Ultrasonic studies of monolithic and powdered carbon materials

Molecular acoustics methods were applied to investigations of monolithic and powdered carbon materials, e.g., to monolithic adsorbent carbon supports (compressed expanded graphite) and powdered bituminous coals. The clear dependencies of ultrasonic velocity and dynamic elastic modulus vs. porosity for compressed expanded graphite were found. It seems that the porosity dependence of dynamic elastic modulus can be used for determination of porosity. Contrary to usually used methods (mercury porosi-metry, BET, etc.), elasticity properties measurements take into account not only open but also closed pores. It was found for bituminous coals that the expression of log (density/velocity) can be interpreted as proportional to mean molecular weight of portion between cross-links and may be used for relative estimation of cross-linking in coal. Our results give evidence that molecular acoustics methods (ultrasounds) can be very useful in the studies of properties of carbon materials in both monolithic and powdered form.