned large-scale sheets and yarns.

    PubMed

    Inoue, Yoku; Nakamura, Kazumichi; Miyasaka, Yuta; Nakano, Takayuki; Kletetschka, Gunther

    2016-03-18

    Multi-walled carbon nanotube (CNT) structures, including unidirectionally aligned sheets and spun yarns, were fabricated by direct dry-spinning methods from spinnable CNT arrays. We improved the mechanical properties of the CNT structures. CNTs were tailored in sheets and yarns using perfluorophenyl azide (PFPA) as a binding agent. The azide group of PFPA bonds to graphene crystal surfaces under UV radiation exposed for 1 h. For the CNT sheet, Young's modulus increased from 1.6 to 32.9 GPa and tensile strength increased from 35.9 MPa to 144.5 MPa. For the CNT yarns Young's modulus increased from 29.5 to 78.0 GPa and tensile strength increased from 639.1 to 675.6 MPa. With this treatment, the CNT sheets became more robust and more flexible materials. Since cross-linking of CNTs by PFPA is a simple and rapid process, it is suitable for fabrication of enhanced CNT materials. PMID:26871413

  17. Cross-linking multiwall carbon nanotubes using PFPA to build robust, flexible and highly aligned large-scale sheets and yarns

    NASA Astrophysics Data System (ADS)

    Inoue, Yoku; Nakamura, Kazumichi; Miyasaka, Yuta; Nakano, Takayuki; Kletetschka, Gunther

    2016-03-01

    Multi-walled carbon nanotube (CNT) structures, including unidirectionally aligned sheets and spun yarns, were fabricated by direct dry-spinning methods from spinnable CNT arrays. We improved the mechanical properties of the CNT structures. CNTs were tailored in sheets and yarns using perfluorophenyl azide (PFPA) as a binding agent. The azide group of PFPA bonds to graphene crystal surfaces under UV radiation exposed for 1 h. For the CNT sheet, Young’s modulus increased from 1.6 to 32.9 GPa and tensile strength increased from 35.9 MPa to 144.5 MPa. For the CNT yarns Young’s modulus increased from 29.5 to 78.0 GPa and tensile strength increased from 639.1 to 675.6 MPa. With this treatment, the CNT sheets became more robust and more flexible materials. Since cross-linking of CNTs by PFPA is a simple and rapid process, it is suitable for fabrication of enhanced CNT materials.

  18. Vertically-Aligned Single-Crystal Nanocone Arrays: Controlled Fabrication and Enhanced Field Emission.

    PubMed

    Duan, Jing Lai; Lei, Dang Yuan; Chen, Fei; Lau, Shu Ping; Milne, William I; Toimil-Molares, M E; Trautmann, Christina; Liu, Jie

    2016-01-13

    Metal nanostructures with conical shape, vertical alignment, large ratio of cone height and curvature radius at the apex, controlled cone angle, and single-crystal structure are ideal candidates for enhancing field electron-emission efficiency with additional merits, such as good mechanical and thermal stability. However, fabrication of such nanostructures possessing all these features is challenging. Here, we report on the controlled fabrication of large scale, vertically aligned, and mechanically self-supported single-crystal Cu nanocones with controlled cone angle and enhanced field emission. The Cu nanocones were fabricated by ion-track templates in combination with electrochemical deposition. Their cone angle is controlled in the range from 0.3° to 6.2° by asymmetrically selective etching of the ion tracks and the minimum tip curvature diameter reaches down to 6 nm. The field emission measurements show that the turn-on electric field of the Cu nanocone field emitters can be as low as 1.9 V/μm at current density of 10 μA/cm(2) (a record low value for Cu nanostructures, to the best of our knowledge). The maximum field enhancement factor we measured was as large as 6068, indicating that the Cu nanocones are promising candidates for field emission applications. PMID:26666466

  19. Exploring the Potential of Turbulent Flow Control Using Vertically Aligned Nanowire Arrays

    NASA Astrophysics Data System (ADS)

    Bailey, Sean; Calhoun, John; Guskey, Christopher; Seigler, Michael; Koka, Aneesh; Sodano, Henry

    2012-11-01

    We present evidence that turbulent flow can be influenced by oscillating nanowires. A substrate coated with vertically aligned nanowires was installed in the boundary wall of fully-developed turbulent channel flow, and the substrate was excited by a piezoceramic actuator to oscillate the nanowires. Because the nanowires are immersed in the viscous sublayer, it was previously unclear whether the small scale flow oscillations imparted into the bulk flow by the nanowires would influence the turbulent flow or be dissipated by the effects of viscosity. Our experiments demonstrated that the nanowires produced perturbations in the flow and contributed energy throughout the depth of the turbulent layer. A parallel investigation using a dynamically scaled surface of vertically aligned wires in laminar flow found that, even at low Reynolds numbers, significant momentum transport can be produced in the flow by the introduction of a travelling wave motion into the surface. These findings reflect the potential for using oscillating nanowires as a novel method of near-wall turbulent flow control. This work was supported by the Air Force Office of Scientific Research under FA9550-11-1-0140.

  20. Scalable synthesis of vertically aligned, catalyst-free gallium arsenide nanowire arrays: towards optimized optical absorption

    NASA Astrophysics Data System (ADS)

    Yao, Maoqing; Madaria, Anuj R.; Chi, ChunYung; Huang, Ningfeng; Lin, Chenxi; Povinelli, Michelle L.; Dapkus, P. Daniel; Zhou, Chongwu

    2012-06-01

    Recently nanostructure materials have emerged as a building block for constructing next generation of photovoltaic devices. Nanowire based semiconductor solar cells, among other candidates, have shown potential to produce high efficiency. In a radial pn junction light absorption and carrier collection can be decoupled. Also nanowires can increase choice of materials one can use to fabricate high efficiency tandem solar cells by relaxing the lattice-match constraint. Here we report synthesis of vertical III-V semiconducting nanowire arrays using Selective-Area Metal Organic Chemical Vapor Deposition (SA-MOCVD) technique, which can find application in various optoelectronic devices. We also demonstrate nanosphere lithography (NSL) patterning techniques to obtain ordered pattern for SAMOCVD. Reflection spectrum of nanowires array made by this technique shows excellent light absorption performance without additional anti-reflection coating layer. Thus, we show that highly ordered nanowire structure is 'not needed' to maximize the absorption in vertical nanowire array. Our scalable approach for synthesis of vertical semiconducting nanowire can have application in high throughput and low cost optoelectronic devices including photovoltaic devices.

  1. High-performance semiconductor optical amplifier array for self-aligned packaging using Si V-groove flip-chip technique

    NASA Astrophysics Data System (ADS)

    Leclerc, D.; Brosson, P.; Pommereau, F.; Ngo, R.; Doussiere, P.; Mallecot, F.; Gavignet, P.; Wamsler, I.; Laube, G.; Hunziker, W.

    1995-05-01

    A high performance four-tilted stripe semiconductor optical amplifier array, with low polarization sensitivity and very low-gain ripple, compatible with self-aligned flip-chip mounting on a Si motherboard is reported. Up to 32 dB of internal gain with 2-dB polarization sensitivity is obtained. A multifiber module has been realized, following an almost static optical alignment procedure, showing no degradation of the SOA array performances. Fiber-to-fiber gain, measured on the four stripes, is 14.4 +/- 1.3 dB with a gain ripple below +/- 0.1 dB.

  2. Self-aligned Ge and SiGe three-dimensional epitaxy on dense Si pillar arrays

    NASA Astrophysics Data System (ADS)

    Bergamaschini, R.; Isa, F.; Falub, C. V.; Niedermann, P.; Müller, E.; Isella, G.; von Känel, H.; Miglio, L.

    2013-11-01

    In this report we present a novel strategy in selective epitaxial growth on top of Si pillars, which results in a tessellated Ge film, composed by self-aligned micron-sized crystals in a maskless process. Modelling by rate equations the morphology evolution of fully facetted crystal profiles is extensively outlined, showing an excellent prediction of the peculiar role played by flux shielding among microcrystals, in the case of dense array configuration. Crack formation and substrate bending, caused by the mismatch in thermal expansion coefficients, are eliminated by the mechanical decoupling among individual microcrystals, which are also shown to be dislocation- and strain-free. The method has been also tested for Si1-xGex alloys, with compositions ranging from pure silicon to pure germanium. There are ample reasons to believe that this approach could be extended to other material combinations and substrate orientations, actually providing a technology platform for several device applications.

  3. Performance assessments of vertically aligned carbon nanotubes multi-electrode arrays using Cath.a-differentiated (CAD) cells

    NASA Astrophysics Data System (ADS)

    Jeong, Du Won; Jung, Jongjin; Kim, Gook Hwa; Yang, Cheol-Soo; Kim, Ju Jin; Jung, Sang Don; Lee, Jeong-O.

    2015-08-01

    In this work, Cath.a-differentiated (CAD) cells were used in place of primary neuronal cells to assess the performance of vertically aligned carbon nanotubes (VACNTs) multi-electrode arrays (MEA). To fabricate high-performance MEA, VACNTs were directly grown on graphene/Pt electrodes via plasma enhanced chemical deposition technique. Here, graphene served as an intermediate layer lowering contact resistance between VACNTs and Pt electrode. In order to lower the electrode impedance and to enhance the cell adhesion, VACNTs-MEAs were treated with UV-ozone for 20 min. Impedance of VACNTs electrode at 1 kHz frequency exhibits a reasonable value (110 kΩ) for extracellular signal recording, and the signal to noise ratio the is good enough to measure low signal amplitude (15.7). Spontaneous firing events from CAD cells were successfully measured with VACNTs MEAs that were also found to be surprisingly robust toward the biological interactions.

  4. Performance assessments of vertically aligned carbon nanotubes multi-electrode arrays using Cath.a-differentiated (CAD) cells.

    PubMed

    Jeong, Du Won; Jung, Jongjin; Kim, Gook Hwa; Yang, Cheol-Soo; Kim, Ju Jin; Jung, Sang Don; Lee, Jeong-O

    2015-08-21

    In this work, Cath.a-differentiated (CAD) cells were used in place of primary neuronal cells to assess the performance of vertically aligned carbon nanotubes (VACNTs) multi-electrode arrays (MEA). To fabricate high-performance MEA, VACNTs were directly grown on graphene/Pt electrodes via plasma enhanced chemical deposition technique. Here, graphene served as an intermediate layer lowering contact resistance between VACNTs and Pt electrode. In order to lower the electrode impedance and to enhance the cell adhesion, VACNTs-MEAs were treated with UV-ozone for 20 min. Impedance of VACNTs electrode at 1 kHz frequency exhibits a reasonable value (110 kΩ) for extracellular signal recording, and the signal to noise ratio the is good enough to measure low signal amplitude (15.7). Spontaneous firing events from CAD cells were successfully measured with VACNTs MEAs that were also found to be surprisingly robust toward the biological interactions. PMID:26222018

  5. Enhanced ionic liquid mobility induced by confinement in 1D CNT membranes

    NASA Astrophysics Data System (ADS)

    Berrod, Q.; Ferdeghini, F.; Judeinstein, P.; Genevaz, N.; Ramos, R.; Fournier, A.; Dijon, J.; Ollivier, J.; Rols, S.; Yu, D.; Mole, R. A.; Zanotti, J.-M.

    2016-04-01

    Water confined within carbon nanotubes (CNT) exhibits tremendous enhanced transport properties. Here, we extend this result to ionic liquids (IL) confined in vertically aligned CNT membranes. Under confinement, the IL self-diffusion coefficient is increased by a factor 3 compared to its bulk reference. This could lead to high power battery separators.Water confined within carbon nanotubes (CNT) exhibits tremendous enhanced transport properties. Here, we extend this result to ionic liquids (IL) confined in vertically aligned CNT membranes. Under confinement, the IL self-diffusion coefficient is increased by a factor 3 compared to its bulk reference. This could lead to high power battery separators. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01445c

  6. Impact of carbon nanotube length on electron transport in aligned carbon nanotube networks

    SciTech Connect

    Lee, Jeonyoon; Stein, Itai Y.; Devoe, Mackenzie E.; Lewis, Diana J.; Lachman, Noa; Buschhorn, Samuel T.; Wardle, Brian L.; Kessler, Seth S.

    2015-02-02

    Here, we quantify the electron transport properties of aligned carbon nanotube (CNT) networks as a function of the CNT length, where the electrical conductivities may be tuned by up to 10× with anisotropies exceeding 40%. Testing at elevated temperatures demonstrates that the aligned CNT networks have a negative temperature coefficient of resistance, and application of the fluctuation induced tunneling model leads to an activation energy of ≈14 meV for electron tunneling at the CNT-CNT junctions. Since the tunneling activation energy is shown to be independent of both CNT length and orientation, the variation in electron transport is attributed to the number of CNT-CNT junctions an electron must tunnel through during its percolated path, which is proportional to the morphology of the aligned CNT network.

  7. Understanding the nanoscale local buckling behavior of vertically aligned MWCNT arrays with van der Waals interactions.

    PubMed

    Li, Yupeng; Kim, Hyung-ick; Wei, Bingqing; Kang, Junmo; Choi, Jae-boong; Nam, Jae-Do; Suhr, Jonghwan

    2015-09-14

    The local buckling behavior of vertically aligned carbon nanotubes (VACNTs) has been investigated and interpreted in the view of a collective nanotube response by taking van der Waals interactions into account. To the best of our knowledge, this is the first report on the case of collective VACNT behavior regarding van der Waals force among nanotubes as a lateral support effect during the buckling process. The local buckling propagation and development of VACNTs were experimentally observed and theoretically analyzed by employing finite element modeling with lateral support from van der Waals interactions among nanotubes. Both experimental and theoretical analyses show that VACNTs buckled in the bottom region with many short waves and almost identical wavelengths, indicating a high mode buckling. Furthermore, the propagation and development mechanism of buckling waves follow the wave damping effect. PMID:26242771

  8. Understanding the nanoscale local buckling behavior of vertically aligned MWCNT arrays with van der Waals interactions

    NASA Astrophysics Data System (ADS)

    Li, Yupeng; Kim, Hyung-Ick; Wei, Bingqing; Kang, Junmo; Choi, Jae-Boong; Nam, Jae-Do; Suhr, Jonghwan

    2015-08-01

    The local buckling behavior of vertically aligned carbon nanotubes (VACNTs) has been investigated and interpreted in the view of a collective nanotube response by taking van der Waals interactions into account. To the best of our knowledge, this is the first report on the case of collective VACNT behavior regarding van der Waals force among nanotubes as a lateral support effect during the buckling process. The local buckling propagation and development of VACNTs were experimentally observed and theoretically analyzed by employing finite element modeling with lateral support from van der Waals interactions among nanotubes. Both experimental and theoretical analyses show that VACNTs buckled in the bottom region with many short waves and almost identical wavelengths, indicating a high mode buckling. Furthermore, the propagation and development mechanism of buckling waves follow the wave damping effect.The local buckling behavior of vertically aligned carbon nanotubes (VACNTs) has been investigated and interpreted in the view of a collective nanotube response by taking van der Waals interactions into account. To the best of our knowledge, this is the first report on the case of collective VACNT behavior regarding van der Waals force among nanotubes as a lateral support effect during the buckling process. The local buckling propagation and development of VACNTs were experimentally observed and theoretically analyzed by employing finite element modeling with lateral support from van der Waals interactions among nanotubes. Both experimental and theoretical analyses show that VACNTs buckled in the bottom region with many short waves and almost identical wavelengths, indicating a high mode buckling. Furthermore, the propagation and development mechanism of buckling waves follow the wave damping effect. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03581c

  9. Growth and structural discrimination of cortical neurons on randomly oriented and vertically aligned dense carbon nanotube networks

    PubMed Central

    Nick, Christoph; Yadav, Sandeep; Joshi, Ravi

    2014-01-01

    Summary The growth of cortical neurons on three dimensional structures of spatially defined (structured) randomly oriented, as well as on vertically aligned, carbon nanotubes (CNT) is studied. Cortical neurons are attracted towards both types of CNT nano-architectures. For both, neurons form clusters in close vicinity to the CNT structures whereupon the randomly oriented CNTs are more closely colonised than the CNT pillars. Neurons develop communication paths via neurites on both nanoarchitectures. These neuron cells attach preferentially on the CNT sidewalls of the vertically aligned CNT architecture instead than onto the tips of the individual CNT pillars. PMID:25247139

  10. Stable field emission from arrays of vertically aligned free-standing metallic nanowires

    NASA Astrophysics Data System (ADS)

    Xavier, Stephane; Mátéfi-Tempfli, Stefan; Ferain, Etienne; Purcell, Stephen; Enouz-Védrenne, Shaïma; Gangloff, Laurent; Minoux, Eric; Hudanski, Ludovic; Vincent, Pascal; Schnell, Jean-Philippe; Pribat, Didier; Piraux, Luc; Legagneux, Pierre

    2008-05-01

    We present a fully elaborated process to grow arrays of metallic nanowires with controlled geometry and density, based on electrochemical filling of nanopores in track-etched templates. Nanowire growth is performed at room temperature, atmospheric pressure and is compatible with low cost fabrication and large surfaces. This technique offers an excellent control of the orientation, shape and nanowires density. It is applied to fabricate field emission arrays with a good control of the emission site density. We have prepared Co, Ni, Cu and Rh nanowires with a height of 3 µm, a diameter of 80 nm and a density of ~107 cm-2. The electron field emission measurements and total energy distributions show that the as-grown nanowires exhibit a complex behaviour, first with emission activation under high field, followed by unstable emission. A model taking into account the effect of an oxide layer covering the nanowire surface is developed to explain this particular field emission behaviour. Finally, we present an in situ cleaning procedure by ion bombardment that collectively removes this oxide layer, leading to a stable and reproducible emission behaviour. After treatment, the emission current density is ~1 mA cm-2 for a 30 V µm-1 applied electric field.

  11. Ultrahigh Density Array of Vertically Aligned Small-molecular Organic Nanowires on Arbitrary Substrates

    PubMed Central

    Starko-Bowes, Ryan; Pramanik, Sandipan

    2013-01-01

    In recent years π-conjugated organic semiconductors have emerged as the active material in a number of diverse applications including large-area, low-cost displays, photovoltaics, printable and flexible electronics and organic spin valves. Organics allow (a) low-cost, low-temperature processing and (b) molecular-level design of electronic, optical and spin transport characteristics. Such features are not readily available for mainstream inorganic semiconductors, which have enabled organics to carve a niche in the silicon-dominated electronics market. The first generation of organic-based devices has focused on thin film geometries, grown by physical vapor deposition or solution processing. However, it has been realized that organic nanostructures can be used to enhance performance of above-mentioned applications and significant effort has been invested in exploring methods for organic nanostructure fabrication. A particularly interesting class of organic nanostructures is the one in which vertically oriented organic nanowires, nanorods or nanotubes are organized in a well-regimented, high-density array. Such structures are highly versatile and are ideal morphological architectures for various applications such as chemical sensors, split-dipole nanoantennas, photovoltaic devices with radially heterostructured "core-shell" nanowires, and memory devices with a cross-point geometry. Such architecture is generally realized by a template-directed approach. In the past this method has been used to grow metal and inorganic semiconductor nanowire arrays. More recently π-conjugated polymer nanowires have been grown within nanoporous templates. However, these approaches have had limited success in growing nanowires of technologically important π-conjugated small molecular weight organics, such as tris-8-hydroxyquinoline aluminum (Alq3), rubrene and methanofullerenes, which are commonly used in diverse areas including organic displays, photovoltaics, thin film transistors

  12. Vertically aligned P(VDF-TrFE) core-shell structures on flexible pillar arrays

    PubMed Central

    Choi, Yoon-Young; Yun, Tae Gwang; Qaiser, Nadeem; Paik, Haemin; Roh, Hee Seok; Hong, Jongin; Hong, Seungbum; Han, Seung Min; No, Kwangsoo

    2015-01-01

    PVDF and P(VDF-TrFE) nano- and micro- structures have been widely used due to their potential applications in several fields, including sensors, actuators, vital sign transducers, and energy harvesters. In this study, we developed vertically aligned P(VDF-TrFE) core-shell structures using high modulus polyurethane acrylate (PUA) pillars as the support structure to maintain the structural integrity. In addition, we were able to improve the piezoelectric effect by 1.85 times from 40 ± 2 to 74 ± 2 pm/V when compared to the thin film counterpart, which contributes to the more efficient current generation under a given stress, by making an effective use of the P(VDF-TrFE) thin top layer as well as the side walls. We attribute the enhancement of piezoelectric effects to the contributions from the shell component and the strain confinement effect, which was supported by our modeling results. We envision that these organic-based P(VDF-TrFE) core-shell structures will be used widely as 3D sensors and power generators because they are optimized for current generations by utilizing all surface areas, including the side walls of core-shell structures. PMID:26040539

  13. Massive transfer of vertically aligned Si nanowire array onto alien substrates and their characteristics

    NASA Astrophysics Data System (ADS)

    Shiu, Shu-Chia; Hung, Shih-Che; Chao, Jiun-Jie; Lin, Ching-Fuh

    2009-07-01

    Si nanowires (NWs) are promising materials for future electronic, photovoltaic, and sensor applications. So far the Si NWs are mainly formed on particular substrates or at high temperatures, greatly limiting their application flexibility. Here we report a low temperature process for forming and massively transferring vertically aligned Si NWs on alien substrates with a large density of about (3-5) × 10 7 NWs/mm 2. The X-ray diffraction spectrum reveals that the transferred NWs exhibit almost the same crystal property as the bulk Si. Our investigation further shows that the transferred NWs have exceptional optical characteristics. The transferred Si NWs of 12.14 μm exhibit the transmittance as low as 0.3% in the near infrared region and 0.07% in the visible region. The extracted absorption coefficient of Si NWs in the near infrared region is about 3 × 10 3 cm -1, over 30 times larger than that of the bulk Si. Because of the low temperature process, it enables a large variety of alien substrates such as glass and plastics to be used. In addition, the exceptional properties of the transferred NWs offer potential applications for photovoltaic, photo-detectors, sensors, and flexible electronics.

  14. Vertically aligned P(VDF-TrFE) core-shell structures on flexible pillar arrays

    SciTech Connect

    Choi, Yoon-Young; Yun, Tae Gwang; Qaiser, Nadeem; Paik, Haemin; Roh, Hee Seok; Hong, Jongin; Hong, Seungbum; Han, Seung Min; No, Kwangsoo

    2015-06-04

    PVDF and P(VDF-TrFE) nano- and micro- structures are widely used due to their potential applications in several fields, including sensors, actuators, vital sign transducers, and energy harvesters. In this study, we developed vertically aligned P(VDF-TrFE) core-shell structures using high modulus polyurethane acrylate (PUA) pillars as the support structure to maintain the structural integrity. In addition, we were able to improve the piezoelectric effect by 1.85 times from 40 ± 2 to 74 ± 2 pm/V when compared to the thin film counterpart, which contributes to the more efficient current generation under a given stress, by making an effective use of the P(VDF-TrFE) thin top layer as well as the side walls. We attribute the enhancement of piezoelectric effects to the contributions from the shell component and the strain confinement effect, which was supported by our modeling results. We envision that these organic-based P(VDF-TrFE) core-shell structures will be used widely as 3D sensors and power generators because they are optimized for current generations by utilizing all surface areas, including the side walls of core-shell structures.

  15. Vertically aligned P(VDF-TrFE) core-shell structures on flexible pillar arrays

    DOE PAGESBeta

    Choi, Yoon-Young; Yun, Tae Gwang; Qaiser, Nadeem; Paik, Haemin; Roh, Hee Seok; Hong, Jongin; Hong, Seungbum; Han, Seung Min; No, Kwangsoo

    2015-06-04

    PVDF and P(VDF-TrFE) nano- and micro- structures are widely used due to their potential applications in several fields, including sensors, actuators, vital sign transducers, and energy harvesters. In this study, we developed vertically aligned P(VDF-TrFE) core-shell structures using high modulus polyurethane acrylate (PUA) pillars as the support structure to maintain the structural integrity. In addition, we were able to improve the piezoelectric effect by 1.85 times from 40 ± 2 to 74 ± 2 pm/V when compared to the thin film counterpart, which contributes to the more efficient current generation under a given stress, by making an effective use ofmore » the P(VDF-TrFE) thin top layer as well as the side walls. We attribute the enhancement of piezoelectric effects to the contributions from the shell component and the strain confinement effect, which was supported by our modeling results. We envision that these organic-based P(VDF-TrFE) core-shell structures will be used widely as 3D sensors and power generators because they are optimized for current generations by utilizing all surface areas, including the side walls of core-shell structures.« less

  16. Vertically aligned P(VDF-TrFE) core-shell structures on flexible pillar arrays.

    PubMed

    Choi, Yoon-Young; Yun, Tae Gwang; Qaiser, Nadeem; Paik, Haemin; Roh, Hee Seok; Hong, Jongin; Hong, Seungbum; Han, Seung Min; No, Kwangsoo

    2015-01-01

    PVDF and P(VDF-TrFE) nano- and micro- structures have been widely used due to their potential applications in several fields, including sensors, actuators, vital sign transducers, and energy harvesters. In this study, we developed vertically aligned P(VDF-TrFE) core-shell structures using high modulus polyurethane acrylate (PUA) pillars as the support structure to maintain the structural integrity. In addition, we were able to improve the piezoelectric effect by 1.85 times from 40 ± 2 to 74 ± 2 pm/V when compared to the thin film counterpart, which contributes to the more efficient current generation under a given stress, by making an effective use of the P(VDF-TrFE) thin top layer as well as the side walls. We attribute the enhancement of piezoelectric effects to the contributions from the shell component and the strain confinement effect, which was supported by our modeling results. We envision that these organic-based P(VDF-TrFE) core-shell structures will be used widely as 3D sensors and power generators because they are optimized for current generations by utilizing all surface areas, including the side walls of core-shell structures. PMID:26040539

  17. One-step growth of well-aligned TiO2 nanorod arrays for flexible dye-sensitized solar cells.

    PubMed

    Chen, Xiaoxu; Tang, Qunwei; Zhao, Zhiyuan; Wang, Xinghui; He, Benlin; Yu, Liangmin

    2015-02-01

    We present here the feasibility of growing well-aligned TiO2 nanorod arrays by a dc reactive magnetron sputtering strategy for flexible dye-sensitized solar cells. These flexible devices yield an efficiency of 5.3% in comparison to 1.2% from traditional TiO2 nanoparticles by a low-temperature technique. PMID:25531300

  18. WIMP detection and slow ion dynamics in carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Cavoto, G.; Cirillo, E. N. M.; Cocina, F.; Ferretti, J.; Polosa, A. D.

    2016-06-01

    Large arrays of aligned carbon nanotubes (CNTs), open at one end, could be used as target material for the directional detection of weakly interacting dark matter particles (WIMPs). As a result of a WIMP elastic scattering on a CNT, a carbon ion might be injected in the body of the array and propagate through multiple collisions within the lattice. The ion may eventually emerge from the surface with open end CNTs, provided that its longitudinal momentum is large enough to compensate energy losses and its transverse momentum approaches the channeling conditions in a single CNT. Therefore, the angle formed between the WIMP wind apparent orientation and the direction of parallel carbon nanotube axes must be properly chosen. We focus on very low ion recoil kinetic energies, related to low mass WIMPs (≈ 11 GeV) where most of the existing experiments have low sensitivity. Relying on some exact results on two-dimensional lattices of circular obstacles, we study the low energy ion motion in the transverse plane with respect to CNT directions. New constraints are obtained on how to devise the CNT arrays to maximize the target channeling efficiency.

  19. Enhanced piezoelectric properties of vertically aligned single-crystalline NKN nano-rod arrays

    NASA Astrophysics Data System (ADS)

    Kang, Min-Gyu; Oh, Seung-Min; Jung, Woo-Suk; Gyu Moon, Hi; Baek, Seung-Hyub; Nahm, Sahn; Yoon, Seok-Jin; Kang, Chong-Yun

    2015-05-01

    Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures.

  20. Enhanced piezoelectric properties of vertically aligned single-crystalline NKN nano-rod arrays

    PubMed Central

    Kang, Min-Gyu; Oh, Seung-Min; Jung, Woo-Suk; Gyu Moon, Hi; Baek, Seung-Hyub; Nahm, Sahn; Yoon, Seok-Jin; Kang, Chong-Yun

    2015-01-01

    Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures. PMID:25955763

  1. Enhanced piezoelectric properties of vertically aligned single-crystalline NKN nano-rod arrays.

    PubMed

    Kang, Min-Gyu; Oh, Seung-Min; Jung, Woo-Suk; Moon, Hi Gyu; Baek, Seung-Hyub; Nahm, Sahn; Yoon, Seok-Jin; Kang, Chong-Yun

    2015-01-01

    Piezoelectric materials capable of converting between mechanical and electrical energy have a great range of potential applications in micro- and nano-scale smart devices; however, their performance tends to be greatly degraded when reduced to a thin film due to the large clamping force by the substrate and surrounding materials. Herein, we report an effective method for synthesizing isolated piezoelectric nano-materials as means to relax the clamping force and recover original piezoelectric properties of the materials. Using this, environmentally friendly single-crystalline NaxK1-xNbO3 (NKN) piezoelectric nano-rod arrays were successfully synthesized by conventional pulsed-laser deposition and demonstrated to have a remarkably enhanced piezoelectric performance. The shape of the nano-structure was also found to be easily manipulated by varying the energy conditions of the physical vapor. We anticipate that this work will provide a way to produce piezoelectric micro- and nano-devices suitable for practical application, and in doing so, open a new path for the development of complex metal-oxide nano-structures. PMID:25955763

  2. Hybrid core-shell nanowire electrodes utilizing vertically aligned carbon nanofiber arrays for high-performance energy storage

    NASA Astrophysics Data System (ADS)

    Klankowski, Steven Arnold

    Nanostructured electrode materials for electrochemical energy storage systems have been shown to improve both rate performance and capacity retention, while allowing considerably longer cycling lifetime. The nano-architectures provide enhanced kinetics by means of larger surface area, higher porosity, better material interconnectivity, shorter diffusion lengths, and overall mechanical stability. Meanwhile, active materials that once were excluded from use due to bulk property issues are now being examined in new nanoarchitecture. Silicon was such a material, desired for its large lithium-ion storage capacity of 4,200 mAh g-1 and low redox potential of 0.4 V vs. Li/Li+; however, a ˜300% volume expansion and increased resistivity upon lithiation limited its broader applications. In the first study, the silicon-coated vertically aligned carbon nanofiber (VACNF) array presents a unique core-shell nanowire (NW) architecture that demonstrates both good capacity and high rate performance. In follow-up, the Si-VACNFs NW electrode demonstrates enhanced power rate capabilities as it shows excellent storage capacity at high rates, attributed to the unique nanoneedle structure that high vacuum sputtering produces on the three-dimensional array. Following silicon's success, titanium dioxide has been explored as an alternative high-rate electrode material by utilizing the dual storage mechanisms of Li+ insertion and pseudocapacitance. The TiO 2-coated VACNFs shows improved electrochemical activity that delivers near theoretical capacity at larger currents due to shorter Li+ diffusion lengths and highly effective electron transport. A unique cell is formed with the Si-coated and TiO2-coated electrodes place counter to one another, creating the hybrid of lithium ion battery-pseudocapacitor that demonstrated both high power and high energy densities. The hybrid cell operates like a battery at lower current rates, achieving larger discharge capacity, while retaining one-third of

  3. Island nucleation, optical and ferromagnetic properties of vertically aligned secondary growth ZnO : Cu nanorod arrays

    NASA Astrophysics Data System (ADS)

    Huang, Jun; Zhu, Liping; Hu, Liang; Liu, Shijiang; Zhang, Jie; Zhang, Honghai; Yang, Xiaopeng; Sun, Luwei; Li, Dehui; Ye, Zhizhen

    2012-02-01

    The paper reports an island nucleation and secondary growth of aligned ZnO : Cu nanorod arrays via thermal vapor phase transport. Results analysis indicates that the secondary segment is epitaxially grown on the ZnO : Cu nanorods with the radius strongly dependent on temperature and the concentration of zinc vapor. The modified characteristic radius (Rc) model is used to explain the nucleation and secondary growth process. Temperature-dependent photoluminescence spectra indicate that the band gap emission of the secondary growth nanorods is greatly restrained. A controversial 3.31 eV emission (A line) and two different donor-acceptor pair (DAP) recombinations at 3.24 eV and 2.48 eV are observed at 13 K. The A line shows a different behavior from the two DAP emissions during the heat-up process. Intrinsic room temperature ferromagnetism (RTFM) is observed in the secondary growth ZnO : Cu nanorods and it can be explained by oxygen vacancy and copper defects related to bound magnetic polar (BMP) or double exchange mechanism.The paper reports an island nucleation and secondary growth of aligned ZnO : Cu nanorod arrays via thermal vapor phase transport. Results analysis indicates that the secondary segment is epitaxially grown on the ZnO : Cu nanorods with the radius strongly dependent on temperature and the concentration of zinc vapor. The modified characteristic radius (Rc) model is used to explain the nucleation and secondary growth process. Temperature-dependent photoluminescence spectra indicate that the band gap emission of the secondary growth nanorods is greatly restrained. A controversial 3.31 eV emission (A line) and two different donor-acceptor pair (DAP) recombinations at 3.24 eV and 2.48 eV are observed at 13 K. The A line shows a different behavior from the two DAP emissions during the heat-up process. Intrinsic room temperature ferromagnetism (RTFM) is observed in the secondary growth ZnO : Cu nanorods and it can be explained by oxygen vacancy and copper

  4. The effect of hydroxylation on CNT to form Chitosan-CNT composites: A DFT study

    NASA Astrophysics Data System (ADS)

    Yu, Rui; Ran, Maofei; Wen, Jie; Sun, Wenjing; Chu, Wei; Jiang, Chengfa; He, Zhiwei

    2015-12-01

    The effect of types of CNTs (pristine and hydroxylated) on the synthesis of Chitosan-CNT (CS-CNT) composites was investigated theoretically. The adsorption energy (Eads) of CS on the pristine CNT and hydroxylated CNTs (CNT-OHn, n = 1-6) as well as the structural and electronic properties of said composites have been investigated. Results show that the adsorption of CS on CNT and CNT-OHn is thermodynamically favored. The Eads of CS on CNTs was calculated to be -20.387 kcal/mol from electrostatic interactions. For CS adsorbed into CNT-OHn, Eads ranges from -20.612 to -37.567 kcal/mol. Hydroxyl groups on CNT are the main adsorption sites for CS loading onto CNT-OHn via hydrogen-bond interactions. The CS-CNT-OH3 is the most sable composite among tested complexes. The energy gap (ΔEgap) of CS-CNT-OH3 was calculated less than pristine CNT and CNT-OH3, indicative of the composites being more reactive than that of pristine CNTs and CNT-OH3. It was proved that CS can transfer electron to the hydroxylated CNTs, thus overcoming the drawbacks of CNTs being chemically inert.

  5. Morphology-tunable assembly of periodically aligned Si nanowire and radial pn junction arrays for solar cell applications

    NASA Astrophysics Data System (ADS)

    Li, Xiaocheng; Liang, Kun; Tay, Beng Kang; Teo, Edwin H. T.

    2012-06-01

    Large-area periodically aligned Si nanowire (PASiNW) arrays have been fabricated on Si substrates via a templated catalytic chemical etching process. The diameter, length, packing density, and even the shape of Si nanowires (SiNWs) could be precisely controlled and tuned. A local coupling redox mechanism involving the reduction of H2O2 on silver particles and the dissolution of Si is responsible for formation of SiNWs. With the as-prepared SiNWs as templates, three kinds of PASiNW radial pn junction structures were fabricated on Si substrates via a solid-state phosphorous diffusion strategy and their applications in solar cells were also explored. The PASiNW radial pn junction-based solar cell with big diameter and interspace shows the highest power conversion efficiency (PCE) of 4.10% among the three kinds of devices. Further optimization, including surface passivation and electrode contact, is still needed for the higher efficiency PASiNW radial pn junction-based solar cells in the future.

  6. Growth of vertically aligned one-dimensional ZnO nanowire arrays on sol-gel derived ZnO thin films

    NASA Astrophysics Data System (ADS)

    Kitazawa, Nobuaki; Aono, Masami; Watanabe, Yoshihisa

    2014-11-01

    Vertically aligned one-dimensional ZnO nanowire arrays have been synthesized by a hydrothermal method on sol-gel derived ZnO films. Sol-gel derived ZnO films and corresponding ZnO nanowire arrays have been characterized by X-ray diffraction and field-emission scanning electron microscopy. The effect of sol-gel derived ZnO film surface on the morphology of ZnO nanowire arrays has been investigated. The authors suggest from our investigation that sol-gel derived ZnO films affect the growth of one-dimensional ZnO nanostructures. Not only crystalline ZnO films but also amorphous ones can act as a scaffold for ZnO nucleus. Tilted ZnO micro-rods are grown on ZnO gel films, whereas vertically aligned ZnO nanowire arrays are grown on nanometer-sized ZnO grains. The average diameter of ZnO nanowire arrays are correlated strongly with the grain size of sol-gel derived ZnO films.

  7. Strain-driven alignment of In nanocrystals on InGaAs quantum dot arrays and coupled plasmon-quantum dot emission

    SciTech Connect

    Urbanczyk, A.; Hamhuis, G. J.; Noetzel, R.

    2010-03-15

    We report the alignment of In nanocrystals on top of linear InGaAs quantum dot (QD) arrays formed by self-organized anisotropic strain engineering on GaAs (100) by molecular beam epitaxy. The alignment is independent of a thin GaAs cap layer on the QDs revealing its origin is due to local strain recognition. This enables nanometer-scale precise lateral and vertical site registration between the QDs and the In nanocrystals and arrays in a single self-organizing formation process. The plasmon resonance of the In nanocrystals overlaps with the high-energy side of the QD emission leading to clear modification of the QD emission spectrum.

  8. Insights into the nature of northwest-to-southeast aligned ionospheric wavefronts from contemporaneous Very Large Array and ionosonde observations

    NASA Astrophysics Data System (ADS)

    Helmboldt, J. F.

    2012-07-01

    The results of contemporaneous summer nighttime observations of midlatitude medium scale traveling ionospheric disturbances (MSTIDs) with the Very Large Array (VLA) in New Mexico and nearby ionosondes in Texas and Colorado are presented. Using 132, 20-minute observations, several instances of MSTIDs were detected, all having wavefronts aligned northwest to southeast and mostly propagating toward the southwest, consistent with previous studies of MSTIDs. However, some were also found to move toward the northeast. It was found that both classes of MSTIDs were only found when sporadic-E (Es) layers of moderate peak density (1.5​ < ​ foEs​ < ​3 MHz) were present. Limited fbEs data from one ionosonde suggests that there was a significant amount of structure within the Es layers during observations when foEs > ​3 MHz that was not present when 1.5​ < foEs < ​3 MHz. No MSTIDs were observed either before midnight or when the F-region height was increasing at a relatively high rate, even when these Es layers were observed. Combining this result with AE indices which were relatively high at the time (an average of about 300 nT and maximum of nearly 700 nT), it is inferred that both the lack of MSTIDs and the increase in F-region height are due to substorm-induced electric fields. The northeastward-directed MSTIDs were strongest post-midnight during times when the F-region was observed to be collapsing relatively quickly. This implies that these two occurrences are related and likely both caused by rare shifts in F-region neutral wind direction from southwest to northwest.

  9. Increased Alignment in Carbon Nanotube Growth

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance D. (Inventor)

    2007-01-01

    Method and system for fabricating an array of two or more carbon nanotube (CNT) structures on a coated substrate surface, the structures having substantially the same orientation with respect to a substrate surface. A single electrode, having an associated voltage source with a selected voltage, is connected to a substrate surface after the substrate is coated and before growth of the CNT structures, for a selected voltage application time interval. The CNT structures are then grown on a coated substrate surface with the desired orientation. Optionally, the electrode can be disconnected before the CNT structures are grown.

  10. Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes.

    PubMed

    Li, Zhiyang; Leung, Calvin; Gao, Fan; Gu, Zhiyong

    2015-01-01

    In this paper, vertically aligned Pt nanowire arrays (PtNWA) with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H₂O₂) detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO) template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM⁻¹·cm⁻²) among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water) was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors. PMID:26404303

  11. Effects of Nanowire Length and Surface Roughness on the Electrochemical Sensor Properties of Nafion-Free, Vertically Aligned Pt Nanowire Array Electrodes

    PubMed Central

    Li, Zhiyang; Leung, Calvin; Gao, Fan; Gu, Zhiyong

    2015-01-01

    In this paper, vertically aligned Pt nanowire arrays (PtNWA) with different lengths and surface roughnesses were fabricated and their electrochemical performance toward hydrogen peroxide (H2O2) detection was studied. The nanowire arrays were synthesized by electroplating Pt in nanopores of anodic aluminum oxide (AAO) template. Different parameters, such as current density and deposition time, were precisely controlled to synthesize nanowires with different surface roughnesses and various lengths from 3 μm to 12 μm. The PtNWA electrodes showed better performance than the conventional electrodes modified by Pt nanowires randomly dispersed on the electrode surface. The results indicate that both the length and surface roughness can affect the sensing performance of vertically aligned Pt nanowire array electrodes. Generally, longer nanowires with rougher surfaces showed better electrochemical sensing performance. The 12 μm rough surface PtNWA presented the largest sensitivity (654 μA·mM−1·cm−2) among all the nanowires studied, and showed a limit of detection of 2.4 μM. The 12 μm rough surface PtNWA electrode also showed good anti-interference property from chemicals that are typically present in the biological samples such as ascorbic, uric acid, citric acid, and glucose. The sensing performance in real samples (river water) was tested and good recovery was observed. These Nafion-free, vertically aligned Pt nanowires with surface roughness control show great promise as versatile electrochemical sensors and biosensors. PMID:26404303

  12. Hierarchical structures of aligned carbon nanotubes as low-density energy-dissipative materials

    NASA Astrophysics Data System (ADS)

    Raney, Jordan R.

    Carbon nanotubes (CNTs) are known to have remarkable properties, such as a specific strength two orders of magnitude higher than that of steel. It has remained a challenge, however, to achieve useful bulk properties from CNTs. Toward that goal, here we develop low-density bulk materials (0.1-0.4 g cm-3) entirely or nearly entirely from CNTs. These consist of nominally-aligned arrays of CNTs that display a dissipative compressive response, with a notable stress-strain hysteresis. The compressive properties of CNT arrays are examined in detail. This analysis reveals interesting features in the mechanical response, such as strain localization (resulting from a gradient in physical properties along the height), recovery after compression, non-linear viscoelasticity, and behavior under repeated compression that depends on the strain of previous cycles (similar to the Mullins effect in rubbers). We observe that in compression the energy dissipation of these materials is more than 200 times that of polymeric foams of comparable density. Next, materials based on CNT arrays are studied as exemplary of hierarchical materials (materials with distinct structure at multiple length scales). Hierarchical materials have pushed the limits of traditional material tradeoffs (e.g., the typical trend that increased strength requires increased weight). Techniques are developed to separately vary the structure of CNT arrays at nanometer, micrometer, and millimeter length scales, and the effects on the bulk material response are examined. Structure can be modified during CNT synthesis, such as by varying the composition of the flow gas or by manipulating the input rate of chemical precursors; it can also be modified post-synthesis, e.g., by the in situ synthesis of nanoparticles in the interstices of the CNT arrays or by the assembly of multilayer structures of multiple CNT arrays connected by polymeric or metallic interlayers. Finally, a mathematical model is applied to capture the

  13. Electrical, Thermal, and Machining Behaviour of Injection Moulded Polymeric CNT Nanocomposites

    NASA Astrophysics Data System (ADS)

    Mahmoodi, Mehdi

    Carbon nanotubes (CNTs) are promising additives for thermoplastics, resulting from their superior electrical, thermal and mechanical properties. Due to the desirable properties of CNT/polymer composites and their wide application in technological devices, these materials have attracted a great deal of attention from both academia and industry. A considerable amount of research has been devoted to the processing of CNT-filled nanocomposites, but only a few investigations have focussed on the injection moulding of these nanocomposites. This research was aimed at the study of the flow-induced alignment of CNT/polymer nanocomposites through the injection moulding process. We focussed on the understanding of the alignment of multi-walled carbon nanotubes (MWCNTs) in a thermoplastic matrix and the investigation of the alignment's effect on the electrical, thermal and machining characteristics of the injection moulded nanocomposites. The nanocomposites were first prepared with a melt mixing technique (i.e. twin screw extrusion), and they were then injection moulded under various processing conditions and mould geometries. High aspect ratio nanotubes could be partially aligned in the parallel-to-flow direction, resulting from the in-plane shear flow exerted on the polymeric melt in the injection cavity. It can be concluded that the volume resistivity of the moulded samples could be varied up to 7 orders of magnitude by changing the processing conditions and gate type in the injection moulding process. The electromagnetic interference shielding effectiveness (EMI SE) of the moulded composites was studied by considering the alignment of the MWCNTs. The EMI SE decreased with an increase in the alignment of the injection moulded MWCNTs in the polymer matrix. Anisotropic thermal conductivity was observed for the injection moulded nanocomposites. It was shown that thermal conductivity can be enhanced by aligning the nanotubes in the parallel-to-flow direction. The post

  14. Altering the catalytic activity of thin metal catalyst films for controlled growth of chemical vapor deposited vertically aligned carbon nanotube arrays

    SciTech Connect

    Rouleau, Christopher M; Christen, Hans M; Cui, Hongtao; Eres, Gyula; Puretzky, Alexander A; Geohegan, David B

    2008-01-01

    The growth rate and terminal length of vertically-aligned carbon nanotube arrays (VANTAs) grown by chemical vapor deposition have been dramatically improved through pulsed KrF-excimer laser pretreatments of multilayer metal catalyst films. Silicon wafers coated with Al, Mo, and Fe layers were laser processed in air with single laser shots of varying fluence through circular apertures, then heated to ~750C and exposed to acetylene and ferrocene-containing gas mixtures typically used to grow vertically-aligned nanotube arrays. In situ videography was used to record the growth kinetics of the nanotube arrays in both patterned and unpatterned regions to understand changes in catalytic activity, growth rates, and termination of growth. The height of the patterned regions varied with fluence, with the most successful treatment resulting in 1.4 cm-tall posts of nanotubes embedded in a 0.4 cm-tall nanotube carpet. High-resolution transmission electron microscopy images from the nanotubes in the posts revealed fewer walls, smaller diameters, and a much narrower distribution of diameters compared to nanotubes grown in the carpet. This information, along with data obtained from weighing the material from each region, suggests that pulsed laser processing can also significantly increase the areal density of VANTAs.

  15. Process of in situ forming well-aligned zinc oxide nanorod arrays on wood substrate using a two-step bottom-up method.

    PubMed

    Liu, Yongzhuang; Fu, Yanchun; Yu, Haipeng; Liu, Yixing

    2013-10-01

    A good nanocrystal covering layer on wood can serve as a protective coating and present some new surface properties. In this study, well-aligned ZnO nanorods (NRs) arrays were successfully grown on wood surface through a two-step bottom-up growth process. The process involved pre-sow seeds and subsequently their growing into NRs under hydrothermal environment. The interface incorporation between wood and ZnO colloid particles in the precursor solution during the seeding process was analyzed and demonstrated through a schematic. The growth process of forming well-aligned ZnO NRs was analyzed by field-emission scanning electron microscopy and X-ray diffraction, which showed that the NRs elongated with increased reaction time. The effects of ZnO crystal form and capping agent on the growth process were studied through different viewpoints. PMID:23880522

  16. A room temperature approach for the fabrication of aligned TiO₂ nanotube arrays on transparent conductive substrates.

    PubMed

    Zeng, Ruosha; Li, Ke; Sheng, Xia; Chen, Liping; Zhang, Haijiao; Feng, Xinjian

    2016-03-14

    A novel solution approach is reported for the fabrication of TiO₂ nanotube arrays on transparent conductive substrates via in situ conversion from nanowires. The as-prepared nanotube arrays not only demonstrate a larger surface area in comparison with the primary NWs, but also longer charge carrier lifetime than that of randomly packed nanoparticle films. PMID:26892268

  17. Photoelectrochemical cell/dye-sensitized solar cell tandem water splitting systems with transparent and vertically aligned quantum dot sensitized TiO2 nanorod arrays

    NASA Astrophysics Data System (ADS)

    Shin, Kahee; Yoo, Ji-Beom; Park, Jong Hyeok

    2013-03-01

    The present work reports fabrication of vertically aligned CdS sensitized TiO2 nanorod arrays grown on transparent conducting oxide substrate with high transparency as a photoanode in photoelectrochemical cell for water splitting. To realize an unassisted water splitting system, the photoanode and dye-sensitized solar cell tandem structures are tried and their electrochemical behaviors are also investigated. The hydrothermally grown TiO2 nanorod arrays followed by CdS nanoparticle decoration can improve the light absorption of long wavelength light resulting in increased photocurrent density. Two different techniques (electrodeposition and spray pyrolysis deposition) of CdS nanoparticle sensitization are carried out and their water splitting behaviors in the tandem cell are compared.

  18. Preparation and Transport Performances of High-Density, Aligned Carbon Nanotube Membranes

    NASA Astrophysics Data System (ADS)

    Zhang, Lei; Zhao, Bin; Jiang, Chuan; Yang, Junhe; Zheng, Guangping

    2015-06-01

    We report a simple and effective method for the preparation of high-density and aligned carbon nanotube (CNT) membranes. The CNT arrays were prepared by water-assisted chemical vapor deposition (CVD) and were subsequently pushed over and stacked into dense membranes by mechanical rolling. It was demonstrated that various gases and liquids, including H2, He, N2, O2, Ar, water, ethanol, hexane, and kerosene, could effectively pass through the aligned carbon nanotube membranes. The membranes exhibited different selections on different gases, indicating that there was a separation potential for the gas mixtures. The selectivities (H2 relative to other gases) of H2/He, H2/N2, H2/O2, and H2/Ar were found to be lower than that of the ideal Knudsen model. For pure water, the permeability was measured to be 3.23 ± 0.05 ml·min-1·cm-2 at 1 atm, indicating that the CNT membranes were promising for applications in liquid filtration and separation.

  19. ZnO nanorod-templated well-aligned ZrO2 nanotube arrays for fibroblast adhesion and proliferation

    NASA Astrophysics Data System (ADS)

    Lu, Zhisong; Zhu, Zhihong; Liu, Jinping; Hu, Weihua; Li, Chang Ming

    2014-05-01

    Cellular responses to porous tubular structures have recently been investigated in highly ordered ZrO2 nanotube arrays fabricated with anodization. However, the potential applications of the nanotube arrays are hindered by instrument requirements and substrate limitations, as well as by the complicated processes needed for synthesis. In this work, ZrO2 nanotube arrays were synthesized by in situ hydrolysis of zirconium propoxide with a zinc oxide nanorod array-based template. Fibroblast cells were able to grow on the nanotube array surface with produced elongated filopodia. Studies of the capability of cell growth and the expression of adhesion- and proliferation-related genes reveal that ZrO2 nanotube arrays may provide a better environment for cell adhesion and growth than a flat titanium surface. These findings not only provide fundamental insight into cell response to nanostructures but also provide an opportunity to use a unique approach to fabricate ZrO2 nanotube array structures for potential implant applications.

  20. Ni foam supported three-dimensional vertically aligned and networked layered CoO nanosheet/graphene hybrid array as a high-performance oxygen evolution electrode

    NASA Astrophysics Data System (ADS)

    Yuan, Weiyong; Zhao, Ming; Yuan, Jia; Li, Chang Ming

    2016-07-01

    The sluggish oxygen evolution reaction (OER) represents a major kinetic bottleneck in water splitting. Herein we report the synthesis of a novel Ni foam (NF) supported 3-D vertically aligned and interconnected layered CoO nanosheet array with controlled density, layer thickness, and interlayer spacing, and the conformal self-assembly of graphene on this nanosheet array. The obtained CoO layered nanosheet/graphene hybrid nanoarray was directly used as an OER electrode, showing a current density of 10 mA cm-2 at an overpotential of 330 mV and a Tafel slope of 79 mV dec-1, both of which are much lower than pristine NF and the nanosheet array without graphene, and are among the lowest reported for Co-based OER catalysts and transition metal oxide-based ones measured under the same conditions. In addition, it can retain 92.4% of the current density after 66 h of chronoamperometry testing at a potential of 1.0 V vs. SCE, and 94.3% of the current density at 1.0 V vs. SCE after 200 cyclic voltammetry cycles (0-1.0 V vs. SCE). The excellent catalytic activity and stability toward OER are ascribed to the 3-D NF supported robustly grown networked layered nanosheet array structure and the synergistic effects between CoO layered nanosheets and graphene.

  1. Fabrication and characterization of vertically aligned carbon-nanotube membranes

    NASA Astrophysics Data System (ADS)

    Castellano, Richard; Akin, Cevat; Purri, Matt; Shan, Jerry; Kim, Sangil; Fornasiero, Francesco

    2015-11-01

    Membranes having vertically-aligned carbon-nanotube (VACNT) pores offer promise as highly efficient and permeable membranes for use as breathable thin films, or in filtration and separation applications, among others. However, current membrane-fabrication techniques utilizing chemical-vapor-deposition-grown VACNT arrays are costly and difficult to scale up. We have developed a solution-based, electric-field-assisted approach as a cost-effective and scalable method to produce large-area VACNT membranes. Nanotubes are dispersed in a liquid polymer, and aligned and electrodeposited with the aid of an electric field prior to crosslinking the polymer to create VACNT membranes. We experimentally examine the electrodeposition process, focusing on parameters including the electric field, composition of the solution, and CNT functionalization that can affect the nanotube number density in the resulting membrane. We characterize the CNT pore size and number density and investigate the transport properties of the membrane. Size-exclusion tests are used to check for defects and infer the pore size of the VACNT membranes. Dry-gas membrane permeability is measured with a pressurized nitrogen-flow system, while moisture-vapor-transfer rate is measured with the ASTM-E96 upright-cup test. We discuss the measured transport properties of the solution-based, electric-field-fabricated VACNT membranes in reference to their application as breathable thin films. We would like to acknowledge DTRA for their funding and support of our research.

  2. Structural CNT Composites Part II: Assessment of CNT Yarns as Reinforcement for Composite Overwrapped Pressure Vessels

    NASA Technical Reports Server (NTRS)

    Kim, Jae-Woo; Sauti, Godfrey; Cano, Roberto J.; Wincheski, Russell A.; Ratcliffe, James G.; Czabaj, Michael; Siochi, Emilie J.

    2015-01-01

    Carbon nanotubes (CNTs) are one-dimensional nanomaterials with outstanding electrical and thermal conductivities and mechanical properties. This combination of properties offers routes to enable lightweight structural aerospace components. Recent advances in the manufacturing of CNTs have made bulk forms such as yarns, tapes and sheets available in commercial quantities to permit the evaluation of these materials for aerospace use, where the superior tensile properties of CNT composites can be exploited in tension dominated applications such as composite overwrapped pressure vessels (COPVs). To investigate their utility in this application, aluminum rings were overwrapped with thermoset/CNT yarn composite and their mechanical properties measured. CNT composite overwrap characteristics such as processing method, CNT/resin ratio, and applied tension during CNT yarn winding were varied to determine their effects on the mechanical performance of the CNT composite overwrapped Al rings (CCOARs). Mechanical properties of the CCOARs were measured under static and cyclic loads at room, elevated, and cryogenic temperatures to evaluate their mechanical performance relative to bare Al rings. At room temperature, the breaking load of CCOARs with a 10.8% additional weight due to the CNT yarn/thermoset overwrap increased by over 200% compared to the bare Al ring. The quality of the wound CNT composites was also investigated using x-ray computed tomography.

  3. A template and catalyst-free metal-etching-oxidation method to synthesize aligned oxide nanowire arrays: NiO as an example.

    PubMed

    Wei, Zhi Peng; Arredondo, Miryam; Peng, Hai Yang; Zhang, Zhou; Guo, Dong Lai; Xing, Guo Zhong; Li, Yong Feng; Wong, Lai Mun; Wang, Shi Jie; Valanoor, Nagarajan; Wu, Tom

    2010-08-24

    Although NiO is one of the canonical functional binary oxides, there has been no report so far on the effective fabrication of aligned single crystalline NiO nanowire arrays. Here we report a novel vapor-based metal-etching-oxidation method to synthesize high-quality NiO nanowire arrays with good vertical alignment and morphology control. In this method, Ni foils are used as both the substrates and the nickel source; NiCl(2) powder serves as the additional Ni source and provides Cl(2) to initiate mild etching. No template is deliberately employed; instead a nanograined NiO scale formed on the NiO foil guides the vapor infiltration and assists the self-assembled growth of NiO nanowires via a novel process comprising simultaneous Cl(2) etching and gentle oxidation. Furthermore, using CoO nanowires and Co-doped NiO as examples, we show that this general method can be employed to produce nanowires of other oxides as well as the doped counterparts. PMID:20614899

  4. Photocatalysis-assisted water filtration: using TiO2-coated vertically aligned multi-walled carbon nanotube array for removal of Escherichia coli O157:H7.

    PubMed

    Oza, Goldie; Pandey, Sunil; Gupta, Arvind; Shinde, Sachin; Mewada, Ashmi; Jagadale, Pravin; Sharon, Maheshwar; Sharon, Madhuri

    2013-10-01

    A porous ceramic was coated with vertically aligned multi-walled carbon nanotubes (MWCNTs) by spray pyrolysis. Titanium dioxide (TiO2) nanoparticles were then coated onto this densely aligned MWCNT. The presence of TiO2/MWCNT interfacial arrays was confirmed by X-ray diffraction (XRD), scanning electron microscope-energy dispersive analysis of X-ray (SEM-EDAX) and transmission electron microscope (TEM). This is a novel report in which water loaded with a most dreadful enterohemorrhagic pathogenic strain of Escherichia coli O157:H7 was filtered through TiO2/MWCNT coated porous ceramic filter and then analysed. Bacterial removal performance was found to be significantly lower in control i.e. plain porous ceramic (P<0.05) as compared to TiO2/MWCNT coated ceramic. The photocatalytic killing rate constant for TiO2-ceramic and MWCNT/TiO2-ceramic under fluorescent light was found be 1.45×10(-2) min(-1) and 2.23×10(-2) min(-1) respectively. Further, when I-V characteristics were performed for TiO2/MWCNT composite, it was corroborated that the current under light irradiation is comparatively higher than that in dark, thus proving it to be photocatalytically efficient system. The enhanced photocatalysis may be a contribution of increased surface area and charge transfer rate as a consequence of aligned MWCNT network. PMID:23910358

  5. New carbon nanotube antenna array simulation and fabrication

    NASA Astrophysics Data System (ADS)

    Zareie, Hosein; Davoudzadeh, Nima; Koohsorkhi, Javad; Mohajerzadeh, Shamsoddin; Rouhi, Nima

    2009-03-01

    A novel THz antenna structure, made of carbon nanotube arrays is suggested. Using CST MICROWAVE STUDIO (CST MWS), the capabilities of carbon nanotube terahertz (THz) antenna arrays have been simulated and this CNT antenna array has been fabricated.

  6. Tough and Flexible CNT-Polymeric Hybrid Scaffolds for Engineering Cardiac Constructs

    PubMed Central

    Kharaziha, Mahshid; Ryon Shin, Su; Nikkhah, Mehdi; Nur Topkaya, Seda; Masoumi, Nafiseh; Annabi, Nasim; Dokmeci, Mehmet. R.

    2014-01-01

    In the past few years, a considerable amount of effort has been devoted toward the development of biomimetic scaffolds for cardiac tissue engineering. However, most of the previous scaffolds have been electrically insulating or lacked the structural and mechanical robustness to engineer cardiac tissue constructs with suitable electrophysiological functions. Here, we developed tough and flexible hybrid scaffolds with enhanced electrical properties composed of carbon nanotubes (CNTs) embedded aligned poly(glycerol sebacate):gelatin (PG) electrospun nanofibers. Incorporation of varying concentrations of CNTs from 0 to 1.5% within the PG nanofibrous scaffolds (CNT-PG scaffolds) notably enhanced fiber alignment and improved the electrical conductivity and toughness of the scaffolds while maintaining the viability, retention, alignment, and contractile activities of cardiomyocytes (CMs) seeded on the scaffolds. The resulting CNT-PG scaffolds resulted in stronger spontaneous and synchronous beating behavior (3.5-fold lower excitation threshold and 2.8-fold higher maximum capture rate) compared to those cultured on PG scaffold. Overall, our findings demonstrated that aligned CNT-PG scaffold exhibited superior mechanical properties with enhanced CM beating properties. It is envisioned that the proposed hybrid scaffolds can be useful for generating cardiac tissue constructs with improved organization and maturation. PMID:24927679

  7. Tough and flexible CNT-polymeric hybrid scaffolds for engineering cardiac constructs.

    PubMed

    Kharaziha, Mahshid; Shin, Su Ryon; Nikkhah, Mehdi; Topkaya, Seda Nur; Masoumi, Nafiseh; Annabi, Nasim; Dokmeci, Mehmet R; Khademhosseini, Ali

    2014-08-01

    In the past few years, a considerable amount of effort has been devoted toward the development of biomimetic scaffolds for cardiac tissue engineering. However, most of the previous scaffolds have been electrically insulating or lacked the structural and mechanical robustness to engineer cardiac tissue constructs with suitable electrophysiological functions. Here, we developed tough and flexible hybrid scaffolds with enhanced electrical properties composed of carbon nanotubes (CNTs) embedded aligned poly(glycerol sebacate):gelatin (PG) electrospun nanofibers. Incorporation of varying concentrations of CNTs from 0 to 1.5% within the PG nanofibrous scaffolds (CNT-PG scaffolds) notably enhanced fiber alignment and improved the electrical conductivity and toughness of the scaffolds while maintaining the viability, retention, alignment, and contractile activities of cardiomyocytes (CMs) seeded on the scaffolds. The resulting CNT-PG scaffolds resulted in stronger spontaneous and synchronous beating behavior (3.5-fold lower excitation threshold and 2.8-fold higher maximum capture rate) compared to those cultured on PG scaffold. Overall, our findings demonstrated that aligned CNT-PG scaffold exhibited superior mechanical properties with enhanced CM beating properties. It is envisioned that the proposed hybrid scaffolds can be useful for generating cardiac tissue constructs with improved organization and maturation. PMID:24927679

  8. Carbon nanotube (CNT) fins for enhanced cooling of shape memory alloy wire

    NASA Astrophysics Data System (ADS)

    Pathak, Anupam; AuBuchon, Joseph; Brei, Diann; Shaw, John; Luntz, Jonathan; Jin, Sungho

    2008-03-01

    A commonly noted disadvantage of shape memory alloys is their frequency response which is limited by how fast the material can be cooled. This paper presents a feasibility study of using vertically aligned carbon nanotubes (CNT) as microscopic cooling fins to improve convective heat transfer. Using DC plasma enhanced chemical vapor deposition (PECVD), aligned CNT's were successfully grown directly on ½ of the surface of a 0.38 mm diameter SMA wire, achieving desirable thermal contact. Cooling speeds were measured with a thermal imaging camera, and the effective convective coefficient was extracted from the temperature profiles using a basic cooling model of the wire. From this model, the effective convective coefficient was estimated to have increased by 24% (from 50 W/m2K for untreated SMA wire to 62 W/m2K for the nanotube treated wire), indicating that the deposition of CNT's indeed increased performance. By extrapolating these results to full wire coverage, up to a 46% improvement in frequency response with zero weight or volumetric penalties is predicted. Further improvements in cooling performance are likely to occur with higher CNT densities and longer nanotube lengths, allowing further developments of this technology to benefit many future applications utilizing high-speed miniature/micro-scale SMA actuators.

  9. YBa2Cu3O7-ALIGN="MIDDLE" SRC="http://www.iop.org/icons/Journals/Common/ delta.gif" ALT="delta" /> dc SQUID array for multichannel magnetometry and multichannel flip-chip current sensors

    NASA Astrophysics Data System (ADS)

    Ramos, J.; Zakosarenko, V.; IJsselsteijn, R.; Stolz, R.; Schultze, V.; Chwala, A.; Hoenig, H. E.; Meyer, H.-G.

    1999-09-01

    We have prepared arrays of single-layer washer-type dc superconducting quantum interference devices (SQUIDs) on 10 mm × 10 mm bicrystal substrates. Each SQUID in the array is equipped with its own modulation loop, which makes a separate operation of them possible. Arrays containing nine or 11 dc SQUIDs have been tested and the crosstalk between neighbouring channels has been found to be 5%. The field sensitivity of the SQUIDs is 85 nT icons/Journals/Common/Phi" ALT="Phi" ALIGN="TOP"/>0-1 and 105 nT icons/Journals/Common/Phi" ALT="Phi" ALIGN="TOP"/>0-1 for the nine- and 11-device array, respectively. The equivalent flux noise is typically icons/Journals/Common/le" ALT="le" ALIGN="TOP"/> 20 icons/Journals/Common/mu" ALT="mu" ALIGN="TOP"/>icons/Journals/Common/Phi" ALT="Phi" ALIGN="TOP"/>0 Hz-1/2 down to 1 Hz with ac bias reversal. A field resolution of less than 2.1 pT Hz-1/2 has been obtained for at least eight channels on a chip. By using multiturn YBa2Cu3O7-icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> input coils and mounting them in a flip-chip configuration together with the single-layer dc SQUIDs we have been able to build three-channel current sensors. The current sensitivity equals 3-3.5 icons/Journals/Common/mu" ALT="mu" ALIGN="TOP"/>A icons/Journals/Common/Phi" ALT="Phi" ALIGN="TOP"/>0-1 depending on the alignment of the flip-chip configuration. The current resolution of the devices is < 70 pA Hz-1/2. We show the possibility of building sensitive magnetometers by connecting the input coil of these current sensors to a normal-conducting pickup antenna.

  10. Seedless Pattern Growth of Quasi-Aligned ZnO Nanorod Arrays on Cover Glass Substrates in Solution

    NASA Astrophysics Data System (ADS)

    Ahsanulhaq, Q.; Kim, Jin Hwan; Kim, Jeong Hyun; Hahn, Y. B.

    2010-03-01

    A hybrid technique for the selective growth of ZnO nanorod arrays on wanted areas of thin cover glass substrates was developed without the use of seed layer of ZnO. This method utilizes electron-beam lithography for pattern transfer on seedless substrate, followed by solution method for the bottom-up growth of ZnO nanorod arrays on the patterned substrates. The arrays of highly crystalline ZnO nanorods having diameter of 60 ± 10 nm and length of 750 ± 50 nm were selectively grown on different shape patterns and exhibited a remarkable uniformity in terms of diameter, length, and density. The room temperature cathodluminescence measurements showed a strong ultraviolet emission at 381 nm and broad visible emission at 585-610 nm were observed in the spectrum.

  11. Synthesis and characterization of vertically aligned carbon nanotube forest for solid state fiber spinning.

    PubMed

    Ryu, Seong Woo; Hwang, Jae Won; Hong, Soon Hyung

    2012-07-01

    Continuous carbon nanotubes (CNT) fibers were directly spun from a vertically aligned CNT forest grown by a plasma-enhanced chemical vapor deposition (PECVD) process. The correlation of the CNT structure with Fe catalyst coarsening, reaction time, and the CNTs bundling phenomenon was investigated. We controlled the diameters and walls of the CNTs and minimized the amorphous carbon deposition on the CNTs for favorable bundling and spinning of the CNT fibers. The CNT fibers were fabricated with an as-grown vertically aligned CNT forest by a PECVD process using nanocatalyst an Al2O3 buffer layer, followed by a dry spinning process. Well-aligned CNT fibers were successfully manufactured using a dry spinning process and a surface tension-based densification process by ethanol. The mechanical properties were characterized for the CNT fibers spun from different lengths of a vertically aligned CNT forest. Highly oriented CNT fibers from the dry spinning process were characterized with high strength, high modulus, and high electrical as well as thermal conductivities for possible application as ultralight, highly strong structural materials. Examples of structural materials include space elevator cables, artificial muscle, and armor material, while multifunctional materials include E-textile, touch panels, biosensors, and super capacitors. PMID:22966627

  12. A laser-assisted process to produce patterned growth of vertically aligned nanowire arrays for monolithic microwave integrated devices

    NASA Astrophysics Data System (ADS)

    Van Kerckhoven, Vivien; Piraux, Luc; Huynen, Isabelle

    2016-06-01

    An experimental process for the fabrication of microwave devices made of nanowire arrays embedded in a dielectric template is presented. A pulse laser process is used to produce a patterned surface mask on alumina templates, defining precisely the wire growing areas during electroplating. This technique makes it possible to finely position multiple nanowire arrays in the template, as well as produce large areas and complex structures, combining transmission line sections with various nanowire heights. The efficiency of this process is demonstrated through the realisation of a microstrip electromagnetic band-gap filter and a substrate-integrated waveguide.

  13. A laser-assisted process to produce patterned growth of vertically aligned nanowire arrays for monolithic microwave integrated devices.

    PubMed

    Kerckhoven, Vivien Van; Piraux, Luc; Huynen, Isabelle

    2016-06-10

    An experimental process for the fabrication of microwave devices made of nanowire arrays embedded in a dielectric template is presented. A pulse laser process is used to produce a patterned surface mask on alumina templates, defining precisely the wire growing areas during electroplating. This technique makes it possible to finely position multiple nanowire arrays in the template, as well as produce large areas and complex structures, combining transmission line sections with various nanowire heights. The efficiency of this process is demonstrated through the realisation of a microstrip electromagnetic band-gap filter and a substrate-integrated waveguide. PMID:27138863

  14. Photolithographic fabrication of gated self-aligned parallel electron beam emitters with a single-stranded carbon nanotube

    NASA Astrophysics Data System (ADS)

    Ho, Justin; Ono, Takahito; Tsai, Ching-Hsiang; Esashi, Masayoshi

    2008-09-01

    In this paper we report on the development of a photolithographic process to fabricate a gated-emitter array with single-stranded carbon nanotubes (CNTs) self-aligned to the center of the emitter gate using plasma-enhanced chemical vapor deposition (PECVD). Si tips are formed on a silicon wafer by anisotropic etching of Si using SiO2 as a mask. Deposition of a SiO2 insulating layer and Cr-W electrode layers creates protrusions above the Si tips. This wafer is polished, and the Cr-W on the tips is removed. Etching of the SiO2 using hydrofluoric acid is performed to expose the gated Si tip. Incorporation of a novel diffusion process produces single-stranded CNTs by depositing a thin Ni layer on the Si tips and thermally diffusing the Ni layer to yield a catalyst particle for single-stranded CNT growth. The large surface to volume ratio at the apex of the Si tip allows a Ni particle to remain to act as a catalyst to grow a single-stranded CNT for fabricating the CNT based emitter structure. Diffusion of the Ni is carried out in situ during the heating phase of the PECVD CNT growth process at 600 °C. The diameters of the observed CNTs are on the order of 20 nm. The field emission characteristics of the gated field emitters are evaluated. The measured turn-on voltage of the gated emitter is 5 V.

  15. Facile construction of vertically aligned EuS-ZnO hybrid core shell nanorod arrays for visible light driven photocatalytic properties

    SciTech Connect

    Ranjith, K. S.; Kumar, D. Ranjith; Kumar, R. T. Rajendra

    2015-06-24

    We demonstrated the development of coupled semiconductor in the form of hybrid heterostructures for significant advancement in catalytic functional materials. In this article, we report the preparation of vertically aligned core shell ZnO-EuS nanorod photocatalyst arrays by a simple chemical solution process followed by sulfudation process. The XRD pattern confirmed formation of the hexagonal wurtzite structure of ZnO and cubic nature of the EuS. Cross sectional FESEM images show vertical rod array structure, and the size of the nanorods ranges from 80 to 120 nm. UV-Vis DRS spectra showed that the optical absorption of ZnO was significantly enhanced to the visible region by modification with EuS surfaces. TEM study confirmed that the surface of ZnO was drastically improved by the modification with EuS nanoparticle. The catalytic activity of EuS−ZnO core shell nanorod arrays were evaluated by the photodegradation of Methylene Blue (MB) dye under visible irradiation. The results revealed that the photocatalytic activity of EuS−ZnO was much higher than that of ZnO under natural sunlight. EuS−ZnO was found to be stable and reusable without appreciable loss of catalytic activity up to four consecutive cycles.

  16. Morphology and composition controlled growth of polar c-axis and nonpolar m-axis well-aligned ternary III-nitride nanotube arrays.

    PubMed

    Li, Huijie; Zhao, Guijuan; Kong, Susu; Han, Dongyue; Wei, Hongyuan; Wang, Lianshan; Chen, Zhen; Yang, Shaoyan

    2015-10-21

    Control over the nanostructure morphology and growth orientation is in high demand for fundamental research and technological applications. Herein we report a general strategy to fabricate polar c-axis and nonpolar m-axis well-aligned III-nitride ternary nanotube arrays with controllable morphologies and compositions. By depositing AlN on the InN nanorod array templates and thermally removing the InN templates, InAlN nanotubes can be obtained. Polar c-axis and nonpolar m-axis nanotubes were formed on the c- and r-plane sapphire substrates, respectively. The nanotubes are single crystalline and highly ordered on the substrates, as revealed by X-ray diffraction, electron microscopy, and selected area electron microscopy characterization. It was found that the In droplets on top of the InN nanorods play a critical role in controlling the morphology of the nanotubes. By keeping or removing the In droplets, the obtained nanotubes exhibited both ends open or only one end open. And by varying the AlN deposition temperature, the In composition in the nanotubes can be changed from 0 to 0.29. The nanotube synthesis method is simple and can be applied to the formation of other III-nitride ternary (InGaN, and AlGaN) or quaternary (InAlGaN) alloy nanotube arrays. PMID:26395389

  17. Integrating Metal-Oxide-Decorated CNT Networks with a CMOS Readout in a Gas Sensor

    PubMed Central

    Lee, Hyunjoong; Lee, Sanghoon; Kim, Dai-Hong; Perello, David; Park, Young June; Hong, Seong-Hyeon; Yun, Minhee; Kim, Suhwan

    2012-01-01

    We have implemented a tin-oxide-decorated carbon nanotube (CNT) network gas sensor system on a single die. We have also demonstrated the deposition of metallic tin on the CNT network, its subsequent oxidation in air, and the improvement of the lifetime of the sensors. The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy. The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way. The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V. The sensor system was successfully tested in the detection of ammonia gas at elevated temperatures. PMID:22736966

  18. Integrating metal-oxide-decorated CNT networks with a CMOS readout in a gas sensor.

    PubMed

    Lee, Hyunjoong; Lee, Sanghoon; Kim, Dai-Hong; Perello, David; Park, Young June; Hong, Seong-Hyeon; Yun, Minhee; Kim, Suhwan

    2012-01-01

    We have implemented a tin-oxide-decorated carbon nanotube (CNT) network gas sensor system on a single die. We have also demonstrated the deposition of metallic tin on the CNT network, its subsequent oxidation in air, and the improvement of the lifetime of the sensors. The fabricated array of CNT sensors contains 128 sensor cells for added redundancy and increased accuracy. The read-out integrated circuit (ROIC) was combined with coarse and fine time-to-digital converters to extend its resolution in a power-efficient way. The ROIC is fabricated using a 0.35 μm CMOS process, and the whole sensor system consumes 30 mA at 5 V. The sensor system was successfully tested in the detection of ammonia gas at elevated temperatures. PMID:22736966

  19. Plasmon enhanced fluorescence studies from aligned gold nanorod arrays modified with SiO2 spacer layers

    NASA Astrophysics Data System (ADS)

    Damm, Signe; Fedele, Stefano; Murphy, Antony; Holsgrove, Kristina; Arredondo, Miryam; Pollard, Robert; Barry, James N.; Dowling, Denis P.; Rice, James H.

    2015-05-01

    Here, we demonstrate that quasi self-standing Au nanorod arrays prepared with plasma polymerisation deposited SiO2 dielectric spacers support surface enhanced fluorescence (SEF) while maintaining high signal reproducibility. We show that it is possible to find a balance between enhanced radiative and non-radiative decay rates at which the fluorescent intensity is maximized. The SEF signal optimised with a 30 nm spacer layer thickness showed a 3.5-fold enhancement with a signal variance of <15% thereby keeping the integrity of the nanorod array. We also demonstrate the decreased importance of obtaining resonance conditions when localized surface plasmon resonance is positioned within the spectral region of Au interband transitions. Procedures for further increasing the SEF enhancement factor are also discussed.

  20. Plasmon enhanced fluorescence studies from aligned gold nanorod arrays modified with SiO{sub 2} spacer layers

    SciTech Connect

    Damm, Signe; Fedele, Stefano; Rice, James H.; Murphy, Antony; Holsgrove, Kristina; Arredondo, Miryam; Pollard, Robert; Barry, James N.; Dowling, Denis P.

    2015-05-04

    Here, we demonstrate that quasi self-standing Au nanorod arrays prepared with plasma polymerisation deposited SiO{sub 2} dielectric spacers support surface enhanced fluorescence (SEF) while maintaining high signal reproducibility. We show that it is possible to find a balance between enhanced radiative and non-radiative decay rates at which the fluorescent intensity is maximized. The SEF signal optimised with a 30 nm spacer layer thickness showed a 3.5-fold enhancement with a signal variance of <15% thereby keeping the integrity of the nanorod array. We also demonstrate the decreased importance of obtaining resonance conditions when localized surface plasmon resonance is positioned within the spectral region of Au interband transitions. Procedures for further increasing the SEF enhancement factor are also discussed.

  1. Optical antenna arrays of carbon nanotubes and their fabrication on polyimide and transparent conducting oxides for direct device integration

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Kempa, K.; Kimball, B.; Ren, Z. F.

    2005-11-01

    Vertically-aligned carbon nanotubes/nanofibers grown on various substrates by a direct-current plasma-enhanced chemical vapor deposition method have been shown experimentally to function as classical low-loss dipole antenna arrays at optical frequencies. Two fundamental antenna effects, e.g., the polarization effect and length matching effect, directly observed on large-scale CNT arrays in visible frequency range, hold them promising for industry-level fabrication of devices including linear/beam-splitting polarizers, solar energy converters, THz demodulators, etc., some of which will, however, require or prefer a flexible and/or transparent conducting substrate to be compatible for multi-level integration and low-cost manufacturing process. A low-energy dark discharge fabrication technique is therefore devised which successfully yields CNT antennas directly on polyimide films and transparent conducting oxides (ITO, ZnO) with the absence of a buffer layer.

  2. A novel method to encapsulate a Au nanorod array in 15 nm radius multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Liao, Gaomin; Pan, Yuanyuan; Wu, Qiang; Li, Shaoyun; Weng, Yuyan; Zhang, Xiaohua; Yang, Zhaohui; Guo, Jun; Chen, Muzi; Tang, Minghua; Tsui, Ophelia K. C.

    2014-11-01

    In this paper we demonstrate a novel complex array structure comprising well-aligned Au nanorods (10 nm in diameter) encapsulated inside 15 nm radius multiwalled carbon nanotubes (MWCNTs). A pre-aligned and open-ended nanoporous MWCNT membrane is used as the starting material. Au nanorods are precisely deposited and aligned inside the hollow channels of CNTs by inter-diffusing the HAuCl4 precursor and the reductant solution. Ultra-long Au nanowires and spherical Au nanoparticles are also observed in the CNT cavity with the same diameter in special cases. Using high-resolution TEM (HRTEM), scanning transmission electron microscopy (STEM), 3-dimensional TEM (3D-TEM) and energy dispersive X-ray spectroscopy (EDX), the precise location and composition of the encapsulated Au components with various structures are confirmed. This aligned Au@CNT endohedral material has important potential applications in nanocatalysis, waveguides, as well as in novel plasmonic devices.In this paper we demonstrate a novel complex array structure comprising well-aligned Au nanorods (10 nm in diameter) encapsulated inside 15 nm radius multiwalled carbon nanotubes (MWCNTs). A pre-aligned and open-ended nanoporous MWCNT membrane is used as the starting material. Au nanorods are precisely deposited and aligned inside the hollow channels of CNTs by inter-diffusing the HAuCl4 precursor and the reductant solution. Ultra-long Au nanowires and spherical Au nanoparticles are also observed in the CNT cavity with the same diameter in special cases. Using high-resolution TEM (HRTEM), scanning transmission electron microscopy (STEM), 3-dimensional TEM (3D-TEM) and energy dispersive X-ray spectroscopy (EDX), the precise location and composition of the encapsulated Au components with various structures are confirmed. This aligned Au@CNT endohedral material has important potential applications in nanocatalysis, waveguides, as well as in novel plasmonic devices. Electronic supplementary information (ESI

  3. Formation of self-assembled InGaAs quantum dot arrays aligned along quasiperiodic multiatomic steps on vicinal (111)B GaAs

    SciTech Connect

    Akiyama, Y.; Sakaki, H.

    2006-10-30

    Dense and highly ordered arrays of self-assembled InGaAs quantum dots are formed by molecular beam epitaxy along multiatomic steps on vicinal (111)B GaAs. This unique structure has been synthesized by depositing a nominally 3-nm-thick In{sub 0.3}Ga{sub 0.7}As layer onto a periodically corrugated surface prepared on a GaAs substrate tilted 8.5 deg. from (111)B. Each dot is typically 30-50 nm in lateral size and about 4 nm in height. Accumulation and release processes of strains in InGaAs layers deposited on stepped surfaces are discussed to suggest a possible mechanism for the aligned dot formation.

  4. Determination of the texture of arrays of aligned carbon nanotubes from the angular dependence of the X-ray emission and X-ray absorption spectra

    SciTech Connect

    Okotrub, A. V. Belavin, V. V.; Bulusheva, L. G.; Gusel'nikov, A. V.; Kudashov, A. G.; Vyalikh, D. V.; Molodtsov, S. L.

    2008-09-15

    The properties of materials containing carbon nanotubes depend on the degree of alignment and the internal structure of nanotubes. It is shown that the degree of misorientation of carbon nanotubes in samples can be evaluated from the measurements of the angular dependences of the carbon X-ray emission and carbon X-ray absorption spectra. The CK{sub {alpha}} emission and CK X-ray absorption spectra of the array of multiwalled carbon nanotubes synthesized by catalytic thermolysis of a mixture of fullerene and ferrocene are measured. A comparison of the calculated model dependences of the relative intensities of the {pi} and {sigma} bands in the spectra with the experimental results makes it possible to evaluate the degree of misorientation of nanotubes in the sample and their internal texture.

  5. Self-aligned tip deinsulation of atomic layer deposited Al2O3 and parylene C coated Utah electrode array based neural interfaces

    NASA Astrophysics Data System (ADS)

    Xie, Xianzong; Rieth, Loren; Negi, Sandeep; Bhandari, Rajmohan; Caldwell, Ryan; Sharma, Rohit; Tathireddy, Prashant; Solzbacher, Florian

    2014-03-01

    The recently developed alumina and parylene C bilayer encapsulation improved the lifetime of neural interfaces. Tip deinsulation of Utah electrode array based neural interfaces is challenging due to the complex 3D geometries and high aspect ratios of the devices. A three-step self-aligned process was developed for tip deinsulation of bilayer encapsulated arrays. The deinsulation process utilizes laser ablation to remove parylene C, O2 reactive ion etching to remove carbon and parylene residues, and buffered oxide etch to remove alumina deposited by atomic layer deposition, and expose the IrOx tip metallization. The deinsulated iridium oxide area was characterized by scanning electron microscopy, atomic force microscopy, x-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy to determine the morphology, surface morphology, composition, and electrical properties of the deposited layers and deinsulated tips. The alumina layer was found to prevent the formation of micro cracks on iridium oxide during the laser ablation process, which has been previously reported as a challenge for laser deinsulation of parylene films. The charge injection capacity, charge storage capacity, and impedance of deinsulated iridium oxide were characterized to determine the deinsulation efficacy compared to parylene-only insulation. Deinsulated iridium oxide with bilayer encapsulation had higher charge injection capacity (240 versus 320 nC) and similar electrochemical impedance (2.5 versus 2.5 kΩ) compared to deinsulated iridium oxide with only parylene coating for an area of 2 × 10-4 cm2. Tip impedances were in the range of 20-50 kΩ, with a median of 32 kΩ and a standard deviation of 30 kΩ, showing the effectiveness of the self-aligned deinsulation process for alumina and parylene C bilayer encapsulation. The relatively uniform tip impedance values demonstrated the consistency of tip exposures.

  6. SELF ALIGNED TIP DEINSULATION OF ATOMIC LAYER DEPOSITED AL2O3 AND PARYLENE C COATED UTAH ELECTRODE ARRAY BASED NEURAL INTERFACES

    PubMed Central

    Xie, Xianzong; Rieth, Loren; Negi, Sandeep; Bhandari, Rajmohan; Caldwell, Ryan; Sharma, Rohit; Tathireddy, Prashant; Solzbacher, Florian

    2014-01-01

    The recently developed alumina and Parylene C bi-layer encapsulation improved the lifetime of neural interfaces. Tip deinsulation of Utah electrode array based neural interfaces is challenging due to the complex 3D geometries and high aspect ratios of the devices. A three-step self-aligned process was developed for tip deinsulation of bilayer encapsulated arrays. The deinsulation process utilizes laser ablation to remove Parylene C, O2 reactive ion etching to remove carbon and Parylene residues, and buffered oxide etch to remove alumina deposited by atomic layer deposition, and expose the IrOx tip metallization. The deinsulated iridium oxide area was characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy to determine the morphology, surface morphology, composition, and electrical properties of the deposited layers and deinsulated tips. The alumina layer was found to prevent the formation of micro cracks on iridium oxide during the laser ablation process, which has been previously reported as a challenge for laser deinsulation of Parylene films. The charge injection capacity, charge storage capacity, and impedance of deinsulated iridium oxide were characterized to determine the deinsulation efficacy compared to Parylene-only insulation. Deinsulated iridium oxide with bilayer encapsulation had higher charge injection capacity (240 vs 320 nC) and similar electrochemical impedance (2.5 vs 2.5 kΩ) compared to deinsulated iridium oxide with only Parylene coating for an area of 2 × 10−4 cm2. Tip impedances were in the ranges of 20 to 50 kΩ, with median of 32 KΩ and standard deviation of 30 kΩ, showing the effectiveness of the self-aligned deinsulation process for alumina and Parylene C bi-layer encapsulation. The relatively uniform tip impedance values demonstrated the consistency of tip exposures. PMID:24771981

  7. Low-Temperature Growth of Well-Aligned ZnO Nanorod Arrays by Chemical Bath Deposition for Schottky Diode Application

    NASA Astrophysics Data System (ADS)

    Yuan, Zhaolin

    2015-04-01

    A well-aligned ZnO nanorod array (ZNRA) was successfully grown on an indium tin oxide (ITO) substrate by chemical bath deposition at low temperature. The morphology, crystalline structure, transmittance spectrum and photoluminescence spectrum of as-grown ZNRA were investigated by field emission scanning electron microscopy, x-ray diffraction, ultraviolet-visible spectroscopy and spectrophotometer, respectively. The results of these measurements showed that the ZNRA contained densely packed, aligned nanorods with diameters from 30 nm to 40 nm and a wurtzite structure. The ZNRA exhibited good optical transparency within the visible spectral range, with >80% transmission. Gold (Au) was deposited on top of the ZNRA, and the current-voltage characteristics of the resulting ITO/ZNRA/Au device in the dark were evaluated in detail. The ITO/ZNRA/Au device acted as a Schottky barrier diode with rectifying behaviour, low turn-on voltage (0.6 V), small reverse-bias saturation current (3.73 × 10-6 A), a high ideality factor (3.75), and a reasonable barrier height (0.65 V) between the ZNRA and Au.

  8. Hydrothermal synthesis of highly crystalline ZnO nanorod arrays: Dependence of morphology and alignment on growth conditions

    NASA Astrophysics Data System (ADS)

    Azzez, Shrook A.; Hassan, Z.; Hassan, J. J.; Alimanesh, M.; Rasheed, Hiba S.; Sabah, Fayroz A.; Abdulateef, Sinan A.

    2016-07-01

    Highly oriented zinc oxide nanorod were successfully grown on seeded p-type silicone substrate by hydrothermal methode. The morphology and the crystallinty of ZnO c-axis (002) arrays were systematically studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) methods. The effect of seed layer pre-annealing on nanorods properties was explained according to the nucleation site of ZnO nanoparticles on silicon substrate. In addition, the variation of the equal molarity of zinc nitrate hexahydrate and hexamine concentrations in the reaction vessel play a crucial role related to the ZnO nanorods.

  9. Self-Aligned Cu-Si Core-Shell Nanowire Array as a High-Performance Anode for Li-Ion Batteries

    SciTech Connect

    Qu, Jun; Li, Huaqing; Henry Jr, John James; Martha, Surendra K; Dudney, Nancy J; Lance, Michael J; Mahurin, Shannon Mark; Besmann, Theodore M; Dai, Sheng

    2012-01-01

    Silicon nanowires (NWs) have been reported as a promising anode that demonstrated high capacity without pulverization during cycling, however, they present some technical issues that remain to be solved. The high aspect ratio of the NWs and their small contact areas with the current collector cause high electrical resistance, which results in inefficient electron transport. The nano-size interface between a NW and the substrate experiences high shear stress during lithiation, causing the wire to separate from the current collector. In addition, most reported methods for producing silicon NWs involve high-temperature processing and require catalysts that later become contaminants. This study developed a new self-aligned Cu-Si core-shell NW array using a low-temperature, catalyst-free process to address the issues described. The silicon shell is amorphous as synthesized and accommodates Li-ions without phase transformation. The copper core functions as a built-in current collector to provide very short (nm) electron transport pathways as well as backbone to improve mechanical strength. Initial electrochemical evaluation has demonstrated good capacity retention and high Coulombic efficiency for this new anode material in a half-cell configuration. No wire fracture or core-shell separation was observed after cycling. However, electrolyte decomposition products largely covered the top surface of the NW array, restricting electrolyte access and causing capacity reduction at high charging rates.

  10. Demonstration of a Segment Alignment Maintenance System on a Seven-Segment Sub-Array of the Hobby-Eberly Telescope

    NASA Technical Reports Server (NTRS)

    Rakoczy, John; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    NASA's Marshall Space Flight Center, in collaboration with Blue Line Engineering of Colorado Springs, Colorado, is developing a Segment Alignment Maintenance System (SAMS) for McDonald Observatory's Hobby-Eberly Telescope (HET). The SAMS shall sense motions of the 91 primary mirror segments and send corrections to HET's primary mirror controller as the mirror segments misalign due to thermo-elastic deformations of the mirror support structure. The SAMS consists of inductive edge sensors supplemented by inclinometers for global radius of curvature sensing. All measurements are sent to the SAMS computer where mirror motion corrections are calculated. In October 2000, a prototype SAMS was installed on a seven-segment cluster of the HET. Subsequent testing has shown that the SAMS concept and architecture are a viable practical approach to maintaining HET's primary mirror figure, or the figure of any large segmented telescope. This paper gives a functional description of the SAMS sub-array components and presents test data to characterize the performance of the sub-array SAMS.

  11. Morphology and composition controlled growth of polar c-axis and nonpolar m-axis well-aligned ternary III-nitride nanotube arrays

    NASA Astrophysics Data System (ADS)

    Li, Huijie; Zhao, Guijuan; Kong, Susu; Han, Dongyue; Wei, Hongyuan; Wang, Lianshan; Chen, Zhen; Yang, Shaoyan

    2015-10-01

    Control over the nanostructure morphology and growth orientation is in high demand for fundamental research and technological applications. Herein we report a general strategy to fabricate polar c-axis and nonpolar m-axis well-aligned III-nitride ternary nanotube arrays with controllable morphologies and compositions. By depositing AlN on the InN nanorod array templates and thermally removing the InN templates, InAlN nanotubes can be obtained. Polar c-axis and nonpolar m-axis nanotubes were formed on the c- and r-plane sapphire substrates, respectively. The nanotubes are single crystalline and highly ordered on the substrates, as revealed by X-ray diffraction, electron microscopy, and selected area electron microscopy characterization. It was found that the In droplets on top of the InN nanorods play a critical role in controlling the morphology of the nanotubes. By keeping or removing the In droplets, the obtained nanotubes exhibited both ends open or only one end open. And by varying the AlN deposition temperature, the In composition in the nanotubes can be changed from 0 to 0.29. The nanotube synthesis method is simple and can be applied to the formation of other III-nitride ternary (InGaN, and AlGaN) or quaternary (InAlGaN) alloy nanotube arrays.Control over the nanostructure morphology and growth orientation is in high demand for fundamental research and technological applications. Herein we report a general strategy to fabricate polar c-axis and nonpolar m-axis well-aligned III-nitride ternary nanotube arrays with controllable morphologies and compositions. By depositing AlN on the InN nanorod array templates and thermally removing the InN templates, InAlN nanotubes can be obtained. Polar c-axis and nonpolar m-axis nanotubes were formed on the c- and r-plane sapphire substrates, respectively. The nanotubes are single crystalline and highly ordered on the substrates, as revealed by X-ray diffraction, electron microscopy, and selected area electron microscopy

  12. The Highly Robust Electrical Interconnects and Ultrasensitive Biosensors Based on Embedded Carbon Nanotube Arrays

    NASA Technical Reports Server (NTRS)

    Li, Jun; Cassell, Alan; Koehne, Jessica; Chen, Hua; Ng, Hou Tee; Ye, Qi; Stevens, Ramsey; Han, Jie; Meyyappan, M.

    2003-01-01

    We report on our recent breakthroughs in two different applications using well-aligned carbon nanotube (CNT) arrays on Si chips, including (1) a novel processing solution for highly robust electrical interconnects in integrated circuit manufacturing, and (2) the development of ultrasensitive electrochemical DNA sensors. Both of them rely on the invention of a bottom-up fabrication scheme which includes six steps, including: (a) lithographic patterning, (b) depositing bottom conducting contacts, (c) depositing metal catalysts, (d) CNT growth by plasma enhanced chemical vapor deposition (PECVD), (e) dielectric gap-filling, and (f) chemical mechanical polishing (CMP). Such processes produce a stable planarized surface with only the open end of CNTs exposed, whch can be further processed or modified for different applications. By depositing patterned top contacts, the CNT can serve as vertical interconnects between the two conducting layers. This method is fundamentally different fiom current damascene processes and avoids problems associated with etching and filling of high aspect ratio holes at nanoscales. In addition, multiwalled CNTs (MWCNTs) are highly robust and can carry a current density of 10(exp 9) A/square centimeters without degradation. It has great potential to help extending the current Si technology. The embedded MWCNT array without the top contact layer can be also used as a nanoelectrode array in electrochemical biosensors. The cell time-constant and sensitivity can be dramatically improved. By functionalizing the tube ends with specific oligonucleotide probes, specific DNA targets can be detected with electrochemical methods down to subattomoles.

  13. A computational study of the quantum transport properties of a Cu–CNT composite† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5cp01470k Click here for additional data file.

    PubMed Central

    Koziol, Krzysztof

    2015-01-01

    The quantum transport properties of a Cu–CNT composite are studied using a non-equilibrium Green's function approach combined with the self-consistent-charge density-functional tight-binding method. The results show that the electrical conductance of the composite depends strongly on CNT density and alignment but more weakly on chirality. Alignment with the applied bias is preferred and the conductance of the composite increases as its mass density increases. PMID:26120607

  14. Vertically-aligned sandwich nanowires enhance the photoelectrochemical reduction of hydrogen peroxide: hierarchical formation on carbon nanotubes of cadmium sulfide quantum dots and Prussian blue nanocoatings.

    PubMed

    Gong, Kuanping

    2015-07-01

    We describe a vertically-aligned array of sandwiched nanowires comprising Prussian blue (PB) nanocoating-carbon nanotube (CNT) core-shell structures with CdS particles positioning at the core/shell interface, viz. PB/CdS/CNT. The PB/CdS/CNT electrode thus constructed are noticeable in synchronically harvesting photon-, ionic-, and chemical-energies, respectively, from visible light radiation, K(+) uptaking and releasing, and the reduction of H2O2. In 0.2 M K2SO4 aqueous solution, the photoelectrocatalytic reduction of 1.5 mM H2O2 at PB/CdS/CNT delivered the current density as high as 1.91 mA/cm(2) at reduced overpotential, that is, three times that at the Pt/C. This superb performance is causally linked to the judicious choice of materials and their assembly into defining sandwich nanostructures wherein the three components closely cooperate with each other in the photoelectrocatalytic reduction of H2O2, including photo-induced charge separation in CdS, spontaneous electron injection into PB due to its relatively low Fermi level, and the electrocatalytic reduction of H2O2 by PB via an electrochemical-chemical-electrochemical reaction mechanism. The structural alignment of PB/CdS/CNT ensures the simplest pathway for the mass diffusion and electron shuttle, and a high surface area accessible to the chemical and electrochemical reactions, so as to minimize the concentration- and electrochemical-polarization and thus ensure the fast overall kinetics of the electrode reaction. PMID:25458868

  15. Microwave Conductivity of Sorted CNT Assemblies

    PubMed Central

    Bulmer, John S.; Martens, Jon; Kurzepa, Lukasz; Gizewski, Tomasz; Egilmez, M.; Blamire, M. G.; Yahya, Noorhana; Koziol, Krzysztof K. K.

    2014-01-01

    Recent progress with tailored growth and post-process sorting enables carbon nanotube (CNT) assemblies with predominantly metallic or semi-conducting concentrations. Cryogenic and microwave measurements performed here show transport dimensionality and overall order increasing with increasing metallic concentration, even in atmospheric doping conditions. By 120 GHz, the conductivity of predominantly semi-conducting assemblies grew to 400% its DC value at an increasing growth rate, while other concentrations a growth rate that tapered off. A generalized Drude model fits to the different frequency dependent behaviors and yields useful quality control parameters such as plasma frequency, mean free path, and degree of localization. As one of the first demonstrations of waveguides fabricated from this material, sorted CNTs from both as-made and post-process sources were inserted into sections of practical micro-strip. With both sources, sorted CNT micro-strip increasingly outperformed the unsorted with increasing frequency-- illustrating that sorted CNT assemblies will be important for high frequency applications. PMID:24446019

  16. Microwave conductivity of sorted CNT assemblies.

    PubMed

    Bulmer, John S; Martens, Jon; Kurzepa, Lukasz; Gizewski, Tomasz; Egilmez, M; Blamire, M G; Yahya, Noorhana; Koziol, Krzysztof K K

    2014-01-01

    Recent progress with tailored growth and post-process sorting enables carbon nanotube (CNT) assemblies with predominantly metallic or semi-conducting concentrations. Cryogenic and microwave measurements performed here show transport dimensionality and overall order increasing with increasing metallic concentration, even in atmospheric doping conditions. By 120 GHz, the conductivity of predominantly semi-conducting assemblies grew to 400% its DC value at an increasing growth rate, while other concentrations a growth rate that tapered off. A generalized Drude model fits to the different frequency dependent behaviors and yields useful quality control parameters such as plasma frequency, mean free path, and degree of localization. As one of the first demonstrations of waveguides fabricated from this material, sorted CNTs from both as-made and post-process sources were inserted into sections of practical micro-strip. With both sources, sorted CNT micro-strip increasingly outperformed the unsorted with increasing frequency-- illustrating that sorted CNT assemblies will be important for high frequency applications. PMID:24446019

  17. A facile method to align carbon nanotubes on polymeric membrane substrate

    PubMed Central

    Zhao, Haiyang; Zhou, Zhijun; Dong, Hang; Zhang, Lin; Chen, Huanlin; Hou, Lian

    2013-01-01

    The alignment of carbon nanotubes (CNT) is the fundamental requirement to ensure their excellent functions but seems to be desolated in recent years. A facile method, hot-press combined with peel-off (HPPO), is introduced here, through which CNT can be successfully vertically aligned on the polymeric membrane substrate. Shear force and mechanical stretch are proposed to be the main forces to align the tubes perpendicular to the substrate surface during the peel-off process. The alignment of CNT keeps its orientation in a thin hybrid membrane by dip-coating cellulose acetate dope solution. It is expected that the stable alignment of CNT by HPPO would contribute to the realization of its potential applications. PMID:24326297

  18. A facile method to align carbon nanotubes on polymeric membrane substrate

    NASA Astrophysics Data System (ADS)

    Zhao, Haiyang; Zhou, Zhijun; Dong, Hang; Zhang, Lin; Chen, Huanlin; Hou, Lian

    2013-12-01

    The alignment of carbon nanotubes (CNT) is the fundamental requirement to ensure their excellent functions but seems to be desolated in recent years. A facile method, hot-press combined with peel-off (HPPO), is introduced here, through which CNT can be successfully vertically aligned on the polymeric membrane substrate. Shear force and mechanical stretch are proposed to be the main forces to align the tubes perpendicular to the substrate surface during the peel-off process. The alignment of CNT keeps its orientation in a thin hybrid membrane by dip-coating cellulose acetate dope solution. It is expected that the stable alignment of CNT by HPPO would contribute to the realization of its potential applications.

  19. Growth of long and aligned multi-walled carbon nanotubes on carbon and metal substrates.

    PubMed

    Delmas, M; Pinault, M; Patel, S; Porterat, D; Reynaud, C; Mayne-L'Hermite, M

    2012-03-16

    Well aligned, long and dense multi-walled carbon nanotubes (CNT) can be grown on both carbon fibres and any metal substrates compatible with the CNT synthesis temperature. The injection-CVD process developed involves two stages, including fibre pretreatment by depositing a SiO(2)-based sub-layer from an organometallic precursor followed by CNT growth from toluene/ferrocene precursor mixture. Carbon substrates, as well as metals, can easily be treated with this process, which takes place in the same reactor and does not need any handling in between the two stages. The aligned CNT carpets obtained are similar to the ones grown on reference quartz substrates. The CNT growth rate is fairly high (ca. 30 μm min(-1)) and it is possible to control CNT length by varying the CNT synthesis duration. The thickness of the SiO(2)-based sub-layer can be varied and is shown to have an influence on the CNT growth. This layer is assumed to play a diffusion barrier layer role between the substrate and the iron based catalyst nanoparticles producing CNT. The CNT anchorage to the carbon fibres has been checked and good overall adhesion proved, which is in favour of a good transfer of electrical charge and heat between the nanotubes and fibre. PMID:22362164

  20. Electrical transport properties of a CNT/C60/CNT hybrid junction with closed end CNT leads using Green's function method

    NASA Astrophysics Data System (ADS)

    Shokri, Aliasghar; Nikzad, Shaghayegh

    2013-01-01

    We investigate transport properties of an all-carbon molecular device consisting of a CNT/C60/CNT hybrid system with closed end (5,5) CNT leads. Two different ways of coupling are considered for C60 molecule through one and five atoms to the cap-edges of CNTs. Our calculations are based on the Green's function method in the nearest neighbor tight-binding approximation in the coherent regime. In this paper, the sensitivity of electron transport on the geometry of the CNT electrodes-C60 interface is shown. Within the framework of the Landauer-Buttiker formalism, the electrical transmission and current-voltage characteristic are calculated at room temperature. We have investigated the effect of a gate voltage on the current in the considered geometry. In the considered structure, the appearance of the conductance resonances is a manifestation of resonant states of CNT caps, which lie within the HOMO-LUMO gap.

  1. Growth of horizontally aligned dense carbon nanotubes from trench sidewalls.

    PubMed

    Lu, Jingyu; Miao, Jianmin; Xu, Ting; Yan, Bin; Yu, Ting; Shen, Zexiang

    2011-07-01

    Horizontally aligned, dense carbon nanotubes (HADCNTs) in the form of CNT cantilevers/bridges were grown from selected trench sidewalls in silicon substrate by chemical vapor deposition (CVD). The as-grown CNT cantilevers/bridges are packed with multiwalled carbon nanotubes (MWCNTs) with a linear density of about 10 CNTs µm(-1). The excellent horizontal alignment of these CNTs is mainly ascribed to the van der Waals interactions within the dense CNT bundles. What is more, the Raman intensity ratio I(G)/I(D) shows a gradual increase from the CNT roots to tips, indicating a defect gradient along CNTs generated during their growth. These results will inspire further efforts to explore the fundamentals and applications of HADCNTs. PMID:21586807

  2. Nucleation, Growth Mechanism, and Controlled Coating of ZnO ALD onto Vertically Aligned N-Doped CNTs.

    PubMed

    Silva, R M; Ferro, M C; Araujo, J R; Achete, C A; Clavel, G; Silva, R F; Pinna, N

    2016-07-19

    Zinc oxide thin films were deposited on vertically aligned nitrogen-doped carbon nanotubes (N-CNTs) by atomic layer deposition (ALD) from diethylzinc and water. The study demonstrates that doping CNTs with nitrogen is an effective approach for the "activation" of the CNTs surface for the ALD of metal oxides. Conformal ZnO coatings are already obtained after 50 ALD cycles, whereas at lower ALD cycles an island growth mode is observed. Moreover, the process allows for a uniform growth from the top to the bottom of the vertically aligned N-CNT arrays. X-ray photoelectron spectroscopy demonstrates that ZnO nucleation takes place at the N-containing species on the surface of the CNTs by the formation of the Zn-N bonds at the interface between the CNTs and the ZnO film. PMID:27333190

  3. Using surface creep rate to infer fraction locked for sections of the San Andreas fault system in northern California from alignment array and GPS data

    USGS Publications Warehouse

    Lienkaemper, James J.; McFarland, Forrest S.; Simpson, Robert W.; Caskey, S. John

    2014-01-01

    Surface creep rate, observed along five branches of the dextral San Andreas fault system in northern California, varies considerably from one section to the next, indicating that so too may the depth at which the faults are locked. We model locking on 29 fault sections using each section’s mean long‐term creep rate and the consensus values of fault width and geologic slip rate. Surface creep rate observations from 111 short‐range alignment and trilateration arrays and 48 near‐fault, Global Positioning System station pairs are used to estimate depth of creep, assuming an elastic half‐space model and adjusting depth of creep iteratively by trial and error to match the creep observations along fault sections. Fault sections are delineated either by geometric discontinuities between them or by distinctly different creeping behaviors. We remove transient rate changes associated with five large (M≥5.5) regional earthquakes. Estimates of fraction locked, the ratio of moment accumulation rate to loading rate, on each section of the fault system provide a uniform means to inform source parameters relevant to seismic‐hazard assessment. From its mean creep rates, we infer the main branch (the San Andreas fault) ranges from only 20%±10% locked on its central creeping section to 99%–100% on the north coast. From mean accumulation rates, we infer that four urban faults appear to have accumulated enough seismic moment to produce major earthquakes: the northern Calaveras (M 6.8), Hayward (M 6.8), Rodgers Creek (M 7.1), and Green Valley (M 7.1). The latter three faults are nearing or past their mean recurrence interval.

  4. Packing morphology of wavy nanofiber arrays.

    PubMed

    Stein, Itai Y; Wardle, Brian L

    2016-01-14

    Existing theories for quantifying the morphology of nanofibers (NFs) in aligned arrays either neglect or assume a simple functional form for the curvature of the NFs, commonly known as the NF waviness. However, since such assumptions cannot adequately describe the waviness of real NFs, errors that can exceed 10% in the predicted inter-NF separation can result. Here we use a theoretical framework capable of simulating >10(5) NFs with stochastic three-dimensional morphologies to quantify NF waviness on an easily accessible measure of the morphology, the inter-NF spacing, for a range of NF volume fractions. The presented scaling of inter-NF spacing with waviness is then used to study the morphology evolution of aligned carbon nanotube (A-CNT) arrays during packing, showing that the effective two-dimensional coordination number of the A-CNTs increases much faster than previously reported during close packing, and that hexagonal close packing can successfully describe the packing morphology of the A-CNTs at volume fractions greater than 40 vol%. PMID:26658525

  5. Development and optimization of a secure injection CVD process to grow aligned carbon nanotubes on large substrates

    NASA Astrophysics Data System (ADS)

    Patel, S.; Magga, Y.; Belkady, L.; Hibert, E.; Porterat, D.; Boulanger, P.; Pinault, M.; Mayne-L'Hermite, M.

    2013-04-01

    Growth of aligned carbon nanotubes (CNT) by a secure injection CVD process on large quartz substrates and carbon fiber (CF) cloths has been reported in this study. Adjustments of CVD setup and synthesis parameters have been achieved to control the CNT growth in terms of homogeneous covering of the substrates and to tailor the length of CNT. Two parameters have been optimized such as the precursor feeding rate per reactor surface unit and the carrier gas flow rate.

  6. Hydrodynamics of CNT dispersion in high shear dispersion mixers

    NASA Astrophysics Data System (ADS)

    Park, Young Min; Lee, Dong Hyun; Hwang, Wook Ryol; Lee, Sang Bok; Jung, Seung-Il

    2014-11-01

    In this work, we investigate the carbon nanotube (CNT) fragmentation mechanism and dispersion in high shear homogenizers as a plausible dispersion technique, correlating with device geometries and processing conditions, for mass production of CNT-aluminum composites for automobile industries. A CNT dispersion model has been established in a turbulent flow regime and an experimental method in characterizing the critical yield stress of CNT flocs are presented. Considering CNT dispersion in ethanol as a model system, we tested two different geometries of high shear mixers — blade-stirrer type and rotor-stator type homogenizers — and reported the particle size distributions in time and the comparison has been made with the modeling approach and partly with the computational results.

  7. Optimally conductive networks in randomly dispersed CNT:graphene hybrids

    NASA Astrophysics Data System (ADS)

    Shim, Wonbo; Kwon, Youbin; Jeon, Seung-Yeol; Yu, Woong-Ryeol

    2015-11-01

    A predictive model is proposed that quantitatively describes the synergistic behavior of the electrical conductivities of CNTs and graphene in CNT:graphene hybrids. The number of CNT-to-CNT, graphene-to-graphene, and graphene-to-CNT contacts is calculated assuming a random distribution of CNTs and graphene particles in the hybrids and using an orientation density function. Calculations reveal that the total number of contacts reaches a maximum at a specific composition and depends on the particle sizes of the graphene and CNTs. The hybrids, prepared using inkjet printing, are distinguished by higher electrical conductivities than that of 100% CNT or graphene at certain composition ratios. These experimental results provide strong evidence that this approach involving constituent element contacts is suitable for investigating the properties of particulate hybrid materials.

  8. Optimally conductive networks in randomly dispersed CNT:graphene hybrids

    PubMed Central

    Shim, Wonbo; Kwon, Youbin; Jeon, Seung-Yeol; Yu, Woong-Ryeol

    2015-01-01

    A predictive model is proposed that quantitatively describes the synergistic behavior of the electrical conductivities of CNTs and graphene in CNT:graphene hybrids. The number of CNT-to-CNT, graphene-to-graphene, and graphene-to-CNT contacts is calculated assuming a random distribution of CNTs and graphene particles in the hybrids and using an orientation density function. Calculations reveal that the total number of contacts reaches a maximum at a specific composition and depends on the particle sizes of the graphene and CNTs. The hybrids, prepared using inkjet printing, are distinguished by higher electrical conductivities than that of 100% CNT or graphene at certain composition ratios. These experimental results provide strong evidence that this approach involving constituent element contacts is suitable for investigating the properties of particulate hybrid materials. PMID:26564249

  9. Vertically aligned carbon nanotube emitter on metal foil for medical X-ray imaging.

    PubMed

    Ryu, Je Hwang; Kim, Wan Sun; Lee, Seung Ho; Eom, Young Ju; Park, Hun Kuk; Park, Kyu Chang

    2013-10-01

    A simple method is proposed for growing vertically aligned carbon nanotubes on metal foil using the triode direct current plasma-enhanced chemical vapor deposition (PECVD). The carbon nanotube (CNT) electron emitter was fabricated using fewer process steps with an acid treated metal substrate. The CNT emitter was used for X-ray generation, and the X-ray image of mouse's joint was obtained with an anode current of 0.5 mA at an anode bias of 60 kV. The simple fabrication of a well-aligned CNT with a protection layer on metal foil, and its X-ray application, were studied. PMID:24245201

  10. Inhalation Exposure to Carbon Nanotubes (CNT) and Carbon Nanofibers (CNF): Methodology and Dosimetry.

    PubMed

    Oberdörster, Günter; Castranova, Vincent; Asgharian, Bahman; Sayre, Phil

    2015-01-01

    Carbon nanotubes (CNT) and nanofibers (CNF) are used increasingly in a broad array of commercial products. Given current understandings, the most significant life-cycle exposures to CNT/CNF occur from inhalation when they become airborne at different stages of their life cycle, including workplace, use, and disposal. Increasing awareness of the importance of physicochemical properties as determinants of toxicity of CNT/CNF and existing difficulties in interpreting results of mostly acute rodent inhalation studies to date necessitate a reexamination of standardized inhalation testing guidelines. The current literature on pulmonary exposure to CNT/CNF and associated effects is summarized; recommendations and conclusions are provided that address test guideline modifications for rodent inhalation studies that will improve dosimetric extrapolation modeling for hazard and risk characterization based on the analysis of exposure-dose-response relationships. Several physicochemical parameters for CNT/CNF, including shape, state of agglomeration/aggregation, surface properties, impurities, and density, influence toxicity. This requires an evaluation of the correlation between structure and pulmonary responses. Inhalation, using whole-body exposures of rodents, is recommended for acute to chronic pulmonary exposure studies. Dry powder generator methods for producing CNT/CNF aerosols are preferred, and specific instrumentation to measure mass, particle size and number distribution, and morphology in the exposure chambers are identified. Methods are discussed for establishing experimental exposure concentrations that correlate with realistic human exposures, such that unrealistically high experimental concentrations need to be identified that induce effects under mechanisms that are not relevant for workplace exposures. Recommendations for anchoring data to results seen for positive and negative benchmark materials are included, as well as periods for postexposure observation

  11. INHALATION EXPOSURE TO CARBON NANOTUBES (CNT) AND CARBON NANOFIBERS (CNF): METHODOLOGY AND DOSIMETRY

    PubMed Central

    Oberdörster, Günter; Castranova, Vincent; Asgharian, Bahman; Sayre, Phil

    2015-01-01

    Carbon nanotubes (CNT) and nanofibers (CNF) are used increasingly in a broad array of commercial products. Given current understandings, the most significant life-cycle exposures to CNT/CNF occur from inhalation when they become airborne at different stages of their life cycle, including workplace, use, and disposal. Increasing awareness of the importance of physicochemical properties as determinants of toxicity of CNT/CNF and existing difficulties in interpreting results of mostly acute rodent inhalation studies to date necessitate a reexamination of standardized inhalation testing guidelines. The current literature on pulmonary exposure to CNT/CNF and associated effects is summarized; recommendations and conclusions are provided that address test guideline modifications for rodent inhalation studies that will improve dosimetric extrapolation modeling for hazard and risk characterization based on the analysis of exposure-dose-response relationships. Several physicochemical parameters for CNT/CNF, including shape, state of agglomeration/aggregation, surface properties, impurities, and density, influence toxicity. This requires an evaluation of the correlation between structure and pulmonary responses. Inhalation, using whole-body exposures of rodents, is recommended for acute to chronic pulmonary exposure studies. Dry powder generator methods for producing CNT/CNF aerosols are preferred, and specific instrumentation to measure mass, particle size and number distribution, and morphology in the exposure chambers are identified. Methods are discussed for establishing experimental exposure concentrations that correlate with realistic human exposures, such that unrealistically high experimental concentrations need to be identified that induce effects under mechanisms that are not relevant for workplace exposures. Recommendations for anchoring data to results seen for positive and negative benchmark materials are included, as well as periods for postexposure observation

  12. Electrodeposition of Various Au Nanostructures on Aligned Carbon Nanotubes as Highly Sensitive Nanoelectrode Ensembles

    NASA Astrophysics Data System (ADS)

    Fayazfar, H.; Afshar, A.; Dolati, A.

    2015-05-01

    An efficient method has been developed to synthesize well-aligned multi-walled carbon nanotubes (MWCNTs) on a conductive Ta substrate by chemical vapor deposition. Free-standing MWCNTs arrays were functionalized through electrochemical oxidation with the formation of hydroxyl and carboxyl functional groups. Facile template-free electrochemical routes were then developed for the shape-selective synthesis of less-common Au nanostructures, including flower, sphere, dendrite, rod, sheet, and cabbage onto the aligned MWCNTs at room temperature. Especially, among all the synthesis methods for Au nanocrystals, this is the first report using electrochemical technique to synthesize wide variety shapes of gold nanostructures (GNs) onto the aligned MWCNTs. The morphology of electrodeposited Au nanostructures was controlled by adjustment of the deposition time and potential, the number of potential cycles, the kind of deposition bath, and electrodeposition method. Transmission electron microscopy and field-emission scanning electron microscopy were used to characterize the products. Cyclic voltammograms showed that the MWCNT/Ta electrodes modified with GNs have higher sensitivity compared to the unmodified electrodes in the presence of Fe2+/Fe3+ redox couple. These kinds of aligned-CNT/Au nanostructure hybrid materials introduced by these efficient and simple electrochemical methods could lead to the development of a new generation device for ultrasensitive catalytic and biological application.

  13. Enhancement in photo-induced hydrophilicity of TiO2/CNT nanostructures by applying voltage

    NASA Astrophysics Data System (ADS)

    Abdi, Yaser; Khalilian, Maryam; Arzi, Ezatollah

    2011-06-01

    Carbon nanotube (CNT) arrays were synthesized by plasma-enhanced chemical vapour deposition on a silicon substrate. Cabbage-like TiO2 nanostructures on the CNTs were produced by atmospheric-pressure chemical vapour deposition. Scanning electron microcopy was used to study the morphology of the TiO2/CNT structures while x-ray diffraction and Fourier transform infrared (FTIR) spectroscopy were used to verify the characteristics of the prepared nanostructures. Their hydrophilicity under UV and visible light was investigated and compared with the activity of thin films of TiO2. The TiO2/CNTs showed a highly improved photocatalytic activity in comparison with the TiO2 film. The excellent visible-light-induced hydrophilicity of the TiO2/CNTs was attributed to the generation of electron-hole pairs by visible light excitation with a low recombination rate. The results of this study showed that the fabricated cabbage-like TiO2/CNT nanostructures have a super-hydrophilic surface without further UV irradiation. Electrical measurements showed that a p-n junction was formed at the interface of the TiO2/CNTs. Consequently, a super-hydrophilic surface was achieved by applying an electric bias voltage. Visible-light- and electro-induced hydrophilicity of the obtained nanostructure was reported in this work.

  14. Photolithographic fabrication of gated self-aligned parallel electron beam emitters with a single-stranded carbon nanotube.

    PubMed

    Ho, Justin; Ono, Takahito; Tsai, Ching-Hsiang; Esashi, Masayoshi

    2008-09-10

    In this paper we report on the development of a photolithographic process to fabricate a gated-emitter array with single-stranded carbon nanotubes (CNTs) self-aligned to the center of the emitter gate using plasma-enhanced chemical vapor deposition (PECVD). Si tips are formed on a silicon wafer by anisotropic etching of Si using SiO(2) as a mask. Deposition of a SiO(2) insulating layer and Cr-W electrode layers creates protrusions above the Si tips. This wafer is polished, and the Cr-W on the tips is removed. Etching of the SiO(2) using hydrofluoric acid is performed to expose the gated Si tip. Incorporation of a novel diffusion process produces single-stranded CNTs by depositing a thin Ni layer on the Si tips and thermally diffusing the Ni layer to yield a catalyst particle for single-stranded CNT growth. The large surface to volume ratio at the apex of the Si tip allows a Ni particle to remain to act as a catalyst to grow a single-stranded CNT for fabricating the CNT based emitter structure. Diffusion of the Ni is carried out in situ during the heating phase of the PECVD CNT growth process at 600 °C. The diameters of the observed CNTs are on the order of 20 nm. The field emission characteristics of the gated field emitters are evaluated. The measured turn-on voltage of the gated emitter is 5 V. PMID:21828872

  15. Ex situ and in situ catalyst deposition for CNT synthesis by RF-magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Scalese, S.; Scuderi, V.; Simone, F.; Pennisi, A.; Privitera, V.

    2008-05-01

    Radio frequency magnetron sputtering has been used for the synthesis of aligned carbon nanotubes (CNTs) on SiO 2/Si substrate. The results were obtained by depositing catalytic nano-particles in advance (ex situ) or simultaneously to the C deposition (in situ), which have been compared showing that the oxidation of the metal catalyst deposited in advance is detrimental for the good outcome of the CNTs growth. An in situ catalyst deposition allows to get rid of the contamination problem and to grow aligned CNTs on a substrate, as shown by scanning electron microscopy. Transmission electron microscopy shows that the so-achieved CNTs own a bamboo-like structure and the catalytic Ni nanoparticle is on the tip of the CNTs. Our method allows to perform catalyst deposition and growth of CNT on a SiO 2/Si substrate simultaneously and its use can be extended to a variety of catalytic elements and substrates, in principle without many efforts.

  16. DFT studies of CNT-functionalized uracil-acetate hybrids

    NASA Astrophysics Data System (ADS)

    Mirzaei, Mahmoud; Gulseren, Oguz

    2015-09-01

    Calculations based on density functional theory (DFT) have been performed to investigate the stabilities and properties of hybrid structures consisting of a molecular carbon nanotube (CNT) and uracil acetate (UA) counterparts. The investigated models have been relaxed to minimum energy structures and then various physical properties and nuclear magnetic resonance (NMR) properties have been evaluated. The results indicated the effects of functionalized CNT on the properties of hybrids through comparing the results of hybrids and individual structures. The oxygen atoms of uracil counterparts have been seen as the detection points of properties for the CNT-UA hybrids.

  17. Disabling CNT Electronic Devices by Use of Electron Beams

    NASA Technical Reports Server (NTRS)

    Petkov, Mihail

    2008-01-01

    Bombardment with tightly focused electron beams has been suggested as a means of electrically disabling selected individual carbon-nanotubes (CNTs) in electronic devices. Evidence in support of the suggestion was obtained in an experiment in which a CNT field-effect transistor was disabled (see figure) by focusing a 1-keV electron beam on a CNT that served as the active channel of a field-effect transistor (FET). Such bombardment could be useful in the manufacture of nonvolatile-memory circuits containing CNT FETs. Ultimately, in order to obtain the best electronic performances in CNT FETs and other electronic devices, it will be necessary to fabricate the devices such that each one contains only a single CNT as an active element. At present, this is difficult because there is no way to grow a single CNT at a specific location and with a specific orientation. Instead, the common practice is to build CNTs into electronic devices by relying on spatial distribution to bridge contacts. This practice results in some devices containing no CNTs and some devices containing more than one CNT. Thus, CNT FETs have statistically distributed electronic characteristics (including switching voltages, gains, and mixtures of metallic and semiconducting CNTs). According to the suggestion, by using a 1-keV electron beam (e.g., a beam from a scanning electron microscope), a particular nanotube could be rendered electrically dysfunctional. This procedure could be repeated as many times as necessary on different CNTs in a device until all of the excess CNTs in the device had been disabled, leaving only one CNT as an active element (e.g., as FET channel). The physical mechanism through which a CNT becomes electrically disabled is not yet understood. On one hand, data in the literature show that electron kinetic energy >86 keV is needed to cause displacement damage in a CNT. On the other hand, inasmuch as a 1-keV beam focused on a small spot (typically a few tens of nanometers wide

  18. PEDOT-CNT coated electrodes stimulate retinal neurons at low voltage amplitudes and low charge densities

    NASA Astrophysics Data System (ADS)

    Samba, R.; Herrmann, T.; Zeck, G.

    2015-02-01

    Objective. The aim of this study was to compare two different microelectrode materials—the conductive polymer composite poly-3,4-ethylenedioxythiophene (PEDOT)-carbon nanotube(CNT) and titanium nitride (TiN)—at activating spikes in retinal ganglion cells in whole mount rat retina through stimulation of the local retinal network. Stimulation efficacy of the microelectrodes was analyzed by comparing voltage, current and transferred charge at stimulation threshold. Approach. Retinal ganglion cell spikes were recorded by a central electrode (30 μm diameter) in the planar grid of an electrode array. Extracellular stimulation (monophasic, cathodic, 0.1-1.0 ms) of the retinal network was performed using constant voltage pulses applied to the eight surrounding electrodes. The stimulation electrodes were equally spaced on the four sides of a square (400 × 400 μm). Threshold voltage was determined as the pulse amplitude required to evoke network-mediated ganglion cell spiking in a defined post stimulus time window in 50% of identical stimulus repetitions. For the two electrode materials threshold voltage, transferred charge at threshold, maximum current and the residual current at the end of the pulse were compared. Main results. Stimulation of retinal interneurons using PEDOT-CNT electrodes is achieved with lower stimulation voltage and requires lower charge transfer as compared to TiN. The key parameter for effective stimulation is a constant current over at least 0.5 ms, which is obtained by PEDOT-CNT electrodes at lower stimulation voltage due to its faradaic charge transfer mechanism. Significance. In neuroprosthetic implants, PEDOT-CNT may allow for smaller electrodes, effective stimulation in a safe voltage regime and lower energy-consumption. Our study also indicates, that the charge transferred at threshold or the charge injection capacity per se does not determine stimulation efficacy.

  19. Variable deflection response of sensitive CNT-on-fiber artificial hair sensors from CNT synthesis in high aspect ratio microcavities

    NASA Astrophysics Data System (ADS)

    Slinker, Keith; Maschmann, Matthew R.; Kondash, Corey; Severin, Benjamin; Phillips, David; Dickinson, Benjamin T.; Reich, Gregory; Baur, Jeff

    2015-03-01

    Crickets, locusts, bats, and many other animals detect changes in their environment with distributed arrays of flow-sensitive hairs. Here we discuss the fabrication and characterization of a relatively new class of pore-based, artificial hair sensors that take advantage of the mechanical properties of structural microfibers and the electromechanical properties of self-aligned carbon nanotube arrays to rapidly transduce changes in low speed air flow. The radially aligned nanotubes are able to be synthesized along the length of the fibers inside the high aspect ratio cavity between the fiber surface and the wall of a microcapillary pore. The growth self-positions the fibers within the capillary and forms a conductive path between detection electrodes. As the hair is deflected, nanotubes are compressed to produce a typical resistance change of 1-5% per m/s of air speed which we believe are the highest sensitivities reported for air velocities less than 10 m/s. The quasi-static response of the sensors to point loads is compared to that from the distributed loads of air flow. A plane wave tube is used to measure their dynamic response when perturbed at acoustic frequencies. Correlation of the nanotube height profile inside the capillary to a diffusion transport model suggests that the nanotube arrays can be controllably tapered along the fiber. Like their biological counterparts, many applications can be envisioned for artificial hair sensors by tailoring their individual response and incorporating them into arrays for detecting spatio-temporal flow patterns over rigid surfaces such as aircraft.

  20. Growth of multiwalled carbon nanotube arrays by chemical vapour deposition over iron catalyst and the effect of growth parameters

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, J. K.; Pandian, P. S.; Padaki, V. C.; Bhusan, H.; Rao, K. U. B.; Xie, J.; Abraham, J. K.; Varadan, V. K.

    2009-04-01

    Multiwalled carbon nanotube (CNT) arrays were grown by catalytic thermal decomposition of acetylene, over Fe-catalyst deposited on Si-wafer in the temperature range 700-750 °C. The growth parameters were optimized to obtain dense arrays of multiwalled CNTs of uniform diameter. The vertical cross-section of the grown nanotube arrays reveals a quasi-vertical alignment of the nanotubes. The effect of varying the thickness of the catalyst layer and the effect of increasing the growth duration on the morphology and distribution of the grown nanotubes were studied. A scotch-tape test to check the strength of adhesion of the grown CNTs to the Si-substrate surface reveals a strong adhesion between the grown nanotubes and the substrate surface. Transmission electron microscopy analysis of the grown CNTs shows that the grown CNTs are multiwalled nanotubes with a bamboo structure, and follow the base-growth mechanism.

  1. Study of adhesion of vertically aligned carbon nanotubes to a substrate by atomic-force microscopy

    NASA Astrophysics Data System (ADS)

    Ageev, O. A.; Blinov, Yu. F.; Il'ina, M. V.; Il'in, O. I.; Smirnov, V. A.; Tsukanova, O. G.

    2016-02-01

    The adhesion to a substrate of vertically aligned carbon nanotubes (VA CNT) produced by plasmaenhanced chemical vapor deposition has been experimentally studied by atomic-force microscopy in the current spectroscopy mode. The longitudinal deformation of VA CNT by applying an external electric field has been simulated. Based on the results, a technique of determining VA CNT adhesion to a substrate has been developed that is used to measure the adhesion strength of connecting VA CNT to a substrate. The adhesion to a substrate of VA CNT 70-120 nm in diameter varies from 0.55 to 1.19 mJ/m2, and the adhesion force from 92.5 to 226.1 nN. When applying a mechanical load, the adhesion strength of the connecting VA CNT to a substrate is 714.1 ± 138.4 MPa, and the corresponding detachment force increases from 1.93 to 10.33 μN with an increase in the VA CNT diameter. As an external electric field is applied, the adhesion strength is almost doubled and is 1.43 ± 0.29 GPa, and the corresponding detachment force is changed from 3.83 to 20.02 μN. The results can be used in the design of technological processes of formation of emission structures, VA CNT-based elements for vacuum microelectronics and micro- and nanosystem engineering, and also the methods of probe nanodiagnostics of VA CNT.

  2. Determination of material constants of vertically aligned carbon nanotube structures in compressions.

    PubMed

    Li, Yupeng; Kang, Junmo; Choi, Jae-Boong; Nam, Jae-Do; Suhr, Jonghwan

    2015-06-19

    Different chemical vapour deposition (CVD) fabrication conditions lead to a wide range of variation in the microstructure and morphologies of carbon nanotubes (CNTs), which actually determine the compressive mechanical properties of CNTs. However, the underlying relationship between the structure/morphology and mechanical properties of CNTs is not fully understood. In this study, we characterized and compared the structural and morphological properties of three kinds of vertically aligned carbon nanotube (VACNT) arrays from different CVD fabrication methods and performed monotonic compressive tests for each VACNT array. The compressive stress-strain responses and plastic deformation were first compared and analyzed with nanotube buckling behaviours. To quantify the compressive properties of the VACNT arrays, a strain density energy function was used to determine their intrinsic material constants. Then, the structural and morphological effects on the quantified material constants of the VACNTs were statistically investigated and analogized to cellular materials with an open-cell model. The statistical analysis shows that density, defect degree, and the moment of inertia of the CNTs are key factors in the improvement of the compressive mechanical properties of VACNT arrays. This approach could allow a model-driven CNT synthesis for engineering their mechanical behaviours. PMID:26011574

  3. Determination of material constants of vertically aligned carbon nanotube structures in compressions

    NASA Astrophysics Data System (ADS)

    Li, Yupeng; Kang, Junmo; Choi, Jae-Boong; Nam, Jae-Do; Suhr, Jonghwan

    2015-06-01

    Different chemical vapour deposition (CVD) fabrication conditions lead to a wide range of variation in the microstructure and morphologies of carbon nanotubes (CNTs), which actually determine the compressive mechanical properties of CNTs. However, the underlying relationship between the structure/morphology and mechanical properties of CNTs is not fully understood. In this study, we characterized and compared the structural and morphological properties of three kinds of vertically aligned carbon nanotube (VACNT) arrays from different CVD fabrication methods and performed monotonic compressive tests for each VACNT array. The compressive stress-strain responses and plastic deformation were first compared and analyzed with nanotube buckling behaviours. To quantify the compressive properties of the VACNT arrays, a strain density energy function was used to determine their intrinsic material constants. Then, the structural and morphological effects on the quantified material constants of the VACNTs were statistically investigated and analogized to cellular materials with an open-cell model. The statistical analysis shows that density, defect degree, and the moment of inertia of the CNTs are key factors in the improvement of the compressive mechanical properties of VACNT arrays. This approach could allow a model-driven CNT synthesis for engineering their mechanical behaviours.

  4. High resolution telescope including an array of elemental telescopes aligned along a common axis and supported on a space frame with a pivot at its geometric center

    DOEpatents

    Norbert, Massie A.; Yale, Oster

    1992-01-01

    A large effective-aperture, low-cost optical telescope with diffraction-limited resolution enables ground-based observation of near-earth space objects. The telescope has a non-redundant, thinned-aperture array in a center-mount, single-structure space frame. It employes speckle interferometric imaging to achieve diffraction-limited resolution. The signal-to-noise ratio problem is mitigated by moving the wavelength of operation to the near-IR, and the image is sensed by a Silicon CCD. The steerable, single-structure array presents a constant pupil. The center-mount, radar-like mount enables low-earth orbit space objects to be tracked as well as increases stiffness of the space frame. In the preferred embodiment, the array has elemental telescopes with subaperture of 2.1 m in a circle-of-nine configuration. The telescope array has an effective aperture of 12 m which provides a diffraction-limited resolution of 0.02 arc seconds. Pathlength matching of the telescope array is maintained by a electro-optical system employing laser metrology. Speckle imaging relaxes pathlength matching tolerance by one order of magnitude as compared to phased arrays. Many features of the telescope contribute to substantial reduction in costs. These include eliminating the conventional protective dome and reducing on-site construction activities. The cost of the telescope scales with the first power of the aperture rather than its third power as in conventional telescopes.

  5. High resolution telescope including an array of elemental telescopes aligned along a common axis and supported on a space frame with a pivot at its geometric center

    DOEpatents

    Norbert, M.A.; Yale, O.

    1992-04-28

    A large effective-aperture, low-cost optical telescope with diffraction-limited resolution enables ground-based observation of near-earth space objects. The telescope has a non-redundant, thinned-aperture array in a center-mount, single-structure space frame. It employes speckle interferometric imaging to achieve diffraction-limited resolution. The signal-to-noise ratio problem is mitigated by moving the wavelength of operation to the near-IR, and the image is sensed by a Silicon CCD. The steerable, single-structure array presents a constant pupil. The center-mount, radar-like mount enables low-earth orbit space objects to be tracked as well as increases stiffness of the space frame. In the preferred embodiment, the array has elemental telescopes with subaperture of 2.1 m in a circle-of-nine configuration. The telescope array has an effective aperture of 12 m which provides a diffraction-limited resolution of 0.02 arc seconds. Pathlength matching of the telescope array is maintained by a electro-optical system employing laser metrology. Speckle imaging relaxes pathlength matching tolerance by one order of magnitude as compared to phased arrays. Many features of the telescope contribute to substantial reduction in costs. These include eliminating the conventional protective dome and reducing on-site construction activities. The cost of the telescope scales with the first power of the aperture rather than its third power as in conventional telescopes. 15 figs.

  6. Ultrafast laser orthogonal alignment and patterning of carbon nanotube-polymer composite films

    NASA Astrophysics Data System (ADS)

    Murphy, Ryan D.; Abere, Michael J.; Zhang, Huanan; Sun, Haiping; Torralva, Ben; Mansfield, John F.; Kotov, Nicholas A.; Yalisove, Steven M.

    2012-11-01

    Dual orthogonal alignment of carbon nanotubes (CNTs) within the plane and perpendicular to a substrate is essential for many applications but difficult to obtain. Here, we demonstrate that it is possible using a combination of layer-by-layer deposition and ultrafast laser irradiation. Single-wall CNT-polymer composites preferentially aligned within the plane are irradiated with ultrafast laser pulses. After irradiation with distinct fluences at ambient conditions, morphology is seen where CNTs are formed into bundled CNTs with some orthogonal alignment. A model is presented to account for thermal expansion of the polymer and the formation of CNT bundles.

  7. Denser and taller carbon nanotube arrays on Cu foils useable as thermal interface materials

    NASA Astrophysics Data System (ADS)

    Na, Nuri; Hasegawa, Kei; Zhou, Xiaosong; Nihei, Mizuhisa; Noda, Suguru

    2015-09-01

    To achieve denser and taller carbon nanotube (CNT) arrays on Cu foils, catalyst and chemical vapor deposition (CVD) conditions were carefully engineered. CNTs were grown to ˜50 µm using Fe/TiN/Ta catalysts in which Ta and TiN acted as diffusion barriers for Cu and Ta, respectively. A tradeoff was found between the mass density and height of the CNT arrays, and CNT arrays with a mass density of 0.30 g cm-3 and height of 45 µm were achieved under optimized conditions. Thermal interface materials (TIMs) with CNT array/Cu foil/CNT array structures showed decreasing thermal resistance from 86 to 24 mm2 K W-1 with increasing CNT array mass densities from 0.07-0.08 to 0.19-0.26 g cm-3 for Cu and Al blocks with surfaces as rough as 20-30 µm. The best CNT/Cu/CNT TIMs showed thermal resistance values comparable to that of a typical indium sheet TIM.

  8. The screening effects of carbon nanotube arrays and its field emission optimum density

    SciTech Connect

    Cai, Dan Liu, Lie

    2013-12-15

    In order to investigate the field emission optimum density of carbon nanotube (CNT) array, the screening effects of CNT array have been studied. It has been shown that the electric field in the vicinity of an individual nanotube of array can be notable distorted due to the screening action of the surrounding neighbors. The optimum normalized spacing s/l(as referred to the length) for the maximum emission current is inversely proportional to aspect ratio l/r and electric field strength for CNT arrays with a fixed dimension.

  9. An in-situ hard mask block copolymer approach for the fabrication of ordered, large scale, horizontally aligned, Si nanowire arrays on Si substrate

    NASA Astrophysics Data System (ADS)

    Ghoshal, Tandra; Senthamaraikannan, Ramsankar; Shaw, Matthew T.; Holmes, Justin D.; Morris, Michael A.

    2014-03-01

    We report a simple technique to fabricate horizontal, uniform Si nanowire arrays with controlled orientation and density at spatially well defined locations on substrate based on insitu hard mask pattern formation approach by microphase separated polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer (BCP) thin films. The methodology may be applicable to large scale production. Ordered microphase separated patterns of the BCP were defined by solvent annealing and the orientation was controlled by film thickness and annealing time. Films of PEO cylinders with parallel orientation (to the surface plane) were applied to create `frames' for the generation of inorganic oxide nanowire arrays. These PEO cylinders were subject to selective metal ion inclusion and subsequent processing was used to create iron oxide nanowire arrays. The oxide nanowires were isolated, of uniform diameter and their structure a mimic of the original BCP nanopatterns. The phase purity, crystallinity and thermal stability of the nanowires coupled to the ease of large scale production may make them useful in technological applications. Here, we demonstrate that the oxide nanowire arrays could be used as a resist mask to fabricate densely packed, identical ordered, good fidelity silicon nanowire arrays on the substrate. The techniques may have significant application in the manufacture of transistor circuitry.

  10. Controlled growth of vertically aligned carbon nanotubes on metal substrates

    NASA Astrophysics Data System (ADS)

    Gao, Zhaoli

    Carbon nanotube (CNT) is a fascinating material with extraordinary electrical thermal and mechanical properties. Growing vertically aligned CNT (VACNT) arrays on metal substrates is an important step in bringing CNT into practical applications such as thermal interface materials (TIMs) and microelectrodes. However, the growth process is challenging due to the difficulties in preventing catalyst diffusion and controlling catalyst dewetting on metal substrates with physical surface heterogeneity. In this work, the catalyst diffusion mechanism and catalyst dewetting theory were studied for the controlled growth of VACNTs on metal substrates. The diffusion time of the catalyst, the diffusion coefficients for the catalyst in the substrate materials and the number density of catalyst nanoparticles after dewetting are identified as the key parameters, based on which three strategies are developed. Firstly, a fast-heating catalyst pretreatment strategy was used, aiming at preserving the amount of catalyst prior to CNT growth by reducing the catalyst diffusion time. The catalyst lifetime is extended from half an hour to one hour on a patterned Al thin film and a VACNT height of 106 mum, about twenty fold of that reported in the literature, was attained. Secondly, a diffusion barrier layer strategy is employed for a reduction of catalyst diffusion into the substrate materials. Enhancement of VACNT growth on Cu substrates was achieved by adopting a conformal Al2O 3 diffusion barrier layer fabricated by a specially designed atomic layer deposition (ALD) system. Lastly, a novel catalyst glancing angle deposition (GLAD) strategy is performed to manipulate the morphology of a relatively thick catalyst on metal substrates with physical surface heterogeneity, aiming to obtain uniform and dense catalyst nanoparticles after dewetting in the pretreatment process for enhanced VACNT growth. We are able to control the VACNT growth conditions on metal substrates in terms of their

  11. Confinement of pure electron plasmas in the CNT stellarator

    NASA Astrophysics Data System (ADS)

    Pedersen, T. Sunn; Berkery, J. W.; Boozer, A. H.; Marksteiner, Q. R.; Brenner, P. W.; Hahn, M.; de Gevigney, B. Durand; Martin, X. Sarasola

    2009-03-01

    The Columbia Non-neutral Torus is a stellarator devoted to non-neutral and electron-positron plasma research. Confinement and transport processes have been studied in some detail now, and an understanding of these processes has emerged. Transport is driven in two ways: The presence of internal rods, and the presence of neutrals. Both transport processes are clearly distinguished experimentally, and a model of the rod driven transport has been developed, yielding very good agreement with experimental data. The neutral driven transport is faster than originally expected and indicates the presence of unconfined orbits in CNT. Numerical modeling of the electron orbits in CNT confirms the existence of loss orbits and shows that a flux surface conforming electrostatic boundary will greatly improve confinement. Such a boundary has now been installed in CNT, with initial results showing an order of magnitude improvement in confinement.

  12. New CNT/poly(brilliant green) and CNT/poly(3,4-ethylenedioxythiophene) based electrochemical enzyme biosensors.

    PubMed

    Barsan, Madalina M; Pifferi, Valentina; Falciola, Luigi; Brett, Christopher M A

    2016-07-13

    A combination of the electroactive polymer poly(brilliant green) (PBG) or conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) with carbon nanotubes to obtain CNT/PBG and CNT/PEDOT modified carbon film electrodes (CFE) has been investigated as a new biosensor platform, incorporating the enzymes glucose oxidase (GOx) as test enzyme, alcohol oxidase (AlcOx) or alcohol dehydrogenase (AlcDH). The sensing parameters were optimized for all biosensors based on CNT/PBG/CFE, CNT/PEDOT/CFE platforms. Under optimized conditions, both GOx biosensors exhibited very similar sensitivities, while in the case of AlcOx and AlcDH biosensors, AlcOx/CNT/PBG/CFE was found to give a higher sensitivity and lower detection limit. The influence of dissolved O2 on oxidase-biosensor performance was investigated and was shown to be different for each enzyme. Comparisons were made with similar reported biosensors, showing the advantages of the new biosensors, and excellent selectivity against potential interferents was successfully demonstrated. Finally, alcohol biosensors were successfully used for the determination of ethanol in alcoholic beverages. PMID:27237835

  13. A study of the polymer-cnt interactions in polymer/cnt composites using experimental and computational methods

    NASA Astrophysics Data System (ADS)

    Meng, Jiangsha

    This dissertation work focuses on research related to understanding and controlling the polymer-carbon nanotube (CNT) interactions during composite fiber processing using both experimental and computational means, in order to achieve consistent formation of the interphase regions for various polymers in the vicinity of CNT. The development of the polymer crystalline interphase is important, since it has been shown to have a significant and positive impact on the mechanical performance of polymer/CNT composites. This is achieved by the improvement of stress transfer mechanisms between the polymer matrix and CNT. The preliminary results (i.e., both experimental and computational) provide insight toward understanding the fundamental mechanisms of polymer-CNT interactions under various processing conditions, as well as the resultant polymer or CNT behaviors and composite fibers performance governed by them. In this thesis work, the initialization and the development of the interphase region in fibers throughout all processing steps are investigated using full-atomistic molecular dynamics (MD) approach as well as experimental means. SWNT dispersion quality with and without polymers present during sonication process is also investigated experimentally, where the polymer-SWNT interactions are impacted by SWNT dispersion qualities. The resultant morphologies and composite fibers properties are also analyzed. The effect of laminar-flow rates (used during spinning) on the polymer/SWNT composite fiber properties as well as on the fundamental polymer-SWNT interactions and the resultant chain morphologies near the SWNT surface are studied in detail. Full-atomistic MD simulations are conducted to study the influence of various laminar-flow rates on the chain morphologies in the vicinity of SWNT. By combining results from both experimentation and computation, a better understanding of the spinning parameters on the microscopic fiber properties as well as on the microscopic

  14. Different signaling pathways utilized by insulin to regulate the expression of ENT2, CNT1, CNT2 nucleoside transporters in rat cardiac fibroblasts.

    PubMed

    Podgorska, Marzena; Kocbuch, Katarzyna; Grden, Marzena; Szulc, Aneta; Szutowicz, Andrzej; Pawelczyk, Tadeusz

    2007-08-15

    In cardiac fibroblasts (CFs), insulin was shown to affect the expression of ENT2, CNT1, and CNT2 transporter. In the present study, we determined the signaling pathways utilized by insulin to regulate the expression of these nucleoside transporters. In the primary culture of rat CFs, insulin increased the mRNA level of ENT2 and suppressed the CNT1 and CNT2 mRNA levels. The insulin-induced increase of the ENT2 mRNA level was blocked by rapamycin (an inhibitor of mTOR) and by cycloheximide (an inhibitor of protein synthesis), whereas neither wortmannin (an inhibitor of PI3K) nor PD98059 (an inhibitor of MEK) affected the insulin action on the ENT2 transcript level. PD98059 completely blocked the insulin-induced decrease of the CNT1 and CNT2 mRNAs levels. Wortmannin prevented the insulin-induced change of the CNT1 mRNA level, but had no effect on the CNT2 mRNA. Rapamycin abolished the insulin effect on the CNT1 mRNA level, but not on the CNT2 mRNA. Cycloheximide prevented the insulin-induced decrease of CNT2 mRNA, but had no effect on the CNT1 mRNA level. Overall, our results demonstrate that the expression level of ENT2, CNT1, and CNT2 transporters in CFs is differentially regulated by insulin. Moreover, in this cell type insulin employs a distinct signaling pathway to regulate the expression of each transporter. PMID:17537394

  15. Thickness-controlled synthesis of vertically aligned c-axis oriented ZnO nanorod arrays: Effect of growth time via novel dual sonication sol-gel process

    NASA Astrophysics Data System (ADS)

    Firdaus Malek, Mohd; Hafiz Mamat, Mohamad; Soga, Tetsuo; Rahman, Saadah Abdul; Abu Bakar, Suriani; Syakirin Ismail, Ahmad; Mohamed, Ruziana; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop Mahmood, Mohamad

    2016-01-01

    Zinc-oxide (ZnO) nanorod arrays were successfully prepared by using dual sonication sol-gel process. Field emission scanning electron microscopy revealed that the nanorods exhibited a hexagonal structure with a flat-end facet. The nanorods displayed similar surface morphologies and grew uniformly on the seed layer substrate, with the average diameter slightly increasing to the range of 65 to 80 nm after being immersed for varying growth times. Interestingly, thickness measurements indicated that the thicknesses of the samples increased as the growth time was extended. In addition, the X-ray diffraction spectra indicated that the prepared ZnO nanorods with a hexagonal wurtzite structure grew preferentially along the c-axis. Therefore, we can conclude that the diameter, length, and orientation of the ZnO nanorod arrays along the c-axis are controllable by adjusting the growth time, motivating us to further explore the growth mechanisms of ZnO nanorods.

  16. Well-aligned Nd-doped SnO2 nanorod layered arrays: preparation, characterization and enhanced alcohol-gas sensing performance.

    PubMed

    Qin, Guohui; Gao, Fan; Jiang, Qiuping; Li, Yuehua; Liu, Yongjun; Luo, Li; Zhao, Kang; Zhao, Heyun

    2016-02-21

    Well-oriented neodymium doped SnO2 layered nanorod arrays were synthesized by a substrate-free hydrothermal route using sodium stannate and sodium hydroxide at 210 °C. The morphology and phase structure of the Nd-doped SnO2 nanoarrays were investigated by X-ray powder diffraction spectroscopy, scanning electron microscopy, transmission electron microscopy, Raman scattering spectroscopy, X-ray photoelectron spectroscopy and the BET method. The results demonstrated that the Nd-doped SnO2 layered nanorod arrays showed a unique nanostructure combined together with double layered arrays of nanorods with a diameter of 12 nm and a length of several hundred nanometers. The Nd-doped layered SnO2 nanoarrays kept the crystal structure of the bulk SnO2 and possessed more surface defects caused by the Nd ions doped into the SnO2 lattice. The Nd dopant acts as a crystallite growth inhibitor to prevent the growth of SnO2 nanorods. An investigation into the gas-sensing properties indicated that the optimized doping level of 3.0 at% Nd-doped SnO2 layered nanorod arrays exhibited an excellent sensing response toward alcohol at a lower temperature of 260 °C. The enhanced sensor performance was attributed to the higher specific surface area, multi-defect surface structure and the excellent catalytic properties of Nd dopant that is able to increase the amount of active sites on the surface of semiconducting oxides. The Nd-doped SnO2 nanoarray sensors were considered to be a promising candidate for trace alcohol detections in environmental gas monitoring. PMID:26863493

  17. Alignment validation

    SciTech Connect

    ALICE; ATLAS; CMS; LHCb; Golling, Tobias

    2008-09-06

    The four experiments, ALICE, ATLAS, CMS and LHCb are currently under constructionat CERN. They will study the products of proton-proton collisions at the Large Hadron Collider. All experiments are equipped with sophisticated tracking systems, unprecedented in size and complexity. Full exploitation of both the inner detector andthe muon system requires an accurate alignment of all detector elements. Alignmentinformation is deduced from dedicated hardware alignment systems and the reconstruction of charged particles. However, the system is degenerate which means the data is insufficient to constrain all alignment degrees of freedom, so the techniques are prone to converging on wrong geometries. This deficiency necessitates validation and monitoring of the alignment. An exhaustive discussion of means to validate is subject to this document, including examples and plans from all four LHC experiments, as well as other high energy experiments.

  18. Photoluminescence enhancement of aligned arrays of single-walled carbon nanotubes by polymer transfer† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05163k Click here for additional data file.

    PubMed Central

    Schweiger, Manuel; Zakharko, Yuriy; Gannott, Florentina; Grimm, Stefan B.

    2015-01-01

    The photoluminescence of as-grown, aligned single-walled carbon nanotubes (SWNTs) on quartz is strongly quenched and barely detectable. Here we show that transferring these SWNTs to another substrate such as clean quartz or glass increases their emission efficiency by up to two orders of magnitude. By statistical analysis of large nanotube arrays we show at what point of the transfer process the emission enhancement occurs and how it depends on the receiving substrate and the employed transfer polymer. We find that hydrophobic polystyrene (PS) as the transfer polymer results in higher photoluminescence enhancement than the more hydrophilic poly(methyl methacrylate) (PMMA). Possible mechanisms for this enhancement such as strain relief, disruption of the strong interaction of SWNTs with the substrate and localized emissive states are discussed. PMID:26400227

  19. Electron Beam Irradiated Intercalated CNT Yarns For Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Waters, Deborah L.; Gaier, James R.; Williams, Tiffany S.; Lopez Calero, Johnny E.; Ramirez, Christopher; Meador, Michael A.

    2015-01-01

    Multi-walled CNT yarns have been experimentally and commercially created to yield lightweight, high conductivity fibers with good tensile properties for application as electrical wiring and multifunctional tendons. Multifunctional tendons are needed as the cable structures in tensegrity robots for use in planetary exploration. These lightweight robust tendons can provide mechanical strength for movement of the robot in addition to power distribution and data transmission. In aerospace vehicles, such as Orion, electrical wiring and harnessing mass can approach half of the avionics mass. Use of CNT yarns as electrical power and data cables could reduce mass of the wiring by thirty to seventy percent. These fibers have been intercalated with mixed halogens to increase their specific electrical conductivity to that near copper. This conductivity, combined with the superior strength and fatigue resistance makes it an attractive alternative to copper for wiring and multifunctional tendon applications. Electron beam irradiation has been shown to increase mechanical strength in pristine CNT fibers through increased cross-linking. Both pristine and intercalated CNT yarns have been irradiated using a 5-megavolt electron beam for various durations and the conductivities and tensile properties will be discussed. Structural information obtained using a field emission scanning electron microscope, energy dispersive X-ray spectroscopy (EDS), and Raman spectroscopy will correlate microstructural details with bulk properties.

  20. CNT Reinforced Hybrid Microgels as Scaffold Materials for Cell Encapsulation

    PubMed Central

    Shin, Su Ryon; Bae, Hojae; Cha, Jae Min; Mun, Ji Young; Chen, Ying-Chieh; Tekin, Halil; Shin, Hyeongho; Farshchi, Saeed; Dokmeci, Mehmet R.; Tang, Shirley

    2012-01-01

    Hydrogels that mimic biological extracellular matrix (ECM) can provide cells with mechanical support and signaling cues to regulate their behavior. However, despite the ability of hydrogels to generate artificial ECM that can modulate cellular behavior, they often lack the mechanical strength needed for many tissue constructs. Here, we present reinforced CNT-gelatin methacrylate (GelMA) hybrid as a biocompatible, cell-responsive hydrogel platform for creating cell-laden three dimensional (3D) constructs. The addition of CNTs successfully reinforced GelMA hydrogels without decreasing their porosity or inhibiting cell growth. The CNT-GelMA hybrids were also photopatternable allowing for easy fabrication of microscale structures without harsh processes. NIH-3T3 cells and human mesenchymal stem cells (hMSCs) readily spread and proliferated after encapsulation in CNT-GelMA hybrid microgels. By controlling the amount of CNTs incorporated into the GelMA hydrogel system, we demonstrated that the mechanical properties of the hybrid material can be tuned making it suitable for various tissue engineering applications. Furthermore, due to the high pattern fidelity and resolution of CNT incorporated GelMA, it can be used for in vitro cell studies or fabricating complex 3D biomimetic tissue-like structures. PMID:22117858

  1. Improved Photoresist Coating for Making CNT Field Emitters

    NASA Technical Reports Server (NTRS)

    Toda, Risaku; Manohara, Harish

    2009-01-01

    An improved photoresist-coating technique has been developed for use in the fabrication of carbon-nanotube- (CNT) based field emitters is described. The improved photoresist coating technique overcomes what, heretofore, has been a major difficulty in the fabrication process.

  2. A conformationally mobile cysteine residue (Cys-561) modulates Na+ and H+ activation of human CNT3.

    PubMed

    Slugoski, Melissa D; Smith, Kyla M; Mulinta, Ras; Ng, Amy M L; Yao, Sylvia Y M; Morrison, Ellen L; Lee, Queenie O T; Zhang, Jing; Karpinski, Edward; Cass, Carol E; Baldwin, Stephen A; Young, James D

    2008-09-01

    In humans, the SLC28 concentrative nucleoside transporter (CNT) protein family is represented by three Na+-coupled members; human CNT1 (hCNT1) and hCNT2 are pyrimidine and purine nucleoside-selective, respectively, whereas hCNT3 transports both purine and pyrimidine nucleosides and nucleoside drugs. Belonging to a phylogenetic CNT subfamily distinct from hCNT1/2, hCNT3 also mediates H+/nucleoside cotransport. Using heterologous expression in Xenopus oocytes, we have characterized a cysteineless version of hCNT3 (hCNT3C-). Processed normally to the cell surface, hCNT3C- exhibited hCNT3-like transport properties, but displayed a decrease in apparent affinity specific for Na+ and not H+. Site-directed mutagenesis experiments in wild-type and hCNT3C- backgrounds identified intramembranous Cys-561 as the residue responsible for this altered Na+-binding phenotype. Alanine at this position restored Na+ binding affinity, whereas substitution with larger neutral amino acids (threonine, valine, and isoleucine) abolished hCNT3 H+-dependent nucleoside transport activity. Independent of these findings, we have established that Cys-561 is located in a mobile region of the hCNT3 translocation pore adjacent to the nucleoside binding pocket and that access of p-chloromercuribenzene sulfonate to this residue reports a specific H+-induced conformational state of the protein ( Slugoski, M. D., Ng, A. M. L., Yao, S. Y. M., Smith, K. M., Lin, C. C., Zhang, J., Karpinski, E., Cass, C. E., Baldwin, S. A., and Young, J. D. (2008) J. Biol. Chem. 283, 8496-8507 ). The present investigation validates hCNT3C- as a template for substituted cysteine accessibility method studies of CNTs and reveals a pivotal functional role for Cys-561 in Na+- as well as H+-coupled modes of hCNT3 nucleoside transport. PMID:18621735

  3. Alignment and Load Transfer in Carbon Nanotube and Dicyclopentadiene Composites

    NASA Astrophysics Data System (ADS)

    Severino, Joseph Vincent

    Individual carbon nanotubes (CNTs) are the strongest materials available but their macroscopic assemblies are weak. This work establishes a new thermosetting dicyclopentadiene (DCPD) and CNT composite that increases the strength of CNT assemblies. These high volume fraction and void free structures constitute advanced materials that could one day replace traditional composite systems. To further the understanding of physical interactions between polymer and CNTs, a novel "capstan" load transfer mechanism is also introduced. Self-supporting assemblies of interconnected carbon nanotubes were stretched, twisted and compressed to fashion composites by the infusion and polymerization of low viscosity DCPD based monomeric resins. The properties of the CNTs, polymer and composite were characterized with thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA) and Raman spectroscopy. The microstructure was analyzed by wide angle X-ray scattering (WAXS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Sheets were drawn at 15 m/min from a growth furnace to impart alignment then stretched to further modify alignment. The mechanical properties were determined in five orientations with respect to the growth direction. The strength was nearly three times higher along this growth direction than it was perpendicular, and modulus was nearly six times higher. Transverse stretching achieved 1.5 times the elongation but alignment was inferior due to CNT kinking that prevented alignment and consolidation. Composites yarns and sheets were investigated for the mechanical properties, microstructure and load transfer. The DCPD resin was found to wet the CNTs and lubricated deformation. This reduced loads during processing, and curing solidified the aligned and consolidated structure. The stretched and twisted composite yarns increased the failure stress 51%. In aligned composite sheet, the failure stress increased 200%. The increased stresses

  4. Using the carbon nanotube (CNT)/CNT interaction to obtain hybrid conductive nanostructures

    SciTech Connect

    Santos, J.; Silva, A.; Bretas, R. E-mail: bretas@ufscar.br

    2015-05-22

    Carbon nanotubes (CNTs) combine unique physical, electrical, chemical, thermal and mechanical properties with a huge surface area that qualify them to a broad range of applications. These potential applications, however, are often limited due to the strong inter-tubes van der Waals interactions, which results in poor dispersion in polymeric matrixes or solvents in general. Thus, the goal of this work was to use this limitation as an advantage, to produce novel conductive hybrid nanostructures, which consist of nonwoven Nylon 6 (PA6) mats of electrospun nanofibers with a large amount of multiwall carbon nanotubes (MWCNT) strongly attached and adsorbed on the nanofibers´ surfaces. To produce such structures, the MWCNT were previously functionalized with carboxylic groups and subsequently incorporated in the nanofibers by two subsequent steps: i) preparation of nonwoven mats of PA6/MWCNT by electrospinning and ii) treatment of the mats in an aqueous dispersion of MWCNT/Triton X–100. Analyses of UV-visible light showed that carboxylic groups were actually inserted in the MWCNT. Thermogravimetric analyzes (TGA) showed that the amount of adsorbed MWCNT on the fibers´ surfaces at the end of the procedure was approximately 12 times higher than after the first step. Micrographs obtained by scanning electron microscopy (SEM) confirmed this result and electrical conductivities measurements of the MWCNT/PA6, after the treatment in the aqueous solution, showed that these structures had conductivity of 10-2 S/m. It was concluded that the adhesion of CNTs at the surface of the nanofibers occurred due a combination of two types of bonding: hydrogen bonds between the carboxylic groups of the functionalized CNT and the PA6 and van der Waals interactions between the CNTs.

  5. Using the carbon nanotube (CNT)/CNT interaction to obtain hybrid conductive nanostructures

    NASA Astrophysics Data System (ADS)

    Santos, J.; Silva, A.; Bretas, R.

    2015-05-01

    Carbon nanotubes (CNTs) combine unique physical, electrical, chemical, thermal and mechanical properties with a huge surface area that qualify them to a broad range of applications. These potential applications, however, are often limited due to the strong inter-tubes van der Waals interactions, which results in poor dispersion in polymeric matrixes or solvents in general. Thus, the goal of this work was to use this limitation as an advantage, to produce novel conductive hybrid nanostructures, which consist of nonwoven Nylon 6 (PA6) mats of electrospun nanofibers with a large amount of multiwall carbon nanotubes (MWCNT) strongly attached and adsorbed on the nanofiberś surfaces. To produce such structures, the MWCNT were previously functionalized with carboxylic groups and subsequently incorporated in the nanofibers by two subsequent steps: i) preparation of nonwoven mats of PA6/MWCNT by electrospinning and ii) treatment of the mats in an aqueous dispersion of MWCNT/Triton X-100. Analyses of UV-visible light showed that carboxylic groups were actually inserted in the MWCNT. Thermogravimetric analyzes (TGA) showed that the amount of adsorbed MWCNT on the fiberś surfaces at the end of the procedure was approximately 12 times higher than after the first step. Micrographs obtained by scanning electron microscopy (SEM) confirmed this result and electrical conductivities measurements of the MWCNT/PA6, after the treatment in the aqueous solution, showed that these structures had conductivity of 10-2 S/m. It was concluded that the adhesion of CNTs at the surface of the nanofibers occurred due a combination of two types of bonding: hydrogen bonds between the carboxylic groups of the functionalized CNT and the PA6 and van der Waals interactions between the CNTs.

  6. Controlled growth of aligned carbon nanotube using pulsed glow barrier discharge

    NASA Astrophysics Data System (ADS)

    Nozaki, Tomohiro; Kimura, Yoshihito; Okazaki, Ken

    2002-10-01

    We first achieved a catalytic growth of aligned carbon nanotube (CNT) using atmospheric pressure pulsed glow barrier discharge combined with DC bias (1000 V). Aligned CNT can grow with the directional electric field, and this is a big challenge in barrier discharges since dielectric barrier does not allow DC bias and forces to use AC voltage to maintain stable plasma conditions. To overcome this, we developed a power source generating Gaussian-shape pulses at 20 kpps with 4% duty, and DC bias was applied to the GND electrode where Ni-, Fe-coated substrate existed. With positive pulse, i.e. substrate was the cathode, random growth of CNT was observed at about 10^9 cm-2. Growth rate significantly reduced when applied negative pulse; Negative glow formation near substrate is essential for sufficient supply of radical species to the catalyst. If -DC was biased, aligned CNT with 20 nm was synthesized because negative bias enhanced negative glow formation. Interestingly, 2 to 3 CNTs stuck each other with +DC bias, resulting in 50-70 nm and non-aligned CNT. Atmospheric pressure glow barrier discharges can be highly controlled and be a potential alternative to vacuum plasmas for CVD, micro-scale, nano-scale fabrication.

  7. Novel Aluminum (Al)-Carbon Nanotube (CNT) Open-Cell Foams

    NASA Astrophysics Data System (ADS)

    Morsi, K.; Krommenhoek, Max; Shamma, Mohamed

    2016-06-01

    This paper presents for the first time the processing of aluminum (Al)-carbon nanotube (CNT) open-cell foams. Al-2wt pct CNT and Al foams were successfully produced using a spark plasma sintering and dissolution process. Al-CNT foams with porosity levels of ~78 pct were produced. The mechanical response of the open-cell foams reveals initial evidence of enhanced damage tolerance of Al-CNT foams over Al foams produced in this study.

  8. Fabrication of a carbon nanotube protruding electrode array for a retinal prosthesis

    NASA Astrophysics Data System (ADS)

    Wang, Ke; Dai, Hongjie; Fishman, Harvey A.; Harris, James S.

    2005-01-01

    Implantable retinal prosthetic devices consisting of microelectrode arrays are being built in attempts to restore vision. Current retinal prostheses use metal planar electrodes. We are developing a novel electro-neural interface using carbon nanotube (CNT) bundles as flexible, protruding microelectrodes. We have synthesized vertically self-assembled, multi-walled CNT bundles by thermal chemical vapor deposition. Using conventional silicon-based micro-fabrication processes, these CNT bundles were integrated onto pre-patterned circuits. CNT protruding electrodes have significant potentials in providing safer stimulation for retinal prostheses. They could also act as recording units to sense electrical and chemical activities in neural systems for fundamental neuroscience research.

  9. Self-assembled ordered carbon-nanotube arrays and membranes.

    SciTech Connect

    Overmyer, Donald L.; Siegal, Michael P.; Yelton, William Graham

    2004-11-01

    Imagine free-standing flexible membranes with highly-aligned arrays of carbon nanotubes (CNTs) running through their thickness. Perhaps with both ends of the CNTs open for highly controlled nanofiltration? Or CNTs at heights uniformly above a polymer membrane for a flexible array of nanoelectrodes or field-emitters? How about CNT films with incredible amounts of accessible surface area for analyte adsorption? These self-assembled crystalline nanotubes consist of multiple layers of graphene sheets rolled into concentric cylinders. Tube diameters (3-300 nm), inner-bore diameters (2-15 nm), and lengths (nanometers - microns) are controlled to tailor physical, mechanical, and chemical properties. We proposed to explore growth and characterize nanotube arrays to help determine their exciting functionality for Sandia applications. Thermal chemical vapor deposition growth in a furnace nucleates from a metal catalyst. Ordered arrays grow using templates from self-assembled hexagonal arrays of nanopores in anodized-aluminum oxide. Polymeric-binders can mechanically hold the CNTs in place for polishing, lift-off, and membrane formation. The stiffness, electrical and thermal conductivities of CNTs make them ideally suited for a wide-variety of possible applications. Large-area, highly-accessible gas-adsorbing carbon surfaces, superb cold-cathode field-emission, and unique nanoscale geometries can lead to advanced microsensors using analyte adsorption, arrays of functionalized nanoelectrodes for enhanced electrochemical detection of biological/explosive compounds, or mass-ionizers for gas-phase detection. Materials studies involving membrane formation may lead to exciting breakthroughs in nanofiltration/nanochromatography for the separation of chemical and biological agents. With controlled nanofilter sizes, ultrafiltration will be viable to separate and preconcentrate viruses and many strains of bacteria for 'down-stream' analysis.

  10. Properties of Retinal Precursor Cells Grown on Vertically Aligned Multiwalled Carbon Nanotubes Generated for the Modification of Retinal Implant-Embedded Microelectrode Arrays.

    PubMed

    Johnen, Sandra; Meißner, Frank; Krug, Mario; Baltz, Thomas; Endler, Ingolf; Mokwa, Wilfried; Walter, Peter

    2016-01-01

    Background. To analyze the biocompatibility of vertically aligned multiwalled carbon nanotubes (MWCNT), used as nanomodification to optimize the properties of prostheses-embedded microelectrodes that induce electrical stimulation of surviving retinal cells. Methods. MWCNT were synthesized on silicon wafers. Their growth was achieved by iron particles (Fe) or mixtures of iron-platinum (Fe-Pt) and iron-titanium (Fe-Ti) acting as catalysts. Viability, growth, adhesion, and gene expression of L-929 and retinal precursor (R28) cells were analyzed after nondirect and direct contact. Results. Nondirect contact had almost no influence on cell growth, as measured in comparison to reference materials with defined levels of cytotoxicity. Both cell types exhibited good proliferation properties on each MWCNT-coated wafer. Viability ranged from 95.9 to 99.8%, in which better survival was observed for nonfunctionalized MWCNT generated with the Fe-Pt and Fe-Ti catalyst mixtures. R28 cells grown on the MWCNT-coated wafers showed a decreased gene expression associated with neural and glial properties. Expression of the cell cycle-related genes CCNC, MYC, and TP53 was slightly downregulated. Cultivation on plasma-treated MWCNT did not lead to additional changes. Conclusions. All tested MWCNT-covered slices showed good biocompatibility profiles, confirming that this nanotechnology is a promising tool to improve prostheses bearing electrodes which connect with retinal tissue. PMID:27200182

  11. Properties of Retinal Precursor Cells Grown on Vertically Aligned Multiwalled Carbon Nanotubes Generated for the Modification of Retinal Implant-Embedded Microelectrode Arrays

    PubMed Central

    Johnen, Sandra; Meißner, Frank; Krug, Mario; Baltz, Thomas; Endler, Ingolf; Mokwa, Wilfried; Walter, Peter

    2016-01-01

    Background. To analyze the biocompatibility of vertically aligned multiwalled carbon nanotubes (MWCNT), used as nanomodification to optimize the properties of prostheses-embedded microelectrodes that induce electrical stimulation of surviving retinal cells. Methods. MWCNT were synthesized on silicon wafers. Their growth was achieved by iron particles (Fe) or mixtures of iron-platinum (Fe-Pt) and iron-titanium (Fe-Ti) acting as catalysts. Viability, growth, adhesion, and gene expression of L-929 and retinal precursor (R28) cells were analyzed after nondirect and direct contact. Results. Nondirect contact had almost no influence on cell growth, as measured in comparison to reference materials with defined levels of cytotoxicity. Both cell types exhibited good proliferation properties on each MWCNT-coated wafer. Viability ranged from 95.9 to 99.8%, in which better survival was observed for nonfunctionalized MWCNT generated with the Fe-Pt and Fe-Ti catalyst mixtures. R28 cells grown on the MWCNT-coated wafers showed a decreased gene expression associated with neural and glial properties. Expression of the cell cycle-related genes CCNC, MYC, and TP53 was slightly downregulated. Cultivation on plasma-treated MWCNT did not lead to additional changes. Conclusions. All tested MWCNT-covered slices showed good biocompatibility profiles, confirming that this nanotechnology is a promising tool to improve prostheses bearing electrodes which connect with retinal tissue. PMID:27200182

  12. Alignment fixture

    DOEpatents

    Bell, Grover C.; Gibson, O. Theodore

    1980-01-01

    A part alignment fixture is provided which may be used for precise variable lateral and tilt alignment relative to the fixture base of various shaped parts. The fixture may be used as a part holder for machining or inspection of parts or alignment of parts during assembly and the like. The fixture includes a precisely machined diameter disc-shaped hub adapted to receive the part to be aligned. The hub is nested in a guide plate which is adapted to carry two oppositely disposed pairs of positioning wedges so that the wedges may be reciprocatively positioned by means of respective micrometer screws. The sloping faces of the wedges contact the hub at respective quadrants of the hub periphery. The lateral position of the hub relative to the guide plate is adjusted by positioning the wedges with the associated micrometer screws. The tilt of the part is adjusted relative to a base plate, to which the guide plate is pivotally connected by means of a holding plate. Two pairs of oppositely disposed wedges are mounted for reciprocative lateral positioning by means of separate micrometer screws between flanges of the guide plate and the base plate. Once the wedges are positioned to achieve the proper tilt of the part or hub on which the part is mounted relative to the base plate, the fixture may be bolted to a machining, inspection, or assembly device.

  13. Hydrothermal synthesis of MnO2/CNT nanocomposite with a CNT core/porous MnO2 sheath hierarchy architecture for supercapacitors

    PubMed Central

    2012-01-01

    MnO2/carbon nanotube [CNT] nanocomposites with a CNT core/porous MnO2 sheath hierarchy architecture are synthesized by a simple hydrothermal treatment. X-ray diffraction and Raman spectroscopy analyses reveal that birnessite-type MnO2 is produced through the hydrothermal synthesis. Morphological characterization reveals that three-dimensional hierarchy architecture is built with a highly porous layer consisting of interconnected MnO2 nanoflakes uniformly coated on the CNT surface. The nanocomposite with a composition of 72 wt.% (K0.2MnO2·0.33 H2O)/28 wt.% CNT has a large specific surface area of 237.8 m2/g. Electrochemical properties of the CNT, the pure MnO2, and the MnO2/CNT nanocomposite electrodes are investigated by cyclic voltammetry and electrochemical impedance spectroscopy measurements. The MnO2/CNT nanocomposite electrode exhibits much larger specific capacitance compared with both the CNT electrode and the pure MnO2 electrode and significantly improves rate capability compared to the pure MnO2 electrode. The superior supercapacitive performance of the MnO2/CNT nancomposite electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport. PMID:24576342

  14. Multifunctional Characteristics of Carbon Nanotube (CNT) Yarn Composites

    NASA Technical Reports Server (NTRS)

    Hernandez, Corey D.; Zhang, Mei; Fang, Shaoli; Baughman, Ray H.; Gates, Thomas S.; Kahng, Seun K.

    2006-01-01

    By forming composite structures with Carbon Nanotube (CNT) yarns we achieve materials capable of measuring strain and composite structures with increased mechanical strength. The CNT yarns used are of the 2-ply and 4-ply variety with the yarns having diameters of about 15-30 micrometers. The strain sensing characteristics of the yarns are investigated on test beams with the yarns arranged in a bridge configuration. Additionally, the strain sensing properties are also investigated on yarns embedded on the surface of a flexible membrane. Initial mechanical strength tests also show an increase in the modulus of elasticity of the composite materials while incurring a weight penalty of less than one-percent. Also presented are initial temperature characterizations of the yarns.

  15. Fabrication and characterization of AZ91/CNT magnesium matrix composites

    NASA Astrophysics Data System (ADS)

    Park, Yong-Ha; Park, Yong-Ho; Park, Ik-Min; Oak, Jeong-jung; Kimura, Hisamichi; Cho, Kyung-Mox

    2008-12-01

    Carbon Nano Tube (CNT) reinforced AZ91 metal matrix composites (MMC) were fabricated by the squeeze infiltrated method. Properties of magnesium alloys have been improved by impurity reduction, surface treatment and alloy design, and thus the usage for the magnesium alloys has been extended recently. However there still remain barriers for the adaption of magnesium alloys for engineering materials. In this study, we report light-weight, high strength heat resistant magnesium matrix composites. Microstructural study and tensile test were performed for the squeeze infiltrated magnesium matrix composites. The wear properties were characterized and the possibility for the application to automotive power train and engine parts was investigated. It was found that the squeeze infiltration technique is a proper method to fabricate magnesium matrix composites reducing casting defects such as pores and matrix/reinforcement interface separation etc. Improved tensile and mechanical properties were obtained with CNT reinforcing magnesium alloys

  16. Humidity sensing properties of CNT-OD-VETP nanocomposite films

    NASA Astrophysics Data System (ADS)

    Saleem, M.; Karimov, Kh. S.; Karieva, Z. M.; Mateen, A.

    2010-11-01

    In this study, the blend of orange dye (OD), C 17H 17N 5O 2 (5 wt%), vinyl-ethynyl-trimethyl-piperidole (VETP), C 12H 19NO, (5 wt%) and carbon nanotube (CNT) powder (10 wt%) in a mixture of distilled water (80 wt%) and spirit were drop-casted on glass substrates with pre-deposited surface-type silver electrodes to fabricate CNT-OD-VETP nanocomposite thin films. In the process of thin films deposition, 2 V DC was applied to Ag electrodes. The thicknesses of the CNT-OD-VETP films were in the range of 10-15 μm. The I-V characteristics of the surface-type Ag/CNT-OD-VETP/Ag samples showed rectification behavior. The effect of humidity on the electrical properties of the nanocomposite films was investigated by measurement of the capacitance and dissipation of the samples at two different frequencies of the applied voltage: 120 Hz and 1 kHz. The resistance of the samples was determined from values of dissipation. It was observed that at 120 Hz and 1 kHz, under humidity of up to 90% RH, the capacitance of the cell increased by 7.4×10 3 and 740 times and resistance decreased by 2.3×10 4 and 3.8×10 4 times, accordingly, with respect to 40% RH conditions. The average response and recovery times of the films were obtained by capacitance-time measurements to evaluate the dynamics of the water vapor absorption and desorption processes. The experimental results have been supported by the simulation of the capacitance-humidity relationship. It is assumed that the humidity response of the cell is associated with diffusion of water vapors and doping of the semiconductor nanocomposite by water molecules.

  17. Nanocrystal-constructed mesoporous CoFe₂O₄ nanowire arrays aligned on flexible carbon fabric as integrated anodes with enhanced lithium storage properties.

    PubMed

    Wang, Bo; Li, Songmei; Wu, Xiaoyu; Li, Bin; Liu, Jianhua; Yu, Mei

    2015-09-01

    A novel and facile two-step strategy is successfully developed for the large-scale fabrication of hierarchical mesoporous CoFe2O4 nanowire arrays (NWAs) on flexible carbon fabric as integrated anodes for highly efficient and reversible lithium storage. The synthesis involves the co-deposition of uniform bimetallic (Co, Fe) carbonate hydroxide hydrate precursor NWAs on carbon fabric and subsequent thermal transformation to spinel CoFe2O4 without damaging the morphology. The as-prepared CoFe2O4 nanowires have unique mesoporous structures, which are constructed by many interconnected nanocrystals with sizes of about 15-20 nm. The typical size of the nanowires is in the range of 70-100 nm in width and up to several micrometers in length. Such a hybrid nanostructure electrode presented here not only simplifies electrode processing, but also promises fast electron transport/collection and ion diffusion, and withstands volume variation upon prolonged charge/discharge cycling. As a result, the binder-free CoFe2O4/carbon fabric composite exhibits a high reversible capacity of 1185.75 mA h g(-1) at a current density of 200 mA g(-1), and a superior rate capability. More importantly, a reversible capacity as high as ∼950 mA h g(-1) can be retained and there is no obvious decay after 150 cycles. PMID:26219540

  18. Vertically aligned TiO2/(CdS, CdTe, CdSTe) core/shell nanowire array for photoelectrochemical hydrogen generation

    NASA Astrophysics Data System (ADS)

    Ai, Guanjie; Mo, Rong; Xu, Hang; Chen, Qiong; Yang, Sui; Li, Hongxing; Zhong, Jianxin

    2015-04-01

    Type-II TiO2/CdS, TiO2/CdTe and TiO2/CdSTe heterostructured core/shell nanowire arrays (NWAs) on FTO substrates are synthesized via physical vapor deposition of CdS, CdTe and the alloyed CdSTe layer onto the hydrothermally pre-grown TiO2 NWAs. Their morphologies, microstructures, and optical properties are characterized in detail. As photoanodes for photoelectrochemical (PEC) hydrogen generation, the ternary CdSTe alloy sensitized TiO2 NWAs exhibits a photocurrent density of 4.52 mA cm-2 under 1 sun illumination at 0.4261 V vs. RHE, much higher than that of the TiO2/CdS (2.97 mA cm-2) and TiO2/CdTe (0.46 mA cm-2) electrodes. This highest photocurrent density level of the alloy TiO2/CdSTe electrode is attributed to the broadened light absorption range and enhanced charge separation efficiency according to the optical and electrochemical impedance spectra investigation. Our result implies a promising application of CdSTe sensitized TiO2 photoelectrode in PEC cell and other photoelectronic devices.

  19. DNA-CNT nanowire networks for DNA detection.

    PubMed

    Weizmann, Yossi; Chenoweth, David M; Swager, Timothy M

    2011-03-16

    The ability to detect biological analytes in a rapid, sensitive, operationally simple, and cost-effective manner will impact human health and safety. Hybrid biocatalyzed-carbon nanotube (CNT) nanowire-based detection methods offer a highly sensitive and specific platform for the fabrication of simple and effective conductometric devices. Here, we report a conductivity-based DNA detection method utilizing carbon nanotube-DNA nanowire devices and oligonucleotide-functionalized enzyme probes. Key to our sensor design is a DNA-linked-CNT wire motif, which forms a network of interrupted carbon nanotube wires connecting two electrodes. Sensing occurs at the DNA junctions linking CNTs, followed by amplification using enzymatic metalization leading to a conductimetric response. The DNA analyte detection limit is 10 fM with the ability to discriminate single, double, and triple base pair mismatches. DNA-CNT nanowires and device sensing gaps were characterized by scanning electron microscopy (SEM) and confocal Raman microscopy, supporting the enhanced conductometric response resulting from nanowire metallization. PMID:21341794

  20. Graphene as an atomically thin interface for growth of vertically aligned carbon nanotubes

    PubMed Central

    Rao, Rahul; Chen, Gugang; Arava, Leela Mohana Reddy; Kalaga, Kaushik; Ishigami, Masahiro; Heinz, Tony F.; Ajayan, Pulickel M.; Harutyunyan, Avetik R.

    2013-01-01

    Growth of vertically aligned carbon nanotube (CNT) forests is highly sensitive to the nature of the substrate. This constraint narrows the range of available materials to just a few oxide-based dielectrics and presents a major obstacle for applications. Using a suspended monolayer, we show here that graphene is an excellent conductive substrate for CNT forest growth. Furthermore, graphene is shown to intermediate growth on key substrates, such as Cu, Pt, and diamond, which had not previously been compatible with nanotube forest growth. We find that growth depends on the degree of crystallinity of graphene and is best on mono- or few-layer graphene. The synergistic effects of graphene are revealed by its endurance after CNT growth and low contact resistances between the nanotubes and Cu. Our results establish graphene as a unique interface that extends the class of substrate materials for CNT growth and opens up important new prospects for applications. PMID:23712556

  1. Quantum analytical modeling and simulation of CNT on insulator (COI) and CNT on nothing (CON) FET: a comparative analysis

    NASA Astrophysics Data System (ADS)

    Mukherjee, Sudipta; Bandyopadhyay, Dipan; Dutta, Pranab Kishore; Sarkar, Subir Kumar

    2016-06-01

    A comprehensive performance analysis by quantum analytical modeling of CNT on insulator (COI) and CNT on nothing (CON) FET having channel length 20 nm has been proposed and investigated on the basis of 2D Poisson's Equation and solution of 1-D Schrodinger's Equation and validated using ATLAS 2D simulator. As classical approximations fail to describe carrier quantization, charge inversion and potential profile of a device at sub-100 nm regime, here for the first time an analytical model in quantum mechanical aspect for COI/CON devices has been derived. Effects of high-k dielectrics in place of conventional SiO2 over the device characteristics have been thoroughly discussed. Moreover, all noticeable benefits of our device to the so called SOI/SON architecture have also been vividly justified.

  2. ALIGNING JIG

    DOEpatents

    Culver, J.S.; Tunnell, W.C.

    1958-08-01

    A jig or device is described for setting or aligning an opening in one member relative to another member or structure, with a predetermined offset, or it may be used for measuring the amount of offset with which the parts have previously been sct. This jig comprises two blocks rabbeted to each other, with means for securing thc upper block to the lower block. The upper block has fingers for contacting one of the members to be a1igmed, the lower block is designed to ride in grooves within the reference member, and calibration marks are provided to determine the amount of offset. This jig is specially designed to align the collimating slits of a mass spectrometer.

  3. A polymeric nanocoating on carbon nanotube arrays for developing imprinted protein sensor

    NASA Astrophysics Data System (ADS)

    Ren, L.; Zhao, H. Z.; Xu, C. J.; Yu, Y.; Wang, H. Z.; Lan, Y. C.; Wagner, D.; Naughton, M. J.; Ren, Z. F.; Chiles, T. C.; Cai, D.

    2010-03-01

    Polyphenol (PPn) was electrodeposited on carbon nanotubes (CNT) arrays at nanoscale thickness. PPn is a non-conductive polymer, so increase of sensor impedance was observed with high density CNT array, low density CNT array, and tip-polished CNT array (tCNTA), while tCNTA was determined to be the best nanosensor platform to incorporate the imprinted PPn coating due to the highest impedance increase. The PPn was characterized by transmission electron microscopy, electrochemical impedance spectroscopy and cyclic voltammetry for its thickness, uniformity, stability, resistivity and permittivity etc., as well as the protein entrapment and removal process. The density of the imprint was also evaluated by a PPn refilling experiment. Finally, ferritin was used as the template to develop a highly sensitive and selective protein nanosensor. Therefore, a novel strategy was demonstrated here to deposit and characterize polymeric nanocoating, also to evaluate imprints and detect proteins.

  4. Energy dissipation due to interfacial slip in nanocomposites reinforced with aligned carbon nanotubes.

    PubMed

    Gardea, Frank; Glaz, Bryan; Riddick, Jaret; Lagoudas, Dimitris C; Naraghi, Mohammad

    2015-05-13

    Interfacial slip mechanisms of strain energy dissipation and vibration damping of highly aligned carbon nanotube (CNT) reinforced polymer composites were studied through experimentation and complementary micromechanics modeling. Experimentally, we have developed CNT-polystyrene (PS) composites with a high degree of CNT alignment via a combination of twin-screw extrusion and hot-drawing. The aligned nanocomposites enabled a focused study of the interfacial slip mechanics associated with shear stress concentrations along the CNT-PS interface induced by the elastic mismatch between the filler and matrix. The variation of storage and loss modulus suggests the initiation of the interfacial slip occurs at axial strains as low as 0.028%, primarily due to shear stress concentration along the CNT-PS interface. Through micromechanics modeling and by matching the model with the experimental results at the onset of slip, the interfacial shear strength was evaluated. The model was then used to provide additional insight into the experimental observations by showing that the nonlinear variation of damping with dynamic strain can be attributed to slip-stick behavior. The dependence of the interfacial load-transfer reversibility on the dynamic strain history and characteristic time scale was experimentally investigated to demonstrate the relative contribution of van der Waals (vdW) interactions, mechanical interlocking, and covalent bonding to shear interactions. PMID:25905718

  5. Image alignment

    DOEpatents

    Dowell, Larry Jonathan

    2014-04-22

    Disclosed is a method and device for aligning at least two digital images. An embodiment may use frequency-domain transforms of small tiles created from each image to identify substantially similar, "distinguishing" features within each of the images, and then align the images together based on the location of the distinguishing features. To accomplish this, an embodiment may create equal sized tile sub-images for each image. A "key" for each tile may be created by performing a frequency-domain transform calculation on each tile. A information-distance difference between each possible pair of tiles on each image may be calculated to identify distinguishing features. From analysis of the information-distance differences of the pairs of tiles, a subset of tiles with high discrimination metrics in relation to other tiles may be located for each image. The subset of distinguishing tiles for each image may then be compared to locate tiles with substantially similar keys and/or information-distance metrics to other tiles of other images. Once similar tiles are located for each image, the images may be aligned in relation to the identified similar tiles.

  6. Influence of matching solubility parameter of polymer matrix and CNT on electrical conductivity of CNT/rubber composite

    PubMed Central

    Ata, Seisuke; Mizuno, Takaaki; Nishizawa, Ayumi; Subramaniam, Chandramouli; Futaba, Don N.; Hata, Kenji

    2014-01-01

    We report a general approach to fabricate elastomeric composites possessing high electrical conductivity for applications ranging from wireless charging interfaces to stretchable electronics. By using arbitrary nine kinds of rubbers as matrices, we experimentally demonstrate that the matching the solubility parameter of CNTs and the rubber matrix is important to achieve higher electrical conductivity in CNT/rubber composite, resulting in continuous conductive pathways leading to electrical conductivities as high as 15 S/cm with 10 vol% CNT in fluorinated rubber. Further, using thermodynamic considerations, we demonstrate an approach to mix CNTs to arbitrary rubber matrices regardless of solubility parameter of matrices by adding small amounts of fluorinated rubber as a polymeric-compatibilizer of CNTs. We thereby achieved electrical conductivities ranging from 1.2 to 13.8 S/cm (10 vol% CNTs) using nine varieties of rubber matrices differing in chemical structures and physical properties. Finally, we investigated the components of solubility parameter of CNT by using Hansen solubility parameters, these findings may useful for controlling solubility parameter of CNTs. PMID:25434701

  7. Highly Stretchable Fully-Printed CNT-Based Electrochemical Sensors and Biofuel Cells: Combining Intrinsic and Design-Induced Stretchability.

    PubMed

    Bandodkar, Amay J; Jeerapan, Itthipon; You, Jung-Min; Nuñez-Flores, Rogelio; Wang, Joseph

    2016-01-13

    We present the first example of an all-printed, inexpensive, highly stretchable CNT-based electrochemical sensor and biofuel cell array. The synergistic effect of utilizing specially tailored screen printable stretchable inks that combine the attractive electrical and mechanical properties of CNTs with the elastomeric properties of polyurethane as a binder along with a judiciously designed free-standing serpentine pattern enables the printed device to possess two degrees of stretchability. Owing to these synergistic design and nanomaterial-based ink effects, the device withstands extremely large levels of strains (up to 500% strain) with negligible effect on its structural integrity and performance. This represents the highest stretchability offered by a printed device reported to date. Extensive electrochemical characterization of the printed device reveal that repeated stretching, torsional twisting, and indenting stress has negligible impact on its electrochemical properties. The wide-range applicability of this platform to realize highly stretchable CNT-based electrochemical sensors and biofuel cells has been demonstrated by fabricating and characterizing potentiometric ammonium sensor, amperometric enzyme-based glucose sensor, enzymatic glucose biofuel cell, and self-powered biosensor. Highly stretchable printable multianalyte sensor, multifuel biofuel cell, or any combination thereof can thus be realized using the printed CNT array. Such combination of intrinsically stretchable printed nanomaterial-based electrodes and strain-enduring design patterns holds considerable promise for creating an attractive class of inexpensive multifunctional, highly stretchable printed devices that satisfy the requirements of diverse healthcare and energy fields wherein resilience toward extreme mechanical deformations is mandatory. PMID:26694819

  8. Fabrication of silicon carbide nanowires/carbon nanotubes heterojunction arrays by high-flux Si ion implantation.

    PubMed

    Liu, Huaping; Cheng, Guo-An; Liang, Changlin; Zheng, Ruiting

    2008-06-18

    An array of silicon carbide nanowire (SiCNW)-carbon nanotube (CNT) heterojunctions was fabricated by high-flux Si ion implantation into a multi-walled carbon nanotube (MWCNT) array with a metal vapor vacuum arc (MEVVA) ion source. Under Si irradiation, the top part of a CNT array was gradually transformed into an amorphous nanowire array with increasing Si dose while the bottom part still remained a CNT structure. X-ray photoelectron spectroscopy (XPS) analysis shows that the SiC compound was produced in the nanowire part even at the lower Si dose of 5 × 10(16) ions cm(-2), and the SiC amount increased with increasing the Si dose. Therefore, the fabrication of a SiCNW-CNT heterojunction array with the MEVVA technique has been successfully demonstrated. The corresponding formation mechanism of SiCNWs was proposed. PMID:21825818

  9. Synthesis of Millimeter-Scale Carbon Nanotube Arrays and Their Applications on Electrochemical Supercapacitors

    NASA Astrophysics Data System (ADS)

    Cui, Xinwei

    This research is aimed at synthesizing millimeter-scale carbon nanotube arrays (CNTA) by conventional chemical vapor deposition (CCVD) and water-assisted chemical vapor deposition (WACVD) methods, and exploring their application as catalyst supports for electrochemical supercapacitors. The growth mechanism and growth kinetics of CNTA under different conditions were systematically investigated to understand the relationship among physical characteristics of catalyst particles, growth parameters, and carbon nanotube (CNT) structures within CNTAs. Multiwalled CNT (MWCNT) array growth demonstrates lengthening and thickening stages in CCVD and WACVD. In CCVD, the lengthening and thickening were found to be competitive. By investigating catalyst particles after different pretreatment conditions, it has been found that inter-particle spacing plays a significant role in influencing CNTA height, CNT diameter and wall number. In WACVD, a long linear lengthening stage has been found. CNT wall number remains constant and catalysts preserve the activity in this stage, while MWCNTs thicken substantially and catalysts deactivate following the previously proposed radioactive decay model in the thickening stage of WACVD. Water was also shown to preserve the catalyst activity by significantly inhibiting catalyst-induced and gas phase-induced thickening processes in WACVD. Mn3O4 nanoparticles were successfully deposited and uniformly distributed within millimeter-long CNTAs by dip-casting method from non-aqueous solutions. After modification with Mn3O4 nanoparticles, CNTAs have been changed from hydrophobic to hydrophilic without their alignment and integrity being destroyed. The hydrophilic Mn 3O4/CNTA composite electrodes present ideal capacitive behavior with high reversibility. This opens up a new route of utilizing ultra-long CNTAs, based on which a scalable and cost-effective method was developed to fabricate composite electrodes using millimeter-long CNTAs. To improve the

  10. The alignment-distribution graph

    NASA Technical Reports Server (NTRS)

    Chatterjee, Siddhartha; Gilbert, John R.; Schreiber, Robert

    1993-01-01

    Implementing a data-parallel language such as Fortran 90 on a distributed-memory parallel computer requires distributing aggregate data objects (such as arrays) among the memory modules attached to the processors. The mapping of objects to the machine determines the amount of residual communication needed to bring operands of parallel operations into alignment with each other. We present a program representation called the alignment distribution graph that makes these communication requirements explicit. We describe the details of the representation, show how to model communication cost in this framework, and outline several algorithms for determining object mappings that approximately minimize residual communication.

  11. The alignment-distribution graph

    NASA Technical Reports Server (NTRS)

    Chatterjee, Siddhartha; Gilbert, John R.; Schreiber, Robert

    1993-01-01

    Implementing a data-parallel language such as Fortran 90 on a distributed-memory parallel computer requires distributing aggregate data objects (such as arrays) among the memory modules attached to the processors. The mapping of objects to the machine determines the amount of residual communication needed to bring operands of parallel operations into alignment with each other. We present a program representation called the alignment-distribution graph that makes these communication requirements explicit. We describe the details of the representation, show how to model communication cost in this framework, and outline several algorithms for determining object mappings that approximately minimize residual communication.

  12. IUS prerelease alignment

    NASA Technical Reports Server (NTRS)

    Evans, F. A.

    1978-01-01

    Space shuttle orbiter/IUS alignment transfer was evaluated. Although the orbiter alignment accuracy was originally believed to be the major contributor to the overall alignment transfer error, it was shown that orbiter alignment accuracy is not a factor affecting IUS alignment accuracy, if certain procedures are followed. Results are reported of alignment transfer accuracy analysis.

  13. Surface control and cryogenic durability of transparent CNT coatings on dip-coated glass substrates.

    PubMed

    Wang, Zuo-Jia; Kwon, Dong-Jun; Gu, Ga-Young; Devries, K Lawrence; Park, Joung-Man

    2012-11-15

    Transparent carbon nanotube (CNT) coatings were deposited on boro-silicate glass substrates by dip-coating. Ultraviolet-visible (UV) spectra, surface resistance measurement, and the wettability tests were used to investigate the optical transmittance and electrical properties of these CNT coatings. The changes in electrical and optical properties of these coatings were observed to be functions of the number of dip-coating cycles. The surface resistance of the CNT coated substrates decreased dramatically as the number of dip-coatings was increased, whereas the increases in the CNT layer thickness beyond that for the first dipping cycle had little effect on the transparent-properties. Static contact angle measurements proved to be an effective means for evaluating the surface morphology of CNT coatings. The interfacial durability of the CNT coatings on a glass substrate was much better than that of ITO coatings over the temperature range from -150°C to +150°C. PMID:22918050

  14. Effect of milling time and CNT concentration on hardness of CNT/Al{sub 2024} composites produced by mechanical alloying

    SciTech Connect

    Perez-Bustamante, R.; Perez-Bustamante, F.; Estrada-Guel, I.; Licea-Jimenez, L.; Miki-Yoshida, M.; Martinez-Sanchez, R.

    2013-01-15

    Carbon nanotube/2024 aluminum alloy (CNT/Al{sub 2024}) composites were fabricated with a combination of mechanical alloying (MA) and powder metallurgy routes. Composites were microstructurally and mechanically evaluated at sintering condition. A homogeneous dispersion of CNTs in the Al matrix was observed by a field emission scanning electron microscopy. High-resolution transmission electron microscopy confirmed not only the presence of well dispersed CNTs but also needle-like shape aluminum carbide (Al{sub 4}C{sub 3}) crystals in the Al matrix. The formation of Al{sub 4}C{sub 3} was suggested as the interaction between the outer shells of CNTs and the Al matrix during MA process in which crystallization took place after the sintering process. The mechanical behavior of composites was evaluated by Vickers microhardness measurements indicating a significant improvement in hardness as function of the CNT content. This improvement was associated to a homogeneous dispersion of CNTs and the presence of Al{sub 4}C{sub 3} in the aluminum alloy matrix. - Highlights: Black-Right-Pointing-Pointer The 2024 aluminum alloy was reinforced by CNTs by mechanical alloying process. Black-Right-Pointing-Pointer Composites were microstructural and mechanically evaluated after sintering condition. Black-Right-Pointing-Pointer The greater the CNT concentration, the greater the hardness of the composites. Black-Right-Pointing-Pointer Higher hardness in composites is achieved at 20 h of milling. Black-Right-Pointing-Pointer The formation of Al{sub 4}C{sub 3} does not present a direct relationship with the milling time.

  15. A flexible and implantable microelectrode arrays using high-temperature grown vertical carbon nanotubes and a biocompatible polymer substrate

    NASA Astrophysics Data System (ADS)

    Yi, Wenwen; Chen, Chaoyang; Feng, Zhaoying; Xu, Yong; Zhou, Chengpeng; Masurkar, Nirul; Cavanaugh, John; Ming-Cheng Cheng, Mark

    2015-03-01

    This paper presents a novel microelectrode arrays using high-temperature grown vertically aligned carbon nanotubes (CNTs) integrated on a flexible and biocompatible parylene substrate. A simple microfabrication process is proposed to unite the high quality vertical CNTs grown at high temperature with the heat sensitive parylene substrate in a highly controllable manner. Briefly, the CNTs electrode is encapsulated by two layers of parylene and the device is released using xenon difluoride (XeF2). The process is compatible with wafer-scale post complementary metal oxide semiconductor integration. Lower impedance and larger interfacial capacitance have been demonstrated using CNTs compared to a Pt electrode. The flexible CNT electrodes have been utilized for extracellular neuronal recording and stimulation in rats. The signal-to-noise ratio of the device is about 12.5. The threshold voltage for initiating action potential is about 0.5 V.

  16. Functional and genetic diversity in the concentrative nucleoside transporter, CNT1, in human populations.

    PubMed

    Gray, Jennifer H; Mangravite, Lara M; Owen, Ryan P; Urban, Thomas J; Chan, Wendy; Carlson, Elaine J; Huang, Conrad C; Kawamoto, Michiko; Johns, Susan J; Stryke, Douglas; Ferrin, Thomas E; Giacomini, Kathleen M

    2004-03-01

    The concentrative nucleoside transporter, CNT1 (SLC28A1), mediates the cellular uptake of naturally occurring pyrimidine nucleosides and many structurally diverse anticancer and antiviral nucleoside analogs. As a first step toward understanding whether genetic variation in CNT1 contributes to variation in the uptake and disposition of clinically used nucleoside analogs, we determined the haplotype structure and functionally analyzed all coding region variants of CNT1 identified in ethnically diverse populations (100 African Americans, 100 European Americans, 30 Asians, 10 Mexican Americans, and 7 Pacific Islanders) (Leabman et al., 2003). A total of 58 coding region haplotypes were identified using PHASE analysis, 44 of which contained at least one amino acid variant. More than half of the coding region haplotypes were population-specific. Using site-directed mutagenesis, 15 protein-altering CNT1 variants, including one amino acid insertion and one base pair (bp) deletion, were constructed and expressed in Xenopus laevis oocytes. All variant transporters took up [3H]thymidine with the exception of CNT1-Ser546Pro, a rare variant, and CNT1-1153del, a single bp deletion found at a frequency of 3% in the African American population. The bp deletion results in a frame-shift followed by a stop-codon. The anticancer nucleoside analog gemcitabine had a reduced affinity for CNT1-Val189Ile (a common CNT1 variant found at a frequency of 26%) compared with reference CNT1 (IC50=13.8 +/- 0.60 microM for CNT1-reference and 23.3 +/- 1.5 microM for CNT1-Val189Ile, p<0.05). These data suggest that common genetic variants of CNT1 may contribute to variation in systemic and intracellular levels of anti-cancer nucleoside analogs. PMID:14978229

  17. Functionalizing CNTs for Making Epoxy/CNT Composites

    NASA Technical Reports Server (NTRS)

    Chen, Jian; Rajagopal, Ramasubramaniam

    2009-01-01

    Functionalization of carbon nanotubes (CNTs) with linear molecular side chains of polyphenylene ether (PPE) has been shown to be effective in solubilizing the CNTs in the solvent components of solutions that are cast to make epoxy/CNT composite films. (In the absence of solubilization, the CNTs tend to clump together instead of becoming dispersed in solution as needed to impart, to the films, the desired CNT properties of electrical conductivity and mechanical strength.) Because the PPE functionalizes the CNTs in a noncovalent manner, the functionalization does not damage the CNTs. The functionalization can also be exploited to improve the interactions between CNTs and epoxy matrices to enhance the properties of the resulting composite films. In addition to the CNTs, solvent, epoxy resin, epoxy hardener, and PPE, a properly formulated solution also includes a small amount of polycarbonate, which serves to fill voids that, if allowed to remain, would degrade the performance of the film. To form the film, the solution is drop-cast or spin-cast, then the solvent is allowed to evaporate.

  18. Preparation and characterization of CNT-CeO2 nanocomposite

    NASA Astrophysics Data System (ADS)

    Kaur, Jasmeet; Anand, Kanika; Singh, Ravi Chand

    2015-06-01

    This paper reports decoration of CeO2 nanoparticles on multi-walled carbon nanotubes through a reflux process in which Ce (NO3) 3.6H2O serves as precursor and hydrazine hydrate (N2H4.H2O) as reducing agent. Successful deposition of cubic fluorite CeO2 nanoparticles onto multi-walled carbon nanotubes has been confirmed by x-ray diffraction (XRD), Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM) and energy dispersive x-ray spectroscopy (EDS). It was found that CeO2 nanoparticles formed in the presence of CNTs were larger as compared to pure CeO2 nanoparticles. Raman analysis showed that CeO2 induced a decrease in the size of the carbon grain in the CNTs. A red shift from 460 cm-1 to 463 cm-1 for F2g mode of CeO2 has also been observed in Raman spectra of CNT- CeO2 nanocomposite as compared to pure CeO2. The CeO2 coated multi-wall carbon nanotubes (CNT-CeO2) nanocomposite would be a promising candidate for practical applications such as catalysis, sensing and power source applications.

  19. Nanoengineered Thermal Materials Based on Carbon Nanotube Array Composites

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

    2007-01-01

    A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

  20. Nanoengineered thermal materials based on carbon nanotube array composites

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Meyyappan, Meyya (Inventor); Dangelo, Carlos (Inventor)

    2010-01-01

    A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

  1. Nanoengineered thermal materials based on carbon nanotube array composites

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

    2007-01-01

    A method for providing for thermal conduction using an array of carbon nanotubes (CNTs). An array of vertically oriented CNTs is grown on a substrate having high thermal conductivity, and interstitial regions between adjacent CNTs in the array are partly or wholly filled with a filler material having a high thermal conductivity so that at least one end of each CNT is exposed. The exposed end of each CNT is pressed against a surface of an object from which heat is to be removed. The CNT-filler composite adjacent to the substrate provides improved mechanical strength to anchor CNTs in place and also serves as a heat spreader to improve diffusion of heat flux from the smaller volume (CNTs) to a larger heat sink.

  2. Enhanced mechanical and thermal properties of CNT/HDPE nanocomposite using MMT as secondary filler

    NASA Astrophysics Data System (ADS)

    Ali Mohsin, M. E.; Arsad, Agus; Fouad, H.; Jawaid, M.; Alothman, Othman Y.

    2014-05-01

    This study explains the influence of secondary filler on the dispersion of carbon nanotube (CNT) reinforced high density polyethylene (HDPE) nanocomposites (CNT/HDPE). In order to understand the mixed-fillers system, Montmorillonite (MMT) was added to CNT/HDPE nanocomposites. It was followed by investigating their effect on the thermal, mechanical and XRD properties of the aforesaid nanocomposite. Incorporation of 3 wt% each of MMT into CNT/HDPE nanocomposite resulted to the increased values for the tensile and flexural strength, as compared to the pure HDPE matrix. The thermal analysis result showed improved thermal stability of the formulated nanocomposites.

  3. CNT manipulation: inserting a carbonaceous dielectric layer beneath using electron beam induced deposition.

    PubMed

    Kurrat, Narendra; Vijaykumar, T; Kulkarni, G U

    2011-02-01

    Electron beam induced carbonaceous deposition has been carried out in the presence of water vapor at 0.4 torr pressure amidst residual hydrocarbons present in the SEM chamber. When performed at a CNT location on a Si substrate with low e beam energy (10 kV), the deposition was taking place beneath the CNT. While higher beam energy (25 kV) causing the deposition on the top surface of the CNT, in agreement with the earlier reports. The insertion of dielectric carbonaceous layer beneath the CNT allowed us to measure the I-V data along the length of the nanotube using CAFM. PMID:21456133

  4. Cross-stacking aligned carbon-nanotube films to tune microwave absorption frequencies and increase absorption intensities.

    PubMed

    Sun, Hao; Che, Renchao; You, Xiao; Jiang, Yishu; Yang, Zhibin; Deng, Jue; Qiu, Longbin; Peng, Huisheng

    2014-12-23

    Aligned carbon-nanotube (CNT) sheets are used as building blocks to prepare light-weight, frequency-tunable and high-performance microwave absorbers, and the absorption frequency can be accurately controlled by stacking them with different intersectional angles. A remarkable reflection loss of -47.66 dB is achieved by stacking four aligned CNT sheets with an intersectional angle of 90° between two neighboring ones. The incorporation of a second phase such as a metal and a conducting polymer greatly enhances the microwave-absorption capability. PMID:25338951

  5. Engineering Vertically Aligned Carbon Nanotube Growth by Decoupled Thermal Treatment of Precursor and Catalyst

    SciTech Connect

    Meshot, E.; Plata, D; Tawfick, S; Zhang, Y; Verploegen, E; Hart, A

    2009-01-01

    We study synthesis of vertically aligned carbon nanotube (CNT) 'forests' by a decoupled method that facilitates control of the mean diameter and structural quality of the CNTs and enables tuning of the kinetics for efficient growth to forest heights of several millimeters. The growth substrate temperature (Ts) primarily determines the CNT diameter, whereas independent and rapid thermal treatment (Tp) of the C2H4/H2 reactant mixture significantly changes the growth rate and terminal forest height but does not change the CNT diameter. Synchrotron X-ray scattering is utilized for precise, nondestructive measurement of CNT diameter in large numbers of samples. CNT structural quality monotonically increases with Ts yet decreases with Tp, and forests grown by this decoupled method have significantly higher quality than those grown using a conventional single-zone tube furnace. Chemical analysis reveals that the thermal treatment generates a broad population of hydrocarbon species, and a nonmonotonic relationship between catalyst lifetime and Tp suggests that certain carbon species either enhance or inhibit CNT growth. However, the forest height kinetics, as measured in real-time during growth, are self-similar, thereby indicating that a common mechanism of growth termination may be present over a wide range of process conditions.

  6. Growth of High-Density Self-Aligned Carbon Nanotubes and Nanofibers Using Palladium Catalyst

    NASA Astrophysics Data System (ADS)

    Vollebregt, S.; Derakhshandeh, J.; Ishihara, R.; Wu, M. Y.; Beenakker, C. I. M.

    2010-04-01

    In this paper we demonstrate vertical self-aligned growth of carbon nanotubes (CNT) and carbon nanofibers (CNF) using 1 nm of Pd as the catalyst material. Results were compared with those obtained using traditional catalysts (Co, Fe, and Ni). Pd is of interest as it has been demonstrated to be an excellent material for electrical contact to nanotubes. CNT were grown using plasma-enhanced chemical vapor deposition (PECVD) at 450°C to 500°C and using atmospheric-pressure chemical vapor deposition (APCVD) between 450°C and 640°C. The results were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy. High-density (1011 cm-2 to 1012 cm-2) self-aligned CNT growth was obtained using APCVD and Pd as the catalyst, while Co and Fe resulted in random growth. TEM revealed that the CNT grown by Pd with PECVD form large bundles of tubes, while Ni forms large-diameter CNF. It was found that the CNT grown using Pd or Ni are of low quality compared with those grown by Co and Fe.

  7. Expression of the nucleoside-derived drug transporters hCNT1, hENT1 and hENT2 in gynecologic tumors.

    PubMed

    Farré, Xavier; Guillén-Gómez, Elena; Sánchez, Lydia; Hardisson, David; Plaza, Yolanda; Lloberas, Jorge; Casado, F Javier; Palacios, José; Pastor-Anglada, Marçal

    2004-12-20

    Deoxynucleoside analogs are used in the treatment of a variety of solid tumors. Their transport across the plasma membrane may determine their cytotoxicity and thus nucleoside transporter (NT) expression patterns may be of clinical relevance. Lack of appropriate antibodies for use in paraffin-embedded biopsies has been a bottleneck to undertake high-throughput analysis of NT expression in solid tumors. Here we report the characterization of 2 new antibodies raised against the low-affinity equilibrative NTs, hENT1 and hENT2, suitable for that purpose. These 2 antisera, along with a previously characterized antibody that specifically recognizes the high-affinity Na-dependent concentrative NT, hCNT1, have been used to analyze, using a tissue array approach, NT expression in gynecologic cancers (90 ovarian, 80 endometrial and 118 uterine cervix carcinomas). Human CNT1 was not detected in 33% and 39% of the ovarian and uterine cervix carcinomas, respectively, whereas hENT1 and hENT2 expression was significantly retained in a high percentage of tumors (91% and 96% for hENT1, 84% and 98% for hENT2, in ovarian and cervix carcinomas, respectively). Only a few endometrial carcinomas (15%) were found to be negative for hCNT1, but they all retained hENT1 and hENT2 expression. In ovarian cancer, the loss of all 3 NT proteins was a more common event in the clear cell histologic subtype than in the serous, mucinous and endometrioid histotypes. In uterine cervix tumors, the loss of expression of hCNT1 was significantly associated with the adenocarcinoma subtype. In summary, hCNT1 was by far the isoform whose expression was most frequently reduced or lost in the 3 types of gynecologic tumors analyzed. Moreover, NT expression is related to the type of gynecologic tumor and its specific subtype, hCNT1 protein loss being highly correlated with poor prognosis histotypes. Since hCNT1, hENT1 and hENT2 recognize fluoropyrimidines as substrates, but with different affinities, this study

  8. Recent molecular advances in studies of the concentrative Na+-dependent nucleoside transporter (CNT) family: identification and characterization of novel human and mouse proteins (hCNT3 and mCNT3) broadly selective for purine and pyrimidine nucleosides (system cib).

    PubMed

    Ritzel, M W; Ng, A M; Yao, S Y; Graham, K; Loewen, S K; Smith, K M; Hyde, R J; Karpinski, E; Cass, C E; Baldwin, S A; Young, J D

    2001-01-01

    The human concentrative (Na+-linked) plasma membrane transport proteins hCNT1 and hCNT2, found primarily in specialized epithelia, are selective for pyrimidine nucleosides (system cit) and purine nucleosides (system cif), respectively. Both have orthologs in other mammalian species and belong to a gene family (CNT) that also includes members in lower vertebrates, insects, nematodes, pathogenic yeast and bacteria. The CNT transporter family also includes a newly identified human and mouse CNT3 transporter isoform. This paper reviews the studies of CNT transport proteins that led to the identification of hCNT3 and mCNT3, and gives an overview of the structural and functional properties of these latest CNT family members. hCNT3 and mCNT3 have primary structures that place them in a CNT subfamily separate from CNT1/2, transport a wide range of physiological pyrimidine and purine nucleosides and antineoplastic and antiviral nucleoside drugs (system cib), and exhibit a Na+:uridine coupling ratio of at least 2:1 (cf 1:1 for hCNT1/2). Cells and tissues containing hCNT3 transcripts include mammary gland, differentiated HL-60 cells, pancreas, bone marrow, trachea, liver, prostrate and regions of intestine, brain and heart. In HL-60 cells, hCNT3 is transcriptionally regulated by phorbol myristate (PMA). The hCNT3 gene, which contains an upstream PMA response element, mapped to 9q22.2 (cf chromosome 15 for hCNT1 and hCNT2). PMID:11396613

  9. Thermal property tuning in aligned carbon nanotube films and random entangled carbon nanotube films by ion irradiation

    SciTech Connect

    Wang, Jing; Chen, Di; Wang, Xuemei; Bykova, Julia S.; Zakhidov, Anvar A.; Shao, Lin

    2015-10-12

    Ion irradiation effects on thermal property changes are compared between aligned carbon nanotube (A-CNT) films and randomly entangled carbon nanotube (R-CNT) films. After H, C, and Fe ion irradiation, a focusing ion beam with sub-mm diameter is used as a heating source, and an infrared signal is recorded to extract thermal conductivity. Ion irradiation decreases thermal conductivity of A-CNT films, but increases that of R-CNT films. We explain the opposite trends by the fact that neighboring CNT bundles are loosely bonded in A-CNT films, which makes it difficult to create inter-tube linkage/bonding upon ion irradiation. In a comparison, in R-CNT films, which have dense tube networking, carbon displacements are easily trapped between touching tubes and act as inter-tube linkage to promote off-axial phonon transport. The enhancement overcomes the phonon transport loss due to phonon-defect scattering along the axial direction. A model is established to explain the dependence of thermal conductivity changes on ion irradiation parameters including ion species, energies, and current.

  10. Alignment of the VISA Undulator

    SciTech Connect

    Ruland, Robert

    1999-04-15

    The Visible-Infrared SASE Amplifier (VISA) undulator consists of four 99cm long segments. Each undulator segment is set up on a pulsed-wire bench, to characterize the magnetic properties and to locate the magnetic axis of the FODO array. Subsequently, the location of the magnetic axis, as defined by the wire, is referenced to tooling balls on each magnet segment by means of a straightness interferometer. After installation in the vacuum chamber, the four magnet segments are aligned with respect to themselves and globally to the beam line reference laser. A specially designed alignment fixture is used to mount one straightness interferometer each in the horizontal and vertical plane of the beam. The goal of these procedures is to keep the combined rms trajectory error, due to magnetic and alignment errors, to 50{micro}m.

  11. Fiber alignment apparatus and method

    DOEpatents

    Kravitz, Stanley H.; Warren, Mial Evans; Snipes, Jr., Morris Burton; Armendariz, Marcelino Guadalupe; Word, V., James Cole

    1997-01-01

    A fiber alignment apparatus includes a micro-machined nickel spring that captures and locks arrays of single mode fibers into position. The design consists of a movable nickel leaf shaped spring and a fixed pocket where fibers are held. The fiber is slid between the spring and a fixed block, which tensions the spring. When the fiber reaches the pocket, it automatically falls into the pocket and is held by the pressure of the leaf spring.

  12. Fiber alignment apparatus and method

    DOEpatents

    Kravitz, S.H.; Warren, M.E.; Snipes, M.B. Jr.; Armendariz, M.G.; Word, J.C. V

    1997-08-19

    A fiber alignment apparatus includes a micro-machined nickel spring that captures and locks arrays of single mode fibers into position. The design consists of a movable nickel leaf shaped spring and a fixed pocket where fibers are held. The fiber is slid between the spring and a fixed block, which tensions the spring. When the fiber reaches the pocket, it automatically falls into the pocket and is held by the pressure of the leaf spring. 8 figs.

  13. Double-walled carbon nanotube array for CO2 and SO2 adsorption.

    PubMed

    Rahimi, Mahshid; Babu, Deepu J; Singh, Jayant K; Yang, Yong-Biao; Schneider, Jörg J; Müller-Plathe, Florian

    2015-09-28

    Grand-canonical Monte Carlo simulations and adsorption experiments are combined to find the optimized carbon nanotube (CNT) arrays for gas adsorption at low pressures and 303 K. Bundles of 3D aligned double-walled carbon nanotube (DWCNT) with inner diameter of 8 nm and different intertube distances were made experimentally. The experimental results show that decreasing intertube distance leads to a significant enhancement in carbon-dioxide (CO2) adsorption capacity at 1 bar. The molecular simulation study on CO2 adsorption onto bundles of 3D aligned DWCNT with inner diameters of 1, 3, and 8 nm and intertube distance of 0-15 nm shows that the intertube distance plays a more important role than the CNT diameter. The simulation results show that decreasing the intertube distance up to 1 nm increases the excess adsorption generally in all the studied systems at pressures 0 < p < 14 bars (the increase can be up to ∼40% depending on the system and pressure). This is in agreement with the experimental result. Further reduction in intertube distance leads to a decrease in the excess adsorption in the pressure range 9 < p < 14 bars. However, at lower pressure, 0 < p < 9 bars, intertube distance of 0.5 nm is found to have the highest excess adsorption. This result is indifferent to tube diameter. Furthermore, molecular simulations are conducted to obtain the optimal parameters, for the DWCNT bundle, for SO2 adsorption, which are similar to those observed for CO2 in the pressure range 0 < p < 3 bars. PMID:26429026

  14. Effect of vertically aligned carbon nanotube density on the water flux and salt rejection in desalination membranes.

    PubMed

    Trivedi, Samarth; Alameh, Kamal

    2016-01-01

    In this paper, vertically aligned carbon nanotube (VACNT) membranes of different densities are developed and their performances are investigated. VACNT arrays of densities 5 × 10(9), 10(10), 5 × 10(10) and 10(11) tubes cm(-2), are initially grown on 1 cm × 1 cm silicon substrates using chemical vapour deposition. A VACNT membrane is realised by attaching a 300 μm-thick 1 cm × 1 cm VACNT array on silicon to a 4″ glass substrate, applying polydimethylsiloxane (PDMS) through spin coating to fill the gaps between the VACNTs, and using a microtome to slice the VACNT-PDMS composite into 25-μm-thick membranes. Experimental results show that the permeability of the developed VACNT membranes increases with the density of the VACNTs, while the salt rejection is almost independent of the VACNT density. The best measured permeance is attained with a VACNT membrane having a CNT density of 10(11) tubes cm(-2) is 1203 LMH at 1 bar. PMID:27504256

  15. Self aligned hysteresis free carbon nanotube field-effect transistors

    NASA Astrophysics Data System (ADS)

    Shlafman, M.; Tabachnik, T.; Shtempluk, O.; Razin, A.; Kochetkov, V.; Yaish, Y. E.

    2016-04-01

    Hysteresis phenomenon in the transfer characteristics of carbon nanotube field effect transistor (CNT FET) is being considered as the main obstacle for successful realization of electronic devices based on CNTs. In this study, we prepare four kinds of CNTFETs and explore their hysteretic behavior. Two kinds of devices comprise on-surface CNTs (type I) and suspended CNTs (type II) with thin insulating layer underneath and a single global gate which modulates the CNT conductance. The third and fourth types (types III and IV) consist of suspended CNT over a metallic local gate underneath, where for type IV the local gate was patterned self aligned with the source and drain electrodes. The first two types of devices, i.e., type I and II, exhibit substantial hysteresis which increases with scanning range and sweeping time. Under high vacuum conditions and moderate electric fields ( |E |>4 ×106 V /cm ), the hysteresis for on-surface devices cannot be eliminated, as opposed to suspended devices. Interestingly, type IV devices exhibit no hysteresis at all at ambient conditions, and from the different roles which the global and local gates play for the four types of devices, we could learn about the hysteresis mechanism of this system. We believe that these self aligned hysteresis free FETs will enable the realization of different electronic devices and sensors based on CNTs.

  16. Fabrication process and electromagnetic wave absorption characterization of a CNT/Ni/epoxy nanocomposite.

    PubMed

    Ryu, Seongwoo; Mo, Chan Bin; Lee, Haeshin; Hong, Soon Hyung

    2013-11-01

    Since carbon nanotube (CNT) was first discovered in 1991, it has been considered as a viable type of conductive filler for electromagnetic wave absorption materials in the GHz range. In this paper, pearl-necklace-structure CNT/Ni nano-powders were fabricated by a polyol process as conductive fillers. Compared to synthesized CNT, pearl-necklace Ni-decorated CNT increased the electrical conductivity by an order of 1 due to the enhancement of the Ni-conductive network. Moreover, the decorated Ni particles prevented the agglomeration of CNTs by counterbalancing the Van der Walls interaction between the CNTs. A CNT/Ni nanocomposite showed a homogeneous dispersion in an epoxy-based matrix. This enhanced physical morphology and electrical properties lead to an increase in the loss tangent and reflection loss in the CNT/Ni/Epoxy nanocomposite compared to these characteristics of a CNT/Epoxy nanocomposite in range of 8-12 GHz. The electromagnetic wave absorption properties of CNT/Ni/epoxy nanocomposites will provide enormous opportunities for electronic applications where lightweight EMI shielding or electro-magnetic wave absorption properties are necessary. PMID:24245312

  17. Nonequilibrium molecular dynamics simulation of pressure-driven water transport through modified CNT membranes

    NASA Astrophysics Data System (ADS)

    Wang, Luying; Dumont, Randall S.; Dickson, James M.

    2013-03-01

    Nonequilibrium molecular dynamics (NEMD) simulations are presented to investigate the effect of water-membrane interactions on the transport properties of pressure-driven water flow passing through carbon nanotube (CNT) membranes. The CNT membrane is modified with different physical properties to alter the van der Waals interactions or the electrostatic interactions between water molecules and the CNT membranes. The unmodified and modified CNT membranes are models of simplified nanofiltration (NF) membranes at operating conditions consistent with real NF systems. All NEMD simulations are run with constant pressure difference (8.0 MPa) temperature (300 K), constant pore size (0.643 nm radius for CNT (12, 12)), and membrane thickness (6.0 nm). The water flow rate, density, and velocity (in flow direction) distributions are obtained by analyzing the NEMD simulation results to compare transport through the modified and unmodified CNT membranes. The pressure-driven water flow through CNT membranes is from 11 to 21 times faster than predicted by the Navier-Stokes equations. For water passing through the modified membrane with stronger van der Waals or electrostatic interactions, the fast flow is reduced giving lower flow rates and velocities. These investigations show the effect of water-CNT membrane interactions on water transport under NF operating conditions. This work can help provide and improve the understanding of how these membrane characteristics affect membrane performance for real NF processes.

  18. Multi-scale numerical simulations of thermal expansion properties of CNT-reinforced nanocomposites

    PubMed Central

    2013-01-01

    In this work, the thermal expansion properties of carbon nanotube (CNT)-reinforced nanocomposites with CNT content ranging from 1 to 15 wt% were evaluated using a multi-scale numerical approach, in which the effects of two parameters, i.e., temperature and CNT content, were investigated extensively. For all CNT contents, the obtained results clearly revealed that within a wide low-temperature range (30°C ~ 62°C), thermal contraction is observed, while thermal expansion occurs in a high-temperature range (62°C ~ 120°C). It was found that at any specified CNT content, the thermal expansion properties vary with temperature - as temperature increases, the thermal expansion rate increases linearly. However, at a specified temperature, the absolute value of the thermal expansion rate decreases nonlinearly as the CNT content increases. Moreover, the results provided by the present multi-scale numerical model were in good agreement with those obtained from the corresponding theoretical analyses and experimental measurements in this work, which indicates that this multi-scale numerical approach provides a powerful tool to evaluate the thermal expansion properties of any type of CNT/polymer nanocomposites and therefore promotes the understanding on the thermal behaviors of CNT/polymer nanocomposites for their applications in temperature sensors, nanoelectronics devices, etc. PMID:23294669

  19. Contribution of CNT1 and ENT1 to ribavirin uptake in human hepatocytes.

    PubMed

    Choi, Min-Koo; Kim, Min-Hye; Maeng, Han-Joo; Song, Im-Sook

    2015-01-01

    The objective of this study was to investigate the contributions of a sodium-dependent concentrative nucleoside transporter (CNT) 1 and an equilibrative nucleoside transporter (ENT) 1 to ribavirin uptake in human hepatocytes. The initial studies in oocytes expressing CNT1 and ENT1 showed increases in ribavirin uptake, indicating that ribavirin was a substrate for both CNT1 and ENT1. The CNT1- and ENT1-mediated ribavirin uptake showed concentration dependency with the following kinetics parameters: Km 26.3 μM and Vmax 426.2 fmol/min/oocyte for CNT1; Km 70.5 μM and Vmax 134.3 fmol/min/oocyte for ENT1. Ribavirin uptake clearance in six human hepatocytes ranged from 21.3 to 300.7 μL/min. Estimation of the contributions of CNT1 and ENT1 to the hepatic uptake of ribavirin by using a relative activity factor method indicated that the relative contribution of ENT1 to the ribavirin uptake was 82.8 ± 3.9%. Real-time polymerase chain reaction analysis of CNT1 and ENT1 expressions in the hepatocytes showed that ENT1 mRNA expression was closely correlated with ribavirin uptake (R = 0.95, P = 0.003) while CNT1 was not. The findings indicated that ENT1 was the major transporter controlling the hepatic uptake of ribavirin. PMID:25011570

  20. Antibacterial activity and reusability of CNT-Ag and GO-Ag nanocomposites

    NASA Astrophysics Data System (ADS)

    Kim, Ji Dang; Yun, Hyosuk; Kim, Gwui Cheol; Lee, Chul Won; Choi, Hyun Chul

    2013-10-01

    A facile approach to the synthesis of novel CNT-Ag and GO-Ag antibacterial materials, in which thiol groups are utilized as linkers to secure silver (Ag) nanoparticles to the CNT and GO surfaces without agglomeration, is reported. The resulting CNT-Ag and GO-Ag samples were characterized by performing TEM, XRD, Auger, XPS, and Raman measurements, which revealed that in these antibacterial materials size-similar and quasi-spherical Ag nanoparticles are anchored to the CNT and GO surfaces. The Ag nanoparticles in CNT-Ag and GO-Ag have narrow size distributions with average diameters of 2.6 and 3.5 nm respectively. The antibacterial activities of CNT-Ag and GO-Ag against Escherichia coli were assessed with the paper-disk diffusion method and by determining the minimal inhibitory concentrations (MICs). CNT-Ag was found to have higher antibacterial activity than the reference Ag colloid. Moreover, both CNT-Ag and GO-Ag retain more than 50% of their original antibacterial activities after 20 washes with detergent, which indicates their potential as antibacterial materials for laboratory and medical purposes.

  1. CNT1 expression influences proliferation and chemosensitivity in drug-resistant pancreatic cancer cells.

    PubMed

    Bhutia, Yangzom D; Hung, Sau Wai; Patel, Bhavi; Lovin, Dylan; Govindarajan, Rajgopal

    2011-03-01

    Overcoming the inherent chemoresistance of pancreatic cancers remains a major goal of therapeutic investigations in this disease. In this study, we discovered a role for the human concentrative nucleoside transporter-1 (hCNT1; SLC28A1), a high-affinity pyrimidine nucleoside transporter, in determining the chemosensitivity of human pancreatic cancer cells to gemcitabine, the drug used presently as a standard of care. Compared with normal pancreas and pancreatic ductal epithelial cells, hCNT1 expression was frequently reduced in pancreatic tumors and tumor cell lines. In addition, hCNT1-mediated (3)H-gemcitabine transport was lower in pancreatic cancer cell lines and correlated with cytotoxic IC(50) estimations of gemcitabine. In contrast to gemcitabine-sensitive pancreatic cancer cell lines, MIA PaCa-2, a gemcitabine-resistant pancreatic cancer cell line, exhibited relatively restrictive, cell cycle-dependent hCNT1 expression and transport. hCNT1 translation was suppressed in the late G1-enriched MIA PaCa-2 cell population possibly in an miRNA-dependent manner, which corresponded with the lowest hCNT1-mediated gemcitabine transport during this phase. Although hCNT1 protein was induced during G1/S transition, increased hCNT1 trafficking resulted in maximal cell surface recruitment and transport-overshoot in the G2/M phase-enriched cell population. hCNT1 protein was directed predominantly to proteasomal or lysosomal degradation in S or G2/M phase MIA PaCa-2 cells, respectively. Pharmacological inhibition of hCNT1 degradation moderately increased cell surface hCNT1 expression and cellular gemcitabine transport in MIA PaCa-2 cells. Constitutive hCNT1 expression reduced clonogenic survival of MIA PaCa-2 cells and steeply augmented gemcitabine transport and chemosensitization. In addition to supporting a putative tumor suppressor role for hCNT1, our findings identify hCNT1 as a potential candidate to render drug-resistant pancreatic cancer cells amenable to chemotherapy

  2. Diameter-Selective Alignment of Carbon Nanotubes on Si (001) Stepped Surfaces

    NASA Astrophysics Data System (ADS)

    Enkhtaivan, Batnyam; Yoshimura, Masahide; Iwata, Jun-Ichi; Oshiyama, Atsushi

    2014-03-01

    The necessity of aligning carbon nanotube (CNT) raises important questions of whether the alignment is energetically feasible and of whether the electronic properties of CNTs are modified on the substrate surface. We report total-energy electronic-structure calculations based on the DFT that provide stable adsorption sites, structural characteristics, and energy bands of CNTs adsorbed on the Si(001) stepped surfaces. We choose (5,5), (9,9) and (13,13) armchair CNTs with the diameters of 6.8 Å, 12.2 Å and 17.6 Å and explore all the possible adsorption sites either on the terrace or at step edges. We find that the (9,9) CNT is most favorably adsorbed at the edge of the double-layer step DB along the <110 > direction, whereas the (5,5) and (13,13) CNTs favor the terrace site where the CNTs are perpendicular to the Si dimer rows. This finding is indicative of the diameter-selective self-organized alignment of CNTs by exploiting the Si surface steps. We also find that the electronic structure of each CNT is modified upon adsorption depending on the adsorption site and the diameter of the CNTs. In particular, the (9,9) CNT at the most stable step edge site becomes semiconducting and also an interesting flat band appears at Fermi level. Present address: Technical Research & Development Bureau, Nippon Steel & Sumitomo Metal Corporation.

  3. Super growth of vertically aligned carbon nanotubes on pulsed laser deposited catalytic thin films

    NASA Astrophysics Data System (ADS)

    Fejes, D.; Pápa, Z.; Kecsenovity, E.; Réti, B.; Toth, Z.; Hernadi, K.

    2015-03-01

    Efficient and reproducible growth of vertically aligned carbon nanotube (CNT) forests by catalytic chemical vapor deposition (CVD) requires precise setting of the properties of the catalyst thin films and CVD conditions. In this work, super growth of vertically aligned CNTs onto Al2O3 support and Fe-Co catalyst layer system is presented. The layers were grown by pulsed laser deposition (PLD) onto silicon wafer pieces. Their thickness and optical properties were controlled by spectroscopic ellipsometry. The effect of heat treatment at 750 °C in nitrogen and in hydrogen of these PLD layers was compared. High-resolution electron microscopic images showed that treatment of catalyst layers in H2 resulted in finer and denser catalytic particles. As a result, well-aligned, dense and few-walled CNT forests with 1-1.5 mm height were deposited by water-vapor-assisted CVD on the hydrogen-treated films, while without hydrogen treatment defected CNT structures were grown. According to these observations, Raman spectroscopy showed a higher degree of crystallinity in case of CNT-s, where reduction by hydrogen influenced the oxidation state of the metallic catalytic particles in a beneficial way.

  4. Strain rate effects on compressive behavior of covalently bonded CNT networks

    NASA Astrophysics Data System (ADS)

    Kirkayak, Levent

    2016-06-01

    In this study, strain rate effects on the compressive mechanical properties of randomly structured carbon nanotube (CNT) networks were examined. For this purpose, three-dimensional atomistic models of CNT networks with covalently-bonded junctions were generated. After that, molecular dynamics (MD) simulations of compressive loading were performed at five different strain rates to investigate the basic deformation characteristic mechanisms of CNT networks and determine the effect of strain rate on stress-strain curves. The simulation results showed that the strain rate of compressive loading increases, so that a higher resistance of specimens to deformation is observed. Furthermore, the local deformation characteristics of CNT segments, which are mainly driven by bending and buckling modes, and their prevalence are strongly affected by the deformation rate. It was also observed that CNT networks have superior features to metal foams such as metal matrix syntactic foams (MMSFs) and porous sintered fiber metals (PSFMs) in terms of energy absorbing capabilities.

  5. Multi-Scale CNT-Based Reinforcing Polymer Matrix Composites for Lightweight Structures

    NASA Technical Reports Server (NTRS)

    Eberly, Daniel; Ou, Runqing; Karcz, Adam; Skandan, Ganesh; Mather, Patrick; Rodriguez, Erika

    2013-01-01

    Reinforcing critical areas in carbon polymer matrix composites (PMCs), also known as fiber reinforced composites (FRCs), is advantageous for structural durability. Since carbon nanotubes (CNTs) have extremely high tensile strength, they can be used as a functional additive to enhance the mechanical properties of FRCs. However, CNTs are not readily dispersible in the polymer matrix, which leads to lower than theoretically predicted improvement in mechanical, thermal, and electrical properties of CNT composites. The inability to align CNTs in a polymer matrix is also a known issue. The feasibility of incorporating aligned CNTs into an FRC was demonstrated using a novel, yet commercially viable nanofiber approach, termed NRMs (nanofiber-reinforcing mats). The NRM concept of reinforcement allows for a convenient and safe means of incorporating CNTs into FRC structural components specifically where they are needed during the fabrication process. NRMs, fabricated through a novel and scalable process, were incorporated into FRC test panels using layup and vacuum bagging techniques, where alternating layers of the NRM and carbon prepreg were used to form the reinforced FRC structure. Control FRC test panel coupons were also fabricated in the same manner, but comprised of only carbon prepreg. The FRC coupons were machined to size and tested for flexural, tensile, and compression properties. This effort demonstrated that FRC structures can be fabricated using the NRM concept, with an increased average load at break during flexural testing versus that of the control. The NASA applications for the developed technologies are for lightweight structures for in-space and launch vehicles. In addition, the developed technologies would find use in NASA aerospace applications such as rockets, aircraft, aircraft/spacecraft propulsion systems, and supporting facilities. The reinforcing aspect of the technology will allow for more efficient joining of fiber composite parts, thus offering

  6. DNA Align Editor: DNA Alignment Editor Tool

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The SNPAlignEditor is a DNA sequence alignment editor that runs on Windows platforms. The purpose of the program is to provide an intuitive, user-friendly tool for manual editing of multiple sequence alignments by providing functions for input, editing, and output of nucleotide sequence alignments....

  7. Effect of electric charging on the velocity of water flow in CNT.

    PubMed

    Abbasi, Hossein Reza; Karimian, S M Hossein

    2016-09-01

    The role of electrical charge in controlling the velocity of water molecules in a finite single-walled carbon nanotube (CNT) was studied in detail using molecular dynamics simulation. Different test cases were examined to determine the parameters affecting the control of water-flow velocity in CNT upon electrically charging the surface of a CNT. The results showed that charge magnitude and volume, as well as the charging scenario, are the parameters having greatest effect. The implementation of electric charge on the surface of a CNT was demonstrated to decrease the resistance of CNT to incoming water flow at the entrance, but to increase friction-type resistance to flow along the CNT. Therefore, through controlling the magnitude of electric charge, water flow through the CNT may be accelerated, or decelerated. The results show that the velocity of molecular flow in the CNT increases to a maximum value, and then decreases with electric charge regardless of its sign. In the case studied here, this maximum velocity occurs at electric charging of ±0.25e/atom. It was also shown that, to reach similar flow velocities in a CNT, it is not sufficient to merely implement equal volumes of electric charge, where the volume of electric charging is defined as charge magnitude × charging time. In fact , both magnitude of charging and volume of electric charging must be equal to each other. These findings, together with options to implement scenarios with alternative charging, provide the means to effectively adjust desired velocities in a CNT. PMID:27488104

  8. Obtaining a Well-Aligned ZnO Nanotube Array Using the Hydrothermal Growth Method / Labi Sakārtotu Zno Nanocauruļu Kopu Iegūšana, Izmantojot Hidrotermālo Metodi

    NASA Astrophysics Data System (ADS)

    Krasovska, M.; Gerbreders, V.; Paskevics, V.; Ogurcovs, A.; Mihailova, I.

    2015-10-01

    Optimal growing parameters have been found using the hydrothermal method to obtain well-aligned vertical ZnO nanorod and nanotube arrays. The influence of different growing factors (such as temperature, growing solution concentration, method of obtaining seed layer and condition) on nanotube morphology and size is described in the paper. Well-structured ZnO nanotubes have been obtained by using a selfselective etching method with lowering temperatures of growth during the hydrothermal process. It is shown that the optical properties of the nanostructure arrays obtained are sensitive to the medium in which they are placed, which is why they can be used as sensors for pure substance detection and in different solutions for impurity determination. Dotajā darbā tika noteikti optimāli parametri labi sakārtotu ZnO nanocaurulīšu kopu iegūšanai, izmantojot hidrotermālo metodi ar temperatūras pazemināšanu, jeb t.s. selektīvu pa\\vskodināšanas metodi (self-selective etching), ir uzsvērtas šās metodes priekšrocības salīdzinājumā ar ķīmiskās kodināšanas metodi, kā arī tika aprakstīta dažādu augšanas faktora (tādu, ka darba šķīduma koncentrācija, augšanas temperatūra un laiks, iedīgļu slāņa iegūšanas veids un iegūšanas parametri) ietekme uz iegūtu nanostraktūra morfoloģiju. Tika konstatēts, ka noteicošu lomu ZnO nanocaurulīšu audzēšanas procesā spēlē iedīgļu slāņa graudu izmēri, kas savā staipā nosaka augošu nanostieņu izmērus un to tendenci pie pa\\vskodināšanas. Rentgenogrannnas parāda, ka iegūtām pie noteiktiem parametriem ZnO nanostruktūrām piemīt augsta kristāliskuma pakāpe un sakārtotība vertikālā virzienā. Optiskie mērījumi parāda, ka ZnO nanocauralītes ir jutīgas gan pret tīrām vielām (ūdens, spirts), gan pret dažādiem šķīdumiem, kas ļauj izmantot tos kā pie­jaukumu sensora. Salīdzinājumā ar ZnO nanostieņiem caurulīšu jūtība pieaug, jo pieaug nanostrakt

  9. Fine alignment of a large segmented mirror

    NASA Technical Reports Server (NTRS)

    Dey, Thomas William (Inventor)

    2010-01-01

    A system for aligning a segmented mirror includes a source of radiation directed along a first axis to the segmented mirror and a beamsplitter removably inserted along the first axis for redirecting radiation from the first axis to a second axis, substantially perpendicular to the first axis. An imaging array is positioned along the second axis for imaging the redirected radiation, and a knife-edge configured for cutting the redirected radiation is serially positioned to occlude and not occlude the redirected radiation, effectively providing a variable radiation pattern detected by the imaging array for aligning the segmented mirror.

  10. Electrochemical studies of CNT/Si–SnSb nanoparticles for lithium ion batteries

    SciTech Connect

    Nithyadharseni, P.; Reddy, M.V.; Nalini, B.; Ravindran, T.R.; Pillai, B.C.; Kalpana, M.; Chowdari, B.V.R.

    2015-10-15

    Highlights: • Si added SnSb and CNT exhibits very low particle size of below 30 nm • A strong PL quenching due to the addition of Si to SnSb. • Electrochemical studies show CNT added SnSb shows good capacity retention. - Abstract: Nano-structured SnSb, SnSb–CNT, Si–SnSb and Si–SnSb–CNT alloys were synthesized from metal chlorides of Sn, Sb and Si via reductive co-precipitation technique using NaBH{sub 4} as reducing agent. The as prepared compounds were characterized by various techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM), Raman, Fourier transform infra-red (FTIR) and photoluminescence (PL) spectroscopy. The electrochemical performances of the compounds were characterized by galvanostatic cycling (GC) and cyclic voltammetry (CV). The Si–SnSb–CNT compound shows a high reversible capacity of 1200 mAh g{sup −1}. However, the rapid capacity fading was observed during cycling. In contrast, SnSb–CNT compound showed a high reversible capacity of 568 mAh g{sup −1} at 30th cycles with good cycling stability. The improved reversible capacity and cyclic performance of the SnSb–CNT compound could be attributed to the nanosacle dimension of SnSb particles and the structural advantage of CNTs.

  11. Uniformly spaced arrays of purely semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Falk, Abram; Kumar, Bharat; Tulevski, George; Farmer, Damon; Hannon, James; Han, Shu-Jen

    Patterning uniformly spaced arrays of carbon nanotubes (CNTs) is a key challenge for carbon electronics. Our group adopts a hybrid approach to meeting this goal. We use top-down lithography to pattern trenches on chips. We then use surface-selective chemical monolayers to facilitate the bottom-up assembly of solution-processed CNTs into these trenches. Previously, we showed large-scale integration of CNTs based on this approach, but modifications to this process have been needed in order to improve the yield and decrease the fraction of non-switching devices. Our latest results show a high degree of selectivity, alignment and yield of successfully placed CNTs at a 100 nm pitch. Electrical measurements confirm that these chemically placed CNTs are nearly 100% semiconducting and of similar quality to randomly dispersed ones. I will then discuss our strategies for increasing the CNT density and extending these results from chip- to wafer-scale electronics. email: alfalk@us.ibm.com.

  12. Synthesis and characterization of multiwalled CNT-PAN based composite carbon nanofibers via electrospinning.

    PubMed

    Kaur, Narinder; Kumar, Vipin; Dhakate, Sanjay R

    2016-01-01

    Electrospun fibrous membranes find place in diverse applications like sensors, filters, fuel cell membranes, scaffolds for tissue engineering, organic electronics etc. The objectives of present work are to electrospun polyacrylonitrile (PAN) nanofibers and PAN-CNT nanocomposite nanofibers and convert into carbon nanofiber and carbon-CNT composite nanofiber. The work was divided into two parts, development of nanofibers and composite nanofiber. The PAN nanofibers were produced from 9 wt% PAN solution by electrospinning technique. In another case PAN-CNT composite nanofibers were developed from different concentrations of MWCNTs (1-3 wt%) in 9 wt% PAN solution by electrospinning. Both types of nanofibers were undergone through oxidation, stabilization, carbonization and graphitization. At each stage of processing of carbon and carbon-CNT composite nanofibers were characterized by SEM, AFM, TGA and XRD. It was observed that diameter of nanofiber varies with processing parameters such as applied voltage tip to collector distance, flow rate of solution and polymer concentrations etc. while in case of PAN-CNT composite nanofiber diameter decreases with increasing concentration of CNT in PAN solution. Also with stabilization, carbonization and graphitization diameter of nanofiber decreases. SEM images shows that the minimum fiber diameter in case of 3 wt% of CNT solution because as viscosity increases it reduces the phase separation of PAN and solvent and as a consequence increases in the fiber diameter. AFM images shows that surface of film is irregular which give idea about mat type orientation of fibers. XRD results show that degree of graphitization increases on increasing CNT concentration because of additional stresses exerting on the nanofiber surface in the immediate vicinity of CNTs. TGA results shows wt loss decreases as CNT concentration increases in fibers. PMID:27217998

  13. Surface activation of CNT Webs towards layer by layer assembly of biosensors.

    PubMed

    Musameh, Mustafa; Huynh, Chi P; Hickey, Mark; Kyratzis, Ilias Louis

    2016-04-25

    Several surface activation methods such as chemical, electrochemical and plasma have been used for enhancing the electrochemical performance of carbon based electrodes for various applications. However, some of these surface activation methods may not be useful depending on the chemical and physical properties of the activated surface. Herein we investigate the surface activation of carbon nanotube (CNT) webs by electrochemical and plasma techniques to enhance their electrochemical performance and enable the fabrication of a biosensor using the layer-by-layer (LBL) approach. The pretreated CNT webs were characterized by SEM, TEM, Raman, XPS and electrochemical methods. TEM images and Raman analysis showed an increase in the level of surface defects upon pretreatment with higher number of defects after electrochemical pretreatment. XPS analysis showed an increase in the level of oxygen functional groups after pretreatment (4 to 5 times increase) which resulted in enhanced water wettability especially for plasma pretreated CNT webs. The pretreated CNT web electrodes also showed an enhanced electrochemical activity towards the oxidation and reduction of different redox probes with higher sensitivity for the electrochemically pretreated CNT web electrode that was accompanied by a higher level of noise in amperometric measurements. A highly linear response was obtained for the untreated and the electrochemically pretreated CNT web electrodes towards the amperometric detection of NADH (R(2) of 0.9996 and 0.9986 respectively) while a non-linear response was observed for the plasma pretreated CNT web electrode (R(2) of 0.8538). The pretreated CNT web electrodes enabled the fabrication of a LBL biosensor for alcohol detection with highest operational stability obtained for the plasma pretreated CNT web surface. PMID:26818435

  14. Three-Day Continuous Exposure Monitoring of CNT Manufacturing Workplaces

    PubMed Central

    Lee, Ji Hyun; Ahn, Kang Ho; Kim, Sun Man; Kim, Ellen; Lee, Gun Ho; Han, Jeong Hee

    2015-01-01

    Continuous monitoring for possible exposure to carbon nanotubes was conducted over a period of 2 to 3 days at workplaces that manufacture multiwall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNTs). To estimate the potential emission of carbon nanotubes (CNTs) and potential exposure of workers, personal sampling, area monitoring, and real-time monitoring using an scanning mobility particle sizer (SMPS) and dust monitor were conducted at workplaces where the workers manufactured CNTs. The personal and area sampling of the total suspended particulate (TSP) at the MWCNT manufacturing facilities ranged from 0.031 to 0.254 and from N.D (not detected) to 0.253 mg/m3, respectively. This 2- to 3-day monitoring study found that nanoparticles were released when opening the chemical vapor deposit (CVD) reactor door after the synthesis of MWCNTs, when transferring the MWCNTs to containers and during blending and grinding. However, distinguishing the background concentration from the work process particle emission was complicated due to sustained and even increased particle concentrations after the work processes were terminated. The MWCNTs sampled for transmission electron microscopy (TEM) observation exhibited a tangled shape with no individual dispersed CNT structures. PMID:26125022

  15. Latest Progress in CNT-Based Composites for Space Applications

    NASA Astrophysics Data System (ADS)

    Klebor, Maximilian; Heep, Felicitas; Pfeiffer, Ernst K.; Linke, Stefan; Roddecke, Susanne; Lodereau, Pierre

    2012-07-01

    Composite materials used in S/C platforms and pay- loads can benefit from the latest developments in carbon fibres and nano-technologies. One of the most relevant novelties is the gradual incorporation of nano-species in the resin systems. This paper addresses the results of several technology studies lead and or performed by HPS. They deal with the incorporation of CNT and other nano-species into CFRP to improve the physical properties and to antagonise specific CFRP drawbacks like e.g. the anisotropic properties based on the respective carbon fibre setup. The most interesting and promising applications for these novel composites were assessed and selected for composite development. Entities from several European countries worked together to establish composite and structure processing methods. Promising results concerning electrical and thermal properties were obtained but also many challenges had and still have to be faced. During the projects it has been found that different ingredient combinations and manufacturing processes are favourable for different applications/improvements. It seems that the CNTs and the processes have to be tailored for one specific target property, e.g. electrical conductivity enhancement. The achieved material improvements were and are still further investigated.

  16. Three-Day Continuous Exposure Monitoring of CNT Manufacturing Workplaces.

    PubMed

    Lee, Ji Hyun; Ahn, Kang Ho; Kim, Sun Man; Kim, Ellen; Lee, Gun Ho; Han, Jeong Hee; Yu, Il Je

    2015-01-01

    Continuous monitoring for possible exposure to carbon nanotubes was conducted over a period of 2 to 3 days at workplaces that manufacture multiwall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNTs). To estimate the potential emission of carbon nanotubes (CNTs) and potential exposure of workers, personal sampling, area monitoring, and real-time monitoring using an scanning mobility particle sizer (SMPS) and dust monitor were conducted at workplaces where the workers manufactured CNTs. The personal and area sampling of the total suspended particulate (TSP) at the MWCNT manufacturing facilities ranged from 0.031 to 0.254 and from N.D (not detected) to 0.253 mg/m(3), respectively. This 2- to 3-day monitoring study found that nanoparticles were released when opening the chemical vapor deposit (CVD) reactor door after the synthesis of MWCNTs, when transferring the MWCNTs to containers and during blending and grinding. However, distinguishing the background concentration from the work process particle emission was complicated due to sustained and even increased particle concentrations after the work processes were terminated. The MWCNTs sampled for transmission electron microscopy (TEM) observation exhibited a tangled shape with no individual dispersed CNT structures. PMID:26125022

  17. Dielectrophoretically aligned carbon nanotubes to control electrical and mechanical properties of hydrogels to fabricate contractile muscle myofibers.

    PubMed

    Ramón-Azcón, Javier; Ahadian, Samad; Estili, Mehdi; Liang, Xiaobin; Ostrovidov, Serge; Kaji, Hirokazu; Shiku, Hitoshi; Ramalingam, Murugan; Nakajima, Ken; Sakka, Yoshio; Khademhosseini, Ali; Matsue, Tomokazu

    2013-08-01

    Dielectrophoresis is used to align carbon nanotubes (CNTs) within gelatin methacrylate (GelMA) hydrogels in a facile and rapid manner. Aligned GelMA-CNT hydrogels show higher electrical properties compared with pristine and randomly distributed CNTs in GelMA hydrogels. The muscle cells cultured on these materials demonstrate higher maturation compared with cells cultured on pristine and randomly distributed CNTs in GelMA hydrogels. PMID:23798469

  18. Nanoscale optical and electrical characterization of horizontally aligned single-walled carbon nanotubes

    PubMed Central

    2012-01-01

    During the recent years, a significant amount of research has been performed on single-walled carbon nanotubes (SWCNTs) as a channel material in thin-film transistors (Pham et al. IEEE Trans Nanotechnol 11:44–50, 2012). This has prompted the application of advanced characterization techniques based on combined atomic force microscopy (AFM) and Raman spectroscopy studies (Mureau et al. Electrophoresis 29:2266–2271, 2008). In this context, we use confocal Raman microscopy and current sensing atomic force microscopy (CS-AFM) to study phonons and the electronic transport in semiconducting SWCNTs, which were aligned between palladium electrodes using dielectrophoresis (Kuzyk Electrophoresis 32:2307–2313, 2011). Raman imaging was performed in the region around the electrodes on the suspended CNTs using several laser excitation wavelengths. Analysis of the G+/G− splitting in the Raman spectra (Sgobba and Guldi Chem Soc Rev 38:165–184, 2009) shows CNT diameters of 2.5 ± 0.3 nm. Neither surface modification nor increase in defect density or stress at the CNT-electrode contact could be detected, but rather a shift in G+ and G− peak positions in regions with high CNT density between the electrodes. Simultaneous topographical and electrical characterization of the CNT transistor by CS-AFM confirms the presence of CNT bundles having a stable electrical contact with the transistor electrodes. For a similar load force, reproducible current–voltage (I/V) curves for the same CNT regions verify the stability of the electrical contact between the nanotube and the electrodes as well as the nanotube and the AFM tip over different experimental sessions using different AFM tips. Strong variations observed in the I/V response at different regions of the CNT transistor are discussed. PMID:23259903

  19. Temperature-dependent gas transport performance of vertically aligned carbon nanotube/parylene composite membranes

    PubMed Central

    2014-01-01

    A novel composite membrane consisting of vertically aligned carbon nanotubes (CNTs) and parylene was successfully fabricated. Seamless filling of the spaces in CNT forests with parylene was achieved by a low-pressure chemical vapor deposition (CVD) technique and followed with the Ar/O2 plasma etching to expose CNT tips. Transport properties of various gases through the CNT/parylene membranes were explored. And gas permeances were independent on feed pressure in accordance with the Knudsen model, but the permeance values were over 60 times higher than that predicted by the Knudsen diffusion kinetics, which was attributed to specular momentum reflection inside smooth CNT pores. Gas permeances and enhancement factors over the Knudsen model firstly increased and then decreased with rising temperature, which confirmed the existence of non-Knudsen transport. And surface adsorption diffusion could affect the gas permeance at relatively low temperature. The gas permeance of the CNT/parylene composite membrane could be improved by optimizing operating temperature. PMID:25246864

  20. Temperature-dependent gas transport performance of vertically aligned carbon nanotube/parylene composite membranes.

    PubMed

    Zhang, Lei; Yang, Junhe; Wang, Xianying; Zhao, Bin; Zheng, Guangping

    2014-01-01

    A novel composite membrane consisting of vertically aligned carbon nanotubes (CNTs) and parylene was successfully fabricated. Seamless filling of the spaces in CNT forests with parylene was achieved by a low-pressure chemical vapor deposition (CVD) technique and followed with the Ar/O2 plasma etching to expose CNT tips. Transport properties of various gases through the CNT/parylene membranes were explored. And gas permeances were independent on feed pressure in accordance with the Knudsen model, but the permeance values were over 60 times higher than that predicted by the Knudsen diffusion kinetics, which was attributed to specular momentum reflection inside smooth CNT pores. Gas permeances and enhancement factors over the Knudsen model firstly increased and then decreased with rising temperature, which confirmed the existence of non-Knudsen transport. And surface adsorption diffusion could affect the gas permeance at relatively low temperature. The gas permeance of the CNT/parylene composite membrane could be improved by optimizing operating temperature. PMID:25246864

  1. Dipole Alignment at the Carbon Nanotube and Methyl Ammonium Lead Trihalide Perovskite Interface - Oral Presentation

    SciTech Connect

    Przepioski, Joshua

    2015-08-25

    This work correlates resonant peaks from first principles calculation on ammonia (NH3) Nitrogen 1s x-ray absorption spectroscopy (XAS) within the methyl ammonium lead iodide perovskite (CH3NH3PbI3), and proposes a curve to determine the alignment of the methyl ammonium dipole if there exists angular dependence. The Nitrogen 1s XAS was performed at varying incident angles on the perovskite with and without a carbon nanotube (CNT) interface produced from an ultrasonic spray deposition. We investigated the peak contribution from PbI2 and the poly(9,9-dioctylfluorene-2,7-diyl) with bipyridine (PFO-BPy) wrapped around the CNT, and used normalization techniques to better identify the dipole alignment. There was angular dependence on samples containing the CNT interface suggesting an existing dipole alignment, but there was no angular dependence on the perovskite samples alone; however, more normalization techniques and experimental work must be performed in order to ensure its validity and to better describe its alignment, and possible controlling factors.

  2. Dipole Alignment at the Carbon Nanotube and Methyl Ammonium Lead Iodide Perovskite Interface

    SciTech Connect

    Przepioski, Joshua

    2015-08-28

    This work correlates resonant peaks from first principles calculation on ammonia (NH3) Nitrogen 1s x-ray absorption spectroscopy (XAS) within the methyl ammonium lead iodide perovskite (CH3NH3PbI3), and proposes a curve to determine the alignment of the methyl ammonium dipole if there exists angular dependence. The Nitrogen 1s XAS was performed at varying incident angles on the perovskite with and without a carbon nanotube (CNT) interface produced from an ultrasonic spray deposition. We investigated the peak contribution from PbI2 and the poly(9,9-dioctylfluorene- 2,7-diyl) with bipyridine (PFO-BPy) wrapped around the CNT, and used normalization techniques to better identify the dipole alignment. There was angular dependence on samples containing the CNT interface suggesting an existing dipole alignment, but there was no angular dependence on the perovskite samples alone; however, more normalization techniques and experimental work must be performed in order to ensure its validity and to better describe its alignment, and possible controlling factors.

  3. Influence of Different Defects in Vertically Aligned Carbon Nanotubes on TiO2 Nanoparticle Formation through Atomic Layer Deposition.

    PubMed

    Acauan, Luiz; Dias, Anna C; Pereira, Marcelo B; Horowitz, Flavio; Bergmann, Carlos P

    2016-06-29

    The chemical inertness of carbon nanotubes (CNT) requires some degree of "defect engineering" for controlled deposition of metal oxides through atomic layer deposition (ALD). The type, quantity, and distribution of such defects rules the deposition rate and defines the growth behavior. In this work, we employed ALD to grow titanium oxide (TiO2) on vertically aligned carbon nanotubes (VACNT). The effects of nitrogen doping and oxygen plasma pretreatment of the CNT on the morphology and total amount of TiO2 were systematically studied using transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. The induced chemical changes for each functionalization route were identified by X-ray photoelectron and Raman spectroscopies. The TiO2 mass fraction deposited with the same number of cycles for the pristine CNT, nitrogen-doped CNT, and plasma-treated CNT were 8, 47, and 80%, respectively. We demonstrate that TiO2 nucleation is dependent mainly on surface incorporation of heteroatoms and their distribution rather than structural defects that govern the growth behavior. Therefore, selecting the best way to functionalize CNT will allow us to tailor TiO2 distribution and hence fabricate complex heterostructures. PMID:27269125

  4. Alignment of the VISA Undulator

    SciTech Connect

    Ruland, Robert E.

    2000-02-09

    As part of the R and D program towards a fourth generation light source, a Self-Amplified Spontaneous Emission (SASE) demonstration is being prepared. The Visible-Infrared SASE Amplifier (VISA) undulator is being installed at Brookhaven National Laboratory. The VISA undulator is an in-vacuum, 4-meter long, 1.8 cm period, pure-permanent magnet device, with a novel, strong focusing, permanent magnet FODO array included within the fixed, 6 mm undulator gap. The undulator is constructed of 99 cm long segments. To attain maximum SASE gain requires establishing overlap of electron and photon beams to within 50 pm rms. This imposes challenging tolerances on mechanical fabrication and magnetic field quality, and necessitates use of laser straightness interferometry for calibration and alignment of the magnetic axes of the undulator segments. This paper describes the magnetic centerline determination, and the fiducialization and alignment processes, which were performed to meet the tolerance goal.

  5. Improving sensitivity of the polyurethane/CNT laminate strain sensor by controlled mechanical preload

    NASA Astrophysics Data System (ADS)

    Slobodian, Petr; Olejnik, Robert; Matyas, Jiri; Gorakh Babar, Dipak

    2016-03-01

    This article describes strain detection potential of polyurethane/CNT layered composite and further possible enhance of its sensitivity to strain, expressed by value of gauge factor, GF, employing its controlled mechanical preload. In course of its fabrication a non-woven polyurethane membrane made by electro spinning was used as filtering membrane for CNT aqueous dispersion. Final CNT polyurethane laminate composite is prepared by compression molding. Produced polyurethane/CNT composite laminate is electrically conductive and high elastic. Its elongation leads to change of its macroscopic electrical resistance. Changes in resistance are further reversible, reproducible and can monitor deformation in real time. Gauge factor reaches very high values around 8 for strain reaching 3.5% comparing with conventional metallic strain gauges. Finally, controlled mechanical preload significantly increases value of GF. For example for value of 8.1% of preload value of GF reaches 23.3 for strain 3.5%.

  6. Allelic isoforms of the H+/nucleoside co-transporter (CaCNT) from Candida albicans reveal separate high- and low-affinity transport systems for nucleosides.

    PubMed

    Slugoski, Melissa D; Loewen, Shaun K; Ng, Amy M L; Baldwin, Stephen A; Cass, Carol E; Young, James D

    2004-11-01

    Contigs 19-10196 and 19-20196 of the Stanford Candida albicans genome sequence databank encode two putative allelic isoforms of C. albicans CaCNT, a recently characterized 608 amino acid residue H+-coupled fungal member of the CNT family of concentrative nucleoside transport proteins. The single Ser/Gly difference between CaCNT/19-20196 and CaCNT occurs at position 328 in putative TM 7, and corresponds to a Ser/Gly substitution previously shown to contribute to the contrasting pyrimidine and purine nucleoside selectivities of human (h) and rat (r) Na+-dependent CNT1 and CNT2. CaCNT/19-10196 differs from CaCNT by four amino acids, but has Gly at position 328. These new proteins were recreated by site-directed mutagenesis of CaCNT and characterized functionally by heterologous expression in Xenopus laevis oocytes. In marked contrast to h/rCNT1/2, both CaCNT/19-10196 and CaCNT/19-20196 exhibited permeant selectivities for purine nucleosides (adenosine, guanosine and inosine) and uridine similar to that of CaCNT. However, although H+-coupled, CaCNT/19-20196 exhibited a approximately 10-fold higher apparent Km for uridine than either CaCNT or CaCNT/19-10196. CaCNT/19-20196 also exhibited a low apparent affinity for inosine. We conclude that the three proteins correspond to high-affinity (CaCNT, CaCNT/19-10196) and low-affinity (CaCNT/19-20196) allelic isoforms of the C. albicans CNT nucleoside transporter. This is the first example of a single amino acid residue substitution altering a CNT protein's overall apparent affinity for nucleosides. PMID:15543539

  7. μ-Patterning of Carbon Nanotube (CNT) forest for MEMS applications

    NASA Astrophysics Data System (ADS)

    Saleh, T.

    2013-12-01

    This paper proposes three new approaches for micro patterning of CNT forest in order to make it useful for MEMS based applications. The first two techniques are based on micro electro discharge machining (μ-EDM). However, the biggest problem associated with μ-EDM is the spark gap which limits the structural resolution of the fabricated pattern. In order to overcome this challenge the first technique proposed in this paper is reverse μ-EDMing of CNT forest where the CNTs are used as cathode instead of tungsten tool. This dramatically reduces discharge voltage hence the spark gap. In the second method Sulphur Hexafluoride (SF6) SF6 was used as dielectric instead of air which has three time higher dielectric strength than air. This helps to reduce spark gap further. This research work also discusses the experimental results when SF6 was used as dielectric medium for reverse EDMing CNT forest. It was observed that at too low voltage (~10V) air gives lower spark gap than SF6, however at moderately high voltage (~25V) SF6 performs better. Finally, the third approach for patterning CNT forest described in this paper is mechanical bending of CNTs. In this method patterning of CNT forest is carried out by moving a rotating cylindrical μ-tool (3000RPM) in X,Y and Z direction. The Z movement of the tool is controlled in step mode to provide the overall depth of the μ-structures with 1 (μm/step. In XY plane the tool moves continuously at 1mm/min speed. The movement of the tool on the CNT forest causes the CNTs to be bent and flattened in the direction of the tool motion hence the patterns are formed on bare CNT forest. The most significant observation made from the processed CNT forest is the visible optical reflection from bent and flattened area. Typically, CNT forest is known to be the darkest material on earth. However, this new processing technique causes the CNT surface to reflect light like mirror. A detail comparison between all proposed techniques (mechanical

  8. Synthesis and electrical properties of PANI-CNT-CdS nanocomposites

    NASA Astrophysics Data System (ADS)

    Goswami, M.; Mukherjee, A.; Ghosh, R.; Meikap, A. K.

    2016-05-01

    Polyaniline-CNT-CdS nanocomposite has been synthesized by the chemical oxidative polymerization reaction. The particle size of nanocomposites lies in between 2.7 to 4.8 nm. I-V characteristics of the nanocomposite shows a non linear behaviour. The dc electrical transport property of Polyaniline-CNT-CdS nanocomposites has been investigated within a temperature range 77≤T≤300K. The dc conductivity follows 3D variable range hopping (VRH) model.

  9. Nonlinear optical and electrical conductivity properties of Carbon Nanotubes (CNT) doped in Sol-Gel matrices

    NASA Astrophysics Data System (ADS)

    Pokrass, Mariana; Burshtein, Zeev; Bar, Galit; Gvishi, Raz

    2014-09-01

    Carbon-nanotubes (CNT) are fascinating compounds, exhibiting exceptional electrical, thermal conductivity, mechanical strength, and nonlinear optical (NLO) properties. Their unique structures involve large π-π* electronic clouds. The energy level schemes thus created allow many electronic transitions between the ground and the excited states. The present work involves CNT-doped hybrid organic-inorganic glass composites prepared by a Fast-sol-gel method. Such composite glasses solidify without shrinkage or crack formation, and exhibit promising properties as optical devices. In this work we have studied nonlinear optical and electrical conductivity properties. The CNT composite glasses exhibited enhanced absorption at 532 nm, and saturable absorption at 1064 nm. The enhanced absorption at 532 was attributed to 2-photon absorption; saturable absorption was attributed to depletion of the absorbing ground-state, and was analyzed using the modified Frantz-Nodvik equation. Absorption cross-sections were extracted for the saturable absorption phenomenon. Such CNT composites glasses may be used as "optical limiting" filters in lasers near 532 nm, or as saturable absorbing filters for passive laser Q-switching near 1064 nm. The CNT composites electrical conductivity was studied as a function of the CNT concentration and modeled by a percolation theory. The maximal measured conductivity was σ ≍10-3 (Ωcm)-1 for the CNT composites, representing a conductivity increase of at least 12 orders of magnitude compared to that of pure silica. A quite low percolation threshold was obtained, φc = 0.22 wt.% CNT. Electrostatic Force Microscopy (EFM) and Conductive mode Atomic Force Microscopy (C-AFM) studies revealed that the conductivity occurs at the micro-level among the CNTs dispersed in the matrix.

  10. Chronic in vivo evaluation of PEDOT/CNT for stable neural recordings

    PubMed Central

    Catt, Kasey; Du, Zhanhong; Na, Kyounghwan; Srivannavit, Onnop; Haque, Razi-ul M.; Seymour, John; Wise, Kensall D; Yoon, Euisik

    2015-01-01

    Objective Sub-cellular sized chronically implanted recording electrodes have demonstrated significant improvement in single-unit (SU) yield over larger recording probes. Additional work expands on this initial success by combining the subcellular fiber-like lattice structures with the design space versatility of silicon microfabrication to further improve the signal-to-noise ratio, density of electrodes, and stability of recorded units over months to years. However, ultra-small microelectrodes present very high impedance, which must be lowered for SU recordings. While poly(3,4-ethylenedioxythiophene) (PEDOT) doped with polystyrene sulfonate (PSS) coating has demonstrated great success in acute to early-chronic studies for lowering the electrode impedance, concern exists over long-term stability. Here, we demonstrate a new blend of PEDOT doped with carboxyl functionalized multi-walled carbon nanotubes (CNTs) which shows dramatic improvement over the traditional PEDOT/PSS formula. Methods Lattice style subcellular electrode arrays were fabricated using previously established method. PEDOT was polymerized with carboxylic acid functionalized carbon nanotubes onto high impedance (8.0±0.1 MΩ: M±S.E.) 250 µm2 gold recording sites. Results PEDOT/CNT coated subcellular electrodes demonstrated significant improvement in chronic spike recording stability over four months compared to PEDOT/PSS recording sites. Conclusion These results demonstrate great promise for subcellular sized recording and stimulation electrodes and long-term stability. Significance This project uses leading-edge biomaterials to develop chronic neural probes that are small (sub-cellular) with excellent electrical properties for stable long-term recordings. High density ultrasmall electrodes combined with advanced electrode surface modification are likely to make significant contributions to the development of long-term (permanent), high quality, and selective neural interfaces. PMID:26087481

  11. SnO2/CNT nanocomposite supercapacitors fabricated using scanning atmospheric-pressure plasma jets

    NASA Astrophysics Data System (ADS)

    Xu, Chang-Han; Chiu, Yi-Fan; Yeh, Po-Wei; Chen, Jian-Zhang

    2016-08-01

    SnO2/CNT electrodes for supercapacitors are fabricated by first screen-printing pastes containing SnO2 nanoparticles and CNTs on carbon cloth, following which nitrogen atmospheric pressure plasma jet (APPJ) sintering is performed at various APPJ scan rates. The APPJ scan rates change the time intervals for which the reactive plasma species and the heat of the nitrogen APPJs influence the designated sintering spot on the carbon cloth, resulting in APPJ-sintered SnO2/CNT nanocomposites with different properties. The water contact angle decreases with the APPJ scan rate. The improved wettability can facilitate the penetration of the electrolyte into the nanopores of the SnO2/CNT nanocomposites, thereby improving the charge storage and specific capacitance of the supercapacitors. Among the three tested APPJ scan rates, 1.5, 3, and 6 mm s‑1, the SnO2/CNT supercapacitor sintered by APPJ under the lowest APPJ scan rate of 1.5 mm s‑1 shows the best specific capacitance of ∼90 F g‑1 as evaluated by cyclic voltammetry under a potential scan rate of 2 mV s‑1. A high APPJ scan rate may result in low degree of materials activation and sintering, leading to poorer performance of SnO2/CNT supercapacitors. The results suggest the feasibility of an APPJ roll-to-roll process for the fabrication of SnO2/CNT nanocomposite supercapacitors.

  12. Embedded Fin-Like Metal/CNT Hybrid Structures for Flexible and Transparent Conductors.

    PubMed

    Jiang, Di; Wang, Nan; Edwards, Michael; Mu, Wei; Nylander, Andreas; Fu, Yifeng; Jeppson, Kjell; Liu, Johan

    2016-03-01

    In this paper, an embedded fin-like metal-coated carbon nanotube (Fin-M/CNT) structure is demonstrated for flexible and transparent conductor wire applications. Embedded in a polydimethylsiloxane polymeric substrate, Fin-M/CNT wires with a minimum width of 5 μm and a minimum pitch of 10 μm have been achieved. Direct current resistances of single Fin-M/CNT wires, where the supporting CNT structures have been covered by Ti/Al/Au metal coatings of different thicknesses, have been measured. The high aspect ratio of the fin-like structures not only improves the adhesion between the wires and the polymeric substrate, but also yields a low resistance at a small surface footprint. In addition, transparent Fin-M/CNT grid lines with hexagonal patterns, with a sheet resistance of as low as 45 Ω sq(-1) , have been achieved at an optical transmittance of 88%. The robustness of the Fin-M/CNT structures has been demonstrated in bending tests up to 500 cycles and no significant changes in wire resistances are observed. PMID:26766128

  13. The Arf GAP CNT-2 regulates the apoptotic fate in C. elegans asymmetric neuroblast divisions

    PubMed Central

    Singhvi, Aakanksha; Teuliere, Jerome; Talavera, Karla; Cordes, Shaun; Ou, Guangshuo; Vale, Ronald D.; Prasad, Brinda C.; Clark, Scott G.; Garriga, Gian

    2011-01-01

    Summary During development, all cells make the decision to live or die. While the molecular mechanisms that execute the apoptotic program are well defined, less is known about how cells decide whether to live or die. In C. elegans, this decision is linked to how cells divide asymmetrically [1, 2]. Several classes of molecules are known to regulate asymmetric cell divisions in metazoans, yet these molecules do not appear to control C. elegans divisions that produce apoptotic cells [3]. We identified CNT-2, an Arf GAP protein of the AGAP family, as a novel regulator of this type of neuroblast division. Loss of CNT-2 altered daughter cell size and caused the apoptotic cell to adopt the fate of its sister cell, resulting in extra neurons. CNT-2’s Arf GAP activity was essential for its function in these divisions. The N-terminus of CNT-2, which contains a GTPase-like domain that defines the AGAP class of Arf GAPs, negatively regulates CNT-2’s function. We provide evidence that CNT-2 regulates receptor-mediated endocytosis and consider the implications of its role in asymmetric cell divisions. PMID:21596567

  14. High Current Emission from Patterned Aligned Carbon Nanotubes Fabricated by Plasma-Enhanced Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Cui, Linfan; Chen, Jiangtao; Yang, Bingjun; Jiao, Tifeng

    2015-12-01

    Vertically, carbon nanotube (CNT) arrays were successfully fabricated on hexagon patterned Si substrates through radio frequency plasma-enhanced chemical vapor deposition using gas mixtures of acetylene (C2H2) and hydrogen (H2) with Fe/Al2O3 catalysts. The CNTs were found to be graphitized with multi-walled structures. Different H2/C2H2 gas flow rate ratio was used to investigate the effect on CNT growth, and the field emission properties were optimized. The CNT emitters exhibited excellent field emission performance (the turn-on and threshold fields were 2.1 and 2.4 V/μm, respectively). The largest emission current could reach 70 mA/cm2. The emission current was stable, and no obvious deterioration was observed during the long-term stability test of 50 h. The results were relevant for practical applications based on CNTs.

  15. High Current Emission from Patterned Aligned Carbon Nanotubes Fabricated by Plasma-Enhanced Chemical Vapor Deposition.

    PubMed

    Cui, Linfan; Chen, Jiangtao; Yang, Bingjun; Jiao, Tifeng

    2015-12-01

    Vertically, carbon nanotube (CNT) arrays were successfully fabricated on hexagon patterned Si substrates through radio frequency plasma-enhanced chemical vapor deposition using gas mixtures of acetylene (C2H2) and hydrogen (H2) with Fe/Al2O3 catalysts. The CNTs were found to be graphitized with multi-walled structures. Different H2/C2H2 gas flow rate ratio was used to investigate the effect on CNT growth, and the field emission properties were optimized. The CNT emitters exhibited excellent field emission performance (the turn-on and threshold fields were 2.1 and 2.4 V/μm, respectively). The largest emission current could reach 70 mA/cm(2). The emission current was stable, and no obvious deterioration was observed during the long-term stability test of 50 h. The results were relevant for practical applications based on CNTs. PMID:26666912

  16. Phased array radars - Present and future

    NASA Astrophysics Data System (ADS)

    Pell, Christopher

    1989-12-01

    The characteristics of tactical defense phased-array radars mainly employing two-dimensional electronic beam alignment are reviewed. Technology issues connected with the phased-array architecture and array control are examined. Technical summaries are then given for a representative selection of projected future operational systems, i.e, EMPAR, Multifire, and MESAR.

  17. Nearest Alignment Space Termination

    2006-07-13

    Near Alignment Space Termination (NAST) is the Greengenes algorithm that matches up submitted sequences with the Greengenes database to look for similarities and align the submitted sequences based on those similarities.

  18. Ultra-high density aligned Carbon-nanotube with controled nano-morphology for supercapacitors

    NASA Astrophysics Data System (ADS)

    Ghaffari, Mehdi; Zhao, Ran; Liu, Yang; Zhou, Yue; Cheng, Jiping; Guzman de Villoria, Roberto; Wardle, B. L.; Zhang, Q. M.

    2012-02-01

    Recent advances in fabricating controlled-morphology vertically aligned carbon nanotubes (VA-CNTs) with ultrahigh volume fractioncreate unique opportunities for developing unconventional supercapacitors with ultra-high energy density, power density, and long charge/discharge cycle life.Continuous paths through inter-VA-CNT channels allow fast ion transport, and high electrical conduction of the aligned CNTs in the composite electrodes lead to fast discharge speed. We investigate the charge-discharge characteristics of VA-CNTs with >20 vol% of CNT and ionic liquids as electrolytes. By employing both the electric and electromechanical spectroscopes, as well as nanostructured materials characterization, the ion transport and storage behaviors in porous electrodes are studied. The results suggest pathways for optimizing the electrode morphology in supercapacitorsusing ultra-high volume fraction VA-CNTs to further enhance performance.

  19. High-performance transparent and stretchable all-solid supercapacitors based on highly aligned carbon nanotube sheets

    PubMed Central

    Chen, Tao; Peng, Huisheng; Durstock, Michael; Dai, Liming

    2014-01-01

    By using highly aligned carbon nanotube (CNT) sheets of excellent optical transmittance and mechanical stretchability as both the current collector and active electrode, high-performance transparent and stretchable all-solid supercapacitors with a good stability were developed. A transmittance up to 75% at the wavelength of 550 nm was achieved for a supercapacitor made from a cross-over assembly of two single-layer CNT sheets. The transparent supercapacitor has a specific capacitance of 7.3 F g−1 and can be biaxially stretched up to 30% strain without any obvious change in electrochemical performance even over hundreds stretching cycles. PMID:24402400

  20. Investigation of the environmental implications of the CNT switch through its life cycle

    NASA Astrophysics Data System (ADS)

    Dahlben, Lindsay Johanna

    Carbon nanotubes (CNTs) are unique allotropes of carbon that have high tensile strength, a high Young's modulus, good thermal conductivity, and depending on the CNT chirality can be metallic or semiconducting. These mechanical, thermal, and electrical properties make CNTs an attractive element in electronic applications such as conductive films, photovoltaics, non-volatile memory devices, batteries, sensors, and displays. Although commercialization of CNT-enabled products is increasing, there remains a significant lack of information regarding the health effects and environmental impacts of CNTs. Some studies have even shown that the behavior, toxicity, and persistence of CNTs may differ from bulk heterogeneous carbon. Given these uncertainties, it is prudent to assess the environmental attributes of CNT products and processes now to discover and potentially prevent adverse effects. This study investigates the environmental implications of a non-volatile bi-stable electromechanical CNT switch through its life cycle. Life cycle assessment (LCA) methodology is used to track the environmental impacts of the CNT switch through its fabrication and expected use and end-of-life (EOL) stages. Process parameters, energy consumption, input materials, output emissions, and yield efficiencies are determined for the laboratory and full-scale manufacture environments. The Ecoinvent(TM) inventory database and Eco-indicator 1999(TM) method are utilized for the impact assessment. Results for the fabrication stage are reported for highest contributions to environmental impact such as airborne inorganics, land use, and fossil fuels due to Au refining processes and electricity consumption. Extension of the LCA scope is evaluated for the potential replacement of CNT switches to current field-effect transistors (FETs) in flash memory for a cellular phone application. First-order predictions are made for the functionality and performance of the CNT switch during the use stage through an

  1. Thermal analysis of Al + 0.1% CNT ribbon

    NASA Astrophysics Data System (ADS)

    Revo, Sergiy; Hamamda, Smail; Ivanenko, Kateryna; Boshko, Oleh; Djarri, Ahmed; Boubertakh, Abdelhamid

    2015-04-01

    The objective of this work is a dilatometric study of Al + 0.1% of multiwall carbon nanotubes nanocomposite material (NCM) in three directions: X - parallel to the rolling direction; Y - perpendicular to the rolling direction and (Z) perpendicular to the ribbon plane. NCM specimens were made in the form of a 0.1-mm-thick ribbon. The temperature range used for measurements was 20°C to 600°C. The obtained results show that presence of nanotubes affects the thermal expansion coefficient (TEC) measured in different directions. αx(T) and αy(T) - TEC plots as a function of temperature along X and Y directions, respectively - have substantially the same shape and overlap in the area of 400°C. The expansion along X-axis becomes greater than along Y-axis below this temperature value. It is clear that the coefficient αz(T) is lower than αx(T) and αy(T) over the entire temperature range. The expansion along Z-axis is smaller compared to that along X- and Y-axes. This behaviour suggests that there is a strong interatomic interaction along this direction (Z). αz(T) becomes monotonous and constant and is equal to 8 × 10-6°C-1 at temperatures above 300°C. Such order of magnitude had not been obtained in earlier studies of aluminium alloys. The obtained TEC shows high anisotropy, which grows with the increase of temperature. The heat flow (differential scanning calorimetry, (DSC)) of Al + 0.1% carbon nanotubes (CNT) NCM is more intense compared to that of pure aluminium produced in similar conditions. The two representative curves have similar shape and are almost entirely overlapped. The thermogravimetry results confirm those of DSC. The Raman spectrum of this nanomaterial shows that intensity of G and D bonds is significantly increased compared to that of the pure material. The infrared diagram also confirms that in this case the mentioned bonds are more intensive NCM. The tensile strength measurements (σB) of the studied NCM also demonstrate that its value

  2. Direct growth of horizontally aligned carbon nanotubes between electrodes and its application to field-effect transistors.

    PubMed

    Hayashi, Yasuhiko; Jang, B; Iijima, T; Tokunaga, T; Hayashi, A; Tanemura, M; Amaratunga, G A J

    2011-12-01

    This paper presents direct growth of horizontally-aligned carbon nanotubes (CNTs) between two predefined various inter-spacing up to tens of microns of electrodes (pads) and its use as CNT field-effect transistors (CNT-FETs). Using the conventional photolithography technique followed by thin film evaporation and lift off, the catalytic electrodes (pads) were prepared, consisting of Pt, Al and Fe triple layers on SiO2/Si substrate. The grown CNTs were horizontally-aligned across the catalytic electrodes on the modified gold image furnace hot stage (thermal CVD) at 800 degrees C by using an alcohol vapor as the carbon source. Scanning and transmission electron microcopies (SEM/TEM) were used to observe the structure, growth direction and density of CNTs, while Raman spectrum analysis was used to indicate the degree of amorphous impurity and diameter of CNTs. Both single- and multi-wall CNTs with diameters of 1.1-2.2 nm were obtained and the CNT density was controlled by thickness of Fe catalytic layer. Following horizontally-aligned growth of CNTs, the electrical properties of back-gate CNT-FETs were measured and showd p-type conduction behaviors of FET. PMID:22409045

  3. Shiva automatic pinhole alignment

    SciTech Connect

    Suski, G.J.

    1980-09-05

    This paper describes a computer controlled closed loop alignment subsystem for Shiva, which represents the first use of video sensors for large laser alignment at LLNL. The techniques used on this now operational subsystem are serving as the basis for all closed loop alignment on Nova, the 200 terawatt successor to Shiva.

  4. Fast statistical alignment.

    PubMed

    Bradley, Robert K; Roberts, Adam; Smoot, Michael; Juvekar, Sudeep; Do, Jaeyoung; Dewey, Colin; Holmes, Ian; Pachter, Lior

    2009-05-01

    We describe a new program for the alignment of multiple biological sequences that is both statistically motivated and fast enough for problem sizes that arise in practice. Our Fast Statistical Alignment program is based on pair hidden Markov models which approximate an insertion/deletion process on a tree and uses a sequence annealing algorithm to combine the posterior probabilities estimated from these models into a multiple alignment. FSA uses its explicit statistical model to produce multiple alignments which are accompanied by estimates of the alignment accuracy and uncertainty for every column and character of the alignment--previously available only with alignment programs which use computationally-expensive Markov Chain Monte Carlo approaches--yet can align thousands of long sequences. Moreover, FSA utilizes an unsupervised query-specific learning procedure for parameter estimation which leads to improved accuracy on benchmark reference alignments in comparison to existing programs. The centroid alignment approach taken by FSA, in combination with its learning procedure, drastically reduces the amount of false-positive alignment on biological data in comparison to that given by other methods. The FSA program and a companion visualization tool for exploring uncertainty in alignments can be used via a web interface at http://orangutan.math.berkeley.edu/fsa/, and the source code is available at http://fsa.sourceforge.net/. PMID:19478997

  5. Hybrid hydrogels containing vertically aligned carbon nanotubes with anisotropic electrical conductivity for muscle myofiber fabrication

    NASA Astrophysics Data System (ADS)

    Ahadian, Samad; Ramón-Azcón, Javier; Estili, Mehdi; Liang, Xiaobin; Ostrovidov, Serge; Shiku, Hitoshi; Ramalingam, Murugan; Nakajima, Ken; Sakka, Yoshio; Bae, Hojae; Matsue, Tomokazu; Khademhosseini, Ali

    2014-03-01

    Biological scaffolds with tunable electrical and mechanical properties are of great interest in many different fields, such as regenerative medicine, biorobotics, and biosensing. In this study, dielectrophoresis (DEP) was used to vertically align carbon nanotubes (CNTs) within methacrylated gelatin (GelMA) hydrogels in a robust, simple, and rapid manner. GelMA-aligned CNT hydrogels showed anisotropic electrical conductivity and superior mechanical properties compared with pristine GelMA hydrogels and GelMA hydrogels containing randomly distributed CNTs. Skeletal muscle cells grown on vertically aligned CNTs in GelMA hydrogels yielded a higher number of functional myofibers than cells that were cultured on hydrogels with randomly distributed CNTs and horizontally aligned CNTs, as confirmed by the expression of myogenic genes and proteins. In addition, the myogenic gene and protein expression increased more profoundly after applying electrical stimulation along the direction of the aligned CNTs due to the anisotropic conductivity of the hybrid GelMA-vertically aligned CNT hydrogels. We believe that platform could attract great attention in other biomedical applications, such as biosensing, bioelectronics, and creating functional biomedical devices.

  6. Hybrid hydrogels containing vertically aligned carbon nanotubes with anisotropic electrical conductivity for muscle myofiber fabrication.

    PubMed

    Ahadian, Samad; Ramón-Azcón, Javier; Estili, Mehdi; Liang, Xiaobin; Ostrovidov, Serge; Shiku, Hitoshi; Ramalingam, Murugan; Nakajima, Ken; Sakka, Yoshio; Bae, Hojae; Matsue, Tomokazu; Khademhosseini, Ali

    2014-01-01

    Biological scaffolds with tunable electrical and mechanical properties are of great interest in many different fields, such as regenerative medicine, biorobotics, and biosensing. In this study, dielectrophoresis (DEP) was used to vertically align carbon nanotubes (CNTs) within methacrylated gelatin (GelMA) hydrogels in a robust, simple, and rapid manner. GelMA-aligned CNT hydrogels showed anisotropic electrical conductivity and superior mechanical properties compared with pristine GelMA hydrogels and GelMA hydrogels containing randomly distributed CNTs. Skeletal muscle cells grown on vertically aligned CNTs in GelMA hydrogels yielded a higher number of functional myofibers than cells that were cultured on hydrogels with randomly distributed CNTs and horizontally aligned CNTs, as confirmed by the expression of myogenic genes and proteins. In addition, the myogenic gene and protein expression increased more profoundly after applying electrical stimulation along the direction of the aligned CNTs due to the anisotropic conductivity of the hybrid GelMA-vertically aligned CNT hydrogels. We believe that platform could attract great attention in other biomedical applications, such as biosensing, bioelectronics, and creating functional biomedical devices. PMID:24642903

  7. Hybrid hydrogels containing vertically aligned carbon nanotubes with anisotropic electrical conductivity for muscle myofiber fabrication

    PubMed Central

    Ahadian, Samad; Ramón-Azcón, Javier; Estili, Mehdi; Liang, Xiaobin; Ostrovidov, Serge; Shiku, Hitoshi; Ramalingam, Murugan; Nakajima, Ken; Sakka, Yoshio; Bae, Hojae; Matsue, Tomokazu; Khademhosseini, Ali

    2014-01-01

    Biological scaffolds with tunable electrical and mechanical properties are of great interest in many different fields, such as regenerative medicine, biorobotics, and biosensing. In this study, dielectrophoresis (DEP) was used to vertically align carbon nanotubes (CNTs) within methacrylated gelatin (GelMA) hydrogels in a robust, simple, and rapid manner. GelMA-aligned CNT hydrogels showed anisotropic electrical conductivity and superior mechanical properties compared with pristine GelMA hydrogels and GelMA hydrogels containing randomly distributed CNTs. Skeletal muscle cells grown on vertically aligned CNTs in GelMA hydrogels yielded a higher number of functional myofibers than cells that were cultured on hydrogels with randomly distributed CNTs and horizontally aligned CNTs, as confirmed by the expression of myogenic genes and proteins. In addition, the myogenic gene and protein expression increased more profoundly after applying electrical stimulation along the direction of the aligned CNTs due to the anisotropic conductivity of the hybrid GelMA-vertically aligned CNT hydrogels. We believe that platform could attract great attention in other biomedical applications, such as biosensing, bioelectronics, and creating functional biomedical devices. PMID:24642903

  8. Low temperature growth of vertically aligned carbon nanotubes by thermal chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Lee, Cheol Jin; Son, Kwon Hee; Park, Jeunghee; Yoo, Jae Eun; Huh, Yoon; Lee, Jeong Yong

    2001-04-01

    Vertically well-aligned carbon nanotubes (CNTs) are grown on Fe-deposited silicon oxide substrate at 550°C by thermal chemical vapor deposition of C 2H 2 gas. We employed two-stage heating technique that the reactants heated at 850°C in the first zone flow into the second zone maintained at 550°C for CNT growth. The CNTs have bamboo structure, closed tip, and defective graphite sheets.

  9. Design, simulation and comparative analysis of CNT based cascode operational transconductance amplifiers.

    PubMed

    Nizamuddin, M; Loan, Sajad A; Alamoud, Abdul R; Abbassi, Shuja A

    2015-10-01

    In this work, design and calibrated simulation of carbon nanotube field effect transistor (CNTFET)-based cascode operational transconductance amplifiers (COTA) have been performed. Three structures of CNTFET-based COTAs have been designed using HSPICE and have been compared with the conventional CMOS-based COTAs. The proposed COTAs include one using pure CNTFETs and two others that employ CNTFETs, as well as the conventional MOSFETs. The simulation study has revealed that the CNTFET-based COTAs have significantly outperformed the conventional MOSFET-based COTAs. A significant increase in dc gain, output resistance and slew rate of 81.4%, 25% and 13.2%, respectively, have been achieved in the proposed pure CNT-based COTA in comparison to the conventional CMOS-based COTA. The power consumption in the pure CNT-COTA is 324 times less in comparison to the conventional CMOS-COTA. Further, the phase margin (PM), gain margin (GM), common mode and power supply rejection ratios have been significantly increased in the proposed CNT-based COTAs in comparison to the conventional CMOS-based COTAs. Furthermore, to see the advantage of cascoding, the proposed CNT-based cascode OTAs have been compared with the CNT-based OTAs. It has been observed that by incorporating the concept of cascode in the CNTFET-based OTAs, significant increases in gain (12.5%) and output resistance (13.07%) have been achieved. The performance of the proposed COTAs has been further observed by changing the number of CNTs (N), CNT pitch (S) and CNT diameter (DCNT) in the CNTFETs used. It has been observed that the performance of the proposed COTAs can be significantly improved by using optimum values of N, S and DCNT. PMID:26349429

  10. Design, simulation and comparative analysis of CNT based cascode operational transconductance amplifiers

    NASA Astrophysics Data System (ADS)

    Nizamuddin, M.; Loan, Sajad A.; Alamoud, Abdul R.; Abbassi, Shuja A.

    2015-10-01

    In this work, design and calibrated simulation of carbon nanotube field effect transistor (CNTFET)-based cascode operational transconductance amplifiers (COTA) have been performed. Three structures of CNTFET-based COTAs have been designed using HSPICE and have been compared with the conventional CMOS-based COTAs. The proposed COTAs include one using pure CNTFETs and two others that employ CNTFETs, as well as the conventional MOSFETs. The simulation study has revealed that the CNTFET-based COTAs have significantly outperformed the conventional MOSFET-based COTAs. A significant increase in dc gain, output resistance and slew rate of 81.4%, 25% and 13.2%, respectively, have been achieved in the proposed pure CNT-based COTA in comparison to the conventional CMOS-based COTA. The power consumption in the pure CNT-COTA is 324 times less in comparison to the conventional CMOS-COTA. Further, the phase margin (PM), gain margin (GM), common mode and power supply rejection ratios have been significantly increased in the proposed CNT-based COTAs in comparison to the conventional CMOS-based COTAs. Furthermore, to see the advantage of cascoding, the proposed CNT-based cascode OTAs have been compared with the CNT-based OTAs. It has been observed that by incorporating the concept of cascode in the CNTFET-based OTAs, significant increases in gain (12.5%) and output resistance (13.07%) have been achieved. The performance of the proposed COTAs has been further observed by changing the number of CNTs (N), CNT pitch (S) and CNT diameter (DCNT) in the CNTFETs used. It has been observed that the performance of the proposed COTAs can be significantly improved by using optimum values of N, S and DCNT.

  11. Optical properties of ordered carbon nanotube arrays grown in porous anodic alumina templates.

    PubMed

    Zuidema, John; Ruan, Xiulin; Fisher, Timothy S

    2013-09-23

    We have synthesized ordered carbon nanotube (CNT) arrays in porous anodic alumina (PAA) matrix, and have characterized their total optical reflectance and bi-directional reflectance distribution function after each processing step of the microwave plasma chemical vapor deposition process (MPCVD). For a PAA sample without CNT growth, the reflectance shows an oscillating pattern with wavelength that agrees reasonably with a multilayer model. During the MPCVD process, heating the sample significantly reduces the reflectance by 30-40%, the plasma treatment reduces the reflectance by another 5-10%, and the CNT growth further reduces the reflectance by 2-3%. After an atomic layer deposition (ALD) process, the reflectance increases to the embedded CNT arrays. After etching and exposure of CNT tips, the reflectance almost returns to the original pattern with slightly higher reflectance. Bi-directional reflectance distribution function (BRDF) measurements show that the CNT-PAA surface is quite specular as indicated by a large lobe at the specular angle, while the secondary lobe can be attributed to surface roughness. PMID:24104097

  12. Girder Alignment Plan

    SciTech Connect

    Wolf, Zackary; Ruland, Robert; LeCocq, Catherine; Lundahl, Eric; Levashov, Yurii; Reese, Ed; Rago, Carl; Poling, Ben; Schafer, Donald; Nuhn, Heinz-Dieter; Wienands, Uli; /SLAC

    2010-11-18

    The girders for the LCLS undulator system contain components which must be aligned with high accuracy relative to each other. The alignment is one of the last steps before the girders go into the tunnel, so the alignment must be done efficiently, on a tight schedule. This note documents the alignment plan which includes efficiency and high accuracy. The motivation for girder alignment involves the following considerations. Using beam based alignment, the girder position will be adjusted until the beam goes through the center of the quadrupole and beam finder wire. For the machine to work properly, the undulator axis must be on this line and the center of the undulator beam pipe must be on this line. The physics reasons for the undulator axis and undulator beam pipe axis to be centered on the beam are different, but the alignment tolerance for both are similar. In addition, the beam position monitor must be centered on the beam to preserve its calibration. Thus, the undulator, undulator beam pipe, quadrupole, beam finder wire, and beam position monitor axes must all be aligned to a common line. All relative alignments are equally important, not just, for example, between quadrupole and undulator. We begin by making the common axis the nominal beam axis in the girder coordinate system. All components will be initially aligned to this axis. A more accurate alignment will then position the components relative to each other, without incorporating the girder itself.

  13. Freestanding carbon-coated CNT/Sn(O2) coaxial sponges with enhanced lithium-ion storage capability

    NASA Astrophysics Data System (ADS)

    Luo, Bin; Qiu, Tengfei; Wang, Bin; Hao, Long; Li, Xianglong; Cao, Anyuan; Zhi, Linjie

    2015-12-01

    Carbon-coated, carbon nanotube (CNT)/tin(oxide) spongy coaxial nanostructures, CNT/Sn(O2)@C, with large areal mass loadings have been developed by employing a three-dimensional CNT sponge as a backbone. The freestanding spongy coaxial nano-architecture demonstrates exceptional electrochemical characteristics of tin-based anode materials with appropriate structural engineering for energy storage application.Carbon-coated, carbon nanotube (CNT)/tin(oxide) spongy coaxial nanostructures, CNT/Sn(O2)@C, with large areal mass loadings have been developed by employing a three-dimensional CNT sponge as a backbone. The freestanding spongy coaxial nano-architecture demonstrates exceptional electrochemical characteristics of tin-based anode materials with appropriate structural engineering for energy storage application. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06613a

  14. Nanostructued core-shell Sn nanowires @ CNTs with controllable thickness of CNT shells for lithium ion battery

    NASA Astrophysics Data System (ADS)

    Zhong, Yu; Li, Xifei; Zhang, Yong; Li, Ruying; Cai, Mei; Sun, Xueliang

    2015-03-01

    Core-shell structure of Sn nanowires encapsulated in amorphous carbon nanotubes (Sn@CNTs) with controlled thickness of CNT shells was in situ prepared via chemical vapor deposition (CVD) method. The thickness of CNT shells was accurately controlled from 4 to 99 nm by using different growth time, flow rate of hydrocarbon gas (C2H4) and synthesis temperature. The microstructure and composition of the coaxial Sn@CNTs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high resolution transmission electron microscopy (HRTEM) techniques. Moreover, the Sn@CNTs were studied as anode materials for Li-ion batteries and showed excellent cycle performance. The capacity was affected by the thickness of outer CNT shells: thick CNT shells contributed to a better retention while thin CNT shells led to a higher capacity. The thin CNT shell of 6 nm presented the highest capacity around 630 mAh g-1.

  15. Aligned Carbon Nanotube Reinforced Silicon Carbide Composites by Chemical Vapor Infiltration

    SciTech Connect

    Gu, Zhan Jun; Yang, Ying Chao; Li, Kai Yuan; Tao, Xin Yong; Eres, Gyula; Howe, Jane Y; Zhang, Li Tong; Li, Xiao Dong; Pan, Zhengwei

    2011-01-01

    Owing to their exceptional stiffness and strength1 4, carbon nanotubes (CNTs) have long been considered to be an ideal reinforcement for light-weight, high-strength, and high-temperature-resistant ceramic matrix composites (CMCs)5 10. However, the research and development in CNT-reinforced CMCs have been greatly hindered due to the challenges related to manufacturing including poor dispersion, damages during dispersion, surface modification, densification and sintering, weak tube/matrix interfaces, and agglomeration of tubes at the matrix grain boundaries5,11. Here we report the fabrication of high-quality aligned CNT/SiC composites by chemical vapor infiltration (CVI), a technique that is being widely used to fabricate commercial continuous-filament CMCs12 15. Using the CVI technique most of the challenges previously encountered in the fabrication of CNT composites were readily overcome. Nanotube pullouts, an important toughening mechanism for CMCs, were consistently observed on all fractured CNT/SiC samples. Indeed, three-point bending tests conducted on individual CNT/SiC nanowires (diameters: 50 200 nm) using an atomic force microscope show that the CNT-reinforced SiC nanowires are about an order of magnitude tougher than the bulk SiC. The tube/matrix interface is so intimate and the SiC matrix is so dense that a ~50-nm-thick SiC coating can effectively protect the inside nanotubes from being oxidized at 1600 C in air. The CVI method may be extended to produce nanotube composites from a variety of matrix

  16. Multiwalled CNT-pHEMA composite conduit for peripheral nerve repair.

    PubMed

    Arslantunali, D; Budak, G; Hasirci, V

    2014-03-01

    A nerve conduit is designed to improve peripheral nerve regeneration by providing guidance to the nerve cells. Conductivity of such guides is reported to enhance this process. In the current study, a nerve guide was constructed from poly(2-hydroxyethyl methacrylate) (pHEMA), which was loaded with multiwalled carbon nanotubes (mwCNT) to introduce conductivity. PHEMA hydrogels were designed to have a porous structure to facilitate the transportation of the compounds needed for cell nutrition and growth and also for waste removal. We showed that when loaded with relatively high concentrations of mwCNTs (6%, w/w in hydrogels), the pHEMA guide was more conductive and more hydrophobic than pristine pHEMA hydrogel. The mechanical properties of the composites were better when they carried mwCNT. Elastic modulus of 6% mwCNT loaded pHEMA was twofold higher (0.32 ± 0.06 MPa) and similar to that of the soft tissues. Electrical conductivity was significantly improved (11.4-fold) from 7 × 10(-3) Ω(-1).cm(-1) (pHEMA) to 8.0 × 10(-2) Ω(-1).cm(-1) (6% mwCNT loaded pHEMA). On application of electrical potential, the SHSY5Y neuroblastoma cells seeded on mwCNTs carrying pHEMA maintained their viability, whereas those on pure pHEMA could not, indicating that mwCNT helped conduct electricity and make them more suitable as nerve conduits. PMID:23554154

  17. Solvothermal synthesis of TiO{sub 2}/CNT composites and its physical and chemical properties

    SciTech Connect

    Venkatraman, M. R. Muthukumarasamy, N.; Agilan, S.; Balasundaraprabhu, R.; Velauthapillai, Dhayalan

    2015-06-24

    Anatase TiO{sub 2}/CNT composites of different CNT ratio were prepared by solvothermal method. The X-ray diffraction analysis result showed that the sample has characteristic peaks of anatase TiO{sub 2}. CNT incorporated TiO{sub 2} showed less peak intensity when compared to bare TiO{sub 2}. The grain size was calculated using the Scherrer equation and it is found to be ∼ 2.38 and 2.46 nm for pure TiO{sub 2} and 5% CNT/TiO{sub 2} composites respectively. Optical properties were studied using UV-visible diffuse reflectance analysis and photo luminescence analysis respectively. UV analysis reveals the shift in absorption peaks towards the visible region for composites when compared to bare TiO{sub 2} powder. Raman spectroscopy studies show the presence of characteristic peaks corresponding to anatase TiO{sub 2}, CNT. Morphological nature of the compounds was studied using High Resolution Transmission Electron Microscopy analysis respectively.

  18. Air-bridge and Vertical CNT Switches for High Performance Switching Applications

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Wong, Eric W.; Epp, Larry; Bronikowski, Michael J.; Hunt, BBrian D.

    2006-01-01

    Carbon nanotubes are attractive for switching applications since electrostatically-actuated CNT switches have low actuation voltages and power requirements, while allowing GHz switching speeds that stem from the inherently high elastic modulus and low mass of the CNT.Our first NEM structure, the air-bridge switch, consists of suspended single-walled nanotubes (SWNTs) that lie above a sputtered Nb base electrode, where contact to the CNTs is made using evaporated Au/Ti. Electrical measurements of these air-bridge devices show well-defined ON and OFF states as a dc bias of a few volts is applied between the CNT and the Nb-base electrode. The CNT air-bridge switches were measured to have switching times down to a few nanoseconds. Our second NEM structure, the vertical CNT switch, consists of nanotubes grown perpendicular to the substrate. Vertical multi-walled nanotubes (MWNTs) are grown directly on a heavily doped Si substrate, from 200 - 300 nm wide, approximately 1 micrometer deep nano-pockets, with Nb metal electrodes to result in the formation of a vertical single-pole-double-throw switch architecture.

  19. CNT Nanobombs for Specific Eradication of Cancer Cells: A New Concept in Cancer Theranostics.

    PubMed

    Omidi, Yadollah

    2011-01-01

    Whole extermination of cancerous cells/tissue seems no longer to be a dream. Exploiting advanced photoactive nanomaterials such as functionalized fullerenes and carbon nano-tubes (CNTs) can act as CNT nanobombs (CNT-NBs) when exposed to the near infrared (NIR) radiation. PEGylated CNTs tagged with an antibody/aptamer can target cancer cells. Once attached to cancer cells, the NIR emission (700-1100 nm), in which body tissues are mostly transparent, can be applied to CNT-NBs which can absorb the light and get heated up. The resultant enhanced temperature can abolish the cancer. Once stealth CNT-NBs are tagged with imaging moieties, it would be a matter of computer gaming for physician who can inject it for real time visualization and destruction of cancer by activation of the NIR laser. While, many nanosystems (NSs) are still in waiting list for clinical translation, our dreams may come true by applying stealth CNT-NBs against cancer. PMID:23678428

  20. Fully Printed, Flexible, Phased Array Antenna for Lunar Surface Communication

    NASA Technical Reports Server (NTRS)

    Subbaraman, Harish; Hen, Ray T.; Lu, Xuejun; Chen, Maggie Yihong

    2013-01-01

    NASAs future exploration missions focus on the manned exploration of the Moon, Mars, and beyond, which will rely heavily on the development of a reliable communications infrastructure from planetary surface-to-surface, surface-to-orbit, and back to Earth. Flexible antennas are highly desired in many scenarios. Active phased array antennas (active PAAs) with distributed control and processing electronics at the surface of an antenna aperture offer numerous advantages for radar communications. Large-area active PAAs on flexible substrates are of particular interest in NASA s space radars due to their efficient inflatable package that can be rolled up during transportation and deployed in space. Such an inflatable package significantly reduces stowage volume and mass. Because of these performance and packaging advantages, large-area inflatable active PAAs are highly desired in NASA s surface-to-orbit and surface-to-relay communications. To address the issues of flexible electronics, a room-temperature printing process of active phased-array antennas on a flexible Kapton substrate was developed. Field effect transistors (FETs) based on carbon nanotubes (CNTs), with many unique physical properties, were successfully proved feasible for the PAA system. This innovation is a new type of fully inkjet-printable, two-dimensional, high-frequency PAA on a flexible substrate at room temperature. The designed electronic circuit components, such as the FET switches in the phase shifter, metal interconnection lines, microstrip transmission lines, etc., are all printed using a special inkjet printer. Using the developed technology, entire 1x4, 2x2, and 4x4 PAA systems were developed, packaged, and demonstrated at 5.3 GHz. Several key solutions are addressed in this work to solve the fabrication issues. The source/drain contact is developed using droplets of silver ink printed on the source/drain areas prior to applying CNT thin-film. The wet silver ink droplets allow the silver to

  1. Biochemical Sensors Using Carbon Nanotube Arrays

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Meyyappan, Meyya (Inventor); Cassell, Alan M. (Inventor)

    2011-01-01

    Method and system for detecting presence of biomolecules in a selected subset, or in each of several selected subsets, in a fluid. Each of an array of two or more carbon nanotubes ("CNTs") is connected at a first CNT end to one or more electronics devices, each of which senses a selected electrochemical signal that is generated when a target biomolecule in the selected subset becomes attached to a functionalized second end of the CNT, which is covalently bonded with a probe molecule. This approach indicates when target biomolecules in the selected subset are present and indicates presence or absence of target biomolecules in two or more selected subsets. Alternatively, presence of absence of an analyte can be detected.

  2. Rheological/Morphological Study of PS/CNT Nanocomposite Electrospun Fibers

    NASA Astrophysics Data System (ADS)

    Mazinani, Saeedeh; Ajji, Abdellah; Dubois, Charles

    2008-07-01

    This work depicts rheological characteristics of Polystyrene (PS)/Carbon Nanotube (CNT) nanocomposite solutions and their incidence on the morphological properties of final electrospun fibers. Nanocomposite fibers were obtained through electrospinning of PS/Di-Methyl Formamide (DMF) solutions containing different concentrations and types of Carbon Nanotubes. The morphology of fibers at different concentrations and types of CNTs was studied using Scanning Electron Microscopy (SEM) and Optical Microscopy. Correlation between initial CNT dispersion and final fibers morphologies was obtained using viscometry results and optical microscopy of initial solutions. The results obtained show that beads presence in fibers are due to nanoparticles agglomerations. A styrenic copolymer (Styrene-Butadiene-Styrene, SBS-Kraton) was employed as a compatibilizing agent to improve CNTs dispersion instead of chemical modification. Addition of copolymer affects both final fiber morphologies and CNT dispersion condition.

  3. Thermal Conductivity of 3D CNT-Polymer Composites with Controlled Dispersion

    NASA Astrophysics Data System (ADS)

    Klittich, Mena; Wang, Xue; Dhinojwala, Ali

    The high thermal conductivity of isolated carbon nanotubes (CNTs) has inspired its use as a thermal filler for insulative polymers. However, the performance of these composites has consistently been sub par. Extensive analyses of these complex systems have resulted in the conclusion that resistance at the CNT/polymer interface due to phonon mismatch and poor physical binding, as well as the weakly bonded tube-tube interactions restrict the effectiveness of CNTs in practice. Experimental comparisons of CNT treatments, coatings, functionalization, and interactions with various polymers have proved challenging, due to the interconnected nature of the composite properties. Here, we have reversed the paradigm and used a constant CNT structure that is then modified post-growth to allow for direct comparisons of polymer composites.

  4. Microfluidic study on CNT dispersion during breakup of aqueous alginic acid drop in continuous PDMS phase

    NASA Astrophysics Data System (ADS)

    Choi, Jae Hong; Nam, Young Woo; Hong, Joung Sook

    2013-02-01

    Microfluidic study is performed to investigate how multi-walled carbon nanotube (CNTs) aggregates disperse in blend system during morphology evolution. As the dispersed phase, a drop containing CNT is generated at the flow focusing and it deforms through a contraction channel (gap and width of contraction ˜ 100 μm). When an aqueous polymeric drop (2 wt% alginic acid) with CNT (0.05 wt% or 0.5 wt%) is stretched through a 4:1 contraction channel, CNT aggregates enhances breakup of the stretched drop. Also, small droplets including CNTs are pinched off during relaxation of the stretched drop. Based on these observations, it is found that CNTs disperse in a multiphase system by repetitive breakup process during mixing rather than migration driven by chemical affinity.

  5. Experimental and theoretical demonstrations for the mechanism behind enhanced microbial electron transfer by CNT network.

    PubMed

    Liu, Xian-Wei; Chen, Jie-Jie; Huang, Yu-Xi; Sun, Xue-Fei; Sheng, Guo-Ping; Li, Dao-Bo; Xiong, Lu; Zhang, Yuan-Yuan; Zhao, Feng; Yu, Han-Qing

    2014-01-01

    Bioelectrochemical systems (BESs) share the principle of the microbially catalyzed anodic substrate oxidation. Creating an electrode interface to promote extracellular electron transfer from microbes to electrode and understanding such mechanisms are crucial for engineering BESs. In this study, significantly promoted electron transfer and a 10-times increase in current generation in a BES were achieved by the utilization of carbon nanotube (CNT) network, compared with carbon paper. The mechanisms for the enhanced current generation with the CNT network were elucidated with both experimental approach and molecular dynamic simulations. The fabricated CNT network was found to be able to substantially enhance the interaction between the c-type cytochromes and solid electron acceptor, indicating that the direct electron transfer from outer-membrane decaheme c-type cytochromes to electrode might occur. The results obtained in this study will benefit for the optimized design of new materials to target the outer membrane proteins for enhanced electron exchanges. PMID:24429552

  6. Crack Formation in Powder Metallurgy Carbon Nanotube (CNT)/Al Composites During Post Heat-Treatment

    NASA Astrophysics Data System (ADS)

    Chen, Biao; Imai, Hisashi; Li, Shufeng; Jia, Lei; Umeda, Junko; Kondoh, Katsuyoshi

    2015-12-01

    After the post heat-treatment (PHT) process of powder metallurgy carbon nanotubes (CNT)/Al composites, micro-cracks were observed in the composites, leading to greatly degraded mechanical properties. To understand and suppress the crack formation, an in situ observation of CNT/Al composites was performed at elevated temperatures. PHT was also applied to various bulk pure Al and CNT/Al composites fabricated under different processes. It was observed that the composites consolidated by hot-extrusion might form micro-cracks, but those consolidated by spark plasma sintering (SPS) showed no crack after PHT. A high-temperature SPS process before hot-extrusion was effective to prevent crack formation. The release of residual stress in severe plastic deformed (SPD) materials was responsible for the cracking phenomena during the PHT process. Furthermore, a good particle bonding was essential and effective to suppress cracks for SPD materials in the PHT process.

  7. Integration and road tests of a self-sensing CNT concrete pavement system for traffic detection

    NASA Astrophysics Data System (ADS)

    Han, Baoguo; Zhang, Kun; Burnham, Tom; Kwon, Eil; Yu, Xun

    2013-01-01

    In this paper, a self-sensing carbon nanotube (CNT) concrete pavement system for traffic detection is proposed and tested in a roadway. Pre-cast and cast-in-place self-sensing CNT concrete sensors were simultaneously integrated into a controlled pavement test section at the Minnesota Road Research Facility (MnROAD), USA. Road tests of the system were conducted by using an MnROAD five-axle semi-trailer tractor truck and a van, respectively, both in the winter and summer. Test results show that the proposed self-sensing pavement system can accurately detect the passing of different vehicles under different vehicular speeds and test environments. These findings indicate that the developed self-sensing CNT concrete pavement system can achieve real-time vehicle flow detection with a high detection rate and a low false-alarm rate.

  8. PEDOT-CNT Composite Microelectrodes for Recording and Electrostimulation Applications: Fabrication, Morphology, and Electrical Properties.

    PubMed

    Gerwig, Ramona; Fuchsberger, Kai; Schroeppel, Birgit; Link, Gordon Steve; Heusel, Gerhard; Kraushaar, Udo; Schuhmann, Wolfgang; Stett, Alfred; Stelzle, Martin

    2012-01-01

    Composites of carbon nanotubes and poly(3,4-ethylenedioxythiophene, PEDOT) and layers of PEDOT are deposited onto microelectrodes by electropolymerization of ethylenedioxythiophene in the presence of a suspension of carbon nanotubes and polystyrene sulfonate. Analysis by FIB and SEM demonstrates that CNT-PEDOT composites exhibit a porous morphology whereas PEDOT layers are more compact. Accordingly, capacitance and charge injection capacity of the composite material exceed those of pure PEDOT layers. In vitro cell culture experiments reveal excellent biocompatibility and adhesion of both PEDOT and PEDOT-CNT electrodes. Signals recorded from heart muscle cells demonstrate the high S/N ratio achievable with these electrodes. Long-term pulsing experiments confirm stability of charge injection capacity. In conclusion, a robust fabrication procedure for composite PEDOT-CNT electrodes is demonstrated and results show that these electrodes are well suited for stimulation and recording in cardiac and neurophysiological research. PMID:22586394

  9. Characterization and photocatalytic performance of SnO2-CNT nanocomposites

    NASA Astrophysics Data System (ADS)

    Kim, Sung Phil; Choi, Myong Yong; Choi, Hyun Chul

    2015-12-01

    Tin oxide-carbon nanotube (SnO2-CNT) nanocomposites were prepared by depositing SnO2 nanoparticles onto thiolated CNT surfaces to develop highly efficient photocatalysts. The structure of SnO2-CNTs was characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the sample was benchmarked using the photodegradation of methylene blue (MB) and methyl orange (MO) in aqueous solution under UV-vis light irradiation. The SnO2-CNTs exhibited enhanced photocatalytic activities compared with bulk SnO2, SnO2 nanoparticles, and commercial P25 TiO2. The enhanced activity was ascribed to the CNT addition. The presence of CNTs effectively suppressed an electron-hole recombination and favored a reactant and product mass transport. A plausible photocatalytic mechanism is proposed.

  10. Atmospheric-pressure-plasma-jet sintered nanoporous AlN/CNT composites

    NASA Astrophysics Data System (ADS)

    Chiu, Yi-Fan; Yeh, Po-Wei; Cheng, I.-Chun; Chen, Jian-Zhang

    2016-07-01

    A nanoporous AlN-5 wt% CNT composite is successfully sintered using atmospheric-pressure plasma jets (APPJs). The AlN in an APPJ-sintered AlN/CNT composite shows a pure hexagonal [space group: P63mc] crystal structure. Optical emission spectroscopy (OES) results indicate that the CN violet emission intensity rapidly increases and then decreases owing to the vigorous interaction between the nitrogen APPJ and the carbonaceous materials in the printed pastes. Because the vigorous interaction may over-burn the CNTs, the conductivity of AlN first increases and then decreases as the APPJ sintering duration increases. APPJ-sintered AlN/CNT composites exhibit good CF4 inductively coupled plasma erosion resistant property.

  11. Enhanced CO2 permeability of membranes by incorporating polyzwitterion@CNT composite particles into polyimide matrix.

    PubMed

    Liu, Ye; Peng, Dongdong; He, Guangwei; Wang, Shaofei; Li, Yifan; Wu, Hong; Jiang, Zhongyi

    2014-08-13

    In this study, polyzwitterion is introduced into a CO2 separation membrane. Composite particles of polyzwitterion coated carbon nanotubes (SBMA@CNT) are prepared via a precipitation polymerization method. Hybrid membranes are fabricated by incorporating SBMA@CNT in polyimide matrix and utilized for CO2 separation. The prepared composite particles and hybrid membranes are characterized by transmission electron microscopy (TEM) with element mapping, field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectra, differential scanning calorimetry (DSC) and an electronic tensile machine. Water uptake and water state of membranes are measured to probe the relationship among water uptake, water state and CO2 transport behavior. Hybrid membranes show significantly enhanced CO2 permeability compared to an unfilled polyimide membrane at a humidified state. A hybrid membrane with 5 wt % SBMA@CNT exhibits the maximum CO2 permeability of 103 Barrer with a CO2/CH4 selectivity of 36. The increase of CO2 permeability is attributed to the incorporation of the SBMA@CNT composite particles. First, SBMA@CNT form interconnected channels for CO2 transport due to the facilitated transport effect of the quaternary ammonium in repeat unit of pSBMA. Second, SBMA@CNT improve water uptake and adjust water state of membrane, which further increases CO2 permeability. Meanwhile, the variation of CO2/CH4 selectivity is dependent on the bound water portion in the membrane. A gas permeation test at a dry state and a pressure test are conducted to further probe the membrane separation performance. PMID:25068977

  12. Electrospinning of unidirectionally and orthogonally aligned thermoplastic polyurethane nanofibers: fiber orientation and cell migration.

    PubMed

    Mi, Hao-Yang; Salick, Max R; Jing, Xin; Crone, Wendy C; Peng, Xiang-Fang; Turng, Lih-Sheng

    2015-02-01

    Unidirectionally and orthogonally aligned thermoplastic polyurethane (TPU) nanofibers were electrospun using a custom-built electrospinning device. The unidirectionally aligned fibers were collected using two parallel copper plates, and the orthogonally aligned fibers were collected using two orthogonal sets of parallel copper plates with alternate negative connections. Carbon nanotubes (CNT) and polyacrylic acid (PAA) were added to modify the polymer solution. It was found that both CNT and PAA were capable of increasing solution conductivity. The TPU/PAA fiber showed the highest degree of fiber orientation with more than 90% of the fibers having an orientation angle between -10° and 10° for unidirectionally aligned fibers, and for orthogonally aligned fibers, the orientation angle of 50% fibers located between -10° and 10° and 48% fibers located between 80° and 100°. Viability assessment of 3T3 fibroblasts cultured on TPU/PAA fibers suggested that the material was cytocompatible. The cells' orientation and migration direction closely matched the fibers' orientation. The cell migration velocity and distance were both enhanced with the guidance of fibers compared with cells cultured on random fibers and common tissue culture plastic. Controlling cell migration velocity and directionality may provide ways to influence differentiation and gene expression and systems that would allow further exploration of wound repair and metastatic cell behavior. PMID:24771704

  13. Electrospinning of unidirectionally and orthogonally aligned thermoplastic polyurethane nanofibers: Fiber orientation and cell migration

    PubMed Central

    Mi, Hao-Yang; Salick, Max R.; Jing, Xin; Crone, Wendy C.; Peng, Xiang-Fang; Turng, Lih-Sheng

    2015-01-01

    Unidirectionally and orthogonally aligned thermoplastic polyurethane (TPU) nanofibers were electrospun using a custom-built electrospinning device. The unidirectionally aligned fibers were collected using two parallel copper plates, and the orthogonally aligned fibers were collected using two orthogonal sets of parallel copper plates with alternate negative connections. Carbon nanotubes (CNT) and polyacrylic acid (PAA) were added to modify the polymer solution. It was found that both CNT and PAA were capable of increasing solution conductivity. The TPU/PAA fiber showed the highest degree of fiber orientation with more than 90% of the fibers having an orientation angle between −10° and 10° for unidirectionally aligned fibers, and for orthogonally aligned fibers, the orientation angle of 50% fibers located between −10° and 10° and 48% fibers located between 80° and 100°. Viability assessment of 3T3 fibroblasts cultured on TPU/PAA fibers suggested that the material was cytocompatible. The cells’ orientation and migration direction closely matched the fibers’ orientation. The cell migration velocity and distance were both enhanced with the guidance of fibers compared with cells cultured on random fibers and common tissue culture plastic. Controlling cell migration velocity and directionality may provide ways to influence differentiation and gene expression and systems that would allow further exploration of wound repair and metastatic cell behavior. PMID:24771704

  14. Horizontal carbon nanotube alignment.

    PubMed

    Cole, Matthew T; Cientanni, Vito; Milne, William I

    2016-09-21

    The production of horizontally aligned carbon nanotubes offers a rapid means of realizing a myriad of self-assembled near-atom-scale technologies - from novel photonic crystals to nanoscale transistors. The ability to reproducibly align anisotropic nanostructures has huge technological value. Here we review the present state-of-the-art in horizontal carbon nanotube alignment. For both in and ex situ approaches, we quantitatively assess the reported linear packing densities alongside the degree of alignment possible for each of these core methodologies. PMID:27546174

  15. Orthodontics and Aligners

    MedlinePlus

    ... Repairing Chipped Teeth Teeth Whitening Tooth-Colored Fillings Orthodontics and Aligners Straighten teeth for a healthier smile. Orthodontics When consumers think about orthodontics, braces are the ...

  16. Alignability of Optical Interconnects

    NASA Astrophysics Data System (ADS)

    Beech, Russell Scott

    With the continuing drive towards higher speed, density, and functionality in electronics, electrical interconnects become inadequate. Due to optics' high speed and bandwidth, freedom from capacitive loading effects, and freedom from crosstalk, optical interconnects can meet more stringent interconnect requirements. But, an optical interconnect requires additional components, such as an optical source and detector, lenses, holographic elements, etc. Fabrication and assembly of an optical interconnect requires precise alignment of these components. The successful development and deployment of optical interconnects depend on how easily the interconnect components can be aligned and/or how tolerant the interconnect is to misalignments. In this thesis, a method of quantitatively specifying the relative difficulty of properly aligning an optical interconnect is described. Ways of using this theory of alignment to obtain design and packaging guidelines for optical interconnects are examined. The measure of the ease with which an optical interconnect can be aligned, called the alignability, uses the efficiency of power transfer as a measure of alignment quality. The alignability is related to interconnect package design through the overall cost measure, which depends upon various physical parameters of the interconnect, such as the cost of the components and the time required for fabrication and alignment. Through a mutual dependence on detector size, the relationship between an interconnect's alignability and its bandwidth, signal-to-noise ratio, and bit-error -rate is examined. The results indicate that a range of device sizes exists for which given performance threshold values are satisfied. Next, the alignability of integrated planar-optic backplanes is analyzed in detail. The resulting data show that the alignability can be optimized by varying the substrate thickness or the angle of reflection. By including the effects of crosstalk, in a multi-channel backplane, the

  17. Tidal alignment of galaxies

    NASA Astrophysics Data System (ADS)

    Blazek, Jonathan; Vlah, Zvonimir; Seljak, Uroš

    2015-08-01

    We develop an analytic model for galaxy intrinsic alignments (IA) based on the theory of tidal alignment. We calculate all relevant nonlinear corrections at one-loop order, including effects from nonlinear density evolution, galaxy biasing, and source density weighting. Contributions from density weighting are found to be particularly important and lead to bias dependence of the IA amplitude, even on large scales. This effect may be responsible for much of the luminosity dependence in IA observations. The increase in IA amplitude for more highly biased galaxies reflects their locations in regions with large tidal fields. We also consider the impact of smoothing the tidal field on halo scales. We compare the performance of this consistent nonlinear model in describing the observed alignment of luminous red galaxies with the linear model as well as the frequently used "nonlinear alignment model," finding a significant improvement on small and intermediate scales. We also show that the cross-correlation between density and IA (the "GI" term) can be effectively separated into source alignment and source clustering, and we accurately model the observed alignment down to the one-halo regime using the tidal field from the fully nonlinear halo-matter cross correlation. Inside the one-halo regime, the average alignment of galaxies with density tracers no longer follows the tidal alignment prediction, likely reflecting nonlinear processes that must be considered when modeling IA on these scales. Finally, we discuss tidal alignment in the context of cosmic shear measurements.

  18. An Investigation of CNT Cytotoxicity by Using Surfactants in Different Ratio

    NASA Astrophysics Data System (ADS)

    Kumar, Sandeep; Kumar, Neeraj; Thakur, Rajesh; Bhanjana, Gaurav; Dilbaghi, Neeraj

    2011-12-01

    This account reports a comparative analysis on dispersion of multiwalled and single walled carbon nanotubes with different surfactants like—Triton X-100, Tween 20, Tween 80, and sodium dodecyl sulfate (SDS). Dispersion of CNTs has been characterized by UV-Vis spectroscopy, electron microscopy and probe microscopy. An optimum CNT-to-surfactant ratio has been determined for each surfactant. Surfactant concentration in different ratio is found to deteriorate the quality of nanotube dispersion. Electron microscopy analysis of a high-surfactant sample concentration enables us to construct a plausible mechanism for increase or decrease in CNT dispersion at high surfactant concentration.

  19. Vertically aligned ZnO@CuS@PEDOT core@shell nanorod arrays decorated with MnO₂ nanoparticles for a high-performance and semi-transparent supercapacitor electrode.

    PubMed

    Rodríguez-Moreno, Jorge; Navarrete-Astorga, Elena; Dalchiele, Enrique A; Schrebler, Ricardo; Ramos-Barrado, José R; Martín, Francisco

    2014-05-30

    Hybrid nano-architectures with high electrochemical performance for supercapacitors have been designed by growing hierarchical ZnO NRs@CuS@PEDOT@MnO2 core@shell heterostructured nanorod arrays on ITO/glass substrates. This hybrid nano-structured electrode exhibits excellent electrochemical performance, with a high specific areal capacitance of 19.85 mF cm(-2), good rate capability, cycling stability and diffused coloured transparency. PMID:24756158

  20. Investigation of H2S separation from H2S/CH4 mixtures using functionalized and non-functionalized vertically aligned carbon nanotube membranes

    NASA Astrophysics Data System (ADS)

    Gilani, Neda; Towfighi, Jafar; Rashidi, Alimorad; Mohammadi, Toraj; Omidkhah, Mohammad Reza; Sadeghian, Ahmad

    2013-04-01

    Separation of H2S from binary mixtures of H2S/CH4 using vertically aligned carbon nanotube membranes fabricated in anodic aluminum oxide (AAO) template was studied experimentally. Carbon nanotubes (CNTs) were grown in five AAO templates with different pore diameters using chemical vapor deposition, and CNT/AAO membranes with tubular carbon nanotube structure and open caps were selected for separation of H2S. For this, two tubular CNT/AAO membranes were fabricated with the CNT inner diameters of 23 and 8 nm. It was found that permeability and selectivity of the membrane with inner diameter of 23 nm for CNT were independent of upstream feed pressure and H2S feed concentration unlike that of CNT having an inner diameter of 8 nm. Selectivity of these membranes for separation of H2S was obtained in the ranges of 1.36-1.58 and 2.11-2.86, for CNTs with internal diameters of 23 and 8 nm, respectively. In order to enhance the separation of H2S from H2S/CH4 mixtures, dodecylamine was used to functionalize the CNT/AAO membrane with higher selectivity. The results showed that for amido-functionalized membrane, both upstream feed pressure and H2S partial pressure in the feed significantly increased H2S permeability, and selectivity for H2S being in the range of 3.0-5.57 respectively.

  1. Anisotropic fiber alignment in composite structures

    DOEpatents

    Graham, A.L.; Mondy, L.A.; Guell, D.C.

    1993-11-16

    High strength material composite structures are formed with oriented fibers to provide controlled anisotropic fibers. Fibers suspended in non-dilute concentrations (e.g., up to 20 volume percent for fibers having an aspect ratio of 20) in a selected medium are oriented by moving an axially spaced array of elements in the direction of desired fiber alignment. The array elements are generally perpendicular to the desired orientation. The suspension medium may also include sphere-like particles where the resulting material is a ceramic. 5 figures.

  2. Anisotropic fiber alignment in composite structures

    DOEpatents

    Graham, Alan L.; Mondy, Lisa A.; Guell, David C.

    1993-01-01

    High strength material composite structures are formed with oriented fibers to provide controlled anisotropic fibers. Fibers suspended in non-dilute concentrations (e.g., up to 20 volume percent for fibers having an aspect ratio of 20) in a selected medium are oriented by moving an axially spaced array of elements in the direction of desired fiber alignment. The array elements are generally perpendicular to the desired orientation. The suspension medium may also include sphere-like particles where the resulting material is a ceramic.

  3. Electronic Switch Arrays for Managing Microbattery Arrays

    NASA Technical Reports Server (NTRS)

    Mojarradi, Mohammad; Alahmad, Mahmoud; Sukumar, Vinesh; Zghoul, Fadi; Buck, Kevin; Hess, Herbert; Li, Harry; Cox, David

    2008-01-01

    Integrated circuits have been invented for managing the charging and discharging of such advanced miniature energy-storage devices as planar arrays of microscopic energy-storage elements [typically, microscopic electrochemical cells (microbatteries) or microcapacitors]. The architecture of these circuits enables implementation of the following energy-management options: dynamic configuration of the elements of an array into a series or parallel combination of banks (subarrarys), each array comprising a series of parallel combination of elements; direct addressing of individual banks for charging/or discharging; and, disconnection of defective elements and corresponding reconfiguration of the rest of the array to utilize the remaining functional elements to obtain the desited voltage and current performance. An integrated circuit according to the invention consists partly of a planar array of field-effect transistors that function as switches for routing electric power among the energy-storage elements, the power source, and the load. To connect the energy-storage elements to the power source for charging, a specific subset of switches is closed; to connect the energy-storage elements to the load for discharging, a different specific set of switches is closed. Also included in the integrated circuit is circuitry for monitoring and controlling charging and discharging. The control and monitoring circuitry, the switching transistors, and interconnecting metal lines are laid out on the integrated-circuit chip in a pattern that registers with the array of energy-storage elements. There is a design option to either (1) fabricate the energy-storage elements in the corresponding locations on, and as an integral part of, this integrated circuit; or (2) following a flip-chip approach, fabricate the array of energy-storage elements on a separate integrated-circuit chip and then align and bond the two chips together.

  4. Synthesis, characterizations and applications of some nanomaterials (TiO2 and SiC nanostructured films, organized CNT structures, ZnO structures and CNT-blood platelet clusters)

    NASA Astrophysics Data System (ADS)

    Srivastava, O. N.; Srivastava, A.; Dash, D.; Singh, D. P.; Yadav, R. M.; Mishra, P. R.; Singh, J.

    2005-10-01

    TiO_{2} nanostructured films have been synthesized by the hydrolysis of Ti[OCH(CH_{3})_{2}]_{4} as the precursor. These films have been utilized for the dissociation of phenol contaminant in water. Free-standing nanostructured film of silicon carbide (SiC) has been synthesized, employing a simple and new route of spray pyrolysis technique utilizing a slurry of Si in hexane. Another study is done on organized carbon nanotube (CNT) structures. These are made in the form of hollow cylinders (50 mm length, 4 mm diameter and 1.5 mm wall thickness). These CNT-based cylinders are made of conventional CNT and bamboo-shaped CNT. The filtrations of heavy hydrocarbons and E. coli bacteria from water have been carried out. In addition to this, ZnO nanostructures have also been studied. Another study concerns CNT-blood platelet clusters.

  5. STAR: ultrafast universal RNA-seq aligner

    PubMed Central

    Dobin, Alexander; Davis, Carrie A.; Schlesinger, Felix; Drenkow, Jorg; Zaleski, Chris; Jha, Sonali; Batut, Philippe; Chaisson, Mark; Gingeras, Thomas R.

    2013-01-01

    Motivation: Accurate alignment of high-throughput RNA-seq data is a challenging and yet unsolved problem because of the non-contiguous transcript structure, relatively short read lengths and constantly increasing throughput of the sequencing technologies. Currently available RNA-seq aligners suffer from high mapping error rates, low mapping speed, read length limitation and mapping biases. Results: To align our large (>80 billon reads) ENCODE Transcriptome RNA-seq dataset, we developed the Spliced Transcripts Alignment to a Reference (STAR) software based on a previously undescribed RNA-seq alignment algorithm that uses sequential maximum mappable seed search in uncompressed suffix arrays followed by seed clustering and stitching procedure. STAR outperforms other aligners by a factor of >50 in mapping speed, aligning to the human genome 550 million 2 × 76 bp paired-end reads per hour on a modest 12-core server, while at the same time improving alignment sensitivity and precision. In addition to unbiased de novo detection of canonical junctions, STAR can discover non-canonical splices and chimeric (fusion) transcripts, and is also capable of mapping full-length RNA sequences. Using Roche 454 sequencing of reverse transcription polymerase chain reaction amplicons, we experimentally validated 1960 novel intergenic splice junctions with an 80–90% success rate, corroborating the high precision of the STAR mapping strategy. Availability and implementation: STAR is implemented as a standalone C++ code. STAR is free open source software distributed under GPLv3 license and can be downloaded from http://code.google.com/p/rna-star/. Contact: dobin@cshl.edu. PMID:23104886

  6. SPEAR3 Construction Alignment

    SciTech Connect

    LeCocq, Catherine; Banuelos, Cristobal; Fuss, Brian; Gaudreault, Francis; Gaydosh, Michael; Griffin, Levirt; Imfeld, Hans; McDougal, John; Perry, Michael; Rogers, Michael; /SLAC

    2005-08-17

    An ambitious seven month shutdown of the existing SPEAR2 synchrotron radiation facility was successfully completed in March 2004 when the first synchrotron light was observed in the new SPEAR3 ring, SPEAR3 completely replaced SPEAR2 with new components aligned on a new highly-flat concrete floor. Devices such as magnets and vacuum chambers had to be fiducialized and later aligned on girder rafts that were then placed into the ring over pre-aligned support plates. Key to the success of aligning this new ring was to ensure that the new beam orbit matched the old SPEAR2 orbit so that existing experimental beamlines would not have to be reoriented. In this presentation a pictorial summary of the Alignment Engineering Group's surveying tasks for the construction of the SPEAR3 ring is provided. Details on the networking and analysis of various surveys throughout the project can be found in the accompanying paper.

  7. Spent fuel container alignment device and method

    DOEpatents

    Jones, Stewart D.; Chapek, George V.

    1996-01-01

    An alignment device is used with a spent fuel shipping container including a plurality of fuel pockets for spent fuel arranged in an annular array and having a rotatable cover including an access opening therein. The alignment device includes a lightweight plate which is installed over the access opening of the cover. A laser device is mounted on the plate so as to emit a laser beam through a laser admittance window in the cover into the container in the direction of a pre-established target associated with a particular fuel pocket. An indexing arrangement on the container provides an indication of the angular position of the rotatable cover when the laser beam produced by the laser is brought into alignment with the target of the associated fuel pocket.

  8. Structural CNT Composites. Part I; Developing a Carbon Nanotube Filament Winder

    NASA Technical Reports Server (NTRS)

    Sauti, Godfrey; Kim, Jae-Woo; Wincheski, Russell A.; Antczak, Andrew; Campero, Jamie C.; Luong, Hoa H.; Shanahan, Michelle H.; Stelter, Christopher J.; Siochi, Emilie J.

    2015-01-01

    Carbon nanotube (CNT) based materials promise advances in the production of high strength and multifunctional components for aerospace and other applications. Specifically, in tension dominated applications, the latest CNT based filaments are yielding composite properties comparable to or exceeding composites from more established fibers such as Kevlar and carbon fiber. However, for the properties of these materials to be fully realized at the component level, suitable manufacturing processes have to be developed. These materials handle differently from conventional fibers, with different wetting characteristics and behavior under load. The limited availability of bulk forms also requires that the equipment be scaled down accordingly to tailor the process development approach to material availability. Here, the development of hardware and software for filament winding of carbon nanotube based tapes and yarns is described. This hardware features precision guidance of the CNT material and control of the winding tension over a wide range in an open architecture that allows for effective process control and troubleshooting during winding. Use of the filament winder to develop CNT based Composite Overwrapped Pressure Vessels (COPVs) shall also be discussed.

  9. Synthesis of TiO2 /CNT Composites and its Photocatalytic Activity Toward Sudan (I) Degradation.

    PubMed

    Miribangul, Amat; Ma, Xiaoli; Zeng, Chen; Zou, Huan; Wu, Yahui; Fan, Tengpeng; Su, Zhi

    2016-07-01

    Semiconductor photocatalysis has the potential for achieving sustainable energy generation and degrading organic contaminants. In TiO2 , the addition of carbonaceous nanomaterials has attracted extensive attention as a means to increase its photocatalytic activity. In this study, composites of TiO2 and carbon nanotubes (CNT) in various proportions were synthesized by the hydrothermal method. The crystalline structures, morphologies, and light absorption properties of the TiO2 /CNT photocatalysts were characterized by PXRD, TEM and UV-Vis absorption spectra. The photocatalytic efficiency of the composites was evaluated by the degradation of Sudan (I) in UV-Vis light. Introducing 0.1-0.5 wt% CNT was shown to substantially improve the photoactivity of TiO2 . The composite with 0.3 wt% CNT showed the best catalytic activity, and its reaction activation energy was calculated as 39.57 kJ mol(-1) from experimental rates. The degradation products of Sudan (I) with different irradiation durations were characterized by Fourier transform infrared spectroscopy, and a degradation reaction process was proposed. PMID:27221342

  10. Molecular dynamics simulation of doxorubicin adsorption on a bundle of functionalized CNT.

    PubMed

    Izadyar, Akram; Farhadian, Nafiseh; Chenarani, Naser

    2016-08-01

    In this study, molecular dynamics simulation is used to investigate the adsorption of an anticancer drug, doxorubicin, on bundles of functionalized single-walled carbon nanotubes (SWNTs) in an aqueous solution. Carboxylic group has been selected as the functional group. Molecular dynamics (MD) simulations are performed for both separated systems containing a SWNT bundle and a functionalized carbon nanotube bundle, and results are compared with existing experimental data. MD results show that doxorubicin can be adsorbed on CNTs using different methods such as entrapment within CNT bundle, attachment to the side wall of the CNT, and adsorption on the CNT inner cavity. For functionalized CNT, the adsorption of drugs on the functional groups is essential for predicting the enhancement of drug loading on the functionalized nanotubes. Furthermore, the adsorption behavior of doxorubicin on CNTs is fitted with Langmuir and Freundlich isotherm models. The results show that Langmuir model can predict the adsorption behavior of doxorubicin on CNTs more accurately than Freundlich model does. As predicted by this isotherm model, the adsorption process of doxorubicin on CNTs is relatively difficult, but it can be improved by increasing the functional groups on the CNTs surface. PMID:26375507

  11. Controlled growth of CNT in mesoporous AAO through optimized conditions for membrane preparation and CVD operation.

    PubMed

    Ciambelli, P; Arurault, L; Sarno, M; Fontorbes, S; Leone, C; Datas, L; Sannino, D; Lenormand, P; Du Plouy, S Le Blond

    2011-07-01

    Anodic aluminium oxide (RAAO) membranes with a mesoporous structure were prepared under strictly controlling experimental process conditions, and physically and chemically characterized by a wide range of experimental techniques. Commercial anodic aluminium oxide (CAAO) membranes were also investigated for comparison. We demonstrated that RAAO membranes have lower content of both water and phosphorus and showed better porosity shape than CAAO. The RAAO membranes were used for template growth of carbon nanotubes (CNT) inside its pores by ethylene chemical vapour deposition (CVD) in the absence of a catalyst. A composite material, containing one nanotube for each channel, having the same length as the membrane thickness and an external diameter close to the diameter of the membrane holes, was obtained. Yield, selectivity and quality of CNTs in terms of diameter, length and arrangement (i.e. number of tubes for each channel) were optimized by investigating the effect of changing the experimental conditions for the CVD process. We showed that upon thermal treatment RAAO membranes were made up of crystallized allotropic alumina phases, which govern the subsequent CNT growth, because of their catalytic activity, likely due to their Lewis acidity. The strict control of experimental conditions for membrane preparation and CNT growth allowed us to enhance the carbon structural order, which is a critical requisite for CNT application as a substitute for copper in novel nano-interconnects. PMID:21576783

  12. Characterization of CNT-MnO2 nanocomposite by electrophoretic deposition as potential electrode for supercapacitor

    NASA Astrophysics Data System (ADS)

    Darari, Alfin; Ardiansah, Hafidh Rahman; Arifin, Rismaningsih, Nurmanita; Ningrum, Andini Novia; Subagio, Agus

    2016-04-01

    Energy crisis that occured in Indonesia suggests that energy supply could not offset the high rate request and needs an electric energy saving device which can save high voltage, safety, and unlimited lifetime. The weakness of batteries is durable but has a low power density while the capacitor has a high power density but it doesn't durable. The renewal of this study is CNT-MnO2 thin film fabrication method using electrophoretic deposition. Electrophoretic deposition is a newest method to deposited CNT using power supply with cheap, and make a good result. The result of FTIR analysis showed that the best CNT-MnO2 composition is 75:25 and C-C bond is detected in fingerprint area. The result is electrode thin film homogen and characterized by X-ray diffraction (XRD) peaks 2θ=26,63° is characterization of graphite, and 2θ=43,97° is characterization of diamond Carbon type and measured by Scherrer formula results 52,3 nm material average size .EIS test results its capacitance about 7,86 F. from the data it can be concluded that CNT-MnO2 potential electrode very promising for further study and has a potential to be a high capacitance, and fast charge supercapacitor which can be applied for electronic devices, energy converter, even electric car.

  13. Flexible transparent conductive films combining flexographic printed silver grids with CNT coating

    NASA Astrophysics Data System (ADS)

    Mo, Lixin; Ran, Jun; Yang, Li; Fang, Yi; Zhai, Qingbin; Li, Luhai

    2016-02-01

    A high-performance ITO-free transparent conductive film (TCF) has been made by combining high resolution Ag grids with a carbon nanotube (CNT) coating. Ag grids printed with flexography have a 20 μm line width at a grid interval of 400 μm. The Ag grid/CNT hybrid film exhibits excellent overall performance, with a typical sheet resistance of 14.8 Ω/□ and 82.6% light transmittance at room temperature. This means a 23.98% reduction in sheet resistance and only 2.52% loss in transmittance compared to a pure Ag grid film. Analysis indicates that filling areas between the Ag grids and interconnecting the silver nanoparticles with the CNT coating are the primary reasons for the significantly improved conductivity of the hybrid film that also exhibits excellent flexibility and mechanical strength compared to an ITO film. The hybrid film may fully satisfy the requirements of different applications, e.g. use as the anode of polymer solar cells (PSCs). The J-V curve shows that the power conversion efficiency (PCE) of the PSCs using the Ag grid/CNT hybrid anode is 0.61%, which is 24.5% higher than that of the pure Ag grids with a PCE of 0.49%. Further investigations to improve the performance of the solar cells based on the printed hybrid TCFs are ongoing.

  14. Flexible transparent conductive films combining flexographic printed silver grids with CNT coating.

    PubMed

    Mo, Lixin; Ran, Jun; Yang, Li; Fang, Yi; Zhai, Qingbin; Li, Luhai

    2016-02-12

    A high-performance ITO-free transparent conductive film (TCF) has been made by combining high resolution Ag grids with a carbon nanotube (CNT) coating. Ag grids printed with flexography have a 20 μm line width at a grid interval of 400 μm. The Ag grid/CNT hybrid film exhibits excellent overall performance, with a typical sheet resistance of 14.8 Ω/□ and 82.6% light transmittance at room temperature. This means a 23.98% reduction in sheet resistance and only 2.52% loss in transmittance compared to a pure Ag grid film. Analysis indicates that filling areas between the Ag grids and interconnecting the silver nanoparticles with the CNT coating are the primary reasons for the significantly improved conductivity of the hybrid film that also exhibits excellent flexibility and mechanical strength compared to an ITO film. The hybrid film may fully satisfy the requirements of different applications, e.g. use as the anode of polymer solar cells (PSCs). The J-V curve shows that the power conversion efficiency (PCE) of the PSCs using the Ag grid/CNT hybrid anode is 0.61%, which is 24.5% higher than that of the pure Ag grids with a PCE of 0.49%. Further investigations to improve the performance of the solar cells based on the printed hybrid TCFs are ongoing. PMID:26758939

  15. Controlled growth of CNT in mesoporous AAO through optimized conditions for membrane preparation and CVD operation

    NASA Astrophysics Data System (ADS)

    Ciambelli, P.; Arurault, L.; Sarno, M.; Fontorbes, S.; Leone, C.; Datas, L.; Sannino, D.; Lenormand, P.; Le Blond Du Plouy, S.

    2011-07-01

    Anodic aluminium oxide (RAAO) membranes with a mesoporous structure were prepared under strictly controlling experimental process conditions, and physically and chemically characterized by a wide range of experimental techniques. Commercial anodic aluminium oxide (CAAO) membranes were also investigated for comparison. We demonstrated that RAAO membranes have lower content of both water and phosphorus and showed better porosity shape than CAAO. The RAAO membranes were used for template growth of carbon nanotubes (CNT) inside its pores by ethylene chemical vapour deposition (CVD) in the absence of a catalyst. A composite material, containing one nanotube for each channel, having the same length as the membrane thickness and an external diameter close to the diameter of the membrane holes, was obtained. Yield, selectivity and quality of CNTs in terms of diameter, length and arrangement (i.e. number of tubes for each channel) were optimized by investigating the effect of changing the experimental conditions for the CVD process. We showed that upon thermal treatment RAAO membranes were made up of crystallized allotropic alumina phases, which govern the subsequent CNT growth, because of their catalytic activity, likely due to their Lewis acidity. The strict control of experimental conditions for membrane preparation and CNT growth allowed us to enhance the carbon structural order, which is a critical requisite for CNT application as a substitute for copper in novel nano-interconnects.

  16. Centaurin-like protein Cnt5 contributes to arsenic and cadmium resistance in fission yeast.

    PubMed

    Vashisht, Ajay Amar; Kennedy, Patrick Joseph; Russell, Paul

    2009-03-01

    Arsenic (As) and cadmium (Cd) are two of the most hazardous substances in the environment and have been implicated in a number of human diseases including cancer. Their mechanisms of toxicity and subsequent carcinogenesis are not understood. To identify the genes involved in As/Cd detoxification, we screened a random insertional mutagenesis library of Schizosaccharomyces pombe for mutants that are hypersensitive to As/Cd. Mutations were mapped to spc1(+) (sty1(+)) and SPBC17G9.08c. Spc1 is a stress-activated protein kinase orthologous to human p38. A fragment of SPBC17G9.08c was previously identified as csx2, a high-copy suppressor of cut6 that encodes an acetyl-CoA carboxylase involved in fatty acid biosynthesis. SPBC17G9.08c is a member of the centaurin ADP ribosylation factor GTPase activating protein family found in a variety of fungi, plants and metazoans, but not in Saccharomyces cerevisiae. Cnt5, so named because its closest human homolog is centaurin beta-5, binds to phosphatidic acid and phosphatidyl serine in vitro. Microscopic localization of Cnt5-GFP indicates significant redistribution of Cnt5 from the cytoplasm to the cell membranes in response to As stress. These data suggest a model in which Cnt5 contributes to As/Cd resistance by maintaining membrane integrity or by modulating membrane trafficking. PMID:19076239

  17. Clinically relevant CNT dispersions with exceptionally high dielectric properties for microwave theranostic applications.

    PubMed

    Xie, Shawn X; Gao, Fuqiang; Patel, Sunny C; Booske, John H; Hagness, Susan C; Sitharaman, Balaji

    2014-11-01

    We present a formulation for achieving stable high-concentration (up to 20 mg/ml) aqueous dispersions of carbon nanotubes (CNTs) with exceptionally high microwave-frequency (0.5-6 GHz) dielectric properties. The formulation involves functionalizing CVD-synthesized CNTs via sonication in nitric and sulfuric acid. The overall chemical integrity of the CNTs is largely preserved, as demonstrated via physical and chemical characterizations, despite significant shortening and functionalization with oxygen-containing groups. This is attributed to the protected inner walls of double-walled CNTs in the samples. The resulting CNT dispersions show greatly enhanced dielectric properties compared to a CNT-free control. For example, at 3 GHz, the average relative permittivity and effective conductivity across several 20 mg/ml CNT samples were increased by ∼ 70% and ∼ 400%, respectively, compared to the control. These CNT dispersions exhibit the stability and extraordinary microwave properties desired in systemically administered theranostic agents for microwave diagnostic imaging and/or thermal therapy. PMID:24876108

  18. Electrostatically clean solar array

    NASA Technical Reports Server (NTRS)

    Stern, Theodore Garry (Inventor); Krumweide, Duane Eric (Inventor)

    2004-01-01

    Provided are methods of manufacturing an electrostatically clean solar array panel and the products resulting from the practice of these methods. The preferred method uses an array of solar cells, each with a coverglass where the method includes machining apertures into a flat, electrically conductive sheet so that each aperture is aligned with and undersized with respect to its matched coverglass sheet and thereby fashion a front side shield with apertures (FSA). The undersized portion about each aperture of the bottom side of the FSA shield is bonded to the topside portions nearest the edges of each aperture's matched coverglass. Edge clips are attached to the front side aperture shield edges with the edge clips electrically and mechanically connecting the tops of the coverglasses to the solar panel substrate. The FSA shield, edge clips and substrate edges are bonded so as to produce a conductively grounded electrostatically clean solar array panel.

  19. Magnetic arrays

    DOEpatents

    Trumper, D.L.; Kim, W.; Williams, M.E.

    1997-05-20

    Electromagnet arrays are disclosed which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness. 12 figs.

  20. Magnetic arrays

    SciTech Connect

    Trumper, David L.; Kim, Won-jong; Williams, Mark E.

    1997-05-20

    Electromagnet arrays which can provide selected field patterns in either two or three dimensions, and in particular, which can provide single-sided field patterns in two or three dimensions. These features are achieved by providing arrays which have current densities that vary in the windings both parallel to the array and in the direction of array thickness.

  1. VISA undulator fiducialization and alignment

    SciTech Connect

    1999-12-13

    As part of the R and D program towards a fourth generation light source, a Self-Amplified Spontaneous Emission (SASE) demonstration is being prepared. The Visible-Infrared SASE Amplifier (VISA) undulator will be installed at Brookhaven National Laboratory by the end of the year. The VISA undulator is an in-vacuum, 4-meter long, 1.8 cm period, pure-permanent magnet device, with a novel, strong focusing, permanent magnet FODO array included within the fixed, 6 mm undulator gap. The undulator is constructed of 99 cm long segments. To attain maximum SASE gain requires establishing overlap of electron and photon beams to within 50 {micro}m rms. This imposes challenging tolerances on mechanical fabrication and magnetic field quality, and necessitates use of laser straightness interferometry for calibration and alignment of the magnetic axes of the undulator segments. This paper describes the magnetic centerline determination, and the fiducialization and alignment processes which were performed to meet the tolerance goal.

  2. Surface-enhanced Raman spectroscopy using gold-coated horizontally aligned carbon nanotubes

    NASA Astrophysics Data System (ADS)

    He, X. N.; Gao, Y.; Mahjouri-Samani, M.; Black, P. N.; Allen, J.; Mitchell, M.; Xiong, W.; Zhou, Y. S.; Jiang, L.; Lu, Y. F.

    2012-05-01

    Gold-coated horizontally aligned carbon nanotube (Au-HA-CNT) substrates were fabricated for surface-enhanced Raman spectroscopy (SERS). The Au-HA-CNT substrates, which are granular in nature, are easy-to-prepare with large SERS-active area. Enhancement factors (EFs) of ˜107 were achieved using the Au-HA-CNTs as substrates for rhodamine 6G (R6G) molecules. Maximum enhancement was found when the polarization direction (E-field) of the incident laser beam was parallel to the aligned direction of the HA-CNTs. Simulations using the finite-difference time-domain (FDTD) method were carried out for the granular Au-HA-CNT samples. Enhancement mechanisms and determination of EFs were analyzed. Biological samples, including 13C- and deuterium (D)-labeled fatty acids and Coccomyxa sp. c-169 microalgae cells, were also measured using this SERS substrate. The limits of detection (LODs) of D- and 13C-labeled fatty acids on the SERS substrate were measured to be around 10 nM and 20 nM, respectively. Significantly enhanced Raman signals from the microalgae cells were acquired using the SERS substrate.

  3. Fabrication of high thermal conductivity arrays of carbon nanotubes and their composites

    DOEpatents

    Geohegan, David B [Knoxville, TN; Ivanov, Ilya N [Knoxville, TN; Puretzky, Alexander A [Knoxville, TN

    2010-07-27

    Methods and apparatus are described for fabrication of high thermal conductivity arrays of carbon nanotubes and their composites. A composition includes a vertically aligned nanotube array including a plurality of nanotubes characterized by a property across substantially all of the vertically aligned nanotube array. A method includes depositing a vertically aligned nanotube array that includes a plurality of nanotubes; and controlling a deposition rate of the vertically aligned nanotubes array as a function of an in situ monitored property of the plurality of nanotubes.

  4. Precision alignment device

    DOEpatents

    Jones, N.E.

    1988-03-10

    Apparatus for providing automatic alignment of beam devices having an associated structure for directing, collimating, focusing, reflecting, or otherwise modifying the main beam. A reference laser is attached to the structure enclosing the main beam producing apparatus and produces a reference beam substantially parallel to the main beam. Detector modules containing optical switching devices and optical detectors are positioned in the path of the reference beam and are effective to produce an electrical output indicative of the alignment of the main beam. This electrical output drives servomotor operated adjustment screws to adjust the position of elements of the structure associated with the main beam to maintain alignment of the main beam. 5 figs.

  5. Precision alignment device

    DOEpatents

    Jones, Nelson E.

    1990-01-01

    Apparatus for providing automatic alignment of beam devices having an associated structure for directing, collimating, focusing, reflecting, or otherwise modifying the main beam. A reference laser is attached to the structure enclosing the main beam producing apparatus and produces a reference beam substantially parallel to the main beam. Detector modules containing optical switching devices and optical detectors are positioned in the path of the reference beam and are effective to produce an electrical output indicative of the alignment of the main beam. This electrical output drives servomotor operated adjustment screws to adjust the position of elements of the structure associated with the main beam to maintain alignment of the main beam.

  6. Hybrid vehicle motor alignment

    DOEpatents

    Levin, Michael Benjamin

    2001-07-03

    A rotor of an electric motor for a motor vehicle is aligned to an axis of rotation for a crankshaft of an internal combustion engine having an internal combustion engine and an electric motor. A locator is provided on the crankshaft, a piloting tool is located radially by the first locator to the crankshaft. A stator of the electric motor is aligned to a second locator provided on the piloting tool. The stator is secured to the engine block. The rotor is aligned to the crankshaft and secured thereto.

  7. Gas composition sensing using carbon nanotube arrays

    NASA Technical Reports Server (NTRS)

    Li, Jing (Inventor); Meyyappan, Meyya (Inventor)

    2008-01-01

    A method and system for estimating one, two or more unknown components in a gas. A first array of spaced apart carbon nanotubes (''CNTs'') is connected to a variable pulse voltage source at a first end of at least one of the CNTs. A second end of the at least one CNT is provided with a relatively sharp tip and is located at a distance within a selected range of a constant voltage plate. A sequence of voltage pulses {V(t.sub.n)}.sub.n at times t=t.sub.n (n=1, . . . , N1; N1.gtoreq.3) is applied to the at least one CNT, and a pulse discharge breakdown threshold voltage is estimated for one or more gas components, from an analysis of a curve I(t.sub.n) for current or a curve e(t.sub.n) for electric charge transported from the at least one CNT to the constant voltage plate. Each estimated pulse discharge breakdown threshold voltage is compared with known threshold voltages for candidate gas components to estimate whether at least one candidate gas component is present in the gas. The procedure can be repeated at higher pulse voltages to estimate a pulse discharge breakdown threshold voltage for a second component present in the gas.

  8. Chemical strategies for die/wafer submicron alignment and bonding.

    SciTech Connect

    Martin, James Ellis; Baca, Alicia I.; Chu, Dahwey; Rohwer, Lauren Elizabeth Shea

    2010-09-01

    This late-start LDRD explores chemical strategies that will enable sub-micron alignment accuracy of dies and wafers by exploiting the interfacial energies of chemical ligands. We have micropatterned commensurate features, such as 2-d arrays of micron-sized gold lines on the die to be bonded. Each gold line is functionalized with alkanethiol ligands before the die are brought into contact. The ligand interfacial energy is minimized when the lines on the die are brought into registration, due to favorable interactions between the complementary ligand tails. After registration is achieved, standard bonding techniques are used to create precision permanent bonds. We have computed the alignment forces and torque between two surfaces patterned with arrays of lines or square pads to illustrate how best to maximize the tendency to align. We also discuss complex, aperiodic patterns such as rectilinear pad assemblies, concentric circles, and spirals that point the way towards extremely precise alignment.

  9. Antares alignment gimbal positioner

    SciTech Connect

    Day, R.D.; Viswanathan, V.K.; Saxman, A.C.; Lujan, R.E.; Woodfin, G.L.; Sweatt, W.C.

    1981-01-01

    Antares is a 24-beam 40-TW carbon-dioxide (CO/sub 2/) laser fusion system currently under construction at the Los Alamos National Laboratory. The Antares alignment gimbal positioner (AGP) is an optomechanical instrument that will be used for target alignment and alignment of the 24 laser beams, as well as beam quality assessments. The AGP will be capable of providing pointing, focusing, and wavefront optical path difference, as well as aberration information at both helium-neon (He-Ne) and CO/sub 2/ wavelengths. It is designed to allow the laser beams to be aligned to any position within a 1-cm cube to a tolerance of 10 ..mu..m.

  10. EINSTEIN Cluster Alignments Revisited

    NASA Astrophysics Data System (ADS)

    Chambers, S. W.; Melott, A. L.; Miller, C. J.

    2000-12-01

    We have examined whether the major axes of rich galaxy clusters tend to point (in projection) toward their nearest neighboring cluster. We used the data of Ulmer, McMillan and Kowalski, who used x-ray morphology to define position angles. Our cluster samples, with well measured redshifts and updated positions, were taken from the MX Northern Abell Cluster Survey. The usual Kolmogorov-Smirnov test shows no significant alignment signal for nonrandom angles for all separations less than 100 Mpc/h. Refining the null hypothesis, however, with the Wilcoxon rank-sum test, reveals a high confidence signal for alignment. This confidence is highest when we restrict our sample to small nearest neighbor separations. We conclude that we have identified a more powerful tool for testing cluster-cluster alignments. Moreover, there is a strong signal in the data for alignment, consistent with a picture of hierarchical cluster formation in which matter falls into clusters along large scale filamentary structures.

  11. CLASP (Capture and Locking alignment Spring Positioner): A micromachined fiber auto-positioning device

    SciTech Connect

    Kravitz, S.H.; word, J.C.; Bauer, T.M.; Seigal, P.K.; Armendariz, M.G.

    1996-03-01

    This work provides a method of mechanical alignment of an array of single mode fibers to an array of optical devices. The technique uses a micromachined metal spring, which captures a vertical, pre- positioned fiber, moves it into accurate alignment, and holds it for attachment. The spring is fabricated from electroplated mickel, using photodefined polyimide as a plating mask. The nickel is plated about 80 {mu}m thick, so that a large fiber depth is captured. In one application, the nickel springs can be aligned to optics on the back side of the substrate. This entire concept is referred to as CLASP (Capture and Locking Alignment Spring Positioner). These springs can be used for general alignment and capture of any fiber to any optical input or output device. Passive alignment of fiber arrays to {plus}/{minus} 2{mu}m accuracy has been demonstrated, with a clear path to improved accuracy.

  12. Implied alignment: a synapomorphy-based multiple-sequence alignment method and its use in cladogram search

    NASA Technical Reports Server (NTRS)

    Wheeler, Ward C.

    2003-01-01

    A method to align sequence data based on parsimonious synapomorphy schemes generated by direct optimization (DO; earlier termed optimization alignment) is proposed. DO directly diagnoses sequence data on cladograms without an intervening multiple-alignment step, thereby creating topology-specific, dynamic homology statements. Hence, no multiple-alignment is required to generate cladograms. Unlike general and globally optimal multiple-alignment procedures, the method described here, implied alignment (IA), takes these dynamic homologies and traces them back through a single cladogram, linking the unaligned sequence positions in the terminal taxa via DO transformation series. These "lines of correspondence" link ancestor-descendent states and, when displayed as linearly arrayed columns without hypothetical ancestors, are largely indistinguishable from standard multiple alignment. Since this method is based on synapomorphy, the treatment of certain classes of insertion-deletion (indel) events may be different from that of other alignment procedures. As with all alignment methods, results are dependent on parameter assumptions such as indel cost and transversion:transition ratios. Such an IA could be used as a basis for phylogenetic search, but this would be questionable since the homologies derived from the implied alignment depend on its natal cladogram and any variance, between DO and IA + Search, due to heuristic approach. The utility of this procedure in heuristic cladogram searches using DO and the improvement of heuristic cladogram cost calculations are discussed. c2003 The Willi Hennig Society. Published by Elsevier Science (USA). All rights reserved.

  13. Implied alignment: a synapomorphy-based multiple-sequence alignment method and its use in cladogram search.

    PubMed

    Wheeler, Ward C

    2003-06-01

    A method to align sequence data based on parsimonious synapomorphy schemes generated by direct optimization (DO; earlier termed optimization alignment) is proposed. DO directly diagnoses sequence data on cladograms without an intervening multiple-alignment step, thereby creating topology-specific, dynamic homology statements. Hence, no multiple-alignment is required to generate cladograms. Unlike general and globally optimal multiple-alignment procedures, the method described here, implied alignment (IA), takes these dynamic homologies and traces them back through a single cladogram, linking the unaligned sequence positions in the terminal taxa via DO transformation series. These "lines of correspondence" link ancestor-descendent states and, when displayed as linearly arrayed columns without hypothetical ancestors, are largely indistinguishable from standard multiple alignment. Since this method is based on synapomorphy, the treatment of certain classes of insertion-deletion (indel) events may be different from that of other alignment procedures. As with all alignment methods, results are dependent on parameter assumptions such as indel cost and transversion:transition ratios. Such an IA could be used as a basis for phylogenetic search, but this would be questionable since the homologies derived from the implied alignment depend on its natal cladogram and any variance, between DO and IA + Search, due to heuristic approach. The utility of this procedure in heuristic cladogram searches using DO and the improvement of heuristic cladogram cost calculations are discussed. PMID:12901383

  14. Children's Reasoning about Spatial Relational Similarity: The Effect of Alignment and Relational Complexity

    ERIC Educational Resources Information Center

    Hribar, Alenka; Haun, Daniel B. M.; Call, Josep

    2012-01-01

    We investigated 4- and 5-year-old children's mapping strategies in a spatial task. Children were required to find a picture in an array of three identical cups after observing another picture being hidden in another array of three cups. The arrays were either aligned one behind the other in two rows or placed side by side forming one line.…

  15. Aligned carbon nanotubes: from controlled synthesis to electronic applications.

    PubMed

    Liu, Bilu; Wang, Chuan; Liu, Jia; Che, Yuchi; Zhou, Chongwu

    2013-10-21

    Single-wall carbon nanotubes (SWNTs) possess superior geometrical, electronic, chemical, thermal, and mechanical properties and are very attractive for applications in electronic devices and circuits. To make this a reality, the nanotube orientation, density, diameter, electronic property, and even chirality should be well controlled. This Feature article focuses on recent achievements researchers have made on the controlled growth of horizontally aligned SWNTs and SWNT arrays on substrates and their electronic applications. Principles and strategies to control the morphology, structure, and properties of SWNTs are reviewed in detail. Furthermore, electrical properties of field-effect transistors fabricated on both individual SWNTs and aligned SWNT arrays are discussed. State-of-the-art electronic devices and circuits based on aligned SWNTs and SWNT arrays are also highlighted. PMID:23969970

  16. Diameter-selective alignment of carbon nanotubes on Si(001) stepped surfaces

    SciTech Connect

    Enkhtaivan, Batnyam; Yoshimura, Masahide; Iwata, Jun-Ichi; Oshiyama, Atsushi

    2014-01-28

    We report total-energy electronic-structure calculations based on the density-functional theory that provide stable adsorption sites, structural characteristics, and energy bands of carbon nanotubes (CNTs) adsorbed on the Si(001) stepped surfaces. We choose (5,5), (9,9), and (13,13) armchair CNTs with the diameters of 6.8 Å, 12.2 Å, and 17.6 Å, respectively, as representatives of CNTs and explore all the possible adsorption sites either on the terrace or at step edges. We find that the (9,9) CNT is most favorably adsorbed at the edge of the double-layer step D{sub B} along the 〈110〉 direction, whereas the (5,5) and (13,13) CNTs favor the terrace site where the CNTs are perpendicular to the Si dimer rows. This finding is indicative of the diameter-selective self-organized alignment of CNTs by exploiting the Si surface steps along the particular direction. We also find that the electronic structure of each CNT is modified upon adsorption depending on the adsorption site and the diameter of the CNTs. In particular, the (9,9) CNT at the most stable step edge site becomes semiconducting and the resultant valence and conduction bands exhibit nearly linear dispersion with the effective mass of 0.085 m{sub 0} (m{sub 0}: bare electron mass), preserving the characteristics of the Dirac electrons. We also find that the flat bands appear near the Fermi level (E{sub F}) when the (13,13) CNT is adsorbed at the metastable D{sub B} step edge, inferring that spin polarization is possible for the CNT on the Si(001) stepped surface.

  17. Separation of methane-nitrogen mixtures using synthesis vertically aligned carbon nanotube membranes

    NASA Astrophysics Data System (ADS)

    Gilani, Neda; Daryan, Jafar Towfighi; Rashidi, Alimorad; Omidkhah, Mohammad Reza

    2012-03-01

    In this paper, capabilities of carbon nanotube (CNT) membranes fabricated in cylindrical pores of anodic aluminum oxide (AAO) substrate to separate the binary mixtures of CH4/N2 are studied experimentally. For this purpose, the permeability and selectivity of three CNT/AAO membranes with different growth time as 6 h, 12 h and 18 h are investigated. CNTs are grown vertically through holes of AAO with average pore diameter of 45 nm by chemical vapor deposition (CVD) of acetylene gas. CNT/AAO membranes with the same CNTs' outer diameters and different inner diameters are synthesized. The AAO are characterized by SEM analysis. In addition, SEM, TEM, BET N2 adsorption analysis and Raman spectroscopy are employed to characterize aligned CNTs. Study on permeability and selectivity of membranes for three binary mixtures of CH4/N2 showed that when the CNT inner diameters are 34 nm and 24 nm, viscous flow is the governing mechanism and insignificant selectivities of 1.2-1.24 are achieved. However, the membrane with CNT inner diameter and wall thickness of 8 nm and 16 nm respectively is considerably selective for CH4 over N2. It was also found that CH4 mole fraction in the feed and upstream feed pressure have major effect on permeability and selectivity. The membrane with 18 h synthesis time showed the selectivity is in the range of 1.8-3.85. The enhancement factor for N2 single gas diffusivity was also found to be about three times larger than that predicted by Knudsen diffusion model.

  18. Mass transport through vertically aligned large diameter MWCNTs embedded in parylene

    NASA Astrophysics Data System (ADS)

    Krishnakumar, P.; Tiwari, P. B.; Staples, S.; Luo, T.; Darici, Y.; He, J.; Lindsay, S. M.

    2012-11-01

    We have fabricated porous membranes using a parylene encapsulated vertically aligned forest of multi-walled carbon nanotubes (MWCNTs, about 7 nm inner diameter). The transport of charged particles in electrolyte through these membranes was studied by applying electric field and pressure. Under an electric field in the range of 4.4 × 104 V m-1, electrophoresis instead of electroomosis is found to be the main mechanism for ion transport. Small molecules and 5 nm gold nanoparticles can be driven through the membranes by an electric field. However, small biomolecules, like DNA oligomers, cannot. Due to the weak electric driving force, the interactions between charged particles and the hydrophobic CNT inner surface play important roles in the transport, leading to enhanced selectivity for small molecules. Simple chemical modification on the CNT ends also induces an obvious effect on the translocation of single strand DNA oligomers and gold nanoparticles under a modest pressure (<294 Pa).

  19. Mass transport through vertically aligned large diameter MWCNT embedded in parylene

    PubMed Central

    Krishnakumar, P; Tiwari, P B; Staples, S; Luo, T; Darici, Y; He, J; Lindsay, SM

    2013-01-01

    We have fabricated porous membranes using a parylene encapsulated vertically aligned forest of multi-walled carbon nanotube (MWCNT, about 7nm inner diameter). The transport of charged particles in electrolyte through these membranes was studied by applying electric field and pressure. Under an electric field in the range of 4.4×104 V/m, electrophoresis instead of electroomosis is found to be the main mechanism for ion transport. Small molecules and 5 nm gold nanoparticles can be driven through the membranes by an electric field. However, small biomolecules, like DNA oligomers, cannot. Due to the weak electric driving force, the interactions between charged particles and the hydrophobic CNT inner surface play important roles in the transport, leading to enhanced selectivity for small molecules. Simple chemical modification on the CNT ends also induces an obvious effect on the translocation of single strand DNA oligomer and gold nanoparticle under a modest pressure (<294 Pa). PMID:23064678

  20. Pairwise Sequence Alignment Library

    2015-05-20

    Vector extensions, such as SSE, have been part of the x86 CPU since the 1990s, with applications in graphics, signal processing, and scientific applications. Although many algorithms and applications can naturally benefit from automatic vectorization techniques, there are still many that are difficult to vectorize due to their dependence on irregular data structures, dense branch operations, or data dependencies. Sequence alignment, one of the most widely used operations in bioinformatics workflows, has a computational footprintmore » that features complex data dependencies. The trend of widening vector registers adversely affects the state-of-the-art sequence alignment algorithm based on striped data layouts. Therefore, a novel SIMD implementation of a parallel scan-based sequence alignment algorithm that can better exploit wider SIMD units was implemented as part of the Parallel Sequence Alignment Library (parasail). Parasail features: Reference implementations of all known vectorized sequence alignment approaches. Implementations of Smith Waterman (SW), semi-global (SG), and Needleman Wunsch (NW) sequence alignment algorithms. Implementations across all modern CPU instruction sets including AVX2 and KNC. Language interfaces for C/C++ and Python.« less