Textural and mechanical characteristics of carbon aerogels synthesized by polymerization of resorcinol and formaldehyde using alkali carbonates as basification agents

Abstract

Five organic aerogels were prepared simultaneously by polycondensation of resorcinol and formaldehyde using different alkali carbonates (M₂CO₃, M = Li, Na, K, Rb and Cs) as basification agents. The gelation time depended on the carbonate used, increasing from Li₂CO₃ to Cs₂CO₃. The porosity of the samples is defined during this process, when the three-dimensional packing of primary particles is formed. The slower the gelation, the greater the overlapping of primary particles and the formation of clusters, leading to a mechanical reinforcement of the samples and the progressive displacement of their pore size distribution (PSD) towards larger pores. Carbonization produces certain shrinkage of the structure and increases the microporosity and the Young modulus of the samples. Carbon aerogels change from mesoporous to macroporous materials as the counter-ion size of the carbonate increases.