A STUDY OF POROSITY AND INTERFACIAL AREA IN ORIGINAL AND OXIDIZED POCO GRAPHITE AXM-5Q1 USING SMALL-ANGLE NEUTRON-SCATTERING

Compact specimens of the nonconventional, i.e., binder-free POCO graphite AXM-5Q1 were studied by SANS. The coherent macroscopic differential neutron scattering cross section dΣ/dΩ decays with h-α, where h is the scattering vector. The exponent α = 3.1, in contrast to Porod's law, which predicts α = 4 for a group of pores with a narrow size distribution. According to Schmidt, such deviations from Porod's law are compatible with scattering from three-dimensional pores with a power law volume/size distribution function, F(R) ∝ R-(4-α). Assuming spherical pore shape, F(R) was estimated using the Harwell Maximum Entropy Code. The data are consistent with F(R) ∝ R-0.9. The scattering curves calculated with the F(R) data agreed with the measured curves within the spread of the data. The concentration of mesopores and the interfacial area Scum increase with the degree of oxidation (Scum = 8.1 m2 g-1 at a burn-off of 2.3 wt%). © 1990.