Preparation of carbon foams with enhanced oxidation resistance by foaming molten sucrose using a boric acid blowing agent

Boric acid was used as a blowing agent as well as a boron precursor for the preparation of boron-doped carbon foams from molten sucrose. The H+ generated, due to the formation of a complex between sucrose and boric acid, catalyzes the –OH to –OH condensation reaction leading to the polymerization and the foaming of the molten sucrose. The char yield of the solid organic foams increased from 24 to 39 wt.% when the boric acid concentration increased from 0 to 8 wt.%, due to the formation of the B–O–C cross-links between sucrose polymer by B–OH to C–OH condensation. The inductively coupled plasma analysis showed the presence of 0.44–3.4 wt.% boron in the carbon foams. The density and compressive strength decreased and cell size increased with boric acid concentration. The room temperature thermal conductivity of the boron-doped carbon foams was in the range of 0.057–0.043 W m−1 K−1. The weight loss studies by dynamic and isothermal heating showed the increased oxidation resistance with boron concentration.