Preparation and Characterization of Glassy Carbon Powder Modified with a Thin Layer of Boron-Doped Ultrananocrystalline Diamond (B-UNCD)

Abstract

The surface of glassy carbon powder (4 μm diam, 2 m2/g) was modified with a thin layer of boron-doped ultrananocrystalline diamond (B-UNCD) for the purpose of improving the dimensional stability and corrosion resistance of the material. The UNCD layer was deposited by microwave-assisted chemical vapor deposition using a 1% CH4, 7% H2, 92% Ar and 1 × 10−3 % B2H6 (10 ppm) source gas mixture at 800 W of microwave powder and a system pressure of 140 Torr. Each sample was coated twice using a 2 h growth period with powder mixing in between to increase the number of particles coated and the coverage over each particle. SEM, XRD, Raman spectroscopy, and electrochemical methods were used to characterize the as received and B-UNCD-GC powders before and after anodic polarization at 1.6 V vs Ag/AgCl (25 °C, 30−60 min) in 0.5 M H2SO4. Most particle surfaces were coated with a thin layer of UNCD and there was some particle aggregation due to diamond overlayer formation over multiple neighboring particles. The results ...