Nanodiamond Synthesis from Coal via Flash Joule Heating

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• The coal industry seeks cleaner production methods and advanced utilization strategies.
• Converting low-value coal into high-value nanodiamonds (NDs) is a promising but challenging approach due to low purity and efficiency of existing coal-based NDs (C-NDs).
• NDs possess exceptional properties and broad application potential.

Purpose of the Study:

• To develop an efficient and scalable method for synthesizing high-purity nanodiamonds from coal.
• To address the limitations of existing coal-based nanodiamond synthesis.
• To evaluate the economic and environmental viability of a coal-to-diamond production system.

Main Methods:

• Development of a fluorine (F)-assisted flash Joule heating (FJH) method using coke as feedstock.
• Synthesis of C-NDs in approximately 1 second.
• Post-treatment to achieve high purity and characterization of C-ND properties.
• Theoretical calculations to understand the role of fluorine in diamond formation.
• Life cycle assessment (LCA) comparing C-NDs with the high-pressure high-temperature (HPHT) method.

Main Results:

• Achieved ∼100% purity C-NDs with an 8% yield using the FJH method.
• Synthesized C-NDs exhibit thermal stability comparable to commercial NDs.
• Theoretical calculations confirmed F atoms promote C-C bond formation.
• C-NDs successfully used as seed crystals for high-quality diamond film production.
• LCA indicated C-NDs outperform HPHT in cost, carbon emissions, water, and electricity usage.

Conclusions:

• The F-assisted FJH method provides an efficient and scalable route to high-purity nanodiamonds from coal.
• This coal-to-diamond technology offers significant economic and environmental advantages.
• The proposed production system supports cleaner coal utilization and advances the coal industry.