Nucleation and evolution of graphitic particles in atmospheric pressure microwave plasma

Graphene’s exceptional electrical, thermal, and mechanical properties have driven two decades of research toward scalable, high-quality synthesis methods for industrial applications. Traditional techniques such as chemical vapor deposition (CVD) offer good material control but are often limited by substrate constraints and low production rates. This study investigates an alternative approach to synthesis using atmospheric pressure microwave plasmas to grow graphene-like carbons without the need for a substrate, thereby enabling volumetric, gas-phase growth and higher production rates. Key reactor parameters, including tube geometry, methane flow rate, and input power, were systematically varied to study their effect on particle formation and material quality, allowing for reactor optimization towards maximizing production rate while yielding good quality carbon. Brunauer-Emmett-Teller (BET) surface area analysis and Raman spectroscopy revealed that straight tube geometries in the place of taper or step tube geometries and higher plasma power favor the formation of more crystalline, lower-defect graphene structures, while increased methane flow generally led to higher defect densities and larger particle sizes. Spatially resolved sampling was achieved for the carbon grown in the reactor via probe arms, and showed that mean particle diameter increased with distance from the plasma core, supporting a nucleation-in-the-bulk, growth-at-the-boundary model consistent with existing literature. These results highlight the sensitivity of plasma-grown carbon to reactor conditions and support the continued development of atmospheric plasma systems for scalable, tunable graphene synthesis. Future work may explore the incorporation of moving substrates or low-pressure variants to further refine the balance between quality and throughput for next-generation graphene-based technologies

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Nuclear, Plasma, Radiolgc Engr

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Hays, E. Parker

Contributors dc:contributor

• Ruzic, David N.
• Qerimi, Dren

• Graphene
• Plasma
• Microwave Plasma
• Atmospheric Pressure Plasma
• Carbon Nanomaterials

Statement dc:rights

• Copyright 2025 E. Hays

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129352

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129352