A fine carbon filament has been used as substrate in a microwave plasma enhanced chemical vapour deposition (MPECVD) process. The carbon filaments were severely etched to form carbon dusts which then served as nucleation seeds. Polycrystalline diamond coatings on the carbon dust and the diamond dust, which was used during the sonication pre-treatment, were obtained at temperatures below 1000 degrees C. A mini-explosion that formed a 120-mu m diamond sphere occurred at a temperature of 950 degrees C. As the processing temperature further increased, several explosions occurred to form protrusions, including glassy carbon spheres with volumes greater than 22 mm(3), and thick glassy carbon coatings, at an average rate as high as 270 mu m per 17 h, on the entire surface. These thick coatings occurred on the untreated surface of a Si coupon, which was used to support the carbon filaments. The explosion has been explained to be as a result of energy absorption from the microwave and plasma.