Methods　GNs were synthesized through a combined ball milling pretreatment and surfactant-assisted aqueous-phase ball milling process. Key parameters， such as surfactant dosage， initial graphite concentration， ball milling time， and ball-to-material ratio， were optimized through univariate analysis with the mass concentration of GNs as the evaluation metric. In addition， the morphological and structural characterization of the resulting GNs were conducted， and the surfactant removal efficiency through calcination was systematically investigated.

Results and Discussion　Experimental studies showed that the optimal processing parameters were determined as follows： 3% surfactant mass fraction， 120 mg/mL initial graphite mass concentration， 4 h ball milling time， and 12∶1 ball-to-material ratio. Under these conditions， the resulting GNs were produced at a maximum solution concentration of 2. 42 mg/mL. Microscopic characterization results， including scanning electron microscopy（ SEM）， transmission electron microscopy（ TEM）， and atomic force microscopy（ AFM）， showed that about 70% of the GNs had lateral sizes between 400 nm and 800 nm and consisted of 5 to 12 layers. Raman spectroscopic analysis confirmed their high structural integrity， as evidenced by the low defect-related I_D/I_G ratio（ the ratio of peak intensity D to peak intensity G ） of 0. 318. In addition， calcination at 400 ℃ for 30 min under a nitrogen atmosphere effectively removed most of the surfactants， while moderately improving the conductivity of the resulting GNs. A higher calcination temperature of 950 ℃ achieved complete surfactant removal， significantly enhancing conductivity of up to 1. 3×10⁴ S/m.

Conclusion　This study demonstrates a green， efficient， and scalable aqueous-phase exfoliation method for producing highquality and low-defect GNs. The combined ball milling approach offers a novel idea for graphene production and holds promise for large-scale graphene preparation. Additionally， the developed calcination-based surfactant removal method further enhances conductivity， enabling flexible application-specific optimization. This work provides a promising pathway toward sustainable， large-scale graphene manufacturing.

Keywords：aqueous-phase exfoliation； ball milling method； graphene nanosheets； surfactant removal