Nanowires and nanotubes, also called 1D-nanoparticles (1D-NPs), can be synthesized by a myriad of techniques, but the floating catalyst chemical vapor deposition (FCCVD) route has the great advantage of being capable of reaching orders of magnitude higher growth rate than the conventional CVD [1]. The reasons for this enhancement seem to lie in the intrinsic growth mechanism governed by the transport and kinetics of the relevant species from the gas phase towards the incipient 1D-NP. The overall reaction rate from reagents toward the desired product is given by the underlying kinetics, which involves consecutive and competitive processes. Some mechanistic pathways for the growth of 1D-NPs have been proposed to apply at low-pressure regimes for CVD [2]. Since CVD and FCCVD show fundamentally different growth rates [3], it can be expected that the rate-limiting processes are fundamentally different.

To gain the intended mechanistic understanding of the growth of FCCVD, it is essential to have appropriate control of the features of the nanoparticles where incipient FCCVD growth occurs. For this reason, it becomes essential to count with a stable and reproducible generator of catalyst nanoparticles floating in the gas phase. We have developed a spark discharge generator (SDG) for the tuneable generation of nanoparticles, which can directly synthesize nanoparticles from any conductive element from the periodic table. We have studied different process variables and present relationships between the variables such as flow rate, gap, current resistance, capacitance, and inductance on the features of the nanoparticles synthesized via spark discharge generator [4].

We apply this SDG as catalyst generator to produce nanowires and nanotubes with controlled initial catalyst size distribution. This enables us to study the factors controlling the diameter distribution of the 1D-NP grown by FCCVD for the two systems, shedding light on the role of catalyst growth promoters, aerosol particle sintering, and catalyst poisoning.

References:

[1] I Gómez-Palos, et al. Nanoscale, 2022, 14(48), 18175-18183.

[2] V. G. Dubrovskii, et al., Physical Review B, 2008, 78.23: 235301.

[3] R. S. Schäufele, et al., Nanoscale, 2022, 14.1 55-64.

[4] M Vazquez Pufleau, et al.,Advanced Powder Technology, 2022, just accepted.