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Penetration based CNT/Sol-gel composite films and there remarkable electrical properties

: Erismis, Harun; Nemec, Dominik; Geiß, Michael; Skakalova, Viera; Kolaric, Ivica; Ritter, Uwe; Roth, Siegmar

Gentili, M. ; Consiglio Nazionale delle Ricerche -CNR-:
MNE 2010, 36th International Conference on Micro & Nano Engineering. Abstracts. CD-ROM : Genoa, Italy, 19-22 September 2010
Genua, 2010
1 pp.
International Conference on Micro and Nano Engineering (MNE) <36, 2010, Genoa>
Conference Paper
Fraunhofer IPA ()
sol-gel; Carbon Nanotube (CNT); composite film; conductivity; Leitfähigkeit; Verbundwerkstoff; carbonfaserverstärkter Kunststoff

A novel preparation method for CNT/Sol-Gel composite films (Fig. 1) and its remarkable electrical properties compared to pure CNT coatings are reported herein. These Coatings are suitable for a wide range of applications like electromagnetic shielding, optical devices or high thermal stable composite electrodes.
The presented method forming highly conductive CNT/Sol-Gel composite films is unconventional but highly favorable for composite film preparation and to our knowledge it is used for the first time. Unlike standard methods where at least two components, in this case CNTs and Sol-Gel material, were homogenously mixed with each other this new approach uses a penetration effect forming the composite film. This method also allows a detailed study of the electrical influence from the Sol-Gel on CNT networks during different phases of process steps like drying and sintering temperatures. Furthermore this new method is independent from dispersant agents or any functionalisation of the CNTs which is reported as a key issue preparing homogenous CNT/Sol-Gel composites.
Beside the novel preparation method the key finding of this work is that it could be observed that the electrical properties of the composite material improved 20% to 60% compared to the pure CNT network which is mainly due to improved inter-tube contacts and there enhanced number after Sol-Gel densification. Comparing the achieved specific values with common results for CNT(SWNTs)/Sol-Gel composites the presented method shows three orders of magnitude optimization even with MWNTs. For MWNTs/Sol-Gel composite films a specific resistivity of 0,01 ohm cm was successfully achieved with this method whereas in the literature 10 ohm cm is the best value we found.
Forming the composite films MWNTs were first coated on a glass substrate followed by thermal treatment for removing residuals. The Sol-Gel was than coated via Dip-Coating at RT forming a composite film with the primarily coated CNTs. The obtained composite is than treated at different temperatures e.g. 500°C to 700°C in argon atmosphere for densifiying the film composites without destroying the CNTs. As references CNT coatings without Sol-Gel where also exposed to the thermal treatment to get a direct comparison and a better understanding of the observed effects. The changes of the electrical properties were measured at each process step and were accomplished with temperature dependent measurements of resistivity and I-U characteristics. Depending on the sintering temperature a continuous enhancement of the electrical properties was observed for the CNT/Sol-Gel composite. The results correlate with the Sol-Gel densification due to thermal treatment.