Influence of the defect morphology on the strength of diamond particles

The influence of particle size and microstructural defect morphology on the strength of diamond powders HPHT, synthesized in a high-pressure anvil device with central concavity, has been studied. The strength was calculated as the breaking load obtained in single grit tests divided by the mesh opening area corresponding to the intervals of particle size classification. The strength values were associated with eight distinct groups of microscopic defect morphology, in which a power law relating the diamond strength to its particle size has been experimentally established. This law was found to apply to other data reported in the literature. For each value of strength, a crack length was derived from the Griffith equation and a rationale has been proposed to justify the eight morphological groups in terms of corresponding defect length. A scanning electron microscopy analysis corroborated this theoretical proposal.