Mechanical milling with capacitively coupled plasma for surface modification of particulate materials

We have developed a new reactor for plasma surface modification of nanoparticles, a mechanical milling apparatus combined with capacitively coupled plasma. Using the reactor, nanosized hydrophobic silica powder due to surface CH3 groups was mechanically milled under He/O2 plasma for 50 min. The specific surface area of the powder was 110 m2/g of which corresponding diameter was 23 nm. The flow rates of He and O2 were 4950 and 50 cm3/min, respectively (pressure:700 Pa), and 30 W of discharged power was applied. For the surface investigation, Diffuse reflectance infrared Fourier transform (DRIFT) spectra was measured. The results obtained indicated that the He/O2 plasma treatment decomposed rapidly the surface CH3 groups. The decomposition rate of CH3 groups was estimated to be approximately 10 m2/min.