Yes, continuous ball milling of graphite in the presence of methanol for 20–30 hours will likely cause particle contamination. There are two main aspects you should consider:

1. Contamination issues: – The dominant contamination arises from mechanical abrasion of the balls and the milling jar. – The extent of contamination depends on the choice of milling materials (e.g., steel, tungsten carbide, zirconia). – Methanol acts as a process control agent (PCA) and can help reduce cold welding and particle agglomeration, but cannot fully prevent mechanical contamination.

2. How to minimize contamination: – Select inert milling media: zirconia (ZrO₂), silicon carbide (SiC), or alumina balls and jars are much more resistant to wear compared to steel. – Limit the milling intensity: reduce rotation speed and use smaller balls to decrease mechanical stress. – Optimize the milling atmosphere: keeping an excess of methanol helps to slightly lubricate contacts and slow down surface abrasion.

Post-milling cleaning procedure: – Immediately rinse the balls and the jar with methanol or acetone after milling. – Use ultrasonic cleaning for 15–20 minutes in methanol or acetone to detach graphite residues. – Gentle mechanical brushing (with a soft polymer brush) can help if residues are persistent. – Avoid strong abrasives, which can damage the jar and balls.

Important additional note: After such prolonged milling, graphite may not only reduce in size but partially exfoliate into few-layer or even monolayer graphene-like structures. You should characterize the final product via Raman spectroscopy, XRD, or TEM to understand the degree of exfoliation and contamination.

Disclaimer: This answer was formulated with the assistance of artificial intelligence (AI) based on current scientific literature and experimental practices in nanomaterials processing.

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