Hybrid structures consisting of functional materials enhanced by carbon nanotubes (CNTs) have potential for a variety of high impact applications, as shown by the impressive progress in sensing and mechanical applications enabled by CNT-enhanced materials. The hierarchical organisation of CNTs with other materials is key to the design of macroscale devices benefiting from the unique properties of individual CNTs, provided CNT density, morphology and binding with other materials are optimized. In this paper, we provide an analysis of a continuous aerosol process to create a hybrid hierarchical sea urchin structure with CNTs organized around a functional metal oxide core. We propose a new mechanism for the growth of these carbon nanotube sea urchins (CNTSU) and give new insight into their chemical composition. To corroborate the new mechanism, we examine the influence of CNT growth conditions on CNTSU morphology and demonstrate a new in-line characterisation technique to continuously monitor aerosol CNT growth during synthesis, which enables industrial-scale production optimization. Based upon the new formation mechanism we describe the first substrate-based chemical vapour deposition growth of CNTSUs which increases CNT length and improves G to D ratio, which also allows for the formation of CNTSU carpets with unique structures.
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The authors thank Davor Copic and Shahab Ahmad for their help with CNT growth by CVD. Shahab Ahmad’s help with Raman measurement is also acknowledged, together with that of Brian Graves and Chris Nickolaus (Cambustion Ltd) for CPMA experiments, and Laura Maggini for TGA experiments. Jean de La Verpilliere is supported by the EPSRC Cambridge NanoDTC, EP/G037221/1, the Cambridge Home EU Scholarship Scheme (CHESS) and the Schiff Foundation Studentships. Adam Boies is supported by the EPSRC ANAM grant (EP/M015211/1). Michael De Volder is supported by an ERC starting grant (HIENA - 337739). Sarah Jessl is supported by the ERC starting grant (HIENA-337739) and the EPSRC Studentship (Hierarchical Carbon nanostructures, 1470335).
© 2018 The Royal Society of Chemistry.