Mechanical Exfoliation of Graphite Nanoparticles from Highly Crystalline Vein Graphite for Electrical Applications

Scalable and economical production of high-quality graphene remains a key challenge in developing carbon-based electronic materials. This study used hydrothermally formed, highly crystalline vein graphite (~97% purity) as the raw material to exfoliate graphite nanoparticles via dry ball milling for 2-14 hours with a constant ball-to-powder ratio of 10:1, followed by acid leaching and material characterization. We observed a gradual lateral particle size reduction of graphite particles from 367 µm to 30 µm with increasing milling time. XRF analysis confirmed 86% reduction in Fe and complete removal of Cu impurity after purification. XRD results revealed partial exfoliation of nanocrystalline multilayer graphene, where layer count gradually reduced from ~145 to ~90, and crystallite thickness reduced from ~50 nm to ~33 nm upon milling. A conducting ink was formulated from exfoliated particles where sheet resistivity increased from 41.25 ± 5 to 161.73 ± 5 Ω/sq with milling time due to oxidative byproducts and defect formation, observed by FTIR and Raman Spectroscopy. These findings demonstrate a scalable method for producing high-purity graphite nanoparticles with tunable electronic and thermal properties from natural vein graphite for applications in flexible electronics and nanofluids.