Formation of metallic nano-crystals from gel-like precursor films for CVD nanotube growth: An in-situ TEM characterization

TL;DR

This study uses in-situ TEM to observe the transformation of gel-like Fe catalyst films into crystalline nano-particles at high temperatures, providing insights into their role in carbon nanotube growth.

Contribution

It offers real-time visualization of catalyst particle formation and mobility during annealing, enhancing understanding of CVD nanotube synthesis mechanisms.

Findings

Crystalline particles form at ~300°C from gel-like films.

Particles are single-crystalline with a log-normal size distribution at 700°C.

High mobility of catalyst particles observed despite crystallinity.

Abstract

The evolution of a continuous Fe(NO3)3 catalyst film was observed by in-situ annealing in a Transmission Electron Microscope (TEM). Such catalysts are routinely used in the catalytic growth of carbon nanotubes. The experiments reveal that crystalline particles form from the gel-like film already around 300C. At usual carbon nanotube growth temperatures of 700C, the particles are single-crystalline with a log-normal size distribution. The observations furthermore show that in spite of the crystalline structure of the particles there is a high mobility. The experiments allow to obtain detailed information about the chemistry and the crystallinity of the catalyst film, which provides valuable information for the interpretation of the carbon nanotube growth by chemical vapor deposition.