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Stuttgart Mühlhausen, Germany

Uddin S.M.,Sineurop Nanotech GmbH | Uddin S.M.,University of Ulm | Mahmud T.,Fraunhofer Institute for Manufacturing Engineering and Automation | Wolf C.,Fraunhofer Institute for Manufacturing Engineering and Automation | And 8 more authors.
Composites Science and Technology

Utilizing the extra-ordinary properties of carbon nanotube (CNT) in metal matrix composite (MMC) for macroscopic applications is still a big challenge for science and technology. Very few successful attempts have been made for commercial applications due to the difficulties incorporating CNTs in metals with up-scalable processes. CNT reinforced copper and copper alloy (bronze) composites have been fabricated by well-established hot-press sintering method of powder metallurgy. The parameters of CNT-metal powder mixing and hot-press sintering have been optimized and the matrix materials of the mixed powders and composites have been evaluated. However, the effect of shape and size of metal particles as well as selection of carbon nanotubes has significant influence on the mechanical and electrical properties of the composites. The hardness of copper matrix composite has improved up to 47% compared to that of pure copper, while the electrical conductivity of bronze composite has improved up to 20% compared to that of the pure alloy. Thus carbon nanotube can improve the mechanical properties of highly-conductive low-strength copper metals, whereas in low-conductivity high-strength copper alloys the electrical conductivity can be improved. © Elsevier Ltd. Source

Erismis H.,Fraunhofer Institute for Manufacturing Engineering and Automation | Nemec D.,Fraunhofer Institute for Manufacturing Engineering and Automation | Geiss M.,Fraunhofer Institute for Manufacturing Engineering and Automation | Skakalova V.,Max Planck Institute for Solid State Research | And 5 more authors.
Microelectronic Engineering

In this work we present a novel method for CNT/Sol-Gel film preparation, combining low resistivity and improved adhesion behaviour on glass substrates. Naturally occurring voids, with diameters of 50-100 nm, in sprayed CNT networks are used for Sol-Gel penetration via dip coating method. Thermal treatments, for composite film densification, in the range of 200-700°C are investigated and electrical properties were compared to identically treated reference samples with the same batch of nanotubes but without Sol-Gel. The resistivity of such composite films, with best value of ∼0.03 cm for MWNTs, is two orders of magnitudes lower than previously reported for CNT/Sol-Gel composites. Surprisingly the surface resistance of the composite film shows 25% improvement compared to thermally equal treated pure CNT films. In addition, crosscut adhesion behaviour is investigated, including tape test, showing good performance for composite films, where Sol-Gel acts as an adhesion promoter. © 2011 Elsevier B.V. All rights reserved. Source

Roth S.,Korea University | Roth S.,Sineurop Nanotech GmbH | Roth S.,Max Planck Institute for Solid State Research | Park H.J.,Max Planck Institute for Solid State Research
Chemical Society Reviews

This tutorial review discusses the contradictory material properties of electrical conductivity and optical transparency for the examples of graphene films and carbon nanotube networks. It is argued that for homogeneous films both properties are linked by basic laws of physics and that for perfect monoatomic layers conductivity and transparency can be calculated from the fine structure constant. To beat these limitations, inhomogeneous films are required, such as graphene with an array of holes or nanotube networks. An overview is given on literature values of transparency and conductivity, both for graphene films and for nanotube networks. © 2010 The Royal Society of Chemistry. Source

Kaymaksiz S.,Max Planck Institute for Solid State Research | Kaskhedikar N.,Max Planck Institute for Solid State Research | Sato N.,Toyota Motor Corporation | Roth S.,Max Planck Institute for Solid State Research | And 3 more authors.
ECS Transactions

We investigated the synthesis of the nanocrystalline LiMnPO4 and its composite with single-walled carbon nanotubes (SWCNT) as me potential material for lithium ion batteries. Three synthesis routes, sol-gel, precipitation in microemulsion and hydrothermal procedure have been evaluated with regard to the morphology, particle size, porosity, phase purity and crystallinity. Even though all preparation methods produce crystalline material with expected olivine type structure, the battery performance strongly differs. We found out that me Li-ion diffusion, not the electrical conductivity, determines the battery capacity. Particles smaller than 30 nm provided by precipitation via microemulsion and incorporated into network of SWNTs significantly improve the battery performance. Our results confirm that the high capacity can only be achieved when the nanocrystalline particles provided by the synthesis are sufficiently separated and prevented from agglomeration in the working electrode. ©The Electrochemical Society. Source

Koizhaiganova R.B.,Korea University | Hwang D.H.,Korea University | Lee C.J.,Korea University | Roth S.,Korea University | And 2 more authors.
Physica Status Solidi (B) Basic Research

We investigated the chemical doping of the single-walled carbon nanotubes (SWCNTs) networks by a treatment with aromatic amines. Adsorption and intercalation of amine molecules in bundled SWCNTs leads to typical n-type doping observed already for alkali metals. The electron donation to SWCNTs is demonstrated by the X-ray-induced photoelectron spectra (XPS), where the carbon C 1s peak observed at 284.4eV for the sp2 carbon in pristine samples is shifted by up to 0.3eV to higher binding energy upon chemical treatment. The development of a Breit-Wigner-Fano component on the lower energy side of the G- mode in the Raman spectrum as well as a shift of the G+ to lower frequency provide evidence for charge accumulation in the nanotube π system, and indication for the n-type doping. The spectroscopic changes are accompanied by the modification of the electrical properties of the SWCNTs. A reduction of conductivity depends on the doping level and implies the decreasing concentration of the charge carriers in the naturally p-doped tubes. Comparing the two selected n-type dopants, the tetramethyl-p-phenylenediamine, shows more pronounced changes in the XPS and the Raman spectra than tetramethylpyrazine, indicating that the sp3 hybridization of nitrogen in the amine groups attached to phenyl ring is much more effective in interaction with the tube π system than the sp2 hybridization of nitrogen in the aromatic pyrazine ring. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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