Study and Fabrication of Cu-Composites for High Ampacity Materials

Le résumé fourni par la source

It is predicted that a commercial airplane is stroke by a lightning strike once a year, making this a common phenomenon, and consequently a threat to flight safety, since the electric discharge caused by the lightning strike can cause the vaporization of both metal cables and metal components on a non-protected airplane. Copper has always been a popular choice regarding various applications because of its remarkable electrical and thermal conductivities, 5.8x105 S cm-1 and 401 W m-1K-1 at 27 oC, respectively. While copper and aluminium mesh were the materials mostly used on airframes with the finality of lighting strike protection, the most recent trends that airspace companies are following is the use of carbon composites to reduce the overall weight of aircraft and for fuel saving. Carbon nanotubes (CNT) are well known weight reducers with high strength and conductivity, makingthem a great candidate for preparation of high ampacity copper-carbon materials composites for lightning strike protection and device miniaturization. Subramanian et al. has previously described the preparation of composites with ampacity one hundred times higher than that of pure copper, and efforts have been made to replicate this work. However, many issues have been presented because of carbon nanotubes and copper weak bonding due to CNT cuprophobic and hydrophobic behaviour. To meet this demand, the study of the interface between carbon nanotubes, copper and all the interface’s secondary components was prioritized. While CNT oxidation by acidic treatment has been described in literature as a successful method for overcoming the hydrophobicity of this material, we did not observe a significant influence of this process on the CNT behaviour. Further studies on time of oxidation and its impact on hydrophobic behaviour of CNT is ongoing. Nevertheless, it is theorized that during the first steps of the dopamine polymerization reaction, the formation of oxidant species could help overcome the CNT aggregation by creation of reaction sites on the CNT surface – such as carboxylic groups.These sites allow further reaction of CNT with PDA building blocks – increasing a hydrophilic nature on the CNT and allowing the growth of a polymeric film on CNT walls. Functionalization with PDA at different pH levels indicated variations in dispersion stability and conductivity. Polymer presence was verified by XPS analysis, which revealed enhanced carbon-oxygen and carbon-nitrogen bonding. Electrical evaluation revealed that PDA-functionalized CNTs had a lower conductivity than pristine or oxidized ones. Finally, it was concluded that due to a higher specific surface area, longer CNT have higher polymeric loading – as proven by TGA analysis. The presence of metal ions during PDA polymerization had a substantial influence on polymer yield and composite characteristics. XPS study demonstrated that the presence of copper or nickel ions promoted polymerization, resulting in higher sheet resistance and lower conductivity. This increase in PDA polymerization and CNT loading should be related to copper chelation by oligomers formed during the polymerization process, which allows the deposition of dispersed PDA molecules, and studies for the understanding of this phenomenon are being developed. Overall, our findings reveal the first link between CNT surface changes and composite characteristics. Metal promoters had a considerable impact on polymerization yield and electrical conductivity, while oxidation and PDA functionalization had little effect on CNT characteristics. These insights are critical for improving composite design and performance in a variety of applications. Figure 1

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.