Synthesis and formation mechanism of pitch-based carbon foam for three-dimensional structural applications.

[Display omitted] • Pitch is treated with nitric acid to produce modified pitch, and the formation mechanism of carbon foam was investigated based on the concentration of nitric acid. • The successful synthesis of carbon foam required pitch modification with a high concentration of nitric acid (60 wt%). • Carbon foam from modified pitch is attributed to the synergistic effect of the functional groups duced onto pitch and the low-molecular-weight components resulting from cracking. • The introduced oxygen-containing functional groups triggered CO 2 production, which could promote pore structure development. Carbon foam is a three-dimensional porous, rigid, and permeable material with applications in many fields owing to its excellent electrical and thermal properties. Pitch is a promising carbon source for carbon foam production, and its modification with nitric and sulfuric acids has been widely investigated. However, the foaming phenomenon resulting from the acid treatment of pitch and the resultant formation of porous structures remain poorly understood. Herein, we clarified the mechanism by which the porous structure of pitch-derived carbon foam is formed by analyzing the components of pitch modified by nitric acid treatment and identifying essential conditions for foam production. Carbon foam was obtained by pitch modification at a high concentration of nitric acid (60 wt%), whereas no carbon foam was formed at low nitric acid concentrations (<60 wt%). Furthermore, at high nitric acid concentrations, carbon foam formation proceeded at a relatively low temperature (280 °C). The formation of carbon foam from modified pitch was attributed to the synergistic effect of the functional groups introduced onto pitch and the low-molecular-weight components resulting from cracking. This work provides new insights into pitch as a precursor and provides a straightforward method for producing carbon foam. [ABSTRACT FROM AUTHOR]