Acoustical characterization of nano-porous carbons

Abstract

The acoustical and related non-acoustical properties of activated carbon were studied to understand better the effect of added catalyst and acid treatment on the nano- and micro-structure of activated, porous nano-carbon. The acoustical impedance was measured in a 45 mm diameter impedance tube with a special adaptor to accommodate a very small material quantity available for this experiment. The presence of the adaptor was compensated using the procedure detailed in Dupont et al. [POMA 19, 065008 (2013); http://dx.doi.org/10.1121/1.4799701]. The acoustic impedance of activated carbon was predicted using the model proposed by Venegas [Section 6.1, Ph.D. thesis, University of Salford, 2011]. The micro- and nano-scale porosities and pore sizes were determined by fitting the model to the acoustic impedance data in the frequency range between 50 and 1000 Hz. It is shown that the acid treatment and addition of catalyst result in the reduced radius of nano-pores and reduced nano-porosity. These effects are small but measurable acoustically. These results are consistent with the results of the BET experiment. This work provides the foundation for the development of acoustical methods for nano-porous material characterization which are rapid and non-invasive.