Applications of Small Angle Neutron Scattering and Small Angle X-ray Scattering to Organic Petrology

attractive alternative to using fluids for probing the pore space. The scattering techniques are inexpensive, non-invasive, require little sample preparation, and can be performed both on oriented whole coal samples and standard crushed pellets. SAXS and SANS have been used for decades to study the geometry of supra-molecular objects. These objects can be suspended in solvents or aggregated into a solid phase. With modern small angle scattering apparatus, the size of objects accessible with SANS and SAXS extends from about 1 nm (10 Å) to about 30 µm (300,000 Å). There is an extensive literature about the theory and practice of SAS (for a review see [1]), including its applications to sedimentary rocks and coals [2-7]. Scattering of X-rays or neutrons occurs because of the scattering contrast between various components within the medium. X-rays probe the fluctuations of the electronic density, whereas neutrons probe the fluctuations of the nuclear scattering cross section. In general, these fluctuations reflect the chemical inhomogeneity and density variations within the sample. In particular, the pore space in coals has high contrast with the coal matrix for both X-rays and neutrons [8]