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. (C) 2012 Elsevier Ltd. All rights reserved.