Packing Behavior and Permeability of Mono- and Bimodal Mixtures of Coarse Granular Diamond Grit as Precursors for Reaction Bonding of Diamond–Silicon Carbide (SiC) Composites

Author(s):

Anthony DiGiovanni and Clifford Hubbard

Abstract:

Packing and permeability relationships in bimodal mixtures of 125- and 25-µm diamond powders were evaluated and compared with established theoretical and empirical relationships for similar-sized spherical powders for future correlations with liquid silicon infiltration (LSI) reaction bonded composite synthesis of diamond composites. Diamond powders were characterized via scanning electron microscopy and laser particle size analysis. The packing characteristics were determined using a commercial tap densometer with 125-µm diamond packing to 64.4% and 25-µm packing to 60.6%. Falling head permeability testing was used to determine corresponding values of 9.34 × 10^-12 m² for the 125-µm diamond packing and 5.31 × 10^-13 m² for the 25-µm diamond packing. Reasonable agreement was found in the packing characteristics with empirical calculations and theoretical computation. Peak permeability was estimated at 40 vol%, 125-µm diamond in the bimodal