Adhesion of nanodiamond seeded CVD diamond on ceramic substrate

Conventional structural ceramic substrates were coated with 1 μm thick polycrystalline CVD diamond layer by using the hot filament CVD system and subsequently tested. The substrates chosen were silicate, alumina, silicon nitride, and silicon carbide ceramics. To achieve a high nucleation density and to improve the adhesion between the diamond and the ceramic substrate, the newly developed Electrostatic Self-Assembly of Nano Diamond (ESAND) seeding method was used. This seeding method initiates the growth of crystalline diamond. For this seeding procedure, each negatively charged substrate surface was covered with a cationic polymer monolayer. Next, anionic polymer coated cationic nanodiamond particles were attached to the substrate by the electrostatic self-assembly process. The degree of adhesion between the diamond film and each substrate was investigated by micro-scratch testing. These tests involved the use of a Rockwell C indenter (r = 0.2 mm), which scratched the samples at a speed of 10 mm/min under a progressive normal load (from 0 to 21N). The morphology of the poly-crystalline diamond films on the various substrates was analyzed using Raman spectroscopy.