Papers

12/2013
Towards the development of carbon nanotube based wiresCarbon 68, 597 (2014)
A. Lekawa-Raus, L. Kurzepa, X. Peng, K.K.K. Koziol

The excellent electrical and mechanical performance of individual carbon nanotubes combined with their extremely low weight make these structures highly interesting materials for electrical wiring applications. The recent manufacture of macroscopic wire-like assemblies made purely of carbon nanotubes – carbon nanotube fibres – has opened up new prospects in this area. The extensive research on the optimization of the morphology of the fibres indicates that it will be soon possible to produce carbon nanotube fibres exceeding both the electrical and mechanical performance of conductive metals currently used in electrical engineering. To enable the application carbon nanotube fibres as wires in everyday electrical circuits it is necessary to provide them with electrical insulation. This paper proposes, for the first time, a method of insulation of the fibres and analyses the parameters which control the successful development of insulating coating on the surface of these highly porous carbon materials. It is shown that the applied insulation does not compromise either the electrical or mechanical performance of the fibres. The proposed insulation method is inexpensive, easy to integrate into a production process for the carbon nanotube fibres and it can be scaled up.

doi: 10.1016/j.carbon.2013.11.039
12/2013
In situ observation of the effect of nitrogen on carbon nanotube synthesisChemistry of Materials 25, 2921 (2013)
S.W. Pattinson, R.E. Diaz, N.A. Stelmashenko, A.H. Windle, C. Ducati, E.A. Stach, K. Koziol
12/2013
Synthesis and characterization of mesoporous multi-walled carbon nanotubes at low frequencies electromagnetic wavesJournal of Nano Research 26, 117 (2013)
H.Soleimani, N. Yahya, N.R. Ahmad Latiff, K. Koziol, B.M. Maciejewska, B.H. Guan

For electromagnetic absorbing and shielding applications, carbon nanotubes (CNT) are widely used due to their excellent electrical and physical properties. Fabrication of microwave absorbing materials involves the use of compounds capable of generating dielectric and/or magnetic losses when impinged by an electromagnetic wave. The presence of lattice defects e.g. vacancies and dislocations contributes to the loss and attenuation in the electromagnetic waves, which in turn remarkably enhance the absorption ability of the material. With the CVD technique which is known to produce several lattice defects in the final product, aligned MWCNTs were successfully synthesized by pyrolizing toluene and ferrocene in an inert argon environment. The morphology analysis of the aligned MWCNTs was conducted via FESEM and TEM analysis, to reveal the average length of approximately 295 μm, with diameters in the range of 60-200 nm. EDS analysis indicates the high yield of CNTs, with more than 90% in weight composition, with less than 5 % Fe impurities presence. Textural properties of MWCNTs were studied by measuring pore size and BET surface area. To understand the response of CNTs to an electromagnetic field, permeability and permittivity measurement were conducted in the frequency range of 100 Hz to 110 MHz. In conclusion, the presence of defects in MWCNTs is desirable for enhanced electromagnetic absorption ability.

doi: 10.4028/www.scientific.net/JNanoR.26.117
12/2013
Carbon nanotube wires for high-temperature performanceCarbon 64, 305 (2013)
D. Janas, A. Cabrero-Vilatela, J. Bulmer, L. Kurzepa, K.K. Koziol

We developed carbon nanotube wires (CNWs) and monitored in-situ their electrical properties at high temperature conditions for the first time. The dominant type of CNTs present in the material and packing density of thereof proved to have a dominant effect on the thermal stability of CNWs. Furthermore, we showed that kinetics of CNW oxidation plays an important role and slow heating rates or prolonged heating times are essential for the proper determination of thermal stability of CNTs. To enhance the stability at high temperatures, we applied SiC coating onto the CNWs, what allowed a 300°C improvement to the operational window, eventually reaching 700°C in the long-haul. Correlation of the change in electrical properties with thermogravimetric response showed that the loss of electrical percolation takes place at 100°C lower temperature than the last observed weight loss in CNTs content. Finally, we demonstrated feasibility of SiC-coated CNWs under high temperature conditions, by creating a heating device out of them. The presence of SiC layer gave rise to a significant improvement to the thermal stability of the CNT heaters, which now offer unprecedented range of operation reaching 700°C, as compared to 400°C when uncoated.

doi: j.carbon.2013.07.067
12/2013
Performance of carbon nanotube wires in extreme conditionsCarbon 62, 438 (2013)
D. Janas, A. Cabrero-Vilatela, K.K. Koziol

Carbon nanotubes are known to obviate many limitations of classically employed conductors, but one finds it difficult to assemble them into macroscopic functional structures, like wires and cables, with appropriate performance. The employed protocols are usually problematic and not viable on a big scale. Herein, we show the durability of carbon nanotube wires (CNWs) obtained in a single step by the continuous direct spinning of fibers from chemical vapor deposition. A comparison study with copper reveals that CNWs fill a gap where traditional materials fail to operate. Not only CNWs survive salty or highly acidic conditions, but they do not seem to degrade over long period of time in harsh environment.

doi: 10.1016/j.carbon.2013.06.029
12/2013
Lipid nanoscaffolds in carbon nanotube arraysNanoscale 5, 8992 (2013)
C. Paukner, K.K. Koziol, C.V. Kulkarni

We present the fabrication of lipid nanoscaffolds inside carbon nanotube arrays by employing the nanostructural self-assembly of lipid molecules. The nanoscaffolds are finely tunable into model biomembrane-like architectures (planar), soft nanochannels (cylindrical) or 3-dimensionally ordered continuous bilayer structures (cubic). Carbon nanotube arrays hosting the above nanoscaffolds are formed by packing of highly oriented multiwalled carbon nanotubes which facilitate the alignment of lipid nanostructures without requiring an external force. Furthermore, the lipid nanoscaffolds can be created under both dry and hydrated conditions. We show their direct application in reconstitution of egg proteins. Such nanoscaffolds find enormous potential in bio- and nano-technological fields.

doi: 10.1039/c3nr02068a
12/2013
Liberation of drugs from multi-wall carbon nanotube carriersJournal of Controlled Release 169, 126 (2013)
S. Boncel, P. Zajac, K.K. Koziol

MWCNTs in the ‘nanotube–drug’ hybrids can play a role of carriers or additives (enhancers) in the more complex formulations. This work reviews qualitative and quantitative analyses of Drug Delivery Systems (DDSs) based on multi-wall carbon nanotubes (MWCNTs) and their chemically modified analogues (mainly oxidised MWCNTs). A special emphasis was placed on the chemical interactions between drug molecules and the nanotube carrier critical both in the stage of preparation/synthesis of the hybrids and liberation of the drug.

doi: 10.1016/j.jconrel.2013.04.009
12/2013
Electroluminescence from carbon nanotube films resistively heated in airApplied Physics Letters 102, 181104 (2013)
D. Janas, N. Czechowski, B. Krajnik, S. Mackowski, K.K. Koziol

Light emission from carbon nanotube (CNT) films was explored in both the near-infrared and the infrared spectral regions upon application of external bias voltage. We obviated the need to use sophisticated vacuum apparatus by employing state-of-the-art optics and detection system. It enabled us to sensitively probe electroluminescence at relatively low temperatures (T ∼ 300 °C) in ambient conditions and investigate the character of emission from CNT assemblies in real life conditions. The observed spectral response revealed distinct features and the results strongly suggest that CNT assemblies are promising candidates for optoelectronic applications, particularly in the field of telecommunication.

doi: 10.1063/1.4804296