Subject Number             :S-20-NI-0001

Support Type                : Technical consultation

Proposal Title (English)      : Graphitization of nanocarbon catalyzed by gallium

Username (English)         : Amr Attia Abuelwafa Qenawe¹⁾, Balaram Paudel Jaisi²⁾

Affiliation (English)             :1) South Valley University, 2) Nagoya Institute of Technology (NITech)

1. Summary

In this study, it was investigated that the amorphous carbon was directly graphitized under the catalysis of a low melting point metal, gallium (Ga), by heating in a vacuum heater as well as by Joule heating during in situ transmission electron microscopy (TEM) operation. For the material system of the mixture of Ga and amorphous carbon (a-C), the graphitization temperature was determined for the first time by the former ex-situ heating experiment and the graphitization process was analyzed in detail by the latter in-situ TEM observation.

2. Experimental

Ga-C nanocomposites were synthesized on an edge of commercially available carbon (graphite) foils by ion beam irradiation with the simultaneous supply of Ga co-sputtered perpendicular to the edge of carbon foil using a carbon nanofiber (CNF) synthesis system (CSS) [1]. The morphology of the samples thus prepared were observed by a scanning electron microscope (SEM). The samples were then heated in a vacuum heater at different temperatures in order to determine the graphitization temperature. The ex-situ and in-situ TEM [2, 3] characterizations were performed using TEM (JEM-ARM200F).  CSS, SEM and TEM were provided by Nanotechnology platform of NITech.

3. Results and Discussion

The high magnification TEM images of the samples annealed at the temperatures 500, 600, 700 and 800^oC, were observed carefully. It was clearly seen that below 500^oC, there was no sign of graphitization. At 600^oC, there were observed some spots of graphitization with agglomeration of Ga nanoparticles (NPs). At 700^oC, the level of graphitization increased to long range with an agglomeration of Ga-NPs, whereas at 800^oC, there occurred the complete evaporation of agglomerated Ga-NPs with the complete graphitization in the surroundings of each agglomerated Ga-NPs. In addition to these ex situ results, in situ TEM showed the tip of a Ga-C nanocomposites completely graphitized in the form of the capped carbon nanotube after the in situ Joule heating.  Thus, the graphitization process was understood in nanoscale by in situ and ex situ TEM observations.

4. Others

[1] P. Ghosh and M. Tanemura: “Low – Temperature Fabrication of 1-Dimensional Metal Nanostructure Arrays by Ion Irradiation” in “Advances in Nanotechnology. Volume 10,” Nova Science Publishers, Chapt. 12 (pp. 337-350) (2013).

[2] S. Sharma, et al., Scientific Reports 5 (2015) 10426-1-9.

[3] S. Sharma, et al., Carbon 132 (2018) 165-171.

5. Publication/Presentation

(1) B. Paudel Jaisi, A. A. Abuelwafa, et al., Phys. Status Solidi B, 257 (2020) p.p. 2000309-1-5.

6. Patent

N/A