Fracture behavior of thick diamond films prepared by DC arc plasma jet method

摘要

The ball-on-ring method was used to investigate the fracture behavior of thick diamond film samplesprepared by high-power DC plasma jet CVD method. Both as-grown and polished samples weretested. Great efforts were made to correlate the data obtained to the microstructural features of thetested samples, particularly to the grain size and the pre-existing defects. For as-grown samples, thedata were widely scattered such that it was hard to find any grain size dependence on fracturestrength and toughness. Whilst for polished samples, a linear relationship of fracture strength to theinverse of the square root of the grain size (the well-known Petch-Hall equation) was found to fit thedata reasonably well. This suggests that grain refinement is also an effective way for improving themechanical properties of CVD diamond films. Pre-existing micro-cracks are also an important factoraffecting the mechanical properties of thick CVD diamond films.