Microstructural characterization of commercial hot-pressed boron nitride

Microstructural characterization of commercially hot-pressed boron nitride (BN) using SEM and mercury porosimetry are described. Commercial material consits of varying amounts of B{sub 2}O{sub 3} (2% to 9%) and fine porosity (2% to 7%) within a bonded three-dimensional network of BN particles. The platelike BN particle morphology, which forms an aggregate by bonding along particle edges, is displayed. A layered structure present within individual BN particles is shown to consist of fine porous layers (<30 nm in thickness), which separate BN regions (100 to 200 nm in thickness) in the plane of the platelets. Size and dispersion of the pores and the continuous B{sub 2}O{sub 3} phase are estimated with mercury porosimetry and with SEM after leaching and filling with a liquid bismuth-tin (Bi-Sn) alloy.