Influence of the raw material on the pore structure and elastic properties of compressed expanded graphite blocks

Highly porous monolithic samples of compressed expanded graphites (CEG) of porosity ranging from 87.5 to 99.5%, produced of three various powders of expanded graphites, were studied. The dynamic elastic moduli of the samples were determined by means of measurement of the velocity of the longitudinal ultrasonic wave propagated along three mutually orthogonal directions: one perpendicular to the bedding plane, and two orthogonal within the bedding plane. The elasticity of the highly porous samples with a porosity up to close to the percolation threshold can be described by the Phani–Niyogi equation. The elastic modulus of the solid matrix, the structure and packing geometry of pores, as well as the true density of the samples were discussed in relation to the kind of the raw material, i.e. expanded graphite.